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Destruction of disinfection byproducts and their precursors in swimming pool water bycombined UV treatment and ozonation
Cheema, Waqas Akram; Kaarsholm, Kamilla Marie Speht; Andersen, Henrik Rasmus
Publication date:2016
Document VersionPublisher's PDF, also known as Version of record
Link back to DTU Orbit
Citation (APA):Cheema, W. A., Kaarsholm, K. M. S., & Andersen, H. R. (2016). Destruction of disinfection byproducts and theirprecursors in swimming pool water by combined UV treatment and ozonation. Abstract from 2016 IUVA WorldCongress, vancouver, Canada.
#12 - Byproduct Formation and Control
Destruction of disinfection byproducts and their precursors in swimming pool water by combined
UV treatment and ozonation
Waqas A. Cheema1, 2
, Kamilla MS Hansen1, Henrik R. Andersen
1
1Technical University of Denmark, Denmark
2 National University of Sciences & Technology, Pakistan
Abstract
Both UV treatment and ozonation are used to reduce different types of disinfection byproducts (DBP) in
swimming pools. UV treatment is most common as it is particularly efficient in removing the repulsive
chlorine like smelling chloramines (combined chlorine). UV treatment of a pool water increased chlorine
reactivity and formation of chlor-organic DBP such as trihalomethanes. Based on the similar selective
reactivity of ozone and chlorine we hypothesized that the created reactivity towards chlorine by UV
treatment of dissolved organic matter in pool water might also be expressed as an increased reactivity
towards ozone and that ozonation might saturate the chlorine reactivity created by UV treatment and
mitigate the increased DBP formation. By experimentally treating pool water samples, we found that UV
treatment makes pool water highly reactive to ozone. The created reactivity towards chlorine decreases
dose dependently with ozone dosage prior to contact with chlorine. Furthermore, the kinetics of ozone in
UV treated pool water changed drastically from a half-life in excess of 20 min to complete consumption
in less than 2 min. We discovered that ozonation in UV treated pool water induced formation of some
DBPs that are not commonly reported in pool water where trichloronitromethane is noteworthy as it is
genotoxic. Therefore, we performed repeated treatment experiments consisting of combined UV/ozone
treatment interchanged with chlorination for 24 h the genotoxicity created during the ozone treatment was
removed by the UV treatments. Based on the experimental results, a treatment system is proposed with a
UV system placed in a side stream to the recirculation flow followed by an ozone dosing point and a
small reaction chamber with a volume that allow 1-2 min reaction time before returning to the main
recirculation flow. This side-stream UV/ozone treatment will improve the swimming pool water quality.
Destruction of disinfection byproducts and their precursors in swimming pool water by combined UV treatment and ozonation
Waqas A. Cheema1,2, Kamilla M.S. Hansen1, Henrik R. Andersen1
1Technical University of Denmark, Denmark 2National University of Sciences and Technology, Pakistan
2016 IUVA World Congress
31 January- 03 February 2016
Vancouver, British Columbia,
Canada
2
Cl2Filter
Conventional treatments Disinfection By-Products
UV/Ozone Ozone UV Introduction
Chlorine + Dissolved Matter
Disinfection By-Products (DBPs) Inorganic e.g. Chloramines
Organic e.g. Trihalomethanes (THMs) Haloacetonitriles (HANs) Haloacetic acids (HAAs)
Particles: Hair, Skin cells
Dissolved matters: Sweat, Urine, Lotion, Shampoo, Make-up
Bacteria & virus
3
Disinfection By-Products
Compound Abbreviation Chemical structure
Trihalomethanes (THMs)
Chloroform TCM CHCl3
Bromodichloromethane BDCM CHBrCl2
Dibromochloromethane DBCM CHBr2Cl
Bromoform TBM CHBr3
Haloacetonitriles (HANs)
Dichloroacetonitrile DCAN CHCl2CN
Bromochloroacetanotile BCAN CHBrClCN
Miscellaneous
Trichloronitromethane TCnitro CCl3NO2
Dichloropropanone DCprop CHCl2COCH3
Trichloropropanone TCprop CCl3COCH3
UV/Ozone Ozone UV Introduction
4
Toxicity estimation
• The toxicity of the different groups
Haloacetonitriles (HANs) > Haloacetic acids (HAAs) > Trihalomethanes (THMs)
• Calculated for water samples by:
• EC50 taken from Plewa et al. 2008
i
i
EC
CToxicity
,50
Hansen et al., 2013
UV/Ozone Ozone UV Introduction
5
Emerging treatment technologies
Particles DOC + chlorine DBPs
Ozonation UV treatment
UV/Ozone Ozone UV Introduction
Can ozonation be effective to remove reactivity of organic matter towards chlorine?
