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Thames Water

Non-Potable Water Reuse as a

Demand Management Option for

WRMP19

Options Appraisal Report

Issue | 9 June 2017

This report takes into account the particular

instructions and requirements of our client.

It is not intended for and should not be relied

upon by any third party and no responsibility

is undertaken to any third party.

Ove Arup & Partners Ltd

13 Fitzroy Street

London

W1T 4BQ

United Kingdom

www.arup.com

Thames Water Non-Potable Water Reuse as a Demand Management Option for WRMP19Options Appraisal Report

Issue | 9 June 2017

Project Team

The project was delivered by a consortium of

Organisation Role

Arup Project Manager / Technical / Modelling

AECOM Planning / Technical

Aquality Industry input / Commercials

SHSWS Regulations / Governance

Report Review

Report version Authors Reviews Signoff

Draft 1 Martin Shouler (MS)

Siraj Tahir (ST)

Mike Henderson (MH)

Melinda Davies (MD)

Lutz Johnen (LJ)

Sian Hills (SH)

Martin Shouler (MS)

ST, MH, MD, LJ, SH

MS

Draft 2 MS, ST, MH, MD, LJ MS, ST, MH, LJ MS

Draft 3 MS, ST, MH, LJ MS, ST, MH, LJ, SH MS

Issue MS, ST, MH, LJ MS, ST, MH, LJ MS

Disclaimer - Information class

Forecasts and assessment are based on information available at the time of the

report, and don’t include:

• Forecast impact of future inflation on costs, such as energy, labour, materials.

• Future or upcoming changes in regulations.


Issue | 9 June 2017

Contents Page

1 Introduction 1

2 Background 3

2.1 Potable and Non-Potable Water Use 3

2.2 Non-Potable Water Sources 3

2.3 Non-Potable Water Systems 4

2.4 Regulatory Requirements for NPWR Systems 5

2.5 Co-Benefits of NPWR 5

3 Methodology 7

3.1 Overview 7

3.2 Stage Criteria 7

3.3 Stage A Methodology – Available Yield 8

3.4 Stage B – Technical Yield 11

3.5 Stage C – Allowable Yield 16

3.6 Stage D – Economically Effective Yield 20

4 Options Appraisal 23

4.1 Stage A – Available Yield Options Appraisal 23

4.2 Stage B – Technical Yield Options Appraisal 26

4.3 Stage C – Allowable Yield Options Appraisal 28

4.4 Stage D – Economically Effective Yield Options Appraisal 32

5 Summary & Conclusions 36

Appendix A

Installation and Performance Review of Systems

Appendix B

Regulations, Standards and Policies

Appendix C

Governance and Perception Review

Appendix D

Detailed Methodology

Appendix E

Case Studies


Issue | 9 June 2017 Page i

List of Abbreviations and Glossary

Term / Acronym Description / Explanation

BCIS Building Cost Information Services

Blackwater Water from foul drainage system

BRE Building Research Establishment

BREEAM BRE Environmental Assessment Method

Brownfield land Land that has previously been built upon

BSI British Standards Institute

BWR Blackwater Reuse

CAPEX Capital Expenditure

CfSH Code for Sustainable Homes (now abrogated)

CIRIA Construction Industry Research and Information Association

DMA District Metering Area

DWI Drinking Water Inspectorate

EA Environment Agency

GFA Gross Floor Area

GIS Geographic Information Systems

GLA Greater London Authority

Greenfield land Land that has not been previously built upon

Greywater Water from showers, sinks and washing machines

GWR Greywater Reuse

IDM model Integrated Demand Management model

Inset Appointee Company replacing the incumbent as monopoly provider of water and /

or sewerage services on new developments level

ISO International Standards Organisation

LPA Local Planning Authority

MUSCo Multi Utility Service Company

NIA Net Internal Area

Non-potable water Water treated to non-potable standards. For this project it is limited to

Rainwater, Stormwater, and Greywater

NPWR Non-potable water reuse

NRM New Rules of Measurement (by RCIS)

OFWAT Water Services Regulation Authority

OPEX Operational Expenditure

OA Opportunity area

Rainwater Water captured primarily from roof surfaces


Issue | 9 June 2017 Page ii

Term / Acronym Description / Explanation

RCIS Royal Chartered Institute of Surveyors

RWH Rainwater Harvesting

SHLAA Strategic Housing Land Availability Assessment

Stormwater Water captured primarily from ground surfaces

SWH Stormwater harvesting

SuDS Sustainable Drainage Systems

TOTEX Total Expenditure

WaSCo Independent Water and Sewerage Services Company (a third party

operator similar to a MUSCo)

WRAS Water Regulations Advisory Scheme

WRMP Water Resource Management Plan


Issue | 9 June 2017 Page i

Executive Summary

The predicted growth of London’s population, coupled with expected changes to the climate and the

need to take less water from the environment, means that Thames Water projects a gap between

supply and demand for water of around 414 million litres per day (Ml/d) by 2040. Thames Water is

exploring a range of options for its Water Resources Management Plan (WRMP19) that will increase

supply and reduce the demand for water to close this gap.

One of the options being considered to reduce the demand for potable water is non-potable water

reuse (NPWR). This is the use of water that does not require being of drinking water quality for non-

potable uses such as toilet flushing, laundry and garden irrigation. The water for NPWR can come

from a number of sources – rainwater, stormwater, greywater and blackwater.

This study focuses on the feasibility, costs and benefits of incorporating NPWR opportunities in new

development. The outcomes of this study will be inputted in the Integrated Demand Management

(IDM) model as part of the WRMP19 programme appraisal modelling.

The study analyses the potential for NPWR in major new developments areas, known as Opportunity

Areas (OAs), in Thames Water’s London Water Resource Zone. It is estimated that these OAs could

support over 336,600 new homes and 529,600 new jobs. Figure (i) presents the location and spatial

distribution of these major new developments.

Figure (i) Major new developments in London’s Opportunity Areas

To establish the scale of impact NPWR could have on reducing demand for water, this study

developed a four-stage approach, outlined in Table A. This approach identifies where NPWR is

appropriate, screens out less suitable options and determines how much water could be saved.

The study found that up to 33 Ml/d of water could be saved through NWPR, by harvesting rainwater

and stormwater, and recycling greywater. This compares favourably when evaluated against small to

medium scale supply side options considered in Thames Water’s 2014 WRMP.

However, achieving this outcome through implementation on NPWR can be complex from a

construction point of view as well as ensuring management of public health risks. In addition, the


Issue | 9 June 2017 Page ii

delivery of NPWR will require cooperation of multiple organisations, such as Local Authority,

Thames Water, the developers, and the eventual operators of NPWR systems.

Table A: Assessment stages - Definition and Water Resources Volume Saved

Assessment Stages Definition Water Resources

Volume Saved

‘Available yield’ estimates the volume of NPWR

assuming all non-potable demand is met. Up to 37 Ml/d

‘Technical yield’ estimates the volume of NPWR based on

ability of new developments to meet their non-potable

water demands. Up to 35 Ml/d

‘Allowable yield’ estimates the volume of NPWR that can

be achieved once regulations, standards, policies,

perception, deliverability and performance are met,

addressed and accounted for.

Up to 33 Ml/d*

‘Economically effective yield’ is the volume of NPWR

that could be delivered economically, in comparison with

other demand management options being considered in

WRMP19 Demand Management Options Screening

Report.

To be confirmed

through IDM

model**

* Options carried forward in the WRMP19 Demand management options screening report.

** NPWR volume will be determined through the IDM modelling.

The study estimated in Stage D the capital and operational costs incurred over a 25-year period in

delivering NPWR in new developments. The unit cost (in £/m3 of non-potable water) is shown for

the different types of systems (i.e. rainwater and stormwater harvesting, and greywater recycling or a

combination of the three (Combined sources)) that were identified at Stage C for each of the OAs in

Figure (ii). This showed that the recycling of greywater or combined sources are more cost effective

than harvesting and reusing rainwater and stormwater.

Figure (ii): Average unit cost estimates of delivering (a) rainwater or stormwater and (b) greywater and

combined sources NPWR systems for each Opportunity Area


Issue | 9 June 2017 Page iii

Note: To be consistent with WRMP19 methodology, options that are mutually exclusives and are least cost efficient

were not inputted into the IDM model. Combined sources NPWR systems are mutually exclusive with RWH, SWH and

RWH and more cost efficient.

In addition to its potential to manage demand for water, NPWR can deliver further co-benefits in

comparison to a business as usual approach. These include:

• Providing more headroom in water supply and drainage networks due to reduced peak demand;

• Deferring or avoiding infrastructure reinforcements to meet the increase in demand from new

developments;

• Reducing surface water flood risk due to capturing and using rain and stormwater onsite.

Table B presents an analysis of where and which NPWR may be suitable (as a minimum

requirement) for each of the identified OAs based on co-benefits. It highlights nine OAs where

NPWR would be most beneficial in terms of its impact on Thames Water assets (categorised as

‘High’ impact). This assessment would help to prioritise any interventions that are screened through

the IDM model.

Table B: NPWR system prioritisation based on benefits to Thames Water’s assets (Highlight colours – Red:

Asset is exceeding capacity, Amber: Asset is reaching capacity, Green: No issue)

Future Network Capacity and Impact

on TW Assets of NPWR NPWR System Prioritisation

Opportunity Area Water

Supply

Waste

Water

Impact on TW

Assets NPWR sources Ml/d

Cost

(£/m3)

Old Oak and Park Royal High Combined 2.70 3.59

Lower Lea Valley (including Stratford) High Combined 1.80 2.83

Upper Lee Valley High Combined 3.40 2.69

Greenwich Peninsula High Combined 0.90 2.82

Earls Court High Combined 0.40 3.22

Vauxhall, Nine Elms & Battersea High Combined 1.00 3.12

White city High Combined 0.60 3.20

Lewisham, Catford and New Cross High Combined 0.40 2.60

City Fringe/Tech City High Combined 1.84 3.26

Croydon Med GWR 0.40 2.71

Royal Docks & Beckton Waterfront Med GWR 0.90 3.70

Canada Water Med SWH 0.10 20.42

Cricklewood / Brent Cross Med GWR 0.60 3.16

Isle of Dogs Med GWR 3.7 3.91

London Bridge, Borough, Bankside Med SWH 0.01 20.42

Elephant & Castle Med RWH + SWH 0.01 17.12

Deptford Creek / Greenwich Riverside Med RWH + SWH 0.03 17.55

Old Kent Road+ Med SWH 0.04 18.42


Issue | 9 June 2017 Page iv


on TW Assets of NPWR NPWR System Prioritisation


Supply

Waste

Water

Impact on TW


Cost

(£/m3)

Thamesmead & Abbeywood Med SWH 0.01 18.95

Bexley Riverside Low RWH 0.02 24.88

Euston Low RWH 0.01 19.65

Kings Cross - St Pancras Low RWH 0.01 30.23

Charlton Riverside Med RWH + SWH 0.01 16.46

Woolwich Low RWH 0.01 30.96

Note: This study has assessed the feasibility of NPWR for the new developments within OAs in the London water

resource zone (WRZ) due to the high availability of information. The methodology applied is universal and can be

applied to other WRZs, when information becomes accessible to Thames Water. It is for similar reasons that the

feasibility of retrofitting NPWR system in existing buildings was not assessed.


Issue | 9 June 2017

Page 1

1 Introduction

Thames Water’s latest Water Resource Management Plan (2014) highlighted a potential 414 Ml/d

deficit in water supply by 2040. This 21% shortfall (Figure 1) stems from a combination of projected

population growth in London and the potential effects of climate change on available water

resources.

This potential shortfall can be reduced by a combination of increasing water resource options and

reducing water demand options. Non-potable water reuse (NPWR) was identified as a potential

option for reducing water demand in parallel with leakage management, metering, and water

efficiency. For this report, non-potable water is the water that is not of drinking water quality, but

can be used for other purposes such as toilet flushing, laundry and garden watering. It can be sourced

from rainwater from roofs, stormwater from paved surfaces, greywater or blackwater1.

Thames Water commissioned a project to investigate the feasibility of NPWR as a demand

management option for the WRMP19. Information from this report will be input into the Integrated

Demand Management (IDM) Model (Figure 2) as part of the WRMP19 process. The IDM model

optimises the Feasible Demand Management Options to produce Constrained Optimised Demand

Management Programmes. Thus this report focusses primarily on the amount of demand reduction

that can be achieved through NPWR (benefit) and the cost of supply of non-potable water.

1 Definitions of rainwater, stormwater, greywater, and blackwater are provided in the glossary and Paragraph 2.2.

Figure 1: The increasing gap in supply and demand (source: Thames Water)


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Page 2

Figure 2: Integrated Demand Management (IDM) Model Process

This report presents the outputs of that project. The rest of the report is structured in the following

manner:

Chapter 2 – Background

• Context overview about NPWR.

Chapter 3 – Methodology & Evaluation Criteria

• Determination of the suitable locations in London where NPWR can be deployed to minimise

demand on the potable water supply.

• Typologies overview of NPWR systems.

• Methodology for evaluating non-potable water demands and undertaking supply-demand balance

assessments.

• Summary of governance and regulatory frameworks and impact on NPWR implementation.

Chapter 4 – Options Appraisal

• Review of the proposed development and estimation of future potable and non-potable demands

(available yield).

• Assessment of potential for NPWR in these new developments (technical yield).

• Impact of regulations and governance frameworks on NPWR (allowable yield).

• Cost assessment of non-potable systems (effective yield).

Chapter 5 – Summary and Conclusions

• Summary of the project

• Recommendations

• Next steps


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2 Background

2.1 Potable and Non-Potable Water Use

Residential or commercial water demand is comprised of various uses that can be met by water that

has a lower quality level than that delivered by the potable water supply. For residential units,

approximately 33% of the water is used to flush toilets and run washing machines. Similarly for

commercial developments, approximately 60% of the water demand is for non-potable purposes

including flushing toilets and urinals (See Figure 3 below).

Figure 3: Water use by use type, non-potable supply and demand

Some of this demand could be met by non-potable water supply, resulting in significant reduction in

the potable water supply requirements.

2.2 Non-Potable Water Sources

Non-potable water can originate from different sources. The sources under review in this report are

listed below and presented in Figure 4:

• Rainwater – Rainwater is captured from buildings’ roofs and treated to meet non-potable water

standards (rainwater harvesting).

• Stormwater – Rainwater captured from pedestrianized surfaces and road run-offs and treated to

meet non-potable water standards (stormwater harvesting).

• Greywater – Water from bath, shower and bathroom sinks collected and treated to meet non-

potable water standards (greywater recycling).

• Blackwater – Wastewater, including municipal and industrial wastewater, and rainwater run-off

(from combined sewers) collected and treated to high quality standards (blackwater recycling).


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Figure 4: On-site sources of non-potable water supply

Further details on these NPWR systems, type of technology and suitability of systems at different

scales of installation is presented in Appendix A.

2.3 Non-Potable Water Systems

Although various systems are available in the market, a NPWR system normally comprises

(i) collection pipes and pre-treatment storage, (ii) water treatment systems to improve its water

quality, (iii) storage for treated non-potable water, and (iv) dual plumbing and pumping system for

the supply of non-potable water.

In addition to the above, the greywater systems require dual plumbing of the drainage system to

capture the water from showers, baths, sinks and washing machines. Figure 5 provides an example of

such a layout.


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Figure 5 Dual plumbing for capture of greywater for reuse

Further details on these NPWR systems, type of technology and suitability of systems at different

scales of installation is presented in Appendix A.

2.4 Regulatory Requirements for NPWR Systems

There are currently no mandatory requirements in the UK for the installation of NPWR systems. In

absence of such requirements, the following stakeholders have expressed their interest in promoting

such systems:

• European Union,

• UK Regulatory Bodies (including DWI, Defra, and Environment Agency),

• Water Utilities,

• Local Government (GLA and Local Planning Authorities),

• Industry Associations (CIRIA, UKRWHA, etc.).

