v>EPA
S268
An Assessment of
Ozone and Chlorine
Dioxide Technologies
for Treatment of
Municipal Water
Supplies
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development. U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously'
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
§. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-78-147
August 1978
AN ASSESSMENT OF OZONE AND
CHLORINE DIOXIDE TECHNOLOGIES FOR
TREATMENT OF MUNICIPAL WATER SUPPLIES
by
G. Wade Miller
Rip G. Rice
C. Michael Robson
Ronald L. Scull in
Wolfgang Klihn
Harold Wolf
Public Technology, Incorporated
Washington, D.C. 20036
Grant No. R804385-01
Project Officer
J. Keith Carswell
Water Supply Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the'Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
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FOREWORD
The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health
and welfare of the American people. Noxious air, foul water, and spoiled
land are tragic testimony to the deterioration of our natural environment.
The complexity of that environment and the interplay between its components
require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem
solution and it involves defining the problem, measuring its impact, and
searching for solutions. The Municipal Environmental Research Laboratory
develops new and improved technology and systems for the prevention, treat-
ment, and management of wastewater and solid and hazardous waste pollutant
discharges from municipal and community sources, for the prevention and
treatment of public drinking water supplies, and to minimize the adverse
economic, social, health and aesthetic effects of pollution. This publica-
tion is one of the products of that research; a most vital communications
link between the researcher and the user community. It is a state-of-the-
art survey of municipal water treatment practices involving the use of ozone
and chlorine dioxide in Europe, Canada, and the United States. The study
was sponsored by the Water Supply Research Division of the EPA Municipal
Environmental Research Laboratory in an effort to assess the performance of
advanced water treatment techniques for use in the production of drinking
water. It is hoped that this report will be interesting and helpful to
those active in water supply treatment.
Francis T. Mayo, Director
Municipal Environmental Research Laboratory
m
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ABSTRACT
This research project and technology transfer effort was initiated in
response to growing national concern about the generation of toxic and
carcinogenic compounds in current U.S. drinking water treatment practices.
The principal focus of this program has been a review of the pertinent
international technology of ozonation and chlorine dioxide usage.
Questionnaires were prepared in French, English, and German, and
mailed to water treatment plants in the U.S., Canada and Europe, requesting
detailed data on use of ozone and/or chlorine dioxide. The questionnaries
were supplemented by a detailed literature survey, a survey of the principal
manufacturers of ozone and CK^ equipment, and telephone contact with many
water treatment plants. Following an evaluation of these data, the project
team conducted on-site surveys at 23 treatment plants in Europe, 7 water
treatment plants in Canada, and 13 water treatment plants in the U.S. These
plants were selected for their significance either as representative of the
current technologies in their respective countries, or as representative of
advanced technology of particular merit.
Special attention was given to collection of on-site data for engineer-
ing design of systems, and for procedures and results of water quality
analysis. Because the organic oxidation products resulting from chlorine
dioxide and ozone application are less well understood than those of chlorine,
a substantial portion of this report is devoted to a comprehensive treatise
of the subject.
Significant advances in the technology and engineering of water supply
treatment equipment and systems were identified by this study and are
discussed in detail herein. The Biological Activated Carbon (BAC)
process, recently discovered and tested full scale in Germany, is also
discussed in great detail because of its potential impact on the present
high cost of activated carbon treatment.
This report was submitted in fulfillment of Grant No. R804385-01 by
Public Technology, Inc., under the sponsorship of the U.S. Environmental
Protection Agency. This report covers the period June 20, 1976 to November
20, 1977.
IV
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CONTENTS
Foreword Hi
Abstract iv
Figures viii
Tables xi
Acknowledgment xiv
1. Introduction 1
2. Conclusions 3
3. Recommendations 8
4. Project Description 9
5. Water Treatment Philosophies 11
France ^ 11
Federal Republic of Germany 13
Switzerland 15
Canada 17
6. Ozone 19
General Overview of Ozonation 19
Summary of Data From European Ozone Questionnaires. 32
Summary of Data From Canadian Ozone Questionnaires. 40
7. Ozone Site Investigations 43
European Plant Visitations 43
Canadian Plant Visitations 65
8. Engineering Aspects of Ozonation Equipment and
Processes 75
Introduction 75
Gas Preparation 75
Electrical Power Supply 85
Ozone Generation Theory 88
Commercial Ozone Generators 95
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CONTENTS (Continued)
Use of Oxygen Rich Feed Gas 105
Contactor Design Considerations 127
Control and Instrumentation 128
Occupational Safety 137
Noise Control 139
Selection of Construction Materials 140
Operation and Maintenance 143
9. Costs of Ozonation 145
Introduction 145
Capital Costs 146
Raw Water Quality and Ozone Requirements 146
System Size 147
Cost of On-Site Power 152
Energy Demand of System Components 152
Instrumentation and Automation 157
Operating Costs 157
Other Factors Impacting Costs 160
Case Histories on Capital Costs 161
Summary 165
10. Public Health Aspects of Ozone Usage 167
11. Chlorine Dioxide 179
History of Use 179
Current Uses of CIO? 180
Characteristics of Chlorine Dioxide 181
Synthesis of Chlorine Dioxide From Sodium Chlorite. 183
Advantages and Disadvantages of Chlorine Dioxide. . 185
Summary of U.S. Plant Visits - Overview 191
European C102 Plant Visitations and Questionnaire
Results 195
Engineering Design For Chlorine Dioxide Generation
Systems 211
12. Oxidation Products of Organic Materials 225
Introduction 225
Chlorine 229
Reactions With Ozone 235
Reactions With Chlorine Dioxide 266
Conclusions 283
13. Biological Activated Carbon 291
Introduction 291
Fundamental Principles 292
vi
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CONTENTS (Continued)
Advantages of Biological Activated Carbon 293
European Background 293
European Drinking Water Experiences With BAC .... 295
Nitrification of Ammonia 321
Case Histories 322
Summary & Recommendations for BAC Operation 329
Literature Cited 333
Bibliography 350
Appendices
A. Blank Questionnaires 385
B. Descriptions of Selected Drinking Water
Treatment Plants Using Ozone 401
C. FIGAWA Technical Papers on Ozone Technology. . . 446
D. Ozone Questionnaire Summary Tables 473
E. Descriptions of Selected U.S.A. Drinking Water
Treatment Plants Using Chlorine Dioxide. ... 521
F. Chlorine Dioxide Questionnaire Summary Tables. . 546
VII
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FIGURES
Figure Number Page Number
1 Process Flow Diagram of Neuilly-sur-Marne Water
Treatment Plant 12
2 Ozone Dosage vs. Time for Two Types of Reaction:
Mass Transfer Rate Controlled and Chemical
Reaction Rate Controlled 28
3 Location of French Plants Visited 50
4 Location of German Plants Visited 55
5 Location of Swiss Plants Visited 62
6 Location of Canadian Plants Visited 68
7 The Four Basic Components of the Ozonation
Process 76
8 High Pressure Gas Preparation System 77
9 Intermediate-Pressure Gas Preparation System ... 79
10 Low-Pressure Gas Preparation System 78
11 Absolute Humidity of Atmospheric Air At
Saturation Point As A Function of Dew Point. . . 82
12 Thermal-Swing Desiccant Drier 83
13 Pressure-Swing Desiccant Drier 83
14 Typical Controlled Voltage, 60 Hz, Electrical
Power Supply System Schematic 86
15 Typical Variable Frequency Electrical Power
Supply 87
16 Formation of Ozone During lonization/Deionization. 93
17 Relationship of Ozone Production and Power Supply
Frequency 94
18 Construction Details of A Tube Type Ozone
Generator 96
19 Typical Details of Tube Type Ozone Generators. . . 97
20 Details of Vertical Tube Ozone Generator 99
21 Otto Plate Ozone Generator Module 100
22 Vertical Tube Double-Cooled Ozone Generator-Tube
Detail 101
23 Lowther Plate Ozone Generator Cell 102
24 Air Cooled Lowther Plate Type Ozone Generator. . . 103
25 Ozone Output in Relation to Inflow Temperature
of Cooling Water 104
26 Duisberg Plant Overall Water Treatment Schematic . 106
27 Duisberg Water Treatment Plant Ozonation System
Schematic 107
28 Composite Oxygen-Rich Ozone Generation System
Schematic 108
vi i i
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FIGURES (Continued)
Figure Number Page Numbeir
29 Total Flow Vacuum Injector Contactor For
Ozonation Ill
30 Partial Flow Vacuum Injector Contactor For
Ozonation Ill
31 Turbine Type Ozone Contactor 112
32 Multi-Turbine Contactor Installation 113
33 Tailfer Water Treatment Plant, Brussels, Ozone
Contact Chamber 114
34 Turbine Detail, Tailfer Water Treatment Plant,
Brussels 115
35 Van der Made Ozone Contactor 116
36 Welsbach Ozone Contactor 116
37 Torricelli Ozone Contactor 117
38 Multi-Compartment, Porous-Tube Contact Chamber. . . 118
39 Choisy-le-Roi (Paris, France) Water Treatment
Plant Ozonation Chamber Detail 119
40 Two-Compartment Ozone Contactor 120
41 Two-Level Ozone Contactor 121
42 Porous Tube Contact Chamber 122
43 Donne Plant, Mulheim, Federal Republic of
Germany 123
44 The Ozonation System At The la Chapelle Plant -
Rouen, France 124
45 Liquid Dispersion Into Ozone-Rich Gas 125
46 Tube Type Ozone Generator-Required Measurements . . 132
47 The Different Possibilities of Energy Consumption
In Ozonation Systems 156
48 Solubility of C102 in Water 181
49 Gaseous Chlorine-Sodium Chlorite C102 Generation
System 214
50 The CIFEC System 215
51 Sodium Chlorite-Hypochlorite—Acid ClOg
Generation System^ 216
52 Lengg Waterworks, Zurich, Switzerland. Chlorine
Dioxide System 218
53 Reactions of Chlorine With Phenol 234
54 Reactions of Ozone With Phenol 243
55 Reactions of Chlorine Dioxide With Phenols 267
56 Formation of Chlorite Ion From the Oxidation of
Phenols By Chlorine Dioxide 268
57 Reactions of Methyl Oleate With Cl02 273
58 Reactions of Cyclohexene With C102 275
59 Reactions of Cellotetrose With Cl02 276
60 Reactions of Pectic Acid With C102 277
61 Pertinent Reactions of Amines With C102 280
IX
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FIGURES (Continued)
Figure Number Page Number
62 Activated Carbon Loading. New Carbon and Carbon
After 2, 3, and 7 Months of Operation at The
Lengg Plant, Zurich, Switzerland. UV Spectra
of Dimethyl forntamide (DMF) Extracts 296
63 Efficiency of Removal of COD From Rapid Filter
And Activated Carbon At Lengg Plant, Zurich,
Switzerland 297
64 Efficiency of COD Removal (measured by UV
absorption at 254 nm cell distance = 1 cm) at
Lengg Plant, Zurich, Switzerland 298
65 Activated Carbon Loading From The Slow Filter at
The Moos Plant, Zurich, Switzerland. New
Carbon and After Filter Operating Times of 1,
2 and 3 Years. UV Spectra of DMF Extracts at
254 nm 299
66 Efficiency of COD Removal of BAC Over 3 Years
at Moos Water Works, Zurich, Switzerland .... 301
67 Bacterial Count After 3 Days Incubation at 20°C
in 1 ml Activated Carbon Filtrate of The
"South" Installation, Lengg Water Works,
Zurich, Switzerland 302
68 Activated Carbon Studies in Amsterdam 304
69 Activated Carbon Column Service Time As A
Function of Filtrate Quality 306
70 Bacterial Counts on ROW 0-8 Supra Activated
Carbon, ROW 0.8 (non-activated) and Sand
(0.85 - 1.00 mm) When Fed With Tapwater
(nominal velocity 3.5 m/hr.) 307
71 Behavior of Microbial Populations on Activated
Carbon Over Three Years at Wiesbaden, Germany. . 308
72 Microbiological Loading of Activated Carbon-
Dependence on Adsorptive Concentration 310
73 Microbiological Loading of Activated Carbon-
Dependence on Time Wiesbaden Studies 311
74 Bremen, Germany Water Works Pilot Plant 313
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TABLES
Table Number Page Number
1 Operational Plants Using Ozone -- 1977 22
2 Applications of Ozone For Water Treatment 23
3 Types of Ozone Contactors 30
4 European Plants Inspected By Site Visit Team . . 33
5 Quebec Plants Using Ozone 41
6 Pertinent Features of European Water Treatment
Plants Visited 44
7 Canadian Ozone Treatment Plants Visited 66
8 City of Pierrefonds (Quebec) Water Treatment
Plant Ozone System Data Recorded 129
9 Comparison of Stainless Steels 141
10 Cost Range of Ozonation Systems (Using Air) ... 148
11 Capital Costs of Small To Medium Ozonation
Systems (Including Housing and Installation). . 148
12 Capital Costs of Installed Ozonation Systems. . . 150
13 Ozone Capital Costs 151
14 Ozone Capital Costs 151
15 Ozone Operating Costs 160
16 Capital Costs at Tailfer/ 163
17 Annual Ozonation System Cost at Tailfer 163
18 Other Pertinent Cost Data From Tailfer 163
19 Ozonation Costs at Lengg 164
20 Effects of Ozone on Anionic Detergents and COD. . 171
21 Effects of Ozone Upon Organics in Water 172
22 Rouen Plant Performance, Organics 173
23 Endotoxin Values and Carbon Adsorption 175
24 Effects of Shipment Time on Bacteriological ... 176
25 Sample Endotoxin Assays 177
26 C102 Questionnaire Results by EPA Regions .... 188
27 Oxidation-Reduction Potentials of Water
Treatment Agents 227
28 Comparison of Oxidation of Organic Compounds
With Ozone, Chlorine Dioxide and Chlorine . . . 284
29 Experiments With Small Doses of Ozone (2/27-
4/10/1969) at Bremen 314
30 Experiments With Higher Ozone Doses Before The
Activated Carbon Filter (9/1-9/22/1969) at
Bremen 315
XI
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TABLES
Table Number Page Number
31 Experiments With Intermediate Ozone Dosages and
Consecutive Filtration Through Activated
Carbon, Then Rapidly Operating Slow Sand
(9/22-10/23/1969) at Bremen 316
32 Experiments With Ozone, Slow Activated Carbon
Filter -- Bremen 317
33 Experiments With Ozone and Activated Carbon
Filters (1/8-2/2/1970) in Bremen 318
34 Organo-Chlorine Compounds From Breakpoint
Chlorination Treatment, Mulheim, Germany
(Dohne) Plant ,., 323
35 Process Data For Dohne Waterworks (Mulheim,
Germany) Before and After Change in Treatment . 324
36 Mean DOC and UV-Extinction Values for the
Different Treatment Steps Mulheim, Germany
(Dohne) Plant — New Ozonation Process 326
37 Geometric Mean Values of Bacterial Counts for
the Mulheim, Germany (Dohne) Plant Using
Ozone 327
38 Performance of Biological Activated Carbon
Filters. Mean Values For 6-Month Operation
After A 3-Month Starting Period (Dohne Pilot
Plant), Mulheim, Germany 327
39 Rouen-la-Chapelle (France) Plant Operational
Data (1976) 329
xn
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ACKNOWLEDGEMENTS
This report could not have been written without the assistance of many
people and organizations throughout the United States, Europe, and Canada.
The researching and writing of the report required the acquisition of
information that had not previously been collected or well documented. It
was only through the cooperation and assistance of many key individuals that
this body of information was successfully put together. Unfortunately, not
everyone who contributed can be mentioned here.
Principal among those persons are the forty-three or so water plant
superintendents who, in most cases, gave much of their valuable time to our
site visit team in order to assure our understanding of their water treat-
ment processes. Their contribution is gratefully acknowledged.
The first persons whose contributions must be acknowledged are two
excellent engineers, Ronald L. Scullin and Daniel H. Houck of the Public
Technology, Inc. staff. Without their efforts, the "nuts and bolts" por-
tions of the report would not have been accomplished.
Grateful acknowledgment is extended to Professor Dr. Heinrich Sontheimer
of the Engler-Bunte Institute, University of Karlsruhe, Federal Republic of
Germany. Professor Sontheimer spent many hours with the project team
answering questions on European water treatment practices. He was also
instrumental in securing the services of Dr. Wolfgang KUhn, one of his
outstanding young research assistants, to work with PTI on this project.
Both of the large, vertically integrated water companies that operate
in France made significant contributions in many different ways. They
forwarded detailed cost information, filled out questionnaires, helped to
arrange for site visits, accompanied the site visit teams to many plants in
France, and also answered hundreds of detailed questions. Our thanks go to
all of those people in Compagnie Generale des Eaux (CGE) and in the Soci§t£
Lyonnaise des Eaux et de 1'Eclairage (SLEE) who assisted us. Pierre Schulhof,
Vice President of CGE and Jean-Jacques Prompsy, Director of Operations of
SLEE receive our special thanks because they not only assisted the team
personally, but provided the services of their key personnel as well.
Several manufacturers of ozone generating equipment spent a great deal
of time discussing philosophy, history, and actual application of ozone.
The contributions of Jacques Le PauloutJ of Trailigaz Corporation, Jean
Mignot of Degremont Corporation, and Dr. Harvey Rosen of Union Carbide
Corporation are gratefully acknowledged. Our thanks go also to Andr6
Gagnaux, formerly of Sauter Corporation in Switzerland, for his assistance.
In Canada, six individuals stand out as having given much time, effort,
and information to the project team. Foremost among these persons is Ron
xi i i
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Larocque of Francis Hankin Ltd. in Montreal. Mr. Larocque accompanied the
site visit team to several Canadian plants and provided substantial detailed
information on ozone systems engineering and costs. The efforts of Olaf
Skorzewski, Vice President of Degremont-Canada, were also substantial and
are acknowledged. Our thanks also go to Meyer Schwartz of Fenco Consultants
in Toronto for the insights into ozone systems which he provided in the
early days of the project. Lastly, the efforts of Dr. Donald MacGregor of
the Department of National Health and Welfare in Canada and of Messrs.
Ronald Lampron and Roland Mercier of the Government of Quebec cannot be
overemphasized. These gentlemen were instrumental in getting questionnaires
completed and returned for 13 plants in the province of Quebec that use ozone.
Several top researchers were instrumental in assessing various aspects
of ozone and chlorine dioxide use. One of the most impressive persons that
the site visit team had the pleasure of meeting was Dr. Willy Masschelein of
the Tailfer (Brussels) waterworks. Dr. Masschelein, who wrote a review book
on chlorine dioxide in 1969 (which is being updated, in English, for publica-
tion in 1978), is an acknowledged expert on ozone contacting and water
treatment in general. His contributions were invaluable.
Another top scientist who assisted Dr. Wolf in determing the public
health aspects of 03/C102 use is Dr. Cyril Gomel la of SETUDE in Paris. Dr.
Cornelia's work in the field of bacterial and viral inactivation is well
known. We thank him for his contribution.
In addition to Dr. Masschelein, two water plant personnel who were most
cooperative and impressive must be mentioned. These are Dr. Dietrich
Maier, Chief Chemist of the Bodensee Wasserversorgung in Sipplingen, Germany,
and Maarten Schalekamp, Director of the Lengg Waterworks in ZUrich, Switzer-
land. Dr. Maier is currently heading up an international committee on ozone
monitors and instrumentation that will publish the first report on this
subject in mid 1978.
The contributions of Jean Chedal of CGE, Paul Thaler Blue of Infilco-
Degremont in Richmond, VA, and Maurice Pare of Degremont deserve mention.
Pare provided some of the best theoretical explanations of ozone energy
demands and balances and control systems which we encountered. Paul Blue
and Jean Chedal accompanied the site visit team to many plants and offered
constant encouragement.
Grateful acknowledgment must also go to Paul Chapsal, Directeur of
Trailigaz Corporation for his theoretical "lectures" on ozone production.
There are many stateside people who have contributed greatly. Foremost
among these is J. Keith Carswell, our EPA project officer, who did an
excellent job of keeping us on schedule, but at the same time letting the
project take its own course. The contributions of Dr. Jay Lehr of the
National Water Well Association and Elroy Spitzer of the American Water Works
Association/Research Foundation are likewise gratefully acknowledged.
Finally, the cooperation of Dr. Morton Klein, President of the Inter-
national Ozone Institute, and all 101 committees and members who contributed
time and information is acknowledged.
xiv
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SECTION 1
INTRODUCTION
The fact that ozone and chlorine dioxide are widely used for treating
drinking water in Europe and Canada has been known for many years in the
United States. Likewise, the fact that chlorine dioxide is used by many
water treatment facilities in the U.S. for some purpose was known. Until
recently, however a full knowledge of specific uses, applications, and
experiences with these chemicals has not existed.
Interest in these so-called advanced treatment techniques and others
has been stimulated by the results of numerous studies that have revealed
the presence of potentially carcinogenic organic chemical compounds in the
drinking water supplies of many U.S. cities. Contributing greatly to this
increased interest by the U.S. water treatment community was the enactment
of PL 93-523, the Safe Drinking Water Act of 1974. Stated simply, the Safe
Drinking Water Act reflects updated knowledge and technology that has
allowed us to learn more about the contents of our drinking water; this
greater body of knowledge has necessitated the establishment of more strin-
gent criteria for water treatment plants to meet in order to protect the
public health. The Safe Drinking Water Act, among its many provisions,
mandates the establishment of maximum contaminant levels for a number of
microbiological, chemical, and physical substances and likewise mandates
investigation of treatment technologies that will permit attainment of
these contaminant levels.
Specific studies that have provided evidence of potential carcinogens
in drinking water and thus provided impetus to investigation of technol-
ogies that can remove these organic materials are the National Organics
Reconnaissance Survey of 1975, the 1976 National Cancer Institute (NCI)
Report on the carcinogenic!"ty of chloroform, and the National Organics
Monitoring Survey (NOMS) of 1977. Each of these studies has contributed to
the growing body of evidence and resulting concern regarding toxic sub-
stances in water.
Specifically, the National Organics Reconnaissance Survey (NORS)
revealed the presence of halogenated organic compounds thought to be
carcinogenic in the drinking water of all 80 U.S. cities surveyed. The NCI
report confirmed the carcinogenicity of chloroform in rats and mice; chloro-
form was one of the five organics whose presence was determined in the NORS
survey. The NOMS expanded on the NORS by including analyses for trihalo-
methanes in 113 cities throughout an entire year, and quantified a number
of other synthetic organic chemicals found in the water. The NOMS demon-
strated that trihalomethanes could form in finished water on the way to a
1
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customer's tap and that other organics, also potentially carcinogenic, such
as certain bromine-containing trihalomethanes, could exceed the concentra-
tion of chloroform.
These events and others led to the current state-of-the-art assessment
of the use of ozone and chlorine dioxide in municipal water supplies. Few
details regarding the engineering, costs, public health aspects, effective-
ness, or even purposes of use of ozone were known in the U.S. prior to the
initiation of this study in June, 1976. Experiences with chlorine dioxide,
though significantly greater, were not well documented.
Therefore, the objective of this study was to obtain as much informa-
tion as possible regarding the actual use of ozone and chlorine dioxide in
water treatment. The several objectives of the project were as follows:
• Documentation of data on known applications of O^/CIO^ for
drinking water treatment;
• Determine how many plants worldwide are using these oxidants for
some purpose;
• To obtain data on engineering designs, operating history and
effectiveness, capital and operating costs, health and safety
aspects, and materials of construction.
In addition, special emphasis was placed on the documentation of what
is currently known about: 1) the use of ozone for removing dissolved organic
materials; and 2) organic oxidation products which may be formed as a
result of the use of ozone or chlorine dioxide. During the course of the
study, the project team discovered a new treatment phenomenon, the use of
ozone in front of granular activated carbon to produce "biological activated
carbon" which is being used in modern European drinking water plants for
removal of organic materials and ammonia. This is reported in detail in
Section 13.
It should be emphasized that the purpose of this study was to gather
information on the various aspects of these treatment technologies and
report on them. It is not, nor was it meant to be, an in-depth analysis or
technology assessment. The primary intent of this report is to characterize
and convey objectively "real world", hands-on experiences and to provide a
knowledge base from which a technology assessment or other studies can be
initiated.
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SECTION 2
CONCLUSIONS
GENERAL
Ozone and chlorine dioxide are well established, proven technologies in
Europe. Use of ozone for treating drinking water is likewise well established
in the Province of Quebec, Canada, the Soviet Union, and to a lesser degree,
Japan. With proper engineering design and operator knowledge of the purposes
and application methods, ozone can be used effectively for a number of
purposes including iron and manganese oxidation, microflocculation, taste
and odor control, organics removal, and viral inactivation and general
disinfection. The project team has inspected plants using ozone that were
beautifully engineered and operated. Similarly, plants were inspected in
which ozone was being grossly misused due to the lack of sophistication of
the designer and the low level of operator training and consequent appreciation
of the technology.
Chlorine dioxide is, in general, not being used optimally in the various
installations in the United States. Little consistency is evident in dosages
or methods of application. There appear to be some questions regarding the
proper usage of this oxidant.
This study has found that ozone is being used quite successfully for a
varied number of purposes in western Europe. This fact tends to render in-
operative the preconceived belief that ozone can be used only as a disinfecting
agent and that it should be viewed as an alternative to chlorine for drinking
water treatment. Europeans and Canadians do not view ozone simply as a dis-
infectant, but rather view ozonation as a treatment process capable of
performing many useful functions, disinfection being one.
Ozone is being used currently by at least 1039 water treatment plants
throughout the world. This is the number identified and located; the number
is believed to be low.
Ozone Applications
Ozone is seldom used as a terminal step in Germany. Ozone causes
chemical transformation of dissolved organic compounds in the water, making
them more easily biodegradable and thus providing food for bacteria which
can lead to regrowth in the water distribution system. Ozone, according to
Professor Dr. Sontheimer, of the University of Karlsruhe, Germany, can be
used as a terminal step only if the dissolved organic carbon concentration
of water to be distributed is less than or equal to 0.2 mg/1. Also, ammonia
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cannot be present, otherwise regrowth of nitro-bacteria can result when
ozonation is applied as the terminal step:
If ozone is used for iron and manganese oxidation, microflocculation,
organics removal, color removal, or for taste and odor control, it is most
effective if applied after a filtration step for removal of coarse particles
in the water and before a second filtration step, either through sand or
carbon, to remove the substances acted upon or produced by the ozonation.
Czone Systems Engineering
European ozonation techniques evolved from country to country. As a
result, national approaches to ozone system design are evident. The French,
Germans and Swiss use ozone successfully, but each has a different approach
to air preparation, generation, and contacting. The degree of sophistication
of European control systems for ozonation is quite high. This level of
control and obvious reliability of equipment has led to a rather casual
approach to operation. That is to say that ozonation technology is estab-
lished to the degree that operation presents no significant problems, other
than proper initial training of plant personnel.
A wide variety of contactor designs is in use in Europe. Much of this
probably is due to the national approaches to ozonation, but some is based
upon energy expenditures and technical performance factors.
Ozone Costs
Economies of scale are realized in larger ozonation systems, those in
the 500 pounds/day and greater generation range. Total capital costs for
these systems, including housing, is $1000/lb of ozone generating capacity/
day or less. Smaller units, less than 100 pounds per day, can cost up to
$4,000/1b capacity/day. This includes the cost of air treatment, ozone
generation, and contacting. Because most existing U.S. water plants fall in
the smaller size range, the latter costs would be most applicable in this
country. By contrast, the general trend in Europe is toward large, regional
plants serving multiple communities, achieving significant economies of
scale on ozonation and other treatment plant equipment and processes.
Operating costs depend on cost of electricity, energy demand of the
system as designed, and average dosage. Total capital and operating costs
of an ozone system, base on limited field cost data acquired, can range from
1.75^/1000 gallons to about 4
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Ozone can produce many new oxidized moieties and biodegradation products,
but in general these are compounds of lesser, not greater toxicity, provided
sufficient oxidation has been caused to occur. This general rule does not
always hold because certain pesticides (parathion and malathion) form their
respective oxons initially before degrading upon further oxidation. The
oxons are more toxic than are the starting compounds.
Chlorine Dioxide
This survey has identified 84 plants in the United States and 10
plants in Canada that use C102 for some purpose. Most of these plants use
it for taste and odor control. Only one plant uses C102 as a final disin-
fectant, Hamilton, Ohio. Chlorine dioxide use in Europe is widespread; the
total number of plants using it is not yet determined, but more than 400
have been identified. A number of plants use C102 for oxidizing organically
complexed iron and manganese, but its predominant use in Europe is for
supplying a residual for the distribution systems. It is applied in concen-
trations of less than 0.5 mg/1 for this purpose.
Chlorine dioxide systems in Europe, for the most part, are automatically
controlled, while those in the U.S. are manually controlled.
Chlorine dioxide is a stronger disinfecting agent than chlorine, does
not react with organics* to form trihalomethanes, does not react with ammonia
to produce chloramines,* and can provide a longer lasting residual in the
distribution system than free residual chlorine. Chemical costs for chlorine
dioxide average about 10 to 15 times those of chlorine at those U.S. plants
reporting costs, depending on the feed ratios. In Europe, C102 application
is reported to cost about three times as much as chlorine.
Concern about the potential toxicity of the chlorite ion (C102~) was
expressed by a number of European and U.S. plant managers whose plants are
using C102-
Chlorine dioxide usage for water treatment began in the United States
in 1944. In reviewing G. C. White's classic text entitled "Handbook for
Chlorination" which contains a chapter on chlorine dioxide, it appears that
little more is known about C102 now than was known a decade ago. The methods
of generation, engineering, applications and methods of analysis have been
well known for some time2.
Biological Activated Carbon
A new treatment phenomenon known as biological activated carbon (BAC)
was discovered during the course of the project. The Germans are using it
effectively for removal of organics and ammonia at the new, full scale Donne
plant in MUlheim, near DUsseldorf. The French plant at Rouen-la-chapelle
has been operating the BAC process on full scale since January, 1976, also
for ammonia and organics removal.
*Except in the presence of free chlorine.
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BAG is a combination of physical/biological processes. It involves
promotion of biological growth on activated carbon columns; the growth is
facilitated through the transformation of non-biodegradable organic com-
pounds into more biodegradable states by the use of pre-ozonation and pro-
vision of an oxygen enriched environment. Bacteria on the carbon then
biologically regenerate the carbon, postponing the necessity for regene-
ration.
Biological activated carbon appears to be the most advanced treatment
technique currently available for removal of organic compounds and ammonia
in drinking water treatment. Use of BAC significantly increases the time
period of activated carbon effectiveness, thus reducing the frequency of
regeneration. BAC has eliminated the need for breakpoint chlorination for
ammonia removal at the French Rouen and German MUlheim plants. In turn,
this has reduced the amounts of organochlorine compounds formed initially,
which formerly (at MUlheim) caused frequent regeneration of activated carbon
columns, used for dechlorination. This process could make a substantial
impact on lowering of activated carbon costs through elimination or reduction
of expensive thermal regeneration requirements, as well as chemical costs
for chlorine.
Organic Oxidation Products
Major conclusions of this phase of the study are as follows:
• Complete oxidation of dissolved organic materials to carbon
dioxide and water in aqueous solution is rare, by means of any
oxidant. In general, if an organic material is resistant to
oxidation by ozone (the most powerful oxidant used in water
treatment), it will also be resistant to oxidation by other
(weaker) oxidants.
• Oxidation products formed by ozonation do not contain halogen
atoms.
• Ozonation of certain pesticides has produced intermediates which
are more toxic than the starting materials. Continued ozonation
produces further oxidation products which are less toxic and more
easily biodegraded.
• Oxidation products•formed upon ozonation, and non-chlorinated
oxidation products from chlorine dioxide are more biodegradable
than are the starting organic materials.
t Oxidation of pesticides with ozone proceeds rapidly in clean
water, but significantly slower when humic materials or soil
particles are present. Thus, dissolved organics can be adsorbed
onto humic or soil materials and be resistant to oxidation.
• In many cases, oxidation products from chlorine dioxide do not
contain halogen atoms. This is not a general rule, however,
-------
because chlorinated compounds often are produced, even when
chlorine dioxide is synthesized so as to contain no free chlorine.
• Both chlorinated and non-chlorinated organic oxidation products
are formed with chlorine. For the most part, many of the non-
halogenated oxidation products from chlorination also can be
formed with chlorine dioxide and with ozone.
• When oxidants are used in drinking water treatment, it is im-
portant to know what oxidizable materials are present and to
incorporate a sufficient quantity of oxidant to produce the
desired end result.
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SECTION 3
RECOMMENDATIONS
Biological activated carbon appears to have great potential for use in
U.S. water treatment. Pilot projects on this treatment combination should
be initiated to determine its effectiveness for organics and ammonia removal.
Engineering and cost details of currently operating BAC plants in Europe
should be investigated.
A thorough investigation of the potential savings in activated carbon
regeneration costs resulting from extended life of the biological activated
carbon also should be investigated.
An in-depth cost analysis of the use of ozone as a unit process
capable of performing a number of useful functions is needed. Various
combinations of air preparation, generation, contacting, and off-gas use or
destruction systems should be studied.
Epidemiological studies of populations using drinking water treated
with chlorine dioxide and ozone should be conducted. Research directed at
determining whether or not the chlorite ion is toxic, and at what levels,
would be a part of that study. Toxicity of residual ozone in water is of
no import because in properly designed systems it is not present at the
tap.
Technical assistance should be made available to those municipalities
currently using chlorine dioxide in order to assure that it is being used
properly and in safe concentrations. This could be provided by EPA, supported
by expert assistance as needed.
8
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SECTION 4
PROJECT DESCRIPTION
OBJECTIVES
The objectives of the project, listed earlier in Section 1, were to
obtain as much information as possible regarding actual operating experiences
with ozone and chlorine dioxide. Ozone has been used in hundreds of water
treatment facilities in Europe, beginning in 1906. Canada opened its first
plant in 1956 and now has 20 operating facilities. Chlorine dioxide has
been used in a number of plants in the U.S. since the 1940s; the latest
survey prior to this one was in 1964 and listed 37 operating facilities.
Most of these were thought to use C102 for taste and odor control. The use
of chlorine dioxide in Europe likewise was known, but the scope of its use
was unknown.
Thus the purpose of this project has been to obtain detailed information
regarding the application and effectiveness of these two oxidants. Informa-
tion has been obtained on: 1) engineering of systerc components and design;
2) operating history and effectiveness; 3) capital and operating costs; 4)
public health aspects; and 5) special emphasis has been given to the effec-
tiveness of ozone for removal of organic compounds in water and the products,
toxic or otherwise, which may be formed as a result of its usage. Likewise,
emphasis has been given to organic oxidation products of chlorine dioxide
usage and, for comparative purposes, those of chlorine.
SCOPE OF WORK
The scope of work involved several distinct tasks. First, detailed
questionnaires on various aspects of chlorine dioxide and ozone usage were
developed for distribution to plants using one or both of the oxidants.
Simultaneously, efforts were made through contact with ozone and chlorine
dioxide manufacturers, professional associations such as the International
Ozone Institute, the Deutscher Verein der Gas und Wasserfaches e.v.--
(German Association of Gas and Waterworks) (DVGW), research institutes, and
the literature to identify and locate plants using the oxidants. Once
plants were identified and located, the detailed questionnaires were mailed
and responses requested. Questionnaires were sent to all plants using ozone
(20) and chlorine dioxide (10) in Canada, to plants thought to be using ClOg
in the U.S.103, and to hundreds of plants using one or both oxidants in
various European countries.
Based on the questionnaire responses and personal contacts with knowledge-
able persons in the field, representative plants were selected for visitation.
-------
Twenty-three plants in four European countries were visited in May, 1977 by
a site visit team consisting of a design engineer, a public health expert,
an expert in ozone, a European water supply research expert, and the principal
investigator. Seven plants in Canada which use ozone were visited in August,
1977. In September and October of 1977, 13 of 84 U.S. facilities using C1CL
were visited.
Concurrent with the questionnaire and site visit activities, a compre-
hensive literature search was conducted. The primary goal of the literature
search was to gather pertinent information on oxidation products formed
through the usage of ozone or chlorine dioxide.
This report is the result of these several tasks. Details on each
aspect of the study are included in later sections. Sample questionnaires
are attached as Appendix A. A detailed bibliography is given in Appendix G.
10
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SECTION 5
WATER TREATMENT PHILOSOPHIES
Prior to discussion of the results of the study, it is necessary to
decribe the water treatment philosophies of various countries. In the
United States, we often speak of a "conventional" water treatment process.
This usually means coagulation, sedimentation, filtration, and chlorination.
This is not the case in Europe. Drinking water treatment practices vary
from country to country, and often from city to city.
The most striking difference between U.S. and European practices is the
concentration on bacteriological quality of water in the U.S. as an indicator
of safety. The Europeans, while concerned with bacteriological and virological
safety of water, are much more concerned with chemical contamination.
Europeans are brought up with the understanding that when there are any
unnatural tastes in water (especially chlorine tastes) the water is contami-
nated. Americans are brought up with the understanding that when chlorine
cannot be tasted, the water may be contaminated. Therein lies one of the
major reasons for the two basic approaches to treating water supplies.
Americans use relatively heavy dosages of chlorine in the water to assure
bacteriological (but not necessarily chemical) safety; Europeans reduce the
chlorine demand of water (insuring chemical safety) so that the residual
chlorine finally used to maintain bacteriological safety in the distribution
systems will be so small as to be tasteless in the water.
The following describes in some detail the treatment philosophies of
France, Germany, Switzerland, and Canada.
FRA.NCE
Since 1906, the city of Nice has been disinfecting its drinking water
supplies solely with ozone, and is credited with being the longest ozone-
using municipal water supply system in the world. Over the years, three
Nice water treatment plants have been constructed (all using ozone for
disinfection), but in 1970 these three plants were combined into a single
plant which incorporates the latest water treatment technologies (including
continued use of ozonation) appropriate to its mountain stream water supply.
Today in France, 593 water supply systems are using ozone for a variety of
purposes.
In France, only 40% of the water plants are owned and operated by
private companies. The remaining 10% are both owned and operated by large,
vertically integrated water companies.
11
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Many of the plants which are owned and/or operated by private companies
are the largest ones. For instance, the Paris suburbs are mostly served by
three large plants, Choisy-le-Roi (on the Seine), Neuilly-sur-Marne, and
Mgry-sur-Oise. Each of these plants was pilot tested, designed, constructed,
equipped, and is now operated by Compagnie GSngrale des Eaux (CGE) for the
Paris suburbs.
CGE is one of two large companies located in Paris that is in the
business of water supply (Soc. Lyonnaise des Eaux et de TEclairage --
SLEE — is the other), which means that they are involved in the operation
of all facets of the systenu similar to the manner in which large oil
companies operate. This "turnkey" approach has the advantage that it tends
to insure that the best treatment process and all necessary and ancillary
equipment will be installed, since the designer, constructor, equipment
supplier, and operator all are part of the same business entity.
Great emphasis is placed on designing a process to produce a finished
water of high quality. One plant process was pilot tested for three years
before design and installation were begun. It is normal for CGE and SLEE to
pilot test several processes for 12.to 18 months before settling on a final
design.
There is no such thing as a "conventional" process employed in France,
since the raw waters contain pollutional loads that vary greatly. In several
plants located along the Seine and Marne rivers, as many as nine different
treatment steps are employed.
A typical process is the one used at the newest plant serving the Paris
suburbs, Neuilly-sur-Marne (Figure 1).
ALUM
ADDITION
SCREENING
CHLORINE DIOXIDE
FOR Fe/Mn OXIDATION
M
POWDERED
ACTIVATED CARBON
FLOCCULATION
OZONATION FOR
DISINFECTION
RAPID GRAVITY
FILTRATION
H
SEDIMENTATION
C12 OR C102
FOR RESIDUAL
Figure I. Process flow diagram of Neuilly-sur-Marne
water treatment plant.
12
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Even though the selling price of water to individual consumers is
significantly higher than in the U.S., there is little concern shown by
consumers regarding the high prices. One reason could be that the French
use much less water than do Americans. French plants normally are designed
based on an assumed per capita consumption of 250 I/day (66.1 gpd). Average
water consumption for four plants visited in the Paris'suburbs was 64 gallons/-
person/day (gpcd).
Considerable emphasis is placed on achieving viral and bacterial
inactivation. This is one of the reasons for the use of ozone. Two now
famous papers by Coin, et jTL1* provide the basis for the French theory of
contacting. This theory, which is practiced widely, is that to achieve
virtually complete viral inactivation, a 0.4 mg/1 residual of ozone must be
maintained for at least 4 minutes following satisfaction of the initial
ozone demand.
A final point of significance is the aversion of the French consumer to
the taste of chlorine. One of the unwritten laws of French water treatment
is that the finished product must have no odor and no undesirable taste.
FEDERAL REPUBLIC OF GERMANY
The predominant philosophy in West Germany is that the best source of
drinking water supply is unpolluted groundwater. If well conditions prove
unobjectionable chemically and bacten'ologically, the groundwater is used
without any treatment and without chlorination. According to Klihn3, there
are still hundreds of European waterworks which provide water without any
chlorination and yet do not have any problems with bacteria in their distribu-
tion systems. Among such waterworks are large cities such as Munich and
Karlsruhe. A common practice in many of these waterworks is to saturate the
water with pure oxygen before it enters the distribution system in order to
maintain a high dissolved oxygen level26.
When water authorities are forced to use surface waters as a source,
which occurs in the densely populated regions along the Rhine and Ruhr
rivers in northern Germany, every effort is made to treat the water to a
quality identical to that of a pure, unpolluted groundwater.
Because of the historically good experiences using groundwater, efforts
are made to use treatment procedures that include passage of water through
the ground. This practice of drawing water from wells located 50 to 250
meters from the bank of the river is known as river sand bank filtration.
Groundwater is extracted in vertical and horizontal wells from large 10 to
30 meter thick water-bearing diluvial gravel and sand sediments. In the
DUsseldorf area, the ratio of bank filtrate to groundwater in the water to
be treated is about 3 to 2, varying with the water level of the river and
changes in the water table.
The effect of natural treatment by ground passage between the Rhine
River and the wells results in a 65 to 75% reduction in the amount of
dissolved organic carbon (DOC)5. During ground passage, numerous physical,
chemical and biological processes occur. Much turbidity and associated
13
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organic and Inorganic substances, such as pesticides, heavy metals and
bacteria, are retained in the gravel and sandstone sediment. The resulting
filtrates combined with groundwater are clear and have low concentrations of
bacteria6.
At one time, river sand bank filtration was the only treatment applied
to surface waters. The goal of treatment is to produce a water which has a
DOC of less than 2 mg/1 and which will require no more than 0.3 to 0.5 mg/1
of chlorine for disinfection purposes3. As the level of pollution increased
over the years, due to increasing population density and industrial pollution,
physical/chemical treatment became necessary in order to achieve this goal.
Thus, 40 years ago, ozone and activated carbon processes were used for the
first time in Germany.
Concurrently, breakpoint chlorination was installed at those plants
having high ammonia contents in their raw waters. Breakpoint chlorination
involves chemical oxidation of ammonia nitrogen to nitrogen gas with chlorine,
and requires the use of 12 grams of chlorine per gram of nitrogen. This
means that very large amounts of chlorine and chlorinated products were
present in the processed water. Since German drinking water regulations
limit residual chlorine concentrations to a maximum of 0.3 to 0.5 mg/1,
granular activated carbon was installed at those plants using breakpoint
chlorination for the purpose of dechlorinating.
Today, both ozone and activated carbon are now used in many plants in
Germany. When the combination was first used in full scale facilities 1n
DUsseldorf during the early 1960s, the application was mainly for iron and
manganese oxidation (ozone) and taste and odor removal (granular activated
carbon). Over the years, the Germans followed the efficiency of activated
carbon in removing dissolved organics, and have found that the ozone/activated
carbon combination was removing more dissolved organics than could be expected
simply on the basis of ozone oxidation alone or by activated carbon adsorption
alone. In addition, ammonia was found to be removed by passage through the
preozonized granular activated carbon.
This prompted detailed investigations at the Bremen water works over a
three year period beginning in 1969' from which it was discovered that this
synergistic organics removal was caused by the bacterial activity present in
the carbon columns. Bacterial activity was optimized by preozonation and
was found to be effective in removing ammonia from the waters as well. Most
significantly, granular activated carbon columns in waters which were devoid
of chlorinated organics and which were subjected to preozonation, were found
to be active for at least two or three years, without requiring regeneration.
This concept, now termed Biological Activated Carbon (BAC) is discussed in
detail in Section 13.
Ozone is seldom used as the terminal treatment step in Germany. This
is because oxidation of organic compounds with ozone leads to transformations
of such organic matter, making many non-biodegradable compounds biodegradable.
This can cause an increase in bacterial growth in the distribution system.
Therefore, an additional filter plus final disinfection by chlorine or
14
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chlorine dioxide should follow ozonation. However, ozone can be used safely
as a terminal step if the Dissolved Organic Carbon (DOC) of the finished
water is less than or equal to 0.2 mg/1.
Also, according to Sontheimer5, ozonation should be preceded by a
filtration step or a flocculation and sedimentation step in order to remove
as much particulate matter as possible. In other words, ozone should not be
used to accomplish what a simpler process can better and rrore cheaply accom-
plish. This approach is endorsed at the majority of European plants using
ozone.
Finally, chlorine dioxide or chlorine is used in very small dosages to
provide residuals in the distribution systems and to prevent bacterial
regrowths. The concentrations added are usually limited to 0.3 mg/1 and
never exceed 0.6 mg/1.
There are two reasons for not using high concentrations of final
disinfectants. First, if the water has been treated properly, many of the
dissolved organic compounds and other reactants will have been removed and
the disinfectant dosages needed to provide residuals are very low. Secondly,
the Germans believe that the water treatment processes also should be designed
to remove bacteria prior to final disinfection. This can be done either by
sand filtration or ozonation. The belief is that since chlorine is harmful
to bacteria, it may likewise be harmful to humans.
SWITZERLAND
In Paris along the Seine, Oise and Marne Rivers and in Germany along
the Rhine and Ruhr Rivers, sophisticated treatment steps are required to
cope with the high concentrations of pollutants in the surface water supplies.
Ozone in concentrations of 3 to 6 mg/1 and activated carbon sometimes are
necessary to treat the waters to qualities suitable for consumption. In
Switzerland, however, the raw waters, which are taken from lakes fed by
mountain streams, or from the streams themselves, are of very high quality.
The TOC is usually 2.0 mg/1 or less. Many countries would like to have
finished waters of such high quality as are many Swiss raw waters.
Swiss waters are basically glacial in origin, from very high altitudes,
and generally are not contaminated with organic compounds. For example,
Schaffhausen requires an ozone dosage of 0.4 mg/1, which produces an ozone
residual of 0.3 mg/1, and this residual lasts for 24 hours. Long term
stability of this ozone residual is due in part to high water quality, but
also to low water temperature.
Swiss people will not accept excessive chlorination in their water
because of tastes. They are used to very cold water, free of undesirable
tastes.
The Swiss began using ozone for drinking water treatment at their very
small and remote plants. Automatic controls became a necessity immediately,
because the communities are sometimes snow bound for months and manual
15
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operation and maintenance is not possible. Modern Otto plate generators
manufactured by Sauter Corporation of Switzerland are used in many of these
small plants.
The next stage of ozone use in Switzerland was to treat lake waters.
The first large Swiss lake water application was at St. Gallen in 1957-58,
whose water supply is the Lake of Constance. The process involved filtration,
chlorination and distribution.
Nearby, however, gas was being produced from coal, and coal processing
drainages were being discharged to the Lake. Over a short period of time,
phenolic compounds built up In the St. Gall en water supply and these imparted
bad tastes and odors when treated by the normal chlorination methods. This
was acutely felt in St. Gallen, where there is a fairly large food processing
industry, and at one time, several days worth of production had to be destroyed
because of contamination with chlorophenols.
Ozone did not produce these tastes when tested on St. Gallon's water
supply, so St. Gallen was the first large Swiss lake water treatment plant
to install ozone. During the next 5 to 6 years, all Swiss Lake of Constance
plants changed over to ozone.
In Germany, ozonation of Lake of Constance water came later, but their
initial efforts were always conducted using ozone as the terminal step for
sterilization.
Using ozone as the final treatment step, the Swiss found bacterial
regrowth, plus slime growth, in the distribution systems. Swiss systems are
100% metered and many repairs had to be made to these water meters because
of slime growths. The Lake Director thought this was caused by the ozone,
and he became very disenchanted with its use. However, when small quantities
of chlorine dioxide were added to the ozonized waters, bacterial regrowth
and slime growths ceased. Today, chlorine dioxide is used as a post-treatment
at Swiss plants on the Lake of Constance, the Lake of Zurich, and others.
During 1963-65, German scientists conducted a 2 year pilot study to
compare the then standard Lake of Constance treatment process with ozonation
and microstraining (ozonation and sand filtration after microstraining).
After only 6 months of this study (at the City of Konstanz treatment plant)
it became clear that ozone must be applied between pre-filtration and post-
filtration.
Plant personnel at the large German waterworks at the Bodensee Wasser-
versorgung (Sipplinger Berg), agree today that it would be a gross misapplica-
tion to use ozone as a terminal step for lake of Constance water.
The modern, fully automated plant at Kreuzlingen (Lake of Constance)
using ozone and activated carbon is the result of this historical move
toward the use of ozone. Pressure filtration occurs prior to ozonation
followed by a bed of activated carbon; chlorine dioxide is then applied as
the terminal treatment step.
16
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Today, there are 150 ozone installations in operation in Switzerland8,
in a country approximately twice the size of the state of New Jersey.
Ozone plus activated carbon facilities have been installed in some
Swiss waterworks for safety reasons, to guard against accidental oil spills.
In plants on the Bodensee (Lake of Constance), for instance, 40% of the
capital costs of the ozone and activated carbon systems were paid by an
international oil company that constructed an oil pipeline under the lake.
The 40% figure was arrived at because this was calculated to be the excess
ozone generation capacity needed to provide safe water should the oil pipeline
ever rupture or leak.
The salient characteristics of Swiss water treatment are the high
quality of the raw water and the "safeguard" treatment processes employed.
CANADA
There is no national water treatment philosophy in Canada. In fact,
drinking water standards are not national mandates, but rather are recommended
standards. Each province decides whether to adopt the Canadian Drinking
Water Standards and Objectives prepared in 1968 by the Joint Committee on
Drinking Water Standards.
The Joint Committee, made up of representatives from each province,
developed these standards in 1968, recognizing the desirability of having
uniform drinking water standards. The current standards will be updated in
1978 and are expected to reflect some of the provisions contained in the
U.S. law, the Safe Drinking Water Act of 1974 (PL 93-523). However, only
one province in Canada (Quebec) is expected to adopt or follow closely the
Primary Drinking Water Standards which went into effect in the U.S. on June
24, 1977.
Because Canadian provinces may differ in philosophy and treatment
standards, it is difficult to pinpoint any particular set of character-
istics. The two most populous provinces, Quebec and Ontario, are the only
two known to use ozone or chlorine dioxide to any major extent. There are
currently 20 plants in Canada, 19 in the province of Quebec, the other in
the Northwest Territories, that use ozone. There are ten plants in Canada
which use chlorine dioxide, all in the province of Ontario.
The history of ozone use in Quebec can be traced back to 1949 when an
engineer having difficulties in eliminating taste and odors from drinking
water decided to learn about ozone experiences in Europe. He consequently
made a trip to European water treatment plants using ozone, was convinced by
what he observed, and decided to try the process on his next project. So in
1956 the first filtration plant using ozone was built in Ste. Therese in
Quebec; the plant had a capacity of 3 mgd9.
Whereas ozone was first used for taste and odor purposes and to improve
appearance, the v/ork of Coin, Hannoun, and Gomel!a* provided impetus to its
adoption through their work which demonstrated its effectiveness in poliovirus
inactivation.
17
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French Canadians soon recognized the multiple advantages of ozonation:
taste and odor removal, improved appearance and taste, viral inactivation,
and, unknown in the 1950s and 1960s, use as an effective oxidant for organic
chemicals. Nadeau and Pigeon9 point out that ozone should not be compared
vn'th chlorine, since chlorine only sterilizes, whereas ozone acts as a
sterilizing agent and removes tastes and odors.
Chlorine dioxide use in Ontario, as far as can be determined, is a
relatively recent occurrence, and is used to remove taste and odors resulting
from phenolic substances.
In Ontario, all surface water supplies are required to have continuous
turbidity and chlorine residual monitoring and recording equipment. Chlorina-
tion equipment is required at all ground water sources. Approximately 85%
of the total population of Ontario is provided with water from municipal
waterworks. In 1975, Ontario had 442 municipal waterworks.
There are approximately 1800 municipal and private waterworks systems
in Quebec. About 92% of Quebec's population obtains its water from surface
supplies, 7% from groundwater supplies, and 0.5% to 1% from a combination of
both. About 20% of the population drink water which is chlorinated only.
According to the "National Inventory of Municipal Waterworks and Wastewater
Systems" from which these data were taken, Quebec's population is presently
provided with a wide distribution of good quality drinking water.
Canada has become concerned recently about the concentration of trihalo-
methanes in drinking water. A national survey was carried out in seventy
municipalities in an attempt to relate levels of trihalomethanes to type of
raw water supply, water treatment and total organic content. Of four trihalo-
methanes investigated, chloroform was found in the highest concentrations,
ranging from 0 to 121 ug/liter. As in the recent U.S. EPA study (NOMS),
trihalomethane levels in water in the distribution systems were found to be
significantly higher than in water sampled in the treatment plants. A
report entitled "National Survey for Halomethanes in Drinking Water" has
been published recently by the Health Protection Branch of the Ministry of
National Health and Welfare.
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SECTION 6
OZONE
GENERAL OVERVIEW OF OZONATION
General History10
In 1785 Van Marum, a Dutch philosopher, noticed that the air in the
neighborhood of his electrostatic machine acquired a characteristic odor
when subjected to the passage of a series of electric sparks. In 1801,
Cruickshank observed the same odor in the gas formed at the anode during the
electrolysis of water. In 1840, Schonbein reported the odor as being due to
a new substance to which he gave the name ozone, derived from the Greek word
"ozein", meaning to smell. Schonbein also was the first to suggest that
ozone may occur naturally in the atmosphere.
The present construction of electric discharge ozone generators evolved
from the apparatus originally designed by Werner von Siemens in 1857 in
Germany. Brodie (England) and Berthelot (France) also designed early ozone
generators. Siemens' first ozonizer essentially consisted of two coaxial
glass tubes, the outer coated externally and the inner coated internally
with tin foil, air feed gas being passed through the annular space. Brodie
substituted water as the electrode material in place of tin foil, and Bertho-
let used sulfuric acid.
The Siemens type of ozone generator has been developed commercially
into a form suitable for commercial production of ozone, and today most of
the ozone generating systems installed in drinking water treatment plants
are of this type. Glass tubes are coated internally with a metal dielectric
and the individual tubes are cooled by means of water.
Modifications to the original Siemens generator have been made, primarily
dealing with the method of cooling, and today many different types of genera-
tors are available. All operate on the same general principal, corona dis-
charge, which requires high voltages and/or high frequencies, thus creating
considerable heat. In turn, this requires that the generators be cooled in
order to maximize ozone production yields and minimize power consumed.
19
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Characteristics of Ozone
Ozone itself is an unstable gas which boils at irinus 112°C at atmospheric
pressure, is partially soluble in water (about 20 times the solubility of
oxygen) and has a characteristic penetrating odor, readily detectable at
concentrations as low as 0.01 to 0.05 part per million. It is a powerful
oxidant, having an oxidation potential of 2.07 volts, and therefore should
be considered a dangerous material, capable of oxidizing many types of
organic materials, including human body tissue. At the relatively low
concentrations of ozone produced by commercial generation equipment (1 to 3%
in air; 2 to 6% in oxygen) no explosive hazard exists, but mixtures of ozone
concentrated to 15 to 20% or higher in air can be explosive. In aqueous
solution, ozone is relatively unstable, having a half-life of about 20 to 30
minutes in distilled water at 20°C. At lower temperatures the half-life of
ozone in water is extended considerably. If there are oxidant-demanding
materials present in solution, the half-life of ozone in such solutions will
be shorter.
On the other hand, ozone in air (especially under dry conditions) is
much more stable than in water. The half-life of ozone in the ambient
atmosphere has been measured by the U.S. Environmental Protection Agency and
determined to be on the order of 12 hours.
History of Ozone Use in Water Treatment
The earliest experiments on the use of ozone as a germicide were con-
ducted by de Meritens in 1886 in France, who showed that even dilute ozonized
air will effect sterilization of polluted water. A few years later (1891),
the bactericidal properties of ozone were reported by Frfllich from pilot
tests conducted at Martinikenfeld in a plant erected by the German firm of
Siemens & Halske. In 1893, the first drinking water treatment plant to
employ ozone was erected at Cudshoorn, Holland. Rhine River water was
treated with ozone, after settling and filtration. Siemens & Halske next
built treatment plants at Wiesbaden (1901) and Paderborn (1902) in Germany
which employed ozone.
A group of French doctors studied the Oudshoorn plant and its ozonized
water and, after pilot testing at St. Maur (in Paris) and at Lille, a 19,000
cu m/day (5 mgd) plant was constructed at Nice, France (the Bon Voyage
plant) in 1906, which employed ozone for disinfection. Because ozone has
been used continuously at Nice since the Bon Voyage plant began operating in
1906, Nice is referred to as "the birthplace of ozonation for drinking water
treatment".
Full scale water treatment plants then were constructed in several
European countries. As of 1916 there were 49 treatment plants having a
total capacity of 319,200 cu m/day (84 mgd)11 in operation, and 26 of these
were in France. By 1940 this number had increased to 119 water treatment
plants, located as follows12:
20
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90 France
14 Italy
5 Belgium
4 England
3 Rumania
2 USA
1 Russia
119
Today there are more than 1000 drinking water treatment plants throughout
the world employing ozone for one or more purposes (see Table 1).
In Canada, the first ozonation plant was built in Ste-Therese, in the
Province of Quebec in 1956. Today Canada has 20 ozonation plants (19 in
Quebec), with 3 more being built. The largest ozone system in the world for
drinking water plant currently is under construction in Montreal.
In the USA there are currently four operating ozone drinking water
treatment plants, with one other under construction. Since 1941, Whiting,
Indiana has been ozonizing about 7 mgd of water for taste and odor control,
followed by chloramination for residual. In 1973, Strasburg, Pennsylvania
constructed a 110,000 gal/day plant using ozone for disinfection, with no
residual disinfectant being employed.
During the National Organics Reconnaissance Survey, conducted by EPA in
early 1975, water from the Strasburg plant contained lower concentrations of
trihalomethanes than any other city examined. Waters of Whiting, Indiana
contained the second lowest amounts of trihalomethanes.
Monroe, Michigan recently has started up a new, 18 mgd plant employing
ozone for taste and odor control. Bay City, Michigan also has started up a
new 30 mgd treatment plant using ozone for taste and odor. Saratoga, Wyoming
will be starting up a 3 mgd plant by mid-1978, also using ozone for taste
and odor control.
Current Extent of Ozone Usage
In conducting the current state-of-the-art analysis, considerable data
were assembled as to the location of drinking water treatment plants using
ozone from the published literature, from manufacturer brochures and from
personal conversations with people who have been involved with the design
and installation of ozonation systems for a number of years. From all of
these sources the approximate number of currently operational drinking water
treatment plants using ozone for one or more purposes was determined to be
21
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1039 (+200,-50) throughout the world. Location of these plants by country
is given in Table 1.
TABLE 1. OPERATIONAL PLANTS USING OZONE - 1977
Country
France
Switzerland
Germany
Austria
Canada
England
The Nether! and
Belgium
Poland
Spain
USA
Italy
Japan
Denmark
Russia
Norway
Sweden
Algeria
Syria
Bulgaria
Mexico
Finland
Hungary
Corsica
Ireland
Czechoslovakia
Singapore
Portugal
Morocco
Total
* Includes expansions. Actual number
with 3 more under construction.
Number of Plants
593
150
136
42
23*
18
12
9
6
6
5
5
4
4
4
3
3
2
2
2
2
1
1
1
1
1
1
1
1
1039
of operating plants in Canada = 20,
Two comments are applicable to the number of plants determined. First,
the number is high because many manufacturers list each expansion of a
particular plant as a separate installation (some ozonation plants have
undergone as many as three expansions). Some plants have ceased operating
or have been consolidated into other plants. This would also make the
number high. On the other hand, it was not possible to contact all ozone
generator manufacturers, and the smaller manufacturers are known to have
many existing ozonation installations for drinking water. On balance, it is
believed that the actual number of plants currently using ozone to be 100 to
200 higher than the 1039 number.
22
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Although France has the greatest number of plants using ozone, the
plant with the largest ozone gneration capacity for treating drinking water
is Moscow, Russia. This 1,200,000 cu m/day (317 mgd) plant, built in 1969,
generates 200 kg/hour of ozone (10,582 Ibs/day.
Montreal, Canada currently is constructing a 2,300,000 cu m/day (608
mgd) plant in two stages. When completed in 1980 the Charles-J. des Baillets
Montreal plant will be capable of generating 300 kg/hour of ozone, and at
that time will be the largest drinking water treatment plant in the world
using ozone.
Applications of Ozone in Drinking Water Treatment
Because ozone is a powerful oxidant and because many contaminants in
raw water supplies are oxidizable, ozone can be used for many specific
applications. The major applications are listed in Table 2. Although the
early uses for ozone were predominantly for disinfection (bacterial kill and
viral inactivation), today oxidative applications account for a significantly
increasing number of applications.
TABLE 2. APPLICATIONS OF OZONE FOR WATER TREATMENT
Bacterial Disinfection
Viral Inactivation
Oxidation of Soluble Iron and/or Manganese
Decomplexing Organically-Bound Manganese (Oxidation)
Color Removal (Oxidation)
Taste Removal (Oxidation)
Odor Removal (Oxidation)
Algae Removal (Oxidation)
Removal of Organics (Oxidation)
such as Pesticides
Detergents
Phenols
Removal of Cyanides (Oxidation)
Suspended Solids Removal (Oxidation)
Preparation of Granular Activated Carbon for
Biological Removal of Ammonia and
Dissolved Organics
In recent years, multiple uses for ozonation in the same water treatment
process have been developed. For example, if ozone is applied for, say,
color removal, near the end of the treatment process, a significant amount
of disinfection also will be obtained. The conjunctive use of contactor
off-gases from the primary purpose ozone contacting chambers can be effective
in such treatment processes. These off-gases (which contain 5 to 10% of the
ozone charged to the primary purpose contact chambers) can be recycled to
the initial steps of the treatment process to oxidize iron and manganese, to
aid in flocculation of suspended solids, or simply to destroy excess ozone
while performing useful work. The reuse of contactor off-gases will not
eliminate the need for ozone destruction facilities (see Section 8 -- Engi-
neering Aspects of Ozonation).
23
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The most recent application of ozonation is before granular activated
carbon beds or columns. This treatment, which can be accomplished by using
primarily contactor off-gases containing ozone and air or oxygen, supplies
considerable dissolved oxygen to the water, oxidizes dissolved organics to
generate more biodegradable organic compounds, and provides an oxygen and
dissolved carbon environment conducive to aerobic bacterial proliferation in
the activated carbon. In turn, these aerobic bacteria biologically remove
dissolved organic carbon compounds as well as ammonia. The phenomenon is
termed "Biological Activated Carbon" and is discussed in detail in Section
13 of this report.
In the future, it appears likely that, as the technology of treating
drinking water supplies with ozone becomes more widely understood, the
application of ozone will increase. One of the most significant points for
the water treatment engineer to learn about ozonation is the multiple applica-
tion aspect. The use of ozone for more than one purpose can effectively
reduce the cost of ozone installations charged to disinfection.
For example, ozone can be installed for a single purpose, say disinfec-
tion, at a cost of X dollars. If this is the only purpose for ozone, then
contactor off-gases must be disposed of safely. This can be done catalytically
or thermally, but at some additional (Y dollars) cost. Therefore, total
ozonation system cost is: $(X + Y).
Instead, the contactor off-gases can be recycled to the front of the
water treatment process and utilized for a second water treatment purpose,
such as the oxidation of iron and manganese, or as a flocculation aid, or
for color removal, organics oxidation, etc. The additional cost for this
second ozonation step (Z dollars) can be of the same order of magnitude as
the cost for ozone destruction (Z = Y). Using some of the off-gas
ozone to perform useful work can be more energy cost-effective than destroying
excess ozone. Costs for utilizing off-gas ozone also would be smaller than
if preozonation were the only ozonation purpose.
Such a dual application of ozone could even require a small amount of
additional ozone generation capacity, which might not be economical if only
the initial ozonation process step were to have been considered without
later disinfection. As part of a dual ozonation process, the relative costs
of ozonation for the disinfection step will be lowered. In addition, the
initial use of ozone can replace chemical usage and lower chemical costs for
the total plant process. '
Generation of Ozone
Nature generates ozone continuously by means of sunlight acting upon
oxygen in the atmosphere, or intermittently by lightning passing through the
air. Man simulates this natural process in generating ozone by passing high
voltage electrical discharges, high or low electrical frequencies, or high
energy radiation through air or oxygen. Ozone is also generated unintention-
ally by man as a by-product during operation of electrical power generation
24
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equipment, electrostatic precipitators, welding equipment, electrostatic
copying machines, ultraviolet lights, and a variety of other electrical
devices.
Commercial quantities of ozone are generated on-site and as needed in
equipment which includes gas preparation, electrical supply, ozone generators.
Generation of ozone is energy intensive, with some 90% of the power supplied
to the generator being utilized to produce light, sound, and primarily heat,
rather than the desired ozone. Thus minimizing electrical power requirements
is a prime target of the ozone generator manufacturer.
A more detailed discussion of the factors affecting ozone generation by
the corona discharge technique is given in Section 8. In general, however,
type, thinness and surface area of the dielectric medium used, discharge gap
between electrodes, quality of the dielectric medium (no pinholes or misalign-
ment), pressure, temperature, rate of flow of gas through the ozone generator,
composition (air vs. oxygen), and moisture content of the feed gas are among
the most important factors. Rosen13 gives an excellent discussion of the
theory of generation of ozone.
Ambient air or recycled oxygen-rich gas contains moisture which, if
allowed to remain in the feed gas during generation of ozone will: 1) reduce
the yield of ozone per kwhr of electrical energy applied: and 2) form nitric
acid, which can result in severe corrosion of some generator components and
downstream ozone handling equipment. For those reasons, air to be fed to
the generator should be adequately dried. This is the function of the gas
handling equipment mentioned earlier. In modern ozone generating systems,
air is dried to a dew point of at least minus 40°C, and preferably to minus
60°C or below.
When dry air is used to generate ozone, a mixture of approximately 1%
ozone in air is produced for the lowest power expenditure consistent with
generation ozone at a reasonably rapid rate. Increasing the rate of flow of
feed gas through the ozone generator at constant power will increase the
amount of ozone generated per unit time and per unit of electrical energy
applied, and will reduce the concentration of ozone in the output gas mixture.
Reducing the rate of feed gas flow will increase the concentration of ozone
per unit of electrical power applied, will decrease the amount of ozone
produced per kwhr of power applied and will decrease the amount of ozone
produced per unit time. Proper choice of parameters for the particular
ozonizing job at hand will guide the user to produce the optimdm amount of
ozone for minimal expenditure of power.
Generation of ozone by electrical discharge produces heat, and heat
causes decomposition of ozone in the product gas. Thus it is important that
the heat generated in producing ozone be removed as quickly and efficiently
as possible. This is normally accomplished by water, air, or heat transfer
fluid cooling of the dielectric.
In recent years, ozone generator efficiency has been increasing. It
has been noted that the Bon Voyage plant of Nice in 1906 originally required
73 kwhr/kg of ozone generated. By contrast, the City of Montreal's
25
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Charles-J. des Baillets drinking water treatment plant, which is under
construction and will house one of the largest ozone generation capabilities
in the world (6750 kg/day) when completed in 1980, is projected to produce
ozone for 23.6 kwhrs/kg of ozone generated15.
Use of oxygen as the feed gas rather than air will allow production of
essentially double the amount of ozone per kwhr of electrical energy (2%
ozone in oxygen). Thus, capital requirements for ozone generation will be
lowered by using oxygen. It should be recognized however, that the gases
now discharging from the ozone generator will be 98% oxygen and 2% ozone.
Therefore, to minimize loss of oxygen, contactor off-gases, still very rich
in oxygen, should be recycled to the ozone generator (after removing contami-
nants and water). Gas handling equipment will normally be required, therefore,
when oxygen is used as the feed gas.
At the present time, only one of the 1039 municipal water treatment
plants is known to be using oxygen to generate ozone (Duisburg, Germany).
The Brussels, Belgium plant (Tailfer) is installing oxygen facilities so as
to be able to use oxygen during summer periods of high ozone dosage require-
ments. The use of oxygen in drinking water treatment plants for generating
ozone currently is very small, but worthy of future consideration.
Contacting of Ozone
Because ozone is only slightly soluble in water at the partial pressure
at which it is generated and applied, contacting ozone with water involves
bringing bubbles of ozone-containing air or oxygen into intimate contact
with the water. Mass transfer of ozone from the gaseous bubbles occurs
across the gas/liquid interface into the water.
Factors which affect the mass transfer of ozone in liquids, and which
themselves are affected by design and operation of the contactor system,
include:
• the miscibility with water and ozone demand of substance(s) to be
ozonized
t concentration of ozone in the gas (with regard to mass transfer)
• method and time of contact
0 bubble size
t pressure and temperature
• presence of interfering substances
Generally speaking, there are two major categories of reaction which
ozone undergoes in solution: 1) those which are so rapid that they are
limited by the rate of mass transfer of ozone into solution; and 2) those
which are slower than the mass transfer rate, thus are limited by the reaction
kinetics of the material to be ozonized. Reaction rates of such constituents
26
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as bacteria, nitrites, hydrogen sulfide, phenols, unsaturated organic com-
pounds, etc., are very rapid, and are limited only by the rate at which
ozone is "mass transferred" into solution.
Other materials react with ozone very slowly, such as acetic acid,
urea, saturated aliphatic alcohols, ammonia and oxalic acid. Even in the
presence of large excesses of ozone, the rates of these reactions are very
slow, and thus are "reaction rate limited".
Therefore, in designing an ozone contacting system, it is important to
minimize the amount of ozone required for the specific purpose for which the
ozone is to be used. If bacterial disinfection only is desired, a contactor
which causes rapid mass transfer of ozone should be used. For oxidation of
biorefractory organic materials, the rate of ozone mass transfer is less
important than maintaining a specific concentration of ozone for a longer
contact period.
These two situations are illustrated graphically in Figure 2. The
upper curve shows that a high ozone dose for a short period of time uses the
minimum amount of ozone for maximum mass transfer. On the other hand, the
lower curve shows that low ozone dosages for long periods of time provides
the minimum amount of ozone for reaction rate controlled reactions.
Basically, there are only six different types of gas/liquid contacting
systems16. These are:
t Spray towers (liquid sprayed into gas)
• Packed beds
§ Bubble plate or sieve plate towers (an intermediate situation
between 1 and 2)
• Mechanical mixers
0 Injectors
• Diffusers
The most common ozone contacting systems are based on some method for
dispersing gas bubbles within a liquid. Generally there are two ways of
accomplishing this:
• Gas is introduced initially into the fluid as bubbles of the
desired size for optimum ozone dispersion into the liquid, or
• A massive bubble or gas stream is disintegrated into the fluid.
27
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OZONE DOSE
FOR MASS TRANSFER
LIMITED REACTIONS
TIME
OZONE
DOSE
FOR CHEMICAL REACTION
RATE CONTROLLED REACTIONS
TIME
Figure 2. Ozone dosage vs. time for two types of reaction: mass transfer
rate controlled and chemical reaction rate controlled.
28
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These two techniques are exemplified by the diffuser (or sparger) and
the injector (or eductor) contactors, respectively. Both of these types of
contactor were developed originally for treating potable water supplies, and
have been utilized throughout the world for this purpose for many years.
Many variations of each type have evolved.
With the diffuser, ozone is added at the bottom of the contact chamber,
through a porous medium (ceramic, Teflon, stainless steel, etc.), and the
gas bubbles rise through the water which is passed cocurrently or counter-
currently through the chamber. Many installations utilize multiple diffuser
chambers, alternating liquid flow first cocurrently then countercurrently
with the gas stream. Diffusers can be operated with little energy being
added, are especially useful when large volumes of water are being passed
through the plant by gravity flow, and also are flexible in terms of changing
flow rates. Additional power costs to effect contacting thus are minimized.
However, contacting chambers to house the diffusers are rather large.
Injectors require added energy, the simplest involving pumping of water
to be ozonized rapidly past a small orifice, through which the ozone is
forced into the liquid under pressure or drawn into the liquid by the vacuum
created by rapid flow of water past the orifice. In those installations in
which water already is being pumped about the plant, injectors are especially
suitable, because of their smaller size and high mass transfer rates. How-
ever, injectors are relatively inflexible in terms of changing flow rates.
Detailed discussions of the theory of contacting have been published by
Nebel,17; Sherwood & Pigford18 and Treybal19. For purposes of this report,
however, it is sufficient to point out that all contactors have their advan-
tages and their limitations (Table 3), and it is necessary to consider the
specifics of the ozonation job at hand, with respect to material(s) to be
ozonized, volume of liquid to be treated, etc. A pilot study should be
conducted with the contactor(s) selected, and the following parameters should
be studied over practical and economic limits17'20'21'22:
• Liquid head or total pressure at initial point of gas/liquid
contact,
• Distribution of ozone throughout the contact period,
• Total contact time necessary,
• Concentration of ozone applied,
• Volume ratio of liquid to gas,
t Ozone residual.
Once these parameters have been determined satisfactorily, design of the
full scale ozone contacting system can proceed with a high degree of confidence.
Specific ozone contacting systems will be discussed in more detail in
Section 8.
29
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TABLE 3. TYPES OF OZONE CONTACTORS
CONTACTOR
TYPE
ADVANTAGES
DISADVANTAGES
SPRAY
TOWERS
PACKED
COLUMNS
PLATE
COLUMNS
SPARGERS
AGITATORS,
SURFACE
AERATORS,
INJECTORS,
TURBINES,
STATIC
MIXERS
- HIGH RATE OF MASS TRANSFER
- UNIFORM 03 IN GAS PHASE
- WIDE GAS/LIQUID OPERATING
RANGE
- SMALL SIZE AND SIMPLICITY
- SAME AS PACKED COLUMNS, BUT
NO CHANNELING AND BROADER
GAS/LIQUID OPERATING RANGE
- REQUIRES ONLY GRAVITY FEED;
NO ADDED ENERGY
- WIDE GAS/LIQUID OPERATING
RANGE ALLOWS INTERMITTENT
OPERATION
HIGH DEGREE OF FLEXIBILITY
SMALL SIZES
INTIMATE CONTACT & GOOD
DISSOLUTION
- REQUIRES HIGH ENERGY TO
SPRAY LIQUID
- SOLIDS CAN PLUG SPRAY
NOZZLES
- SHORT CONTACT TIME
- EASILY CHANNELLED & PLUGGED
EASILY CLOGGED, BUT EASIER
TO CLEAN
BEST SUITED FOR VERY LARGE
INSTALLATIONS
INTERMITTENT FLOWS MAY CAUSE
PLUGGING OF POROUS MEDIA
LONGER CONTACT TIMES REQUIRE
LARGER HOUSINGS
TENDENCY TO VERTICAL
CHANNELING OF GAS BUBBLES,
REDUCING CONTACT EFFICIENCY
REQUIRE ENERGY
NARROW GAS/LIQUID OPERATING
RANGES
CANNOT ACCOMODATE SIGNIFI-
CANT FLOW CHANGES (INJECTORS
AND STATIC MIXERS), THERE-
FORE REQUIRE MULTIPLE
CONTACTOR STAGES
Ozone Analysis and Control
The most generally used technique for determing ozone (actually total
oxidants) in water is by the starch-potassium iodide technique. Recently,
however, many other colorimetric techniques have proved to be successful as
well. Instrumental techniques include ultraviolet adsorption and amperometric
titration23.
Process control of some types of modern ozonation systems can be
achieved readily by monitoring residual ozone in the water just after the
contacting chamber exit. This technique is employed in many modern European
drinking water treatment plants, and is planned for the Charles-J. des
Baillets plant being constructed in Montreal2". The analyzer is coupled
with the ozone generators so that if the level of dissolved ozone drops
30
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below a pre-determined level, the generators are signaled to increase produc-
tion.
By thus instrumenting, programming, and monitoring dissolved ozone
after contacting, the normally varying loadings of ozonizable materials in
water treatment plants can be handled on an automated basis using minimum
quantities of ozone.
In an exactly similar manner, the amount of ozone present in ambient
plant atmospheres can be monitored by another analyzer, or series of analyzers.
In the event of an ozone leak from the generators or their associated down-
stream piping, the ozone sensors will react by signaling the ozone generators
to be turned off and sound an alarm. Once electricity ceases to pass through
the ozone generator, ozone generation ceases immediately.
Operational Experiences With Ozone
A large portion of this report is based on findings and observations
made during site visits to twenty municipal water treatment plants in Europe
and seven plants in Canada which use ozone. The 20 plants in four European
countries were visited in May 1977 by a team of scientists and engineers.
In August 1977, this team inspected seven plants in the province of Quebec,
Canada.
Plants were selected on the basis of variability and uniqueness of
application, size, and ozone treatment train variability. The site visit
team inspected plants in Europe ranging in size from Annet-sur-Marne (25,000
cu m/day), and the large plant in the Federal Republic of Germany, Sipplinger
Berg (650,000 cu m/day).
Plants containing ozone equipment from each of the major European manu-
facturers were inspected. These included Trailigaz and Degremont of France,
Gebruder Hermann and Demag of Germany, and Kerag and Sauter Corporation of
Switzerland. Plants were inspected in Canada supplied with Canadian made
equipment (Degremont Infilco Ltd.). Also plants using U.S. manufactured
equipment were observed in Europe (Welsbach) and Canada (Welsbach and PCI
ozone.
The only operating municipal plant (Duisburg, Germany) using oxygen as
the starting material for ozone production was visited. Five plants in the
Dtlsseldorf area which practice river sand filtration and which place heavy
emphasis on ozone, plus activated carbon were inspected. The newest concepts
in German drinking water practice were viewed at the Dohne plant in Mdlheim
near Dtlsseldorf. In southern Germany, a large plant which uses ozone primarily
for microflocculation, followed by activated carbon, was seen (Langenau).
Rouen-la-chapelle, located about 70 miles northwest of Paris, uses two
stage ozonation, practices river sand bank filtration, and is the first
French plant to use biological activated carbon (BAG). This process began
operating at Rouen in early 1976. Two plants in southern France using ozone
as the terminal step in the process, Clarifont in Toulouse and Super Rimiez
31
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in Nice, were visited. Several plants having highly sophisticated control
systems were visited. The most notable ones in this category were Neuilly-
sur-Marne, (600,000 cu m/day) in the Paris suburbs and Kreuzlingen on the
Bodensee (Lake of Constance) in southern Germany.
Ozone systems that had been in operation for a number of years were
also of interest. Two such plants, Choisy-le-Roi in Paris and the Holtausen
plant in Cusseldorf have had their current systems in operation for more
than 10 years.
A complete list of European plants listed in the order visited is shown
in Table 4. Contrasts among plants are covered in detail in Section 7.
Six of 19 operating plants in the province of Quebec, using ozone, were
visited. A seventh, the new Charles-J. des Baillets plant in Montreal,
scheduled to go on-line in 1980, also was visited. The largest ozone plant
in Canada, Quebec City (218,000 cu m/day), was inspected. The other five
visited were Sherbrooke, Pierrefonds, Laval-Chomedey, St. Denis, and He
Perrot. Pierrefonds and Sherbrooke are the two newest ozone facilities in
Canada and thus represent the most recent efforts 1n North American practices
of the technology. St. Denis is a very small plant (27,000 cu m/day, 7.2
mgd) that has PCI ozone equipment. He Perrot is an older small system that
has a Welsbach ozonator. The Chomedey plant, located in the City of Laval,
is rated at 39 million Imperial gallons per day (177,990 cu m/day). One side
of the plant, the older side, uses powdered activated carbon for taste and
odor control; the newer side uses ozone for taste and odor removal.
The selection of plants to visit in Canada was based on the same criteria
as in the case of Europe. The team wanted to see systems made by U.S. manu-
facturers (Welsbach and PCI), small systems, Otto plate systems, and newer
systems using French technologies. Additionally, if any plant used ozone as
a terminal step, the conditions were to be observed and evaluated. Plants
chosen exhibited one or more of these criteria. Table 5 gives pertinent
information for each of the Canadian ozone plants located in the province of
Quebec.
SUMMARY OF DATA FROM EUROPEAN OZONE QUESTIONNAIRES
General
Eleven hundred ninety-two (1192) questionnaires were mailed to municipal
water plants in western Europe in mid-1977. These questionnaires (see copy
in Appendix D) asked for detailed information on various aspects of ozone
usage. Questionnaires were mailed to plants in France, the Federal Republic
of Germany (FRG), Switzerland, Austria, The Netherlands and Great Britian.
One questionnaire was sent to Brussels (Tailfer) for review; it was completed
and returned.
The number of questionnaires mailed to those water plants thought to be
using ozone is actually much smaller than 1192. In Germany (FRG), the
32
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TABLE 4. EUROPEAN PLANTS INSPECTED BY SITE VISIT TEAM
Name
Choisy-le-Roi
Morsang-sur-Seine
Rouen-la-Chapelle
Aubergenville
Neuilly-sur-Marne
Annet-sur-Marne
Clairfont
Super-Rimiez
Tailfer
Holthausen
Flehe
Am Staad
Dohne
Wuppertal
Wittlaer III
Lengg
Kreuzlingen
Konstanz
Sipplinger Berg
Langenau
Location
Paris suburbs
Paris suburbs
NW of Paris
NW of Paris
Paris suburbs
Paris suburbs
Toulouse
Nice
Brussels
DUsseldorf
DUsseldorf
DUsseldorf
MUlheim
Wuppertal
Duisburg
Zurich
Kreuzlingen
(Switzerland)
Konstanz
(Germany)
Sipplingen
(Germany)
near Ulm
(Germany)
Design
Capacity
(cu m/day)
800,000
150,000
30,000
100,000
600,000
25,000
110,000
90,000
260,000
192,000
88,000
144,000
48,000
168,000
48,000
250,000
34,560
50,000
650,000
198,700
Ozone Generator
Manufacturer
Trail igaz
Degremont
Trail igaz
Welsbach
Trail igaz
Trail igaz
Trail igaz
Trail igaz
Trail igaz
Hermann
Hermann
Hermann
Trail igaz
Hermann
Demag
Kerag
Sauter
CEO
(Trail igaz)
Hermann
Degremont
Type
Tube
Tube
Tube
Tube
Tube
Tube
Tube
Tube
Tube
Tube
Tube
Tube
Tube
Tube
Tube
Tube
Otto Plate
Otto Plate
Tube
Tube
33
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German Association of Gas and Waterworks mailed out 835 questionnaires to
waterworks, most of which do not use ozone; thirty-one of the 136 plants in
Germany (FRG) thought to be using ozone have responded to date.
Thus, the number of water plants (using ozone) that received the question-
naire totalled approximately 400.
Questionnaire mailings and responses by country are as follows:
County
France
Germany (FRG)
Great Britain
The Netherlands
Austria
Switzerland
Belgium
Mailed
Total
Received
63
31
6
7
5
9
1
122
Total Municipal
Plants Using
Ozone
593
136
18
12
42
150
9
960
The total number of ozone water plants by country is shown in Table 1.
Total number of plants listed for western Europe is 999. With responses
numbering 122, this means that the response rate for all western Europe
plants using ozone to date is 12.2%.
The following pages summarize questionnaire results by country. Tables
giving details on each plant responding to the survey are included in Appendix
D.
Great Britain
Fifteen questionnaires were mailed to British plants using ozone and
six responses were received. There are 18 water plants in Great Britain
known to be using ozone. The plants responding averaged 105,000 cu m in
size, and ranged from 5,000 cu m/day to 450,000 cu m/day (Watchgate Plant).
The primary application of ozone in Great Britain is for color removal.
Each of the six plants responding indicated ozone use for this purpose.
Other uses indicated include: bacterial disinfection (2 plants); iron and
manganese oxidation (2 plants); taste and odor removal (1 plant); and viral
inactivation (1 plant).
Ozone usage is relatively new in Great Britain. The oldest of the six
ozone facilities which responded is the Loch Turret treatment works which
installed ozone in 1967, but is not now operating.
Treatment processes vary. Ozone is used after a filtration step in
each of the six plants. In four of the plants microstraining is the filtration
method used. Chlorine is used as a final disinfectant in each of the six
plants. In 3 of 6 plants chlorination follows ozonation with no filtration
step in between.
34
-------
Ozone generation equipment in 5 of the 6 plants reporting was supplied
by Trailigaz of France. Five of the six plants have tube type, water cooled
ozone generators. Ozone contacting in three plants is by porous tubes
(diffusers). Other methods of contacting are: injector (2 plants); and
submerged turbine (1 plant).
Off-gas treatment is practiced in 5 of the 6 plants. The methods vary
from destruction by passing through wet activated carbon (2 plants), recycling
(1 plant), thermal destruction (1 plant), and catalytic destruction (1
plant).
Power consumption for ozone generation and application (including air
preparation, generation, contacting, and off-gas treatment) averaged 29.7
kwh/kg of ozone produced. Consumption ranged from 23 kwhr/kg to 37 kwhr/kg.
Ozone dosage averaged 2.37 mg/1 for the four plants that responded to
that portion of the questionnaire. It should be noted that chlorine dioxide
and ozone are not used jointly in all British plants. Chlorine dioxide is
often used as a distinct unit process, added stepwise to insure a better
residual.
The Netherlands
Questionnaires were mailed to the 10 major plants in the Netherlands
using ozone. Seven were returned. Results of the survey show that there
are 12 water plants in the Netherlands which use ozone.
The prevalent water treatment philosophy is that physical and biological
treatment processes are best. Chemicals and disinfecting agents are used
only in cases where they are unavoidable. Chlorine dioxide currently is not
used. Chlorine is used as a terminal disinfecting agent although many
plants have plans to switch to CKL in the future.
The plants responding to the questionnaire are relatively large, averaging
49,500 cu m/day. The range in size was 1000 cu in/day to 120,000 cu m/day.
Five of seven facilities have used ozone for five years or less. The Noorden-
dijk Plant in Dordrecht has used ozone for nine years. Average age of the
ozone facilities is 3.7 years.
The primary application of ozone appears to be for color removal (6
plants), taste removal (6 plants), and odor removal (4 plants). Other
applications are for bacterial disinfection (2 plants), viral inactivation
(2 plants), organics removal (3 plants) and as a filtration aid (1 plant).
Ozone dosages range from 0.23 mg/1 to 5 mg/1. Average dosage for seven
plants was 2.59 mg/1.
Each of the seven plants reporting has tube type, water cooled ozone
generators. Kerag, a Swiss manufacturer, furnished the equipment for 4 of
7 plants.
Contacting in 5 of 7 plants is accomplished by means of submerged
turbines; one plant uses an injector and one uses porous tubes for dispersion.
35
-------
Power consumption ranges from 17 to 20 kwh/kg of ozone produced at the
Houdsweg plant to 50 kwh/kg of ozone produced at the Engelse Werks plant.
Power consumption averages 29.85 kwh/kg at the six plants reporting data.
Contactor off-gas treatment is by thermal destruction at 4 plants and
thermal destruction plus a catalyst at another. One plant uses filtering
through wet activated carbon for ozone destruction. The seventh plant does
not treat the off-gas.
Chlorine is used as a final disinfectant in 3 of the 7 plants; a fourth
applies 0.2 mg/1 sodium hypochlorite. Ozone is used as the terminal step in
the Engelse Werk plant. In the other two plants, sand filtration is the
terminal step and immediately follows the ozonation process.
River sand bank filtration is practiced at two of the seven plants.
Austria
There are 42 municipal water plants in Austria currently using ozone.
Questionnaires were mailed to the 11 largest water companies in Austria
which serve 50% of the Austrian people. Five questionnaires were returned
from water companies in Salzburg, St. Ptilten and Linz.
Ozone has been used in the five facilities an average of 6.6 years,
with the oldest plant having used ozone for 12 years. Plant size ranges
from 4,000 cu m/day to 58,000 cu m/day, average size being 21,000 cu m/day.
Bacterial disinfection is the main purpose of ozonation. Other applica-
tions indicated are for viral inactivation (2 plants), color removal (1
plant), and organics removal (1 plant).
Ozone dosages are relatively low, ranging from 0.06 mg/1 to 1.2 mg/1,
averaging 0.48 mg/1 for the five plants reporting data. The low dosage can
be attributed to the high raw water quality. The water sources for each of
the plants are deep wells.
Ozone generators in three plants are tube type, water cooled units. In
the other two plants, plate type water cooled units are used. Contacting is
by injection in three plants. The other two plants use a "schwimmbegaser",
which has been described to the project team as a surface aeration device
which induces turbulence and thus mass transfer of gas into liquid.
Contactor offgases are handled by dilution (2 plants), partial reinjection
(1 plant), filtration through wet activated carbon (1 plant) and are not
treated in the fifth plant.
Power consumption for ozone production, contacting, and off-gas treatment
averages 34.4 kwh/kg of ozone produced. Consumption ranges from 16 kwh/kg
at the two St. Pttlten plants to 55 kwh/kg at the Salzburg City Waterworks.
36
-------
The only oxidant other than ozone used in the five Austrian plants is
chlorine; in the form of sodium hypochlorite at one plant. In four of the
five plants, ozonation is the only treatment of the water. The fifth plant
applies ozone and then adds 0.8 mg/1 of sodium hypochlorite.
