in UV/Chlorine

160 Pages·2015·3.44 MB·English

Application of the UV/Chlorine Advanced Oxidation Process
for Drinking Water Treatment

by

Ding Wang

A thesis submitted in conformity with the requirements
for the degree of Doctor of Philosophy

Graduate Department of Civil Engineering
University of Toronto

© Copyright by Ding Wang 2015
Application of the UV/Chlorine Advanced Oxidation Process
for Drinking Water Treatment
Ding Wang
Doctor of Philosophy, 2015
Graduate Department of Civil Engineering
University of Toronto

ABSTRACT
This research investigated the feasibility of a novel advanced oxidation process (AOP)
using ultraviolet light combined with free chlorine (UV/chlorine) in drinking water treatment.
A bench-scale study using a medium pressure UV collimated beam apparatus showed that
the UV/chlorine process was more efficient than the UV combined with hydrogen peroxide
(UV/H O ) AOP for the destruction of trichloroethylene (TCE) at pH 5 in a laboratory prepared
2 2
water, but was less efficient than the latter at pH 7.5 and 10. A Matlab® mathematical model
made accurate predictions of the observed experimental rates of TCE decay. The model
predicted that increasing concentrations of hydroxyl radical scavengers in the treated water
would tend to raise the pH at which UV/chlorine would remain competitive relative to
UV/H O .
2 2
Full-scale experiments at the City of Cornwall Water Purification Plant (Ontario, Canada)
and pilot-scale tests in a Rayox® batch UV reactor using water from the Keswick Water
Treatment Plant (Ontario, Canada) demonstrated comparable performance of UV/chlorine AOP
to UV/H O for geosmin, 2-methylisoborneol (MIB), and caffeine destruction.
2 2
ii
Organic and inorganic disinfection by-products (DBPs) were also monitored in the full-
and pilot-scale tests. Minimal trihalomethane and haloacetic acid formation was observed across
the UV reactor, while dichloroacetonitrile and bromochloroacetonitrile were produced rapidly,
although overall concentrations were below 6 µg L–1. Adsorbable organic halide was formed
rapidly (up to 70 µg Cl L–1) in water that had not been prechlorinated, while little formation was
observed in previously chlorinated water. Chlorate and bromate were formed, equivalent to
approximately 2–17% and 0.01–0.05% of the photolyzed chlorine, respectively, while no
perchlorate or chlorite formation was observed. In addition, the 24 h organic DBP formation
potential was increased by UV/chlorine pretreatment to an extent that was similar to that
observed when the water was pretreated with UV/H O .
2 2
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ACKOWLEDGEMENTS
I would like to express my sincere gratitude to my supervisor, Professor Ron Hofmann, for
his suggestions, guidance, encouragement, understanding, patience, and support throughout my
research. I would like to thank Prof. James R. Bolton for his continuously invaluable help and
advice on UV technology since my Master’s study. I also appreciate Prof. Susan Andrews for
being on my supervisory committee and providing excellent suggestions in my research. I am
grateful to Prof. Robert Andrews for his encouragement.
I also appreciate Leigh McDermott from Stantec Consulting Ltd., Owen O'Keefe, Daniel
Drouin, and Morris McCormick from Cornwall Water Purification Plant, Dr. Vasile Furdui from
the Ontario Ministry of Environment and Climate Change, Dr. Hong Zhang, Dr. A.H.M. Anwar
Sadmani, Zhen (Jim) Wang, and Jiafan (Kevin) Yang from Drinking Water Research Group for
their great help in my research.
Last but not least, I would like to give my special thanks to my wife and parents for their
endless support and encouragement.
This work was financially supported by Natural Sciences and Engineering Research
Council of Canada (NSERC) through the Engage Grant program and the Industrial Research
Chair program, and by Stantec Consulting Ltd. and the Centre for Control of Emerging
Contaminants (CCEC).