The interests of the organisations range from sustainable water management, sustainable building

design, and infrastructure capacity management. These organisations are likely to be part of any

stakeholder groups when NPWR is to be pursued as a demand management option now or in the

future.

2.5 Co-Benefits of NPWR

The reduction in potable water demand from new developments could help avoid or delay

infrastructure upgrades (in particular sewers and drinking water mains), which would likely cause

disruption through, for example, road works.

Table 1 summarises the local benefits added when NPWR is implemented.


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Table 1: Additional local benefits of NPWR

Water

resources

Potable

network

capacity

Urban

runoff

Sewer

network

capacity

Reduce

CSO

incidents

STW

capacity

Rainwater harvesting � � � �

Stormwater harvesting � � � �

Greywater Reuse � � � �

Blackwater Reuse � � � � �

Part of these co-benefits is assessed through other WRMP work streams, taking into consideration

the requirements for network reinforcement and water treatment plant upgrades. In addition, Thames

Water is publishing its Blueprint for Water and Wastewater System that will also take into

consideration future infrastructure requirements.

Finally, these co-benefits on local infrastructure upgrades and reinforcements are being explored

within Integrated Water Management Strategies that are being supported by Thames Water and

undertaken by Greater London Authority and London’s Local Authorities.


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3 Methodology

3.1 Overview

The methodology adopted uses a four-stage process assessment to determine the best options based

on a suite of assessment criteria.

The application of these stage criteria enables the estimation of the ‘available yield’ based on

locations where NPWR is most feasible and potential demand, the ‘technical yield’ based on supply

demand balance, the ‘allowable yield’ with focus of regulatory frameworks, and the ‘economically

effective yield’ taking into consideration the cost of delivering non-potable water supply (Figure 6).

Figure 6: NPWR Yields assessment stages

3.2 Stage Criteria

The options are evaluated against each stage criteria based on a ‘pass / fail’ system or a Red Amber

Green (RAG) traffic light system to display the findings of the systems and to demonstrate how the

options perform.

Options selection using

stage criteria for inclusion

into WRMP19 Demand

management options

screening report

Options to be confirmed

through the IDM model


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3.3 Stage A Methodology – Available Yield

The first stage in the assessment process focusses on the locations and buildings where NPWR can

realistically be delivered with minimal disruption to residents and subsequently on the potential

demand of non-potable water.

Figure 7: Stage A – Available yield

To define this available yield (i.e. non-potable water demand), two steps are required:

• Step 1 – Site identification through methodical selection,

• Step 2 – Estimation of non-potable water demand for each usage application (residential or

commercial).

The paragraphs below provide information on methodology and assumption used for each of those

steps.

3.3.1 Site Selection Methodology

The London Plan’s future housing needs assessment estimates that over 1,000,000 new homes will

be required in London by 2035 to meet the demands of the growing population as well as replace

some of the existing building stock (GLA, 2016). The main focus for delivering these new homes, as

well as significant numbers of jobs, will be within strategic Opportunity Areas (or OAs) identified in

the London Plan. With limited areas for large scale development, the OAs are London’s major

source of brownfield land which have significant capacity for development. Typically they can

accommodate at least 5,000 jobs, 2,500 new homes or a combination of the two, along with other

supporting facilities and infrastructure.

Although some OAs, such as Lower Lea, Old Oak Common and Nine Elms, are a contiguous

homogeny of brownfield sites that will be developed in totality, other Opportunity Areas are broader

areas with a number of strategic development sites within them. This is of relevance for selecting the

type of NPWR system.

The location of the identified sites in the OAs and their housing targets and jobs targets have been

captured from the GLA Strategic Housing Land Availability Assessment (SHLAA) database as well


Issue | 9 June 2017

Page 9

as the Local Development Plans from the Local Authorities. Their locations have been mapped to

enable identification of relationships with particular District Metering Areas (DMAs). Only the OAs

that fall within Thames Water’s Supply Area are investigated in this study. These OAs, in relation to

Thames Water Supply Area, can be seen in Figure 8.

In addition to growth in OAs, there is potential for NPWR within commercial developments (new

build and refurbishment) outside of the OAs. Estimates of such commercial developments have been

made using projection by GLA and Local Planning Authorities.

A large proportion of London’s housing and commercial demand will be smaller infill developments

whose location is currently not identified and as such excluded from this assessment as their location,

scale and specific impact on particular DMA can’t be evaluated.

Figure 8 London Opportunity Areas and Thames Water's Supply Area

3.3.2 Population Estimation

Residential

A gross occupancy of 2.1 persons per unit has been utilised where detailed unit breakdown is not

available. General occupancy estimates based on census figures have been used for occupancy.

Commercial

The London Plan targets for the OAs are being used in the assessment and appraisal.


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3.3.3 Non-Potable Water Demand

The total water demand, as well as potable and non-potable water demand are based upon the usage

assumptions presented in the Building Regulations 2010 Part G (2015 Edition) and British Standard

BS 8542:2001 ‘Calculating domestic water consumption in non-domestic buildings. Code of

practice’, and BS8525:2010 ‘Code of Practice for Greywater Reuse’. The numbers used in this

assessment are summarised in Table 2.

Non-potable water demands from residential and commercial developments include uses such as

toilet and urinals flushing, washing machine, and garden / landscape irrigation.

Table 2 Total, potable and non-potable water demand assumptions

Type Residential (l/p/d) Non-residential (l/p/d) Total Water Demand 105 24 Potable Water Demand 65 8 Non-potable Water Demand 40 16 * Higher water efficiency targets

3.3.4 Selection Criteria for Stage A

Although NPWR systems can be installed in existing and new buildings, installation in existing

buildings is extremely difficult and only likely to happen during major refurbishment. As a result the

primary selection criterion for Stage A is whether the developments are new builds.

The secondary selection criterion for Stage A is on the size and location of the developments. The

criteria is whether the identified individual or group of sites for redevelopment lie within

Thames Water’s London supply zones and which deliver 2,500 or more residential units or 5,000 or

more jobs.

The source of the information is from the Mayor of London’s growth strategy outlined in the London

Plan and updated information from the Mayor of London’s website.


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3.4 Stage B – Technical Yield

While the available yield (Stage A) represents the total volume of non-potable water that can be

used, the technical yield indicates the ability of individual developments to meet their non-potable

demands from on-site water sources. The estimation of the technical yield is dependent on the

typologies (i.e. configuration, layout, scale of the development), the non-potable water source and

the achievable balance between non-potable water supply and non-potable water demand.

Figure 9: Stage B – Technical Yield

3.4.1 NPWR System Typologies

Four typologies have been considered for this assessment, with view to the nature of the

developments and to their deliverability within the OAs.

The following considerations were also incorporated in the development of these typologies:

• In strategic OAs with large scale regeneration, there is high likelihood that all site utility

infrastructures will be upgraded. This will provide opportunity to lay a new external piped

network for a central NPWR system.

• The topography, density of development and type of buildings (low rise, high rise) and type of

use (residential, mixed use, non-residential) are key components of potential typologies.


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Typology 1 – Organic Growth – Individual Systems

Characteristics of Typology 1 are:

• Individual building across London with dual plumbing

installed by developers (new build or refurbishment).

• Treatment systems installed by developer or independent

Water and Sewerage Service Company (WaSCo)2.

• Treatment system likely to be owned and operated by

building owner or the development’s management

company.

• Treatment system may be operated by independent

WaSCo.

Advantage: Ease of installation and clear ownership and operational setup.

Disadvantage: NPWR potential is not maximised.

Examples: New commercial developments and ad-hoc redevelopment across London.

Typology 2 – Development Level - Individual Systems

The characteristics of Typology 2 are:

• Non-potable systems delivered in a coordinated but not

in an integrated manner.

• Building dual plumbing installed by developers.

• Treatment systems installed by developer or

independent WaSCo.

• Treatment system owned and operated by building

owner, development’s management company or

independent WaSCo.

Advantage: Ease of installation and clear ownership and

operational setup.

Disadvantage: NPWR potential is not maximised

Example: Old Oak Common & Nine Elms – building by building solution. (See Appendix E for

more information).

2 An WaSCo is similar to the Multi-Utility Service Companies (MUSCos) and could offer wide range of water supply and management

services, including non-potable water supply.


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Typology 3 - Development Level - Mix of Systems

The characteristics of typology 3 are:

• NPWR systems delivered in a coordinated and integrated

manner between multiple buildings and developments, e.g.

excess supply from residential development could be used

by neighbouring commercial development.

• Building dual plumbing delivered by developers.

• Building level treatment systems installed by developer or

independent WaSCo.

• Building operated by building owner, independent

WaSCo or the local water utility.

• Communal treatment system and external network

delivered by developer or water utility.

• Communal treatment system and network owned and operated by site management company,

independent WaSCo or water utility.

Advantage: NPWR potential is optimised.

Disadvantage: More complex installation and ownership and operational setup.

Example: Nine Elms – development or multi-development scale non-potable system. (See Appendix

E for more information).

Typology 4 – Development level – Central system

Characteristics of typology 4 are:

• Building dual plumbing delivered by developers.

• Central piped network for non-potable supply delivered by

independent WaSCO or the local water utility.

• Internal building system delivered by developers.

• External piped network and NPWR treatment system

owned and operated by an independent WaSCo or the local

water utility.

• Potential for NPWR infrastructure to be delivered in

advance of the developments (e.g. Olympic Park in

London).

• Potential for developments built ‘fitted-for’ NPWR for connection to a future NPWR network

(e.g. San Francisco required dual plumbing for NPWR in all new developments with footprint

greater than 40,000 ft2 or 3,716 m

2).

Advantage: NPWR potential is maximised. Clear ownership and operational setup.

Disadvantage: More complex installation.

Examples: Old Oak Common – Central non-potable system(s) option; Olympic Park System in

London. (see Appendix E for more information)


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3.4.2 Typology and NPWR Relationship

Due to type of treatment systems required, not all sources of non-potable water (rainwater or

stormwater harvesting, greywater or blackwater recycling) will be suitable for all of the system

typologies. For this report, the relationship summarised in Table 3 were assumed to be feasible.

Table 3: Matrix mapping typology and non-potable water sources

Typology RWH SWH GWR BWR Combined

RWH, SWH,

GWR

Typology 1 – Organic growth – Individual Systems � � � �

Typology 2 – Development – Individual Systems � � � �

Typology 3 – Development – Mix of systems � � �

Typology 4 – Development – Central �* �* � �*

* Suitable for small scale developments and not at large scale development (e.g. Olympic Park or Old Oak Common)

3.4.3 Estimates of Non-Potable Water Supply

Table 4 outlines the estimated volume of non-potable water that can be captured for reuse (as l/p/d)

from the four assessed sources, namely harvested rainwater and stormwater, greywater and

blackwater. This estimated non-potable water supply volumes are based on BS 8542:2001,

BS 8525:2010 and case studies of Integrated Water Management Strategies (IWMS) for Nine Elms

and Old Oak Common. These case studies are presented in Appendix E.

Table 4: Non-potable water supply potential

Type Residential Non-residential

NP Supply

(l/p/d)

NP Demand

satisfied (%)

NP Supply

(l/p/d)

NP Demand

satisfied (%)

Rainwater Harvesting (RWH)* 1.3 3% 0.5 3%

Stormwater Harvesting (SWH)* 1.6 5% 1.6 4%

Greywater Reuse (GWR) 50 100% 8 50%

Blackwater Reuse (BWR)** 80 100% 20 100%

Combined (RWH, SWH, GWR) 53 100% 9 57%

* estimated figures based on Nine Elms case study

** estimate of blackwater reuse supply volumes set at 80% of water use.

Notes:

• At the time of this study, the future developments in the OAs were not at a design stage to have

readily available information about site layout, development density and plot areas – key

information required for estimating the potential of rainwater and stormwater per capita.

• In absence of this information, the information from the Nine Elms IWMS case study was used as

a proxy as it had information about development density, number of units (thus population),

building footprint (i.e. roof area) and plot areas.


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3.4.4 Selection Criteria for Stage B

Based on information captured from Old Oak Common and Nine Elms Integrated Water

Management Strategies and input from industry experts, it was ascertained that the cost effectiveness

for NPWR systems would be low for systems below a certain threshold.

Below this threshold, the impact of implementing NPWR on water demand and local infrastructure

would be low; therefore the effectiveness of implementing NPWR would be limited.

For purposes of this assessment, a minimum threshold of 10 m3/d was set for each OAs.


Issue | 9 June 2017

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3.5 Stage C – Allowable Yield

The allowable yield estimated the volumes from NPWR systems taking into consideration number of

criteria, including regulations governing the various NPWR systems, standards for their design,

installation and operation, stakeholder perceptions, and risk management on performance of NPWR

systems.

Figure 10: Stage C - Allowable Yield

3.5.1 Review Methodology

Regulation, Standards, Policy

A desk study review was carried out to understand how current and upcoming regulations, standards

and policies could benefit, or disbenefit, the implementation of NPWR. The desk study reviewed

regulations, standards and policies at local (when relevant), national, European and international

level (when relevant), for each non-potable water sources. This review has allowed us to ascertain

the RAG matrix presented in selection criteria. Details of the review are presented in Appendix B.

Stakeholders perception

Support from the public for such options was assessed through the review of past studies on user

perception related to NPWR from rainwater, stormwater, greywater and blackwater sources within

UK and internationally. Details of the review are presented in Appendix C.

Deliverability

The deliverability of a non-potable scheme is dependent on how difficult or complex it will be to

install all the various components necessary for NPWR systems and is summarised in Table 5 below.

This assessment was based on expert knowledge and discussion with non-potable water supplier,

owner, operator and developers.

The level of difficulty in delivering the components of NPWR systems was assumed to be dependent

on:

• Land ownership.

• Space availability within buildings and outside.


Issue | 9 June 2017

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• Ownership of NPWR systems (incl. external pipes and treatment systems).

• Presence of other infrastructure services, or space required for their delivery in new development.

Table 5: Assumption about the level of difficulty in delivery of various components of NPWR systems

System types

Rainwater &

Stormwater

(Typologies 1,

2, 3)

Greywater

(Typologies 1,

2, 3)

Greywater

(Typologies 4)

Blackwater

(Typologies 4)

Rainwater,

Stormwater,

Greywater

(Typologies 4)

Internal Storage Low / Medium Low N / A N / A Low

External Storage Medium N / A High High Medium

External pipework – outflow Low N / A High High High

Treatment system Location Low / Medium Low High High High

External pipework – Inflow Low N / A High High High

The following assumptions were made based on expert judgement:

• Communal and Central NPWR systems (Typologies 3 and 4) have ‘high’ difficulty in delivery of

external dual plumbing infrastructure in mixed land ownership model as well as issues related to

utility routing and availability of space.

• From land ownership, system ownership and network delivery viewpoints, the implementation of

NPWR is easiest for systems that source their supply from rainwater & stormwater harvesting

systems, and the distributed greywater systems (with systems in each building unit).

• The difficulty is deemed ‘high’ where agreement with multiple parties will be necessary to

implement the system, and ‘low’ where single party (such as a developer) can implement the

whole system. This is likely to be the case with Typology 4 NPWR systems.

Risk management

In addition to the various challenges in delivering parts of the NPWR system, there are issues with

ensuring system performance for water quality as well as reduction in water use forming the basis of

the system design. Table 6 highlights the level of risks in relation to water quality and system

meeting their design specification for the options under review. This assessment was based on expert

knowledge and discussion with non-potable water supplier, owner, operator and developers.

Table 6: System operations and performance

Rainwater &

Stormwater

(Typology 1, 2, 3)

Greywater

(Typology 1, 2, 3)

Greywater

(Typology 4)

Blackwater

(Typology 4)

Greywater,

Rainwater &

Stormwater

(Typology 3,4)

Risks from water

quality Low risk Medium – High Low – Medium Medium Medium

Likelihood of meeting

design performance Low Low – Medium Medium Medium Low – Medium

Note:

1. The risks from water quality would be present if the NPWR systems were not operated as designed and specified.

2. The design performance refers to ability to meet design reduction in demand


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In the UK, the regulations & guidelines do not include requirements for water quality or system

operation monitoring of installed NPWR systems. This could disincentivise water companies from

implementing such solution as water companies; water companies are responsible up to the

customer’s meter, but are liable up to the customer tap (i.e., a cross-connection between the non-

potable and the potable supply is therefore regarded as a high risk for water companies).