Switzerland
There are approximately 150 water plants in Switzerland which use
ozone. Many of these are very small plants. Questionnaires were not mailed
to all plants, but rather to 20 representative waterworks which serve more
than one million people. Nine of 20 questionnaires have been completed and
returned.
The raw water for the nine plants comes from wells or glacial supplied
lakes. Thus the raw water quality is very high and the ozone dosage is very
low, ranging from 0.3 to 1.5 mg/1. For the nine plants reporting, the
average dosage is about 0.7 mg/1.
Ozone is used for several purposes, among them bacterial disinfection
(7 plants), viral inactivation (7 plants), odor removal (7 plants), taste
removal (6 plants) and organics removal (4 plants).
Five of the nine plants have been using ozone for more than 10 years;
average time of usage is about 12 years.
The plants reporting data range in size from about 2,500 cu m/day (Water-
works Alstatten) to the Lengg Plant in ZUrich which has a capacity of 250,000
cu m/day. Average plant size for the nine plants is about 65,600 cu m/day.
Five of nine plants have tube type, water cooled ozone generators. The
other four have plate type, water cooled generators. Contacting is accom-
plished by a number of methods: submerged turbines (4 plants), injector (3
plants), porous tubes (2 plants).
Power consumption ranges from 17 to 81 kwh/kg. Average power consumption
for ozone generation and contacting for the five plants reporting data is
about 33.5 kwh/kg.
Contactor off-gases are not treated at all in five plants; two dilute
the off-gases before venting to the atmosphere; two thermally destroy the
ozone.
Six of nine plants use chlorine dioxide as a terminal step. It is
estimated that 80% of the Swiss plants which use ozone also use C102.
Chlorine dioxide is applied in very small amounts. The Lengg plant in
ZUrich adds only 0.06 mg/1. Chlorine is used as a disinfectant at two
plants. Ozone is the only treatment applied at the small (2500 cu m/day)
Altstatten plant.
Four plants reported the use of granular activated carbon (GAC) directly
following ozonation.
37
-------
Germany (Federal Republic of Germany)
There are approximately 136 municipal waterworks in Germany which use
ozone. Thirty-one of these waterworks responded to a questionnaire mailed
out by the DVGW (German Association of Gas and Waterworks).
Ozone usage in Germany, based on site visits conducted in May 1977, is
more varied than in any other country. Purposes of ozonation, dosage,
methods of contacting, and the number of manufacturers supplying equipment
do not fall into a consistent pattern as is the case in other countries.
Power consumption also varies greatly.
The average period that ozone has been installed in the German plants
responding is 7.6 years. The plant that has been using ozone for the longest
period is the Neustadt-Sisch plant, which installed ozone facilities in
1959.
The average plant size is about 54,100 cu m/day. This number can be
misleading, however. Many small plants of less than 1,000 cu m/day use
ozone as their only treatment. Ozone is also used at the large German water
treatment plant, the Bodensee Wasserversorgung (Lake of Constance) which has
a capacity of 650,000 cu m/day.
In Section 5, it was noted that the Germans try to use groundwater as
a source whenever possible and that their water treatment philosophy is to
try to restore waters to the quality of a pure, unpolluted groundwater. The
questionnaires received substantiate this stated philosophy. Nineteen of
the 31 plants responding use groundwater as then raw water source, 6 practice
river sand bank filtration, and 4 take their water from the Lake of Constance.
Only three plants (Dliren, Donne and Langenau) uses river water directly
without ground passage first (Donne uses ground passage after treatment).
Czone is used for many purposes in Germany. Twenty-four of the 31
plants indicate its use for organics removal, taste (13 plants), viral
inactivation (8 plants), iron oxidation (7 plants), manganese oxidation (6
plants), odor removal (7 plants), turbidity reduction (6 plants), and color
removal (5 plants). Ozone dosages range from 0.15 mg/1 at the Diez/Lahn
plant to 5.7 mg/1 at the Osterode plant.
Ten different manufacturers of ozone generators supplied equipment to
the 31 plants. Twenty-six facilities have tube type, water cooled generators
while 5 have plate type, water cooled generators.
Contacting of ozone with the water stream is accomplished mainly by
means of injection (21 of 31 plants). Other methods are submerged turbine
(2 plants), packed column (3 plants), and porous tubes (1 plant). Wuppertal
uses spray towers. Three plants did not specify contacting method in their
responses.
Power consumption for ozone generation, air preparation, contacting,
and off-gas treatment appers to be higher at some German plants than in
38
-------
other countries surveyed. Interestingly, the lowest power consumption cited
(15 kwh/kg) is at Duisburg, the only known municipal water plant that
produces ozone from oxygen.
No offgas treatment is practiced at 14 of the 31 plants; six plants
indicate some form of treatment, but do not specify the method. Destruction
of ozone on wet activated carbon is practiced in 4 plants, 3 use catalytic
destruction, 1 plant recycles ozone and 1 plant uses a combination of
activated carbon and a catalyst. Thermal destruction is not practiced at
any of the 31 plants.
For final disinfection, 9 plants use C102» 8 use Cl? and 2 use sodium
hypochlorite. Nine plants apply ozone as their only treatment step. In 3
other plants, ozone is the only oxidant used.
Ten of 31 plants use granular activated carbon as an adsorbent. In
every case, it is used after the ozonation step.
France
Ozone is used in approximately 600 French water plants. Questionnaires
were mailed to 300 of these plants. A total of 63 questionnaires has been
received.
Ozone usage for water treatment began in France in 1906. Thus, one
would expect many of the plants responding to the questionnaire to be older
plants. While there were 10 plants that have used ozone for more than 10
years (the oldest having used ozone for 52 years), the average period of use
is about 8 years. There are many new ozone plants in France, which substan-
tiates the findings earlier in this Section that ozone use has doubled in
the past decade.
The average size of plants responding to the questionnaire was 29,100
cu m/day. Sizes ranged from 350 cu m/day to 240,000 cu m/day.
Unlike Germany, most of the plants use surface water as a raw water
source. Forty-three of 63 plants indicated use of surface water while only
8 use groundwater as a source.
Ozone is used for many purposes, but the primary purposes are bacterial
disinfection (59 plants), viral inactivation (35 plants), taste removal (31
plants), and organics removal (24 plants). Other indicated uses include
color removal (18 plants), turbidity reduction (10 plants), iron (7 plants)
and manganese (5 plants). Ozone dosages range from 0.15 mg/1 to 10 mg/1.
Only 3 manufacturers supplied ozone generation equipment to the 63
plants reporting. Most of them were equipped by the large French companies,
Degremont (32 plants) and Trailigaz (24 plants). Most of the plants use
tube type, water cooled generators. Only nine indicated usage of plate
type, water cooled units.
39
-------
Contacting is accomplished primarily by porous plate diffusers, this
method being used in 44 plants. Injectors are used in 1C plants, packed
columns in 3 plants and spray towers in 2 plants. The remaining plants did
not report data.
Forty-two of 63 plants vent off-gases from the contactor directly to the
atmosphere. Nine plants thermally destroy the off-gases, 3 recycle and 2
dilute before discharging.
Power consumption overall is fairly consistent for the 33 data points
reported. Average power consumption is 31.3 kwh/kg for the total ozonation
subsystem.
Chlorine is used as a final disinfecting agent in 26 plants. Chlorine
dioxide is used in 13 plants. In twenty-two of 63 plants, ozone is the only
oxidant used and often it is the terminal step.
The classic French water treatment process is remarkably similar to the
U.S. "conventional" process. The process used in many plants involves
prechlorination, coagulation, sedimentation, filtration, ozonation, and use
of chlorine or chlorine dioxide as a terminal treatment step. The only
marked difference is the ozonation step. This allows small quantities of
chlorine to be used as the residual disinfectant. Normally less than 1 mg/1
of chlorine is added, or less than 0.6 mg/1 of C102, to provide a protective
residual for the distribution system.
SUMMARY OF DATA FROM CANADIAN OZONE QUESTIONNAIRES
Eighteen questionnaires were distributed in Canada, and all were
completed and returned. These comprise all of the plants in Canada using
Ozone with the exception of a plant at Frobisher Bay in Northwest Territories,
and the Chomedey Plant at Laval. Data for the latter, obtained at the time
of the plant visits, are given in Table 5 which summarizes all of the
plant data from Canada.
The philosophy of ozone usage in Canada evolved from a need to deal
with largely seasonal taste and odor problems, plus continuous disinfection
needs with surface water supplies9. Ozone has been viewed in Canada as an
alternate for two processes: chlorine disinfection and activated carbon
treatment. Nadeau and Pigeon9 argued that, when the costs of the latter
two processes combined are compared to ozone costs, they are comparable,
particularly when the side benefits of decolorization and superior appearance,
plus improved taste and odor of ozonated waters are taken into consideration.
Chlorine still is used in the majority of plants to provide a disinfectant
residual for preventing bacterial regrowth in the distribution system.
Energy consumption for ozone treatment reported by the Canadian plants
falls mainly in the 20 to 30 kwh/kg range. One old plant, He Perrot, reported
45 kwh/kg; whereas one of the newest Canadian plants, Pierrefonds, reported
18 kwh/kg. Off gas destruction is not normally practiced in Canada. Only one
plant, Riviere du Loup, reported using catalytic off gas destruction.
40
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TABLE 5. QUEBEC PLANTS USING OZONE
Name
1 . Terrebonne
2. RIviSre-du-Loup
3. Lac Etchetnln
4. Roberval
5. *Quebec City
6. St. Eustache
7. Oka (Deux Montagnes)
8. *Sherbrooke
9. Laval (Pont-Vlau)
10. Laval (Stc Rose)
ll.*I1e Perrot
!2.*P1errefonds
33. L'Assomption
14. Repentigny
\5. Drummondvllle
16.*St. Denis sur Richelieu
17. L'Epiphanie
18. Buckingham
19.*Laval (Chomedey)
Flow U.S.
cu in/day
15,120
15,120
2,383
7,714.5
218,000
1,060
2,192
98,862
95,850
11,410
6,800
95,500
9,988
22,730
54,000
27,300
4,500
18,900
176,900
mdg
4
4
.63
2.04
57.6
3.0
0.3
26.0
25.3
3.0
7.8
25.2
2.64
6.0
14.3
7.2
1.2
5.0
46.8
Ozone Generator
Manufacturer
CEO
PCI
CEO
Welsbach
CEO
CEO
CEO
Degr&nont
InfUco
CEO
CEO
Welsbach
Traillgaz
CEO
TralHgaz
CEO
PCI
CEO
Degreniont
Infllco
Welsbach
Type
Otto
Tube
Otto
Tube
Otto
Otto
Otto
Tube
Otto
Otto
Tube
Tube
Otto
Tube
Otto
Tube
Otto
Tube
Tube
No. Units
2
1
}
1
12
3
1
4
12
3
1
2
1
1
3
2
1
1
2
Unit cap.
kg 03/hr.
0.6
1.5
0.3
1.8
1.25
-
-
2.36
0.6
0.66
0.3
3.0
-
1.9
0.57
0.58
-
1.2
-
Instld. Cap.
kg 03/hr
1.2
1.5
0.3
1.8
15.0
-
0.3
9.44
7.2
2.0
0.3
6.0
-
1.9
1.71
1.16
-
1.2
-
Yr. 0,
start-up
1963
1977
1966
1977
1969
1957
1958
1977
1957/62/68
1961/68
1963
1976
1966
1973
1966
1972
1962
1976
1973
*Plants visited by survey team.
-------
Porous diffusers and injectors are the most widely used form of ozone
contacting. Only one plant, lie Perrot, uses submerged turbines. Contact
times, where given, ranged from 5 to 20 minutes with most reporting in the
2 to 10 minute range. The Roberval plant doses with ozone twice, utilizing
ozone for both coagulation and disinfection.
A summary table of the Canadian ozone questionnaire responses is given
in Appendix D.
42
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SECTION 7
OZONE SITE INVESTIGATIONS
EUROPEAN PLANT VISITATIONS
Table 6 lists some of the pertinent features of the 20 European plants
visited by the site survey team. As is evident, ozone is used for numerous
purposes and is applied by many methods. In this section we will discuss
the most striking points of similarity and differences in the purposes for
which ozone is being utilized and in the methods of application in the
various drinking water treatment plants visited. Detailed discussions of
engineering and cost aspects will be addressed in later sections.
France
Eight plants were visited in various locations in France (see Figure
3.) Six plants visited use river water, but the raw water quality varies
considerably. Two plants use well water which is partially affected by
river water. Two plants visited are located on the Marne River (Annet —
upstream of Paris and Neuilly — Paris suburbs), four on the Seine (Morsang —
upstream of Paris, Choisy-le-Roi -- Paris suburbs, Aubergenville and Rouen-
la-Chapelle -- both downstream of Paris), one on the Garonne in southwestern
France (Toulouse, Clairfont plant) and one on a mountain stream at Nice,
southeastern France. The Rouen.and Aubergenville plants use well water.
All eight French plants visited use ozone for disinfection. Most of
these plants also use ozone for oxidation of organics, two additionally use
ozone for color removal and taste and odor control. One employs two stage
ozonation for all these purposes, plus preparation of Biological Activated
Carbon for ammonia and organics removal.
Raw water qualities of the Marne and Seine rivers upstream of Paris are
higher than in the Paris suburbs. The large AschSres sewage treatment plant
for Paris is located on the Seine, and Seine river water quality west of
Paris is lower still. In fact, French public health officials prohibit raw
Seine river water from being taken directly into drinking water treatment
plants located downstream of the Asch^res plant. Instead, wells are dug
into the river banks and water is drawn from these wells.
This technique of drawing groundwater instead of highly polluted river
water is used at the Aubergenville and la Chapelle plants along the Seine,
and at all other drinking water treatment plants on the Seine west of
Paris. Ground filtration of highly polluted river waters allows considerable
43
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TABLE 6. Pertinent Features of European Water Treatment Plants Visited
Plant, Location, Water
Source & Year Ozone
Installed
Annet-sur-Marne, France,
Marne River, east of Paris
(1973)
Des 1 gn
Capacity
(cu m/day)
25,000
Ozone
Generation
Capacity
(kq/day)
162
Treatment Process
-C102 presterlllzatlon, FeC^, floccula-
tlon, neutralization with soda, activated
carbon, filtration, decantatlon, ozona-
tlon, post-chlor1nat1on
Purpose(s)
of
Ozonatlon
disinfection &
organlcs
Type of
Contacting
4 chambers; dlf-
fusers 1n 2,3 &
4; turbine in #1
Cholsy-le-Rol, Paris, France 800,000
Seine River (1968)
Morsang-sur-Se1ne, France,
Seine River, east of Paris
(Stage 1-1970)
150,000
being expanded
to 1 MM
2760
317
Rouen-la-Chapelle, France,
Seine River, west of Paris,
Uses deep well water
50,000
137
Aubergenvllle, France, Seine
River, west of Paris (1961),
Uses deep well
(continued)
100,000
276
(Uelsbach 550
tube generator)
-C102, A1C13, powdered activated carbon,
soda, coagulation, flocculatlon, decan-
tatlon, sand filtration, dechlorlnatlon
with bisulfite, ozonatlon, C102
(Line #1) -75,000/day, breakpoint chlorl-
natlon (for NH3), AMSO/jh + silica
+ powd act. carbon, flocculatlon,
rapid decantatlon, sand filtration,
dechlorlnatlon with SO? (1f excess C12
remains) or add Cl2 (1f Insufficient
residual), pH correction with soda,
ozonatlon, Cl?
(Line 92) -75,000/day, breakpoint chlorl-
nattonT A^fSOa^ + silica (no powd.
act. carbon) flocculatlon, rapid
decantatlon, sand filtration. Now
split stream Into halves:
-a) ozonatlon, GAC, Cl2
-b) GAC, ozonatlon, Cl2
-preozonatlon, sand filtration, GAC filtra-
tion, post-ozonatlon, chlorlnatlon
disinfection A
organlcs, color
& tastes & odor
disinfection 8
organlcs removal
+ silica + powd. act. C, coagu-
lation, flocculatlon, phosphate addition,
aeration, nitrification (to remove 0.5-3
mg/1 NHi). sand filtration, ozonatlon,
cnloMnatlon
4 chambers; dlf-
fusers 1n 1, 2
& 3
2 chambers, both
countercurrent;
dlffusers
pre; Fe & Mn, pre: turbine
pHe"nols & deter- post: 2 chamber
gents, oxygenate dlffusers; counter-
water to develop ther. cocurrent
aerobic nitrify-
ing bacteria
post: disinfec-
tion tastes,
odors & color
disinfection &
organlcs
dlffusers, 2 count-
ercurrent chambers,
60% 03 In #1, 40%
03 In n
-------
lAlill (>. ((onMnuuJ)
CJ1
Plant Name
Annet-sur-Marne
Choisy-le-Roi
Morsang-sur-Seine
Rouen-la-Chapelle
Aubergenvllle
Energy Demand,
Ozone Dosage Kwh/kg
2 mg/1 (0.4 mg/1 NA
after 7 min) In
3 & 4
3-5 mg/1 (0.4 mg/1 24
after 10 min)
2-4 mg/1 (0.4 mg/1 37.5
after 10 min)
pre: 0.7 mg/1, NA
3 min contact time
post: 1.4 mg/1
(074 mg/1 after 12
min contact time
0.5 mg/1 1n both NA
chambers for 6 min
(total • 12 mtn).
Dosage varies in
first chamber
Contactor off-gas
Treatment
15 min 1n
chamber 01.
then atmosphere
thermal or
discharge
post contactor
off-gases to
pre contactor
with added 03, then
discharge to
atmosphere
thermal destruction
Type of
Generators
tube type.
water cooled
Tratllgaz
tube type.
water
cooled
Trail igaz
tube type,
water
cooled,
Degr&nont
tube type,
water
cooled
Trail Igaz
tube type.
water
cooled,
Melsbach
Conjunctive
In Pretreatment
1 mg/1 C102
C1FEC CIO, system
since 7/76
1.5 mg/1 C102 to
destroy organic
Mn complexes
3-6 mg/1 Cl? for
0.5 mg/1 NHj
--
0
Use of Cl, or CIO,
As Post-Trtatnuiit
0.5 mg/1 CIO., in sunnier; 0.4
mg/1 Cl? in winter (lower cost)
0.4-0.5 mg/1 C102 at least
6 mos of the year. Uilorine
during the balance (up to
0.5 mg/1) (using ClFtC C102
generator since June hJ76)
0.2-05 mg/1 Cl<> to a tut n
0.02-0.03 mg/1 in distribution
system
0.4-0.5 mg/1 Cl?
.2 mg/1 f.\2 added •? pui'.iuing
-------
TABLE 6. Pertinent Features of European Water Treatment Plants Visited
Plant, Location, Water
Source & Year Ozone
Installed
DUsseldorf, Germany,
Holthausen plant (1964),
Bank filtered, Rhine River
water
DOsseldorf, Germany, Flehe
plant (1964). Bank filtered,
Rhine River water.
DUsseldorf, Germany, Am Staad
(early 1970's). Bank
Design
Capacity
(cu m/day)
192,000
88,800
119,200
Ozone
Generation
Capacity
(kg/day}
1840
816
1056
Treatment Process
river bank filtration, ozonatlon,
holding tank, anthracite filtration,
GAC. C102
river bank filtration, ozonatlon,
holding tank, anthracite filtration,
GAC, ClOj
river bank filtration, ozonatlon,
holding tank, anthracite filtration,
Purpose(s)
of
Ozonatlon
Fe 4 Mn 4
organlcs
Fe & Mn &
organlcs
Fe 4 Mn 4
organlcs
Type of
Contacting
partial Injection
Into It of product
water
partial Injection
Into 1% product
water
partial Injection
Into It of product
filtered, Rhine River water.
Wuppertal, Germapy (1967).
Bank filtered, Rhine River
water
168,000
Outsburg, Germany (1965), Bank 65,000
filtered Rhine River water.
Only plant generating ozone
from "oxygen" (actually 60S
02: 40* NZ)
MOlhelm, Germany, (Donne 48,000
plant) Ruhr River water
(4/15/77)
Konstanz, Germany, Bodensee 50,000
water (1965)
Slppllngen, Germany (Slpp- 648,000
linger Berg plant) Bodensee
(1970)
360
672
192
72
816
GAC, C102
river bank filtration, aeration (with p_re: Fe + Mn
preozonatlon), rapid sand filtration, major; organlcs
GAC, C102
river bank filtration, ozonatton Fe, Mn &
(101 of product water), ozonized organlcs
water combined with raw water,
sand filtration, GAC filtration
(0. added before GAC to 10-12 mg/1),
CIO?. NaOll
preozonatlon, Al7(504)3, lime, pre: floccula-
flocculatlon, sedimentation, flltra- tTon & Mn
tlon, ozonatlon, At9(504) 3 + poly- major; organlcs
electrolyte, flocculatton, filtration,
GAC, ground storage, chlorlnatton
mlcrostralnlng, ozonatlon, sand disinfection &
filtration, C102 organlcs
mlcrostralnlng, ozonatlon, holding disinfection &
tank, rapid sand filter, Clj organlcs
water
pre: with aeration
3e7fce
post: spray water
1nto ozone/air mixture
101 product water
countercurront In
packed column. This
Is combined with raw
water In second packed
column, cocurrently
pre; turbine
major: dlffusers
partial pretnjectlon
(similar to DUsseldorf)
packed columns,
countercurrent
(continued)
-------
TABLE 6. (continued)
Plant Name
Hoi thausen
Flehe
Am Staad
Wuppertal
Duisburq
MQlhelm
Konstanz
SlppHnger Berg
Ozone Dosage
3-3.5 mg/1
(5-7 mln)
3-3.5 mg/1
(5-7 m1n)
3-3.5 mg/1
(5-7 m1n)
pre: unknown
post: 1--2 mg/1
total : 1-3 mg/1
10-25 mg/1 In
packed column,
1.5-3 mg/1 total.
8-10 mln. total
pre: 1 mg/1
major: 2 mg/1
Energy Demand,
Kwh/kg
10-gas preparation
20-03 generators
10-gas preparation
20-Oj generators
10-gas preparation
20-Oj generators
35
13
-
1.1 mg/1 (0.4 mg/1
after 8 mln. contact
time)
0.9-1 mg/1 (2 mln
contact time)
29.5 total
2.5 gas prepa-
ration
17 ozone
generators
10 contacting
Contactor off-gas
Treatment
GAC, but changing
to catalyst
GAC, but changing
to catalyst
GAC, but changing
to catalyst
pretreatment, then
to atmosphere
recycled totally
to preozonatlon,
then catalytic
destruction
GAC or thermally
GAC
Type of
Generators I
14-Herrmann
horlzonatal
tube, water
cooled
6-Herrmann
horizontal
tube water
cooled
10- Herrmann
horizontal
tube, water
cooled
8-Herrmann
horizontal
tube, water
cooled
4 OEMAG
vertical tube,
water cooled
2 Tralllgaz,
horizontal tube,
water cooled
3 VAR (Sauter)
plate, water
cooled
6 Herrmann
horizontal tube,
water cooled
Conjunctive Use of C1, or CIO,
Pretreatment As Post-Treatment
0.1-0.3 mg/1 C102 made
from excess C12 * NaC102
0.1-0.3 mg/1 C102 made
from excess C12 ^ NaC102
0.1-0.3 mg/1 C102 made
from excess C12 <•
0.1-0.15 mg/1 ClO^ made
from C12 + NaC102
0.2-0.25 tng/1 C102 made
from C12 + NaClO^ to
attain 0.1 mg/1 at plant
exit. Then NaOH to
neutralize C02
0.2-0.3 mg/1 C12
0.25-0.3 mg/1. CIO? made
from C12 + NaC102
0.6 mg/1 C12
-------
TABLE 6. Pertinent Features of European Water Treatment Plants Visited
00
Plant, Location, Water Design
Source & Year Ozone Capacity
Installed (cu in/day)
Langpnau, Germany, Danube 198,720
River (BOX max. during
summer) + ground water
Heu1lly-sur-Marne, 600,000
Paris suburbs, France,
Marne River water (1974)
Toulouse, France (Clalrfont 110,000
Plant), on the Garonne River
In southern France (1970)
Mice, France on Mediterranean, 90,000
Super Rlmlez plant, mountain
stream water (1972)
Brussels, Belgium, (Tallfer 195,000
plant) 30 miles northeast
of Brussels (1973), River
Heuse water
ZBrlch, Switzerland (Lengg 250,000
plant) on Lake of Zurich,
(1975)
Kreuzllngen, Switzerland, 32,400
on Lake of Constance (1977,
but same process as was
operated since 1957 at older
plant). Also uses some ground-
water which receives CIO, treat-
ment only
Ozone
Generation
Capacity
(kg/day)
Treatment Process
20G River Water: prechlorlnatlon at Intake
for slime control, breakpoint chlori-
natlon, FeSO., lime, preozonatlon,
flocculatlon, filtration, ozonatlon,
FeSO^, filtration, GAC, mix with ground
water and chlorinate
2640 prechlorlnatlon (C102), Fed3, soda,
flocculatlon, sedimentation,' rapid
sand filtration, ozonatlon, chlorl-
natlon
216 CIO- + ^2(304)3 + A1C13, floccula-
tlon, decantatlon, sand filtration,
ozonatlon, pH adjustment + Na sili-
cate 1-2 days/months at 1 mg/1
216 mlcrostralnlng, AlgtSO*^, coagu-
lation, flash mixing, flocculatlon,
sedimentation, rapid sand filtra-
tion, ozonatlon
456 tUSOf, C12, ClOg, coagulation,
powd. act. C, settling & sedimen-
tation, filtration, ozonatlon,
chloramlnatlon
780 pre-chloHnat1on for molluscs,
Al2(504)-,, lime, ozonatlon, GAC,
slow sand filtration, C102
96 prechlorlnatlon for molluscs (If
necessary), AlzlSOa^, pressure
filtration, ozonatlon, GAC (70 cm)
and sand filtration, CIO?
Purpose(s)
of
Ozonatlon
Type of
Contacting
pre: floccula- pre; turbines
Mon * destruc- major: dlffusers
tlon of off-gases
major: dlslnfec-
TTonT make water
blue, and organlcs
disinfection &
organlcs
disinfection
disinfection S
organlcs
4 chambers; dlffusers
In 2, 3 \ 4, turbine
1n 1st
2 dlffuser chambers,
counter - then
cocurrent
chambers, d1Ffusers
viruses, tastes 2 turbines
& odors, color &
organlcs
disinfection,
viruses, 4
organlcs
disinfection
organlcs
3 turbines
2 stacked dlffusers
(continued)
-------
TABLE 6. (continued)
Plant Name
Langenau
Neui 1 ly-sur-Marne
Toulouse
Nice
Tallfer
Lengg
Kreuzlingen
Energy Demand,
Ozone Dosage Kwh/kg
pre: 0.2-0.3 mg/1
major; 1-1.2 mg/1,
20 min. contact
time
2-4 mg/1 (0.4 tng/1
after 4 min)
1-8 mg/1 (0.4 mg/1
after 8 minutes)
0.4 mg/1 after 6 min
1.5-2 mg/1,
8 min contact
time
1.25-3.0 mg/1
(6-10 min)
1.3 mg/1 Into #1;
0.1 mg/1 In #2, 1f
-
21 at 600 Hz
19 at 50 Hz
43
~
38 total
6 air pre-
treatment
20 03 generators
12 contacting
12 total
8 03 generators
-
Contactor off-gas
Treatment
to preozonatlon
then atmosphere
to ffl contact
chamber, then
vent to atmos-
phere
thermally in
dlesel generator
stacks
dilute & dis-
charge to
atmosphere
thermally
thermally
dilute & dis-
charge to atmos-
Type of
Generators
Conjunctive Use
In Pre treatment
2 Degr&nont
horizontal tube
water cooled
4 Tralligaz
horizontal
tube, water
cooled
4 TralUgaz
horizontal
tube, water
cooled
4 Trail igaz
horizontal
tube, water
cooled
6 Trail 1gaz
horizontal
tube, water
cooled
6 Kerag
vertical
tube, water
cooled
4 Sauter
plate, water
C10? for pre-
steflllzation X
oxidation
(probably of com-
plexed metals)
C102 for taste &
odors, color re-
moval & pre-
disinfection
Injected after pre-
^2 for organically
complexed Fe & Mn;
made under pressure
(C12 & NaC10z)
1 mg/1 Clz to pre-
vent molluscs
C\2 available to
prevent mollusc
of Cl, or CIO,
As Post-Treatftlent
0.4 mg/1 C12
0.5 mg/1 Cl2
at reservoir prior
to distribution
system
pH adjustment w/
NaOH and Na sili-
cate 1-2 days/mo.
at 1 mg/1. No
residual disinfec-
tant added
0.25 mg/1 post-
ammonlation to
produce C1NH2
0.1 mg/1 ClOg,
made from HCl
+ NaC102
0.2 mg/1 CIO?,
made from HCT
at outlet of #1.
5 min In 9 2
-------
• r,
o
KEY
CITY
CITY OF PLANT VISITED
GERMANY
SWITZERLAND
AUBERGENVILLE
(SEINE)
FRANCE
NEUILLY-SUR-MARNE
NICEj}
MARSEILLE
CHOISY-LE-ROI
(SEINE)
MEDITERRANEAN SEA
/
Figure 3. Location of French plants visited.
-------
amounts of organic materials to be removed, both by filtration and by biologi-
cal action. The concept of river sand bank filtration is practiced in
Germany all along the Rhine River. Some 60 to 75% of the organic material
in the raw river water, along with some ammonia, is removed by passage,
through sand banks located along the river.
Ammonia content of river waters upsteam of Paris is low (0.005 mg/1 at
Annet-sur-Marne; 0.5 mg/1 at Morsang-sur-Seine). In the Paris suburbs, the
ammonia content is 0.43 mg/1 at Choisy-le-Roi, but at Aubergenville is 0.5
to 3 mg/1 (averaging 0.6 to 0.7) and at Rouen is 2 to 3 mg/1. At these last
two plants, ammonia is removed biologically.
Water treatment processes at Annet, Choisy, Neuilly and Toulouse are
similar, involving pre-chlorination with C102, chemical addition (FeCl3,
A1C13, alum and/or silica), powdered activated carbon, neutralization with
caustic soda, coagulation, sedimentation, decantation and rapid sand
filtration -- all before ozonation.
Ozonation at these four plants is accomplished by means of porous
diffusers in multiple contact columns. A minimum ozone residual of 0.4 mg/1
is maintained and monitored continuously after 4 to 10 minutes of contacting
time.
In the two chamber porous diffuser contactor at Toulouse (as well as at
Morsang and Aubergenville), some 60% of the total ozone applied is fed to
the first chamber (which has water containing the highest ozone demand), and
the balance of the ozone feed is added to the second chamber. Using this
two chamber technique, the first contacting chamber is referred to by the
French as the "oxidation chamber", in which the initial ozone demand is
satisfied. The second contact chamber is called the "residual chamber",
wherein the requirement of maintaining 0.4 mg/1 of residual ozone in solu-
tion for at least 4 minutes is attained in order to insure viral inactiva-
tion (bacterial disinfection is attained in lesser contact times).
Ozone contactor off-gases from the two chambers at Toulouse are sent to
the hot exhaust stack of the diesel generators where ozone is destroyed
thermally. At Morsang, the off-gases are sent to a cold stack where they
can be destroyed catalytically or diluted with atmospheric air (10:1) and
discharged to the atmosphere (the Morsang plant is in a rural area).
Choisy, Annet and Neuilly utilize four chamber contactor systems.
Choisy has diffusers in all four chambers, and diffuses ozone into the
chambers in staged amounts. Recovery of spent off-gases is not practiced at
Choisy. Annet diffuses fresh ozone into the second and third chambers, and
recovers spent off-gases in the fourth. The off-gases are injected using a
turbine into the first chamber. Neuilly diffuses ozone into just three
chambers, recovers spent off-gases in the fourth chamber, and reinjects the
off-gases with a turbine in a compartment immediately proceeding the first
diffusion chamber. Exhaust gases from the turbine chambers in both plants
either are discharged to the atmosphere through a tall stack, or are destroyed
by passage through wet granular activated carbon.
51
-------
Ozone dosages at Annet-sur-Marne average 2 mg/1 to attain the 0.4 mg/1
residual after 7 minutes contact time. At Choisy, the ozone dosages required
average 3 to 5 mg/1, and at Neuilly-sur-Marne the ozone dosages required
average 2 to 4 mg/1. At Toulouse, 1.5 to 1.8 mg/1 of ozone is required to
attain the 0.4 mg/1 residual after 8 minutes of contacting time.
Chlorination follows ozonation at the above mentioned plants (except
for Toulouse), either through the use of chlorine or chlorine dioxide.
However, only small amounts of these chlorine compounds are employed for
residual -- usually 0.5 mg/1 or less, depending upon the distribution
system length, complexity and residence time. It is apparent that the
objective of the water treatment processes at these plants is to produce
water of high quality which minimizes the amount of chlorine or chlorine
dioxide that must be employed. From the consumers point of view, the
objective is to produce a bacterially and chemically safe potable water with
no chlorinous taste.
At Aubergenville, the pretreatroent steps involving alum, silica, powdered
activated carbon and coagulation are followed by biological nitrogen removal.
This is accomplished by addition of phosphate and aeration, then passage
through a wet mass (sludge blanket) maintained in an upflow-filter. After
sand filtration the water is ozonized in a two chamber contactor as described
earlier, then it is chlorinated just before entering the distribution system.
Water supply for the City of Nice comes from a mountain stream and is
of very high quality. The Super Rimiez plant is situated high above the
city. Mountain stream water flows by gravity through microstrainers, then
into the treatment plant, where alum addition, coagulation, flash mixing,
coagulation, sedimentation, rapid sand filtration and ozonation processes
are applied. No chlorination or other treatment is practiced after ozona-
tion. Water is sent to underground reservoirs and flows into a three level
distribution system into the various sections of the city. Water does not
need to be pumped at Super Rimiez -- water flows into the plant, through the
plant and throughout the distribution system entirely by gravity.
Although the Super Rimiez plant began operation in 1972, the previous
three Nice plants (which were combined when Super Rimiez was constructed)
all used the same treatment process involving terminal ozonation. The
oldest Nice plant, Bon Voyage, first installed ozonation in 1906.
Toulouse's Clairfont plant (on the Garonne River) also does not use
post-chlorination after ozonation. However, pH adjustment is employed after
ozone treatment, and for 1 to 2 days/month, 1 mg/1 of sodium silicate is
added to protect the distribution system from corrosion.
The distribution systems at Toulouse and Nice are short and the average
residence time of treated water in these systems is rather short (less than
12 hours). Because of the low temperature of the raw and treated waters
(both plant raw waters originate in the mountains), the low carbon and
ammonia contents, as well as the short residence time in the distribution
52
-------
systems, the French find no necessity for residual chlorine in the treated
drinking waters of Toulouse or Nice. More than 70 years of experience
attest to the safety of this practice at Nice.
The Morsang-sur-Seine plant (east of Paris) is planned eventually to
have five individual treatment lines, each capable of treating 75,000 cu
m/day. By May of 1977, two lines were operating and the third was being
completed. The two operating lines employ breakpoint chlorination at the
plant entrance, followed by alum. Line 1 then continues with poly-aluminum
chloride then powdered activated carbon, flocculation, rapid decantation,
sand filtration, chlorine residual adjustment, pH correction with soda, then
ozonation (2 to 4 mg/1 to maintain the 0.4 mg/1 residual over 10 minutes of
contact time), followed by chlorination for residual.
Line 2 receives breakpoint chlorination, alum, silica, flocculation,
rapid decantation and sand filtration. This stream then is split into
halves. Line 2A now receives ozonation, then granular activated carbon
(GAC) then chlorination. Line 2B receives GAC, then ozonation and chlorina-
tion.
Details of the Morsang plant are included in a comprehensive paper by
Richard & Fiessinger25. For purposes of this section, however, it suffices
to say that Line #1 represents the process initially installed at Morsang.
Line #2 represents two attempts to improve the water quality by incorporating
granular activated carbon, before ozonation and after ozonation. To date,
although the qualities of the waters from lines 2A and 2B are similar, there
are some distinct advantages observed in the line in which ozonation precedes
the GAC. These advantages are: 1) extended operating life of the carbon
column; and 2) better performance efficiency of the carbon. Both of these
advantages are attributed to beneficial bacterial growths in the carbon
columns.
Finally at Morsang, a pilot process recently has been set up and is
being studied in which breakpoint chlorination is eliminated, chemical
treatment remains the same, and ozonation followed by granular activated
carbon (biological activated carbon) is employed to remove ammonia and
organics. Morsang is one of only two French plants known to be using or
studying Biological Activated Carbon (see Section 13).
At Rouen-la-Chapelle, on the Seine, west of Paris, well water is preozon-
ized to oxidize iron & manganese, oxidize organics (phenols and detergents
particularly) and to prepare GAC for optimum biological growths. After pre-
ozonation, the water is sand filtered, filtered through Biological Activated
Carbon, then post-ozonized (for disinfection, tastes, odors and colors),
then chlorinated to obtain a residual.
The major portion of ozone at Rouen is used in post-ozonation. Ozone
dosages in this stage average 1.4 mg/1 to achieve the 0.4 mg/1 ozone residual
after satisfying the initial ozone demand and after 12 minutes of contacting
in a two chamber diffuser apparatus. Off-gases from the post-ozonation
contactor are recompressed and sent to the pre-ozonation turbine contactor,
which has a three minute contact time. If necessary, make-up ozone is added
53
-------
at this point so as to provide an average pre-ozonation dosage of 0.7 mg/1.
This dosage is sufficient to oxidize iron and manganese, to partially oxidize
phenols and detergents, and to aerate the water so as to cause proliferation
of aerobic bacteria and nitrifying bacteria in the sand filters and in the
subsequent granular activated carbon filters.
The beneficial effect upon ozonation costs of a second ozonation step
at the plant, utilizing some of the off-gases from the ozone contacting
system, is significant. Installing ozone generation capacity for the single
purpose of disinfection near the end of the treatment process, involves
installing generation capacity for the amount of ozone required, plus some
backup generation capability. If ozone is used only for a single process
such as disinfection, then all contactor off-gases must be treated before
discharge to the atmosphere — at some cost increment.
If some of these contactor off-gases are utilized instead for a pretreat-
ment purpose, say oxidation of iron and manganese, then the main additional
cost involved will be that of compression (for conveyance), contacting and
piping for the pretreatment step. Even if supplementary ozone must be
generated for the pretreatment step, this small increased need for ozone
generation capacity can be determined during pilot studies and purchased at
the time of ozonation system installation. On the other hand, not all of
the ozone in primary contactor off-gases will be utilized even in a reuse
application such as just described. Therefore ozone destruction facilities
still will be required. The amount of ozone to be destroyed after recycle
will be less, however ~ see Section 8.
Conversely, if the ozone has not been installed for disinfection, the
installation of ozone as a pretreatment step to oxidize iron and manganese
will require ozone generation capacity (with backup generation capacity)
higher than in the case of using contactor off-gases.
U.S. water treatment engineers can conclude from the Rouen plant (and
others like it which the site visitation team visited in other countries)
that once having installed ozone for one specific purpose, its use for other
purposes may be cost-effective and should be evaluated.
Germany
Nine plants were visited in Germany, seven of which use river water and
two of which are located on the Lake of Constance (the Bodensee), (see
Figure 4.) Five of the river plants are located on the Rhine in the DUssel-
dorf area, one is on the Ruhr river near DUsseldorf, and one is on the
Danube river in southern Germany.
None of the plants on the Rhine River draw water directly from the
river for processing in water treatment plants. Instead, river sand bank
filtration is practiced. Wells are dug along the Rhine and water is drawn
from these wells for the water treatment plants. The average time of
passage of river water from the Rhine to these wells is 20 days. Because of
the bacterial activity in the ground, some 60 to 70% of the total organic
54
-------
KEY
• CITY
® CITY OF PLANT VISI
NORTH SEA
DENMARK
•DUISBURG
•MULHEIM
WUPPERTAL
I— 7 m
DUSSELDORF CITY PLANTS
-HOLTHAUSEN
BERLIN
• -AM STAAD
\ xDUISBURG(SEE INSERT)
i
MULHEIM
^,
®WUPPERTAL
DUSSELDORF
.BONN
EAST GERMANY
SCALE
50 100 150
I I I I 1
MILES
-N-
I
FRANKFURT
\LUX)
*-V ^f \
• I-KMNM-UK ">r
CZECHOSLOVAKIA
-\WEST GERMANY V
V ^ ^^«.
FRANCE
•
J
}
S
LANGENAU
SIPPLINGEN
(SIPPLINGER BERG)
-« - LAKE OF
CONSTANCE
.^ i—nnu UtVlU
(DANUBE) r*
.MUNICH C
N
J~^ \
•* \o
U S T R I A
SWITZERLAND
Figure k. Location of German plants visited.
55
-------
carbon contained in the Rhine river water is removed during ground passage.
River sand bank filtration has been practiced along the Rhine for many years
(at the Am Staad plant since the late 1800s) in the DUsseldorf area, and
today is considered to be an essential first step in water treatment process-
ing.
Waters of the Ruhr and Danube rivers in this part of Europe are not as
polluted as those of the Rhine River, and river bank filtration is not
considered necessary. Consequently, raw water is drawn directly from these
rivers and treated in the two plants visited.
All plants on the Lake of Constance (German and Swiss) take water from
the Lake for treatment without bank filtration. The Rhine River flows
through the Lake of Constance, but the river is not highly polluted at this
point.
All plants along the Rhine in the DUsseldorf area use ozone for oxidizing
iron & manganese (which is present because of filtration through the sand
banks) and for oxidation of organics. The three DUsseldorf city plants
(Holthausen, Flehe and Am Staad) all use the same water treatment process.
River bank filtered water is ozonized as it enters the plant. Lower valent
iron (II) and manganese (II) are oxidized to the iron (III) and manganese
(IV) states, at which states these metal ions quickly hydrolyze and precipitate.
During ozonation, dissolved organic compounds also are oxidized, at least
partially.
The ozonized waters then are sent to a holding tank for 20 to 30
minutes. The primary purpose of the holding tank is to allow the concentra-
tion of residual ozone to decay to nearly zero before the ozonized water
comes into contact with the granular activated carbon. Otherwise, activated
carbon will be oxidized by the ozone present, in a wasteful manner both of
carbon and of ozone. During this holding time, residual ozone concentration
decreases because of continued oxidation of dissolved organics. Any perman-
ganate formed upon initial ozonization also is reduced to the Mn (IV) state
by oxidizing dissolved organics. After this holding period, the water then
is filtered through anthracite (to remove precipitated solids) then through
granular activated carbon. Finally, small dosages of chlorine dioxide (up
to 0.3 mg/1) are added for residual. Ozone contactor off-gases have been
destroyed in the past by passage through wet granular activated carbon.
However, all three plants have tested and now are installing catalytic ozone
destruction units for this purpose.
The three DUsseldorf city plants are unique in that there is little
reservoir capacity in the distribution system served by the plants for
treated water (two small reservoirs store water for the highest elevations
of the city). Therefore the three plants operate almost totally on demand.
When demand is low, the plants operate at low levels. When demand is high,
the plant operates at full capacity. Consequently, the three plants are
sized to produce water at the peak demand rate.
56
-------
The combination of ozonation followed by granular activated carbon was
first installed in the Dusseldorf City plants in the late 1950s, and other
German plants using this combination are generally patterned after what has
come to be known as "the Dllsseldorf process". Activated carbon was installed
originally for taste and odor control, but now is used also for adsorption
of chlorinated organic compounds, which are prevalent in the Rhine River,
and which are only partially removed during river sand bank filtration, and
for biological removal of ammonia. When activated carbon columns were first
installed in these Dllsseldorf plants, reactivation was required as infre-
quently as every two years. However, because of the buildup of chlorinated
organic materials in the Rhine River water and their adsorption onto the
activated carbon, today regeneration is required every 5 to 6 months26.
It was observed that removal of organics by the combined ozonation/-
granular activated carbon process at Dusseldorf was greater than expected if
the expected removals by ozonation and by activated carbon were added
separately. In addition it was found that ammonia levels were being reduced
during passage through the granular activated carbon filters. These observa-
tions prompted studies which led to the development of the Biological Acti-
vated Carbon process recently installed at the Dohne plant in Mulheim (on
the Ruhr River). Details of Biological Activated Carbon technology are
presented in Section 13 of this report.
At the Wuppertal plant (on the Rhine near Dusseldorf), river bank
filtered Rhine river water is aerated an preozonized, using off-gases from
the ozone contactors employed later in the process. This oxidizes iron and
manganese, partially oxidizes organics, and also serves to dispose of off-
gas ozone. Any excess ozone in the preozonation off-gases is diluted with
air during the aeration step and vented to the atmosphere. After pre-ozona-
tion, the water is filtered, then ozonized, filtered through rapid sand,
then through granular activated carbon and treated with chlorine dioxide.
The sequence of primary ozonation, rapid sand and granular activated carbon
ffltration, all take place in a series of 16 units which house all three
steps in a single structure.
At Wuppertal the ozone contacting system is one in which water to be
ozonized is forced through narrow orifices into a gas atmosphere which
contains ozone and air. The effect is much like that of spray drying, and
the small droplets of liquid fall slowly to the bottom of the chamber, in
constant contact with ozone-containing air.
The Duisburg plant employs a process similar to the Dusseldorf process,
the major difference being in the method of ozone generation. Duisburg is
the only known operational municipal plant that uses oxygen as the feed gas
for generating ozone. As a result, the oxygen/ozone system operates in a
closed loop, and only a single pump is used to move water through the total
plant. Because of the closed loop design, all gases, including ozone con-
tactor off-gases, are recycled through gas drying equipment to the ozone
generator. Carbon dioxide (formed upon oxidation of organics) does not have
a chance to escape from the system. Therefore, after carbon filtration,
sodium hydroxide is added to adjust the pH of the treated water. A full
description of the Duisburg plant is given in Appendix B.
57
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Contacting in the closed loop system at Duisburg also is by means of a
two stage partial injection system, but through two Raschig ring packed
towers. In this case, 10% of the product water is treated with the total
amount of ozone countercurrently through the first tower, called an "ozone
washer". The output of this column then is passed upwards through the
second Raschig ring packed tower, termed the "contactor".
Ozone contacting at the three DUsseldorf city plants (and at the City
of Konstanz) is by partial injection. About 1% of the finished Rhine River
water is subjected to direct ozonation. The total amount of ozone to be
added is passed into a pipe through which 1% of the finished water is pumped.
Within seconds after the ozone has mixed with the 1% water volume in the
pipe, the ozonized water meets the remaining 99% as it is pumped down through
a wider diameter pipe to the bottom of the contact chamber. From the bottom
of the 10 meter deep contactor, water and ozone bubbles rise co-currently.
Ozone contacting is described in greater detail in Section 8.
The Dohne plant at MUlheim recently has installed a new water treatment
process which involves ozonation and Biological Activated Carbon, and is
similar to the process employed at the Rouen-la-Chapelle plant in France.
Ruhr river water is pre-ozonized (partially with ozone-containing off-gases
from the oxidation contactor used later in the process), then treated with
alum, lime, then subjected to coagulation, sedimentation, then ozonation for
oxidation of organics, more alum plus a polyelectrolyte, coagulation,
filtration, granular activated carbon, ground storage, then chlorination for
residual as the water enters the distribution system. Ozone-containing off-
gases from the pre-ozonation step are destroyed by passage through a catalytic
ozone destruction unit.
The older process at MUlheim began with breakpoint chlorination (for
ammonia removal), followed by chemical addition, coagulation, sedimentation,
filtration, granular activated carbon (for dechlorination) then ground
storage and chlorination. As pollution in the Ruhr river has increased the
ammonia level has increased, necessitating an increase in the amount of
chlorine required during the initial treatment step (10 to 50 mg/1). In
turn, this produced increasingly large quantities of chlorinated organics,
which required increasingly more frequent reactivation of the GAC columns.
Even with fresh activated carbon, unacceptably large quantities of chlorinated
organics were noted in the product water.
MUlheim's new process, which became operational on April 15, 1977,
eliminates the breakpoint chlorination step and effects ammonia removal in
the Biological Activated Carbon. Thus, considerable quantities of chlorine
are saved. In addition, rather than having to reactivate the GAC as often
as every 2 to 3 months (by the old process), the anticipated life of the
carbon columns before regeneration now is at least two years27. After 9
months of operation, the carbon columns at Dohne are performing as efficiently
as when they were installed, and show no signs of requiring regeneration28.
58
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Long operating life of the activated carbon columns at Mulheim is to be
expected on the basis of the 24 month operation of the biological activated
carbon columns beds (without regeneration as yet) at Rouen-la-chapelle in
France.
Dusseldorf city plants use ozone dosages of 3 to 3.5 mg/1 and contact
times of 5 to 7 minutes. Wuppertal uses 1 to 3 mg/1 total ozone dosage
(pre- and post-ozonation), Duisburg adds 1.5 to 3 mg/1 for 10 minutes, and
Donne (MUlheim) uses 3 mg/1 (1 in pre-ozonation, 2 in post-ozonation) ozone
dosages.
Contactors at MUlheim include a turbine for pre-ozonation and 2-chamber
diffusers for post-ozonation. The high degree of agitation provided by the
turbine has been found to be beneficial in causing improved flocculation28.
In southern Germany, the water qualities are much higher than in the
DUsseldorf area. Both the City of Konstanz and Sipplinger Berg plants are
located on the Lake of Constance. Both treatment processes start with
microstraining, followed by ozonation (for disinfection and oxidation of
organics), sand filtration, then chlorine dioxide (at Konstanz) and chlorine
(at Sipplinger Berg). The Sipplinger Berg plant incorporates a holding tank
after ozonation. Off-gases containing ozone at Konstanz are destroyed
thermally and/or by passage through wet granular activated carbon. At
Sipplinger Berg, off-gases are passed through wet granular activated carbon
for destruction of excess ozone.
The contactor at Konstanz is a partial injector, similar to the DUssel-
dorf contactors, whereas the Sipplinger Berg contactors are Raschig ring
packed towers. Water flows downward through the packed columns while
ozone-containing air flows upward. Ozone dosages at Konstanz average 1.1
mg/1 and are 0.9 to 1 mg/1 at Sipplinger Berg. Konstanz monitors an ozone
residual of 0.4 mg/1 after 8 minutes of contact, but Sipplinger Berg uses
only a 2 minute contact time. However, the ozonized water is allowed to
stand 30 minutes in a holding tank before sand filtration.
Sipplinger Berg is the largest municipal water treatment plant in
Germany using ozone, with a design capacity of 648,000 cu m/day. Uniquely,
this water, treated at the Lake of Constance, is sent 150 kilometers north
to Stuttgart and other communities along the line. The highest amount of
residual chlorine (0.6 mg/1) observed by the site visitation team at any of
the plants visited is added here. The fact that residual chlorine still is
present in the treated water when it reaches Stuttgart attests to the high
quality of water produced by microstraining, ozonation and sand filtration.
There is one chlorination station in the distribution system on the way to
Stuttgart, but this is present only for safety reasons, and is rarely used.
Sipplinger Berg plant personnel advise that without ozonation, the residual
of chlorine could not be maintained in the distribution system without
adding considerable chlorine at several points along the way to Stuttgart.
As pointed out in Section 5, all water treatment plants on the Lake of
Constance have installed excess ozonation capacity and activated carbon
59
-------
capabilities to be used in the event of leakage of an oil pipe which runs
through the Lake connecting Switzerland and Germany.
The plant at Langenau treats a combination of groundwater and Danube
River water. The maximum amount of river water treated, however, occurs
during periods of peak water demand during summer,, and is a maximum of only
one-half of the plant flow at that time. The amount of Danube River water
treated during winter is minimal, and is necessary only when the groundwater
volumes are insufficient to meet demands.
Raw Danube water is prechlorinated (1 mg/1) at the intake for slime
control (the intake is 7 km from the plant), then treated by breakpoint
chlorination (4 to 6 mg/1 for ammonia), FeSO-, lime, preozonation (using
off-gases from the final ozonation), filtration, final ozonation, FeSO,
addition, sand filtration, then granular activated carbon. At this point,
treated river water is mixed with groundwater (which has not been treated to
this point) and the combined stream chlorinated.
Pre-ozonation is employed to aid flocculation and to destroy contactor
off-gases containing excess ozone. Post-ozonation is used for disinfection,
organics oxidation and "to make the water blue" (the plant director stated
that Langanau is the only place in Europe where the Danube is blue -- because
of ozonation). The pre-ozonation contactors are high speed turbines and the
post-ozonation contactors are two chamber porous diffusers. Ozone dosages
are 0.2 to 0.3 mg/1 in pre-ozonation (sometimes additional make-up ozone is
required) and 1 to 1.2 mg/1 for post-ozonation (10 minute contact time plus
10 minutes travel time to the filters). Off-gases from the pre-ozonation
contactors are vented to the atmosphere (the Langenau plant is located in a
rural area).
The Langenau plant has a number of unique features. First, the plant
process is controlled at every step by turbidity monitors. Secondly, it is
the only plant visited in which ferrous sulfate is added to the post-ozonized
water. The purpose of this second iron addition is to provide an additional
flocculation step for removing soluble organics which are oxidized to less
soluble and/or more easily flocculated states during post-ozonation.
Granular activated carbon columns at Langenau are biologically active,
but are only 1.5 meters deep, compared to 5 meters in the DUsseldorf area.
Carbon reactivation times here range from 4 months to 2.5 years. This
widely varying operational life of carbon is attributed to the relatively
low amounts of chlorinated organics produced by the prechlorination and
breakpoint chlorination steps. Ammonia levels in the Langenau raw water are
much lower (0.2 to 0.5 mg/1) than in the Rhine or Ruhr Rivers near DUsseldorf.
At MUlheim, breakpoint chlorination required 10 to 50 mg/1 of chlorine as
the old treatment process was practiced. At Langenau, only 4 to 6 mg/1 is
required presently. Nevertheless, a pilot Biological Activated Carbon
program is being studied at Langenau with the objectives of replacing the
breakpoint chlorination step, thus saving chlorination costs and prolonging
the activated carbon life even further.
60
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Finished water from Langenau is sent to Stuttgart, through a 350 km
distribution system, and is treated with 0.4 mg/1 of chlorine for residual
at the plant reservoir.
Switzerland
Two plants were visited in Switzerland, both of which treat lake water
(see Figure 5). The Lengg plant in ZUrich is large (250,000 cu m/day), and
the Kreuzlingen plant is small (30,000 cu m/day). Both of these plants
incorporate ozonation plus activated carbon in their treatment processes.
Zurich's Lengg plant is situated on the Lake of ZUrich, which is fed by
mountain streams. Raw water from this lake is very high in quality, having
a TOC of only 2 mg/1, for example. Water is prechlorinated (1 mg/1 to
prevent growth of molluscs), then treated with alum, lime, ozonation, granular
activated carbon, slow sand filtration and chlorine dioxide.
Ozone is used at Lengg for disinfection, viral inactivation and oxidation
of organics. Dosages are 1.25 to 3 mg/1 (yearly average 1.5) and contact
times are 6 to 10 minutes. Contactors at Lengg are turbines, and three of
these are installed in each of the two treatment lines. Water to be ozonized
passes through each contacting chamber, however only during periods of
maximum flow are all three turbines utilized at the same time. Contactor
off-gases are destroyed thermally.
Before distribution, Lengg water is treated with 0.1 to 0.15 mg/1 of
chlorine dioxide.
At Kreuzlingen, on the Lake of Constance (Bodensee) (which is fed by
the Rhine River in its early stages), ozonation has been used since the late
1950s. The original treatment plant employing ozone was situated on the
lake's edge, and in recent years began to sink into the lake. As a conse-
quence, a new plant was constructed, and was placed in operation early in
1977.
The Kreuzlingen treatment process includes prechlorination for mollusc
control alum, pressure filtration, ozonation (for disinfection and oxidation
of organics), granular activated carbon, sand filtration, and chlorine
dioxide for residual.
Ozone contacting at Kreuzlingen takes place in two chamber porous
diffusers, but the two chambers are stacked one on top of the other. Water
flows through the upper chamber then into the lower chamber. The geometry
of the lower chamber is such that its off-gases collect at the top of the
lower chamber beneath the inlet of the porous diffusers of the upper chamber.
When the pressure of off-gases in the lower chamber exceeds the head of
pressure in the upper chamber, these off-gases will pass into the upper
chamber. Off-gases from the upper chamber are diluted with atmospheric air
and discharged to the atmosphere.
61
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KEY
01
i i
® CITY OF PLANT VISITED
• CITY
r^/GENEVA f
(A
KREUZLINGEN
LAKE OF CONSTANCE
® ZURICH
AUSTRIA
U-...
• BERN
SWITZERLAND
T A
- N-
SCALE
0 10 20 30 40 50
I 1 I 1 —i=j
MILES
Figure 5. Location of Swiss plants visited.
-------
Ozone dosages of about 1.3 mg/1 are used in the first (lower) contacting
chamber with contact times of 6 minutes. A residual ozone concentration of
0.4 mg/1 is measured at the outlet of the lower chamber. The ozone concentra-
tion in the upper chamber is 0.1 mg/1, and the contact time in the upper
chamber is 5 minutes (total contact time = 11 minutes).
The Kreuzlingen plant is designed to operate unattended. Finished
water is stored in two reservoirs, and when demand lowers the level in one
reservoir, the plant starts up. The plant superintendent lives in a house
adjacent to the plant, and he prepares chemicals, checks operation of equipment
and controls and provides maintenance services.
Belgium
Only one Belgian plant was visited, the Tailfer plant which serves
Brussels. This plant treats Meuse river water with sulfuric acid, chlorine,
chlorine dioxide (to decompose organic complexes of iron and manganese),
coagulation, powdered activated carbon, settling, filtration, then ozonation
(for viral inactivation, tastes & odors, color and oxidation of organics),
followed by chloramination for residual.
Contacting at Tailfer is accomplished with two turbines per contactor.
Dosages of ozone are 1.7 mg/1 (yearly average) over 8 minutes contact
time. Off-gases are destroyed thermally.
Tailfer currently is installing oxygen facilities so as to study the
advantages of having higher ozone generation capacity during periods of peak
ozone demand. When installed (late 1977 or early 1978), ozone will be
generated from oxygen for a one year period to allow the ozone generation
and associated processes to be studied on full scale in one of its treatment
lines during all seasons. After this year of operation, Tailfer will decide
upon whether to utilize this ozone generation technique during summer periods
of highest ozone demand or to use oxygen continuously.
General Comments on European Plant Practices
With the exception of the Tailfer, Belgium plant, all plants visited
had installed excess ozone generation capacity. This allows the generators
to be operated routinely at less than their maximum production rate, thereby
reducing deterioration of the generator dielectrics. Such practice allows
maintenance to be performed on one generator while others are being operated.
Maintenance of ozonation equipment is provided on a scheduled basis, rather
than waiting until malfunction occurs unexpectedly.
Ozone demand varies seasonally, particularly as raw water temperatures
change. In winter, ozone demands generally are lower than in summer. With
those raw waters having relatively constant temperatures the year around,
the ozone demands are also relatively constant the year around.
None of the plants visited had open reservoirs for treated water. The
visitation team was repeatedly advised in all four countries visited and by
63
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respresentatives of other European countries not visited that there are no
uncovered reservoirs for treated drinking water in Europe.
All plants visited are concerned about and prepared for accidental
ozone leakages in the plants. All rooms where ozone can be present either
are monitored for ozone in the air, or operators are instructed not to enter
rooms when ozone can be smelled. Normally, plant personnel do not work in
the rooms containing ozone generators or ozone contactors. These rooms all
have exhaust fans which are programmed to start automatically when the
ambient ozone monitors signal the presence of 0.1 mg/1 (by volume), or
greater, of ozone, or are turned on manually when ozone can be smelled by
plant personnel.
Modern European plants have installed ozonation systems and entire
treatment plant processes which are highly automated, and the degree of
automation is not related to plant size. For example, there are many small
water treatment plants in the Alps of Austria and Switzerland which are
inaccessible throughout much of the year. The storage, handling and preparing
of chemical solutions is impractical under these circumstances, and so the
plants are designed with physical and/or mechanical treatment steps to
operate unattended, with controls and warning alarms being installed in
central facilities, such as the town hall. Filtration, ozonation and post-
treatment are controlled automatically.
Operations at the Kreuzlingen plant (30,000 cu m/day), also are automated,
even though the plant is not isolated in location. The plant superintendent
visists the plant periodically to prepare solutions and check equipment
operation, otherwise the plant is designed to operate unattended.
Some of the largest ozonation plants also are highly automated. At
Neuilly-sur-Marne, in the suburbs of Paris, France, this 600,000 cu m/day
treatment plant employs chemical and mechanical pretreatment on one side of
the river Marne, and ozonation and post-chlorination on the other side. The
entire plant process is operated and controlled by two plant operators who
are stationed at the control panel around the clock. Analytical data obtained
from the laboratory (automatic sampling ) are fed to the control panel and
adjustments in process parameters are made automatically.
Several water treatment plants visited contained one or more aquaria
with trout to indicate the presence of toxic materials. The simplest trout
"monitors" are aquaria through which product water is passed. If materials
toxic to these sensitive trout are present in the finished water, the trout
will die, or at least show visible signs of distress. These aquaria are
located in areas of the plants which operating personnel frequent in conduct-
ing their duties. Plant personnel are trained to check the condition of the
trout as often as they pass them.
A more sophisticated trout monitoring system has been developed by the
Keuringsinstitut voor Waterleidingsbedrijven (KIWA — the Netherlands Water
Research Institute) and is operating at the Tailfer (Brussels, Belgium)
plant. Another unit is to be installed at the Lengg plant in Zurich,
64
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Switzerland shortly. This system uses the response of the trout to an
electrical stimulus to monitor the raw water quality.
In the Netherlands trout monitoring system, fish are first conditioned
to the raw water of the plant. After one week of conditioning, a trout is
placed into a U-shaped, narrow raceway, through which the raw water flows at
a constant rate. At the start of the raceway, provision is made for an
electrical impulse across the channel. If the trout backs into this area,
he triggers the electrical impulse and receives a small electrical shock.
Upon receiving this shock, the trout swims to the other end of the raceway,
and the time required to pass a specific point in the raceway is measured in
relation to the time of the original electrical impulse. The raceway is
narrow, so as to prevent the trout from turning around and swimming in the
wrong direction upon receiving the electrical impulse.
To establish the swimming time of a new fish, each trout is impulsed
several times and the times required for it to swim past the timing point
are averaged to provide a calibration time. The new trout then is kept in
the raceway for a one week period. During this time, he will occasionally
back into the impulse area. When this occurs and the time to swim to the
timing point is within the calibration range, nothing happens. But if the
trout takes longer to swim to the timing point than his calibration time,
this indicates that something has affected his ability to swim and an alarm
rings.
There are four such trout raceways at the Tailfer plant. When one
alarm rings, plant personnel are alerted that something may be amiss. If
three of the four trout alarms ring, the plant is shut down and the raw
water analyzed for toxic chemicals.
At the Sipplinger Berg plant in southern Germany, plant scientists have
found that water fleas (daphnia) and a species of African electric eel can
be used similarly for monitoring of toxic materials in the raw water. These
chemists have also found that the rate of oxygen release from certain algae
is greatly reduced in the presence of many water pollutants, and a monitoring
procedure based upon this technique is being developed.
Overall, the most striking features of the European ozonation plants
visited include the design of the water treatment processes to reduce oxidant-
demanding materials to such low levels that either no residual disinfectant
is required, or if one is required, levels of only 0.1 to 0.3 mg/1 of chlorine,
chlorine dioxide or chloramine generally are sufficient. Only in the case
of Sipplinger Berg, which sends treated water 150 km north to Stuttgart, is
a post-chlorination dosage as high as 0.6 mg/1 necessary.
CANADIAN PLANT VISITATIONS
Table 7 lists some of the pertinent features of the six operational
Canadian municipal water treatment plants visited by the site survey team.
All of these treatment plants are located in the Province of Quebec (see
Figure 6). The only other currently operating Canadian water treatment
65
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TABLE 7. CANADIAN OZONE TREATMENT PLANTS VISITED
en
en
Plant, Location, Water
Source S Year Ozone
Installed
Quebec City, St. Charles
River, (1969)
Design
Capacity
(cu m/day)
218,000
Ozone
Generation
Capacity
(kg/day)
360
Treatment Process
Prechlorlnatlon, alum, Hme,
polyelectrolyte, coagulation,
flocculatlon, sedimentation, filtra-
tion, ozonatlon, chlorlnatlon, pH
adj.
Purpose(s)
of
Ozonatlon
tastes, viruses,
viruses, organlcs
(phenols), disin-
fection
Type of
Contacting
4 Injectors
(4 tnln)
Laval (Chomedey), Riviere des
Prairies (1959), river
polluted with pulp & paper
wastes
Plerrefonds, Riviere des
Prairies (1976)
177,295 total
113,651 using
ozonatlon
63,644 using
Powd. Act. C.
95,500
St. Denis, R1v16re Richelieu 27,300
(1972)
Sherbrooke, Lake Hemphremagog 98,262
(1977 plant replaced 15 yr
old plant)
He Perrot, Lake St. Louis 6,800
(1963)
(two 160 tube Prechlorlnatlon, alum, silica, lime disinfection,
ozonators) addition, settling, filtration, tastes, odors
ozonatlon, final chlorlnatlon.
250 Screening, Intermittent prechlorlna- disinfection,
tlon, caustic soda ammonium sul- odors
fate, sodium silicate, flocculatlon,
settling, filtration, ozonatlon,
pH correction, final chlorlnatlon
and fluorldatlon. Chlorinate also
In dlstr. system.
28 Chlorlnatlon, alum, coagulation, tastes, odors,
settling, filtration, ozonatlon, disinfection
chlorlnatlon, soda ash addn.
227 Occasional prechloHnation, micro- tastes, odors,
straining, ozonatlon, final chlorl- disinfection
nation
9 Chlorlnatlon, alum & silica, color, taste,
coagulation, settling, filtration, odors, dlsln-
ozonatlon, lime, fluorldatlon fectlon
3-chamber,
porous dlffusers
Cocurrent In #1,
Countercurrent
In n. #3 1s
detention tank.
2-chamber,
porous dlffusers
2-porous
dlffusers
(10 m1n)
2-porous
dlffusers
1-submerged
turbine (20 m1n)
(continued)
-------
TABLE 7. (continued)
Plant Name
Quebec
Ozone Dosage
1.3 mg/1 gives 0.4
mg/1 residual
0, after 4 min.
Energy Demand,
Kwh/kg
30
Contactor off-gas
Treatment
none
Type of
Generators
Trail 1gaz
(plates)
water cooled
Conjunctive Use
In Pretreatment
1.2-2.4 mg/1 to
kill fly larvae
(max. in summer)
of CU or CIO,
As Post-Treatment
1 .2-4 mg/1 provides
0.35 mg/1 at plant
exit and 0.10 mg/1
7 mi. from pit
Laval
en
•vl
Pierrefonds
St. Denis
Sherbrooke
lie Perrot
Unknown -- 8 min
total contact
time
2.0 mg/1 to
provide 0.4
mg/1 after 4 min.
2.2-2.3, 13 mfns.
contact time
2.0 dosage,
8-13 mins contact,
provides 0.4 mg/1
0.8-1.0, 20 min
contact time
none
18 total
6-air prep.
12-0, generators
19.0 (theor.)
not measured
29.1 total
7.9 air prep.
21.2 0, generators
45 total
9-air prep.
21 03 generators
15 contactor
dilute and
discharge
to atm.
none
none
2 Welsbach 120 Ibs/day to
horizontal maintain 0.3
tube, water mg/1 residual
cooled on filters
Trailigaz
horizontal
tubes, water
cooled
PC I-Ozone
horizontal
tube, water
S air cooled
Degr£mont
horizontal
tube, water
cooled
0.8 mg/1 summer
for bacteria on
filters
1-3 mg/1 for
bacteria
prechlorinate to
kill algae on
micros trainers
1-Welsbach 1.3 mg/1 to raw
horizontal water at coagu-
tube, water lation basin
cooled
(0.8-1.0 mg/1
dose)
250 Ibs/day in 2
additions: 235 at
entrance of reser-
voir, 15 at exit
gives 0.15 mg/1
residual at exit
1 mg/1 dose in
reservoir gives 0.5
mg/1 at exit, 0.1
in distr. system
0.2-0.3 mg/1 dosage
gives 0.5 mg/1 total
oxidant (CI-,+0,) at
exit * J
1.4 mg/1 in
reservoir, 0.2 mg/1
at exit (88 kg/day)
none
-------
IERREFONDS
ILE PERROT
Q U
LAVAL
®MONTREAL(SEE INSERT)
VERMONT
ONTARIO
KEY
® CITY OF PLANT VISITED
• CITY
Figure 6 Location of Canadian plants visited
-------
plant employing ozone is located in Frobisher Bay, Northwest Territories, on
Baffin Island, near Greenland.
At the six Canadian plants visited, ozone is used primarily for disinfec-
tion and taste and odor control. However, color removal and organics removal
are also important applications of ozone in Canada.
Four of the six plants use river water and two use lake waters. Although
Canadian river waters are considered by local water treatment plant personnel
to be "highly polluted", water taken directly from the source is treated, as
opposed to river sand bank filtration practices before treatment along the
lower Rhine river and drawing deep well water along the Seine downstream of
Paris, France.
Age of the plants visited ranged from new to 14 years old. The oldest
plant visited was He Perrot, on Lake St. Louis. The newest plants visited
were Sherbrooke (mid-1977) and Pierrefonds (late 1976). Both of these newer
plants are patterned after modern French water treatment plants, but with
some modifications. The site of the new 500 mlgd (million Imperial gallons
per day) (2,281,920 cu m/day) Charles-J. des Baillets plant currently being
constructed to provide water for the city of Montreal also was visited.
This is being constructed in two 250 mlgd (1,140,960 cu m/day) stages, the
first of which will be operational in 1980. When fully completed in the
mid-1980s, this plant will generate the world's largest amount of ozone per
day for drinking water treatment (6750 kg/day). The des Baillets plant, as
currently designed and under construction, represents the closest attempt to
duplicate a modern French ozonation plant (Neuilly-sur Marne) in North
America. When completed, the plant will be fully automated and computer
controlled.
Water treatment capacities at the plants visited ranged from 6,800 cu
m/day at He Perrot to 218,000 cu m/day at Quebec City (currently the largest
Canadian water treatment plant using ozone). Three of the plants visited
use ozonation systems manufactured in the United States.
An excellent discussion of the introduction of ozone technology into
Canada, and in particular, into the Province of Quebec, is given by Nadeau
and Pigeon29. The first ozonation plant for treating municipal drinking
water in Canada was installed at Ste. Therese in 1956. Today there are 19
operational plants in Quebec employing ozone (see Table 5) and one in Frobisher
Bay. In addition, water treatment plants in St. John's Newfoundland (41,800
cu m/day — 11 mlgd) and in Portage la Prairie (199,000 cu m/day — (5
mlgd), Manitoba are under construction. Both should be operational in 1979.
Several other Canadian municipal water treatment plants in Quebec are being
designed which will employ ozonation.
Five of the six plants visited employ post-chlorination after ozone
treatment, but in low dosages (0.5 to 2.5 mg/1) to provide residuals of 0.1
to 0.2 mg/1 of chlorine in the local distribution systems. One plant visited
(He Perrot) does not use chlorination after ozonation, but does adjust pH
and adds fluoride.
69
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In Quebec, 11 of the 19 plants use the older, Otto plate type ozone
generators, which operate at slightly negative pressure and generate 1 kg of
ozone/hour. The other plants use water cooled, tube type ozonizers. Nine
of the plants have only a single ozone generator. Back-up ozone generation
capacity is provided by installing excess generation capacity initially.
This allows the generator to be operated routinely below its rated capacity.
In turn, this results in longer operation times for the dielectrics without
unexpected downtime of the ozone generators.
Quebec City
Twelve water-cooled, Otto plate type ozone generators are at this
plant, and maintenance is performed every 18 months by one maintenance man
over a two week period (per generator). Thus the plant programs one-third
of a man-year for ozone generator maintenance. This involves changing
gaskets, cleaning cooling water tubing, washing glass plates and restarting.
This last step requires that dried air from the pretreatment system be
passed through the cleaned and reassembled ozone generator for at least one
hour to insure the presence of dried and cooled air in the generator.
Electrical power then is turned on, but at the lowest setting. Gradually
the voltage is increased (over a period of hours) to the normal operational
level (about 50% of the maximum capacity).
The ozonation process of Quebec City is controlled by measuring a
residual ozone concentration of 0.4 mg/1 after 4 minutes contacting time.
An ambient air ozone monitor recently has been installed in the ozone generator
room, because of some leakage of ozone from the generators. This occurs
when the Otto generators are operated above atmospheric pressure.
Contactor off-gases containing excess ozone are discharged to the
atmosphere (the plant is situated in a rural location).
Until 1969, the St. Charles River (water source for Quebec City plant)
received no treatment other than prechlorination (for fly larvae), primary
screening and chlorination.
Laval (Chomedey)
Ozonation was introduced 20 years ago into this Chomedey plant, which
at that time was the TAbord-S-Plouffe plant. During expansion of this
plant in 1961, the treatment process was converted back to conventional
chlorination, but with powdered activated carbon added for taste and odor
control. This 53,200 cu m/day (14 mlgd) activated carbon/chlorination plant
still operates today at the Chomedey site using this process.
In 1973, however, an additional 95,000 cu m/day (25 mlgd) expansion was
made at Chomedey, but as a second operational line which utilizes ozonation.
Today at Chomedey, there are two operational plants on the same site, treating
the same raw water for taste and odor control and disinfection by two different
treatment processes (activated carbon/chlorination in one, ozonation/post-
chlorination in the other). Therefore, Chomedey would appear to be a good
installation at which to conduct a comparative study of these two processes,
70
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not only to compare their process efficiencies, but also for their effect
upon production of halogenated organics as well as for cost-effectiveness.
The study team was advised by Laval water treatment personnel that such a
study is desired, but funds have not been available.
Two Welsbach ozone generators are at the plant, and although the genera-
tors themselves have provided satisfactory service, there have been problems
with the air preparation units. When designed, no backup air compression
capacity was installed. Therefore, when one of the air compressors malfunc-
tions, insufficient air is dried and insufficient ozone is generated. Mal-
function of the air compressors has occurred frequently at Laval, and the
Installation of larger air compression capacity to avoid this situation
currently is being planned.
Ozone contacting at Laval is by means of injectors, which are similar
to those used in the Dtlsseldorf and Konstanz, Germany plants. Contactor
off-gases containing excess ozone are discharged to the atmosphere, although
the consulting engineer is studying other disposal methods (thermal, catalytic
or 6AC destruction), since the plant is situated in an urban location.
Standby diesel power generators are on hand in case of electrical
failure. These diesels can provide power for all of the Chomedey plant
operations, except for ozone generation. Standby chlorination and powdered
activated carbon will be used in the event of power failures. The presence
of diesel power generators in Chomedey (and at other Canadian plants) parallels
standby procedures in European ozonation plants.
Ozone generator tubes at Chomedey are individually fused, but the plant
superintendent would prefer no fuses, because of economics. He advises that
fuses (costing $30 each) fail much more frequently than tubes (costing $190
each). He feels that he would save more money by not having to replace
fuses than he would lose in the cost of tube failures.
St. Denis
This 27,300 cu m/day plant currently uses two PCI Ozone tube type,
water cooled generators. The first ozone generator was installed in 1972,
and the second in early 1977. Both generators contain 6 dielectric tubes,
and are rated at 32 Ibs/day of ozone production. However, they are operated
normally at production rates of 15 to 20 Ibs/day. It is the opinion of the
plant manager that alternate daily operation of the units is desirable from
the standpoint of maintenance. Therefore, only one generator is used each
day, for 18 hours of operation, and each generator is operated every other
day. This causes greater than normal maintenance problems with respect to
gaskets, fuses and the like, but no major maintenance problems.
Maintenance on the PCI Ozone generators is performed after every 2500
hours of use. Accurate records are kept during their operation, so that
tube cleaning and other maintenance can be performed at the proper time
intervals. Since 1972, the older generator has been cleaned only twice. No
dielectric tubes have had to be replaced to date. As replacement tubes for
71
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these ozone generators cost $500 each, no spare tubes are stocked at St.
Denis. Service from the supplier is very good, and in the event of tube
failure, the plant superintendent feels that a replacement should be available
within a day or two.
After ozonation, the plant laboratory measures a combined (ozone +
chlorine) residual, which should be 0.5 mg/1. Usually, 0.3 mg/1 of chlorine
must be added to bring this combined residual up to 0.5 mg/1 at the plant
exit.
Monitors for detecting ozone in the ambient plant air are present in
the rooms above the contacting chambers, but not in the ozone generation
room. Contactor off-gases are discharged to the atmosphere through an
exhaust pipe in the roof of the 3-story building. This exhaust pipe is
pointed toward the ground, and underneath it, at ground level, is a box of
flowers. Several of these flowers had been adversely affected by the waste
ozone, but no other signs of damage were noticed in the discharge area. The
plant is in a rural location.
Pierrefonds
This new plant went into operation in late 1976 and uses Trail igaz
water cooled, tube-type ozone generators. The plant is patterned after
Neuilly-sur-Marne, in the Paris, France suburbs (screening, prechlorination,
chemical addition, decantation, filtration, ozonation, chlorination and
fluoridation). Ozonation is controlled by maintaining 0.4 mg/1 residual
ozone after 4 minutes of contact time (2 mg/1 dosage). Post-chlorination
requires an average dosage of 1 mg/1 to produce 0.5 mg/1 at the plant exit.
Residual chlorine in the distribution system averages 0.1 mg/1.
Analytical instruments monitor the ambient air for ozone in those plant
areas where ozone can be present. Contactor off-gases are discharged to the
atmosphere (the plant is located in a rural area).
Sherbrooke
This is the newest Canadian plant using Degremont tube type, water
cooled ozone generators. The 90-day commissioning phase of operation was
completed in July, 1977. Air pretreatment at this plant uses a high pressure
(100 psi) desiccant drying system. Ozone contacting is accomplished in two
chambers, each of which contains porous diffusers. Water and ozone flow is
counter-current in each chamber. Between the two chambers is a narrow
passage which changes direction of water flow before the second chamber
(similar to Degr&nont contacting chambers seen in European treatment plants).
Two-thirds of the ozone generated is dosed into the first contacting
chamber, and one-third to the second. Excess ozone in the contactor off-
gases is vented to the atmosphere. There are dissolved ozone monitors at
the outlets of both contact chambers. Residual ozone concentration of 0.4
mg/1 is attained at the outlet of the first chamber, and this first ozone
monitor controls the process. The second ozone monitor at the outlet of the
72
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second contact chamber signals an alarm if it measures less than 0.4 mg/1.
Total contact time in both chambers is 8 to 13 minutes.
Since the plant break-in phase, the plant superintendent has been
running the ozone generating systems at their maximum production capacity to
study their operational performance capabilities. Starting January 1, 1978,
the plant will be operated normally (ozone generation at less than rated
capacity) and accurate records of operational parameters, costs, etc., will
be maintained.
Contactor off-gases currently are discharged to the atmosphere, but the
plant superintendent advised that he is going to study other disposal tech-
niques. The plant is situated adjacent to the campus of the University of
Sherbrooke, and the plant finished water reservoir is underneath the univer-
sity track.
He Perrot
This small (6800 cu m/day) and older (1963) plant has been operating
with a single Welsbach ozone generator since its installation. Each year,
the generator is shut down and cleaned. Contacting is by means of porous
diffusers and off-gases are discharged to the atmosphere.
City of Montreal
This plant is currently under construction, and is scheduled to begin
operations in 1980. At that time the treatment capacity will be 250,000
mlgd (1,140,660 cu m/day), which is one-half of its ultimate capacity. The
process will be an exact copy of the Neuilly-sur-Marne plant in the Paris
suburbs, except for the cooling water system which will be modified because
of differences in water temperatures. The process will be fully automated
and computer controlled.
Montreal's Charles-J. des Baillets plant will treat St. Lawrence river
water. At the time of site visit, 13 Trailigaz, Choisy 7500, water cooled,
tube type ozone generators had been delivered, 12 for generation and one for
backup. These generators operate at 600 Hz and can produce 27 kg/hr of
ozone each.
Ozone contacting will be conducted in three-chamber contactors. Porous
diffusers are present in chambers #2 and #3. Ozone will be introduced into
these last two chambers through the diffusers, and off-gases will be injected
(by turbines) into the first chamber.
An excellent description of the new Montreal plant has been published
by Bouchard15. One year pilot studies leading to adoption of the planned
process have been described in detail by Dellah21*.
Comparison of Canadian Plants With European Plants
All 20 Canadian plants generate ozone from air. No Canadian plants
employ granular activated carbon after ozonation. All Canadian plants
73
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currently discharge excess ozone in contactor off-gases to the atmosphere,
without using thermal, catalytic, or granular activated carbon destruction.
None of the Canadian water treatment plants using ozone also use chlorine
dioxide, either for pre- or post-treatment. Ozone contacting at all Canadian
plants is by means of porous diffusers or injectors.
Canadian water treatment plants are designed by consulting engineering
firms and usually the low bid equipment is purchased. This sometimes leads
to cost cutting on the installation of controls and monitoring equipment.
For example, at Laval—Chomedey, back-up air compression capability was not
installed initially, which causes an insufficiency of ozone generation
whenever an air compressor is down.
By contrast, modern European water treatment plants utilizing ozone,
activated carbon, chlorine dioxide, and other water treatment processes
provide back-up capabilities for these processes. When such European plants
are designed, constructed, and operated by fully integrated water supply
companies, the municipality merely contracts to purchase a given amount of
water per unit time at a specified price. The capital and operating costs
of these treatment plants thus are the concern of the water company, not of
the municipality.
When an equipment supplier to the integrated water company is asked to
bid on a designed treatment process, he is assured that the water company is
sophisticated in the specification and use of that equipment (such as ozone
generation). Controls and monitoring equipment usually are specified. On
the other hand, when an engineering concern designs an ozonation system or
chlorine dioxide system and does not have the operational experience with
these processes to specify the installation of excess capacity, advanced
analytical monitors, controls, etc., and is concerned only with installing
the lowest price process design, costly operation and maintenance problems
can develop early on during plant operations.
74
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SECTION 8
ENGINEERING ASPECTS OF OZONATION EQUIPMENT AND PROCESSES
INTRODUCTION
Current U.S. waterworks design standards21 and texts22'23 provide
little or no guidance for process applications of ozone in water treatment.
Although this subject is well covered in ozone specialty literature21*'25"26
very little practical information has entered the waterworks trade publica-
tions. It is not surprising therefore, that the detailed guides and standards
required to evaluate and design ozonation systems for any process application
are not readily available. This lack of authoritative information dis-
courages consideration of ozonation as a water treatment process and hampers
the design of cost-effective, reliable, operative applications of ozone.
Ozone process selection and design criteria currently must be based on
published information and on-site evaluation of operating facilities which
are few in number in the United States. This section is intended to provide
a basic background on the essential components of the ozonation process as
applied for various water treatment purposes. It is by no means exhaustive
and more detailed information may have to be obtained by visits to operational
ozonation facilities and from knowledgeable equipment suppliers.
The ozonation system may be divided into four main parts: gas prepa-
ration, electrical power supply, ozone generation, and contacting (Figure
7). Associated with these basic components are additional subunits such as
controls, instrumentation, cooling water and/or cooling air supply, as well
as environmental provisions including noise control and ventilation. In
view of the sparsity of U.S. experience with ozone, special concern must be
given to materials of construction.
GAS PREPARATION
Feed-gas to the ozone generator must be nominally free of oil, dust and
moisture. Oil will reduce the capacity of the desiccant driers by covering
portions of the active surface of the adsorbent. Dust will collect in the
ozonizer tubes, slowly reduce the efficiency of ozone generation, and require
more frequent opening of the generators and cleaning of the tubes. Moisture
in the feed gas will reduce the amount of ozone generated per unit power
input, increase maintenance, and potentially decrease dielectric life.
75
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1
GAS
PREPARATION
2
ELECTRICAL
POWER SUPPLY
^
DRY GAS ^
™
3
OZONE
GENERATOR
UNOZONATED
WATER
1
OZONE-RICH^J »\
GAS CONTACTOR
^
1
OZONATED WATER
Figure 7. The four basic components of the ozonation process.
Factors to be considered in selection of a gas preparation system
include the following:
1. Type of feed gas: air, high purity oxygen, oxygen-rich gas mixture.
2. Type of ozone generation system, including the gas pressure at
which the generator 1s capable of operating.
3. Type of ozone contactor, including the pressure requirements of
the gas diffusion system.
4. Temperature of plant water or other water to be used for cooling
water purposes.
5. The capacity of the ozone generation system (a large system could
justify a more complex system).
The objective of preparing gas is to provide a clean, dry and cool
feed-gas for preparation of ozone. The cleaner and drier the gas, the less
frequently the ozone generator will have to be maintained. The dryer and
colder the gas, the more ozone will be produced per unit power input.
Furthermore, the capacity of the generator will be constant when these
factors are held constant.
76
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Inlet Gas Filters
Air for the system is drawn from the outside through a duct or chimney.
The air supply also may be drawn from within the building, apparently to
maintain negative pressure within the ozone generation rooms. Dust and
other particulate matter is filtered from the air through modular paper or
fabric filters which remove material larger than five microns.
Inlet Gas Pressurization
Gas must be pressurized to draw gas through the inlet air filters and
push it through the air preparation system to the ozone generation system.
Depending upon the selected contactor design it may also be necessary to
push the air through porous diffusers submerged under 4 to 6 meters of
water. The following three types of gas pressurization were observed:
High Pressure (70 to 100 psi)--
This level of pressurization was required to enable use of a high
pressure desiccant drier and the advantages of such a system are discussed
in the Desiccant Gas Drier portion of this subsection. Compressors are
required to provide this level of gas pressurization. This pressure level
necessitates the provision of a gas pressure reducer prior to the ozone
generator. This system was observed only at Sherbrooke, Quebec, and is
illustrated by Figure 8.
12
VENT FOR
OFF-GASES
I. AIR FILTER
2. COMPRESSOR
3. AIR CONTROL VALVE
k. HEAT EXCHANGER/COOLER
5. DESICCANT DRIER
6. HYGROMETER
7. AIR FLOW METER .
8. OZONE GENERATOR
9. SWITCHGEAR CONSOLE
10. PRESSURE REDUCING VALVE
I I. TRANSFORMER
12. CONTACTOR
Figure 8. High pressure gas preparation system
36
77
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Intermediate Pressure (6 to 12 psi)--
This level of pressurization is required with -contactor systems which
discharge ozone-rich gas at the contactor bottom, such as through porous
tubes, or with contactor systems which do not draw the ozonized gas from the
ozone generator. Positive displacement or centrifugal blowers are commonly
used for this application. This system is illustrated by Figure 9.
Low Pressure (0 to 8 inches
This level of pressurization is used with a contactor system that draws
the ozone-containing gas from the ozone generator. Therefore, only sufficient
pressure to draw air through the inlet filter and push it through the cooler
and drier components of the air preparation system is required. This system
is illustrated in Figure 10.
REFRIGERANT DRIER
AIR FILTER
r
LOW PRESSURE FAN
DESICCANT TYPE DRIERS
TURBINE CONTACTOR
Figure 10. Low-pressure gas preparation system.
Some ozonation systems are essentially fixed capacity trains in which
fixed capacity air pressurization units are used. These are primarily the
Otto plate-type generators which are designed to operate at slightly negative
78
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I. AIR FILTER
2. BLOWER
3. HEAT EXCHANGER/COOLER
k. REFRIGERANT DRIER,
5. DESICCANT-TYPE DRIERS
6. HYGROMETER
7. STEP-UP TRANSFORMER
8. OZONE GENERATOR
9. SWITCHGEAR CONSOLE
10. CONTACTOR
I I. OZONE SPARGERS
Figure 9. Intermediate-pressure gas preparation system
36
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or at atmospheric pressure. However, some form of gas flow control is
provided with the majority of tube type ozone generators. This includes
local, manual blower discharge control and remote manual control. Several
installations, such as the Morsang and Aubergenville plants near Paris, are
equipped with control systems which integrate air flow with ozone generation
to maintain a constant ozone concentration in the gas.
Selection of the type of gas pressurization unit is important. Con-
tamination of the gas by oil from the pressurization units must be considered
unless "oil less" units are used. The gas temperature increase resulting
from gas pressurization must be overcome in the subsequent cooling and
drying steps of the air preparation system.
Considerable energy is consumed in the gas pressurization step and
attention must be paid to control of noise generated by these units. The
noise problem is addressed in the Occupational Safety portion of this section.
Water Cooled Heat Exchanger
Shell and tube heat exchangers are used as aftercoolers to compensate
for the gas temperature increase resulting from gas pressurization by com-
pressors in the high pressure gas preparation system and by blowers in the
medium pressure system. The source of cooling water is normally pressurized,
finished water. Cooling water generally is returned to the raw water
supply but is sometimes returned immediately upstream of final disinfection.
Design of the water cooled heat exchanger would be based on the gas temperature
reduction required in the heat exchanger and on the temperature of the
cooling water. The amount of temperature reduction possible in this unit is
water temperature plus 10°C. Maximum gas temperatures emerging from these
units appears to be approximately 25°C.
The simplicity of these units and lack of moving parts should render
them relatively maintenance free. This inferred reliability should eliminate
the need for redundant units in an ozone generation train or system. Few or
no noise problems would be expected from this unit.
Refrigerant Gas Cooler
The refrigerant gas cooler is a major component of medium pressure and
low pressure gas preparation systems. Gas temperature is reduced by this
unit to approximately 5°C, which is just above the level of frost formation
on piping and equipment. The primary function of the refrigerant cooler is
gas drying. Lowering the gas temperature causes the condensation of 70% of
the water vapor in the gas, thereby reducing the size and cost of the
downstream desiccant drier. High pressure gas preparation systems do not
normally use refrigerant gas coolers, as pressure swing desiccant driers are
relatively insensitive to inlet gas temperatures.