Can UV treatment be effective to remove the DBPs?
6
UV treatment
0 10 20 300.0
0.2
0.4
0.6
0.8
1.0
1.2Morning
Evening
With UV (4 Lamps) Without UV
Experiment day no.
Con
centr
atio
n (m
g/L
)
Combined chlorine
Kristensen et al., 2010
Advantage (established) UV treatment followed by Cl2 decreased combined Cl2
Cl2
Filter UV
UV/Ozone Ozone UV Introduction
Disadvantage ( still need to be established) UV treatment followed by Cl2 Increased chloro-organic byproducts
7
Experimental setup
24 hr 25 C
Residual Chlorine 1±0.3 mg/L
Water samples
Swimming Pool
Sampling Treatment Analysis
UV
Purge & trap GC/MS
UV/Ozone Ozone UV Introduction
8
Control,Cl2 UV½d,Cl2 UV2d,Cl2 UV10d,Cl2
0.0
0.5
4%
5%5.3%
21%
Br-tTHM
tTH
M (
mm
ol/L)
Results
Control,Cl 2 UV½d,Cl2 UV2d,Cl2 UV10d,Cl2
0
12
Cl 2
co
nsu
mp
tio
n (
mg
/L)
UV/Ozone Ozone UV Introduction
Increasing UV dose followed by Cl2 no effect on Total THMs
UV treatment followed by Cl2 increased Cl2 reactivity
Increasing UV dose followed by Cl2 increased Br-THMs
Cl2 consumption Total Trihalomethane
9
COOHCH3 CH
Cl
CH3 CH3C
O
CH2
.OHCOOHCHCH3
Cl
CH3
OH
HOBr
HOBr
HOBr
CH2
Cl
CH3
COOH
CH3
CH3 CH
COOHCH
CH3
CH3
CH3C
O
CH2
Br-
Br-
.OH
Cl
CH2
Cl
Cl-
OH
Cl
CH3
Br-
COOHCH3 CH
Cl
CH
Cl
Cl
Br
CH
Cl
BrBr
COOHCH3 CH
Cl
CH3 CH3C
O
CH2
.OH
COOHCHCH3
Cl
CH3
CH2
Cl
CH3
OH
Br-Cl-DBP Formation Theory
UV Irradiation
COOH
COOH
CH2
CH
CH3CHCH
CH2
C CH2 CHCH2C
C
Cl
Cl
Br
OH
OBr
Br
OH
CH2
Cl
Cl2 Addition
Further reaction
UV/Ozone Ozone UV Introduction
Spiliotopoulou et al., (2015)
10
Initi
al 2
Contr
ol,Cl
UV 2
UV,C
lUV 2
UV,C
lUV 2
UV,C
l
0.0
0.2
0.4
0.61st cycle 2nd cycle 3rd cycle
2.7%2.5% 2.5%
3.1%
2.9%
3.3%
3.0%
3.5%
tTH
M (
µm
ol/L)
0 20 40 60 80
0.0
0.2
0.4
0.6
0.8
1.0Chloroform
Bromodichloromethane
Dibromochloromethane
Bromoform
2 4
Time (min)
EED (kWh/m3)6 8
C/C
0
Effect of repeated treatments
UV/Ozone Ozone UV Introduction
Hansen et al., (2013)
UV treatment decreased total THM
UV treatment followed by Cl2 increased total THM
Total Trihalomethane UV photolysis
Increased bromine substitution increasing UV photolysis
11
Ozone in pools
Oxidation of pollutants
I. Direct reaction
II. Radical reaction
H2O + O3 → O2 + 2 HO•
DOC + HO• → DOCradical oxidized
DOC + O3 → DOCselectively oxidized Fast consumption of ozone Decrease chlorine reactivity of pollutants Low ozone life time no reaction with bromide
