potential for formation of disinfection by-products from

Report Reference: DWI 12852.02

March 2018

Potential for Formation of Disinfection By-

Products from Advanced Oxidation

Processes

RESTRICTION: This report has the following limited distribution:

External: DWI

Any enquiries relating to this report should be referred to the Project Manager at the

following address:

WRc plc,

Frankland Road, Blagrove,

Swindon, Wiltshire, SN5 8YF

Telephone: + 44 (0) 1793 865000

Website: www.wrcplc.co.uk

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Potential for Formation of Disinfection By-

Products from Advanced Oxidation Processes

Authors:

Abraham Negarash

Senior Processes Engineer

Treatment Processes

Date: March 2018

Report Reference: DWI 12852.02

David Shepherd

Senior Process Engineer

Treatment Processes

Project Manager: James Froud

Project No.: 16700-0

Leon Rockett

Senior Toxicologist

National Centre for Environmental Toxicology

Client: DWI

Client Manager: Peter Marsden

Anwen Clementson

Toxicologist

National Centre for Environmental Toxicology

Richard Hooper

Materials Technologist

Resource Efficiency

Justin Silver

Senior Process Engineer

Treatment Processes

This report was funded by Defra. The views expressed in it are those of the authors, and not necessarily those of Defra or DWI.

Document History

Version

number

Purpose Issued by Quality Checks

Approved by

Date

V1.0 Draft report issued for comment. Justin Strutt James Froud 24/11/2017

V2.0 Final report issued to client. James Froud Abraham Negaresh 08/03/2018

© WRc plc 2018 The contents of this document are subject to copyright and all rights are reserved. No part of this document may be reproduced, stored in a retrieval system or transmitted, in any form or by any means electronic, mechanical, photocopying, recording or otherwise, without the prior written consent of WRc plc.

This document has been produced by WRc plc.

Contents

Glossary ................................................................................................................................... 1

Summary .................................................................................................................................. 4

1. Objective 1: Definition of the range of advanced oxidation processes that are or may soon be in use in England and Wales ............................................. 10

1.1 Introduction ................................................................................................................ 10

1.2 Literature search ....................................................................................................... 10

1.3 Water company survey ............................................................................................. 22

1.4 Conclusions ............................................................................................................... 24

2. Objective 2: Review of chemical reactions and potential formation of Disinfection by-products ............................................................................................ 27

2.1 Introduction ................................................................................................................ 27

2.2 Radical Chain Reactions ........................................................................................... 27

2.3 Advanced Oxidation Processes ................................................................................ 28

2.4 Conclusion ................................................................................................................. 38

3. Objective 3: Systematic review of the formation of DBPs by AOPs ......................... 39

3.1 Introduction ................................................................................................................ 39

3.2 Search methodology ................................................................................................. 39

3.3 Outcome .................................................................................................................... 48

4. Objective 4: Prioritisation and Toxicity Review ......................................................... 49

4.1 Prioritisation of DBPs ................................................................................................ 49

4.2 Literature Search and Data Collation ........................................................................ 53

4.3 Toxicity Summary ...................................................................................................... 55

5. Objective 5: Risk Assessment ................................................................................... 89

5.1 Hazard Identification ................................................................................................. 89

5.2 Hazard Characterisation ........................................................................................... 89

5.3 Exposure Assessment .............................................................................................. 90

5.4 Risk Characterisation ................................................................................................ 91

5.5 Risk Communication ................................................................................................. 91

5.6 2-Hydroxy-5-nitrobenzoic acid .................................................................................. 91

5.7 2-Methoxy-4,6-dinitrophenol ..................................................................................... 92

5.8 2-Nitrohydroquinone .................................................................................................. 94

5.9 3,5-Dinitrosalicylic acid .............................................................................................. 95

5.10 4-Hydroxy-3-nitrobenzoic acid .................................................................................. 96

5.11 4-Nitrobenzene-sulfonic acid ..................................................................................... 98

5.12 4-Nitrocatechol .......................................................................................................... 99

5.13 4-Nitrophthalic acid.................................................................................................. 101

5.14 5-Nitrovanillin ........................................................................................................... 102

5.15 Summary and Conclusions ..................................................................................... 103

6. Objective 6: Review of analytical methods for detecting disinfection by-products from advanced oxidation processes ......................................................... 106

6.1 Introduction .............................................................................................................. 106

6.2 Literature Review .................................................................................................... 106

6.3 Method Reviews ...................................................................................................... 107

6.4 Nitrobenzene diol .................................................................................................... 110

6.5 Conclusions ............................................................................................................. 113

7. Objective 7: Sampling and analysis strategy for future research projects .............. 115

7.1 Introduction .............................................................................................................. 115

7.2 Removal of prioritised DBPs ................................................................................... 115

7.3 Outline of strategy ................................................................................................... 115

7.4 Analytical method development .............................................................................. 116

7.5 Identification of sites for sampling ........................................................................... 118

7.6 Communication ....................................................................................................... 119

7.7 Sampling strategy for AOP treatment works ........................................................... 120

7.8 Conclusions and Suggestions ................................................................................. 122

References ........................................................................................................................... 124

Appendices

Appendix A Water company survey .......................................................................... 137

Appendix B Water company responses .................................................................... 142

Appendix C Inclusion and exclusion criteria used in the literature review ................ 165

Appendix D Search strings and outcomes of searches, for formation of

DBPs ..................................................................................................... 169

Appendix E Summary of reviewed literature ............................................................. 185

Appendix F Literature Review ................................................................................... 236

Appendix G Ozone DBP Assessment ....................................................................... 239

List of Tables

Table 1.1 Flow rates and AOP doses – UV/H2O2/O3 .............................................. 23

Table 1.2 Summary of current and potential future usage of AOPs ....................... 24

Table 2.1 DBPs formed following peroxone treatment process (US EPA, 1999) ....................................................................................... 30

Table 2.2 DBPs from the ozonation of raw water .................................................... 32

Table 2.3 DBPs from the UV / Cl2 of raw water ....................................................... 35

Table 3.1 Search terms specifically related to AOP techniques ............................. 40

Table 3.2 Search terms for the formation and occurrence of DBPs........................ 41

Table 3.3 Inclusion and exclusion criteria used....................................................... 41

Table 3.4 List of DBPs found (UV / H2O2) .............................................................. 43

Table 3.5 List of DBPs found (O3 / H2O2) .............................................................. 44

Table 3.6 List of DBPs found (O3 / UV / H2O2) ...................................................... 45

Table 3.7 List of DBPs found (UV and Hypochlorous acid) .................................... 46

Table 3.8 List of DBPs (UV and persulfate) ............................................................ 47

Table 3.9 DBPs found (UV and titanium dioxide) .................................................... 47

Table 4.1 Thirteen DBPs excluded based on existing available toxicity data .......................................................................................................... 52

Table 4.2 Final list of DBPs for assessment in this project ..................................... 52

Table 4.3 Table 4.4 VEGA predictions for 2-hydroxy-5-nitrobenzoic acid .......................................................................................................... 57

Table 4.5 VEGA predictions for 2-methoxy-4,6-dinitrophenol ................................ 59

Table 4.6 OECD Toolbox predictions for 2-methoxy-4,6-dinitrophenol .................. 60

Table 4.7 VEGA predictions for 2-nitrohydroquinone .............................................. 63

Table 4.8 VEGA predictions for 3,5-dinitrosalicylic acid .......................................... 65

Table 4.9 OECD Toolbox predictions for 3,5-dinitrosalicylic acid ........................... 66

Table 4.10 VEGA predictions for 4-hydroxy-3-nitrobenzoic acid .............................. 69

Table 4.11 VEGA predictions for 4-nitrobenzene-sulfonic acid ................................. 71

Table 4.12 OECD Toolbox predictions for 4-nitrobenzene-sulfonic acid .................. 72

Table 4.13 VEGA modelling software toxicity predictions for 4-nitrocatechol ............................................................................................ 75

Table 4.14 OECD Toolbox predictions for 4-nitrocatechol ........................................ 76

Table 4.15 VEGA predictions for 4-nitrophthalic acid ............................................... 78

Table 4.16 OECD Toolbox predictions for 5-nitrovanillin .......................................... 80

Table 4.17 VEGA predictions for 5-nitrovanillin ......................................................... 82

Table 4.18 Summary of PoD for each DBP ............................................................... 83

Table 5.1 Uncertainty Factor considerations ........................................................... 89

Table 5.2 Summary of risk characterisation of DBPs based on their estimated daily intake ............................................................................ 105

Table 6.1 DBPs assessed ..................................................................................... 106

Table 7.1 DBPs for further assessment ................................................................ 116

Table C.1 Inclusion and exclusion criteria applied to the selection of relevant papers for the each AOP ......................................................... 166

Table C.2 List of words used for the exclusion of irrelevant papers for ozonation ............................................................................................... 168

Table D.1 Search string for formation of DBPs from UV / H2O2 using Scopus ................................................................................................... 169

Table D.2 Summary of numbers of papers identified, excluded and assessed (UV / H2O2) ............................................................................ 170

Table D.3 Search string for formation of DBPs from hydrogen peroxide and ozone treatment using Scopus ....................................................... 171

Table D.4 Search string for formation of DBPs from hydrogen peroxide and ozone treatment using Science Direct ........................................... 171

Table D.5 Summary of numbers of papers identified, excluded and assessed (O3 / H2O2) ............................................................................. 172

Table D.6 Search string for formation of DBPs from ozone and UV treatment using Scopus ......................................................................... 173

Table D.7 Summary of numbers of papers identified, excluded and assessed (O3 / UV) ................................................................................ 173

Table D.8 Search string for formation of DBPs from hydrogen peroxide and onzone and UV treatment using Scopus ........................................ 174

Table D.9 Summary of numbers of papers identified, excluded and assessed (UV / H2O2) ............................................................................ 175

Table D.10 Search string for formation of DBPs from UV and hypochlorous acid using Scopus ........................................................... 176

Table D.11 Summary of numbers of papers identified, excluded and assessed (UV / HOCl) ........................................................................... 177

Table D.12 Search string for formation of DBPs from UV and persulphate using Scopus ..................................................................... 178

Table D.13 Summary of numbers of papers identified, excluded and assessed (UV / S2O8) ............................................................................ 178

Table D.14 Search string for formation of DBPs from UV and titanium dioxide treatment using Scopus ............................................................ 179

Table D.15 Summary of numbers of papers identified, excluded and assessed (UV / TiO2) ............................................................................. 180

Table D.16 Search string for formation of DBPs from UV, titanium dioxide and hydrogen peroxide treatment using Scopus ...................... 181

Table D.17 Summary of numbers of papers identified, excluded and assessed (UV / TiO2 / H2O2) .................................................................. 181

Table D.18 Search string for formation of DBPs from ozone treatment using Scopus ......................................................................................... 182

Table D.19 Search string for formation of DBPs from ozone treatment using Science Direct .............................................................................. 183

Table D.20 Additional ‘In Any Field’ Exlusion Words ............................................... 183

Table E.1 DBP formation from UV / H2O2 process ................................................ 185

Table E.2 DBP formation from O3 / H2O2 ............................................................... 201

Table E.3 DBP formation from O3 / UV .................................................................. 207

Table E.4 DBP formation from O3 / UV / H2O2 ....................................................... 211

Table E.5 DBP formation from UV / Cl2 ................................................................. 214

Table E.6 DBPs formation from UV / S2O8 ............................................................ 219

Table E.7 DBP formation from UV / TiO2 ............................................................... 221

Table E.8 DBP formation from Ozonation ............................................................. 223

Table E.9 References ............................................................................................ 234

Table F.1 Generic search terms used within Scopus ............................................ 236

Table F.2 Generic search terms used within PubMed .......................................... 236

Table F.3 Results from literature searches in Scopus and PubMed search .................................................................................................... 237

Table G.1 High priority DBPs formed by ozone ..................................................... 239

Table G.2 VEGA predictions for 1-bromo-1,1-dichloropropanone ......................... 241

Table G.3 OECD Toolbox predictions for 1-bromo-1,1-dichloropropanone ................................................................................. 242

Table G.4 VEGA predictions for dichloroacetaldehyde .......................................... 245

Table G.5 OECD Toolbox predictions for dichloroacetaldehyde ........................... 246

Table G.6 Summary of risk characterisation ozone DBPs ..................................... 251

List of Figures

Figure 2.1 Reaction mechanism for UV / H2O2 treatment ......................................... 28

Figure 2.2 Potential reaction mechanism for UV / H2O2 treatment ........................... 29

Figure 2.3 Reaction mechanism for O3 / H2O2 treatment .......................................... 30

Figure 2.4 Reaction mechanism for O3 / UV treatment ............................................. 31

Figure 2.5 Reaction mechanism for O3 / UV / H2O2 treatment ................................. 33

Figure 2.6 Potential reaction mechanism for O3 / UV / H2O2treatment ..................... 33

Figure 2.7 Reaction mechanism for UV / Cl2 treatment ............................................ 34

Figure 2.8 Reaction mechanism for UV/[S2O8]2−

treatment ...................................... 35

Figure 2.9 Reaction mechanism for UV/TiO2 treatment ........................................... 36

Figure 4.1 Prioritisation of DBPs to identify those chemicals to be considered for toxicological assessment ................................................. 50

Figure 6.1 Structures of compounds ...................................................................... 107




Figure 6.5 GC-MS trace for 4-nitrobenzene sulfonic acid ...................................... 113

DWI

Report Reference: DWI 12852.02/16700-0 March 2018

© WRc plc 2018 1

Glossary

[S2O8]2-

Persulphate ion

2–MIB 2-Methylisoborneol

ADI Acceptable daily intake

AOP Advanced oxidation pathway

ATSDR Agency for Toxic Substances and Disease Registry

Br- Bromide ion

BrO3- Bromate ion

bw Bodyweight

CIP2 UKWIR Chemicals Investigation Programme 2

Cl- Chloride ion

Cl• Chlorine radical

Cl2 Chlorine

CO2 Carbon dioxide

CO3•- Carbonate radical anion

CO32-

Carbonate anion

DBP Disinfection by-product

DNA Deoxyribonucleic acid

DOC Dissolved organic carbon

DWI Drinking Water Inspectorate

ecb- Photo-excited electron

ECD Electron capture detector

ECHA European Chemicals Agency

EFSA European Food Safety Authority

Fe(OH)3 Ferric hydroxide

Fe2+

Ferrous ion

FeCO3 Ferrous carbonate

FePO4 Ferric phosphate

GAC Granular activated carbon

GC Gas chromatography

GC-MS Gas chromatography – mass spectroscopy

GDWQ Guidelines for Drinking-water Quality

DWI


© WRc plc 2018 2

GHS Globally harmonised system

h+ Positive hole

H+ Hydrogen ion

H2O Water

H2O2 Hydrogen peroxide

HAA Haloacetic acid

HBGV Health-based guidance value

HCO3- Bicarbonate ion

HCO3• Bicarbonate radical

HO2- Hydroperoxide ion

HOCl Hypochlorous acid

HSDB Hazardous substances databank

hv UV irradiation

ITSD eq. Internal Standard equivalent

JECFA Joint Food and Agriculture/World Health Organization Expert

Committee on Food Additives

LC / HR-MS Liquid chromatography / high resolution mass spectroscopy

LD50 Median lethal dose

LDLo Lethal dose low

LO(A)EL Lowest observed (adverse) effect level

LOD Limits of detection

LP Low pressure UV (monochromatic)

M moles/litre (mol/l)

M+O3

- Metal-ozone compound

MLD Mega-litre per ray

MOE Margin of exposure

MP Medium pressure UV (polychromatic)

MtBE Methyl tert-butyl ether

N-DBP Nitrogenous disinfection by-product

NDMA N-Nitrosodimethylamine

NO(A)EL No observed (adverse) effect level

NOM Natural organic matter

O(1D) Excited singlet state

O•- Oxygen atom radical anion

DWI


© WRc plc 2018 3

O• Oxygen radical

O2 Oxygen

O2•- Superoxide radical

O3 Ozone

OCl- Hypochlorite ion

OECD Organisation for Economic Co-operation and Development

OH• Hydroxyl radical

PAA Peracetic acid

PoD Point of departure

QSAR Quantitative structure-activity relationship

QToF Quadrupole time of flight

RfD Oral reference dose

RO Reverse osmosis

ROS Reactive oxygen species

SCF European Scientific Committee for Food

SO4•- Sulphate radical anion

SO4• Sulphate radical

TDI Tolerable daily intake

THM Trihalomethane

TiO2 Titanium dioxide

TOC Total organic carbon

TTC Threshold of Toxicological Concern

UF Uncertainty factor

US EPA United States Environment Protection Agency

UV Ultraviolet

UVT UV transmittance

VOC Volatile organic carbon

WHO World Health Organisation

DWI


© WRc plc 2018 4

Summary

i Reasons

Due to the introduction of the EU Drinking Water Directive (98/83) (implemented in England

through regulation 26(2)(a) of the Water Supply (Water Quality) Regulations 2016) there is a

legal requirement to minimise disinfection by-product (DBP) formation. The regulatory focus

has primarily been on DBPs arising from chlorine (notably trihalomethanes, THMs) and ozone

(bromate). Concern about chlorinated by-products has contributed to the adoption of

alternative oxidants in water treatment, notably ozone, and the wider application of UV

disinfection. Advanced oxidation processes (AOPs) have also been introduced to degrade

micropollutants such as pesticides. Advanced oxidation processes generate highly reactive

hydroxyl radicals (OH•), which are potent, but non-selective, oxidants that react orders of

magnitude faster than molecular ozone. Advanced oxidation processes that have application

in drinking water treatment utilise combinations of ozone (O3), hydrogen peroxide (H2O2) and

ultraviolet (UV) light to generate the free radicals. Alternative approaches are available in

other industrial sectors, for example UV in combination with titanium dioxide (TiO2). In

practice, AOPs mineralise only a small proportion of organic material such that a wide range

of organic and potentially inorganic disinfection by-products are formed.

Previous studies have been carried out by the Drinking Water Inspectorate (DWI) regarding

the formation of DBPs produced following ozonation. There is, however, less knowledge of

the types of DBPs produced following AOPs. Therefore the aim of this project is to identify

potential DBPs that may be formed as a consequence of AOPs, identify potential hazard

posed by the DBPs and to carry out a risk assessment to estimate the risk they may pose to

public health.

ii Objectives

This project has been divided into seven objectives:

Objective 1. Define the range of advanced oxidation techniques that are or may soon

be in use in England and Wales.

Objective 2. Review of chemical reactions and potential formation of Disinfection by-

products (DBPs).

Objective 3. Conduct a systematic review of the published and grey literature issued

since 1990 on the formation of by-products from the advanced oxidation processes

identified under objective 1 and their potential removal by subsequent treatment

processes.

DWI


© WRc plc 2018 5

Objective 4. Review existing knowledge of toxicity of the DBPs identified under

objective 3 above.

Objective 5. Conduct a high level risk assessment based on the outcome of objectives

3 and 4.

Objective 6. Review the availability of methods of analysis for the DBPs identified.

Objective 7. Devise a sampling and analysis strategy that could be employed as part of

a future research project to investigate any issues arising.

iii Conclusions

Objective 1

A scoping study identified 14 AOPs with actual or potential application for drinking water

treatment. Of these, one is currently used in England and Wales, and seven were judged as

being realistic options for use within 10 years. The review of DBPs in subsequent objectives

focussed on these eight AOPs.

AOP Overview Status

UV / H2O2 Worldwide applications for potable water and water

re-use. Currently used in the UK. In use in the UK

O3 / H2O2 Worldwide applications for potable water. Has been

trialled in UK at pilot scale.

Possible use in

the UK in the near

future

O3 / UV

Available commercially, has been used in US for

groundwater treatment and remediation. UK

experience as individual processes. Including O3 and

UV is potentially expensive.

Possible use in

the UK in the near

future

O3 / UV / H2O2

Available for industrial wastewater applications, with

potential use for potable water. May offer improved

treatment efficacy than a two-component AOP.

Including O3 and UV is potentially expensive.

Possible use in

the UK in the near

future

UV / Cl2

Potential users may have DBP concerns because of

Cl2. No trials identified in UK. However, available

commercially in US. May have operational cost

benefits relative to UV / H2O2.

Possible use in

the UK in the near

future

DWI


© WRc plc 2018 6

AOP Overview Status

UV / S2O8

Available commercially for industrial wastewater

treatment. Tested at bench-scale for odour treatment

but no trials identified in UK, but has potential due to

high oxidation level.

Possible use in

the UK in the near

future

UV / TiO2

Commercially available outside of UK, used for

wastewater, groundwater remediation and water

treatment applications. Has only been investigated at

laboratory scale in UK. An AOP with no chemical

addition may be of particular interest as would

represent lower costs.

Possible use in

the UK in the near

future

UV / TiO2 /

H2O2

No commercial applications found. Data from pilot and

bench-scale research in wastewater. Process has

been researched for over 10 years. No trials identified

in UK. Conceptually straightforward extension of UV /

TiO2, to potentially enhance treatment efficiency.

Possible use in

the UK in the near

future

Objective 2

The radicals formed by AOPs are strong oxidising agents that will react with organic and

inorganic constituents of water to produce various DBPs. Oxidation by molecular ozone, or

photolysis by UV, can also contribute to the formation of DBPs. Types of DBPs identified in

treated water are therefore dependent on the nature of the water being treated and the AOP

applied. The formation of DBPs by each of the eight AOPs identified in Objective 1, were

reviewed in Objective 3.

Objective 3

Systematic literature reviews of each of the eight AOPs from Objective 1 identified a total of

78 DBPs.

Objective 4

A 5-step prioritisation process was applied to the 78 DBPs identified in Objective 3, to exclude

those which had already been assessed for potential risk by WHO or DWI, or for which

UKWIR/WRc Toxicity datasheets already exist; or are not likely to be formed under conditions

of relevance to UK treatment processes. By this approach, nine DBPs were prioritised for high

level risk assessment in Objective 5.

DWI


© WRc plc 2018 7

DBP

2-Hydroxy-5-nitrobenzoic acid

2-Methoxy-4,6-dinitrophenol

2-Nitrohydroquinone

3,5-Dinitrosalicylic acid

4-Hydroxy-3-nitrobenzoic acid

4-Nitrobenzene-sulfonic acid

4-Nitrocatechol

4-Nitrophthalic acid

5-Nitrovanillin

Objective 5

A summary of the risk characterisation of the nine DBPs prioritised in Objective 4 is given

below.

DBP

TDI

(µg/kg

bw/day)

TTC

(µg/kg

bw/day)

Estimated Daily Intake

(TDI)


(TTC)

Adult Child Adult Adult Child Infant

2-Hydroxy-5-nitrobenzoic

acid - 0.0025 - - - Below Above Above

2-Methoxy-4,6-

dinitrophenol 90.6 0.0025 Below Below Below Below Above Above

2-Nitrohydroquinone - 0.0025 - - - Below Below Below

3,5-Dinitrosalicylic acid 29.6 0.0025 Below Below Below Below Below Below



4-Nitrobenzene-sulfonic

acid 871 1.5 Below Below Below Below Below Below

4-Nitrocatechol 1472 0.0025 Below Below Below Below Above Above

4-Nitrophthalic acid - 0.0025 - - - Below Below Below

5-Nitrovanillin 166 0.0025 Below Below Below Below Below Below

- No data; modelled NO(A)EL/LO(A)EL could not be derived

Below; estimated daily intake is below the proposed TDI/TTC value, adverse health effects are not anticipated

Above; estimated daily intake is above the proposed TDI/TTC value, adverse health effects cannot be excluded

DWI


© WRc plc 2018 8

Objective 6

Analytical methods for the prioritised nine DBPs that were potentially formed in water

following AOP processes and for which a human health risk assessment was carried out have

been investigated. Some methods are well developed such as nitrobenzene diols and

dinitrophenols whereas other methods for compounds such as the hydroxynitrobenzoic acids,

4-nitrobenzene sulfonic acid, 4-nitrophthalic acid and 5-nitrovanillin will need further

development to ensure they are robust and reliable. Additionally problems with limits of

detection for these methods may not be low enough to detect the concentrations of these

compounds in drinking water. Advances in chromatography during the past twenty years has

allowed for better quantification of hydroxynitrobenzoic acids without the need to use less

accurate colorimetric spectrophotometry. However these methods are yet to be verified as

industry standards.

Objective 7

A range of potential DBPs may arise as a result of the use of AOP treatment. However, the

identified DBPs went through a prioritisation process as part of Objective 4. Nine DBPs were

identified requiring further consideration.

As part of Objective 1 it was identified that currently only two plants are using AOP within

England and Wales. The research undertaken has identified that both of these plants

currently employ the use of GAC.

Based on the data currently available, it may be a reasonable expectation that, following

formation of these potential DBPs via AOP treatment, their concentrations in drinking water

will subsequently be reduced by GAC adsorption, assuming effective operation of the GAC.

This conclusion is based on limited data and further monitoring may be required to validate it.

Prior to instigating a full sampling programme, a number of preliminary steps are required to

ensure that the sampling programme is fit-for-purpose. Further analytical method

development is required using ‘spiked’ water samples to optimise detection limits in UK

drinking water and ensure that results are repeatable. This includes optimisation of calibration

curves and further refinement of LODs.

There is also a lack of understanding as to the conditions that may favour the formation of

these DBPs. Prior to full-scale sampling, bench-scale analysis should conducted with different

water conditions to determine these conditions. This information can then be used to

determine sites where, should AOPs be employed, there is a reasonable expectation that

these DBPs will be formed. These sites should be the primary focus of the sampling survey.

Once the survey sites have been identified, a number of approaches can be taken. A one-

year, bimonthly sampling strategy is proposed, and has been broadly described in this report.

DWI


© WRc plc 2018 9

However, due to a number of unresolved questions, this approach may need to be adjusted

once bench-scale results are known. The approach of sampling over the course of one year

allows for the determination of any seasonal variability of the surface water quality that may

influence the formation of these DBPs.

Within this sampling programme, sampling at each water treatment works will be conducted

over a range of times of the day (morning, afternoon, evening) to address this question. To

fully understand the effects of changes in water conditions that may potentially affect DBP

formation (such as high rainfall events), a sampling programme has also been recommended

to determine the influence of these events.

Sampling in this manner allows for the majority of samples being collected immediately after

AOP treatment. Assuming this represents the highest concentration of DBPs in water this

represents a ‘worst-case’ by which to estimate exposure to the consumer. Sampling after

GAC has also been proposed to confirm the effectiveness of this treatment in reducing DBP

concentrations.

DWI


© WRc plc 2018 10

1. Objective 1: Definition of the range of advanced oxidation processes that are or may soon be in use in England and Wales

1.1 Introduction

Objective 1 aims to establish the range of AOPs that are available and their likelihood to be

used in England and Wales either currently or within 10 years of this report. Information was

collated through a desk based scoping study utilising literature available in the public domain

and through a survey of water utilities in England and Wales.

1.2 Literature search

1.2.1 Methodology

The desk-based scoping study examined publically available literature to identify AOPs that

are commercially available, at a pilot feasibility stage or are currently in development. This

search was not limited geographically; any AOPs identified as being commercially available or

in development globally were considered.

The scoping study consisted of a number of areas of interrogation.

The initial search strategy on commonly applied processes, such as UV / H2O2 and O3 /

H2O2, was based on information gained from previous projects carried out by WRc.

A brief high level search of peer reviewed journals was undertaken in Scopus and

Science Direct using the keywords “AOP”, “Advanced Oxida*” and “Oxida* Treatment”.

This search did not, however, identify the less commonly practiced AOPs, some of which are

not commercially available. As such, a further search of the following online resources was

conducted:

Research Gate

Google

LinkedIn

Suppliers of AOP technology (e.g. Xylem Water Solutions and Trojan Technologies) were

also contacted to enquire about AOP systems that are either currently commercialised or in

development. In addition, the Water Science & Technology department at Cranfield

DWI


© WRc plc 2018 11

University, active in the field of AOP research, was contacted to discuss the future use of

AOPs in water treatment.

1.2.2 Identified AOPs

The following AOPs were identified from the scoping study:

Ultraviolet / hydrogen peroxide (UV / H2O2)

Ozone / hydrogen peroxide (O3 / H2O2)

Ozone / ultraviolet (O3 / UV)

Ozone / ultraviolet / hydrogen peroxide (O3 / UV / H2O2)

Ultraviolet / hypochlorous acid (UV / Cl2)

Ultraviolet / persulphate (UV / S2O8)

Ultraviolet / titanium dioxide (UV / TiO2)

Ultraviolet / titanium dioxide /hydrogen peroxide (UV / TiO2 / H2O2)

Ultraviolet / titanium dioxide / ozone (UV / TiO2 / O3)

Ultraviolet / peracetic acid (UV / PAA)

Hydrogen peroxide / ferrous ion (Fenton’s Reagent)

Ultraviolet / ferrous ion / hydrogen peroxide (photo-Fenton) (UV / Fe2+

/ H2O2)

Hydrodynamic cavitation

E-Beam

1.2.3 Ultraviolet / Hydrogen peroxide

In this process, UV light is applied to the water containing H2O2 to form OH• (Kommineni et

al., 1999) according to the equation below:

H2O2 → 2OH•

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© WRc plc 2018 12

Absorbance of UV by H2O2 increases at wavelengths below 254 nm and has a peak at a

wavelength of 240 nm. Therefore, in principle, medium pressure UV lamps produce a greater

number of hydroxyl radicals than low pressure lamps (Munter, 2001). However, overall UV

absorption by the organic and inorganic constituents of water may be higher for a medium

pressure UV lamp than a low pressure UV lamp, leaving less UV available for absorption by

the H2O2. Hence low pressure UV may be more energy-efficient for this application (KWR,

2011).

Generation of UV is energy-intensive at the doses applied for an AOP, particularly if the UV

transmittance (UVT) of the water is low. Only a small proportion of the H2O2 is consumed,

therefore removal of excess H2O2 is required. For this purpose the process is typically

followed by granular activated carbon (GAC); the GAC may also remove DBPs (Hofman-Caris

and Beerendonk, 2011).

Current status and applications

Ultraviolet / H2O2 has been used for water re-use and potable water applications. Proprietary

UV / H2O2 processes include Rayox and Sentinel (Calgon Carbon, 2017); UVPhox and

UVSwiftECT (Trojan, 2017); and MiPROphoto (Xylem, 2017). In the UK, Anglian Water has

installed a Trojan UV / H2O2 system at Hall Water Treatment Works, and other water

companies are known to have undertaken pilot trials.

1.2.4 Ozone / Hydrogen peroxide

Radicals, notably OH•, are formed to some extent by the decomposition reactions of ozone

when it is dissolved in water. The generation of OH• from ozone is enhanced by the

simultaneous introduction of H2O2 (Hoigné, 1998), hence the combination of H2O2 and O3

provides more effective oxidation than the individual use of O3 or H2O2 (Paillard et al., 1988).

Hydrogen peroxide reacts slowly with O3, but it dissociates in water to form hydro-peroxide

ion (HO2-) which reacts readily with O3 to produce the OH• (Hoigné, 1998) according to the

equation below:

H2O2 + H2O ↔ HO2- + H3O

+

O3 + HO2- → OH• + O2

- + O2

If the water contains bromide there is potential for bromate formation when using this process,

which can be minimised by adjusting the O3:H2O2 ratio and the pH (Von Gunten and Oliveras,

1998). Only a small proportion of the H2O2 is consumed during this process therefore

quenching of the excess H2O2 is required typically by GAC. In addition, treatment of O3 off-

gas is required.

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The application of H2O2 to enhance ozonation has long been recognised and some

conventional ozone contact tanks have provision for H2O2 dosing. The concept has been

developed as an AOP, for which ozone doses are potentially much higher than normally

applied in a conventional ozone contact tank.

Xylem is the principal supplier of O3 / H2O2 processes and currently markets its proprietary

MiPro™, eco3 and Pro3mix® products. This company has built a 34.4 Ml/d plant for K-Water

in Sung-Nam South Korea for taste and odour removal. The process has been trialled by

Anglian Water at one of their treatment works (Scheideler and Holden, 2015).

1.2.5 Ozone / Ultraviolet

In this process, low or medium pressure UV is applied to ozonated water to form OH•.

Ultraviolet at 254 nm wavelength produces H2O2 as an intermediate, which then decomposes

to form OH• (Munter, 2001) according to the equation below:

O3 + H2O → O2 + H2O2

2O3 + H2O2 → 2 OH• + 3O2

H2O2 → 2 OH•

This combined process is more effective than O3 or UV applied separately. At an equal

oxidant concentration, using low pressure (monochromatic) UV lamps, O3 / UV is more

efficient at generating OH• than UV / H2O2 (the most commonly applied AOP for potable water

treatment, with which alternative AOPs are frequently compared) (Glaze et al., 1987; Munter,

2001) because O3 absorbs more UV at 254 nm than H2O2. However, UV / H2O2 may be more

favourable with medium pressure (polychromatic) UV lamps (Kommineni et al., 1999). Ozone

generation requires electrical energy and thus raises operating costs relative to UV / H2O2,

particularly if high concentrations of OH• are required (when the lower solubility of O3 than

H2O2 becomes a factor (Kommineni et al., 1999). The capital cost of ozone generation plant is

also high relative to the provision of storage and dosing plant for H2O2 (Grote, 2012).

There is a potential for bromate formation when using O3 / UV if the water contains bromide.

Treatment of O3 off-gas is also required and diffusion of O3 can result in mass transfer

limitations. UV is energy-intensive at the doses applied for an AOP and the energy will

increase based on water quality deterioration, such as if the UVT of the water is low.


Ozone / UV has been used for groundwater treatment and remediation (for example in the US

(Patterson et al., 2013). The capital and operating costs are likely to be higher than UV / H2O2

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© WRc plc 2018 14

because of the O3 generation. However, many UK water companies have experience of O3

and/or UV as individual processes, and the combination might be considered on a case-by-

case basis.

1.2.6 Ozone / Ultraviolet / Hydrogen peroxide

In this process, O3 and H2O2 are dosed simultaneously (or O3 dosed into water containing

H2O2), into a chamber exposed to UV (Arslan et al., 2017; Kutz, 2007). Photolysis initiates

radical formation from O3 and H2O2. The radicals then promote further decomposition of

ozone, but also react with each other (Arslan et al., 2017):

O3 + H2O2 → OH• + O2 + HO2•

O3 + OH• HO2• + O2

O3 + HO2• OH• + 2O2

OH• + HO2• H2O + O2

This process has the potential to improve micropollutant removal relative to AOPs utilising two

of the three components, as was evident in (Dillon et al., 2011), but there are cost implications

of introducing a third component.

This is not the same process as commercialised by Xylem, the MiPROeco3 plus process, in

which MiPRO O3 / H2O2 treatment is immediately followed by UV; this is a two stage AOP

which utilises the residual H2O2 (from the O3 AOP stage) at the inlet of the UV, and provides

an extra AOP barrier.


This process is commercially available, for example Esco’s CATADOX process (ESCO

International, 2017), which also incorporates a proprietary catalyst. Although the marketing of

CATADOX emphasises industrial wastewater treatment, drinking water treatment is listed as

a potential application. Xylem does not sell O3 / UV / H2O2 as a commercialised AOP unit but

could provide it as a bespoke system. This three-component AOP potentially provides greater

treatment efficacy relative to two-component systems, so might be an option in some

circumstances.

1.2.7 Ultraviolet / Hypochlorous acid

The photolysis of HOCl generates chlorine (Cl•) and OH• radicals, while the photolysis of

hypochlorite ion (OCl-) generates oxygen radicals (O•) according to the equation below:

HOCl → Cl• + OH•

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© WRc plc 2018 15

OCl ˉ→ Clˉ + O•

Cl2 + H2O → HOCl + HCl

Ultraviolet / Cl2 has consequently been investigated as an alternative to UV / H2O2, and has a

number of potential advantages (Rosenfeldt et al., 2013):

a) HOCl absorbs UV more strongly than H2O2, thus generating more radicals than an

equivalent quantity of H2O2;

b) HOCl and H2O2 are sources of, but also react with (scavenge), radicals. The nett

production of radicals is therefore the result of competing production/consumption

reactions. HOCl reacts with its product radicals more slowly than does H2O2, thus

scavenging fewer radicals than an equivalent quantity of H2O2;

c) Because of a) and b), less HOCl should be needed than H2O2 for effective treatment.

Any residual HOCl is potentially useful for final disinfection, and for both reasons the

requirement to quench excess HOCl may be avoided; and

d) HOCl is lower in cost than H2O2.

However, OCl- reacts with radicals faster than H2O2. Because of the pH dependency of HOCl

dissociation, this means that UV / Cl2 is expected to be more efficient as an AOP at pH < 7

than at pH > 7.


Boal (2014) investigated the use of UV / Cl2 for groundwater remediation at two sites for the

removal of perchlorate, N-Nitrosodimethylamine (NDMA) and volatile organic carbon (VOCs),

as a potential alternative to the UV / H2O2 currently used. UV / Cl2 was found to achieve

treatment targets at half the operating cost of UV / H2O2 at one site, and c. 30% of the

operating cost at the other site. UV / Cl2 has been investigated at pilot scale for the removal of

2-Methylisoborneol (2MIB) and geosmin (Rosenfeldt et al., 2013; Springer and Kashinkunti,

2015). The first full-scale UV / Cl2 AOP plant was commissioned in late 2016 at the Terminal

Island Water Reclamation Plant, Los Angeles (Robinson, 2016). Pilot trials had compared UV

/ Cl2 with UV / H2O2 and O3 / H2O2 and concluded that UV / Cl2 was the least costly option,

primarily because chemical costs would be about 25% of those for UV / H2O2 (the latter would

have used sodium hypochlorite to quench residual H2O2).

No trials or full-scale potable water applications of UV / Cl2 have been identified in the UK.

Potential users may have concerns about formation of chlorinated DBPs in an AOP which

uses chlorine. The published case studies noted above did not identify such DBPs as a

problem, but this would have to be verified for any proposed application.

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1.2.8 Ultraviolet / Persulphate

Photolysis of persulphate ion ([S2O8]2-

) generates sulphate radicals (SO4•) according to the

equation below (Heidt, 1942) .

S2O82-

→ 2SO4•-

Hydroxyl radicals are also formed from sulphate radical anions:

SO4•- + H2O → SO4

2- + OH• + H

+

Ultraviolet / S2O8 has consequently been investigated as an alternative to UV / H2O2. In a

study by (Criquet and Leitner, 2009), the radicals generated by UV / S2O8 yielded a greater

mineralization of acetic acid than OH radicals. In addition the study suggested that this

process produces less DBP. Lutze (2013) compared UV / S2O8 with UV / H2O2 for its potential

to degrade micropollutants in water treatment. Lutze (2013) observed that sulphate radicals

generally react with micropollutants at a similar rate or slower than hydroxyl radicals, but there

are some compounds with which they react, albeit slowly, that don’t react with hydroxyl

radicals (for example perfluorinated carboxylic acids). Sulphate radicals were found to react

more slowly with natural organic matter than hydroxyl radicals, but to be inhibited by chloride

and bicarbonate ions.


Evoqua market the Vanox™ UV / S2O8 process for industrial wastewater treatment

specifically targeting certain organics (e.g. urea) but also for removal of total organic carbon

(TOC) in general (Evoqua, 2017).