Conventional refrigeration systems are used with this unit. The
reliability and operational noise level of the compressors and other equipment
incorporated into this unit must be evaluated in the design. The compressors
of the refrigerant units at Pierrefonds, Quebec were being replaced while
80
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observed to be noisy. Stand-by refrigerant gas cooler units may be provided
if the ozonation system is designed on the basis of an overall system rather
than individual trains.
Oil Removal Device
An oil removal unit such as an oil "trap" or oil coalescer is recom-
mended to protect the desiccant drier, particularly if an "oil free" gas
pressurization unit is not used.
Desiccant Gas Drier
The desiccant gas drier is the key unit in all types of gas preparation
systems. Weiner provides an excellent discussion of this method of gas
drying32. Desiccant driers are necessary for reduction of the gas moisture
content to a dew point (the temperature at which a given gas is saturated
with water vapor and below which water vapor will start to condense and
liquid appears) of minus 40°C to minus 60°C for low maintenance costs and
high efficiencies for both the Otto plate and the tube type ozone generator
units. Gas drying to a minus 40°C dew point is reportedly sufficient for
the Lowther air-cooled plate unit.
Figure 11 is a chart illustrating the moisture contents associated with
various dew points. When discussing gas dew points, it must be stated
clearly whether the dew point is at line pressure or at atmospheric pressure.
A desiccant drier unit consists of two compartments in which the
adsorbent in one compartment is being used for adsorption while the adsorbent
in the other compartment is being reactivated and purged. The major difference
among the various types of desiccant driers is the mode of adsorbent regenera-
tion. These include heated desiccant regeneration and heatless desiccant
regeneration.
Heat desiccant regeneration utilizes thermal swing desorption and
operates at the low pressures utilized in the medium and low pressure gas
preparation systems. The thermal swing desorption cycle is one in which
temperature differential is the major factor causing desorption. Cooling
generally is required before the adsorbent is ready for the subsequent
adsorption step. This was the desiccant regeneration method generally
observed during the inspection trip. Normally, this would be the unit of
choice for ozone generation systems with a capacity in excess of 150 Ibs of
ozone per day. In this type of unit, adsorbent heating may be provided by
means of an external heat source, or by an internal heat source. The latter
would be considered for only the smallest of installations. A regeneration
period of eight to twelve hours is customary with this type of unit.
Figure 12 illustrates the thermal swing method of desiccant drier regenera-
tion.
Heatless desiccant regeneration utilizes a pressure swing cycle in
which desorption is carried out at a pressure lower than that of the adsorption
step, and in which the pressure differential is the major factor bringing
81
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about desorption. These units normally are used in high pressure air prepara-
tion systems. Regeneration cycles of one to two minutes may be expected
with this type of unit. (A drier cycle is defined as the time required for
the unit to pass through one drying period and one regeneration period).
Pressure swing driers are significantly smaller than the thermal swing
driers, making the high pressure systems appropriate for modular, skid
mounted ozone generator systems. Also, the pressure swing driers do not
require refrigerant coolers or regeneration heaters, thereby resulting in a
simpler system which should be easier to operate and maintain. Pressure
swing desiccant driers were observed at two Quebec plants, St. Denis and
Sherbrooke. This type of drier normally would be considered for installations
with ozone generation capacities up to 150 pounds per day. Figure 13 illus-
trates the pressure swing method of desiccant drier regeneration.
1000
ABSOLUTE HUMIDITY IN g/cu m
D
O
cr>r\
pUU
100
10
c
: J
1.
0.5
O.I
On c
. lo
0.01.
0.005
0.001
Onnnc
. uuup
0.0001.
1
j
/
80°
7
t
|
rrfr
7
/
60°
0° 5
/
^
/
40°
0° 3
U
^
20°
0° 1
/
/-
•*
/
x
s
s
/
'
'•
^
^
J
J
^
DEW-POINT TEMPERATURE. °C
0°
0° 1
20°
0° 3
A0°
0° 5
60° 1 80°
0° 70° 9
100°
0°
Figure II. Absolute humidity of atmospheric air at saturation point
as a function of dew point ^".
Silica gel and activated alumina are the two most commonly used desiccants
(moisture adsorbers) although molecular sieves (crystalline zeolites) are
promoted for similar applications. Molecular sieve material also is used as
an initial layer in some desiccant dryers which contain activated alumina or
silica gel. Advantages are claimed for each adsorbent. For example, silica
82
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4 WAY VALVE-N WET GAS
CHECK VALVE- \ '"LET -PKKSURIZIH6 VALVE
RELIEF VALVE
HEATER —
DRYER
TOWER
DEPRESSURIZING VALVE
REACTIVATION
AIR INLET
BLOWER
RELIEF VALVE
DRYER
TOWER
-- REACTIVATING
REACTIVATION OUTLET
WAY VALVE
DRY GAS
OUTLET
33 39
Figure 12. Thermal-swing desiccant drier '
©
I ) WET AIR INLET
VALVE
2)REGENERATED AIR
OUTLET VALVE
3) SILENCER
MOIST AIR
INTAKE
DRY AIR
OUTLET
REGENERATED
AIR OUTLET
(V) ADSORBER
(T) ORIFICE PLATE
VALVE
Figure 13. Pressure-swing desiccant drier
39
83
-------
gel is claimed to be more fragile than activated alumina and is subject to
decomposition in the presence of water. However, the Federal Republic of
Germany silica gel installations reported no operational problems based on
long term (more than 10 years) operational experience.
An interesting feature of the Kreuzlingen plant in Switzerland was the
provision of view ports at two levels of the silica gel desiccant drier
units. The plant operator therefore could visually determine the condition
of the desiccant by observing the color of the silica gel (which was impreg-
nated with a color changing indicator).
Pressure Reducing Valve
The 70 to 100 psi operating pressure associated with the high pressure
air preparation system requires the provision of a pressure reducing valve
prior to discharge of the dried gas to the ozone generator. This is because
the normal operating pressures of the Otto plate type ozone generator are
slightly negative or close to atmospheric pressure. The tube type generator
operates up to approximately 9 psi while the Lowther, air cooled plate ozone
generator operates up to 12 psi. While operational experience demonstrates
the reliability of these units, a pressure switch normally is provided at
the ozone generator as a back-up to the pressure reducing valve.
Desiccant Drier After-Filter
A filter normally is required to capture adsorbent dust escaping from
the desiccant drier. It may be argued that purging of any "fines" from the
drier during the start-up of the system would eliminate the need for the
after-filter. However, consideration of the numerous regeneration cycles
involved in operation of the desiccant drier would appear to confirm the
need for this unit. A filter unit capable of removing particles as small as
one micron is recommended. Modular paper or fabric filter media normally
would be used.
Ozone-rich Gas Compressor
Application of a low pressure gas preparation system in conjunction
with a positive pressure diffusion system (see Ozone Contacting portion of
this section) will require pressurization of the ozone-rich gas discharged
from the ozone generator. The Kreuzlingen, Switzerland ozonation system is
operated in this manner using a low pressure gas preparation system, Otto
plate ozone generator, and positive pressure diffuser contactor. The concept
apparently is based on successful application elsewhere in Switzerland.
Selection of a mode of pressurization must take into consideration that
ozone decomposes at elevated temperatures. A liquid-ring compressor apparently
serves the required purpose.
Ozone contactor off-gases similarly must be pressurized if they are to
be recycled to a positive pressure diffusion system. Systems of this type
were observed at Rouen-la-Chapelle, Annet-sur-Marne and Neuilly-sur-Marne in
France and is to be installed at the Montreal, Quebec plant. The pressuriza-
tion blowers used for this application are said to be made of aluminum.
84
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ELECTRICAL POWER SUPPLY
A critical element in the overall ozonation system is the electrical
power supply. Descriptions of this portion of the system are sparsely
covered in the literature and it is generally isolated and well hidden in
the plants themselves.
The power input to the ozone generator is expressed by the following
empirical equation:
= 4fCgeo(em - Ca/C>eo
Where:
W = power
f = frequency
C = capacity of dielectric (insulator)
Ca = capacity of discharge gap
a
C = (CaCg)/(Ca + Cg)
e = discharge potential across gap
em = peak value of voltage across electrodes
For a given ozonator, C , C and e are constant and independent of voltage
and frequency. Therefore, power consumption is directly proportional to
frequency and peak voltage (above a minimum threshold voltage). Therefore,
two ways of controlling the ozone production of a given unit are to vary the
voltage or the frequency.
Diagrammatically, three frequently used electrical power supply control
systems are shown as follows1*0:
A. Fixed line low frequency (60 Hz), variable voltage1*0
PS
POWER
SOURCE
VT
POWERSTAT H
OR VARIABLE
TRANSFORMER T
HIT
— 1— OZONE
~T~ GENERATOR
GH TENSION
STEP-UP
^ANSFORMER
85
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B. Fixed medium frequency (600 Hz), variable voltage1*0
PS
FC
VBL
HTT
J
n
POWER FREQUENCY VARIABLE HIGH TENSION
SOURCE CONVERTER TRANSFORMER STEP-UP
TRANSFORMER
OZONE
GENERATOR
C. Fixed voltage variable frequency11
PS
HTT
1 OZONE
-y— GENERATOR
POWER VARIABLE HIGH TENSION
SOURCE FREQUENCY STEP-UP
CONVERTER TRANSFORMER
Typical controlled voltage and controlled frequency electrical power
supply systems schematics are shown in Figures 14 and 15"°:
0
o
0
0
1
4:
» VARIABLE S
» «
» 0
» ,-IQT- - • - - «
S ^lOUgOOOO1 T
\ 4\ 4
LINE VOLTAGE
§ 60 Hz
OZONE
GENERATOR
AUTO TRANSFORMER
(SOMETIMES CONNECTED
TO A POWERSTAT)
vINDUCTANCE
TO CORRECT
POWER FACTOR
HIGH TENSION
TRANSFORMER
Figure l*t. Typical controlled voltage, 60 Hz, electrical
power supply system schematic .
86
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SERIES
INDUCTANCE
0000
FOUR THYRISTERS
ADJUST RECTIFIED
POWER AND CHANGE
TO DESIRED FREQUENCY
(THIS IS WHERE CONTROL
IS EXERCISED)
PARALLEL
INDUCTANCE
000 0 0 0
RECTIFIER BRIDGE
(CONVERT AC TO DC)
L
v
HIGH TENSION
TRANSFORMER
OZONE
GENERATOR
Figure 15. Typical variable frequency electrical power supply .
A constant frequency of 60 Hz (or 50 Hz in Europe) typically would be
used for ozone generation. Production, therefore, is controlled by varying
the voltage to the ozonator. Voltage may be varied by applying the line
current to one of a series of tappings on the primary side of the transformer,
thereby changing the transformer ratio and the resultant secondary voltage.
Otherwise, a variable autotransformer may be used to feed the primary side
of the transformer with a constantly variable current.
Ozone production requirements in excess of 10 kg of ozone per hour may
justify the use of variable frequency ozone generation control. The use of
a frequency converter to increase the frequency from 60 Hz to levels up to
2,000 Hz at the primary side of the transformer is becoming more common
because of the availability of solid state electronic control systems.
Ozone generation at 600 Hz produces nearly double the amount of ozone from
the same generator operated at 50 Hz, but at a higher power consumption per
unit weight of ozone produced.
The following table shows typical operational ranges of the various
units.
87
-------
VOLTAGE FREQUENCY
(Volts) (Hertz)
OTTO PLATE 7,500 to 20,000 50 to 500
SIEMENS TUBE 15,000 to 20,000 50 to 600
LOWTHER PLATE 9,000 60 to 2,000
No guidance can be provided regarding the reliability of the various
electrical power units. Very little information is available on the quality
required to provide a high degree of efficiency and reliability. A number
of problems with dry-type transformers were noted at startup of the ozonation
systems at the Chomedey Plant of Laval, Quebec, Canada. Ten separate trans-
former failures occurred before the dry-type transformers were converted to
oil cooling through immersion in an oil bath. Problems with transformers at
the Belmont Plant in Philadelphia, Pennsylvania (not operating) are described
in the literature"0.
The ozone generator supplier should be responsible for providing the
electrical power supply subsystem in view of the dependence of the ozone
generation on the power supply. Transformers should be units especially
designed for ozone service, and the ozone generator supplier should provide
a record of successful tranformer performance at other ozonation installations,
In view of the need to substitute other oils for the non-flammable polychlori-
nated biphenyls (PCBs) previously used, the system designer must consider
the possibility of transformer fires should flammable oils be employed. In
any case, drainage of the transformer room must not cause oil contamination
of the product water. Dry type, or air-cooled, transformers also have
operational problems, and these units are less common in ozonation service.
OZONE GENERATION THEORY
The silent electrical (corona) discharge currently is considered to be
the only practical method of generating ozone in plant scale quantities;
hence, it is the only mode of ozone generation considered for this report.
Any individual ozone generating element essentially consists of a pair
of electrodes separated by a gas space and a layer of insulation (dielectric)
such as glass. Oxygen-containing gas. is passed through the empty space and
high voltage alternating current is applied. The ozone generator acts as a
leaky condenser which allows energy to pass through. A corona discharge
occurs across the gas space. A portion of the oxygen in the feed gas is
converted to ozone in the following manner:
_ heat
and
88
-------
Overall, the reaction is 302 + electrical energy=^=^ 203 + heat. It
is important to realize that the reaction is an equilibrium reaction, meaning
that the reverse reaction is occurring at the same time as the forward
reaction. This is the major reason that yields of ozone are so low (i.e.,
1% to 3% concentrations of ozone are generated in air; 2% to 6% concen-
trations are generated in oxygen). In fact, at temperatures above 40°C the
reverse reaction is dominating and very low yields of ozone are obtained.
Since some 90% of the electrical energy fed to the ozone generator is
lost as radiation, sound and mainly heat, it is essential that efficient
cooling of the electrodes be provided, so as to minimize the ozone decomposi-
tion and thereby maximize the yields of ozone generated. Therefore there is
a cost tradeoff involving the energy penalty incurred in cooling the generator
to conserve the ozone generated.
The basic ozone generator with the required electrical power supply is
shown below1*0.
— "N" PARALLEL PLATE,
OR TUBULAR DIELECTRICS,
CONNECTED IN PARALLEL
PS
R
ELECTRICAL REGULATION
OF
||
II
||
ii
_il
POWER
SUPPLY
FREQUENCY AND/OR
VOLTAGE
•
*^rr" GROUND
Prior to the application of power, the ozone generator is a group of
capacitors connected in parallel. A single capacitive element (tube or pair
of parallel plates) is shown below.1*0
HIGH TENSION ELECTRODE
DIELECTRI
— GROUND
TENSION ELECTRODE
GAS SPACE
(AIR OR OXYGEN)
89
-------
The electrical properties of this single capacitive element are shown
in the following sketch which represents the system before the ionization
potential of the air or oxygen in the gas space is reached.1*0
Cd
Ce
V
Cd: CAPACITANCE OF GLASS DIELECTRIC,
Ce: CAPACITANCE OF THE FEED-GAS (AIR OR 03),
V: POTENTIAL DIFFERENCE ACROSS DIELECTRIC AND DISCHARGE GAP,
Re: RESISTIVE ELEMENT
As the ionization level of the gas space is reached, the gas space
conducts electricity and becomes a resistive element as illustrated below.1*0
Cd
C'e
Re
The electrical characteristics of the ozone generator change. As
alternating current power is applied to the circuit, an alternating cyclical
variation in the circuit occurs when the ionization level of the air or
oxygen in the gas space is traversed.1*0
IONIZATION
LEVEL
90
-------
The gas (air or oxygen) remains partially ionized and the voltage drops
below the ionization potential. The complicated waveform for the potential
difference across the gas space (Ue) is shown below.
IONIZED
For a conventional ozone generator
,2
where,
£ a FEV
A ~D
Q = ozone production
A = electrode surface area
F = frequency
E = dielectric constant
V = applied voltage
D = distance between electrodes
For a given type of ozone generator (and therefore a given electrode
configuration) the ionization voltage is a function of gas pressure and the
discharge gap:
Vi a pg
where,
91
-------
Vi = ionization voltage
p = pressure
g = discharge gap
Ozone is generated during the period that the oxygen-containing gas is
present. Free electrons resulting from ionization are accelerated by the
applied voltage and frequently collide with oxygen molecules. Collisions
are more frequent when the feed gas is high purity oxygen because the
density of the oxygen molecules is greater.
If the excited electron possesses sufficient energy at collision, the
oxygen molecule is split into oxygen units. Each oxygen unit is available
either to combine with an oxygen molecule (thus forming CL) or to recombine
with another unit to reform 02.
The gas (air or oxygen) is being ionized continuously and deionized
within the gas space by the alternating current. The free electrons,
travelling from one electrode to the other as the polarity reverses, collide
with oxygen molecules. Clearly, increasing the frequency of operation will
increase the number of potential collisions. Ionization voltage normally is
in the neighborhood of 10,000 volts; however, the voltage required to cause
ionization would be greater for wider discharge gaps and less for narrow
discharge gaps. Figure 16 illustrates the activity within the gas space.
The possible outcomes of electron collisions with an oxygen molecule are
illustrated below."0
\
/
RESULTS IN (a)
OR
(b)
OR
\
92
-------
UD
CO
i
COR
IONI2
PERIC
/
BUILD
IONIZ
THRESI
RESPON
O— 0 =
•-*• :
v •
UJ A o Qv
"I °- o
3: < o°-o r
O C3 \ d
co b
Q i o
en
I
x:
o
_i
LU
Lu
ED77— J_J
>TNT
^'- rA
^ ^, '"•
*• •" A
^ 7T2
UP TO
OiTION
HOLD
3INGLY. IN THE
PERIOD
„ n r i n KI
* UL 1 UN
OF
ZATION
\ WAVEFORM OF, /
\ POWER SOURCE /
DISCHARG
= OXYGEN
= FREE ELECTRON & DIREC
= OZONE
<•">/ ~S)
~% 1 *3
~'n\^" * «
t N I
1 i >
IONIZATION
LEVEL REACHED,
FREE ELECTRONS
COLLIDE WITH 02,
SOME 02 ATOMS
RECOMBINE INTO 03.
£^ l
LU CO
f \ i l
Z 0 \-
o to <£
Q 0 O OQ
E GAP:
riON OF TRAVE
1 • O^^^
w T^^^
o^_ t / o^ ~^^
LU
CO
CfL
LU
LU
oi "Z. co cs r^i
>- 2 u) O O O
K- 1- h- . , ,
— < UJ
c£ M _1
< — CL ' ' '
— i z z:
o o o ^ ^jfT1
An
L
vu
DEIONIZATION,
SOME 03
DECOMPOSES.
^-^
\
•••mm-'umj-uourum.^-^,!,'^'
5/27T
^5?
CYCLE REPEATS
.
37T t
"A^
Figure 16. Formation of ozone during ionization/deionization
-------
Frequency can be increased to a maximum level as illustrated by Figure
17 which is a curve for an ozone generator with cylindrical dielectric tubes
and an ionization gap of approximately 3mm. For this particular ozone
generator the optimum frequency appears to be about 600 Hz.
MAXIMUM POSSIBLE OZONE PRODUCTION
FREQUENCY (Hz)
0 200 *»00 600 800 1000 1200
Figure 17. Relationship of ozone production and power supply frequency
It would appear, therefore, that:
t since ozone production per unit area of electrode surface varies
as the square of voltage, the higher the applied voltage the
greater the production of ozone,
0 the longer the period that the air is ionized, the greater the
chance of ozone being generated, and,
• the higher the frequency, the greater the chance of generating
ozone.
However, these statements each taken out of context can be misleading.
As stated initially, the temperature within the corona discharge area is
critical. The reverse reaction of ozone to produce oxygen dominates above
40°C. Above a maximum applied voltage, the amount of heat liberated can
exceed the cooling capability. In addition, dielectric media are subject to
deterioration at high voltages. Thus there is a practical maximum voltage
which will produce the highest yield of ozone at the most efficient cooling
cost and most efficient dielectric life.
94
-------
Exposure of the generated ozone to lom'zation in the discharge gap will
result in decomposition of ozone back to an oxygen molecule and a single
oxygen moiety. Therefore, prolonged residence time of the air feed gas in
the discharge area will expose the produced ozone to conditions of temperature
and ionization which will reverse the formation reaction.
The production rate of ozone varies linearly with frequency, and
higher frequencies cause less deterioration of dielectric media than do high
voltages. On the other hand, power consumption efficiency at higher frequen-
cies is less than at lower frequencies. Therefore, although more ozone can
be produced from the same generator operated at frequencies of 600 Hz than
at 50 Hz, the number of kilowatts required to generate a unit weight of
ozone also is higher at the higher frequency.
Therefore, maximizing the yield of ozone for the lowest expenditure of
electrical energy involves a balance between the many factors cited. The
different types of commercially available ozone generators observed during
this study are described below.
COMMERCIAL OZONE GENERATORS
There is a variety of types of commercial scale ozone generators
available. These include the following types:
t horizontal tube, water cooled
• vertical tube, water cooled
• vertical tube, doubled cooled (oil and water)
• Otto plate type, water cooled
• Lowther plate type, air cooled
The current interest in ozone generators makes it likely that other
types of ozone generators will be developed, but those listed above currently
are the only types currently marketed actively.
Horizontal Tube. Water Cooled Ozone Generator
The horizontal tube, water cooled ozone generator currently is the most
commonly used. Rated maximum capacities of typical ozone generators range
from approximately 0.4 kg/hr (0.88 Ib/hr) to 27.5 kg/hr (60.5 Ib/hr) using
air as the feed gas. Rated capacities would be approximately doubled if
oxygen were used as the feed gas. Normally, however, plants operate ozone
generators at 50% to 75% of rated capacity to minimize operation and mainte-
nance costs and to minimize the amount of electrical energy required to
generate a unit weight of ozone.
Figure 18 represents construction details of a typical tube ozonator.
Figure 19 provides more detailed views of typical horizontal, tube type,
water cooled ozone generators. These units are normally designed to operate
95
-------
LEGEND
A-AIR INLET
B-OZON1ZED AIR OUTLET
C-COOLANT INLET
D-COOLANT OUTLET
E-DI ELECTRIC TUBE
F-DISCHARGE ZONE
G-TUBE SUPPORT
H-H.V. TERMINAL
I - PO RT
J-METALLIC COATING
K-CONTACT
1
Figure 18. Construction details of a tube type ozone generator
96
-------
A. SINGLE-BAY
7 12
AIR
' i 5 9 WATER
2 5 6
B. DOUBLE-BAY
AIR WATER
I
AIR
H.V. TERMINAL
I. DIELECTRIC TUBE
2. METALLIC COATING
3. H.V. TERMINAL
4. CONTACT
5- CENTERING PIECE
6. IONIZATION GAP
WATER
DIELECTRIC TUBES
7. AIR INLET
8. FRONT CHAMBER
9. REAR CHAMBER
10. AIR OUTLET
I I. WATER INLET
12. WATER OUTLET
Figure 19- Typical details of tube type ozone generators
97
-------
at feed gas pressures of 8 to 10 psi and are, therefore, frequently used in
pressurized porous diffuser contactor installations.
Ozone production rate typically is about 18 g/hr per generator tube at
an ozone concentration ranging from 18 to 40 g/cu m at an internal pressure
of 8 psi employing 60 Hz power for air dried to minus 60°C dew point and at
a cooling water temperature of 15°C.
The majority of ozone generators utilize electrical supply at 50 or 60
Hz. However, when ozone production requirements exceed 10 kg/hr, it may be
cost-effective to use frequencies up to 600 Hz, which will produce approxi-
mately double the ozone from the same equipment operating at 50 Hz.1*1
Vertical Tube, Water Cooled Ozone Generator
The vertical tube, water cooled ozone generator utilizes the cooling
water both as the grounding electrode and the coolant. Input gas is pushed
through the gas preparation system to the ozone generator by means of a low
pressure blower. The ozone-rich air is drawn to the contactor under negative
pressure for transfer into the liquid. The ozonator tubes are comparatively
small in diameter.
The ozone generator consists of three chambers, or compartments,
arranged vertically. As illustrated by Figure 20, dried gas is drawn into
the upper compartment where it enters metal tubes which are the high tension
(voltage) electrodes. The gas is drawn downward past the tubular metal
electrode to emerge into the closed end of the glass dielectric tube.
The glass dielectric tube is almost entirely immersed in cooling water
in the lower compartment. The cooling water bath acts as the ground electrode.
The dried gas passes upward through the corona discharge area which is
established in the annular space between the high tension electrode and the
glass dielectric. The ozonized gas is discharged from the top of the
dielectric tubes into the middle compartment, from which it is drawn to the
contactor.
Otto Plate, Water Cooled Ozone Generator
The water cooled plate type (Otto) ozone generator consists of pairs of
flat hollow blocks, separated by two glass plates and a gas space, as
illustrated by Figure 21. One block serves as the low tension electrode and
is water cooled, while the adjacent water spray-cooled block is at high
potential.
Air enters the housing enclosing a number of generator elements and
passes through the corona discharge area in the space between the glass
plates to a central manifold passing through the glass plates and metal
blocks. The ozone-rich gas is drawn through the manifold to the point of
ozone application.
98
-------
W//////X////////,
UPPER
COMPARTMENT
MIDDLE
COMPARTMENT
LOWER
COMPARTMENT
"n
DRY AIR INLET
HIGH TENSION
FUSE
OZONE-RICH
GAS OUTLET
v//////,
COOLING
WATER LEVEL
GLASS TUBE
DIELECTRIC
METAL
ELECTRODE
-SPACER PIN
ini
\^
OZONE GENERATOR TUBE
DRY AIR
NLET
JU
OZONE-RICH GAS
OUTLET
COOL NG
WATER LEVEL
GAS FLOW IN OZONE GENERATOR TUBE
COOLING
WATER
I A A A A I I"
DRY AIR
^J OZONE-RICH
COOLING
WATER
OUTLET
TYPICAL OZONE GENERATOR
Figure 20. Details of vertical tube ozone generator.
99
-------
AIR
C TRANSFORMER
AIR
_
A
4.
OZONE
AIR
AIR
LEGEND: A. GROUND POTENTIAL WATER-COOLED BLOCK; B. GLASS DIELECTRIC;
C. DISCHARGE GAP; D. HIGH TENSION WATER-COOLED BLOCK.
Figure 21. Otto Plate ozone generator module
The Otto plate ozone generator operates at atmospheric or negative
pressure. Its application typically is limited to negative pressure dissolu-
tion methods, such as by vacuum injection or inductive turbine applications.
Alternatively, the ozonized gas emerging from the generator at atmospheric
pressure can be pressurized by means of a water-seal compressor for dissolution
by means of submerged porous diffusers.
Otto plate units are not as subject to damage due to high dew points as
are the tube type units. Otto type units can operate with dew points as
high as minus 30°C but at reduced production efficiency. One standard
element produces up to 20 g of ozone/hr when operating on 450 watts of a 60
Hz service with air containing less than 0.1 g of water/cu m and at a
cooling water temperature of 15°C. '20,000 Volts are applied across the
electrodes at a maximum energy application of 250 watts/sq ft of single
electrode area.
Vertical Tube, Double Cooled Ozone Generator
Vertical tube, double cooled ozone generators utilize both water and a
non-conducting oil or other fluid for cooling. This unit incorporates a
more complex tube design as illustrated by Figure 22. The high voltage
100
-------
GLASS DIELECTR C
HIGH VOLTAGE
ELECTRODE
!
r
^ —
STAINLESS STEEL
GROUND ELECTRODE
AIR OR
02 IN
COOLING WATER
INLET
t
-s'*.' ..
.v , •
--*.'V
OUT
COOLING WATER
DISCHARGE
COOL ING OIL
Figure 22. Vertical tube double-cooled ozone generator-tube detail
101
-------
electrode is cooled by a non-conducting oil or other fluid contained in a
closed loop cooling system. The oil, in turn, is cooled by means of a heat
exchanger. The low voltage electrode is cooled directly by water.
The current vertical tube, double cooled units operate at 10,000 volts
and are controlled by varying the frequency from 60 to 2,000 Hertz by means
of a frequency inverter. An apparent disadvantage of this unit is higher
dielectric cost. However, ozone production rates, per ozone generator tube,
are claimed to be more than 6 times those of conventional tube type ozone
generators. A discharge ozone concentration of 2% in ozonized air and 3% in
ozonized high purity oxygen is claimed. This type of unit was observed at
St. Denis, Quebec, Canada, and is installed in the Riviere-du-Loup plant in
Quebec. Units of this type also are installed in the Monroe, Michigan water
treatment plant which began operation in early 1978.
Lowther Plate, Air Cooled Ozone Generator
The Lowther plate, air cooled ozone generator is a relatively new unit.
The basic element or cell (illustrated by Figure 23) currently consists of
the following components; an aluminum heat dissipator, a steel electrode
coated with a ceramic dielectric, a silicone rubber spacer to establish the
discharge gap, a second ceramic coated steel electrode with gas inlet and
ozonized gas outlet and a second aluminum heat dissipator. Thirty or forty
cells are manifolded to form a module. The unit, which uses ambient air for
cooling, operates at an upper frequency range of 2,000 Hz at 9,000 volts at
an upper gas pressure of approximately 15 psi. Figure 24 illustrates a
typical Lowther type unit.
HIGH
VOLTAGE
STEEL
ELECTRODE
ALUMINUM
HEAT
DISSIPATOR
CERAMIC
DIELECTRIC
GROUND STEEL
RODE
— — - r-
GE GAP
.^*c
_j
• -i
*
&
/
i'
^
^ ,js
/^/'
##
^
>
— il
D
E
SILICONE
RUBBER
SEPARATOR
CERAMIC
DIELECTRIC
COATED
STEEL
ELECTRODE
SILICONE RUBBER
SEPARATOR
SECTION "A-A"
Figure 23- Lowther Plate ozone generator cell
102
-------
EXHAUST COOLING AIR
RECESSED
CONTROL PANEL
COOLING AIR INTAKE
OZONE GENERATOR CELLS
SOLID STATE ELECTRONICS
BEHIND LOUVERED PANELS
COOLING AIR INTAKE
Figure 24. Air cooled Lowther plate type ozone generator.
There are presently no operational Lowther type ozone generators in
municipal water treatment facilities, although such a facility is under
construction in St. Johns, Newfoundland, Canada. The St. Johns plant will
install six units, each capable of generating 115 pounds of ozone per hour.
These units will use air as the feed gas to treat a nominal flow rate of
14,000 gpm (20.2 mgd peak flow) for color removal at an ozone dose rate of
2 mg/1. Two pairs of ozone generators will be in normal operation, with the
third pair of generators being available for peak flow and backup. Full
scale, municipal wastewater treatment applications of the Lowther ozone
generator, to be in operation in 1978, will include the plants at Meander
Creek, Ohio and Springfield, Missouri. Both of these plants will use the
oxygen activated sludge sewage treatment process and, thus, will use oxygen
as the feed gas for ozone generation.
103
-------
OZONE GENERATOR COOLING
Cooling is required for the ozone generator to remove heat from the
generator as rapidly as possible to prevent the decomposition of ozone back
to oxygen, to assure maximum ozone production and to minimize dielectric
heat stress. Water, oil and air are used as coolants. Figure 25 illustrates
the effect of cooling water temperature on ozone production of a typical
tubular type, water cooled ozone generator. The temperature of waters in
the lakes of Switzerland and Austria remain relatively constant at about 4°C
all year round and are used to provide cooling. However, the temperatures
of many of the rivers in France and Germany can be as high as 20°C in the
summer months, and supplementary cooling methods sometimes are required.
uj 105
100
± 95
Q- Z
1-
=5 LL.
O O
•Z. eg
O <
LU
Q.
90
85
80
75
\
15 25 35 45
55 65
INFLOW TEMPERATURE OF COOLING WATER
Figure 25. Ozone output in relation to inflow temperature of cooling water
A maximum temperature rise of 6°C is considered allowable for the
cooling water of tube type ozone generators. However, at the sites visited
during May, 1977, a temperature rise of approximately 3°C was observed while
the ozone generator was operating at less than maximum production capacity.
Approximately 3 to 4 liters of cooling water at 20°C are required for each
gram of ozone produced1*3.
Finished water typically is used for cooling which, after having
passed through the generator cooling system, is returned to the water
treatment process ahead of disinfection. Closed loop cooling systems were
observed at the three DUsseldorf plants in which boiler quality is used in
the closed loop generator cooling system. The closed loop system is cooled
by water from the treated water system. The large ozone generator facility
104
-------
at Neuilly-sur-Marne near Paris, France provides a separate refrigerant
cooling system to cool the ozone generator cooling water in the summer
months when both ozone demands and Marne River water temperatures are high.
The parameters of the ozone generator cooling system that should be
measured include inlet water temperature, inlet water flow measurement,
inlet water flow indicating and outlet water temperature (Figure 25). The
size of the installation and degree of control sophistication determine the
types of sensors used for measuring the various parameters. Standard
thermometers inserted in pipe wells would be adequate in many installations,
while more sophisticated temperature sensors could be used for remotely
monitored facilities. In any case, high outlet temperatures should be
sufficient reason to shut down the generator unit to protect the dielectric
tubes.
Rotameters are sufficient for flow measurement for even large installa-
tions such as Neuilly-sur-Marne. Some means of sensing the flow of cooling
water in the system is required.
Air Cooling
The Lowther plate-type, air cooled ozone generator does not require
cooling water. Ambient air is claimed to provide sufficient cooling of the
generator. A fan moves ambient air across aluminum heat dissipators removing
heat from both electrode surfaces simultaneously. This generation is
designed to operate at 85°F (29.5°C). Ozone generation efficiency drops
0.5% per degree F rise in temperature, so that if the generator is operated
at 100°F (30.8°C) it will produce 7% less ozone than its rated capacity at
85°F.
USE OF OXYGEN RICH FEED GAS
It is well recognized that the use of a feed gas with oxygen levels
higher than the normal 20 to 21 percent of ambient air will result in
higher rates of ozone production for a given power input. The use of high
purity oxygen for wastewater ozonation has been widely promoted and a
number of wastewater ozonation facilities using oxygen as feed gas will be
placed in operation in the United States during 1978. However, in wastewater
treatment, there is a potential use of oxygen-rich ozone contactor off-gases
for application in the activated sludge process. In order to use oxygen-
rich gas to generate ozone for drinking water applications, economics
dictate that oxygen-rich contactor off-gases be recycled to the inlet of the
gas preparation system so that the off-gases can be conditioned prior to
their return to the ozone generator.
The Wasserwerk III Wittlaer of Duisburg, Federal Republic of Germany,
is the only known municipal water treatment plant in the world in which high
purity oxygen is used for generating ozone (Figure 26). The Duisburg Plant
ozonation system schematic is provided in Figure 27. There are several
industrial facilities using ozone generated from oxygen to treat industrial
water, including the Hoechst Works near Frankfort, Federal Republic of
Germany. The process diagram of the Hoechst Works industrial water ozonation
105
-------
system displayed at the May, 1977 Nasser Berlin meeting appears to be similar
to the Duisburg System. It should be noted that the Duisburg Plant employs
neither contactor off-gas ozone destruction nor purging of off-gas to maintain
a certain level of oxygen in the recycle gas.
OZONE WASHER-,
OZONE GENERATOR-
LIQUID OXYGEN STORAGE-
- OZONE CONTACTOR
FILTER/GAC
REACTOR
VACUUM PUMP
TO DISTRIBUTION
SYSTEM
Figure 26. Duisburg Plant overall water treatment schematic.
The lack of operational data from municipal water treatment ozonation
systems using recycled, high purity oxygen, despite the promise of the
concept, necessitates taking guidance from industrial applications and other
information. For example, ozone generated by a recycle oxygen system is
used for the processing of oleic acid by Emery Industries, Inc., of Cinci-
nnati, Ohio. Figure 28 is a composite Oxygen Recycle Ozonation System
schematic incorporating the concepts promoted by Emery Industries, Inc. and
Union Carbide Corporation. It should be noted that these systems incorporate
destruction of contactor off-gas ozone and a purge system to maintain recycle
off-gas oxygen levels.
The key to successful use of oxygen is an economical and reliable
source of oxygen. This may take the form of liquid delivered from an off-
site, cryogenic oxygen generating system, on-site oxygen generation by means
of pressure swing adsorption units (PSA), or by an on-site cryogenic oxygen
generation system. The use of liquid oxygen is practiced at the Duisburg,
Germany plant and at the Hoechst (Germany) industrial water treatment plant.
The Tailfer Plant in Brussels, Belgium is installing the capability to use
liquid oxygen as the ozone generator feed gas in place of air for a period
106
-------
of one year. After this one year test period, a decision will be made
either to continue using oxygen, return to air, or to use oxygen only during
periods of high ozone requirements.
FINISHED WATER (0. I
-------
WATER-COOLED
HEAT EXCHANGER
(SYSTEM "A")
PURGE
V
YYYYY
REFRIGERANT
DRIER
WATER
1
COMPRESSOR
rOl
-o
DESICCANT
TYPE
DRIER
OZONE
DESTRUCTOR
r
OXYGEN
GENERATOR
OZONE
GENERATOR
OFF-GAS
CONTACTOR
OZONATED
WATER
UNOZONATED
WATER
Figure 28. Composite oxygen-rich ozone generation system schematic.
(proposed for installation in U.S.)
OZONE CONTACTING
Efficient diffusion of ozonized gas into the water is necessary from
the standpoints of economics and achieving the intended process results.
The ozonized gas and water generally are brought into close proximity in a
contactor. The advantages and disadvantages of various types of contactors
have been summarized in Table 3. The choice of an ozone contactor depends
primarily upon the ozone process application. However, other factors
include the pressure of the ozonized gas discharged from the ozone generator,
local design practice, ozonation philosophy, regulatory agency requirements
and allowable off-gas ozone concentrations. The various types of ozone
contactors are well described in the ozone specialty literature.1*7"*8"*9
The primary applications of ozone observed during the site visits are
listed below. Some of these applications are dependent on the mass transfer
(M.T.) of ozone and others are chemical reaction rate (C.R.R.) dependent.
Thus different types of contactors are used to optimize the efficient use of
ozone in the various applications.
• Disinfection and Viral Inactivation (M.T., but regulated over 6 to
10 minutes).
108
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• Iron and Manganese Oxidation (M.T.).
• Micropollutant Oxidation (M.T. or C.R.R., depending upon the
nature of chemicals present).
• Microflocculation (M.T.)-
• Taste and Odor Removal (M.T. or C.R.R. depending upon the nature
of chemicals present).
• Pre-Conditioning of Biological Activated Carbon (M.T.).
If disinfection if the primary goal, the most prevalent technology is
a two or three stage porous diffuser concept. Sufficient time and the
proper amount of ozone must be provided initially to meet the initial ozone
demand of the water. After this initial demand has been satisfied, additional
ozone and contact time is provided to maintain a 0.4 mg/1 ozone residual for
a minimum four-minute period of time. These conditions have been adopted by
French public health authorities for viral inactivation and disinfection by
ozonation. The porous diffuser contactor satisfies these contacting require-
ments for this application of ozone.
A contactor for iron and manganese oxidation should be relatively
unaffected by deposition of iron and manganese. Therefore, an injector or
turbine contactor would be preferable to the use of the porous tube type.
In the interest of simplicity contactors have been divided into two
classifications, negative pressure contactors and positive pressure contactors.
Negative pressure contactors are those which draw ozone from the generator
by negative pressure at the point of initial gas-water contact. Positive
pressure contactors are those in which the ozonized gas is under positive
pressure at the initial gas-water contact.
Negative Pressure (Low Pressure) Contactors
Contacting systems that require little or no pressurization of the
ozonized gas include vacuum injection and inductive turbine types. Energy
is required to provide the pressure head for vacuum injection or for turbine
rotation.
Vacuum Injection--
Vacuum ozone injection is a negative pressure method by which the water
to the contactor is passed through a Venturi under pressure. Ozonized gas
is drawn into the water by the negative pressure at the Venturi throat. One
variation of this method is the total vacuum injection method in which the
entire plant water flow is passed through one or more Venturi sections, as
illustrated by Figure 29.
Based on the observations of this survey, total vacuum injection and
partial vacuum injection apparently have provided satisfactory service in
all the required applications, but these applications were oxidation and for
109
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purposes other than viral inactivation at the visited plants. Overall
system considerations are also important factors in contactor selection.
An example of this system was observed at Quebec City, Quebec, Canada.
A variation on this method is partial vacuum injection in which only a
portion of the water flow is passed through the Venturi section. The
ozone-rich side stream subsequently is mixed with the remainder of the main
flow in the contactor as illustrated in Figure 30.
Examples of this contacting method include the Konstanz plant, Germany
(FRG). The three DUsseldorf, Germany plants (Holthausen, Flehe, and Am
Staad) use a similar approach, with the exception that the side stream is
finished water.
Turbine Diffusion--
Another means of low pressure contacting is the use of a motor driven
inductive turbine which draws ozonized gas into water as it pumps water
through the eye of the impeller and outward to the impeller tips. Figure 31
illustrates this type of mechanism while Figure 32 illustrates the multistage
installation at the Lengg Plant, Zurich, Switzerland. The technique is used
at many plants employing the Kerag ozonation system. Figure 33 illustrates
a different impeller and ozonation chamber configuration applied at the
Tailfer Plant of Brussels, Belgium. This unit is fabricated by Frings, but
functions in the same manner as the Kerag impeller. Figure 34 shows details
of the turbines used at Tailfer.
Positive Pressure Contactors
There is a wide range of positive pressure contactor systems which
includes:
• Porous Diffusers
t Mechanical Turbines
• Packed Beds or Columns
• Spray Towers
They have been developed mainly in conjunction with the tube type
ozone generators which discharge ozone-containing gas at pressures up to
10 psi. However, ozone-containing gas at atmospheric pressure from
plate type ozone generators can be pressurized after generation for
application in these units.
110
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UNOZONATED WATER
OZONE-RICH GAS
CONTACT
CHAMBER OFF-GAS
OZONATED
WATER
CONTACTOR
Figure 29. Total flow vacuum injector contactor for ozonation.
PUMP FOR
MAKEUP WATER
OZONE-RICH GAS
UNOZONATED WATER
I
CONTACT
CHAMBER
A OFF-GAS
—~ OZONATED WATER
Figure 30. Partial flow vacuum injector contactor for ozonation.
Ill
-------
DRIVE MOTOR
t
OZONE-RICH GAS
CONTACT
CHAMBER
OFF-GAS
OZONAT
. • i
n_H
ED WATER
mmimm
\ \
\V ^
T
•f
•t'o
« «
0 0 •
» o
0 0 0 0
« a
•^
i
H
i
_
P
y \
T
t.
i
Y ^
0 .»
:BV°
^ V
<
}
^ UNOZONATED WAT
~D
/
Figure 31- Turbine type ozone contactor
50
112
-------
Im 3m , 5m
Om , 2m . 4m
I Om
SCALE IN METERS
WATER FLOWS IN
FROM OTHER BAY
TURBINE CONTACTOR
WATER FLOWS OUT TO OTHER BAY
Figure 32. Mul t i -turb i ne contactor installation (Lengg Plant, Zurich)30.
-------
96.91 METERS
TIME OF
DETENTION
PREOZONATION
TO RESERVOIR
OZONATION
DETENTION
Figure 33. Tailfer water treatment plant, Brussel s, ozone contact chamber .
-------
20CM
PLAN VIEW
SECTION VIEW
Figure 3^. Turbine detail, Tailfer water treatment plant, Brussels
Porous Diffusers--
Innumerable configurations of porous diffusers are possible, and many
have been applied, some in combination with turbine mixing devices. Counter-
current flow of gas and water appears to be a more efficient method of
bringing ozone-rich air and water into intimate contact. Early applications
of this mode of ozone contacting are illustrated in the following figures.
Figure 35 illustrates the configuration of the Van der Made contactor which
utilizes cocurrent contacting at a wat;er depth of 5 meters (16.33 feet) in
a covered tank.
115
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•OFF-GAS
RAW WATER INLET
.T^
••,.. r / • »
-£«*"Xvl*:
^••n n Q poo
". " ' r
._jilL__lM-_
— OZONATING TOW
COMPRESSED Oi
-^*
DEGASSER
OZONATED
WATER OUTLET
GAS DIFFUSERS
Figure 35. Van der Made ozone contactor
51
Figure 36 illustrates the Welsbach contactor which utilizes counter-
current contacting in an uncovered tank. This configuration is used at
Whiting, Indiana.
PURE WATER
OUTLET FLUME
s
vD
RAW WATER
CHAMBER
• i
J_L
OZONE UNDER
PRESSURE
.^-DIFFUSERS FOR INJECTING THE
GAS INTO THE WATER
Figure 36- Welsbach ozone contactor
Figure 37 illustrates the Torricelli contactor (a combination of
injection and porous diffusion) which injects ozone at an equivalent water
depth of 10 meters (32.75 feet) and recycles the covered contactor off-gas
to the contactor inlet stream in a form of preozonation step.
116
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RAW WATER INLET
CHANNEL FOR RECOVERING
OZONE FROM THE OZONATION
CHAMBER FOR PREOZONATION
COMPARTMENT FOR
DISSOLVING OZONE
OZONE UNDER PRESSURE
OFF-GAS
i»h
CM
j
i
\
V
\
INJECT
OF GAS
f/£?rjc
-
J
^
s
&,
i?
V0
?
\
ION
*?•%£'
7^
\-
\
\
V
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z*
I
^
r~ »•
r\
~—f F
C
RF£
UNI
.-- — F
0
p
/-nun
OWI'll
:fc=-*~ OZONATED WATER OUTLET
OUTLET CHANNEL FOR THE
WATER AND PRESSURE
REGULATOR FOR
OZONATION CHAMBER
RESIDUAL OZONE
UNDER PRESSURE
RESIDUAL
OZONE UNDER
PRESSURE
COMPARTMENT FOR WATER
SEPARATED FROM THE GAS
COMPARTMENTED OZONE CHAMBER
UNDER HYDRAULIC PRESSURE
Figure 37- Torricelli ozone contactor
36
Porous diffuser, multi-chambered contactors are more commonly used
for disinfection purposes, particularly in France, and for viral inactivation
where a specific ozone residual content in water must be maintained for at
least four minutes. Multiple stage contactors (countercurrent - cocurrent -
countercurrent - etc.) are common configurations as illustrated by Figure
38. Figure 39 represents the application of this concept at the Choisy-le-
Roi plant near Paris. With multiple contact chambers, successively decreasing
amounts of ozone can be fed into the chambers as the ozone demand of the
water is satisfied.
Two stage countercurrent contactors are installed at the Morsang and
Aubergenville plants in France and at the Sherbrooke plant in Quebec,
(Canada) as illustrated by Figure 40. As with the multiple stage diffuser
contactors, it is customary to feed less ozone into the second chamber
(about 33% of the total ozone applied) because there is less ozone demand in
the once-ozonated water.
Figure 41 illustrates an interesting two-level diffuser contactor
system installed at the Kreuzlingen, Switzerland plant and in several other
Swiss plants. Ozone-containing gas from the ozone generator is fed into
the lower chamber which is configured so that the off-gases collect in a
small air space above the liquid. When the pressure in this small air
space exceeds that of the head created in the upper chamber by the influent
chamber, the off-gases from the first (lower) chamber "escape" into the
upper chamber. Since the upper chamber contains influent water which has the
highest ozone demand, and since the off-gases from the lower chamber contain
117
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oo
UNOZONATED WATER
-»
OZONE-RICH AIR
CONTACT CHAMBER
OFF-GAS
Figure 38. Multi-compartment, porous-tube contact chamber,
-------
T
CONTACT CHAMBER
OFF-GAS
«$?T
:_i::
_H ...
0 RESERVO
4
RS
-——--. :•_:..- . .
e
o %
* * * e „ c
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OZONE-RICH
AIR
FILTERED
WATER
Figure 39. Choisy-1e-Roi (Paris, France) water treatment plant ozonation chamber detail ,
-------
UNOZONATED
WATER
CONTACT
CHAMBER
OFF-GAS
ro
o
OZONE-RICH
AIR
FLOW METER (TYPICAL)
VALVE (TYPICAL)
Figure kO. Two-compartment ozone contactor.
-------
only 10 to 20% of the ozone feed, the technique effectively "recycles"
the off-gases from the primary (lower contactor). Off-gases from the
upper contactor at Kreuzlingen, which contain very small amounts of
residual ozone, are discharged to the ambient atmosphere. Alternatively,
they may be passed through an ozone destruction unit before discharge.
I
"RECYCLED" OFF-GAS
UNOZONATED
WATER
OZONATED
WATER
OZONE
GENERATOR
PRESSURE REGULATED POROUS UNIT
ALLOWS TRAPPED 03 TO ESCAPE TO
RAW WATER INFLUENT
PRESSURIZED
OZONE-RICH GAS
Figure kI. Two-level ozone contactor .
Turbine contactors are used in ozone disinfection applications but
appear more frequently in ozone recycle systems or in processes where
the primary purpose is destruction of waste ozone, at the same time
accomplishing useful work (lowering ozone demand of the influent water,
or assisting flocculation). Figure 42 illustrates two similar applications
for Paris (Neuilly-sur-Marne) and Montreal, Quebec, Canada plants in
which off-gases from the last porous tube contactor chamber are recycled
to a preozonation chamber of the contactor.
Ozone-containing gas from the generators is fed to the porous tube
contactors in different quantities (since once-ozonated water requires
less ozone to main required residual). Ozone in the off-gas from these
chambers is effectively "destroyed" by passing it into the influent
water (which has the highest ozone demand).
121
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AIR FILTER
HEAT
EXCHANGER
INLET
COMPRESSOR
r-Oi
OZONATOR
REFRIGERATION
UNIT
SUPPLY
TRANSFORMER
FREQUENCY HIGH'TENSION
MODULATOR TRANSFORMER
DESTRUCTION
FURNACE
RECIRCULATION
BLOWER AND
TURBINE
FIRST
OZONE DOSE
(HIGHEST)
SECOND
OZONE DOSE
(LOW)
THIRD
OZONE DOSE
(LOWEST)
IF NEEDED
Figure 42. Porous tube contact chamber (Paris and Montreal)
In the MUlheim (Figure 43), Rouen (Figure 44) and Langenau plants the
ozone contactor off -gases are recompressed and recycled to a turbine ozone
contactor in the influent to the plant. At Wuppertal, off-gases are fed to
the influent plant water at the aeration step.
Packed Bed Contactor—
The packed bed or column is another means of promoting intimate
contact between the water and ozone-rich gas. Water flows downward,
countercurrently through ozone-containing gas through ceramic Raschig rings.
Two examples of this are Duisburg (Figure 26) and Sipplinger Berg,
Germany (FRG).
122
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RECYCLE
OZONE
^
FLOW
PREOZONATION
CHAMBER
OZONATION CHAMBER
Figure ^3- Dohne plant, Mulheim, Federal Republic of Germany.
Spray Nozzle Contactor--
The use of spray nozzles through which water to be treated is sprayed
into a pressurized, ozone-rich atmosphere was observed at the Wuppertal
plant, Benrath, Federal Republic of Germany. This application is used for
iron and manganese oxidation, oxidation of organics and conditioning of
granular activated carbon for biological removal of ammonia in a single
contacting vessel. Figure 45 illustrates the contactor configuration.
123
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COMPRESSOR
FLOW
ro
PREOZONATION
CHAMBER
OZONE
GENERATORS
OZONE CHAMBER
Figure
The ozonation system at the la Chapel le plant-Rouen, France.
-------
OZONE-RICH
AIR
\I/W\
* SPRAY , ,
\ !//"\\\ '
/'/ \\,i
OZONATED
WATER
Figure 45 Liquid dispersion into ozone-rich gas.
OFF-GAS TREATMENT (OZONE DESTRUCTION)
Safety considerations require that efforts be made to reduce the ozone
levels of contactor off-gases to 0.1 mg/1 or less before discharge to the
atmosphere. Methods of reducing ozone levels include the following:
• Dilution either by natural wind patterns in the areas of the
treatment plant or by the provision of a blower which is designed
to dilute the off-gas stream with air by either 10:1 or 20:1
ratios.
• Dry, granular activated carbon has been used for destruction of
off-gases. However, there are reports of explosion problems with
this form of ozone destruction, especially if the carbon is not
kept wet. This method is in use at several plants visited, but
should be approached cautiously, if at all.
a Wet, granular activated carbon is frequently effective. Examples
of this type of installation include the Holthausen, Flehe, and Am
Staad plants at DUsseldorf and Konstanz, Federal Republic of
Germany. The effective life of the carbon beds is indicated to be
approximately six months, although Konstanz used one charge of
carbon for more than two years for this purpose.
125
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0 Thermal destruction of ozone contactor off-gas is commonly practiced.
Ozone breaks down rapidly at temperatures in excess of 200°C. The
applications of this concept appear to be satisfactory, but there
are complaints about the fuel cost associated with raising the
off-gases to the required temperature. A novel application of
thermal ozone destruction was observed at the Clairfont plant in
Toulouse, France where the exhaust pipes from the plant's diesel-
driven electric generators supply the heat required for the ozone
destruction. Contactor off-gases are sent directly to the diesel
engine exhaust stacks.
• Several plants, including those of DUsseldorf, were making plans
to convert to catalytic ozone destruction units. Plant operators
expressed concern regarding the capital and operation cost of
these units. However, the projected two year life of the catalyst
in such units and the lower operating temperatures said to be
required apparently justifies the initial investment. The proprie-
tary nature of the catalysts supplied precludes further description
of the material.
t Recycling of contactor off-gases to points in the water treatment
system having a high ozone demand is another means of off-gas
treatment. Advantage frequently is taken of this recycling for
other treatment applications of ozone within the water treatment
system. This concept was observed at several plants, such as the
la Chapelle Plant of Rouen, France, and the MUlheim, Langenau and
Wuppertal plants of the Federal Republic of Germany. On.the other
hand, contactor off-gases are recycled to the first compartment of
the disinfection units at the following plants: Tailfer (Belgium),
Neuilly-sur-Marne, Annet-sur-Marne (France) and Montreal (Canada).
The following four methods of recycling contactor off-gases were
observed:
• Off-gas pressurization, submerged turbine diffusion in first
compartment of disinfection contactor - Annet-sur-Marne, Neuilly-
sur-Marne, Montreal (Figure 40).
• Off-gas pressurization, submerged turbine diffusion/flash mixing
upstream of chemical clarification - Dohne, (MUlheim), Rouen-la-
Chapelle (Figures 43 and 44).
• Vacuum induction, turbine mixing upstream of chemical clarification -
Langenau.
• Inductive turbine recycling to first compartment of disinfection
contactor - Tailfer (Brussels).
• Diffusion to plant influent tower - Wuppertal.
126
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Provision is made for further treatment (destruction) of the recycled
off-gas in some of the plants. In others, these gases are simply dis-
charged.
The reuse of contactor off-gases is applicable when these gases
contain quantities of ozone of 5 to 10% of that originally generated for
the primary application. However, it should be realized that although
reinjection will further reduce the concentration of ozone, the off-
gases from this secondary contacting still contain ozone, and in amounts
such that destruction or dilution should be considered before discharge
to the atmosphere.
On the other hand, when the contactor off-gases contain smaller
quantities of ozone (less than 5% of the original concentration) it may
be more cost-effective to destroy or dilute and discharge these gases
and utilize fresh ozone at a much higher concentration, for a second
application.
CONTACTOR DESIGN CONSIDERATIONS
Process applications of ozone frequently will determine the type of
contactor to be used. However, other factors such as flexibility, site
constraints and plant size also must be considered. It is good practice
to provide more than one contactor for many reasons, including maintenance.
However, the question arises, how many contactors should be provided? A
large number of contactors would result in flow distribution problems as
well as high construction costs. It is understood that many of the
Swiss plants are designed to operate on a multiple train basis. An
ozonation train (ozone generator and contactor) is associated with a
single raw water pump. If a second raw water pump were to be brought
into operation, a second ozonation train would become operational as
well. This independent train concept is likely to. be inappropriate for
larger plants where higher degrees of interdependence are economically
justified.
The contactor configuration relates to the contactor selection and
the layout of the overall facility. Economics dictate that common wall
construction be used wherever possible. A depth of five meters is
common to many porous diffuser contactor installations and is considered
to be the minimum depth necessary to provide maximum mass transfer from
porous diffusers. On the other hand, the effective water depth in
vacuum injectors such as the three DUsseldorf water treatment plants and
the Quebec City plant is ten meters. The inductive turbines are installed
at water depths of 4 and 5 meters at Tailfer (Belgium) while those at
Lengg (Switzerland) are at 3 meters water depth.
Measurement and control of the ozonized gas at each point of ozone
application is necessary. Economics dictate that the ozone supplied not
exceed the ozone required by more than the specified amount despite
variable ozone demands due to flow rate changes and water quality varia-
tions. For example, a two compartment, countercurrent porous diffuser
contactor used for disinfection should provide for ozonized gas flow
127
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measurement and control to each compartment. A means of measuring
residual ozone levels should be provided at the discharge from both the
first and second compartments. If virus inactivation is to be practiced,
sufficient ozone should be supplied to satisfy the initial ozone demand
and to enable a residual ozone level of 0.4 mg/1 to be maintained in the
second compartment. While this frequently means that two-thirds of the
overall ozone dosage is added to the first compartment and one-third is
added to the second compartment, there is no assurance that this situation
will exist over the four seasons of a year or over the operational life
of the facility. Ozonized gas measuring devices such as rotameters
should be provided, as well as diaphragm or butterfly valves, and all should
be fabricated from appropriate construction materials.
Access to the interior of the contactor should be provided through
gasketed, low pressure hatchways. A method for dewatering the structures
is required. The question of being able to observe the gas bubble
pattern within the contactor appears to be one of process application
and the desires of the operating agency.
The viewing ports of contactors used for iron and manganese oxidation
appear to be generally useless, since they quickly become coated with
opaque films of metal hydroxides. However, viewports on porous diffuser
contactors appear to provide valuable visual access for the determination
of diffuser deficiencies and the need for repairs or adjustments.
CONTROL AND INSTRUMENTATION
The degree of control incorporated into ozonation systems may be
simple or sophisticated and may be localized or centralized. The trend
in France and Switzerland appears to be toward highly sophisticated and
centralized control, extreme examples being the small, remotely operated
Kreuzlingen plant (Switzerland) and the large Neuilly-sur-Marne plant in
France. At Kreuzlingen, the single plant operator merely checks plant
equipment daily and prepares analytical solutions. His residence is
alongside the plant, and he is immediately available in case of trouble,
in which event alarms are signalled to his residence.
At the large Neuilly-sur-Marne plant, the ozonation system is
highly automated, and there are only two operators for this section of
the plant. They are present on a three-shift/day basis, and are trained
in handling and maintaining automation equipment.
In contrast to this are the water treatment plants of the Federal
Republic of Germany and the Province of Quebec, where higher degrees of
local control and monitoring are practiced to ensure that the system is
physically inspected.
Table 8 is a translation and summary of the ozone system record
sheet used by the City of Pierrefonds (Quebec) water treatment plant to
record data from their daily operations.
128
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TABLE 8. CITY OF PIERREFONDS (QUEBEC) WATER TREATMENT PLANT
OZONE SYSTEM DATA RECORDED
REFRIGERANT COOLER
Units in operation
Air discharge temperature (°C)
Refrigerant flow indication
DESICCANT DRIER
Jnits in operation
Inversion air pressure
Regeneration temperature (°C)
Pressure loss across the filter
Gas discharge pressure (kg/sq cm)
OZONE GENERATOR
Units in operation
Inlet air temperature
Inlet air flow rate (cu m/hr)
Cooling water flow rate (cu m/hr)
Cooling water inlet temperature (°C)
Cooling water discharge temperature (°C)
Discharge cooling water pressure (bar)
Inlet air dew point (°C)
Voltage (volts)
Amperage (amperes)
Power (KWAC)
Power level selector
COOLING WATER
Pressure of ozonation, cooling
water, and pressure at the
cooling water inlet
COMPRESSORS
Units in operation
Discharge pressure (kg/sq cm)
Air discharge temperature (°C)
Pressure loss across the filter
WATER COOLED HEAT EXCHANGER
Air discharge temperature (°C)
OZONE CONTACTOR
Ozone residual, column 1
Ozone residual, column 2
GENERAL INFORMATION
Ambient ozone level
Plant water flow (cu m/hr)
While other ozonation systems may suggest other data to measure and
record, Table 8 indicates the amount of information regarded as necessary
to control this operational facility. These data may be obtained by
remotely reporting sensors; however, in the case of Pierrefonds, personnel
take direct readings of the sensing devices, thereby performing visual
inspections of the system for process control and for detection of
potential operational problems.
A number of parameters must be measured to provide a fully operable
system; these include the following:
129
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• There must be a means of providing a full temperature and pressure
profile of the ozone generator feed-gas from the initial pressuri-
zation (by fan, blower, or compressor) to the ozone generator
inlet. These measurements should be taken regularly, either in
the form of simple mercury thermometers and pressure gauges or by
more sophisticated sensors.
• There must be a means of measuring the moisture content of the
feed-gas to the ozone generator. This procedure should be conducted
with a continuously monitoring dew point meter or hygrometer.
Without this device, the operation is unable to prevent ozone
generator maintenance problems which arise from the use of uncertain
feed-gas quality. Most dew point monitors and hygrometers were
provided as direct reading instruments. However, it was understood
that ozonation systems such as those installed at Quebec City and
Kreuzlinger incorporate a lithium chloride sensing device which
senses a high moisture content and sounds an alarm. It would
appear that a direct reading instrument would be a more appropriate
operational tool. Since either the dewpoint monitor or hygrometer
are relatively expensive instruments, they must be specified or
they would not be supplied on a competitive, low bid equipment
supply basis.
• There must be a means of measuring the temperature, pressure,
flow, and ozone concentration of the ozone-containing gas being
discharged from an individual ozone generator and from the combined
discharge from all the ozone generators. This is the only effective
method by which ozone dosage and the ozone production capacity of
the ozone generator can be determined. In view of the increasing
reliability of gas phase ozone analyzers it should be possible to
have continuous and accurate measurement of these parameters.
At the very minimum, there should be frequent manual determination
of these parameters.
i There must be a means of measuring the electrical power supply to
the ozone generators. The parameters measured include amperage,
voltage, power, and, if a controllable variable, frequency.
i There must be a means of measuring the flow and temperature of
the cooling water to all water-cooled ozone generators. Reliable
cooling is important to maintain constant ozone production and to
protect the dielectrics. A drop in the rate of cooling water
flow through the unit (or an excessive cooling water temperature)
should be required to cause an automatic shut-down of the ozone
generation system.
» There must be a means to monitor the several cycles of the
desiccant drier, particularly the thermal swing unit. The plant
130
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superintendent of the Quebec City, Quebec water treatment plant
found it necessary to add a high temperature shut-down switch on
the discharge line from the heat regeneration system. This was
to prevent the recurrence of a condition in which an excessively
high regeneration temperature occurred with a resultant fire and
desiccant destruction.
Figure 46 illustrates the required measurements for ozone generator
operation. Ozonation control requires the measurement of ozone concentrations
in:
t The ozone-rich gas from the ozone generator,
• The water after ozonation,
§ The gas from the contactor, and,
• The ambient air in the rooms of the treatment plant using ozone,
and possibly in the ambient atmosphere outside the treatment
plant.
Means of ozone measurement include the following:
• Simple "sniff" test
• Dra"ger type detector tube
• Wet chemistry potassium iodide method
• Amperometric type instruments
• Gas phase chemiluminescence
• Ultraviolet radiation (254.7 nm) absorption
The smaller and older water treatment plants employ the more simple
methods of ozone measurement. However, more sophisticated methods of ozone
measurement are being incorporated into larger, newer plants as operational
personnel become more confident of the accuracy and reliability of such
methods.
The "sniff" test makes use of the fact that a worker is able to
detect the odor of ozone at a concentration level of approximately 0.01
mg/1. This test is used for safety control in ozone hazard areas. This
level of control is also used by the DUsseldorf pi ants.to control the ozone
dosage. The off-gas from the holding tank after ozonation is "sniff"
tested to ensure that a trace of ozone remains in the off-gas. If no ozone
can be detected, the generator output is increased.
131
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FLOW,
CONCENTRATION,
TEMPERATURE,
PRESSURE
VOLTAGE,
AMPERAGE,
WATTAGE
TRANSFORMER
OZONE OUT-
TEMPERATURE,
FLOW SENSING,
FLOW MEASUREMENT,
PRESSURE
AIR OR
OXYGEN IN
WATER
IN
LEGEND: A. COOLING WATER;
B. STAINLESS STEEL TUBE;'
C. DISCHARGE GAP;
D. GLASS TUBE.
DEW POINT,
TEMPERATURE,
PRESSURE
Figure 46. Tube type ozone generator- required measurements.
The Draper type detector tube test utilizes portable equipment by
which a specified volume of gas is drawn through a tube containing absorbing
media. The absorbing media reacts immediately with the ozone in the gas
and a constant colored stain is produced which varies in length according
to the ozone concentration being measured. A calibration scale on the
exterior of the tube enables direct reading of the ozone level in the gas.
Literature indicates that ozone concentrations as low as 0.05 mg/1 to as
high as 300 mg/1 by volume51*'55 can be measured by proper selection of
detector tubes and volume of gas passed through the absorbent media.
The wet chemistry, potassium iodide (KI) method is the classical
method for measuring ozone both in the gaseous phase and dissolved in
water. The reation involves the oxidation of iodide ion to iodine in water
as shown by the following equation:
03 + 21
H0
02 + 2(OH)
132
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Starch is added as an indicator and the solution is titrated with sodium
thiosulfate. The volume of thiosulfate consumed can be converted into an
ozone value.
The KI procedure may be used as a day to day method of measuring ozone
concentrations or as a means of calibrating instruments. The 14th Edition
of Standard Methods for the Examination of Water & Wastewaters recommends the
iodide method as the calibration standard for ozone instrumentation and
provides a detailed description on how the test is to be performed for ozone
in the gaseous form and dissolved in water.
It should be noted that in using the KI analytical method to determine
the concentration of ozone in water, any oxidant present in solution that
is capable of oxidizing iodide ion to iodine also will show up as "ozone".
Thus, the KI procedure really measures total oxidants present. Examples of
other oxidants that will be measured by this method are chlorine, chlorine
dioxide, hydrogen peroxide, potassium permanganate, etc. At the Choisy-le-
Roi (Paris) plant where chlorine dioxide is used in pretreatment to decompose
organic complexes of iron and manganese and the subsequent ozonation
process is controlled by monitoring an ozone residual of 0.4 mg/1, sodium
bisulfite is added to destroy the excess chlorine dioxide before ozonation,
so as not to produce a false "ozone residual" measurement.
Amperometric type instruments are familiar to the U.S. water treatment
industry because of their common use to measure residual chlorine levels.
This type of instrument utilizes a flow-through measurement (Jell containing
two dissimilar metal electrodes. As the water sample flows past the elec-
trodes, a current is generated which is proportional to ozone concentration
in the water. The metals frequently used for electrodes in this instrument
when measuring ozone are gold and copper. One requirement in the proper
operation of such units is keeping the electrodes clean. Units of this
type which have a successful record of application in closed loop control
of ozonation are the Amperazur (Degremont), Chlorosis and Degox instruments.
Gas phase chemiluminescence is used to measure ozone concentration in
gases. The range is from 3.9 yg ozone/mV (0.002 mg/1) to more than 1962 ug
ozone/mV (1 mg/1)56. Commercial gas phase chemiluminescence equipment is
readily available.
Absorption of ultraviolet light radiation is a method which can be
applied to measure ozone concentrations in both gas and water phases. In
ambient air containing ozone, ozone is the only component that absorbs
ultraviolet light in the 240 to 300 nm wave length range. The wave length
used in these types of analyzers is 254.7 nm. The Dasibi ultraviolet ozone
monitor for ambient air monitoring is used successfully at the Pierrefonds,
Quebec water treatment plant and at the Union Carbide ozone generator test
facility at Tonawanda, New York. The Si grist single and double-beam
spectrophotometric instruments measure ozone dissolved in water by the
ultraviolet technique.
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The use of control systems based on the measurements described above
varies considerably in the water treatment plants that were inspected. The
French plants using ozonation primarily for disinfection incorporate a
closed loop control system by which the residual ozone level in the ozonized
water is used to control the amount of ozone supplied to maintain that
ozone residual. The key to successful operation of such a system is an
accurate and reliable residual ozone analyzer. On the other hand, the
older German ozonation systems which are used primarily for oxidation are
manually controlled through a periodic "sniff" test of off-gas from the
holding tanks after ozonation (ozone is used for iron, manganese and organics
oxidation, and conditioning of biological activated carbon).
At present, it appears that continuous residual ozone monitoring
equipment may be successfully applied to water that has already received a
high level of treatment, as in the most common French application of ozone
(disinfection and viral inactivation). However, a more cautious approach
must be taken with the application of continuous residual ozone monitoring
equipment for water that has received only chemical clarification. Continuous
monitoring of ozone concentrations in gas phases appears to be reliable.
•**
The Ozone Working Group of the German FIGAWA (Technischen Vereiningung
der Firmen im Gas und Wasserfach eV) organization currently is evaluating
methods for monitoring ozone concentrations in gas and in water. FIGAWA,
which is roughly equivalent to the U.S. WWEMA organization (Water and
Wastewater Equipment Manufacturers Association), already has published
three "Technical Information" documents on various aspects of ozone technology
which are included in this report as Appendix C. The FIGAWA Ozone Working
Group reports on Ozone Analysis and Ozone Monitoring Equipment are expected
to be published in 1978.
Various levels of controlling ozone generation are described below.
Ozone production rates should be changed as water quality changes for
several reasons. First, since excess ozone cannot be stored, power is
wasted in generating excesses. Secondly, excess ozone must be destroyed
before discharging, and this also requires energy. On the other hand, when
water quality decreases, additional ozone is required immediately, since
under-ozonation of certain organic contaminants present can produce partially
oxidized intermediates which can, under certain circumstances, be more
toxic than the initial materials (See Section 12, Oxidation Products of
Organic Materials).
Manual Operation - Manual Sampling
The change in water characteristics brought about by ozonation is
determined by visual inspection or chemical procedures. The required ozone
production rate is controlled by manually changing either the voltage or
the frequency of the electrical power supply.
134
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f
f
1
J
I
\ VMM VULIHbC./
" ' I
-^ h
)
I/
OZONE
1ENERATOR
r rtc.y.utN
1,1 riMIMUMUUI
OZONE CONTACTOR
r
Or* *^ **\
-------
VARY VOLTAGE/FREQUENCY AUTOMATICALLY
TO 20 MA SIGNAL
MONITOR
OZONE
GENERATOR
OZONE CONTACTOR
Closed Loop Control of Voltage/Frequency and Air Flow - Automatic Sampling
This system is fully automatic and is designed to operate at peak
electrical efficiency with ozone-containing gas concentration controlled
for optimum dissolution. Many system parameters are monitored and a pre-
programmed controller adjusts both gas flow and the voltage or the frequency.40
1
II
AIR
FLOW
T
AIR
PREPARATION
L.
03
CONCENTRATION
1
H
OZONE
CONTACTOR
GENERATOR
136
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Full Computer Control - Automatic Sampling
The computer receives the same information as just above, and more
from the control ozonation system, including diagnostics, pre-failure shut-
downs, optimum energy balance, etc.1*0
COMPUTER
OUTGOING COMMANDS
J INCOMING INFORMATION
OCCUPATIONAL SAFETY
Ambient Air Quality
The plants visited varied in their approach to ozone safety. The
ozone generator rooms of most facilities opened off control rooms, galleries
or heavily used hallways. The ozonation processes of the Tailfer
(Brussels, Belgium) and Neuilly-sur-Marne (Paris, France) plants are housed
in structures separate from the remainder of the plant. However, it appears
that the size of the ozonation facility dictated the separate structures
rather than an intent to isolate the ozonation facility. In other plants,
such as Lengg in Zurich and Annet-sur-Marne near Paris, the ozone generation
facilities are placed in the heart of the treatment facilities. In general,
while the European plants pay an extremely high degree of attention to
safety with respect to chlorine storage and application, a far lower degree
of concern appears to be paid to ozonation facilities.
A great deal of reliance appears to be placed in man's ability to
detect the odor of ozone at levels far below the critical exposure level of
0.1 mg/1 (by volume). Exceptions to this were the Tailfer plant of Brussels,
Belgium and many plants in the Federal Republic of Germany. The Tailfer
plant maintains negative pressure in the ozone generator room and the room
over the ozone contactors. Continuous monitoring instruments are maintained
to monitor levels of ozone in the rooms. Self-contained breathing apparatuses
are located in hallways outside the rooms liable to ozone hazards. Many
German (FRG) plants provide emergency high rate ventilation of ozone generator
rooms as well as maintain self-contained breathing apparatuses. It was
understood that it is standard practice to design ozonation systems to
137
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operate under negative pressure. Continuous monitoring instruments were
observed in the ozonation rooms of the Pierrefonds, Quebec plant.
Ambient ozone exposure levels which have been proposed by appropriate
U.S. organizations have been summarized in a recent paper.1*5 The maximum
recommended ozone levels are as follows:
• Occupational Safety and Health Administration (OSHA):
Maximum permissible exposure to airborne concentrations of ozone
not in excess of 0.1 mg/1 (by volume) averaged over an eight hour
work shift.
t American National Standards Institute/American Society for
Testing and Materials (ANSI/ASTM):
Control occupational exposure such that worker will not be
exposed to ozone concentrations in excess of a time weighted
average of 0.1 mg/1 (by volume) for eight hours or more per
workday, and that no worker be exposed to a ceiling concentration
of ozone in excess of 0.3 mg/1 (by volume) for more than ten
minutes.
• American Conference of Government Industrial Hygienists (ACGIH):
Maximum ozone level of 0.1 mg/1 (by volume) for a normal eight
hour work day or 40 hour work week, and a maximum concentration
of 0.3 mg/1 (by volume) for exposure of up to 15 minutes.
• American Industrial Hygiene Association:
Maximum concentration for eight hour exposure of 0.1 mg/1 (by
volume).
Concern for safety, even at the risk of being overcautious, would be
to follow practice that has been successfully applied to other oxidants
over the years. This would be to generally isolate the ozonation system
from the remainder of the plant. This should not be interpreted to mean a
separate building but rather separate rooms, separate exterior entrances,
separate heating and ventilation systems, noise control, etc. This method
already is manifested in some of the European ozonation plants, but on a
lesser scale.
There is a question whether prolonged exposure to ozone may impair a
worker's ability to smell or be aware of ozone levels at less than critical
levels.lt5 Awareness of an odor of ozone should not be relied upon. Instru-
mentation and equipment should be provided to measure ambient ozone levels
and perform the following safety functions:
• Initiate an alarm signal at an ambient ozone level of 0.1 mg/1
(by volume). Alarms should include warning lights in the main
138
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control panel and at entrances to the ozonation facilities as
well as audible alarms.
• Initiate a second alarm signal at ambient ozone levels of 0.3
mg/1 (by volume). This signal would immediately shut down ozone
generation equipment and would initiate a second set of visual
and audible alarms at the control panel and at the ozone generation
facility entrances. An emergency ventilation system capable of
exhausting the room within a period of 2 to 3 minutes also would
be interconnected to the 0.3 mg/1 ozone level alarm.
Self-contained breathing apparatuses would be permanently stored at
the entrance doors to the ozonation facilities. Controls for the high rate
room ventilation system also should be provided at the exterior of entrance
doors. Hand operated gas detector devices, such as the units of National
DrSger of Bendix/Gastec, consisting of a volumetric pump and direct reading
ozone detector tubes should be permanently stored in the vicinity of the
self-contained breathing apparatuses. Use of the Drflger tube apparatus was
demonstrated several times at Federal Republic of Germany water treatment
plants as part of their safety program.
NOISE CONTROL
The control of noise is of obvious concern for installations in the
United States. Noise from the water cooled ozone generation system (aside
from the air preparation system) is very low. Therefore, most attention is
paid to the air preparation system, particularly to those involving high
pressure compressors or medium pressure blowers.
The most common solution to the noise resulting from medium pressure,
positive displacement blowers, is isolation of the unit. These units
commonly are located in a separate room at the lowest level of the building
and air is brought to the intake filter by means of a vertical duct from
the roof. The walls, ceiling, and floor generally are made of plain concrete
having no special noise treatment properties.
There are special noise treatment rooms at the Donne, MUlheim (Germany)
and the Tailfer, Brussels (Belgium) plants. Perforated metal, false wall
attachments are used at the Donne plant while the Tailfer plant uses special
sound-proofed doors for the blower room.
Facilities using low pressure fans in advance of refrigerant cooler
and desiccant drier frequently were noisy. There seemed to be little
concern with this problem, although the ozone generators often were in the
same room. An example of a facility having this noise problem is the
Holthausen plant at DUsseldorf, Germany.
Close attention should be paid to noise control of these facilities.
Reference to current experience in the wastewater treatment field can
provide significant guidance. For example, careful selection of positive
139
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displacement blower rotational speed and tip speed will minimize problems
with this potentially noisy unit.
Isolation of noisy components of the system is a partial solution;
however, the use of special construction materials would further reduce the
problem and increase the value of preventive maintenance. The requirements
of the Occupational Safety and Health Administration offer sufficient
design guidance, provided the designer is aware of the major sources of
noise generation within the system.
SELECTION OF CONSTRUCTION MATERIALS
Considerable effort was made during the study to identify and evaluate
materials used in operational ozonation systems. Although special care
must be given to selection of materials in contact with "dry" and "wet"
ozonized gas, very little other concern in construction material selection
appears necessary.
The materials of construction used in the air preparation systems
appear to be those which are common to air preparation systems for other
applications. The piping material used throughout the air preparation
systems observed were common steel or galvanized steel of an appropriate
pressure rating. No special coatings of reinforced concrete ozone contact
structures were observed. Normal piping materials were used to convey the
ozonized waters from the contactors. Ozone concentrations of less than 5
mg/1 do not appear to pose threats to the normal cast iron or concrete
pipes used in such service. It does not appear that special coatings of
these types of piping, in this service, are necessary.
Selection of materials for surfaces in contact with "dry" or "wet"
ozonized gas requires care. Further information is required to enable
determination of the most cost-effective material. For example,, there is
considerable difference between the United States and European manufacturer's
choice of material for ozone generator fabrication. Problems have been
reported with the use of plastic piping systems in ozone service both in
the United States and Europe.
European ozone generator manufacturers appear to use 316 or 316L
stainless steel for those portions of the generator in contact with ozonized
gas. In contrast, United States manufacturers use 304, 304L and 321
stainless steel and aluminum. Table 9 provides information on the various
grades of stainless steel.
140
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TABLE 9
COMPARISON OF STAINLESS STEELS
DESCRIPTION
Chromium
Nickel
Carbon
Manganese
Silicon
Other Elements
RELATIVE
COST*
AISI STAINLESS STEEL GRADES
304 304L 316 31 6L 321
ANALYSIS (PERCENT)
18 to 20
8 to 12
0.08 max
2.00 max
1 . 00 max
1.00
18 to 20
8 to 12
0.03 max
2.00 max
1 .00 max
-
1.06
16 to 18
10 to 14
0.08 max
2.00 max
1.00 max
Mo 2 to 3
1.33
16 to 18
10 to 14
0.03 max
2.00 max
1.00 max
Mo 2 to 3
1.38
17 to 19
9 to 12
0.08
2.00 max
1.00 max
Ti=5x%C min
1.34
* Relative cost based on prices provided by Midwest stainless steel supplier
for 3/16" x 96" steel plate in 10,000 pound lots in January 1978.
Extra low carbon grades (304L and 316L) and the stabilized grade
(321) are used in welding applications. Tungsten Inert Gas (TIG) arc
welding is recommended. The relatively high cost of 316L stainless
steel may be one of the reasons that United States ozone generator
manufacturers prefer to use 304L and 321.
Selection of system piping material entails consideration of the
gas being conveyed and its pressure. The gas piping material commonly
used for the gas preparation system is carbon steel or galvanized steel
of an appropriate pressure rating. Stainless steel piping generally is
used for "dry" or "wet" ozonized gas service. As previously discussed,
European plants would use 316L stainless steel for welded piping systems
and 316 pipe for non-welded systems. On the other hand, United States
manufacturers would use 304L and 304 stainless steel piping for similar
applications. If a flanged piping system is used, Viton and silicone
rubber are appropriate gasket materials.
141
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The use of plastic pipe in ozonized gas service must be considered
with caution, as illustrated by problems in European applications and a
recent United States wastewater installation. Contacts with representatives
of the plastic pipe industry indicate that little if any research has been
expended on studies of the effect of ozone on plastic piping materials.
So-called "hard" or unplasticized polyvinyl chloride (UPVC) is the only
plastic piping material which is considered acceptable by those with experi-
ence in conveying ozone in plastic pipe. The authors have cautiously
interpreted this to mean materials as described under ASTM Designation
D1784-75 to be rigid poly(vinyl chloride) compounds, Class 12454-B. Class
12454-B is that material previously described as Type 1, Grade 1 under the
previous ASTM D1784-65T. Unplasticized PVC may include ASTM D1784-75 Class
12454-C (Type 1, Grade 2). Pipe designations for these two materials are
covered in ASTM Specification D1785-74 as PVC 1120 and PVC 1220, respectively.
Solvent welded joints should not be used. Only flanged couplings or
threaded couplings should be used. Viton or silicone rubber gaskets or
restrained Teflon gaskets should be used with flanged couplings. Threaded
couplings should be prepared on schedule 80 or 120 pipe with a sharp, clean
threading machine. Teflon tape should be used to wrap the threads. Ozone
has been found to embrittle PVC pipe and to destroy the beam strength of
this material. "Hard" PVC pipe was observed to provide satisfactory service
under negative pressure ozonized gas applications. It was observed at only
one positive pressure ozonized gas application, Langenau, Federal Republic
of Germany.
Plastic pipe technical personnel have suggested the consideration of
polyethylene (PE) plastic pipe as covered by ASTM specification D2239-74.
The recommendation would be for pipe material described as PE 2306, 3306,
3406. This pipe material is fusion welded. Another suggestion is for a
newly marketed piping system using FRP (Fiberglass Reinforced Plastic)
lined with Teflon. The caution must be added that there is no known
published information on ozone testing or application of these materials.
"Wet", pressurized, ozone-rich gas from the contactors would be
expected to require the highest quality material, such as 316L stainless
steel. However, it has been stated that the blowers used to repressurize
the contactor off-gases from the Rouen-la-Chapelle plant in France and the
Montreal, Quebec, Canada plant are constructed of aluminum. Selection of
aluminum for the blowers has been explained on the basis that the ozone
concentrations in the contactor off-gas are very low.
Another word of caution must be added; these comments should not be
extended to include systems using oxygen-rich gases such as high purity
oxygen. Time constraints precluded a detailed evaluation of materials used
in construction of the Duisburg, Federal Republic of Germany plant. It is
well recognized that special attention must be taken in the design of
systems handling high-purity oxygen.
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OPERATION AND MAINTENANCE
The cost of operating and maintaining an ozonation system is of
obvious concern to those evaluating the total cost of applying ozone as
part of a water treatment facility. These costs may be assigned to the
four components of the ozonation system (i.e., air preparation, electrical
power supply, ozone generator, and ozone contactor).
Operation and maintenance of the air preparation subunit generally is
predictable in terms of difficulty and cost. The frequency with which the
filter medium is changed is a function of the ambient air quality. How-
ever, the inspected plants indicated that filter media cleaning or replace-
ment initially should be scheduled twice per year. The power cost and
maintenance requirements of the gas compresser and refrigerant units (such
as oil changes) can be derived from manufacturers' literature. There are
reportedly few operational problems with these units. Experience indicates
a minimum absorber media life in excess of ten years for the desiccant
driers. The energy costs to regenerate the desiccants depend upon the
moisture loadings on the unit, but 16 hours is a reasonable estimate for an
exhaustion-regeneration cycle. The desiccant should be checked regularly
as should the regeneration cycle controls.
The operation and maintenance of the electrical power supply subunit
is difficult to estimate since there is little available information.
Apparently few (or no) problems have been experienced with this subsystem.
Guidance may be taken from industrial experience with auto transformers.
Transformer dielectrics and casings should be checked regularly.
Two factors that affect operation and maintenance of the ozone generators
observed include the effectiveness of the air preparation system and the
period at which the ozone generator is required to operate at maximum
capacity. Maintenance of the ozone generators commonly is scheduled once
per year, or twice a year in some plants. Approximately one man-day is
necessary to service a 240 tube unit. Dielectric replacement due to failure
as well as breakage during maintenance may be as low as 1 to 2%. However,
it appears reasonable to predict an average tube life of ten years if a
feed gas dew point of minus 60°C is maintained and if the ozone generator
is not required to operate for prolonged periods at its rated capacity. An
exception to this generalization is the major ozonation system of the
Tailfer water treatment plant that serves Brussels, Belgium. The Tailfer
plant currently maintains its ozone generators every six months and replaces
the ozone generator tubes every two years, due to the deterioration of
glass dielectric subjected constantly to high voltages.
The ozone generator production efficiency should be checked frequently
in terms of ozone output per kilowatt hour of electrical energy input.
Operation and maintenance of the contactor also must be considered.
Turbine diffusers require electricity to power the drive motors, while
porous diffusers require regular inspection and maintenance to ensure a
uniform distribution of ozone-rich gas in the contact chambers. Experience
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with maintenance of the ozone contact chambers in the Morsang plant (France)
indicates that even after air purging of the contact chambers, maintenance
personnel entering the chambers should be equipped with self-contained
breathing apparatuses, because of the presence of ozone.
The following maintenance schedule is based on operational experience
in Quebec City (Canada):
Monitor or measure major operating parameters including the following:
- Temperatures
- Pressures
- Dew points
- Production rates (Ibs/KW)
Every Six Months
- Check oil level in compressors
- Check desiccant unit switchovers
- Check transformers
Every Year
- Complete overhaul of system
- Change parts where required
- Clean ozone generator thoroughly
Several of the inspected plants maintain a service contract with the
ozonation system supplier for regular maintenance of the system. Both the
Annet-sur-Marne plant near Paris and the Lengg plant in Zurich use this
method to provide the expertise to.maintain the various components of the
system. Trailigaz suggests this approach to their customers, especially
those new to the operation of ozonation systems.
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SECTION 9
COSTS OF OZONATION
INTRODUCTION
No assessment of a given technology is complete without a review of
its capital and operating costs. These costs are important both in terms
of total magnitude and in terms of their relationship to each other. In
the case of equipment or engineered systems for municipal use, the tradeoff
between capital and operating costs, along with total cost magnitude, is of
principal interest to both the municipal government and its consulting
engineers. Thus, a principal objective of this investigation was to gather
and document cost data for ozonation systems.
There is very little U.S. experience in ozonation systems; thus, the
data presented herein are drawn largely from European and Canadian experiences.
Further, the information presented in this section is not an in-depth
economic analysis based on a rigorous analysis of a large data base.
Rather, this section is a report on the content of various conversations
and inquiries of knowledgeable and respected persons and firms in the ozone
technology field. Most of the cost information contained herein was obtained
from European and U.S. equipment manufacturers, European water treatment
plant personnel, European research institute officials, and European and
Canadian equipment suppliers.
Since most of the data presented were obtained from European operating
experiences, the use of these data without defining precise conditions
could lead to inaccurate conclusions. Costs vary greatly from country to
country. Economic conditions within a country vary, personnel costs differ,
and the price of energy is not constant. Moreover the cost of materials of
construction may vary. With regard to capital investments, amortization
periods are rarely the same and depreciation and interest data are difficult
to obtain.
Ozone can be used for many purposes as evidenced by the multiple
applications in Europe. Ozone cost data presented should not be viewed as
the "cost of a disinfectant". In fact, ozone can be applied in such a way
as to aid in microflocculation of previously coagulated water, improve
organics removal, bacterial disinfection and viral inactivation. These
beneficial side effects can be achieved as part of the disinfection and
oxidation process and thus allow the designer to "spread" the cost of the
ozonation system over other functions besides disinfection/oxidation.
Ozonation was also found to be highly beneficial to the operation of activated
145
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carbon facilities (Section 13), another advantageous side effect. Thus, in
evaluating the capital and operating costs of ozonation relative to the
entire plant process, it may be misleading to consider it only as a disinfec-
tant/oxidant.
CAPITAL COSTS
Capital costs* of an ozonation system generally include the costs of
ozone generators, air preparation equipment, associated instrumentation,
costs of needed ancillary facilities including the contactors, housing and
power supplies, and installation. During the course of this investigation,
the following key variables were identified as the principal determinants
of installed system cost:
• Raw Water Quality and Ozone Requirements
0 System Size and Cost of Housing
• Cost of On-Site Power
• ' Energy Demand of System Components
• Degree of Automation
These are discussed in turn below, followed by several illustrative case
histories.
RAW WATER QUALITY AND OZONE REQUIREMENTS
Sizing of ozonation systems is critical, both from the standpoint of
cost and process performance. For this reason, the common practice in
Europe is to conduct pilot studies of 18 to 36 months in duration. Through
the pilot studies, in which ozone is tested in conjunction with other unit
treatment processes, the capacity required for accomplishing the desired
objective can be determined. The duration of the pilot study allows evalua-
tion of variations in temperature and water quality over several seasons.
The pilot plant approach is well suited to the common European practice of
turnkey construction and/or private ownership of water treatment plants.
In the U.S. and Canada, the more common practice is separate design and
purchase of equipment and facilities through competitive bidding. Thus, it
is incumbent upon the municipality and its consulting engineers to conduct
pilot studies.
* Capital costs typically are defined as equipment depreciation plus
interest. Amortization of capital investment (the European terminology)
is the terminology used throughout this section. Amortization (in
European terminology) is the same as depreciation plus interest (North
American terminology).
146
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For smaller systems where pilot studies may be too costly, a more
limited approach to ozone demand determination has been reported recently.
Legeron57 has defined a method whereby the ozone demand of a raw water
supply can be closely estimated in the laboratory. The method was compared
with actual operating plant experiences and found to be approximately
equivalent, except where processing included physical-chemical treatment.