For greater acceptance of NPWR systems, guidelines for monitoring and reporting of the systems

may be necessary. There are international examples where local regulations have been enacted for

monitoring and reporting of NPWR systems to manage the risks associated with these systems.

3.5.2 Selection Criteria for Stage C

The deliverability of the NPWR systems is dependent on regulatory requirements, presence of

standards and guidance, local planning policies supporting their inclusion, the ease of delivery of the

systems, the perception about the systems and how well the risks from such systems can be managed.

The current regulatory framework for NPWR and relevant governance models are detailed in

Appendix B and Appendix C. The RAG assessment criteria based on these issues is summarised in

Table 7.


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Table 7: Stage C Assessment Criteria

Basis for assessment

Criterion title Selection Criteria Green Amber Red

Regulation Are regulations in

effect?

Regulations are

present

Regulations are in

development

Regulations are not

being pursued at this

time

Standards Are standards

present?

Standards are

present

Standards are in

development

Standards are not

being pursued at this

time

Policy Are policies present? Approved

government policy

(national, regional,

local) are present

Policies are

published but not

approved.

No policies exist at

this time

Perception Do the solutions

have a positive

perception by

owners?

Full support Some support No support

Deliverability Complexity in

delivery of NP

treatment and supply

systems

Low complexity Medium Complexity High complexity

Complexity in

operation and maintenance of NP

treatment and supply

systems

Low complexity Medium complexity High complexity

Likelihood of

meeting design

specification

(volumes)

High Medium Low

Risk Management Risk to public health

from cross

connections

Low risk Medium risk High risk

Ability to manage

risks

High Medium Low

Likelihood of

meeting design

specification

(quality)

High Medium Low


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3.6 Stage D – Economically Effective Yield

Feasible options identified in Stage C will be included in the WRMP19 Demand management option

fine screening report along with other demand management options and will be compared in terms of

cost. Stage D aims at provided the cost of NPWR at DMA level for inclusion into the WRMP19

Integrated Demand Management (IDM) model. Stage D also identified NPWR options that have

highest impact in terms of co-benefits associated with NPWR.

Figure 11: Stage D - Economically Effective Yield

3.6.1 Cost Assessment

The detailed assessment of NPWR in the OAs was undertaken along DMA boundaries to enable its

inclusion into the IDM model. The estimates used the identified sites from London Development

Database, Local Development Plans and assigned them to particular DMA based on their

approximate postcodes location. As the identified sites did not account for all the target

developments, the residual capacity was allocated to identify sites on a basis of proportional

weighting. It was assumed that the developments will be delivered in phases over the 25 year period

of WRMP. The process implemented to undertake this assessment is outlined in Figure 12.

To enable the cost estimation method to be replicated for all OAs, a high level estimation has been

established. The estimation process is outlined in Figure 13 and detailed in Table 8.The cost

Figure 12: Assessment process for NPWR at DMA level


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estimates utilise the New Rules of Measurement (NRM) and Building Cost Information Service

(BCIS) from Royal Chartered Institute of Surveyors (RCIS).

Figure 13: Process flow diagram of cost estimation method used

Table 8: Cost Item Description

Cost Items Description

Capital

Expenditure

(CAPEX)

Internal pipework &

storage (water supply and

sanitary services)

• Capital cost of additional internal water and sanitary services, based on

Gross Floor Area (GFA) using the New Rules of Measurement

(NRM)3 approach.

External piped network

& storage • Capital cost of additional external water and sanitary services based on

network flow capacity and standard costing estimates based on pipe

sizes and lengths.

Treatment Plant &

treated water interim

storage

• The rainwater, stormwater and greywater system costs have been

estimated using cost information sourced from Aquality.

Operating

Expenditure

(OPEX)

Maintenance and energy

for treatment • Operational cost for rainwater, stormwater, and greywater system have

been estimated using cost information sourced from Aquality.

Cost of risk management (e.g. monitoring) was excluded from the assessment to be consistent with

WRMP19 methodology applied for other options.

The process is explained in more detail in the Appendix D.

The unit cost outputs have been categorised as ‘low’ (<£3.00/m3), ‘medium’ (£3.00-6.00/m

3), or

‘high’ (>£6.00/m3) for comparison and visualisation.

3 BCIS (2013) Elemental Standard Form of Cost Analysis, 4

th NRM Edition, BCIS, London


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Note: Although the non-potable water demand and cost assessments were undertaken at DMA levels,

the outputs in the report are aggregated and presented along the OA boundaries for purpose of

consistency and presentation.

3.6.2 Co-Benefit Evaluation

As mentioned in paragraph 2.5, the implementation of NPWR system could have a wider impact

than just the reduction in water demand.

Thames Water identified the OAs for which new development could pose high risk on its current

assets. Table 9 summarise the RAG matrix used for classifying potential constraints on its water

supply and drainage networks capacity.

Table 9: Network Capacity Evaluation (Based on information from TW)

Basis for Assessment

Green Amber Red

Future potable network capacity no issue reaching capacity exceeding capacity

Future drainage network capacity no issue reaching capacity exceeding capacity

This will allow assessing which options are likely to have a higher impact in term of water demand

reduction and co-benefits.

3.6.3 Selection Criteria for Stage D

Economic effectiveness of the options is not a stage selection criterion as the selection will be

undertaken within the IDM model.

The selected options are included within IDM model where the options are compared with other

options.


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4 Options Appraisal

4.1 Stage A – Available Yield Options Appraisal

Figure 14: Stage A - Available Yield

4.1.1 Residential Developments

The assessment has focussed on the new developments in the OAs. The housing targets for each of

the OA have been published by the Mayor of London and have been used for estimating the overall

water demand and the non-potable water demand. Cumulatively in the OAs, there will be around

739,500 new residents in 352,150 new homes. These target growth figures for the OAs provide an

upper estimate of the available supplies of non-potable water that can be captured for reuse.

4.1.2 Commercial Developments

Similar to the residential developments, each of the OA has a target for new jobs. Cumulatively,

these amount to more than 550,000 new jobs to be delivered by 2035. These figures have been used

for the estimation of the future potable water demand and non-potable water yields.

There is an estimated 28 million m2 of office space in Greater London. To accommodate the

projected growth of 575,000 new office based jobs, it is predicted an upper demand for net additional

office floor space of 5.3 million m2 is required by 2036. Based on historic rates, the gross increase in

office floor space across Greater London is around 2.5 times greater than the net (4 times higher in

the Central Activity Zone where there is 70% of London’s office stock (PBA 2013)). As such, the

total office space requirement will increase by 13.25 million m2 within the next 25 years.

As highlighted above, around 575,000 jobs will be supplied within the OAs. Taking a conservative

estimate that the profile of jobs in the OAs will mirror the rest of London, two thirds (385,000) will

be office based. Following the average occupancy assumption of 12 m2 with 8% vacancy, this would

equate to 4.44 million m2. This leaves around 8.8 million m

2 of office space to be delivered outside

the OAs.


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Again taking the same office density assumptions, this new office space outside OAs would

accommodate 705,000 office employees.

4.1.3 Potential NPWR Demand

Table 10 below provides the estimates of potential non-potable water demand expected in the new

developments in London’s Strategic Opportunity Areas (or OAs).

Table 10: Summary of potential non-potable water demand in Opportunity Areas

Residential

Population

Employment

Population

Total Water

Demand

(m3/d)

Non-Potable

Potential

Demand (m3/d)

Meeting

criteria

1 Bexley Riverside+ 16,500 7,500 3,820 1,500 Yes

2 Bromley 2,500 2,000 600 240 Yes

3 Canada Water 6,600 2,000 1,510 580 Yes

4 Charlton Riverside 3,500 1,000 800 310 Yes

5 City Fringe/Tech City 15,000 53,000 4,580 2,100 Yes

6 Cricklewood / Brent Cross 10,000 20,000 2,690 1,160 Yes

7 Croydon 7,300 7,500 1,790 730 Yes

8 Deptford Creek/Greenwich Riverside+ 5,000 4,000 1,200 484 Yes

9 Earls Court 7,500 9,500 1,890 780 Yes

10 Elephant & Castle 5,000 5,000 1,230 500 Yes

11 Euston 3,800 14,100 1,180 540 Yes

12 Greenwich Peninsula 20,000 7,000 4,580 1,790 Yes

13 Isle of Dogs 30,000 110,000 9,260 4,280 Yes

14 Kings Cross - St Pancras 1,900 25,000 1,020 550 Yes

15 Lewisham, Catford and New Cross 8,000 6,000 1,910 760 Yes

16 London Bridge, Borough, Bankside 1,900 25,000 1,020 550 Yes

17 Lower Lea Valley (including Stratford) 32,000 50,000 8,260 3,480 Yes

18 Old Kent Road+ 20,000 5,000 5,530 1,760 Yes

19 Old Oak and Park Royal 53,500 65,000 13,360 5,530 Yes

20 Paddington 1,000 5,000 390 160 Yes

21 Royal Docks & Beckton Waterfront 25,500 40,000 6,590 2,790 Yes

22 Thamesmead & Abbeywood 5,000 1,000 1,340 430 Yes

23 Tottenham Court Road 500 5,000 260 120 Yes

24 Upper Lee Valley+ 20,100 15,000 4,800 1,920 Yes

25 Vauxhall, Nine Elms & Battersea* 10,000 15,000 2,810 1,240 Yes

26 Victoria 1,000 4,000 360 140 Yes

27 Waterloo 2,500 15,000 920 450 Yes

28 White city 6,000 10,000 1,570 660 Yes

29 Woolwich 15,000 1,000 3,340 1,270 Yes


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Residential

Population

Employment

Population

Total Water

Demand

(m3/d)

Non-Potable

Potential

Demand (m3/d)

Meeting

criteria

Sub-Total: Opportunity Areas 336,600 529,600 89,000 37,000

30 Commercial – outside opportunity areas - 705,000 17,000 11,000 No

Sub-Total: Outside opportunity Areas - 705,000 17,000 11,000

Total 336,600 1,234,600 106 Ml/d 48 ML/d

* Developments at Vauxhall is at an advanced stage and some of the sites have been excluded

4.1.4 Estimates of Available Yield

A total available yield was estimated to 48 Ml/d. However as information for the commercial

development outside OAs about their size and location is not available in Local Plans, it was

assumed that those developments would probably be not large enough and not meet Criteria 2. For

this reason, the potential yield for these developments is not carried forward to Stage B.

Therefore, the available yield based on non-potable water demand has been estimated as 37 Ml/d,

which is being taken forward for further assessment.

4.1.5 Summary – Stage A

The new residential developments within the OAs and commercial developments within/outside the

OA will result in an increase in potable water demand by 106 Ml/d.

The new developments in the OAs, which will provide more than 336,650 new homes and 529,600

new jobs, will increase the potable water demand by 89 Ml/d (Commercial development outside the

OAs are discounted by applying selection criteria 2). This is almost one quarter of the 414 Ml/d

supply deficit by 2040 that has been estimated by Thames Water. The implementation of NPWR

could potentially reduce this demand by up to 37 Ml/d. This compares favourably when compared to

small to medium scale supply side options considered in Thames Water’s 2014 WRMP.


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4.2 Stage B – Technical Yield Options Appraisal

Figure 15: Stage B - Technical Yield

4.2.1 Typology vs. Development

A review of each development in the different opportunities area (as identified in Table 10) show

that typology 2, 3 and 4 are likely to be applied for such scale. Typology 1 would have been

considered for the commercial development outside opportunity areas. Typology 1 will thus not be

carried forward during this assessment.

4.2.2 NPWR – Estimates of Technical Yield

The technical yield estimates for NPWR systems were undertaken using a supply and demand

balance of NP water demands and potential NP water supply from rainwater, stormwater, greywater,

and blackwater.

The estimates presented in Table 11 summarise the top level reduction in demand that can be

achieved by implementing these options, after discounting areas where the impact was below the

assumed threshold of 10 m3/day. In a number of OAs, RWH and SWH options were thus excluded.

Table 11: Estimate of NPWR Technical Yield and percentage satisfaction of demand of NPWR

Residential (Ml/d) Non-residential

(Ml/d)

Total (Ml/d) % of total

potential NPWR

demand

RWH only 0.9 0.2 1.1 3%

SWH only 1.3 0.3 1.6 4%

GWR only 28 4 32 86%

Combined 28 5 33 89%

BWR only 28 9 37 100%


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With the exception of blackwater reuse, where all the non-potable demand can be met, the supply-

demand balance was undertaken for type of development within each DMA.

These options are taken forward for further assessment in Stage C.

4.2.3 Technical Yield Estimates for Affected DMAs

The total volume of NPWR that can be captured for reuse and the impact on the DMAs varies across

London and the various OAs. These volumes are presented in Figure 16 below.

The estimated annual reduction in demands as result on NPWR for each OA is presented in

Appendix D6.

Figure 16 Technical Yields over 25 year by DMA Boundaries

4.2.4 Summary – Stage B

There is a large range in the amount of potable water demand reduction that can be achieved based

on various non-potable water supply options.

Rainwater harvesting and stormwater harvesting are at lower end with potential to reduce demand by

1.1 Ml/d and 1.6 Ml/d respectively. Greywater reuse, combined systems (with greywater, rainwater

and stormwater), and blackwater reuse provide greater level of demand reduction at 32 Ml/d,

33 Ml/d and 37 Ml/d respectively.

These options will be further assessed for suitability and screened out in following assessment

stages.

The assessment was undertaken at each DMA and Figure 16 highlights that some of them will have a

greater level of opportunity for NPWR. The local infrastructure in the same areas will also

experience a greater level of impact.


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4.3 Stage C – Allowable Yield Options Appraisal

Figure 17: Stage C - Allowable Yield

Allowable yield takes into account the presence of regulations and standards governing NPWR,

policies promoting their inclusion, issues with perception, deliverability of systems, and management

of risk – both in terms of water quality as well as volumes.

4.3.1 Assessment Background

The regulations and standards in effect in UK and Europe were reviewed as part of the assessment.

Full details of this review are presented in Appendix B. Based on the desk study, the selection

criteria were assessed.

The London Plan has policy to promote capture and reuse of rainwater and stormwater at source

(Policy 5.13). The Plan also has policies promoting higher water efficiency targets within homes,

which can be achieved through the use of NPWR (Policy 5.15).

The assessment of the acceptability of NPWR is based on desk study of published articles and

reports by various water utilities within UK and abroad. The review found that there is general

acceptability of NPWR systems. Further information on the review of user perception is presented in

Appendix C.

The deliverability of the NPWR systems is based on industry experience of the project team, which

includes NPWR system suppliers and consulting engineers involved in design of new developments

and infrastructure. There are certain challenges with respect to routing of pipework, space take,

ownership of system and network, as well as responsibilities for MPWR systems operation and

maintenance. This information has been used in evaluating the NPWR systems in Section 4.3.2.

Further detail is presented in Appendix C.

The risk management assessment has been undertaken based on industry experience of the project

team, which includes design engineers and system suppliers and other water industry experts.

Governance models also help manage and mitigate the risks associated with the NPWR systems.

These governance models are discussed in more detail in Appendix C.


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4.3.2 System Suitability Analysis

Table 12 presents the suitability of the various NPWR system types based on the above criteria.

Table 12: Suitability matrix of NPWR systems

Criterion title Criteria RWH SWH GWR Combined BWR

Regulation Are regulations in

effect?

Not being

pursued at

this time

Not being

pursued at

this time

Not being

pursued at

this time

Not being

pursued at

this time

Not being

pursued at

this time

Standards Are standards

present?

Standards are

present

Standards are

present

Standards are

present

Standards are

present

Not being

pursued at

this time

Policy Are policies

present?