Ultraviolet / S2O8 has been investigated at laboratory scale for odour control (removal of MIB

and geosmin) (Xie et al., 2015) and various individual compounds or groups of compounds

(for example iodoacids) (Xiao et al., 2016).

No full-scale potable water applications of UV / S2O8 have been identified, and no UK trials

are known. Despite the limited information regarding the applicability of this AOP process, this

process might have potential if micropollutants resistant to other AOPs are encountered.

1.2.9 Ultraviolet / Titanium dioxide

The TiO2 electrode acts as a photocatalyst when exposed to UV at wavelengths below

380 nm (Tran et al., 2009). Energy from the light causes electrons to become excited and

jump from valence bands to conduction bands, leaving highly reactive ‘positively charged

holes’. These holes have a higher oxidation potential than that of OH•, and can either oxidise

directly or generate OH• from water molecules (Tran et al., 2009). The excited electrons can

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© WRc plc 2018 17

react with dissolved oxygen to generate superoxide anions (O2-), which can further react to

generate OH• (Azrague and Osterhus, 2009) according to the equation below:

TiO2 + → eˉ cb (TiO2) + h

+ vb (TiO2)

h+ vb (TiO2) + OHˉ → TiO2 + OH•

where cb is conduction band and vb is valence band.

The TiO2 catalyst can be immobilised or maintained in suspension. As the photocatalysed

reactions occur on the surface of the TiO2, surface area is an important factor in performance.

Immobilising the TiO2, for example, as a coating on the reactor vessel wall, avoids having to

separate and recover the catalyst from treated water, but limits the surface area. Dosing

particulate TiO2 substantially increases surface area but requires separation and recovery,

which adds additional stages to the process.

Factors that affect this AOP are organic load, catalyst concentration, UV exposure and light

intensity, reactor design, temperature and pH of solution. The use of excessive amounts of

catalyst in suspension may impede UV transmission and thus reduce process efficiency

(Gogate and Pandit, 2004).


Various companies have commercialised UV / TiO2 systems.

An integrated system which combines a UV / TiO2 reactor with ceramic ultrafiltration for

continuous TiO2 recovery, ‘Photo-Cat®’, has been developed by the Canadian company

Purifics ES Inc (Purifics, 2017). It is available in units up to 120 MLD. Purifics have reference

sites for potable water, wastewater, remediation and industrial applications. There are no

known Purifics applications in the UK.

ATG have developed the Keratox process that combines a fixed TiO2 catalyst with UV (Atguv,

2017). The process is being promoted for the treatment of a wide range of micro-pollutants.

UK site trials are on-going as part of the UKWIR Chemicals Investigation Programme 2 (CIP2)

in relation to wastewater treatment.

Brightwater Environmental Ltd (Brightwater, 2017) has also developed a UV reactor with a

TiO2 coating, marketed primarily for disinfection. It is used in Europe and Asia for process

water, swimming pool and potable water disinfection although it also has been used in the UK

for disinfection of private water supplies. However, it does not have the validation required for

a UV disinfection process so is currently unlikely to be acceptable for public supply use in the

UK.

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© WRc plc 2018 18

Overall, UV / TiO2 is commercially available (Purifics, non-UK), or close to, commercial

availability (ATG) in forms that may be of interest to the UK public water treatment sector. At

least one UK water company has investigated UV / TiO2 at laboratory scale for the removal of

metaldehyde (Dillon et al., 2011), but no subsequent pilot trials have emerged using TiO2.

Having a fixed catalyst does simplify the process, potentially making Keratox a more attractive

proposition than Photo-Cat®. An AOP with no chemical addition may be of particular interest

to water companies in the UK as this would lower both the on going operational cost of

purchasing chemicals and the capital cost involved with ensuring suitable storage is available.

Ultraviolet / Titanium dioxide / Hydrogen peroxide

This process includes addition of H2O2 to the reaction occurring using TiO2 and UV (Yano et

al., 2005a; Garcia et al., 2007) according to the equation below:


+ vb (TiO2)


Yano et al. (2005a) found that addition of H2O2 to UV / TiO2 greatly increased the rate and

degree of decomposition of propyzamide relative to UV / TiO2 without H2O2. A more recent

study evaluated the effectiveness of UV / TiO2 in the degradation of 44 organic pesticides

(Miguel et al., 2012). This research included comparison with and without H2O2. It showed an

increase in degradation of the pesticides of up to 57% with H2O2.


While this AOP is not at the stage of commercial application, there is evidence of performance

enhancement relative to UV / TiO2. Additional research will be needed to understand the

effect of H2O2 on decomposition of emerging micropollutants such as metaldehyde.

Quenching of H2O2 would have to be accounted for in the overall cost of the process.

1.2.10 Ultraviolet / Titanium dioxide / Ozone

The photocatalytic action of UV on TiO2 is enhanced by the addition of O3. The O3 provides a

source of hydroxyl radicals, by reaction with electrons on the surface of the TiO2 that have

been excited by UV (Mehrjouei et al., 2012):


+ vb (TiO2)


O3 + eˉ → O3•ˉ

O3•ˉ + H

+ → HO3

ˉ

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© WRc plc 2018 19

HO3ˉ → O2 + OH•

Giri et al. (2008) compared the efficacy of combinations of UV, TiO2 and O3 for degradation of

2,4-D, using a laboratory-scale batch UV reactor with immobilised TiO2 fibres. The initial

concentration of 2,4-D was 10 mg/l and each experiment proceeded for 2 hours, thus

conditions were not representative of potable water treatment. The degradation rate of 2,4-D

by UV / TiO2 / O3 (photocatalytic ozonation) was about five times higher than by UV / TiO2. It

was concluded that OH• were the major oxidant species for 2,4-D degradation and that UV /

TiO2 / O3 provided a source of OH• from the ozone decay induced by the UV / TiO2


This AOP is not at the stage of commercial application but is currently at bench or pilot scale.

In the near future, this process may be feasible for degradation of recalcitrant organic

compounds. While adding ozonation to this process will increase the capital and operational

costs, the addition of ozone improves the transmittance of the water increasing the

effectiveness of the UV in performing the photo-catalysis (Wiley, 2010).

1.2.11 Ultraviolet / Peracetic acid

Peracetic acid exists in equilibrium with acetic acid, hydrogen peroxide and water according to

the equation below:

CH3COOH + H2O2 ↔ CH3COOOH + H2O

Exposure to UV splits the O-O bond to generate OH• (Caretti and Lubello, 2003):

CH3COOOH → CH3COO• + OH•


Caretti and Lubello (2003) observed that UV/PAA, at pilot scale, was capable of achieving

economically ≥ 6 log inactivation of Total Coliforms in wastewater intended for irrigation,

whereas PAA or UV alone were not.

A disadvantage of PAA is that it adds biodegradable organic carbon, promoting biofilm growth

downstream (Beber de Souza et al., 2015). No potable water applications have been

identified.

1.2.12 Hydrogen peroxide / Ferrous ion (Fenton’s Reagent)

Fenton’s Reagent generates OH• as a product of the oxidation of ferrous ion to ferric ion by

H2O2 (Kommineni et al., 1999) according to the equation below:

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© WRc plc 2018 20

Fe2+

+ H2O2 → Fe3+

+ OH- + OH•

Ferric ion is reduced to ferrous ion by H2O2, thereby enabling further generation of OH•.

Fe3+

+ H2O2 → Fe2+

+ H+ + OOH•

The reaction is sensitive to pH. If the pH is too high, the ferric ion precipitates and the

resultant ferric hydroxide catalytically decomposes H2O2 to O2. The general requirement is for

initial pH to be in the range 3-5 (Peroxide., 2017). MacAdam and Parsons (2009) state that

maximum effectiveness is at pH 2.8-3.

Conventional Fenton’s reagent is a homogeneous process as all reactants are in solution.

The dosed iron must be separated, by raising pH to precipitate the iron as ferric hydroxide.

This separation might be avoided, or at least simplified, by attaching the iron to a solid support

material. Various support materials have been investigated to provide a heterogeneous

Fenton process, including minerals, resins and activated (Blanco et al., 2014).

He et al. (2016) have reviewed the catalytic reaction mechanisms of the heterogeneous

Fenton process, noting that it is not yet fully understood but classifying the activity in terms of

heterogeneous reactions on the surface of the support media and homogeneous reactions by

ions leached from the surface.

Current Status and applications

It is considered unlikely that homogeneous Fenton’s reagent is a practical process for potable

water treatment. The heterogeneous Fenton process is potentially more practical, but a fully

developed process has yet to emerge.

1.2.13 Ultraviolet / ferrous ion / Hydrogen peroxide (photo-Fenton)

Exposing Fenton’s Reagent to UV increases the rate of regeneration of ferric ions from

ferrous ions, and generates additional OH• (Al-Tawabini, 2003) according to the equation

below:

Fe3+

+ H2O2→ Fe2+

+ OOH• + H+

The above reaction occurs because ferric ion strongly absorbs UV light. UV intensity may be

reduced by precipitation of iron salts on the lamp surface (e.g. FePO4, FeCO3) and

transmittance by precipitation of Fe(OH)3 (US EPA, 1999).

Photo-Fenton AOP is multi-component, of which the overall performance for degrading any

particular compound is the sum of different reaction mechanisms, including direct oxidation by

H2O2, direct photolysis by UV and oxidation by OH•. Hydroxyl radicals may be generated by

H2O2 / UV, H2O2 / Fe2+

and Fe3+

/ UV.

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© WRc plc 2018 21


It is considered unlikely that photo-Fenton is a practical process for potable water treatment.

Huston and Pignatello (1999) investigated the performance of photo-Fenton for degradation of

13 pesticides. They used substantially higher initial pesticide concentrations than would be

experienced in potable water treatment and observed > 95% degradation of all pesticides

after 30 minutes reaction time except for methoxychlor (79%) and malathion (94%), which

indicates that many common pesticides are susceptible to photo-Fenton.

1.2.14 Hydrodynamic cavitation

In relation to AOPs, hydrodynamic cavitation refers to the formation and subsequent

implosion of microbubbles in aqueous solution. The implosion results in the localised release

of heat which raises the temperature at the interface between bubble and water. The elevated

temperature can cause direct thermal degradation of organic compounds or the thermal

dissociation of water molecules into radicals (Benito et al., 2005) according to the equation

below:

H2O → H• + OH•

Performance can be enhanced by using hydrodynamic cavitation in combination with ozone,

hydrogen peroxide or UV (Dindar, 2016; Kommineni et al., 1999).

Microbubbles can be formed by the application of ultrasound (sonication), high voltage

discharge (pulse plasma cavitation) or by inducing acceleration/deceleration of liquid flow

(hydrodynamic cavitation) (Kommineni et al., 1999).


Hydrodynamic cavitation has been demonstrated at large scale. The proprietary Hydrox

(hydrodynamic cavitation with optional H2O2and UV) and CAV-OX (hydrodynamic cavitation

with H2O2 and UV) processes were commercialised in the 1990s and implemented for

groundwater remediation (Kommineni et al., 1999; Eilers, 1994), but are no longer available.

WRc tested a pilot-scale combined ultrasonic / ozone reactor for removal of pesticides,

including metaldehyde, but the results were inconclusive as to the contribution of cavitation to

removal (Camm et al., 2013). No examples of implementation in the UK have been identified.

1.2.15 E-beam

When water is exposed to an electron beam, various oxidising species (including OH•) and

reducing species (including hydrogen atoms and free electrons) are generated. X-rays are

also generated by the electron beam generator, and the apparatus must be shielded. The

electron beam penetrates only a few centimetres into water (Kommineni et al., 1999).

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© WRc plc 2018 22


This AOP has some industrial applications, including in the food and beverage sector. It

requires specialist operators, and is not considered applicable for potable water treatment.

1.3 Water company survey

A survey was designed to provide a comprehensive review of current use of AOPs at water

treatment works as well as those that will be potentially used over the next 5 – 10 years

(Appendix A). The survey was designed to review the different types AOPs used or

considered; the reasons (if applicable) for not using AOPs; the process parameters including

doses and water quality; and which DBP were being monitored. An additional section of the

survey was included regarding use of ozonation at treatment works. The rationale of this was

to enquire if the water companies are monitoring non-regulated DBPs.

The survey was sent out in March 2017 to the R&D managers of 15 water companies with a

request to complete the survey by 7th April 2017. For the first part of the survey, in total there

were 14 responses comprising 10 email responses, 1 phone call and 3 completed

questionnaires. Due to lack of response on the second part of the survey it was re-issued in

August 2017 at the request of DWI in order to increase the response rate. Of the 15

companies contacted, 7 returned the ozone section of the questionnaire (Appendix B) and 5

responded by email.

1.3.1 Current of future use of AOPs

Only three of the responses relating to AOP usage were in the form of completed

questionnaires (Appendix B).

The majority of the companies do not employ AOPs at treatment works and do not intend to

do so in the near future. Two companies have considered AOP treatment, including UV / H2O2

and O3 / H2O2, but do not plan full-scale implementation because of concerns about by-

products (THM formation potential, bromate). Several companies are hesitant to consider the

use of AOP due to the additional costs associated with UV and / or ozone processes. In other

cases, regulatory compliance can be achieved with existing (non-AOP) processes.

The AOP’s that are currently employed at full scale, have been piloted, or would at least be

considered are:

Ozone / H2O2

UV / H2O2

The operational parameters of these AOPs and basic water characteristics that came from the

survey are presented in Table 1.1 below.

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© WRc plc 2018 23

Table 1.1 Flow rates and AOP doses – UV/H2O2/O3

Site No.

Flow Rate

Scale H2O2 Dose

UV Dose O3

Dose Water type

Additional information

1 500 m3/h Full 5 mg/l 650 mJ/cm

2 X

Soft water

Lowland

Metaldehyde,

other

pesticides,

T&O

2 833 m3/h Full NA NA X

Hard

water

Lowland

To achieve

0.6 log

reduction

metaldehyde

3 40 m3/h Pilot

4 – 40

mg/l X

2 – 13

g/m3

Soft water

Surface

4 0.3 – 0.6

m3/h

Pilot 20 – 40

mg/l

1300 – 2600

mJ/cm2

X

Soft

Water

Surface

In addition to the surveys sent out to the water companies, Xylem and Trojan were contacted,

as they provide AOP systems and could provide insight to AOP technologies currently being

developed. WRc also contacted the Water Science & Technology department at Cranfield

University, due to their involvement in researching AOPs.

From these contacts, suppliers see potential in UV / Cl2 and UV / S2O8. There is on-going

research and development to improve efficiency of conventional UV lamps and in the use of

LEDs as an alternative source of UV. AOP technologies in an early stage of research include:

Alternative photocatalysts to TiO2;

Boron doped diamond electrodes; and

Dry and wet plasma.

The second part of the questionnaire requested information regarding DBPs from ozonation.

(Appendix B). Of the 12 companies that responded, 7 currently use ozone, with downstream

GAC. In terms of monitoring for DBPs other than bromate or THMs, one monitors for HAAs

while another monitors for chlorate at one site (albeit related to the use of sodium hypochlorite

used on the site rather than the ozone).

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© WRc plc 2018 24

1.4 Conclusions

A review of the literature on the type and use of AOPs in England and Wales and the survey

of water companies to establish current or potential future usage were carried out. Table 1.2

presents the status of each AOP and which were chosen for further review based on current

usage or feasible usage in the near future for drinking water applications.

Table 1.2 Summary of current and potential future usage of AOPs

AOP Overview Status Outcome

UV / H2O2 Worldwide applications for

potable water and water re-use.

Currently used in the UK.

In use in the UK Will be reviewed for

DBPs in next

objectives.

O3 / H2O2 Worldwide applications for

potable water. Has been trialled

in UK at pilot scale.

Possible use in

the UK in the near

future

Will be reviewed for

DBPs in next

objectives.

O3 / UV Available commercially, has

been used in US for

groundwater treatment and

remediation. UK experience as

individual processes. Including

O3 and UV is potentially

expensive.

Possible use in

the UK in the near

future


DBPs in next

objectives.

O3 / UV /

H2O2

Available for industrial

wastewater applications, with

potential use for potable water.

May offer improved treatment

efficacy than a two-component

AOP. Including O3 and UV is

potentially expensive.

Possible use in

the UK in the near

future


DBPs

in next objectives.

UV / Cl2 Potential users may have DBP

concerns because of Cl2. No

trials identified in UK. However,

available commercially in US.

May have operational cost

benefits relative to UV / H2O2.

Possible use in

the UK in the near

future


DBPs in next

objectives.

UV / S2O8 Available commercially for

industrial wastewater treatment.

Tested at bench-scale for odour

treatment but no trials identified

in UK, but has potential due to

high oxidation level.

Possible use in

the UK in the near

future


DBPs in next

objectives.

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© WRc plc 2018 25


UV / TiO2 Commercially available outside

of UK, used for wastewater,

groundwater remediation and

water treatment applications.

Has only been investigated at

laboratory scale in UK. An AOP

with no chemical addition may

be of particular interest as would

represent lower costs.

Possible use in

the UK in the near

future


DBPs in next

objectives.

UV / TiO2 /

H2O2

No commercial applications

found. Data from pilot and

bench-scale research in

wastewater. Process has been

researched for over 10 years.

No trials identified in UK.

Conceptually straightforward

extension of UV / TiO2, to

potentially enhance treatment

efficiency.

Possible use in

the UK in the near

future


DBPs in next

objectives.

UV / TiO2 / O3 No commercial applications

found, reported experience is at

bench-scale or pilot scale. No

trials identified in UK. Adding O3

to UV / TiO2 would be

appreciably more expensive

than adding H2O2. Considered

unlikely to yield a cost-effective

process in the foreseeable

future.

Unlikely to be

used in UK in

near future

Will not be reviewed

in next objectives.

UV / PAA Pilot scale reviewed. Process

does not appear applicable for

potable water treatment

because of the residual PAA.

No trials identified in UK.

Unlikely to be

used in UK in

near future


in next objectives.

Fenton’s

Reagent

Extensive research base exists,

and may have applications in

industrial wastewater treatment.

Process in its homogeneous

form is not suitable for potable

water treatment because of

acidic pH and requirement for

Unlikely to be

used in UK in

near future


in next objectives.

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separation of iron.

Heterogeneous process would

obviate need for separation, but

considered unlikely to yield a

practicable process in the

foreseeable future.

UV / Fe2+

/

H2O2

An extension of Fenton’s

Reagent, and for similar

reasons considered unlikely to

yield a practicable process in

the foreseeable future.

Unlikely to be

used in UK in

near future


in next objectives.

Hydrodynamic

cavitation

Demonstrated at large scale

and implemented for

groundwater remediation in

1990s in US but that particular

proprietary process is no longer

available. A number of different

approaches to achieving

cavitation remain subjects of

research, but are considered

unlikely to yield a practicable

process in the foreseeable

future.

Unlikely to be

used in UK in

near future


in next objectives.

E-beam Some industrial applications,

including in the food and drink

sector. It requires specialist

operators and is not considered

practicable for potable water

applications.

Unlikely to be

used in UK in

near future


in next objectives.

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2. Objective 2: Review of chemical reactions and potential formation of Disinfection by-products

2.1 Introduction

As discussed in Section 1, eight different AOPs have been identified as currently or potentially

used in UK drinking water treatment works. These AOPs include:

UV / H2O2 ;

O3 / H2O2 ;

O3 / UV;

O3 / UV / H2O2;

UV / Cl2;

UV / S2O8

UV / TiO2; and

UV / TiO2 / H2O2.

The objective of this task is to describe the main types of reaction mechanisms that take place

for the above AOPs and the potential DBPs that could potentially be formed from these AOPs.

2.2 Radical Chain Reactions

The strong oxidising agents such as OH• generated by AOPs are produced by chemical

mechanisms known as radical chain reactions. The section below briefly outlines the

reactions involved in radical-type reactions in AOPs.

Radical chain reactions consist of three main reaction mechanisms (Clayden et al., 2001).

These include:

initiation;

propagation; and

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termination.

2.2.1 Initiation

At the initiation stage a molecule such as H2O2 or chlorine Cl2 is homolytically cleaved by

either heat or light to produce two radicals.

2.2.2 Propagation

The propagation stage involves radicals produced during initiation abstracting other

constituents in the solution producing further radicals, creating a chain reaction. At this stage

one radical is consumed and another radical formed.

2.2.3 Termination

Termination mechanisms involve the reaction of two radicals causing the chain reaction to

terminate, forming spin-paired molecules, which are more stable.

2.3 Advanced Oxidation Processes

The section below describes the eight different AOPs which were highlighted in Objective 1.

The mechanism of AOPs includes oxidation of contaminants in raw water, predominantly via

OH•. Therefore each AOP is separated into the most likely reaction mechanisms which

describes the chemistry involved in generating the more reactive OH•. Following on from the

reaction mechanisms to produce OH•, the likely DBPs that will occur in treated water following

reactions are between contaminants and the individual AOPs.

2.3.1 Ultraviolet / Hydrogen peroxide

Reaction mechanism

The photolysis of H2O2 leads to the initiation of OH•. There are two main mechanisms

generating OH• including the direct photolysis of H2O2 (Figure 2.1) and the photolysis of

hydroperoxide ion (HO2-) (Munter, 2001).

The direct photolysis of H2O2 involves the homolytic cleavage of H2O2 to initiate OH• (Munter,

2001); OH• are also produced via propagation chain reactions, as seen below (Jo, 2008).

Figure 2.1 Reaction mechanism for UV / H2O2 treatment

H2O2 → 2OH•

OH• + H2O2 HO2• + H2O

HO2• + H2O2 HO• + H2O + O2

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Hydrogen peroxide is also in equilibrium with HO2- and a hydrogen ion (H

+). The HO2

- also

absorbs UV radiation at 254 nm and undergoes photolysis also producing OH• (Munter,

2001).

Figure 2.2 Potential reaction mechanism for UV / H2O2 treatment

H2O2 ↔ H+ + HO2

-

HO2- → OH• + O•

-

Disinfection by-products

The main reaction mechanisms of UV / H2O2 are absorption of UV photons, which break

bonds in the contaminant and oxidise pollutants via OH•. The UV dose in the UV /

H2O2process is greater when compared to UV disinfection alone, this facilitates increased

breakage of bonds and production of OH• (IJpelaar et al., 2007).

One of the advantages of using the direct photolysis of H2O2 in raw water is that it does not

produce bromate (BrO3-) (Jo, 2008). Ultraviolet / H2O2 treatment has “been successfully used

for the destruction of chlorophenols and other chlorinated compounds”, although it is unclear

what the products of these reactions are. Atrazine, desethylatrazine and simazine are

reported to be mineralised via the UV / H2O2 process (Munter, 2001).

The pressure of UV irradiation is also reported to affect chemicals such as nitrate. If medium

pressure UV lamps are used, nitrate will be reduced to nitrite, but this reaction is not

anticipated to occur using low-pressure UV lamps (IJpelaar et al., 2007).

Like other AOPs, pH of raw water is a major factor which affects the rate of oxidation.

Increase in pH (alkaline conditions) increases the rate of OH• generation (Andreozzi et al.,

1999).

2.3.2 Ozone / Hydrogen peroxide

Reaction mechanism

The disinfection process using H2O2 and O3 is known as the peroxone process. This process

involves the oxidation of organic substances either via direct oxidation using O3 or via OH•

from O3 decomposition (Lenntech, 2017). Direct oxidation using O3 is a relatively slow

process compared to the more reactive and faster oxidation by OH• (US EPA, 1999). The rate

constants of OH• attack on organic molecules such as benzene, toluene, chlorobenzene,

trichloroethylene, tetrachloroethylene, n-butanol and tert-butanol are reported to be in the

range of 106 – 10

9 mol/l (M

-1) s

-1, while direct ozonation has rate constants for the same

chemicals in the range of 0.03 – 17 M-1

s-1

(Andreozzi et al., 1999).

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Figure 2.3 shows the reaction mechanism for oxidation of organic compounds via the

production of OH•. In aqueous solutions H2O2 dissociates into HO2- and a H

+. The HO2

- acts

as the initiator in the peroxone process as it reacts rapidly with O3 forming a chain reaction

producing OH• (Andreozzi et al., 1999; Collins and Cotton, 2009).

Figure 2.3 Reaction mechanism for O3 / H2O2 treatment

H2O2 H+ + HO2

-

HO2- + O3 OH• + O•

-

HO2• ↔ H+ + O2•

-

O2•- + O3 O2 + O3•

-

O3•- + H

+ HO3•

HO3• OH• + O2


Compounds in raw water react via direct oxidation with aqueous O3 or by OH• (US EPA,

1999). There are various different DBPs, depending on the constituents of raw water; the

likely DBPs following the direct peroxone treatment process are listed in Table 2.1. Haloacetic

acids (HAAs) and trihaloacetic acids (THMs) are also present in finished water. The formation

of HAAs and THMs are reduced following peroxone and chloramination as primary and

secondary treatment processes, respectively (US EPA, 1999).

The pH of raw water is a major factor which affects the rate of oxidation; increase in pH

(alkaline conditions) increases the rate of OH• generation (Andreozzi et al., 1999).

Table 2.1 DBPs formed following peroxone treatment process (US EPA, 1999)

Type of chemical Disinfection By-product

Aldehydes

Formaldehyde

Acetaldehyde

Glyoxal

Methyl glyoxal

Acids

Oxalic acid

Succinic acid

Formic acid

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Type of chemical Disinfection By-product

Ethanoic acid

Aldo- and ketoacids Pyruvic acid

Brominated substancesa

Bromate ion

Bromoform

Brominated ethanoic acids

Bromopicrin

Brominated acetonitriles

Additional substances Hydrogen peroxide

a: In the presence of bromide ions (Br-).

2.3.3 Ozone / Ultraviolet

Reaction mechanism

The photolysis of O3 during advanced oxidation produces OH•. Figure 2.4 describes the type

of reactions occurring during O3 / UV treatment. Ozone absorbs UV radiation at 254 nm which

generates molecular oxygen (O2) and an oxygen in an excited singlet state (O(1D)). In an

aqueous solution O(1D) reacts with water (H2O) producing H2O2 as an intermediate, which

forms OH• under UV irradiation (hν) (Munter, 2001; Andreozzi et al., 1999; Malley, 2008).

Additionally, it is important to note that the H2O2 intermediate produced may also initiate OH•

via a peroxone process as described in Section 2.3.1.

Figure 2.4 Reaction mechanism for O3 / UV treatment

O3 → O2 + O(

1D)

O(1D) + H2O H2O2

H2O2 → 2OH•


It is anticipated that OH• (as described above) is the main reactant with substances in raw

water, which has the potential to generate DBPs.

Table 2.2 summarises the main DBPs from ozonation of raw water (WHO, 2000). However, it

is not clear if all these DBPs are observed with the addition of UV irradiation.

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Table 2.2 DBPs from the ozonation of raw water

a: In the presence of natural organic matters (NOM), hypobromous acid generates various organobromine

compounds (Glaze et al., 1993).

b: (WHO, 2000).

c: In the presence of bromide ions (Br-) (WHO, 2000).

d: Ozonation of unsaturated organic compounds (Bailey, 1978).

e: Forms metal-ozone compounds (M+O3

-) (Bailey, 1978).

Some of the main by-products of O3 treatment process are aldehydes, which are reported to

increase with higher doses of O3 (Nawrocki et al., 2003). One study looking at the seasonal

variations of DBPs identified benzaldehyde as the only aromatic aldehyde in treated water

following ozonation (Zhong et al., 2017).

The main carboxylic acids observed following ozonation of natural organic matters (NOMs)

are formic, ethanoic and oxalic acids, while the main ketoacids DBPs are pyruvic, glyoxalic

and ketomalonic acids (Nawrocki et al., 2003). Higher levels of carboxylic acids are reported

Disinfection by-product

Bromoforma

Monobromoacetic acida

Dibromoacetic acida

Dibromoacetonea

Cyanogen bromidea

Chlorateb

Iodateb

Bromatec

Hydrogen peroxided

Hypobromous acidc

Epoxidesb

Ozonatese

Formaldehydeb

Acetaldehydeb

Glyoxalb

Methylglyoxalb

Ketoacidsb

Ketonesb

Carboxylic acidsb

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to be produced when compared to levels of aldehydes, such as formaldehyde, acetaldehyde,

glyoxal and methylglyoxal (Nawrocki et al., 2003). Zhong et al. (2017) also reported the

formation of carboxylic acids, fumaric acid, benzoic acid, protocatechuic acid and

3-hydroxybenzoic acid in the treated water at two treatments works.

One study identified that O3 / UV treatment process has the potential to mineralise 50% of

total organic carbon to carbon dioxide (CO2) and H2O at an O3 and UV dose of

0.62 ± 0.019 mg O3/ml and 1.61 W s/cm2, respectively (Chin and Bérubé, 2005).

2.3.4 Ozone / Ultraviolet / Hydrogen peroxide

Reaction mechanism

The addition of H2O2 to the photolytic reaction of O3 promotes the formation of OH• (Figure

2.5) (Malley, 2008; Munter, 2001).

Figure 2.5 Reaction mechanism for O3 / UV / H2O2 treatment

O3 → O2 + O(

1D)

O(1D) + H2O H2O2

H2O2 → 2OH•

The H2O2 facilitates additional propagation reactions, which generates more reactive oxygen

species, including OH• (Figure 2.6) (Malley, 2008; Munter, 2001).

Figure 2.6 Potential reaction mechanism for O3 / UV / H2O2treatment

OH• + H2O2 O2•- + H2O + H

+

O2•- + O3 O2 + O3•

-

O3•- + H

+ HO3•

HO3• OH• + O2


Hydrogen peroxide is added to the O3 / UV process to accelerate the production of OH•; the

major reaction mechanism is via pollutants and OH•.

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Limited data were located on the formation of DBPs following the O3 / UV / H2O2 process. One

study investigating the oxidation of NOMs, identified an increase in aldehydes and carboxylic

acids in treated water and a decrease in HAAs and THMs. Bromate was also reported in

treated water following ozonation (Agbaba et al., 2016).

2.3.5 Ultraviolet / Hypochlorous acid

Reaction mechanism

The photolysis of HOCl involves the initiation of HOCl generating OH• and Cl•. Additionally,

HOC also dissociates into hypochlorite (OCl-) and H

+. The photolysis of OCl

- generates Cl•

and oxygen atom radical anions (O•-) in an initiation reaction mechanism, propagation of O•

-

with H2O leads to the generation of OH• (El-Kalliny, 2013). Figure 2.7 summarises the likely

reaction mechanisms.

Figure 2.7 Reaction mechanism for UV / Cl2 treatment

HOCl → OH• + Cl•

HOCl ↔ OCl- + H

+

OCl- → O• + Cl•

O•- + H2O OH• + OH

-


Hypochlorous acid is reported to be a more effective disinfectant than hypochlorite ions and is

the more dominant species at pH <7.5 (WHO, 2000). As described above, the photolysis of

HOCl generates OH•, which is the main reactant for the oxidation contaminants in raw water.

Hypobromous acid is identified in treated water in the presence of OCl-, which is generated in

OH• production, and Br-. This can eventually lead to BrO3

- formation.

Table 2.3 summarises other potential DBPs following UV / Cl2 treatment (WHO, 2000).

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Table 2.3 DBPs from the UV / Cl2 of raw water

Disinfection by-product

Trihalomethanes

Haloacetic acids

Haloacetonitriles

Chloral hydrate

Chloropicrin

Chlorophenols

N-Chloramines

Halofuranones

Bromohydrins

Chlorate

Aldehydes

Cyanoalkanoic acids

Alkanoic acids

Benzene

Carboxylic acids

2.3.6 Ultraviolet / Persulphate

Reaction mechanism

In aqueous solutions persulphate salts dissociate into persulphate anions. Photolysis of

persulphate ([S2O8]2-

) directly produces sulphate radical anions (SO4•-), which are a highly

reactive species. Sulphate radical anions react with H2O in aqueous solutions and generate

OH• (Figure 2.8) (Ocampo, 2009).

Figure 2.8 Reaction mechanism for UV/[S2O8]2−

treatment

S2O82-

→ 2SO4•

-

SO4•- + H2O HSO4

- + OH

-


Both SO4•- and OH• can directly react with pollutants (Ocampo, 2009). Bromate ions are

produced in the presence of Br- and SO4•

- in raw water via several radical chain reaction

mechanisms; however, levels of BrO3- have reported to decrease with increased pH (Fang

and Shang, 2012). No additional data were located on the potential DBPs from UV / S2O8

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treatment process, although one study highlighted that additional disinfection (such as

chlorination or hydrogen peroxide) will affect the levels and the types of DBPs in treated

water.

2.3.7 Ultraviolet / Titanium dioxide

Reaction mechanism

During disinfection, the semiconductor TiO2, is used as a photocatalyst. Figure 2.9 shows the

likely reaction mechanism of the UV / TiO2 treatment process. Titanium dioxide absorbs UV

radiation causing a series of complex reactions to produce OH•. The outer electrons of TiO2

(a semiconductor) are located in two energy bands, the valence band and conduction band.

UV wavelengths of approximately 385 nm have sufficient energy to promote a photo-excited

electron (ecb-) from the valence band into the conduction band. This transfer of an electron

creates a “positive hole” (h+) in the valence band.

Delocalised electrons in the conduction band and positive holes can undergo several

oxidation and reduction (redox) reactions. The conduction band electrons can react with O2

producing the superoxide radical (O2•-), while positive holes react with H2O producing OH•

(Gilmour, 2012; Stasinakis, 2008). The indirect oxidation of pollutants produces OH•. The

positive holes are also capable of direct oxidation of pollutants (Gilmour, 2012).

Figure 2.9 Reaction mechanism for UV/TiO2 treatment

TiO2 → ecb

- + h

+

ecb- + O2 O2•

-

h+ + H20 H

+ + OH•


Organic compounds typically undergo degradation via oxidation reactions with valence band

holes and OH•. A variety of organic compounds are reported to undergo oxidation and

mineralisation to CO2 and H2O (Gilmour, 2012; Stasinakis, 2008).

Reduction in Total Organic Carbon (TOC) was reported after ultrafiltration and UV / TiO2

photocatalytic treatment. However, the level of reduction (40%) was likely have been

enhanced by the configuration of the experiment (samples were re-circulated for 24 hours)

(Richardson et al., 1996). The same study also identified chlorinated DBPs (halomethanes

and halonitriles) in treated water, following secondary chlorination. Concentrations of these

halogenated by-products were lower when compared to the levels following chlorination as

the only disinfectant. One organic by-product, 3-methyl-2,4-hexanedione, was tentatively

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identified in treated water from ultrafiltration and UV / TiO2 photocatalytic treatment

(Richardson et al., 1996).

2.3.8 Ultraviolet / Titanium dioxide /hydrogen peroxide

Reaction mechanism

The inclusion of both the photocatalyst (TiO2) and H2O2 in the UV / TiO2 / H2O2 process is

reported to enhance the production of OH•. Although the exact chemical mechanism of the

UV / TiO2 / H2O2 processes is unclear, below are the main anticipated reactions (Yano et al.,

2005b).

As shown in Section 2.3.1, the photolysis of H2O2 generates OH•, but at high H2O2

concentrations these radicals can also be “mopped up” by H2O2. As seen in Section 2.3.4

positive holes in the valence band of TiO2 also generate additional OH• (Bokhari et al., 2015;

Yano et al., 2005b).

In the presence of a photocatalyst, such as TiO2, UV irradiation aqueous solutions maintain

an equilibrium of electron migration between the valence and conduction bands (Gilmour,

2012). With the addition of H2O2, which is reported to be an effective “electron trapper”, this

shifts the equilibrium allowing a greater availability of positive holes in the valence band,

which maintains reactions generating OH• (Yano et al., 2005b).


It is anticipated that pollutants react with the positive holes in the valence band of TiO2 and

with OH• radicals.

Limited data were located on potential DBPs following UV / TiO2 / H2O2 treatment. One study

reported that the herbicide, propyzamide decomposed into intermediates and only with

additional treatment of ultrasonic waves did it mineralise to CO2 and H2O (Yano et al., 2005b).

2.3.9 Other considerations

Water hardness

It is clear that the production of OH• is a key process required to oxidise and/or degrade

contaminants in raw water. However, the hardness of water can affect the rate of OH•

production. Bicarbonate (HCO3-) and carbonate anions (CO3

2-) act as scavengers and react

with OH•, producing carbonate radical anions and bicarbonate radicals (CO3•- and

HCO3•). As

well as reducing the production of the highly reactive OH•, reactions between carbonate

radical anions and bicarbonate radicals, and pollutants in raw water is reported to not be

“significant” (Jo, 2008). Therefore, the oxidation of pollutants is reduced in waters with higher

carbonate and bicarbonate levels.

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Inorganic anions

Anions such as chloride (Cl-) and bromide (Br

-) are also OH• scavengers, with Br

- reacting

more quickly. These ions “mop up” the OH• reducing the magnitude of oxidation of

contaminants in raw water.

Natural organic matters

In photolysis (UV) processes, it has been reported that NOM with higher UV absorbing

properties produce OH• at a higher rate than ozonation processes. However, NOMs such as

humic and fulvic compounds reduce the effectiveness of AOPs by acting as a OH• scavenger

and adsorb UV radiation (Jo, 2008).

2.4 Conclusion

There are eight AOPs that have been identified as currently or potentially being used in

England and Wales over the next ten years. The OH• formed are strong oxidising agents that

are readily produced in AOP radical reactions and will react with pollutants to produce various

DBPs.

Types of DBPs identified in treated water are dependent on factors such as the hardness of

the water, constituents present in the raw water (inorganic ions, bromine and NOM) and the

types/sequence of disinfection. Some AOPs mineralise pollutants to CO2 and H2O, while

others can generate DBPs, depending on the constituents of raw water. Common DBPs found

in treated water, following AOPs include:

aldehydes (formaldehyde, acetaldehyde, glyoxal and methyl glyoxal);

carboxylic acids (oxalic, succinic, formic and ethanoic acids);

ketoacids (pyruvic acid);

hydrogen peroxide;

haloacetic acids (monobromoacetic acid and dibromoacetic acid);

haloacetonitriles;

trihalomethanes (bromoform);

hypobromous acid;

bromate; and

chlorate.

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3. Objective 3: Systematic review of the formation of DBPs by AOPs

3.1 Introduction

Objective 3 of this project is to undertake a systematic review of the published and grey

literature issued since 1990 on the formation of by-products from the AOPs identified under

Objective 1.

This section describes the approach taken to carry out the review, and summarises the

findings for each of the included AOPs.

3.2 Search methodology

To ensure that as many relevant records are captured as possible and also to ensure quality

of the data retrieved a staged approach was followed, as shown below:

Development of search terms;

Literature screening and evaluation; and

Data extraction.

3.2.1 Development of search terms

Under Objective 1, several AOPs were identified either as being currently in use in England

and Wales, or of potential application in the future. These AOPs formed the basis of the

search terms (Table 3.1). Additional search parameters (Table 3.2) were used in conjunction

with those listed in Table 3.1 to identify DBPs formed from AOPs. Searching was restricted to

studies published after 1990 and in the English language.

Two databases were initially interrogated namely Scopus and Science Direct1. Each search

was customised for the database that was investigated. An example of a search string for one

database i.e. Scopus is given in Appendix D.