In these cases, the procedure greatly over-predicted the amounts of ozone
required. A full pilot plant study would be needed in this case.
The yearly average ambient air temperature, the peak temperature
and water temperature are key factors in providing refrigeration and
desiccation equipment. The air fed to an ozonator must be cooled and
dried. The less it must be cooled, the lesser the capacity of refrigerant
equipment that must be provided. In the case of water temperature, the
colder the water is initially, the less expense that must be incurred for
cooling. Most tube type generators are water cooled. If, as in the case
of the Lake of Constance in southern Germany, the water temperature is a
constant 4° to 6°C, very little refrigeration is ever required. In a much
warmer climate, refrigeration equipment must accomplish much more work
and thus must be designed and sized accordingly.
Thus the design engineer should work to: 1) define the application
for which ozone is intended; 2) look at the ozone application in the context
of the other unit processes; and 3) determine present and future ozone
demands by analyzing raw water supply and providing standby capacity. As
many manufacturers of ozonation equipment are well versed in its application,
the designer should gather information from this source also.
SYSTEM SIZE
The capital costs of ozonation systems demonstrate significant economics
of scale (decreasing unit cost versus output). The equipment is quite
costly in small sizes, less so in larger sizes. System costs in various
size ranges are given in this section. These general costs were obtained
through conversations with equipment suppliers and manufacturers, both in
North America and Europe.
Ozonation systems normally are considered to be in one of four size
ranges: laboratory units (less than 0.9 kg/day, 2 Ibs/day); very small
units (0.9 to 45 kg/day, 100 Ibs/day); medium size units (45 to 225 kg/day,
100 to 500 Ibs/day); and large systems (greater than 225 kg/day, 500 Ibs/day),
Table 10 shows various system sizes and related costs. Costs given are for
equipment only and do not include housing and installation. Costs are
expressed in dollars/pound of ozone generation capacity/day using air as
the feed gas.
147
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TABLE 10. COST RANGE OF OZONATION SYSTEMS (USING AIR)
System Size
Approximate Cost
$/1b/dav I $/kq/day
lLaboratory [Unit (up to 2 Ibs)
jVery small systems (2-100 Ibs)
Medium size systems (100-500 Ibs)
Large systems (>500 Ibs)
$3,000 - 10,000
$2,000 - 4,000
$1,000
$600 - 800
$6,667 - 22,222 j
$4,444 - 8,888
$2,222
$1,333 - 1,778
The figures shown in Table 11 were supplied by a large vertically
integrated* water company located in Paris. The costs were converted to
dollars using the exchange rate of 4.8 French francs/dollar.
It can be noted that the costs given here correlate well with the more
generalized costs in Table 10. The added cost increments are due to the
substantial costs for housing and installation which amount to 22.2 to 33%
of the total. All costs given are for systems which generate ozone using
air as the oxygen source material.
TABLE 11. CAPITAL COSTS OF SMALL TO MEDIUM OZONATION SYSTEMS
(INCLUDING HOUSING AND INSTALLATION)
Daily Production
Capacity
Ibs
3.3
6.6
13.2
30.8
66.0
132.0
kg
1.78
3.0
5.9
13.9
29.7
59.4
Cost vs capacity
Ibs/day
$15,783
9,470
7,102
4,058
2,841
2,052
kg/day
35,073
21 ,044
15,792
9,018
6,313
4,560
Costs for
Housing and
Installation
($)
$16,667
20,833
25,000
31,250
41,667
62,500
Total
$ 52,083
62,500
93,750
125,000
187,500
270,833
Cost Of
Housing
as % of
Total
32
33
26.7
25
22.2
23
* The company referred to designs, constructs, manufactures equipment and
installs and operates waterworks, hence the term "vertically integrated"
148
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Overall, this investigation has shown that housing and installation
can constitute 20 to 33% of total costs (European and Canadian experience)
depending on the size of installation. Thus, one should attempt to minimize
housing needs by purchasing larger ozone generator unit modules, if feasible.
For example, tube type ozonators are available in unit sizes which can
produce much more ozone than an Otto plate type generator of roughly the
same size, offering potential for major space sayings in larger systems.
The Lowther plate type unit is said to be competitive with tube type
ozonators in terms of output per unit space.
Table 12 shows capital costs for a wider range of systems. These
figures were supplied by a major U.S. manufacturer. The costs given include
the following system components and services including installation:
• ozone generators
• dissolution equipment
• gas preparation equipment including compressors, dryers and
residual ozone decomposition equipment
• instrumentation and valving
• oxygen generation including process and equipment design
support
0 engineering assistance to enable the buyer's consultant to
accomplish plant layout and design, specification, purchase
and procurement of equipment
• safety review
0 ozonation system engineering data package which includes process
design drawings, instrument and control system drawings and
installation specifications
0 field engineering support for operator training, plant checkout
and start-up.
The cost data presented do not include costs for:
0 liquid pumping
0 inter-process piping
0 ozone contact chamber
0 structure (housing)
149
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TABLE 12. CAPITAL COSTS OF INSTALLED OZONATION SYSTEMS
Production Capac
Ibs/day
10
100
500
1,000
2,000
3,500
:ity of Ozone
kg/day
4.5
45
225
450
900
1,575
Total Cost
$ 125,000
325,000
800,000
1,000,000
1,550,000
2,150,000
Cost ($/lb c
$/lb-day
12,500
3,250
1,600
1,000
775
614
apacity/day)
$/kg-day
27,778
7,222
3,555
2,222
1,722
819
Again, it can be noted that generalized figures given in Table 10 are
consistent with these figures and that significant economics of scale are
realized in larger systems.
Several comments should be made here, in order that the reader not be
misled. The wide range of services furnished for the above costs will not
necessarily be provided by every manufacturer or equipment supplier. Each
manufacturer or equipment supplier provides levels of equipment and service
depending on: 1) the company's objectives and policies; 2) the relationship
of the supplier to the consulting engineer designing the plant; and, 3) the
degree of system sophistication desired by the customer.
In the laboratory size units, for instance, the manufacturer/supplier
may view a sale as a one time transaction and ask a very high price. On
the other hand, the small unit may be a test unit which will, if the test
proves successful, lead to the sale of a much larger system. In this case,
the manufacturer/supplier may choose to offer the laboratory size unit at
a greatly reduced price or on a rental basis.
Also, the market for ozonation systems in the U.S. is not yet well
established; thus, many U.S. and European firms are competing for future
shares of this market when and if it develops. For these reasons, the list
of system components and services listed above should not be viewed as
"typical". The list does provide a good checklist of services which are
available and should be supplied by every manufacturer and/or supplier.
One further qualification should be made. In smaller size units, the
manufacturer and/or supplier normally is asked to supply a unit capable of
producing a given amount of ozone per day. Engineering or other services
may not be requested by the design engineering firm and thus are not provided.
150
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Finally, the reader 1s referred to another report prepared recently
for the EPA's Office of Drinking Water which documents capital and operating
costs of ozonation systems as well as adsorbents and other oxidants. The
report, prepared by Temple, Barker and Sloane, Inc. and dated August 1977
is entitled "Economic Impact Analysis of A Trihalomethane Regulation for
Drinking Water". Capital costs for ozonation systems cited in the report
on page C-39 are shown in Table 13.
TABLE 13. OZONE CAPITAL COSTS
Design Capacity
(MGD)
0.015
0.075
0.184
0.457
1.058
1.457
12.665
79.790
728.013
Cost of
Complete Unit
$ 4,550
$ 7,530
$ 18,280
$ 35,515
$ 65,080
$ 82,780
$ 401,345
$1,538,290
$7,726,415
*Assumes unit sized for maximum day to deV
Cost includes all capital expenditures.
Cost per MGD
of Capacity
$303,000
$100,400
$ 99,350
$ 77,700
$ 61,500
$ 56,800
$ 31,700
$ 19,300
$ 10,000
ver 2 mg/1.
Note that data in Table 13 are not stated in terms of dollars per unit
of ozone production. Computation of costs on this basis, assuming 2 mg/1
ozone dosage and design flow, yields the data shown in Table 14.
TABLE 14. OZONE CAPITAL COSTS
Design Capacity
(MGD)
0.015
0.075
0.184
0.457
1.058
1.457
12.665
79.79
728.013
Production Capacity
1 bs/day
0.25
1.25
3.07
7.62
17.65
24.30
211.25
1,330.90
12,143.26
Co
$/lb 03/day
18,186
6,092
5,956
4,659
3,688
3,406
1,900
1,156
636
st
$/kg-03 day
40,713
13,538
13,235
10,353
8,195
7,569
4,222
2,569
1,413
151
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In this report, ozone was viewed as a substitute disinfectant for
chlorine and not as an oxidant capable of performing other functions. The
capital costs are expressed in terms of plant design capacity.
In reporting on total capital and operating costs of ozonation systems,
the Temple, Barker and Sloane study cites costs in terms of ozone followed
by a chloramine residual. Again, this assumes use of ozone only as a
disinfectant and further assumes use of chloramine as a terminal treatment
step for residual. Combining these two costs can be misleading if not
studied carefully. Under certain conditions (low TOC, cold finished water
temperature, absence of ammonia,), ozone can be used as a terminal treatment
step. Each treatment situation must, therefore, be reviewed on an individual
basis. A plant owner or operator should not assume that chloramine or
other oxidant is needed.
COST OF ON-SITE POWER
An important variable in total capital cost is the availability,
reliability, and cost of on-site power. Ozonation systems are highly
energy intensive, typically requiring about 22 kwh/kg (from air) for produc-
tion in the 8 to 20 kilovolt range needed for ozone production. Because of
the energy intensive nature of the production, it is important to optimize
the use of incoming electrical power, i.e., use incoming energy as efficiently
as possible to do real work. Thus, power factor* the ratio of power used
to do "real work" versus the total amount needed to induce magnetic induction
in motors plus accomplish work, becomes extremely important. Ozone generators
and auxiliary equipment provided usually have a power factor rating of 0.80
to 0.97. A higher power factor represents more efficient use of input
power.
ENERGY DEMAND OF SYSTEM COMPONENTS
Since the production of ozone is highly energy intensive, the various
equipment components of an ozonation system will be discussed briefly in
order to show relative energy demands and equipment tradeoffs.
Much of the information presented here is excerpted from a paper by
Maurice Pare of Degremont Corporation in France and is entitled "Operational
Cost of Ozone and Energetic Balance". For a more rigorous discussion of
system component alternatives and tradeoffs, the reader is referred to that
paper58.
The reader should be aware that conclusions of Pare's paper are based
on equipment costs, energy costs, and amortization practices in France, and
are valid and applicable in Europe. In North America, energy and equipment
costs may be quite different. In some cases, for example, a high pressure
air supply and preparation system consisting of compressors, water cooled
heat exchangers, air filters and pressure swing type driers can be signifi-
cantly lower in first cost than a comparable low pressure system. The cost
effectiveness considerations therefore must take into account capacity and
the redundancy of the components of the air preparation subsystem.
152
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Fare's paper examines ozonation systems between 1 kg/hr and 30 kg/hr
production capacity. It is a fairly rigorous theoretical examination of a
"typical" water cooled, tube type ozone generation system using diffusers
for contacting. As noted above, equipment costs, amortization rates, and
other factors indigenous to North American practices may tend to reduce the
value of the data presented. However, the reader can learn about the
relative energy costs of various ozonation subsystem components and the
comparison of capital and operating costs of the equipment itself.
The production of ozone and its utilization in water treatment can be
characterized by the following sequence:
• supplying and drying of air
• production of ozone
• contacting with the water to be treated
• recovery or eventual destruction of excess ozone
Each of these system components has been discussed in detail in the
earlier section dealing with engineering. The purpose of discussing them
briefly again is to permit an insight into equipment selection with energy
demand as the principal concern.
The largest portion of energy required for ozonation processing is in
its generation and contacting. Lesser percentages are required for air
preparation and destruction or recovery of excess ozone.
Supplying and Drying Air
Pare examines two methods of supplying air:
• supplying at high pressure starting with compressors (relative
pressure between 5 and 7 bars);
0 supplying at low pressure starting with a blower (pressure lower
than 0.7 bar).
These possibilities are dependent upon the procedure adopted for air
drying. Pare considers drying by means of refrigerant cooling and high
pressure, heatless (pressure swing) desiccant drying and two stage drying
by means of refrigerant cooling followed by low pressure, thermally regene-
rated desiccant drying.
With regard to these two system components, the following conclusions
were reached: Energy demand for the system using water cooled heat exchangers
for cooling at high pressure, and heatless, desiccant drying amounts to 0.1
kwh/cu m of air; energy demand for the system using blowers, refrigerant
cooling, and thermally regenerated desiccant drying amounts to 0.06 kwh/cu m.
153
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Fare's study indicated that, as a comparison of the total cost (amor-
tized capital investment plus operation and maintenance) of the air prepara-
tion subsystem, the high pressure air preparation system is 50% to 85% more
costly than the low pressure air preparation system. However, taking the
entire ozone generation system costs into account, Pare notes that the
total cost difference between a system using a high pressure air preparation
system and a system using a low pressure air preparation system would be
approximately 10% for a system in the 1 to 2 kg/hr range. Pare concludes
that this small difference explains the great number of small installations
which are equipped with high pressure systems. The additional 10% in total
cost is compensated for through ease of operation and maintenance, largely
due to compactness of the installation58.
Although not discussed by Pare, the lower capital investment would
make the low pressure air preparation system more attractive in the "low
bid" U.S. method of equipment supply.
Ozone Production
Pare considers only one method of ozone generation, that being a
horizontal, dielectric tubular type generator operated at a frequency of 50
Hz, using air as the starting material. Four concentrations of ozone (by
weight) in air are considered: 0.5, 1.0, 1.5, and 2.0%. Energies consumed
for ozone production only at these concentrations are, respectively, 16,
17, 19 and 21.2 kwh/kg.
The conclusion is drawn that, using the various system combinations
considered, the optimal working concentration of ozone made from air lies
between 1.0 and 1.25% by weight (approximately 1.15%).
Ozone Contacting
The energy demand of the method of contacting considered by Pare is
taken into account in the air supply system. The contacting is accomplished
by means of porous tubes located at the base of the contact chamber which
is 4 to 5 meters in depth. The water depth of the contact chamber determines
the operating pressure of the ozone generator. Thus, the pressure supplied
by the air supplying/drying system also furnishes the energy for contacting
in this example. This is not always the case. It will be shown in a
specific case study later in this section that energy for contacting using
turbines can amount to as much as 75% of the amount of energy required for
generation.
Ozone Destruction
Pare considers four methods of destruction of the excess ozone: 1)
thermal destruction at 150°C, 2) thermal destruction with partial recovery
of energy using a gas/gas cross flux exchanger, 3) destruction by catalytic
action and 4) recycling of excess ozone.
154
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Thermal destruction is calculated to demand energy at 0.05 kwh/N cu m
of air. It is estimated that up to 50% savings of energy can be realized
using thermal destruction with partial energy recovery. This is accomplished
by using flux exchangers to preheat the air leaving the contact chambers.
No energy demands are cited for catalytic destruction, although it is noted
that air must be preheated to 60° to 80°C in order to enhance the catalytic
action. Experiences with catalysts have been recent and the working lives
can only be estimated. The estimate is that the catalytic material must be
replaced every two years.
It is concluded that the most favorable solution for ozone destruction
in the first three cases is thermal destruction with partial energy recovery.
Pare determines that the cost of thermal destruction at a production capacity
of 15 kg/hr is optimized at 1.3 weight % concentration of ozone. At this
concentration, the cost of destruction represents 6% of total system cost
and is not cost-effective relative to thermal destruction with partial energy
recovery.
Other methods of destruction not discussed are 10:1 dilution with air,
destruction on wet activated carbon, chemical destruction, and combined
thermal-catalytic destruction. The latter uses heat at much lower levels
(60 to 80°C) plus the catalyst to effectively degrade the excess ozone.
Because of the lower temperature requirements of the combined process, the
needed heat often can be provided by using waste heat from other plant
processes.
Using the various treatment trains shown in Figure 47, Pare estimates
the ranges and distribution of costs for air supply/drying systems and
ozone generation. The cost distributions are for production at the determined
optimal concentration of ozone in air of 1.15%. Amortization of equipment
is over a 20 year period. Breakdown of annual equipment amortization and
operating costs is as follows:*
Air production
amortized equipment cost 4 - 7%
energy cost of operation 15 - 18%
Ozone generation
amortized equipment cost 18 - 28%
energy cost of operation 50 - 60%
* This breakdown assumes that ozone contacting is accomplished using diffusers
for which gas pressure is developed in the air production train, and
appears in the cost as an air preparation cost. It does not include
other components of annual cost, such as the cost of personnel and
maintenance.
155
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en
COMPRESSION
5 BARS 1 P 1 7 BARS
DRYING AT HIGH PRESSURE-
WITH REFRIGERATION
WITHOUT HEAT
DRYING AT LOW PRESSURE-
WITH
THERMAL REGENERATION
t
REFRIGERATION
OZONE
PRODUCTION
BLOWER
P10.7 BARS
1
DIRECT DRYING AT
LOW PRESSURE WITH
CONTACTING
I
T
THERMAL |
j REGENERATION I
CONTACTOR
OFF-GAS
TREATMENT
THERMAL
DESTRUCTION
THERMAL
DESTRUCTION
WITH ENERGY
RECOVERY
CATALYTIC
DESTRUCTION
WITH HEAT
RECYCLING
Figure ^7. The different possibilities of energy consumption in ozonation systems
-------
One can readily conclude that the energy demand for ozone production
constitutes the greatest cost of ozonation system costs, including amortiza-
tion of capital costs of the equipment.
INSTRUMENTATION AND AUTOMATION
One of the most important variables in capital costs of ozone generation
and contacting systems is the desired sophistication of the control system.
The most inexpensive system is a manual system with some type of feedback
to the operator which allows a necessary adjustment in treatment. An
example of this type of control system was seen by the site visit team at
the Quebec City, Canada, plant. See Appendix B for a detailed description
of this plant.
The second level of sophistication is a semi-automatic system. Here,
several key control variables are monitored. The most important variables
are: 1) the residual ozone concentration in the treated water; 2) the
concentration of ozone being produced; and 3) the concentration of excess
ozone coming off the contact chamber which must be recycled or destroyed.
A semi-automatic system would provide automatic control for these variables
and manual control with feedback for other variables. The semi-automatic
system requires interruption by the operator for control. An example of a
plant exhibiting this type of control is the Pierrefonds plant in the
Montreal, Canada, suburbs. A description of this plant is included in
Appendix B.
The most sophisticated system, and the one requiring the largest
initial capital outlay, is a fully automatic system. This system requires
no operator interruption for control and it provides measurement of many
key variables of operation in addition to the ones mentioned above. An
example of this type of system is the 600,000 cu m/day Neuilly-sur-Marne
plant in the Paris suburbs.
To summarize, choice of a control system can affect cost greatly. One
should not assume that purchase of a manual system, since the initial
capital investment is much less, is indeed more inexpensive. An automatic
system, complete with sensors, a software package and a computer or micropro-
cessor can optimize control, thus making system operation much more efficient.
The added investment for a more sophisticated control system could be
recovered through savings in personnel, energy and chemical costs.
OPERATING COSTS
Operating costs of an ozonation system are defined as including
energy, maintenance, and spare parts. Personnel costs are not included
except in maintenance costs. During site visits to 27 plants using ozonation
processes, questions were asked regarding personnel needed for ozonation
system operation. The site visit team was told repeatedly that additional
personnel were not needed for operation of the systems over those required
for operation of the remainder of the treatment plant.
157
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Costs included in this section were obtained largely through site
visits to 20 European plants in May 1977 and 7 Canadian plants during
August 1977, all of which use ozone for some purpose. Additional cost data
were obtained from recent literature.
Categories of Operating Costs
Each category of operating costs merits a brief description. Energy
demand of an ozonation system depends on the 1) method of ozone generation;
2) method of air preparation; 3) amount of refrigeration that is required
for generator cooling water; 4) method of contacting; 5) the dosage required;
6) ozone destruction requirements; 7) coolant pumping; and 8) cost of
generating or purchasing oxygen.
The subject of energy required for different methods of contacting is
complex and cannot be covered in detail here (the different methods are
discussed in detail in the engineering section). There are several methods
ranging from the diffusion sparger which requires little or no energy
expenditure to the submerged turbines which generally are recognized as
being the most efficient mass transfer devices but highest energy demanding
methods of contacting.
A brief example of tradeoffs serves to place energy demand of contactors
in the proper perspective. At Rouen-la-Chapelle, France (described in Appendix
B), porous diffuser contactors are used for disinfection. In France, the
standard contacting practice for disinfection is that ozone must be supplied
in sufficient quantity over a minimum period of time so that a residual of
0.4 mg/1 of dissolved ozone can be measured after 4 minutes of contact time
once the initial ozone demand is satisfied. The rationale behind this
theory can be traced to the work of Coin, Cornelia, and Hannoun in 1964 and
1967 which showed that for viral inactivation to be assured, this period of
contacting is necessary59'60. If ozone must be applied for this period of
time in a concentration great enough to satisfy initial demand and leave the
desired residual after an additional 4 minutes, one should strive to
acccomplish this objective in the least expensive way. Thus, at Rouen and
other French plants, porous diffusers are commonly used when ozone is
applied at or near the end of the treatment process for disinfection.
In Belgium and Germany, there exist no disinfection standards of this
kind. At Tailfer (Brussels), for example, submerged turbines are used for
contacting because ozone can be used more efficiently (i.e., the mass
transfer of gas to liquid is greater than with porous diffusers. But,
in order to gain this efficiency, more energy must be used.
When the cases presented later in this section are studied, one can
see that contacting at Tailfer demands 75% as much energy as does ozone
production. At Lengg (ZUrich) the figures are more difficult to analyze;
total energy demand for both production and contacting is about 35 kwh/kg
of ozone generated and applied. If one accepts 22 kwh/kg as an average
amount of energy required to produce ozone, this means that 13 kwh/kg is
158
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required for contacting at Lengg which also uses submerged turbines for
contacting. The point to be made is that energy demand of the total ozonation
system varies greatly, depending on the system components.
Maintenance and spare parts sometimes are grouped together as one cost
item. Ozone generators of the tubular type normally are shut down once per
year, sometimes every six months, for cleaning of the tubes and other
general maintenance. This requires several man-weeks of time, depending on
the number of ozone generators in the system. Spare parts normally consist
of replacement tubes, broken during cleaning or which have deteriorated
from years of operation at high voltages. A "rule of thumb" for maintenance
costs, related to the study team by a large manufacturer, is that maintenance
cost should be about 15 to 20% of the production cost. If ozone production
cost is $0.35/lb ($0.78/kg), then maintenance costs, in order to operate at
a high efficiency, should be about $0.07/lb (0.16/kg) of ozone generated.
Actual Operating Costs
A number of cost figures were obtained during site visits to Europe
and Canadian plants. Few have been defined precisely enough, however, to
report them with complete confidence. Lest the reader be misinformed, only
those costs for which operating conditions have been defined and verified
will be reported. Two of these sets of operating costs, those for Tailfer
(Brussels, Belgium) and Lengg (ZUrich, Switzerland) are summarized in the
case histories which follow later in this section. Additional data are
given in the following paragraphs.
A large, fully automated plant in the Paris, France area, which doses
ozone at an average rate of 2.5 mg/1, has an ozone operating cost of 0.035
French francs/cu m of water. The plant is amortized at an annual interest
rate of 11% for a period of 20 years. Costs include all aspects of operation
and maintenance plus amortization of capital investment, and an assumed
inflation rate of 10%. Costs are based on annual production at half of
rated capacity. The price paid for electrical energy is 0.10 French franc/kwh.
Converted to $/1000 gallons, using a currency exchange rate of 4.8
francs/dollar (the exchange rate in mid-1977), costs amount to $0.0276/1000
gallons. Electrical energy costs at this plant are 2.1
-------
The second highest cost reflects a relatively high average dosage of 2.5
mg/1. The Lengg plant, which has the lowest operating cost, pays less for
electricity and has a lower average ozone dosage than do the other plants.
TABLE 15. OZONE OPERATING COSTS
Plant(s)
Tailfer
I (Belgium)
Lengg
[Switzerland)
Large Automatec
Paris Plant
Several French
Plants
Ozone
Operating Costs
t/1000 qal 4/cu m
2.52
1.75
2.76
3.95
0.66
0.46
0.73
1.04
Electrical
Cost (
-------
Another development in the marketplace that can affect overall water
plant operating costs is the use of waste heat from the ozone generators to
heat plant buildings. This approach is to be used in the St. John's,
Newfoundland plant, currently under construction and which will use air
cooled ozone generators. Estimated savings using this approach, assuming
an annual ambient temperature of 60°F, are about $3600/yr. In colder
temperatures, more savings would accrue while wanner temperatures would
reduce savings.
CASE HISTORIES ON CAPITAL COSTS
Two cases are given here, one for the Brussels, Belgium waterworks and
the other for the Lengg waterworks serving Zurich, Switzerland.
Tailfer (Brussels)
The Tailfer plant, described in detail in Appendix B, is a 260,000 cu
m/day plant (68.7 mgd) located about 75 km northeast of Brussels. The
water is treated at Tailfer and pumped 75 km to the city of Brussels.
The ozone production capacity at Tailfer, as actually installed, is 24
kg/hr (1267.2 Ibs/day). Six horizontal, tube type dielectric units, each
capable of producing 4 kg/hr, are installed. Currently, air is used as the
feed gas, although the plant will be studying the use of pure oxygen feed
to allow production of more ozone from the same number of ozone generators
during periods of peak ozone demands in the summer. If oxygen is used in
the future on a part-time (peak load) basis, this will make Tailfer a truly
unique ozonation plant, and only the second municipal water treatment plant
known to be generating ozone from oxygen.
The building which houses the ozone generation system plus contact
chambers is large enough to enable the installation of additional ozone
generators to increase production to 32 kg/hr (1690 Ibs/day) when air is
used as the feed gas.
The complete cost of the current system including the building plus
equipment was 148,000,000 Belgian francs in 1976. Using 35.2 Belgian
francs/dollar as the exchange rate (as of mid 1977) this equates to $4.024
mi 11i on.
The cost for the building, including the contacting chambers, was
approximately 50 million Belgian francs or $1.42 million.
Equipment cost, which includes the transformer, the ozone production
chain, thermal destruction, venting, safety analyzers and process analyzers
with transmitters, amounted to 98 million francs or $2.784 million.
Building costs thus comprise 33.8% of total costs, which is roughly
consistent with figures given in Tables 10, 11 and 12. Cost of ozonation
expressed in $/lb capacity/day amounts to approximately $2200, which is
high for system costs at that capacity. Much of this cost is due to the
method of contacting chosen and the standby housing capacity.
161
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Tailfer amortizes buildings and equipment over a 20 year period at an
annual fixed cost of 15,000,000 Belgian francs, or $426,000.
The energy required for ozone generation varies between 13.5 and 19
kwh/kg of ozone produced. Energy for air compression and desiccation is
about 3 to 4 kwh/kg of ozone. Consequently, total energy costs for ozone
production vary between 17 and 22 kwh/kg. The cost of electricity is 1.06
BF/kwh (S.OWkwh).
Operating Costs at Tailfer—
Operating costs for an ozonation system have been defined as including
the following items: energy, maintenance and spare parts.
Total energy costs of ozonation at Tailfer amount to 3.34 million
Belgian francs/year ($94,886) for ozone production and 2.487 million BF
($70,653) for ozone injection. Total energy cost of ozonation is 0.03
BF/cu m of water treated. Total amount of water treated/year amounts to
94,900,000 cu m.
Converted to U.S. dollars, energy for ozone production at 1.7 mg/1
average yearly dosage, amounts to $94,886. Energy for injection costs
$70,693, for a total energy bill of $165,579.
Manpower costs for maintenance, calculated for 6 ozone generators, is
approximately $28,400 year. This is based on twice per year cleaning of
the generators.
Spare parts, mostly tubes and fuses for the ozone generators, amount
to about $11,600 per year. Uniquely, Tailfer replaces all dielectric tubes
once every two years. Other plants visited never replace all dielectric
tubes, only the ones that fail or are broken at the time of routine cleaning.
Summing, total annual ozonation system costs amount to $631,450 or
2.52 cents/1000 gallons (0.66<£/cu m) of water produced.
Cost of water production is 32<£/1000 gal (8.44<£/cu m). Thus, ozonation
costs are 7.9% of total operating costs.
Capital costs of ozonation at Tailfer are quite high and are not
considered to be truly representative of ozonation system costs. Operating
costs are likewise somewhat high, the twice annual maintenance, high rate
of tube replacement and energy for turbine contacting contributing to that
factor.
The following Tables 16, 17 and 18 summarize capital and operating
costs at Tailfer.
162
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TABLE 16. CAPITAL COSTS AT TAILFER
Item
Building & Injection Chambers
Equipment
TOTAL
Cost ($)
$1,420,000
2,784.000
$4.204.000
TABLE 17. ANNUAL OZONATION SYSTEM COST AT TAILFER
Item
Amortization
Maintenance
Spare Parts
Energy: Ozone Production
Energy: Ozone Injection
Cost ($)
$426,136
28,409
11,364
94,886
70.653
$631,448
TABLE 18. OTHER PERTINENT COST DATA FROM TAILFER
Item
Cost of Electricity
Yearly Average Ozone Dosage
Energy Demand of Ozonation System
Current Ozone Production Capacity
Unit Cost of Ozonation/1000 gal water
Datum
3.0U/kwh
1.7 mg/1
up to 10 kwh/lb
1267.2 Ibs/day (472.97 kg/day)
2.52
-------
costs for the 6 vertical, tube type Kerag ozonators, including the ozonator
building section in the Lengg lake waterworks, were 2.8 million Swiss
francs. Using an exchange rate of 2.49 Swiss francs/dollar (prevalent in
mtd-1977), this amounts to $1.12 million.
Capital costs at Lengg are amortized at a 12% interest rate, which
amounts to 336,000 Swiss francs per year. Maintenance costs are 2% of
total costs or 56,000 Swiss francs. Service costs (assumed to be parts and
labor for replacement thereof) are 16,000 francs. Energy for ozone generation
and refrigerant water amount to 0.13 Swiss cent (Rp)/cu m. Summing,
total operating costs amount to 1.15 Rp/cu m of water treated. These
figures are based on an annual average ozone dosage of 1.5 mg/1 and
water production of 48 million cu m/year.
Converted to dollars, operating costs are 1.75<£/1000 gallons of
water produced. Costs are summarized in Table 19.
TABLE 19. OZONATION COSTS AT LENGG
Energy and Water Costs
Dzone Production and Contacting (0.016 kw/cu m)
Auxiliary Services (0.0062 kw/cu m)
Refrigeration Water (5 cu m/hr)
Amortization (12% of 2,800,000 Fr)
Maintenance Cost (2% of 2,800,000 Fr)
Maintenance Service Cost (by Manufacturer)
Total
Total Cost
Cost in U.S. Dollars
=0.08 Rp/cu m
= 0.031 Rp/cu m
= 0.021 Rp/cu m
Total = 0.132 Rp/cu m
(Rp=Swiss cent)
336,000 Fr
56,000 Fr
16.000 Fr
408,000 Fr = 1.02 Rp/cu m
= 1.15 Rp/cu m
= 1.75 <£/1000
gallons
The cost of electricity in ZUrich is 0.05 Swiss francs/kwh or
2.0
-------
Compared with Tailfer costs, Lengg capital costs are much lower,
$643/lb of ozonation capacity/day versus $2200/lb. Operating costs are
somewhat lower, 1.75<£/1000 gallons versus 2.52(^/1000 gallons at Tailfer.
Direct comparisons of Lengg with Tailfer can lead to inaccurate
conclusions unless specific conditions are studied carefully. Some of
the obvious differences in the two systems are as follows:
• Tailfer's ozonation system is housed in a separate building
which also includes the ozone contacting chambers and capacity
for expansion. Lengg's system was retrofitted into existing
building space. Contact chamber costs may not be included in
capital costs of the ozonation system, but rather in plant capital
costs.
• The amount of safety equipment at Lengg is not as great as in
Tailfer.
• Ozone production is accomplished at 50 Hz frequency in Tailfer,
350 Hz at Lengg.
• Amortization periods and interest rates are different for the two
systems.
• The ozone generation equipment was supplied by different manufac-
turers.
• Annual maintenance costs at Lengg are $22,490 and $28,409 at
Tailfer. This could mean that personnel costs are different or
that ozone generators are cleaned once/yr (which is normal practice)
versus twice/yr at Tailfer or both. Lengg also has a service
contract with the manufacturer for ozone generator maintenance.
Tailfer has a high rate of maintenance and more frequent replacement
of tubes.
SUMMARY
The capital costs of ozonation systems can range from a low of $600/1b
capacity/day for a large system to a high of $4000/lb capacity/day for a
relatively small system. An added cost is the housing for the system which
can range from approximately 20 to 33% of equipment costs.
Total capital and operating costs depend on energy demand, amount of
maintenance required, amortization period, interest rates and cost of
energy. Based on limited data, total costs for ozonation process steps were
found to range from 1.75
-------
demonstrated in Europe to be an effective combination for the simultaneous,
biological removal of dissolved organic carbon compounds and ammonia. Under
ideal circumstances (see Section 13), the biological activated carbon
created by the ozone-granular activated carbon combination also can result
in longer operating lifetimes of the carbon and much longer periods between
regeneration. Cost savings of the biological activated carbon (BAG) approach
have not yet been investigated, but they are believed to be substantial.
166
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SECTION 10
PUBLIC HEALTH ASPECTS OF OZONE USAGE
Ozone (03) is an allotrope of oxygen (02). It is 1.5 times as dense as
oxygen and 13 times more soluble in water. It can be manufactured from dry
air or from oxygen by passing these gases through an electric field of high
potential sufficient to generate a "corona" discharge between the electrodes.
Up to 3% by weight of ozone in air or 6% by weight in oxygen are about the
maximum yields61 of ozone for optimum use of electrical energy.
Ozone is highly unstable and must be generated on site. Its oxidation
potential (-2.07V) is greater than that of hypochlorous acid (-1.49 V)
or chlorine (-1.36 V), the latter agents being widely used in water treatment
practice. It is thought to decompose according to62:
03 + H02' >HO' +
HO' +
The free radicals (HO/ and HO') may react with a variety of impurities
such as metal salts, organic matter including microorganisms, hydrogen and
hydroxide ions. They are more potent germicides than hypochlorous acid -- by
factors of 10- to 100-fold. Experimental evidence indicates Gram-negative
bacteria to be on the order of 10- fold more susceptible than viruses to
ozone63.
Morris63 observes that the criteria of Coin e£ a]_.59>6° for ozone
disinfection appear to comprise a valid standard. These criteria are based
upon poliovirus inactivation rates which showed 0.3 mg/1 ozone residual after
a 3 minute contact time to be the theoretical concentration-contact time
relationship61*. A safety factor is added, however, so that the criteria of
Coin et al. are 0.4 mg/1 of residual ozone after a 4-minute contact time.
GomelIa63~~observes these relationships to be as effective for the several
river waters tested as for distilled water. Further, he notes that the 0.4
mg/1 ozone residual corresponds to an oxidation potential of 600 to 650 mv,
whereas an equivalent application of chlorine compounds corresponds to 550 to
650 mv.
167
-------
Several plants in European cities that use ozone were visited: ZUrich,
Kreuzlingen, Konstanz, Sipplingen, Langenau, Paris, Rouen, and Toulouse.
Microbiological data were requested at each plant, but were only available at
ZUrich, Rouen and Toulouse. By law, all German plants sample for microbio-
logical analyses. Often, the samples are analyzed at other laboratories. By
German law, all total plate counts/ml and coliforms/100 ml must be zero.
Finished water data for plants in ZUrich, Rouen and Toulouse show:
Location.
Zurich
Rouen
Toulouse
Record
Exami ned
1 year
6 months
18 samples
5 months
24 samples
Total Plate
Count/ml
5 (0-624)
116 (0-600)
avg (min-max)
Total
Coliforms/100 ml
0 (0-3) C102 added at end
0 (0-0) C102 added at end
15 (0-125) 0 (0-0) C102 added at
flash mix
Ozone is terminal
disinfectant
It is important to note that chlorine in some form is used at all three
of the above plants. In ZUrich, chlorine dioxide (CIO?) is added terminally,
and at Rouen C\2 1S added terminally. At Toulouse, ClOo is added at the
flash mix. In all cases, chlorine compounds added at all of the European
plants visited are used minimally — below taste levels. Thus, any discussion
of the public health aspects of ozone usage based upon data from these plants
cannot be divorced from chlorine usage. As the two processes (ozone and
chlorine) are used in these European plants, it appears that microbiological
quality control is as good as that in the U.S. where higher concentrations of
free or combined chlorine alone are utilized.
An important additional aspect of ozonation that relates to microbiologi-
cal control is its ability to convert some biorefractory organic compounds to
biodegradable forms. The discovery of this effect occurred in Kreuzlingen,
Switzerland when ozonation was substituted for terminal chlorination in the
late 1950s. In Europe this is referred to as the "Kreuzlingen experience".
The Kreuzlingen plant obtains its water from Lake of Constance (the
Bodensee) through which the Rhine River flows. Ozone, applied as a terminal
treatment about 20 years ago, resulted in massive slime growths in the
distribution system and. water meters. Interestingly, Dr. Cyril Gomella
observed that Paris had similar experiences after World War II -- but never
before that time (when half the city's water was obtained from wells and the
other half from surface sources which were treated with slow sand filters, a
process which could be expected to decrease the biodegradable component).
Dr. H. Sontheimer from the Engler-Bunte Institut, University of Karlsruhe
has developed some criteria for drinking water as a result of his studies of
the experiences of a number of plants. These criteria utilize the parameter
168
-------
DOC (dissolved organic carbon) which is the same as the dissolved TOC (total
organic carbon) method familiar in the U.S.
• Water with a DOC ^ 2 mg/1 is not suitable for distribution.
• Water with a DOC <. 0.2 mg/1 can be ozonated terminally without any
real problem of aftergrowths.
• Application of 1 mg/1 03:1 mg/1 DOC results in 75% conversion of
DOC to biodegradable materials.
• Application of 2 mg/1 03:1 mg/1 DOC results in 90% conversion of
DOC to biodegradable materials.
• Ozonated water applied to a normal granular activated carbon
filter will result in 30% DOC removal across the carbon unit
process. (The sometimes considerable froth which accumulates on
the water surface after ozonation accounts for 5% of the DOC
loss.) Usual data at different plants range between 100 and 200 g
DOC removed per cubic meter of GAC (BAC) per day.
Dr. Sontheimer and his colleagues recommend the practice of providing
carbon adsorption beds following ozonation. The carbon removes the residual
ozone and allows bacterial growth to develop which removes some of the biode-
gradable organics and ammonia. The resulting water is then chlorinated
minimally, and the total plate count procedure is used to regulate chlorine
application thusly:
t If the total plate count (TPC) is >.100/ml, at least 0.1 mg/1 free
chlorine must be used by German law. This requires that 0.1 mg/1
free chlorine residual must be present after a reaction time of 15
to 30 minutes.
• If the TPC is <100/ml, less chlorine can be used.
Hence, aftergrowth problems in distribution systems are well recognized
in Europe and the ozone users of Europe resort to the same basic control
technique as does the American art -- namely the use of chlorine. In Europe,
however, ozone contact is relied upon for the main disinfection process and
chlorine is added for distribution system control, whereas in the U.S.,
chlorine is relied upon for both functions. The main difference is a much
lower chlorine residual in Europe than in the U.S. along with the potential
for a lower total trihalomethane content. For example, the Sipplinger Berg
plant of West Germany uses microstrainers, ozonation, and rapid sand filtration
and delivers the water to a 150 km-long distribution system. The water is
chlorinated to the maximum allowed by law - 0.6 mg/1 - at the entrance to the
system.
Dr. Dietrich Maier66 stated that total haloforms in treated Sipplinger
Berg waters are 5 micrograms/1 (yg/1) with chloroform accounting for 2.5 to
3 yg/1. He also said that Lake Zurich water treated at the Lengg Plant
results in a similar haloform distribution. Bromine in the Bodensee water
169
-------
(water source for Sipplinger Berg) is less than 10 ug/1, and after ozonation
the brominated portion of the haloform concentration is higher than before
ozonation (13 mg/1).67
The effects of ozone upon some organic compounds have been studied.
Dr. Cyril Cornelia supplied the data of Table 20 which shows the effects of
varying concentrations of ozone at three different contact times upon anionic
detergents and COD. Ozone has much more effect on detergents than on the
gross organic parameter, COD.
The data of Table 21 showing the effects of ozone upon a number of
specific organics also were supplied by Dr. Cornelia. There is a very broad
range of effects by ozone from compound to compound. Two were not touched
at all -- n-tetradecane and n-pentadecane and only one slightly -- dihexyl-
phthalate. (di-2-ethylhexylphthalate). Two phthalates present in trace
amounts appear also to have been little affected — diisobutylphthalate and
butylisobutylphthai ate. However, n-octane and trichlorobenzene show greater
than 90% removals.
It is necessary to be cautious in interpreting such data. First the
study team did not determine the ozone content or contact time that effected
these changes. But more importantly, for almost each and every compound an
oxidized product is produced and the health effects of these products presently
are unknown. Also, Dr. Gomella is quite aware of this problem and hopes to
initiate such research this coming year.
The only data available which reflect the performance of an activated
carbon bed acting as a biological filter after an ozonation process was
supplied by Mr. Daniel Versanne, Table 22. These are based upon the perform-
ance of the Rouen Plant in northwestern France two months after it commenced
operation. Mr. Versanne stated that more recent results show even better
performance.
Summing the chemicals present (except for DBF and DEHP which ~ judging
by their high concentration probably were been added as internal standards)
gives an estimate of unit process efficiencies in oxidizing or decreasing
the concentrations of these materials. The first ozonation step (0~ concentra-
tion = 1 mg/1, time of contact = 3 minutes) results in a 63% quantitative
decrease, and the filtration through sand followed by carbon yields a 34%
decrease. Both processes together-effect a 76% decrease. The post ozonation
step (0-> concentraton = 1 mg/1, time of contact = 12 minutes) yields a 39%
decrease, and all processes together yield an 85% efficiency in removing
impurities.
Only one class of chemicals shows an increase, this being equal to or
greater than C 20 isoalcane, but the amounts are so small it is likely not
significant. The 34% decrease across the filtration step using sand followed
by carbon is quite close to the 30% DOC removal noted by Dr. Sontheimer for a
biological carbon bed.
The chemical evidence available does not indicate any untoward health
hazard to be associated with the use of ozone in water treatment. The
potential exists as indicated by an increase in concentration of one group
170
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TABLE 20 EFFECTS OF OZONE ON ANION 1C DETERGENTS AND COD
Ozone, mq/1
Dose
1.35
1.66
0.70
2.05
2.03
2.40
2.50
3.85
3.31
2.95
3.80
3.85
3.17
4.10
4.83
6.90
Residual
0.19
0.34
0.45
0.48
0.68
0.80
0.93
1.13
1.30
0.34
0.90
1.18
0.27
0.75
0.90
2.95
Time
of
Contact
(min)
4
4
4
4
4
4
4
4
4
10
10
10
20
20
20
20
After Ozonation
Detergent* COD*
mg/1
0.052
0.048
0.083
0.043
0.048
0.031
0.035
0.015
0.016
0.025
0.012
0.003
0.013
0.003
0.002
t
removal
58
61
27
65
58
73
72
87
87
80
90
98
90
98
99
100
mg/1
8
7.5
8
8.5
7.5
7.5
8
6
6
7
6
6
7.5
6.5
6
6
removal
16
21
20
11
25
25
16
40
37
26
40
40
25
32
40
40
* Initial sample concentrations:
Detergent: 0.114 or 0.124 mg/1
COD: 10.0 or 9.5 mg/1
Data courtesy Dr. Cyril Gomel la
171
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TABLE 21 EFFECTS OF OZONE UPON ORGANICS IN WATER
Compound
Chloroform
Carbon tetrachloride
Trichloroethylene
n-Octane
1 ,2-Hexanediol
n-Undecane
Trichlorobenzene
Trichlorobenzene isomer
n-Dodecane
n-Tridecane
Diphenyl ether
n-Tetradecane
n-Pentadecane
Dibutylmaleate
n-Hexadecane
n-Heptadecane
n-Octadecane
Di i sobutyl phthal ate
Butyl i sobutyl phthal ate
n-Nonadecane
Di butyl phthal ate*
n-Eicosane
Dihexylphthalate
Di-(2-ethylhexyl) phthal ate
Dioctyl phthal ate
Octy 1 decyl phthal ate
Didecyl phthal ate
Filtered
Water
yg/1
102
6
15
1
10
8
3
2
0.5
1
1.5
-
0.2
1.5
0.5
<0.1
0.4
t
t
0.8
138
0.3
7.1
127
42
41
18
Ozonated
Water
yg/1
60
4
13
0
2
3
0.2
0.3
0.2
0.7
0.3
0.3
0.2
0.2
0.2
<0.1
0.3
t
t
0.3
25
-
6.9
84
38
37
16
Percent
i Removal
41
33
13
>90
80
60
>90
85
60
30
80
0
0
85
60
-
25
-
-
60
82
>66
3
34
10
10
10
Data courtesy Dr. Cyril Gomel la, SETUDE, Paris, France
* High vapor pressure
172
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TABLE 22 ROUEN PLANT PERFORMANCE, ORGANICS
Retention
Time
Relative
to DBP
0.08
0.09
o.io
0.13
0.16
0.18
0.20
0.27
0.31
0.33
0.36
0.38
0.44
0.47
0.50
0.51
0.54
0.59
0.63
0.67
0.71
0.75
0.78
0.85
0.88
0.92
0.94
0.97
1.00
1.05
1.07
1.10
1.15
1.16
1.22
1.27
1.32
Compound
isoalcane >C 8
methyl cycl ohexane
isoalcane >C8
isoalcane >C 8
isoalcane >C 8
n-nonane
isoalcane >C 8
n-decane
isoalcane >C 10
isoalcane >C 10
n-undecane
isomers of 4-tert-
butylcresol or of
tert-butylanisole
bicyclohexyl
not identified
n-tetradecane
not identified
n-pentadecane
isoalcane >C 15
n-hexadecane
n-heptadecane
not identified
n-octadecane
DIBP
DIBP
DBP
n-eicosane
isoalcane >C 20
isoalcane >C 20
isoalcane >C 20
not identified
not identified
isoalcane >C 20
DEHP
E(less DBP + DEHP)
% Removal by process
bv train
Approximate Concentration, ug/1
After
Raw Pre-Ozone
80
14
16
72
4
4
4
2
2
0.4
1
18
22
6.5
6
0.8
70
10
0.7
0.4
0.5
0.2
1.5
1
0.4
1.5
7
4
650
1.2
0.4
0.4
0.4
3
t
0
330
355.3
17
10
8
40
4
t
t
t
t
t
0.5
2.5
2.5
1
1
0.8
33
t
0.3
0.4
0.2
t
0.6
0.3
t
0.5
3.5
2.5
390
t
0.4
t
t
2
t
t
220
131.0
63%
After
Filt+AC
13
5
6
17
3
t
t
t
t
t
0.5
1
1
0.5
0.5
0.8
30
t
0.3
0.4
0.2
t
0.6
0.3
t
0.5
3
2
320
t
t
t
t
1
t
t
130
86.6
34%
76%
After
Post-Ozone
2
5
t
5
t
t
t
t
t
t
t
5
1
0.5
0.4
0.5
0.8
30
t
0.3
0.4
0.2
t
0.6
0.3
t
0.5
3
2
240
0
0
0
0
0.1
t
0.2
117
52.8
39%
85%
Data courtesy Mr. Daniel Versanne, two months after start-up of
Rouen Plant. More recent results show even better performance.
173
-------
of materials. But even if that indication is real, it is likely for most
compounds to be of much less potential hazard than is the use of chlorine
and chloro-organics that result from chlorine's use. And there appears to
be no escaping the need for continued chlorination of most public water
supplies. It must be remembered, however, that many new oxidized moieties
and biodegradation products are being produced and we do not know what these
are, but in general, these are compounds of less — not greater -- toxicity.62
U.S. water treatment professionals have been somewhat reluctant to
include a biological process in water treatment. Two very real possibilities
must be studied before such a treatment can be recommended. First, such a
unit process would most certainly result in an increase in Pseudomonas
bacteria content. These organisms are ubiquitous, have a propensity to grow
in minimal media, and some strains are opportunistic-pathogens. They are
genuinely hazardous to infants and the elderly -- population groups at high
risk due to their lesser resistance.
Secondly, a biological bed intuitively can be expected to produce an
increased endotoxin content in the treated waters. Endotoxins are lipopoly-
saccharides which are synthesized in the outer cells of Gram-negative bacteria.
They have the capability of producing fever (pyrogenic effect) when injected
into the blood stream of some animals. Many endotoxins when in the intestines
have the capacity to produce effects similar to gastrointestinal infections.
However, endotoxins in the intestines — and in water wherever Gram-negative
bacteria are present — are a part of our natural daily lives, and hence are
not ordinarily hazardous agents. Nonetheless, it would be desirable not to
increase the concentrations of these materials by virtue of a water treatment
unit process.
The endotoxin content can now be quantified down to yg/1 levels by use
of the Limulus (horse shoe crab) lysate assay. Analyses of renovated waste-
waters showed values ranging from less than 0.313 yg/1 (which employed a
reverse osmosis unit in the treatment sequence) to 1250 g/1 (which samples
had been delayed in shipment). Analyses of drinking water samples showed
values ranging from less than 0.625 yg/1 (lime softening plant, no carbon
used) to 125 yg/1 (granular activated carbon in the complete treatment
sequence) to 500 yg/1 (only chlorination practiced).68 However, this work
did not examine any of the specific unit processes in a before and after
mode.
Recent unpublished work69 on filtered activated sludge effluent in
Dallas, Texas, in which two carbon columns were used in series and from
which samples were taken before, in between, and after the carbon columns
is shown in Table 23. Looking at both total (bound + free) and filtered
(free) endotoxins, there is a 73 to 83% decrease across the first carbon
column, but a small increase in endotoxin levels occurs through the
second carbon column, the entire process resulting in a 67 to 69% decrease
for total and filtered endotoxins, respectively.
174
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TABLE 23. ENDOTOXIN VALUES AND CARBON ADSORPTION
Sample
12-14 Total
Flit
12-21 Total
Flit
1-25 (SA) Total
Filt
1-25 (CS) Total
Filt
X Total
X Filt
% Change, Total
% Change, Filt
Endotoxin Equivalents, ng/ml
Before
Carbon
600
480
500
250
250
125
300
120
412.5
243.8
Midpoint
192
48
100
50
100
50
60
30
113
44.5
73
82
After
Carbon
192
96
200
100
100
75
60
30
138
75.25
67
69
SA = San Antonio data
CS = College Station Data
Total = not filtered
filt = filtered through 0.45 urn Millipore
Additional information of public health interest can be obtained
from the data of Table 24. These data compare the standard plate count
and total coliform values of samples (activated sludge + filtration +
carbon adsorption) subjected to four different disinfection procedures.
The bacteriological tests were run on samples before shipment from
Dallas to College Station, Texas (Texas A&M University) and after their
arrival. According to both tests, the ozonated samples performed just
as well as the chlorinated samples. The endotoxin values of these
samples are shown in Table 25.
175
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TABLE 24. EFFECTS OF SHIPMENT TIME ON BACTERIOLOGICAL
QUALITIES OF WATER SAMPLES-PYROGEN1C PROJECT
Date of
Sample
(1977)
2/8 before
after
2/28
ii
3/14
ii
3/28
it
4/4
n
4/n
n
4/18
Before
X Shipment
After
X Recei pt
Standard Plate Count/ml
UV
112
1,820
24
125
81
50
280
235 -
140
5,540
240
63
79
7
137
1,120
ci2
43
475
4
35,000
8
10
3
11
26
3,800
5
14
65
128
22
5,634
PH
1
500
0
44,000
27
25
13
59
26
9,340
17
13
60
96
21
7,719
0 =
-------
TABLE 25. SAMPLE ENDOTOXIN ASSAYS
Sample
Date
2/8
2/28
3/14
1 3/20
4/4
4/11
4/18
Endotoxin Equivalents, yg/1
Total (Free)
UV
320 (320)
-
80 (48)
30 (22)
90 (30)
30 (22)
47 (25)
ci2
160 (80)
-
80 (8)
30 (22)
30 (30)
47 (25)
47 (25)
PH
32 (16)
-
80 (8)
9 (2)
12 (6)
5 (3)
47 (25)
°3
32 (8)
-
80 (8)
30 (3)
15 (12)
30 (6)
30 (6)
The impact of biological activated carbon treatment on drinking water
supplies presently is being studied at Texas ASM University. At the time of
this report, data from two water samples were available:
Sample
#22 Filt.
Total
#77 Filt.
Total
Endotoxins
Before GAC
yg/1
1.56
3.12
3.12
3.12
After GAC
yg/i
1.56
1.56
3.12
3.12
The GAC (granular activated carbon) for #22 had been in use since 1968
without regeneration and for #77 had been in use only 5 weeks. In neither
case is there an increase in endotoxins through the GAC.
Additional data is necessary, but the following presumption is possible:
Biologically treated wastewater has a high level of endotoxin (-6000 yg/1)
which is reduced by both filtration and adsorption mechanisms in GAC columns.
Since there is still a biodegradable carbonaceous component remaining in the
wastewater, additional growth of Gram-negative bacteria can occur in subsequent
GAC. In the case of drinking water supplies, higher quality waters (in terms
of a biodegradable carbonaceous component) are utilized and thus less substrate
177
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is available for the growth of Gram-negative bacteria. If ozone is applied
prior to the GAC, the biodegradable carbonaceous component will be increased,
but the amount of increase will be relatively small and consequently should
impact on the endotoxin levels in only a minor manner.
In order to answer the above presumption (or hypothesis) as it pertains to
drinking water, it is necessary to expand current research efforts to include:
• pseudomonas assays on samples from water treatment plants taken before
and after GAC beds;
• apply pseudomanas, limulus, and biodegradable component assays to GAC
beds functioning as Biological Activated Carbon (BAC) beds which are
immediately preceeded by ozonation.
Of course, it is also necessary to implement rather strenous efforts to
identify oxidized organics specifically that result from the 03 - BAC
unit process.
178
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SECTION 11
CHLORINE DIOXIDE
HISTORY OF USE
Chlorine dioxide was first discovered in 1811 in the form of a greenish
yellow gas by Sir Humphrey Davy70. Davy prepared the compound by reacting
potassium chlorate with hydrochloric acid and named the resulting compound
"euchlorine". In 1834, Watt and Burgess identified the bleaching properties
of the compound. Around 1900, it was discovered that C10? could be used in
a dilute acetic acid solution for the bleaching of paper pulp. Other experi-
mentation with C102 was carried out during this period, but it had little
practical application due to the lack of a safe and economical way of synthe-
sizing the chemical. In the 1930s, the Mathieson Alkali Works developed the
first commercial process for making C102 from sodium chlorate70. By 1939,
Mathieson Chemical Corporation had succeeded in making sodium chlorite a
commercial product.
With the advent of this commercial feed stock for ClOo generation, C102
processes quickly found practical application. The No. 2 Niagara Falls, New
York, Water Treatment Plant was the first U.S. water plant to use C102
(1944). The oxidant was used to treat a potable water supply for taste and
odors arising from phenolic compounds. Other plants that soon adopted the
C102 process for water treatment were Greenwood, South Carolina and Tonawanda,
North Tonawanda, Lockport and Port Col bourne, New York2. The use of ClOo
was not only gaining favor by the water treatment plants, but in 1946, tnree
pulp mills, one in Canada, and two in Sweden, began using C102 for bleaching
wood pulp. This use grew rapidly thereafter; today 60 or more U.S. pulp
mills are using C102 for pulp bleaching.
The use of C102 has continued to expand in the treatment of potable
water. A 1958 survey of 150 municipal water works believed to be using C102
reported that 56 were using the oxidant predominantly for taste and odor
control71. In addition to taste and odor (T/0) control, these plants
listed other uses for C102: disinfection (15 plants), algae control (7
plants) and iron and manganese removal (3 plants).
The use of C102 in U.S. municipal water supplies has leveled off in the
last 15 years. Our current survey of C102 usage found 84 U.S. plants using
this oxidant and most of these plants were older plants. The results of
this survey are summarized later in this Section.
179
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CURRENT USES OF C102
Considerable quantities of chlorine dioxide are used daily for bleaching
in the pulp and paper industry. Some 500+ tons of chlorine dioxide per day
are produced in the 60 U.S. pulp mills for this purpose. It is also used in
large amounts in the textile industry for bleaching and dye stripping, as
well as in the bleaching of flour, fats, oils and waxes70.
In treating drinking water, chlorine dioxide is used for taste & odor
control, color removal, iron and manganese oxidation, oxidation of organics,
disinfection and for providing a lasting residual in distribution systems.
Chlorine dioxide currently is used in 84 U.S. water treatment plants.
Of this number, 63 responded to the C102 questionnaire and the results are
summarized in Appendix F. The Hamilton, Ohio water plant is the only U.S.
plant adding C102 to its process water to serve as the final disinfectant.
Other U.S. plants supplement C102 dosages with surplus chlorine in order to
achieve the prescribed chlorine residual in the finished plant water.
Besides providing disinfection to plant water, C102 is most frequently used
to control taste and odor problems as well as undesirable concentrations of
iron, manganese and algae. Average dosages of C102 can range from 0.10 to
1.5 mg/1, depending on whether the oxidant is used for final treatment
(disinfection) or for pretreatment (removal of algae, Fe, Mn, etc).
In Europe, at least 495 water treatment plants are known to be using
chlorine dioxide for water treatment. C102 is more commonly used in Europe
as a final disinfectant or for residual for finished water than for pretreat-
ment purposes as frequently practiced in United States. European plants
report that C102 provides a longer oxidant residual than chlorine and accord-
ingly, add lesser concentrations of CIO? than the U.S. plants. The average
dosage of C102 in Europe ranges from O.T to 0.5 mg/1. Other than providing
an oxidant residual for disinfection, C102 also is used in Europe for controll-
ing taste and odor problems and to a lesser degree for destroying organic
complexes of iron and manganese early in the treatment process.
There are 10 water treatment plants in Canada, all in the Province of
Ontario, that are reportedly using C102 for water purification.
Before continuing the discussion of C102 practices it is important for
the reader to understand that plant water in the United States and Europe is
not routinely analyzed solely for C102 residual. Rather, plant water is
analyzed by techniques normally used to determine residual chlorine. These
techniques include the col orimetrie OTA and DPD methods as well as amperometric
titration methods. Each of these methods determines free chlorine, hypochlo-
rite, chlorine dioxide, chlorite, chlorate and ozone. When chlorine dioxide
is synthesized using excess chlorine or hypochlorite, these analytical
procedures applied to measure "chlorine dioxide" also measure other oxidants
present.
180
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If care is taken to control the stoichiometry of reactants to produce
chlorine dioxide, the amount of chlorine dioxide measured by the OTA, DPD or
amperometric titration methods can be calculated from the total oxidant
concentration actually measured.
CHARACTERISTICS OF CHLORINE DIOXIDE
Chlorine dioxide (whose color in water changes from yellow-green to
orange-red as the concentration increases) is soluble in water at room
:emperature to about 2.9 g^C102/l at 30 mm Hg partial pressure, or more
The boiling point of liquid
10 grams in chilled water (see Figure 48).
than
C102
59°C. ClOo has a density of 2.4 (air
TI . • i (— ,
is 11°C and the melting point is minus
1) and its molecular weight is 67.5. The oxidant normally is used in
aqueous solution, is 5 times more soluble in water than chlorine gas, and
; not react with water or ammonia as does chlorine. It should also be
noted that C102 is quite volatile and therefore can be removed easily from
solution with minimum aeration2.
The compound has a disagreeable odor, similar to chlorine gas, and is
detectable by humans at 17 mg/1. Chlorine dioxide is distinctly irritating
to the respiratory tract at a concentration of 45 mg/1 in air. Concentrations
of C102 in air above 11% can be mildly explosive71.
1
- 16
\
-
t
Q
i i
o
.
o
o 4
/Z/
20 160
PARTIAL PRESSURE C102 mm Hg
Figure 48. Solubility of C102 in water.
181
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Chlorine dioxide, as a gas or liquid, may be readily decomposed upon
exposure to ultraviolet light. It is also sensitive to temperature and
pressure, which are two reasons why C102 is generally not shipped in bulk
concentrated quantities. Industrially, C102 gas is mixed with inert gases
to about 10% concentration of C102- This greatly reduces the hazard of
explosion.
Although C102 has about 1.15 times the oxidation potential of chlorine70,
this capacity to oxidize is not usually realized at the narrow pH ranges
normally encountered in water or wastewater treatment practices2. Chlorine
dioxide does not belong to that family of "available chlorine" compounds
(those compounds which hydrolyze to form hypochlorous acid), nevertheless
the oxidizing power of C102 has been referred to as having an "available
chlorine" content of 263%, calculated as follows2:
The amount of chlorine in chlorine dioxide is 52.6% by weight. Since
the chlorine atom undergoes five valence changes in the process of oxidation
to the chloride ion:
C102 + 5e~ = Cl~ + 20~2
the equivalent available chlorine content is 52.6 x 5 = 263%. In effect,
this indicates that chlorine dioxide theoretically has about 2.5 times the
oxidizing power of chlorine. This can be substantiated by the reactions
liberating iodine from iodide in the acid/starch-iodide analytical procedure:
Chlorine dioxide:
C102 + 51" + 4H+ >> Cl" + 2.5I2 + 2H20
Chlorine:
HOC1 + 21" >> OH" + Cl" + I
2
However, the oxidizing capacity of chlorine dioxide is not all used in
water treatment practice because the majority of its reactions with substances
in water only cause the chlorine dioxide reduction to chlorite:
C102 + e" = C102"
The redox potential of this couple is 1.15 V. Now compare this to the
action of chlorine using the hypochlorous acid to chloride couple:
HOC1 + H+ = 2e"= Cl" + H20 (EQ = 1.49V)
It is common knowledge that the last reaction shown does occur. In
waterworks practice therefore, it is safe to say that chlorine is a better
oxidant than chlorine dioxide except under special conditions. One of these
special conditions is the reaction of chlorine dioxide with phenols where
six valence changes take place. In this instance chlorine dioxide utilizes
its full oxidizing potential of 263% "available chlorine" and a little
more2
182
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SYNTHESIS OF CHLORINE DIOXIDE FROM SODIUM CHLORITE
Three processes for the synthesis of ClOo from sodium chlorite have
been developed and are commercially applied to water treatment operations.
The optimum efficiency of C102 is a function of chemical feed rates, pH and
retention time in the C102 reactor. The processes, which are designed to
operate with commercially available feedstock chemicals are presented as
fol1ows:
Preparation of C100 From Acid and Sodium Chlorite:
SNaCIO,
(Sodium
Chlorite)
4HC1
(Hydrochloric
Acid)
4C10
(Chlorine
Dioxide)
5NaCl
(Salt)
2H20
or
lONaCIO,
• 5H2S04
(Sulfuric
Acid)
8C10,
5Na2S04 + 4H20
(Sodium
Sulfate)
This process can use either hydrochloric acid or sulfuric acid as the
acid reagent for C102 generation. The HC1 reagent is more commonly used in
water treatment operations. It should be noted that although the HC1 method
above requires 25% more NaC102 than the NaC102/Cl2 method (as discussed in
the next section), the NaC102/HCl method theoretically does not result in
free chlorine in the product water as does the NaC102/Cl2 method. The
latter method uses excess chlorine in the reagent mix to lower the pH for a
more complete generation of CIO? with free chlorine carrying over into the
product water. Analytical results gathered over a three year period at the
ZUrich, Switzerland Lengg plant76, however, have shown that the so produced
C109 solutions in fact contain 4 to 7.5% free chlorine, 0 to 4.5% NaC102 and
90 to 96% C102.
Extra care must be exercised when mixing NaC102 and acids. Sulfuric
acid must never come into contact with solid NaC102 as the reaction is
explosive. Therefore, solutions of NaC102 in water are employed exclusively
in water treatment.
Preparation of CIQg From Gaseous Chlorine and Sodium Chlorite:
This process is a two step reaction, first beginning with the formation
of an aqueous chlorine compound -- hypochlorous acid.
Cl.
H20
HOC1
HC1
(Hydrochloric Acid)
(Chlorine Gas) (Water) (Hypochlorous
Acid)
These intermediate products in turn react with sodium chlorite to form C102.
183
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HOC! + HC1 + ZNaClCL > 2C10- + ZNaCl + H00
• C. C. {_
The summation of these two equations is:
C12 + 2NaC102 —> 2C102 + 2NaCl
and the stoichiometry of reactants is 1 mole Cl^/Z moles NaClOo, or 0.5
molar.
In practice, however, it is recommended that the chlorine to chlorite
ratio be 1:1 by weight (1.28 molar). This provides an excess of chlorine
which increases the reaction rate necessary to attain a high yield of ClOo.
At molar ratios of less than 1:2 of chlorine to sodium chlorite, the activation
is incomplete and unreacted chlorite carries over into the product water71.
Stoichiometrically, 1.68 Ibs (0.762 kg) of 80% pure NaCIO? (commer-
cially referred to as technical grade) are mixed with 0.5 Ib (6.227 kg) of
chlorine to produce 1.0 pound of C102- Thus water treatment plants maintain
at least a 1:1 ratio of these reagents for C102 production. The chlorine
solution is normally at a minimum concentration of 500 mg/1. When a 1:1
weight ratio of chlorine to technical grade NaC102 is used to prepare C102
and this solution is analyzed by OTA, DPD or amperometric techniques, the
total oxidant measured will consist of approximately 50% C102 and 50% free
residual chlorine.
It is also important to note another reaction that takes place during
the NaC102/Clo production of C102. The excess chlorine that is added
causes the following reaction:
HOC1 + C102 ^ — C103" + HC1
(as excess chlorate
chlorine) ion
The true amount of free available chlorine residual therefore can be reduced
because of the oxidation of the C10? by the free chlorine to the chlorate
ion (C103")72.
C10? Preparation From Sodium Hypochlorite and Sodium Chlorite:
Smaller localities that use hypochlorite feed systems find it advantageous
to generate C10? by acidifying the chlorite solutions with HC1 or H2SO..
The stepwise reactions of hydrochloric acid and sodium hypochlorite forming
C102 are as follows:
NaOCl + HC1 > NaCl + HOC1
HC1 + HOC1 + 2NaC102 > 2C102 + 2NaCl + H20
Although the three reagents are stored separately, the NaCIO- and NaOCl can
be fed into the C102 generator using one pump. The system atso can be
184
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arranged to combine streams of NaC102 and acid proportionally into a single
stream of hypochlorite solution.
For much larger uses of C102, such as for bleaching paper pulps,
generally greater than the demana of most water treatment operations,
chlorine dioxide can be synthesized from sodium chlorate (NaClCU). For
large scale operations, this approach has been found to be more economical,
since sodium chlorite actually is manufactured by reacting sodium chlorate
with hydrogen peroxide in a basic solution of sodium hydroxide. The inter-
mediate step which produces sodium chlorite from sodium chlorate is circum-
vented in large scale production of C10?.
ADVANTAGES AND DISADVANTAGES OF CHLORINE DIOXIDE
Chlorine dioxide offers many advantages for water treatment operations.
One feature is that its oxi dative efficiency is not impaired over a wide
range of pH. A second desirous feature is that it does not react with such
chlorine-demanding materials as ammonia and nitrogenous compounds. In
addition, EPA has noted that when C102 is synthesized with no free chlorine
present as an end product and added to the water being processed, no tri halo-
methanes (THMs) are formed73.
There are other advantages to using ClOp. Chlorine dioxide destroys
taste-producing phenolic compounds in the water supply. Of particular
interest, this oxidant also can destroy the chlorophenol compounds which
have objectionable tastes and odors and which result from chlori nation.
ClOo also serves as an algaecide. Chlorine dioxide has been shown to
be successful in controlling musty and fishy tastes that are characteristic
of the preZ.sence of such algae as Anabena , Asterionella, Synura and
Vorticella2.
Manganese can cause offensive black waters when the metal is present in
minute concentrations. Chlorine dioxide quickly oxidizes the manganese
compound according to the overall reaction:
2C102 + MnS04 + 4NaOH - > MnOp^ + ?NaC102 + Na2$04 + 2H20
The rate of reaction is much faster than that of chlorine. Manganese is
slowly oxidized by chlorine and may require 24 hours before complete oxidation
has occurred. By this time, the water may be well into the distribution
system with the black MnO~ compound precipitating inside the pipes. Because
of its high cost, C102 use is generally limited to water operations containing
manganese in concentrations of 1 mg/1 or less.
Chlorine dioxide also can be used to remove iron from the water supply,
although the reaction rate is not as rapid as it is for manganese. Both
metal compounds are oxidized more efficiently by C102 at pH 7 or above. The
overall reaction of iron with C102 is as follows:
185
-------
C102 + Fe++ + NaOH + H20 —> Fe(OH)3 + NaC102
The C102 is not consumed by other chlorine-demanding materials and oxidizes
soluble ferrous iron to insoluble ferric hydroxide. This heavy, brown floe
typically is removed by sedimentation and filtration.
Chlorine dioxide is as effective as chlorine as a disinfectant and, as
previously mentioned, is less sensitive to changes in pH. At a typical
operating range of pH 6 to 10, chlorine partially loses its effectiveness
for disinfecting; C102 does not. Also, because C102 does not react with
ammonia and other nitrogenous compounds, it can achieve a higher residual and
bacteriological kill than chlorine6.
Chlorine dioxide can be generated at any water plant that uses chlorine
or hypochlorite. The oxidant is produced either seasonally or year-round
depending on the need. Most plants in the United States operate the C10?
generation system on a manual basis, whereas most European countries have
automated systems. The manual system is applicable to plants of constant
flow and water quality. For variable flows or variable water quality, the
manual system can be adjusted to proportion the chemical reagent feed rates
to meet the C102 demand.
One concern of using chlorine dioxide in a water treatment process is
the excess chlorine that typically carries over into the product water.
Excess chlorine in the product water is common to C102 production in U.S.
water plants and in many European plants in Germany, France and England.
Excess free chlorine that is discharged from the C102 reactor vessel may
react with organics and form trihalomethanes - several of which are suspected
carcinogens. These products are not formed when C102 is produced in the
absence of free chlorine residual.
Chlorine dioxide does not react chemically with water as does chlorine,
and therefore is expelled from solution by aeration. The strength of C102
deteriorates under these conditions and the remaining solution will contain
neglible amounts of chloric acid (HClOo)2. Aqueous solutions of C102 are
also sensitive to photodecomposition, the rate of degeneration being a
function of both exposure time and intensity of ultraviolet light. The end
products from such a reaction are chloric and hydrochloric acids2.
There are current uncertainties regarding the health effects of chlorine
dioxide in drinking water -- particularly the effects of the chlorite ion
(C102~). When C102 oxidizes organics (or any other reducing agent), the
following reaction can take place:
organic + C102 > oxidized organic + C102~
The C102 reverts to the chlorite ion which then can remain in solution.
Incomplete chemical reactions within the C102 reaction vessel also can
produce chlorite ions from the NaC102 reagent. Although there are reportedly
no epidemiological or toxicological studies that identify adverse health
risks due to the chlorite ion, the EPA, HEW and many European organizations
186
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currently are examining, in closer detail, the potential health effects of
the chlorite ion. More definitive data are expected in 1978.
The chemical reagent NaClCL is safe to use for water treatment operations,
provided that the operator understands proper handling and storage of the
chemical. Rubber gloves, apron and safety goggles are recommended when the
chemical is handled. NaClOo is readily combustible in the presence of
organic material (i.e., straw, leather, rags, etc.) and therefore should
never be allowed to splash on clothing or remain or evaporate on the floor.
Sodium chlorite also can explode if reacted directly with an acid because of
the rapid evolution of C102 gas. Stored NaC10? should be protected from
heat. When the temperature of the chemical reaches 347°F, NaClCL decomposes
rapidly with sufficient heat liberated to make the decomposition self-
sustaining. An explosion will result if the chemical is contained in closed
drums or tanks and subjected to such temperatures.
U.S.A - C102 QUESTIONNAIRE AND PLANT VISITATION SUMMARY
General
A total of 105 questionnaires was forwarded to U.S. water treatment
plants which were reported by state health departments to operate C102
systems for water treatment operations. Based on the questionnaires returned,
it was learned that 63 plants have ClOp systems in use. A follow-up telephone
survey to those plants not responding verified that 21 more water plants
operate C102 systems. Thus, a total of 84 U.S. water treatment plants use
C102 for water treatment processes. The following is a brief summary of
those 63 plants that responded to the questionnaires. Pertinent data are
presented in Table 26.
Distribution of Plants Using C102 based on Plant Flows
Almost 48% of those respondents (30 plants) confirming the use at CIO-
on their questionnaires, have plant flows of less than 5 mgd. Most of these
30 water plants are located in EPA Regions 4 and 5. There are 18 plants
(29%) using C10? that have plant flows between 5 and 10 mgd. Region 5 has 8
of these plants: Of the remaining plants, there are 6 water plants using
ClOo having plant flows between 10 and 20 mgd and 9 plants with flows greater
than 20 mgd. Only 4 of the 63 U.S. plants are privately owned and operated.
Uses of C100
The water treatment plants responding to the questionnaires indicated
that the major reason for using C10? is to control taste and odor problems
in the water supplies. Other than controlling T/0 problems, C102 is used
frequently to reduce levels of iron, and manganese, to disinfect and to
provide a chlorine residual in the plant water (this latter objective is
accomplished by adding excess chlorine to the C102 reactor to insure that
free chlorine passes through the reactor and into the plant water). Most
plants list multiple uses for adding C102 at their plants.
187
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TABLE 26. C102 QUESTIONNAIRE RESULTS BY EPA REGIONS
EPA Regions 1
No. Plants Surveyed 3
No. Plants Responding 1
Public 1
Private
Process:
Acid-NaClOp
CU-NaClO-
HCT-Hypocnl ori te/Nacl 02
Plant Size (mgd)
<5 mgd
5-10 mgd 1
10-20 mgd
>20 mgd
Purpose for C102 addition (c)
Taste and Oaor 1
Organics
Disinfection
Fe & Mn
Color
Cl? residual (d)
2
10
3
2
1
2
1
1
2
3
2
1
3
21
9
8
1
7
1
2
4
1
2
7
4
3
2
4
30
21
20
1
21
14
4
2
1
1
3
7
17
3
7
5
35
26
25
1
1
23
1
11
8
3
4
24
2
11
1
2
10
6
2
2
2
1
1
1
1
7
4
1
1
1
1
1
1
1
1
Total
105
63
59
4
1 (b)
55 (b)
3 (b)
30
18
6
9
37
12
21
18
5
12
(continued)
-------
TABLE 26. (continued)
CO
EPA Regions 12345
C10? Dosage
^Range (mg/1) 0.1-0.2 0.1-0.4 0.25-7.0 0.1-2.0
Average (mg/1) 0.15 0.17 1.23 0.63
Measured Residuals (e)
Disinfection
Range (mg/1) 0.5-1.0 0.5-3.0 1.0-2.0 0.6-2.6
Average (tug/1 ) 0.75 0.9 1.5 1.36
Taste & Ordor
Range (mg/1) 1.0 0.1-0.9 0.3-10 0.1-2.0
Average (mg/1) 1.0 0.2 3.0 0.62
Number of Plants Using
Constant Dosage 59 9
Intermittant Dosage 1 3 6
6 7 Total
0.6 (b)
0.6 (b)
0.3 (b)
0.3 (b)
0.12 (b)
0.12 (b)
1 (b)
(b)
(a) 105 U.S. water treatment plants were surveyed but, based on questionnaire results and follow-up
telephone surveys, the best estimate is that 84 of these plants use C102. The above data
summarize only 63 plants which responded to the questionnaire.
(b) For the line items, not all plants provided all the information requested. Information presented
is for those plants responding.
(c) Many plants list multiple purposes for ClOn addition.
(d) Excess C12 added to CIO- generation process to provide chlorine carry over to plant water for
achieving chlorine residual.
(e) U.S. water treatment plants generally do not measure specifically for C^ residual but rather
for the summation of oxidants that are anlayzed collectively by the test used: DPD,
amperometric, etc.
-------
Dosages
The dosage of C102 in U.S. water treatment operations depends on
whether the oxidant is used to pretreat the influent water, treat the plant
water, or to treat the effluent water. Higher dosages of ClOo generally are
used to pretreat raw water supplies for controlling algae, iron and manganese.
Taste and odor problems also can require higher dosages of CICL. Adding
ClOo as a disinfectant requires much lower concentrations. For U.S. water
plants, the approximate range of C102 added is 0.1 to 1.5 mg/1. Many plants
seasonally add higher dosages of ClOo, depending on the raw water quality.
Generation of
The most common method of generating CK^ at U.S. water treatment
plants is by the chlorine/sodium chlorite reaction. Of the 63 plants
responding, 59 use this process. Many plants using the chlorine/sodium
chlorite technique add chlorine in excess of the recommended 1:1 weight
ratio of chlorine to sodium chlorite (technical grade). U.S. manufacturers
recommend this 1:1 ratio to insure a maximum yield of chlorine dioxide.
Chlorine is fed to the ClOo reactor using single pass chlorination. There
are 3 water treatment plants using the acid/hypochlorite/sodium chlorite
technique for ClOo production. One plant (Ann Arbor, Michigan) uses the
hydrochloric acid/sodium chlorite method for generating ClOo. A second
plant in Contra Costa County, California is using the sulfuric acid/sodium
chlorite method of generation.
Most of the responding U.S. plants have been in service for at least 15
years. As a result many of the older C102 systems do not reflect the more
recent improvements in C102 generation.
Methods of Analysis and Monitoring
Only a limited amount of information was provided by the plant respondents
on this subject. From the data available, however, it is concluded that
U.S. water treatment plants generally do not analyze plant waters specifically
for ClOp residual. Rather, the plant water is analyzed for total oxidant or
"chlorine residual", as this is the standard practice of U.S. plants. A
portion of the "chlorine residual" measured, however, can be attributed to
CIO- residual by knowing the stoichiometry of reactants employed and the
chemical reactions involved. Therefore, although several U.S. water treatment
plants reported that "C10?" is measured at the plant, their incomplete
explanations of the test procedures used indicates that C102 is measured
conjunctively with chlorine, and together these oxidant resTduals are regi-
stered as the "chlorine residual" or "chlorine dioxide" reported.
The common methods used to measure C102 and/or chlorine in the plant
water are DPD, amperometric titration, spectrophotometry and OTA (which has
been deleted from the 14th edition of Standard Methods). Of these, only the
spectrophotometric procedure can be conducted so as to determine C102 in
the presence of free residual chlorine.
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Other
Responding U.S. plants often noted the high cost of sodium chlorite as
a disadvantage of using CICL for water treatment. A few plants reported
their concern for the potential explosiveness of sodium chlorite if not
properly handled and stored.
Most plants operating a C1CL generating system use polyvinyl chloride
piping and appurtenances.
Limited operational problems are reported with chemical feed pumps,
particularly with the suction tubing from the pump to the NaClCL solution
tank. Thin walled rubber tubing becomes limp and weak after several months
of service. Pump suction causes the walls to collapse and the chemical feed
stops. Heavy walled tubing or PVC pipe does not prevent this problem.
Several plants expressed concern about the public health risks regarding
the addition of chlorite to potable water. No plants reported any knowledge
of the organic oxidation products formed as a result of C102 treatment.
SUMMARY OF U.S. PLANT VISITS - OVERVIEW
During September and October 1977, 13 water treatment plants in the
United States were visited. The purpose of these visits was to learn first
hand information about the engineering and operational aspects of C102 in
water treatment operations. Of the thirteen plants visited, five were
located in Georgia, five in Ohio, and one each in West Virginia, Kentucky
and Michigan. These plants offered a broad picture of the use of CIO- in
United States water treatment works. The reasons for choosing these T3
plants for visitation include the following:
• purpose of C102 application
• type of C102 generation systems
t type of water treatment process
• source of raw water supply
• size of plant
• type of oxidant analysis
Most of the plants visited use C102 for the control of taste and odor
problems. The sources of these T/0 contaminants are attributed to phenols,
algae and organics in the raw water supplies. Most of these taste and odor
bodies are natural in origin. Those plants that are supplied water (directly
or indirectly) from surface reservoirs typically use CIO- to reduce the
concentration of manganese and iron in the raw water. TRe occurrence
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of these metals is generally seasonal. Of the 84 water plants that are
reportedly using C102, Hamilton, Ohio, and Fayetteville, Georgia are the
only plants using the chemical solely for disinfection. Fayetteville adds
C102 with excess chlorine to the raw water. Hamilton, however produces C109
storchiometrically and adds it as a final disinfectant. No other oxidant is
added at this plant, whereas other plants supplement C10? addition with a
prechlorination and/or post-chlorination step.
Seven of the thirteen plants visited use C102 for the removal of
manganese and iron. The point of application is typically ahead of the
filters in order that the insoluble compounds can be filtered from the plant
water. The other six plants that are troubled with phenolic compounds or
other taste producing agents add the C102 either before or after the filtration
process. The Hamilton, Ohio plant adds C102 in the clearwell for disinfection.
The method of C102 generation is predominantly the sodium chlorite/
chlorine system. 01 in Corporation manufactures the NaC102 supplied to the
water plants although the chemical generally is delivered to the plant by a
local retailer. Several plants purchase liquid sodium chlorite either in
150 to 200 pound drums (37% concentration) or by tank truck (approximately
28 to 30% concentration). The other form of NaC102 is the anhydrous technical
grade which is 80% pure NaCIO,,. The larger plants such as Columbus, Ohio
(35 mgd) and Atlanta, Georgia (70 mgd) prefer the liquid NaC102 because
there is no need to bother with storing the drums, mixing the ary chemical
or working with a potentially explosive chemical. (Powdered NaC102 has been
known to "spark" when walked upon with shoes.) Production of C102 from
liquid NaC102 is easily controlled because the exact concentration of the
liquid NaC102 feed can be controlled. With batch mixes, the operator must
add the correct proportions of NaC102 to water in order to prepare the
desired concentration of NaC102 feed. Smaller plants, such as Bethesda,
Ohio (0.079 mgd) and Covington, Kentucky (10 mgd), have elected to use
anhydrous NaC102 or liquid NaC102 which are both delivered in drums. These
plants do not have the facilities or money to operate large scale liquid
feed systems as discussed above. Water treatment plants also use C102 on a
seasonal basis and thereby can easily accommodate the storage of several
drums of NaC102 in the plant in anticipation of using the chemical for a few
months each year.
Only one of the thirteen plants uses acid as a reagent for C102 produc-
tion — Ann Arbor, Michigan. The plant formerly used chlorine with NaC102
to generate C102 but the plant manager could not satisfactorily control tne
pH inside the CTO? reactor vessel. Chlorine costs were escalating and at
the time and the chlorinators were requiring frequent service. The plant
therefore switched to hydrochloric acid which is delivered to the plant in
150 pound drums. The C102 production reportedly works much more efficiently.
The C10? reactor vessels at the plants visited were made by one of two
manufacturers— Wallace & Tiernan or Fischer & Porter. The only apparent
difference between the two brands of equipment is that the Fischer & Porter
unit has an effluent sampling port on the reactor vessel. Both reactors are
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upflow units. Those plants that have the Fischer & Porter type of unit do
not sample routinely and analyze the chemistry of the C10? product in the
reaction chamber. The Ann Arbor plant has installed a sampling port on its
C102 generator and reportedly analyzes the sample periodically. Hamilton,
Ohio and Toledo, Ohio fabricated their plant C10? reactors. The implicit
reasoning for doing this is that the design and construction of the reactor
is simple enough for most plant personnel to master. The reactors reportedly
are performing satisfactorily and the construction appeared acceptable.
Most of the ClOo reactors observed are transparent for purposes visual
inspection of tne C102 color produced. A few reactors were opaque (Hamilton,
Ohio and Columbus, Ohio) but viewing tubes were installed on the discharge
piping for visual inspection of the C102 product.
Chemical feed pumps for NaC102 typically are of the diaphragm type.
Manufacturers of this equipment include Wallace & Tiernan, Fischer & Porter
and BIF. Only one plant reported problems with the diaphragm pump. For
some undetermined reason, the plastic diaphragm cracks and causes the feed
system to malfunction. The pumps can be metered to provide variable flow
rates. Less than half of the plants visited have back up NaC102 feed pumps.
The piping for the C102 system generally is consistent from plant to
plant. Most piping from the NaC102 pumps and from the gas chlorinators to
the C102 reactor is polyvinyl chloride—presumably schedule 80, solvent
welded. The effluent piping from the C102 reactor is PVC (schedule 80) or a
heavy walled rubber tubing approximately f.5 to 2 inches in diameter. This
latter material reportedly can be furnished by the manufacturer of the C102
reactor vessel. The piping from the chlorine cylinders to the gas chlorinators
is welded black steel. There is some variance from plant to plant as to the
tubing material that is for the suction line of the NaC102 feed pumps. Some
plants use Tygon tubing and others use PVC (schedule 40 or 80). Tygon
tubing has a tendency to lose its rigidity after several months of use and
is subsequently replaced. If the tubing walls are weakened too much, the
pump suction partially collapses the tubing and thereby restricts the flow
of NaC102 liquid.
Most of the C102 systems lack chlorine gas leak detectors, although
such units are found in the chlorine storage rooms of many of the larger
plants. About half of the plants have floor drains around the NaC102 feed
system. These drains generally empty into either a municipal sewer or into
a gravel trap. At least half of the plants visited have an air exhaust
system in the chlorine storage room. The switch to activate this system
typically is next to the entrance door (some inside and some outside the
entrance door). Each plant has a glass panelled entrance door for visual
inspection of the chlorine room interior. Nearly every plant has one or
more gas masks for emergencies in the chlorine room.
During each plant visit, the plant operator was asked about the opera-
tional controls on the C102 system. For example, when was the last
time the dials and gauges were calibrated on the chlorinators, what is the
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proper operating water pressure for the injection of chlorine gas into the
water feed system, what is the correct flow of water into the C102 reactor
vessel, etc. Most operators did not know this information and haa no
records of what the answers might be. It appears that most of the plants
are content to operate the various pressure and vacuum settings of the C102
system that have been used at the plant in the past. Several of the plants
are operating the CICU reactor vessels at too high a water pressure. This
can be detected by the initial formation of the red-brown color of C102 at
the very top edge of the reaction vessel. One plant is producing C102 in a
plug flow manner as evidenced by the cyclic formation of the red-brown color
in the reactor. In this case, much of the chlorine solution passes through
the vessel without reacting with chlorite ions. A few of the plants are
producing very pale lime-yellow C102 solutions, whereas others are producing
rich red-brown C102 solutions. The intensity of the color that is formed
indicates the different concentrations of chlorine dioxide produced, and is
dependent upon proper mixing action inside the C102 reactor vessel. Equally
important are the feed ratios of the chemical reagents.
Manufacturers of CIO, generation systems recommend a 1:1 feed ratio by
weight of chlorine and soaium chlorite. Most plants that were visited
achieved this ratio and even higher. Columbus, Ohio and Hamilton, Ohio
operate the C102 generation system using a 1:1 ratio of Cl? and NaClOo.
Other plants such as Bethesda, Ohio and Toledo, Ohio operate the Cl2/NaC102
feed systems at 1:5.6 and 6.5:1 weight ratios, respectively. The reasons
for this wide range of ratios differ from plant to plant. Several plants
add excess chlorine to provide the necessary chlorine residual in the finished
water. Other plants are surcharging the C102 reactor with chlorine in order
to lower the pH in the reactor for a better rate of C102 production. There
is evidence that a few other plants may not have a complete understanding of
how to feed the chemical reagents properly. The NaC102 concentrations in
the process water range from 0.2 to 1.0 mg/1 for most plants visited. The
concentration of NaC102 in Fayetteville, Georgia water 1s 4 mg/1 NaC102
where the C10? is used to control manganese problems. Bethesda, Ohio Ts
estimated to nave a concentration of 17.4 mg/1 NaC102 in the plant water
added for the abatement of problems due to manganese and algae. This is an
unusually high concentration to be added in any case, and it is of compounded
concern when knowing that is is being added to the finished water and not
the raw water.
In addition to being fed into the C102 reactors, chlorine also is added
to the plant water in other treatment processes. It is interesting to note
that free chlorine residuals in the finished water of the plants visited
reportedly range from approximately 0.2 to 1.5 mg/1. The free residuals in
the distribution systems are about 0.1 to 0.5 mg/1. One plant is reportedly
chlorinating the finished water far above what would appear to be an adequate
dosage: 2.5 to 4.0 mg/1 free chlorine residual with an upper limit of 6
mg/1.
Only one plant specifically monitors the C102 residual in the finished
water « Hamilton, Ohio. The C102 is measured spectrophotometrically to
levels of less than 0.2 mg/1 as CT02. The other plants measure chlorine
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residual (free and/or combined) to assure that an oxidant level is achieved
in the treated water. The OTA and DPD analytical methods are the common
tests to measure chlorine residual. One plant uses the H-acid technique.
These methods are further discussed in Standard Methods75 and the Handbook
of Chlorination2. At a few plants it is difficult to determine how well
the ClOp is performing because of the abundance of other chemicals that are
added to the plant water; i.e, alum, lime, soda ash, polyphosphates, powdered
activated carbon, potassium permanganate and chlorine.
EUROPEAN C102 PLANT VISITATIONS AND QUESTIONNAIRE RESULTS
In Appendix F are listed the pertinent features of 74 European drinking
water treatment plants which responded to the questionnaire and which employ
chlorine dioxide in one or more places in their treatment processes. It was
not possible to develop an accurate count as to the total number of European
water treatment plants employing chlorine dioxide for several reasons.