Policies are

present

Policies are

present

Policies are

present

Policies are

present

Not excluded

as a solution,

but there are

no specific

policies in

support.

Perception Do the solutions

have a positive

perception by

owners?

Full support Some support Some support Some support Some support

(non-

residential)

Deliverability Complexity in

delivery of NP

treatment and

supply systems

Low Medium Medium Medium High

Complexity in

operation and maintenance of

NP treatment and

supply systems

Low Medium Medium Medium High

Likelihood of

meeting design

performance

(volumes)

Low Medium High High High

Risk

Management

Risk to public

health from

operational

incidents and

undetected cross

connections

Low risk Medium risk Medium risk Medium risk High risk

Ability to manage

risks

High Medium Medium Medium Medium

Likelihood of

meeting design

performance

(quality)

High Medium Medium Medium High

Red 2 1 1 5

Amber 0 7 6 3

Green 8 2 3 2


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As the worst performing options, blackwater recycling system, as a non-potable water source, is not

carried forward in the assessment.

4.3.3 Estimate of Allowable Yields

Table 13 presents the cumulative allowable yield for the options put forward for inclusion and

assessment in the WRMP19 Demand management options screening report. Note that each option is

applied for each DMA (and subsequently OAs).

Table 13: NPWR options for assessment

Option # Specific Option Allowable

yield

(Ml/d)

Rainwater

harvesting

1 Typology 2 – Development Level - Individual Systems - Commercial only 0.2

2 Typology 2 – Development Level - Individual Systems - Residential only 0.9

3 Typology 2 – Development Level - Individual Systems - Commercial & residential 1.1

Stormwater 4 Typology 3 – Development Level - Mix of Systems - Commercial only 0.3

5 Typology 3 – Development Level - Mix of Systems - Residential only 1.3

6 Typology 3 – Development Level - Mix of Systems - Commercial & residential 1.6

7 Typology 4 – Development level – Central system - Commercial only 0.3

8 Typology 4 – Development level – Central system - Residential only 1.3

9 Typology 4 – Development level – Central system - Commercial & Residential 1.6

Greywater 10 Typology 2 – Development Level - Individual Systems - Commercial only 4

11 Typology 2 – Development Level - Individual Systems - Residential only 28

12 Typology 2 – Development Level - Individual Systems - Commercial & residential 32

13 Typology 3 – Development Level - Mix of Systems - Commercial only 4

14 Typology 3 – Development Level - Mix of Systems - Residential only 28

15 Typology 3 – Development Level - Mix of Systems - Commercial & Residential 32

16 Typology 4 – Development level – Central system - Commercial only 4

17 Typology 4 – Development level – Central system - Residential only 28

18 Typology 4 – Development level – Central system - Commercial & Residential 32

Combined 19 Typology 2 – Development Level - Individual Systems - Commercial only 5

20 Typology 2 – Development Level - Individual Systems - Residential only 28

21 Typology 2 – Development Level - Individual Systems - Commercial & residential 33

22 Typology 3 – Development Level - Mix of Systems - Commercial only 5

23 Typology 3 – Development Level - Mix of Systems - Residential only 28

24 Typology 3 – Development Level - Mix of Systems - Commercial & Residential 33

25 Typology 4 – Development level – Central system - Commercial only 5

26 Typology 4 – Development level – Central system - Residential only 28

27 Typology 4 – Development level – Central system - Commercial & Residential 33


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4.3.4 Summary - Stage C

The assessment at this stage and selection criteria established that NPWR based on blackwater reuse

systems was unsuitable primarily due to complexity in delivery and operation, and lack of supporting

policies at national or local levels.

Following this assessment, 27 options for each OAs were put forward for assessment in theWRMP19

Demand management options screening report and cumulative allowable yields are summarised for

each option in Table 14.

Table 14: Option for demand management options screening

Option Categories RWH SWH GWR Combined

Development Level - Individual Systems – Commercial

only 0.3 - 4 5

Development Level - Individual Systems – Residential only 0.9 - 28 28

Development Level - Individual Systems – Commercial &

residential 1.2 - 32 33

Development Level - Mix of Systems – Commercial only - 0.4 4 5

Development Level - Mix of Systems – Residential only - 1.4 28 28

Development Level - Mix of Systems – Commercial &

Residential - 1.8 32 33

Development level – Central system - Commercial &

Residential – Commercial only - 0.4 4 5


Residential – Residential only - 1.4 28 28


Residential development – Commercial & Residential - 1.8 32 33


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4.4 Stage D – Economically Effective Yield Options Appraisal

Figure 18: Economically Effective Yield

4.4.1 NPWR in the Opportunity Areas

The NPWR supply and demand will be in the new residential and commercial developments in the

OAs. Figure 19 presents the location of these potential future developments and enables the

estimation of the NPWR volumes and unit costs for delivering NPWR for each corresponding OA

and DMA.

Figure 19: Opportunity Areas and large development sites.


Issue | 9 June 2017

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4.4.2 Unit Cost Estimates

The costs were only estimated for Typology 2 and 3 due to the assessment at DMA level precluding

assessment on centralised infrastructure provision necessary for Typology 4.

These unit cost (£ per m3 of non-potable water) includes the cost of delivery of the dual plumbing

within and outside the building, as well as the operation and maintenance of the systems over 25 year

period. It is also assumed that the new housing will be delivered annually in a staged manner.

Although the costs have been estimated along the DMA boundaries, they have been aggregated

along the boundaries of Opportunity Areas for presentation in this report.

Figure 20 and Figure 21 represents the unit cost range of NPWR system respectively for GWR and

combined systems (Figure 20), and RWH and SWH (Figure 21).

Figure 20: Unit Cost range of NP water supply from GWR and Combined (RWH, SWH, GWR) system

Figure 21: Unit Cost range of NP supply from RWH and SWH systems


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4.4.3 Estimate of Economically Effective Yield

Cost is not a stage selection criteria and the appraisal will be undertaken in the IDM model. The

Economically Effective Yield will be based on the outputs of the latter process.

However, in order to be consistent with WRMP19 methodology, options that are mutually exclusives

and are least cost efficient were not selected for input into the IDM model. Combined NPWR

systems are mutually exclusive with RWH, SWH and RWH and the most cost efficient NPWR

option for each OAs.

4.4.4 Co-Benefit Impact Evaluation

Table 15 presents an analysis of where and which NPWR may be suitable (as a minimum

requirement) for each of the identified OAs based on co-benefits. It highlights nine OAs where

NPWR would be most beneficial in terms of its impact on Thames Water assets (categorised as

‘High’ impact). This assessment would help to prioritise any interventions that are screened through

the IDM model.

Table 15: Prioritisation of type of NPWR systems based on potential of derived co-benefits


on TW Assets of NPWR NPWR system prioritisation


Supply

Waste

Water

Impact on TW


Cost

(£/m3)

Old Oak and Park Royal High Combined 2.70 3.59

Lower Lea Valley (including Stratford) High Combined 1.80 2.83

Upper Lee Valley High Combined 3.40 2.69

Greenwich Peninsula High Combined 0.90 2.82

Earls Court High Combined 0.40 3.22

Vauxhall, Nine Elms & Battersea High Combined 1.00 3.12

White city High Combined 0.60 3.20

Lewisham, Catford and New Cross High Combined 0.40 2.60

City Fringe/Tech City High Combined 1.84 3.26

Croydon Med GWR 0.40 2.71

Royal Docks & Beckton Waterfront Med GWR 0.90 3.70

Canada Water Med SWH 0.10 20.42

Cricklewood / Brent Cross Med GWR 0.60 3.16

Isle of Dogs Med GWR 3.7 3.91

London Bridge, Borough, Bankside Med SWH 0.01 20.42

Elephant & Castle Med RWH + SWH 0.01 17.12

Deptford Creek / Greenwich Riverside Med RWH + SWH 0.03 17.55

Old Kent Road+ Med SWH 0.04 18.42

Thamesmead & Abbeywood Med SWH 0.01 18.95

Bexley Riverside Low RWH 0.02 24.88


Issue | 9 June 2017

Page 35


on TW Assets of NPWR NPWR system prioritisation


Supply

Waste

Water

Impact on TW


Cost

(£/m3)

Euston Low RWH 0.01 19.65

Kings Cross - St Pancras Low RWH 0.01 30.23

Charlton Riverside Med RWH + SWH 0.01 16.46

Woolwich Low RWH 0.01 30.96

The RAG coding is based on data provided by TW on future network capacity assessment:

• Red: exceeding capacity

• Amber: reaching capacity

• Green: no issue

4.4.5 Summary – Stage D

The cost evaluation excluded the cost of risk management to be consistent with other Demand

Management options being evaluated.

The assessment at this stage established unit costs for delivering NPWR systems for inclusion into

the WRMP19 Demand Management Fine Screening process, where all demand management options

will be compared at individual DMA level and selected based on unit cost and amount of demand

reductions.

The consideration of co-benefits is important and NPWR options with high co-benefit impact are

likely to be most cost effective.

In some of the OA’s, the unit cost of preferred solution may be higher but the overall volumes of

NPWR are low. In these locations consideration of the TOTEX may be appropriate, including the

costs of upgrades or reinforcements to Thames Water’s assets as well as the benefits derived from

reducing flood risk from surface water and foul sources.


Issue | 9 June 2017

Page 36

5 Summary & Conclusions

The project has evaluated the potential of NPWR to reduce potable water demand. It has shown that

NPWR in new developments can have a material impact on the overall demand for potable water

within London. However the level of impact varies across the Opportunity Areas and the District

Metered Areas.

The unique four stage methodology was used to establish the overall potential and systematically

screen out less suitable options. The results of this staged assessment are outlined in Table 16.

Table 16 Maximum NPWR in Opportunity Areas

Total NP potential

Total water demand 89 Ml/d

Stage A - Available Yield 37 Ml/d

Stage B - Technical Yield 37 Ml/d

Stage C - Allowable Yield 33 Ml/d

Stage D - Effective Yield To be established in WRMP19

programme appraisal

The assessment process also proved the efficacy of the methodology and enabled the development of

multiple options to be assessed in comparison with other options in the IDM model, including water

efficiency and metering.

It is worth noting that the volumetric reduction is significant in terms of volume delivered into

supply when referenced against the preferred water resource options in the 2015-2040 Water

Resource Management Plan. This suggests the NPWR is a reasonable option to be considered in

WRMP19, with the feasibility dependent on comparison with other demand management options

being considered.

The unit cost of non-potable water supply (taking into account all capital and operational costs)

range from £2.5 per m3 for GWR and combined systems (RWH, SWH, GWR) to up to £32 per m

3

for RWH. These costs are inclusive of all capital costs as well as operational and maintenance costs

over 25 years, and estimated on simple payback costs and on the presumption that new developments

and NPWR systems will be delivered annually over this period.

In certain locations, where lack of infrastructure capacity may prevent new developments due to

impact on infrastructure, the NPWR systems may enable such development to progress. They may

also enable Thames Water to defer or avoid infrastructure reinforcements or upgrades, thereby

saving capital expenditure. However, these co-benefits will need to be assessed outside of this

appraisal process.

Therefore to get maximum benefit of NPWR system, they should be targeted in areas where they

will deliver multiple benefits of water demand reduction, infrastructure upgrade deferment or

avoidance, and potential reduction in combined sewer overflows in the water bodies.

Appendix A

Installation and Performance

Review of NPWR systems


Issue | 9 June 2017 Page A1

A1 Technology Overview

Various systems are available in the marketplace for capture and reuse of harvested rainwater, and

stormwater, greywater and blackwater (or wastewater) for non-potable applications.

A1.1 Rainwater Harvesting

Rainwater from roof surface is the least polluted source of non-potable water and in most

circumstances it can be used without further treatment. Therefore, physical treatment systems, such

as filtration, can suffice. However, for large installations, filtration and disinfection of the harvested

rainwater using chlorine dosing or UV disinfection is commonly applied to minimise risks to health

and wellbeing of building occupants.

A1.2 Stormwater Harvesting

Stormwater from pedestrianized areas or road surfaces have a higher pollutant load than rainwater

and requires physical and chemical treatment prior to NPWR. Where pollutant loads are highest,

such as highly urbanised areas, a number of pre-filtration solutions are available that use

geosythentic membranes for filtration (e.g. fibrous geotextiles) and treatment (e.g. Biomat by

Polypipe).

To manage risk to health and wellbeing from NPWR within buildings, following initial filtration the

harvested stormwater can be treated using similar treatment systems that are used to treat greywater.

A1.3 Greywater Recycling

Greywater is collected from bath, shower and bathroom sinks. For greywater recycling there is not

yet an established treatment process. Different processes have entered the market and some are no

longer available. Below are some illustrative examples of systems and technologies that have entered

the market.

a) Short retention systems

Although small and fairly cost effective, short retention systems such as the EcoPlay have not meet

required water quality standards set by the BS 8525:2010 and have been removed from the market.

Similarly, a later version from ReAqua with chemical dosing was taken off the market as the system

was not as ‘maintenance free’ as expected.

b) Biological system with UV disinfection

A biological treatment process combined with UV disinfection, mainly introduced by Pontos, has

had initial success but was withdrawn from the market. The process relies heavily on the biology

operating effectively at all times and any disturbance of the biology can have an impact on the water

quality and operation of the system.

c) Physical treatment systems with chemical disinfection

A sand filter system called “Spruce” filter has been used to treat greywater. As the water quality does

not achieve BS 8525 standards, it uses a chlorine disinfection component. Although the system can

treat water quickly, the treatment process seems unreliable, the biological characterisitcs of the raw



greywater having an impact. The use of chemicals makes the system less sustainable and adds to

operational issues that come with chemical dosing.

d) Bio-mechanical systems

Bio-mechanical systems are dominating the market using all types of membranes. Although using

biology for pre-treatment, the various systems do not reliable completely on the biology. The final

treatment step is a membrane. Using ultra-filtration membranes, it withholds bacteria and viruses

thus disinfecting the treated water. The system only uses electricity to operate which makes the

system very sustainable.

A1.3.1 Trends in System Costs

Greywater recycling systems were introduced in the domestic market over 20 years ago. Early

designs aimed for standard one family houses using all types of “treatment”. With time, systems for

apartments or hotels etc. were introduced. In order to cope with larger treatment capacity, a multiple

of smaller systems were used to achieve this. Due to rising demand for larger systems suppliers

started to offer larger standardised systems at reduced cost. With further demand, especially for

membranes due to MBR technology becoming the dominating treatment process, membrane

suppliers started to develop bespoke membranes for greywater treatment. This allowed the treatment

efficiency to increase by 30% and therefore a reduction in price per m3 treatment capacity.

A1.3.2 Change Factors

Prices are influenced by three factors: competition, technological development and market size.

Competition forces suppliers of systems to apply discounts in order to win projects. These discounts

can differ quite significantly depending on how keen the suppliers are to win a project.

Greywater recycling is undergoing quite a development in terms of the technology used. The market

is young and new concepts constantly evolve to treat greywater more effectively or to higher

standards. Not only has the technology itself an impact on the price but also the standardisation of

the process and the way this is assembled.

With a growing market, supply chain and manufacturing further reduces price simply due to number

of system produced and increased competition as it will attract more players

A1.3.3 Technology Trends

There are new membrane systems developed offering further treatment efficiencies, space and

operational cost reductions. They are being developed and tested and should hit the market within the

next two years.

Detailed information about their operational capabilities, capital costs and cost of operation are not

available. However, based on historic improvements, they are likely to be more efficient in terms of

treatment and thus cost.

A1.4 Blackwater Recycling

Blackwater (or wastewater) is the waste effluent within municipal sewerage network and the

blackwater treatment systems capture and treat the waste effluent stream for further use. The treated

effluent from the blackwater treatment systems around the world are predominantly used for non-

potable uses (e.g. reclaimed water networks in San Francisco and Bay Area).



Some of wastewater treatment systems and technologies suitable for decentralised solutions are

presented in Table A1.