Slow consumption of ozone Ozone converts to hydroxyl radicals with time Radical attack of inactive carbon increased
chlorine reactivity Long ozone life time oxidation of bromide to
bromate
UV/Ozone Ozone UV Introduction
Hansen et al.,(2016)
12
Experimental setup
O3
Residual Chlorine 1±0.3 mg/L
Water samples
Swimming Pool
Sampling Treatment Analysis
24 hr 25 C
Purge & trap GC/MS
UV/Ozone Ozone UV Introduction
13
0 1st 2nd 3rd 0 1st 2nd 3rd
0.0
0.5
1.0
1.5
2.0Pool water Polluted pool water
Cl 2
-co
nsu
mp
tio
n (
mg
/L)
Cl2 consumption
Hansen et al.,(2016)
Ozonation of polluted pool water decreased Cl2 reactivity
Ozonation of pool water increased Cl2 reactivity
Artificial body fluid
UV/Ozone Ozone UV Introduction
Polluted pool water
+ +
14
0 1st
2nd
3rd
0 1st
2nd
3rd
0.0
0.2
0.4
0.6
0.8
Polluted pool waterPool water
tTH
M (
µm
ol/L
)
Total Trihalomethane
Ozonation of polluted pool water decreased total THM
Ozonation of pool water increased total THM
UV/Ozone Ozone UV Introduction
Polluted pool water direct ozone reaction short ozone life time
Hansen et al.,(2016)
15
UV and ozone treatments Summary
DOC
O3
DBPs
Cl2
Fast-reactive
UV
Rad
ical
oxid
ati
on
Dir
ect
oxid
ati
on
Lo
w e
xp
osu
re
Hig
h
exp
osu
re
Slow-reactive
UV/Ozone Ozone UV Introduction UV Ozone
17
Experimental setup
UV O3
Residual Chlorine 1±0.3 mg/L
Water samples
Purge & trap GC/MS
Swimming Pool
Sampling Treatment Analysis
24 hr 25 C
UV/Ozone Ozone UV Introduction
18
Control,Cl 2 UV,Cl 2 O3,Cl2 UV/O3,Cl2
0
2
4
6
Cl 2
co
ns
um
pti
on
(m
g/L
)
UV/Ozone Ozone UV Introduction
Cl2 consumption
Single Treatments
Repeated UV treatments
Repeated O3 treatments
Control,Cl2 1st
cycle 2nd
cycle 3rd
cycle0
2
4
6
Cl 2
co
ns
um
pti
on
(m
g/L
)
Repeated UV/O3 treatments
Control,Cl 2 1st
cycle 2nd
cycle 3rd
cycle0
2
4
6
Cl 2
co
ns
um
pti
on
(m
g/L
)
Repeated UV treatments increased Cl2 consumption
Repeated O3 treatments had no effect on Cl2 consumption
Repeated UV/O3 treatments decreased Cl2 consumption
Control,Cl 2 1st
cycle 2nd
cycle 3rd
cycle0
2
4
6
Cl 2
co
ns
um
pti
on
(m
g/L
)
19 Control,Cl 2 1
st cycle 2
nd cycle 3
rd cycle
0.0
0.1
0.2
0.3
0.4
Tri
ha
lom
eth
an
e (
µm
ol/
L)
Control,Cl 2 1st
cycle 2nd
cycle 3rd
cycle0.00
0.15
0.30
0.45
Tri