First the chlorine dioxide market is served by a great many more companies
smaller than those who serve the ozone generation market. Secondly, there
is no association representing the interests of chlorine dioxide suppliers,
similar to the International Ozone Institute, through which we could work to
develop such data.
Nevertheless, we have been able to determine that there are at least
495 European water treatment plants employing chlorine dioxide. This number
was derived from discussions with suppliers of chlorine dioxide generation
equipment who were exhibiting at the Third International Symposium on Ozone
Technology, Paris, France, May, 1977, and at Wasser Berlin, Berlin, Germany,
May 1977,
Degremont, Reuil Malmaison, France 100
CIFEC, Paris, France 35
Wallace & Tiernan, Germany 60
CFG (Chemie und Filter GmbH), Heidelberg, Germany 250
ALLDOS 20
Fischer & Porter, USA (all in Italy) 30
Total 495_
In Canada, only 10 water treatment plants are known to be using chlorine
dioxide, mainly for taste and odor control, and these are all located in the
Province of Ontario, in the vicinity of Toronto. Seven plants are known in
Africa, 3 in Asia, 3 in South America, one in Iceland, one in New Zealand
and 3 in the Indonesian area. Therefore, at least 523 plants throughout the
world are known to be using chlorine dioxide for some purpose.
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During May, 1977, the site visitation team visited 15 European water
treatment plants which employ chlorine dioxide. Four of these plants are in
France, one in Belgium, eight are in Germany and two in Switzerland. Only
two of the chlorine dioxide plants visited did not also employ ozonation,
either before or after use of chlorine dioxide.
As a general statement, Europeans use chlorine dioxide when chlorine
cannot be used, mainly because of higher costs. In Europe, chlorine dioxide
is said to cost 3 to 3.5 times more than does chlorine. The two primary
purposes for which chlorine dioxide is utilized are for pretreatment and
post-treatment. In pretreatment, chlorine dioxide is utilized at the Paris
suburb plants of Choisy-le-Roi (on the Seine), Neuilly-sur-Marne (on the
Marne), and at Annet-sur-Marne (upstream of Paris on the Marne) for breaking
up organically bound manganese and iron and for predisinfection of water
before filtration. At Toulouse, in southwestern France on the Garonne
River, chlorine dioxide is used in pretreatment for predisinfection, taste
and odor control, and for color removal.
At the Brussels, Belgium Tailfer plant, both chlorine and chlorine
dioxide are used in pretreating Meuse River water. Chlorine performs the
predisinfection function, while chlorine dioxide decomposes the organic
complexes of iron and manganese and also predisinfects.
Dosages of chlorine dioxide employed for pretreatment generally range
from 1 to 1.5 mg/1 in Europe. These and other dosage or residual levels
must be considered in terms of the method of preparing ClOo and the method
of analysis employed, as discussed earlier in this section.
It is generally agreed by Europeans that chlorine dioxide, having a
stronger oxidation potential than chlorine, is capable of oxidizing organic
complexes of iron and manganese, whereas chlorine is not. Once converted to
their ionic states, both iron and manganese will be oxidized to stages at
which they easily hydrolyze and can be removed by settling and filtration.
In post-treatment (for residual), chlorine dioxide was being used only
at Choisy-le-Roi and Annet-sur-Marne of the plants visited in France and
Belgium.
In Germany and Switzerland, chlorine dioxide was being used only for
post-treatment at all 10 water treatment plants visited in these countries.
Germans and Swiss use a maximum of 0.3 mg/1 of chlorine or chlorine dioxide
(or a combination of the two) to provide residual for distribution systems.
This dosage level provides trace amounts of chlorine or chlorine dioxide in
the distribution systems. The tacit rule in these countries is that if the
finished water leaving the plant requires greater than 0.3 mg/1 chlorine or
chlorine dioxide to provide stable residuals in the distribution system,
then the water treatment process must be modified to reduce oxidant demand
until this level of dosage is attained.
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There are four methods of synthesizing chlorine dioxide on-site at
European drinking water treatment plants that the survey team observed:
0 Technique #1. Addition of chlorine gas to water, followed by
addition of excess chlorine water solution to aqueous solutions
of sodium chlorite.
• Technique #2. Addition of chlorine gas to water under pressure,
then addition of this solution under pressure to aqueous
solutions of sodium chlorite under pressure.
• Technique #3. Addition of chlorine gas to water and recirculation
of this aqueous solution in a closed loop with continued
addition of chlorine until a pH below 2.7 has been attained. Then
addition of this pH 2.7 chlorine solution to aqueous solutions of
sodium chlorite.
• Technique #4. Addition of dilute HC1 solution to aqueous solutions
of sodium chlorite.
Technique #1 is the most common and widespread method in Europe, and
is the basis for the older Wallace & Tiernan generators and for those units
marketed by Chi orator (Karlsruhe, Germany). In technique #1, excess chlorine
deliberately is added to sodium chlorite solution so as to maximize conversion
of chlorite ion to chlorine dioxide. However, this results in free residual
chlorine also being present.
Technique #2 is the newer Wallace & Tiernan procedure, which is in use
at the Brussels, Belgium Tailfer plant and is to be installed at the Berlin,
Germany Jungfernheide plant.
Technique #3 is the basis for the patented CIFEC system, introduced
during the past 2 to 3 years and which has been installed in some 35 European
water treatment plants. The site survey team observed CIFEC equipment in
operation in France at Choisy-le-Roi, Annet-sur-Marne and at the Toulouse
Clairfont plant.
Techniques #2 and #3 are claimed by their manufacturers to provide 98
to 100% conversion of chlorite ion to chlorine dioxide with no excess free
chlorine being present.
Technique #4 uses mineral acid to convert chlorite ion to chlorine
dioxide. Since chlorine gas is not used in this process, there should be no
"excess" chlorine present with the desired chlorine dioxide. However,
Valenta & Gahler76 have shown over a period of three years at the ZUrich
Lengg plant, that there is an average of 4 to 7.5% free chlorine present in
the so-produced ClOg.
Details of these methods of generating chlorine dioxide are described
later in this Section under "Engineering Aspects of Chlorine Dioxide Generation
Systems".
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European plants analyze for C102 colorimetrically (OTA, DPD, H-acid)
or amperometrically. As noted under the discussion of USA plants, these
procedures actually determine the "total oxidant" present, C102, chlorine,
OC1~, CIO", C10,T and ozone. However, when controlled excesses of chlorine
are added to sodium chlorite solutions the amounts of free chlorine dioxide
present are known from the stoichiometry used.
Pertinent Features of Plant Visitations
France--
At Choisy-le-Roi, on the Seine River in the Paris suburbs, chlorine
dioxide is used in pretreatment, as necessary, for oxidation of organics
(the plant personnel suspect the presence of geosmin) and for oxidizing
manganese. Raw and settled waters (before and after pretreatment with
chlorine dioxide) are analyzed daily for manganese and the dosage of chlorine
dioxide is adjusted accordingly. Chlorine dioxide for pretreatment is dosed
at about 1.5 mg/1.
Later in the process and before ozonation, any residual chlorine
dioxide is destroyed by treatment with bisulfite. This step is necessary so
that extraneous concentrations of chlorine dioxide oxidant will not be
measured during ozone monitoring. The Choisy ozone disinfection step is
controlled by monitoring residual ozone.
There are currently 10 chlorine dioxide generators used at Choisy for
pretreatment at the 10 chemical mixing sites. All use the older generation
process involving addition of excess chlorine in water to sodium chlorite
solution. Equipment for chlorine dioxide generation for pretreatment is
manufactured by Trailigaz of Garges-les-Gonesse. The plant is being modified
to combine these 10 chlorine dioxide addition points into a single operation.
At that time, a single CIFEC generator (see Engineering Design subsection)
will replace the 10 existing C102 generators.
For post-treatment with chlorine dioxide, a CIFEC generator was installed
in mid-1976. Before this, post-treatment after ozonation had been provided
with chlorine. However, it has been found that residuals of chlorine dioxide
last longer in the Choisy-le-Roi distribution system than do residuals of
free chlorine.
Post-treatment dosage of chlorine dioxide at Choisy-le-Roi is 0.5 mg/1
for 6 months of the year, with lower dosages being applied in winter. Plant
personnel are concerned with this "high" level of chlorine dioxide being
dosed, because of the probable re-formation of chlorite ion. As a result,
there is a pilot program being conducted to "super-ozonize" the water so as
to lower the amount of chlorine dioxide to be added. Super-ozonation involves
dosing with as much as 10 mg/1 of ozone, to obtain a residual ozone concentra-
tion of 0.6 to 0.7 mg/1 after 10 minutes of contact time.
Controls for addition of chlorine dioxide in pretreatment at Choisy are
manual, but are automatic in the CIFEC system used for post-treatment.
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At Neuilly-sur-Marne, on the Marne River in the Paris suburbs, chlorine
dioxide is used in pretreatment only for oxidation of organics and predisin-
fection. Dosage is 0.5 mg/1.
At Annet-sur-Marne, on the Marne River upstream of Paris, chlorine
dioxide is used both for pre- and post-treatment. In pretreatment, 1 mg/1
dosage is used for predisinfection. For post-treatment, 0.5 mg/1 of chlorine
dioxide is added after ozonation to provide a residual of at least 0.05 mg/1
at the extremities of the distribution system. Pretreatment with chlorine
dioxide is practiced the year around, but post-treatment with chlorine
dioxide is practiced only in summer. During winter months, chlorine alone
is adequate and is less costly.
Generation of chlorine dioxide at Annet originally was conducted with
Trailigaz equipment (excess chlorine water added to sodium chlorite), but
since late 1976 the material has been generated in a CIFEC apparatus, which
has given satisfactory performance.
The Annet-sur-Marne plant is being constructed in stages, with the
first 25,000 cu m/day capacity train having been placed in operation in
1973. Chlorine dioxide was installed for post-treatment as a security
measure, since it already was present for predisinfection. However, because
of the high quality of treated water, Annet is planning to install chlorine
as the only post-treatment step in the second 25,000 cu m/day treatment
stage. Chlorine dioxide will be used as a predisinfectant in the second
train, and will be available for post-treatment if necessary.
At the Clairfont plant in Toulouse (southwestern France on the Garonne
River), chlorine dioxide is used in 1.5 mg/1 dosages for pretreatment only
(predisinfection, tastes, odors and color). Chlorine dioxide is prepared in
a CIFEC apparatus, and its performance has been satisfactory since it was
installed in 1975.
Although not installed today at Aubergenville and at Rouen-la-Chapelle,
chlorine dioxide was used at these plants before ozonation was incorporated.
At Aubergenville, chlorine dioxide was used when phenols were present in the
raw water. Today the phenol content of the plant raw water is much lower
than it was, and ozonation can handle any surges.
Before the new ozone/activated carbon treatment system was installed at
Rouen-la-Chapel!e, the treatment process from 1964 to 1975 involved drawing
deep well water and treating with chlorine dioxide. Since the newly installed
ozonation process removes phenols, there is no longer a need to use chlorine
dioxide. The cheaper chlorine is used at Aubergenville and at Rouen to
provide residuals for the distribution systems.
Belgium—
At the Brussels, Belgium Tailfer plant, chlorine dioxide is used in
pretreatment for decomposing organic complexes of iron and manganese, for
color removal and for bacterial disinfection. It is added early in the
treatment process along with chlorine, sulfuric acid, alum and silica.
Production of chlorine dioxide is monitored in the analytical laboratory by
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analyzing for the amounts of reactants added (chlorine, water and sodium
chlorite solution). Residual chlorine dioxide is monitored two minutes
after addition.
The Tailfer chlorine dioxide reactor is a glass column 5 feet high and
1 foot in diameter, packed with Raschig rings. Chlorine addition to water
is conducted under pressure with a pulsator, and both water and chlorine
flows are monitored. Plant personnel consider it necessary to achieve a
chlorine concentration in water of 2 g/1 in order to attain 98 to 99% conver-
sions of chlorite ion to chlorine dioxide and to use stoichiometric amounts
of both reactants (chlorine and chlorite). If this concentration of 2 g/1
chlorine in water is not attained, then excess chlorine is required to
convert all chlorite ion to chlorine dioxide.
Tailfer plant personnel also advise that chlorine dioxide is much less
stable in the presence of excess chlorine than when the stoichiometric
amount of chlorine is employed.
Reaction time in the Tailfer chlorine dioxide reactor is about 1
minute. After passage through the reactor (both reactants under pressure),
the product stream is diluted with water to the concentration at which
addition is made to the process water stream. Dilution of reactants is not
practiced before the reactor, since the necessary 2 g/1 concentration of
chlorine in water then would not be obtained.
Safety features of the Tailfer chlorine dioxide reactor include monitors
for the chlorine flow, water flow and sodium chlorite flow. If any of these
flows drop below a preset rate, the chlorine pump will shut off.
Germany--
German water treatment plants are not usually allowed to generate
chlorine dioxide from acid and sodium chlorite (SONTHEIMER, 1977, private
communication). This is because the pH must be controlled accurately, and
many of the smaller German water treatment plants do not have this control
capability. On the other hand, by adding excess chlorine water to sodium
chlorite, complete conversion of chlorite ion to chlorine dioxide is assured,
and some free residual chlorine is provided as well. Finally, since German
water treatment techniques normally require that a maximum of only 0.3 mg/1
of chlorine, chlorine dioxide or a mixture of the two can be dosed to product
water to provide residuals, the combination of chlorine dioxide containing
excess chlorine has been selected as the "standard" for German water treatment
plants using C^.
None of the German water treatment plants visited use chlorine dioxide
for pretreatment -- all of these plants use chlorine dioxide as a post-
treatment to provide residual for their distribution systems.
At all three City of Dllsseldorf plants (Holthausen, Flehe and Am
Staad), 0.1 mg/1 of chlorine dioxide (containing excess chlorine) is added
to the plant outlet water for residual. At the Holthausen plant, chlorine
dioxide is generated by means of an Alldos International system. In this
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generator, 2,000 g of chlorine are mixed with 2,000 liters of water per
hour, and this solution is passed through the Raschig ring packed reactor
with a solution containing 2,000 g of sodium chlorite per hour to produce
chlorine dioxide solution. There are two reactors at this plant, each 3
feet high by 4 inches in diameter. Since the plants in DUsseldorf
operate on demand (there are only two small reservoirs to handle product
water from all three DUsseldorf plants), chlorine dioxide production
operates intermittently. The Alldos unit at Holthausen is automated,
and safety features are programmed with the plant water flow. If this
drops, the unit is programmed to shut down.
At the Flehe plant, a Chlorator chlorine dioxide generator system is
used. In this unit 3 parts by weight of chlorine are added to 1 part of
sodium chlorite. Thus the 0.1 mg/1 dosed to the plant outlet actually
contains 0.07 mg/1 of chlorine plus 0.03 mg/1 of chlorine dioxide.
During winter, Flehe uses chlorine for residual, because it is cheaper.
Flehe also uses chlorine whenever the granular activated carbon is changed.
Use of chlorine dioxide at the DUsseldorf Am Staad plant is similar to
its use at Flehe.
At the Duisburg plant (Rhine River near DQsseldorf), chlorine dioxide
is generated in a Chlorator system. Dosages of 0.20 to 0.24 mg/1 are added
to provide residuals in the distribution system. The stoichiometry at
Duisburg is 300 g of chlorine in water per hour added to solution containing
150 g of sodium chlorite per hour (a 400 molar % excess of chlorine). After
addition of chlorine dioxide plus chlorine, the total oxidant concentration
is monitored 15 minutes later, to be sure to attain a residual concentration
of 0.1 mg/1 before the water enters the distribution system for its 20 km
travel to the city.
The Duisburg plant has two chlorine dioxide generators on line, one of
which is for standby, but which will be used in the coming plant expansion.
At that time, a third chlorine/water system will be installed, but not a
third chlorine dioxide generator.
At the Wuppertal plant (Rhine River near DUsseldorf), 0.1 to 0.15 mg/1
of chlorine dioxide plus residual chlorine is added at the reservoir just
before product water enters the distribution system. A Chlorator system is
used at Wuppertal. The distribution system is 1100 km long, has a 12 hour
average residence time, and consists of two main pipes. The older pipe is
more than 100 years old. Residual chlorine dioxide is less stable in the
older distribution line than in the newer one.
At the city of Konstanz (southern Germany on the Lake of Constance),
chlorine dioxide is prepared in a Chlorator system, then added at the
outlet of the plant reservoir before water enters the distribution system.
Normal dosage of chlorine dioxide plus free chlorine at Konstanz is 0.25
mg/1 for the 7 km distribution system. Whenever Konstanz water is sent
longer distances, however, the dosage is raised to 0.35 mg/1.
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The Styrum West plant of MUlheim, Germany treats drinking water by
breakpoint chlorination, flocculation, sedimentation, rapid sand filtration,
ground water storage in wells, then chlorine dioxide when pumping water from
the storage wells into the distribution system. Chlorine dioxide is generated
in a 22 year old Bran & LUbbe system (excess chlorine water is added to
sodium chlorite solution). The stoichiometry here is 300 g of chlorine (in
water) to 300 g/1 of sodium chlorite solution. This plant was one of two
visited in Germany that does not use ozone in the water treatment process
(an ozone system is planned for addition within the next year).
West Berlin has 7 water treatment plants, but only one, Oungfernheide,
uses chlorine dioxide. This plant draws river Spree water, then filters it
through sand in the ground which has bullrushes growing on it. Passage
through this medium adds oxygen to the water and at the same time destroys a
large portion of the bacteria. Filtration rate in the sand/bull rushes beds
is 2.5 to 3 m/day. Aeration of the filtered water follows (for iron &
manganese oxidation), then filtration and chlorine residual.
During summer, taste and odor causing components are present in the
Spree, and chlorine dioxide is employed rather than chlorine. A Chlorator
generation apparatus was at the plant in May, 1977, but a new Wallace &
Tiernan unit was to be installed shortly.
During winter when chlorine alone is used, the sodium chlorite portion
of the chlorine dioxide generation system is operated once each month to
keep it in operational condition. Residual chlorine concentration in water
leaving the plant is less than 0.1 mg/1, with no traces being detected at
distribution system sampling taps throughout the city. Water from Jungfern-
heide is mixed with waters from the other six Berlin water treatment plants
in the city distribution system.
The water works at Langenau in southern Germany used to treat groundwater
and add chlorine dioxide before distribution. In recent years, however,
Danube River water is treated along with groundwater, especially during
periods of high water demand in summer. The advanced water treatment process
includes ozonation, followed by addition of ferrous sulfate, then filtration
through sand, then granular activated carbon. When chlorine dioxide was
added to this water, the color changed from blue to green (apparently caused
by higher dissolved iron contents). Since it is desired to maintain the
blue color of ozonized water at Langenau, chlorine dioxide has been replaced
by chlorine. At the small dosages of chlorine applied (0.3 mg/1 maximum),
the blue color of the plant water is unaffected.
Switzerland—
The use of chlorine dioxide in Zurich water treatment plants began in
1971, when it replaced chlorine for residual in the Moos and Lengg plants
serving the city of Zurich. Raw water drawn from the Lake of Zurich is of
high quality. When first installed, chlorine dioxide was prepared from
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excess chlorine/water and sodium chlorite. In 1974, the preparative method
was changed at the Lengg plant to the technique involving acid. This change
may have been caused by complaints of chlorine tastes in the treated waters.
An excellent discussion of the use of chlorine dioxide at Zurich is given by
Valenta and Gahler76.
HC1 (33%) and 24.2% sodium chlorite solution are stored in individual
9 cu m, reinforced polyester tanks. Each ingredient is stored in a separate
room beneath the plant in an area surrounded by a concrete lip, which will
contain the total content of each storage vessel in the event of leakage or
a spill. These catchment basins are not drained, to prevent the acid or
chlorite from passing into the sewage treatment plant. If a spill occurs,
the material would be pumped to ground level, then into a tank for disposal.
Valenta and Gahler76 report that chlorine dioxide concentrations above
10% in air are explosive. Aqueous solutions greater than 30 g/1 in concentra-
tion also pose this danger. Generation of an equivalent amount of chlorine
dioxide from acid requires 25% more sodium chlorite than by using chlorine,
but acid eliminates the presence of excess chlorine in the product.
From the 9 cu m storage tanks, HC1 and sodium chlorite solutions are
pumped to 100 liter tanks in which they are diluted automatically with water
to 9% (HC1) and 7.5% (sodium chlorite). Both of these diluted solutions now
are pumped at equal volumes and rates through a double metering pump to the
Raschig ring packed reactor column, where chlorine dioxide solution is
produced. Following production, the chlorine dioxide solution is further
diluted to 10 to 20 mg/1 concentration for addition to the product water.
Because chlorine dioxide mixtures with air can be explosive, air is continuously
drawn out of the reactor product by means of an injector and diluted with
the vacuum-causing water flow.
Dilution water at Zurich is softened to avoid precipitation of calcium
compounds in the chlorine dioxide generation equipment. The Lengg chlorine
dioxide reactor is a Raschig ring packed column 5 feet tall and 6 inches
outside diameter. The pumping rate of both feed solutions through the
double metering pump is 40 1/hr. Conduits are made of PVC piping.
There are 3 metering pumps in each chlorine dioxide line at Lengg, and
these are coupled with the pump which regulates plant water flow. When the
plant flow slows, the chlorine dioxide unit will shut off. If any of the
chemical storage tanks become cloudy due to precipitation of salts, an alarm
sounds, notifying plant personnel that there is a problem with the
chlorine dioxide unit. All pumping operations of the chlorine dioxide
generators are automated, controlled at the plant control panel, and are
paced by the water flow from the plant reservoir, where dosage occurs.
The Lengg chlorine dioxide generation and addition system is manu-
factured by Wallrabenstein, Remchingen, Germany, and all operations are
automatically controlled.
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Analytical control of the chlorine dioxide system at Lengg is accomplished
by monitoring the stream of combined HC1 and sodium chlorite solutions and
determining residual chlorine dioxide, chlorine and sodium chlorite in the
treated water. Control of the starting chemicals is by density measurements.
For the analysis of chlorine dioxide and related materials in product
water, the following procedure is used: Two parallel 10 ml samples of water
are subjected to 3 or 4 step iodometric titration with 0.05N sodium thiosulfate
in various pH ranges using starch indicator. Each sample is diluted with 90
ml of double distilled water, and the iodine produced is titrated as follows:
• The first titration is conducted in neutral solution, and
determines 20% of the chlorine dioxide and all of the chlorine.
• The solution from the step above is acidified, then titrated
again. This determines 80% of the chlorine dioxide plus
sodium chlorite.
• The second 10 ml sample is acidified and titrated as the control.
This determines the total of chlorine, sodium chlorite and chlorine
dioxide present, and the number should total the sum of values
obtained from titrations in the first two steps above.
• The titrated solution from the three steps above is mixed with
NaOH, allowed to stand in indirect light until the solution is
colorless (the chlorine dioxide disproportionates), phosphoric
acid is added and the solution again is titrated. This determines
40% of the chlorine dioxide plus the chlorine and sodium chlorite
present.
When the acid system was first installed at Lengg, the above analytical
titrations were conducted several times daily. It has been found that the
amount of chlorine dioxide present is always in the 90% to 96% range, sodium
chlorite ranges from zero to 4.5%, and chlorine ranges from 4.0% to 7.5%.
Since there has been a three year period of these analyses, indicating the
water to contain these ingredients in the ranges presented, analyses
currently are conducted weekly. These data show that when chlorine
dioxide synthesized from acid and NaC102 is added to water, 90 to 96% of
the oxidant present is C102.
The ZUrich distribution system is fed by all local treatment plants and
groundwater pumping stations. The network surrounds the city and is 1430 km
in total length, but the average residence time of water in this system is
only 1 day. Electricity costs are lower at night, so most of the plant
operations involving electrical power are performed at night.
At the present time, the total distribution system of Zurich and each
of the 20 reservoirs is being interconnected (see plant description in
Appendix B). When this is completed, all water treatment plant operations
at the Lengg and new Moos plants and all reservoir operations will be controlled
by a computerized system housed in a new facility being constructed at the
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Hardhof pumping station site. This facility is being constructed to withstand
bombings, with the subterranean levels being protected against nuclear
explosions. These new facilities will house the analytical laboratories and
all water supply services for the city.
Separate chlorine dioxide generation facilities are being installed in
the Hardhof subterranean level. The pumping station currently can draw
75,000 cu m/day of groundwater and treat it with chlorine dioxide for addition
to the ZUrich water supply system. This capability is being extended to
allow an additional 75,000 cu m/day to be drawn from the Limmat River,
treated with chlorine dioxide, then recharged to the ground for emergency
use.
The Kreuzlingen plant is located in northern Switzerland, on the Lake
of Constance, and treats this lake water by chemical addition, coagulation,
filtration, ozonation, final filtration (sand then granular activated carbon)
then chlorine dioxide for residual. Dosages of chlorine dioxide added at
the exit of the plant reservoirs are 0.2 mg/1 to maintain a residual of 0.05
mg/1 in the Kreuzlingen distribution system. HC1 and sodium chlorite solutions
are used to generate the chlorine dioxide, by a system very close in design
to that used in the Lengg plant, but manufactured and installed by Schnellen-
braun & Co., Winterthur, Switzerland.
There are two separate chlorine dioxide generating units installed at
Kreuzlingen. Concentrated solutions of acid and sodium chlorite are pre-
diluted to the proper concentrations, then pumped through a double metering
pump at equal rates into the reactor, taking care to exclude air from the
system. Product chlorine dioxide solution is stored until use in an air-
tight container, being careful to prevent entry of atmospheric air, which
could produce an explosive mixture. The off-gases from the reactor and
storage tank are passed through a granular activated carbon column for
destruction.
All chlorine dioxide operations at Kreuzlingen are designed to operate
automatically and unattended. When more chlorine dioxide solution is
required, the double metering pump is signalled to begin operation.
When the first dilution tanks become low in acid or chlorite, the dilution
pumps automatically turn on to draw the starting materials from the main
storage tanks. Levels in the main acid and sodium chlorite tanks are
checked daily.
The older plant at Kreuzlingen also used chlorine dioxide as a post-
treatment for the past twenty years or so. When ozonation was first installed
at the old Kreuzlingen plant, no post-treatment was practiced after ozonation.
This led to the growth of slimes in the distribution system. When chlorine
dioxide post-treatment was installed at Kreuzlingen, however, the slimes
problem disappeared. In the ozone literature, this situation has come to be
referred to as "the Kreuzlingen experience".
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Summary of European Use of Chlorine Dioxide
Chlorine dioxide is used mostly for providing a residual for distri-
bution systems. High quality groundwater can be treated just with small
amounts of chlorine or chlorine dioxide and sent directly to distribution
systems. Surface waters which require additional processing steps are
treated so that the dosage of chlorine dioxide employed as post-treatment
remains less than 0.6 mg/1. Only in France are levels as high as 0.5 to 0.6
mg/1 of chlorine dioxide being added as post-treatment, and efforts are
being made to lower this level. Choisy-le-Roi personnel are studying
superozonation to reduce the oxidant demand of treated Seine River water,
thus allowing less chlorine dioxide to be used.
In European distribution systems, the residual of chlorine dioxide is
more stable than chlorine residuals.
German water treatment practice for post-treatment with chlorine or
chlorine dioxide limits dosage to no more than 0.3 mg/1 (calculated as free
chlorine or total oxidant). If the oxidant demand is higher, German water
works may add as much as 0.6 mg/1 (calculated as free chlorine) of chlorine
or chlorine dioxide, but then the circumstances must be presented to the
proper health authorities and special permission obtained.
In pretreatment, chlorine dioxide is used primarily to break down
organic complexes of iron and manganese. Prechlorination will oxidize free
iron and manganese, but not the organically complexed heavy metals. Pretreat-
ment with chlorine dioxide also will destroy phenolic tastes and odors and
remove color in some cases. The addition of chlorine dioxide early in the
process also can provide a degree of predisinfection, as will pretreatment
with chlorine, ozone, potassium permanganate, and other strong oxidants.
Europeans agree that the unit cost of generating chlorine dioxide on-
site is about 3 to 3.5 times the cost of using gaseous chlorine. Thus,
where both oxidants can be employed, chlorine generally is the choice.
During summer months, the oxidant demands at some plants are sufficiently
high (and residual life therefore is sufficiently short) so that chlorine
dioxide is used rather than chlorine. In the colder winter months, these
plants then switch back to chlorine.
European systems generate chlorine dioxide by adding:
1) excess chlorine in water to sodium chlorite solutions
at ambient pressure;
2) stoichiometric chlorine in water to sodium chlorite solutions
under pressure;
3) stoichiometric chlorine in water to sodium chlorite solutions
at low pH; or,
4) HC1 solution to sodium chlorite solutions.
Chlorine dioxide generation systems generally are instrumented and the
process is controlled at the plant control panel. Failure of any component
in the system triggers alarms at the control panel. In all water treatment
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plants visited, chlorine dioxide is generated either in a separate building
away from the main plant processing, or in a separate enclosed room having
access and exit only from the outside of the building. The only exception
to this was the Berlin Jungfernheide plant, which has chlorine dicx-'^;
generation in a room accessible only from the inside of the main plant
building. At Jungfernheide, however, access to the chlorine dioxide room is
by means of double doors, which can only be opened one at a time.
European drinking water plant personnel are aware that sodium chlorite
in the dry state can spark if spills are allowed to dry out and are walked
upon. Thus, spills are cleaned up quickly. Similarly, plant personnel are
aware that chlorine dioxide gas in air can form explosive mixtures under
certain conditions, and chlorine dioxide generators are designed to avoid
building up gaseous concentrations in air.
Most of the treatment plants visited in Europe using chlorine dioxide
regard its generation and application as quite simple and routine. If any
problem occurs with the chlorine dioxide generation or application systems,
a call to the supplier or his local representative brings quick response.
Plant personnel generally were not as knowledgeable about the chemistries
involved with generating and using chlorine dioxide as about the technology
of ozone and activated carbon, for example. They advise that chlorine
dioxide generation and application is so simple and gives such few problems
that there is little need to be concerned about its scientific intricacies.
The usually employed colorimetric and amperometric analytical procedures
determine total oxidant, when oxidants other than C102 are present in solution,
Miscellaneous Comments on European Chlorine Dioxide Systems
CFG (Chemie und Filter GmbH), Heidelberg, Germany—
CFG manufactures dosing pumps, and such a pump is designed into their
chlorine dioxide generator, which uses HC1 and sodium chlorite solution. A
monitor reads the redox potential of the HC1 solution and automatically
adjusts its feed rate so as to guarantee the proper stoichiometry of HC1
being added for the amount of sodium chlorite being pumped.
During operation of this generator, the product chamber is deaerated
every five minutes automatically so as to prevent buildup of gaseous chlorine
dioxide in air which may produce an explosive mixture.
CFG claims to have some 250 of these chlorine dioxide generators
installed in water treatment plants throughout Europe, although the acid-
chlorite generation system is not allowed in Germany. CFG is represented in
the United States by Fluid Controls Ltd., Clearwater, Florida.
Wallace & Tiernan, Germany—
W & T representatives state that some 60 European drinking water
treatment plants have been using W & T chlorine dioxide generators since
about 1960. All are based upon addition of excess chlorine in water to
solutions of sodium chlorite.
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A new generator has been developed recently, and has been installed in
about 20 water treatment plants as of May, 1977. The maximum production
rate of this new generator is 5 kg/hr. Chlorine/water solution at a chlorine
concentration of 5 g/1 produces a pH below 2.0. Normally the solubility of
chlorine in water at ambient pressure is 0.5 to 3 g/1, but at 7 bars, the
5.0 g/1 concentration can be obtained. The new W & T generator thus operates
at 7 bars pressure. Adding 1 part of chlorine in water under 7 bars pressure
to 1 part of sodium chlorite (in solution, also at 7 bars pressure) normally
produces a solution containing 7.5 g/1 of chlorine dioxide.
However, at 7.5 g/1, chlorine dioxide solutions can produce explosive
mixtures more easily, thus W & T has designed their reactor to produce
maximum C102 concentrations of 5.0 g/1 in solution. In addition, the
chlorine/chlorine dioxide gas phase is drawn through an injector where
excess gases are dissolved in water, and the danger of explosion is eliminated,
At the same time, the newly formed chlorine dioxide solution is diluted to
10 to 20 mg/1, at which concentration it is added to water at the treatment
plant.
All operations in the new W & T system are controlled automatically.
Fischer & Porter, USA--
Representatives of F & P advise that there are 30 operational C102
plants in Italy using F & P generators. All of these plants have been
installed within the past three years, and all generate C102 by adding acid
to NaC102 solution.
European CIO? Questionnaire Results Summary
In mid-1977, questionnaires were mailed to 835 water plants in the
Federal Republic of Germany (F.R.G.), 150 plants in France, the key plants
in Great Britain which use C102, 20 plants in Switzerland, and plants in
Austria. As with ozone, more than 1000 European plants received the C102
questionnaire, a blank copy of which is included in Appendix A.
Seventy-four questionnaires have been returned. Most of these are from
the Federal Republic of Germany — 44, while 23 were received from French
plants, 5 from Great Britain, and 2 from Austria.
A brief summary of the information derived from the questionnaires is
given by country in the following pages.
Federal Republic of Germany--
Of the 44 German plants responding, 19 are between 1,000 and 10,000 cu
m/day in size, 17 are 10,000 to 50,000 cu m/day capacity, 4 are less than
1,000 cu m/day capacity, and 6 are larger than 50,000 cu m/day. Eighteen of
the plants began using ClOo between 1960 and 1970, 15 have initiated use
since 1970, and only 6 initiated its use before 1960.
Chlorine dioxide use in Germany is primarily for bacterial disinfection
(33 plants) and to provide a chlorine residual (22 plants). Other uses
include taste removal (9 plants), and iron and manganese oxidation (2
plants each).
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Dosages of C102 are very low in Germany, averaging 0.1 to 0.3 mg/1 for
disinfection. The highest dosage reported was 0.6 mg/1. The residual in
the distribution system is likewise very low, usually less than 0.1 mg/1.
Dosages of C102 for taste and odor removal are slightly higher than for
disinfection, usually 0.3 to 0.5 mg/1.
Chlorine dioxide is prepared by the same method in all plants responding
to the questionnaires except one, by reacting chlorine gas plus water with
sodium chlorite, usually a 30% solution. The only plant which prepares C102
by the acid method is the Vallendar waterworks, which uses both the chlorine
plus sodium chlorite and the hydrochloric acid plus sodium chlorite methods
of preparation. Therefore most German plants add both C102 and chlorine to
their treated water.
Ten different manufacturers supplied chlorine dioxide equipment to the
forty-four plants.
Several methods are used to analyze for C102 or total oxidants, which
is what the plants actually measure. Many plants use the DPD method, 3
measure electrochemically, and several use the orthotolidine method and
iodometric titration. Each of these methods measures total oxidants, rather
than C102 specifically.
Ten of 44 plants reporting data indicated that C102 is their only water
treatment processing step.
Austria--
Questionnaires were mailed to the 11 largest water companies which
serve nearly half of the Austrian population. Only two of the eleven use
C102, but they are by far the two largest ones, producing at least 80% of
the total water treated by the 11 waterworks, more than 100,000 cu m/day.
Chlorine dioxide has been used since 1967 and 1973, respectively, at their
two plants (Ntissdorf Groundwater Works and Obergangskammer d. II).
Both plants use C102 for bacterial disinfection and to provide a
residual in the distribution system. The average dosage at both plants is
0.25 mg/1. The total oxidant residual in the distribution system is 0.08
mg/1 from one plant and is not measured by the other. Total oxidant is
measured using the DPD method.
Chlorine dioxide is prepared by reacting sodium chlorite and chlorine
gas plus water in a Wallace and Tiernan reactor.
Great Britain--
Five questionnaires were received from British plants out of the
approximately 20 that were mailed. The plants reporting data have an
average design capacity of 97,000 cu m/day. The longest period that C102
has been in use is 16 years in the Sutton Hall Treatment Works. Overall,
C102 has been used an average of 9 years in the five plants.
The purposes for which C10n is used are taste and odor control (3
plants), bacterial disinfection^ plants), to provide a chlorine residual
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(4 plants), prevention of nuisance growths (1 plant), and to remove phenolic
tastes (1 plant). Dosages range from 0.05 mg/1 to 0.5 mg/1, averaging 0.28
mg/1 of total oxidant.
As in Germany and Austria, ClOj? is prepared in all reporting plants by
reacting NaC102 solution and chlorine gas, using excess chlorine.
In Great Britain, C102 is used not only as a disinfectant, but quite
often is used as a distinct treatment step or added in a series of unit
processes. The British believe that by adding it in multiple steps, a
better residual will be maintained. In many cases, a reaction tank or basin
is provided immediately after C102 dosing.
Chlorine dioxide and ozone are not both used in any reporting plant in
Great Britain.
France--
Questionnaires were mailed to 150 plants in France. Twenty-three
plants completed and returned the questionnaire. The plants range in size
from 1,000 cu m/day to 600,000 cu m/day. The average size is 57,300 cu
m/day. Many of the plants have been using C102 for 15 years or more. The
plant that has used C102 for the longest period is the Carcassone Plant
which has used it since 1946. The average period of usage for 18 plants is
10.3 years.
Each of the French plants reporting prepare ClOo in the same way, by
reacting chlorine gas with water, then with sodium chlorite solution.
Chlorine dioxide is used for 11 different purposes in France, more than
in any other country. The primary purpose is for bacterial disinfection,
reported by 22 plants. Other uses include organics removal (10 plants),
taste removal (12 plants), odor removal (10 plants), color removal (10
plants), viral inactivation (6 plants), iron oxidation (5 plants), turbidity
reduction (3 plants), and manganese oxidation (2 plants). Only one plant
reported the use of CIO? for the purpose of providing a chlorine residual.
Also, one plant notes that it uses C102 to prevent the formation of chloro-
phenols.
Dosages are somewhat higher in France than in other countries because
of the multiple applications. The highest dosage reported was 2.3 mg/1 at
the LeMans plant which adds C102 after filtration and before ozonation, then
adds more CIO? as a terminal treatment step. The average dosage for 17
plants reporting data is about 0.66 mg/1. It should be noted that when C102
is used for taste and odor control, the dosage ranges from 0.6 to 1.3 mg/1.
The residual chlorine dioxide concentration measured in the distribu-
tion system is very low, usually reported as zero. The highest residual
concentration reported was 0.25 mg/1. The actual amount of C102 measured
depends upon how the Cl2 + NaC102 reaction was conducted as well as upon the
stoichiometry of reactants used.
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ENGINEERING DESIGN FOR CHLORINE DIOXIDE GENERATION SYSTEMS
Introduction
As discussed, there are two basic types of chlorine dioxide generation
systems used in water treatment plants: the NaC102/Cl2 system and the
NaClOp/HCl system. Both methods employ the same type of C102 reactor; only
the feed systems for the CWHCl chemicals are different, me following
text will discuss engineering aspects of the design and operation of both
ClOo systems. Much of the discussion is typical of United States operations.
Chlorine Dioxide Generator
C102 reactor vessels are designed as mixing chambers, providing for the
continuous production of chlorine dioxide. The aqueous reagents are merged
at the bottom of the vessel and flow upward through the vessel where chlorine
dioxide is produced. The solution exits from the top of the reactor and
travels through the discharge piping to a dilution or storage tank and/or to
the point of application in the treatment process.
The typical C10? reactor vessel is made from Pyrex glass or polyvinyl
chloride (PVC). The PVC material is used for higher operating pressures.
Dimensions of the overall vessels may vary, but typically are from 36 to 42
inches high and 8 inches in diameter. The approximate weight of the unit is
50 to 60 pounds. Most C102 reactors are wall mounted and positioned at eye
level for easy viewing. The glass generating units allow the operator to
inspect the color of C102 visually that is being produced. If the chamber
is made of opaque PVC, a sight glass is installed on the discharge tubing.
The mixing action inside the C102 vessel is caused by the solution
flowing around and through Raschig rings. These porcelain rings are about 1
inch in size and are placed inside the vessel in a random manner. Some
plant-fabricated units use PVC rings (cut from PVC pipe) instead of porcelain
rings. Both materials are inert.
CIO? reactor vessels are sized according to maximum C102 production
rates. At least three sizes are available based on the following approxi-
mate rates: 140 pounds C102/day; 370 pounds/day; and 1500 pounds/day.
Other reactor sizes are available.
A sampling valve is a desired feature to have on a C102 generator.
Mounted at the discharge end of the vessel, this port can be made of PVC,
tygon tubing, or glass. Samples can be drawn off periodically in order to
check the composition of the reactor product. Chemical feed inlets on the
reactor vessel are made of PVC, glass, or certain types of rubber tubing.
Teflon, glass, and Lucite are suitable but not practical. Rubber-lined pipe
should be avoided2.
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Feed System
The NaClCL reagent is delivered to the plant either as an anhydrous
technical grade solid (80% pure NaClOp) or as a liquid (20% to 37% concentra-
tion). The powdered NaClOp (readily soluble in water) is mixed with water
in open drums. Batch mixes normally are 2 to 3 pounds of NaClOo per gallon
of water. NaCIO^ solutions are fed directly to the ClOp generator.
Diaphragm metering pumps are used commonly to feed NaClO? solutions to
the C102 reactor. These positive displacement pumps are simple to operate
and can be metered over a wide range of flow rates. The diaphragm or piston
compartment is made from PVC material. The pump and motor (120 volt, single
phase) are usually small enough to operate on top of a drum or a bench.
The piping for aqueous NaClOo is either PVC, rubber or Tygon. Tygon
tubing looses its rigidity after several months in service and must be
replaced. The softened walls occasionally collapse due to the pump suction
and subsequently restrict the flow of NaClC^ to the pump.
The NaC102 is relatively stable in either the dry flake or fluid phase
but is very combustible in the presence of organic material (rags, gloves,
brooms, etc.). Therefore, the solution never should be allowed to evaporate
on the floor. Any spills should be washed down the floor drain or mopped
with a technical sulfite solution. Solid NaClOo is also explosive when
contacted with acids. The oxidant decomposes rapidly when heated above
347°F (175°C). If the heat is confined, such as in a building on fire, the
chemical drums will explode. Thus, the chemical should be handled with
appropriate caution.
HC1 Feed System
This is similar to the NaC102 feed system. The same types of pump and
piping that are recommended for NaCICL solutions are also recommended for
HC1. *•
The HC1 solution can be stored either in inert plastic tanks (such as
polyester, polyethylene, etc.) or in fiberglass tanks. NaC102 solutions
also can be stored in these types of containers. Some plastic tanks become
increasingly opaque after months of storing these chemicals. When the
transparency is reduced to the point where the operator cannot see the
liquid level of the chemical through the tank wall, the tank is replaced
with a new tank. The tanks, however, remain structurally safe. Storage
tanks are readily available on the market.
In the event of an accident, the floor area around the liquid chemical
storage tanks and pump equipment should be confined by a continuous concrete
step 6 to 8 inches high and 6 to 8 inches wide. This barrier prevents the
liquid from escaping to the surrounding floor areas if a line ruptures or a
tank fractures. It is recommended to have floor drains inside the barrier
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which empty to a sanitary sewer system. Some European systems do not have
floor drains; instead the spilled chemicals are pumped to trucks for trans-
porting to hazardous waste disposal sites.
Piping for all chemical feed systems is exposed and mounted along the
walls and ceiling. This allows the plant personnel to inspect and repair
the lines if a leak should occur.
The Clo Feed System
Most chlorination systems can be modified to produce C10?. The standard
chlorinator regulates the rate at which chlorine gas is injected into the
water feed system. Chlorine solution then is piped to the CICU reactor
vessel for C102 production. The chlorinator should have at least a vacuum
regulator, a ffow valve and a flow meter. The flow meter indicates the rate
in pounds/day at which chlorine is injected into the feed water. The chlori-
nator can be controlled manually or automatically, the latter system responding
to a water flow transmitter and/or a chlorine residual analyzer controller.
The chlorine ejector is sized according to the maximum chlorine feed
rate and the hydraulic conditions of the water supply line and chlorine
solution line.
Liquid chlorine is supplied in either one-ton cylinders (2000 pounds of
chlorine) or 150 pound cylinders (150 pounds of chlorine).
Different materials are used for transporting chlorine liquid, chlorine
gas and aqueous chlorine. Liquid chlorine is always packaged in steel
containers. The chemical will not react with iron and steel in the absence
of free moisture. Schedule 80 seamless steel pipe (with at least 300 pound
malleable iron, and preferably 2000 pound forged steel fittings) is used for
liquid chlorine. The liquid oxidant readily attacks and dissolves PVC.
Chlorine gas that is dry is also inert to ferrous materials. When chlorine
gas is contained above atmospheric pressure, PVC should never be used, as it
becomes porous. If the chlorine gas should reliquify, the PVC will deteriorate
more rapidly. Chlorine gas under vacuum can be piped using PVC, reinforced
fiberglass and steel2. Aqueous chlorine solutions generally are piped with
PVC, fiberglass, Saran or rubber-lined steel once beyond the injector.
Neoprene-lined hose will decompose if used with chlorine solution.
Production of ClOp From Chlorine-Sodium Chlorite System
This approach uses aqueous chlorine (commonly as HOC1) and aqueous
NaC109 to produce C10?. Figure 49 is a schematic of such a system, which
consists of a C10? generator, a gas chlorinator, a storage reservoir for
liquid NaClOo, ana a chemical metering pump. Sodium chlorite solution can
be prepared from the dry chemical by adding it to water. The minimum
recommended feed ratio of Clo to NaClOo is 1:1 by weight. Further, additional
chlorine can be injected into the reactor vessel without changing the overall
production of chlorine dioxide.
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PUMP
C102 SOLUTION TO
TREATMENT PROCESS
GENERATOR
CHLORINATOR
•Cl
•H20
Figure ^9- Gaseous chlorine-sodiurn chlorite
CIO,, generation system.
NaC102
A disadvantage of this process is the limitation of the "single pass"
gas chlorination. Unless using increased pressure, this equipment is not
able to achieve high concentrations of chlorine which provide for a more
complete and controllable reaction with the chlorite ion. A French firm,
CIFEC, recently has developed a variation of this process using a multiple
pass enrichment loop on the chlorinator to achieve a higher concentration of
chlorine in water and thereby maintain better yields of chlorine dioxide
without having to use excess chlorine (Figure 50).
The purpose of the multiple pass recirculation system is to allow
enrichment of the chlorine solution to a level of 5 to 6 g/1. At this
concentration, the pH of the solution will drop to 3.0 and below. A "single
pass" results in a chlorine concentration in water of about 1 g/1, which
produces a pH of 4 to 5. If the NaC102 solution is mixed with the aqueous
chlorine at this pH, only a 60% yield of chlorine dioxide reportedly is
obtained. The remainder is unreacted chlorine (in solution) and chlorite
ion. When quantitative yields of C102 are achieved, there is virtually no
free chlorite or free chlorine carrying over into the product water.
Using the CIFEC recirculating loop approach with the injector, some 46
kg/hr (2434 pounds/day) of chlorine can be dissolved in the recirculating
water. Makeup water to the loop is added at the rate of 1 cu m/hr
(4.4 gal/min) through an aspirator in which the water is mixed with
chlorine. Thus a chlorine/water solution of 6,000 mg/1 is made at the
rate of 1 cu m/hr (4.4 gal/min).
214
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VACUUM LINE
OF CHLORINE
CHLORINATOR
CHLORINE
FLOW METER
r
EJECTOR WITH CHECK
VALVE ASSEMBLY
J=OC102 EXIT
JT_
-ENRICHMENT-
LOOP
-CHLORINE CYLINDER
RECIRCULATING PUMP
FLOW METER
ELECTRIC VALVE
—C102
REACTOR
CONTROL
EQUIPMENT
SODIUM CHLORITE
METERING PUMP—i
MAKE-UP WATER SUPPLY
SODIUM
CHLORITE
TANK
Figure 50. The CIFEC System.
Both the aqueous chlorine and the aqueous NaC10? solutions are pumped
to the C102 reactor. A control system monitors the equipment. When the
chlorine cylinder empties, the unit shuts down automatically. If the recircu-
lating pump fails, or if the water pressure drops, the unit also will shut
down and alert the operator that the system has malfunctioned.
The chlorine dioxide solution is injected directly into the process
water by a remote controlled injector, which is also connected to or is a
part of the control panel. The aqueous stream containing chlorine dioxide
is under pressure to avoid explosive hazard from entrapped air. Pressurizing
the system prior to the C102 reactor avoids the need to pump the chlorine
dioxide solution after it is formed. The injector is set to a predetermined
feed rate, and the system operates automatically.
If variable feed rates are desired on the CIFEC system, the injector
can be connected to an analytical monitor. As the residual chlorine dioxide
values go up or down, the meter will automatically increase or decrease its
output. All of these operations can be recorded, so that the system requires
only periodic inspection by plant personnel. The entire CIFEC unit operation
also can be connected to the central control panel of the water treatment
plant.
215
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The CIFEC system thus claims to address three problems inherent
with generation of chlorine dioxide:
• It automatically adjusts the chlorine/water solution to the
proper pH for synthesizing chlorine dioxide in maximum yield,
and minimizes the presence of either excess chlorite ion or
chlorine;
• It eliminates the necessity for a chlorine dioxide reservoir
or for a pump which must pass chlorine dioxide solution;
• The flow of chlorine dioxide solution can be readily adjusted
downward from the maximum production rate by a factor of 20.
That is, if the maximum production rate is 10 kg/hr (530
pounds/day), the CIFEC equipment can be programmed to produce
as little as 0.5 kg/hr (26.5 pounds/day) at a constant rate.
Competitive units are reported (by CIFEC) to be adjustable
over more narrow ranges.
Wallace and Tiernan offers a single pass system which is pressurized
to produce a higher concentration of aqueous chlorine for C10? production.
Gaseous chlorine is injected into feed water at about 7 bars fl02 psi)
to produce a chlorine concentration of 5 g/1 which is added to the
NaC102 solution also under 7 bars pressure, and ClOo is produced. The
C102 solution then is diluted to 10 to 20 mg/1 (as C102) for water
treatment operations. This system is described in greater detail in
Appendix B under the Tailfer (Brussels, Belgium) plant description.
Production of CIO? From Hypochlorite-Hydrochloric Acid-Sodium
Chlorite System
The production of C102 using the chemical reagents NaOCl, HC1 and
NaC102 is shown schematically in Figure 51. NaOCl solution is reacted
with NaC102 solution with the pH adjusted to a maximum of 4 using hydro-
chloric acid (or sulfuric acid). The reactions are as follows:
NaOCl + HC1 *• NaCl + HOC1
HOC! + 2NaC102 + HC1 ^ 2C102 + 2NaCl + H20
The flow scheme is arranged whereby the acid for both reactions is added
simultaneously, with the excess from one reaction carrying over to react
with the HOC1. The NaClOo is added last, just before the combined
solution enters the packed bed.
Production of C1Q2 From the Acid - Sodium Chlorite System
The combination of acid and sodium chlorite is claimed to produce
an aqueous solution of C102 with no free chlorine being present. It is
for this reason that many plants prefer this approach for CIO, production.
The acid based process minimizes the difficulty of differentiating
216
-------
between chlorine and chlorine dioxide for establishing an oxidant residual
Fischer and Porter is introducing an automatic C102 generator which uses
chlorite and hydrochloric acid as reagents.
C102 SOLUTION TO
TREATMENT PROCESS
GENERATOR
DILUTION WATER
PUMP
b
PUMP
-GAGE FOR LIQUID
DEPTH INSPECTION
NaCIO'
NaOCl
HC1 OR
Figure 51. Sodium chlorite-hypochlorite-acid C102 generation system.
To illustrate a large scale operation of CIO? production, Figure 52
presents a schematic of the Lengg Waterworks of ZQrich, Switzerland (acid-
sodium chlorite layout). This system uses liquid chemicals delivered
by tank trucks as feed stocks. Each storage tank has a level sensor to
avoid overfilling. The tanks are installed below ground in concrete
bunkers which are capable of withstanding an explosion. There are no
floor drains in these bunkers (to avoid contamination of local sewers),
and any spillage must be pumped with non-corrosive pumps. Primary and
backup sensors with alarms warn of any spillage. The extreme safety
precautions are required because of the explosiveness of the chemicals
when combined in these concentrations (32%-HCl; 24% NaC102).
217
-------
ro
oo
METERING DOUBLE
HC1 DILUTION ) PUMP | C102 TREATMENT | METERING PUMP |NaC102 DILUTION
C102 TO
TREATMENT
PROCESS -
MAKE UP-
WATER
1
HC1
3%
:*:
VENTURI
INJECTOR
Li..
j
i
.1
•Ir^rn:
5*
C102
SOLUTIO
-REACTOR
|
C102 WASTE i
EFFLUENT
STORAGE TANK
HC1 32%
_L_L
'I t
I I
! i
r-
\
.-..-.-.. _.«_.u n
STORAGE TANK
NaC102 2k%
Jo
JL_L
J.
SODIUM CHLORITE:NaC102
SYSTEM WATER
C102 WASTE
HYDROCHLORIC ACID: HC1
CHLORINE DIOXIDE: C102
SYSTEM WATER
SOFTENED
Figure 52. Lengg Waterworks, Zurich, Switzerland.
Chlorine Dioxide System.
-------
Because of the potential explosiveness, the reagent chemicals are
diluted prior to the production of C102- The dilution is carried out on a
batch basis which is controlled by level monitors. Proportionate quantities
of softened dilution water, along with the chemical reagents, are pumped to
mixing vessels. After the reactor is properly filled, an agitator within
the container mixes the solution for 15 minutes. Solutions of 9% HC1 and
7.5% NaC102 are produced in the chemical preparation process. Pumping equal
volumes of these reactant concentrations into the reactor provides the
proper stoichiometry.
C102 subsequently is manufactured on a batch basis and the rate of
production is controlled by the liquid level in the final C1C>2 reservoir.
A level switch activates a calibrated double metering pump which feeds the
diluted reagent chemicals to the reactor at an identical rate. The reactor
is a small cylindrical vessel packed with Raschig rings in which the exothermic
reaction of the two chemicals occurs. The C102 product is diluted again
prior to passing into the CIC^ storage tank.
The metering pumps operate in conjunction with the main plant pumps.
The C102 solution is subjected to a final 1:100 dilution and mixed with
process water in an hydraulically mixed chamber. The C102 solution is
metered into the treated water stream at the end of the treatment process as
well as before injection into the plant reservoir.
The process is monitored in the laboratory to accomplish three objectives:
• Control of stock concentrations of HC1 and NaC102
• Control of chemical mixing and dilutions
• Control of C12 and C102 residuals in the treated water.
The control of the initial concentrations of chemical reagents is made at
the time of delivery by a simple determination of density. Weight per unit
volume (density) is checked against known values from tables.
Control of process chemical concentrations and final residuals is
accomplished by using a three or four step iodometric titration. More
detail on the Lengg C102 system is provided in the plant description in
Appendix B.
Other Design Precautions
A C102 system should be well designed for efficient and safe production
of CIO?. In addition to the preceding discussion regarding the operation
and maintenance of a C102 system, the following items also should be considered
for any plant producing this oxidant:
• Use of inert materials where contact is made with oxidants;
219
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• Provision of separate rooms for each of the chemical components
with monitors and alarms for failure warning. The rooms should be
designed to isolate and contain spilled or leaked chemicals and
facilitate their cleanup;
• Provision of any off-gas collection and neutralization from the
C102 production;
• Adequate ventilation and air sensing/alarm systems in working
areas;
• Provision of gas masks and first aid kits outside of entrance
doors to chemical storage room(s);
• Provision for wash down in chemical storage and mixing areas;
t Clear glass housing on the reactor for visual check of the reaction;
• Flow monitoring equipment on influent and effluent lines;
• Provision of softened process water to avoid calcium buildup in
the system;
• Management program for frequently checking solution strengths of
chemicals. Testing equipment should be on-site;
• Management programs for routine shutdown and careful inspection of
system components;
• Avoidance of air contacting C102 solutions after generation so as
to avoid forming explosive concentrations of C102 in air.
Costs for Producing Chlorine Dioxide
The cost for generating C102 on-site is dependent on what method is
used to generate the oxidant: chlorine/sodium chlorite, acid/sodium chlorite,
etc., and particularly the costs for chlorine, acid and sodium chlorite.
There are other factors that affect capital and operating costs for on-site
C102 production. These include:
• rate of C102 production
• level of automation
• back up equipment
• availability of existing equipment to be incorporated into a C102
system
• chemical storage facilities
220
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t reagent chemicals ordered--!iquid, powdered, drums, tank car, rail
car, etc.
• size and frequency of chemical shipments
• level of training of plant operators
Although it is difficult to assign cost figures to C102 production
because it is site-specific, C102 production costs generally follow economics
of scale. Larger plants that generate CICL on-site normally can produce it
at a lower cost per pound than can smaller water treatment plants. However,
the larger plants typically will incur higher capital costs for ClOo production
because of higher levels of system automation, chemical storage facilities,
stand-by equipment, etc.
It is most important to realize that when the acid/sodium chlorite
method is used for generation more than 90% of the oxidant contained in
solution is C102. However, when the chlorine/sodium chlorite method is used
in 1:1 weight ratio, particularly when the NaClCL is technical grade, the
total oxidant in solution contains about 50% C102 and 50% other oxidants,
primarily free residual chlorine. Therefore, when a treatment plant synthe-
sizes C10? by the chlorine/sodium chlorite methods, analyzes for C102 by a
method which determines total oxidants and reports the results as "CT02",
the true concentration of C102 is about half that reported.
Estimated Costs in the United States
With this brief introduction, cost analyses for C102 should be based on
the stoichiometry of producing C102. Examining first the HCl/NaC102 method
in the United States, C102 costs approximately $1.80 to $2.60 per pound
produced using hydrochloric acid and sodium chlorite as the chemical reagents
(1977). If, however, the Cl2/NaC102 method is used, C102 costs approximately
$1.35 to $2.00 per pound in the United States. These estimates are based on
the following chemical costs in the United States furnished by several
chemical distributors (1977): $0.25/lb of hydrochloric acid, $0.0675 to
$0.15/lb of chlorine and $0.78 to $1.15/lb of technical grade sodium chlorite.
Capital costs for a C102 generation system are largely dependent on the
method of C10? production, production rate and chemical feed systems. The
major equipment required for a ClOo generation system includes a C102
reactor, chemical feed pump(s), chemical storage tank(s), chlorinator(s)
(only for chlorine/sodium chlorite method), weighing scales and piping/
electrical appurtenances. The following costs for this equipment are
quoted as 1977 prices, FOB.
The price of a CIO, reactor ranges from $650 to $1200, the price
variance being based on>eactor capacity, operating pressure, and valve/piping
appurtenances.
Feed pumps that are capable of handling such chemical oxidants generally
cost between $400 and $800. These are plunger pumps and proportion the
221
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chemical feed rates by a manual metering system. Automatic feed pumps,
which proportion the chemical feed rates according to the plant flow or the
chlorine residual in a process tank, typically cost more than manual feed
pumps.
Chemical storage tanks with lids are made either from fiberglass or
PVC. Steel tanks are not recommended. The smaller storage tanks cost from
$75 to $500 for capacities up to 250 gallons. Larger tanks must be special
ordered. Chemical mixers are optional depending on daily requirements of
chemical reagents.
Chlorination systems generally are available at most U.S. water treatment
plants. Several U.S. water plants have used an on-site chlorinator(s) to
furnish chlorine to a newly installed ClOp reactor for ClOp production
(Clo/NaClO^ method). The chlorine feed rate then is adjusted so that the
desired chlorine residual in the plant water continues to be maintained.
Using this strategy, a plant will not necessarily require a second chlorinator
to be used for a C102 generating system. If such an option is not feasible
at a water treatment plant, however, then a second chlorinator (or more) is
needed for the new C102 generation system.
Most plants, however, use a separate chlorinator for their C102 generation
system. Weighing scale(s) for measuring chlorine contents in the cylinders
also should be provided. Chlorinators for C102 reactors range from $1700
(wall mounted, 500 Ibs chlorine per day) to $4000 (floor mounted, 2000 IDS
chlorine per day). Evaporating chlorinators are more expensive. Weighing
scales for 150 pound chlorine cylinders cost from $300 to $500.
If a water treatment plant contracts the work for furnishing and
installing a C10? generation system, installation charges can be expected to
cost roughly 100% to 200% of the material costs. For example, if a 10 to 15
mgd water treatment plant determines that it needs a C102 generating system
to abate a seasonal taste and odor problem in its raw water, the plant then
requires (using the chlorine/sodium chlorite method) a dCL reactor, a
chlorinator (wall mounted), a chlorine cyclinder weighing scale, a storage
tank for aqueous NaC102> a chemical feed pump for NaC102, and piping/electrical
appurtenances.
For purposes of this example, it is assumed that there is adequate room
for chemical storage, chemical tank, C102 reactor and proper ventilation and
safety equipment for the CIO- generating system. A rough estimate for the
material cost for this simple system is $3000 to $4000. The final cost for
furnishing and installing such a C102 system may range from $6000 to $9000.
Nominal maintenance expenses for a system like this may range from $50 to
$100 per year. These figures were reported from several U.S. plants visited
and are said to be conservative. Larger CICL installations for 50 to 100
mgd plants where chemicals may be delivered By tank car or rail car will
experience higher operating costs.
This quick estimating exercise should not in any way be considered as
a substitute for the thorough and detailed analysis that is required for
222
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estimating capital costs for a C1CL generating system. Each water treatment
plant will be different and therefore the cost for implementing a
system will be site-specific.
CIO,
There are water treatment plants that purchase C102 equipment directly
and install the system without procuring outside services. This approach
requires experienced professionals within the plant labor force who fully
understand the work involved. If this approach is taken, it is highly
recommended to have the equipment manufacturer inspect the overall C102
system with the plant personnel prior to startup. The manufacturer's
service person also can assist with fine adjustments of the system for
increasing efficiency. (In the United States, the major manufacturers of
chlorinators also manufacture C1CL reactors and some chemical feed pumps.)
Services of the equipment manufacturer's representative cost around $300 to
$400 per day, with one day normally being sufficient time to complete the
work.
Estimated Costs in Europe
During the May, 1977 visitations to European drinking water treatment
plants, the survey team was advised repeatedly that the costs for using C102
in Europe are about 3 to 3.5 times greater than those for chlorine -- on an
equivalent dosage basis.
Costs for chlorine and sodium chlorite as of late 1977 are given in
Table 26.
TABLE 26. EUROPEAN CHEMICAL COSTS FOR C102
Country
Italy
Netherlands
England
USA
C19
$/kg $/lb
0.40 0.18
0.62 0.28
0.43 0.20
0.16 0.07
NaClOo
$/kg $/Tb
1.82 0.83
1.50 0.68
1.96 0.89
2.96- 1.34-
2.49 1.13
Cost
ratio
NaC102/Cl2
4.55
2.42
4.56
18.5-
15.6
Chemical costs for 1
mg/1 dosage C102
prepd. from 1:1 ratio of
C12 + NaC102, in
-------
method using 1:1 weight ratios of the two reactants on the basis of
this chemical cost alone, the cost of ClOo should be from 3 to 8 times
higher in the USA than in Europe. However* the cost of chlorine in the USA
is 25% to 40% lower than the cost of chlorine in Europe. Therefore, the
relative cost of chemicals required to prepare chlorine dioxide (from a 1:1
weight ratio of chlorine to sodium chlorite) is 110% to 150% the costs in
Europe.
Costs of Chlorine Dioxide at Tailfer—
Tailfer plant personnel made available a series of four quarterly
expense reports on water production costs for the year 1976. During 1976,
the Tailfer plant produced 21,671,385 cubic meters of water at a total
chemical cost (including costs for producing ozone) of 16,355,039 Belgian
francs (Bf, or $464,632, or $0.0214/cu m). Of this, the total costs for
sodium chlorite were 2,760,463 Bf ($78,422). Therefore, costs for sodium
chlorite at Tailfer during 1976 were $0.00362/cubic meter of water processed.
To this should be added the cost of associated chlorine, plus some electrical
energy, to arrive at the cost for chlorine dioxide (35.2 Bf = $1 U.S. in
mid-1977).
Schalekamp2 cites the operating cost for chlorine dioxide in Zurich,
Switzerland at an average dosage of 0.5 mg/1 as 0.4 Swiss Roppen/cu m
(0.85^/1000 gal). The cost of using sodium chlorite in ZUrich to generate
chlorine dioxide at this average dosage is given by Schalekamp as 0.22 Swiss
Roppen/cu m (0.42^/1000 gal).
The city of Karlsruhe, Germany installed a new 104,500 cu m/day
(27.6 mgd) water treatment plant in 1977 which employs aeration, coagulation,
filtration and C102 addition (average dosage 0.20 mg/1). Capital costs
for the chlorine dioxide generation equipment (4 kg/day, Cl? + NaC10~) were
15,000 DM (7,000 at 2.0 DM/$ exchange rate). The cost of chlorine is 0.6
DM/kg (18
-------
SECTION 12
OXIDATION PRODUCTS OF ORGANIC MATERIALS
In this section we will discuss the results of an extensive survey of
the literature dealing with current knowledge of the nature of specific
organic products formed when aqueous solutions are treated with ozone or
with chlorine dioxide. For a more complete understanding and comparison we
are also including a brief discussion of reactions of organic materials with
chlorine.
INTRODUCTION
There does not exist a great deal of literature in which the investigators
deliberately set out to isolate and identify the oxidation products of
organic compounds from actual drinking water supplies or wastewaters. Most
of the research has been pointed at determining the dosage of oxidant necessary
to reduce the concentration of a particular organic compound to below a
limit detectable by means of an analytical technique specific for that
compound. It has not been generally recognized that oxidation products
formed from these materials may still be present, may not be detectable by
the analytical technique used to determine the original compound, and may
pose a public health concern. It has only been relatively recently that
Rook77 has shown chloroform to be a product of the chlorination of drinking
water supplies containing humic materials. Since then, research into the
formation and nature of organic oxidation products under drinking water
treatment conditions has accelerated.
Most of the experiments dealing with organic oxidation products from
ozonation and from treatment with chlorine dioxide have not been conducted
under controlled water or wastewater treatment plant conditions, i.e.,
dilute aqueous solutions of compounds, low dosages of oxidant, short contact
times, no pH control, etc. At the rather low concentrations of organic
materials normally encountered in water and wastewater treatment plants,
oxidation of one organic compound usually produces other compounds in even
lower concentrations. Therefore, recent research studies have utilized the
approach of starting with relatively concentrated solutions of organic
compounds, and using high dosages of oxidants for prolonged periods of time,
in order to force the oxidations to proceed to later stages. Others have
started with high concentrations of organic compounds, but have deliberately
underdosed with oxidant in order to be sure of producing partially oxidized,
early intermediate materials for isolation and study.
225
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We have reviewed the available literature on the use of ozone and
chlorine dioxide with the intent of determining specific oxidation products
which have been isolated and identified without regard to the relationship
of their experimental synthetic conditions (mostly laboratory studies) to
actual drinking water treatment plant conditions under which ozone and
chlorine dioxide normally are employed. A list of specific organic chemicals
known to be formed upon oxidation by ozone and/or chlorine dioxide will be
useful to toxicologists and will allow incorporation of these materials into
toxicological testing programs, if desired.
Similarly, once it is known with certainty which specific organic
compounds can be formed upon oxidation with ozone, reaction conditions can
be designed for drinking water treatment processes which will minimize their
formation.
Background
The capability of one substance to oxidize another is measured by its
"Oxidation Potential", normally expressed in volts of electrical energy
(referenced to the hydrogen electrode). The Oxidation Potential is a measure
of the relative ease by which an atom, ion, molecule or compound is able to
lose electrons, thereby being converted to a higher state of oxidation. If
the oxidation potential of substance A is higher than that of substance B,
then substance B will be oxidized in the presence of substance A. Oxidation
potentials of representative oxidants encountered in drinking water treatment
are listed in Table 27.
Although the relative position of an oxidant in this table is indicative
of its ability to oxidize other materials, it does not indicate how fast one
material will be oxidized by another, nor how far toward completion the
oxidation reaction will proceed. One cannot tell from oxidation potentials
alone whether a specific organic compound will be oxidized completely (to
carbon dioxide and water) or only to the first of several intermediate
stages.
One significant fact can be learned from this table, however, at this
point. As will be discussed in detail later in this section, it is rare
that organic compounds treated with even as powerful an oxidant as ozone
will be converted totally to carbon dioxide and water, under conditions
normally encountered in drinking water treatment plants.
Therefore, no other commonly employed and less powerful water treatment
oxidant (such as chlorine, bromine, chlorine dioxide, etc.), all of which
have lower oxidation potentials than ozone, will oxidize an organic material
completely to carbon dioxide and water if ozone will not.
All oxidants weaker than ozone will be_ less effective than ozone in
converting organic compounds tp_ carbon dioxide and water, and thus mav
produce higher quantities of partially oxidized organic materials under
water treatment plant conditions. This fact has not yet been fully appre-
ciated by the water supply industry. Once understood, a logical conclusion
226
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TABLE 27. OXIDATION-REDUCTION POTENTIALS OF WATER TREATMENT AGENTS*
Reactions Potential In
F2 + 2e = 2 F"
03 + 2H+ + 2 e = 02 + H20
H202 + 2H+ + 2e = 2H20 (acid)
Mn04" + 4H+ + 3e = Mn02 + 2H20
HC100 + 3H+ + 4e = Cl" + 2H90
+ 2+
MnO»~ + 8H 5e = Mn + 4H20
HOC! + H+ 2e = Cl~ + H20
C12 + 2e = 2 Cl"
HOBr + H+ + 2e = Br~ + H20
0- + H20 + 2e = 02 + 2 OH"
C102 (gas) + e = C102"
Br2 + 2e = 2Br~
HOI + H+ + 2e = I" + H20
C102 (aq) + e = C102~
CIO" + 2H20 + 2e = Cl~ + 20H"
H202 + H30+ + 2e = 4H20 (basic)
C102~ + 2H20 + 4e = Cl~ + 40H"
OBr" + H20 + 2e = Br~ + 40H"
I2 + 2e = 2 I"
I3 + 2 e = 3 I"
01" + H20 + 2e = I" + 20H"
02 + 2H20 + 4e = 40H"
*Handbook of Chemistry & Physics, 56th Edition,
Press Inc., Cleveland, Ohio, p. D-141-143.
Volts (E°) 25 °C
2.87
2.07
1.76
1.68
1.57
1.49
1.49
1.36
1.33
1.24
1.15
1.07
0.99
0.95
0.9
0.87
0.78
0.70
0.54
0.53
0.49
0.40
1975-76. CRC
227
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to be drawn is that when oxidants are used as the terminal step in treating
water supplies, the water should contain minimal amounts of dissolved organic
materials.
Fundamental Principles
All oxidants react with organic materials by one or more of three
different mechanisms:
• Addition
• Substitution
• Oxidation
In some cases, oxidants will react with organic compounds by all three
mechanisms, although in sequential steps.
Addition —
Occurs with organic compounds containing aliphatic unsaturation, such
as olefins. Chlorine can add across an olefinic double bond to produce a
di chloride:
RR'C = CRR1 + C19 - ?• RR'C -CRR'
2 I I
Cl Cl
Hypochlorous acid can add across a double bond to form a chlorohydrin:
RR'C = CRR1 + HOC1 - >RR'C - CRR1
I I
Cl OH
Ozone can add across a double bond to form an ozonide:
0-0-0
I I
RR'C = CRR' + 03 - > RR'C — CRR1
This last reaction occurs readily in non-aqueous solvents, but as soon
as water is added, the ozonide hydrolyzes to other products, with cleavage
of the former double bond:
0-0-0
nni p PDP'
ozonide
>. DD' ru nu 4-
alcohol
0=CRR'
ketone
Substitution-
Involves replacement of one atom or functional group with another. For
example, chlorine can react with phenol to produce o-chlorophenol . In this
reaction the ortho-hydrogen atom is replaced by chlorine:
228
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ci2
Phenol o-chlorophenol
Oxidation--
Involves the introduction of oxygen into the organic molecule, with or
without degradation of the organic compound. For example, oxidation of
phenol with either chlorine, chlorine dioxide or ozone can produce catechol
as a first oxidation product:
OH OH
C12 or C102
or ozone
^^
catechol
This specific reaction also can be viewed as an insertion reaction,
whereby oxygen is inserted between the ring carbon and hydrogen to form the
hydroxy group on the ring.
Oxidation also can involve cleavage of carbon-carbon bonds to produce
fragmented organic compounds. For example, ozonation of styrene produces
formaldehyde, benzaldehyde, and benzoic acid""
130
CH=CH2 U3 urun ^S^CHO
benzaldehyde benzoic acid
At the last stage in treatment of organic compounds with oxidants,
oxidation also can involve production of carbon dioxide and water:
HCOOH + 03 > C02 + H20
formic acid
CHLORINE
There is considerable literature dealing with the reactions of chlorine
with organic compounds in aqueous solution. This will not be reviewed in
detail, but representative reactions will be cited to illustrate the signifi-
cant points for drinking water treatment scientists. Before discussing
specific organic oxidation products, however, a brief synopsis of the chemistry
229
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of chlorine in water is in order, since many of the aqueous reactions of
"chlorine" do not involve free chlorine, but rather hypochlorite ion or
hypochlorous acid.
Reactions of Chlorine With Water
When chlorine gas is dissolved in water the following reaction
occurs78:
The HOC! (hypochlorous acid) can ionize in water as follows:
OC1~
At pH below 6.5, the solution contains almost 100% of the chlorine
in the form of HOC179, but at pH 9.0 or higher, nearly all of the chlorine is
in the form of hypochlorite ion, OC1~. In the pH range of 6.5-9.0, therefore,
dissolved chlorine will be present as both HOC1 and hypochlorite ion, in
varying amounts depending upon the specific pH.
As indicated in the table of Oxidation Potentials, HOC1 is a stronger
oxidizing agent (1.49 v) than is free chlorine (1.36 v), so that HOC! is
actually more to be desired when using chlorine as an oxidant in aqueous
solution. Hypochlorite ion is the weakest of the three species (0.9 v).
Reactions of Chlorine With Organic Compounds
The direct reaction of chlorine with unsaturated compounds proceeds
mostly by addition. For example, maleic acid treated with chlorine will
produce dichloromaleic acid:
B H SB
HOOC-t = C-COOH + C19 - >HOOC-d - C-COOH
^ Cl Cl
However, since chlorine forms hypochlorite ion or hypochlorous acid
when added to water, reactions of HOC1 with organic compounds are more
germane to this discussion.
Ethyl ene reacts with an alkaline solution of chlorine to give ethyl ene
chlorohydrin. The reaction was once thought to involve the simple addition
of HOC! across the ethyl em" c double bond. However, the reaction mechanism
is now understood to be a two-step process in which chlorine cation attacks
one of the unsaturated carbon atoms, followed by combination with an hydroxide
ion. The overall effect, however, still can be viewed as addition of HOC1
across the unsaturation80:
H2C = CH2 + HOC!
Cl OH
230
-------
Treatment of ethylene chlorohydrin with strong alkali results in elimina-
tion of the elements of hydrogen chloride with formation of ethylene oxide,
which is an epoxide containing no chlorine:
H0C -
2|
CH,
Cl OH
H0C - CH0
V
Thus there is the possibility of forming epoxides by chlorination of
drinking water supplies if aliphatic double bonds are present in dissolved
organic materials, and if alkaline conditions are encountered during treatment
— such as lime treatment after prechlorination.
Hypobromous acid adds similarly across aliphatic double bonds. In both
cases, the organic chlorohydrin compounds, which may be isolated as intermedi-
ates, contain halogen.
The Haloform Reaction--
The uni-halogen containing trihalomethanes, chloroform, bromoform and
iodoform, are formed by a process known as the haloform reaction. The
reaction seqence occurs when acetone is treated with hypochlorite in alkaline
solution:
CH0CCH0 + SNaOCl
3ii 3
CHC13 +
•CH-CCCK + 3NaOH
3H 3
0
CHjCOONa
trichloroacetone
(sodium acetate)
In the first phase of the reaction, one of the methyl groups in acetone
becomes fully substituted by chlorine. Since sufficient alkali is produced
in this first step to cause cleavage in the second step, both reactions
proceed together80. Notice that in addition to chloroform, a non-halogen-
containing, oxidized organic compound (sodium acetate) also is produced.
Recently, Suffet, et. a]..81 have identified 1,1,1-trichloroacetone in
chlorinated drinking water supplies in two Philadelphia treatment plants.
One of these plants employs post-ammoniation for disinfection, but the
trichloro intermediate in the haloform reaction was produced by chlorination
and not upon chlorammoniation.
Chloroform also is produced by the action of hypochlorite upon ethanol,
which is first oxidized to acetaldehyde, followed by chlorination80:
231
-------
CH3CH2OH + NaOCl
• CH3CHO + Nad
^
CC10CHO
•SNaOCl
+ 3NaOH
CHC1. + HCOONa
(sodium formate)
Similarly, reaction of HOC1 with acyl substituted aromatic compounds
proceeds by substitution of chlorine for alkyl hydrogen atoms, followed by
oxidation with formation of chloroform. Thus methyl 3-naphthyl ketone
undergoes hypochlorite oxidation readily80, to produce chloroform:
C-CH-
NaOCl
C-OH
b + HCC1.
3-naphthoic acid
Similarly, trihalo derivatives of the type CgH5COCX3 are intermediates
in the conversion of acetophenone into benzoic acid and chloroform by the
action of NaOCl or NaOBr80:
C-CH,
NaOX
C-CX
3 HOH
C-OH
+ HCX,
acetophenone
3-Acetophenanthrene treated with hypochlorite produces 75% yields of 3-
phenanthroic acid and chloroform80:
NaOCl
C-CH
+ HCC13
COOH
3-phenanthroic acid
Rook82 has determined the chloroform-producing potentials of a series
of aromatic compounds that served as models for the more chemically complex
fulvic acids. Resorcinol (1,3-dihydroxybenzene), 1,3-dihydroxynaphthalene,
3,5-dihydroxybenzoic acid and phloroglucinol (1,3,5-trihydroxybenzene) all
232
-------
produced high yields of chloroform when 0.001 M solutions in water were
treated with 0.012M chlorine 2 hours at 15°C at pH 7 and pH 11. Rook considers
the mechanisms to involve ring chlorination, followed by ring rupture to
produce fragments which then form chloroform.
resorcinol
Cl.
CHC1
OH
phloroglucinol
Reactions of Chlorine With Phenol —
Burttschell, e_t aj_.83 followed the chlorination of phenol in laboratory
studies simulating drinking water plant conditions. Aqueous solutions of 20
ppm of phenol were treated with 40 ppm solutions of chlorine (2/1 ratio of
chlorine/phenol, previously dissolved in water, at pH 8. Products were
isolated and identified by paper chromatography, infrared and ultraviolet
spectrophotometry. The course of reaction is indicated in Figure 53 (parenthe-
tical percentages are those of products found after 18 hours of reaction).
2,6-Dichlorophenol was shown to be the major product responsible for taste
and odors in chlorinated drinking waters.
These same chlorinated phenolic materials were produced when phenol was
treated with chloramine, but much more slowly. After 18 hours of reaction
with chloramine, nearly all phenol was recovered unreacted. However, after
5.5 days of reaction, significant amounts of 2,6- and 2,4-dichlorophenols
were isolated.
Miscellaneous Reactions--
Reaction of NaOBr with nicotinamide produces 67% yields of 3-aminopyri-
dine80:
NaOBr
Finally, Mills81* cites the work of Jolley85 who analyzed chlorinated
municipal wastewaters. The yield of chlorinated organic compounds isolated
at any location totalled less than 1% of the chlorine dosed. Furthermore,
nearly all the chlorinated compounds identified contained only a single
chlorine atom. Thus, most of the chlorine added reacted by oxidation,
forming chloride ion and non-chlorinated organic compounds.
233
-------
OH
OH
ro
co
[0]
Cl
(40-50%)
Cl
(-25%)
• parenthetical numbers = amounts isolated after 18 hours ~ chlorination of a
20 mg/1 phenol solution with 40 mg/1 chlorine at pH = 8.
ring ruptured,
non-aromatic
products
(with 4/1
C12/00H ratio)
Figure 53. Reactions of chlorine with phenol83.
-------
Summary of Chiorination Reactions
The major points involving chlorine reactions with organic materials
are:
§ Chlorine in water forms HOC1, over pH ranges normally employed in
water treatment plants. HOC! is both an actual chlorinating and
oxidizing material in aqueous solution.
• HOC! adds to isolated double bonds present in dissolved organic
compounds to form chlorohydrins. In alkaline solution, chloro-
hydrins eliminate HC1, producing epoxides.
• The haloform reaction is unique to chlorine, bromine and iodine
and involves both halogenation and oxidation by hypohalite. With
chlorine, an organic methyl group adjacent to an activating carbonyl
group first is perchlorinated, then is cleaved oxidatively. This
cleavage produces a molecule of chloroform and a molecule of an
oxidized organic material which does not contain halogen — normally
an organic acid.
0 Chlorination of phenol proceeds stepwise, producing mono-, di- and
tri-chlorophenols. Ring Chlorination is maximum at 2/1 chlorine/-
phenol molar ratios.
• Chlorination of phenol using 4/1 molar ratios of chlorine/phenol
or higher proceeds past the ring Chlorination stage by oxidative
ring rupture, producing aliphatic compounds.
0 Many aromatic di- and poly-hydroxy compounds produce chloroform
when treated with chlorine.
0 Chlorination of organic materials can produce a wide variety of
organic oxidation products, which do not necessarily contain
chlorine. Non-chlorinated aldehydes and acids have been isolated
from alcohols. Non-chlorinated organic acids (and chloroform) are
produced upon Chlorination of methyl ketones. If all chloroform
measured in a given water supply was produced by the haloform
reaction involving carbonyl-activated methyl groups, there will
also be present an equivalent molar amount of non-halogen-containing
organic acids, or their degration products.
REACTIONS WITH OZONE
Reactions With Phenol
Eisenhauer86 ozonized aqueous solutions of phenol for 30 minutes (until
phenol was destroyed) and isolated catechol, p-quinone, cjj5_-muconic acid,
oxalic acid and fumaric acid:
235
-------
30 minutes
catechol
COOH
COOH
p-quinone
muconlc
acid
H
HOOC-C=C-COOH
+ HOOC-COOH
(fumaric acid)
(oxalic acid)
When ozonation was conducted for only 10 minutes, Eisenhauer isolated
a 20% yield of catechol, but only 70% of the phenol was destroyed. This
indicates that upon oxidation of phenol, other organic compounds (10%) or
COp are produced along with the catechol.
Gabovich, e_t al_.87 treated 10 mg/1 aqueous solutions of phenol with
ozone dosages of 0.7 to 2.3 mg/1. To attain 90% destruction of phenol (to
1 mg/1 concentration) required 1.85 mg of ozone/mg of phenol; complete
destruction of phenol required 2.3 mg ozone/mg phenol.
Bauch, et. al_.88 found monobasic and polybasic (aliphatic) acids upon
ozonation of water solutions of phenol. They concluded that oxidation of
phenol by ozone proceeds via the ozonide and produces hydrogen peroxide.
Initial phenolic oxidation products themselves consume additional ozone.
Bauch & Burchard89 ozonized aqueous solutions of phenol and isolated
and identified maleic acid, tartaric acid, glyoxylic acid, oxalic acid and
C0~:
2 OH
H H
HOOC-C"=C-COO
maleic acid
HOOC-CHO
glyoxylic
acid
OH OH
:-CH-CH-(
HOOC-CH-CH-COOH
tartaric acid
+ HOOC-COOH
oxalic
acid
CO 2
236
-------
Smith, e^aJL 90 found that the rate of disappearance of phenol upon
ozonation in water is increased by combining ultrasonics and/or Raney nickel
with ozonation. After 2.5 hours of ozonation, an initial solution of 500
mg/1 phenol showed the complete absence of phenol. On the other hand, the
COD of the original solution decreased only slowly, and was still fairly
high after the phenol had disappeared, indicating the presence of intermediate
oxidation products. Considerable carbon loss indicated the formation of
some C02-
Mallevialle91 ozonized 100 to 200 mg/1 aqueous solutions of phenol with
25 mg/1 ozone doses and identified catechol, o-quinone, hydroquinone and
p-quinone as oxidation products:
(100-200
mg/1)
catechol
o-quinone
hydroquinone
quinone
Spanggord & McClurg92 were the first investigators to identify resorcinol
as an initial oxidation product, along with catechol, upon ozonation of
phenol in water:
resorcinol
catechol
Gould & Weber93 have made the most complete study to date on the ozonation
of phenol. They found that the early oxidation products (catechol and
hydroquinone) are further oxidized as ozonation continues, and fall to
relatively insignificant concentrations as the reactions proceed. Glyoxal
is formed by ring rupture, but itself decreases to a low concentration level
as the reactions proceed. Glyoxylic acid is the main oxidation product
isolated after 30 minutes of treatment with ozone, together with smaller
amounts of oxalic acid.
237
-------
OH
hydroquinone
OHC-CHO HOOC-CHO + HOOC-COOH
glyoxal glyoxylic oxalic
acid acid
(major product after 30 minutes)
Throop9" showed that ozone dosages of 5.32 mg/1 produced non-
detectable quantities of phenol, starting with concentrations of 110 ppb of
phenol in water. This dosage is equivalent to 48 parts ozone/part of
phenol. However, ozone dosages of 25.5 mg/1 (200 parts ozone/part phenol)
were required to produce a measureable (trace) amount of residual ozone in
the solution. This confirms that although ozone rapidly destroys phenol
itself, significant amounts of ozone-demanding oxidation products are
formed.
Reactions With Other Phenols
Hi 11 is95 studied the oxidation of 14 phenols with ozone over the pH
range 4 to 10, but did not identify oxidation products. With 30 mg/1
concentrations of phenols and bzonation conducted 4 to 12 minutes [except
for pentachlorophenol (PCP), which required 35 minutes], residual concentra-
tions of phenols of less than 0.10 mg/1 were obtained. However, COD values
were reduced only about 50%, indicating that organic carbon-containing
oxidation products still present.
With solutions of phenol, phenolsulfonic acid, hydroquinone and
pyrogallol, COD was destroyed steadily upon ozonation. However, with
pentachlorophenol and g-naphthol, there was a steady rise in COD values
during the first few minutes of ozonation, followed by a steady reduction
in COD values.
238
-------
The amount of ozone required to lower the concentration of these
phenols from 30 mg/1 to below 0.5 mg/1 in 10 minutes (except for PCP) was
2.0 to 3.0 g/g phenol (4 to 6 moles ozone/mole phenol).
Bauch, Burchard & Arsovic88 compared the rates of ozonation of phenol
with cresols and xylenols, and also isolated and identified ring ruptured
oxidation products. Crcsols decomposed more rapidly than phenol, and m-
cresol decomposed faster than the o- and p-isomers. Cresols reacted faster
with ozone in acid solution than in basic solution. 80% Decomposition of
cresols was accomplished with 2 moles of ozone/mole of cresol (85 g ozone/-
100 g cresol).
Upon initial ozonation, the methyl group in cresols oxidized to the
carboxylic acid. o-Cresol, for example, produced salicylic acid:
H
o-cresol
COOH
salicylic acid
Continued ozonation of cresols ruptured the aromatic ring and produced
maleic acid (which further oxidized to mesotartaric acid), acetic acid,
propionic acid, glycolic acid, glyoxylic acid, oxalic acid and C02:
HOOC-CH=CH-COOH
maleic acid
CH3CH2COOH
CH3COOH
•HOOC-CH(OH)-CH(OH)-COOH
mesotartaric acid
HOCH2COOH
OHC-COOH
HOOC-COOH + C02
All 3 cresols (o-, m- and p-) formed the same oxidation products upon
ozonation. Only the rates of oxidation varied.
Xylenols with ortho or para hydroxy groups reacted fastest with ozone
and produced the same oxidation products as the cresols88. In addition,
1,2,3- and 1,2,4-xylenols produced diacetyl, glyoxal (which disproportionates
to glyoxylic acid), hydroxyphthalic acid and ketoaldehydes:
239
-------
CH3
°3
u u
"S TH r rTH
diacetyl
+ OHC-CHO
/
HOOC-CHO
glyoxylic
acid
hydroxy-
phthalic
acid
Gilbert96 ozonized 1 mmole/1 of 2-nitro-p-cresol with 10 mg of ozone/-
minute until the cresol was destroyed. He found that 90% of the original
nitrogen was converted to nitrate ion, indicating rupture of the aromatic
ring.
OH
NO,
(90%)
Reactions With Chlorinated Phenols
Shuval & Peleg97 compared the ozonation of phenol with o-chlorophenol.
At the same initial pH, the rates of oxidation with ozone are the same for
both compounds, but the rate is fastest at higher pH. Starting at pH 10
the reactions are faster when the pH is maintained at 10, rather than
letting it drop (to 2.5) as ozonation proceeds.
In addition, the rate of formation of chloride ion was followed
during ozonation of chlorophenol. In all experiments, about 80% of the
aromatic chlorine was converted to chloride ion upon ozonation, indicating
that covalent C-C1 bonds are broken with ozone. There was an induction
period during which the concentration of o-chlorophenol decreased but
without formation of chloride ion. On the other hand, after all o-chloro-
phenol had disappeared, chloride ion still was being produced upon continued
ozonation. This indicates that the active oxidation species attacks the
aromatic ring at a site or sites other than the chlorine site, producing
chlorinated aliphatic compounds as intermediates.
Gilbert96 ozonized aqueous solutions of 2-chloro-, 4-chloro-, 2,3-
dichloro-, 3,5-dichloro- and 2,4,6-trichlorophenols until the phenols could
not be detected by gas chromatography and no phenolic functionality could
be detected by 4-aminoantipyrine. This required 3.2 to 5 mmoles of ozone/-
mmole of phenol. The rate of oxidation increased from mono- to trichloro-
phenol.
240
-------
After ozonation, 60 to 95% of the chlorine was found as chloride ion.
Ozonation of 4-chlorophenol produced chloride ion at the start of ozonation;
chloride ion was found only after 40% of the 2-chlorophenol had been degraded.