Table A1: Blackwater treatment systems comparison

System Advantages Disadvantages

Membrane Bioreactor

(MBR)

Most compact system

Most scalable to future capacity

Fully automated/low maintenance

Accepts high pollutant load

Higher level of operator training

Higher energy use for treatment

Activated Sludge

(CAS)

Most common system type Higher energy use for mixing

Rotating Biological

Contactor (RBC)

Accepts high pollutant load Higher energy use

Potential for odour / noise

Living Machine® Visual amenity – can be showcased

Quiet & low cost operation

High level of maintenance

Larger footprint/system size

Insufficient water quality

MBR systems are the most suited technology as water reuse system in dense urban areas due to their

small footprint, higher loading rates, shorter hydraulic retention time, and more manageable odour

control. The downside is the higher operating costs.



A2 Technology Suitability

Table A2 below presents the suitability of non-potable supply from various sources for the four

identified typologies. The suitability is based on combination of footprint, capital cost, and

operational requirements for the treatment systems.

Table A2: Suitability of treatment technology

Influent Technology

Ty

po

log

y 1

, 2

Ty

po

log

y 3

Ty

po

log

y 4

Footprint

(L/M/H)

CAPEX

(L/M/H)

Borehole Water No treatment x x x Low N/A

Rainwater

Harvesting

No treatment x - - Low N/A

Greywater Recycling No treatment x x x Medium N/A

Multimedia x x x Medium Medium

Membrane bioreactor x x x Low High

Constructed wetlands - x x High Medium

Blackwater

Recycling

Activated Sludge - - x High High

Membrane bioreactor - - x Low High

Rotating Biological

Contactor - - x Low High

Constructed wetlands - - x High Medium

Appendix B

Regulations, Standards and

Policies


Issue | 9 June 2017

Page B1

B1 Regulations Relevant to NPWR

Table B1: Regulations, standards and guidance on NPWR

Document Agency Relevance Date

WRAS Guidance Note 9-02-04.

Installing, Modifying and maintaining

reclaimed water systems

WRAS Overview of rain and greywater systems including

Hazard Assessment protocol

1999

Water Supply Water Fittings

Regulations 1999

UK Govt Regulations enforced by Water Companies regarding

pipe making, air gaps etc

1999

Rainwater and Greywater in

Buildings (BSRIA)

BSRIA Decision making, best practice and case studies, 2001

BS 8515, 2009 +A1:2013 Rainwater

harvesting systems – code of practice

BSi Recommendations for design, installation, testing

and maintenance, with water quality guidelines

2009 &

2013

BS 8525-1, 2010 Greywater systems –

code of practice

BSi Recommendations on design, installation, alteration

maintenance and testing with water quality

guidelines.

2010

Harvesting rainwater for domestic

uses: An information guide (EA).

EA Aimed at domestic users. Refers to other guidance

including BS 8515

2010

Water Supply (Water Quality)

Regulations 2010

DWI, UK

Govt

Potable supplies must meet standards for

wholesomeness (not so if cross connections)

2010

WRAS Guidance Note No. 9-02-05

Issue 4 –

Marking and Identification of Pipe

Work for Water Reuse Systems

WRAS Updated guidance on pipework marking 2011 &

2014

BS 8525-2, 2011 Greywater systems –

domestic greywater treatment

equipment, requirements and

test methods

BSi Companion to Part 1, includes a testing methodology

to prove systems

2011

Greywater for domestic users: An

information guide (EA)

EA Comprehensive with references to other guidance

(WRAS, and BS 8525), not fully encouraged due to

costs & unproven reliability

2011

BS 8595:2013 Code of Practice for

Selection of Water Reuse Systems

BSi Supplements Rainwater & Greywater CoP, includes

stormwater and more reference to risk management

2013

BS 1710:2014 Specification for

identification of pipelines and services

BSi Specification for all services 2014

Water Act 2014 UK Govt, Aims to make it easier for business to change their

water suppliers. It will also open up the water and

sewerage market to new companies.

2014

Building Regulations for England and

Wales Requirement - Part G1

UK Govt Reasonable provision must be made for water

efficiency – reuse can be used to meet 125 l/p/d or

110 l/p/d targets

2015

CIRIA C753 SuDS manual has been CIRIA Comprehensive update on approach to SuDS 2015


Issue | 9 June 2017

Page B2

Document Agency Relevance Date

published

SuDS Non-Statutory technical

standards

UK Govt Government guidance, very general - reflecting

principles of quality, quantity, amenity and

biodiversity

2015

CD2 20426 EU Guidelines for health risk assessment and

management for NPWR

Forth-

coming

EN 16941-1 EU EU Standard on rainwater Forth-

coming

EN 16942-2 EU EU Standard on greywater Forth-

coming

ISO/CD 20760-1 ISO ISO Water Reuse in Urban Areas – Design

Principals

Forth-

coming

ISO/CD 20760-2 ISO ISO Water Reuse in Urban Areas – Management of

System

Forth-

coming

B1.1 WRAS Guidance (Water Industry Act 1991)

The only legally-binding Regulations pertinent to NPWR systems are encapsulated within the Water

Supply Water Fittings / Water Quality Regulations. Although Water Companies may not have direct

involvement with a rain or greywater recycling system, they nonetheless have legal responsibility

under the Water Industry Act 1991 and related legislation to ensure that such systems do not

compromise drinking water quality.

Therefore Water Companies are required to enforce the Water Supply (Water Fittings) Regulations

1999 in relation to the area for which they hold an appointment. This means that companies are

responsible for checking for WRAS compliance, suitable air gaps, pipe marking, integrity of

pipework, etc., of systems in their areas.

WRAS has produced a number of guidance documents on reclaimed water, including a 1999 leaflet

on installing modifying and maintaining reclaimed water systems (9-02-04), and a 2014 update on

reclaimed water pipework marking and identification (9-02-05).

This latter guidance, which is currently under review, states that a water supplier must be notified in

advance, and grant approval for, any reused water system to be installed in a new development also

supplied with potable water.

Under the Water Supply (Water Quality) Regulations 2010, potable supply must meet standard for

wholesomeness, which would not be so in the case of inadvertent cross connections. The 2010 Upton

Eco-Housing Development cross-connection incident in Anglian Water’s area was an example of the

DWI referring to these legal instruments.

It should be noted that Public Health England have an oversight remit concerning safeguarding

public health and their laboratories at Colindale and Proton list water as one of their specialities,

although it is unlikely that they have the resources to oversee water recycling installations.


Issue | 9 June 2017

Page B3

B2 British Standards

According to the British Standards Institute, a standard is an agreed way of doing something. The

difference between a standard and a technical regulation lies in compliance. While conformity with

standards is voluntary, technical regulations are by nature mandatory.

Standards can be about making a product, managing a process, delivering a service or supplying

materials – standards can cover a huge range of activities undertaken by organizations and used by

their customers. The point of a standard is to provide a reliable basis for people to share the same

expectations about a product or service. This helps to:

• Facilitate trade,

• Provide a framework for achieving economies, efficiencies and interoperability,

• Enhance consumer protection and confidence.

There are a number of British Standards related to NPWR:

B2.1 BS8515 - Rainwater Code of Practice

This Code of Practice (CoP) came into effect on 31 January 2009 and was updated in 2013. It sets

out recommendations on the design, installation, testing and maintenance of rainwater harvesting

systems supplying non-potable water in the UK. It states that a system conforming to filtration

technology as set out in Section 4.3 of the standard (maintainable, 90% efficient and passes

maximum particle size <1.25 mm) should produce water of a suitable quality for WC, laundry and

garden watering in most situations.

The implementation of additional UV or chemical disinfection is advised in some situations. The

CoP gives installation and air gap requirements and monitoring recommendations. Guideline

microbiological and physiochemical water quality parameters are provided in Section 6 and risk

assessments are recommended.

B2.2 BS 8525 - Greywater Systems Code of Practice

This Code of Practice is in two parts. It solely concerns the use of greywater from bathrooms. The

end uses are the same as the rainwater CoP, i.e. WC, laundry and garden watering. Guideline

microbiological and physiochemical water quality parameters are provided in Section 6 of the CoP

(see Appendix 3).

Part 1 (2010) gives recommendations on the design, installation, alteration, testing and maintenance

of greywater systems. Guideline microbiological and physic-chemical water quality parameters are

provided.

Part 2 (2011) concerns specifications for the greywater equipment (e.g. flows, controls, markings and

fail safes) as well as a methodology for testing the systems using synthetic greywater against a set of

water quality criteria for different end uses.


Issue | 9 June 2017

Page B4

B2.3 BS 8595 - Code of Practice for Selection of Water Reuse

Systems

This Code of Practice (CoP) is very much a supplement/addition to the aforementioned rainwater and

greywater CoP. In addition to greywater and rainwater, it considers the utilisation of stormwater. It

gives information on how to select appropriate schemes giving consideration to site-specific

conditions and relevant supply/demand issues in the relevant locations.

The CoP also considers the design and complexity of different configurations. It makes the point (in

section 8) that there are no current legislative water quality criteria (i.e. only guidelines as presented

in the rainwater & greywater CoP). In more detail than in previous CoP, it makes reference to risk

management requiring Health Impact Assessments (HIAs) and the use of Water Safety Plans.


Issue | 9 June 2017

Page B5

B3 Other Related UK Guidance

B3.1 Rainwater / Greywater – Guidance

There have been a number of guidance and recommendation documents produced (aside from the

British Standards and WRAS Guidance Notes) by bodies and organisations aiming to summarise the

relevant information available at the time and encourage good practice in rainwater and greywater

recycling.

These have included BSRIA, CIRIA, UKRHA, Water Companies (e.g. Alternative Water Systems –

Information Leaflet and Guide available from the WRAS website), The Market Transformation

Programme, the Environment Agency and others.

Also the recent updated SuDS manual from CIRIA details how rainwater harvesting systems can be

used to help manage surface runoff. However the British Standards and WRAS publications should

be referred to as the primary sources of guidance.

B3.2 Blackwater – Guidance

There is no current guidance on the use of treated effluent (blackwater) for non-potable purposes in

UK, with the British Standards and other guidance focussing on rainwater and greywater use.

In the absence of such guidance, Thames Water chose to use US regulations (by the US EPA

unrestricted urban reuse quality guidelines) for the reclaimed water on their two recent blackwater

schemes (BedZed and the Olympic Park).

In addition, the EA were consulted about classification on the treated effluent as it was being stored.

Further to discussions, the EA issued a “regulatory position statement” that a permit was not required

at the Olympic Park.

The most recent British Standard (BS 8595:2013 Code of Practice for the Selection of Water Reuse

Systems) explicitly states that it does not cover treated effluents.

B3.3 SuDS – Guidance

There have been some recent outputs related to SuDS (Sustainable Urban Drainage Systems) which

have relevance to approaches for rainwater and stormwater management on sites.

As mentioned above, a recent update of the CIRIA SuDS manual has been published (CIRIA C753)

and the Thames Water region the Mayor’s London Plan and initiatives such as the Sustainable

Drainage Action Plan are also relevant.

The Government have released 14 Non-Statutory Technical Standards to guide planning authorities,

designers and developers (March 2015) but these are considered to be much less prescriptive than the

much more detailed regulations drafted, but never enacted, as a part of the Flood and Water

Management Act.


Issue | 9 June 2017

Page B6

B4 Forthcoming Standards & Guidance

There has been recent activity by the European and International Standards bodies related to water

reuse. In the UK this is being coordinated through BSi (British Standards Institution) who circulate

the various documents for comment. The current, live working documents cover both proposed ISO

standards and EU standards.

The ISO (International Organisation for Standardisation) is a worldwide federation of national

standards bodies (ISO member bodies). The work of preparing International Standards is normally

carried out through ISA technical committees. Each member body interested in a subject has the

right to be represented on that committee. Other organisations may also take part in the work. Draft

standards adopted by the technical committees are circulated to member bodies for voting and are

only approved if agreed by at least 75% on the member bodies voting.

The ISO water reuse technical subcommittee (TC 282/SC3) of the Water Group of ISO (WG50) met

in Beijing in November 2015 which also expedited the production of a number of new drafts for

comment.

In parallel, the relevant EU committees (CEN TC 165/WG50) are working on European standards

which are again being co-ordinated in the UK through BSi.

It should be noted that none of the following standards/guidance are yet adopted; they are at various

stages of consultation and as such are not fully in the public domain.

The following are referred in this report for reference purposes and should not be quoted outside of

this report.

B4.1 ISO Guidelines for Health Risk Assessment and Management

for Non-Potable Water Reuse

On 4 March 2016, a draft of Guidelines for Health Risk Assessment and Management for Non-

potable water reuse (CD2 20426) was circulated via the UK’s BSi. The aim of this guidance is to

provide a consistent approach to water reuse focussing on people’s health. Working towards an ISO

International Standard it is based on health risk assessments and disability-adjusted life year

(DALY). It is very much influenced by the Australian Guidelines for Water Recycling: Managing

Health and Environmental Risk (Phase 1) published in 2006.

It is a complex document that requires comprehension of health risk characterisation and dose-

response rates. However a particular advantage, if striving for a consistency of approach, maybe that

it is applicable to all sources of reclaimed water (black, grey, rain, storm, etc.) treated for non-

potable purposes.

B4.2 EU Standards on NPWR Systems

These two documents are being circulated by the CEN technical committee via the BSI. CEN is one

of three European Standardization Organizations (together with CENELEC and ETSI) that have been

officially recognized by the European Union and by the European Free Trade Association (EFTA) as

being responsible for developing and defining voluntary standards at European level. The two

documents both appear to mirror the two related UK British standards for rainwater and greywater

(BS 8515 & BS 8525-1).


Issue | 9 June 2017

Page B7

B4.2.1 EN 16941-1 on Rainwater Harvesting

This proposed EU standard follows a similar approach to the British Standard for systems for the use

of rainwater. However, unlike the British Standard, the current draft (circulated via BSi on 25/11/15)

does not give recommendations on water quality standards, with the only comment on water quality

being that the reclaimed rainwater should be “fit for purpose and present no undue health risk”.

B4.2.2 EN 16941-2 on Greywater Reuse

Part 2 refers to systems for the use of treated greywater. (EN-16941-2 greywater). This standard was

circulated via BSi on 7/1/2016 as a draft from the CEN technical committee 165/WG50. In the same

way as Part 1 concerning rainwater, it appears informed by the British Standard for greywater

(Part 1). It is comprehensive, covering design, installation, commissioning and includes annexes with

water quality guidelines and dye testing etc.

It should be noted that there is no EU equivalent to the section in the British Standard (Part 2) that

refers to test methods for the specification of equipment.

B4.3 ISO Guidelines for Water Quality Grade Symbols for Water

Reuse.

The latest draft (dated 12 Feb 2016 – ISO WD2 20469) proposes a very simplistic marking system

based on two types of star ratings: (i) related to the health risk to end-users, and (ii) risks to the

environment.

The proposal has been prepared by ISO committee TC/262. For comparison, some Australian States

still use a similar classification concept (Class A* to Class D) but, in the national Australian

Guidelines, they have moved away from this concept, to that of reclaimed water being “fit for

purpose” (rather than conforming to a particular standard).

B4.3.1 ISO Water Reuse in Urban Areas – Guidelines for Centralised Water

Reuse Systems (ISO/CD 20760-1 & 2)

These currently draft guidelines are targeted at centralised water reuse systems, principally from

municipal waste water. The guidelines are in two parts. The drafts are currently out for consultation

and in the UK and being coordinated through BSI.

Part 1 – covers the Design Principals. It appears informed by Australian and USA approaches. It

considers various models / configurations of centralised systems and subsequent treatment,

distribution systems, storage, monitoring etc.

Part 2 – covers Management of Systems. It covers risk management of the systems and guidelines

for management of individual elements, such as the storage, reclaimed water distribution systems

(labelling /colour coding), monitoring, management of incidents etc.


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Page B8

B5 Position of various bodies on NPWR

B5.1 European Union

The EU promotes water recycling and reuse.

• The “Blueprint to Safeguard Europe’s Water Resources”, adopted by the European Commission

in November 2012, makes it clear that maximisation of water reuse is a specific objective.