Using these terms, separate searches were undertaken for each AOP to identify the formation

of DBPs. Titles and abstract retrieved were stored in the reference management software

EndNote X8 for further evaluation.

1 A technical issue with Science Direct when using multiple search terms and wildcards meant that

robust searches using the data was not possible.

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Table 3.1 Search terms specifically related to AOP techniques

Type of AOP Search terms(a)

Generic terms AOP [OR] Advanced Oxid* [OR] Advanced Treatme*

Terms related

to O3 / H2O2

Hydrogen peroxide [OR] H2O2

[OR] Hydrogen dioxide [OR]

7722-84-1

[AND] Ozone [OR] O3 [OR] Triatomic

oxygen [OR] 10028-15-6

Terms related

to UV / H2O2

Hydrogen peroxide [OR] H2O2

[OR] Hydrogen dioxide [OR]

7722-84-1

[AND] UV [OR] ultraviolet

Terms related

to O3 / UV

Ozone [OR] O3 [OR] Triatomic

oxygen [OR] 10028-15-6


Terms related

to O3 / UV /

H2O2

Hydrogen peroxide [OR]

H2O2 [OR] Hydrogen

dioxide [OR] 7722-84-1

[AND] Ozone [OR]

O3 [OR]

Triatomic

oxygen [OR]

10028-15-6


Terms related

to UV / TiO2

UV [OR] ultraviolet [AND] Titanium dioxide [OR] TiO2 [OR]

Titanium oxide [OR] 13463-67-7

Terms related

to UV / TiO2 /

H2O2

UV [OR] ultraviolet [AND] Titanium

dioxide [OR]

TiO2 [OR]

Titanium

oxide [OR]

13463-67-7

[AND] Hydrogen peroxide [OR]

H2O2 [OR] Hydrogen

dioxide [OR] 7722-84-1

Terms related

to UV / Cl2

UV [OR] ultraviolet [AND] Hypochlorous acid [OR] OCl [OR]

7790-92-3

Terms related

to UV / S2O8

UV [OR] ultraviolet [AND] Persulphate [OR] persulfate [OR]

*S2O8

a.) Terms in brackets [ ] represent connecting phrases that vary between database, but are used to ensure the

correct use of the search terms in combination.

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Table 3.2 Search terms for the formation and occurrence of DBPs

Search terms related to the formation/occurrence of DBPs from AOPs

React* [OR] Form* [OR] Produc* [OR] Level* [OR] Occur* [OR] Generat*

[AND]

DBP [OR] disinfect* [OR] by-product* [OR] byproduct* [OR] by product*

Common search terms related to drinking water

[AND]

Water [OR] Drink* [OR] treat* [OR] WTW

3.2.2 Literature review and screening

A systematic selection of the publications retrieved from the literature search was carried out

by applying inclusion and exclusion criteria described in Table 3.3, to firstly the titles and then

abstracts of the retrieved papers.

A list of the keywords searched to exclude irrelevant publications is given in Appendix C.

Table 3.3 Inclusion and exclusion criteria used

Inclusion criteria Exclusion criteria

Articles that were published between 1990

and today.

Articles outside of these dates.

Articles that are published in English. Articles that are in other languages.

Articles concerning the formation of

disinfection by-products from the following

treatment processes:

O3 alone

O3 / H2O2

O3 / UV

UV / H2O2

O3 / UV / H2O2

UV / TiO2

UV / TiO2 / H2O2

UV / Cl2

UV / S2O8

Articles concerning the formation of

disinfection by-products from the following

treatment processes:

Ultraviolet and peracetic acid

Hydrogen peroxide and ferrous ion

(Fenton’s Reagent )

Ultraviolet and hydrogen peroxide and

ferrous ion (photo -Fenton )

Cavitation

E-beam

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Inclusion criteria Exclusion criteria

Articles concerning the formation or

occurrence of DBP following treatment with

the included processes.

Articles concerning the occurrence of DBP

following treatment with the excluded

processes.

Articles concerning the treatment of drinking

water.

Articles concerning the treatment of any

other products such as wastewater, food,

petroleum, solid waste or textiles.

Articles concerning the atmosphere, such as

ozone depletion, climate change or air

pollution.

Articles related to solar radiation or by-

products produced in the environment.

Articles concerning plants or plant health.

Articles pertaining to the removal of DBP from

drinking water subsequent to ozone or an

AOP.

Articles, reviews, evaluations and reports that

report original studies or provide reworking of

data (such as authoritative evaluations.

Retracted articles

Articles, reviews, evaluations and reports that

report original studies or provide reworking of

data (such as authoritative evaluations.

Articles that are based on opinion such as

editorials or commentaries.

Abstracts were used to exclude articles where the primary content was considered

inappropriate due to any of the following:

Experiments related to non-drinking water.

Data not including information about DBPs.

General discussions about DBPs but lacking specific DBP names.

3.2.3 Data extraction

The full publications for abstracts found to be relevant were retrieved and the relevant

information was extracted. The information of interest included the type of AOP used, the

experimental conditions and the doses applied, the type and concentration of DBPs detected

upon treatment and parameters describing the initial influent water quality. Other details found

to be pertinent to the interpretation of the results were also included.

Tables showing the numbers of papers excluded in each step of the assessment process, for

each AOP, are included in Appendix D.

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A tabulated summary of the reviewed literature (relating to AOPs and ozone) is provided in

Appendix E.

3.2.4 Ultraviolet and hydrogen peroxide

Initial search

The outcome of the search and subsequent application of inclusion/exclusion criteria is

summarised in Table D.2. In summary, 14716 papers were initially identified, of which 25

remained after the exclusion process.

Findings

A summary of the DBP’s identified is given in Table 3.4. This AOP is the most commonly

used, therefore the number of DBPs referenced in research data is greater than for other

AOPs.

Table 3.4 List of DBPs found (UV / H2O2)

Name Name Name

2,4-dinitrophenol Bromodichloroacetamide Haloacetic acid

2-hydroxy-3-nitrobenzoic acid Bromodichloromethane Haloacetonitriles

2-hydroxy-5-nitrobenzoic acid Chloral hydrate Haloketone

2-methoxy-4,6-dinitrophenol Chlorate Halonitromethane

2-nitrohydroquinone Chlorite Methylglyoxal

3,5-dinitrosalicylic acid Chloroacetamide NDMA

4-hydroxy-3-nitrobenzoic acid Chloropicrin Nitrate

4-nitro-1,3-benzendiol Dibromoacetamide Oxalate

4-nitrobenzene-sulfonic acid Dibromoacetic acid Oxalic acid

4-nitrocatechol Dibromomethane Perchlorate

4-nitrophenol Dichloroacetamide Propanoic acid

4-nitrophtalic acid Dichloroacetic acid Tribromoacetic acid

5-nitrovanillin Dichloroacetonitrile Tribromomethane

Acetaldehyde Dichloronitromethane Trichloroacetamide

Acetate Dinoterb Trichloroacetonitrile FP

Acetic Acid Formaldehyde Trichloromethane

Aniline Formate Trichloronitromethane

Bromate

Trichloronitromethane FP

Bromoacetic acid Glyoxal Tricholoacetic acid

Bromochloroacetamide Haloacetamide FP

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3.2.5 Ozone and hydrogen peroxide

Initial search




Findings

A summary of the DBP’s identified is given in Table 3.5.

Table 3.5 List of DBPs found (O3 / H2O2)

Names

Acetone

Aldehydes

Aniline

Bromate

Chlorobenzene

Glyoxal

Isopropyl alcohol

Nitrobenzene

Tertiary-butyl alcohol

Tertiary-butyl formate

3.2.6 Ozone and Ultraviolet

Initial search




Findings

A total of 10 papers were evaluated. The main DBPs found from articles were common DBPs

found in previous tables, such as THM, HAA and aldehydes.

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3.2.7 Ozone and Ultraviolet and hydrogen peroxide

Initial search




Findings


Table 3.6 List of DBPs found (O3 / UV / H2O2)

Name

Acetaldehyde

Acetate

Aldehydes

Bromate

Carboxylic acids

Formaldehyde

Formate

Glyoxal

Haloacetic acids

Ketones

Methylglyoxal

Oxalate

Trihalomethane

3.2.8 Ultraviolet and hypochlorous acid

Initial search




Findings


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Table 3.7 List of DBPs found (UV and Hypochlorous acid)

Name

Bromate

Chloral hydrate

Chlorate

Chlorite

Chlorodiiodomethane

Chloroform

Chloropicrin

Dichloroacetonitrile

Dichloroiodomethane

HAA

Haloacetonitriles

Haloketone

Halonitromethane

Iodoform

p-chlorobenzoic acid (pCBA)

Perchlorate

THM

Trichloronitromethane

3.2.9 Ultraviolet and persulphate

Initial search




Findings


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Table 3.8 List of DBPs (UV and persulfate)

Name

Monobromoacetic acid

Dibromochloromethane

Dibromoacetonitrile

Dibromoacetic acid

Bromoform (TBM)

Bromochloroacetonitrile

Bromate (BrO3-)

3.2.10 Ultraviolet and titanium dioxide

Initial search




Findings


Table 3.9 DBPs found (UV and titanium dioxide)

Name

1,3-dihydroxybenzene

2,2-dihydroxy-4-methoxybenzophenone

2-hydroxybenzaldehyde

2-methylphenol

2-methylphenyl benzoate

4-methylphenol

Benzaldehyde

Benzoic acid

Benzyl alcohol

Phenols

THM

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3.2.11 Ultraviolet, titanium dioxide and hydrogen peroxide

Initial search




Findings

From the articles found relevant to this process, the only DBP found was phenol.

3.3 Outcome

A total of 78 DBPs were carried forward to Objective 4.

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4. Objective 4: Prioritisation and Toxicity Review

4.1 Prioritisation of DBPs

The systematic review of the literature outlined in Objective 3 identified 78 DBPs that may be

produced during the use of AOPs.

It is not possible or necessary to assess the toxicity of each of these DBPs within this project

as many of these DBPs have already been assessed by other organisations. Therefore, a

systematic prioritisation process was developed that excluded DBPs that have been

previously assessed by other organisations or in previous DWI reviews. This prioritisation

process is detailed in Figure 4.1.

An important feature of this process is that at each stage of the prioritisation process,

objective evidence is required to justify the exclusion of a DBP. Therefore, in the absence of

such evidence, a DBP cannot be excluded. This reduces the likelihood of prioritising DBPs for

which a large body of data already exists, ensuring the focus of this project is on those DBPs

that are formed by AOPs where the consequences of their formation in UK waters is largely

unknown.

Two DBPs formed by ozone alone were identified as ‘high priority’ and so these are

considered in Appendix G.

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Figure 4.1 Prioritisation of DBPs to identify those chemicals to be considered for

toxicological assessment

4.1.1 Prioritisation Activity 1: Has a WHO GDWQ or English and Welsh drinking water standard been established?

Of the 78 DBPs identified in the literature review, 19 were excluded as they were either:

Subject to World Health Organization (WHO) Guidelines for Drinking-water Quality

(GDWQ);

Reviewed by WHO, but it was determined that a guideline was not appropriate;

No

No

Yes

Yes

No

Yes

Disinfection By-Product (DBP)

Is the DBP formed under conditions that are of

relevance to UK treatment processes?

Exclude from further

assessment

Has the DBPs been quantified in drinking

water?


assessment

Has DWI previously considered the DBP and

assessed the potential risk to human health?

Does TTC indicate that the DBP

is class I (low oral toxicity)?


assessment Low priority grouping

No

Yes

Has a WHO GDWQ or English and Welsh

drinking water standard been established?


assessment

Yes

No

Prioritisation

Activity 1

Prioritisation

Activity 2

Prioritisation

Activity 3

Prioritisation

Activity 4

Prioritisation

Activity 5

Expert review and exclusion of DBPs that are not considered to be of

relevance to this project

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Subject to a drinking water standard in England and Wales; or

Not subject to a drinking water standard per se, but subject to tiered guidance by DWI.

4.1.2 Prioritisation Activity 2: Has DWI previously considered the DBP and assessed the potential risk to human health?

Of the remaining DBPs, 22 had previously been considered within research funded by DWI.

However during such projects, a human health risk assessment was only carried out for 13 of

these DBPs. Therefore, these 13 were excluded from further evaluation.

4.1.3 Prioritisation Activity 3: Is the DBP formed under conditions that are of relevance to UK treatment processes?

Following further review of the literature from which the initial list of DBPs were identified,

24 DBPs were excluded from further evaluation as they were formed under conditions that are

not relevant to the UK.

4.1.4 Prioritisation Activity 4: If the DBPs were not detected in drinking water, does TTC indicate that the DBP is class I (low oral toxicity)?

Prioritisation Activity 4 was focussed on excluding those chemicals that had not been

detected in drinking water and that were not considered to be a concern, assessed using the

Threshold of Toxicological Concern (TTC) approach. In this process, each chemical that had

not been detected in drinking water was modelled in ToxTree, and if the model assigned it to

‘Class I’ (i.e. low oral toxicity) the DBP was excluded. However, no DBPs met this criteria, and

therefore, there were no exclusions on this basis.

4.1.5 Prioritisation Activity 5: Expert review and exclusion of DBPs that are not considered to be of relevance to this project

There are UKWIR/WRc Toxicity Datasheets available for 13 DBPs hence these were

excluded from the risk assessment (Table 4.1). However, a summary of the toxicity and fate

of each chemical in drinking water is provided in Section 4.3.11.

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Table 4.1 Thirteen DBPs excluded based on existing available toxicity data

Excluded DBP CAS RN UKWIR/WRc Toxicity Datasheet

2,4-Dinitrophenol,

4-Nitrophenol

51-28-5,

100-02-7 2,4-Dinitrophenol

Acetaldehyde 75-07-0 Acetaldehyde

Acetic acid,

Acetate

64-19-7,

71-50-1 Acetic acid

Acetone 67-64-1 Acetone

Aniline 62-53-3 Aniline

Benzoic acid 65-85-0 Benzoic acid

Bromochloroacetonitrile 83463-62-1 Bromochloroacetonitrile

Formate 71-47-6 Formic acid

Nitrobenzene 98-95-3 Nitrobenzene

Oxalate 144-62-7 Oxalic acid

Propanoic acid 79-09-4 Propanoic acid

4.1.6 Final list of DBPs

After applying the exclusion criteria specified in each prioritisation activity, nine DBPs were

identified (Table 4.2).

Table 4.2 Final list of DBPs for assessment in this project

DBP CAS Number

2-Hydroxy-5-nitrobenzoic acid 96-97-9

2-Methoxy-4,6-dinitrophenol 4097-63-6

2-Nitrohydroquinone 16090-33-8

3,5-Dinitrosalicylic acid 609-99-4


4-Nitrobenzene-sulfonic acid 138-42-1

4-Nitrocatechol 3316-09-4

4-Nitrophthalic acid 610-27-5

5-Nitrovanillin 6635-20-7

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4.2 Literature Search and Data Collation

4.2.1 Experimental toxicity data

Selection of information sources and search terms

Data on each DBP were collated from ToxPlanet, which covers over 100 databases and

authoritative bodies. When available, opinions from toxicology databases were primarily

considered, including the Hazardous Substances Databank (HSDB), or authoritative bodies

such as the US Agency for Toxic Substances and Disease Registry (ATSDR), the National

Toxicology Programme, US Environment Protection Agency (US EPA) etc.

In cases where data were scarce, primary literature, such as scientific publications, was

searched using Scopus and PubMed. The general search terms used for each of these

databases are provided in Appendix F. The search terms were adapted according to the

information source being interrogated. Synonyms and CAS numbers were also used where

appropriate.

Following preliminary searches, the titles and abstracts of the published data were screened

to select the relevant publications.

Data extraction

Retrieved literature was systematically and critically reviewed where possible, and relevant

data were extracted, including type of study, type and number of animals and toxicological

endpoint as well as the results presented.

4.2.2 Alternative approaches to deriving a Point of Departure (PoD)

As one of the exclusion criteria applied was the exclusion of DBPs with established drinking

water guidelines, it was anticipated that experimental toxicity data for the remaining DBPs

may be limited. Therefore, where no data were retrieved in the literature search, various

alternative methods were applied in order to determine a point of departure (PoD).

Identification of structural alerts and QSAR modelling

VEGA

Quantitative structure-activity relationship (QSAR) modelling software (VEGA) was used to

predict the toxicity of a chemical based on its chemical structure. The purpose of the software

is to relate the target chemical to results obtained for structurally similar chemicals, by

performing ‘trend analysis’ or ‘read across’. VEGA was also used to identify structural alerts

for sensitisation, mutagenicity, carcinogenicity and reproductive toxicity for each chemical.

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OECD QSAR toolbox

The OECD toolbox can be used to group chemicals based on their mechanism of action or

their structural similarity, to extract data for similar chemicals and fill data gaps using read

across, trend analysis or QSAR models. This approach is underpinned by a large database of

experimental studies. To undertake QSAR assessments, a step-wise approach of grouping

and refining potentially similar chemicals is used to identify those experimental studies that

could be used to predict the toxicity of the chemical under investigation.

Depending on the data available, repeat-dose predictions for PoDs such as a No Observed

(Adverse) Effect Level (NO(A)EL) or Lowest Observed (Adverse) Effect Level (LO(A)EL)

could be determined using the modelling software. However, due to the limited size of the

data sets behind some of the endpoints under investigation (oral repeat-dose and

reproductive/developmental toxicity); the predictions that have been developed may not be

robust. Therefore, caution should be applied in their use for the purposes of risk assessment.

Threshold of Toxicological Concern approach

The TTC approach is intended to be used as a screening tool for chemicals for which

substance-specific toxicity data are not available (European Food Safety and World Health,

2016; European Commission, 2009). The TTC values equating to low, moderate or high

toxicity (Cramer class I, II or III, respectively) have been established for substances of similar

chemical structure and likelihood of toxicity. These were based on extensive toxicity data,

from which NOAELs were derived. The 5th percentile NOAEL were divided by a factor of 100

to calculate the TTC value for each class. Substances, for which no toxicity data are available,

may be conservatively assessed by comparing the appropriate TTC value (based on the

chemical’s structure) with human exposure data. If the exposure is below the TTC value then

the likelihood of adverse health effects occurring is low.

The TTC values are as follows:

Cramer Class I

A TTC value of 30 µg/kg bw/day is derived for simple chemical structures that are known to

be efficiently metabolised to innocuous products; a low order of oral toxicity is anticipated.

Cramer Class II

A TTC value of 9 µg/kg bw/day is derived for intermediate structures that are less innocuous

than Class I but the chemical does not contain structures similar to those in Class III.

Cramer Class III

A TTC value of 1.5 µg/kg bw/day is derived for complex chemical structures that have no

indication of safety or may be metabolised to a reactive functional group; significant toxicity is

anticipated.

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The decision tree software, ToxTree, was used to generate Cramer Class data and also to

provide structural alerts that indicate genotoxic potential.

Structural alert for genotoxicity

For chemicals with structural alerts for genotoxicity, a TTC value of 0.0025 µg/kg bw/day was

derived. This value is considered to be ‘sufficiently protective’ for mutagenic compounds and

is associated with a 1 in 106 excess lifetime cancer risk (European Food Safety and World

Health, 2016; European Commission, 2009).

4.3 Toxicity Summary

4.3.1 2-Hydroxy-5-nitrobenzoic acid

Experimental toxicity data

Acute toxicity

No data are available.

Irritation and sensitisation

2-Hydroxy-5-nitrobenzoic acid has been classified as a ‘skin irritant, category 2; H315’ and

‘eye irritant, category 2; H319’ under European Globally Harmonised System (GHS)

Classification and Labelling regulations (PubChem, 2017g). No information on the study was

available. No sensitisation data are available.

Chronic toxicity


Mutagenicity/carcinogenicity

The European Chemicals Agency (ECHA) registration document for 2-hydroxy-5-nitrobenzoic

acid reports a negative result in the Ames assay and in vitro mammalian chromosome

aberration test based on read across from a chemical of a similar structure (no further details

reported) (Vughs et al., 2016). A potential for DNA binding through the production of nitrenium

ions and reactive oxygen species (ROS) was also predicted and a structural alert for

genotoxic carcinogenicity was noted (no further data available). It was concluded that the

structure of 2-hydroxy-5-nitrobenzoic acid has ‘genotoxic potential’ but is not mutagenic

(Vughs et al., 2016).

Reproductive/developmental toxicity


Alternative approaches to deriving a PoD

Modelled toxicity data

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© WRc plc 2018 56

VEGA

Based on the chemical structure, 2-hydroxy-5-nitrobenzoic acid is predicted to be mutagenic.

It is also predicted to be non-sensitising to the skin, carcinogenic and both a toxicant and non-

toxicant in developmental and reproductive activity models, although all these predictions are

deemed unreliable. The results of these findings are summarised in Table 4.3.

OECD toolbox

The OECD QSAR toolbox was applied to determine either a NO(A)EL or LO(A)EL for repeat

dose toxicity and for developmental and reproductive toxicity. Unfortunately, due to the limited

databases, the amount of data was insufficient to develop any predictions.

TTC

2-Hydroxy-5-nitrobenzoic acid is categorised as a Cramer Class III using ToxTree modelling

software. However a structural alert for genotoxic carcinogenicity (QSA27 nitro aromatic) has

been identified. Therefore, a TTC value of 0.0025 µg/kg bw/day is appropriate.

Selection of PoD

No PoDs for 2-hydroxy-5-nitrobenzoic acid were available based on experimental data or

OECD toolbox predictions. Due to structural alerts for genotoxicity, the TTC value of

0.0025 µg/kg bw/day is considered the most appropriate for the risk characterisation.

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Table 4.3 Table 4.4 VEGA predictions for 2-hydroxy-5-nitrobenzoic acid

Model Prediction Reliability of

Assessment

Similarity with

molecules of known

experimental value

Accuracy of

prediction for

similar molecules

Concordance for similar

molecules (experimental

Vs predicted)

Identified

structural

alerts

Sensitisation

(CAESAR)

Non-

sensitising Not optimal Strong Good Disagree -

Mutagenicity

(CAESAR, ISS) Mutagenic Appears reliable Strong Good Agree

SA27 nitro

aromatic

Mutagenicity

(KNN) Mutagenic Appears reliable Strong Good Agree -

Mutagenicity

(SarPy) Mutagenic Appears reliable Strong Good Agree SM52; SM189

Carcinogenicity

(CAESAR) Carcinogenic Not reliable

a Strong Not adequate Some disagree -

Carcinogenicity

(IRFMN/Antares) Carcinogenic Not optimal Strong Not optimal Disagree

Carcinogenic

no: 33, 63, 64

Carcinogenicity

(ISS) Carcinogenic Not optimal Strong Not optimal Some disagree

SA27 nitro

aromatic

Carcinogenicity

(ISSCAN-CGX) Carcinogenic Not reliable Strong Not adequate Disagree

Carcinogenic

no: 21, 36, 42

Reproductive/developmental

toxicity (CAESAR) Toxicant Not reliable Moderate Not adequate Disagree -


toxicity (PG) Non-toxicant Not reliable Moderate Good Disagree -

a Model class assignment is uncertain

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4.3.2 2-Methoxy-4,6-dinitrophenol


Acute toxicity

Limited data are available. A lowest lethal dose (LDLo) of 40 000 µg/kg in the pigeon has

been reported following intraperitoneal exposure (RTECs, 2017a), however no further details

on the study were available.



Chronic toxicity



(Vughs et al., 2016) reviewed the toxicological properties of 2-methoxy-4,6-dinitrophenol

based on read across data. A potential for DNA binding was predicted, however details on the

structural alerts for this chemical were not available. In addition, a positive response in the

Ames assay, with and without metabolic activation was predicted (no further data available). It

was concluded that 2-methoxy-4,6-dinitrophenol is ‘potentially mutagenic’ in the Ames test;

however there were ‘insufficient data’ available to further assess genotoxic or carcinogenic

potential (Vughs et al., 2016).





VEGA

Based on the chemical structure, 2-methoxy-4,6-dinitrophenol is predicted to be sensitising to

the skin. It is also predicted to be mutagenic, with two of the four models used being classed

as reliable. It is also predicted to be carcinogenic and as both a toxicant and non-toxicant in

developmental and reproductive activity models although these predictions were unreliable.

The results of these findings are summarised in Table 4.5.

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Table 4.5 VEGA predictions for 2-methoxy-4,6-dinitrophenol


Assessment

Similarity with

molecules of known

experimental value

Accuracy of

prediction for

similar molecules



Vs predicted)

Identified

structural alerts

Sensitisation

(CAESAR) Sensitising Appears reliable Strong Good Agree -

Mutagenicity

(CAESAR) Mutagenic Appears reliable Strong Good Agree

SA27 nitro

aromatic

Mutagenicity

(ISS) Mutagenic Not optimal Strong Not adequate Disagree

SA27 nitro

aromatic

Mutagenicity

(KNN) Mutagenic Not reliable Strong Not adequate Some disagree -

Mutagenicity

(SarPy) Mutagenic Appears reliable Strong Good Agree SM95

Carcinogenicity

(CAESAR)

Non-

carcinogenic Not reliable

a Strong Not optimal Some disagree -

Carcinogenicity

(IRFMN/Antares) Carcinogenic Not optimal Strong Not optimal Some disagree

Carcinogenic no:

37,40, 63, 64

Carcinogenicity(ISS) Carcinogenic Not optimal Strong Not adequate Disagree SA27 nitro

aromatic

Carcinogenicity

(ISSCAN-CGX) Carcinogenic Not optimal Strong Not optimal Some disagree

Carcinogenic no:

42


toxicity(CAESAR) Toxic Not optimal Moderate Good Disagree -


toxicity (PG) Non-toxic Not reliable Strong Good Disagree -

a Predicted substance falls into a network that is populated by no compounds of the dataset.

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OECD toolbox

Using the OECD QSAR Toolbox, two NOELs and six LOELs were predicted for repeated

dose toxicity. These results are presented in Table 4.6. However, it should be noted that

these predictions, whilst falling within the prediction domain, and featuring acceptable

statistical measures of fit, are considered to be of low reliability due to the small size of the

dataset upon which they are based.

The experimental database for developmental and reproductive toxicity was too limited to

derive estimates for these endpoints.

Table 4.6 OECD Toolbox predictions for 2-methoxy-4,6-dinitrophenol

En

dp

oin

t

Init

ial

Pro

file

r

Su

b-c

ate

go

ris

ati

on

pro

file

s

Nu

mb

er

of

ca

teg

ory

me

mb

ers

In d

om

ain

?

R2

sta

tis

tic

Re

su

lt

Re

lia

bil

ity

NOEL

(rat or

mouse or

rabbit)

Ecosar None 4 Yes 0.942 123 000 µg/kg bw/day Low

LOEL

(rat or rabbit) Ecosar None 3 Yes 1.00 90 600 µg/kg bw/day Low

NOEL

(SD rat, oral

gavage)

Repeat dose

(HESS)

Repeat dose (HESS)

Ecosar

Chemical elements

3 Yes 0.991 97 700 µg/kg bw/day Low

LOEL

(SD rat, oral

gavage or

diet)

Repeat dose

(HESS)

Repeat dose (HESS)

Ecosar

Chemical elements


LOEL

(SD rat, oral

gavage)

Repeat dose

(HESS)

Repeat dose (HESS)

Ecosar

Chemical elements


LOEL

(SD rat, oral

gavage)

Repeat dose

(HESS)

Repeat dose (HESS)

Structural similarity

(>70%)


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TTC

2-Methoxy-4,6-dinitrophenol is categorised as a Cramer Class III using ToxTree modelling

software. However a structural alert for genotoxic carcinogenicity (QSA27 nitro aromatic) was

identified. Therefore, a TTC value of 0.0025 µg/kg bw/day is appropriate.

Selection of PoD

No experimental PoDs were available for 2-methoxy-4,6-dinitrophenol. Based on the

modelled data, the following PoDs are proposed:

A NOEL of 97 700 µg/kg bw/day derived from the OECD toolbox,

A LOEL of 90 600 µg/kg bw/day derived from the OECD toolbox,

A TTC value of 0.0025 µg/kg bw/day.

The reliability of both the NOEL and LOEL values is considered to be ‘low’ due to the

limitation of the dataset behind their derivation so should be used with caution.

4.3.3 2-Nitrohydroquinone


Acute toxicity




Chronic toxicity



Vughs et al. (2016) reviewed the toxicological properties of 2-nitrohydroquinone based on

read across data. A potential for DNA binding through the production of nitrenium ions and

ROS was predicted and a structural alert for genotoxic carcinogenicity was noted (no further

data available). It was concluded that the structure of 2-nitrohydroquinone ‘suggests

genotoxic potential’ (Vughs et al., 2016).



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VEGA

Based on the chemical structure, 2-nitrohydroquinone is predicted to be sensitising to the

skin. It is also predicted to be mutagenic, with two of the four models used being reliable. It is

also predicted to be both a toxicant and non-toxicant in developmental and reproductive

activity models and carcinogenic, although the developmental and reproductive toxicity and

carcinogenicity predictions were unreliable. The results of these findings are summarised in

Table 4.7.

OECD toolbox




TTC

2-nitrohydroquinone is categorised as a Cramer Class III using ToxTree modelling software.

However a structural alert for genotoxic carcinogenicity (QSA27 nitro aromatic) has been


Selection of PoD:

As no PoDs for 2-nitrohydroquinone were available based on experimental data or OECD

toolbox predictions, and structural alerts for genotoxicity have been reported, the TTC value

0.0025 µg/kg bw/day is considered the most appropriate PoD for risk characterisation.

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Table 4.7 VEGA predictions for 2-nitrohydroquinone


Assessment

Similarity with

molecules of known

experimental value

Accuracy of

prediction for

similar molecules



Vs predicted)

Identified

structural alerts

Sensitisation

(CAESAR) Sensitising

Appears

reliable Strong Good Agree -

Mutagenicity

(CAESAR) Mutagenic

Appears

reliable Strong Good Agree

SA27 nitro

aromatic

Mutagenicity

(ISS) Mutagenic Not optimal Strong Not adequate Disagree

SA27 nitro

aromatic

Mutagenicity


Mutagenicity

(SarPy) Mutagenic

Appears

reliable Strong Good Agree SM95

Carcinogenicity

(CAESAR)

Non-


a Strong Not optimal Some disagree -

Carcinogenicity


Carcinogenicity no:

37, 40, 63, 64

Carcinogenicity (ISS) Carcinogenic Not optimal Strong Not adequate Disagree SA27 nitro

aromatic

Carcinogenicity


Carcinogenicity no:

42


toxicity (CAESAR) Toxicant Not optimal Moderate Good Disagree -


toxicity (PG) Non-toxicant Not reliable Strong Good Disagree -

a Predicted substance falls into a network that is populated by no compounds of the dataset.

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4.3.4 3,5-Dinitrosalicylic acid


Acute toxicity

Limited data are available. Oral median lethal doses (LD50) of 270 000 µg/kg bw (mouse) and

860 000 µg/kg bw (rat) have been reported (RTECs, 2017b), however no further details on

these studies are available.


3,5-Dinitrosalicylic acid has been classified as a ‘skin irritant, category 2; H315’ and ‘eye

irritant, category 2; H319’ under European GHS Classification and Labelling regulations

(PubChem, 2017a). No information on the study was available. No sensitisation data are

available.

Chronic toxicity



Vughs et al. (2016) reviewed the toxicological properties of 3,5-dinitrosalicylic acid based on

read across data. A potential for DNA binding through the production of nitrenium ions and

was predicted and a structural alert for genotoxic carcinogenicity was noted (no further data

available). It was concluded that the structure of 3,5-dinitrosalicylic acid ‘suggests genotoxic

potential’ (Vughs et al., 2016).





VEGA

Based on the chemical structure, 3,5-dinitrosalicylic acid is predicted to be sensitising to the

skin and carcinogenic. Three of the four models predict it to be mutagenic; however, only one

of these predictions (ISS) is reliable. It is also predicted as both a toxicant and non-toxicant in

developmental and reproductive activity models; however, these predictions were unreliable.


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Table 4.8 VEGA predictions for 3,5-dinitrosalicylic acid


Assessment

Similarity with

molecules of known

experimental value

Accuracy of

prediction for

similar molecules


molecules

(experimental Vs

predicted)

Identified

structural alerts

Sensitisation


Mutagenicity

(CAESAR) Mutagenic Not reliable Strong Not adequate Disagree

SA27 nitro

aromatic

Mutagenicity

(ISS) Mutagenic Appears reliable Strong Good Agree

SA27 nitro

aromatic

Mutagenicity


Mutagenicity

(SarPy)

Non-

mutagenic Not optimal Strong Not optimal Some disagree -

Carcinogenicity

(CAESAR) Carcinogenic Appears reliable Strong Good Agree -

Carcinogenicity

(IRFMN/Antares) Carcinogenic Appears reliable Strong Good Agree

Carcinogenicity

no: 64

Carcinogenicity

(ISS) Carcinogenic Appears reliable Strong Good Agree

SA27 nitro

aromatic

Carcinogenicity

(ISSCAN-CGX) Carcinogenic Appears reliable Strong Good Agree

Carcinogenicity

no: 42


toxicity (CAESAR) Toxic Not reliable Moderate Not adequate Disagree -


toxicity (PG) Non-toxic Not reliable Moderate Good Disagree -

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OECD toolbox

Using the OECD QSAR Toolbox, one NOEL and two LOELs were predicted for repeated

dose toxicity. These results are presented in Table 4.9. However, it should be noted that

these predictions, whilst falling within the prediction domain, and featuring acceptable





Table 4.9 OECD Toolbox predictions for 3,5-dinitrosalicylic acid

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NOEL

(SD rat,

oral

gavage)

Repeat dose

(HESS)

Repeat dose (HESS)

Chemical elements


(>60%)


LOEL

(rat, oral

gavage or

diet)

Repeat dose

(HESS)

Repeat dose (HESS)

Chemical elements 5 Yes 0.927 35 500 µg/kg bw/day Low

LOEL

(SD rat,

oral

gavage)

Repeat dose

(HESS)

Repeat dose (HESS)

Chemical elements


(>60%)


TTC

3,5-Dinitrosalicylic acid is categorised as a Cramer Class III using ToxTree modelling


been identified. Therefore, a TTC value of 0.0025 µg/kg bw/day is appropriate.

Selection of PoD

No experimental toxicity PoDs for 3,5-dinitrosalicylic acid were available. Based on the

modelled data obtained, the following PoDs are proposed:


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A TTC value of A TTC value of 0.0025 µg/kg bw/day.



4.3.5 4-Hydroxy-3-nitrobenzoic acid


Acute toxicity



4-Hydroxy-3-nitrobenzoic acid has been classified as a ‘skin irritant, category 2; H315’ and

‘eye irritant, category 2; H319’ under European GHS Classification and Labelling regulations

(PubChem, 2017c). No information on the study was available. No sensitisation data are

available.

Chronic toxicity



Vughs et al. (2016) reviewed the toxicological properties of 4-hydroxy-3-nitrobenzoic acid

based on read across data. A potential for DNA binding through the production of nitrenium

ions and ROS was predicted and a structural alert for genotoxic carcinogenicity was noted (no

further data available). It was concluded that the structure of

4-hydroxy-3-nitrobenzoic acid ‘suggests genotoxic potential’ (Vughs et al., 2016).





VEGA

Based on the chemical structure, 4-hydroxy-3-nitrobenzoic acid is predicted to be mutagenic.

It is also predicted to be non-sensitising to the skin, carcinogenic and as both a toxicant and

non-toxicant in developmental and reproductive activity models, although these predictions

were unreliable. The results of these findings are summarised in Table 4.10.

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OECD toolbox




TTC

4-hydroxy-3-nitrobenzoic acid is categorised as a Cramer Class III using ToxTree modelling


been identified using ToxTree modelling software. Therefore, a TTC value of

0.0025 µg/kg bw/day is appropriate.

Selection of PoD


OECD toolbox predictions. Due to structural alerts for genotoxicity, the TTC value of

0.0025 µg/kg bw/day is considered the most appropriate for the risk characterisation.

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Table 4.10 VEGA predictions for 4-hydroxy-3-nitrobenzoic acid


Assessment

Similarity with

molecules of known

experimental value

Accuracy of

prediction for

similar molecules



Vs predicted)

Identified

structural alerts

Sensitisation

(CAESAR)

Non-

sensitising Not optimal Strong Good Disagree -

Mutagenicity

(CAESAR, ISS) Mutagenic Appears reliable Strong Good Agree

SA27 nitro

aromatic

Mutagenicity

(KNN) Mutagenic Appears reliable Strong Good Agree -

Mutagenicity

(SarPy) Mutagenic Appears reliable Strong Good Agree SM52

Carcinogenicity

(CAESAR) Carcinogen Not reliable

a Strong Not adequate Some disagree -

Carcinogenicity

(IRFMN/Antares) Carcinogen Not optimal Strong Not optimal Disagree

Carcinogenicity no:

33, 37, 63, 64

Carcinogenicity

(ISS) Carcinogen Not optimal Strong Not optimal Some disagree

SA27 nitro

aromatic

Carcinogenicity

(ISSCAN-CGX) Carcinogen Not reliable Strong Not adequate Disagree

Carcinogenicity no:

36, 42


toxicity(CAESAR) Toxic Not reliable Moderate Not adequate Disagree -



a Model class assignment is uncertain

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4.3.6 4-Nitrobenzene-sulfonic acid


Acute toxicity



4-Nitrobenzene-sulfonic acid has been classified as a ‘skin irritant, category 1, H314’ and ‘eye

irritant, category 1, H318’ under European GHS Classification and Labelling regulations

(PubChem, 2017d). No information on the study was available. No sensitisation data are

available.

Chronic toxicity



Measured genotoxicity data are limited to a negative response in an Ames assay (with and

without metabolic activation (Kawai et al., 1987). No further details on this study were

available.

Vughs et al. (2016) reviewed the toxicological properties of 4-nitrobenzene-sulfonic acid

based on read across data. No structural alerts for mutagenicity of carcinogenicity were found

hence it was concluded that 4-nitrobenzene-sulfonic acid does not indicate any signs of

mutagenicity or genotoxicity (Vughs et al., 2016).





VEGA

Based on the chemical structure, 4-nitrobenzene-sulfonic acid is predicted to be non-

sensitising to the skin although the reliability of the prediction was not optimal. It is also

predicted to be non-mutagenic, with two of the four models used being reliable. The models

for carcinogenicity have equivocal results and all predictions were either not reliable or not

optimal. It is also predicted as a non-toxicant in developmental and reproductive activity

models but again the models were not reliable. The results of these findings are summarised

in Table 4.11.