The different rates of dechlorination are explained in terms of different
electron density distributions on the aromatic rings.
2,4-Dichlorophenol produced formic and oxalic acids upon ozonation, in
addition to chloride ion:
OH
HCOOH + HOOC-COOH + Cl'
Biodegradability of the ozonized products was higher with increasing
degree of oxidation and with decreasing chlorophenol concentration. After
total oxidation of the phenols, the COD had been reduced from 200 to 100
mg/1 and TOC had been reduced from 72 to 59 mg/1.
After chlorophenols had disappeared, thin layer chromatography techniques
indicated the presence of carbonyl or carbonyl/carboxylic acid functionalities.
In instances of incomplete dechlorination, chlorinated aliphatic moieties
were isolated but not identified.
Gilbert96 ozonized 4-chloro-o-cresol and identified 67% of its oxidation
products. After 80 minutes of treatment with ozone (800 mg of ozone total
dosage added to 1 mmole of chlorocresol) none of the starting cresol was
present and 100% of the chlorine was found as chloride ion. In the ozonate,
methylglyoxal, pyruvic acid, acetic acid, formic acid and oxalic acid were
isolated and identified, along with CO,,. The course of reaction is as
follows:
80 min
OHC-C=0
CH3
methyl
glyoxal
0
CH3C-COOH
pyruvic
acid
CHCOOH
acetic
acid
HCOOH + HOOC-COOH + CO,
formic oxalic
acid acid
241
-------
Methylglyoxal was produced from the beginning of the reaction, its
concentration reaching a maximum after 60 minutes of reaction, then slowly
decreasing. This means that its rate of formation from the cresol is
faster than its rate of oxidation.
Pyruvic acid and acetic acid concentrations increased steadily during
ozonation, even after complete elimination of the cresol, indicating that
these two acids are produced from the initial oxidation products of the
cresol.
All TOC was accounted for by these organic compounds at various times
during ozonation. Therefore, the above compounds, plus C0o> water and
chloride ion are the only oxidation products of this cresof.
Figure 54 summarizes the reactions of phenols with ozone.
Reactions With Other Aromatics
Ahmed & Kinney" ozonized 0.8693 g of 3,8-pyrenequinone 33 hours in
water and isolated 0.56 g of 1,2,3,4-benzenetetracarboxylic acid plus
acetic acid:
3,8-pyrenequinone
COOH
COOH
COOH
+ CH3COOH
OOH
0.56 g
1,2,3,4-benzenetetra-
carboxylic acid
Kinney & Friedman100 ozonized an alkaline solution of phthalic acid 24
hours and isolated 28% of the carbon as oxalic acid, 34% as C02» 3% as
acetic acid and 35% as other water soluble acids:
COOH
;OOH
phthalic acid
24 hrs
CH3COOH +
HOOC-COOH + C02
(28%) (34%) (3%)
other, water soluble acids
Kinney & Friedman100 also ozonized a solution of pyrene 24 hours and
isolated 2.4% of the carbon as acetic acid, 0.6% as C02, 0.1% as oxalic
acid and 19.9% as water soluble acids.
242
-------
ro
-p»
oo
Cl
OH
Cl
OH
°
plus CT
HOOC-C=C-COOH
A f\
CH-C
6H O
HOOC-CH-CH-COOH
H
HOCH2-COOH
OHC-COOH + HCOOH
OHC-CHO
HOOC-COOH + C00
Figure 54. Reactions of ozone with phenol.
OH
R -+• -H- R
(R = Q
etc.)
COOH
plus:
CHoCOOH + CH.CH9COOH +
CH.-C-C-CH, +
3 II II 3
0 0
CH3-C-COOH + 0=C-CHO
0 CH3
-------
24 hrs
pyrene
CH3COOH + C02 + HOOC-COOH +
(2.4%) (0.6%) (0.1%)
other, water soluble acids
Sturrock, e_t al_.101 ozonized phenanthrene in a 1/1 water/methanol
solution (methanol is resistant to ozone). Water was used to avoid the
formation of explosive ozonides or peroxides, which are formed under neat
or non-aqueous solvent conditions. After ozonation of 15 g of phenanthrene,
1.3 g of unreacted phenanthrene was recovered, along with 16.4 g of oxidation
products. These were identified as 2l-formylbiphenylcarboxylic acid, 2'-
hydroxymethyl-2-biphenylcarboxylic acid, diphenide and diphenic acid.
It is of significance that only one ring in phenanthrene was opened by
treatment with ozone. This indicates that the material is fundamentally
resistant to ozone.
Il'nitskii, e_t al_.102 found that 3,4-benzopyrene in distilled water
was destroyed much more rapidly than when the pyrene was added to raw
drinking water containing added soil particles. In 1 minute, ozone destroyed
61% of the pyrene in distilled water, but only 33% in naturally occurring
raw water. In 2.5 minutes of ozonation, 100% of the pyrene was destroyed
in distilled water, but only 60% was destroyed in this time (same concentra-
tion) in raw water containing added soil particles.
H2OH
phenanthrene
diphenide
diphenic acid
244
-------
These investigators concluded that 3,4-benzopyrene is adsorbed onto
fine soil particles and thus is "protected" from oxidation. In designing
the ozonation treatment for waters containing 3,4-benzopyrene, an effective
filtration step should precede ozonation. Protection of organic compounds
from oxidation by naturally occurring colloidal materials also was noted by
Mallevialle1*8 in studies with aldrin (see-- "Reactions With Pesticides").
II'Nitskii103 ozonoized 0.6 to 1.2 mg/1 concentrations of 3,4-benzo-
pyrene in water maintaining a 0.4 mg/1 residual of ozone. In 7.5 minutes
the pyrene had been oxidized to below the detectable limit.
Gabovich, et^ aK lolt compared the oxidation rate of 3,4-benzopyrene
when treated with chlorine and'with ozone. Chlorine reduced the concentration
of the pyrene 5 to 10 times in 0.5 to 2 hours. Ozonation for 3 to 5 minutes
reduced the concentration 10 to 50 times.
3,4-Benzopyrene (4 yg/1) treated 3 minutes with 2.5 mg/1 of ozone was
reduced in concentration to 0.06 ug/1; treating the same concentration 3
minutes with 4.5 mg/1 of ozone lowered the pyrene concentration to 0.04
ug/111.
Reichert139 dissolved 3,4-benzopyrene in 1 ml of acetone, then diluted
this to 1000 ml with water. Samples containing 1 to 100 microg/1 of pyrene
were ozonized with 0.5-1.5 mg/1 doses. In 30 minutes of ozonation, 99%
decomposition of the pyrene was observed.
Gabovich, et aK87 also studied the rates at which ozone would reduce
the concentrations of other aromatic compounds in water. Diethylbenzene in
concentrations of 10 to 100 mg/1 upon treatment 7 to 10 minutes with quanti-
ties of ozone similar to those used in drinking water treatment (1 to 5
mg/1) was reduced in concentration to 0.5 to 0.8 mg/1. 2,4-Dinitrophenol
at 50 mg/1 was reduced in concentration to 0.35 mg/1 using 2 mg ozone/mg of
phenol; using 5 mg ozone/mg phenol, the final concentration of 2,4-dinitro-
phenol was lowered to 0.05 mg/1.
Chlorobenzene reacts with ozone slower than does phenol, probably
because of its lower solubility in water, but gives the same oxidation
products as does phenol. In addition, HC1, chlorotartaric acid and o-, m-
and p-chlorophenols are formed88:
OH
(o-, m- and p-chlorophenols)
(products continued on next page)
245
-------
.-£
+ HOOC-CH(OH)-C-(OH)-COOH + HC1 +
same ring-ruptured, aliphatic
oxidation products as from
ozonation of phenol
Chlorocresols, chlorophenols, naphthols, thiophenols and polyhydroxy-
phenols give similar oxidation products as do phenols upon ozonation88.
Hoigne106 showed that ozonation of benzoic acid caused 10% decarboxyla-
tion to produce C02.
Mallevialle91 ozonized 100 to 200 mg/1 aqueous solutions of salicyclic
acid. The TOC remained constant during the first 10 minutes of ozonation
(25 mg/1 total dosages), but then dropped steadily. Phenol, catechol and
three unidentified phenols were isolated from the ozonate. 2,3-Dihydroxy-
benzoic acid was shown to be absent. Three moles of ozone/mole of salicylic
acid were required to destroy all of the starting acid. Infrared analyzes
showed the products to have strong -OH and -COOH absorptions, indicating
that a mixture of carboxylic acids was formed.
OH
OH
OOH
salicylic acid
+ 3 unidentified
phenols
;OOH
.OH
NO
Spanggord & McClurg92 ozonized aqueous solutions of N,N-diphenylhydrazine
hydrochloride at pH 7 and identified ring- and N-hydroxylated derivatives,
plus free uns-diphenylhydrazine:
246
-------
-NH2.HC1
-NH-OH
JUrs107 reviewed the then current literature and concluded that ozonation
of benzene (in benzene) produced a triozonide which, when treated with
water, rapidly decomposes to form glyoxal, glyoxylic acid and oxalic acid:
°3 1n
>
benzene
HOH^ OHCOCHO +
HOOC-CHO +
HOOC-COOH
(a triozonide)
JUrs also concluded that ozonation of phenol, even in water, proceeds
through a triozonide, which is transient, decomposing into aldehydes,
oxalic acid, glyoxal and hydroperoxides:
aldehydes +
HOOC-COOH +
OHC-CHO +
hydroperoxides
HOH
Ozonation of naphthalene in water produced salicylic acid107.
OH
3
HOH
COOH
247
-------
Ozonation of indole and skatole proceeds through ozonides which, when
treated with water, form o-aminobenzaldehyde and/or o-aminobenzoic acid107.
.COOH
or
Yocum108 studied the ozonation of styrene under aqueous conditions,
but only to the benzoic acid stage of oxidation. He found that initial
cleavage of the exocyclic double bond occurred rapidly, producing benzal-
dehyde and formaldehyde. Further oxidation of formaldehyde to CO? and
water occurred rapidly, as did the oxidation of benzaldehyde to benzoic
acid. This last step (benzaldehyde to benzoic acid) required 1.47 moles of
ozone/mole of aldehyde.
CH=CHo 0,
styrene
HCHO
COOH
benzoic acid
\
C0
H20
Further ozonation of benzoic acid solutions caused attack at the o-, m-
and p- positions on the aromatic ring. After 30 minutes of ozonation of
a 300 mg/1 solution of acid with 4 moles ozone/mole 0COOH, the benzoic acid
was 85% oxidized to other products.
COOH
30 min
85% oxidation to
other products
Finally, Yocum108 determined that the biodegradability of ozonized
styrene is much higher than that of styrene itself. The starting BODn/TOC
ratio was 0.47, but after 150 minutes of ozonation it had increased to
2.69. This shows that ozonation in aqueous solution can convert relatively
non-biodegradable compounds into compounds which are biodegradable.
248
-------
Ozonation of naphthalene-2,7-disulfonic acid96 for 120 minutes produced
formic, oxalic and mesoxalic acids, (accounting for 25% of the TOC) sulfate
ion, plus organic carbonyl compounds and organic sulfonic acids. After 300
minutes of ozonation, nearly complete desulfonation was achieved (nearly
quantitative yield of sulfate ion). Glyoxal and mesoxalic acid semialdehyde
were also identified. The BOD,-/COD ratio increased from 0 to 0.8, indicating
that the oxidation products are biodegradable.
120 min HCOOH + HOOC-COOH +
> HOOC-C(:0)-COOH +
-2
organic carbonyl + sulfonic
acids
300
nearly complete desulfonation +
OHC-CHO + HOOC-C(:0)-CHO
Ozonation of 4-aminobenzoic acid96 gave formic and oxalic acids,
ammonia and nitrate. After 80 minutes of ozonation, only 70% of the organical
ly-bound nitrogen was measured as ammonia and nitrate. This indicates that
organic compounds containing nitro or ami no groups still were present. The
BOD5/COD ratio increased from 0 to 0.4.
.COOH
80 min
HCOOH + HOOC-COOH +
+ N0
Chian & Kuo109 ozonized aqueous solutions of o-toluidine and found
acetic and oxalic acids:
o-toluidine
H20
HOOC-COOH + CH3COOH
Ozonation of aqueous solutions of N,N-diethyl-m-toluamide produced
formic, acetic and oxalic acids109 .
249
-------
°3
_ >. HCOOH + CH3COOH + HOOC-COOH
(j-N-(C2H5)2
0
Gilbert110 found that 3 to 8 kg of ozone are required to remove 1 kg of
aromatic sulfonic acids from aqueous solutions. Ozonation of p-toluene
sulfonic acid in water formed organic peroxides, the concentrations of which
decreased to zero in 120 minutes, plus H202-
Many papers by Prengle and his co-workers111'112'113, which have
appeared since 1973 describe the combination of ozone with ultraviolet
radiation. The combination oxidizes compounds at a faster rate than does
ozone alone. Prengle, e_t al_.112 followed the UV/ozonation of pentachloro-
phenol (PCP) by gas chromatography. After 1 hour of treating a 7 mg/1
aqueous solution at pH 9.6 with ozone/UV, the PCP concentration had dropped
and the amount of chlorine found in solution as chloride ion was more than
50% of that available. In addition, the TOC value had dropped. This
indicates that the aromatic ring had been ruptured, forming C02, in addition
to chloride ion.
Similarly, a 100 mg/1 solution of o-dichlorobenzene treated 30 minutes
by UV/ozonation showed 100% destruction of the aromatic compound, but only
50% of the available chlorine was recovered as chloride ion.
Reactions With Aliphatic Compounds
Dobinson111* ozonized aqueous solutions of malonic acid and identified
hydroxymalonic acid and ketomalonic acid as products:
HOOC-CH2-COOH > HOOC-CH(OH)-COOH +
HOOC-C-COOH
ketomalonic acid
OUrs107 in reviewing the literature, concluded that in non-aqueous,
non-polar solvents (carbon tetrachloride, hexane, etc.) ozonation of aliphatic
double bonds proceeds through polymeric ozonides. In non-aqueous polar
solvents (such as acetic acid), monomeric ozonides are favored.
In water, however, JUrs concluded that ozonides hydrolyze to peroxy-
diesters, which further hydrolyze to dialcohols and aldehydes107. Peroxyacids
decompose in water to aldehydes or acids and H^O,,. Acids and aldehydes can
recombine to form dialcohols.
Pryde, £tal_.115 studied the ozonolysis of aliphatic unsaturated
materials in water. Methyl oleate (5 g in 25 g of distilled water) ozonized
20 to 30 minutes with 2 to 3% ozone in oxygen produced an 82% yield of
compounds containing new carbonyl groups.
250
-------
^
CH3(CH2)7-CH = CH-(CH2)7COOCH3 - * — > compounds
containing
methyl oleate .
C = 0 groups
1-Decene (0.2 to 0.5 g) ozonized 16 hours in water produced an aldehyde,
a dimethyl acetal , a methyl ester and a hydrocarbon, all from cleavage of
the double bond:
°3
CH3(CH2)7CH = CH2 (or R-CH=CH2) - >• RCHO +
C
• ,
decene decene
'" h3
RCOOCH. + RCH
0
3
These authors concluded that ozonolysis of dispersions of slightly
soluble (in water) organics in water proceeds through hydroperoxides and/or
dihydroxyperoxides, both of which rearrange readily in water to produce
acids, hydrocarbons + C02 or aldehydes + CO.
°3
RR'CH = CH9 - ?->> RR'CH - CH9 or RR'CH - CH,
2 ^^ l | 2 I I 2
OOH OH OOH OOH
I
acids + C02 aldehydes + CO
Dorfmann11& ozonized cysteine in water and isolated cystine as an
initial oxidation product. Cystine then formed unidentified degradation
products upon continued ozonation:
HSCH2CH(NH2)COOH —> -[SCH2CH(NH2)COOH]2
cysteine cystine
7
degradation
products
Kraznov, elt al_.116 ozonized aqueous solutions of aliphatic alcohols and
aldehydes. Ethanol, butanol and octanol in dilute aqueous solution with 33
mg/1 ozone dosages produced aldehydes, then acids, but n£ C02. The rate of
oxidation increased with increasing pH:
251
-------
CH3CH2CH2CH2OH
CH3(CH2)6CH2OH 33 mg/1
°3
aldehydes —>acids (no C02)
Secondary alcohols readily produced ketones upon ozonation, which
oxidized further to organic acids +.H20116. Ketonic intermediates were
lower boiling than the alcohols, and were more readily stripped into the gas
phase:
R °3 R 0,
\ \ 3
CH2-OH > C=0 >
R1 R'
R-COOH + R'-COOH + H202
Aldehydes formed peroxy acids, which produced organic acids + H?0~ on
continued ozonation in dilute aqueous media116.
°3 9 °3
RCH = 0 —^-> R-C-0-O-H —:L>RCOOH + H,0,
H20 ^ i
Gilbert110 ozonized 1 liter solutions (0.001 mole/1) of maleic acid at
an initial pH of 5. After 50 minutes of ozonation, during which time 195 mg
of ozone (39%) was utilized, oxidation of maleic acid was complete. Degrada-
tion of maleic acid was rapid, and glyoxylic and formic acids were formed
simultaneously as maleic acid disappeared. After complete disappearance of
maleic acid, formic acid was ozonized to C02 and water, and glyoxylic acid
was ozonized to oxalic acid:
HOOC-C=C-COOH —> HOOC-CHO + HCOOH
HCOOH > C02 + H20
HOOC-CHO —>-HOOC-COOH
The total amounts of maleic, glyoxylic, oxalic and formic acids and C02
determined on each sample analyzed was equal to the amounts calculated on
the basis of this mechanism. Therefore, these specific materials are the
only oxidation products of maleic acid. Gilbert also concluded that under
his experimental conditions, little oxidation of oxalic acid occurs upon
ozonation.
Prengle, ejt al_.112 studied the UV/ozonation of 1,4-dichlorobutane and
of chloroform in water. With ozone alone, 1,4-dichlorobutane was 50%
252
-------
destroyed in 1 hour of ozonation, whereas UV/ozonation destroyed 100% of the
material in 1 hour. The stoichiometric amount of chloride ion was found
after 1 hour of UV/ozonation.
UV/ozonation for 2 hours resulted in 80% destruction of chloroform.
However, only 25% of the theoretical amount of chloride was recovered,
therefore, much of the "destroyed" chloroform must have been stripped out of
solution. The rate of decrease of TOC was almost as rapid as the rate of
decrease of chloroform concentration, therefore there are few non-volatile,
carbon-containing organic oxidation products of chloroform.
Chian & Kuo109 studied the oxidation of several refractory aliphatic
compounds in aqueous solution with ozone and ozone/UV combinations, and with
the pH contolled by addition of HC1 or NaOH solutions as needed during the
reactions. 1-Propanol (408 mg/1) ozonized 1 hour at pH 9 (1980 mg total
ozone dose) produced a solution with zero ozone concentration. Propionaldehyde
(85 mg/1) was produced, and carbon balance analyses showed that this compound
and 1-propanol'(145 mg/1 remaining) were the only two organic materials
present. TOC was reduced from 225 to 210 mg/1, indicating that some C09 had
been formed. CH3CH2CHO + C02
UV/ozonation of 1-propanol (410 mg/1) under the same conditions produced
95 mg/1 of propionaldehyde; 120 mg/1 of propanol remained, and TOC was
reduced to 205 mg/1.
In both cases of ozonation of 1-propanol, TOC levels did not begin to
fall significantly until after aldehyde production had peaked (45 minutes
with ozone alone, 40 minutes with UV/ozone).
Propionic acid (490 mg/1) was ozonized at pH 9 for 2 hours (2960 mg
total ozone dose). Again, dissolved ozone concentration was zero, indicating
that the ozone demand had not been satisfied. Unreacted acid concentration
was 235 mg/1 and TOC had dropped from 235 to 200 mg/1. Oxidation products
were not identified.
For the balance of this work of Chian & Kuo109 lower concentrations of
organic compounds were chosen so that ozone residual concentrations of 4
mg/1 or higher were present. Ozonation of propionic acid at pH 7 resulted
in 17% TOC reduction and formation of acetone. No monocarboxylic acids were
detected and acetone accounted for over 85% of the TOC of the reaction
mixture:
CH3CH2COOH >CH3-C-CH3 (85% yield)
UV/ozonation of 2-propanol substantially increased the rate of TOC
removal. An initial TOC of 110 mg/1 was reduced to 20 mg/1 (85%) after 135
minutes of UV/ozonation. 2-Propanol disappeared after 30 minutes and the
concentration of acetone formed reached its maximum value at this time. On
continued UV/ozonation, the acetone level decreased to zero after 75 minutes.
253
-------
C2 to Cg monocarboxylic acids were not detected in the ozonate, but NaOH
aadition was required throughout the reaction in order to maintain the pH
constant. This indicates that formic and/or oxalic acids were produced from
the ozonation of acetone.
CH3CH(OH)CH3—> CH3-C-CH3 —>HCOOH and/or HOOCCOOH
Ozonation of methyl ethyl ketone (MEK) 2 hours at pH 7 produced a small
amount of acetate ion. MEK accounted for over 85% of the ozonate TOC. Much
of the loss of MEK was attributed to air stripping (40% TOC removed after.2
hours). By contrast, after 2 hours of UV/ozonation, MEK was completely
eliminated. Acetate ion reached its maximum concentration after 35 minutes,
then decreased to zero at 105 minutes. Trace amounts of acetone and ethanol
were detected.
CH3CH2C(:0)CH3 > CH3COO"
Ozonation of acetic acid 2 hours at pH 7 (adjusted at the beginning,
but allowed to rise during treatment) resulted in 14% removal of TOC.
Glyoxylate anion concentration increased with time, but was always low:
0.
ChUCOOH
J UV
UV/ozonation of acetic acid was much more rapid. After 75 minutes, no
acetate was detected. Glyoxylate ion (at lower concentrations than with
ozone alone) remained level in concentration during the first hour, but then
decreased to zero. No alcohols were found, nor formic acid, but oxalate ion
was found in the ozonate:
CH-COOH 2>OHC-COO" >-"OC-COO"
6 UV
Ozonation of diethyl ether 2 hours at pH 9 produced ethyl acetate and
acetate ion as the major oxidation products, but small amounts of acetaldehyde,
methyl formate, ethanol, acetone and ethyl formate also were isolated.
During the later stages of ozonation, TOC reduction rates became slower,
when ethyl acetate and acetate ion were the major constituents. Good
agreement between the calculated and experimentally determined TOC indicated
that all the oxidation products were accounted for and that C02, therefore,
is not an oxidation product:
0.
CH3CH2OCH2CH3 *>• CH3COOC2H5 + CH3COO" (major) +
CH0CHO + HCOOCH., + CH7CH9OH + CH,C(:0)CH, + HCOOC-Ht-
3 6 6 £. o j £3
UV/ozonation of diethyl ether resulted in 94% removal of TOC under the
same conditions, because of further oxidation of ethyl acetate and acetate
ion to C02. Formation of acetate ion occurs by 2 routes: from the ether and
254
-------
from ethyl acetate. Small amounts of the same other organics as obtained
with ozone alone also were isolated after UV/ozonation.
Quantitative determination of oxalate and glyoxylate showed that
acetate concentration reached zero when oxalate concentration reached its
maximum. This indicates that the degradation route of acetate by UV/ozonation
is through glyoxylate and oxalate to COo. Since the amount of oxalate
formed was not equal to the amount of acetate present, it is likely that
glyoxylate (the precursor of oxalate) can be oxidized directly to COo.
CH3COO" —> OHC-COO" + "OOC-COO" > C02
Spanggord & McClurg92 ozonized aqueous solutions of oleic acid and
isolated three organic acids. During ozonation, the pH dropped to 3.8:
CH3(CH2)7CH=CH(CH2)7COOH + 03 -> CgH-^COOH +
OHC(CH2)7COOH +
HOOC(CH2)7COOH
Ozonation of diethy!amine produced acetaldoxime plus an unidentified
nitrogen-containing compound, not a nitrosamine92:
(C2H5)2NH 92—*» CH3CH=NOH + unidentified compound
Spanggord & McClurg92 ozonized concentrated solutions of ethanol in
water (several percent) with very large doses of ozone (several thousand mg)
for 1 to 2 hours. Acetaldehyde and acetic acid were identified along with
a dihydroperoxide, which was shown to exhibit mutagenic activity:
CH3CH2OH + 03 —-> CH3CHO + CH3COOH +
OCH-0
2\
CH,CH CHCH,
3l I 3
OOH OOH
These authors do not believe that the dihydroperoxide will form in
drinking water supplies containing low concentrations of ethanol and when
ozonized under conditions normally employed in drinking water treatment (low
ozone dosages, short contact times).
Gilbert96 ozonized 1 liter samples of 1 mmole/1 aqueous solutions of
aliphatic compounds with 10 mg ozone/ minute until the initial compound
became undetectable. Oxalacetic acid consumed 1.8 mmole of ozone/mmole of
acid and a 60% yield of oxalic acid was isolated along with mesoxalic acid
(both formed by oxidation of glyoxylic acid intermediate) and formic acid:
255
-------
HOOCC(:0)CH2COOH + 03 - ^ OHCCOOH + HOOC-COOH (60%) +
HOOC-C(:0)-COOH + HCOOH
Dihydroxyfumaric acid consumed 1.4 mmoles ozone/mmole of acid and
rapidly produced oxalic acid as the major product, plus traces of dihydroxy-
tartaric acid, mesoxalic acid and the semi aldehyde of this acid:
HOOC-C(OH)=C(OH)COOH + 03 —^ HOOC-COOH (major) +
HOOC-C(OH)2C(OH)2COOH +
HOOC-C(:0)-COOH +
HOOC-C(:0)-CHO
Malonic acid consumed 4 mmoles ozone/mmole acid. Oxalic acid and
mesoxalic acids were the major oxidation products isolated. The concentration
of tartronic acid increased from the start of ozonation, then decreased,
forming mesoxalic acid and H202:
HOOCCH2COOH + 03 — ^ HOOC-COOH + HOOCCH(OH)COOH
HOOC-C(:0)-COOH + H202
Tartronic acid was converted totally to mesoxalic acid and in 40
minutes of ozbnation had used 1 mmole ozone/mmole acid. There was no
decrease in TOC during this time nor formation of H^:
HOOC-CH(OH)-COOH + 03 — > HOOC-C(:0)-COOH
Glyoxal disappeared after 50 minutes of ozonation, producing glyoxylic
acid which further oxidized to oxalic acid, then disappeared after 60
minutes of total ozonation. No H202 was formed:
OHC-CHO + 03-> HOOC-CHO —> HOOC-COOH
Ozonation of the 6-carbon containing muconic acid, HOOCCH=CHCH=CHCOOH,
produced 2-carbon containing fragments and only traces of 3-carbon containing
compounds. The 4-carbon containing fumaric acid, HOOCCH=CHCOOH, behaved
similarly upon ozonation.
Kuo, Chian & Chang118 treated 2-propanol and acetic acid with ozone and
UV/ozone. 2-Propanol formed acetone, which then formed acetic acid and
oxalic acid plus traces of formaldehyde and formic acid upon continued
ozonation:
CH3CHOHCH3 + 03— ^ CH3C(:0)CH3— > CH3COOH + HOOC-COOH +
HCHO + HCOOH
256
-------
Acetic acid produced glyoxylic acid initially, which rapidly formed
oxalic acid, which slowly formed C02 upon continued ozonation or UV/ozonation:
CH3COOH + 03—^HOOC-CHO >HOOC-COOH *• C02
Schalekamp119 reported that the Lake of Ztlrich water contains various
organic aldehydes (heptanal through tetradecanal) in concentrations of 8 to
40 nanog/1. After ozonation (1 ,to 1.5 mg/1 dosages) these aldehydes plus
hexanal were present in higher concentrations (up to 920 nanog/1). Passage
of ozonized Lake Ztlrich water through activated carbon reduced the concentra-
tions of these aldehydes to below the levels originally present.
Schalekamp concludes that ozonation should be used only before an
adsorption step in processing drinking waters.
Gilbert110 ozonized aqueous solutions of several aliphatic compounds.
In pure solutions at pH 3 to 7, 1 kg of COD is removed from solution with
1.2 kg of ozone. In wastewaters, 2 to 5 kg of ozone are required to remove
1 kg of COD. Ethanol ozonized 350 minutes produced acetaldehyde, acetic
acid, formic acid, C02 and H202:
CH0CHoOH + 0,—>CHQCHO + CH^COOH + HCOOH + C09 + H909
3 c. o .3 o • c. c- c.
Tartar!c acid ozonized 80 minutes,at pH 3 and pH 7 produced dihydroxy-
tartaric acid, glyoxal, oxalic acid, mesoxalic acid and H202:
HOOCCH-CHCOOH + 0, —T-> HOOCC(OH)?C(OH)2COOH +
OH OH 6
OHC-CHO + HOOC-COOH +
HOOC-C(:0)-COOH + H202
Malonic acid ozonized 90 minutes at pH 4 produced tartronic acid,
mesoxalic acid, oxalic acid and C02 plus H202:
HOOCCH9COOH + 0^—>HOOC-CH(OH)-COOH + HOOC-C(:0)-COOH +
L. O
HOOC-COOH + C02 + H202
Finally, Gilbert110 showed that the presence of H202 has a remarkable
catalytic effect on the oxidative decomposition of oxalic acid. In the
absence of peroxide, ozonation of oxalic acid produces C02 very slow y, but
when small amounts of H202 are added, oxalic acid produces C02 rapidly.
0.
HOOC-COOH > C02 + H20
slowly
03 + \
rapidly
x siowiy *
\ 03 + H2°2 7
257
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Reactions With Miscellaneous Compounds
Fremery & Fields120 studied the reactions of cyclic olefins with ozone
in aqueous alkaline emulsions containing hydrogen peroxide. In general,
a,o>-dicarboxylic acids were isolated, depending upon the specific cyclic
olefin starting material:
HOOC-CH2-CH2-CH-CH2-COOH
R
Cyclohexene upon treatment with ozone prepared from oxygen gave a
mixture of products containing peroxides and peroxypolymers. These were
shown to be side products of the main reaction, for when nitrogen was substi-
tuted for oxygen as the ozone carrier gas, cyclohexene gave 20 to 28% adipic
acid plus small amounts of S-hydroxyvaleric acid and its lactone:
HOOC-(CH2)4-COOH (adipic acid) +
HOCH2CH2CH2CH2COOH
Weber & Waters121 ozonized aqueous, 0.0005M solutions of dimethyl
mercury. After 10 minutes of ozonation, the alkyl mercury compound became
undetectable.
Shapiro ejt al_.122 ozonized aqueous solutions of caffeine (660 mg/1)
with 1630 mg of ozone over 90 minutes; 4.2 moles of ozone were consumed/-
mole of caffeine. Four major products were isolated (above 5% each) plus 4
minor products., One of the major products was shown to be dimethylpara-
banic acid by independent synthesis. Caffeine has been shown to be a
constituent of sewage treatment plant effluents:
caffeine
dimethyl
. .
parabamc acid
258
-------
Reactions With Pesticides
Robeck, e_t al_.123 ozonized aqueous solutions of lindane, dieldrin, DDT
and parathion and found that dosages of 10 to 38 mg/1 of ozone were required
to destroy these pesticides to acceptable levels. These dosages were
considered to be too high to be practical. These authors also concluded
that the more usual drinking water treatment plant ozone dosages of 1 to 2
mg/1 probably would oxidize parathion to paraoxon, a compound which is more
toxic than is parathion.
Gabovich, e_t aj_.87 ozonized aqueous solutions containing 10 mg/1 of
malathion. Ozone dosages of 3.5 mg/1 (0.5 mg ozone/mg malathion reduced the
concentration of malathion to 2 mg/1. Increasing the ozone dosage to 9.8
mg/1 (1/1 ozone/malathion) reduced malathion concentration to 1 mg/1. A
dosage of 26 mg/1 of ozone caused 100% destruction of malathion.
Hoffman & Eichelsdorfer121* dissolved various pesticides in hexane or
acetone, then diluted with water to make aqueous solutions as high in
concentration as 2 mg/1 of pesticide. These were ozonized over 45 minutes
with total ozone dosages up to 240 mg/1. At these dosages, aldrin and
heptachlor were "quantitatively" reacted to destruction, but oxidation
products were not identified. On the other hand, solutions of dieldrin,
heptachlorepoxide, chlordane, lindane, DDT and endosulfan were hardly
affected by ozone at all. This raises the question as to whether the
ozonation of heptachlor produces heptachlor epoxide. If so, the epoxide
will be stable to further ozonation, and itself is a toxic material.
Cl
Cl
Cl
heptachlor
heptachlorepoxide
Richard & Brener125 showed that ozonation of parathion with 3 mg/1
ozone dosage forms paraoxon, a more toxic material than parathion itself.
The reaction proceeds fastest in acid medium. Continued ozonation of
paraoxon (5 mg/1 ozone dosage) proceeds slower, with destruction of paraoxon
and formation of 2,4-dinitrophenol, picric acid, H2S04 and H3P04:
parathion
paraoxon
259
-------
paraoxon
5 mg/1
(basic)
NO,
H2S04
H3P04
Similarly, Richard & Brener125 ozonized malathion and isolated malaoxon
as the first step intermediate. Continued ozonation destroyed the malathion,
producing H^PO. and unidentified, degraded organic compounds.
CH~0V S
3 \II
xP-S-CH-COOC-H,-
CH rr i 2 5
LH3U CH2COOC2H5
malathion
CH30 - CH2COOC2H5
malaoxon
oPO* •*• degraded oxidation
products
Phosalone upon ozonation did not produce an oxon intermediate. Instead
the benzoxalone moiety was cleaved to produce the parent alcohol. This
alcohol also underwent self-condensation to produce an ether. Both the
alcohol and the ether were isolated and identified by Richard & Brener125:
C2H5\||
P-S-CH2-N
C2H50X
-CH2-0-CH2-N
N-CH2OH
Richard & Brener125 concluded that under-ozonation of an organic
material can produce other organic materials that are toxic, and that it is
essential to know the chemical content of waters to be treated with ozone
(or any oxidant).
260
-------
Mallevialle et al_.126 ozonized aqueous solutions of aldrin, and found
this compound to be easily degraded by ozone. On the other hand, when
aldrin was added to aqueous solutions containing humic acids, 0.45 microg/1
of aldrin was detected even after 10 minutes of ozonation. These researchers
concluded that ozonation studies on organic compounds conducted in pure
solutions can be misleading. It is necessary to know the humics or soils
content of water to be ozonized, since these materials can adsorb dissolved
organics and thereby "protect" them from the oxidizing action of ozone.
Prengle & Mauk113 showed that ozonation of DDT in water proceeds very
slowly, but the oxidation rate is accelerated by combining UV radiation with
ozonation.
Weil et al.127 ozonized 0.001M solutions of 2,4,5-T with 0.048 mole/hour
of ozone and" identified oxalic acid, glycolic acid, dichloromaleic acid,
chloride ion and C02 as oxidation products. No ozonides or polymeric
peroxides could be found. The concentration of dichloromaleic acid peaked
after 8 to 9 minutes, that of glycolic acid peaked after 12 minutes and that
of oxalic acid peaked after 20 minutes of ozonation, after which the concentra-
tions of all three intermediate products decreased with time of ozonation.
The concentration of dichloromaleic acid became zero in 25 minutes:
+ HOOC-CH2OH
0-CH2COOH HOOC-CH-CH-COOH peaked in 8 to 9 min
Cl Cl
peaked in 12 min
+ HOOC-COOH peaked in 20 min
+ Cl" + C02
2,4,5-T
Reactions With Humic Materials
Ahmed & Kinney99 ozonized KOH solutions containing 2 g of humic materials.
Water soluble, ozone-resistant acids were isolated, and 65% of the original
carbon was Isolated as C02.
Kinney & Friedman100 ozonized aqueous alkaline solutions of humic acids
and isolated and identified small amounts of acetic acid, terephthalic acid,
C02 and traces of oxalic acid:
humic acids
•> CH3COOH +
CO,
HOOC-COOH
261
-------
Dobinson & Lawson128 ozonized solutions of humic acids isolated from
coal and identified small amounts of acetic acid and C02 as reaction products.
Kinney & Leonard129 ozonized aqueous solutions of kerogen and isolated
water soluble organic acids of molecular weights 200 to 400. The equivalent
weight of these acids was 120, and they were shown to be polyfunctional.
Shevchenko & Taran130 ozonized 1 g/1 aqueous solutions of humic acids
80 minutes and identified formic, acetic and oxalic (2.23%) acids.
Buydens131 ozonized samples of raw water from the River Meuse and
found higher suspended solids, higher phenol and higher COD contents after
using 0.87 to 1.58 mg/1 ozone doses. The author concluded that ozonation
decomplexes iron and manganese from organic ligands, thereby liberating
more phenolic and COD constituents. In addition, ozone decomposes high
molecular weight polymeric humic materials into shorter (phenolic) fragments.
Mallevialle91 ozonized neutral waters containing 100 to 200 mg/1 of
humic acids to attain 90% color reduction in 10 minutes. After 20 minutes
of ozonation, the solution turned violet, which was ascribed to the decomplex-
ing of manganese followed by oxidation to permanganate. Chromatography of
this solution showed the presence of phenolic compounds and formic acid.
The author concludes that insufficient ozonation will increase the concentra-
tions of these materials, but for most water supplies, maintaining a residual
of 0.4 mg/1 ozone over 6 minutes will be a sufficient dosage.
Waters containing 525 mg of humic acids required 100 mg of ozone to
destroy 95% of the color and 320 mg of ozone to destroy 95% of the polyhydroxy-
aromatics91.
Rook132 coagulated and filtered River Meuse water, then ozonized it 8
minutes with 2 mg/1 doses, then chlorinated. After 8 minutes of ozonation,
haloform formation was reduced by 65%. However after the ozonized water
had stood for 24 hours, then was chlorinated, the amount of haloforms
produced was about the same as without ozonation.
Summary of Ozonation Reactions
With Aromatic Compounds—
• Phenol reacts readily with ozone in aqueous solution to produce the
dihydroxybenzenes catechol, hydroquinone and resorcinol. These last
two compounds are further oxidized to o- and p-benzoquinone, respectively.
• All of the above oxidized aromatic compounds, upon further oxidation
with ozone, undergo ring cleavage to produce the aliphatic unsaturated
diacids: muconic, fumaric and maleic, plus the hydroxylated saturated
diacids: tartaric and mesotartaric. In addition, glyoxal, glyoxylic
acid, glycolic acid and oxalic acid are formed, along with C02-
• Oxalic and acetic acids are relatively stable to ozonation in the
absence of a catalyst such as UV light or H202, and thus can be considered
262
-------
to be relatively stable oxidation products of ozonation of phenol in
water.
• Ozonation just to the point of destruction of phenol requires 2 to 3
mg of ozone/mg of phenol, but COD is reduced only 50%. To destroy
phenol and reduce COD to zero requires 8 to 12 mg of ozone/mg of
phenol.
0 Ozonation of chloro-substituted phenols ultimately cleaves the aromatic
C-C1 linkages, forming chloride ion plus the same types of ring-
ruptured aliphatic compounds as does phenol.
• Cresols and xylenols undergo oxidation with ozone at faster rates than
does phenol. Before ring cleavage occurs, o-cresol forms salicylic
acid.
• Upon ring rupture, ozonized cresols produce the same types of aliphatic
products as does phenol, plus mesotartaric, propionic and acetic
acids.
• Xylenols produce all these aliphatic products plus hydroxyphthalic
acid (before ring-rupture) and diacetyl and glyoxal (after ring-
rupture).
• Nitro, amino and sulfonic acid groups on aromatic rings are split off
by ozonation, but at much slower rates than is chlorine. Amino groups
are converted to ammonia and nitrate ion. Sulfonic acid groups are
converted to sulfate.
t Aromatic hydrocarbons such as pyrene, phenanthrene and naphthalene
oxidize by ring rupture. Only one ring in phenanthrene opens readily,
however. When aliphatic hydrocarbon groups are present on the aromatic
rings, these oxidize first, before the ring ruptures.
• Chlorobenzene reacts with ozone slower than does phenol, but gives the
same ring ruptured, aliphatic oxidation products as phenol. Intermediate
oxidation products include o-, m- and p-chlorophenols plus chlorotartaric
acid. Chlorocresols, chlorophenols and thiophenols give similar
ozonation products as does phenol.
With Aliphatic Compounds—
• There is no evidence that ozone reacts with saturated aliphatic hydro-
carbons under water or wastewater treatment conditions.
• There is also no evidence that ozone oxidizes trihalomethanes. Reduction
in concentration of THMs upon ozonation appears to occur by air stripping
of aqueous solutions. Ozone combined with ultraviolet radiation does
oxidize chloroform to produce chloride ion, but no identified organic
oxidation product.
263
-------
Unsaturated aliphatic or alicyclic compounds react with ozone, usually
at the unsaturated bond, cleaving the molecule into two oxidized
fragments (aliphatics) or into diacids or carbonyl-carboxylic acids
(alicyclics). The two aliphatic fragments normally are an acid plus
an aldehyde or ketone.
Primary aliphatic alcohols generally are oxidized to aldehydes, then
to acids, but at slower rates than phenol oxidation with ozone.
Secondary aliphatic alcohols produce ketones, then acids plus H202
upon ozonation.
Formic acid readily produces C02 and water upon ozonation, but oxalic
acid is relatively stable to ozonation in the absence of UV radiation
or H202. Acetic acid and propionic acid also are relatively stable to
ozonation.
Oxalic acid oxidizes directly to C02 without producing formic acid.
Reaction with ozone alone is very STOW, but proceeds rapidly in the
presence of UV radiation or
• Maleic acid produces glyoxylic and formic acids initially. Glyoxylic
acid then produces oxalic acid, C02 and water. These are the sole
products of ozonation of maleic acid.
• Propionic acid and 2-propanol produce acetone upon ozonation. Acetone
can undergo the haloform reaction and produce chloroform if present
during post-chlorination of ozonized water.
• Ozonation of acetate ion and acetic acid ultimately produces glyoxylate
ion or glyoxylic acid, respectively, which then form oxalic acid.
t Di ethyl am ine produces acetaldoxime upon ozonation, plus an unidentified
nitrogen-containing compound, not a nitrosoamine.
• Prolonged ozonation of a concentrated ethyl alcohol solution in water
produces a stable dihydroperoxide which exhibits mutagenic activity.
• Ozonation of Lake of ZUrich raw water increased the aldehyde concentra-
tions. Ozonation followed by activated carbon adsorption reduced the
aldehyde concentrations below their original concentrations. This
indicates that ozonation for oxidation should be followed by a adsorption
step.
• UV/ozonation of refractory organic materials increases the rate at
which they are oxidized by ozone, but not the nature of the oxidation
products.
With Pesticides—
• Ozonation of parathion and malathion produces paraoxon and malaoxon,
respectively, as intermediates, which are more toxic than are the
264
-------
starting materials. Continued ozonation degrades the oxons, but
requires more ozone than does the initial thion oxidation. Phosalone
oxidizes without forming an oxon intermediate. Thus, under-ozonation
can produce intermediates which are more toxic than the starting
materials.
t Ozonation of heptachlor produces a stable product, not yet identified.
Heptachlorepoxide is known to be stable to ozonation. This suggests
that ozonation of heptachlor may produce the epoxide, which then would
be unaffected by further ozonation.
• Aldrin and 2,4,5-T are readily oxidized by ozone, but dieldrin,
chlordane, lindane, DDT and endosulfan are only slightly affected by
ozone.
• UV/ozonation destroys DDT, PCBs, malathion and many other pesticides,
but requires more extended contact times and ozone doses than normally
encountered in drinking water treatment plants.
• Ozonation of aldrin in pure water proceeds rapidly, but at a much
slower rate in the presence of humic acids. Similar oxidation rates
were observed with solutions of benzopyrene in pure water (rapid)
versus water containing colloidal soil particles (slow). This indicates
that dissolved organic materials can be adsorbed by humics or soil
particles and be "protected" from oxidation, at least partially. This
would also indicate that ozonation of water supplies for oxidation
should follow a filtration step.
With Humic Materials—
• Humic materials are resistant to ozonation, requiring lengthy times of
ozonation to produce small amounts of acetic, oxalic, formic and
terephthalic acids, C02 and phenolic compounds.
• Ozonation of humic materials in water followed by immediate chlorina-
tion (within 8 minutes) reduced trihalomethane formation by 65%.
However, when ozonized waters containing humics were allowed to stand
24 hours and then chlorinated, there was no change in the amounts of
trihalomethanes formed. This indicates that although ozone changes
the chemical nature of trihalomethane precursors, there is continued
reaction upon standing, not entirely with residual ozone, to form
materials equally capable of producing trihalomethanes upon chlorination.
• Ozonized organic materials generally are more biodegradable than the
starting, unoxidized, compounds. If ozonation is used as the terminal
treatment step with waters containing dissolved organics, bacterial
regrowth in distribution systems is not only likely, but is probable.
Thus, Swiss and German water treatment authorities conclude that
ozonation always should precede a adsorption step.
265
-------
t As a general rule (which does not always hold, it should be empha-
sized), ozonation used specifically for oxidation of organic materials
advantageously should follow and/or precede adsorption steps.
**********
Dellah133 conducted extensive pilot plant studies for the new Charles-
J. des Baillets drinking water treatment plant being constructed in Montreal,
Canada. This plant will use ozone for a major portion of disinfection, and
when fully operational will require generation of 15,000 Ibs/day of ozone.
In assessing the effects of ozonation, followed by chlorination for residual,
on the St. Lawrence River raw water, he concluded:
"With 5 minute contact times and ozone doses sufficient to maintain
residual concentrations of 0.4 mg/1, COD reduction was about 50% when
the water quality was at its best. When it was at its worst, COD
reduction was about 60% after filtration, but little changed after
subsequent ozonation. Therefore, ozonation does not eliminate all
organics. Ozonation plus chlorination still will produce organo-
chlorine compounds in drinking water."
REACTIONS WITH CHLORINE DIOXIDE
Several excellent review articles on the reactions of chlorine dioxide
with organic materials are available. These include Stevens, et al.13**;
Rosenblatt135; Gordon136 and Masschelein137.
Ractions With Phenol
Masschelein137 has reviewed the reactions of phenol and chloro-substituted
phenolic compounds with chlorine dioxide, and the known oxidation products
are shown in Figure 55. Phenol itself reacts either by oxidation (to
produce p-quinone), or by chlorination and oxidation, producing 2-chloro-p-
benzoquinone and 2,5-dichloro-p-benzoquinone. Chlorophenols unsubstituted
in the position para to the aromatic hydroxy group readily form the correspond-
ing p-benzoquinone. 2,4,6-Trichlorophenol produces a 55% yield of 2,6-
dichloro-p-benzoquinone, indicating that the 4-chlorosubstituent is first
broken away from the aromatic ring by the C102, followed by substitution of
oxygen at the 4-carbon. Similarly, 2,4-dichlorophenol gave a 36% yield of
2,6-dichloro-p-benzoquinone, rather than 2,4-dichloro-o-benzoquinone.
Guaicol (o-methoxyphenol) first produced catechol, then o-benzoquinone,
then ring-ruptured products, including monomethylmuconic acid as the
primary product.
p^Benzoquinone, isolated from chlorine dioxide oxidation of phenol,
reacted further with C102 forming the ring-ruptured 4-carbon products,
fumaric and maleic acids, and then the 2-carbon oxalic acid.
266
-------
ro
OH
0
10%
Cl
0
0
0
36%^
iH
Cl
Cl
OH
Cl
Cl
OH
\
HOOC-C = C-COOH +
HOOC-C = C-COOH +
H
HOOC-COOH
Cl
Cl
15%
Cl
\
;35%
OH
Cl
Cl
OH
OCH
3 ,
no!
OH
CIO,
0
.OOCH,
Figure 55. Reactions of chlorine dioxide with phenols
1 37
-------
Masschelein137 has also shown the relationship between reaction of
chlorine dioxide with phenolics and the by-product chlorite ion formed. In
Figure 56 are plotted the amounts of ClOg consumed by phenol, o-chlorophenol
and p-chlorophenol versus the amount of C102~ produced. The relationship
is linear in all three cases.
Xs '2
2 10
Q
I •
o
"- 6
I CM
O
• PHENOL
• ORTHOCHLOROPHENOL
o PARACHLOROPHENOL
Figure 56. Formation of chlorite i
on
from the oxidation of phenols
by chlorine dioxide •
2 k 6 8 10 12
C102 CONSUMED IO~5MOLE/1
From his literature review of reactions with phenolics, Masschelein137
concludes that reaction of gaseous C102 (14 to 18%) with phenol at 0°C, in
water, produces p-benzoquinone as the major product. Prolonged oxidation
with chlorine dioxide then produces ring-chlorinated compounds, then ring
rupture, forming aliphatic diacids. Many of the ring-ruptured products do
not contain chlorine, and are the same products formed upon ozonation.
none
p-Nitrophenol treated with C102 produced 8.5% yield of p-benzoqui-
137*
OH
CIO,
Benzoic, phenylsulfonic and cinnamic acids at pH 7 in water do not
react with C102137(138 for cinnamic acid):
or
or
H=CH-COOH
CIO,
No
Reaction
268
-------
Cardey139 reviewed experiments performed by the Ohio River Valley
Water Commission in Hamilton, Ohio, on steel mill wastewaters containing
phenolic compounds. This work showed that the use of C102 destroyed the
phenols, did not form chlorinated phenols, and that the oxidant functioned
equally well in acid or basic solution. Reaction times of 15 minutes
destroyed 100 to 130 mg/1 of phenol, and caused a drop in final pH to 2 to
4, attributed to the formation of organic acids (which were not identified).
Very recent work by Spanggord and co-workers at Stanford Research
Institute, under contract to EPA, has been conducted with chlorine dioxide
synthesized from sodium chlorite solution and sulfuric acidluo. This
synthesis guarantees the absence of free residual chlorine in solution.
Reaction of C102 thus prepared with aqueous phenol has produced mixtures of
chlorinated and unchlorinated products. A solution of 0.67 mmole of phenol
was treated with chlorine dioxide to allow only 48% reaction. The products
isolated and identified are:
2-chlorophenol
4-chlorophenol
2,6-dichlorophenol
2,4-di chlorophenol
2,4,6-trichlorophenol
resorcinol (1,3-dihydroxybenzene)
fumaric acid (trans-2-butenedioic acid)
2-chlorohydroqui none
Reactions With Other Aromatic Compounds
Paluch, ejtaj_.llfl found that benzylic acid in water produced small
amounts of benzoic acid when treated with C102:
CHCOOH
CIO,
benzylic acid
COOH
benzoic acid
However, chlorite ion in the presence of HC1 produced o-, m- and p-
chlorobenzoic acids, o- and p-chlorobenzylic acids and o- and p-chlorobenz-
aldehydes171:
COOH
269
-------
Otto & Paluch11*2 reported that an aqueous dispersion of benzaldehyde
reacts violently with chlorine dioxide.
Reichert11*3 treated 1 to 10 yg/1 concentrations of 3,4-benzopyrene in
water with 0.11 yg of C102 over 15 to 30 minutes. He observed a logarithmic
decrease in benzopyrene concentration to 0.01 yg/1. The lower the original
concentration of organic, the longer was the contact time required to reach
this concentration.
A subsequent study by Reichert11*" describes the identification of
organic compounds produced when 1 to 10 yg/1 concentrations of 3,4-benzopyrene
were treated with 1 mg of ClOo in Water. Eight individual compounds were
isolated, of which 3 accounted for 90% of the yield isolated. These three
compounds are: 3,4-benzopyrene-l, 5-quinone, 3,4-benzopyrene-5,8-quinone
and 3,4-benzopyrene-5,10-quinone:
3,4-benzo
pyrene
The other 5 compounds isolated by Rei chertlltlf all were chlorinated,
and two of these were identified as 5-chloro-3,4-benzopyrene and 5,8,10-
trichloro-3,4-benzopyrene.
Cl
270
-------
Subcutaneous injection of all above pyrene compounds isolated by
Rei chert143'1'*It into rodents gave negative results in all cases.
In 1969 Reichert1"5 showed that 10 yg/1 of 3,4-benzopyrene was 90%
decomposed in 60 minutes when treated with 0.1 mg/1 of ClO^. By way of
comparison, 0.5 to 1.5 mg/1 ozone dosage caused 99% decomposition in 30
minutes in pure water. In natural water, 99% decomposition of the pyrene
was obtained with 0.2 mg/1 ozone with 15 minutes contact time.
Spanggord et^al.11*0 treated aqueous solutions of diphenylamine hydro-
chloride with ClOjTTprepared from chlorite and acid so as not to contain
free chlorine) and found chlorinated derivatives. The following compounds
have been isolated from the reaction mixture:
Diphenylamine
2-chloro-diphenylamine
4-chloro-di phenylami ne
2 isomers of a dichlorodiphenylamine
a ring hydroxylated diphenylamine
2 isomers of chloro-hydroxy-diphenylamine
2 isomers of dichloro-hydroxy-diphenylamine
Vanillin reacts with ClOo at pH 4 to produce the non-chlorinated B-
formylmuconic acid, monomethyl ester136 which further oxidized to the
diacid:
vanillin
CIO,
pH 4
OHC
COOH
COOCH,
HOOO
OOCH,
Vanillyl alcohol reacts with C102 at low pH to produce both 2-chloro-
5-methoxy-l,4-benzoquinone and a non-chlorinated lactone product of ring
cleavage136:
8
CH-C-ChL
CH2OH
vanillyl
alcohol
271
-------
Veratryl alcohol reacts with C102 to produce 4,5-dichloroveratrole
147.
CH2OH
veratryl
alcohol
Reactions With Heterocyclics
4,5-di chloroveratrole
Kawasaki ejt aJLllf7 treated thiamine (vitamin B-l) with C102 in
water, at pH below 4.7 under prolonged reaction conditions and isolated
2-methyl-4-amino-5-aminomethy!pyrimidine:
CIO,
CH2CH2OH
2*
HOH
pH < 7
CH2NH2
CH3
Thianine was found to be stable to C102 or to chlorite under acid
conditions1"*7.
Fujii & Ukita1"8 treated tryptophane with chlorine dioxide and
isolated a mixture of products including indoxyl, isatine, indigo red
plus unidentified, colored, probably polymeric compounds:
other
compounds
Reactions With Aliphatics
No evidence exists that chlorine dioxide (or chlorine) undergoes
reactions with saturated aliphatic hydrocarbons under water treatment
conditions131*. Masschelein137 states that aliphatic alcohols are often
oxidized to aliphatic acids by C102 in aqueous solution:
272
-------
RCH2OH
C10
RCOOH
H20
The stability of aliphatic acids to further oxidation by C1CL is
supported by the findings of Sarkar138 that crotonic, maleic and fumaric
acids do not react with C102 in aqueous solution. These findings are
significant also in that these three acids contain an aliphatic double
bond conjugated with a carboxyl carbonyl group. Such a double bond
normally is reactive with ozone, hypochlorite and chlorine.
Leopold & Mutton1W and Lindgren & Svahn150 treated methyl oleate
60 hours with ClOg in aqueous solution under a nitrogen atmosphere and
have isolated the compounds shown in Figure 57. It was found that
oxidation can occur at the carbon atoms adjacent to the double bond,
producing conjugation of the type encountered in crotonic, maleic and
fumaric acids, which were found by Sarkar138 to be stable to further
oxidation with C102.
methyl oleate
CH3 - (CH2)6 - CH2 -\CH = CH\- CH2-(CH2)6-COOCH3 + C102
\ \
\ (CH ) \
- C -
II
0
- (CH2)? -
- (CH2)7 -
- (CH2)? -
CH = CH>
CH = CH
CH = C
1 II
Cl 0
CH - CH
1 1
Cl Cl
CH - CH
0
C-(CH) - +
0
- CH2 - (CH2)6 +
- (CH2)7 - +
- (CH2)7 - +
- (CH2)?
Figure 57. Reactions of methyl oleate with C1021M>15°.
Treatment of methyl oleate with C102 also produced a dichloro
compound, which appears to have been formed by simple addition of chlorine
across the double bond. Other types of compounds include the chloro-
carbonyl compounds, which could have formed by addition of HOC1 across
the double bond to produce the chlorohydrin, followed by oxidation of
the alcoholic hydroxy moiety to the ketone by chlorine dioxide.
273
-------
The possibility of addition of HOC! across the double bond of
methyl oleate is supported by isolation of the epoxide, which forms by
elimination of HC1 from the intermediate chlorohydrin. These products
isolated by Mutton1M and by Lindgren & Svahn150 confirm the chemistry
of chlorine dioxide discussed earlier in this chapter.
Leopold & Mutton1M consider that C102 cleaves the oleic double bond,
producing aldehydic fragments and an equivalent amount of chlorine (not
chlorite), which then adds across another double bond.
Somsen151 found that butane-2,3-diol and diacetyl treated with C10~
produced primarily acetic acid:
CH3-CH-CH-CH3 or CH3-C-C-CH3 + C102 > CH3COOH
OH OH 00
Lindgren, Svahn & Widmark152 treated aqueous suspensions of cyclohexene
with gaseous C102 (free of excess chlorine) and isolated and identified 7
products. Three different ratios of cyclohexene/C102 were used, and the
product distribution was found to vary. The results are shown in Figure 58.
Reaction usually occurred at the double bond, but in most of the compounds
isolated the ring was retained intact. Adipaldehyde was isolated, but at pH
below 2. Using a 1.5/1 cyclohexene/C10o ratio, glutaric acid was the principal
non-cyclic reaction product isolated, afong with adipic and succinic acids.
The epoxide was not isolated in the final products, evidently having been
destroyed by the acids formed during the oxidation.
Flis ejt al_.153 treated excess glucose with C102 at pH 2 and at 20 to
609C, and observed oxidation of hydroxymethyl groups to produce aldehydic
and carboxylic functions, apparently without ring rupture. They also observed
that 8 ,D-glucose reacted faster than ot,D-glucose. This lack of rupture of
carbodydrate rings by small amounts of C102 may explain why trihalomethanes
are not produced from humic materials.
However, Becker, Hamilton & Lucke151f treated cellotetrose at pH 3 and
56°C over 1 to 7 hours with 10 to 100/1 molar ratios of C102 and isolated
gluconic, carbohydrate rings did rupture under the reaction conditions employed
(large excesses of C102). (See Figure 59.)
Zienus & Purves155 treated pectic acid at 70 to 75°C with aqueous
0.14M C102 or NaC102 at a molar ratio of C102/pectic acid of 10/1, and
identified galacturonic acid (most abundant product), muric and d,l-
tartaric acids as products. Sodium chlorite produced tartronic acid,
which was not found when using C102. Results are summarized in Figure
60. Again, the carbohydrate rings ruptured when treated with large
excesses of C102.
274
-------
o
+ cio.
Cyclohexene
cycl ohexene/Cl 0~ cycl ohexene/Cl 09
35/1 * 7/1 ^
Cyclohex-l-ene-3-one 16% 13%
2-Chlorocyclohexanone 11 7
1 ,2-Epoxycyclohexane 3 0
Adipic acid 3 4
trans-2-Chl orocycl ohexanol 11 15
3-Chlorocyclohexene 13 14
trans-1 ,2-Dichlorocyclohexane 5 7
Using 1.5/1 cycl ohexene/Cl 02 gave the above compounds plus (in order
of importance): adipic acid, glutaric acid, succinic acid, 2-chloro-
cyclohexane - 1 ,3-dione
Using excess C102 over cyclohexene gave carboxylic di acids
Figure 58. Reactions of Cyclohexene with C102152.
Spanggord j^t al-1"0 treated citral with C102 containing no excess
free chlorine and identified chlorinated products (apparently chlorohydrins)
and oxidation products not containing chlorine:
(CH3)2C=CH(CH2)2C(CH3)CHO - > chlorohydrins + non-halogenated
oxidation products
(citral)
Reactions With Aminoacids
Shirle156 treated cystine with excess C102 or C102" at pH 3.54 and
isolated cystine bisulfoxide. Further oxidation produced cysteic acid:
275
-------
CH2OH
CH2OH
CH2OH
ro
•vl
en
cello
tetrose
CH2OH
COOH
HCOH
HO{H
HCOH
HCOH
CH2OH
gluconic acid
H2OH
CO COOH
OH
CH2OH
HCOH
HOCH
CHO
COOH
glyoxylic
acid
OH
COOH
HCOH
HCOH
CH2OH
V.
HOCH \
!„ go \ erythronic acid
arabonic acid \
Figure 59. Reactions of cellotetrose with C102151*.
-------
mucic acid
PO
COOH
O' '
pectic acid
COOH
HCOH
HOCH
CHO
HCOH
1 ^
HOCH ^
^ HOCH
HCOH
1
COOH
n galacturonic
acid
HOCH
S* HCOH
COOH \
^
\
f
COOH
HCOH
COOH
COOH
^ HOCH
HCOH
1
COOH
d-tartaric acid
L
\
\
\
\
\
\
^ COOH
HCOH
HOCH
COOH
tartronic
acid
1-tartaric
acid
Figure 60. Reactions of pectic acid with C109155.
-------
HOOCCH(NH2)CH2-S-S-CH2CH(NH2)COOH H
cystine
HOOCCH(NH2)CH2-S-S-CH2CH(NH2)COOH >
0 0
cystine bisulfoxide
HOOC-CH(NH2)-CH2S03H
cysteic acid
Methionine was found to react similarly through the sulfoxide to
produce the sulfone156:
CH3S(CH2)2CH(NH2)COOH + C102
methionine
CH,S(CH9)9CH(NH9)COOH
3,, 2 2 2
0
methionine
sulfoxide
CH3-S02-(CH2)2CH(NH2)2COOH
methionine sulfone
Hodgen & Ingols157 treated tyrosine at pH 4.5 with excess C102 (3
moles/mole of tyrosine) and identified dopaquinone along with isolating
other unidentified colored products:
CH2CH-COOH
NH0
CHCH-COOH
NH2
+ HC10,
In the presence of free chlorine, Moran ejt a]L_158, found that
tyrosine also produces monochlorotyrosine and dichlorotyrosine.
On the other hand, Kennaugh159 found that the ami no acids glycine,
leucine, serine, alanine, phenylalanine, valine, hydroxyproline, phenylami no-
acetic acid, aspargic acid and glutamic acid are only slightly reactive
278
-------
to chlorine dioxide. Only after standing 3 weeks at ambient temperatures
in acetic acid 50% saturated with C1CL did these compounds react with
chlorine dioxide.
Reactions With Amines
In aqueous solution, primary and secondary amines react very slowly
with chlorine dioxide, but tertiary amines react rapidly to produce
aldehydes. That primary amines are unreactive with C102 is borne out by
the lack of reactivity of amino functions in the aminoacids.
Triethylamine reacts with C1CL to produce acetaldehyde and diethyla-
mine, along with chlorite ion, at pH 4.7 to 7.I160.
Et,N + H90 + C109-> CH.CHO + Et0NH + 2H* + 2C10 ~
•J f- f- -3 c. £.
At lower pH, however, a secondary reaction occurs, by which chlorite
reforms chlorine dioxide:
H+ + CH3CHO + 3C102" —> CH3COO" + Cl" + 2C102 + H20
Rosenblatt160 also points out that triethyl amine reacts with
chlorine dioxide without forming an N-oxide. This is significant since
once an N-oxide forms, it is possible that further oxidative degradation
might proceed through formation of a nitrosamine.
Rosenblatt161 reviewed the reactivity of chlorine dioxide with
organic substances, and discussed the pertinent chemistry involved with
chlorine species- Quinuclidine forms an N-oxide when treated with ClOn,
but triethylenediamine forms piperazine. Ring substituted benzylIdlmetnyl-
amines react faster with C102 the greater is their initial basicity. A
summation of the pertinent reactions of amines with C102 is given in
Figure 61.
Reactions With Humic Materials
Fuchs & Leopold162 reported that humic acids react with CICL, but
they did not identify any of the reaction products. In 1970, Buydens131
treated River Meuse (Belgium) raw water (containing humic acids) with
C109, and found much the same effects as were obtained with pre-ozonation.
Phenolic content and COD content increased. However, when C102 was
added just ahead of the clarification/flocculation step in the drinking
water treatment process, phenols were removed to nearly complete disappearance.
Organically complexed iron and manganese also were decomposed by addition
of C102 at this step, and the ozone demand also was reduced.
Mallevialle163 in France found that humic materials treated with
pure ClOo (containing no free chlorine) do not form trihalomethanes. This
finding was confirmed independently in Cincinnati, Ohio by Love et al_. *
with Ohio River waters.
279
-------
NH-, + CIO,
O L.
RNH2 + C102
R2NH + C102
(C2H5)3N + C102
No Reaction
No Reaction
Slow Reaction
CHnCHO + (CnH[
3 £ *
H + 2C10
CH
H2CX CH2
H2C CH2
^CH,
^CH,
CIO,
^^
H20
quinuclidine
N
C
0
CH
CH,
quinuclidine
M-oxide
N
H2C CH2 CH2
H2C\CvH2 ^ CK2
\\
CIO,
H20
H2C
H2C
l
+ HCHO
tri ethylenedi ami ne
piperazine
82
Figure 61. Pertinent Reactions of Amines with C102
Vilagenes et^ al_.165 studied the use of C102 at the Paris, France, St.
Maur drinking water treatment plant where ammonia is removed biologically in
slow sand filters. This plant has two treatment lines, and C102 and NaOCl
were compared as terminal treatment steps for their ability to produce
trihalomethanes. Resorcinol was added as the trihalomethane precursor so
that sufficient quantities of trihalomethanes could be produced deliberately.
Trihalomethane production was found to occur only with hypochlorite,
and not with CIO?. Furthermore, the rate of trihalomethane production
was dependent only upon the concentration of resorcinol precursor, not
280
-------
upon the concentration of chlorine. When excess chlorine was used with
the C102, trihalomethane formation occurred.
These authors also found that chlorodibromomethane was formed in
higher concentrations (20 to 35 microg/1) using hypochlorite than was
chloroform (1 to 20 microg/1). Since no bromine-containing trihalomethane
was produced when chlorine dioxide alone was employed, it was concluded
that bromide ion is not oxidized by ClOo.
Summary of Chlorine Dioxide Reactions
• Treatment of organic compounds with pure ClOo containing no excess
free chlorine produces oxidation products containing no chlorine in
some cases, but products containing chlorine in others.
• When excess free chlorine is present with the C102, chlorinated
organics usually are produced, but in lower yield (as compared to
the yield when chlorination alone is used, depending upon the
concentration of chlorine and its reactivity with the particular
organic(s) involved.
• Phenol in water treated with CIO? containing no free chlorine
produces 2- and 4-chlorophenol, 2,4- and 2,6-dichlorophenol, 2,4,6-
trichlorophenol, 2-chlorohydroquinone, resorcinol and p-benzoquinone as
the major oxidation products. Prolonged oxidation with C102 then
produces ring-chlorinated compounds, then ring rupture, producing
aliphatic diacids. Many of the ring-ruptured products do not contain
chlorine and are the same as products formed upon ozonation.
• Chlorite ion in the presence of HC1 ring-chlorinates and oxidizes
benzylic acid to benzoic acid, o-, m- and p-chlorobenzoic acids, o-
and p-chlorobenzaldehydes and o- and p-chlorobenzylic acids.
• 3,4-benzopyrene treated with CIO? produces the non-chlorinated
1,5-,5,8- and 5,10-benzopyrenequinones (total yield 90%) plus five
chlorinated compounds, two of which were identified as 5-chloro- and
5,8,10-trichloro-3,4-benzopyrene. None of these compounds gave positive
responses when injected subcutaneously into rodents.
• Using large excesses of C10? over the organic materials appears to
favor oxidation reactions (without chlorination), but slight excesses
appear to favor chlorination.
• Benzoic acid, phenylsulfonic acid, thianine and cinnamic acid do not
react with C102. The first two are oxidized by ozone; the reactivity
of the last two with ozone is not known.
t In oxidizing organic materials, ClOo can revert back to chlorite ion,
C10?~. In the presence of excess chlorine (or other strong oxidant)
chlorite can be reoxidized to C102.
281
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Diphenylamine with C102 containing no excess chlorine produced 2- and
4-chloro-diphenylamine, two dichlorodiphenylamines, a ring-hydroxylated
diphenylamine, two chlorohydroxy- and two dichlorohydroxydiphenylamine
isomers.
Substituted nitrogen heterocyclics, such as thiamine and tryptophane,
undergo oxidation of the substitutents, retain the heterocyclic
ring (at least in the intermediate stages) and products isolated to
date are not chlorinated.
Saturated aliphatic hydrocarbons are not reactive with ClOp.
Alcohols are oxidized to the corresponding acids.
Crotonic, maleic and fumaric acids (all containing an aliphatic
double bond conjugated with a carbonyl oxygen) are unreactive to
C102 in aqueous solution. Such unsaturation normally is reactive
to ozone, hypochlorite and chlorine.
Treatment of methyl oleate (containing an isolated aliphatic double
bond) produces dichloro, chloroketonic, a-unsaturated ketones,
epoxy, and chlorohydrin compounds, all from reactions with or
adjacent to the oleic double bond. The methyl ester moiety was
retained in all cases.
Butane-2,3-diol and diacetyl cleave upon treatment with C102 and
produce acetic acid.
Cyclohexene with C102 free of excess chlorine produced 9 ring-contain-
ing compounds, chlorinated and non-chlorinated. Functional groups
present in the oxidized products included epoxy, chloro, hydroxy
and keto. Ring unsaturation was maintained in some compounds, but
not in others. Adipaldehyde, glutaric acid and succinic acid were
the only ring ruptured compounds isolated, with glutaric acid
predominating at pH below 2. The epoxy compound was not isolated
in the final products, apparently being destroyed under the aqueous
acid conditions.
Hydroxymethyl groups in glucose produce aldehydic and carboxylic
groups, apparently without ring rupture. Stability of the polymeric
carbohydrate structure to C102 oxidation may explain why trihalomethanes
do not form when humic acids are treated with C102.
When carbohydrates are treated with large excesses of C102 (10/1 to 100/1
molar ratios) the carbohydrate rings do rupture. However, trihalomethanes
have not been reported as products.
Aminoacids such as glycine, leucine, alanine, phenylalanine and others
are stable to oxidation by C102. Sulfur in aminoacids oxidizes to
sulfoxides and sulfones and initial -S-S- bonds cleave and oxidize to
produce the fragmented organic sulfonic acids.
282
-------
• Primary aliphatic amines are nearly unreactive with C102 and secondary
amines are only slightly more reactive. Tertiary aliphatic amines are
reactive, triethyl amine forming acetaldehyde and the less reactive
diethylamine, along with chlorite ion.
• Triethyl amine reacts with C102 without forming an N-oxide. Quinuclidine
does form an N-oxide, but triethylenediamine produces piperazine (no
N-oxide).
• River Meuse water containing humic materials and treated with C102
showed increases in phenolic and COD contents. This behavior is
analogous to that found upon ozonation.
• Under drinking water treatment plant conditions, humic materials
and/or resorcinol do not produce trihalomethanes with C102 even when a
slight excess of chlorine (1 to 2%) is present.
CONCLUSIONS
A comparative summary of reactions of organic materials with ozone,
chlorine dioxide and chlorine is given in Table 28. From this table and
the prior discussions, the following conclusions can be drawn:
t Complete oxidation of dissolved organic materials to carbon dioxide
and water in aqueous solution is rare, by means of any oxidant.
t In general, if an organic material is resistant to oxidation by ozone
(the most powerful oxidant used in water treatment), it will also be
resistant to oxidation by other (weaker) oxidants.
• Conversely, ozone will oxidize some materials that chlorine dioxide
will not oxidize (such as primary and secondary amines, amino acids,
double bonds conjugated with carbonyl groups, etc.).
• Oxidation products formed by ozonation do not contain halogen atoms,
unless bromide ion is present. In this case, bromide is oxidized to
bromide, which then may react with organic materials present.
• In many cases, oxidation products from chlorine dioxide do not contain
halogen atoms. This is not a general rule, however, because chlorinated
compounds often are produced, even when chlorine dioxide is synthesized
so as to contain no free chlorine.
• Oxidation of phenols with ozone or chlorine dioxide produces oxidized
aromatic compounds as intermediates, which undergo ring rupture upon
treatment with more oxidant and/or longer reaction times. In many
cases, the same, non-chlorinated, ring-ruptured aliphatic products are
produced using ozone or chlorine dioxide.
• Oxidation of phenols with chlorine dioxide or chlorine produces chlori-
nated aromatic intermediates before ring rupture.
283
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TABLE 28. COMPARISON OF OXIDATION OF ORGANIC COMPOUNDS WITH OZONE, CHLORINE DIOXIDE AND CHLORINE
Type of
Organic
Oxidation Products Isolated Upon Treatment With
ozone
chlorine dioxide
chlorine
Phenol
intermediates; polyhydroxy-
aromatics and quinones.
Then ring ruptured, non-
halogenated difunctional
products (alcohol-aldehyde;
aldehyde-acid; alcohol-
acid). End Products:
oxalic acTd, C02+H20
Same as for ozone plus chlori-
nated phenols and chloroqui-
nones. Upon ring rupture, the
same non-chlorinated products
as for ozone are obtained, plus
some chlorinated aliphatics
chlorophenols plus
ring-ruptured
products (presumably
chlorinated); also
non-chlorinated
products (aromatic
and ring-ruptured)
oo
Cresols and xylenols
Same products as from
phenol, p_l_us^ methyl-substi-
tuted compounds (salicyclic
acid as aromatic intermedi-
ate, propionic and acetic
acids after ring rupture).
Acetic acid, oxalic acid,
C02+H20 end products
probably chlorinated
aromatics, then ring
rupture.
Chlorinated phenols
Chloride ion plus same
products as from phenol
Oxalic acid + C02 end
products.
Chioroquinones plus ring-
ruptured, halogenated and
non-halogenated aliphatics
probably more highly
chlorinated phenols,
then ring rupture.
(continued)
-------
Table 28. Continued
Ozone
Chlorine Dioxide
Chlorine
Chlorinated benzenes
Chlorophenols, then chlo-
ride ion and non-chlori-
nated, ring-ruptured pro-
ducts, as with chloro-
phenols, plus some chloro-
tartaric acid.
probably more highly
chlorinated products
miscellaneous
aromatics
nitro, amino and sulfonic
acid groups are cleaved,
but more slowly than chlo-
rine. Oxalic acid + C02
are end products.
benzoic, phenysulfonic and
cinnamic acids are not reactive
to ClOp. Nitro groups are
split off during ring oxidation
ro
00
tn
polycyclic
aromatics
undergo ring rupture
producing polycarboxylic
aromatics, which become
increasingly resistant
to further oxidation.
produces polycyclic non-halo-
genated quinones plus chlori-
nated polycyclic aromatics.
Eventual ring rupture likely,
but at slower rate than with
Probably same
products as with
chlorine dioxide.
ozone.
di phenylhydrazi ne
or diphenylamine
hydroxylamines and ring
hydroxylated
diphenylamine.
ring-chlorinated, ring-hydro-
xylated and ring-chlorinated +
hydroxylated diphenylamine.
nitrogen heterocycles
ring rupture to amino
acids, then further
degradation to aliphatic
end products
thianine stable. Pyrimidine
and indole rings apparently
stable. Substituents oxidize,
but do not chlorinate
(continued)
-------
Table 28. Continued Ozone
Chlorine Dioxide
Chlorine
unsaturated
aliphatics
cleavage of double bond
to aldehydes, ketones and
acids. Possible formation
of epoxides.
dichloro compounds, chloro-
ketones, chlorohydrins, then
epoxides
dichloro compounds,
chlorohydrins, then
epoxides under
alkaline conditions.
primary
aliphatic
alcohols
yield aldehydes, then
acids, then COy Ethanol
forms a dihydroperoxide
with mutagenic properties
under stringent conditions.
yield acids which are stable
to further oxidation. Un-
saturated acids (crotonic,
maleic and fumaric) are
stable to
secondary alcohols
yield ketones, then
fragmented acids, then C02-
yield ketones, then acetic
acid, which is stable.
00
cr>
primary aliphatic
amines
no reaction.
secondary aliphatic
amines
aldoxlmes + other N-con-
talning compounds, not
nitrosamines
very slow reaction
tertiary
aliphatic amines
secondary amine + aldehyde
chloroform
no reaction except in
presence of UV
probably no reaction
no reaction
(continued)
-------
Table 28. Continued
Ozone
Chlorine Dioxide
Chlorine
humic materials
slowly reactive, producing
phenols, ozone - resistant
acids (increasing COD) and
C02-
slowly reactive, producing
phenols and increasing COD
trihalomethanes
sugars, carbohydrates
ring substituents oxidize
without ring rupture until
excess C102 employed.
ro
00
trihalomethane
precursors
1) 03 + rapid chlorination
65% lowering of THM
2} OT + chlorination after
24 hrs. no effect on
THM yield.
no THMs produced from pure C102
(containing no free chlorine)
trihalomethanes
phosalone, aldrin
readily oxidized to
destruction.
2.4,5-T
ring rupture to oxalic acid
+ C02 + chloride ion.
parathion,
ma lathion
produces oxons, then
degradation products.
dieldrin, chlordane,
lindane, DDT,
PCBs, PCP,
endosulfan
only slightly reactive
with ozone, but will
oxidize with ozone/UV.
-------
Ozonation of chlorinated aromatic compounds ruptures the rings and
cleaves carbon-chlorine bonds, forming chloride ion, non-chlorinated
aliphatic oxidation products and CC^.
Oxidation products formed upon ozonation, and non-chlorinated
oxidation products from chlorine dioxide are more biodegradable
than are the starting organic materials.
Oxalic and acetic acids are only slowly reactive with ozone, and
are the most stable organic end products of oxidation of organic
materials with ozone.
Combination of ozone with ultraviolet light increases the rate of
oxidation of ozone-resistant organic materials, but the same organic
oxidation products are obtained as with ozone alone.
During oxidation, chlorine dioxide is reduced to chlorite ion,
which itself is a chlorinating agent. Chlorite ion may also be re-
oxidized to chlorine dioxide.
Epoxide compounds have been isolated from reactions of compounds
containing double bonds with chlorine or chlorine dioxide. Heptachlor-
epoxide is stable to ozonation, indicating that it may form upon
ozonation of heptachlor.
Oxidation of aldrin or 3,4-benzopyrene with ozone in clean water
proceeds rapidly, but proceeds significantly slower when humic materials
or soil particles are present. Thus dissolved organics can be adsorbed
onto humic or soil materials and be resistant to oxidation.
Oxidation of parathion and malathion with ozone proceeds through
the more toxic oxon intermediates (paraoxon and malaoxon, respectively).
These same intermediate may form with other oxidants, but no literature
has been found to confirm this.
Polysaccharides (cyclic sugars, starches, cellulosics, etc.) do not
undergo ring rupture with small amounts of chlorine dioxide, but do
ring rupture when treated with excess oxidant. This may explain why
humic acids treated with ClOg free of residual chlorine do not form
trihalomethanes.
Bromide and iodide ions are readily oxidized to the free halogens by
chlorine or by ozone. The free halogens then can undergo the haloform
reaction to produce trihalomethanes, tf the proper organic compounds
are present. Formation of bromine-containing trihalomethanes upon
treating humic materials with chlorine dioxide (even containing a
slight excess of free chlorine) has not been observed.
288
-------
Ozonation of humic materials followed by immediate chlorination shows a
significant reduction in trihalomethane formation. However, ozonation
followed by chlorination 24 hours later shows rro reduction of trihalo-
methane formation.
Regardless of the oxidant employed, many (possibly all) of the same
organic oxidation products will be present in the water or wastewater
at the same treatment point. More significantly, in the case of
chlorine, these same (non-chlorinated) oxidation products probably have
been present all along. A detailed review of the organic oxidation
products of chlorine should be made for comparison with the current
survey of oxidation products of organic compounds with ozone and chlorine
dioxide.
Trihalomethane formation in drinking waters can be eliminated by
changing the disinfecting oxidant, but this will have no effect upon
formation of the other, non-chlorinated organics.
These last two conclusions indicate that in considering an "alternative
disinfectant to chlorine" for treating drinking water, "alternative
treatment schemes for removing organic materials" before residual
disinfectant is added should be considered. Depending on the source of
organic pollution and its nature, little may be gained by simply changing
the disinfectant.
There are three basic approaches to minimize the amount of oxidized
organic materials remaining in water supplies treated with oxidants:
Add sufficient oxidant (and oxidation catalyst) to convert all
organic materials to C02 and water. This may be the most costly
approach, in terms of oxidant, and may not even be possible,
depending upon the specific organic materials present.
Eliminate or significantly reduce the amount of organic materials
present before oxidant is added. This would involve better filtra-
tion, use of more or improved flocculants, etc.
Oxidation with a non-halogenating reagent (ozone, chlorine dioxide
in some cases, permanganate, H202, etc.) will form more biodegradable
organic materials. Following oxfdation with a biological filtration
step (such as Biological Activated Carbon—see next section) will
allow significant reduction of dissolved organics (and ammonia)
using smaller amounts of oxidant than in the first two approaches.
Since halogenated organic materials are both more difficult to oxidize
and are less biodegradable, their formation during the early stages
of water treatment processes should be avoided, if at all possible. If
early-stage emphasis is placed on removal of organics to the maximum
degree practicable under specific plant conditions, the following
benefits can accrue:
289
-------
1) chlorine demand will be reduced.
2) amounts of oxidized organics formed later in the process will
be reduced.
3) amounts of trihalomethanes formed will be reduced.
4) Detrimental effects on finished water caused by high
organic and high chlorine levels will be reduced.
If the presence of halogenated organic compounds cannot be avoided (for
example, if they are present in high concentration in the raw water),
pretreatment with the combination of ozone with ultraviolet radiation
should be considered, especially as a pretreatment before Biological
Activated Carbon columns. Engineering and cost aspects of the ozone/UV
approach to destruction of chlorinated organics in drinking water
treatment are unknown at this point in time.
290
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SECTION 13
BIOLOGICAL ACTIVATED CARBON
A Review of the Status of Pre-ozonation of Granular
Activated Carbon for the Simultaneous Removal of Dissolved
Organics & Nitrification of Ammonia
INTRODUCTION
During the November 1976 Workshop on Ozone/Chlorine Dioxide Oxidation
Products of Organic Materials, sponsored by the International Ozone
Institute and the U.S. Environmental Protection Agency, KUhn, Sontheimer
& Kurzs discussed the use of pre-ozonation of granular activated carbon
columns to more effectively process drinking water supplies. During
plant visitations in Europe, the team observed the use of Biological
Activated Carbon at the Donne plant in MUlheim, Germany and at Rouen-la-
Chapelle, France, introduced for the primary purpose of removing ammonia
biologically, with the secondary purpose of removing organics biologically.
In this section we will describe the concept, and will review the
literature which has been published on the process to date as applied to
treatment of drinking water supplies. The use of Biological Activated
Carbon has been developed independently for sewage treatment at the
Cleveland Regional Sewer District in the United States, but this aspect
of BAG will not be reviewed here. The reader is referred to Y.A. Hanna
at the Cleveland Regional Sewer District, Cleveland, Ohio, and to a
chapter by Rice et. al_.166 in Carbon Adsorption, for further details on
the subject.
In a recent article which discusses the use of granular activated
carbon in water treatment, McCreary & Snoeyink167 state that "beds of
granular activated carbon (GAC) are a convenient place for microorganisms
to grow because bacteria attach themselves to the irregular external
surfaces of the carbon particles and are very difficult to dislodge via
backwashing procedures." In the presence of soluble carbonaceous matter,
which serves as food for these organisms, and in the absence of oxygen,
anaerobic bacteria can develop. There are numerous instances in which
sulfidic odors have been reported emanating from granular activated
carbon columns used for the removal of dissolved organic materials
contained in sewage treatment plant effluents168'169 and drinking water
supplies170.
On the other hand, with sufficient dissolved oxygen and carbonaceous
matter, the bacteria which develop in carbon beds will be aerobic.
These do not produce sulfidic odors.
291
-------
Many of the advantages of biological activated (granular activated)
carbon (BAG) were first recognized by German water treatment scientists
in the 1960s in drinking water plants along the Rhine River in the
Dlisseldorf area. Subsequently, BAC processes also have been installed
in Swiss and French drinking water treatment plants, and are subjects of
active pilot studies in Holland and Belgium. In the United States, the
U.S. Environmental Protection Agency's Water Supply Research Laboratory
in Cincinnati, Ohio has been testing a pilot BAC column since late in
1976171.
FUNDAMENTAL PRINCIPLES
Granular activated carbon is made biologically active by the delibe-
rate introduction of sufficient dissolved oxygen (DO) to aqueous streams
just before they are passed through GAC columns. As long as the water
contains sufficient DO to maintain aerobicity of the bacteria and suffi-
cient dissolved carbon to provide food, the aerobic bacteria will thrive
in this environment. Eberhardt172 has likened bacterial activity in
such an ideal environment to a "herd of cows grazing in a luscious
meadow".
At our present stage of understanding, there are two mechanisms by
which biological activity occurs in the BAC columns. Microorganisms are
present both on the surface of the carbon and in the carbon pores.
Organics will be adsorbed both at the surface and in the carbon pores,
and will be biodegraded in both instances. However, those surface
adsorbed organics do not have to be well adsorbed, provided that they
are biodegradable. Preozonation can convert larger, less biodegradable
organic molecules into smaller, more biodegradable organics, for example,
into acetic and oxalic acids.
Sontheimer173 has summarized the German findings to date which have
led to the current theories of operation of BAC.
Although aerobic bacteria are necessary to obtain the benefits from
BAC, so also is the adsorptive capacity of the GAC for the dissolved
organic materials which will serve as food for these bacteria. This
means that the surface area and pore volume of the carbon should be
high. Stated another way, it is important that the organic materials
present in solution which are not easily biodegradable or easily oxidized,
are adsorbable onto the activated carbon column, since the contact times
of solutions with the carbon particles in the columns or beds in water
and wastewater treatment plants are normally short (15 to 30 minutes --
empty bed). This does not necessarily give the bacteria sufficient time
to degrade larger organic carbon molecules, ideally to carbon dioxide
and water. Therefore, it is important to be able to retain the dissolved
organic molecules in the carbon columns so that the bacteria then will
have sufficient time to degrade them, even though the actual contact
times involved are rather short.
292
-------
Many organic materials are readily adsorbed onto GAC, but many
others are not. It is well known, for example, that high molecular
weight natural humic acids, so prevalent in drinking water supplies, are
not readily adsorbed by activated carbon17".
If solutions of these non-sorbable organic materials are ozonized
before passage through the GAC columns, they are converted to more
readily biodegradable organic materials171"175'176. At the same time,
ozonation introduces a large quantity of oxygen into the water which
promotes aerobic bacterial growth, and also breaks down the larger
molecules, leading to improved adsorption kinetics.
ADVANTAGES OF BIOLOGICAL ACTIVATED CARBON
In European pilot studies and in drinking water treatment plants it
has been shown by many workers172'173'171"*177'378'179*180'181'182*183
that preozonation followed by granular activated carbon adsorption
results in:
t Increased capacity of the activated carbon to remove dissolved
organics,
• Increased operating life of the carbon columns before having
to be regenerated (up to 3 years), especially if the GAC can
be kept free of halogenated organics,
• Biological conversion of ammonia (to nitrate) in the GAC
columns,
• Use of less ozone for removing a given amount of organics than
using ozonation alone. (BAC may be more cost-effective over
ozonation in removing Dissolved Organic Carbon - DOC),
t Filtrates from BAC columns in drinking water plants can be
treated with small quantities (0.1 to 0.5 mg/1) of chlorine or
chlorine dioxide, which produces drinking water of acceptable
bacterial quality (zero fecal coliforms) and provides a residual
disinfectant for distribution systems.
Independent studies on physical/chemical treated sewage at Cleveland
Regional Sewer District18" and in Israel185 have confirmed these advantages
with respect to removing organic materials.
EUROPEAN BACKGROUND
Introduction of granular activated carbon into European drinking
water treatment practices occurred after World War II. Its initial
application was for dechlorination, then for tastes and odors1®6. Many
surface waters containing ammonia undergo breakpoint chlorination at the
beginning of the treatment process. This technique effectively removes
ammonia, but produces considerable amounts of residual chlorine and
293
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chlorinated products in the water182. German water treatment objectives
are to process surface waters to the same quality as that of natural
groundwater (which does not have to be treated in many cases). Therefore,
waters treated by breakpoint chlorination have to be dechlorinated
before they are treated further or distributed187'178. Schalekamp178
points out that in Switzerland a residual chlorine concentration of only
0.05 mg/1 is permitted in drinking water. Therefore, surplus chlorine
must be removed when it is present above this level in treated drinking
water.
Lower Rhine River water quality is poor, and advantage is taken of
biological removal of organic materials by filtration of the river water
through the sand banks of the Rhine. Wells are dug into the river banks
and water is drawn from these wells as the treatment plant raw water.
It has been found that some 65 to 75% of the organic material in
the Rhine (as measured by DOC and/or UV absorbance) is removed by this
technique of river bank filtration188. These reductions in organic
content are attributed to biological degradation that occurs in the sand
filters, as well as to some dilution by underground water as it flows
through the wells and toward the Rhine.
River bank filtration today is practiced all along the Rhine River;
an excellent discussion of river bank filtration is given by Poggenburg190.
River bank filtration in the DUsseldorf area introduces dissolved
iron and manganese compounds into the plant raw water; however, this is
removed effectively by ozonation, followed by sand filtration. Passage
of the sand filtered water through GAC now removes tastes, odors, ammonia
and dissolved organics, to produce high quality drinking water.
Although combinations of ozone and granular activated carbon first
were installed in the DUsseldorf area in the early 1960s186, it was not
until nearly ten years later that the biological activity in the carbon
columns was recognized as being beneficial. In the intervening years
since the introduction of ozone/activated carbon at DUsseldorf, the
beneficial effects of biological activity in the carbon columns have
been recognized, characterized and optimized. After ozonation, the
water is allowed to stand for 20 to 30 minutes to allow the more refractory
organic compounds sufficient time to react with residual ozone. This
retention time also allows residual ozone to be utilized in performing
useful work, rather than simply to be destroyed when passed through the
activated carbon column.