iv
TABLE OF CONTENTS
ABSTRACT.............................................................................................................................. ii
ACKOWLEDGEMENTS ....................................................................................................... iv
TABLE OF CONTENTS ..........................................................................................................v
LIST OF TABLES .................................................................................................................. ix
LIST OF FIGURES ..................................................................................................................x
LIST OF ACRONYMS .......................................................................................................... xii
1. INTRODUCTION .............................................................................................................1
References ..............................................................................................................................2
2. LITERATURE REVIEW .................................................................................................5
2.1 Advanced Oxidation Processes (AOPs) ..........................................................................5
2.1.1 Theory of Advanced Oxidation Processes (AOPs) ......................................................5
2.1.2 Miscellaneous Methods for AOPs ...............................................................................7
2.2 UV Combined with Chlorine as an AOP ........................................................................7
2.2.1 Fundamental Chemistry of Aqueous Free Chlorine .....................................................7
2.2.2 Fundamental Chemistry of the UV/Chlorine AOP..................................................... 10
2.3 Formation of Disinfection By-Products (DBPs) in UV/Chlorine ................................. 17
2.3.1 Chlorinated DBPs ..................................................................................................... 17
2.3.2 DBP Formation Kinetics ........................................................................................... 19
2.3.3 DBP Formation by UV and AOPs ............................................................................. 22
2.4 Summary of Literature Review .................................................................................... 25
References ............................................................................................................................ 26
3. MEDIUM PRESSURE UV COMBINED WITH CHLORINE ADVANCED
OXIDATION FOR TRICHLOROETHYLENE DESTRUCTION IN A MODEL
WATER ................................................................................................................................... 36
Abstract ............................................................................................................................... 36
3.1 Introduction ................................................................................................................... 36
3.2 Materials and Methods .................................................................................................. 40
3.2.1 Reagents and Materials ............................................................................................. 40
3.2.2 UV Exposure and Irradiance Measurements .............................................................. 40
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3.2.3 Analytical Methods ................................................................................................... 41
3.3 Results and Discussion .................................................................................................. 41
3.3.1 Molar Absorption Coefficients of TCE, Active Chlorine, Peroxide and Hydroxide
Species .............................................................................................................................. 41
3.3.2 Quantum Yields of Active Chlorine and Hydrogen Peroxide Photolysis.................... 42
3.3.3 TCE Decay Rates by UV Alone, and the UV/Chlorine and the UV/H O AOPs ........ 44
2 2
3.3.4 Mathematical Modeling of the TCE Decay ............................................................... 51
3.3.5 Comment on Active Chlorine Reaction with •OH ..................................................... 52
3.4 Conclusions .................................................................................................................... 54
Acknowledgements .............................................................................................................. 55
References ............................................................................................................................ 55
4. FULL-SCALE COMPARISON OF ULTRAVIOLET/CHLORINE ADVANCED
OXIDATION TO ULTRAVIOLET/HYDROGEN PEROXIDE FOR TASTE AND
ODOUR CONTROL IN DRINKING WATER TREATMENT .......................................... 60
Abstract ............................................................................................................................... 60
4.1 Introduction ................................................................................................................... 60
4.2 Material and Methods ................................................................................................... 62
4.2.1 Reagents and Materials ............................................................................................. 62
4.2.2 Experimental Facilities and Procedures ..................................................................... 62
4.2.3 Sample Analysis ....................................................................................................... 64
4.3 Results and Discussion .................................................................................................. 65
4.3.2 Free Chlorine Decay ................................................................................................. 65
4.3.3 Geosmin and MIB Decay .......................................................................................... 66
4.3.4 Caffeine Decay ......................................................................................................... 70
4.3.5 Electrical Energy per Order (E ) ............................................................................. 71
EO
4.3.6 Comment on Chlorine Radical (•Cl) and Disinfection By-Product (DBP)
Formation during Chlorine Photolysis ............................................................................... 73
4.4 Conclusions .................................................................................................................... 74
Acknowledgements .............................................................................................................. 74
References ............................................................................................................................ 74
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5. FORMATION OF DISINFECTION BY-PRODUCTS IN THE
ULTRAVIOLET/CHLORINE ADVANCED OXIDATION PROCESS .............................. 78
Abstract ............................................................................................................................... 78
5.1 Introduction ................................................................................................................... 78
5.2 Material and Methods ................................................................................................... 80
5.2.1 Experimental Procedures .......................................................................................... 80
5.2.2 Analytical Methods ................................................................................................... 83
5.3 Results ............................................................................................................................ 84
5.3.1 THMs ....................................................................................................................... 89
5.3.2 HAAs ....................................................................................................................... 89
5.3.3 HANs, HKs, and CP ................................................................................................. 90
5.3.4 AOX ......................................................................................................................... 90
5.3.5 Inorganic DBPs: ClO –, ClO –, ClO –, and BrO – ...................................................... 92
4 3 2 3
5.4 Discussion....................................................................................................................... 94
5.4.1 Rapid DBP Formation within the UV/Chlorine Reactor ............................................ 94
5.4.2 Impact of UV/Chlorine on 24 Hour DBP-FP ............................................................. 95
5.4.3 Role of the Chlorine Radical (•Cl) ............................................................................ 95
5.5 Conclusions .................................................................................................................... 96
Acknowledgements .............................................................................................................. 96
References ............................................................................................................................ 97
6. SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS ................................. 102
6.1 Summary and Conclusions .......................................................................................... 102
6.2 Recommendations for Future Work ........................................................................... 103
APPENDICES ....................................................................................................................... 105
A. Pulse Radiolysis Analysis for Determination of Rate Constant of Free Chlorine
with Hydroxyl Radical ...................................................................................................... 105
B. Determination of the Fluence Rate of the MP Lamp in the Collimated Beam
Apparatus .......................................................................................................................... 108
C. Example of Matlab® Codes ......................................................................................... 110
C.1 Matlab® Codes for Simulation of Trichloroethylene Decay by the UV/Chlorine
AOP at 11 mg L–1 and pH 5 ............................................................................................. 110
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C.2 Matlab® Codes for Simulation of Trichloroethylene Decay by the UV/Chlorine
AOP at 11 mg L–1 and pH from 5 to 10............................................................................ 112
D. Estimation of OH Radical Concentration Using an Excel Spreadsheet ..................... 113
E. UV Dose Estimation Using UVCalc® Version 2B ........................................................ 115
F. Absorption Spectra of Geosmin, MIB, and Caffeine ................................................... 116
G. Sample Analysis ............................................................................................................ 118
G.1 Geosmin and MIB..................................................................................................... 118
G.2 Caffeine .................................................................................................................... 120
G.3 Trihalomethanes (THMs), Haloacetonitriles (HANs), Haloketones (HKs),
Chloropicrin (CP), and Trichloroethylene (TCE) ............................................................. 125
G.4 Haloacetic Acids (HAAs) ......................................................................................... 129
G.5 Chlorate .................................................................................................................... 134
H. Quality Assurance / Quality Control (QA/QC) ........................................................... 135
I. Experimental Data ......................................................................................................... 140