ha
lom
eth
an
e (
µm
ol/
L)
Control,Cl2 UV,Cl2 O3,Cl2 UV/O3,Cl2
0.0
0.1
0.2
0.3
Tri
ha
lom
eth
an
e (
mo
l/L)
Total Trihalomethane
Single Treatments
UV/Ozone Ozone UV Introduction
Control,Cl 2 1st
cycle 2nd
cycle 3rd
cycle0.0
0.1
0.2
0.3
0.4
0.5
Tri
ha
lom
eth
an
e (
µm
ol/
L)
Repeated UV treatments increased THM concentration
Repeated O3 treatments had no effect on THM concentration
Repeated UV/O3 treatments decreased THM concentration
Repeated UV treatments
Repeated O3 treatments
Repeated UV/O3 treatments
20
Control,Cl2 UV,Cl2 O3,Cl2 UV/O3,Cl2
0.000
0.035
0.070
tHA
N (
µm
ol/L
)
Total Haloacetonitrile
UV/Ozone Ozone UV Introduction
Control,Cl 2 1st
cycle 2nd
cycle 3rd
cycle0.00
0.05
0.10
0.15
tHA
N (
µm
ol/L
)
Control,Cl 2 1st
cycle 2nd
cycle 3rd
cycle0.00
0.03
0.06
0.09
0.12
tHA
N (
µm
ol/L
)
Control,Cl2 1st cycle 2nd cycle 3rd cycle0.00
0.02
0.04
0.06
0.08
0.10
tHA
N (
µm
ol/L)
Single Treatments
Repeated UV treatments increased tHAN concentration
Repeated O3 treatments had no effect on tHAN formation
Repeated UV/O3 treatments decreased tHAN formation
Repeated UV treatments
Repeated O3 treatments
Repeated UV/O3 treatments
21
Control,Cl2 UV,Cl2 O3,Cl2 UV/O3,Cl2
0
2
4
6
TC
nitro
(µ
g/L
)
Trichloronitromethane
UV/Ozone Ozone UV Introduction
Control,Cl2 1st cycle 2nd cycle 3rd cycle0
2
4
6
8
TC
nitro
(µ
g/L
)
Control,Cl2 1st cycle 2nd cycle 3rd cycle0.0
3.5
7.0
TC
nitro
(µ
g/L
)
Control,Cl2 1st cycle 2nd cycle 3rd cycle0
2
4
6
TC
nitro
(µ
g/L
)
Single Treatments
Repeated UV treatments increased TCnitro concentration
Repeated O3 treatments increased TCnitro concentration
Repeated UV/O3 treatments decreased TCnitro conc.
Repeated UV treatments
Repeated O3 treatments
Repeated UV/O3 treatments
22
Control,Cl2 UV,Cl2 O3,Cl2 UV/O3,Cl2
0
1
2
3
4
Genoto
xic
ity (
x10
-4)
Predicted toxicity
UV/Ozone Ozone UV Introduction
Control,Cl2 1st cycle 2nd cycle 3rd cycle0
1
2
3
4
5
Genoto
xici
ty (
x10
-4)
Control,Cl2 1st cycle 2nd cycle 3rd cycle0
1
2
3
4
Genoto
xic
ity (
x10
-4)
Control,Cl2 1st cycle 2nd cycle 3rd cycle0
1
2
3
4
Genoto
xic
ity (
x10
-4)
Single Treatments
Repeated UV treatments increased toxicity
Repeated O3 treatments increased toxicity
Repeated UV/O3 treatments decreased toxicity
Repeated UV treatments
Repeated O3 treatments
Repeated UV/O3 treatments