On the other hand, the Rhine River also contains considerable
amounts of chlorinated organic materials which are not removed during
river bank filtration. These halogenated materials also are more resistant
to oxidation by ozone than are non-halogenated organics and thus are
less likely to be converted into easily biodegradable materials. In
addition, halogenated organics are more strongly adsorbed onto GAC191'192.
294
-------
Combining the stronger adsorptivity of halogenated organics on granu-
lar activated carbon with their lesser reactivity upon ozonation and their
lower biodegradability simply means that breakthrough of halogenated organ-
ics can occur more rapidly than does breakthrough of non-halogenated organic
compounds from GAC columns, even if the GAC columns are biologically
active. Thus German water works along the Rhine in the Dusseldorf area
monitor their carbon column capacities for Total Organic Chlorine
(TOC1)193'191"195'196 as well as by DOC197 and/or UV absorption. Carbon
columns at three Dusseldorf plants along the Rhein (Flehe, Am Staad,
Holthausen) are backwashed every 4 to 6 weeks and regenerated every 5 to
6 months.
When Dusseldorf carbons are regenerated, however, only some 80% of the
carbon charge is taken out of the columns. This leaves a portion of biologi-
cally active carbon in the column so that the level of bioactivity will not
drop significantly when fresh or regenerated carbon is added. With fresh
carbon columns, about 15 days of operation usually are required for biological
activity to build up to an effective "steady state", particularly for
ammonia removal198.
EUROPEAN DRINKING WATER EXPERIENCES WITH BAC
Switzerland
Granular activated carbon was installed at Zurich initially to protect
against oil spillage, later for protection against phenol spills, and for
dechlorination178. The Zurich Lengg plant raw water comes from the Lake of
Zurich, which contains very low concentrations of chlorinated organics and
is otherwise a very clean raw water. There" is no need for breakpoint
chlorination because of very low ammonia content, but a small dose of
chlorine (1 mg/1 maximum) j_s_ added at the intake to prevent growth of
mussels. Activated carbon insures dechlorination of this amount of chlorine.
In plant studies178 (Figure 62) fresh Pittsburgh 400 granular activated
carbon was shown to have an organic loading of 4 g of organics/kg of carbon
(measured by extraction with dimethylformamide -- DMF). However, after
operating in the plant for 2 months, this same carbon had an organic loading
of 37 g/kg; after 3 months operation 63.5 g/kg, and after 7 months 68.5
g/kg. At the end of 7 months, both the top and bottom layers of the carbon
beds showed equal loadings of organics, thus indicating the need -for regenera-
tion. However, regeneration of this carbon was not required because the
efficiency of removal of dissolved organic carbon from the aqueous medium
by this carbon remained nearly the same as that of the new carbon (Figures
63 and 64). This behavior was attributed by Schalekamp178 to biological
activity within the carbon bed.
At the Zurich Moos plant (also using Lake Zurich water), the slow sand
filter was fitted with a 5 cm layer of PKST granular activated carbon.
Initially, fresh carbon exhibited an organic loading capacity of 5 g/kg of
carbon, but after three years of operation the loading had increased to
29.2 g/kg (Figure 65). Such low total organic loadings again attest to the
295
-------
68.5
63.5
C7>
\
Ol
C3
Z
O
o
37.0
o
CQ
an
4.0
300
350
400
450
WAVE LENGTH nm
Figure 62. Activated carbon loading. New carbon and carbon
after 2,3 and 7 months of operation at the Lengg Plant, Zurich,
Switzerland. UV Spectra of Dime thy Iformamide (DMF) Extracts1^.
296
-------
l\3
1C
• :
RAPID FILTER
ACTIVATED CARBON
35TH
50TH
WEEK
Figure 63- Efficiency of removal of COD from rapid filter and activated carbon
at Lengg Plant, Zurich, Switzerland 178.
-------
ro
RAPID FILTER
ACTIVATED CARBON
O.kO
0.30
\
Q_
oc
s °-
to
20
0. 10
-------
uv
COEFFICIENT
1.982
1.370
0.491
0.037
DMF
g/kg
29.2
23
16
300
I
350
400
450
WAVE LENGTH nm
Figure 65. Activated carbon loading from the slow filter at the Moos plant,
Zurich, Switzerland. New carbon and after filter operating times
of I, 2 and 3 years. UV spectra of DMF extracts at 254 nm'78.
299
-------
high quality of the raw water. As with the carbon at Lengg, however, the
efficiency of DOC removal from the aqueous solution remained essentially
constant over the three year period (about 2.8 mg/1 residual COD in the
filtrate) (Figure 66). This performance, again attributed to bacterial
degradation of the adsorbed organics, was obtained without reactivation of
the carbon, although twice weekly backwashes were required.
When one first considers the deliberate use of biological growth in an
activated carbon column for treating drinking water, one imagines that the
carbon filtrates will contain high quantities of bacteria. That this is
not the case with properly designed and operated BAC columns will be shown
in a later section discussing a three-year research program at Germany's
Bremen water works.
Bacteria need both oxygen and dissolved biodegradable organic carbon
for growth. If the activated carbon bed is too large, there will be little,
if any, dissolved carbon in the column outlet, thus high bacterial counts
within the column will decrease171**le7.
Figure 67 shows the bacterial counts/ml of activated carbon effluents
at the Lengg plant after 3 days of incubation at 20°C. Values varied from
maximum counts of 42/ml in August to 9 in December.
Operational filters at the Lengg plant are 44 sq meters in area. On
the bottoms are 75 plastic nozzles/sq meter. The filters are charged with
50 cm of quartz sand (0.7-1.0 mm grain size) then 1.2 meters of Pittsburgh
F 400 granular activated carbon. Operational costs for the carbon beds at
the Zurich Lengg plant are $0.016/cu meter (6.05
-------
i
CO
o
o
o
RAPID
•FILTRATE
•SLOW
FILTRATE
SLOW ACTIVATED
CARBON FILTRATE
1972
1973
1974
1975
Figure 66. Efficiency of COD removal of BAC over 3 years at Moos Water Works, Zurich, Switzerland
178.
-------
50
30
20
10
JULY
AUG
SEPT.
OCT.
NOV,
DEC.
JAN.
Figure 67. Bacterial count af^er 3 days incubation at 20°C in I ml activated carbon
filtrate of the "South" installation, Lengg Water Works, Zurich, Switzerland
-------
Process #1: Ozonation, rapid sand filtration, biological activated
carbon, slow sand filtration,
Process #2: Rapid sand filtration, granular activated carbon, slow
sand filtration,
Process #3: Granular activated carbon, slow sand filtration.
These researchers concluded (Figure 68) that:
• Ozonation increased bacterial counts considerably after rapid and
slow sand filtration,
• Water treated by Process #1 (with ozone) produces water with
better color, UV absorption and KMnCh consumption than waters
treated by Processes #2 or #3 without ozone,
• Slow sand filtration in all 3 systems reduces bacterial counts,
color and KMnO^ consumption,
• Water qualities by Processes #2 and #3 (without ozonation) are
about the same, but the frequency of backwashing of the slow sand
filters is significantly different in these processes. Replacement
of sand in the rapid filters was not attractive because of the
increased backwashing of the following slow sand filters.
• Service time of the granular activated column with ozone was much
longer (300 days) than those without ozone (175 days) as measured
by UV absorption (Figure 69) of the filtrates.
For the same applied DOC, the amount of DOC removed by the carbon in
summer is much greater than in the winter. This is explained on the basis
of biological activity in the carbon column.
Oxygen consumption in the winter was found to be 0.006 g/hr/kg of
carbon and 0.024 to 0.030 g/hr/kg of carbon in summer.
Longer service times were observed for BAC columns which had optimum
empty bed contact times of 20 to 25 minutes.
Costs of operating carbon filters decreased with increasing retention
times. Costs of 6 Dutch <£/cu meter (2.55 U.S. <:) were estimated for 25 to
30 minute retention times. Reactivation costs were estimated at 3 Dutch
tf/cu meter (1.23 U.S.
-------
03+RF+ACF+SF
RF+ACF+SF
ACF+SF
COUNTINGS
3 DAYS 22° C
ON PEPTONE-
AGAR
10.000
1,000
100
10
AFTER SF
COLOR
mg/l
\
UV-
ABSORPTION
0.60
0.50
0.40
0.30
0.20
0.10
KMnO.
NUMBER
mg/l
13
3 MONTH
3
1974
2
1975
23412
1974 1975
234
1974
2
1975
TURBIDITY
0.37
0.39
0.35
TASTE NUMBER
0.2
0.2
0.2
BACKWASH ING FREQUENCY?
)F SLOW FILTERS £
16
03=Ozonation RF=Rapid Filtration ACF=Activated Carbon Filtration SF=Slow Filtration
Figure 68. Activated Carbon Studies in Amsterdam'79.
304
-------
Filter #2: Non-Activated Carbon — (Norit ROW 0.8)
Filter #3: Sand — (0.85 to 100 nun in size)
Each filter was fed with tap water at 13 to 17°C and 3.5 m/hour* (3
minutes contact time) flow-through rates over a 10 month period (side-by-
side experiments). Bacterial counts were made at regular intervals by the
colony count technique on diluted agar (0.35 g/1 beef extract, 0.65 g/1
peptone, 10 g/1 agar) after incubation 10 days at 25°C. Bacterial counts
were highest in activated carbon filter #1 (Figure 70). The number of
bacteria on the activated carbon column was always 10 times higher than the
number found on sand or on non-activated carbon.
From these experiments Van der Kooij180 calculated the average carbon
surface area occupied by a single bacterial cell to be 40 sq microns when
the colony count is 108/cu cm. Since the surface area of the activated
carbon used for these tests was greater than 40 sq cm/cu cm, it was concluded
that the density of bacteria on the carbon surface is very low. This was
confirmed by electron microscopy. It was also concluded that normal
adsorption processes on granular activated carbon are not hindered by the
presence of the bacteria on the carbon.
Germany
Wiesbaden—
Klotz ejt aJL199 studied the microbiology of granular activated carbon
filters at the Schierstein plant in Wiesbaden. At this plant, Rhine River
water is aerated, settled, chlorinated to the breakpoint, flocculated,
filtered through sand, then granular activated carbon, then sent to
ground infiltration. There is no pre-ozonation of the -activated carbon
column.
Bacterial counts were found to decrease between the Rhine River and
the entrance to the carbon filters, the largest effect being seen after
break-point chlorination. However, fresh populations of microorganisms
were formed in the activated carbon filters. Within 20 days the bacterial
counts in the carbon filter effluents reached their maximum concentrations
of 105-106/ml in pilot filters (4 to 20 m/hr velocities) but have been
found to be as high as 10° to 107/ml in plant carbon filters. After 3
years of operation, bacterial counts in the carbon columns effluents were
103 to 104/ml (Figure 71), and were about the same as those in the raw
water. Biological activity in the sand filter during the fourth year rose
to the level of that in the carbon filter.
Studies of the carbon columns at Wiesbaden over a period of 3 years
have shown that seasonal influences are only slight. There is a tendency
* The term m/hour is derived from a flow rate of cu m/hr divided
by sq m of surface area. Cu m/hr per sq m = m/hr.
305
-------
in
(_>
>
350
300
250
200
150
100
50
O 03+ RAPID FILTRATION + ACTIVATED CARBON + SLOW FILTRATION
A RAPID FILTRATION + ACTIVATED CARBON + SLOW FILTRATION
Q ACTIVATED CARBON + SLOW FILTRATION
PLACE: AMSTERDAM
PARAM: UV-ABSORPTION
0 0.050 0.100 0.150 0.200 0.250 0.300 0.350
UV-EXTINCTION (A=240nm, l
Figure 69- Activated carbon column service time
as a function of filtrate quality'79.
306
-------
A ACTIVATED CARBON, NOR IT ROW 0.8 SUPRA
A NON-ACTIVATED CARBON, NORIT ROW 0.8
O SAND (0.85-1.0 MM)
c
-
:
_
c
-
o
u
105
Figure 70. Bacterial counts on ROW 0.8 supra activated carbon, ROW 0.8
(non-activated) and sand (0.85 - 1.00 mm) when fed with
tapwater (nominal velocity 3-5 m/hr.) ' '0.
307
-------
RAW WATER INLET
SAND FILTRATE
CARBON FILTER OUTLET
BACTERIAL COLONIES/ML OF WATER
10'
I0:
10'
10-
V,
•^ * I x
VN
/
•>._ y
i
Ns.
I A
A
u
i
IA--
^/ \
f
*
7Y*
v A
f-~
M I J I J I A I S I O I N I D
1972
J|F'|M|A|M|J|J|A|S| o T NT "
1973
J|F|M| A | M | J I J I A | S | O | N I D
197^
J|F|M|A|M|J|J|A
1975
Figure 71. Behavior of microbial populations on activated carbon over three
Behavior of microbial populatio
years at Wiesbaden, Germany'-^.
-------
for decreased microbial activity in winter, as indicated by oxygen consumption
and carbon dioxide production values. However, changes in raw water quality
can cause substantial and distinct changes in the colony numbers.
Pilot tests at Wiesbaden were conducted in two granular activated
carbon units, each consisting of four series-connected glass tubes, 6 cm
inside diameter, with 2 meters of activated carbon layer height. One unit
was kept free of bacteria for more than 2 months, by sterile filtration.
In the uppermost carbon layers the chlorine content falls below 0.1
mg/1, where it no longer has any perceptible influence in preventing the
growth of bacteria in the columns. During passage through the activated
carbon filters, 1.5 mg/1 of oxygen is consumed and 4.5 mg/1 of carbon
dioxide is produced. DOC (measured by UV absorbance) decreases about 55%,
but KMnO, values decrease by about 45%. BOD2, BODc and BOD20 values showed
that changes in biodegradability of the solutions Before ana after passage
through the column were slight.
To increase the amount of biodegradable organic substances in the raw
water, the inlet was spiked with 50 mg/1 of phenol. Biological activity
was found to be higher when phenol, a relatively more readily biodegradable
material, was present. This means that regrowth of bacteria that can occur
in distribution systems (when activated carbon is not used in the treatment
processs) can be made to occur in the plant itself by installing granualar
activated carbon.
Investigations on the adsorption of microorganisms onto granular
activated carbon were made using starved and washed populations (mixed
populations) in a nitrogen-free environment. Figure 70 shows an adsorption
isotherm for bacterial loading onto granular activated carbon as a function
of the concentration of bacteria (adsorptive concentration) in 200 ml of
phosphate buffer; pH = 7.2. At high colony counts (larger than 10IU/2007
ml) the carbon system tends to become saturated. At'colony counts of 10
to 10°/200 ml, up to 90% of the bacteria are adsorbed onto the carbon.
After an incubation period of 20 to 30 hours, adsorption and desorption
of bacteria were nearing the steady state (Figure 73) of about 108 colony
numbers/g of activated carbon. In this figure, colony counts refer to
living bacteria and cell numbers refer to dead bacteria. The authors199
state that dead bacteria are slightly better adsorbed than living bacteria.
Electron scan microscopic analysis of granular activated carbons
treated differently showed that the bacteria are always present in the form
of a single bacterial layer. Thus the carbon surface is only fractionally
utilized (about 1%) by the adsorbed bacteria, leaving 99% of the surface
area of the carbon free for adsorption of dissolved organic materials and
dead bacteria.
Bremen—
Extensive pilot plant studies have been conducted by Eberhardt et
al.172. The original Bremen plant treats Weser River water by flocculation,
309
-------
I012
(_>
£ 10
<
10
i;
^ ID-'
CO
OC
LJJ Q
CD IQO
^5
Z
S ^ I07
o /•
" I06
I06 I07 I08 I09 I010 I01 ' I012
ADSORPTIVE CONCENTRATION
(COLONY NUMBERS/200 ml BUFFER)
100
75
z 50
o
§
25
I06 I07 I08 I09 10
JO
10
l2
ADSORPTIVE CONCENTRATION
(COLONY NUMBERS/200 ml BUFFER)
Figure 72. Microbiological loading of activated carbon-dependence
on adsorptive concentration'!^.
310
-------
A COLONY COUNTS
O CELL NUMBERS
50
a
<
c
:• -
20
10
10 20 30 *K) 50 60
TIME (HOURS)
Figure 73. Microbiological loading of activated carbon-dependence on time
Wiesbaden studies!99.
311
-------
rapid filtration, slow filtration and chlorination. A semi-works size
pilot facility employing activated carbon with preozonation was constructed
in 1969, and research reported in this article was conducted on biological
activated carbon over a 3 year period. DOC of the raw water was 5 to 10
mg/1, and the permanganate numbers varied from 10 to 22 mg/1.
The test facility (Figure 74) originally consisted of an ozone contact
chamber (0.7 m diameter, 3 m high), two temporary storage tanks (each 2.5
cu m), a slow sand filter (0.7 m diameter, 3 m height), and a granular
activated carbon filter (0.8 m diameter, 3 m height). Provision was also
made to periodically close off the flow of water through the carbon column.
At these times, the water in the carbon columns was recycled back through
the carbon beds, and analytical parameters were measured. These included
dissolved oxygen, DOC, carbon dioxide, ammonia, nitrate, etc. In this
manner, material balances were determined. In later experiments, a rapidly
operating slow sand filter was added after the activated carbon filter.
Water from theVapid filter was treated in this pilot facility, at
first with the same dosages of ozone as used in water plants along the
lower Rhine (2.1 mg/1 ozone). Ozonized water was held 1 to 3 hours, then
filtered through 1 m of sand, then 1 m of activated carbon at 5 m/hr.
Data in Table 29 (taken over 6 weeks of operation) show that although
this low ozone dosage reduced KMn04 consumption somewhat (15.4 to 13.7
mg/1), no further decrease was observed in the carbon or sand filters
(which were placed in parallel for this test). The decisive parameter for
comparison, however, is the slow filter performance (last line of data in
Table 29). This shows that it is possible to obtain better (lower) values
of potassium permanganate consumption without ozonation at the low level
used for these tests.
Ammonium ion concentration was lowered significantly in the carbon
column, however, from 0.65 to 0.08 mg/1. This reduction in ammonium ion
concentration was attributed to nitrification occurring in the biologically
active carbon bed. The amount of nitrification which occurred in the
carbon under these conditions was significantly higher than that which
occurred in the parallel slow sand filter.
Although low colony counts were found after ozonation, after BAG
filtration or after parallel sand filtration (48 hours incubation), extra-
ordinarily high colony counts were found on gelatine medium after 72 hours
incubation at 22°C. These data indicate that immediate treatment of the
BAC column filtrate with chlorine or chlorine dioxide would maintain residual
bacterial counts in the effluent at or near zero.
312
-------
u>
_J
CO
WATER FROM
RAPID FILTER
TREATED
WATER
Figure Ik. Bremen, Germany water works pilot plant 172.
-------
TABLE 29. EXPERIMENTS WITH SMALL DOSES OF OZONE
(2/27-4/10/1969) AT BREMEN172
*Clarifier Outlet
*Rapid Filter
After Ozonation
After Act Carbon
or
After Sand Filtrn
*Slow Filter
(for Comparison)
pH
7.85
7.61
7.59
7.40
7.57
7.41
KMn04
consump
mg/1
17.3
15.4
13.7
13.3
13.2
11.9
<
mq/1
1.05
0.65
0.08
0.55
0.06
Turbidity
x 10-3
abs E
2.49
0.95
0.92
0.95
0.94
Colony Count/ml
after
48 hr
2,900
1,380
1
6
11
45
72 hr
1
5,200
53
2.1 mg/1 ozone dose. 1-3 hr holding tank. Activated carbon and Sand
filter in parallel with 5 m/hr filtration time at 1 m height. Raw water
temperature 4.1°C.
Geometric averages
*0riginal treatment process
The next series of experiments was conducted using the treatment train
shown in Figure 72 and the ozone dosage was increased considerably. Table
30 shows data obtained when the ozone dosage was increased from 2.1 mg/1 to
an average 8 to 10 mg/1. A much larger decrease in permanganate consumption
was observed after ozonation (14.1 to 10.5 mg/1), but also a further decrease
after the carbon column (10.5 to 8.8). The decrease observed after the
carbon column was attributed to biological activity within the carbon
column, since a similar reduction in permanganate consumption (which would
have been due to adsorption only) was not observed in the-experiments of
Table 29.
As with the first experiment, low colony counts were observed in the
activated carbon filtrate after 48 hours incubation, but very high counts
were found after 72 hours incubation.
On the basis of good experiences gained in full scale operations at
the St. Gallen and ZUrich, Switzerland water works, a so-called "fast-
driven" slow filter (i.e., a slow filter operated at a flow rate between
0.5 and 1 m/hr) was added downstream of the activated carbon filter. The
314
-------
ozone dosage rate also was reduced. All subsequent data were obtained
using the treatment train shown in Figure 72, with the added "fast-driven"
slow filter.
TABLE 30. EXPERIMENTS WITH HIGHER OZONE DOSES BEFORE
THE ACTIVATED CARBON FILTER (9/1-9/22/1969) AT BREMEN172
*Clarifier
Outlet
*Rapid
Filter
After
Ozonation
After Acti-
vated C
*Slow Filter
Comparison
PH
7.77
7.60
7.50
7.40
7.51
KMn04
consump
mq/1
17.3
14.1
10.5
8.8
10.3
°2
mq/1
7.8
5.7
12.1
10.4
5.6
Turbidity
x 10"3
abs E
4.22
0.98
0.78
0.89
Colony Count/ml
after
48 hrs
235
104
0
119
27
72 hrs
~ •- •>
___
—
2,700
—
E. coli and
Col i form B.
in 100 ml
...
10
0
0
0
8.5 - 10.0 mg/1 0, dose. 3 hrs in holding tank. Activated Carbon
filtration rate 4 m/hr at 1 m height. Temperature 17.5°C (average).
*0riginal treatment process
Table 31 shows data obtained with an ozone dose rate of 5.8 mg/1. The
desired effects of reduced KMn04 consumption were achieved with the BAC,
but hardly any organic material was removed in the fast-driven slow filter
placed downstream. On the other hand, this filter exhibited high efficiency
in removing bacterial colony counts, particularly in the values after 72
hour incubation.
It can be concluded from these results that it should be possible to
obtain even better results if the residence time in the biologically active
carbon filter were to be increased from 15 minutes to 30 minutes, in terms
of the empty bed volume. Results from such longer residence time experiments
are given in Tables 32 and 33.
315
-------
TABLE 31. EXPERIMENTS WITH INTERMEDIATE OZONE DOSAGES AND CONSECUTIVE
FILTRATION THROUGH ACTIVATED CARBON, THEN RAPIDLY OPERATING SLOW SAND
(9/22-10/23/1969) AT BREMEN172
*Clarifier Outlet
*Rapid Filter
After Ozonation
After Act Carbon
After Rapid/Slow
Filter
*Slow Filter
Comparison
pH
7.80
7.59
7.52
7.38
7.39
7.52
KMnO^
consump
mg/1
17.8
14.7
11.5
9.2
9.2
11.1
Colony Count/ml
after
48 hrs
210
65
>1
52
42
25
72 hrs
—
—
—
3,100
400
___
E. coli and
Colif. B
in 100 ml
—
15
0
0
0
0
5.8 mg/1 ozone after holding time. Raw water from rapid filtration step.
Activated carbon filtration rate 3.5 m/hr at 1 m height. Filtration rate
of rapid/slow filter: 1 m/hr at 1 m height. Temperature: 12.6°C
(average).
*0riginal treatment process
Data of Table 32 were obtained at a filter flow rate of only 2 m/hr
in the BAC column (1 m bed height) and a 30 minute theoretical empty bed
residence time, corresponding to 12 to 15 minutes effective residence
time. An appreciable reduction in KMnO, consumption was observed, not
only after the BAC column, but also after the sand filter which followed.
The final values in this respect were considerably better than those
obtained after the slow filters of the plant itself.
Data of Table 33 show that very satisfactory levels of water quality
can be achieved from the highly polluted Weser River, which sometimes had
water temperatures below 2°C. Biological processes occurring in the
carbon column are credited with lowering the amounts of contained organics,
and particularly in lowering the ammonium ion concentrations. Also
noticeable are the very low bacterial colony counts obtained after the BAC
column and after the fast-driven slow filter (48 hour incubation). These
data also support the conclusion that addition of small amounts of residual
disinfectant (chlorine, chlorine dioxide, etc.) after Biological Activated
Carbon treatment would keep the so-processed drinking water bacteria-free.
316
-------
TABLE 32. EXPERIMENTS WITH OZONE, SLOW ACTIVATED CARBON FILTER — BREMEN172
*Clarifier Outlet
*Rapid Filtrate
After Ozonation
After Act Carbon
After Rapid/Slow
Filter
*Slow Filter for
Comparison
Experiment Times:
Average Temperature
KmnO^ Consumption
mg/1
I II S
20.1 17.5 18.5
16.8 15.2 16.0
13.7 13.2 13.5
11.3 11.3 11.3
10.7 10.0 10.5
12.8 12.6 12.7
°2
mg/1
I II S
9.6 11.0 10.3
6.0 9.0 7.5
14.2 16.6 15.4
11.8 13.6 12.7
11.0 12.4 11.7
7.4 7.8 7.6
Colony Counts/ml
after 48 hrs
I II S
446 1701 871
86 458 198
57 134 87
35 12 20
39 45 41
after 72 hrs
I II S
4038 179 2673
1116 155 416
[ = 10/23 - 11/27/1969; II = 11/27 - 12/31/1969; S = 10/23 - 12/31/1969
: 9.3°C 3.2°C
4.3 mg/1 Oo dose into the rapid filtrate, then holding time (sample for ozone). Then through 1 m BD
activated carbon which had been in service for a long time; 2 m/hr filtration rate. Then rapid/slow
filter, 1 m in height, 0.5 and 1 m/hr filtration rate.
*0riginal treatment process
GO
-------
TABLE 33. EXPERIMENTS WITH OZONE AND ACTIVATED CARBON FILTERS (1/8-2/2/1970) IN BREMEN
1 72
*Clarifer
Outlet
*Rapid
Filtrate
After 03
After
Act C
After Rapid-
Slow Filter
*Slow Filter
Comp
PH
7.75
7.63
7.59
7.22
7.18
7.30
DOC
mg/1
4.3
3.7
4.1
2.2
2.4
3.2
COD
mg/1
12.9
11.4
10.6
9.1
7.9
9.5
UV-ext
(corr.)
0.278
0.257
0.163
0.160
0.151
0.225
KMn04
mg/1
21.4
18.4
15.9
13.0
11.7
16.5
°2
mg/1
11.7
10.5
16.9
10.1
8.8
6.7
NH/
mg/1
2.68
2.37
2.16
0.49
0.21
1.41
Turbidity
x 10"3
abs. E.
4.54
0.92
0.99
0.97
0.90
0.89
Colony Counts/ml
after
48 hrs
6600
2700
0
49
9
114
72 hrs
___
___
4600
320
___
4,7 mg/1 ozone dose. Activated carbon filtration rate: 2 m/hr at 1 m height. Rapid/slow filtration
rate: 0.5 m/hr at 1 m height. Slow filtration as normal in plant. DOC, COD and UV values from only
2 samples. Average Temperature: 1.6°C.
*0riginal treatment process
CO
•wj
00
-------
Eberhardt, Madsen & Sontheimer172 concluded that Biological Activated
Carbon provides the following performance advantages in producing drinking
water from the River Weser:
• About 100 g of dissolved organic carbon was bacterially
oxidized/cu m of activated carbon per day. Consumption
of oxygen during the summer was 360 g/cu m of activated
carbon/day and 240 g/cu in/day during winter.
• After three years of operation without regeneration, the
total bacterial count reduction averaged 97% and the E. coli
reductions averaged 96%.
• The amount of organic substance removed is dependent upon
its concentration in the influent and the residence time
in the biological activated carbon filter. Theoretical
empty bed residence times of 30 minutes are sufficient
for optimum organics removal.
• Higher efficiencies of organics removal are obtained at
lower filtration rates.
• Increased efficiencies of organics removal are obtained
with smaller grain sizes of GAC.
• Best results are obtained from activated carbons which have
high adsorptive capacities (for organics) and high pore
volumes.
• BAC columns are 10 to 100 times more biologically active per
unit volume of carbon than are slow sand filters, probably
because of the high concentrations of organic materials in the
carbon pores.
Once the bacterial activity in the granular activated carbon has been
fully established, the organics removal process starts with adsorption of
organics, biological mineralization of the adsorbed organics and biological
regeneration of the activated carbon. The process kinetics at Bremen were
found to follow a zero order reaction, but Eberhardt205 cautions that each
water should be checked before applying this as a general conclusion, since
different waters and different pretreatments (before the ozone/activated
carbon step) may affect the reaction kinetics.
The operative process is adsorption with water containing only organic
substances and fresh granular activated carbon. However after 2 to 3
months of operation, biochemical processes have reached a steady state and
are in full swing. After biological buildup has occurred, then adsorption
and biochemical degradation (mineralization) of the organic substances both
occur in parallel, and either adsorption or mineralization processes may
predominate. At constant temperature and bed loading, the mineralization
319
-------
rate was found to be constant and independent of the concentration of
organics in the feed water.
The following mathematical relationships have been developed by Eber-
hardt205.
For the biological conversion of carbohydrates to carbon dioxide and
water:
CaHJ) + (a + b/4 - c/2) x 0, = a x CO, + (b/2) x H90
dDC £. c. L
Therefore, the ratio of degraded organic carbon to inorganic carbon
produced should equal unity, or:
ADOC/AC02 = 12a/44a =3/11 = constant
Therefore, stoichiometrically, 3 g of DOC should produce 11 g of
co2.
When ADOC - A(inorganic carbon) = 0, then organic materials are being
mineralized only. If ADOC - A(inorganic C) < 0, then mineralization processes
are predominating.
The following equation has been found to be valid for the reaction
kinetics205:
-d(DOC)/dt = k
Therefore,
ADOC = DOCQ - DOC = kt
where DOCQ = DOC in the influent to the BAC column water and
DOC = DOC in solution after the carbon filter (in g/cu m).
Since: t = e x lp/Vp,
where: e = ratio of water volume to bed volume
IP = filter length in meters and
Vp = filter velocity in m/hr.
Therefore: the Specific Biochemical Filter Degradation Effectiveness
per cubic meter (in g of DOC/cu m/hr), Np:
NF = k x e = ADOC(Vp/lF)
320
-------
increases with increasing temperature, with decrease in the size of
activated carbon granules, with improved adsorption capacity, with larger
pores in the carbon and when the substances in water are more biodegradable.
It would also appear logical that the effectiveness would be dependent upon
dissolved oxygen content, at least below a certain critical concentration,
although Eberhardt205 does not discuss this point.
Tests at Bremen showed that the Specific Biochemical Filter Degradation
Effectiveness, Np, is 1 to 4 g DOC/cu m of activated carbon/hour. Knowing
Np and the amount of DOC to be removed from solution per unit time, then
the length of the filter medium and the flow rate of water to be treated
can be deduced. Since both parameters can vary, local conditions at the
site will be determining.
In other tests conducted at Bremen, prechlorination of the water was
found to have an adverse effect on the operation and the effectiveness of
biological activated carbon columns, even with pre-ozonation172. Pre-
chlorination reduced both the growth of bacteria and efficiency of removal
of the organics by the carbon. In addition, chlorinated organics are less
biodegradable. Detrimental prechlorination effects are not a function of
the oxidative powers of chlorine, since pretreatment with KMnCty did not
reduce the biochemical degradation effectiveness.
It now can be appreciated that terminal ozonation of drinking waters
which contain organics can promote bacterial growth in distribution systems.
When such water is sent to distribution systems without containing a residual
disinfectant, the chances for bacterial regrowths are very high. On the
other hand, if biological activated carbon filters follow ozonation, then
this bacterial regrowth activity is caused to take place within the plant,
and is not allowed to occur in the distribution system. Addition of small
amounts of residual disinfectant, such as chlorine or chlorine dioxide, now
should insure that regrowth does not occur in the distribution system.
NITRIFICATION OF AMMONIA
Under aerobic conditions, ammonia nitrogen is converted biologically
to nitrate ion in two discrete steps:
NH4+ + 1.502 > N02" + 2H+ + H20 (step 1)
N02" + 0.502 > N03" (step 2)
Step 1 is accomplished by means of Nitrosomonas bacteria; step 2 is accom-
plished by Nitrobacter. During nitrification, some ammonia nitrogen becomes
part of the cell tissues of the bacteria.
The nitrification process is known to occur in rapid sand filters if
the temperature is above 5°C205. It is only necessary to assure that there
is sufficient oxygen in the water and sufficient retention time for the
bacteria to work (see Tables 29 and 33).
321
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Nitrification of ammonia takes place in activated carbon media at the
same rate as in sand filters, which is not surprising since ammonia is not
adsorbed by the carbon. There is some indication, however, that activated
carbon may be somewhat more efficient at temperatures below 5°C205, possibly
because of the large surface area and increased pore volumes of carbon as
compared with sand. These may provide more space or volume for the nitrifying
bacteria.
Ammonia nitrification in carbon columns usually requires 3 months to
attain steady state conditions, and during this time there may be problems
caused by sudden surges of ammonia in surface waters. However, if fresh
activated carbon columns are dosed with small amounts of ammonium salts,
nitrification is attained more rapidly, sudden surges in ammonia concentra-
tions can be handled better, and the efficiency below 5°C also will improve205.
Stoichiometrically, total nitrification of 1 gram of ammoniacal nitrogen
requires 4.57 g of oxygen. However, Cornelia & Versanne181 found that only
3.2 g of oxygen is required for nitrification at the drinking water treatment
plant at Rouen-la-chapelle, France. Since aerobic bacteria on activated
carbon columns and nitrification processes both consume dissolved oxygen,
it is therefore necessary to provide oxygen to the water before it enters
the carbon columns. This can be done by simple aeration, by addition of
oxygen, or by pre-ozonizing the water.
It should be realized also that if all the ammonia nitrogen is converted
into nitrate bacteriologically on a 1/1 basis, then the level of nitrate in
the finished water will rise as the ammonia concentration decreases.
It is also necessary to prevent the presence of bacterial growth
inhibitors, such as toxic heavy metals and halogenated organic micropollutants
from entering the BAG columns and interfering with the growth of bacteria
and/or the progress of the biological oxidation processes.
Specific examples of removal of ammonia by the use of Biological
Activated Carbon in two new European drinking water treatment plants are
given in the following sub-section.
CASE HISTORIES
Mulheim. Germany
The Rheinisch-Westfalische Wasserwerksgesellschaft mbH182 has taken
advantage of biological activated carbon to radically change the drinking
water treatment process at the 48,000 cu m/day (12.7 mgd) Dohne plant in
Mulheim, Germany. Raw water for this plant is the River Ruhr, which until
mid-April, 1977 was treated by breakpoint chlorination for ammonia removal,
flocculation, sedimentation, then granular activated carbon for dechlorination
and ground filtration. Over the years, ammonia concentrations have increased,
requiring prechlorination doses of 10 to 50 mg/1. In turn, these high
chlorine doses produced large amounts of chlorinated organics (Table 34),
which not only were incompletely adsorbed by the carbon columns and passed
322
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through the plant into the distribution system, but also caused frequent
regeneration of granular activated carbon columns (every 4 to 6 weeks).
TABLE 34. ORGANO-CHLORINE COMPOUNDS(1 FROM BREAKPOINT
CHLORINATION TREATMENT, MULHEIM, GERMANY
(DOHNE) PLANT182
Raw water (Ruhr)
After flocc + sedimn
After filtration
After act carbon
filters
After ground passage and
safety chlorination
DOC1*
ppb
17
203
151
92
DOC1N**
ppb
5
30
17
18
* DOC1 = Dissolved Organic Chlorine
** DOC1N = Non-Polar Dissolved Organic Chlorine
Sum of Haloforms
ppb
9
15
23
21
23
CHCK
ppb J
<1
6
7
7
9
During a two year pilot study on the use of pre-ozonation of activated
carbon for removal of chlorinated organics, it was found that break-point
chlorination could be eliminated completely and the BAG operation could be
relied upon totally for removal of ammonia. At the same time the DOC was
reduced to the desired levels.
This process, involving pre-ozonation of activated carbon, was installed
and began operating in mid-April, 1977. After the first five months, the
performance of the full scale plant process is as effective as was the
pilot process at the same stage of development173'187.
The newly installed process at Dohne (Table 35) involves pre-oxidation
with about 1 mg/1 of ozone with addition of poly-aluminum chloride and lime
as flocculants. Pre-ozonation oxidizes manganese and aids in flocculating
the organics. After flocculation and sedimentation, 2 mg/1 of ozone is
added to oxidize dissolved organics. After a retention time of 15 to 30
minutes, the ozonized water is preflocculated using 0.2 mg/1 aluminum
chloride and 0.1 mg/1 polyelectrolyte, filtered (rapid sand), then passed
through biological activated carbon where the bulk of DOC and ammonia are
removed. Filter rates at the start of plant operations were 18 m/hr through
2 m carbon bed depths. However, the carbon bed depths recently have been
increased to 4 m to increase the bed retention time to 15 minutes, to
323
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TABLE 35. PROCESS DATA FOR DOHNE WATERWORKS (MOlHEIM, GERMANY)
BEFORE AND AFTER CHANGE OF TREATMENT182
Old Process
Treatment step
New Process
10-50 mg/1 C12
4-6 mg/1 A13+
0.1 kw/cu m
Ret time - 0.5 min
Dosing
Mixing
Preoxidation
1 mg/1 03
4-6 mg/1 A13+
2.5 kw/cu m
Ret time - 0.5 min
5-15 mg/1 Ca(OH)2
Ret time - 1.5 hr
Flocculation
Sedimentation
5-15 mg/1 Ca(OH)2
Ret time - 1.5 hr
Ozonation
2 mg/1 03
Ret time - 5 min
v = 10.7 m/hr
Filtration with
preflocculation
v = 9 m/hr
,3+
0.2 mg/1 AT
0.1 mg/1 Polyelect
v = 22 m/hr
h = 2 m
Activated
carbon filter
v= 18 m/hr
h = 2 m (4 m)
Ret time 12-50 hr
Ground passage
Ret time 12-50 hr
0.4-0.8 mg/1 C12
Safety
chlorination
0.2-0.3 mg/1 C12
324
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further improve process efficiencies and to protect against possible surges
in organic pollution or ammonia in the raw water.
After activated carbon filtration the treated water is sent to ground
infiltration (12 to 50 hours retention time) after which it is chlorinated
(0.2 to 0.3 mg/1) and sent to the MUlheim distribution system.
A comparison of the performance of the new process versus the older
one is given in Table 36. The DOC of treated water today is less than half
that of water treated by the old process. Even lower DOC values are expected
since the carbon column depths have been increased.
Table 37 shows the bacterial content of waters at the various points
in the new treatment process. E. coli counts/100 ml are essentially zero
after filtration-and remain essentially zero after BAC filtration as well.
Pilot plant data are presented in Table 38 which shows the effects of
variation of activated carbons on removal of DOC, inorganic carbon, ammonia
and dissolved oxygen. In addition, this table also compares the removal of
these same parameters with carbon column depths of 2.5 m and 5.0 m for two
different activated carbons.
Removal of ammonia and dissolved oxygen are fairly independent of
carbon type or column depth. On the other hand, removals of DOC and inorganic
carbon are affected by the carbon type.
Most significant, the amount of DOC removed with 5.0 m columns is
about 50% higher than with 2.5 m columns, although the amount of inorganic
carbon measured increases only slightly.
During pilot studies at the Dohne plant with the BAC process, activated
carbon columns were found to have operational lives of at least one year,
and in some cases two years, without requiring regeneration. Life of the
full scale carbon columns at Dohne is now estimated to be at least 20
months173'187. No signs of loss in performance have been noted during the
first five months of operation173'187
Elimination of breakpoint chlorination at the beginning of the MUlheim
process eliminates formation of chlorinated organics which caused the
activated carbon columns to have to be regenerated every 2 months under the
old process. The 10 to 50 mg/1 of chlorine previously required for this
step now has been replaced with 3 mg/1 of ozone. Additional cost savings
associated with this change include the labor which was required with
breakpoint chlorination. Formerly, a technician was required to sample
water every two hours and to analyze for chlorine and for ammonia. This
labor requirement has been eliminated.
Additionally, because the Dohne plant is located in the center of a
residential neighborhood, considerable attention had to be paid to the
safety aspects of handling such large quantities of chlorine as were required
by the former process. This also consumed considerable operating
labor173'187.
325
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TABLE 36. MEAN DOC AND UV-EXTINCTION VALUES FOR THE DIFFERENT TREATMENT STEPS
MOLHEIM, GERMANY (DOHNE) PLANT -- NEW OZONATION PROCESS182
Raw water (Ruhr)
After flocc + sedim
After filtration
After act carbon
After ground passage
1975
DOC
ppm
3.9
3.2
3.2
3.0
1.8
UV(254 nm)
m-1
6.8
4.5
4.4
4.0
3.1
UV/DOC
1.8
1.4
1.4
1.3
1.8
1976
DOC
ppm
5.0
4.0
3.8
3.7
2.1
UV(254 nm)
en"1
9.1
5.5
5.6
5.3
4.0
UV/DOC
1.8
1.4
1.4
1.4
1.9
April-July 1977
DOC
ppm
3.6
2.9
2.6
2.3
0.9
UV(254 nm)
m-1
6.1
3.2
1.8
1.6
1.4
UV/DOC
1.7
1.0
1.0
0.7
1.6
CO
ro
01
-------
TABLE 37. GEOMETRIC MEAN VALUES OF BACTERIAL COUNTS
FOR THE MOLHEIM, GERMANY (DOHNE) PLANT
USING OZONE182
Sampling place
Raw water (Ruhr)
After flocc + sedim
After filtration
After act carbon
After ground passage
* M = geometric mean
** °q = geometric standard
Tntal
v
14,490
2,340
6,010
3,700
27
deviation
Bacteria
count/ml
a **
g
2.0
4.2
4.9
4.0
2.3
E-Coli/10
v
1,620
6.7
«1
«1
«1
Oml
a **
g
1.7
3.2
__
_
_.._,
TABLE 38. PERFORMANCE OF BIOLOGICAL ACTIVATED CARBON
FILTERS. MEAN VALUES FOR 6-MONTH OPERATION
AFTER A 3-MONTH STARTING PERIOD (DOHNE PILOT
PLANT, MIJLHEIM, GERMANY182
Activated carbon
type
LSS
LSS
ROW
ROM
NK12
F400
BKA
bed depth
(m)
2.5
5.0
2.5
5.0
2.5
2.5
2.5
ADOC
mg/1
0.92
1.69
1.09
1.59
0.99
1.26
1.00
Ainorg C
mg/1
0.83
0.96
0.97
1.05
1.36
1.11
0.97
ANH4
mg/1
1.31
1.34
1.31
1.34
1.28
1.32
1.28
A02
mg/1
6.32
6.67
6.49
6.71
6.03
6.95
5.99
327
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Rouen-la-chapel1e» France
At the 50,000 cu m/day (13.2 mgd) plant at la Chapelle St. Etienne de
Rouvray in Seine Maritime (west of Paris near the Atlantic Ocean), well
waters drawn from near the Seine contain 2 to 3 mg/1 of ammonium ion, 0 to
0.2 mg/1 of manganese, various micropollutants [detergents, phenols, Sub-
stances Extractable With Chloroform (SEC), etc.] and are practically devoid
of dissolved oxygen. Since 1968, the ammonia content of the raw water has
risen from an average of 0.3 mg/1 to an average of 2.6 mg/1. This increase
required that the treatment process be improved. Breakpoint chlorination
was discarded because it would have required very large contact chambers
(close to 7,000 cu m).
After three years of piloting, the following process was developed,
was installed and began operating in early 19761®1:
• Pre-ozonation (0.7 mg/1) for Mn and organics oxidation plus
adding dissolved oxygen
t Filtration through quartz sand
t Filtration through BAC
• Ozonation for disinfection (1.4 mg/1)
• Post-chlorination (0.4 to 0.5 mg/1)
Any residual ozone remaining from the pre-ozonation step will be
decomposed to oxygen when it enters the carbon column, providing further
quantities of DO for the bacteria. This single operation of pre-ozonation
assures the following:
• oxygen demands of the materials in water are satisfied,
• water is oxygenated,
• complex, biorefractory molecules are broken down and become
biodegradable,
t the content of various micropollutants is lowered,
• manganese is oxidized and precipitated, to be retained on the
sand filter so that it does not block adsorption sites on the
biological activated carbon.
Initial nitrification is observed in the sand filters. Periodic back-
washing of these sand filters to remove oxides of manganese does not upset
the action of these bacteria. Similarly, bacterial activity on the
activated carbon columns is not displaced during backwashing.
328
-------
This plant began operating in February, 1976 and showed the performances
listed in Table 39 for the first year of operation. The average performance
for the first several months of 1977 are stated to be superior to those for
the same period of 1976181.
TABLE 39. ROUEN-LA-CHAPELLE (FRANCE) PLANT
OPERATIONAL DATA (1976)181
Turbidity
Ammonia
(mg/1 NH/)
Mn (mg/1)
detergents
mg/1 DBS
phenols
(microg/1)
SEC (microg/1)
Subs. Extble
w/cyclohexane
Raw
Water
4
1.80
0.15
0.12
6.5
590
1,335
Pre-
ozoni-
zed
-
1.80
0.07
0.09
4.0
470
740
Filtered
(sand &
carbon)
-
0.40
0.04
0.06
1.5
250
535
Post-
ozoni-
zed
2
0.26
0.02
0.03
0
150
410
% Elimination
—
86%
87%
75%
100%
75%
69%
av. NH^> content of raw water: 0.3 mg/1 in 1968
2.6 mg/1 in 1975
A second French plant, Morsang-sur-Seine (east of Paris), also is
piloting a similar biological activated carbon process200. Performance
data were not yet available as this report was being written.
SUMMARY & RECOMMENDATIONS FOR BAG OPERATION
Activated carbon columns were installed in West German drinking water
treatment plants about 20 years ago, primarily for dechlorination but also
for taste and odor removals. Today carbon still is used for taste & odor
removal, but this is no longer as important a useage because when the water
treatment process is optimized to lower the concentration of total dissolved
organic materials or for lowering the concentration of chlorinated
organics, tastes & odors are also fully eliminated183.
For taste & odor elimination only, filtration rates through activated
carbon can be as high as 30 m/hour. For removing chlorinated organics,
329
-------
however, 2 to 3 times longer contact times are required, and under such
circumstances competitive adsorption processes must be considered201'202.
Carbon quantities necessary for DOC removal are reduced by at least a
factor of 10 upon preozonation of the water. Chlorine has an identical
oxidizing effect, but rapidly loads the carbon filter with chlorinated
organics, requiring more frequent regeneration of the carbon.
Dosages of ozone normally applied in drinking water treatment plants
for effective removal of organics and of ammonia via biological activated
carbon columns vary from 1 to 5 mg/1 . Dosages of ozone applied to treated
municipal wastewater at Cleveland Regional Sewer District prior to biological
activated carbon are 5 mg/1203.
For optimum pollutant removals, activated carbon bed depths should be
4 to 5 meters (13 to 16 feet) in depth, although columns half this height
also are effective. Contact times of ozonized water in the beds should be
at least 15 minutes (empty bed contact time), preferably 20 to 30 minutes.
Carbon quantities should be sufficient to allow for sudden but temporary
surges in pollutant concentrations. Dissolved oxygen in the effluent
should be at least 2 mg/1 and preferably above 3.5 mg/1. This will guarantee
sufficient DO to insure optimal bacterial activity within the carbon columns.
Eberhardt205 suggests using the following formula when designing a
biological activated carbon column for removal of dissolved organic carbon:
IP = ADOC(VF)/Np
where: IF = length of carbon column
Vp = velocity of water flow (m/hr)
NF = specific filter efficiency (g/cu m/hr) 187
(conservatively, assume 1 to 5 for BAC)
ADOC = desired reduction of DOC concentration by the
filter, in g/cu m
If the DOC of the water influent to the BAC column is assumed to be 4
g/cu m, and the DOC of the product is desired to be 1, then ADOC is:
ADOC =4-1=3 g/cu m (mg/1 )
If the rate of flow through the column is selected to be 10 m/hr and Hf =
1, then: ""
= 3 x 10/1 = 30 meters
and for Np = 4:
IP = 3 x 10/4 = 7.5 meters
330
-------
Similarly, if the rate of flow through the column is selected to be 3
m/hr, then for Nr = 1:
IP = 3 x 3/1 =9 meters,
and for Np = 4:
lp = 3 x 3/4 = 2.25 meters.
The single carbon column 9 meters in height can be divided into 2
columns, each 4.5 meters in height, with aeration in between (to provide
additional dissolved oxygen for added efficiency in the second column.
This equation does not contain a factor relating to the dissolved
oxygen content of the influent or the effluent stream, and consideration is
not given to parameters which may affect nitrification. It is advisable187
that dissolved oxygen concentrations of the carbon column effluent be main-
tained above 2.0 mg/1 (preferably above 3.5) and that column detention
times of 20 to 30 minutes be provided.
For slow sand filters to provide the same efficiency of COD removal (3
g/cu m), filter volumes 50 to 100 times larger are required172. For slow
sand filters:
NF = 0.02 g DOC/cu m of sand/hr.
If insufficient oxygen is being supplied to the bacteria for the
dissolved carbon to be converted, more oxygen should be introduced just
before the carbon column. This can be accomplished by aeration, by oxygena-
tion, or by increasing the ozone dosage. Specific oxygenation approaches
to be used will depend upon the local circumstances, such as organic type
and content of the raw water, whether or not a filter is used after ozonation
but before the carbon column, etc.
DOC of the influent stream to the carbon column should be monitored as
should that of the effluent. In addition, the effluent stream should be
monitored for inorganic carbon (carbon dioxide) produced by the biological
action. Such monitoring will provide a carbon mass balance which will
assure that the operation of the column is proceeding as desired.
With those raw waters which contain dissolved chlorinated organics, or
process waters which have been treated by chlorine during the early process
stages, the carbon column influent and effluent also should be monitored
for Total Organic Chlorine. In addition, the carbon itself should be
analyzed periodically for adsorbed organic chlorine193'191"195. These
analyses will indicate breakthrough of chlorinated organics and the need
for regeneration of the carbon.
When regenerating spent BAC, about 20% of the column charge should be
left in place, so as to allow the full nitrifying biological activity of
the recharged carbon to be re-attained in a period of time shorter than the
90 days required for fresh carbon.
331
-------
Virgin carbon charges used for biological removal of ammonia should be
treated with small doses of ammonium salts until the nitrifying bacteria
develop their full activities. Ammonia content before and after the column
should be monitored.
Different water pretreatment techniques practiced at different plants
require that biological activated carbon pilot studies be performed at each
plant so as to determine the optimum column design, carbon type and operating
parameters.
Biological Activated Carbon columns, properly designed and operated,
can greatly extend the period of carbon column performance. At present, in
the absence of chlorinated organics, properly designed and operated BAG
columns can be expected to operate effectively for periods of at least 1 to
2 years without requiring regeneration. In the presence of chlorinated
organics, however, breakthrough of these halogenated materials will occur
sooner, and require the carbon to be regenerated at that time. Plants
using breakpoint chlorination before the BAG can expect to have to reactivate
BAG every 6 to 8 weeks. With lesser quantities of halogenated organics
present, longer useful lives can be expected, but never as long as in the
absence of halogenated organics.
BAG columns used for treating drinking water should be backwashed from
time to time, when head loss increases (about once per week). The Rouen-
la-Chapelle plant in France backwashes the BAG beds once per month201*.
Particles of some carbons have been found to stick together, as a result of
bacterial action. In such cases, air scouring before water backwashing has
overcome this problem187. Other carbons may need such aeration at lesser
frequencies during backwashing, to break up clumps which may have formed.
332
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334
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as Model Compounds in Chlorine Dioxide Bleaching", Tappi 48(l):60-64
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155. Zienus, R.H. & Purves, C.B., "Degradation of Pectic Acid by Some
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344
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156. Scherle, C., Bull. Inst. Textile de France 41:21-43 (1953).
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160. Rosenblatt, D.H., Hayes, A.J., Jr., Harrison, B.L., Streaty, R.A. &
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162. Fuchs, W. & Leopold, H., Brennstoff Chem. 8:101 (1927).
163. Mallevialle, J., "Ozonation des Substances de Type Humique dans les
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(1976), p. 262-270.
164. Love, O.T., Jr., Carswell, J.K., Miltner, R.J. & Symons, J.H., "Treatment
for the Prevention or Removal of Trihalomethanes in Drinking Water",
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and Other Trihalomethanes", U.S. Environmental Protection Agency,
Water Supply Research Division, Cincinnati, Ohio, 1976.
165. Vilaginds, R., Monteil, A., Derreumaux, A. & Lambert, M., "A Comparative
Study of Halomethane Formation During Drinking Water Treatment by
Chlorine or Its Derivatives in a Slow Sand Filtration Treatment Plant
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Water Works Assoc., Anaheim, Calif., May 8, 1977.
166. Rice, R.G., Miller, G.W., Robson, C.M. & KUhn, W., "Biological Activated
Carbon", in Carbon Adsorption, P. Cheremisinoff & F. Ellerbusch,
editors, Ann Arbor Science Publishers, Inc., Ann Arbor, Michigan
(1978).
167. McCreary, J.J. & Snoeyink, V.L., "Granular Activated Carbon in Water
Treatment", J. Am. Water Works Assoc. 69(8):437-444 (1977).
168. Guirguis, W.A., Melnyk, P.B. & Harris, J.P., "The Negative Impact of
Industrial Waste on Physical-Chemical Treatment", presented at 31st
Purdue Indl. Waste Conf., Lafayette, Indiana, May, 1976.
169. Directo, L.S., Chen, C.-L. & Kugelman, I.J., "Pilot Plant Study of
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2081-2098 (1977).
345
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170. Monsitz, J.T. & Ainesworth, L.D., "Detection and Control of Hydrogen
Polysulfide in Water", Public Works 101:113 (1970).
171. Carswell, J.K., U.S. Environmental Protection Agency, Cincinnati,
Ohio, Private Communication, 1977.
172. Eberhardt, M., Madsen, S. & Sontheimer, H., "Untersuchungen zur
Verwendung Biologisch Arbeitender Aktivkohlefilter bei der Trink-
wasseraufbereitung", Heft 7, Verflffentlichungen des Bereichs u. des
Lehrstuhls fur Wasserchemie Leitung: Prof. Dr. H. Sontheimer; Univ.
Karlsruhe, Germany (1974); also Wasser/Abwasser 116(6):245-247 (1975).
173. Sontheimer, H., "Biological Treatment of Surface Waters in Activated
Carbon Filters", presented at Seminar on Current Status of Wastewater
Treatment & Disinfection With Ozone, Cleveland, Ohio, Sept. 15, 1977.
Intl. Ozone Inst., Cleveland, Ohio.
174. KOhn, W., Sontheimer, H. & Kurz, R., "Use of Ozone and Chlorine in
Water Works in the Federal Republic of Germany", in Ozone/Chlorine
Dioxide Oxidation Products of Organic Materials, R.G. Rice & J.A.
Cotruvo, editors, Intl. Ozone Inst., Cleveland, Ohio (1978), p. 426-
441.
175. Guirguis, W.A., Jain, J.S., Hanna, Y.A. & Srivastava, P.K., "Ozone
Application for Disinfection in the Westerly Advanced Wastewater
Treatment Facility", in Forum on Ozone Disinfection, E.G. Fochtman,
R.G. Rice & M.E. Browning, editors. Intl. Ozone Inst., Cleveland,
Ohio (1977), p. 363-381.
176. Guirguis, W.A., Cooper, T., Harris, J. & Ungar, A., "Improved Performance
of Activated Carbon by Preozonation", presented at 49th Ann. Conf.
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Poll. Control Fed. 50(2):308-320 (1978).
177. Scheidtmann, W., "Investigations of the Optimization of Pretreatment
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98-111.
178. Schalekamp, M., "Use of Activated Carbon in the Treatment of Lake
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179. Van Lier, W.C., Graveland, A., Rook, J.J. & Schultink, L.O., "Experiences
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346
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180. Van Der Kooij, D., "Some Investigations Into the Presence and Behaviour
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Special Problems of_ Water Technology. Vol. 9_ -_ Adsorption, op. cit.,
p. 348-354.
181. Cornelia, C. & Versanne, D., "Le Role de 1'Ozone dans la Nitrification
Bacterienne de 1'Azote Ammoniacal -- Cas de 1'Usine de la Chapelle
Banlieue Sud de Rouen (Seine Maritime) France". Presented at 3rd
Intl. Symp. on Ozone Techno!., Paris, France, May 1977. Intl. Ozone
Inst., Cleveland, Ohio.
182. Sontheimer, H., Heilker, E., Jekel, M., Nolte, H. & Vollmer, F.-H.,
"The MUlheim Process - Experience With a New Process Scheme for
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184. Guirguis, W.A., Hanna, Y.A., Prober, R., Meister, T. & Srivastava,
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Materials, R.G. Rice & J.A. Cotruvo, editors. Intl. Ozone Inst.,
Cleveland, Ohio (1978), p. 291-301.
185. Wachs, A., Narkis, N. & Schneider, M., "Organic Matter Removal From
Effluents by Lime Treatment; Ozonation and Biologically Extended
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Technology, Paris, France, May 1977. Intl. Ozone Inst., Cleveland,
Ohio.
186. Hopf, W., "Versuche mit Aktivkohlen zur Aufbereitung des DUsseldorfer
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187. Sontheimer, H., Univ. Karlsruhe, Germany, Private Communication, 1977.
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189. Robert, A., Degremont, Reuil Malmaison, France. Private Communi-
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347
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191. Kdhn, W. & Fuchs, F., "Untersuchungen zur Bedeutung der Organischen
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192. Kfllle, W., Sontheimer, H. & Steiglitz, L., "Eignungsprdfung von
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193. KUhn, W. & Sontheimer, H., "Einige Untersuchungen zur Bestimmung von
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194. KUhn, W. & Sontheimer, H., "EinflUss Chemischer Umsetzungen auf die
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195. KUhn, W. & Sontheimer, H., "Zur Analytischen Erfassung Organischer
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196. Ktlhn, W., "Untersuchungen zur Bestimmung von Organischen Chlorverbin-
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197. WtJlfel, P. & Sontheimer, H., "Ein Neues Verfahren zur Bestimmung von
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198. Poggenburg, W., Wasserwerk DUsseldorf, Germany. Private Communication,
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199. Klotz, M., Werner, P. & Schweisfurth, R., "Investigations Concerning
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200. Richard, Y. & Fiessinger, F., "Emploi Complementaire des Traitments
Ozone et Charbon Actif", presented at 3rd Intl. Symp. on Ozone Technol.,
Paris, France, May, 1977. Intl. Ozone Inst., Cleveland, Ohio.
201. Weber, W.J., Jr. & Morris, J.C., "Adsorption in Heterogeneous Aqueous
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202. Koppe, P., "Untersuchungen Uber die Konkurrierende Adsorption an
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203. Hanna, Y.A., Meister, T. & Slough, J., Jr., "Ozone As a Pre-Treatment
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348
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204. Le Pauloue1, J., Trailigaz, Garges-les-Gonesse, France. Private
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205. Eberhardt, M., "Experience with the Use of Biologically Effective
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349
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BIBLIOGRAPHY
In this section we are listing as much of the published literature
dealing with the use of ozone and of chlorine dioxide in treating drinking
water as was possible to gather during the study period.
For convenience of the reader, we have listed these literature
references in three separate sections entitled:
• Technical Articles, Ozone in Drinking Water Treatment
(pages 351-367).
• Technical Articles, Chlorine Dioxide in Drinking Water
Treatment (pages 368-372).
• Technical Articles, Organics in Drinking Water
(pages 373-384).
Each section of this bibliography contains references listed alphabeti-
cally by the last name of the senior author.
350
-------
Technical Articles—Ozone/Drinking Water
Anon., "Ozone Treatment Licks Color Problem", Water & Sewage Works, (April,
1975), p. 52-54.
Anon., "Ozonation of drinking Water", Societ§ Industrielle du Traitement
des Liquides et des Gaz. 31:1347 (1958).
Anon., "Ozonation", U.S. Department of Agriculture, Beltsville Md. Farmers
Bulletin No. 2248, page 12.
Anon., "Watchgate Treatment Works", British Water Supply 9:7-12 (1972)
Manchester, England.
Anon, "Pollution of the Rhine and the Abstraction of Drinking-water," JAWR
Memorandum, May (1973). Engler-Bunte Inst., Univ. Karlsruhe, Federal
Republic of Germany.
Axt, G., "Uber ein indirektes Verfahren zur Wasserozonisierung und dessen
apparative und physikalisch-chemische Grundlagen". Vom Wasser 25:93-
106 (1958).
Bartuska, J. F., "Ozonation at Whiting, Indiana", J. Am. Water Works Assoc.
33(11):2035-2050 (1941).
Bartuska, J. F., "Ozonation at Whiting (Indiana): 26 years Later" Public
Works, (Aug. 1967).
Bays, L.R., Burman, N.P. and Lewis, W.M., "Taste and Odour in Water
Supplies in Great Britain: A Survey of the Present Position and
Problems for the Future". Water Treatment and Examination. 19(2):
136-160 (1970).
Bean, E.L., "Taste and Odor Control at Philadelphia", J. Am. Water Works
Assoc. 49:205-216 (1957).
Benedek, A., "The Effect of Ozone on Activated Carbon Adsorption-A
Mechanistic Analysis of Water Treatment Data", presented at Symp. on
Advanced Ozone Technol., Toronto, Ontario, Canada, November, 1977.
Intl. Ozone Inst., Cleveland, Ohio.
Berger, K.V., "Uber den Betrieb der Ozonanlage Kdnizberg der Wasserver-
sorgung Bern", Wasser-Abwasser 105(48):1338-1343 (1964).
351
-------
Bernier, M. "Sterilisation par 1"ozone des Eaux d'alimentation de la ville
de Nice et des Communes du Littoral". La Technique Sanitaire et
Municipale, 45:117 (1950).
Black, A.P. and Christman, R.F., "Chemical Characteristics of Fulvic Acids",
J. Amer. Water Works Assoc. 55:897-912 (1963).
Blankenfeld, D., "Keimfreies Wasser durch Ozonanlagen", CZ-Chemie-Technik
l(ll):527-528 (1972).
Blazejewski, M., "The Necessity of Using Ozone for Drinking Water in Poland",
Gaz, Wada Tech. Sanit., (3)50: (1976).
Bollyky, J., "Ozone Provides Powerful Disinfectant for Water", Water &
Sewage Works, 123:66-67 (1976).
Botzenhart, K., "Effects of Ozone on Microorganisms", Presented at Intl.
Symp. on Ozone & Water, Wasser Berlin, May 1977. Intl. Ozone Inst.,
Cleveland, Ohio.
Bouchard, J.C., "Ozone for Water Treatment", The Municipal Utilities
Magazine 93(5):58-9, 73-4 (1955).
Bouchard, J.C., "Twenty Years of Ozone in the Treatment of Potable Waters",
in Proc. Sec. Intl. Symp. on Ozone Technology, R. G. Rice, P. Pichet
& M.-A. Vincent, Editors, Intl. Ozone Inst., Cleveland, Ohio (1976),
p. 705-714.
Boucher, P.L., "Micro-Straining and Ozonization of Water and Wastewater",
Proc. 22nd Industrial Waste Conf., Purdue Univ., Engrg. Extn. Ser. No.
129:771-787 (1967)
Bryant, A. A., "Saving Money With Pre-pilot Plant Studies. Water and
Sewage Works (April 1976), p. 72-75.
Buydens, R. and G. Fransolet, "Etudes et Memoires 1'Action de Tozone sur
le chlore, le bioxyde de chlore et le chlorite contenus dans les eaux
traitees," Tribune du Cebedeau, 326:4-6, (January 1971).
Buydens, R., "La Reviviscence Microbienne dans les Eaux et, Particuliere-
ment, dans les Eaux OzonSes", Tribune du Cebedeau 25(338):3-9 (1972).
Buydens, R., "L'ozonation et ses repercussions sur le mode d'epuration des
eaux de rivieres", Tribune du Cebedeau, 319-320:286-291 (1970).
Campbell, R.M., "The Use of Ozone in the Treatment of Loch Turret Water".
J. Inst. Water Engrs. 17:333-346 (1963).
Cerkinskij, S.N. and N. Trahtman, "The Present Status of Research on the
Disinfection of Drinking Water in the USSR", Bull. WHO 46(2):277-283
(1972).
352
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Chedal, J. "Effect of Ozone on Micropollutants", in Forum on Ozone
Disinfection, E. Fochtman, R.G. Rice & M.E. Browning, editors. Intl.
Ozone Inst., Cleveland, Ohio (1970) p. 178-185.
Chedal, J. "Modes of Disinfecting Action of Ozone", Presented at Intl. Symp.
on Ozone & Water, Wasser Berlin, May 1977. Intl. Ozone Inst.,
Cleveland, Ohio
Chian, E.S.K., P.P.K. Kuo, "Fundamental Study on the Post Treatement of RO
Permeates from Army Wastewaters", Sec. Annual Summary Rept. U.S. Army
Medical R & D Command, Washington, D.C., Rept. No. UILU-ENG-76-2019,
Oct. 1976.
Cheremisinoff, P.N., F. Valent, D. Wright, R. Fortier and J. Magiliaro,
"Potable Water Treatment: Technical and Economic Analysis. Chapt. 3,
Water and Sewage Works 123(5):7073 (1976).
Coin, L., C. Hannoun & C. Cornelia, "Inactivation of Poliomyelitis Virus by
Ozone in the Presence of Water", la Presse Med. 72(37):2153-56 (1964).
Coin, L., C. Gomella, C. Hannoun & J.C. Trimoreau, "Ozone Inactivation of
Poliomyelitis Virus In Water", la Presse Med. 75(38):1883-84 (1967).
Cromley, T.J. & J.T. O'Connor, "Effect of Ozonation on the Removal of Iron
From a Ground Water:, J. Am. Water Works Assoc. 68:315-319 (1976).
Dahi, E., "Impact of Ultrasonic Disaggregation of Microorganisms in Ozone
Water Sterilization Methods". Presented at 3rd Intl. Symp. on Ozone
Technol., Paris, France, May, 1977, Intl. Ozone Inst., Cleveland, Ohio.
Damez, F., "Neuilly-sur-Marne/Nosy-le-Grand", in Forum on Ozone Disin-
fection, E. Fochtman, R.G. Rtce & M.E. Browning, editors, Intl. Ozone
Inst., Cleveland, Ohio (1977) p. 306-311.
Dellah, A., "Study of Ozone Reactions Involved in Water and the Present
Chiorination Controversy", Sec. Intl. Symp. on Ozone Technol., R.G.
Rice, P. Pichet, and M.-A. Vincent, editors, Intl. Ozone Inst., Cleve-
land, Ohio (1975), p. 161-168.
Dellah, A., "Ozonization at Charles-J. Des Baillets Water Treatment Plant",
in Proc. Sec. Intl. Symp. on Ozone Techno!., R. G. Rice, P. Pichet &
M.-A. Vincent, editors, Intl. Ozone Inst., Cleveland, Ohio (1976), p.
715-725.
Diaper, E.W.J., "Microstraining and Ozonation of Water and Wastewater",
Water and Wastes Engrg., p. 56-58 (1968).
353
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Dobia, 0, and F. Starz, "Ozone Application in Small Potable Water Supply
Plants", Presented at Intl. Symp. on Ozone & Water, Wasser Berlin, May
1977. Intl. Ozone Inst., Cleveland, Ohio.
Drobek, W., "Ozom'sierung Des Trinkwassers", Arch. Badewesens (16)4:98-101
(1963).
Dyachkov, A.V., "Recent Advances in Water Disinfection". Presented at
Sept. 1976 Water-Meeting, Amsterdam, Holland, pp. Gl-68.
D'Yakov, V.I., "Organization and Sanitary-Hygienic Evaluation of the Drinking
Water Supply of Oil & Gas Regions of the Northern Ob. Area", Gig. y
Sanit. 37(10):95-96 (1972).
Evison, L.M., "Disinfection of Water With Ozone: Comparative Study With
Entero Viruses, Phage and Bacteria". Presented at 3rd Intl. Symp. on
Ozone Technol., Paris, France, May 1977. Intl. Ozone Inst., Cleveland,
Ohio.
Falk, H.L. and J.E. Moyer, "Ozone As a Disinfectant of Water", in Ozone/
Chlorine Dioxide Oxidation Products of Organic Materials, R.G. Rice, &
J.A. Cotruvo, editors. Intl. Ozone Inst., Cleveland, Ohio, (1978).
p. 38-57.
Fontalirant, F., M. Pare & J. Guiblais, "Un Exemple De Regulation Automatique
de la Production D'Ozone L'Usine de Nantes-La-Roche", Presented at 3rd
Intl. Symp. on Ozone Techno!., Paris France, May, 1977. Intl. Ozone
Inst., Cleveland, Ohio.
Furgason, R. and R. 0. Day, "Iron and Manganese Removal with Ozone, Pt. I,"
Water and Sewage Works, June 1975, 42, 45-47; Part II, ibid., July,
1975, p. 61-63.
Gabovich, R.D., K.K. Vrochinskii and I.L. Kurinnyi, "Decoloration, Dedoration
and Decontamination of Drinking Water By Ozone", Gig. y Sanit. 34(6):18-
22 (1969).
Gabovich, R. D., G. G. Rudenko, and M. A. Chaikovskaya, "Ozonization of
Dnieper Water", Gig. y Sanit. 36(10):16-21 (1971).
Gad, G. & Columbus, C., "Chemische Auswirkung der Wasserozonisierung",
Health Engineer 76:268-9'(1955).
Gagnaux, A., "Aspects Techniques du Traitement des Eaux par 1'Ozone",
p. 435-444, year and publication unknown.
Giebler, G. and Koppe, P., "Methode Zur Bestimmung der Wirkung des Ozons bei
der Aufbereitung von Wasser", Wasser-Abwasser 106(8):215-219 (1965).
354
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Glaze, W.H., R. Rawley, F. Huang, and S. Lin, "Ozone and Ozone/UV Destruc-
tion of Tribalomethane Precursors and other Refractory Organic Compounds
in Water", presented at Symp. on Advanced Ozone Technol., Toronto,
Ontario, Canada, November, 1977. Intl. Ozone Inst., Cleveland, Ohio.
Glaze, W.H., R. Rawley and S. Lin, "By-Products of Organic Compounds in the
Presence of Ozone and Ultraviolet Light: Preliminary Results", in
Ozone/Chlorine Dioxide Oxidation Products of Organic Materials", R.G.
Rice, & J.A. Cotruvo, editors, Intl., Ozone Inst., Cleveland, Ohio,
(1978). p. 321-331.
Gomel la, C., "Ozone Practices in France", J. Am. Water Works Assoc.
64(1):39-45 (1972).
Cornelia, C., "DifficultSs de TAffinage des Eaux Dues aux Micropolluants",
Chimie and Industrie, Genie Chimique, 104(13):1633-1642 (1971).
Cornelia, C., "L'Ozonation Vraie et TAffinage des Eaux Potables," Sci.
Progr. la Nature 3409:161-6 (1969).
Cornelia, C., "Pollutions and Micropollutions of Surface Water, Technical
and Economic Difficulties In the Production of Drinking Water", 1'Eau
55(2):67-73 (1968).
Gomella, C., & D. Versanne, "The Function of Ozone in Bacterial Nitri-
fication of Ammonia Nitrogen - The Plant of la Chapel!e at Saint-
Etienne-du-Rouvray (Seine Maritime-France). Presented at 3rd Intl.
Symp. on Ozone Technol., Paris, France, May 1977. Intl. Ozone Inst.,
Cleveland, Ohio.
Gomella, C., "Utilization of Ozone When Treating Potable Water in France",
Presented at Intl. Symp. on Ozone & Water, Wasser Berlin, May 1977,
Intl. Ozone Inst., Cleveland, Ohio.
Grad, B.R., M. Gagnon, R. Charbonneau and C. Doggenweiller, "The Effect of
Ozone on Ehrlich Adenocarcinoma Cells in Vitro", in Proc. Sec. Intl.
Symp. on Ozone Techno!., R.G. Rice, P. Pichet & M.-A. Vincent, editors.
Intl. Ozone Inst., Cleveland, Ohio, (1975) p. 465-471.
Gubelmann, H.V., "Bau der Filter- und Ozonanlage Kdnizberg der Wasserver-
sorgung Bern", 35(12):311-327 (1955).
Gubelmann, H.V., and H. Scheller, "Desinfektion des Wassers durch Ozone",
Montasbull Schweiz Verein von Gas - und Wasserfachmclnnern, 33:99-107
(1953).
Guillerd, J. and R. Leviel, "Quelques Aspects du Traitement des Eaux Potables
en France" TEau 48:138-142 (1961).
Guillerd, J. and C. Valin, "Traitment Par 1'Ozone", TEau 48:138-142 (1961).
355
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Hallopeau, J., "Ozonation", General Report No. 4, International Water
Supply Congress and Exhibition on Water. Stockholm, Sweden, June
1964.
Hann, V., "Water Quality Improvement With Ozone", Engineering News Record.
139(54):125-127 (1947).
Hann, V., "Disinfection of Drinking Water With Ozone", J. Am. Water Works
Assoc. 48(10):1316-20 (1956).
Hann, V., "Ozone Purification of Water". Tappi 35(9):394-397 (1952).
Hann, V., "Ozone Treatment for the Removal of Taste, Odor and Color from
Water," J. New England Water Works Assoc., (Sept. 1947),
Harris, W.C., "Ozone Disinfection", J. Am. Water Works Assoc. 64(3):182-83
(1972).
Harris, W. C., "Practical Considerations of Ozone in Water Treatment",
Presented at Symposium on New Trends in Water and Sewage Treatment
Using Pure Oxygen and Ozone, Denver, Colo., Oct. 12, 1974.
Harris, W., "Ozone Disinfection of the Strasburg, Pennsylvania Water Supply
System", in Proc. 1st Intl. Symp. on_ Ozone for Water &^ Wastewater
Treatment, R.G. Rice, & M.E. Browning, editors, Intl. Ozone Inst.,
Cleveland, Ohio (1975), p. 186-193.
Heinonen, E., "Use of Ozone in Treatment of Raw Water Affected by Effluents
From the Paper Making Industries". Presented at 3rd Intl. Symp. on
Ozone Technol., Paris, France, May, 1977. Intl. Ozone Inst., Cleve-
land, Ohio.
Hill, A.G. and J.B. Howell, "Compression of 03/02 and 03/Air Gas Mixtures",
Presented at Symp. on Advanced Ozone TecnnoT., Toronto, Canada, November
1977. Intl. Ozone Inst., Cleveland, Ohio.
Hoehn, R.C., "Comparative Disinfection Methods", J. Am. Water Works Assoc.
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Proliferation Microbienne dans le RSseaux de Distribution d'Eau," Gas,
Wasser, Abwasser, 50(3):67-70 (1970).
Valenta, J., "Simultaneous use of Chlorine and Ozone in Water Treatment".
Gas, Wasser, Abwasser, S5(9):490-494 (1975).
Van Hoof, F., "Some Aspects of Ozone Toxicity", Presented at 3rd Intl.
Symp. on Ozone Technol., Paris, France, May, 1977. Intl. Ozone Inst.,
Cleveland, Ohio.
Vrochinsky, K. K., "Hygienic Problems of Ozonization of Water from the
North Donets—Donbas Canal," Gig. y Saint. 28(9):11-17 (1963).
Wallentin, A. and Nyberg, I., "Ozonbehandling av Zygnerns Vatten". Vatten-
hygien 2:38-52 (1962). In Swedish.
366
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Weil, L., B. Struif and K.E. Quentin, "Mechanisms of Ozone Degradation of
Organic Substances", presented at Intl. Symp. on Ozone & Water, Wasser
Berlin, May 1977. Intl. Ozone Inst., Cleveland, Ohio.
Weissenhorn, F.J., "Application of Ozone in a Closed Circuit", DUsseldorf,
Presented at Intl. Symp. on Ozone & Water, Wasser Berlin, May 1977.
Intl. Ozone Inst., Cleveland, Ohio.
Whitson, M.T., "The Treatment of Water by Ozone," J. Inst. Civil Engrs.,
London, 2:83-100 (1943).
Whitson, M.T., "Treatment of Water by Ozone". The Surveyor 103:111-112
(1944).
WUrster, E. and Werner, G., "Die Leipheimer Versuche zur Aufbereitung von
Donauwasser", Z. fUr Gas-und Wasserfach 112:193 (1971).
Zeff, 0. D., Final Rept No. 1401 of Contract DADA 17-73C-3138, "UV-Ozone
Water Oxidation/Sterilization Process," U.S. Army Medical R & D Com-
mand, Washington, D.C., Sept. 1974.
367
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Chlorine Dioxide Articles ~ Drinking Water
Adamski, H. and Hoffman, W., "Z praktyki zwalczania fenoli w wodzie na
stacji wodociagowei Pomorzany w Szczecinie". Gas, Woda I Technika
Sanitarna, 34:154 (1960). (In Polish)
Anon., "Water Quality and Treatment—A Handbook of Public Water Supplies,"
Am. Water Works Assoc., 3rd. ed. (1971), Pages 181, 547-550.
Anon., "Treatment of Water Supplies with Chlorine Dioxide (CIO,,), 01 in
Water Services Co., Stamford, Conn., March, 1976.
Aston, R. N. and J. F. Synan, "Chlorine Dioxide as a Bactericide in Water
Works Operation". J. New England Water Works Assoc. 62:80-94 (1948).
Atkinson, J. W., "The Control of Taste in the River Dee Supply of the West
Cheshire Water Board," Water & Water Engrg., pp. 146-149 (April,
1962).
Augenstein, H. W., "Use of Chlorine Dioxide to Disinfect Water Supplies,
J. Am. Water Works Assoc. 66:716-717 (1974).
Bays, L. R.., N. P. Burman and W. M. Lewis, "Taste and Odour in Water
Supplies in Great Britain: A Survey of the Present Position and
Problems for the Future", Water Treatment and Examination 19(2):136-
160 (1970).
Bean, E. L., "Taste and Odor Control at Philadelphia", J. Am. Water Works
Assoc. 49:205-216 (1957).
Bernardi, M. A., B. A. Israel, V. P. Olivieri and M. L. Granstrom "Efficiency
of Chlorine Dioxide as a Bactericide", Appl. Microbiol. 13(5):776-780
(1965).
Black, A. P. and R. F. Christman, "Chemical Characteristics of Fulvic
Acids", J. Am. Water Works Assoc. 55:897-913 (1963).
Bouille, S., "La Station de la Ville d'Alencon—Emploi du Bioxyde de Chlore
dans le Traitment des Eaux," L'Eau, 44(1): 3-8 (1957).
Buydens, R. and G. Fransolet, "L'action de 1'ozone sur le chlore, le
bioxyde de chlore et le chlorite contenus dans les eaux traitees,"
Tribune du Cebedeau, 326:4-6 (1971).
368
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Buydens, R. and G. Fransolet, "Le bioxide de chlore: sa synthese et
son comportement dans les eaux," Tribune du Cebedeau, 316:116-126
(1970).
Cardey, F., "Le Traitement des Eaux Residuaires Phenolees par le Chlore",
L'Eau 40:75 (1953).
Corson, B. I., "Chlorine Dioxide Licked Puzzling Tastes and Odors in Well
Supply". Water Works Engrg. 112:372-374 (1959).
Coote, R. "Chlorine Dioxide Treatment at Valparaiso, Ind"., Water
& Sewage Works, January, 1950, 13-16.
DeGroot, J. C. "Safe and Palatable Water at Northampton", Public Works,
79:36-37 (1948).
Derby, J. C., "Operating Experience with Chlorine Dioxide". J. New
England Water Works Assoc., 69(3):231-235 (1955).
Dowling, L. T., "Chlorine Dioxide In Potable Water Treatment," Water Treat-
ment and Examination, 23(2):190-204 (1974).
Draves, H. J. "Results at Michigan City, Indiana", Public Works, May
1948, p. 36-37.
DuByne, F. T., "Taste and Odor Problems of a Maumee River Supply", J. Am.
Water Works Assoc. 55:710-714 (1963).
Gallaher, W. U., Chloro-Phenol Tastes Removed", Public Works, May 1948,
p. 38.
Gibbons, M. M., "Experiences with Filtered River Water", Public Works,
May 1948, p. 38.
Granstrom, L. and G. Lee, "Generation and Use of Chlorine Dioxide in
Water Treatment," J. Am. Water Works Assoc., 50:1453-1466 (1958).
Harlock, R. and R. Dowlin, "Use of Chlorine for Control of Odors Caused
by Algae", J. Am. Water Works Assoc. 50:29-32 (1958).
Haynes, L., "Treatment of Industrial Water Pollution at Nitro and Charleston,
W. Va.", J. Am. Water Works Assoc. 49:309-312 (1957).
Hermanowicz, 0., I. Sikorowska and K. Bernacki, "Stosowanie dwutlenku chloru
do usuwania smaku i zapacha chlorofenoTi z wody w wodociagu w Szczeci-
nie," Gas, Woda i Technika Sanitarna 33:145-148 (1959) (in Polish).
Holluta, J. and Haberer, K., "Uber die Geruchsentwicklung bei der Chlordi-
oxydbehandlung phenolhaltiger Wasser", Wasser-Abwasser 98:552-555
(1952).
369
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Holluta, J. and U. Linger, "Die Keimtfltung von Bact. Coll Esch. durch Chlor-
dioxyd und Ozon". Vom Wasser 21:129-42 (1954).
Hopf, E., "Erfahrungen mit chlordioxid zur Trinkwasser-behandlung", Wasser-
Abwasser 108(30):852-854 (1967).
Ingols, R. S. and T. F. Craft, "Manganese Removal From Water Supplies", J.
Am. Water Works Assoc. 39:561-567 (1947).
Kabler, P. W., N. A. Clarke, 6. Berg and S. L. Chang, "Viricidal Efficiency
of Disinfectants in Water," Public Health Reports, 76(7):565-70, (July
1961).
Kretch, C. J. H., "Contemporary Chlorine Disinfection Practices in Ontario,
Canada," J. Am. Water Works Assoc. 68(4):197-201 (1976).
Lambert, M., and C. Bernard, "Disinfection of Urban Waste Water by Chlorine
and Chlorine Dioxide, TEau et T Industrie, Feb., 1977.
Melpas, J. F., "Disinfection of Water Using Chlorine Dioxide," Water Treat-
ment and Examination, 22(3):209-221 (1973).
Malpas, J. F., "Use of Chlorine Dioxide in Water Treatment," Effluent and
Water Treatment J., July 1965, p. 370-3.
Masschelein, W., "Progres de la chimie du bioxyde de chlore et ses applica-
tions," Part II. Chemie & Industrie-Genie Chimique, 97(3):346-354
(1967).
Masschelein, W., "Preparation of Pure Chlorine Dioxide", I & EC Prod.
Research and Dev. 6:137-142 (1967).
Masschelein, W., Spectrophotometric Determination of Chlorine Dioxide
With Acid Chrome Violet K", Anal. Chem. 38:(13)1839-1841 (1966).
Middlebrooks, E.J., "Taste and Odor Control", Water & Sewage Works, 1965,
p. R-122-R-134.
Misnakiewicz, W., J. Podkowka, A. Zajac-Chmielewska, "Badania nad dzialaniem
dwutlenku chloru na scieki zawierajace fenol," Gaz, Woda i Technika
Sanitarna, 32:252-256 (1958), (in Polish).
MUlheim, M. E.f "Versuche zur Geschmacksverbesserung von Trinkwasser mit
Chlordioxyd". Wasser-Abwasser 101(14):340-342 (1960).
Reichert, J. K., "Kanzerogene Substanzen in Wassen and Boden XXIII. Die
Enfernung polyzyklischer aromaten bei der Trinkwasseraufberitung durch
C109: Isolierung and identifizierung der 3,4-benzpyren-folge-produkte".
Arcfi Hyg. 152:265 (1968).
370
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Reichert, J. K., Kanzerogene Substanzen in Wasser and Boden XXI. Die
Entfernung Polyzyklischer, Aromaten bei der Trinkwasseraufbereitung
durch Chlordioxid: Quantative Befunde". Arch Hyg. 152:37 (1968).
Reissaus, K. & W. Rummel, "Wasseraufbereitung mit Ozon bei der Trink-
wasserschOnung 2. Mitteilung: Vergleichende Untersuchungen der Schdn-
nungwirkung von Ozon und Chlordioxid", Fortschr. Wasserchem, Grenzgeb.
6:139-159 (1967).
Ridenour, G. M. and Armbruster, E. H., "Bactericidal Effect of Chlorine
Dioxide" J. Am. Water Works Assoc. 41:537-550 (1949).
Ringer, W. C. & S. J. Campbell, "Use of Chlorine Dioxide for Algae Control
at Philadelphia", J. Am. Water Works Assoc. 47:740-746 (1955).
Rook, J. J., "Chlorination Reactions of Fulvic Acids in Natural Waters",
Environ. Sci. & Technol. ll(5):478-482 (1977).
Sikorowska, C., "Wptyw rodzaju zanieczyszczen wody na zapotrzebowanie
dwutenoku chloru". Gaz, Woda I Technika Sanitarna, 35:464 (1961). (in
Polish).
Simmons, P. D., "Chlorine Dioxide Treatment for Taste and Odor Control".
Waterworks Engrg. 100:1258-1259 (1947).
StSheli, Th., "L1utilisation pratique de bioxyde de chlore pour la steri-
lisation de 1'eau potable", Transl. from Monatsbull, Schweiz. Ver. Gas
U. Wasserfachm. 42:244-252 (1962).
Synan, J. F., J. D. MacMahon and G. P. Vincent, "Chlorine Dioxide-A New
Development in the Treatment of Potable Water", J. New England Water
Works Assoc., 58:264-269 (1944).
Synan, J. F., J. D. MacMahon, and G. P. Vincent, "Tastes and Odors Removed
by Chlorine Dioxide Treatment", Water Works Engrg. 98:192, 211-12
(1945).
Symons, J. M., "Chlorine Dioxide Use in the United States - January 1964
- From Municipal Water Facilities - Communities of 25,000 Population
and Over; U.S. Department of HEW, Public Health Service Publication
No. 661," U.S. Environmental Protection Agency, Water Supply Research
Division, Cincinnati, Ohio.
Toussaint, M., "Le bioxyde de chlore et le traitment des eaux potables,"
Centre Beige d1Etude et de Documentation des Eaux, May 1972, pp. 260-
266.
Valenta, J., "Simultaneous Use of Chlorine and Ozone in Water Treatment".
Gas, Wasser-Abwasser, 55(9):490-4 (1975).
371
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Valenta, J. and W. Gahler, "Chlordioxidanlage", Gas-Wasser-Abwasser
55(9):566-569 (1975).
Wallwork, J. F., M. Bentley and D. C. Symonds, "Identification of Phenols
In the River Test and Their Treatment With Chlorine Dioxide", Water
Treatment & Examination, Vol. 18 (1969).
Widemann, 0., "4 Jahre praktische Erfahrung mit Chlordioxyd," Vom Wasser,
24:50-70 (1957).
372
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Technical Articles -- Drinking Water/Organics
Ahmed, M. and Kinney, C. R., "Ozonization of Humic Acids Prepared from
Oxidized Bituminous Coal", J. Am. Chem. Soc. 72:559-561 (1950).
Am. Water Works Assoc., T & P Council Statement: "Organic Contaminants
in Drinking Water", Willing Water, December 1974. 3 p.
Arsovic, H. M.s and H. Burchard, "Ergebnisse und Neue Erkenntnisse zur
Oxidation von o-Chlorophenol mit Ozon, Unter Anwendung des ETIZON-
Verfahrens", Gesundheits-Ingenieur 98(9):230-239 (1977).
Balasubramanian, V. and V. Thiazarajan, "Chlorination of Substituted
Phenols With Chloramine T. A Kinetic Study", Intl. J. Chem. Kinetics
7:605-623 (1975).
Bauch, H., H. Burchard, & H. M. Arsovic, "Ozone as an Oxidative Dis-
integrant for Phenols in Aqueous Solutions". Gesundheit Ingenieur
91(9):258-262 (1970).
Bauch, H. and H. Burchard, "Investigations Concerning the Influence of
Ozone on Water with Few Impurities," Wasser Luft & Betrieb 14(7):270-
273 (1970).
Becker, E. S., J. K. Hamilton & W. E. Lucke, "Cellulose Oligosaccharides
as Model Compounds in Chlorine Dioxide Bleaching", TAPPI 48(1):60-
64 (1965).
Belevtzev, A. N. and Ju. L. Maximenko, "Studies on Oxidation Processes
of Cyanides and Phenols in Waste and Natural Waters by Using Chlorine
Dioxide," in Symposium pji Physical-Chemical Treatment for Municipal
and Industrial Sources, USA-USSR Working Group on the Prevention of
Water Pollution from Municipal and Industrial Sources, US/EPA, Cinci-
nnati, Ohio. pp. 105-110, November 12-14, 1975.
Bernatek, E. and A. N. Soteland, "Ozonolysis of Naphthoquinones III.
1,2-Naphthoquinone", Acta Chem. Scand. 16(8):2054-2056 (1962).
Bellar, R. A., J. J. Lichtenberg, and R. C. Kroner, "The Occurence of
Organohalides in Chlorinated Drinking Water" J. Am. Water Works
Assoc. 66(12):703-6 (1974).
373
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Block, J. C., M. Morlot, and J. M. Foliguet, "Problemes Lies i V Evolution
du Caractere d'Oxydabilite de Certains Corps Organiques Presents dans
TEau Traitee par 1'Ozone", TEAU 71(l):29-34 (1976).
Bollyky, L. J. "Reactions of Ozone With Trace Organics In Water and Waste-
water", Presented at the Univ. of Michigan Seminar on Viruses and
Trace Contaminants in Water and Wastewater, Jan. 1977. 43 pages.