• The development of a regulatory instrument to ensure this was proposed, with a (now passed)

target for this to be achieved by 2015.

• The Urban Wastewater Directive (1991) states that wastewater should be reused wherever

appropriate (although there is no clear definition of what is “appropriate”).

B5.2 UK Regulatory Bodies

UK Regulatory Bodies such as the Environment Agency can likewise promote consideration of

recycling schemes and do produce guidance for those wishing to consider such schemes.

• Defra’s “Future Water - The Government’s Water Strategy for England” 2008, (Ref 3) cites

rainwater and greywater harvesting as future opportunities.

• The EA’s Water Resources Strategy - Water for People and the Environment 2009 (Ref 4)

welcomes the increased interest in rainwater and greywater harvesting schemes, with the proviso

that they are cost-effective and appropriate.

B5.3 Water Utilities

Water companies may promote the uptake of non-potable systems as one measure towards securing

the gap between current and projected water supply and demand (e.g. Thames Water WRMP14). In

the past they have also helped with the implementation of schemes to further understanding through

research, such as Thames Water’s Millennium Dome, BedZed and Olympic Park initiatives.

B5.4 Local & Regional Government (GLA, LPA)

The 2011 London Plan’s policy 5.13 sets out the drainage hierarchy, where storage of rainwater for

later use is identified as they first option, thereby promoting the use of non-potable water within new

developments.

GLA with Thames Water and the EA (London Sustainable Drainage Action Plan Consultation Oct

2015) aims for a 25% reduction in surface water flows to sewers by 2040. The capture and use of

rainwater at local level is one means of achieving this target.

Local Government can also champion incorporation of non-potable systems in new developments.

Mayor of London’s Sustainable Design and Construction Policy (Implementation Framework 2011)

directs the London Boroughs to ensure “Developers maximise the opportunities for water saving

measures and appliances in all developments, including the reuse and using alternative sources of

water. Boroughs should negotiate and secure from developers as many as of the water saving

initiatives listed as practical.”


Issue | 9 June 2017

Page B9

The initiatives listed include rainwater harvesting, groundwater and reuse (grey & black, although

black is recognised as being more energy-intensive).

B5.5 Industry Associations

Industry associations such as CIRIA, BSRIA, BSi, and RHA have, over recent years, produced

guidance documents which increase knowledge and hence confidence in implementing such

schemes.

The recent 2015 CIRIA C753 ‘The SuDS Manual’ recommends rainwater harvesting as one

approach to managing surface run-off. The Governments Market Transformation Scheme has also

provided useful work.

B5.6 Summary

There are no direct legislative requirements to mandate the use of non-potable water systems. Hence

the drivers for developers and individuals to install NPWR systems are “second order”.

Some of these drivers are listed below:

• being part of a general consideration of more sustainable water use on a development site;

• a response to local borough planning directions;

• a solution to local infrastructure challenges;

• an approach to alleviating flood risk;

• an aspiration to save money on potable water charges;

• to align with “green” values and branding (such as demonstrating high BREEAM ratings).


Issue | 9 June 2017

Page B10

B6 International Examples

B6.1 Water Quality Monitoring Regulations

There are currently no requirements for monitoring of water quality or system operation on the

NPWR systems in the United Kingdom. For greater acceptance of NPWR systems, guidelines for

monitoring and reporting of the systems may be necessary.

In San Francisco, where the local city authorities have enacted local ordinance requiring on-site

NPWR systems for all developments with footprint greater than 250,000 ft2 (23,226 m

2), monitoring

and reporting requirements have been set for performance monitoring of the systems (See Table B2)

Table B2 San Francisco - Water Quality Reporting Requirements

Commissioning Operation

Monitoring Reporting Monitoring Reporting

Rainwater Weekly / Monthly* Monthly Monthly Yearly

Stormwater Weekly Monthly Monthly Yearly

Greywater Weekly Monthly Monthly Yearly

Blackwater Daily Monthly Daily Monthly

B6.2 International Guidance not Applicable to UK

The US Water Alliance (http://uswateralliance.org) has partnered with the Water Environment &

Reuse Foundation (https://www.werf.org/) to establish the National Blue Ribbon Commission for

Onsite Non-potable Water Systems to progress innovative solutions for water management.

The commission will develop and advance state and federal guidance and policy frameworks, as well

as regulatory recommendations that support implementation of onsite water reuse projects. It will be

based on best practices underway in local communities and world-class research in order to support

local implementation of onsite non-potable water systems. The commission will also identify new

opportunities for water utilities to facilitate implementation of onsite non-potable systems.

The two year project commences in 2016 and is expected to provide recommendations and

guidelines in late 2018.

Although these regulations and guidelines would not be applicable to UK, they are likely to be

comprehensive and based on latest research in the field and potentially adoptable following review

by bodies such as the regulators (OFWAT, DWI, Environment Agency, Public Health England,

DCLG), standards organisations (BSi, ISO), water utilities and local authorities (e.g. GLA, London

Boroughs).


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B7 UK Guidance on NPWR Schemes

A lack of clear regulations in the UK for operational schemes has hindered the uptake of non-potable

reclaimed water schemes. This had led to a variety of approaches, some schemes being informed by

UK guidance as it has become available, some looking to regulations from countries where non-

potable recycling is more established, and others seemingly demonstrating unawareness of even

good practice.

Rainwater harvesting is the most readily taken-up example of non-potable reuse, and because of the

perceived good quality of rainwater. Despite the seasonal nature of supply, it is often considered

more favourably than greywater or blackwater.

The use of blackwater as a source for non-potable supplies is a more recent development (e.g.

BedZED and the Olympic Park).

There are a few instances where treated effluent from municipal STWs has been used for non-

municipal purposes. Two such examples are:

• Wessex Water at Avonmouth supply 30 Ml/d of treated sewage effluent as cooling water for a

gas turbine power station, and

• Seven Trent provide non-potable water for golf course watering of Coventry Golf Club from

Finham Sewage treatment works.

A lack of standardised terminology has been identified with greywater, with the term being used both

for ‘treated’ as well as ‘untreated’ greywater. In one instance the treated sewage effluent is termed as

“greywater” on golfing websites.

Early 2000 Guidance

The UK guidance on non-potable supplies has mainly been produced post 2000 and building upon

research work in the late 1990s (e.g. BSRIA) and the implementation of a non-potable water supply

at the Millennium Dome in 2000. The latter was the first such large-scale schemes in the UK and

stimulated the production of the Water Regulations Advisory Scheme (WRAS) initial 1999 guidance

note concerning the marking and identification of reclaimed water pipework.

Recent Guidance

The majority of UK guidance, mainly concerning rainwater and greywater, has been produced since

2009. It evolved from a number of initiatives including the Government’s Market Transformation

Programme.

Other bodies, such as the EA, have also produced guidance documents. The drivers have changed

over time, which may not have helped implementation.

The cessation of the Code for Sustainable Homes was considered unfortunate although some water

efficiency related targets were incorporated into Building Regulations. The key codes of practice are

now incorporated into British Standards, which take the form of Guidance and Recommendations.

However, it should be noted that these do not specifically cover blackwater. The only legally-binding

regulations are encapsulated within the Water Supply Water Fittings / Water Quality

Regulations (2010) described later, and concern preventing contamination of potable supplies.

Appendix C

Governance and Perception

Review


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Page C1

C1 Governance Models

Governance issues can be considered on a number of levels. At a UK Government level, the way the

water market is regulated and managed is crucial. With deregulation, OFWAT is moving towards a

model where the water market looks after itself through pricing mechanisms, so recycling initiatives

have to be considered in this context.

We have already noted that there are no UK regulations to mandate water recycling, so with the cost

of potable water being relatively inexpensive there is an on-going challenge to develop financing

models to encourage the uptake and management of recycling systems on new developments. In

addition, even where a mechanism to fund the additional assets is achieved, local governance issues

surrounding long term ownership and operation of the non-potable systems can also prove a barrier.

The particular issue being considered in this report is how non-potable recycling could potentially be

used to improve the supply/demand balance. With that objective in mind, what entity actually

provides reclaimed water to achieve this, may be of secondary importance.

This section reviews governance models, in particular issues of ownership/operation in relation to

these typologies and upcoming deregulation, and discusses the implications for Thames Water with

respect to maximising non-potable reuse.

There are a variety of ways that Thames Water could be involved in supply of non-potable water,

these are illustrated from a governance perspective in Figure 2 and then discussed in more detail.

Figure C1 Overview of various governance arrangements for the supply of non-potable water

C1.1 Building Scale

At a building-scale level it is unlikely that a water utility would be involved in the ownership or

operation of recycling equipment, unless perhaps as a research initiative. However, it is possible that

a non-regulated division of a water utility could identify this as a new market opportunity. Apart

from the obligations under Water Regulations, a regulated water utility’s governance would end at

the meter point.


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C1.1.1 Design

Observations of examples where developers (or their architects/designers) have specified stand-

alone, building-scale systems (usually rainwater or greywater) have identified a number of issues.

The driver for initial installation of such systems is usually for the building to gain high ratings under

BREEAM, for marketing / branding purposes to the advantage of the building developer or owner

(i.e. not primarily for the reasons of potable water cost-saving) or for water security / scarcity

reasons.

The procurement of a stand-alone, in-building system is relatively straight forward in that it fits

within a standard contractual model. The rainwater / greywater systems and necessary pipework are

specified in the design, and procured in the usual way.

C1.1.2 Operation

Often the ultimate occupants or tenants of the building have not appreciated the requirements or

costs of operating and maintaining the systems over the lifetimes of the building and the necessary

risk management procedures. Systems are usually operated and maintained either by the building

facilities team or sub-contracted to a specialist company.

Unfortunately, following building occupation, with the cost of potable water in the UK (and

particularly the Thames Water area) being generally low, there can be little financial incentive for

building managers to keep systems operational. Unmaintained systems usually fail safely and revert

to potable water, as part of the design for risk mitigation.

Fears over liability issues related to perceived risks from non-potable water supply and ensuring

appropriate water quality, may also influence decisions on whether to keep systems running. The

responsibility and liability for the systems may be discharged through the building’s facilities

management arrangements.

From a water-saving stand-point there is an argument to incentivise both the installation of such in-

building systems, but more importantly the on-going operation and demonstration of water savings

achieved. For example, a mechanism used by developers to comply with Building Regulations to

enable high water-using fittings (e.g. high flow power showers) to be installed, usually in “high

value” residential developments, in water stressed areas, is to offset with recycling initiatives.

It is particularly important that the recycling systems are kept operational in these instances, to

ensure water savings are realised in perpetuity. There is a significant lack of evidence of actual

water-savings achieved over time in buildings with such recycling systems, as on-going metering and

monitoring is often overlooked.

C1.2 Development Scale and Larger Systems

At the scale of development-level or greater, the governance issues are more complex, particularly

with the introduction of competition. The most simplistic example would be where the incumbent

water utility maintains the licence to supply the development in the conventional way and each

individual customer is metered.

A non-potable water supply could be provided, which was the model that was adopted at the

Olympic Park. Outside of this model there numerous other governance options.

It should be noted that buildings would have to be designed with dual-plumbing to accept a

reclaimed water supply.


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C1.2.1 Water Utility Owned and Operated (to Designated Water Meter Point)

From a governance perspective, a water utility owned and operated model is the simplest and is the

primary model for water reuse systems in United States. This would usually involve the water utility

being responsible for the supply of non-potable quality water to a customer meter point. Typically,

the water utility owns and operates the assets upstream of that point.

Beyond the meter point the “customer” takes responsibility, although the water utility still has a

requirement under the relevant Water Regulations for inspections to prevent unintentional

contamination of potable water supplies (through cross-connections, etc.).

This was in essence the model undertaken for the non-potable water supply to the Olympic Park in

London. Thames Water owns and operates the blackwater treatment plant and the non-potable water

distribution system. The utility is responsible for all assets and activities upstream of the non-potable

water meter.

The responsibility for safe use of the non-potable water beyond the customer meter is a somewhat

ambiguous area, as in addition to the specific Water Regulations requirements. The Water

Companies (or other supplier of non-potable water) may be considered to have some “duty of care”

obligations, particularly if the non-potable water quality is specified only for certain uses.

Thames Water discharged its “duty of care” at the Olympic Park through an auditable

communications strategy and programme of comprehensive briefings to the end users.

Water companies understand the systems, procedures and costs necessary to safely manage treatment

and distribution systems and mitigate risk. This model is usually best suited to the larger scale

“development level” schemes using blackwater or municipal sewage effluent as the source water.

Such a model could also include the collection of rainwater and stormwater from a site, although

combining multiple different sources can provide an additional challenge to selecting the appropriate

treatment technology. Under this model it is still possible that the water utility could sub-contract

the operation of the assets to third parties, if they did not have sufficient resources in-house.

In the current UK regulatory regime the financing of such schemes can be a challenge for a water

utility. Funding for the use of treated effluent to augment potable supplies (not considered in this

report) can be managed under the current WRMP methodologies in the regulated business.

The mechanisms for funding of a separate, non-potable, reclaimed water supply through the

regulated business require further investigation.

The Olympic Park reclaimed water provision was delivered as a research project by Thames Water,

and included substantial contribution from the Olympic Delivery Authority (ODA).

In the same way as the building-scale examples, the building owner or operator is responsible

downstream of the meter point. This would include the dual plumbing, compliance with Water

Regulations and any additional treatment considered necessary for building-specific purposes. A

regulated Water utility has no remit to be involved with the in-building infrastructure, apart from

ensuring Water Regulations compliance through the inspection regime (and possible duty of care as

mentioned above).


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C1.3 International Examples

The provision of non-potable water has always been a challenge in the UK, especially with the cost

of potable water being relatively low. Similar challenges have been experienced elsewhere, such as

Australia where the prolonged drought might have been expected to facilitate change.

A recent Australian study4 highlighted the difficulties of delivering non-potable water schemes –

particularly in a changing regulatory regime (Figure C2). As at the Olympic Park, often as a

development site moves through its different phases, key contacts move on and continuity is an

issue.

The regulatory landscape is changing in the UK and there is a potential that it will increase

uncertainty due to changes in interpretations of the “rules”, which is a barrier to increase in uptake of

NPWR systems.

The recent review of greywater uptake in the USA has also highlighted governance challenges.

There are a number of examples from overseas where financial incentives have been successful. In

New York or in Germany, rebates are available for non-potable water end users, with recipients

having to demonstrate that the relevant standards are being met. In case of New York, the rebate is

given annually based on achieved savings.

However, public perception and cultural norms also play a part in some countries. In Europe, Austria

has the highest uptake of rainwater recycling, although there is little price incentive to save potable

water, rainwater recycling is just considered the “norm”.

4 Navigating the Institutional Maze - Australian Institute for Sustainable Futures 2013

Figure C2: Example of governance barriers to uptake of non-potable

schemes - Australian context with similarities to UK


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C2 Constraints to Delivery

The implementation of NPWR systems is limited due to perception about the water quality, lack of

regulatory requirements, up-front costs and return on investment, and the deliverability of the

infrastructure within and outside buildings.

C2.1 Regulatory Requirements for Inclusion in New Developments

There are no mandatory requirements for inclusion of NPWR systems in new developments. A lack

of clear regulations in the UK for operational schemes has hindered the uptake of NPWR systems.

As a comparison, San Francisco became the first utility in USA to mandate new developments with

footprint greater than 40,000 ft2 to have dual plumbing installed and new developments with 250,000

ft2 or more footprint to have onsite NPWR systems installed.

The mandatory requirements were introduced in 2015 alongside grants for building or district scale

system above certain thresholds; for onsite systems for buildings with footprint greater than 100,000

ft2, or district system (typology 4) that connects two or more developments.

C2.2 Standards

Lack of standards is a constraint for the delivery of NPWR systems.

There are no current standards for Blackwater reuse in UK or Europe, and recent meeting at EU have

indicated that there is no current plans to publish one for blackwater reuse.