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Table 4.11 VEGA predictions for 4-nitrobenzene-sulfonic acid


Assessment

Similarity with

molecules of known

experimental value

Accuracy of

prediction for

similar molecules



Vs predicted)

Identified

structural alerts

Sensitisation (CAESAR) Non-sensitising Not optimala Strong Good Agree -

Mutagenicity (CAESAR) Non- Mutagenic Appears

reliableb

Strong Good Agree -

Mutagenicity (ISS) Non-mutagenic Not reliable Strong Not adequate Some disagree -

Mutagenicity (KNN) Non-mutagenic Appears

reliableb

Strong Good Agree -

Mutagenicity (SarPy) Mutagenic Not reliableb Strong Not adequate Disagree -

Carcinogenicity (CAESAR) Non-carcinogenic Not reliablec

Strong Not optimal Some disagree -

Carcinogenicity


Carcinogenicity

no: 63, 64

Carcinogenicity (ISS) Non-carcinogenic Not reliable Strong Not adequate Some disagree -

Carcinogenicity (ISSCAN-CGX) Carcinogenic Not reliable Strong Not adequate Disagree Carcinogenicity

no: 42


toxicity(CAESAR) Non-toxic Not reliable

c Moderate Good Disagree -


toxicity (PG) Non-toxic Not reliable

d Moderate Not optimal Disagree -

a Some atom centred fragments of the compound have not been found in compounds of the dataset or are rare fragments (1 inadequate fragment found).

b Experimental value is non-mutagenic.

c A prominent number of atom centred fragments of the compound have not been found in the compounds of the data set or are rare fragments (1 unknown

fragment and 1 infrequent fragment found). d

Some number of atom centred fragments of the compound have not been found in the compounds of the data set or are rare fragments (1 infrequent

fragment found).

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OECD toolbox

The database of experimental data for chemicals that are similar to 4-nitrobenzene-sulfonic

acid, and thus its appropriateness for developing predictions, is extremely limited. However,

the OECD Toolbox predicted a NOEL and a LOEL (Table 4.12). Although these predictions

meet various criteria for, they are considered to be of low reliability due to the small size of the


Due to this small dataset, it has not been possible to develop any predictions for reproductive

endpoints.

Table 4.12 OECD Toolbox predictions for 4-nitrobenzene-sulfonic acid

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LOEL

(SD rat,

oral

gavage)

Repeat dose

(HESS)

Repeat dose (HESS)


NOEL

(SD rat,

oral

gavage)

Repeat dose

(HESS)

Repeat dose (HESS)


TTC

4-hydroxy-3-nitrobenzoic acid is categorised as a Cramer Class III, and no structural alerts for

genotoxicity have been identified using ToxTree modelling software. Therefore, a TTC value

of 1.5 µg/kg bw/day is appropriate.

Selection of PoD

No experimental toxicity PoDs for 4-nitrobenzene-sulfonic acid were available. Based on the

modelled data obtained, the following PoDs are proposed:




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4.3.7 4-Nitrocatechol


Acute toxicity



4-Nitrocatechol has been classified as a ‘skin irritant, category 2; H315’ and ‘eye irritant,

category 2; H319’ under European GHS Classification and Labelling regulations (PubChem,

2017e). No information on the study was available. No sensitisation data are available.

Chronic toxicity



Vughs et al. (2016) reviewed the toxicological properties of 4-nitrocatechol based on read

across data. A potential for DNA binding was predicted, however details on the structural

alerts for this chemical were not available. It was concluded that 4-nitrocatechol is ‘probably

not’ mutagenic in an Ames assay; however, there were insufficient data available to assess

further genotoxic or carcinogenic potential (Vughs et al., 2016).





VEGA

Based on the chemical structure, 4-nitrocatechol is predicted to be sensitising to the skin and

carcinogenic. It is also predicted to be mutagenic and both a toxicant and non-toxicant in

developmental and reproductive activity models although these predictions were unreliable.


OECD toolbox

Using the OECD QSAR Toolbox two NOELs were predicted for repeated dose toxicity. These

results are presented in Table 4.14. However, it should be noted that these predictions, whilst

statistically falling within the prediction domain, and featuring acceptable statistical measures

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of fit, are considered to be of low reliability due to the small size of the dataset upon which

they are based.



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Table 4.13 VEGA modelling software toxicity predictions for 4-nitrocatechol


Assessment

Similarity with

molecules of known

experimental value

Accuracy of

prediction for

similar molecules



Vs predicted)

Identified

structural alerts

Sensitisation


Mutagenicity

(CAESAR, ISS) Mutagenic Not optimal Strong Not optimal Some disagree

SA27 nitro

aromatic

Mutagenicity


Mutagenicity

(SarPy)

Non-

mutagenic Not reliable Strong Not adequate Disagree -

Carcinogenicity

(CAESAR) Carcinogenic Appears reliable Strong Good Agree -

Carcinogenicity

(IRFMN/Antares) Carcinogenic Appears reliable Strong Good Agree

Carcinogenicity

no: 63, 64

Carcinogenicity


SA27 nitro

aromatic

Carcinogenicity


Carcinogenicity

no: 42


toxicity (CAESAR) Toxic Not reliable Moderate Not adequate Disagree -


toxicity (PG) Non-toxic Not reliable Moderate Not optimal Disagree -

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Table 4.14 OECD Toolbox predictions for 4-nitrocatechol

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NOEL

(F344 or SD

rat, oral

gavage)

Ecosar

Ecosar

Chemical elements

Structural similarity (>40%)


NOEL

(F344 rat,

oral gavage

or diet)

Ecosar

Ecosar

Chemical elements

Organic functional groups


TTC

4-Nitrocatechol is categorised as a Cramer Class III using ToxTree modelling software.



Selection of PoD

No experimental toxicity PoDs for 4-nitrocatechol were available. Based on the modelled data

obtained, the following PoDs are proposed:



4.3.8 4-Nitrophthalic acid


Acute toxicity


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4-Nitrophthalic acid has been classified as a ‘skin irritant, category 2; H315’ and ‘eye irritant,


2017f). No information on the study was available. No sensitisation data are available.

Chronic toxicity



Vughs et al. (2016) reviewed the toxicological properties of 4-nitrophthalic acid based on read

across data. A potential for DNA binding through the production of nitrenium ions and ROS

was predicted and a structural alert for non-genotoxic carcinogenicity was noted (no further

data available). It was concluded that the structure of 4-nitrophthalic acid suggests genotoxic

potential (Vughs et al., 2016).





VEGA

Based on the chemical structure, 4-nitrophthalic acid is predicted to be sensitising to the skin

and mutagenic. It is also predicted to be carcinogenic and as both a toxicant and non-toxicant

in developmental and reproductive activity models although these predictions are unreliable.


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Table 4.15 VEGA predictions for 4-nitrophthalic acid


Assessment

Similarity with

molecules of known

experimental value

Accuracy of

prediction for

similar

molecules

Concordance for

similar molecules

(experimental Vs

predicted)

Identified structural

alerts

Sensitisation

(CAESAR) Sensitising

Appears

reliable Moderate Good Agree -

Mutagenicity

(CAESAR, ISS) Mutagenic

Appears

reliable Strong Good Agree SA27 nitro aromatic

Mutagenicity

(KNN) Mutagenic

Appears


Mutagenicity

(SarPy) Mutagenic

Appears

reliable Strong Good Agree

SM19, SM52, SM72,

SM104, SM118

Carcinogenicity

(CAESAR)

Non-


a Strong Not adequate Disagree -

Carcinogenicity


Carcinogenicity no: 31,

32, 33, 63, 64

Carcinogenicity


SA27 nitro aromatic,

SA42 phthalate

diesters and

monoesters

Carcinogenicity


Carcinogenicity no: 36,

41, 42


toxicity (CAESAR) Toxic

Appears

reliable Moderate Good Agree -



a Predicted value falls into a network that is populated by no compounds of the dataset.

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OECD toolbox




TTC

4-nitrophthalic acid is categorised as a Cramer Class III using ToxTree modelling software.

However structural alerts for genotoxic (QSA27 nitro aromatic) and non-genotoxic (QSA42

phthalate diesters and monoesters) carcinogenicity have been identified. Therefore, a TTC

value of 0.0025 µg/kg bw/day is appropriate.

Selection of PoD


OECD toolbox predictions. Due to structural alerts for genotoxicity, the TTC value of 0.0025

µg/kg bw/day is considered the most appropriate for the risk characterisation.

4.3.9 5-Nitrovanillin


Acute toxicity



5-Nitrovanillin has been classified as a ‘skin irritant, category 2; H315’ and ‘eye irritant,


2017b). No information on the study was available. No sensitisation data were located.

Chronic toxicity


Mutagenicity/genotoxicity

Vughs et al. (2016) reviewed the toxicological properties of 5-nitrovanillin based on an ECHA

registration document formed from read-across predictions, whereby negative results in the

Ames assay and an in vitro mammalian chromosome aberration test were noted. A potential

for DNA binding through the production of nitrenium ions and ROS was also predicted and a

structural alert for genotoxic carcinogenicity was noted (no further data available). It was

concluded that the structure of 5-nitrovanillin has ‘genotoxic potential’ but is not mutagenic

(Vughs et al., 2016).

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VEGA

Based on the chemical structure, 5-nitrovanillin is predicted to be non-sensitising to the skin

and mutagenic. It is also predicted to be carcinogenic and as both a toxicant and non-toxicant

in developmental and reproductive activity models, although these predictions are unreliable.


OECD toolbox

Using the OECD QSAR Toolbox, one LOEL and one NOEL were predicted for repeated dose

toxicity. These results are presented in Table 4.16. However, it should be noted that these

predictions, whilst statistically falling within the prediction domain, and featuring acceptable





Table 4.16 OECD Toolbox predictions for 5-nitrovanillin

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Res

ult

Reli

ab

ilit

y

LOEL

(F344 or SD

rat, oral

gavage or

diet)

Repeat dose

(HESS)

Repeat dose (HESS)


NOEL

(F344 or SD

rat, oral

gavage)

Repeat dose

(HESS)

Repeat dose (HESS)


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TTC

4-Nitrophthalic acid is categorised as a Cramer Class III using ToxTree modelling software.



Selection of PoD

No experimental toxicity PoDs for 5-nitrovanillin were available. Based on the modelled data

obtained, the following PoDs are proposed:


ALOEL of 166 000 µg/kg bw/day derived from the OECD toolbox,




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Table 4.17 VEGA predictions for 5-nitrovanillin


Assessment

Similarity with

molecules of known

experimental value

Accuracy of

prediction for

similar molecules

Concordance for

similar molecules

(experimental Vs

predicted)

Identified structural

alerts

Sensitisation (CAESAR) Non-

sensitising

Appears


Mutagenicity (CAESAR) Mutagenic Appears

reliable Strong Good Agree SA27 nitro aromatic

Mutagenicity (ISS) Mutagenic Not reliablea Strong Not adequate Disagree

SA11 simple aldehyde,

SA27 nitro aromatic

Mutagenicity (KNN) Non-

mutagenic Not optimal Strong Good Some disagree -

Mutagenicity (SarPy) Mutagenic Appears

reliable Strong Good Agree SM52

Carcinogenicity (CAESAR) Non-

carcinogenic Not optimal

a Strong Good Disagree -

Carcinogenicity


Carcinogenicity no: 33, 37,

63, 64

Carcinogenicity (ISS) Carcinogenic Not reliable Strong Not adequate Disagree SA11 simple aldehyde,

SA27 nitro aromatic

Carcinogenicity (ISSCAN-CGX) Carcinogenic Not reliablea Strong Not adequate Disagree Carcinogenicity no: 36, 42


toxicity (CAESAR) Toxic Not reliable

a Moderate Not adequate Disagree -


toxicity (PG) Non-toxic Not reliable

a Moderate Good Disagree -

aSome atom centred fragments of the compound have not been found in the compounds of the dataset or are rare fragments (1 infrequent fragment found).

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4.3.10 Summary

A PoD for all DBPs has been determined using a variety of methods, a summary of which is

presented as Table 4.18. Limited experimental data were available for each DBP and so

alternative approached to derive a PoD using modelled toxicity data has been applied. Where

possible, modelled NOELs and LOELs have been derived and TTC values have been

determined based on each DBP’s chemical structural alerts. Due to the low reliability of the

modelling due to the limited databases, the TTC approach was recommended to be

precautionary.

Table 4.18 Summary of PoD for each DBP

DBP PoD (µg/kg bw/day)

TTC (µg/kg bw/day) NOEL LOEL

2-Hydroxy-5-nitrobenzoic acid - - 0.0025

2-Methoxy-4,6-dinitrophenol 97 700 90 600 0.0025

2-Nitrohydroquinone - - 0.0025

3,5-Dinitrosalicylic acid 31 800 29 600 0.0025

4-Hydroxy-3-nitrobenzoic acid - - 0.0025

4-Nitrobenzene-sulfonic acid 876 000 871 000 1.5

4-Nitrocatechol 736 000 - 0.0025

4-Nitrophthalic acid - - 0.0025

5-Nitrovanillin 279 000 166 000 0.0025

4.3.11 Summaries of other DBPs for which Toxicity Datasheets exist

The following chemicals were also identified as DBPs as part of this project’s objective (see

Section 4.1.5 for further details). As toxicity data for these chemicals was already collated and

available to DWI through the UKWIR/WRc Toxicity Datasheet subscription service, it was

agreed that a comprehensive risk assessment for these chemicals was not required.

However, a summary of each chemical’s toxicity profile and, where appropriate, a

health-based guidance value (HBGV) is provided.

2,4-Dinitrophenol and 4-nitrophenol

2,4-Dinitrophenol (and the structurally similar chemical 4-nitrophenol) is highly water soluble.

It causes moderate to high acute oral toxicity in experimental animals, and anticipated signs

of toxicity following short-term human exposure include gastrointestinal irritation, muscle

cramps and increased basal metabolism. Chronic human exposure is associated with

irreversible cataracts. Both 2,4-dintrophenol and 4-nitrophenol are skin irritants and

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4-nitrophenol has been classed as a potential skin sensitiser. 2,4-Dinitrophenol has a

cytotoxic mode of action, and genotoxic studies have provided equivocal results.

The US Environmental Protection Agency (EPA) reviewed over 100 cases of cataracts arising

in patients using 2,4-dinitrophenol therapeutically and determined a LOAEL of

2 mg/kg bw/day. The US EPA applied an uncertainty factor (UF) of 1000 (10 to account for

intra-species variation, 10 to account for the use of subchronic rather than chronic data, and

10 for the use of a LOAEL) to the LOAEL to derive an oral Reference Dose (RfD) of

0.002 mg/kg bw/day (2 µg/kg bw/day).

Acetaldehyde

Acetaldehyde is a volatile chemical that is highly water soluble. It causes low acute oral

toxicity in experimental animals and anticipated signs of toxicity following short-term human

exposure include central nervous system depression, reduced respiratory rate and pulmonary

oedema. Acetaldehyde has been classed as an irritant (in particular to the respiratory tract

following inhalation); however, there is no evidence to suggest that it is a skin sensitiser. The

overall data indicate the acetaldehyde is genotoxic.

As limited chronic toxicity data for acetaldehyde are available, the European Scientific

Committee for Food (SCF) derived a Tolerable Daily Intake (TDI) of 0.1 mg/kg bw/day

(100 µg/kg bw/day) based on results from a 2-year oral rat study and a 3-generation oral rat

study which both used methaldehyde (formaldehyde) as the test substance (no further details

available).

Acetic acid and acetate

Acetic acid (and the conjugate base, acetate) is a volatile chemical that is highly water

soluble. It causes low acute oral toxicity in experimental animals and anticipated signs

following short-term human exposure include corrosion and irritation of the gastro-intestinal

tract and reduced pulmonary function. Chronic human oral exposure is associated with kidney

damage and liver cirrhosis. Acetic acid is classified as a skin irritant. Skin sensitisation is rare,

but some cases have been reported. Overall, there is some evidence that it is genotoxic in

vivo.

Due to the widespread use of acetic acid in food, and the endogenous occurrence in

mammalian metabolism, the Joint Food and Agriculture/World Health Organization (WHO)

Expert Committee on Food Additives (JECFA) and the European Food Safety Authority

(EFSA), concluded that it was not necessary to derive a HBGV.

Acetone

Acetone is a volatile chemical that is highly water soluble. It causes low acute oral toxicity in

experimental animals and anticipated signs of toxicity following short-term human exposure

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include gastro-intestinal irritation, sedation, headache, ataxia, hypothermia and convulsions.

Chronic human exposure is associated with metabolic acidosis, ketosis and eventual liver and

kidney damage. Acetone has been classed as an eye irritant. There is no evidence to suggest

that it is a skin sensitiser. The overall data indicate the acetone is not genotoxic.

In a 13-week toxicity study, F344/N rats were administered acetone via drinking water at

concentrations of 0, 2500, 5000, 10 000, 20 000 or 50 000 mg/l (average doses were reported

to be 0, 200, 400, 900, 1700 and 3400 mg/kg bw/day for males, and 0, 300, 600, 1200, 1600

and 3100 mg/kg bw/day for females, respectively). A NOAEL of 900 mg/kg bw/day was

identified based on nephropathy. The US EPA applied an UF of 1000 (10 to account for intra-

species variation, 10 to account for inter-species variation and 10 to account for a limited

database) to this NOAEL to derive an oral RfD of 0.9 mg/kg bw/day (900 µg/kg bw/day).

Aniline

Aniline is a semi-volatile chemical that is highly water soluble. It causes low to moderate acute

oral toxicity in experimental animals and anticipated signs following short-term human

exposure include methaemoglobinaemia and haemolysis. Chronic human oral exposure is

associated with anaemia, weight loss, hypoxia and cutaneous lesions. Aniline has been

classed as a skin and eye irritant and a skin sensitiser. The overall genotoxicity data for

acetone are equivocal.

In a 104-week dietary carcinogenicity study, F344 rats were administered aniline

hydrochloride at aniline-equivalent doses of 0, 7, 22 or 72 mg/kg bw/day. A LOAEL of 7 mg/kg

bw/day was identified based on an increased incidence of chronic capsulitis (inflammation of

ligaments) in females at all dose levels when compared with controls. By applying an UF of

1000 (10 to account for intra-species variation, 10 to account for inter-species variation and

10 to account for the use of a LOAEL) to the LOAEL, a TDI of 0.007 mg/kg bw/day can be

derived (7 µg/kg bw/day).

Benzoic acid

Benzoic acid is a non-volatile chemical that is highly water soluble. It causes low acute oral

toxicity in experimental animals, and anticipated signs following short-term human exposure

include loss of balance and vision, stomach pains and gastro-intestinal irritation. It is also

reported to provoke recurrences of asthmas and skin conditions in individuals that are prone

to the conditions. No chronic human exposure data are available. Benzoic acid has been

classed as a skin and eye irritant. There is no evidence to suggest that it is a skin sensitiser.

Whilst no in vivo genotoxicity data are available, the overall in vitro data indicate that benzoic

acid is not genotoxic.

In a 16-week dietary toxicity study, rats were administered benzoic acid at concentrations of

0, 5000 or 10 000 mg/kg diet (equivalent to 0, 250 and 500 mg/kg bw/day, respectively). As

no significant effects were reported throughout the study, a NOAEL of 500 mg/kg bw/day

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(highest dose tested) was identified. The EFSA applied an UFof 100 (10 to account for intra-

species variation, 10 to account for inter-species variation) to this NOAEL to derive an

Acceptable Daily Intake (ADI) of 5 mg/kg bw/day (5000 µg/kg bw/day).

Bromochloroacetonitrile

Bromochloroacetonitrile is a semi-volatile chemical that is highly water soluble. No acute

toxicity data are available and chronic oral exposure data are limited to a single-dose mouse

comparative study, whereby an increased incidence in lung tumours were observed when

compared to mice administered other haloacteonitriles (no further details are available).

Bromochloroacetonitrile has been classed as an eye irritant. There are no data to suggest it is

a skin sensitiser. Whilst limited in vivo genotoxicity data are available, the overall in vitro data

indicate that benzoic acid is genotoxic.

In a developmental oral (gavage) toxicity study, bromochloroacetonitrile was administered to

pregnant Long-Evans rats at dose levels of 0, 5, 25, 45 or 65 mg/kg bw/day on days 6 to 18 of

gestation. A developmental LOAEL of 5 mg/kg/day was identified based on increased

incidences of cardiovascular foetal abnormalities. However, it should be noted that caution

must be applied to the interpretation of these results, as tricaprylin was used as a vehicle to

administer bromochloroacetonitrile, and tricaprylin is also associated with embryotoxic and

developmental effects. By applying an UFof 1000 (10 to account for intra-species variation, 10

to account for inter-species variation and 10 for the use of a LOAEL and the limited database)

to the LOAEL, a TDI of 0.005 mg/kg bw/day is derived (5 µg/kg bw/day).

Formate

Formic acid (and the conjugate base, formate) is a semi-volatile chemical that is miscible in

water. It causes low acute oral toxicity in experimental animals and anticipated signs following

short-term exposure include salivation, a burning sensation in the mouth, vomiting, ulceration

of gastric membranes and circulatory pain. No chronic human exposure data could be located

and experimental animal data are limited to inhalation studies. Formic acid has been classed

as a skin and eye irritant. There is no evidence to suggest it is a skin sensitiser. Overall the

data indicate that formic acid is not genotoxic.

JECFA derived an ADI of 3 mg/kg bw/day (3000 µg/kg bw/day) for formic acid and formate

(for their sum and individually); however, the basis for this derivation was not reported.

Nitrobenzene

Nitrobenzene is a volatile chemical that is soluble in water. It causes low acute oral toxicity in

experimental animals and anticipated signs following short-term human exposure include

methaemoglobinaemia, cyanosis, headache and dyspnoea. No data on chronic human

exposure were located, however multiple repeat-dose experimental data in rats report clinical

signs including ataxia and lethargy, and microscopic lesions to the brain. Nitrobenzene is not

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classified as an irritant or a skin sensitiser. Overall, the data indicate that nitrobenzene may

be weakly genotoxic.

In the WHO Guidelines for Drinking-water Quality (GDWQ), a formal guideline value was not

established because nitrobenzene was ‘rarely found in drinking water at concentrations of

health concern’. However, short-term health based value and hence a short-term TDI was

derived by WHO. This is based on a 28-day oral (gavage) toxicity study in F344 rats that were

administered nitrobenzene at doses of 0, 5, 25 or 125 mg/kg bw/day. A LOAEL of 5 mg/kg

bw/day was identified based on spongiotic changes to the cerebellum. WHO applied an UFof

1000 (10 to account for intra-species variation, 10 to account for inter-species variation and

10 to account for the use of a LOAEL) to the LOAEL to derive a TDI of 0.005 mg/kg bw/day.

WHO noted in this derivation that nitrobenzene exposure may result in

methaemoglobinaemia, which is a particular concern for bottle-fed infants. However, WHO

stated that ‘available data were inadequate’ to derive a value for this endpoint.

Oxalate

Oxalic acid (and its conjugate base, oxalate) is a non-volatile chemical that is highly water

soluble. It causes low to moderate acute oral toxicity in experimental animals and anticipated

signs following short-term human exposure include immediate corrosive damage to the mouth

and gastrointestinal tract, gastrointestinal irritation, depression of the nervous system and

convulsions. Chronic human oral exposure is associated with excessive formation of calcium

oxalate, leading to bladder calculi and renal damage. Oxalic acid has been classified as an

eye and skin irritant. There is no evidence to suggest it is a skin sensitiser. No in vivo

genotoxicity data for are available, however the limited in vitro data available indicate that

oxalic acid is not genotoxic.

In a 2-year dietary carcinogenicity study, rats were administered oxalic acid at dose levels of

0, 0.1, 0.5, 0.8 or 1.2% (equivalent to 0, 60, 300, 480 and 720 mg/kg bw/day in males and 0,

40, 250, 400 and 600 mg/kg bw/day in females, respectively). A LOAEL of 40 mg/kg bw/day

(lowest dose administered) was identified based on hepatocellular hypertrophy. By applying

an UFof 100 (10 to account for intra-species variation, 10 to account for inter-species

variation), a TDI of 0.4 mg/kg bw/day is derived (400 µg/kg bw/day). As the LOAEL was

considered to be based on a relatively minor effect (enlargement of liver cells), no additional

UFwas applied to account for the use of a LOAEL.

Propanoic acid

Propanoic acid is an involatile chemical that is miscible with water. It causes low acute oral

toxicity in experimental animals. No short-term or chronic human exposure data could be

located; however repeat dose studies in experimental animals have reported gastro-intestinal

hyperplasia and ulceration (20-week dietary rat study, effects observed at 270 or

2700 mg/kg bw/day) and diffuse epithelial hyperplasia of the oesophagus (100-day dietary

dog study, effects observed in 3/8 dogs at 1832 mg/kg bw/day). Propanoic acid is classified

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as a skin and eye irritant. There is no evidence to suggest it is a skin sensitiser. Overall, data

indicate that propanoic acid is not genotoxic.

JECFA set an ADI of “not limited” for propanoic acid and confirmed that there are no safety

concerns for its current levels of intake, based on its use as a flavouring agent.

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5. Objective 5: Risk Assessment

5.1 Hazard Identification

During the hazard identification phase, the type and nature of potential adverse effects

(hazards) are identified (see Section 4.3 for further details).

5.2 Hazard Characterisation

Hazard characterisation encompasses a qualitative or quantitative description of inherent

toxicological properties of the DBP. Health based guidance values such as an ADI or TDI are

used to provide an estimate of the amount of chemical that can be ingested over a lifetime

without appreciable risk to health.

5.2.1 Proposed PoDs

The PoD, usually in the form of a NO(A)EL or LO(A)EL is identified from the literature search

or determined from the alternative methods applied i.e. modelling. If no PoD was derived, the

TTC value has been used.

5.2.2 Selection of proposed Uncertainty Factors (UF)

In general, a default UFof 100 is typically used, consisting of a factor of 10 for inter-species

variability (4 for toxicokinetics and 2.5 for toxicodynamics) and 10 to account for intra-species

differences (3.2 for toxicokinetics and 3.2 for toxicodynamics) (WHO, 2001). However, in

some cases, such default factors may not be applicable, or additional UFs may need to be

considered. In cases where the TTC value was identified as the most appropriate PoD,

uncertainty factors are not required. A summary of the considerations for the UFs used in this

hazard characterisation is presented in Table 5.1.

Table 5.1 Uncertainty Factor considerations

Assessment

Factor

Possible

Range Comment

Inter-species

differences 1-10

UF used to account for difference in sensitivity between species:

10 is proposed if animal data are used

Intra-species

differences 1-10

UF used to account for differences in sensitivity between

individuals:

10 is proposed to account for human variability

QSAR data 3-10

UF used to account for use of QSAR data:

3 is proposed if a NO(A)EL is used

10 is proposed if a LO(A)EL is used*

* In some cases the NO(A)EL and LO(A)EL are similar. In such situations the additional UF is used as worse-case

scenario to be sufficiently protective. It is noted that this approach may be over-conservative

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5.2.3 Derivation of proposed TDI

The TDI is calculated by using equation:

5.3 Exposure Assessment

During the exposure assessment phase, the maximum measured concentration of the DBP in

drinking water is converted to an intake value. This is achieved by using default assumptions

on bodyweight and volume of water ingested for different receptors to allow the intake to be

expressed on a bodyweight basis. The following assumptions are used:

60 kg adult drinking 2 litres per day,

10 kg child drinking 1 litres per day,

5 kg infant drinking 0.75 litres per day.

The concentrations of DBPs used in this assessment were identified by Vughs et al. (2016). In

this paper, artificial water based on ultrapure water, KNO3 and extracts of NOM2 were treated

with medium pressure (MP) UV to simulate the work of Kolkman et al. (2015). The

concentrations of nitrate and NOM are representative of what can occur in natural raw waters.

Kolkman et al. (2015) had reported the formation of 84 DBPs following treatment of similar

artificial water with MP UV, of which 22 had also been detected in samples from a full-scale

MP UV / H2O2 AOP plant at a water treatment works. Following a comparison of reference

standards, retention times and MS/MS fragmentation, Vughs et al. (2016) confirmed the

identity of 14 DBPs that were previously reported by Kolkman et al. (2015). Five of the 14

identified DBPs were excluded from further evaluation based on the prioritisation criteria

(Section 4.1).

Vughs et al. (2016) fractionated the DBPs into 8 fractions using HPLC for analysis by LC-

Orbitrap Mass Spectroscopy. As part of the identification process, each DBP was semi-

quantified by comparing the relative abundance of the chemical to the known concentration of

the internal standards used in the analysis. As such, the unit of quantification for each

chemical is referred to as ‘µg/l internal standard equivalents’ (ITSD eq.).

Only data for the five highest concentrations of DBPs in each fraction were presented, the

concentrations of which all exceeded 0.015 µg/l ITSD eq. These DBPs were considered to be

2 10.4 mg/l nitrate; 2.5 mg/l C (Standard fulvic acid solution using Pony Lake NOM obtained from

International Humic Substances Society).

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the ‘most intensive’ by-products detected i.e. were present at the highest concentrations. All

such DBPs were identified, with the exception of one chemical (m/z; 316.1413, concentration;

0.0349 µg/L ITSD eq.) (Vughs et al., 2016).

It should also be noted that the DBP concentrations were detected following the use of AOPs

but prior to GAC treatment. Research has shown that the mutagenic response observed in

Ames assays using water treated by AOPs no longer occurs following GAC filtration, implying

that the nitrogenated DBPs to which the mutagenic is partially attributed may be removed by

GAC. Therefore, the exposure assessments conducted here represent a worst case scenario.

5.4 Risk Characterisation

During risk characterisation, the estimated intake of a DBP via drinking water is compared

with HBGVs. Where possible, the risk of each DBP has been characterised against both a

modelled TDI and a TTC value.

5.5 Risk Communication

To aid risk communication, the margin of exposure (MOE) approach is commonly used. The

MOE is defined as the ratio of a defined PoD for an adverse effect to the estimated exposure.

For this project, an MOE has been calculated for adult, child and infant exposure, calculated

using the following equation (WHO, 2009):

The MOE approach has been endorsed by WHO; for effects with a biological threshold, an

MOE of at least 100 would be considered acceptable, and for effects without a threshold, an

acceptable MOE of greater than 10 000 has been suggested (WHO, 2009; COC, 2006). In

general however, the magnitude of the MOE gives an indication of the level of concern, for

example; the larger the MOE, the smaller the potential risk.

5.6 2-Hydroxy-5-nitrobenzoic acid

5.6.1 Hazard identification

Limited experimental data for 2-hydroxy-5-nitrobenzoic acid were available. Modelling

software identified structural alerts for genotoxicity.

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5.6.2 Hazard characterisation

Proposed PoDs

No modelled PoD for 2-hydroxy-5-nitrobenzoic acid could be derived. Based on the data

obtained in Section 4.3.1, a TTC value of 0.0025 µg/kg bw/day is considered an appropriate

PoD.

5.6.3 Exposure assessment

The maximum concentration of 2-hydroxy-5-nitrobenzoic acid measured in drinking water was

0.0562 µg/l ITSD eq. (Vughs et al., 2016). Based on default factors the daily intake would be:

0.00187 μg/kg bw/day for an adult,

0.00562 μg/kg bw/day for a child,

0.00843 μg/kg bw/day for an infant.

5.6.4 Risk characterisation

TDI

No TDI for 2-hydroxy-5-nitrobenzoic acid could be derived.

TTC

The maximum intake of 2-hydroxy-5-nitrobenzoic acid via drinking water by adults

(0.00187 μg/kg bw/day is less than the TTC value (0.0025 µg/kg bw/day) and therefore,

adverse health effects are not anticipated in adults.

The maximum intake in children and infants (0.00562 to 0.00843 µg/kg bw/day) is greater

than the TTC value. Therefore, additional research into the occurrence in drinking water and

toxicological properties of this DBP may be prudent.

5.6.5 Risk communication

No MOE for 2-hydroxy-5-nitrobenzoic acid could be derived.

5.7 2-Methoxy-4,6-dinitrophenol


Limited experimental data for 2-methoxy-4,6-dintrophenol were available. Modelling software

identified structural alerts for sensitisation and genotoxicity.

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Proposed PoDs

The NOEL and LOEL modelled in Section 4.3.2 are very similar hence the lowest value was

selected as the PoD, namely the LOEL of 90 600 µg/kg bw/day. The reliability of these values

is considered to be ‘low’ due to the limitation of the dataset so should be used with caution.

Therefore the TTC approach using a TTC value of 0.0025 µg/kg bw/day will also be used in

the risk assessment.

Selection of proposed UFs

The proposed UFs for use with the PoD selected are as follows:

10 for inter-species variability

10 for intra-species variability

10 for the use of a modelled LOEL

Total UF used = 1000

Derivation of proposed TDI

The proposed TDI is 90.6 µg/kg bw/day.


The maximum concentration of 2-methoxy-4,6-dinitrophenol measured in drinking water was

0.0454 μg/l ITSD eq (Vughs et al., 2016). Based on default factors the daily intake would be:





TDI

The maximum intake of 2-methoxy-4,6-dinitrophenol via drinking water by adults, children and

infants (0.00151 to 0.00681 μg/kg bw/day) is less than the proposed TDI (90.6 μg/kg bw/day).

Therefore it is not anticipated that any adverse public health effects will occur following

exposure to 2-methoxy-4,6-dinitrophenol via drinking water. The TDI and hence the risk

characterisation should be used with caution due to the limitations in the dataset used to

derive the LOEL.

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TTC

The maximum intake of 2-methoxy-4,6-dinitrophenol via drinking water by adults

(0.0015 μg/kg/day) is less than the TTC value (0.0025 µg/kg bw/day), and therefore, adverse

health effects are not anticipated in adults.

The maximum intake by children and infants (0.00454 to 0.00681 μg/kg bw/day) exceeds the

TTC value. Therefore, additional research into the occurrence in drinking water and


Risk communication

Although it is possible to calculate MOEs for 2-methoxy-4,6-dinitrophenol, it is not

recommended due to the uncertainty and lack of reliability in the TDI .

5.8 2-Nitrohydroquinone


Limited experimental data for 2-nitrohydroquinone were available. Modelling software

identified structural alerts for sensitisation and genotoxicity.


Proposed PoDs

No modelled PoD for 2-nitrohydroquinone could be derived. Based on the data obtained in

Section 4.3.3, a TTC value of 0.0025 µg/kg bw/day is considered an appropriate PoD.


The concentration of 2-nitrohydroquinone was measured by Vughs et al. (2016) but was not

reported as it was not considered to be an ‘intensive by-product’. However, as the

concentration of each ‘intensive by-product’ is reported to exceed 0.015 µg/l ITSD eq, it is

therefore assumed that the concentration of ‘non-intensive by products’ would be <0.015 µg/l

ITSD eq. (see Section 5.3 for further information).Therefore, for the purpose of this project, a

maximum concentration of 0.015 µg /l will be used. However it should be noted that this value

may be an over-conservative representation of 2-nitrohydroquinone in typical drinking water.

Based on default factors the daily intake would be,




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TDI

No TDI for 2-nitrohydroquinone could be derived.

TTC

The maximum intake of 2-nitrohydroquinone via drinking water by adults, children and infants

(0.0005 to 0.00225 μg/kg bw/day) is less than the TTC value (0.0025 µg/kg bw/day), and

therefore, adverse health effects are not anticipated.


No MOE for 2-nitrohydroquinone could be derived.

5.9 3,5-Dinitrosalicylic acid


Limited experimental data for 3,5-dinitrosalicylic acid were available. Modelling software

identified structural alerts for sensitisation, genotoxicity and carcinogenicity.


Proposed PoDs

Based on the data obtained in Section 4.3.4, a modelled LOEL of 29 600 µg/kg bw/day has

been selected as the most conservative modelled PoD. The reliability of this LOEL is

considered to be ‘low’ due to the limitation of the dataset so should be used with caution.










The proposed TDI is 29.6 µg/kg bw/day.

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The maximum concentration of 3,5-dinitrosalicylic acid measured in drinking water was

0.0073 μg/l ITSD eq. (Vughs et al., 2016). Based on default factors the daily intake would be,





TDI

The maximum intake of 3,5-dinitrosalicylic acid via drinking water by adults, children and

infants (0.00024 to 0.0011 µg/kg bw/day) is less than the proposed TDI (29.6 µg/kg bw/day).


exposure to 3,5-dinitrosalicylic acid via drinking water. The TDI and hence the risk


derive the LOEL.

TTC

The maximum intake of 3,5-dinitrosalicylic acid via drinking water by adults, children and

infants (0.00024 to 0.0011 µg/kg bw/day) is less than the TTC value (0.0025 µg/kg bw/day),

and therefore adverse health effects are not anticipated.


Although it is possible to calculate MOEs for 3,5-dinitrosalicylic acid, it is not recommended

due to the uncertainty and lack of reliability in the TDI .

5.10 4-Hydroxy-3-nitrobenzoic acid


Limited experimental data for 4-hydroxy-3-nitrobenzoic acid were available. Modelling

software identified structural alerts for genotoxicity.

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Proposed PoDs

No modelled PoD for 4-hydroxy-3-nitrobenzoic acid could be derived. Based on the data

obtained in Section 4.3.5 therefore, a TTC value of 0.0025 µg/kg bw/day is considered an

appropriate PoD.


The maximum concentration of 4-hydroxy-3-nitrobenzoic acid measured in drinking water was

0.0422 μg/l ITSD eq. (Vughs et al., 2016). Based on default factors the daily intakes would be:





TDI

No TDI for 4-hydroxy-3-nitrobenzoic acid could be derived.

TTC

The maximum intake of 4-hydroxy-3-nitrobenzoic acid via drinking water by adults

(0.00141 μg/kg bw/day) is less than the TTC value (0.0025 µg/kg bw/day), and therefore,

adverse health effects following adult exposure to this level of 2-hydroxy-5-nitrobenzoic acid

are not anticipated.

The maximum intake in children and infants (0.00422 to 0.00633 μg/kg bw/day) is greater

than the TTC value. Therefore, additional research into the occurrence in drinking water and



No MOE for 4-hydroxy-3-nitrobenzoic acid could be derived.

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5.11 4-Nitrobenzene-sulfonic acid


Limited experimental data for 4-nitrobenzene-sulfonic acid were available. Modelling software

identified structural alerts for carcinogenic endpoints, however the results were equivocal and

all predictions were either not reliable or not optimal.


Proposed PoDs

The NOEL and LOEL modelled in Section 4.3.6 are very similar hence the lowest value was

selected as the PoD, namely the LOEL of 871 000 µg/kg bw/day. The reliability of these

values is considered to be ‘low’ due to the limitation of the dataset so should be used with

caution. Therefore the TTC approach using a TTC value of 1.5 µg/kg bw/day will also be used

in the risk assessment.








The proposed TDI is 871 µg/kg bw/day.


The concentration of 4-nitrobenzene-sulfonic acid was measured by Vughs et al. (2016) but

was not reported as it was not considered to be an ‘intensive by-product’. However, as the

concentration of each ‘intensive by-product’ is reported to exceed 0.015 µg/l ITSD eq, it is

therefore assumed that the concentration of ‘non-intensive by products’ would be <0.015 µg/l

ITSD eq. (see Section 5.3 for further information). Therefore, for the purpose of this project, a

maximum concentration of 0.015 μg/l will be used, however it should be noted that this value

may be an over-conservative representation of 4-nitrobenzene-sulfonic acid in typical drinking

water. Based on default factors the daily intake would be:



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TDI

The maximum intake of 4-nitrobenzene-sulfonic acid via drinking water by adults, children and

infants (0.0005 to 0.00225 μg/kg bw/day) is less than the proposed TDI (871 µg/kg bw/day).


exposure to 4-nitrobenzene-sulfonic acid via drinking water. The TDI and hence the risk


derive the LOEL.

TTC

The maximum intake of 4-nitrobenzene-sulfonic acid via drinking water by adults, children and

infants (0.0005 to 0.00225 μg/kg bw/day) is less than the TTC value (1.5 µg/kg bw/day), and

therefore adverse health effects are not anticipated.