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LIST OF TABLES
Table 2.1 Application of AOPs in different areas and for different contaminants ....................... 6
Table 2.2 Quantum yields of OCl– decay and photochemical product formation .......................16
Table 2.3 Halogenated by-products in drinking water treatment ...............................................20
Table 3.1 Fluence-based rate constants (10–6 m2 J–1) for active chlorine and peroxide
photolysis .................................................................................................................44
Table 3.2 Comparison of reported quantum yields of active chlorine photolysis .......................45
Table 3.3 TCE Fluence-based decay rate constants (10–4 cm2 mJ– 1) (excluding evaporation)
by UV alone, and the UV/chlorine and the UV/H O AOPs from experimental
2 2
and model results .....................................................................................................48
Table 3.4 Calculated hydroxyl radical concentrations (10–13 M) in TCE solutions treated by
the UV/chlorine and the UV/H O AOPs at various pH values .................................50
2 2
Table 3.5 Reaction mechanisms of TCE decay by UV alone, the UV/chlorine and the
UV/H O AOPs ........................................................................................................53
2 2
Table 4.1 Post-filtration water quality parameters for full- and pilot-scale tests ........................63
Table 4.2 Full- and pilot-scale E values (kWh m–3 order–1) for geosmin, MIB, and
EO
caffeine removal .......................................................................................................72
Table 5.1 Full- and pilot-scale post-filtration water quality parameters .....................................80
Table 5.2 Monitored organic and inorganic DBPs ....................................................................83

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LIST OF FIGURES
Figure 2.1 Percentage distribution of HOCl as a function of pH ................................................ 9
Figure 2.2 Molar absorption coefficients of HOCl, OCl–, and NH Cl .......................................11
2
Figure 3.1 Absorption spectra of TCE, chlorine, peroxide and hydroxide species .....................38
Figure 3.2 Relative spectral emittance of the MP lamp in this research .....................................38
Figure 3.3 Rates of active chlorine (a) and hydrogen peroxide (b) photolysis at various pH
values. Error bars represent the standard deviations of triplicate runs. Straight
lines represent the linear regression. ........................................................................43
Figure 3.4 Experimental TCE decay rates by UV alone, the UV/chlorine and the UV/H O
2 2
AOPs at various pH values. Error bars represent the standard deviations of
triplicate runs. Straight lines represent the linear regression.....................................47
Figure 3.5 Solution pH at which the UV/chlorine and the UV/H O AOPs are equally
2 2
efficient as a function of TOC concentration ...........................................................54
Figure 4.1 Full-scale Trojan UVSwift reactor (left) and pilot-scale Rayox® reactor (right) .......63
Figure 4.2 Percentage of free chlorine photolysis by UV exposure. Error bars represent the
values of experimental duplicates. ...........................................................................66
Figure 4.3 Geosmin (top plot) and MIB (bottom plot) decay in the 1st full-scale test. Error
bars represent the values of experimental duplicates. ...............................................67
Figure 4.4 Geosmin decay in the 2nd full-scale test. Error bars represent the values of
experimental duplicates. ..........................................................................................69
Figure 4.5 Caffeine decay in the 1st full-scale (top plot) and pilot-scale (bottom plot) tests.
Error bars represent the values of experimental duplicates.......................................71
Figure 5.1 Full-scale Trojan UVSwift reactor (left) and pilot-scale Rayox® reactor (right) .......81
Figure 5.2 THM formation in full- and pilot-scale tests. Plots on the left show THMs after
various treatment processes for short reaction time (30–60 s contact time). Plots
on the right show THM formation potentials (free chlorine dose: 6.5 mg L–1 for
24 h) in the water pretreated by selected processes shown on the x-axis. Error
bars represent the values of the duplicates measured. ..............................................85
x