C2.3 Policy

The ‘now withdrawn’ Code for Sustainable Homes was the closest the UK came to requiring

adoption of NPWR in new developments.

The London Plan has a policy promoting higher water efficiency standards. However, as it is only a

policy, there is no requirement to implement it in new developments.

C2.4 Perception of Water Quality

The perceived health risk associated with NPWR acts as a barrier to people having these systems

installed. These concerns are based on reports of historic incidents of cross-connection of NPWR

systems and potable water supply.

C2.5 Qualified Installers

There is lack of adequate number of qualified plumbers that can install, maintain and ensure the

systems are running in good operating state.

A number of training courses are available to provide Certification for plumbers, however there is

low uptake of these certifications – primarily due to limited market of the NPWR systems

Appendix D

Detailed Methodology


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D1 Stage A

The potential future development site information was captured from the Housing and Jobs Targets

set by the Mayor of London in the London Plan and development strategies.

The methodology for estimating water demand has already been outlined in Section 3.3.

D2 Stage B

The methodology is detailed in Section 3.4.

In absence of information about plot area, site layout and building footprint, the non-potable water

yield from rainwater and stormwater were estimated based on the Nine Elms Case Study, which is

presented in Appendix E2.

D3 Stage C

The allowable yield was evaluated based on presence of regulations and standards addressing

NPWR, as well as governance and policy measures to enable NPWR systems being installed and

operated, as well as issues around perceptions and deliverability.

The above items reviewed in detail in Appendix B, and Appendix C.


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D4 Stage D

D4.1 NPWR Assessment for WRMP19

The cost evaluation for WRMP required information was assessed along the DMA boundaries.

The process utilised is outlined in the Figure D1 below:

The process is explained in more detail in the following sub-sections.

D4.1.1 Opportunity Areas

A number of Opportunity Areas (OA) lies partially or completely out of the Thames Water’s water

supply zone. These OAs or parts of the OAs have been excluded from the assessment for this project.

The Mayor of London has published the aspirational targets for housing and jobs for some of the

Opportunity Areas that fall within Thames Water’s water supply areas.

The SHLAA sites do not meet the growth targets in all areas. The approach to address this shortfall

has been outlined in following sub-sections.

As such, to understand the remaining strategic scale growth suitable for consideration in this Non-

Potable Water Study has taken consideration of:

• Completions to date;

• Identified residual capacity within OAs and other strategic development sites;

• Growth projections without identified sites;

Figure D1: Assessment process for NPWR at DMA level


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D4.1.2 Completions to Date

The greatest opportunity to incorporate non-potable water management approaches into new

development is prior to the granting of planning permission or build out. Several of the OAs have

already experienced significant growth.

To estimate the extent of the completions and as such the remaining growth expectation for each of

the OAs a review of the London Development Database cross checked against the potential OAs was

undertaken.

The London Development Database is the system used by the Mayor to monitor planning

permissions and completions across London since 2004. It records and classifies development as

‘completed’, ‘started’ and ‘not started’.

This would rule out the opportunity for developments classed as ‘completed’ and, depending on the

size of development, a decision could be taken upon whether there was still an opportunity for any

developments classed as ‘started’; and as such identified and rule out those sites where the

development as progressed to far to influence.

D4.1.3 Identification of Residual Capacity

As highlighted above, some OAs, such as Bexley Riverside, cover a wide area and include a number

of sites that could accommodate significant growth. To identify the sites where growth is planned,

the Local Development Documents (LDD) (Core Strategies, Local Plans, Area Action Plans and

Supplementary Planning Documents) for each of the London Boroughs which contain all or part of

an OA were reviewed.

Where sites and growth areas were clearly identified, these were mapped and growth aspirations

recorded. In a number of cases, however, the LDDs predate the growth aspirations of the OAs or did

not contain sufficient information.

As such, the GLA’s 2013 Strategic Housing Land Availability Assessment (SHLAA), which

provides an indicative housing capacity and a postcode, was used to identify potential growth sites in

the OAs.

These were also cross referenced to the London Development Database to ensure they had not been

built out or planning permission had not been received. Although the exact sites could not be

mapped, the postcode and indicative capacity were used to identify a centre of gravity of future

development through which a land take area could be calculated using housing density assumptions

as necessary.

D4.1.4 Growth Projections without Identified Sites

Using the LDDs and cross referencing with the SHLAA, it has been possible to identify sites to meet

OA growth aspirations in a number of the OAs. However, where there was still a shortfall between

the identified sites and the growth aspirations, for the purposes of this study, this residual shortfall

was applied to the identified sites through an assumed increase in development quantum.

D4.2 Cost Estimation Methodology

To enable replication of the cost estimation method to all opportunity areas, a high level estimation

has been established. The cost estimates utilise the New Rules of Measurement (NRM) and Building


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Page D4

Cost Information Service (BCIS) from Royal Chartered Institute of Surveyors (RCIS). The

estimation process is outlined Figure D2.

Figure D2 Process flow diagram of cost estimation method used

D4.3 Population and Floor Area Estimation

Residential

A gross occupancy of 2.1 persons per unit has been utilised where detailed unit breakdown is not

available. General occupancy estimates based on census figures have been used for occupancy

The London Plan5 guidance for residential floor area have been used for estimation of gross floor

area for Nine Elms as breakdown of unit configuration was available.

Commercial

The number of projected jobs has been provided for the Opportunity Areas. Floor area per employee

guidance has been used to estimate Gross Floor Area (GFA).

D4.4 Water Demand Estimation

Residential

Building Regulations (Part G) and British Standard BS 8525:2010 ‘Code of Practice for Greywater

Reuse’ have been used to estimate residential potable and non-potable water demands.

5 Greater London Authority. "The London Plan." London, GLA (2016).


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Commercial

CIRIA C657 guidance and other industry information has been used to estimate water demand for a

typical non-residential uses.

D4.5 Costing Estimation Method

Table D1 Costing method details

Cost Items Description

Capital

Expenditure

(CAPEX)

Internal pipework (water

supply and sanitary

services)

• Capital cost of additional internal water and sanitary services,

based on Gross Floor Area (GFA) using the New Rules of

Measurement (NRM)6 approach.

External piped network - • Capital cost of additional external water and sanitary services

based on network flow capacity and standard costing

estimates based on pipe sizes and lengths.

Treatment Plant • The rainwater, stormwater and greywater system costs have

been estimated using cost information sourced from Aquality.

• Blackwater system costs were estimated based on plant

capacity and expert opinion of system costs,

Operating

Expenditure

(OPEX)

Maintenance and energy

for treatment • Operational cost for rainwater, stormwater, and greywater

system have been estimated using cost information sourced

from Aquality.

Note: OPEX for blackwater treatment plants suitable for NPWR were not readily available and therefore in agreement

with Thames Water, the project did not pursue this further.

D4.6 Key Costing Assumptions

The costs were all based on current day pricing and therefore do not take into account development

phasing. The costs are inclusive of:

• Main contractors preliminaries & overheads and profit at 15%

• Professional Fees at 10%

• Contingency Risk at 15%

The above costs exclude the following cost items:

• Inflation

• VAT

• Land Acquisition

• Encountering abnormal ground conditions including remediation, archaeology, excavations

below water table level and unexploded ordnance




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D5 Notes on Costs for Rainwater and Greywater systems

1. OPEX cost for RWH and GWH systems are based on single systems with dual yearly

maintenance visits at current prices.

2. CAPEX for RWH and GWH systems include for pumping systems to convey the water within

the buildings to end use.

3. The OPEX costs exclude energy costs of pumping water internally within buildings. For high

rise, any energy costs for pumping non-potable water would be offset by reduction in pumping

costs of potable water.


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D6 Detailed Outputs

D6.1 Technical Yield

The assessments were undertaken on DMA basis and supplied in excel spreadsheet in such format.

However, for consistency with rest of the assessments, the outputs have been presented on

Opportunity Area boundaries. The ones highlighted in red have been discounted from assessment as

they fall below the 10 m3/d threshold.

Table D2 Technical non-potable yields in residential developments

OA RWH

(Ml/d)

SWH

(Ml/d)

GWR

(Ml/d)

BWR

(Ml/d)

Combined

(Ml/d)

1 Bexley Riverside+ 0.044 0.067 1.733 2.599 1.843

2 Bromley 0.007 0.010 0.263 0.394 0.279

3 Canada Water 0.018 0.027 0.693 1.040 0.737

4 Charlton Riverside 0.009 0.014 0.368 0.551 0.391

5 City Fringe/Tech City 0.040 0.060 1.575 2.363 1.676

6 Cricklewood / Brent Cross 0.027 0.040 1.050 1.575 1.117

7 Croydon 0.020 0.029 0.767 1.150 0.816

8 Deptford Creek/Greenwich Riverside+ 0.013 0.020 0.525 0.788 0.559

9 Earls Court 0.020 0.030 0.788 1.181 0.838

10 Elephant & Castle 0.013 0.020 0.525 0.788 0.559

11 Euston 0.010 0.015 0.399 0.599 0.425

12 Greenwich Peninsula 0.054 0.081 2.100 3.150 2.234

13 Isle of Dogs 0.081 0.121 3.150 4.725 3.352

14 Kings Cross - St Pancras 0.005 0.008 0.200 0.299 0.212

15 Lewisham, Catford and New Cross 0.022 0.032 0.840 1.260 0.894

16 Lower Lea Valley (including Stratford) 0.005 0.008 0.200 0.299 0.212

17 Old Kent Road+ 0.092 0.137 3.581 5.371 3.810

18 Old Oak and Park Royal 0.054 0.081 2.100 3.150 2.234

19 Paddington 0.144 0.216 5.618 8.426 5.977

20 Royal Docks & Beckton Waterfront 0.003 0.004 0.105 0.158 0.112

21 Thamesmead & Abbeywood 0.063 0.094 2.457 3.686 2.614

22 Tottenham Court Road 0.013 0.020 0.525 0.788 0.559

23 Upper Lee Valley+ 0.001 0.002 0.053 0.079 0.056

24 Vauxhall, Nine Elms & Battersea 0.054 0.081 2.111 3.166 2.246

25 Victoria 0.027 0.040 1.050 1.575 1.117

26 Waterloo + London Bridge, Borough &

Bankside 0.003 0.004 0.105 0.158 0.112

27 White city 0.007 0.010 0.263 0.394 0.279

28 Woolwich 0.016 0.024 0.630 0.945 0.670


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Table D3 Technical non-potable demand met in residential developments

OA RWH

(Ml/d)

SWH

(Ml/d)

GWR

(Ml/d)

BWR

(Ml/d)

Combined

(Ml/d)


2 Bromley 0.007 0.010 0.210 0.394 0.227

3 Canada Water 0.018 0.027 0.554 1.040 0.599




7 Croydon 0.020 0.029 0.613 1.150 0.662

8 Deptford Creek/Greenwich

Riverside+ 0.013 0.020 0.420 0.788 0.454

9 Earls Court 0.020 0.030 0.630 1.181 0.680

10 Elephant & Castle 0.013 0.020 0.420 0.788 0.454

11 Euston 0.010 0.015 0.319 0.599 0.345


13 Isle of Dogs 0.081 0.121 2.520 4.725 2.722


15 Lewisham, Catford and New

Cross 0.022 0.032 0.672 1.260 0.726

16 London Bridge, Borough,

Bankside 0.005 0.008 0.160 0.299 0.172

17 Lower Lea Valley (including

Stratford) 0.092 0.137 2.864 5.371 3.094

18 Old Kent Road+ 0.054 0.081 1.680 3.150 1.814


20 Paddington 0.003 0.004 0.084 0.158 0.091

21 Royal Docks & Beckton

Waterfront 0.063 0.094 1.966 3.686 2.123



24 Upper Lee Valley+ 0.054 0.081 1.688 3.166 1.823

25 Vauxhall, Nine Elms &

Battersea 0.027 0.040 0.840 1.575 0.907

26 Victoria 0.003 0.004 0.084 0.158 0.091

27 Waterloo 0.007 0.010 0.210 0.394 0.227

28 White city 0.016 0.024 0.504 0.945 0.544

29 Woolwich 0.040 0.060 1.260 2.363 1.361


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Table D4 Technical non-potable yields in non-residential developments

OA RWH

(Ml/d)

SWH

(Ml/d)

GWR

(Ml/d)

BWR

(Ml/d)

Combined

(Ml/d)


2 Bromley 0.001 0.001 0.016 0.040 0.018

3 Canada Water 0.001 0.001 0.016 0.040 0.018




7 Croydon 0.004 0.005 0.060 0.150 0.068

8 Deptford Creek/Greenwich Riverside+ 0.002 0.002 0.032 0.080 0.037

9 Earls Court 0.005 0.006 0.076 0.190 0.087

10 Elephant & Castle 0.003 0.003 0.040 0.100 0.046

11 Euston 0.007 0.009 0.112 0.280 0.128


13 Isle of Dogs 0.058 0.069 0.902 2.254 1.029


15 Lewisham, Catford and New Cross 0.003 0.004 0.048 0.120 0.055

16 London Bridge, Borough, Bankside 0.013 0.015 0.200 0.500 0.228

17 Lower Lea Valley (including Stratford) 0.026 0.031 0.400 1.000 0.456

18 Old Kent Road+ 0.003 0.003 0.040 0.100 0.046


20 Paddington 0.003 0.003 0.040 0.100 0.046

21 Royal Docks & Beckton Waterfront 0.019 0.023 0.294 0.734 0.335



24 Upper Lee Valley+ 0.008 0.009 0.120 0.300 0.137

25 Vauxhall, Nine Elms & Battersea 0.008 0.009 0.120 0.300 0.137

26 Victoria 0.002 0.002 0.032 0.080 0.037

27 Waterloo 0.008 0.009 0.120 0.300 0.137

28 White city 0.005 0.006 0.080 0.200 0.091

29 Woolwich 0.003 0.003 0.040 0.100 0.046


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Table D5 Technical non-potable demand met in non-residential developments

OA RWH

(Ml/d)

SWH

(Ml/d)

GWR

(Ml/d)

BWR

(Ml/d)

Combined

(Ml/d)


2 Bromley 0.001 0.001 0.016 0.040 0.018

3 Canada Water 0.001 0.001 0.016 0.040 0.018




7 Croydon 0.004 0.005 0.060 0.150 0.068

8 Deptford Creek/Greenwich

Riverside+ 0.002 0.002 0.032 0.080 0.037

9 Earls Court 0.005 0.006 0.076 0.190 0.087

10 Elephant & Castle 0.003 0.003 0.040 0.100 0.046

11 Euston 0.007 0.009 0.112 0.280 0.128


13 Isle of Dogs 0.058 0.069 0.902 2.254 1.029


15 Lewisham, Catford and New

Cross 0.003 0.004 0.048 0.120 0.055

16 London Bridge, Borough,

Bankside 0.013 0.015 0.200 0.500 0.228

17 Lower Lea Valley (including

Stratford) 0.026 0.031 0.400 1.000 0.456

18 Old Kent Road+ 0.003 0.003 0.040 0.100 0.046


20 Paddington 0.003 0.003 0.040 0.100 0.046

21 Royal Docks & Beckton

Waterfront 0.019 0.023 0.294 0.734 0.335



24 Upper Lee Valley+ 0.008 0.009 0.120 0.300 0.137

25 Vauxhall, Nine Elms &

Battersea 0.008 0.009 0.120 0.300 0.137

26 Victoria 0.002 0.002 0.032 0.080 0.037

27 Waterloo 0.008 0.009 0.120 0.300 0.137

28 White city 0.005 0.006 0.080 0.200 0.091

29 Woolwich 0.003 0.003 0.040 0.100 0.046


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D7 Supplementary Information

D7.1 Costing of Non-Potable Alternative Water Supply Options

The costs associated with water reclamation and reuse varies widely, particularly depending on the

technology, scale, water source and end use. In general, alternative water sources, and recycled water

in particular, typically exceed the cost of the centralised potable water supplies – from a purely

potable water supply perspective.