Although it is possible to calculate MOEs for 4-nitrobenzene-sulfonic acid, it is not

recommended due to the uncertainty and lack of reliability in the TDI.

5.12 4-Nitrocatechol


Limited experimental data for 4-nitrocatechol were available. Modelling software identified

structural alerts for sensitisation, as well as genotoxic and carcinogenic endpoints.


Proposed PoDs

Based on the data obtained in Section 4.3.7, a modelled NOEL of 736 000 µg/kg bw/day has

been selected as the most conservative modelled PoD. The reliability of these values is






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5 for the use of a modelled NOEL

Total UF used = 500




The maximum concentration of 4-nitrocatechol measured in drinking water was 0.027 μg/l

ITSD eq. (Vughs et al., 2016). Based on default factors the daily intake would be,





TDI

The maximum intake of 4-nitrocatechol via drinking water by adults, children and infants

(0.00090 to 0.00405 μg/kg bw/day) is less than the proposed TDI (1472 µg/kg bw/day).


exposure to 4-nitrocatechol via drinking water. The TDI and hence the risk characterisation

should be used with caution due to the limitations in the dataset used to derive the NOEL.

TTC

The maximum intake of 4-nitrocatechol via drinking water by adults (0.00090 μg/kg bw/day) is

less than the TTC value (0.0025 µg/kg bw/day) and therefore, adverse health effects following

adult exposure to this level of 4-nitrocatechol via drinking water are not anticipated in adults.

The maximum intake in children and infants (0.00270 to 0.00405 μg/kg bw/day) exceeds the

TTC value. Therefore, additional research into the occurrence in drinking water and



Although it is possible to calculate MOEs for 4-nitrocatechol, it is not recommended due to the

uncertainty and lack of reliability in the TDI.

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5.13 4-Nitrophthalic acid


Limited experimental data for 4-nitrophthalic acid were available. Modelling software identified

structural alerts for sensitisation and genotoxicity.


Proposed PoDs

No modelled PoD for 4-nitrophthalic acid could be derived. Based on the data obtained in

Section 4.3.8, a TTC value of 0.0025 µg/kg bw/day is considered an appropriate PoD.


The maximum concentration of 4-nitrophthalic acid measured in drinking water was

0.0007 μg/l ITSD eq. (Vughs et al., 2016). Based on default factors daily intakes would be,





TDI

No TDI for 4-nitrophthalic acid could be derived.

TTC

The maximum intake of 4-nitrophthalic acid via drinking water by adults, children and infants

(0.00002 to 0.00011 μg/kg/day) is less than the TTC value (0.0025 µg/kg bw/day). Therefore,

adverse health effects following exposure to 4-nitrophthalic acid via drinking water are not

anticipated.


No MOE for 4-nitrophthalic acid could be derived.

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5.14 5-Nitrovanillin


Limited experimental data for 5-nitrovanillin were available. Modelling software identified

structural alerts for genotoxicity.


Proposed PoDs

Based on the data obtained in Section 4.3.9, a modelled LOEL of 166 000 µg/kg bw/day has

been selected as the most conservative modelled PoD. The reliability of these values is








10 for the use of a low-reliably modelled LOEL





The concentration of 5-nitrovanillin was measured by Vughs et al. (2016) but was not reported

as it was not considered to be an ‘intensive by-product’. However, as the concentration of

each ‘intensive by-product’ is reported to exceed 0.015 µg/l ITSD eq, it is therefore assumed

that the concentration of ‘non-intensive by products’ would be <0.015 µg/l ITSD eq. (see

Section 5.3 for further information). Therefore, for the purpose of this project, a maximum

concentration of 0.015 µg /l will be used, however please note that this value may be an over-

conservative representation of 5-nitrovanillin in typical drinking water. Based on default factors

daily intakes would be,



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TDI

The maximum intake of 5-nitrovanillin via drinking water by adults, children and infants

(0.00050 to 0.00225 μg/kg bw/day) is less than the proposed TDI (166 µg/kg bw/day).

Therefore adverse health effects following exposure to 5-nitrovanillin via drinking water are

not anticipated. The TDI and hence the risk characterisation should be used with caution due

to the limitations in the dataset used to derive the LOEL.

TTC

The maximum intake of 5-nitrovanillin via drinking water by adults, children and infants is less

than the TTC value (0.0025 µg/kg bw/day), and therefore adverse health effects following

exposure to 5-nitrovanillin via drinking water are not anticipated.


Although it is possible to calculate MOEs for 5-nitrovanillin, it is not recommended due to the

uncertainty and lack of reliability in the TDI.

5.15 Summary and Conclusions

A summary of the risk characterisation for the DBPs is presented in Table 5.2. Where

possible, a PoD based on a modelled data and the TTC approach was used in order to

provide a weight of evidence approach to the risk assessment. When comparing the TDI

derived from modelled data and the TTC values for each DBP, a large difference in

magnitude was observed. This difference is largely based on the method of prediction behind

each approach.

The modelled PoDs have been derived using the OECD toolbox, based on existing data for

repeated dose toxicity and reproductive/developmental toxicity of chemicals with structural

similarities to the DBP in question. The lack of data in the data sets used for the predictions,

the complexity of endpoints and the limited number of chemicals with structural similarity to

the DBPs in question all contribute to the low reliability of the modelled PoDs.

Threshold of toxicological concern values however, are calculated based on NOAELs derived

for the three classes of chemicals, namely Cramer class I, II or III. The 5th percentile of the

NOAEL is divided by a factor of 100 to derive the TTC value. Application of the TTC approach

when chemical-specific data are not available is a pragmatic approach that allows the safety

evaluation of chemicals and it is a form of risk characterisation that balances uncertainties

inherent in extrapolation of TTC values to an unknown substances, against the level of human

exposure.

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Eight DBPs were noted to have structural alerts for mutagenicity and therefore are considered

to be potentially genotoxic. It is generally accepted that genotoxic chemicals exhibit no

threshold for their mutagenic potential (Fukushima, 2010). Therefore, it is widely

recommended that exposure levels be kept to as low as reasonably practicable, and thus it is

considered impossible to define a ‘safe’ level of exposure (Humfrey, 2007) As such, a TTC

value of 0.0025 µg/kg bw/day is used as it is thought to be of ‘negligible risk’ in the event that

a substance may later be defined as carcinogenic (European Commission, 2009; Humfrey,

2007). Whist the TTC approach has been criticised as being ‘overly conservative’ (Delaney,

2007), particularly in terms of calculating impurities in pharmaceuticals (European

Commission, 2009), it is considered to be an appropriate method for risk characterisation for

chemicals with limited existing data.

Overall, in cases where modelled PoDs were derived, the estimated exposure values for each

DBP were below the proposed TDI, indicating that the exposure to these DBPs via drinking

water is not anticipated to cause adverse health effects. However, due to the limitations in the

toxicity databases on which each PoD was based, caution should be used in their

interpretation.

Analysis of the chemical structure of 4-nitrobenzene-sulfonic acid did not identify any

mutagenic structural alerts, and carcinogenic VEGA predictions for carcinogenicity were

equivocal and unreliable. The estimated exposure of 4-nitrobenzene-sulfonic acid in drinking

water did not exceed the proposed TDI or the TTC value, therefore, it is considered to be of

low concern to public health.

When characterising each DBP against the genotoxic TTC value of 0.0025 µg/kg bw/day, the

estimated exposure of four DBPs (2-hydroxy-5-nitrobenzoic acid, 2-methoxy-4,6-

dinitrophenol, 4-hydroxy-3-nitrobenzoic acid and 4-nitrocatechol) exceed the threshold value

for children and infants, but not adults. Therefore for such chemicals additional research on

their occurrence in drinking water and the hazard potential would be prudent.

Of the remaining DBPs that were identified as potentially genotoxic (2-nitrohydroquinone,

3,5-dinitrosalicylic acid, 4-nitrophthalic acid and 5-nitrovanillin), the estimated exposure levels

were below the TTC value and hence adverse health effects are not anticipated.

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Table 5.2 Summary of risk characterisation of DBPs based on their estimated daily

intake

DBP

TDI

(µg/kg

bw/day)

TTC

(µg/kg

bw/day)


(TDI)


(TTC)

Adult Child Adult Adult Child Infant



2-Methoxy-4,6-

dinitrophenol 90.6 0.0025 Below Below Below Below Above Above

2-Nitrohydroquinone - 0.0025 - - - Below Below Below

3,5-Dinitrosalicylic acid 29.6 0.0025 Below Below Below Below Below Below



4-Nitrobenzene-sulfonic

acid 871 1.5 Below Below Below Below Below Below

4-Nitrocatechol 1472 0.0025 Below Below Below Below Above Above

4-Nitrophthalic acid - 0.0025 - - - Below Below Below

5-Nitrovanillin 166 0.0025 Below Below Below Below Below Below

- No data; modelled NO(A)EL/LO(A)EL could not be derived

Below; estimated daily intake is below the proposed TDI/TTC value, adverse health effects are not anticipated

Above; estimated daily intake is above the proposed TDI/TTC value, adverse health effects cannot be excluded

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6. Objective 6: Review of analytical methods for detecting disinfection by-products from advanced oxidation processes

6.1 Introduction

The systematic review in Objective 3 identified 78 DBPs that are produced during the use of

AOPs.

A systematic prioritisation process outlined in Objective 4 identified nine DBPs that were

potentially formed in water following AOP processes and for which a human health risk

assessment was carried out. These compounds were prioritised and grouped into similar

functional group moieties e.g. Nitrobenzene diols

The following Table 6.1 shows the DBPs to be reviewed.

Table 6.1 DBPs assessed

Disinfection by-product CAS RN Group

2-Hydroxy-5-nitrobenzoic acid 96-97-9 Hydroxynitrobenzoic acids

2-Methoxy-4,6-dinitrophenol 4097-63-6 Dinitrophenols

2-Nitrohydroquinone 16090-33-8 Nitrobenzene diols

3,5-Dinitrosalicylic acid 609-99-4 Dinitrophenols

4-Hydroxy-3-nitrobenzoic acid 616-82-0 Hydroxynitrobenzoic acids

4-nitrobenzene-sulfonic acid 138-42-1 Miscellaneous

4-Nitrocatechol 3316-09-4 Nitrobenzene diols

4-nitrophthalic acid 610-27-5 Miscellaneous

5-nitrovanillin 6635-20-7 Miscellaneous

6.2 Literature Review

A literature review was undertaken to identify the most common analytical techniques used to

quantify the concentration of the compounds present in drinking water. Data sources used

included the World Health Organisation, European Commission, Defra and the United States

Environmental Protection Agency and the following:

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Researchgate

ChemSpider

Google

PubMed

PubChem

The review aimed to identify the most common analytical technique for identifying the DBPs,

including a summary of the methodology. Where possible, standards and reagents used to

assist in the quantification of the compound are listed as well as the type of equipment used.

Depending on the analytical method identified, and date of the literature, a limit of detection is

reported for compound assessment.

The method of isotopic substitution, employed by Vughs et al. (2016) using 15

N to substitute 14

N in the sample, provides a reliable and quantitative result. However, the level of equipment

and expertise involved make it impractical for frequent analyses. The methods described

below have been accepted as the industry standards for rapid qualitative analyses and are

easier to replicate in the field.

6.3 Method Reviews

6.3.1 Dinitrophenol

Introduction

Nitrogenous DBPs (N-DBP) are formed in drinking water treatment processes, during the

reaction with NOM.

The two compounds assessed in this section are 2-methoxy-4,6-dinitrophenol and 3,5-

dinitrosalicylic acid (Figure 6.1).

Figure 6.1 Structures of compounds

2-methoxy-4,6-

dinitrophenol

3,5-dinitrosalicylic

acid

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Analytical methodology

Principle of method

Quantification of N-DBPs is based on modifications of US EPA method 551.1.

Samples of water are extracted with methyl tert-butyl ether (MtBE ) prior to analysis using gas

chromatography – mass spectroscopy (GC-MS) coupled with an electron capture detector

(ECD) using a HP-5 capillary column (30 m x 0.25 mm x 0.25 µm). Recently, pentane has

been introduced as an extraction solvent owing to safety concerns. The injector and detector

temperature were 200°C and 290°C, respectively, and the nitrogen carrier gas had a flow rate

of 30 ml/min and pressure of 69.8 kPa. The temperature program for the N-DBP analyses

was as follows: hold at 37°C for 10 min, ramp to 50°C at 5°C/min and hold for 5 min, and

finally ramp to 260°C at 15°C/min and hold for 10 min.

Standards and reagents

Pure analytes are added to the AOP treated water sample,. These are added to generate a

calibration curve to quantify the concentration of the AOP treated water sample being tested.

A laboratory blank is also used as a control sample to ensure interferences are not

encountered.

Standards are available from:

Sigma-Aldrich 48027 – MtBE

D0550 Sigma Aldrich – 3,5-dinitrosalicylic acid

AKOS000282909 AKos – 2-methoxy-4,6-dinitrophenol

Pentane, acetone, methanol, sodium chloride and sodium sulphate can also be purchased

from standard laboratory suppliers.

Equipment

Gas chromatography with detection by an ECD or GC-MS if concentrations are sufficient.

Non-polar methyl polysiloxane (silica-fused) capillary column, at 30 m x 0.25 mm x 0.25 µm.

Oven set to 200°C, detection temperature at 290°C. An alternative column can be used which

incorporates a 6% chemically bonded cyanopropylphenyl to the methyl polysiloxane, oven

temperatures are the same (Hodgeson et al., 1990).

Limit of detection

The method detection limit should be 0.1 mg/l for dinitrophenols (ChemSpider, 2017). No data

could be found for detection of N-DBPs.

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6.3.2 Hydroxynitrobenzoic Acids

Introduction

Nitrobenzoic acids (nitrosalicylic acids) are by-products from the oxidation of drinking water

treatment processes (H2O2).

The two compounds assessed in this section are 2-hydroxy-5-nitrobenzoic acid and 4-

hydroxy-3-nitrobenzoic acid (Figure 6.2).


2-hydroxy-5-

nitrobenzoic acid

4-hydroxy-3-

nitrobenzoic acid

6.3.3 Analytical methodology

Principle of method

The method below is applicable to salicylic acid compounds having a content of 0.1 mg/l

(Lide, 1998).

On heating the AOP treated water sample in the presence of a reducing sugar (such as

glucose, fructose) the colour of the solution changes from yellow to orange/red. One of the

nitro groups is reduced to the amine at temperatures above 90°C after 5 to 15 minutes.

Analysis is completed using a colorimeter (spectrophotometer) with a wavelength between

500 and 560 nm. The ideal wavelength is 540 nm (green light).


Pure analytes are added to the AOP treated water sample. These are added to generate a

calibration curve to quantify the concentration of the AOP treated water sample being tested.

A laboratory blank is also used as a control sample to ensure interferences are not

encountered.

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Sigma-Aldrich 247871 – 2-hydroxy-5-nitrobenzoic acid

Sigma-Aldrich 228575 – 4-hydroxy-3-nitrobenzoic acid

Equipment

Colorimeter and standard laboratory glassware.

6.3.4 Limit of detection

Compounds should be detected above 0.1 mg/l (LoD). This methodology is neither robust nor

reliable to accurately quantify an LoD.

6.4 Nitrobenzene diol

Introduction

The two compounds assessed in this section are 2-nitrohydroquinone and 4-nitrocatechol

(Figure 6.3).


2-nitrohydroquinone 4-nitrocatechol


Principle of method

This method is applicable for nitrobenzene derivatives. The sample is extracted using an

organic solvent (dichloromethane) and analysed by GC analysis. Flame ionisation or MS may

also be used for detection.

Firstly the sample is extracted with dichloromethane at pH 11 and then a separate extraction

at pH 2 followed by evaporation of dichloromethane to increase the sample concentration.

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Analysis is completed using a gas-phase chromatograph, coupled with a mass spectrometer

(Agency for toxic substances and disease registry, 1995). A non-polar column, as supplied by

SGE, with dimensions of 50 m x 0.32 mm x 0.25 µm. Injector and detector temperatures of

250°C and 280°C are used; the oven is set to 60°C, programmed to increase by 2°C/min to

230°C and maintained for a minimum of 20 minutes. Volume injected is 10 µl.


Analytical grade dichloromethane can be purchased from Sigma-Aldrich (24233-M).


FR-2180 RD Chemicals – 2-nitrohydroquinone

11450063 Fisher Scientific – 4-nitrocatechol

Equipment

Gas chromatograph coupled with detection by mass spectroscopy (GC-MS).

Non-polar capillary columns, typically 50 m x 0.32 mm x 0.25 µm.

Standard laboratory glassware.

Limit of detection

Water sample detection limits have been reported as 1.9 µg/l (Hodgeson et al, 1990).

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6.4.2 Miscellaneous Compound

Introduction

The three compounds assessed in this section of the report are 4-nitrobenzene sulfonic acid,

4-nitrophthalic acid and 5-nitrovanillin (Figure 6.4) (ChemSpider, 2017).


4-nitrobenzene

sulfonic acid 4-nitrophthalic acid 5-nitrovanillin

There are limited data available for analytical methods associated with determination of the

above compound concentrations within water samples.


Principle of method

Although not identical in structure, these compounds contain the nitro grouping, similar to the

dinitrophenols. Gas chromatography traces exist for all three compounds (Figure 6.5). As with

the phenols, it should be possible to extract the compounds into the organic phase using a

relatively polar solvent such as dichloromethane (NCBI, 2017).

Analysis is completed by gas chromatography coupled with detection by mass spectroscopy.

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Figure 6.5 GC-MS trace for 4-nitrobenzene sulfonic acid


Data lacking.

Equipment

Gas chromatograph, mass spectrometer detector, non-polar capillary column. Standard

laboratory glassware.

6.4.3 Limit of detection

Data lacking.

6.4.4 Availability of standards

ACM138421 Alfa Chemistry – 4-nitrobenzene sulfonic acid

274755 Sigma Aldrich – 4-nitrophthalic acid

N28000 Sigma Aldrich – 5-nitrovanillin

6.5 Conclusions

Analytical methods for the prioritised nine DBPs that were potentially formed in water

following AOP processes and for which a human health risk assessment was carried out have

been investigated. Some methods are well developed such as nitrobenzene diols and

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dinitrophenols whereas other methods for compounds such as the hydroxynitrobenzoic acids,

4-nitrobenzene sulfonic acid, 4-nitrophthalic acid and 5-nitrovanillin will need further

development to ensure they are robust and reliable. Additionally, problems with limits of

detection for these methods may not be low enough to detect the concentrations of these

compounds in drinking water. Advances in chromatography during the past twenty years has

allowed for better quantification of hydroxynitrobenzoic acids without the need to use less

accurate colorimetric spectrophotometry. However these methods are yet to be verified as

industry standards.

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7. Objective 7: Sampling and analysis strategy for future research projects

7.1 Introduction

As evident from Objective 3, a range of potential DBPs may arise as a result of the use of

AOP treatment. Under Objective 4, these identified DBPs were subject to a prioritisation

process to identify those DBPs that were considered of potential relevance to UK drinking

water, had not been identified in research with more ‘conventional’ water treatment, and as

such, were considered to be of highest priority subject to a high-level risk assessment. The

prioritised compounds comprise of nine DBPs, which were identified in studies carried out by

Vughs et al. (2016) and Kolkman et al. (2015). These studies investigated the potential

generation of DBPs after UV/H2O2. However, it was found that these DBPs were no longer

present after GAC treatment, which was located downstream of the AOP process and was

intended to quench residual H2O2.

The two UV / H2O2 plants currently operated in England and Wales also have GAC

downstream of the AOP as part of the normal practice (to quench residual H2O2). Therefore,

based on the limited data currently available, it may be a reasonable expectation that the

concentrations of DBPs formed via UV / H2O2 will be reduced by GAC, assuming its effective

operation. However, it should be emphasised that this is based on limited data and further

monitoring may be required to validate this assumption.

7.2 Removal of prioritised DBPs

The prioritised compounds comprise of nine DBPs, which were identified in studies carried out

by Vughs et al. (2016) and Kolkman et al. (2015). Vughs et al. (2016) used genotoxicity as an

indicator for DBPs formed by UV / H2O2, and isolated compounds that contributed to the

genotoxicity. During the study it was observed that the genotoxicity was no longer present

after GAC adsorption, implying that the DBPs had been removed. The analytical strategy

outlined below would help confirm both formation and removal of these DBPs.

7.3 Outline of strategy

The data reviews in the previous objectives have identified a number of gaps in the available

information. Therefore, prior to instigating a full sampling programme, a number of preliminary

steps are required to ensure that the sampling programme is fit-for-purpose. This report

considers a number of developmental stages that need to be undertaken prior to the sampling

strategy. A preliminary approach to sampling is also provided; however, the details of this

strategy are contingent upon the outcome of the development stages below:

Analytical method development

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Identification of sites for sampling

Communication

Sampling strategy.

7.4 Analytical method development

The purpose of this section is to recommend a strategy that develops a more encompassing

analytical method applicable to the nine prioritised DBPs described in Table 7.1. All nine

compounds have standards available for purchase from a variety of suppliers and a further

review of literature has shown a methodology capable of detecting all these chemicals using

similar analytical procedure.

During this method development, ‘spiked’ water samples would be utilised over a range of

concentrations and calibration curves would be developed for each standard. This

methodology would be repeated to ensure that detection limits (LODs) are repeatable and

standardised for anticipated DBP formation during AOP treatment.

The nine DBPs identified during the prioritisation process are shown in Table 7.1.

Table 7.1 DBPs for further assessment

DBP CAS RN Structure


2-Methoxy-4,6-dinitrophenol 4097-63-6

2-Nitrohydroquinone 16090-33-8

3,5-Dinitrosalicylic acid 609-99-4


4-nitrobenzene-sulfonic acid 138-42-1

4-Nitrocatechol 3316-09-4

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DBP CAS RN Structure

4-Nitrophthalic acid 610-27-5

5-Nitrovanillin 6635-20-7

Kolkman et al. (2015) used a liquid chromatography / high resolution mass spectroscopy (LC /

HR-MS) approach to analyse a variety of DBPs possibly formed during AOP treatment of

drinking water. This method has shown to be effective in matching reference standards of

DBPs to the DBPs found in an artificial water sample that was treated by medium pressure

UV – specifically the nine compounds listed above have all been identified with this method.

For the analysis, a quadrupole time of flight (QToF) mass spectrometer was utilised as better

structural elucidation could be obtained than using a LC-Orbitrap analyser, i.e. where

compounds are isomers of each other and higher resolution assists in structure determination.

The work from Kolkman et al. (2015) did not report any LOD, but the literature values

described in Objective 6 using standard GC-MS analysis should be realisable, i.e. 2-

nitrohydroquinone was reported to be detected at 1.9 µg/l (Hodgeson et al, 1990). Repeated

testing of standard ‘spiked’ water samples will establish the actual LODs and development of

the analytical method can be used to adjust the methodology to reduce the LOD as far as

possible.

Should the monitoring of DBPs show they are not present or present in limited concentrations,

pre-concentration of samples can be undertaken. Use of such analytical process can be

employed to back calculate the concentration of the DBP present and further assist in

developing the actual LOD for the nine DBPs of potential concern.

Once the methodology has been satisfactorily developed, a range of conditions can be

progressed with ‘spiked’ DBPs in a variety of water sources (e.g. hard water, soft water). The

recovery of these spikes will have been optimised, such that, confidence in the analysis of

actual water samples will be robust and reflect ‘real’ drinking water samples for the general

public.

Suggested sample bottles from an external laboratory are amber glass jars. In discussion with

the laboratory no preservatives for these types of compounds would be required as the

stability of the samples would be up to 28 days. This information requires verification and

validation should a sampling programme be developed.

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7.5 Identification of sites for sampling

It is recognised that the use of AOPs are not commonplace in England and Wales at the

present time. Although earlier investigations indicate that this may remain the position of

water companies for the near future, should the use of AOPs become commonplace, it is

critical to understand the circumstances where their use may favour the formation of DBPs.

Those sites that favour their formation can be considered ‘high risk’ in the sense that

consumers may potentially be exposed to higher concentrations of DBPs than consumers at

sites where DBP formation is lower. Sampling at these ‘high risk’ sites would allow the

investigation of the risk of exposure to the DBPs, to determine whether or not there is likely to

be a concern to human health, and thus determine whether regulatory action would be

required.

The review of the literature on the formation of DBPs following AOPs has revealed significant

gaps in the available data on the understanding of their formation in water conditions relevant

to the UK; therefore, prior to full-scale sampling, it is recommended that bench-scale analysis

is conducted with different water conditions to determine the best approach to identify these

‘high-risk’ sites.

7.5.1 Bench-scale pre-sampling study

Bench-scale pre-sampling would be conducted whereby changes to water conditions, such as

pH and other parameters that may influence the formation of potential DBPs, are

systematically investigated to determine those conditions that favour DBP formation. Each of

the following parameters (and any other parameters that may influence DBP formation) would

be sequentially adjusted in water prior to treatment with a bench-scale AOP unit and the

DBPs in the water post-treatment will be quantified:

pH

Conductivity

Water hardness

TOC

DOC

Nitrate

7.5.2 Identification of ‘high risk’ sites for sampling

As stated above, sites that favour the formation of the DBPs can be considered ‘high risk’ as

consumers may potentially be exposed via their drinking water.

The information collated in the bench-scale tests can be used to inform which drinking water

treatment works that employ AOPs are likely to be ‘high risk’ sites. For example, if it is

established that ‘high’ TOC levels result in increased DBP formation, further investigation

should be conducted where it is known that TOC levels are atypically high. Those sites that

are identified as such are subsequently included in the sampling programme.

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The scale of any survey will be subject to resourcing constraints. With the current gaps in

knowledge on the number of parameters that can influence AOP formation, it is not currently

possible to recommend a set number of sites to sample; however, the number of ‘high risk’

sites should be selected to ensure that all parameters (pH, conductivity etc.) that are

established as increasing DBP formation are represented.

In terms of the current use of AOPs, whereby only two sites are in operation across England

and Wales, the results of the bench-scales may provide information on whether one of these

sites is likely to favour DBP formation over the other. Should this be the case, intensive

sampling could be conducted at this site.

By way of controls and validation of the bench-scale tests, it is also recommended that two

sites are selected that would be considered ‘low risk’ by bench-scale tests. After three

sampling periods, if the results of these ‘low risk’ sites are consistent with the bench-scale

tests (i.e. concentrations of DBPs at these sites are lower than their high-risk counterparts),

these sites can be removed from the sampling programme, and more frequent sampling can

be conducted at ‘high risk’ sites.

7.6 Communication

In order to conduct a successful sampling regime, coordination between the operations team

on site, the water sampler and the analytical centre is essential. The following strategy should

be applied to maximise the effectiveness of the suggested sampling protocol:

1. A sampling protocol should be prepared that clearly states the sample point(s) and the

sampling procedure that will cover various aspects of the sampling such the volume of

water to be collected, the types of bottles to be used and the handling conditions of

those bottles (for example, storing in cold conditions), and the intended times and dates

of sampling at each site.

a. These documents should be written in plain English and easy to follow by all

parties involved.

b. The sampling protocol will be subject to versioning controls, to ensure that any

changes to the protocol are logged and all parties are using the most up-to-date

protocol.

2. An inventory form should be prepared identifying the sample points, label for sample

bottles and water quality determinand. This inventory form will also serve as a chain-of-

custody to ensure that all samples can be ‘tracked’ through the sampling procedure.

3. Designated operational team members will be identified, as will named individuals in

the analytical laboratory and the water treatment works.

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a. Each of these individuals will have copies of the sampling protocol and any

subsequent revisions to these protocols.

b. Each individual will also provide a contact telephone number and email address,

as well as the contact details of a nominated stand-in, to ensure effective

communication.

c. A minimum of 24 hours prior to sampling, the sampler will contact the water

treatment works to confirm the logistics of the intended sampling and

arrangements for prompt analysis of the samples.

4. Regular and direct communication between the designated personnel will be ensured

to highlight any issues or circumstantial changes which may influence the

commencement of the sampling. The use of nominated stand-in personal will be

applied whenever necessary to minimise the risk of ‘missed’ sampling due to

unforeseen changes in circumstances.

7.7 Sampling strategy for AOP treatment works

The European Drinking Water Directive sets out a minimum frequency for sampling based on

the volume of water distributed each day. In the UK, it was suggested that two levels of

monitoring under the Directive be undertaken; audit and check monitoring. For audit

monitoring, four samples per year are suggested to measure the general microbial quality of

the water and treatment effectiveness. Check monitoring is carried out using higher sampling

frequencies and is usually employed for monitored for pesticides and for water supplies of

10 000 m3/day. In this case, a minimum of 34 samples is suggested. In all cases, the samples

should be representative of the quality of water supplied during the course of a year

(Ratnayaka et al., 2009).

The primary interest of sampling in this survey is to confirm the presence of the DBPs after

AOP treatment. Therefore, it is not strictly necessary to follow the minimum sampling

frequencies laid out within the Drinking Water Directive; however, they do offer a useful basis

to determine an appropriate minimum number of samples, based on volume of water treated.

As a secondary consideration, it is also important to understand whether the DBPs are being

removed after GAC treatment. Therefore, sampling should be conducted after the AOP unit to

monitor the formation of potential DBPs, with some concurrent sampling also occurring after

GAC treatment to ensure the effectiveness of the GAC in removing the DBPs (if formed). The

rationale for sampling at these two points is two-fold:

firstly, sampling immediately after the AOP unit should allow for the detection of these

DBPs at their highest concentrations in water; therefore, should a consumer drink this

water, these would represent a ‘worst-case’ for exposure. Comparison of the

concentration of the DBPs at this point in the treatment process with any health-based

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guidance values would allow a determination of the risk to these consumers in an

‘extreme’ case; and

sampling after the GAC should act as a confirmation of the effectiveness of this

treatment process in reducing these DBPs, and, assuming that GAC does reduce their

concentrations, allow for a more realistic assessment of consumer exposure. The

frequency of sampling after GAC may vary depending on the efficiency of this unit in

removing DBPs.

The sampling strategy below should be followed at least for one full calendar year to allow for

any seasonal variability of the surface water quality. The strategy should be reviewed

regularly and at least after one year as more data become available. The following sampling

strategy is suggested to reflect the minimum frequencies and volumes mentioned above. AOP

treatment is typically not continuously operated.

Monitor DBP formation during AOP operation (before the GAC).

a. Samples should be collected from the AOP treated stream twice a month, as a

minimum, while the AOP is in operation.

b. A control sample should be collected from the raw water prior to entering the AOP

system. This is to understand the water quality entering the AOP system and detect

any pre-existance of DBP in the raw water prior to the AOP.

c. During seasonal changes (such as high rainfall occurrences) additional samples should

be collected as the nature of organics in surface water can exhibit seasonal variation. In

addition, agricultural run-off may contribute to nitrate concentration in the surface water.

The frequency of sampling should be increased to a daily sampling programme for one

week, or the duration of the event (whichever is shorter). These results should then be

assessed and three possible scenarios considered:

i) if the event has ended, or the apparent event has no influence on DBPs

formation, sampling can be reduced to twice per month;

ii) if the sampling event is continuing beyond one week, such that the DBP

concentrations are elevated, but there is no evidence of a significant variation in

the day-to-day concentrations of DBPs, sampling can be reduced to twice per

week, with a reassessment of the sampling frequency occurring after four weeks;

or

iii) if the sampling event is continuing beyond one week, such that the DBP

concentrations are elevated, and there is evidence of a significant variation in the

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day-to-day concentrations of DBPs, daily sampling should continue until the

concentrations of DBPs return to ‘normal’.

Monitor performance of the GAC unit in removing DBPs:

a. if DBPs are not detected after the AOP, there is no requirement for sampling of the

GAC treated stream; and

b. if DBPs are detected after the AOP, then twice weekly sampling of the GAC product

stream is recommended and should commence with immediate effect. It is anticipated

that GAC would reduce the DBPs. Any detection of DBPs may suggest the failure of

the GAC for removal of the DBPs and therefore trigger a more rigorous sampling

regime. This may ultimately result in termination of AOP and replacement of the GAC.

Prior to the sampling, the external laboratory will be informed of the analysis required

(detailed further in Section 7.6). The analytical centre will provide adequate sampling bottles

containing appropriate preservative chemicals in accordance with the analytical method used

for detecting the requested DBPs. Transport of the solution bottles should be completed in

cool boxes with ice packs and to minimise the risk of Legionella, samples should be kept in

the dark. A range of experimental parameters would be established with the external

laboratory with initial LODs being established during experimental analyses (detailed further in

Section 7.4).

7.8 Conclusions and Suggestions

A range of potential DBPs may arise as a result of the use of AOP treatment. However, the

identified DBPs went through a prioritisation process as part of Objective 4. Nine DBPs were

identified requiring further consideration.

As part of Objective 1 it was identified that currently only two plants are using AOP within

England and Wales. The research undertaken has identified that both of these plants

currently employ the use of GAC.

Based on the data currently available, it may be a reasonable expectation that, following

formation of these potential DBPs via AOP treatment, their concentrations in drinking water

will subsequently be reduced by GAC adsorption, assuming effective operation of the GAC.

This conclusion is based on limited data and further monitoring may be required to validate it.

Prior to instigating a full sampling programme, a number of preliminary steps are required to

ensure that the sampling programme is fit-for-purpose. Further analytical method

development is required using ‘spiked’ water samples to optimise detection limits in UK

drinking water and ensure that results are repeatable. This includes optimisation of calibration

curves and further refinement of LODs.

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There is also a lack of understanding as to the conditions that may favour the formation of

these DBPs. Prior to full-scale sampling, bench-scale analysis should conducted with different

water conditions to determine these conditions. This information can then be used to

determine sites where, should AOPs be employed, there is a reasonable expectation that

these DBPs will be formed. These sites should be the primary focus of the sampling survey.

Once the survey sites have been identified, a number of approaches can be taken. A one-

year, bimonthly sampling strategy is proposed, and has been broadly described in this report.

However, due to a number of unresolved questions, this approach may need to be adjusted

once bench-scale results are known. The approach of sampling over the course of one year

allows for the determination of any seasonal variability of the surface water quality that may

influence the formation of these DBPs.

Within this sampling programme, sampling at each water treatment works will be conducted

over a range of times of the day (morning, afternoon, evening) to address this question. To

fully understand the effects of changes in water conditions that may potentially affect DBP

formation (such as high rainfall events), a sampling programme has also been recommended

to determine the influence of these events.

Sampling in this manner allows for the majority of samples being collected immediately after

AOP treatment. Assuming this represents the highest concentration of DBPs in water this

represents a ‘worst-case’ by which to estimate exposure to the consumer. Sampling after

GAC has also been proposed to confirm the effectiveness of this treatment in reducing DBP

concentrations.

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WHO (2001) Guidance Document for the Use of Data in Development of Chemical-Specific Adjustment

Factors (CSAFs) for Interspecies Differences and Human Variability in Dose/Concentration–Response

Assessment. World Health Organisation.

WHO (2009) A Risk-Based Decision Tree Approach for the Safety Evaluation of Residues of Veterinary

Drugs. World Health Organisation.

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Wiley, J. (2010) White’s handbook of chlorination and alternative disinfectant. New York: Black and

Veatch Corporation.

Wu, T. and Englehardt, J.D. (2016) Mineralizing urban net-zero water treatment: Field experience for

energy-positive water management. Water Research, 106, 352-363.

Wu, Z., Fang, J., Xiang, Y., Shang, C., Li, X., Meng, F. and Yang, X. (2016) Roles of reactive chlorine

species in trimethoprim degradation in the UV/chlorine process: Kinetics and transformation pathways.

Water Research, 104, 272-282.

Xiao, Y., Zhang, L., Zhang, W., Lim, K.-Y., Webster, R.D. and Lim, T.-T. (2016) Comparative evaluation

of iodoacids removal by UV/persulfate and UV/H2O2 processes. Water Research, 102, 629-639.

Xie, P., Ma, J., Liu, W., Zou, J., Yue, S., Li, X., Wiesner, M.R. and Fang, J. (2015) Removal of 2-MIB

and geosmin using UV/persulfate: contributions of hydroxyl and sulfate radicals. Water research, 69,

223-233.

Xue, Y., Dong, W., Wang, X., Bi, W., Zhai, P., Li, H. and Nie, M. (2016) Degradation of sunscreen agent

p-aminobenzoic acid using a combination system of UV irradiation, persulphate and iron(II).

Environmental Science and Pollution Research, 23, 4561-4568.

Xylem (2017) Available from: www.xylem.com

Yang, X., Sun, J., Fu, W., Shang, C., Li, Y., Chen, Y., Gan, W. and Fang, J. (2016) PPCP degradation

by UV/chlorine treatment and its impact on DBP formation potential in real waters. Water Research, 98,

309-318.

Yano, J., Matsuura, J.-i., Ohura, H. and Yamasaki, S. (2005a) Complete mineralization of propyzamide

in aqueous solution containing TiO2 particles and H2O2 by the simultaneous irradiation of light and

ultrasonic waves. Ultrasonics sonochemistry, 12, 197-203.

Yano, J., Matsuura, J., Ohura, H. and Yamasaki, S. (2005b) Complete mineralization of propyzamide in

aqueous solution containing TiO2 particles and H2O2 by the simultaneous irradiation of light and

ultrasonic waves. Ultrason Sonochem, 12, 197-203.

Zhong, X., Cui, C. and Yu, S. (2017) Seasonal evaluation of disinfection by-products throughout two

full-scale drinking water treatment plants. Chemosphere, 179, 290-297.

Zoschke, K., Dietrich, N., Börnick, H. and Worch, E. (2012) UV-based advanced oxidation processes

for the treatment of odour compounds: Efficiency and by-product formation. Water Research, 46, 5365-

5373.

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Zúñiga-Benítez, H., Aristizábal-Ciro, C. and Peñuela, G.A. (2016) Heterogeneous photocatalytic

degradation of the endocrine-disrupting chemical Benzophenone-3: Parameters optimization and by-

products identification. Journal of Environmental Management, 167, 246-258.

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Appendix A Water company survey

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Appendix B Water company responses

B1 Company 1

1. Current Use of Advanced Oxidation Processes (AOPs)

1.1. Is your company currently employing AOPs at any

drinking water treatment works?

Yes ☒ Please proceed to Question 1.2

No ☐ Please proceed to Question 2

1.2. At how many drinking water treatment works does your

company currently employ AOPs?

…………………………….

For each works employing an AOP, please complete the following table. This table can be

copied/duplicated multiple times if required.

1.3. Description of currently used AOP process (please copy and paste this table as many times as

required)

1.3.1. Please describe the AOP. Ozone/Hydrogen peroxide ☐

UV/Hydrogen peroxide ☒

Ozone/UV/Hydrogen peroxide ☐

Titanium dioxide/UV ☐

Other ☐ Please describe below

………………………………

1.3.2. Please describe the main treatment

objective(s) of the AOP (e.g.

metaldehyde, other pesticides).

Metaldehyde, clopyralid and general pesticides

……………………………….

1.3.3. Please describe the main driver for

the selection of this AOP (e.g.

achieving the treatment objective,

cost, reducing DBP formation).