Considering costs for alternative water supplies systems, key factors influencing the capital and

operational costs include:

• Distance and lift required from the source of water to consumption;

• Type and quality of water source;

• Level of treatment required, which is related to national regulatory requirements; and

• Density of development, which determines the cost of distributing the water across an urban area.

Generally, energy cost, operational and maintenance cost, and capital investment are the main

contributors to the water production cost. Of these, operational and maintenance can be two of the

largest and most variable costs, and are also difficult to ascertain due to variability in applications,

regulations, building costs, and other project specific factors.

Simple cost analysis of treatment and reuse is therefore difficult to calculate, and it is important that

differences in assumptions and factors associated with allocation of costs be correctly understood.

Furthermore, a purely economic assessment often does not take full account of social and

environmental externalities and avoided costs. Avoided costs are those which may be incurred

without the initiative proceeding and may include:

• Reduced wastewater system operating and capital investment as a result of:

• Reduced loads into the wastewater system,

• Reduced water demand from the potable water system,

• Avoided upstream investments (such as alternative supply sources) as a result of reduced water

demand,

• Avoided expensive private water investment on a lot scale (such as building scale initiatives to

achieve desired sustainability accreditations); and

• Synergistic cost reduction activities in incorporating infrastructure within:

• Wider investment to reduce sewage overflows or improve system reliability; or

• Major infrastructure strategies and development areas.

• Extended Infrastructure lifecycles

Social and environmental externalities may additionally be difficult to define and evaluate,

particularly in quantifiable or monetary terms. These may include improved health of surface and

ground water resources and associated ecosystems, greater urban resilience and flexibility to respond

to climate change, and improved urban liveability.

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Appendix E

Case Studies

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E1 Old Oak Common

E1.1 Overview of the Area

Covering 650 hectares of land in West London, Old Oak Common and Park Royal Opportunity

Areas are important strategic locations for major urban regeneration, targeted to deliver a significant

contribution to crucial housing, employment and strategic growth with London.

The proposals in this area comprise a mixture of ambitious industrial, residential and commercial

regeneration and development. However, the proposals are heavily constrained by an acute lack of

capacity within the combined drainage infrastructure, contributing to downstream flood risk, and an

increasing deficit of available water to meet demand in the rapidly expanding city.

In an attempt to meet these challenges, an Integrated Water Management Strategy was developed for

these Opportunity Areas to set a framework for how water, wastewater and flood risk should be

managed, in order to move towards a more sustainable new development.

E1.2 Development Context and Assumptions

Major new development will be focused at Old Oak Common, which is proposed to be a high density

mixed-use development accommodating approximately 25,500 new homes and an indicative 65,000

new jobs.

Park Royal is proposed to be retained as a strategic industrial location, with the majority of existing

businesses retained. In addition, the Park Royal development will provide approximately 10,000 new

employment opportunities. The primary area for this development will be at the site of the High

Speed 2 (HS2) construction sites following their release upon completion of the project. The current

preferred option is for site re-development as an industrial business park, incorporating 125,750 m2

of new floor space. In addition, 1,500 new homes will be constructed to the west of Park Royal and

additional employment opportunities created through regeneration and densification of the existing

land use.

Existing and proposed development areas, land use information and occupancy were derived using

GIS layers and masterplan information provided by the Old Oak and Park Royal Development

Corporation (OPDC). The population assumptions are summarised below for the two areas:

Old Oak Common

• 50,658 residential population, assuming a 2.1 persons per dwelling occupancy rate.

• 40,000 office employment population.

• 10,000 retail employment population

Park Royal

• 3,150 additional residential population, assuming a 2.1 person per dwelling occupancy rate.

• 10,000 new industrial population.

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It should be noted that these numbers are in addition to existing population in the retained areas of

the development. In particular this includes approximately 2,000 businesses with 30,000 employees,

which will be retained and enhanced within Park Royal. Building and population characteristics for

these areas were obtained from GIS layers provided by the Old Oak and Park Royal Development

Corporation.

Building footprints were assumed to be 60% of plot coverage for new buildings. Residential floor

space was based on an assumption of 81m²/apartment.

The building and floor space assumptions for new build areas across the two Opportunity Areas are

summarised below:

• Old Oak Common

• 140 buildings, including 24,670 residential apartments, with assumed gross external area of

1,998,170 m², 35,392 m² gross external area of offices and 102,720 m² gross external area of

retail.

• Park Royal

• 1,500 residential apartments and 239,659 m² gross external area of new industrial development.

E1.3 Water Balance

An annual water balance model was developed for the Opportunity Areas to characterise and

quantify the water cycle flows anticipated from the proposed development.

Water demand and wastewater generation were estimated using usage assumptions based upon the

Building Regulations 2010 Part G (2015 Edition) and British Standard BS 8524:2001.

For both of these methodologies, the total water demand is based on assumptions on the use of

sanitary fittings. A range of efficiency scenarios were tested for the existing and new land uses;

however, it has been generally assumed that all new development would meet the maximum

‘optional’ standard of water efficiency on 110 litres per person per day, supporting the latest

guidance within the London Plan.

The anticipated pre and post development water balance for the opportunity areas is illustrated in

Figure E1 and Figure E2.

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Figure E1: Pre development annual water balance (annual)

Figure E2: Post development annual water balance (annual)

The magnitude of the anticipated increase in water demand and wastewater generation anticipated

from the proposed development is further illustrated in Figure E3.

As these figures illustrate, without intervention, the proposed development of the Opportunity Areas

will significantly increase demand on the regional water supply and wastewater assets. The capacity

of these systems to cope with increased demand of this magnitude is limited, unless provisions are

made to mitigate this impact.

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Figure E3 Anticipated increase in flows in opportunity area

However, the figures also illustrate that there are several opportunities present to mitigate this

impact. Significant streams of water are exiting the system, discharged as waste streams which could

be recycled to significantly reduce the overall external demands and discharges.

E1.4 Water Management Measures

In order to meet the substantial challenges of the proposed development, a range of water

management options were considered. A total of 13 options were scoped, using an assumed

technology, and their performance assessed across the key project objectives, and a range of wider

deliverability and sustainability criteria. The options considered ranged across the following themes:

• Achieving the maximum possible standards of demand management, by achieving the highest

current and future industry standards in water efficiency, utilisation of smart network

technologies, community engagement and targeted water efficiency retrofits and process

improvements.

• A cohesive integrated approach to managing surface water quality and quantity, including

attenuation, conveyance and discharge of runoff, across the development areas.

• A strategic approach to water recycling, considering non-potable use of water as a minimum,

with allowance for future implementation of potable water recycling.

These measures were combined into a number of scenarios, in order to determine a preferred strategy

for water management across the Opportunity Areas.

The individual measures associated with NPWR, and therefore relevant to this study are summarised

below.

• Greywater recycling (GWR) was considered at a building scale for new developments,

comprising installation of building scale greywater collection and treatment with non-potable

distribution for toilet flushing.

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• Rainwater Recycling (RWH) was considered at a building scale for new developments,

comprising installation of building scale rainwater collection, storage and treatment with non-

potable distribution for toilet flushing.

• Wastewater Recycling (BWR) was considered at a site-wide scale across the new build area,

comprising a package wastewater treatment plant to treat incoming sewage, incorporating

advanced water treatment, and redistribution for NPWR within homes and businesses.

• Stormwater Recycling (SWH) was considered at a site-wide scale for the new build areas,

comprising downstream stormwater harvesting system incorporating wetland secondary

treatment train, disinfection, balancing storage and re-distribution for non-potable re-use.

During the composition of the strategy, preliminary high level costing was undertaken for each of

these opportunities. These costs were based on assumed technologies and demands, at a scale

appropriate to the development.

E1.5 Costing Summary

Costing for each measure was undertaken based on preliminary scoping of infrastructure

requirements, derived from the water flow characteristics and assumed technologies. Where possible,

a unit costing approach was adopted, in particular:

• Capital cost of treatment systems was estimated based on assumed system capacity,

• Capital cost of storage tanks was estimated based on assumed tank capacity,

• Capital cost of additional internal water and sanitary services was estimated based on the gross

floor area.

It should be noted that these estimates were undertaken at a high level, based upon a limited

resolution of information.

The costs outlined below and presented in Table E1 were all based on current day pricing and

therefore did not take into account development phasing:

• Capital cost estimates associated with the water recycling measure in new build areas have been

included in Table E1 below. Ongoing operational costs associated with treatment, pumping and

system monitoring and maintenance were not estimated as a part of this study.

• Typical operational costs for greywater treatment have been defined earlier; however, these have

not been included below to maintain consistency for comparison over the four different measures.

• The estimated non-potable demand which may be met by these measures is additionally shown

below. Considering a 25 year supply period, an estimated value of capital cost per m3 water

supply has been determined.

• In considering these figures, it should be noted that only estimated capital costs (in current values)

have been included, without consideration of future cost discounting (arising from development

phasing), or future OPEX costs.

• Additionally, the ability to harness the non-potable volumes presented will be dependent on the

final system and storage configuration (particularly for the stormwater and roofwater recycling

options).

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Table E1 Old Oak and Park Royal cost estimates

Representative

typology

Estimated non-

potable demand met

(ML/ year)

Offset of potable

demand

Capital cost per m3

water supply (over

25 years)

Rainwater Harvesting Typology 2 320 12% £9

Greywater reuse Typology 2 550 20% £7

Blackwater reuse Typology 4 550 20% £3

Stormwater harvesting Typology 4 550 20% £3

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E2 Nine Elms

Vauxhall Nine Elms and Battersea Regeneration Zone covers approximately 195 hectares of

riverside and near riverside land, and it is currently the largest regeneration area within the boundary

of London.

The Nine Elms on South Bank redevelopment will create more than 21,000 new homes and 25,000

new jobs in the area. The developments is delivered in 69 phased developments between 2010 and

2035 with over 100 new buildings being constructed – both mixed use and single use (residential,

commercial or warehouses).

The landmark developments within the zone is the redevelopment of the Battersea Power Station and

the development of the New Embassy Quarter, with American Embassy currently under construction

and a number of other countries exploring options to relocate their embassies in the area.

Nine Elms Summary

Residential Units 22,419 units

Residential GFA (m2) 1,271,071 m2

Jobs 25,000

Non-residential GFA 1,287,327 m2

Mixed Use Buildings 111

Residential Only Building 16

Offices only buildings 5

Retail only buildings 4

The overarching objective of the Nine Elms Integrated Water Management Strategy was to identify

whether demand management by displacing mains water demand with alternate sources of water

would have resulted in reduction in demands on infrastructure that will delay or avoid the need of

infrastructure upgrades.

The applicable solutions and their scope of impacts are outlined in Table E2 below.

Table E2 Multiple benefits of interventions

Measures

Systems

Water efficient fixtures Rainwater

Harvesting

Stormwater

Harvesting Greywater Reuse

Water Supply Yes Yes Yes Yes

Foul Sewers Yes No No Yes

Combined Sewers Yes Yes Yes Yes

Surface Water

Sewers No Yes Yes No

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The initial assessment identified that due to high density of developments (primarily tower blocks),

the rainwater and stormwater harvesting would not provide significant reduction in water use

reduction by itself.

In addition, the existing infrastructure (road, rail track) segmented the development sites and

prevented a central system being considered.

This assessment therefore provides information about two scenarios.

4. NPWR at individual buildings (Typology 2)

5. NPWR at development or multi development scale (Typology 3)

E2.1 Assessment of Strategies

Each of the overarching strategies can be implemented at all of the identified sites. The reduction in

overall water demand varies on the strategy implemented, as does the costs and impacts of the

solutions. These are compared in a generalised manner in this section.

E2.1.1 NPWR Systems – Individual Buildings (Typology 2)

The distributed water reuse systems are likely to be installed within individual unit or within

individual buildings. This will require storage vessel at basement to hold the used water from

showers, baths, washing machines at a central location for treatment prior to conveyance to the upper

level supply storage (usually within the plant room at or close to roof level). The layout of the

building may warrant multiple independent systems.

Potential interconnections of storage vessels from various buildings, if implemented, can enable

sharing of surplus supply and provides redundancy (e.g. where treatment system is taken offline for

maintenance or repair). This can also enable diversion of surplus supply from one building with

significantly greater supply to another building where the demand can be met by this surplus supply,

thereby reducing the need for another treatment system. This is likely to increase difficulty in

delivery of the scheme but can be more cost effective.

Depending on the design of the buildings, innovative solutions can be implemented that will reduce

the pumping and conveyance costs. For example, if there are intermediate service levels within a

building, the water reuse treatment systems to be installed at these intermediate levels and some of

the treated non-potable water can then be supplied by gravity to lower levels.

The surplus water from the system can be utilised for external irrigation using appropriately labelled

pipework, thus integrating with the Sustainable Drainage Systems.

CapturePre-

treatment Storage

Treatment Systems

Post treatment Storage

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E2.1.2 NPWR Systems – Mixed (Typology 3)

Typology 3 communal system boundaries were set taking into consideration site adjacency and when

the developments are planned to be delivered (Figure E4). This approach would reduce the difficulty

in delivery of communal NPWR systems.

There is additional challenge for communal systems in relation to the phasing of the developments,

the land required for a central pre-treatment storage and the water reuse treatment system. To enable

such systems will require agreements between different developers and with the local planning

authorities.

Although this assessment limited the extent of the communal system to contiguous developments,

the analysis supports a more centralised water reuse network would be more cost effective solution.

However, it will be more challenging to deliver due to multiple land ownerships and potential

liability issues with ownership and operation of the treatment systems.

Issues related to operations, monitoring and compliance may be resolved if the water reuse system or

systems were operated by an independent operator (e.g. a Water Service Company or WaSCo).

However implications related to land ownership or land lease will remain, with further challenges

related to access and egress and any ‘buffer’ alongside service network pipes.

Such a network could be laid alongside a new surface water drainage network, which is necessary for

management of the surface water runoff in the area. A centralised system may also enable centralised

storage provisions for captured water before treatment as well as storage after treatment.

If a more centralised solution is selected, a detailed network model will need to be developed for

such a water reuse system. Such modelling will also help to identify the appropriateness of locations

for storage systems and the water reuse treatment systems. There may be opportunity to combine the

storage with any rainwater and stormwater storage systems, as well as any surface water attenuation

systems.

Figure E4 Communal water reuse system configuration

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E2.2 Cost Estimation Approach

The costs have been estimated using the following approach:

1. Capital cost of additional internal water and sanitary services, based on gross floor area using

the New Rules of Measurement (NRM)7 approach.

2. Capital cost of additional external water and sanitary services based on network flow capacity

and standard costing estimates

3. Capital cost of treatment system(s).

4. Professional fees.

5. Operational cost of treatment system.

The cost estimation does not estimated the value of external benefits, but may be considered in the

assessment exercise by Thames Water.

These external benefits include:

• Reduction in mains water supply cost (of benefit to end user).

• Reduced pumping cost of foul water (of benefit to Thames Water).

• Reduced infrastructure reinforcements and upgrades for mains, foul and storm systems (of

benefit to end user and Thames Water).

The land use in the Nine Elms on South Bank area was changing from low rise and light industrial to

high density and high rise residential and commercial developments. Once complete, the new

developments would have resulted in an eight fold increase in water demand and wastewater

discharge.

To enable all of the developments to take place, it required upgrades and reinforcements to meet this

growing demand. These were estimated at £13 million for potable water network and £16 million for

new stormwater system.



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E2.3 Cost Estimates

The costs (Table E3) have been calculated with the assumption that all the infrastructure will be

delivered now and phasing has not been considered.

Table E3 Nine Elms Cost summary

Typology 2

NP systems

Typology 3

NP systems

NP Demand (m3/year) 1,150,400 1,150,400

NP Supplied (m3/year) 1,391,600 1,391,600

NP Satisfied (m3/year) 1,036,800 1,035,900

Total non-potable water used over 25 years (m3) 25,920,000 25,897,500

Net Present Cost (£/m3) £2.24 £2.22

Net Present cost excluding internal building services

(£/m3)

£0.89 £0.91