At the time only company with process guarantee for

metaldehyde was offering UV /H2O2

……………………………….

1.3.4. Is this installation a permanent or

trial installation?

Trial/Pilot plant ☐

Permanent ☒

1.3.5. When was this system installed?

……March 2015…………. (month/year)

1.3.6. What are the typical dose rate(s) or

dose range(s) for the AOP?

works to 0.6 log reduction metaldehyde

1.3.7. What is the flow rate?

up to 20 mld……….

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1.3.8. Please describe the characteristics

of the water at this works.

Hardwater ☒

Softwater ☐

Groundwater ☐

Upland surface water ☐

Lowland surface water ☒


………………………………

1.3.9. Please describe the typical summer

and winter water quality

characteristics of this water (as

measured at, or as close as possible)

to the inlet of the AOP.

Summer:

pH 7.6

Alkalinity: 160 .mg/l CaCO3

Turbidity: …………0.1… ……NTU

Bromide: …………150 ………μg/l Br-

TOC: ………………4.0……………...mg/l

UVT: …………………87…………%

or

UV254abs:…………………………cm-1

Winter

pH

Alkalinity: …………155…………mg/l CaCO3

Turbidity: …………0.1…………….NTU

Bromide: …………177…………….μg/l Br-

TOC: ………………5.2……………mg/l

UVT: ………………86……………….%

or

UV254abs:………………………….cm-1

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1.3.10. Please identify the DBPs you are

encountering in the final water at this

works and approximate

concentration ranges.

1.3.11. Have you noticed periods of

increase or decrease in DBPs (e.g.

seasonal)?

1.3.12. Please describe what measures, if

any, are being used to control these

DBPs.

1.3.13. Do you have a procedure in place

for responding to elevated

concentrations of DBPs? (What is

considered elevated?)

1.3.14. Which methods are used to

identify/analyse the DBP?

1.3.15. Was an analysis performed to

identify potential DBPs prior to

installation of the AOP?

1.3.16. Have concentrations of DBPs

changed since installation?

Some brominated THM

……………………………….……………………………….

.

Seasonal with water temperature.

……………………………….……………………………….

Roughing GAC regeneration to aid precursor removal

……………………………….……………………………….

Yes when total THM approaches 50µg/l….

……………………………….……………………………….

……………………………….……………………………….

Standard laboratory method, tried multisensor online with no

success……………………………….……………………………….

Site is new and designed from day 1 with AOP…………….

……………………………….……………………………….

Yes lower due to change in GAC regeneration frequency.

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

2. Future Use/Anticipated Use of Advanced Oxidation Processes (AOPs)

For each AOP that may potentially be used in the future, please complete the following table. This table

can be copied/duplicated multiple times if required.

2.1. Please tick, as appropriate, any of the following trials if

your company is undertaking such research using AOPs.

Bench-scale ☒

Laboratory-scale ☐

2.2. If you ticked either option in question 2.1, please describe

the AOPs you are currently investigating.

Ozone/Hydrogen peroxide ☒

UV/Hydrogen peroxide ☐



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………………………………

2.3. Do you anticipate installing AOPs at your drinking water

treatment works within the next five years?

Yes ☐ Please proceed to Question 2.3.1

No ☒ Please proceed to Question 2.4

2.3.1. Please describe which AOPs you expect to install and

the rationale behind that choice of AOP.

Ozone/Hydrogen peroxide ☐





………………………………

Rationale for choice

………………………………


treatment works within the next ten years?

Yes ☒ Please proceed to Question 2.4.1




Ozone/Hydrogen peroxide ☒





………………………………


reuse of existing ozone plant……

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3. Ozonation by-products:

WTW Name**

Volume

output

(MLD)

Water

Source *

Reason for O3 use.

(pesticide removal,

disinfection)

O3 Dose

(mg/l)

Does the

works have

GAC? (Y/N)

Are DBP monitored?

(Exclude Bromate and THM).

Which and concentration (µg/L)

Other comments

Site 1 45 L Pesticide removal 1.0 Y No Ozone split pre plant/post filters

Site 2 30 L Pesticide removal Y No Ozone split pre plant/post filters








Site 10 24 L Pesticide removal 1.2 Y No Post membrane ozone only



* G – ground; U – upland; L – lowland.

** Either site name or Site 1, Site 2, etc.

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Thank you for your time in completing this questionnaire. If you have any additional information that

you would like to share, or wish to elaborate on any responses to these questions further, please

enter this information in comment box below.

4. Additional comments

Sites 3,4, 5 and 10 are direct abstraction others are reservoir sites

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B2 Company 2




Yes ☐ Please proceed to Question 1.2

No ☒ Please proceed to Question 2

1.2. At how many drinking water treatment works does your

company currently employ AOPs?

………………none…………….




required)

1.3.1. Please describe the AOP. Ozone/Hydrogen peroxide ☐





………………………………

1.3.2. Please describe the main treatment

objective(s) of the AOP (e.g. metaldehyde,

other pesticides).

……………………………….

1.3.3. Please describe the main driver for the

selection of this AOP (e.g. achieving the

treatment objective, cost, reducing DBP

formation).

……………………………….

1.3.4. Is this installation a permanent or trial

installation?

Trial/Pilot plant ☐

Permanent ☐

1.3.5. When was this system installed?

………………………………. (month/year)

1.3.6. What are the typical dose rate(s) or dose

range(s) for the AOP?

……………………………….

1.3.7. What is the flow rate?

……………………………….

1.3.8. Please describe the characteristics of the

water at this works.

Hardwater ☐

Softwater ☐

Groundwater ☐

Upland surface water ☐

Lowland surface water ☐


………………………………

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1.3.9. Please describe the typical summer and

winter water quality characteristics of this

water (as measured at, or as close as

possible) to the inlet of the AOP.

Summer:

pH

Alkalinity: ………………………..mg/l CaCO3

Turbidity: …………………………NTU

Bromide: …………………………μg/l Br-

TOC: ……………………………...mg/l

UVT: ………………………………%

or

UV254abs:…………………………cm-1

Winter

pH

Alkalinity: …………………………mg/l CaCO3

Turbidity: ………………………….NTU

Bromide: ………………………….μg/l Br-

TOC: ………………………………mg/l

UVT: ……………………………….%

or

UV254abs:………………………….cm-1

1.3.10. Please identify the DBPs you are

encountering in the final water at this works

and approximate concentration ranges.

1.3.11. Have you noticed periods of increase or

decrease in DBPs (e.g. seasonal)?

1.3.12. Please describe what measures, if any,

are being used to control these DBPs.

1.3.13. Do you have a procedure in place for

responding to elevated concentrations of

DBPs? (What is considered elevated?)

1.3.14. Which methods are used to

identify/analyse the DBP?

1.3.15. Was an analysis performed to identify

potential DBPs prior to installation of the

AOP?

1.3.16. Have concentrations of DBPs changed

since installation?

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

……………………………….……………………………….

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2.1. Please tick, as appropriate, any of the following trials if

your company is undertaking such research using AOPs.

Bench-scale ☐

Laboratory-scale ☐

2.2. If you ticked either option in question 2.1, please describe

the AOPs you are currently investigating.






………………………………


treatment works within the next five years?


No ☒ Please proceed to Question 2.4








………………………………


………………………………


treatment works within the next ten years?



Don’t know








………………………………


………………………………

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WTW Name**

Volume

output

(MLD)

Water

Source *

Reason for O3 use.

(pesticide removal,

disinfection)

O3 Dose

(mg/l)

Does the

works have

GAC? (Y/N)

Are DBP monitored?



Other comments

Site 1 45 Lowland

river pesticide

Main

ozone Run

to residual

of 0.1mg/l

y Chlorate primarily due to

hypochlorite use Pre and main ozone

Site 2 68

Lowland

River or v

small

reservoir

pesticide

Run to

residual of

0.1mg/l

y N Main ozone prior to GAC

Site 3 22 Lowland

reservoir pesticide

Run to

residual of

0.1mg/l


Site 4 22 Lowland

reservoir pesticide

Run to

residual of

0.1mg/l




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Thank you for your time in completing this questionnaire. If you have any additional information that

you would like to share, or wish to elaborate on any responses to these questions further, please

enter this information in comment box below.


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B3 Company 3




Yes ☐ Please proceed to Question 1.2

1.2. At how many drinking water treatment works does

your company currently employ AOPs?

1




required)

1.3.1. Please describe the AOP. Hydrogen peroxide/UV (pre GAC)

c5.0mg/l of H2O2, 450-650mj/cm2 UV dose.

1.3.2. Please describe the main treatment objective(s) of

the AOP (e.g. metaldehyde, other pesticides).

Other pesticides & Geosmin/MIB.

1.3.3. Please describe the main driver for the selection

of this AOP (e.g. achieving the treatment

objective, cost, reducing DBP formation).

Uncertainty at the time over metaldehyde risk,

more absolute barrier (in combination with GAC)

to general pesticide risk from horticultural

catchment.

Secondary benefit that it would potentially

address seasonal geosmin/MIB events in the

raw water (generally related to algal blooms).

1.3.4. Is this installation a permanent or trial

installation?

Permanent

1.3.5. When was this system installed? July 2012

1.3.6. What are the typical dose rate(s) or dose range(s)

for the AOP?

450-650mj/cm2, 5.0mg/l H2O2

1.3.7. What is the flow rate? c5.5 - 12MLD

1.3.8. Please describe the characteristics of the water at

this works.

Softwater

Lowland surface water

Eutrophic reservoir source with horticultural

catchment

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1.3.9. Please describe the typical summer and winter

water quality characteristics of this water (as

measured at, or as close as possible) to the inlet

of the AOP.

All available sample results from 01/01/2012 to

date used to calculate average concentrations:

[*Filtered water (immediately prior to AOP)

++ Raw Water]

Average concentrations Summer (April –

September inclusive):

*pH – 6.14

*Turbidity – <current laboratory LOD (0.22NTU)

*Bromate – 1.84ug/l

++Bromide – 151.3ug/l

*TOC – 1.84mg/l

*UV Transmittance at 254nm – 94.45%

Average concentrations Winter (October – March

inclusive):

*pH – 6.52

*Turbidity – <current laboratory LOD (0.22NTU)

*Bromate – 1.78ug/l

++Bromide – 129.43ug/l

*TOC – 2.02mg/l

*UV Transmittance at 254nm – 94.58%

1.3.10. Please identify the DBPs you are encountering

in the final water at this works and approximate

concentration ranges.

All available sample results since the AOP was

commissioned in July 2012 reviewed:

Bromate – All results below laboratory LOD

HAAs:

Bromochloroacetic Acid (BCA) – zero to 2.4ug/l

Bromodichloroacetic Acid (MBA) – zero to 0.7ug/l

Dalapon – zero to 0.2ug/l

Dibromoacetic Acid (DBA) – zero to 4.7ug/l

Dibromochloroacetic Acid – zero to 1.5ug/l

Dichloroacetic Acid – zero to 2.7ug/l

Monobromoacetic Acid (MBA) – zero to 0.5ug/l

Monochloroacetic Acid – zero to 1.0ug/l

Tribromoacetic Acid – zero to 2.2ug/l

Trichloroacetic Acid – zero to 1.0ug/l

Total HAAs – zero to 13.3

THMs:

Bromodichloromethane – 0.1 to 37.3ug/l

Dibromochloromethane – 0.1 to 27.7ug/l

Tribromomethane – 0.1 to 36.1ug/l

Trichloromethane – 0.2 to 9.3ug/l

Total THMs – 0.9 to 77.4ug/l

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1.3.11. Have you noticed periods of increase or

decrease in DBPs (e.g. seasonal)?

Yes.

Higher concentrations are evident during the

summer. Decreases in DBP concentrations are

observed following GAC regeneration.

1.3.12. Please describe what measures, if any, are

being used to control these DBPs.

Process optimisation to remove DBP precursors

and reduce the formation potential in final water.

Management of water age within distribution

network.

1.3.13. Do you have a procedure in place for

responding to elevated concentrations of DBPs?

(What is considered elevated?)

The Company’s internal action limit for THMs is

75 ug/l (individual result), action plan for all

zones where average is >50ug/l.

1.3.14. Which methods are used to identify/analyse the

DBP?

GCMS (by head space)

1.3.15. Was an analysis performed to identify potential

DBPs prior to installation of the AOP?

Yes, genotoxicity testing with KWR, DBP

formation (system mimic method) undertaken

with Trojen (HAA and THM). Post installation /

stabilisation of GAC further DBPFP testing

undertaken for TTHMs (max formation potential

method).

Bromate and biological stability testing

undertaken as part of pilot work.

Plus we have an ongoing operational monitoring

programme.

1.3.16. Have concentrations of DBPs changed since

installation?

Yes, generally reduced/no significant increase in

bromate.

Note: The AOP was commissioned in

conjunction with a GAC process stage (minimum

20 min EBCT). Reduction is associated with

GAC process. All data we have suggested no

significant impact of AOP operated in the manner

we do (low pressure, relatively low peroxide

dose) and with good quality/low DOC water prior

to application of AOP. I expect different results in

different operating conditions. The PhD by Bram

Martijn provides an interesting insight into by-

product formation at the PWNT sites (but this is a

chlorine free environment).

Average final water sample results reviewed for

four years prior to, and four years post

commissioning.

Pre commissioning (July 2008 to June 2012

inclusive):

Bromate – All results below LOD (0.6ug/l at time)

Total HAAs – 3.79ug/l

Total THMs – 45.3ug/l

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Post commissioning (July 2012 to June 2016

inclusive):

Bromate – All results below LOD (2.4ug/l at time)

Total HAAs – 3.36ug/l

Total THMs – 32.6ug/l




2.1. Please tick, as appropriate, any of the following

trials if your company is undertaking such research

using AOPs.

None currently but we have a good

understanding from previous pilot work and full

scale experience what to expect.

2.2. If you ticked either option in question 2.1, please

describe the AOPs you are currently investigating.






………………………………

2.3. Do you anticipate installing AOPs at your drinking

water treatment works within the next five years?

No ☐ Please proceed to Question 2.4

2.3.1. Please describe which AOPs you expect to install

and the rationale behind that choice of AOP.






………………………………


………………………………

2.4. Do you anticipate installing AOPs at your drinking

water treatment works within the next ten years?


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2.4.1. Please describe which AOPs you expect to install

and the rationale behind that choice of AOP.



Possible emergence of harder to treat pesticides

may lead to wider application of AOP

Rationale for choice:

Experience, confidence, disinfection and AOP,

relative cost provided you have good pre-

treatment to provide suitable quality of water into

the AOP reactor and some downstream

remediation in the form of GAC.


WTW Name**

Volume

output

(MLD)

Water

Source *

Reason for O3 use.

(pesticide removal,

disinfection)

O3 Dose

(mg/l)

Does the

works have

GAC? (Y/N)

Are DBP monitored?



Other comments



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Thank you for your time in completing this questionnaire. If you have any additional information that you

would like to share, or wish to elaborate on any responses to these questions further, please enter this

information in comment box below.


An investigation into the impact of UV/H2O2 advanced oxidation and subsequent GAC treatment on disinfection

byproduct (DBP) formation potential in two of Company 3’s drinking water treatment works was completed by

Trojan technologies in 2013. Specifically, six samples were collected from the Site1 treatment works and six

samples from a pilot system operating at the Site2 treatment works. The samples were sent to Trojan

Technologies’ lab in London, Canada, where the DBP formation tests were performed. Chlorine incubation was

performed on each of the samples plus two blank samples to provide a 0.5 ppm free chlorine residual after a four

day hold time. Each of the samples was then analyzed in triplicate for haloacetic acid compounds and

trihalomethane compounds.

In general, the results indicated that UV/H2O2 treatment does not increase THMs, while subsequent GAC

treatment provides a slight decrease. For HAAs it’s not quite as clear. For the Site1 samples a significant

decrease in HAAs after UV/H2O2 was observed primarily due to monochloroacetic acid (MCAA) reduction.

Significant reductions were also observed after GAC treatment. For the Site2 samples, an increase in HAAs was

observed following UV/H2O2 due to both MCAA and dichloroacetic acid (DCAA). Again, carbon reduced the levels

to below the pre-UV levels. The post GAC samples were all collect at half the full scale EBCT to understand a

worst case scenario if we choose to apply this technology with limited downstream GAC.

SITE1

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I don’t send the Site2 pilot plant data as I feel the GAC at this site was not fully biological due to the intermittent

operation of the pilot plant at this time.

A study of genotoxicity was also performed with KWR on the Site1 pilot facility. The summary of this research

was that there was a mild genotoxic effect observed in water throughout the treatment train. This did not improve

or worsen across the AOP/GAC at pilot scale.

Company3 performed DBPFP tests looking at THMs. This showed no significant change in TTHM values post

AOP (<<5%) and moderate reduction post GAC (c25%).

Sampling Point Total THMFP (µg/l) DOC (mg/l)

Site1 – Filtered (pre AOP) 119,23 2

Site1 - GAC Inlet (Post AOP peroxide/UV) 118,67 1,8

Site1 - GAC No.1 Mid Bed 85,63 1,2

SITE1

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B4 Company 4 (Ozone only)

WTW Name** Volume output

(MLD) Water Source *

Reason for O3 use.

(pesticide removal,

disinfection)

O3 Dose

(mg/l)

Does the

works have

GAC? (Y/N)

Are DBP monitored?

(Exclude Bromate

and THM). Which

and concentration

(µg/L)

Other comments

Site 1 (Pre and

Inter) 125 Lowland river Disinfection/Pesticide 1.5 / 0.1 -

None (Other than

THM / Bromate)

Site 2 (Pre and

Inter) 80 – 100 Lowland river Disinfection/Pesticide 1.5 / 0.1 -

Site 3 (Pre and


Do not use inter

dosing point

during summer

months.

Site 4 (Pre and




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WTW Name**

Volume

output

(MLD)

Water

Source *

Reason for O3 use.

(pesticide removal,

disinfection)

O3 Dose

(mg/l)

Does the

works have

GAC? (Y/N)

Are DBP monitored?


Which and concentration

(µg/L)

Other comments

Site 1 35-45 ML/d L Pesticide removal 100 Y No See additional comments

below

Site 2 45-65 ML/d L/GW Pesticide removal 100 Y No See additional comments

below



Currently no sampling is undertaken for additional DBPs. A proposal is being drawn up to implement additional sampling at the relevant sites.

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WTW Name**

Volume

output

(MLD)

Water

Source *

Reason for O3 use.

(pesticide removal,

disinfection)

O3 Dose

(mg/l)

Does the

works have

GAC? (Y/N)

Are DBP monitored?



(µg/L)

Other comments

Site 1 650 L pesticide 1.5 Y No Pre and Main Ozone

Site 2 600 L pesticide 1.5 Y No Main



All the above are SSF works

Site 5 50 L pesticide 1.5 Y No Pre


Site 7 80 L pesticide 1.5 Y No Pre and Main Ozone & SSF

Site 8 70 L pesticide 1.5 Y No Pre




All Works output flows are approximate, given daily output is subject to variation.

It should be noted that ozone has benefits to water quality other than pesticide removal, such as colour, taste and odour, algal toxins, bacteria, virus and

protozoan disinfection, increase in biodegradability of organics in water, improvements in particle capture on filters and GAC adsorbers, improvement of

coagulation process etc.

Ozone is not currently combined with UV or H2O2 (which is widely taken to be the definition of an AOP).

The first four works on the list have SSF and no chemical coagulation. The bottom 5 have chemical coagulation.

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WTW Name**

Volume

output

(MLD)

Water

Source *

Reason for O3 use.

(pesticide removal,

disinfection)

O3 Dose

(mg/l)

Does the

works have

GAC? (Y/N)

Are DBP monitored?



(µg/L)

Other comments

Site 1

Max 46

Av 25

Min 8

U

To breakdown

organics for

subsequent removal

by GAC

103mg/l

on 181l/s

flow

Y HAAs – mean 52 ug/l

Works investment for front end

Coagulation, Clarification &

DAF. Due on line 2018. Ozone

will be decommissioned &

removed from site

Site 2

Max 0.24

MLD

Av 0.15MLD

U

To breakdown

organics for

subsequent removal

by GAC

14.5mg/l Y HAAs – mean 58 ug/l Aerators in final water tank as

additional reduction in THM.



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© WRc plc 2018 165

Appendix C Inclusion and exclusion criteria used in the literature review

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© WRc plc 2018 166

Table C.1 Inclusion and exclusion criteria applied to the selection of relevant papers for the each AOP

Inclusions Exclusions

In Any Field In Title

Name of the AOP: Ozone AND Hydrogen Peroxide Ultraviolet AND Hydrogen Peroxide Ultraviolet AND Ozone and Hydrogen Peroxide etc.

Wastewater OR Waste water

Chemical Compound of the AOP: O3 AND H2O2 UV AND H2O2 UV AND O3 AND H2O2 etc.

Retracted

Words:

AOP OR Advanced Oxidation

Bacteria NOT by product NOT by-product NOT byproduct

Words:

By product OR by-product OR byproduct

Cryptosporidium NOT by product NOT by-product NOT byproduct

Words:

Disinfection by product OR Disinfection by-product OR Disinfection byproduct OR DBP

E. coli NOT by product NOT by-product NOT byproduct

In Keywords

Wastewater OR Waste water NOT by product NOT by-product NOT byproduct

Bacteria NOT by product NOT by-product NOT byproduct

Cryptosporidium NOT by product NOT by-product NOT byproduct

E. coli NOT by product NOT by-product NOT byproduct

In Any Field

Solar

Pathogen

Leachate

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© WRc plc 2018 167

Inclusions Exclusions

Patent

Waste Management

Petroleum

Pulp

Textile

Activated sludge

Pulse

Fouling

Atomic layer deposition

Food

Air pollution

Vegetable

Solid waste

Implant

Hospital

Membrane filtration NOT by product NOT by-product NOT byproduct

Microwave NOT by product NOT by-product NOT byproduct

Plasma NOT by product NOT by-product NOT byproduct

Clinical NOT by product NOT by-product NOT byproduct

Virus NOT by product NOT by-product NOT byproduct

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© WRc plc 2018 168

Table C.2 List of words used for the exclusion of irrelevant papers for ozonation

Exclusions words

Alga X

Atmosphere

Troposphere

Stratosphere

Sun X

Solar X

Air pollution X

Journal - Vet

Journal - plant

Fouling X

Membrane

Biological X

Cryptosporidium X

E. coli X

Iron or ferrous X

Swimming pool

Ballast water

Potable reuse

Electrolysis

Seawater

‘X’: Word is present in title or keywords

DWI


© WRc plc 2018 169

Appendix D Search strings and outcomes of searches, for formation of DBPs

D1 Ultraviolet and hydrogen peroxide

Table D.1 Search string for formation of DBPs from UV / H2O2 using Scopus

Information

source

Scopus

Date accessed 15th May 2017

Search terms (("AOP" OR "Advanced Oxid*" OR "Advanced Treatme*") OR (("Hydrogen peroxide"

OR "H2O2" OR "Hydrogen dioxide" OR CASREGNUMBER(7722-84-1)) AND (UV

OR ultraviolet))) AND (react* OR form* OR produc* OR level* OR occur* OR

generat*) AND (water OR drink* OR treat* OR WTW) AND (DBP OR disinfect* OR

"by-product*" OR "byproduct*" OR "by product*") AND PUBYEAR > 1989 AND

(LIMIT-TO (LANGUAGE,"English"))

Number of

records

retrieved

14716

Specific

exclusions

applied to

search

Date restriction: 1990 to present (PUBYEAR > 1989)

Language restriction: English-language only (LIMIT-TO (LANGUAGE, "English"))

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© WRc plc 2018 170

Table D.2 Summary of numbers of papers identified, excluded and assessed (UV /

H2O2)

Total number of articles 14716

Steps Inclusions Exclusions

1 Articles that contained “UV” or “Ultraviolet”

in any field

4741 Articles that contained

neither “UV” or “Ultraviolet”

in any field

9975

2 Articles that contained “H2O2” or “Hydrogen

peroxide” in any field


neither “H2O2” or

“Hydrogen peroxide” in any

field

3089

3 Articles that contained “Advanced oxidation”

or “AOP” in any field


neither “Advanced

oxidation” or “AOP” in any

field

957

4 Articles that contained “byproduct” or “by-

product” or “by product” in any field


neither “byproduct” or “by-

product” or “by product” in

any field

514

4.1 Articles in step 4 that contained “disinfection

byproduct” or “disinfection by-product” or

“disinfection by product” in any field

Articles in step 4 that contained “formation”

54 Articles in step 4 that

contained neither

“disinfection byproduct” or

“disinfection by-product” or

“disinfection by product” in

any field

127

4.2 Articles in step 4 that contained “formation” 103 Articles in step 4 that did

not contain “formation”

78

5 Combination of 4.1 and 4.2 excluding

duplicated results

92 Combination of 4.1 and 4.2

excluding duplicated

results

89

6 Articles included by reading abstracts 25 Articles excluded by

reading abstracts

67

Final

list

Total articles Included 25 Total articles Excluded 14691

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© WRc plc 2018 171

D2 Ozone and hydrogen peroxide

Table D.3 Search string for formation of DBPs from hydrogen peroxide and ozone

treatment using Scopus

Information

source

Scopus


Search terms ((“AOP” OR “Advanced Oxid*” OR “Advanced Treatme*”) OR (“Hydrogen peroxide”

OR “H2O2” OR “Hydrogen dioxide” OR CASREGNUMBER(7722-84-1)) AND

(“Ozone” OR “O3” OR “Triatomic oxygen” OR CASREGNUMBER(10028-15-6)))

AND (react* OR form* OR produc* OR level* OR occur* OR generat*) AND (water

OR drink* OR treat* OR WTW) AND (DBP OR disinfect* OR "by-product*" OR

"byproduct*" OR "by product*") AND PUBYEAR > 1989 AND (LIMIT-TO

(LANGUAGE,"English"))

Number of

records

retrieved

8150

Specific

exclusions

applied to

search


Language 0restriction: English-language only (LIMIT-TO (LANGUAGE, "English"))

Table D.4 Search string for formation of DBPs from hydrogen peroxide and ozone

treatment using Science Direct

Information

source

Science Direct

Date accessed 11th

May 2017

Search terms ((“AOP” OR “Advanced Oxid*” OR “Advanced Treatme*”) OR (“Hydrogen peroxide”

OR “H2O2” OR “Hydrogen dioxide”) AND (“Ozone” OR “O3” OR “Triatomic

oxygen”)) AND (react* OR form* OR produc* OR level* OR occur* OR generat*)

AND (water OR drink* OR treat* OR WTW) AND (DBP OR disinfect* OR "by-

product" OR "byproduct" OR "by product")

Number of

records

retrieved

5079

Specific

exclusions

Date restriction: 1990 to present

DWI


© WRc plc 2018 172

Information

source

Science Direct

applied to

search

Table D.5 Summary of numbers of papers identified, excluded and assessed (O3 /

H2O2)



1 Articles that contained “O3” or

“Ozone” and “H2O2” or “Hydrogen


882 Articles that contained:

“O3” or “Ozone” but not

“H2O2” or “Hydrogen

peroxide”


peroxide” but not “O3” or

“Ozone”

in any field

12804

2 Articles that contained “Advanced

oxidation” or “AOP” in any field


neither “Advanced


field

526

2.1 Articles in step 2 that contained

“formation” in any field

23 Articles in step 2 that did

not contain “formation” in

any field

333




“disinfection by product” or “DBP” in

any field


not contain “disinfection

byproduct” or “disinfection

by-product” or “disinfection

by product” or “DBP” in any

field

340


duplicated results

23 Duplicated articles after

combination of 2.1 and 2.2

16

4 Remaining articles after exclusion 18 Articles excluded based on

list of words in Table D.20

5


reading abstracts

6

Final list Total articles Included 12 Total articles Excluded 13674

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© WRc plc 2018 173

D3 Ozone and Ultraviolet

Table D.6 Search string for formation of DBPs from ozone and UV treatment using

Scopus

Information

source

Scopus


Search terms ((“AOP” OR “Advanced Oxid*” OR “Advanced Treatme*”) OR ((“Ozone” OR “O3”

OR “Triatomic oxygen” OR CASREGNUMBER(10028-15-6))) AND (UV OR

ultraviolet)) AND (react* OR form* OR produc* OR level* OR occur* OR generat*)


product*" OR "byproduct*" OR "by product*") AND PUBYEAR > 1989 AND (LIMIT-

TO (LANGUAGE,"English"))

Number of

records

retrieved

11968

Specific

exclusions

applied to

search



Table D.7 Summary of numbers of papers identified, excluded and assessed

(O3 / UV)



1 Articles that contained “UV” or

“Ultraviolet” in any field



in any field

7056

2 Articles that contained “O3” or

“Ozone” in any field



in any field

3292

3 Articles that contained “AOP” or

“Advanced oxidation” in any field


“AOP” or “Advanced

oxidation” in any field

1202

4 Articles that contained “byproduct” or

“by-product” or “by product” in any

field




any field

179

DWI


© WRc plc 2018 174






“disinfection by product” in any field


contained neither



“disinfection by product” in

any field

78


“formation”



48


duplicated results



25

6 Remaining articles after exclusion 54 Articles excluded based on

list of words in Table D.20

11


reading abstracts

44


D4 Ozone and Ultraviolet and hydrogen peroxide

Table D.8 Search string for formation of DBPs from hydrogen peroxide and onzone

and UV treatment using Scopus

Information

source

Scopus


Search terms (("AOP" OR "Advanced Oxid*" OR "Advanced Treatme*") OR (("Hydrogen peroxide"

OR "H2O2" OR "Hydrogen dioxide" OR CASREGNUMBER(7722-84-1)) AND

(“Ozone” OR “O3” OR “Triatomic oxygen” OR CASREGNUMBER(10028-15-6))

AND (UV OR ultraviolet))) AND (react* OR form* OR produc* OR level* OR occur*

OR generat*) AND (water OR drink* OR treat* OR WTW) AND (DBP OR disinfect*

OR "by-product*" OR "byproduct*" OR "by product*") AND PUBYEAR > 1989 AND

(LIMIT-TO (LANGUAGE,"English"))

Number of

records

retrieved

11438

Specific

exclusions

applied to



DWI


© WRc plc 2018 175

Information

source

Scopus

search


(UV / H2O2)




“UV” or “Ultraviolet” in

any field


neither “UV” or


6565


“O3” or “Ozone” in any

field


neither “UV” or


2608





neither “H2O2” or

“Hydrogen peroxide” in

any field

1860


“Advanced oxidation” or

“AOP” in any field


neither “Advanced

oxidation” or “AOP” in

any field

173


“byproduct” or “by-

product” or “by product”

in any field


neither “byproduct” or

“by-product” or “by

product” in any field

179

5.1 Articles in step 5 that

contained “disinfection

byproduct” or

“disinfection by-product”

or “disinfection by

product” or “DBP” in

any field


contained neither

“disinfection byproduct”

or “disinfection by-

product” or “disinfection

by product” or “DBP” in

any field

39

5.2 Articles in step 5 that

contained “formation”



24

6 Combination of 5.1 and

5.2 excluding

duplicated results


combination of 5.1 and

5.2 and articles that

1

DWI


© WRc plc 2018 176



contained “Wastewater”

or “waste water” in title

or keywords*

7 Articles included by

reading abstracts

5 Articles excluded by

reading abstracts

37


D5 Ultraviolet and hypochlorous acid

Table D.10 Search string for formation of DBPs from UV and hypochlorous acid

using Scopus

Information

source

Scopus


Search terms (("AOP" OR "Advanced Oxid*" OR "Advanced Treatme*") OR ((UV OR ultraviolet)

AND (“Hypochlorous acid” OR “OCl” OR CASREGNUMBER(7790-92-3)))) AND

(react* OR form* OR produc* OR level* OR occur* OR generat*) AND (water OR

drink* OR treat* OR WTW) AND (DBP OR disinfect* OR "by-product*" OR



Number of

records

retrieved

10270

Specific

exclusions

applied to

search



DWI


© WRc plc 2018 177


(UV / HOCl)







in any field

1614

2 Articles that contained “Hypochlorous

acid” or “Chlorine” or “HOCl” or “ClO”

or “HClO” or “Cl” in any field


neither “Hypochlorous acid”

or “HClO” or “ClO” in any

field

8282




neither “Advanced oxidation”


268


“by-product” or “by product” in any field




any field

51


“disinfection byproduct” or “disinfection

by-product” or “disinfection by product”

or “DBP” in any field


contained neither



“disinfection by product” or

“DBP” in any field

23


“Formation” in any field

33 Articles in step 4 that did not

contain “Formation” in any

field

22


duplicated results



25

6 Articles that did not contain

“wastewater” or “waste water” in title or

keywords


“wastewater” or “waste

water” in title or keywords

2

7 Articles included by reading abstracts 7 Articles excluded by reading

abstracts

31

Final list Total Inclusions 7 Total Exclusions 10263

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© WRc plc 2018 178

D6 Ultraviolet and persulphate

Table D.12 Search string for formation of DBPs from UV and persulphate using

Scopus

Information

source

Scopus


Search terms (("AOP" OR "Advanced Oxid*" OR "Advanced Treatme*") OR ((UV OR ultraviolet)

AND (Persulphate OR Persulfate OR “*S2O8”))) AND (react* OR form* OR produc*

OR level* OR occur* OR generat*) AND (water OR drink* OR treat* OR WTW) AND

(DBP OR disinfect* OR "by-product*" OR "byproduct*" OR "by product*") AND

PUBYEAR > 1989 AND (LIMIT-TO (LANGUAGE,"English"))

Number of

records

retrieved

10048

Specific

exclusions

applied to

search




(UV / S2O8)






“UV” or “Ultraviolet” in any

field

6825

2 Articles that contained “Persulphate” or

“Persulfate” or “S2O8” in any field


neither “Persulphate” or

“Persulfate” or “S2O8”in any

field

3086




neither “Advanced oxidation”


83


“formation”

17 Articles in step 3 that did not

contain “formation”

37

DWI


© WRc plc 2018 179




“byproduct” or “by-product” or “by

product”


contained neither

“byproduct” or “by-product”

or “by product”

34

3.2.1 Articles in step 3.2 that contained

“disinfection” or “DBP”

3 Articles in step 3.2 that

contained neither

“disinfection” or “DBP” in

any field

17

4 Combination of 3.1 and 3.2 and 3.2.1

excluding duplicated results



and 3.2.1

10

5 Articles included by reading abstracts 6 Articles excluded by reading

abstracts

24


D7 Ultraviolet and titanium dioxide

Table D.14 Search string for formation of DBPs from UV and titanium dioxide

treatment using Scopus

Information

source

Scopus


Search terms (("AOP" OR "Advanced Oxid*" OR "Advanced Treatme*") OR ((“Titanium dioxide”

OR “TiO2” OR “Titanium oxide” OR CASREGNUMBER(13463-67-7)) AND (UV OR

ultraviolet))) AND (react* OR form* OR produc* OR level* OR occur* OR generat*)


product*" OR "byproduct*" OR "by product*") AND PUBYEAR > 1989 AND (LIMIT-

TO (LANGUAGE,"English"))

Number of

records

retrieved

16484

Specific

exclusions

applied to

search



DWI


© WRc plc 2018 180


(UV / TiO2)







in any field

10134

2 Articles that contained “Titanium

dioxide” or “TiO2” in any field

2527 Articles that contain neither

“Titanium dioxide” or “TiO2”

in any field

5937




neither “Advanced


field

2281


“by-product” or “by product” in any

field




any field

189


“disinfection” or “DBP” in any field


not contain “disinfection” or

“DBP” in any field

41


“formation” in any field


not contain “formation” in

any field

30


duplicated results



11


“wastewater” “or “waste water” in title

or keywords


“wastewater” or “waste

water” in title or keywords

3


reading abstracts

24


DWI


© WRc plc 2018 181

D8 Ultraviolet and titanium dioxide and hydrogen peroxide

Table D.16 Search string for formation of DBPs from UV, titanium dioxide and

hydrogen peroxide treatment using Scopus

Information

source

Scopus


Search terms (("AOP" OR "Advanced Oxid*" OR "Advanced Treatme*") OR (“Titanium dioxide”

OR “TiO2” OR “Titanium oxide” OR CASREGNUMBER(13463-67-7)) AND (UV OR

ultraviolet) AND (“Hydrogen peroxide” OR “H2O2” OR “Hydrogen dioxide” OR

CASREGNUMBER(7722-84-1))) AND (react* OR form* OR produc* OR level* OR

occur* OR generat*) AND (water OR drink* OR treat* OR WTW) AND (DBP OR

disinfect* OR "by-product*" OR "byproduct*" OR "by product*") AND PUBYEAR >

1989 AND (LIMIT-TO (LANGUAGE,"English"))

Number of

records

retrieved

6202

Specific

exclusions

applied to

search




(UV / TiO2 / H2O2)



1 Articles that contained “UV” or “Ultraviolet” in any field

2776 Articles that contained neither “UV” or “Ultraviolet” in any field

3426

2 Articles that contained “Titanium dioxide” or “TiO2” in any field

776 Articles that contain neither “Titanium dioxide” or “TiO2” in any field

2000

3 Articles that contained “Hydrogen peroxide” or “H2O2” in any field

235 Articles that contain neither “Hydrogen peroxide” or “H2O2” in any field

541

4 Articles that contained “Advanced oxidation” or “AOP” in any field

84 Articles that contained neither “Advanced oxidation” or “AOP” in any field

151

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© WRc plc 2018 182



4.1 Articles in step 4 that contained “formation” in any field

18 Articles in step 4 that did not contain “formation” in any field

66

4.2 Articles in step 4 that contained “byproduct” or “by-product” or “by product” in any field

19 Articles in step 4 that contained neither “byproduct” or “by-product” or “by product” in any field

65

4.2.1 Articles in step 4.2 that contained “disinfection” or “DBP” in any field

3 Articles in step 4.2 that did not contain “disinfection” or “DBP” in any field

16

5 Combination of 4.1 and 4.2 and 4.2.1 excluding duplicated results

24 Duplicated articles after combination of 4.1 and 4.2 and 4.2.1

16

6 Articles that did not contain “wastewater” or “waste water” in title or keywords

22 Articles that contained “wastewater” or “waste water” in title or keywords

2

7 Articles included by reading abstracts

4 Articles excluded by reading abstracts

20


D9 Ozone

Table D.18 Search string for formation of DBPs from ozone treatment using Scopus

Information

source

Scopus

Date accessed 10th

May 2017

Search terms (Ozone OR "O3" OR "Triatomic oxygen" OR CASREGNUMBER (10028-15-6)) AND

(react* OR form* OR produc* OR level* OR occur* OR generat*) AND (water OR

drink* OR treat* OR WTW) AND (DBP OR disinfect* OR "by-product*" OR



Number of

records

retrieved

17455

Specific

exclusions

applied to

search



DWI


© WRc plc 2018 183

Table D.19 Search string for formation of DBPs from ozone treatment using Science

Direct

Information

source

Science Direct

Date accessed 11th

May 2017

Search terms (Ozone OR "O3" OR "Triatomic oxygen") AND (react* OR form* OR produc* OR

level* OR occur* OR generat*) AND (water OR drink* OR treat* OR WTW) AND

("DBP" OR disinfect* OR "by-product" OR "byproduct" OR "by product")

Number of

records

retrieved

23887

Specific

exclusions

applied to

search

Date restriction: 1990 to present

Table D.20 Additional ‘In Any Field’ Exlusion Words

Exclusion Words

Solar

Pathogen

Leachate

Patent

Waste Management

Petroleum

Pulp

Textile

Activated sludge

Pulse

Fouling

Atomic layer deposition

Food

Air pollution

Vegetable

Solid waste

Implant

Hospital

Membrane filtration NOT by product NOT by-product NOT byproduct

Microwave NOT by product NOT by-product NOT byproduct

DWI


© WRc plc 2018 184

Exclusion Words

Plasma NOT by product NOT by-product NOT byproduct

Clinical NOT by product NOT by-product NOT byproduct

Virus NOT by product NOT by-product NOT byproduct

DWI


© WRc plc 2018 185

Appendix E Summary of reviewed literature

Table E.1 DBP formation from UV / H2O2 process

AOP Treatment

Condition/Dose

Summary of relevant water conditions

DBPs Formed by AOP process

DBP concentrations formed during AOP

treatment (µg/l)

Final DBP formed

Final DBP concentration

(µg/l)

Other details reported within the

paper Ref

H2O2 at 0, 5, 10 mg/L MP-reactor 850 mJ/cm2 LP-reactor

1140 mJ/cm2

River water pre-treated by coagulation,

microstraining and sand filtration

UVT: >80 - 74% nitrate: 8.65 - 16 mg/l

DOC: 3.36 - 4 mg/l bicarbonate: 137 -

151mg/l

Nitrite Nitrite AOC formation is enhanced in the

presence of hydrogen peroxide

63

436 - 504 (MP)

Nitrite formation using LP lamps was

negligible regardless of the hydrogen

peroxide dose. It was higher using MP

lamps in the absence of the hydrogen

peroxide.

10 - 15 (LP) In the absence of hydrogen peroxide,

AOC formation using MP lamps is twice as

high as AOC formation using LP

lamps.

UV: 3000 mJ/cm2

H2O2 10-20 mg /L

Surface raw water THM-FP 54 Blank water: THM - FP: 198, 258

2

DCAA-FP 292 Blank water: DCAA - FP: 168, 220

TCAA-FP 149 Blank water: TCAA - FP: 475, 345

UV: 500 mJ/cm2

THM-FP 238

DCAA-FP 297

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© WRc plc 2018 186

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

H2O2 10-20 mg /L

TCAA-FP 317

250 min UV irradiation H2O2: 4 - 16 mg/l

River surface water THM-FP Experiment on preoxidation by AOP,

followed by chlorination, to

investigate removal potential of DBP PRECURSORS

6

DOC: 2.03 mg/l 110% at 4 mg/l H2O2

pH: 7.6 107 - 124% at 8 mg/l H2O2

105% at 16 mg/l H2O2

UV 3000 mJ/cm2 + 13 mg/L H2O2

pH: 7.5, 7.8, Turb (FTU): 4.2, 3.1

Nitrite 0.8 mg/l Initial nitrate concentration in raw

water influences post-AOP nitrite

concentrations. Water quality for two samples provided but

it is not specified which one the results

refer to.

22

UV 1000 mJ/cm2 + 13 mg/L H2O2

Bromide: 103, 204 Nitrite 0.25 mg/l

UV 2000 mJ/cm2 + 4.2 mg/L

H2O2

Bromate: <0.2 Nitrite 1.15 mg/l

UV 1000 mJ/cm2 + 4.2 mg/L

H2O2

Nitrate: 2.3, 9.8 Nitrite 0.6 mg/l

AOC: 11, 37

Blend of surface river water (30%) and

dechlorinated municipal drinking water (70%)

TOC: 3.61 mg/l UVT: 89.9%

THM-FP initial: 42 THM-FP THM-FP, FA, AA

Considerable transformation of

NOM (reduction of aromaticity, higher

biodegrability) No relevant reduction

in DBP formation

28

LP 0.09 kWh/m3 + 10 mg/L

Formaldehyde initial: 7 Formaldehyde 52,16,14

LP 0.18 kWh/m3 +

Acetic Acid initial: 8 Acetic Acid 56,19,16

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© WRc plc 2018 187

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

10 mg/L potential Considerable increase in

biodegradable carbon content of effluent

MP 0.18 kWh/m3 + 10 mg/L

45,12,13

MP 0.54 kWh/m3 + 10 mg/L

43,19,20

UV=678 mJ/cm2 H2O2=3

mg/L

Post MF effluent (total hardness 332.9 mg/l as

CaCO3)

NDMA 0.196 THMs were the only pollutants that

couldn’t be removed by at least 98% at the optimal UV and H2O2

dose applied

62

UV=739 mJ/cm2 H2O2=3

mg/L

THM 25

UV=1845 mJ/cm2 H2O2=3

mg/L

Post RO effluent (total hardness <29 mg/l as

CaCO3)

NDMA 0.198

UV=1861 mJ/cm2 H2O2=3

mg/L

THM 34

UV=1200 mJ/cm2; H2O2=6

mg/L

No info on water quality Trichloromethane 60 - 500 Trichloromethane 49 - 410 No substantial difference in

degradation is observed between

presence and absence of H2O2

39

Tribromomethane 90 Tribromomethane 1

Dibromomethane 80 Dibromomethane 16

Bromodichloromethane 80 - 550 Bromodichloromethane

54 - 534

Tribromoacetic acid 160 Tribromoacetic acid

2

Dibromoacetic acid 190 Dibromoacetic acid

38

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© WRc plc 2018 188

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

Dichloroacetic acid 190 Dichloroacetic acid

190

bromoacetic acid 200 bromoacetic acid 200

Tricholoacetic acid 180 Tricholoacetic acid

180

H2O2 - 23 mg/l

UV - 1140 mJ/cm2

2.83 mg/l DOC; 0.092 cm-1 UV254 abs; <5 mg/l

CaCO3 alkalinity; >35 OH.

THMFP (raw) 325 THMFP 77 % reduction

(Chlorination method = Summers RS et al, JAWWA 81 (7) pp 80-

93 1996)

23

HAAFP 62% reduction

THM 75 Precursors of THMs tend to be aromatic, precursors of HAAs tend to be aliphatic.

AOPs tend to decrease aromaticity, hence greater effect

on THMFP is expected.

HAAFP (raw) 168 HAA 64

MP UV 1800 mJ/cm2

H2O2 - 1 - 4.8 mg/l

2 treated river water sources

THM Source 2: >10 THM-FP 30% - 110% Source 1: increasing THMFP with

increasing pH. The impacts of the two AOPs were similar, except at pH 6.5,

where UV/Cl increased THMFP

more than UV/H2O2.

29

Source 1, pre-chlorinated: Alkalinity 85-92 mg/l CaCO3, TOC 1.5 mg/l, UV254abs 0.02 cm-

1, turbidity 0.02-0.04, bromide 2-3 mg/l

HAA Source 2: 13 HAA-FP 20% - 110%

Haloacetonitriles 5

Haloketone No formation observed.

Chloropicrin No formation observed. Source 2: decreasing HAAFP with

increasing pH. The impacts of the two AOPs were similar, except at pH 6.5,

where UV/Cl

Source 2, NOT pre-chlorinated: Alkalinity 123

mg/l CaCO3, TOC 3.5 mg/l, UV254abs 0.04 cm-

1, turbidity 0.2 NTU, bromide 2-3 mg/l

Chlorite

Chlorate

Perchlorate

Bromate 0.1 - 2 (UV/Cl)

DWI


© WRc plc 2018 189

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

pH = 6.5, 7.5 and 8.5 increased HAAFP more than UV/H2O2.

H2O2 - 4 - 12 mg/l

Dilute humic acid in drinking water, 1.1-3.4

mg/l DOC.

THMFP 44 - 58.3 (initial)

10% - 25% FP

FP test was 20 mg/l FAC dose and 48

hours contact time. Comparison to

formation potential without treatment

35

UV - 300-1800

mJ/cm2

HAAFP 33.7 - 44.1 (initial)

No change

UV dose not stated

H2O2- 20 - 30 mg/l

COD reduction as in a pilot DPR system.

Followed by chlorination to a residual of 2-4 mg/l

DCAA 15.7 Water contained approximately 100

µg/l bromide.

37

TCAA 1.6

LP UV 800-2000

mJ/cm2 / 10

mg/l H2O2 MP UV 200-500 mJ/cm

2

/ 10 mg/l H2O2

AOPs applied to water after conventional

treatment and after conventional treatment + GAC. Mean TOC after

conventional treatment = 1.9 mg/l; after GAC = 0.9

mg/l.

THMFP Conventionally treated water: c. 90 µg/l in

spring and c. 220 µg/l in autumn.

Approximately 50% higher than without

AOP. Conventionally + GAC treated water: c. 50 µg/l in spring and c. 75 µg/l

in autumn. Approximately 100% higher than without

AOP.

Chlorination: dose sufficient chlorine to achieve residual of 0.6-1.2 mg/l after 3

days.

40

DWI


© WRc plc 2018 190

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

HAAFP Conventionally treated water:

52 µg/l on average. 34 µg/l without

AOP. Conventionally + GAC treated water: 20 µg/l on average.

14 µg/l without |AOP.

10 mg/l H2O2 /LP UV 600 mJ/cm

2

Groundwater: TOC 5.8 mg/l, UV254abs 0.23 cm-

1, Alkalinity 753 mg/l CaCO3, 623 µg/l bromide, pH 8.

Total aldehydes 26 Raw: 11.2 43

Formaldehyde 10 Raw: 6.6

Acetaldehyde 12 Raw: 2.6

Glyoxal 3 Raw: 1.5

Methylglyoxal 1 Raw: 0.5

Total carboxylic acids 70 Raw: < 10

Oxalate 40

Acetate 20

Formate 10

Bromate < 5 Raw: < 5

THMFP 390 Chlorination: 7 day. Raw: 305

HAAFP 275 Chlorination: 7 day. Raw: 348

10 mg/l H2O2 /LP UV

3000 mJ/cm

2

Total aldehydes 49 Raw: 11.2



Glyoxal 8 Raw: 1.5

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© WRc plc 2018 191

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref



Oxalate 90

Acetate 50

Formate 20

Bromate < 5 Raw: < 5



5 mg/l H2O2 / 1000 mJ/cm

2

Lake water treated in pilot plant by

coagulation/clarification/filtration. H2O2 / UV applied after filtration. Raw water: DOC 1.6 mg/l; alkalinity

83 mg/l CaCO3, hardness 99 mg/l.

THMFP 90.5 Chlorination test: apply range of chlorine dose ,

measure residuals and THMs after 5

days (targets: initial chlorine residual 1 - 2 mg/l; residual after 5

days ≥ 0.2 mg/l). Note: chlorine relied

upon to quench H2O2. No control

(without either AOP) reported.

51

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© WRc plc 2018 192

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

10 mg/l H2O2 / LP UV 585 mJ/cm

2

Filtered water from three water treatment plants, two treating river water, one treating lake water.

DOC 2.3 - 2.7 mg/l; DON 0.24 - 0.49 mg/l; bromide 21 - 139 μg/l; iodide <10 -

15 μg/l.

Haloacetamide FP (chloroacetamide + dichloroacetamide +

bromochloroacetamide +

dibromoacetamide + trichloroacetamide +

bromodichloroacetamide)

1 - 2 Chlorination: 24 h, 1 mg/l residual.

Chlorine relied upon to quench H2O2. Raw: 2.7 - 5.9 μg/l (17 - 37

nM). UV doses < 585

mJ/cm2, and H2O2

doses 2 - 50 mg/l also explored: Reducing UV dose increased formation. Optimum H2O2 dose in range

10 - 15 mg/l; formation increased at lower doses, and higher doses either had no additional

benefit or resulted in increased formation. Dichloroacetamide

was most prevalent (> 50% of total formation).

1

10 mg/l H2O2 / LP UV 585 mJ/cm

2

Filtered water from a water treatment plant

treating lake water. DOC 2.5 mg/l; DON 0.49 mg/l; bromide 21 μg/l; iodide

<1 μg/l.

DichloroacetonitrileFP 3.7 Chlorination: 24 h, 1 mg/l residual.

Chlorine relied upon to quench H2O2.

Raw: 7.4 μg/l.

Trichloroacetonitrile FP <0.1

Dichloronitromethane FP

0.12

Trichloronitromethane FP

0.31

H2O2 - 10.5 mg/l - 105.5

mg/l

Synthetic water 3 mg/l TOC

pH 8.3 20 +/- 1 C

thiosulphate quenching THMs

90.5 A comparison of 3 different inorganic H2O2 quenching

chemicals: sodium hypochlorite, sodium thiosulphite, sodium

5

hypochlorite quenching THMs

85.6

sulphite 88.6

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AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

quenching THMs sulphite with an alternative (Bovine

catalase). Standardised

conditions for AOP and chlorination to

simulate a distribution network.

thiosulphate quenching HAAs

59.1

hypochlorite quenching HAAs

58.7

sulphite quenching HAAs

56.4

thiosulphate Aldehydes

LDL

hypochlorite Aldehydes

LDL

sulphite Aldehydes

LDL

LP UV (19.5-585 mJ/cm2, 254 nm),

H2O2 (2-20 mg/l x 10 minutes), UV with

H2O2 (585 mJ/cm2, 10

mg/l).

Raw and inter-stage treated water from 3

surface water sources in China, selected for

difference in DOC and DOC:DON ratio.

Site: MH, high SUVA SUVA: 4.5L/mg.m in raw

water, 3.4L/mg.m in filtered water

DOC: 3.7mg/l in raw water, 2.3mg/l in filtered

water Site: SY, low SUVA

SUVA: 2.4L/mg.m in raw water, 1.6L/mg.m in

filtered water DOC: 6.1mg/l in raw

water, 2.7mg/l in filtered water

Site: ZQ, low SUVA SUVA: 2.6L/mg.m in raw

HAcAms (H2O2 10mg/l, followed by

chlorination)

2.7 - 5.9 Concluded that UV/H2O2 pre trt may be more effective in reducing HAcAms in low-SUVA waters. Colimated beam

apparatus for batch tests with UV and UV with H2O2. Chlorine dose calculated to quench residual

H2O2, and a residual of 1 +/- 0.5 mgCl2/l

after 24 hours, adjusted to pH 7.5.

12

HAcAms (H2O2 alone) DOM changed from high to lower molecular weight

matter

HAcAms (UV combined with H2O2)

HAcAms concentration

decreased with increased UV

dose, for a given dose of H2O2,

due to increased hydroxyl radicals and destruction of pre-cursors. At a given UV dose,

HAcAms concentration

decreased with

DWI


© WRc plc 2018 194

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

water, 1.7L/mg.m in filtered water

DOC: 5.9mg/l in raw water, 2.5mg/l in filtered

water DON: 0.62mg/l in raw

water, 0.49mg/l in filtered water

For all waters, UV irradiation alone, followed

by chlorination, had no significant effect on precursors or in the ultimate formation of

HAcAms compared to chlorination alone.

increasing H2O2 dose (0-20 mg/l), but increased at greater H2O2

doses (scavenging of

hydroxyl radicals).

UV / Clorination:

UV at 3 mg/L, H2O2

at 5 mg/L

Removal of personal care products using

UV/Chlorine and UV/Hydrogen peroxide and formation of DBPs

after chlorination. Three sources of water were tested. One of the tested water samples

was ammonia-rich. The water sources were previously treated

through coagulation, flocculation,

sedimentation and sand filtration. Reaction time with AOP: 1.5 or 3 min.

treated water was sampled and quenched with sodium sulfite and

clorinated for 24 h at 0.9 + 0.1 mg/l free chlorine

Chloral hydrate The higher radical exposure in the

UV/Chlorine AOP over UV/H2O2 AOP

likely resulted in alteration of dissolved organic matters and thus enhanced the formation potentials

of CH, HKs and TCNM but reduced

the formation potential of HANs .

On the other hand, in the ammonia rich

water, the formation potentials of THMs,

HKs and TCNM were slightly higher and the formation potentials

of CH and HANs were lower during the

32

Haloketone

trichloronitromethane

Haloacetonitriles

Halonitromethane

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© WRc plc 2018 195

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

residual. sub-sequent post-chlorination with

UV/chlorine AOP than with UV/H2O2 AOP.

Meuse: H2O2 at 10 mg/L; UV

dose at 550 mJ/cm2;

GAC treatment at flow of 5 L/h Ohio river: H2O2 at

10mg/L; UV dose at 400

mJ/cm2; GAC at flow

of 57 L/h Comparison study: H2O2 at 10mg/L;

Different UV reactors of MP, LP and

DBD

Studied genotoxic activity of 3 surface waters

before and after treatment with UV/H2O2 and after subsequent GAC, for MP and LP

lamps. To detect gene mutations, the Ames II

assay and for a complementary assay

detecting chromosomal damage, the Comet assay in HepG2 liver cells were used. No

genotoxic activity was observed after UV/H2O2 in the Comet assay and

in the Ames II TAMix strain with and without S9

under all applied conditions. An increase in genotoxic activity in the

Ames II TA98 strain both with and without S9 was measured in three tested

waters after MP UV/H2O2. After LP and

DBD UV/H2O2 a lower or no increase was

observed in genotoxic activity. GAC post

treatment effectively reduced the formed genotoxic activity to

Genotoxity Reduced level with the use of

GAC

64

DWI


© WRc plc 2018 196

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

control levels for all but one study and to below

the level of the pre-treated water in the other study; no health risks are

expected as long as UV/H2O2 is followed by

GAC adsorption.

23mg/l H2O2

1140mJ/cm2 UV

2.83mg/l DOC; 0.092cm-1 UV254abs; <5mg/l

CaCO3 alkalinity: >35 OH.

THMFP (raw) 325 THMFP 77 (Chlorination method = Summers RS et al, JAWWA 81 (7) pp 80-

93 1996) % Mineralisation of TOC: UV < O3 <

H2O2/O3 < UV/H2O2 < UV/O3

(3:6:10:23:31) % reduction in

THMFP: UV < O3 < H2O2/O3 < UV/O3 <

UV/H2O2 (15:69:70:75:77) % reduction in

HAAFP: UV < O3 < H2O2/O3 < UV/O3 <

UV/H2O2 (0:8:31:52:62)

Precursors of THMs tend to be aromatic, precursors of HAAs tend to be aliphatic.



23

HAAFP (raw) 168 HAAFP 62

No specified Artificial raw water Identified DBPs: - - High mutagenicity 47

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© WRc plc 2018 197

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

doses; Lamp

specifications: MP lamp,

3 kW, irradiation path=19.5

mm

[NOM]=2.5 mg C/l [NO3-]=10.4 mg/l

4-nitrophenol - observed, but it could not be related to any

N-DBP group; 81 DBPs were formed

in total, but only 14 identified; Relative

concentrations detected expressed in

the paper as ng/L ISTD eq;

4-nitrocatechol -

4-nitro-1,3-benzendiol -

2-nitrohydroquinone -

2-hydroxy-5-nitrobenzoic acid

-


High concentration' (unspecified)


-

2,4-Dinitrophenol -

5-Nitrovanillin -

4-Nitrobenzene-sulfonic acid

-

4-Nitrophtalic acid High concentration' (unspecified)

2-Methoxy-4,6-dinitrophenol

High concentration' (unspecified)

3,5-Dinitrosalicylic acid High concentration' (unspecified)

Dinoterb High concentration' (unspecified)

DWI


© WRc plc 2018 198

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

UV: 500 - 2000

mJ/cm^2 H2O2: 1 - 5

mg/l Treatment followed by coagulation-filtration, in some cases

pre-ozonation)

Upper and lower-bound parameters of waters

tested Turbidity: 0.96-6.59 NTU

DOC: 2.78-7.70 mg/L UV_254: 0.0548-0.206

cm^-1 Alkalinity: 87-250 mg/l as

CaCO3 Hardness: N/A-227 mg/l

as CaCO3 Iron: N/A-0.58 mg/l

Manganese: N/A-2.1 mg/l

THM-FP ~70 - ~670 UV/H2O2 + does not reduce DOC and

SUVA significantly more than

conventional treatment alone

UV/H2O2 + conv treat, generate

significantly more THM-FP than conventional

treatment alone (in one instance 203%

more)

50

UV: 0 - 150 mJ/cm^-2 H2O2: 0 - 10 mg/l

Ultrapure water with addition of:

TOC: 2.8 mg/l Ca: 29.1 mg/l CO3: 90 mg/l pH: 6.3, 8.3

Nitrate 0.02 mg N/l (pH: 8.3, H2O2 dosed)

0.018 mg N/l (pH: 8.3, H2O2 not dosed) 0.02 mg N/l (150

mJ/cm^-2, H2O2 not dosed)

0.06 mg N/l (150 mJ/cm^-2, H2O2

dosed)

- - Slightly more nitrite formed with 10 mg/l H2O2 than 5 mg/l. About 25% more

nitrite formed at pH 8.3 than at pH 6.5.

4

LP UV lamp (laboratory

scale). 18.5 g L-1

H2O2 Ozone 2.2

gO3/h

pH 7.0. Water type not stated, but assume

distilled or de-ionised water.

8.9 mmol L-1 p-arsanic acid treated.

Aniline *by product of p-arsanic acid

is removed after 30 min irrad.

Degradation of PPA was pseudo first

order kinetic reaction with linear

relationship ln (c/co) as a function of time.

Rate constants of decomposition were calculated, UV/O3 >

O3 > UV/H2O2 > H2O2 > UV.

Decomposition of p-arsanilic acid (PPA),

44

Acetic acid 70

Propanoic acid 20

Oxalic acid

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© WRc plc 2018 199

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

kinetics and by-products.

68 mg/l H2O2 / LP

UV 48,000 - 186,000 mJ/cm

2

Solution of l-glutamic acid at 7.5 mg/l (= 3 mg/l

DOC).

DCAAFP 60 Chlorination: 4 h, 35

oC. Untreated = 0

μg/l

8

TCAAFP 27 Chlorination: 4 h, 35

oC. Untreated = 0

μg/l


oC. Untreated = 6

μg/l


oC. Untreated = 51

μg/l


oC. Untreated =

374 μg/l


oC. Untreated =

188 μg/l

5 mg/l H2O2 / LP/MP UV 500 mJ/cm2

Effluent of sand filtration unit at drinking water

works. Quality: Br = 49.7 mg/l;

hardness = 111 mgCaCO3/l; TOC 1.51

mg/l; UV254abs = 0.035 cm

-1

THMFP THMFP 65 - 66 Chlorination: 24 h, 1 mg/l residual.

Untreated = 47 μg/l

41

10 mg/l H2O2 /

LP/MP UV 1000

mJ/cm2

THMFP THMFP 92 - 97


HAAFP HAAFP 39 - 45 Chlorination: 24 h, 1 mg/l residual.


10 mg/l H2O2 /

LP/MP UV

HAAFP HAAFP 48

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© WRc plc 2018 200

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

1000 mJ/cm2


THMFP THMFP 39 Chlorination: 24 h, 1 mg/l residual.


10 mg/l H2O2 /

LP/MP UV 1000

mJ/cm2

THMFP THMFP 49 - 53


HAAFP HAAFP 24 - 30

10 mg/l H2O2 /

LP/MP UV 1000

mJ/cm2

HAAFP HAAFP 23 - 30

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© WRc plc 2018 201

Table E.2 DBP formation from O3 / H2O2

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

O3:H2O2 molar ratio = 4:1 and 2:1

No Info THMFP 90% initial Concentration

9

O3:H2O2 molar ratio = 1:1 and 1:2

100% initial Concentration

H2O2 - 23 mg/l / O3 - 4

mg/l



THMFP 98 Raw water THMFP = 325 μg/l

23

HAAFP 116 Raw water HAAFP = 168 μg/l

(Chlorination method = Summers RS et al, JAWWA 81 (7) pp 80-93 1996). Precursors of THMs tend to be

aromatic, precursors of HAAs tend to be

aliphatic. AOPs tend to decrease

aromaticity, hence greater effect on

THMFP is expected.

H2O2 - 1-7 mg/l / O3 - 2-14 mg/l


mg/l DOC.

THMFP 20 - 31 FP test was 20 mg/l FAC dose and 48

hours contact time. Untreated THMFP =

44 -58.3 μg/l

35

HAAFP 21 - 25 FP test was 20 mg/l FAC dose and 48

hours contact time. Untreated HAAFP =

33.7 -44.1 μg/l

DWI


© WRc plc 2018 202

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

0.2 mg/l H2O2 / 2 mg/l O3

Lake water treated in pilot plant by

coagulation/clarification/filtration. H2O2 / O3

applied either to raw water or to clarified

water. Raw water: DOC 1.6 mg/l; alkalinity 83

mg/l CaCO3, hardness 99 mg/l.

THMFP 27.2 Chlorination test: apply range of chlorine dose ,

measure residuals and THMs after 5

days (targets: initial chlorine residual 1 - 2 mg/l; residual after 5

days ≥ 0.2 mg/l). Note: chlorine relied

upon to quench H2O2. No control

(without either AOP) reported.

51

0.34 mg H2O2/mg O3 (0.5 M/M).

2 and 4 mg/l O3.

Three types of raw water from Switzerland. All prefiltered (0.45um), buffered to pH 7 or 8.

Water spiked with bromide (to achieve 50 ug/l) and MTBE (176 ug/l). Temp 5 to 20 C.

pH7

Principle aim to investigate

degradation of MTBE by ozone and OH

radicals. Sub-aim, to compare formation of

bromate from ozonation with ozone combined with H2O2.

Concluded that,

compared to ozonation, H2O2 reduced bromate

formation but did not eliminate it: a

combination of reaction of bromide

with molecular ozone and hydroxyl radicals.

H2O2 reduces hypobromous acid

(HOBr) limiting formation of bromate.

33

low alkalinity & low DOC Bromate 8.8

high alkalinity & high DOC

Bromate 12.5

high alkalinity & low DOC Bromate 5.6

DWI


© WRc plc 2018 203

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

Solutions of 8.9 mmol L-1 p-arsanic

acid treated. LP UV lamp (laboratory scale). 18.5 g L-1 H2O2 dosed at 5

min intervals to batch reactor.

Ozone 2.2 gO3h-1.



Aniline Degradation of PPA was pseudo first




O3 > UV/H2O2 > H2O2 > UV.

Decomposition of p-arsanilic acid (PPA),

kinetics and by-products.

Intermediates included nitrophenol,

azobenzenes and phenylazophenol

44

Nitrobenzene

0-1.5 gO3/g TOC; 0.5 O3:H2O2

molar ratio; ozonation time 60(?)

0-1.5 gO3/g TOC; 0.5 O3:H2O2

molar ratio; ozonation

Wastewater with residual chlorobenzene: pH=9.4;

TOC=1150mg/l; COD=3920 mg/L

Synthetic solution: pH=8.4; TOC=250mg/l;

COD=792 mg/L Wastewater with residual chlorobenzene: pH=9.4;

TOC=1150mg/l; COD=3920 mg/L

Chlorobenzene ~ 80-100% Chlorebenzene

removal (ozonation time

30)

Better removal by O3/H2O2 compared

to O3 alone Low reduction in TOC

and COD indicate only incomplete

mineralisation to CO2 (Lists 4 possible Chlorobenzene

removal %'s, have chosen the 2 that

53

DWI


© WRc plc 2018 204

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

time 30(?) Synthetic solution: pH=8.4; TOC=250mg/l;

COD=792 mg/L

Better removal by O3/H2O2 compared to O3 alone Low reduction

in TOC and COD indicate only incomplete

mineralisation to CO2

best relate to the info above, assuming the

stated ozonation time)

23mg/l H2O2

4mg/l O3



THMFP 325 (Chlorination method = Summers RS et al, JAWWA 81 (7) pp 80-



(3:6:10:23:31) % reduction in




UV/H2O2 (0:8:31:52:62)



23

HAAFP 168

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© WRc plc 2018 205

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref


Unspecified Unspecified Bromate varying the chemical ratio of O3 to H2O2 is

effective at minimizing bromate

formation. In addition, research has

demonstrated that bromate formation is

reduced by approximately 20

percent at a slightly acidic pH (~6.5),

when compared to the ambient pH.

59

Tertiary-butyl formate

Tertiary-butyl alcohol

Acetone

Aldehydes

Glyoxal

Isopropyl alcohol

O3: 0.8 - 4.4 mg/l

H2O2: 0.02 - 0.25 mg/l Treatment followed by coagulation-filtration, in some cases

pre-ozonation

Upper and lower-bound parameters of waters

tested Turbidity: 0.96-6.59 NTU

DOC: 2.78-7.70 mg/L UV_254: 0.0548-0.206

cm^-1 Alkalinity: 87-250 mg/l as

CaCO3 Hardness: N/A-227 mg/l

as CaCO3 Iron: N/A-0.58 mg/l

Manganese: N/A-2.1 mg/l

THM-FP ~30 - ~320 O3/H2O2 + conven treatment does not reduce DOC and

SUVA significantly more than

conventional treatment alone

O3/H2O2 + conven treatment reduces

THM-FP significantly compared to conventional

treatment alone

50

DWI


© WRc plc 2018 206

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

H2O2: 8.8 mg/l

O3: 2.4 mg/l

Reported parameters for three samples:

DOC:2.2 mg/l;Br-:~250 µg/l; pH:7.8 + 1.5µg/l of 7

herbicides

DOC: 2.2 mg/l;Br-:~125 µg/l; pH:7.4

DOC: 0.8 mg/l;Br-:~70 µg/l; pH:5.5

Bromate 5 Study on herbicides removal efficacy

52

DWI


© WRc plc 2018 207

Table E.3 DBP formation from O3 / UV

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

O3 - 4 mg/l UV - 1140 mJ/cm2



Raw water THMFP 325 THMFP THM-FP % reduction 75

(Chlorination method = Summers RS et al, JAWWA 81 (7) pp 80-

93 1996)

23

HAAFP HAA-FP % reduction 52

Raw water HAAFP 168 THM 81 Precursors of THMs tend to be aromatic, precursors of HAAs tend to be aliphatic.



HAA 81

O3 - 2 - 12 mg/l

UV - 300-1800

mJ/cm2


mg/l DOC.

THMFP 44 - 58.3 (initial)

80% - 65% FP

FP test was 20 mg/l FAC dose and 48

hours contact time. Comparison to

formation potential without treatment

35

HAAFP 33.7 - 44.1 (initial)

55% - 70% FP

UV -270 mJ/cm2, O3

- 8 mg/l

Raw water quality: TOC 1.8 mg/l, alkalinity 3.7 mg/l CaCO3, pH 6.6,

UV254abs 0.074 cm-1.

THM 140 THMFP From 140 to 275

Chlorination: 10 - 20 mg/l residual for 8

days.

38

HAA 160 HAAFP From 160 to 364

UV - 810 mJ/cm2, O3

- 26 mg/l

THM 50 THMFP from 50 to 275

HAA 90 HAAFP From 90 to 340

2.9 mg/l O3 / LP UV 600

mJ/cm2


1, Alkalinity 753 mg/l CaCO3, 623 µg/l




DWI


© WRc plc 2018 208

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

bromide, pH 8. Glyoxal 28 Raw: 1.5



Oxalate 260

Acetate 220

Formate 60

Bromate 51 Raw: < 5



2.9 mg/l O3 / LP UV 3000

mJ/cm2




Glyoxal 10 Raw: 1.5



Oxalate 220

Acetate 170

Formate 60

Bromate 35 Raw: < 5



DWI


© WRc plc 2018 209

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

H2O2 - 10.5 mg/l - 105.5

mg/l


pH 8.3 20 +/- 1 C




sulphite with an alternative (Bovine




5


85.6

sulphite quenching THMs

88.6


59.1


58.7


56.4


LDL


LDL

sulphite Aldehydes

LDL


scale). 18.5 g L-1

H2O2 Ozone 2.2

gO3/h



8.9 mmol L-1 p-arsanic acid treated.


is removed after 30 min irrad.

Degradation of PPA was pseudo first




O3 > UV/H2O2 > H2O2 > UV.

Decomposition of p-

44

Acetic acid 70

Propanoic acid 20

Oxalic acid

DWI


© WRc plc 2018 210

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

arsanilic acid (PPA), kinetics and by-

products.

1140mJ/cm2 UV

4mg/l O3



THMFP (raw) 325 THMFP 75 (Chlorination method = Summers RS et al, JAWWA 81 (7) pp 80-



(3:6:10:23:31) % reduction in




UV/H2O2 (0:8:31:52:62)




23

HAAFP (raw) 168 HAAFP 52

UV=193/200/205

O3=0.085 mg/l

Pure and Raw reservoir water

Bromate 25 (in pure water) 43

nitrate=10 mg/l;

bromine=100 μg/l

DWI


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Table E.4 DBP formation from O3 / UV / H2O2

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

2.9 mg/l O3 10 mg/l H2O2

LP UV 600 mJ/cm2


1, Alkalinity 753 mg/l CaCO3, 623 µg/l bromide, pH 8.




Glyoxal 11 Raw: 1.5



Oxalate 190

Acetate 190

Formate 60

Bromate 31 Raw: < 5



2.9 mg/l O3 10 mg/l H2O2

LP UV 3000 mJ/cm

2




Glyoxal 22 Raw: 1.5



Oxalate 190

Acetate 250

DWI


© WRc plc 2018 212

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

Formate 70

Bromate 23 Raw: < 5



H2O2 - 10.5 mg/l - 105.5

mg/l


pH 8.3 20 +/- 1 C




sulphite with an alternative (Bovine




5


85.6

sulphite quenching THMs

88.6


59.1


58.7


56.4


LDL


LDL

sulphite Aldehydes

LDL

O3: 190mg/h UV: 15W H2O2: 20mg/l

Solution: humic acid 20mg/l, pH ranging 4 -

8.5

~80% UV_254 removal; 17% TOC

removal ~90% UV_254

removal; >30% TOC removal

Study on NOM (humic acid) removal

54

DWI


© WRc plc 2018 213

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

efficiency for the four processes

Acidic pH shows slightly favourable for

Humic acid degradation

6, 10, 15 W

(UV) 60, 118, 190 mg/h (O3) 5, 10, 20,

40, 80 mg/l (H2O2)

Humic acid concentration: 20 mg/l

pH: 4, 5.5, 7, 8.5 UVT: 89.3%

Trihalomethane - - - The results showed that after

UV/O3/H2O2 treatment, the

molecular weight of humic acid and

unsaturated bonds decreased while

small molecules of aldehydes, ketones

and acids increased. The chemical

structure of the humic acids changed a lot after the advanced oxidation process (UV/O3/H2O2). Especially the

unsaturated C=C decreased

considerably, whereas, the C=O

and C-O increased a lot.

Hydroxyl radicals can further oxidize HA

into acids and esters.

54

Haloacetic acids

Ketones

Aldehydes

DWI


© WRc plc 2018 214

Table E.5 DBP formation from UV / Cl2

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

LPUV= 5400 mJ/cm2 /

Cl=9.8 mg/L

Synthetic water with increased polyamine

conc (10 mg/l) and pH=7

trichloronitromethane 3.08 TCNM formation resulted slightly

higher under low pH TCNM formation

potential according to precursor tested

follows trend MA>DMA>polyamine

11

LPUV= 5400 mJ/cm2 /

Cl=4.2 mg/L

0.83

LP 3020 mJ/cm2 / Cl

12.5 µM

Drinking water from WTPs spiked with iohexol

dichloroiodomethane 67.5 Experiment of pH influence also carried

out

30

LP 3020 mJ/cm2 / Cl

12.5 µM

chlorodiiodomethane 18.4

LP 3020 mJ/cm2 / Cl

12.5 µM

iodoform 18

LP 3020 mJ/cm2 / Cl

200 µM

dichloroiodomethane 10.5

LP 3020 mJ/cm2 / Cl

200 µM

chlorodiiodomethane 5.7

LP 3020 mJ/cm2 / Cl

200 µM

iodoform 3.6

LP 890 mJ/cm2 / Cl

- 200 µM

Unspecified, supposedly synthetic solution with

10µM trimethoprim

Comparison of chlorination and

UV/Cl for degradation of TMP and

investigation of by-

31

pH=6.1 Chloroform > 5

Chloral hydrate > 4

DWI


© WRc plc 2018 215

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

Dichloroacetonitrile > 0.5 products formation

Trichloronitromethane > 0

pH=8.8 Chloroform > 22

Chloral hydrate > 5

Dichloroacetonitrile > 0.9

Trichloronitromethane > 0

LP UV 3900 mJ/cm2 / Cl - 0 - 50 mg/l

Pre-chlorinated river water (78 mg/l Ca; 138 mg/l CaCO3 alkalinity;

2.6 mg/l TOC; UV254abs 0.045 cm-1; turbidity < 0.5 NTU). pH = 6, 7.5

and 9.

THM 14 With no UV: TTHM = 14 μg/l, HAA5 = 17

μg/l, HAA9 = 27 μg/l, TOX = 97 μg/l

No mineralisation of TOC evident, but UV254abs was

reduced (33% by UV alone; with 5-50 mg/l FAC: 80-90% at pH6, 65-80% at pH7.5, 60-75% at pH9) by the AOP reducing the aromaticity of the organic matter.

27

HAA5 37

HAA9 42

TOX 56

MP UV 1800 mJ/cm2 / Cl = 2-10 mg/l

Source 1, treated river water, pre-chlorinated: Alkalinity 85-92 mg/l

CaCO3, TOC 1.5 mg/l, UV254abs 0.02 cm-1,

turbidity 0.02-0.04, bromide 2-3 mg/l. pH =

6.5, 7.5 and 8.5

THM 14 - 17 THM-FP 45 - 52 THM without AOP: 18 μg/l. THMFP without

AOP: 30 - 40 μg/l THMFP increased with increasing pH.

29

HAA 10 - 15 HAA-FP 40 - 90 HAA without AOP: 10 - 15 μg/l. HAAFP

without AOP: 30 - 40 μg/l

Haloacetonitriles 1.5 - 4 HANFP 6 - 13 HAN without AOP: 1 μg/l. HANFP without

AOP: 3 - 4 μg/l

DWI


© WRc plc 2018 216

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref


Chloropicrin No formation observed.

Chlorite > 99% pre-existing chlorite removed

Chlorate Up to 17% by mass of the chlorine consumed in the UV/Cl AOP was converted to chlorate.

Perchlorate Pre-existing concentration unchanged

Bromate 0.1 - 2 (UV/Cl)

Source 2, treated lake water, NOT pre-

chlorinated: Alkalinity 123 mg/l CaCO3, TOC 3.5

mg/l, UV254abs 0.04 cm-1, turbidity 0.2 NTU,

bromide 2-3 mg/l. pH = 6.5, 7.5 and 8.5

THM 5 - 10 THMFP 100 - 120 THM without AOP: 3 μg/l. THMFP without

AOP: 50 - 85 μg/l

HAA 4 - 15 HAAFP 65 - 135 HAA without AOP: < 1 μg/l. HAAFP without

AOP: 50 - 70 μg/l HAAFP decreasing with increasing pH. The impacts of the

two AOPs were similar, except at pH

6.5, where UV/Cl increased HAAFP

more than UV/H2O2.

Haloacetonitriles 1.5 - 5 HANFP 4 - 28 HAN without AOP: 0 μg/l. HANFP without

AOP: 2 - 8 μg/l


DWI


© WRc plc 2018 217

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

Chloropicrin No formation observed.

UV ? mJ/cm2 / Cl = 3 mg/L

Removal of personal care products using

UV/Chlorine and UV/Hydrogen peroxide and formation of DBPs

after chlorination. Three sources of water were tested. One of the tested water samples

was ammonia-rich. The water sources were previously treated

through coagulation, flocculation,

sedimentation and sand filtration. Reaction time with AOP: 1.5 or 3 min.

treated water was sampled and quenched with sodium sulfite and

clorinated for 24 h at 0.9 + 0.1 mg/l free chlorine

residual.

Chloral hydrate The higher radical exposure in the

UV/Chlorine AOP over UV/H2O2 AOP

likely resulted in alteration of dissolved organic matters and thus enhanced the formation potentials

of CH, HKs and TCNM but reduced

the formation potential of HANs .

On the other hand, in the ammonia rich

water, the formation potentials of THMs,

HKs and TCNM were slightly higher and the formation potentials

of CH and HANs were lower during the

sub-sequent post-chlorination with

UV/chlorine AOP than with UV/H2O2 AOP.

32

Haloketone


Haloacetonitriles

Halonitromethane

Unspecified p-chlorobenzoic acid (pCBA)

pCBA is an intermediate product

during the chlorination of

pesticides. High reactivity with

hydroxyl radicals (,OHpCBAk = 5·109

M-1s-1). Pseudo first-order reaction

58

DWI


© WRc plc 2018 218

AOP Treatment

Condition/Dose




treatment (µg/l)

Final DBP formed


(µg/l)


paper Ref

behaviour for pCBA reacting with OH

radicals using the UV chlorine process.

DWI


© WRc plc 2018 219

Table E.6 DBPs formation from UV / S2O8

AOP Treatment Condition/Dose



DBP concentrations formed during AOP treatment

(µg/l)

Final DBP

formed


(µg/l)

Other details reported within the paper

Ref

UV ? mJ/cm2 / S208(2-) = 10

mM

Synthetic water Bromate (BrO3-) The performance of UV/S2O8(2─) was

investigated on a synthetic water. In addition, a model

was developed and an attempt was made to fit the model to the experimental

results of bromate formation. It was stated that

UV/S2O8(2─) has no significant tendency to form

BrO3(─) in presence of Br(─) and natural organic matter.

66

LP UV: 12kW (no further info)

S2O8 = 5 - 10mM

50 mL solutions with: 0.02 mM p-aminobenzoi

acid (approx) different concentrations

of NO3 CO3 Cl PO4 and NOM per sample

Degradation efficiency of p-aminobenzoi acid by

UV/Fe/persulfate Even low concentrations of carbonate and sulfat

considerably slowed kinetics (possible

reactions proposed) Very high efficiency

reported for UV/Fe/S2O8 on p-aminobenzoic acid

48

DWI


© WRc plc 2018 220




DBP concentrations formed during AOP treatment

(µg/l)

Final DBP

formed


(µg/l)


Ref

UV ? Mj/cm2 / PAS = 100 uM

TOC: 2.25 mg/l Br: 200 ug/l

pH: 7.5 T: 20 C

Bromoform (TBM) 7 Actually used CuFe2O4 catalyst rather than UV but by-

products should still be applicable

6

Dibromoacetic acid 2

Monobromoacetic acid 2

Dibromoacetonitrile 2

Bromochloroacetonitrile 4

Dibromochloromethane 7

DWI


© WRc plc 2018 221

Table E.7 DBP formation from UV / TiO2





treatment (µg/l)


Ref

UV = 7000mJ/cm2 THM 24

100 mg/L TiO2 (5 kWh) Raw 1 - CAP canal (0.046 cm^-1

UV_254)

150 µg TTHM/l

400 mg/L TiO2 (2 kWh) Raw 2 Cap Canal (0.049 cm^-1

UV_254)

220 µg TTHM/l

400 mg/L TiO2 (10-20 kWh)

Raw 1 Salt River (0.110 cm^-1

UV_254)

130 µg TTHM/l

400 mg/L TiO2 (20 kWh) Raw 2 Salt River (0.110 cm^-1

UV_254)

180 µg TTHM/l

400 mg/L TiO2 (10 kWh)+4 mg/l Cl

Raw 2 Cap Canal 200 µg TTHM/l

400 mg/L TiO2 (5-10 kWh)+4 mg/l Cl

Raw 2 Salt River 260 µg TTHM/l

UV = 291 W/m2 1.5 g TiO2 dissolved in

200 mL

Synthetic groundwater phenols >400 Synthetic groundwater with initial BTEX concentration of

1000 µg/L removal efficiency of petroleum aromatic

hydrocarbons

26

Xenon light 35 mJ/m^2 TiO2: 0.2, 0.85 1.5 g/l

H2O2: 50, 100, 150 mg/l

pH: 3, 6, 9 2,2-dihydroxy-4-methoxybenzophenone

300 min treatment time 34

Benzaldehyde

1,3-dihydroxybenzene

4-Methylphenol

Benzoic acid

2-Methylphenol

DWI


© WRc plc 2018 222





treatment (µg/l)


Ref

2-Hydroxybenzaldehyde

2-Methylphenyl benzoate

Benzyl alcohol

50mg/l TiO2; powder immobilised on glass

beads; unquantified UV

Injection of benzene, toluene, ethylbenzene and xylene to review

DBPs

Phenols Decomposition of BTEX compounds generates

phenols as by-products. The phenols are themselves degradable by the AOP.

10

DWI


© WRc plc 2018 223

Table E.8 DBP formation from Ozonation

AOP Treatment Condition/

Dose

Summary of relevant

water conditions


DBP concentration

s formed during AOP treatment

(µg/l)

Final DBP formed


(µg/l)

Other details reported within

the paper Ref

O3 - 4 mg/l 2.83 mg/l DOC; 0.092 cm-1 UV254 abs; <5 mg/l

CaCO3 alkalinity; >35

OH.

THMFP 101 Unozonated THMFP = 326 μg/l

23

HAAFP 155 Unozonated HAAFP = 168 μg/l

(Chlorination method =

Summers RS et al, JAWWA 81 (7) pp 80-93 1996). Precursors of

THMs tend to be aromatic,

precursors of HAAs tend to be aliphatic. AOPs

tend to decrease aromaticity, hence greater effect on

THMFP is expected.

Raw water THMFP = 325

mg/l; HAAFP = 168

mg/l.

4 mg/l Raw water quality: TOC

1.8 mg/l, alkalinity 3.7 mg/l CaCO3,

pH 6.6, UV254abs 0.074 cm

-1

THMFP 150 µg/l Chlorination: 10 - 20 mg/l residual

for 8 days. THMFP without

ozone = 275 µg/l. Increasing ozone

dose up to 24 mg/l did not result in

any further change in THMFP.

38

HAAFP 190 µg/l

DWI


© WRc plc 2018 224


Dose

Summary of relevant

water conditions


DBP concentration


(µg/l)

Final DBP formed


(µg/l)


the paper Ref

2.9 mg/l Groundwater: TOC 5.8 mg/l,

UV254abs 0.23 cm-1,

Alkalinity 753 mg/l CaCO3,

623 µg/l bromide, pH 8.




Glyoxal 29 Raw: 1.5



Oxalate 160

Acetate 100

Formate 60

Bromate 14 Raw: < 5



0.5 mg O3/ mg DOC (2.06mg/l)

River surface water

82% (18% reduction)

Experiment on preoxidation by

AOP, followed by chlorination, to

investigate removal potential

of DBP PRECURSORS

6

1 mg O3/ mg DOC (2.12mg/l)

DOC: 2.3 mg/l THM-FP 76% (24% reduction)

1.5 mg O3/ mg DOC (2.12mg/l)

pH: 7.6 68% (32% reduction)

Unspecified Bottled water Butanone 39.7 Focus of paper was

demonstration of analytical method.

45

Acetone 30.6

Formaldehyde 16.6

Acetaldehyde 15

Propanal 5.8

DWI


© WRc plc 2018 225


Dose

Summary of relevant

water conditions


DBP concentration


(µg/l)

Final DBP formed


(µg/l)


the paper Ref

Unspecified From three pairs of

treatment works, where

each pair treated same raw water but

one works used ozone

and the other didn't. DBPs reported here are those for

which the implication is that ozone increases formation potential.

1-bromo-1,1-dichloropropa

none FP

3 After chlorination of chloramination

(unspecified conditions). Haloketone.

55

1,1,3,3-tetrachloropropanone FP

1-bromo-1,3,3-

trichloropropanone FP

1,1-dibromo-3,3-

dichloropropanone FP

1,3-dibromo-1,3-

dichloropropanone FP

1,1,3-tribromo-3-

chloropropanone FP

dichloroacetaldehyde FP

10 - 16 After chlorination of chloramination

(unspecified conditions).

Haloaldehyde.

1,1,3,3-tetrabromopropanone FP

Chloropricrin FP

After chlorination of chloramination

(unspecified conditions).

Halonitromethane.

DWI


© WRc plc 2018 226


Dose

Summary of relevant

water conditions


DBP concentration


(µg/l)

Final DBP formed


(µg/l)


the paper Ref

Unspecified Known reaction

products of ozone with

NOM

Phenols 56

Aldehydes

Carboxylic acids

Aldonic acids

Keto acids

Unspecified Unspecified Chloropricrin FP

1 - 5 160 - 380% greater formation

than without ozone.

57

2 and 4 mg/l O3.

Three types of raw water from

Switzerland. All prefiltered

(0.45um), buffered to pH

7 or 8. Bromide = 50

μg/l.

Principle aim to investigate

degradation of MTBE by ozone and OH radicals.

Sub-aim, to compare

formation of bromate from ozonation with

ozone combined with H2O2.

Concluded that,

compared to ozonation, H2O2 reduced bromate formation but did not eliminate it: a combination of

reaction of bromide with

molecular ozone and hydroxyl

33

low alkalinity & low DOC

Bromate 15.1

high alkalinity & high DOC

Bromate 20.7

high alkalinity & low DOC

Bromate 12

DWI


© WRc plc 2018 227


Dose

Summary of relevant

water conditions


DBP concentration


(µg/l)

Final DBP formed


(µg/l)


the paper Ref

radicals. H2O2 reduces

hypobromous acid (HOBr) limiting

formation of bromate.


scale). 18.5 g L-1

H2O2 Ozone 2.2

gO3/h

pH 7.0. Water type not

stated, but assume

distilled or de-ionised water. 8.9 mmol L-1 p-arsanic acid

treated.


is removed after 30 min

irrad.

Degradation of PPA was pseudo first order kinetic

reaction with linear relationship

ln (c/co) as a function of time.

Rate constants of decomposition

were calculated, UV/O3 > O3 >

UV/H2O2 > H2O2 > UV.

Decomposition of p-arsanilic acid (PPA), kinetics

and by-products.

44

Acetic acid 70

Propanoic acid 20

Oxalic acid

4mg/l O3 2.83mg/l DOC; 0.092cm-1 UV254abs;

<5mg/l CaCO3 alkalinity: >35

OH.

THMFP 325000 (Chlorination method =

Summers RS et al, JAWWA 81 (7)

pp 80-93 1996) % Mineralisation of TOC: UV < O3

< H2O2/O3 < UV/H2O2 <

UV/O3 (3:6:10:23:31) % reduction in

THMFP: UV < O3

23

HAAFP 168000

DWI


© WRc plc 2018 228


Dose

Summary of relevant

water conditions


DBP concentration


(µg/l)

Final DBP formed


(µg/l)


the paper Ref

< H2O2/O3 < UV/O3 < UV/H2O2

(15:69:70:75:77) % reduction in

HAAFP: UV < O3 < H2O2/O3 <

UV/O3 < UV/H2O2

(0:8:31:52:62) Precursors of

THMs tend to be aromatic,

precursors of HAAs tend to be aliphatic. AOPs

tend to decrease aromaticity, hence greater effect on

THMFP is expected.

Ozone followed by

chloramination (unspecified conditions)

Groundwater Trihaloacetaldehydes HNM 6.9 . Additional new DBPs found:

haloquinones;halocyclopentenoic

acids;nitrosamines derived from alkaloids and nitrosamides; halonitriles.

20

Halonitrimethanes Trihalogenatacetaldehydes

w/o bio-filter 16 (site specific)

Chloroacetaldehyde

Ozone followed by biofiltration (unspecified conditions)

High-bromide source

(unspecified type)


Iodinated THMs

Chloral Hydrate

Dichloroacetaldehyde 13

Ozone Low-bromide Bromonitromethane

DWI


© WRc plc 2018 229


Dose

Summary of relevant

water conditions


DBP concentration


(µg/l)

Final DBP formed


(µg/l)


the paper Ref

(unspecified conditions)

source (unspecified

type)

Di- and Tri-halogenated halonitromethanes (HNMs)

(Hi br) 5.7, (low Br) 2.9

Dihalogenated acetaldehydes 5-12

Ozone (unspecified conditions)

16 drinking water plant influents;

Most of the plants were impacted by

algae or WWTP

effluents in their

catchments

Mean DOC: 3.3 mg/l

Mean DON: 0.29 mg/l as N

THM 4.3 - 167 (36) THMFP 57-492 (158) Filtration following ozonation has

showed high removal of

FP for trihalogenated acetaldehydes, chloropicrin and

NDMA; Ozonation tended to incread FP of trihalogenated acetaldehydes and cyanogen

halides, while tended to

reduce NDMA FP

25

Trihalogenated acetaldehydes ND - 19 (4.5) Trihalogenated

acetaldehydes FP

7.4-85 (30)

Dihalogenated acetaldehydes ND - 11 (ND) Dihalogenated

acetaldehydes FP

ND-7.1 (2.1)

Dihalogenated HANs ND - 9.9 (4) Dihalogenated HANs FP

0.9-12 (3.4)

Cyanogen halides ND - 8.4 (2.6) Cyanogen halides FP

ND-34 (11)

DWI


© WRc plc 2018 230


Dose

Summary of relevant

water conditions


DBP concentration


(µg/l)

Final DBP formed


(µg/l)


the paper Ref

Chloropicrin ND - 7.6 (0.5) Chloropicrin FP

ND-5.9 (0.9)

Dihalogenated nitromethanes ND - 2.0 (ND) Dihalogenated

nitromethanes FP

ND-3.6 (<0.1)

NDMA ND - 20 (ND) NDMA FP ND-261 (22)

Ozone (unspecified conditions)

0.6 mg/l chlorate

Bromate 60

Bromohydrins

Chloral hydrate

Chlorate 10 - 106

O3: 2 - 10 mg/l Unspecified, reference

given

Bromate No bromate formed below about 3 mg/l

dose; at higher doses,

bromate concentration (ug/l) follows regression equation:

[Br (ug/l)]=8.28*[O3 (mg/l)] - 25.9

Other potential ozone DBPs listed but not quantified

(other than statement that

approximately 4 x more carboxylic

acids than aldehydes

produced under equal conditions).

3

Aldehydes

Carboxylic acids

Ketones

Brominated THMs

Phenols

DWI


© WRc plc 2018 231


Dose

Summary of relevant

water conditions


DBP concentration


(µg/l)

Final DBP formed


(µg/l)


the paper Ref

Acetic acids

Cyanogen halides

Nitromethanes

Acetonitriles

Unspecified Three sources: Ozonated

water from one full-scale treatment

works and one pilot plant;

distilled water spiked with humic and fulvic acid

extracted from river water.

Aldehydes: Formaldehyde Acetaldehyde

Propanal Butanal

2-methyl propenal pentanal

3-methyl butanal hexanal heptanal octananl nonanal

undecanal dodecanal tridecanal

benzaldehyde

Paper reported DBPs detected

but not concentrations.

(Only DBPs confirmed by

analysis against standards are given here).

46

Ketones: acetone

2-butanone 3-methyl-2-butanone

2-pentanone 3-hexanone 2-hexanone

3-methyl cyclopentanone 6-methyl-5-hepten-2-one 6-hydroxy-2-hexanone



2-methyl propanoic acid; butanoic acid; 3-methyl butanoic acid; pentanoic acid;

hexanoic acid; heptanoic acid octanoic acid


but not

DWI


© WRc plc 2018 232


Dose

Summary of relevant

water conditions


DBP concentration


(µg/l)

Final DBP formed


(µg/l)


the paper Ref

nonanoic acid decanoic acid undecanoic acid dodecanoic acid tridecanoic acid

tetradecanoic acid pentadecanoic acid hexadecanoic acid heptadecanoic acid

octadecanoic acid phenylacetic acid benzoic acid ethanedioic acid propanedioic acid butanedioic acid tert-butyl maleic acid

pentanedioic acid hexanedioic acid heptanedioic acid octanedioic acid nonanedioic acid decanedioic acid

undecanedioic acid tridecanedioic acid phthalic acid isophthalic acid terephthalic

acid 1,2,4-benzenetricarboxylic acid 1,3,5-benzenetricarboxylic acid 1,2,4,5-

benzenetetracarboxylic acid

concentrations.

Keto-acids: 3-keto-butanoic acid

3-methyl-2-keto-butanoic acid



Nitriles: benzeneacetonitril

heptanenitrile



Di-carbonyls: glyoxal

2-ketopropanal (methylglyoxal) 2,3-butanedione (dimethlyglyoxal)

5-keto-hexanal



Halo-alkanes/alkenes: 2,3-dichlorobutane

hexachlorocyclopentadiene

Chlorinated or chloraminated at 2

- 3 mg/l, contact time not specified.

Haloaldehydes: chloroacetaldehyde

trichloroacetaldehyde (chloral hydrate)

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Dose

Summary of relevant

water conditions


DBP concentration


(µg/l)

Final DBP formed


(µg/l)


the paper Ref

dichloroacetaldehyde

Haloketones: 1,1-dichloropropanone 1,3-dichloropropanone

1,1,1-trichloropropanone 1,1,3,3-tetrabromopropanone

Haloacids: chloroacetic acid bromoacetic acid

dichloroacetic acid trichloroacetic acid

bromochloroacetic acid dibromoacetic acid

2-chloropropanoic acid 2,2-dichloropropanoic acid

Haloacetonitriles: dichloroacetonitrile

bromochloroacetonitrile dibromoacetonitrile

Haloalcohols: 2-bromoethanol

Halo-nitro-methanes: dibromonitromethane

trichloronitromethane (chloropicrin) tribromonitromethane (bromopicrin)

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Table E.9 References

1 Chu et al. (2014) 29 Wang et al. (2015) 50 Borikar et al. (2015)

2 Toor and Mohseni (2007) 30 Wang et al. (2016) 51 Jasim et al. (2012)

3 Rieder et al. (2007) 31 Wu et al. (2016) 52 Upelaar et al. (2000)

4 Sharpless et al. (2003) 32 Yang et al. (2016) 53 Cortés et al. (1996)

5 Liu et al. (2003) 33 Acero et al. (2001) 54 Mo et al. (2015)

6 Kleiser and Frimmel (2000) 34 Zúñiga-Benítez et al. (2016) 55 Krasner et al. (2006)

7 Wang et al. (2014) 35 Čehovin et al. (2017) 56 Onstad et al. (2008)

8 Bond et al. (2009) 36 Wu and Englehardt (2016) 57 Shah and Mitch (2012)

9 Frimmel et al. (2000) 37 (36 and 37 are the same paper) 58 Mehrjouei (2012)

10 Alizadeh Fard et al. (2013) 38 Chin and Bérubé (2005) 59 Kommineni et al. (2008)

11 Deng et al. (2014) 39 Jo et al. (2011b) 60 Amy et al. (2000)

12 Chu et al. (2014) 40 Metz et al. (2011) 61 Adedapo (2005)

20 Krasner (2009) 41 Dotson et al. (2010) 62 James (2013)

21 Jo et al. (2011a) 42 Zoschke et al. (2012) 63 Derks (2010)

22 Ijpelaar et al. (2002) 43 Agbaba et al. (2016) 64 Hofman-Caris and Beerendonk (2011)

23 Lamsal et al. (2011) 44 Czaplicka et al. (2015) 65 Barceló and Petrovic (2008)

24 Gerrity et al. (2009) 45 Neng and Nogueira (2010) 66 Lutze (2013)

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25 Krasner et al. (2012) 46 Richardson et al. (2000) 67 Lekkerkerker-Teunissen (2012)

26 Alizadeh Fard et al. (2013) 47 Vughs et al. (2016) 68 Agbaba et al. (2015)

27 Pisarenko et al. (2013) 48 Xue et al. (2016)

28 Sarathy et al. (2011) 49 Andrews and Huck (1994)

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Appendix F Literature Review

F1 Generic search terms

Table F.1 Generic search terms used within Scopus

Search terms

(CASREGNUMBER(xxx) OR CHEMNAME(xxx) OR CHEM(xxx))

AND

(oral OR gavage OR intuba! OR diet OR feed OR capsule) AND (“health-based guidance val!” OR “acceptable

daily intake” OR “tolerable daily intake” OR “no observed adverse effect level” OR “benchmark dose” OR “lethal

dose” OR “margin of safety” OR “margin of exposure” OR toxic! OR epidem! OR carcin! OR tumor! OR tumour! OR

reproduc! OR development! OR foetox! OR fetotox! OR genotox! OR mutagen! OR cytotoxic! OR immunotox! OR

neurotox! OR “in vitro” OR “in vivo”) AND (LIMIT-TO (LANGUAGE, "English"))

Table F.2 Generic search terms used within PubMed

Search terms

(xxx[EC/RN Number] OR xxx)

AND

(oral[All Fields] OR gavage[All Fields] OR intuba*[All Fields] OR diet[All Fields] OR feed[All Fields] OR capsule[All

Fields]) AND ("health-based guidance val*"[All Fields] OR "acceptable daily intake"[All Fields] OR "tolerable daily

intake"[All Fields] OR "no observed adverse effect level"[All Fields] OR "benchmark dose"[All Fields] OR "lethal

dose"[All Fields] OR "margin of safety"[All Fields] OR "margin of exposure"[All Fields] OR toxic[All Fields] OR

toxicolo*[All Fields] OR epidemiol*[All Fields] OR carcinog*[All Fields] OR tumor[All Fields] OR tumour[All Fields]

OR tumorogen*[All Fields] OR tumourogen![All Fields] OR reproduc*[All Fields] OR development*[All Fields] OR

foetox*[All Fields] OR fetotox*[All Fields] OR genotox*[All Fields] OR mutagen*[All Fields] OR cytotoxic*[All Fields]

OR immunotox*[All Fields] OR neurotox*[All Fields] OR "in vitro"[All Fields] OR "in vivo"[All Fields]) AND

("english"[Language])

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Table F.3 Results from literature searches in Scopus and PubMed search

Chemical Search terms - Scopus

Number

of

records

retrieved

Search terms - Pubmed

Number

of

records

retrieved

2-Hydroxy-5-

nitrobenzoic acid

(CASREGNUMBER(96-97-

9) OR CHEMNAME(“2-

Hydroxy-5-nitrobenzoic

acid”) OR CHEM(“2-


acid”))

4 (96-97-9 [EC/RN Number] OR “2-

Hydroxy-5-nitrobenzoic acid”)

0

2-Methoxy-4,6-

dinitrophenol

CASREGNUMBER(4097-

63-6) OR CHEMNAME(2-

Methoxy-4,6-dinitrophenol)

OR CHEM(2-Methoxy-4,6-

dinitrophenol))

0 (4097-63-6 [EC/RN Number] OR 2-

Methoxy-4,6-dinitrophenol)

0

2-

Nitrohydroquinone

(CASREGNUMBER(16090-


Nitrohydroquinone) OR

CHEM(2-

Nitrohydroquinone))

0 (16090-33-8 [EC/RN Number] OR

2-Nitrohydroquinone)

0

3,5-Dinitrosalicylic

acid

(CASREGNUMBER(609-

99-4) OR

CHEMNAME(“3,5-

Dinitrosalicylic acid”) OR

CHEM(“3,5-Dinitrosalicylic

acid”))

3 (609-99-4 [EC/RN Number] OR

“3,5-Dinitrosalicylic acid”)

3

4-Hydroxy-3-

nitrobenzoic acid

(CASREGNUMBER(616-

82-0) OR CHEMNAME(“4-




acid”))

0 (85-38-1 [EC/RN Number] OR “2-

Hydroxy-3-nitrobenzoic acid”)

6

4-Nitrobenzene-

sulfonic acid

(CASREGNUMBER(138-

42-1) OR CHEMNAME(“4-

Nitrobenzene-sulfonic


Nitrobenzene-sulfonic

acid”))

4 (138-42-1 [EC/RN Number] OR 4-

Nitrobenzene-sulfonic acid)

8

4-Nitrocatechol (CASREGNUMBER(3316-


Nitrocatechol) OR

CHEM(4-Nitrocatechol))

10 (3316-09-4 [EC/RN Number] OR 4-

Nitrocatechol)

1

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Chemical Search terms - Scopus

Number

of

records

retrieved

Search terms - Pubmed

Number

of

records

retrieved

4-Nitrophthalic

acid

(CASREGNUMBER(610-


Nitrophthalic acid) OR

CHEM(4-Nitrophthalic

acid))

0 (610-27-5 [EC/RN Number] OR 4-

Nitrophthalic acid)

7

5-Nitrovanillin (CASREGNUMBER(6635-


Nitrovanillin) OR CHEM(5-

Nitrovanillin))

0 (6635-20-7 [EC/RN Number] OR 5-

Nitrovanillin)

1

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Appendix G Ozone DBP Assessment

G1 Introduction

As part of this project, DBPs formed following O3 treatment alone were also identified.

Following the prioritisation process, two DBPs were categorised as being ‘high priority’ (Table

G.1) and so the toxicity of these chemicals in drinking water has been reviewed as part of this

addendum.

Table G.1 High priority DBPs formed by ozone

DBP CAS Number

1-Bromo-1,1-dichloropropanone 1751-16-2

Dichloroacetaldehyde 79-02-7

G2 Toxicity Summary

G2.1 1-Bromo-1,1-dichloropropanone

G2.1.1 Experimental toxicity data

Acute toxicity




Chronic toxicity




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G2.1.2 Alternative approached to deriving a PoD


VEGA

Based on the chemical structure, 1-bromo-1,1-dichloropropanone is predicted to be

sensitising to the skin and mutagenic whereas the the predictions for carcinogenicity and

reproductive/developmental toxicity were equivocal. However these should be treated with

caution as all of the predictions are considered to be unreliable. The results of these findings

are summarised inTable G.2.

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Table G.2 VEGA predictions for 1-bromo-1,1-dichloropropanone


Assessment

Similarity with

molecules of known

experimental value

Accuracy of

prediction for

similar molecules



Vs predicted)

Identified structural alerts

Sensitisation (CAESAR) Sensitising Not reliable

Moderate Good Agree -

Mutagenicity(CAESAR) Mutagenic Not reliable Strong Good Agree -

Mutagenicity (ISS) Non-mutagenic Not reliable

Moderate No adequate Disagree

Mutagenicity (KNN) Mutagenic Not reliablea

Strong Good Agree

Mutagenicity (SarPy) Mutagenic Not reliablea

Strong Good Agree SM93, SM106

Carcinogenicity (CAESAR) Carcinogenic Not reliablea,b

Moderate Good Some disagree -

Carcinogenicity (IRFMN/Antares) Carcinogenic Not reliablea

Moderate Not adequate Disagree Carcinogenic no: 57, 58, 59

Carcinogenicity (ISS) Non-


a Moderate Good Some disagree -

Carcinogenicity (ISSCAN-CGX) Non-


a Moderate Not optimal Disagree -


toxicity (CAESAR) Toxicant Not reliable

c,d No Good Disagree -


toxicity (PG) Non-toxicant Not reliable

e Moderate Good Disagree -

a A prominent number of atom centred fragments of the compound have not been found in the compounds of the dataset or are rare fragments (1 unknown

fragment found) b

Predicted substance falls into a network that is populated by no compounds of the dataset c 1 descriptor for this compound has values outside the descriptor range of the compounds of the dataset

d A prominent number of atom centred fragments of the compounds have not been found in the compounds of the dataset or are rare fragments (2 unknown

fragments found) e

A prominent number of atom centred fragments of the compounds have not been found in the compounds of the dataset or are rare fragments (1 infrequent fragment found).

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OECD toolbox

Using the OECD QSAR Toolbox, one NOAEL was predicted for repeated dose toxicity (Table

G.3). However, it should be noted that this prediction, whilst falling within the prediction

domain, and featuring an acceptable statistical measure of fit, is considered to be of low

reliability due to the small size of the dataset upon which it is based.


derive estimates for this endpoint.

Table G.3 OECD Toolbox predictions for 1-bromo-1,1-dichloropropanone

En

dp

oin

t

Init

ial

Pro

file

r

Su

b-c

ate

go

ris

ati

on

pro

file

s

Nu

mb

er

of

ca

teg

ory

me

mb

ers

In d

om

ain

?

R2

sta

tis

tic

Re

su

lt

Re

lia

bil

ity

NOAEL

(mice, oral

gavage,

drinking

water or diet)

Repeat dose

(HESS)

Repeat dose (HESS)

Chemical elements



TTC

1-Bromo-1,1-dichloropropanone is categorised as a Cramer Class III, using ToxTree

modelling software. Therefore, a TTC value of 1.5 µg/kg bw/day is appropriate.

G2.1.3 Selection of PoD

No experimental PoDs were available for 1-bromo-1,1-dichloropropanone. Based on the

modelled data, the following PoDs are proposed:

A NOAEL of 404 000 µg/kg bw/day derived from the OECD toolbox,




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G2.2 Dichloroacetaldehyde

G2.2.1 Experimental toxicity data

Acute toxicity



Dichloroacetaldehyde has been classified as a ‘skin irritant, category 1; H314’ and ‘eye

irritant, category 1; H318’ under European GHS (PubChem, 2017h). No information on the

study was available. No sensitisation data are available.

Chronic toxicity



Both negative and positive results for mutagenicity have been reported in vitro for

dichloroacetaldehyde.

Negative results for mutagenicity include an unscheduled DNA synthesis assay in human

epithelial-like cells at 6-6000 mMol (ChemEXPERT™, 2017), and a genetic mutation assay in

Chinese hamster (V79) cells at 0.12-1.2 mMol (Aquilina et al., 1984). Positive results for

dichloroacetaldeyhe have been reported by EPA (1995) and Fischer et al. (1977), however,

no further details on these studies are available.



G2.2.2 Alternative approached to deriving a PoD


VEGA

Based on the chemical structure, dichloroacetaldehyde is predicted to be non- sensitising to

the skin. It is also predicted to be mutagenic, with three of the four models used considered to

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be reliable. The predictions for carcinogenicity and reproductive/developmental toxicity were

equivocal and also considered to be either not optimal or not reliable. The results of these

findings are summarised in Table G.4

OECD toolbox

Using the OECD QSAR Toolbox, one LOAEL was predicted for repeated dose toxicity. This

result is presented in Table G.5. However, it should be noted that this prediction, whilst falling

within the prediction domain is considered to be of low reliability due to the small size of the

dataset upon which it is based and the measure of fit is relatively poor.



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Table G.4 VEGA predictions for dichloroacetaldehyde

Model Prediction Reliability of Assessment

Similarity with molecules of known experimental value

Accuracy of prediction for

similar molecules

Concordance for similar molecules

(experimental Vs predicted)

Identified structural alerts

Sensitisation (CAESAR) Non-

sensitising Not reliable

a Moderate Good Disagree -

Mutagenicity (CAESAR) Mutagenic Appears reliable

Strong Good Agree SA8 aliphatic halogens

Mutagenicity (ISS) Mutagenic Appears reliable

Strong Good Agree SA8 aliphatic halogens, SA11

simple aldehyde

Mutagenicity (KNN) Mutagenic Not optimal Strong Not optimal Agree -

Mutagenicity (SarPy) Mutagenic Appears reliable

Strong Good Agree SM106

Carcinogenicity (CAESAR) Non-

carcinogenic Not optimal Strong Good Disagree -

Carcinogenicity (IRFMN/Antares)

Carcinogen Not optimal Strong Not optimal Some disagree Carcinogenicity alert no: 57

Carcinogenicity(ISS) Carcinogen Appears reliable

Strong Good Agree SA8 aliphatic halogens, SA11simple aldehyde

Carcinogenicity (ISSCAN-CGX) Non

carcinogen Not reliable Strong Not adequate Disagree -

Reproductive/developmental toxicity (CAESAR)

Toxicant Not reliableb,c

No Good Disagree -

Reproductive/developmental toxicity (PG)

Non toxicant Not reliable Moderate Good Disagree -

a A prominent number of atom centred fragments of the compound have not been found in the compounds of the dataset or are rare fragments (1 unknown

fragment found) b

1 descriptor for this compound has values outside the descriptor range of the compounds of the dataset c A prominent number of atom centred fragments of the compounds have not been found in the compounds of the dataset or are rare fragments (2 infrequent

fragments found

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Table G.5 OECD Toolbox predictions for dichloroacetaldehyde E

nd

po

int

Init

ial

Pro

file

r

Su

b-c

ate

go

ris

ati

on

pro

file

s

Nu

mb

er

of

ca

teg

ory

me

mb

ers

In d

om

ain

?

R2

sta

tis

tic

Re

su

lt

Re

lia

bil

ity

LOAEL

(B6C3F1

mice, F344

rats or

Wistar rats)

Repeat dose

(HESS)

Repeat dose (HESS)

Chemical elements



TTC

Dichloroacetaldehyde is categorised as a Cramer Class III using ToxTree modelling software.

However a structural alert for genotoxic carcinogenicity (QSA8 aliphatic halogen) was


G2.3 Selection of PoD

No experimental PoDs were available for dichloroacetaldehyde. Based on the modelled data,

the following PoDs are proposed:

A LOAEL of 276 000 µg/kg bw/day derived from the OECD toolbox,




G3 Risk Assessment

G3.1 1-Bromo-1,1-dichloropropanone

G3.1.1 Hazard identification

No experimental data for 1-bromo-1,1-dichloropropanone were available, and modelled data

predictions were considered to be unreliable.

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G3.1.2 Hazard characterisation

Proposed PoDs

Based on the data obtained in Section G2.1 a NOAEL of 404 000 µg/kg bw/day has been

selected as the modelled PoD. The reliability of this value is considered to be ‘low’ due to the

limitation of the dataset so should be used with caution. Therefore the TTC approach using a

TTC value of 1.5 µg/kg bw/day will also be used in the risk assessment.


The proposed UF for use with the PoD selected is as follows:



5 for the use of a modelled NOAEL

Total UF used = 500



G3.1.3 Exposure assessment

The maximum concentration of 1-bromo-1,1-dichloropropanone measured in drinking water

was reported as <3 µg/L (Krasner et al., 2006). For the purpose of this project, a maximum

concentration of 3 µg/L will be used, however it should be noted that this value may be an

over-conservative representation of 1-bromo-1,1-dichloropropanone in typical drinking water.

Based on default factors the daily intake would be:




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G3.1.4 Risk characterisation

TDI

The maximum intake of 1-bromo-1,1-dichloropropanone via drinking water by adults, children

and infants (0.10 to 0.45 μg/kg bw/day) is less than the proposed TDI (808 μg/kg bw/day).


exposure to 1-bromo-1,1-dichloropropanone via drinking water. The TDI and hence the risk


derive the NOAEL.

TTC

The maximum intake of 1-bromo-1,1-dichloropropanone via drinking water by adults, children

and infants is less than the TTC value (1.5 µg/kg bw/day), and therefore, adverse health

effects are not anticipated.

G3.1.5 Risk communication

The MOEs for Although it is possible to calculate MOEs for 1-bromo-1,1-dichloropropanone, it

is not recommended due to the uncertainty and lack of reliability in the TDI .

G3.2 Dichloroacetaldehyde

G3.2.1 Hazard identification

Limited experimental data for dichloroacetaldehyde were available, with equivocal in vitro

mutagenic effects reported. Modelling software identified structural alerts for sensitisation and

genotoxicity.

G3.2.2 Hazard characterisation

Proposed PoDs

Based on the data obtained in Section G2.2 a LOEL of 276 000 µg/kg bw/day has been

selected as the most conservative modelled PoD. The reliability of this value is considered to

be ‘low’ due to the limitation of the dataset so should be used with caution. Therefore the TTC

approach using a TTC value of 0.0025 µg/kg bw/day will also be used in the risk assessment.

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The proposed UF for use with the PoD selected is as follows:







G3.2.3 Exposure assessment

The maximum concentration of dichloroacetaldehyde measured in drinking water was 14 µg/l

(Krasner et al., 2006). This was at a groundwater treatment works which applied ozonation

and chloramination, but did not have GAC; Krasner et al. (2006) concluded that “it should be

possible to minimise formation of haloaldehydes at ozone plants through the use of biological

filtration” (i.e. GAC). Based on default factors the daily intake would be:




G3.2.4 Risk characterisation

TDI

The maximum intake of dichloroacetaldehyde via drinking water by adults, children and

infants (0.47 to 2.1 μg/kg bw/day) is less than the proposed TDI (276 μg/kg bw/day).


exposure to dichloroacetaldehyde via drinking water. The TDI and hence the risk


derive the LOEL.

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TTC

The maximum intake of dichloroacetaldehyde in adults, children and infants exceeds the TTC

value. Therefore, additional research into the occurrence in drinking water and toxicological

properties of this DBP may be prudent.

G3.2.5 Risk communication

Although it is possible to calculate MOEs for dichloroacetaldehyde, it is not recommended due

to the uncertainty and lack of reliability in the TDI.

G4 Summary and Conclusions

A summary of the risk characterisation for the high priority DBPs is presented in Table G.6.

Analysis of the chemical structure of 1-bromo-1,1-dichloropropanone did not identify any

mutagenic structural alerts, and VEGA predictions for sensitisation, mutagenicity and

carcinogenicity were unreliable. The estimated exposure of 1-bromo-1,1-dichloropropanone in

drinking water did not exceed the proposed TDI or the TTC value, therefore, it is considered

to be of low concern to public health.

Dichloroacetaldehye was noted to have a structural alert for mutagenicity and therefore is

considered to be potentially genotoxic. Experimental in vitro data for mutagenicity is equivocal

however. When characterising dichloroacetaldehyde against the genotoxic TTC value of

0.0025 µg/kg bw/day, the estimated exposures for adults, children and infants exceeds the

threshold values. Therefore, additional research the occurrence of dichloroacetaldehyde in

drinking water and the hazard potential would be prudent.

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Table G.6 Summary of risk characterisation ozone DBPs

DBP

TDI

(µg/kg

bw/da

y)

TTC

(µg/kg

bw/day)

Estimated Daily

Intake (TDI)

Estimated Daily

Intake (TTC)

Adu

lt

Chil

d

Ad

ult

Adu

lt

Chi

ld

Infa

nt

1-Bromo-1,1-

dichloropropan

one

808 1.5 Belo

w

Belo

w

Bel

ow

Belo

w

Bel

ow

Bel

ow

Dichloroacetald

ehyde 276 0.0025

Belo

w

Belo

w

Bel

ow

Abo

ve

Ab

ove

Abo

ve

Below; estimated daily intake is below the proposed TDI/TTC value, adverse health effects are not

anticipated.

Above; estimated daily intake is above the proposed TDI/TTC value, adverse health effects cannot be

excluded.

potential for formation of disinfection by-products from

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