Brooks, J. & 6. Shaw, "Ozone in the Chemical Industry. Ozone Reactions with
Saturated Organic Aliphatic Compounds", presented at Third Intl. Symp.
on Ozone Technol., Paris, France, May 1977. Intl. Ozone Inst.,
Cleveland, Ohio.
Buescher, L. A., J. H. Dougherty, and R.-T. Skrinde, "Chemical Oxidation
of Selected Organic Pesticides", J. Water Poll. Control Fed. 36(8):1005-
1014 (1964).
Bunn, W. W., B. B. Haas, E. R. Deane, and R. D. Kleapfer, "Formation of
Trihalomethanes by Chlorination of Surface Water." U.S. EPA, Region
VII; Kansas City, Kansas 66115. August 20, 1975.
Buydens, R., "Ozonation and its Effects on the Method of Purification of
River Waters", Trib. du Cebedeau 319-320:286-291 (1970),
Carlson, R. M., "Organic Compounds Produced During Wastewater Chlorination",
Seminar presented on the Symp. on the Identification and Transformation
of Aquatic Pollutants, Athens, Ga., April, 1974.
Chen, K. Y., and R. W. Okey, "Ozone Effect on Synthetic Rubber Waste Treat-
ment", Indl. Wastes, March/April 1977, pp. 47-49.
Cherkinskv:, S. N., and A. A. Korolev, "Comparative Assessment of the Efficacy
of Ozonization and Other Means of Treatment of Water Contaminated with
Oil Products," Gig. y Sanit. 37(4):14-18 (1972).
Chian, E. S. K., & P. P. K. Kuo, "Fundamental Study on the Post-Treatment
of RO Permeates From Army Wastewater". Sec. Annual Summary Rept.,
U.S. Army Medical R & D Command, Washington, D.C., Rept. No. UILU-ENG-
76-2019, Oct. 1976.
Coppock, J. B. M., N. W. R..Daniels and P. W. Russell Eggitt, "Essential
Fatty Acid Retention in Flour Treatment", Chem. & Ind., Jan. 2, 1960,
p. 17-18.
Dellah, A. "Study of Ozone Reactions Involved in Water Treatment and the
Present Chlorination Controversy", in Proc. Sec. Intl. Symp. on Ozone
Techno!., R. G. Rice, P. Pichet & M.-A. Vincent, editors, Intl. Ozone
Inst., Cleveland, Ohio (1976), 161-168.
Dobinson, F., "Ozonisation of Malonic Acid in Aqueous Solution", Chem. &
Ind. (6):853-854 (1959).
374
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Dobinson, F. and G. J. Lawson, "Chemical Constitution of Coal VI—Optimum
Conditions for the Preparation Of Sub-humic Acids from Humic Acid by
Ozonization", Fuel 38:79-87 (1959).
Dowty, B., D. Carlisle and J. L. Laseter: "Halogenated Hydrocarbons in
New Orleans Drinking Water and Blood Plasma", Science 187:75-77 (1975).
Dowty, B., D. R. Carlisle, and J. L. Laseter. "New Orleans Drinking Water
Sources Tested by Gas Chromatography-Mass Spectrometry," Env. Sci. &
Techno!. 9(8):762-5 (1975).
Drapeau, A. J., "Du Chloroforms Dans Votre Eau Potable", Eau Du Quebec
8(2):19-23 (1975).
Eisenhower, H. R., "The Ozonization of Phenolic Wastes". J. Water Poll.
Control Fed. 40(11)=1887-1899 (1968).
Environmental Defense Fund, "The Implications of Cancer-Causing Substances
in Mississippi River Water," November 6, 1974, Washington, D.C.
Falk, H. L. & J. E. Moyer, "Ozone As a Disinfectant of Water", in
Ozone/Chlorine Oxidation Products of Organic Materials, R.G. Rice &
J.A. Cotruvo, editors. Intl. Ozone Inst., Cleveland, Ohio, p. 38-57
(1978).
Fremery, M. I., and E. K. Fields, "Emulsion Ozonization of Cycloolefins in
Aqueous Alkaline Hydrogen Peroxide", J. Org. Chem. 28:2537-41 (1963).
Furgason, R. R., H. L. Harding and M. A. Smith, "Ozone Treatment of Waste
Effluent". Research Technical Completion Report, U.S. Dept. of
Interior, Office of Water Resources Rsch. (Washington, D.C.) Rept. No.
UC A-037-IDA, Water Resource Research Inst., Univ. of Idaho, April
1973. NTIS Rept. No. PB 220,008.
Gabovich, R. D., K. K. Vrochinskii, and I. L. Kurinnyi, "Decolorization,
Deodorization and Decontamination of Drinking Water By Ozonization,"
Hygiene and Sanitation (Gig. y Sanit.) 34:336-340 (1969).
Gabovich, R. D., I. L. Kurinnyi, and Z. P. Fedorenko, "Effects of Ozone
and Chlorine on 3,4-Benzopyrene During Water Treatment". Gig. Naselennikh
Mest. (1969), p. 88.
Gabovich, R. D. and Kurinnyi, I.L., "Ozonization of Water Containing
Petroleum Products, Aromatic Hydrocarbons, Nitrogen Compounds and
Chloro-Organic Pesticides. Gigiene Naselennykh Mest. (USSR) Izd.
"Zdorov'ya", (1967), p. 315.
Gad, G., and C. Columbus, "Chemische Auswirkungen der Wasserozonisierung",
Health Engineer 76:268-9 (1955).
375
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Gauntlett, R. B. and R. F. Packham, "The Removal of Organic Compounds in
the Production of Potable Water", Chem. & Ind., Sept. 1, 1973, p. 812-
817.
Gilbert E., "Ozonolysis of Chlorophenols and Maleic Acid in Aqueous Solu-
tion," in Proc. Sec. Intl. Symp. on Ozone Technol., R. G. Rice,
P. Pichet and M.-A. Vincent, editors, Intl. Ozone Inst., Cleveland,
Ohio (1976), 253-261.
Gilbert, E., "Reactions of Ozone with Organic Compounds in Dilute Aqueous
Solution: Identification of Their Oxidation Products", in Ozone/Chlorine
Dioxide Oxidation Products of Organic Materials, R.G. Rice & J.A.
Cotruvo, editors, Intl. Ozone Inst., Cleveland, Ohio (1978), p. 227-
242.
Gilbert, E., "Chemical Reactions Upon Ozonation", Presented at Intl. Symp.
on Ozone and Water, Wasser Berlin, May, 1977, Intl. Ozone Inst. Cleve-
land, Ohio.
Glaze, W. H., R. Rawley and S. Lin, "By-Products of Organic Compounds in
the Presence of Ozone and Ultraviolet Light: Preliminary Results", in
Ozone/Chlorine Dioxide Oxidation Products of Organic Materials, R.G.
Rice & J.A. Cotruvo, editors, Intl. Ozone Inst., Cleveland, Ohio,
(1978), p. 321-331.
Glaze, W. H., R. Rawley, F. Huang, and S. Lin "Ozone and Ozone/UV Destruction
of Trihalomethane Precursors and Other Refractory Organic Compounds in
Water", Presented at Symp. on Advanced Ozone Technology, Toronto,
Ontario, Canada, November 1977. Intl. Ozone Inst., Cleveland, Ohio.
Gregersen, J. K., "Evaluation of an Ozonation-Activated Carbon Treatment
for a Colored Industrial Waste". Thesis, Iowa State Univ., Ames, Iowa
(1971).
Hann, V., "Water Quality Improvement With Ozone", Engr. News Record
139(59):125-127 (1947).
Harrison, R. M., R. Perry and R. A. Wellings, "Effect of Water Chlorination
Upon Levels of Some Polynuclear Aromatic Hydrocarbons in Water", Env.
Sci. & Technol. 10(12):! 151-1160 (1976).
Heertjes, P. M. and A. P. Meijers, "Untersuchung nach organischen Sub-
stanzen in Fluss- and Trinkwasser," Wasser-Abwasser lll(2):61-66
(1970).
Helz, G. R., R. Y. Hui and R. M. Block, "Bromoform Production by Oxidative
Biocides in Marine Waters", in Ozone/Chlorine Dioxide Oxidation
Products of Organic Materials", R.G. Rice & J.A. Cotruvo, editors,
Intl. Ozone Inst., Cleveland, Ohio, (1978), p. 68-76 (1978).
376
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Hoehn, R. C., C. W. Randall and F. A. Bell, Jr., "Trihalomethanes and
Viruses In a Water Supply", 0. Env. Engrg. Div. of Am. Soc. Civil
Engrs., Oct. 1977, p. 803-812.
Hoffman, J., and D. Eichelsdflrfer, "Zur Ozon Einwirkung auf Pestizide der
Chlorkohlenwasserstoffgruppe im Wasser," Vom Wasser 38:197-206 (1971).
Hoign§, J., "Comparison of the Chemical Effects of Ozone and of Irradiation
on Organic Impurities in Water", Proc. Radiation for a Clean Environment,
Intl. Atomic Energy Agency, Vienna (1975), p. 297-305.
HoignS, J. and H. Bader, "Beeinflussung der Oxidationswirkung von Ozon und
OH-Radikalen durch Carbonat", Vom Wasser 48:283-304 (1977).
Hoign§, J. & H. Bader, "Ozonation of Water: Selectivity and Rate of Oxidation
of Solutes", Presented at 3rd Intl. Symp. on Ozone Technol., Paris,
France, May 1977. Intl. Ozone Inst., Cleveland, Ohio.
Hoigne, J. and H. Bader, "Rate Constants for Reactions of Ozone With Organic
Pollutants and Ammonia in Water", Symp. on Advanced Ozone Technol.,
Toronto, Ontario, Canada, November, 1977. Intl. Ozone Inst., Cleveland,
Ohio.
Hoigne, J. and H. Bader, "Ozonation of Water: Kinetics of Oxidation of
Ammonia by Ozone and Hydroxyl Radicals", Environ. Sci. & Technol.
12(l):79-84 (1978).
Hubbs, S. A., "The Oxidation of Haloforms and Haloform Precursors Utilizing
Ozone", in Ozone/Chlorine Oxidation Products of Organic Materials.
R.G. Rice & J.A. Cotruvo, editors. Intl. Ozone Inst., Cleveland,
Ohio. p. 200-209 (1978).
Il'nitskii, A. P., "Effect of Ozonation upon Aromatic Hydrocarbons Including
Carcinogens", Hygiene and Sanit. (Gig. y Sanit.) 33(3):323-7 (1968).
Il'm'tskii, A. P., "Experimental Investigation of the Elimination of Carcin-
ogenic Hydrocarbons from Water During its Classification and Disinfec-
tion", Hygiene and Sanit. (Gig. y Sanit.) 34(9):317-321 (1969).
Ingols, R. S., "Ozonation of Seawater", in "Ozone/Chlorine Dioxide Oxidation
Products of Organic Materials". R. G. Rice & J. A. Cotruvo, editors,
Intl. Ozone Inst., Cleveland, Ohio, (1978), p. 77-81.
Ishizaki, K., R. A. Dobbs and J. M. Cohen, "Ozonation of Hazardous and
Toxic Organic Compounds in Aqueous Solution", in Ozone/Chlorine Dioxide
Oxidation Products of Organic Materials, R.G. Rice & J.A. Cotruvo,
editors. Intl. Ozone Inst., Cleveland, Ohio, (1978), p. 210-226.
Junk, G. A., and S. E. Stanley, "Organics in Drinking Water. Part I -
Listing of Identified Chemicals", Prepared for U. S. Energy Research
and Development Administration under Contract W-7405-eng. 82. July
1975.
377
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Junk, G. A., J. J. Richard, M. D. Grieser, D. Witiak, J. L. Witiak, M. D.
Arguello, R. Vick, H. J. Svec, F. S. Fritz and F. V. Calder, "Use of
Macroreticular Resins in the Analysis of Water for Trace Organic
Contaminants," J. Chromatography 99:745-762 (1974).
JUrs, R. H., "Die Wirkung des Ozons auf im Wasser gelOste Stoffe" ("The
effect of ozone on materials which are dissolved in water") Fortschr.
Wasserchem. Ihrer Grenzgebiete 41:40-64 (1966).
Kennaugh, J., "Action of Diaphanol on Arthropod Cuticles", Nature, 180:238
(1957).
Kinney, C. R. and L. T. Friedman, "Ozonization Studies on Coal Constitu-
tion", J. Am. Chem. Soc. 74:57-61 (1952).
Kopfler, F. C., R. G. Milton, R. D. Lingg and W. E. Coleman, "GC/MS
Determination of Volatiles for the National Organics Reconnaissance
Survey (NORS) on Drinking Water." in Identification and Analysis of
Organic Pollutants in Water, 1st ed., L. H. Keith, Ed., Ann Arbor
Science Publishers, Inc., Ann Arbor, Michigan, 1975, Chapter 6.
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378
-------
Lawrence, J. "Identification of Ozonation Products in Natural Waters",
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s
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379
-------
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Cleveland, Ohio (1978), pp 169-188.
380
-------
Robeck, G.G., K.A. Dostal, J.M. Cohen and J.F. Kreissl, "Effectiveness
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"Ozone/Chlorine Dioxide Oxidation Products of_ Organic Materials",
R.G. Rice & J.A. Cotruvo, editors. Intl. Ozone Inst., Cleveland,
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Scassellati-Sforzolini, G., A. Savino, S. Monarca and M.N. Lollini,
"Decontamination of Water Contaminated With Polycyclic Aromatic
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"Ozonization Products From Caffeine in Aqueous Solution", in
"Ozone/Chlorine Dioxide Oxidation Products of_ Organic Materials",
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(1978), p. 284-290.
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381
-------
Sierka, R.A., "The Effects of Sonic and Ultrasonic Waves on the Mass Trans-
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Solution", Presented at 3rd Intl. Symp. on Ozone Technology, Paris,
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Sigworth, E.A., "Identification & Removal of Herbicides and Pesticides",
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Water", Presented at Symp. on Advanced Ozone Technol., Toronto,
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382
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^
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383
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384
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APPENDIX A
BLANK QUESTIONNAIRES
Page
Ozone Questionnaire 386
Chlorine Dioxide Questionnaire 394
385
-------
OZONATION QUESTIONNAIRE
Section 1: General Plant Information
Note: The purpose of this section is to provide background data
for the plant
A. Location:
(country)
(city)
Address:
Check one: publicly owned investor owned
B. Person to be contacted for further information:
Name: Ti tl e:
Address:
Telephone:
C. Plant capacity:
Present design capacity: cu in/day
Present average daily flow: cu m/day
Present maximum daily flow: cu m/day
Present minimum daily flow: cu m/day
Original construction cost: Year Constructed:
Expansion construction cost: Year expanded: ~
(continued)
386
-------
D. Basic process layout:
Provide in the form of a simple block diagram, e.g.:
coagulation
ozonation
sedimentation
filtration
chlorination
Be sure to show all points in the process where ozone is used.
E. Purpose of Ozonation (check all that apply)
Jron removal
_color removal
_odor removal
_bacterial disinfection
organic compound removal
jnanganese removal
"taste removal
_turbidity removal
_viral inactivation
_other (please specify)
F. History:
Year plant started operation
designed capacity_
Year ozonation equipment began operation
ozonation capacity
cu m/day
Year of latest ozonation plant expansion
present ozonation capacity ~
_kg/day
kg/day
G.
Is your plant open for visits by our project team?
yes no
Contact:
(address and telephone if different from above)
(continued)
387
-------
Section II: Ozonation System
Note: This section provides more details as to the design and operation
of your ozonation system.
A. Feed gas
1. Gas used: air oxygen _air/oxygen mixture 5
2. Gas pretreatment: air compressor silica gel scrubber
alumina scrubber other
manufacturer
B. Ozonation system
1. Design capacity kg/hr
2. Average daily output kg/hr
3. Number of generators
4. Capacity per unit kg/hr
5. Type of unit (plate, tube, air cooled, water cooled, etc.)
6. Manufacturer
7. Cooling water used? yes no
source
quality: raw water chemically treated solids removed
drinking water quality
maximum input temperature °C.
minimum input temperature °C.
average temperature °C.
Ozone contacting system:
number of contacting units: detention time:
type: sparger injector submerged turbine
packed column spray tower plate column
other:
number of stages per contactor
manufacturer
use of supplemental processing with contactor? yes~ no
sonics ultraviolet catalysis other:
are off-gases processed to remove excess ozone? yes no
describe how:
9. Power consumption per kg of ozone produced: at average daily
output or_ at maximum capacity of unit for
jgas pretreatment unit _ozone generating unit _pzone contacting
system
(continued)
388
-------
Section III: Process Parameters
Note: This section provides information on the analytical procedures
and monitoring used by the plant to control the ozonation
facility.
A. Analytical procedures
1. What is the average ozone dosage?
How is it measured?
2. How is the ozone residual measured?
At what point(s) in the process is it measured? (indicate on
the block diagram in question I-D)
B. What analytical procedures do you use to determine the effective-
ness of the ozone process?
(What is measured?How are the results reported?Units?)
1. What analyses?
2. Where sampled?_
3. How often?
4. For what period of time have you been performing the
analyses?
5. Comments on ease or difficulty of employing analytical pro-
cedure: "
C. Removal of specific chemical compounds
1. By ozonation only:(Please fill out table) For What Period of Time
Has the Analyses Been
Chemicals Removed Verifying Analysis Performed
2. By combination of process steps: For What Period of Time
Has the Analyses Been
Chemicals Removed Verifying Analysis Performed
(continued)
389
-------
Please show the process steps involved with a block diagram
as in question I-D
D. Final products of ozonation
Do you have any information as to the final products of
the organic compounds which have been ozonized? yes no
describe the analytical data: (analyses used, where taken,
how often)
E. Use of residual disinfectant.
disinfectant used
where added
dosage_
free residual attained in the plant effluent: mg/1, at the
extremity of the distribution system mg/1.
total residual attained in the plant effluent: mg/1; at
the extremity of the distribution system: mg/1.
has the residual disinfectant been successful in controlling
slime and microbiological growths in the distribution
system?
yes no.
how frequently are microscopic examinations for nuisance
organisms conducted on distribution samples?
(continued)
390
-------
F. Ozonation process controls
1. How do you control the ozonation process? (check all that
apply)
_by water quality parameters (color, COD, etc.)
by ozone residual
j>y ozone dosage
_by ozone contact time
other:
Are controls manual or automatic?
3. Is a copy of a typical plant operational sheet containing the
actual hourly/daily chemical doses fed to the water in all
stages of treatment available? If so, please attach. Typical
physical, chemical, bacteriological, and microscopic analyses
of the raw and finished water would also be appreciated.
G. What effect has ozonation had on quantities of solid waste (sludge)
generated by your process and which must be disposed?
H. Any observed negative effects of ozone usage? (e.g., corrosion,
high cost, workers' objections, development of scum or color after
the water has left the treatment plant, etc.)
I. If ozone is relied upon exclusively for disinfection, do slime and
nuisance biological growths occur in the distribution system? yes no.
Section IV: Plant Water Quality
Note: The purpose of this question is to determine quality of
plant influent versus plant effluent.
A. Source of raw water:
Physical, chemical, bacteriological, and microscopic tests on raw
water, together with their individual frequency:
(continued)
391
-------
B. Physical, chemical, bacteriological, and microscopic tests on
product water, together with their individual frequency:
Section V: Other Information
A. Does the plant have any unique features? Please describe:
B. Are there restrictions (national, local, public health) on the use
of ozone? Are they subject to governmental enforcement?
C. Comments on experience with operation of ozone generation and
associated equipment:
1. Maintenance requirements:
2. Unusual maintenance problems (e.g., corrosion):
3. Any safety problems or accidental exposures to ozone?
D. Additional comments
(continued)
392
-------
Section VI: Chlorine Dioxide Use
A. Do you use chlorine dioxide in your facility? yes no
If yes, please complete the following questions.
B. Where in the process is it injected? (Please show this on the
block diagram in question I-D)
C. For what purpose is it used?
iron removal manganese removal
color removal taste removal
odor removal turbidity removal
bacterial disinfection provide residual chlorine
_organic compound removal other (specify)
D. How do you generate your chlorine dioxide?
1. Chemicals used
2. Techniques of combination
(attach a copy of your in-plant instructions to operators
if you have it)
E. Is there any excess free chlorine present in the chlorine
dioxide? yes no
F. Do you use any other analytical methods to monitor chlorine
dioxide addition and results, other than those listed in
Section III of this questionnaire? If so, please describe:
(continued)
393
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CHLORINE DIOXIDE QUESTIONNAIRE
Section I; General Plant Information
Note: The purpose of this section is to provide background data for
the plant
A. Location:
(country)
(city)
Address:
Check one: publicly owned investor owned
B. Person to be contacted for further information:
Name: Title:
Address:
Telephone:
C. Plant capacity:
Present design capacity: cu m/day mgd
Present average daily flow: cu m/day mgd
Present maximum daily flow: cu m/day mgd
Present minimum daily flow: cu m/day mgd
Original construction cost: Year Constructed:
Expansion construction cost: Year expanded:
394
(continued)
-------
D. Basic process layout:
Provide in the form of a simple block diagram, e.g.
coagulation
sedimentation
filtration
ozonation
chlorination
Be sure to show all points in the process where chlorine dioxide
is used.
E. Purpose of chlorine dioxide (check all that apply):
_iron removal
_color removal
_odor removal
_bacterial disinfection
_organic compound removal
jnanganese removal
_taste removal
_turbidity removal
_chlorine residual
other (please specify)_
1. If chlorine dioxide is fed solely for disinfection purposes:
(a) What is the residual in mg/1 leaving the treatment
plant? mg/1
(b) What is the residual in mg/1 prevailing at the
extremity of the distribution system? mg/1
(c) Do slime and nuisance biological growths occur in the
distribution system? yes no
2. If chlorine dioxide is fed for taste and odor control:
(a) Is the chlorine dioxide fed intermittently as the
taste and odor bodies appear in the raw water, or at
a constant dosage as a precautionary measure?
(b) What is the range of intermittent dosage in mg/1?
mg/1
(c) What is the constant dosage in mg/1? mg/1
(d) Are the taste and odor bodies of a natural or
industrial origin?
(e) Please note their chemical composition, if known or
suspected. .
(continued)
395
-------
History
Year plant started operation:
designed capacity_
cu m/day or_
Year chlorine dioxide equipment began operation:
chlorine dioxide capacity kg/day or "
mgd
Ibs/day
Year of latest chlorine dioxide plant expansion
present chlorine dioxide capacity kg/day or Ibs/day
G. Is your plant open for visits by our project team?
yes
Contact:
no
Address and telephone if different from above:
Section II; Chlorine Dioxide System
Note: This section provides more details as to the design and operation
of your chlorine dioxide system.
A. Please list the chemicals you use to make chlorine dioxide:
B. What is the chemical consumption? (Give units)
maximum:
average:"
minimum:
C. Please describe the chlorine dioxide generating system:
(Attach a copy of the plant operator's guidelines for chlorine
dioxide process operation if one is available)
Who is the manufacturer of the equipment?^
(continued)
396
-------
D. Please describe the chlorine dioxide contacting system:
Who is the manufacturer of the equipment?_
number of contacting units:
number of stages per contactor:
Section III: Process Parameters
Note: This section provides information on the analytical procedures
and monitoring used by the plant to control the chlorine dioxide
facility.
A. Analytical Procedures
1. What is the average chlorine dioxide dosage? (units)
How is it measured?
2. How is the chlorine dioxide residual measured?
At what point(s) in the process is it measured?(indicate
on the block diagram in question I-D)
3. What species are measured? Check one or more if known:
Cl 09 Cl Q; HOC1 Chi orami nes Cl 0^ Cl"
C12_ Other
B. How do you determine if the chlorine dioxide is accomplishing its
purpose?
1. What analyses?
2. Where sampled?_
3. How often?
4. How long have you been performing the analyses?
5. Comments on ease or difficulty of employing analytical pro-
cedures:
(continued)
397
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C. Removal of specific chemical compounds
1. By chlorine dioxide only:
Chemicals Removed Verifying Analysis How Long Analyzed
2. By combination of process steps:
Chemicals Removed Verifying Analysis How Long Analyzed
Please show the process steps involved with a block diagram as in
question I-D.
(continued)
398
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D. Final products of chlorine dioxide
Do you have any information as to the final products of the organic
compounds treated by chlorine dioxide? yes no
Describe the analytical data: (analyses used, where taken, how
often)
E. Is there any free chlorine formed along with the chlorine dioxide?
yes no
Comments:
F. Chlorine dioxide process controls
1. How do you control the chlorine dioxide process? (Check all
that apply)
_by water quality parameters (color, COD, etc.)
_by chlorine dioxide residual
Jay chlorine dioxide dosage
by chlorine dioxide contact time
other
2. Are the controls manual or automatic?
Is a copy of a typical data plant operational sheet containing
the actual hourly/daily chemical doses fed to the water in all
stages of treatment available? If so, please attach. The
physical, chemical, bacteriological, and microscopic analyses
of the raw and finished water would also be appreciated.
G. Any observed negative effects of chlorine dioxide? (e.g.,
corrosion, high cost, workers' objections, etc.)
Section IV: Plant Water Quality
Note: The purpose of this section is to determine quality of plant
influent versus plant effluent.
(continued)
399
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A. Source of raw water:
Physical, chemical, bacteriological, and microscopic tests on raw
water, together with their individual frequency:
B. Physical, chemical, bacteriological, and microscopic tests on
product water, together with their individual frequency:
Section V: Other Information
A. Does the plant have any unique features? Please describe:
B. Are there restrictions (national, local, public health) on the
use of chlorine dioxide? Are they subject to governmental
enforcement?
C. Comments on experience with operation of chlorine dioxide genera-
tion and associated equipment:
1. Maintenance requirements:
2. Unusual maintenance problems (e.g., corrosion):
3. Any safety problems or accidental exposures to chlorine
dioxide?
D. Additional Comments:
400
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APPENDIX B
DESCRIPTIONS OF SELECTED DRINKING WATER TREATMENT PLANTS USING OZONE
Plant Page
Tailfer (Brussels, Belgium) 402
Clairfont (Toulouse, France) 406
Rouen-la-chapelle (France) 411
Dusseldorf (Germany) 414
Duisburg|( (Germany) 418
Lengg (Zurich, Germany) 423
Sipplinger Berg (Germany) 432
St. Denis (Quebec, Canada) 436
Sherbrooke (Quebec, Canada) 438
Pierrefonds (Quebec, Canada') 440
Quebec City (Quebec, Canada) 443
401
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BRUSSELS, BELGIUM - TAILFER PLANT
This plant is located 75 km northeast of Brussels, on the river Meuse
upstream of Brussels. There are four water treatment trains, each having a
design capacity of 65,000 cu m/day. Three are complete and are operating;
the fourth was being constructed at the time of plant visitation (May,
1977). Although the original projections were that three lines would be
required during the summer and two in winter, it has been found that only
two lines are needed in summer to satisfy current water demands and one in
winter. The fourth line is being installed as a spare.
The new Tailfer plant was designed, constructed and is operated by the
Compagnie Intercommunale Bruxelloise des Eaux (GIBE, a public company) and
began operating in 1973. About 40 km upstream of the plant is a nuclear
power plant which uses chlorine as the cooling water biocide. Discharges
from this power plant are sent to a holding pond where radioactivity (Co-
60) and chlorine levels decay. However, the Tailfer plant analyzes for
heavy metals and radioactivity in the intake water and on sludges produced
during the water treatment process. In addition, a series of four raceways
have been installed at Tailfer in which trout are maintained to monitor the
intake water for toxic materials. Details of this trout monitoring system
(developed by the Netherlands Water Research Institute—KIWA) are described
in Section 7.
At the plant there is an extensive analytical laboratory which monitors
and analyzes raw, process and treated waters. At each chemical addition
step, a portion of the plant water flows continuously into the laboratory
where it is sampled and analyzed at regular intervals or monitored constantly.
The laboratory has its own analytical control panel where each chemical
addition step is controlled. Alarms are set to ring if the addition rates
of chemicals exceed set minima or maxima or if turbidities exceed set
limits.
Raw water is monitored for turbidity, pH, temperature, conductivity,
redox potential and dissolved oxygen. In addition, other analyses are
performed from time to time, including radioactivity, ammonia, COD, etc.
The Meuse at Tailfer contains 0.2 mg/1 of ammonia and 10 to 30 mg/1 of COD
(with occasional high levels of 70 to 80 mg/1).
Water treatment occurs in three separate blocks at Tailfer (Figure B-
1). Block A contains the chemical treatment, Block B decantation and
filtration, and Block C the ozonation. As water enters Block A, it is
treated, in order, with sulfuric acid (to control alkalinity), chlorine
(for predisinfection), chlorine dioxide (to break up organically complexed
manganese), alum (to neutralize colloidal charges on suspended materials)
and activated silica (as a flocculant aid).
Water containing these chemicals is sent to Block B where powdered
activated carbon (7 to 10 mg/1 for taste, odor and color causing micro-
pollutants) and caustic soda (for neutralization of the sulfuric acid) are
added. Chemically treated waters are sent through a Pulsator, which is a
unique flocculator-clarifier, manufactured by Degremont.
402
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96-91 METERS
O
CO
COMPRESSOR
TIME OF
DETENTION
TO RESERVOIR
PREOZONATION
OZONATION
DETENTION
FIGURE B-l. Ja\]fer water treatment plant, Brussels, Belgium..
-------
In the Pulsator, water flows upward through a sludge blanket in a
cyclic, pulsating flow. The sludge blanket is maintained in suspension by
periodic pulsations. Water passes vertically through this homogeneous
blanket which provides efficient contact of chemicals, floe and water. As
the size of the sludge blanket increases, excess sludge is drained off.
The sludge flows to the center zone of the tank into a sludge concentrator,
where it is gravity thickened and discharged at regular intervals by auto-
matic, time controlled valves. The sludge blanket normally is on the order
of 2.5 meters thick, although the total water depth may be 5 meters.
Pulsators also were observed at Annet-sur-Marne (France), the Dohne
plant in MUlheim (Germany) and at Pierrefonds (Canada).
Following passage through the Pulsator, water then is sent to settling
(for 3 hours) and sand filtration. Chemical additions form a 5 m thick
sludge layer which expands and overflows into a central sludge tank. Water
passes through this blanket over a 30 minute period. Waste sludges are
press filtered to 40% dry weight, then 20% lime is added and the sludges
are sent to landfill.
Ozonation is conducted in Block C, a separate building. Each water
treatment train has two ozone contacting chambers, each chamber containing
a submerged turbine. About 90% of the ozone generated is fed to the first
chamber and 10% to the second. Off-gases from the second chamber are
recycled to the first chamber. Total efficiency of ozone use at Tailfer is
99.5-99.7%.
Ozone dosages vary over the year from 1.5 mg/1 in winter to 3.3 mg/1
in summer. Contact time in the first turbine chamber is just over 2
minutes and is 2.5 minutes in the second chamber. Ozonized water then
passes into a retention chamber where ozone residual is monitored manually
at a point representing a total contact time of 6 minutes. Off-gases from
this chamber containing small amounts of ozone are thermally destroyed
before vent gases are discharged to the atmosphere.
Treated water then is sent to the plant reservoir, then to a pumping
station 10 km from the plant where it is treated with 0.2 mg/1 of chlorine
to produce a chloramine residual of 0.2 mg/1 before entering the distri-
bution system to Brussels (the raw water contains 0.2 mg/1 of ammonia).
Chlorine dioxide is prepared in a generator designed by Dr. Willy
Masschelein, Deputy Director of.the CIBE Laboratories. Dr. Masschelein has
authored a monograph on Oxides of_ Chiorine and Sodiurn Chlorite which was
publised in French in 1969. A revised and updated English version will be
published in 1978 by Ann Arbor Science Publishers, Inc., Ann Arbor, Michigan,
USA, with the title, Chlorine Dioxide.
This chlorine dioxide generator operates on the same general principle
as the new Wallace & Tiernan chlorine dioxide generator, described in
Section 11. Chlorine gas is added to water under pressure so as to obtain
a minumum chlorine concentration of 2 g/1. This solution then is mixed
with a solution of sodium chlorite (also under pressure) in a Raschig ring
404
-------
column. Stoichiometn'c quantities of both reagents are employed so as to
obtain 98 to 99% conversion of sodium ch-lorite to chlorine dioxide. If the
2 g/1 concentration of chlorine in water is not attained, then excess
chlorine is required to insure conversion of chlorite.
After 1 minute of contacting time in the generator (time of passage
through the reactor), the product solution is diluted for feeding to the
raw water at the appropriate point in Block A.
Microbiological analyses are conducted every 8 hours on the product
water for pseudomonas, total plate counts, actinomycetes and other coliform
organisms. The average time for treated water to reach Brussels from
Tailfer is 18 hours. During this time the residual 0.2 mg/1 of chloramine
falls to 0.05 mg/1. The city of Brussels analyzes water at 20 points in
the distribution system weekly.
Currently Tailfer has eight Trailigaz water cooled, horizontal tube
ozonizers installed, each capable of producing 4 kg/hr of ozone from air at
60 Hertz. More ozone generation capacity will be required for the fourth
stage, but CIBE is not planning to install additional ozone generators.
Instead, tests have been conducted using oxygen as the feed gas to increase
the ozone output of each generator, and this approach is cost-effective at
Tailfer. As a result, provisions have been made to install two 25,000 cu m
liquid oxygen tanks. One tank was being installed at the time of the plant
visit (May, 1977), and as soon as this has been completed, the plant plans
to operate at least one water treatment train using ozone generated from
oxygen. This treatment will continue for a full year to develop operational
data, then a decision will be made to continue constant use of oxygen or to
use oxygen only in the summer months when demands for ozone are highest.
Details of the study performed by CIBE of oxygen versus air for
generating ozone are described in a recent publication by W. Masschelein,
in collaboration with G. Fransolet, J. Genot and R. Goossens entitled,
"Perspectives de TOzonation de TEau au Depart d'Air Enrichi en Oxygene",
T.S.M. TEau 71(8-9):385-399 (1976). Dr. Masschelein also is studying the
feasibility of installing high frequency equipment to allow operation of
the Tailfer ozone generators at 600 Hertz, at which more ozone will be
generated per unit time than by using the present 60 Hertz frequency.* The
objective would be to allow Tailfer to generate ozone at 60 or 600 Hertz
and using air or oxygen, without having to invest in additional ozone
generators.
Maintenance of the Tailfer ozone generators is performed every six
months and an accurate record is kept of the service life of each dielectric
tube. Every two years of service, tubes are discarded whether they give
evidence of wear or not. In this manner, unprogrammed ozone generator
downtime is avoided.
* W.J. Masschelein, Private Communication to R.G. Rice & G.W. Miller,
January, 1977.
405
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The writers believe that this unusually high rate of tube replacement
(15-20% of the tubes are replaced every 6 months) is a result of insufficient
ozone generation capacity having been installed originally. This would
cause plant personnel to generate ozone at its maximum production rate most
of the time, which all ozone generator manufacturers advise will reduce
service life of dielectric tubes.
CLAIRFONT WATER TREATMENT PLANT, TOULOUSE, FRANCE
Introduction
The Clairfont water treatment plant provides 110,000 cu m/day of water
to the water system that serves the 400,000 people of Toulouse, France
(Figure B-2). The plant provides full treatment to 100,000 cu m/day drawn
from the Garonne River just downstream from the confluence of the Garonne
and the Ari&ge Rivers, as well as ozonation and post chemical treatment to
10,000 cu m/day of groundwater pumped from the wells in the vicinity of the
plant. The second Toulouse water plant, Pech-David, produces an additional
130,000 cu m/day by incorporating semi-rapid filtration in its treatment
processes, but not ozonation. The Clairfont plant serves 180,000 Toulouse
residents while Pech-David serves the remaining 220,000.
The Garonne River originates in the Pyrenees and has wide variations
in flow, becoming torrential at times. A pulp and paper mill is situated
some 90 km upstream of the Clairfont plant on the Ariege River. Also on
the Aridge River and upstream of the Clairfont plant is an aluminum processing
plant, which discharges some heavy metals into the river.
Water from the treatment plant is pumped to the reservoir and distri-
bution system. The distance from Clairfont to the furthermost point in the
distribution system is 15 km. The average residence time in the distri-
bution system is 6 to 7 hours, with an average 8 to 12 hours between ozone
contacting and the consumer's taps.
Water quality sampling points are located at various points throughout
the distribution system. Local public health personnel sample two times
each day at various points for bacteriological analyses. The Toulouse
Public Health Authority is the municipal laboratory for physical and chemical
analyses, while the regional laboratory performs bacteriological analyses.
The Clairfont plant was designed to be constructed in three phases.
• 1970 - 50,000 cu m/day from Garonne River
• 1975 - 50,000 cu m/day from Garonne River
10,000 cu m/day of groundwater (for ozone disinfection
and post chemical treatment)
• Future - 50,000 cu m/day from Garonne River.
The construction cost for the initial 50,000 cu m/day (13.16 mgd) was
13 million French francs ($2.71 million). The second phase cost 27 million
406
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POWDERED
ACTIVATED
CARBON
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SECONDARY
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SECONDARY DISINFECTION
-
-------
French francs ($5.625 million*). The increase was partially due to inflation
but also because all chemical handling and other basic facilities for the
third phase were included in the second phase.
Cost of water treatment at Clairfont, exclusive of the distribution
system is 0.216 French francs (Ff) per cubic meter of water (17.1<£/1000
gal*). Of this, 0.0112 Ff (0.9<£) is for ozonation and 0.0098 Ff (0.8
-------
• Considered to be a better predisinfectant
Chlorine dioxide contact time is 50 seconds in the contactor plus 2.5
minutes before clarification.
Clarification
Each 50,000 cu m/day water treatment stream is further divided into
two 25,000 cu m/day streams for coagulation and flocculation. Vertical
shaft flocculation is used. Each 25,000 cu m/day stream is further divided
into three streams which enter the clarification units, each of which
contains two compartments. The first compartment discharges to a two level
second compartment which also serves as the bottom floor of the filters.
Sludge is withdrawn from the first third of the secondary clarifier compart-
ment by means of perforated sludge collection pipes. Sludge is discharged
back to the Garonne River downstream of the plant.
Filtration
The clarified effluent proceeds to filtration units, three per 25,000
cu m/day stream or 62 sq m/100,000 cu m of plant flow. Each 75 sq m filter
uses a depth of 1.2 m of sand to filter at a rate of 5 cu m/sq m/hr.
An air, then air/water, filter backwash system is used. A short air
backwash cycle at a 4500 cu m/hr rate is followed by a ten minute air/water
backwash at a 1000 cu m/hr rate followed by a ten minute water rinse at a
1500 cu m/hr rate. Ozonized water is used for backwashing. The interval
between filter backwashes varies between one and three days.
The 100,000 cu m/day flow of filtered water is mixed with 10,000 cu
m/day of groundwater pumped from adjacent wells.
Ozonation System
The ozonation system includes the following units:
• 4 fixed speed, positive displacement blowers
• 2 water cooled heat exchangers
• 2 refrigerant air coolers
• 2 activated alumina, desiccant drier, two cell units
• 4 horizontal tube dielectric, water cooled ozone generators, each
containing 148 tubes
• 4 porous tube ozone diffuser contactors
Inlet air is filtered through paper cartridge filters which are
replaced once per year at the same time the ozone generator tubes are
409
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cleaned. Discharge pressure from the blowers is 0.8 to 0.9 bar. Total
head loss through the ozonation system, including the contactor porous
diffusers, is 0.3 bar.
The air temperature entering the water cooled heat exchanger is 70° to
80°C and exiting is 23 to 25°C with a cooling water temperature of 20°C.
The air leaving the refrigerant air cooler is at 4 to 6°C. Desiccant unit
regeneration cycles are timer controlled and the normal regeneration cycle
is 8 to 12 hours, based on normal air flow. If air flow is reduced, time
between regeneration cycles is extended to conserve energy.
The. air from the desiccant drier and to the ozone generators is
monitored by means of a dew point monitor and is controlled at a dew point
of minus 60°C. The calibration of the dew point monitor is checked every
two months but adjustment has not been necessary for the past two years.
The four Trailigaz ozone generators each are capable of producing 2.25
kg/hr of ozone. These are the only Trailigaz ozone generators in France
which have individually fused dielectric tubes. It is not a normal Trailigaz
practice to provide individually fused dielectrics. Mr. Michael Croises,
Principal Engineer of the Toulouse Water Authority, favors the provision of
individual fuses from an operational point of view. He feels that it is
better to have a fuse costing approximately 50 French francs ($10) fail
than a dielectric tube costing approximately 350 French francs ($70).
Failure of an unfused dielectric in an ozone generator results in the
shut-down of the entire ozone generator. If the tube is fused and fails,
the ozone generator continues to operate but at reduced capacity (reduced
by the capacity of that tube—or l/148th in this case). Mr. Croises
stated that the Clairfont facility replaces many fuses which must withstand
33 kv peak voltage, but replaces very few tubes. Sometimes the plant runs
short of fuses. The plant uses approximately 50 fuses per year but replaces
only four or five tubes per year, generally during the annual tube cleaning
period. Trailigaz claims that tubes fail in service only every two to
three years.
Ozonation system maintenance is performed annually by plant operational
staff but Trailigaz would provide the same service under contract if called
upon. The annual maintenance is performed in June, usually a dry period,
but when water consumption is not yet at its peak. The ozonation system is
shut down for three days and chlorine is used for disinfection. Although
users are advised when chlorination is to be substituted for ozonation
(including sensitive industries such as electronic element manufacturers
who shut down operations during maintenance of the ozone generators), there
are numerous complaints regarding the taste of the chlorinated water.
All piping of the air preparation system is galvanized steel while all
piping in contact with ozone is stainless steel. Compressor belts are
changed every three months.
410
-------
Four ozone contactors provide eight minute contact time with a
sidewater depth of 4.8 meters. A maximum dosage of 1.8 mg/1 ozone is used
to provide an almost constant ozone residual of 0.4 to 0.7 mg/1. No residual
ozone monitor is used at Clairfont (controlled manually). Each contactor
consists of four ozonation compartments. The flow pattern in the ozonation
compartments is as follows: countercurrent, cocurrent, countercurrent,
cocurrent. Ozone is injected into the contactor through porous diffusers
at the bottom of the contactor. Contactor off-gases are destroyed by
injection into the exhaust stacks of diesel generators that are used to
supply power to the plants.
Post Treatment
Two treatment steps follow ozonation: continuous pH adjustment with
soda and intermittent addition of silicate to control corrosion in the
distribution system. Silicate addition at a dosage of 1.0 mg/1 is practiced
for a period of one to two days per month.
ROUEN-LA-CHAPELLE, FRANCE
This plant is situated on the Seine River, about 120 km west (and
downstream) of Paris. All water utilities along the Seine below the Paris
sewage plant are forbidden to draw water directly from the river for
processing into drinking water. Instead, water is drawn from deep wells
located near the river banks. This practice is similar, but not equivalent,
to river sand bank filtration, prevalent along the lower Rhine River in
Germany (see DOsseldorf plant description).
Until 1976, the Chapel!e plant at Rouen merely drew groundwater and
treated it with chlorine dioxide before sending it to the distribution
system. However, increases in pollution, particularly in ammonia content
(which has risen to 2 to 3 mg/1 today) has forced adoption of more sophisti-
cated treatment. Phenols and detergents also are present in the Rouen well
waters.
After pilot plant testing for three years (1968 to 1971), the following
treatment scheme was designed, installed, and began operating in January of
1976 (Figure B-3):
t Well water is pre-ozonized for manganese oxidation and for
oxidation of micropollutants (dissolved organic materials). This
step renders the dissolved organic materials more readily bio-
degradable and also increases the dissolved oxygen content of the
water.
• Preozonized water then is filtered through a 100 cm deep sand bed
(to remove the insoluble manganese and some oxidized and flocculated
organics) then through a 75 cm deep bed of granular activated
carbon which has been rendered biologically active by the pre-
ozonation step. Biogrowth also is present in the sand filters,
and some of the ammonia is removed here. The balance is removed
in the GAC filters, along with some of the organic materials.
411
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IN)
Figure B-3. Rouen-la-Chapelle, Rouen France, plant treatment scheme.
-------
• Post-ozonation follows filtration for disinfection and to destroy
any remaining organic micropollution (taste and color bodies).
• Post-chlorination with 0.4 to 0.5 mg/1 chlorine prior to distri-
bution.
The pre-ozonation contactors are high speed turbines because porous
tubes would clog in the presence of precipitating oxides of manganese and
iron. Contact time in the pre-ozonation chamber is short, 3 minutes, and
the source of some of the ozone for this step is the off-gases from the
disinfection ozonation contactors. This second use of ozone contactor off-
gases insures 98% utilization of the generated ozone at Rouen.
The post-ozonation contactors consist of 2 columns, each 4.5 meters
deep, containing porous diffusers. Contact time in these diffuser chambers
is 12 minutes, after which a residual ozone concentration of 0.4 mg/1 is
monitored to assure bacterial disinfection and viral inactivation.
Two-thirds of the total amount of ozone generated is sent to post-
ozonation, and one-third to pre-ozonation. Total dosage of ozone produced
is 2.1 mg/1, so that the. pre-ozonation dosage is 0.7 mg/1 and the post-
ozonation dosage is 1.4 mg/1.
There are six sand filters which operate at 5 m/hour. There are also
three ozone generators at the plant, and each generator services the water
flow to two sand filters. One sand filter operates while the second is
being backwashed. Backwashing is conducted with air and water.
Carbon filters are backwashed once each month. Through January, 1978,
after 24 months of service, the activated'carbon columns have shown no
tendency toward breakthrough and have not yet been thermally regenerated
(C. Gomella, SETUDE, Paris. Private Communication). The expected operating
time between carbon regeneration is at least two years. Analyses are made
quarterly before and after passage through the GAC columns for substances
extractable with chloroform and also for substances extractable with cyclo-
hexane to determine the need for regeneration.
The Rouen distribution system is 430 km long, and the most distant
water tap is 15 km from the plant. Trihalomethane analyses were conducted
once, but none were found.
Four people operate this 50,000 cu m/day plant during the day, and
four more people work in the distribution system. Analyses are carried out
in a central laboratory in Rouen, and not at the plant. Operation of the
plant is paced by the level of water in the plant reservoir. When this
level drops, the plant starts operations automatically.
There are three ozone generators at the plant, capable of being
operated at 32 kw, but normal operation is at 14 kw. If one of the ozone
generators were to shut down, its capacity could be made up by increasing
the power to the other two.
413
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In Section 10, Public Health Aspects of Ozone Usage, a table of data
is presented which were taken at Rouen two months after startup of the new
treatment process. These data show the degrees of removal of a variety of
organic materials by the new process at Rouen. In Section 13, Biological
Activated Carbon is presented a table of plant operational data for this
plant. More than 80% removal of pollutants was obtained by this process
during its first year of operation181.
Rouen-la-Chapelle is the first French plant known to be using Biological
Activated Carbon (pre-ozonation of granular activated carbon) without
having breakpoint chlorination in the initial stages of treatment. The
plant at Morsang-sur-Seine has Biological Activated Carbon after initial
breakpoint chlorination, but is piloting BAG without initial chlorination.
DUSSELDORF, GERMANY
The City of DUsseldorf currently processes water at three treatment
plants, Holthausen, Flehe and Am Staad. All three plants are situated
along the Rhine River and all three plants draw water from wells located
along the river banks. The process of allowing the river water to filter
through the sand banks into these wells is called "river sand bank filtration".
Passage of river water through these sand banks takes about 20 days.
During this time some 60 to 75% of the dissolved organic material is
removed. In exchange, however, considerable amounts of manganese and iron
salts dissolve into the water. Some portion of the water drawn from these
wells (about 25 to 35%) is groundwater flowing in the opposite direction,
that is, into the Rhine. River bank filtration wells at Am Staad are over
100 years old.
During the late 1950s, DUsseldorf became the first European city to
adopt a water treatment process consisting of ozonation followed by granular
activated carbon. In the language of ozone historians, the process has
come to be known as "the Dllsseldorf process", because the first description
of these installations was published under that title. The process was
adopted, installed and became operational in the early 1960s.
Ozonation was installed specifically to oxidize the iron and manganese
salts and the granular activated carbon was installed to remove dissolved
organic compounds which cause taste and odor problems. However, over the
intervening years, pollution of the Rhine has increased and the combination
of ozone followed by activated carbon has become better understood. When
first installed, only 1 g/cu m of ozone dosage was required and only 1 g of
carbon/cu m of water treated were required. Today, 3 to 3.6 g/cu m of
ozone must be added and 35 g of activated carbon/cu m of water are required
to attain the same water quality that was attained in the early 1960s.
Because of the large increase in the amount of granular activated carbon
required in the DUsseldorf plants today, the city has installed carbon
regeneration facilities at the Holthausen plant site. As soon as this
facility is operational and has been debugged, DUsseldorf plans to construct
carbon regeneration facilities at the two other plants.
414
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During the years following introduction of the ozone/granular activated
carbon system in DUsseldorf, treatment plant scientists have noted that the
amount of organics removal was more than could be expected simply by
summing the known removals of the ozonation and GAC processes. In addition,
ammonia is removed by the activated carbon columns, which was unexpected on
the basis of adsorption. These observations led to studies of the mechanisms
occurring in the activated carbon columns by bacterial action. These
studies, conducted at the Bremen Water Works, are described in Section 13,
"Biological Activated Carbon". For maximum biological benefit, filtration
rates through the carbon columns today are about one-third of the designed
rate (10 m/hr today versus 25 to 30 m/hr).
The ozone/activated carbon process has been practiced at the three
DUsseldorf plants for 15 to 17 years. The older Am Staad plant was redesigned
and rebuilt in the early 1970s, and is the latest operating version of "the
DUsseldorf process" of water treatment. It is laid out in a circle with
the plant reservoir beneath the plant.
All three Dtlsseldorf plants treat river sand bank filtered Rhine water
by the identical process (Figure B-4). When water enters the plant it is
ozonized as the first step. This is accomplished by injecting all of the
required ozone into 1% of the treated water. As soon as the ozone has been
mixed with 1% of treated water, the ozonized water is mixed with the raw
water at the top of a vertical 10 meter long pipe, one-half foot in diameter.
This pipe leads to within 1 foot of the bottom of the contact chamber.
Details of this type of injector contacting are given in Section 8, Enginee-
ring Aspects of Ozonation.
Off-gases from the ozone contactors are sent to wet granular activated
carbon beds for destruction. However, each plant has tested catalytic
ozone destruction devices and was planning to install these shortly after
the site visits were made (May 1977).
The original ozone generators at DUsseldorf were Otto plate type,
water cooled generators. These were large (for their ozone generation
capacity) and produced only 1 kg/hour per unit. The newer generators are
Herrmann tube type, water cooled ozone generators, each capable of generating
1.3 kg/hour. These were installed in 1964.
Many of the alumina glass dielectrics originally installed in 1964
still are operating in the Herrmann generators, which are cleaned every two
years. DUsseldorf personnel consider that if one dielectric tube is lost
per generator during cleaning, they are disappointed and consider this loss
to be high. New tubes cost about $40.
After ozonation, the water flows to a holding tank, where it remains
for a period of 20 to 30 minutes. During this time oxidized iron and
manganese hydroxides coagulate and begin to precipitate. Residual ozone
concentrations also become lower, as the dissolved ozone continues to
oxidize dissolved organic material. Finally, any permanganate (which may
have been formed during ozonation) also oxidizes dissolved organic com-
pounds, and itself is reduced back to the insoluble manganic state.
415
-------
en
TREATED
WATER
ACTIVATED CARBON
FILTER
OZONE CONTAINING 3AS
FROM OZONE GENERATOR
INJECTOR
CARRIER WATER
RAW WATER INLET
INTERMEDIATE CONTAINER
GASSING TANK
FIGURE B-4. SCHEMATIC OF WATER TREATMENT PLANTS IN
DUSSELDORFj GERMANY (HOLTHAUSEN,
FLE^E AND AM STAAD)
-------
After the ozonized water has stood 20 to 30 minutes it is tested
manually for ozone by sniffing and for permanganate by observing a slight
pink color. If neither ozone nor permanganate can be detected by these
methods, then the dosage of ozone is raised.
Water then is filtered through pre-activated carbon (which is a
special grade of anthracite coal), to remove iron and manganese precipitates,
plus any coagulated organics. This filtered water then is passed through
granular activated carbon columns, which are 5 meters high and 2.5 meters
in diameter. Filtration rates today are 10 m/hr, versus 25 to 30 m/hr when
first installed. The lower filtration rates are optimum for the biological
activity contained in the DUsseldorf columns, which remove the 0.2 to 1.2
mg/1 of ammonia in the river bank filtered Rhine River water. This raw
water also contains 0.3 to 1.2 mg/1 manganese and 0.05 to 0.1 mg/1 iron.
After carbon contacting, the water is treated with 0.1 mg/1 of chlorine
dioxide solution (prepared by adding excess chlorine to sodium chlorite
solution). This provides a residual in the distribution systems of 0.05 to
0.10 mg/1.
Granular activated carbon columns currently are backwashed every 4 to
6 weeks and are regenerated every 5 to 6 months. When first installed, the
DUsseldorf activated carbon columns required reactivation every two years.
However the increase in concentration of chlorinated organics in the Rhine
River, which are not removed by river sand bank filtration and are not
readily degraded biologically in the activated carbon filters, causes the
more frequent regeneration. Carbon in the columns is analyzed periodically
for total organic chlorine (TOC1) at the top and 6 inches from the bottom,
and before this parameter breaks through the column, the carbon is regene-
rated. If there were not high concentrations of chlorinated organics in
the Rhine River water, the need for carbon regeneration at Ddsseldorf would
not be as frequent as it is. Only 80% of the carbon in a column is removed
for regeneration, so as to maintain high bacterial levels in the columns,
particularly of the nitrifying bacteria.
DUsseldorf currently has very little reservoir capacity in which to
store treated water. Therefore, treated water is produced on demand only.
This situation causes wide variations in water flows through the plants
during the day. These, in turn, caused changes in air pressures in the
older, plate-type ozone generators, which sometimes resulted in cracking of
the plate glass dielectrics. Additionally, flow rates of water through the
granular activated carbon columns are highly variable, and sometimes cause
the bacterial activity within these columns to function non-uniformly.
The City of DUsseldorf has a rule concerning the handling of ozone in
water treatment plants. In all rooms through which piping passes which
carries ozone, exhaust fans capable of providing 10 air changes per hour
must be present. These do not have to operate constantly, only when there
is an ozone leak in a pipe. This has not happened very often in the Ddssel-
dorf plants.
417
-------
Additionally, in each room in which ozone is generated or handled,
there must be an ambient atmosphere analyzer to monitor ozone. If the
concentration of ozone in plant air reaches the Maximum Allowable Konzentra-
tion (MAK) of 0.1 mg/1 (by volume), an alarm must sound to warn of faulty
operation.
DUISBURG WASSERWERK III WITTLAER PLANT, GERMANY
The Wasserwerk III Wittlaer of the Municipal Public Works of Duisburg,
Federal Republic of Germany is the only known municipal water treatment
plant which makes ozone from oxygen. It draws raw water from wells situated
along the Rhine River through the process of river sand bank filtration.
The capacity of the treatment plant was originally 2700 cubic meters per
hour (cu m/hr), but in view of decreasing raw water quality, the current
peak capacity is now 2000 cu m/hr. The current average flow rate through
the treatment plant is 1500 cu m/hr. The Duisburg analytical laboratory
takes samples of the process and product drinking water and the quality of
the raw water is tabulated as follows:
• Manganese 1.2 to 1.5 mg/1
• Iron 0.3 to 0.6 mg/1
• Dissolved Oxygen 0.5 to 1.0 mg/1
• Ammonia 0.5 to 1.4 mg/1
The Wittlaer plant was constructed in 1964 and began operation in
1965. It is one of three water treatment plants that serve the 370,000
inhabitants of the Duisburg area through a distribution system about 720 km
in length. River sand bank filtered water from the Rhine is pumped through
the water treatment plant to the distribution system at a pressure of 6
bars from one horizontal and 18 vertical wells. Figure B-5 shows a schematic
of the process. The raw water is pumped into the ozone contact chamber
where it mixes with an ozone-rich sidestream prepared from 10% of the
finished water volume having an ozone concentration of 10 to 25 grams of
ozone per cubic meter of water. (The overall ozone dosage is 1.0 to 3.0
mg/1 ozone.) The raw water and ozone-rich sidestream mix and flow cocurrently
upward through the Raschig rings in the contactor. A contact time of 8 to
10 minutes is provided in the stainless steel chamber with a residual of
0.2 to 0.5 mg/1 ozone. An additional five minute contact time is provided
in the piping ahead of the pressure filters and pressure granular activated
carbon (GAC) columns.
There are sixteen, 3 meter diameter, two-stage pressure vessels in
which the functions of a sand filter and a GAC reactor are combined.
Figure B-5 illustrates a typical unit. Each unit provides a filter area of
seven square meters (sq m). Four new pressure filter/GAC reactors, each
having an area of 25 sq rh, are under construction. The pressure filter
consists of one meter of porous silicate (heat treated pumice) above 30
418
-------
OZONE GENERATOR
PUMP LIQUID OXYGEN
STORAGE
VACUUM PUMP
OZONE
WASHER
Lf. L-^-Jf^., a
FILTER/GAC
REACTOR
NaOH
FIGURE B-5
WATER TREATMENT SCHEMATIC OF
DUSBURG PLANT, FEDERAL REPUBLIC OF GERMANY
TO DISTRIBUTION
SYSTEM
-------
centimeters of quartz sand. A two meter deep GAC reactor is situated
beneath the filters.
Raw water is ozonated so that organics, manganese and iron are oxidized.
Flocculated oxidation products are captured in the pressure filters. An
aerobic biomass maintained in the GAC bed removes soluble organics and
ammonia. The final treatment steps are the addition of chlorine dioxide
(0102) to maintain a disinfectant level within the distribution system and
the addition of sodium hydroxide (NaOH) for pH control. The ozonation
system is unique among the municipal water treatment plants that were
inspected in that liquid oxygen (LOX) is employed as the feed-gas for ozone
generation. LOX apparently was installed to allow a single pump per treatment
train to be used. This is possible because use of LOX requires a closed
system in order to recycle oxygen-rich ozone contactor off-gases.
Two suppliers deliver LOX to two separate storage tanks. Figure B-6
illustrates the ozonation system schematic. Each storage tank feeds the
ozonation system through an evaporator. The gas emerges from the evaporator
at a pressure of 0.5 bar where it meets the recycled contactor off-gas.
The mixture of makeup oxygen and recycled gas is fed to the four water-
cooled, DEMAG tube-type ozone generators. The ozone-rich feed gas is
further pressurized to 1.3 bar pressure by means of a water-sealed compressor
and then is injected into the water at the bottom of the ozone washer/con-
tactor at ozone concentrations ranging from 30 to 60 g/cu m. The ozone-
rich gas passes upward, countercurrently to the downward flow of a sidestream
of finished water in the Raschig ring washer/contactor. The plant has two
equal sized process trains.
The contactor off-gases (still containing 10 g/cu m ozone) are passed
first through a refrigerant drier and then a silica gel desiccant drier.
The dried gas is at an equilibrium concentration and consists of approximately
40% nitrogen and 60% oxygen. The dried and cooled off-gas is recirculated
to the point at which high purity oxygen is added as make-up gas. Approxi-
mately 5 g of ozone/cu m is lost (by decomposition back to oxygen) in the
drier.
The milk-white, ozone-rich sidestream from the washer/contactors is
pumped to the ozone contactor at a concentration of 10 to 25 grams of ozone
per cubic meter of water. Raw water and the ozone-rich sidestream mix and
flow cocurrently upward through Raschig rings in the main contactor providing
a contact time of 8 to 10 minutes.
Ozone Generators
Each of the four DEMAG ozone generators contains 206 individually
fused dielectric tubes. The ozone generators are installed so that the
tubes are in a vertical position, although DEMAG ozone generators are more
commonly installed so that the tubes are horizontal. The tubes are 1.5
inches in diameter and approximately 1 meter in length. A steel wool-like
electrode is used in place of the metallic tube coating used by other
suppliers. The units operate at 200 Hertz (Hz) and 6000 to 8000 volts.
420
-------
ro
DESICCANT
TYPE DRIER
FINISHED WATER (Q.IQ)
OZONATED
WATER'
GENERATOR COMPRESSOR
RAW WATER (0)
FIGURE B-6 OZONATION SYSTEM SCHEMATIC OF
DUISBURG WATER TREATMENT PLANT
-------
Dr. Uhlig, the plant chemist, described the recycle gas treatment
system as old and "not the best". The dew point of the feed gas to the
ozone generators ranges from minus 35 to minus 45°C. There are problems
with the formation of nitric acid as the dew point rises and approaches
minus 35°C. Therefore, operating personnel maintain the dew point in the
minus 40C to minus 45°C range. Duisburg plant personnel normally wait
until 10 or 20 dielectric tubes fail before scheduling maintenance for an
ozone generator. The tube failure rate at Duisburg is approximately ten
tubes per ozone generator every 6 to 12 months. At the time of the site
visit, two of the four ozone generators were out of service for maintenance.
One hundred extra dielectric tubes are stored at the plant.
Ozone generator cooling water is circulated in a closed-loop system
using phosphate-conditioned finished water. The cooling loop is cooled, in
turn, by means of a heat exchanger in the raw water supply. Cooling water
temperature rises from 10° to 12°C at the ozone generator inlet to 25° to
30° at the outlet.
Originally, there were corrosion problems with the V2A stainless steel
(believed to be the equivalent to U.S. 304 or 304L), particularly at weld
points near the ozone generators. No corrosion problems have been experienced
since the V2A stainless steel has been replaced by V4A (believed to be the
equivalent to U.S. 316 or 316L).
The ozone washer is backwashed regularly, while sludge is removed once
a year. The Raschig rings are removed once every two years for cleaning
and inspection to determine whether or not the rings should be discarded.
Ozone in the gas phase is monitored by a Bran & Ltlbbe monitor. The
unit was purchased originally to monitor ozone in water, but it proved to
be unreliable for that purpose. All ozone residuals in water are now
measured manually. The operations staff is convinced that continuous ozone
monitoring in the gas phase is practical with any of the numerous instruments
available. However, they have no confidence in instruments designed to
measure residual ozone in water.
Ambient ozone levels in the ozone generator room are not monitored.
However, there are several operating exhaust fans in the room. Operators
are instructed not to enter rooms whenever they can smell ozone. They are
to notify the plant manager and then use Draper tubes to check the ozone
level. If the ozone level is 0.1 mg/1 or lower, the room may be occupied.
The operating personnel have never had to use the self-contained breathing
apparatuses which are available.
Chlorine dioxide is made by an automatically controlled Wallace &
Tiernan Chlorinator system located in a separate building. Two chlorine
dioxide reactors are installed. One is in operation, and the other is a
standby unit. A third unit will be installed as part of the on-going plant
expansion. A strong chlorine odor was noticeable during visitation in the
chlorine dioxide reactor room in which the temperature was approximately
25°C.
422
-------
Chlorine dioxide is produced by mixing an aqueous chlorine solution
with a sodium chlorite solution. Each solution is fed from individual
"day" tanks which are, in turn, fed by a level-controlled supply from
larger storage tanks. Stoichiometrically, 300 grams of chlorine solution
per hour should react with 150 grams of sodium chlorite solution per hour
to provide the proper chlorine dioxide dose at the lowest water treatment
plant flow rate. However, Duisburg plant personnel actually add 4 times
the amount of chlorine required by stoichiometry. Chlorine dioxide (C102)
dosage is controlled by a continuous chlorine monitor which normally reaas
0.20 to 0.24 mg/1. Fifteen minutes after the ClOp is added, a chlorine
dioxide residual of 0.1 mg/1 is measured and the water enters the distribution
system (the city is 20 kilometers away). Water pressure in the ClO^
system is monitored from the control room. If pressure drops below a
minimum level, the C102 system automatically shuts down.
After chlorine dioxide is added, sodium hydroxide is added to control
pH. Chemical dosage is metered and monitored in the main control room.
Two Kalkas pH monitors (based on the principle of Dr. Gunther Axt) are
housed in another room.
It is not clear whether the ozone dosage was sufficient to provide
oxygen required to maintain aerobic conditions in the GAC columns. However,
an additional 10 to 12 mg/1 of oxygen apparently is added ahead of the two
stage filters, resulting in a dissolved oxygen level of 6 to 8 mg/1 in the
finished water.
ZURICH (LENGG PLANT), SWITZERLAND
Introduction & Overview
The water system for the city of ZUrich began in the 15th century with
the construction of a cistern system fed by springs in the vicinity of the
city. In 1430, the city's first fountain with running water was constructed,
fed from the Limrnat River.
Between the 15th and 19th centuries improvements to the water system
consisted principally of expansion to the well system. In 1868, construction
began on a pressurized water system for the entire city, drawing Lake of
ZUrich water through slow filters in the Limmat River and pumping it to
elevated reservoirs. Following a typhus epidemic in 1884, a filtration
plant directly drawing water from the Lake of ZUrich was constructed. With
growing population and pollution of the lake, service was expanded and
improved to the present system, shown in Figure B-7, of four main waterworks
on a circumferential transmission system.
The Lake of ZUrich is a moderate sized catchment of 4 cu km capacity
and an average discharge rate of 100 cu m/sec. It is highly significant as
a reservoir to communities along its shores, the largest of which is the
City of ZUrich, drawing 75% of its water supply from the lake. Because of
the discharge of domestic and industrial wastewater and runoff, the lake
has become mildly eutrophic. A policy of requiring nutrient removal on all
423
-------
wastewater plants has reduced this problem somewhat in recent years. Since
1972, there has also been an intensive program of water quality monitoring
in the lake. This, supported by extensive earlier efforts, shows that
nitrates and phosphates in the late peaked out in the late 1960s and declined
slightly after 1970 from peaks of 0.36 mg/1 phosphates and 3.6 mg/1 nitrates
(annual mean at 30 m depth). Chlorides have risen steadily over the period
of record from less than 1 mg/1 in 1945, to an average of 3 mg/1 in 1973.
-^. ^isik • %¥> ^ ^
Hardhof-Strickhof-Stollen
\ Frauental
w, ,-
ItStfvaLAjJ i
S&3O
P lUAWM^*^. a~-C-, -*. '
Stollen/Leitungen
— CXBT1N t
..UNDER
*~v X \t ^l
^^'
CONSTIWCTIOH
'
fl '- . '"s
.,•
•*mf\ •••'
-: Sihl u. Lorze VI
FIGURE B-7 OVERALL MAP OF VYATER
TREATMENT AND DISTRIBUTION SYSTEM
FOR ZURICH.SWITZERLAND.
Plant Description
The Lengg plant is one of two plants in the system which draws its
supply from the Lake of Ztlrich. The plant was constructed between 1956 and
1960 with a capacity of 160,000 cu m/day and was expanded from 1972 to 1975
to a capacity of 250,000 cu m/day. The plant was initially constructed to
424
-------
include prechlorination at the intake for destruction of nuisance organisms
(molluscs) followed by pumping to the plant site, 60 meters above the lake
on the north shore. In the initial plant, rapid and slow sand filtration
was followed by final chlorination and distribution.
The expanded Lengg plant process includes improved filtration plus
ozonation, granular activated carbon and final chlorination with chlorine
dioxide. The plant is constructed with two parallel treatment streams,
each with 1200 cu m/hr capacity. Each train has 10 rapid sand filters, 3
ozonators and 3 turbine contactors, 6 granular activated carbon filters, 7
slow sand filters, and one chlorine dioxide production and dosing assembly.
The basic elements of the process include the following:
• Intake Prechlorination
• Microflocculation
• Rapid Sand Filtration
• pH Adjustment
• Ozonation
t Granular Activated Carbon
• Slow Sand Filtration
• Chlorine Dioxide Dosing
These are discussed in turn below, with emphasis on the ozonation, granular
activated carbon and chlorine dioxide processes.
Intake Prechlorination—
Prechlorination is required to destroy organisms which are native to
the lake and which can collect in the pumping and treatment works. Principal
among these are small mussels, phytoplankton and zooplankton. Depending on
conditions, dosage is normally 1.0 mg/1 during the summer and 0.5 mg/1
during the winter, added at the intake line. Following this, the raw water
is pumped to the water works.
Micro Flocculation—•
Chemical micro-flocculation is employed to improve the efficiency of
the rapid sand filters. The water quality of the lake of ZUrich is quite
high, thus coagulation and sedimentation are not required. Rather, 2 mg/1
of aluminum sulfate (alum) are added to produce pinpoint floes which are
readily removed on the rapid sand filters. This is supplemented with a
polymer added at the rate of 0.2 mg/1. The system utilizes powdered alum
which is first mixed in a dissolving tank with water prior to being dosed
to the raw water. Powdered activated carbon also can be added before the
rapid sand filters, if required.
425
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Rapid Sand Filters--
Twenty rapid sand filters, each 15 m long by 3 m wide by 4 m deep
comprise the first filtration step in the Lengg plant. The filters are the
dual media type, with 1 meter of quartz sand (0.4 to 0.8 micron particle
size) covered by 70 cm of pumice (1 to 3 mm particle size). The normal
filtration rate is 20 m/hour and the filters usually require backwashing
every 4 days. Clean reservoir water is used for a combined water/air
backwash at a rate under 70 m/hour. The rinse water, approximately 2% of
total production, itself is filtered and returned to the plant headworks.
Filter washwater from rapid sand and activated carbon filters is
filtered in two basins 15 m long, 3 m wide and 6 m deep. A 50 cm layer of
quartz gravel, grain size 1 to 2 mm, serves as the filter medium. Filtered
backwash water is returned to the plant headworks. The washwater filters
are operated at a 7 m/hour rate and backwashed with raw water. Backwash
from these filters is sent to the Zurich sewer system.
pH Adjustment—
pH Adjustment is necessary to remove carbon dioxide from the lake
water. Lime is used for this purpose and it is added in sufficient quantity
to raise the pH of the water to 8.2. Initial lakewater pH ranges between
7.6 and 7.9. As with its alum system, dry lime is mixed with water prior
to dosing into the water. The lime is added into the outlet channel of the
rapid sand filters.
Ozonation—
Ozonation is used for virus and bacterial control, and oxidation of
organic compounds in the filtered water. The Lengg plant has two banks of
Kerag ozonators, with three sub-units in each bank. A common cast iron
housing surrounds each bank allowing for common cooling of each group of
three units. Table B-l gives known and observed data for the ozonation
systems at the Lengg plant. There are two ozone contactors, each having
three chambers. Each ozonator feeds a contactor turbine located in series,
one to each chamber (Figure B-8). Detention time in the chamber averages
30 minutes at low flow in the daytime and 10 minutes at night. Total
volume is 765 cu m divided into three chambers in series of equal volume.
There are no internal baffles in the chambers.
Excess ozone from the process is vented at the final chamber, broken
down in a thermal destruction system at 250°C and discharged through a tall
stack to the outside air.
Maintenance on the ozone process is handled by the manufacturer who
services the units once per year, under contract. At that time, 10 to 20
tubes per unit generally require replacing. The cost for this maintenance
service ranges from 5000 to 10,000 Swiss francs per year ($2084 to $4100
U.S. dollars ~ figured at an exchange rate of 2.4 Sf/$ in early 1977) plus
materials, which includes full servicing on the air preparation equipment,
the ozone generators, and the ozone contacting equipment. Reported capital
costs for the ozonation equipment and contactors were 0.6 cents/cubic meter
of capacity. Operating costs as of 1977 are as follows:
426
-------
Dosage
Cost*
Ozone
(mg/1)
1.5
5 (4 to 6 range)
-------
oo
m t
OZONE
DESTRUCTOR—1
TURBINE CONTACTOR
Im 3m , 5m
Om . 2m , km
SCALE IN METERS
WATER FLOWS IN
FROM OTHER BAY
WATER FLOWS OUT TO OTHER BAY
FIGURE B-8. Multi-turbine contactor installation (Lengg Plant, Zurich)30.
-------
The layout of the ozonator equipment at the Zttrich plant is highly
compact. Piping and appurtenances in the air drying system are of coated
welded steel. Ozone-containing air lines are of PVC plastic pipe. Each
bank of ozone generators is housed in a large cast iron vessel through
which the cooling water is pumped. Internal parts are of glass or stainless
steel. The use of PVC for the ozone-containing air line is unusual.
Although the plant personnel did not indicate problems with the PVC, there
was some evidence of previous breaks on one line.
Granular Activated Carbon--
GAC removes organic compounds and residual ozone from the potable
water stream. The Ztlrich Lengg plant has 12 activated carbon filters, 6
for each treatment train. The filters measure 5.8 m deep, 9.7 m long and
4.5 m wide, and 130 cm of carbon are placed over 40 cm of quartz sand. The
carbon Is regenerated annually and the plant has a regeneration furnace for
this purpose. The carbon is regenerated at 700°C in a fluidized bed. The
contaminating substances are incinerated at 900°C and the effluent gases
are water scrubbed. The furnace treats 100 kg of carbon per hour and is
fully automatic.
Laboratory analysis indicates that a regenerated carbon will remove
TOC (Total Organic Carbon) at the rate of 1 g TOC/4 g of carbon. Exhausted
carbon removes TOC at the rate of 1 g TOC/14 g of carbon. TOC breaks
through the carbon columns at Lengg before organic chlorine compounds;
however, samples are monitored for both at three points in the carbon beds.
Backwashing of the carbon filters is accomplished in three stages.
First, the bed is backwashed with air, then with air plus water, and finally
with water only. The last phase of backwashing separates the carbon from
the sand. For backwashing, air flow is 20 m/hour, air plus water flow is
25 m/hour, and water flow alone is 50 m/hour. The filters must be backwashed
approximately every 2 days.
Slow Sand Filtration-
Slow sand filtration is the final filtration step at the Lengg plant.
There is a total of 14 slow sand filters, each of which is 48 m long, 24 m
wide and 4 m deep. All of the filters are fully enclosed. Rate of filtration
is 15 m/hour for these filters. The filters are manually cleaned by laborers
who shovel the upper two centimeters of sand into a small wheeled hopper
which is connected by hoses to the sand washing machine in another room.
The sand is sluiced to the sand cleaning machine by water and returned the
same way. The plant presently is testing a floating sand cleaning machine
which would accomplish cleaning without shoveling. Addition of a final
stage of carbon filtration also is being studied by placing a shallow layer
of activated carbon on the filters. The slow sand filters, which are
cleaned infrequently and only when their head loss reaches 2 m, serve as
the final solids removal step in the Lengg plant.
Chlorine Dioxide Addition--
C102 addition is provided to avoid bacterial regrowth in the product
water, ft is manufactured on-site by combining sodium chlorite (NaC102)
solution and hydrochloric acid (HC1). The reaction is as follows:
429
-------
NaC102 + HC1 >C102 + NaCl
A schematic of the Lengg C102 system is shown in Figure B-9. Basically,
the system dilutes stock solutions of the feed chemicals which are stored
in reinforced fiberglass tanks 9 cu m in volume and then combines them to
produce an aqueous solution of CICL. The stock HC1 is diluted to a 7%
solution and the stock NaClOo is diluted to a 9% solution prior to combina-
tion, as the reaction is exothermic and potentially explosive in stronger
concentrations. The solutions are stored in separate tanks made of reinforced
polyester/fiberglass. The chlorine dioxide solution is conveyed to the
mixing point through six proportioning pumps operated in conjunction with
the six raw/finished water pumps.
Combination of the two chemicals is carried out in a Raschig ring
packed column 5 feet tall and 6 inches wide. Pumping rate through the
reactor is 40 I/hour, of both solutions. Each solution is pumped through
a separate line and into the reactor by the same dual chamber pump. The
reactor effluent is stored in the chlorine dioxide storage tank for use.
The system is fully automatic and is controlled by the level in the chlorine
dioxide tank. Level controls in this tank control the reaction system, and
similar level controls in the dilution storage tanks control the dilution
process.
Because of the dangerous nature of the process chemicals, safety
precautions are numerous. Acid and chlorite solutions are stored in separate
concrete rooms below the chlorine dioxide preparation room. There are no
drains in the storage rooms to prevent escape of the chemicals in the event
of a rupture. Rather, there are leakage alarms in both of the rooms, and
another leakage alarm in the room which serves as an entrance to the
storage rooms. In the event of a spill, the chemicals would be fully
contained and would be pumped out into other tanks for disposal. The
control room for this dual chlorine dioxide system is located in a third
room. Sprinklers are installed in all chlorine dioxide rooms in case of
accidental spills.
The product water from the final filters is dosed to a residual level
of 0.05 mg/1 of C102 prior to being pumped into the system. Standards call
for a minimum of 0.01 mg/1 residual chlorine at the most distant customer.
Pilot Plant—
The Lengg plant has a small scale pilot facility which mirrors the
larger process, as an aid to study and monitoring of the system. Raw water
is run through the pilot plant, which is fully automated, and sampled and
analyzed in similar fashion to the full scale process. Three trout aquaria
are also present, one containing small, one containing medium, and one
containing large fish in a treated drinking water flow. This serves as a
living biological monitor for treated water from the plant. At the first
sign of general distress in any of the tanks, the system is shut down and
analyses performed.
430
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SYSTEM WATER
SOFTENED
, FrFK|r) SODIUM CHLORITEiNaC102 HYDROCHLORIC ACID: HC I
' SYSTEM WATER CHLORINE DIOXIDE: C102
C102 WASTE
FIGURE B-9. Lengg Waterworks, Zurich, Switzerland.
Chlorine Dioxide System.
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The entire pilot facility is housed in a separate room near the labora-
tories and is operated full time as an aid to overall plant operation. It
also serves as a study area for proposed process modifications.
SIPPLINGER BERG, SIPPLINGEN, (LAKE OF CONSTANCE) BODENSEE, FEDERAL REPUBLIC
OF GERMANY
Introduction & Overview
The Bodensee Wasserversorgung (BWV) water treatment plant was constructed
near Sipplingen, West Germany in 1956 to 1958 by a joint consortium of
nearly 100 towns and 500 communities in the Baden-WOrttemberg region of
West Germany. This area, located in southern and central regions of West
Germany was plagued with repeated water shortages as a result of the geology
and climate of the region. Reliance on groundwater was not possible with
growing populations because of its unreliability. The nearest large body
of fresh water was the Bodensee (Lake of Constance), one of the largest
natural reservoirs in Europe and approximately 50 cubic kilometers in
volume.
The water from this plant is pumped north through a dual pipeline a
distance of over 150 kilometers, terminating considerably north of Stuttgart.
The unusual length of this pipeline, coupled with the need to maintain a
chlorine residual over its entire length, was one of the major reasons for
the addition of ozonation equipment when the plant was expanded in 1966 to
1970. German drinking water standards allow a maximum chlorine dosage of
0.3 mg/1 at the outlet of the waterwork, and 0.6 mg/1 in special cases.
Without ozonation, this amount of residual chlorine would disappear before
the product water reaches Stuttgart. With ozonation, however, residual
chlorine is present in the Stuttgart mains. Today the plant is the largest
single water treatment plant in Germany using ozone, with a capacity of 7.5
cu m/sec (648,000 cu m/day), up from 4.5 cu m/sec at its initial construction.
The water quality of the Bodensee is generally good, particularly in
the arm of the lake from which the BWV draws water. There is very little
adjacent development and the average 0.08 mg/1 phosphorus concentration (as
P) and 1 to 2 mg/1 TOC (Total Organic Carbon) reflects the relatively good
water quality. Nitrates average 3 mg/1, sulfates 35 mg/1, COD 4 mg/1 and
hardness 8.9 degrees (German measure of hardness). This is a soft water.
The age of the lake lies somewhere between the oligotrophic and eutrophic
stages. Water is withdrawn at 60 m depth, 420 feet from the shoreline and
pumped 312 meters (in elevation) to the hilltop on which the plant is
located. The water is subjected to microstraining, ozonation, filtration
and chlorination prior to being pumped into the distribution system.
Microstraining
The initial process in the BWV plant is microstraining to remove algae
and plankton, and to extend the working capacities and rates of the sand
filters. The microstrainersr sized for 40 micron mesh size, are normally
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stationary, being rotated and backwashed only when head loss exceeds 150
millimeters pressure. Maximum flow rate through all 12 microstrainers is
2200 cu m/hour. Each microstrainer has about 20 cu m filter area and
approximately 2/3rds of the screen is exposed to water.
Ozonation
Six Herrmann ozonators (860 tubes/unit) dose the microstrained water
to an average level of 1 mg/1. Capacity of the units is 40.5 kg/day total
maximum. The ozonators prepare ozone from air dried and cooled in two air
preparation units with one on standby. The air is compressed to 0.8 bar,
filtered through 3 micron pore size cloth and refrigeration cooled to 16°C
before being passed through a silica gel desiccator. Air flow rate is
variable, depending on the number of ozonators in service, at a constant
rate of 180 cu m/hr per ozonator (thus, ozone concentration varies from 18
g/cu m at the lowest voltage to 32 g/cu m at the highest voltage). After
cooling and drying, air enters the ozone generator and its moisture content
is monitored continuously by a Panametrics model 3000 dew point meter. The
meter is calibrated every six months and plant personnel report satisfactory
operation. A maximum dew point of minus 40 degrees is the setpoint on this
instrument which will shut down the ozone generators if the dew point rises
above this level.
The ozone generators are cooled with 8 cu m/hr (each) raw water which
averages 4°C in temperature year-round. After use, the raw water is returned
to the inlet well of the plant. Each generator can be operated manually in
10 steps from 10,000 to 18,000 volts (50 Hz). Eighteen watt-hours of power
are consumed per gram of ozone produced (18 kwh/kg).
Normal production of the ozone generator is 23 kg/hr, with a maximum
of 34 kg/hr. Normal ozone dosage rates "are 0.9 mg/1 with capacity to
achieve 1.2 mg/1 dosage if needed. Excess ozone-containing gases are
passed through wet activated carbon filters and then vented to the outside
air. Off-gases from these carbon units contain approximately 0.8 g of
ozone/cubic meter of air. No evidence of ozone odor was detected in the
buildings or outside at the time of the plant visit.
Air pressure upon leaving the ozone generators is approximately 0.46
bar, which is approximately 0.08 bar above the pressure at which it enters
the contactors.
Maintenance experience on the air cleaning and ozonation train has
been good. The silica gel has not required replacement in over seven years
of usage and ozone generator tube breakage has been minimal. Some initial
difficulty with the drying system was encountered, due to carryover of
silica gel dust into the ozonators. This was cured by installing a finer
air filter after the desiccator. The ozonators have been cleaned once,
after 5 years service, and very little tube breakage had occurred at that
time. Ozonized air is moved to the contactors through steel pipes coated
with a special corrosion resistant paint at a considerable savings over the
cost of the more common stainless steel pipe. Performance of the coating
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system has been quite satisfactory. Earlier, the facility had tested PVC
and polyethylene pipe for this application and found them to be unsatisfac-
tory. Overall, the ozonation facility appeared in like-new condition-
there were no overt signs of deterioration.
Ozone Contactors
Ozonation at the BWV plant utilizes packed beds for contacting with
the microstrained water. Physically, the 12 contactors are located directly
under the 12 microstrainers. The contactors are designed as shown in
Figure B-10. Ozone is added at the bottom and meets the countercurrent
flow of water falling through the perforated plate onto a packed bed of
Raschig rings 2 m in depth. The ozone is fed in at a pressure above ambient
of 0.35 bar and total water head loss through the contactor is approximately
3.7 meters. Contact time is about 2 minutes in the contactor. Measured
transfer efficiency in the contactors is 98%. The ozonated water passes
through two parallel detention reservoirs of 35,000 cu m each, for a minimum
detention time of 75 minutes. These chambers serve as final detention
basins for the ozonated water and as equalization/storage basins for water
from the sand filters.
About 67 cu m of ozonized air is passed through each contactor in one
hour. The system is coupled to the operation of the 6 intake pumps such
that when only one intake pump is operating, only 2 ozonators are operating.
When 2 pumps are operating, 3 ozonators are operating. A maximum of 4
pumps and all 6 ozonators can be operating at the same time, with two pumps
on standby.
Safety precautions were numerous throughout the ozonator-contactor
system. Every room in which an ozone process was present had ozone detectors
coupled to alarms. Exhaust fans also were provided in these areas. In the
packed bed contactor, the Raschig ring packing has performed without visible
deterioration for 7 years and there is still no apparent need for replacement.
Sand Filtration
Sand filtration at the BWV plant is carried out in a large semicircular
building housing 27 rapid sand filters. Each filter has a bed of sand over
0.8 m of pumice, with a thin layer of pebbles at the bottom. Filter surface
area totals 3000 sq m and normal flow rate is 9 m/hr. Backwashing is
accomplished using product water only at a rate of 37 m/hr. No air back-
washing is practiced. There Is also provision to place a 20 cm thick layer
of carbon on the filters in the event of pollution emergencies.
Injecting the ozone under super-atmospheric pressure has led to
shortened filter runs in some cases, due to air bubbles forming in the
media. Nevertheless, filter runs are quite long, averaging 3 weeks between
backwashings.
Plant personnel stated that ozonation has lengthened filter runs and
improved retention of the final chlorine residual. Microflocculation was
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GAS OUTLET
ENTRAPMENT
SEPARATOR
DISTRIBUTOR
llQUID INLET
REDISTRIBUTOR
SUPPORT PLATE
1 GAS INLET
LIQUID OUTLET
FIGURE B-IO
SCHEMATIC OF PACKED BED SIMILAR TO THE ONE
USED AT WATER TREATMENT PLANT IN SIPPLINGEN
BERG FEDERAL REPUBLIC OF GERMANY
435
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evident in the filter feed water and floes have been measured at an average
diameter of 0.4 mm. The filters can retain particles 0.04 mm and above.
Dissolved organic carbon (DOC) measurements indicate that 30 to 40% of the
DOC is removed by the sand filters.
Chlorination
The product water is treated with 0.6 mg/1 of gaseous chlorine added
for residual. Chlorination is accomplished through 6 gas chlorinators fed
from multiple cylinders. Near the end of the distribution system in
Stuttgart, 150 km to the north, the residual has decreased to 0.05 mg/1.
Studies have shown that the chlorine residual will last 500 hours in
ozonized water. Prior to the incorporation of ozonation, residuals would
last only 150 hours, and problems with regrowth were experienced in the
extremities of the distribution system.
After dosing, the water is held in two 20,000 cu m reservoirs prior to
pumping into the transmission mains.
Pilot Plant
Similar to the Lengg Plant, the BWV plant has a pilot facility to aid
in studies of the basic process and potential modifications. The pilot
plant processes raw water at 10 cu m/hr. Considerable research work using
biological monitors for detection of toxic substances is being done in the
raw water pumping station on the lake shore. Algae which give off oxygen
at a specific rate, which changes only with the introduction of toxic
substances, and water fleas, whose rate of swimming is affected by toxics,
are two of the biological monitors. Still a third technique uses a Grathone-
mus fish, which is an electric eel from Africa. Change in electrical
emissions from these fish is an indicator of the presence of toxic pollutants,
and the fish can detect 0.2 mg/1 of cyanide. Normal reaction time for
these biological monitors is in the two hour range, though early responses
can be noted within one hour.
Full laboratory monitoring is provided at this site on the raw water
supply. Mercury, lead, copper, arsenic, selenium, chromium, zinc, cadmium,
iron, and manganese are monitored to assure compliance with German drinking
water standards. This laboratory also monitors nutrients, organic compounds,
and biological growth in the raw water. Monitoring of effluents from area
wastewater treatment plants is an aid to anticipating changes in lake
chemistry. Raw water is also monitored for oil, pH, dissolved oxygen,
temperature, redox potential, turbidity, and polyaromatic hydrocarbons
(PAH).
ST. DENIS, QUEBEC, CANADA
Background
The St. Denis water treatment treatment plant located in the Province
of Quebec, Canada, was constructed in 1972 with a design capacity of 27,300
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cu m/day. It is a publicly owned and operated plant which draws its supply
from the Richelieu River. Present flows average 9100 cu m/day (2.4 mgd),
peak is 15,900 cu m/day (4.2 mgd). Both the raw and finished waters are
tested for turbidity, alkalinity and bacteria on frequent schedules.
The plant process involves pre-chlorination, coagulation, sedimentation,
filtration, ozonation, and chlorination. Ozonation is used primarily for
the control of taste and odors.
Process Description
The water treatment process at St. Denis begins with the injection of
1 mg/1 of gaseous chlorine for controlling biological growth in the process.
There is also provision for pH adjustment of the finished water as needed,
using soda ash. The raw water is then coagulated with alum, settled in
clarifiers, filtered, ozonated, and chlorinated.
Two PCI Ozone generators are used at this plant, each of 0.58 kg/hr
capacity. They are normally operated at about 65% of capacity. Normal
current drawn at this load is 1.5 to 2 amps at 550 volts and 60 Hz. The
units are double cooled (oil and water), tube type with 6 tubes per ozonator.
The first unit was installed in 1972; the second was put into operation in
early 1977. The units are operated 18 hours per day, alternately, on
successive days. Air for the units is drawn from within the ozonator room
at about 14 cfm at 70°F and 14 psi. The air is refrigerant cooled and then
passed through a desiccant dryer. Dew point of the outlet air is not
monitored.
The ozonized air is contacted with the filtered water in each of two
chambers that are 8 ft wide, 15 ft long and 20 ft deep (18 ft water depth),
through 6 porous stainless steel diffusers in each chamber. The chambers
are operated in series with differing amounts of ozone added to each chamber.
At the time of the plant visit, 9 cfm of ozonized air was flowing to the
first basin and 5 cfm was going to the second basin. Total ozone dosage is
2.2 to 2.3 mg/1 and detention time is 10 minutes. Contactor off-gases are
blown out of the building with a 1 hp fan equipped with a sealed motor.
The exhaust gas stack is constructed of stainless steel. In addition,
chlorine is added in sufficient amount to equal 0.5 mg/1 of total oxidant.
Normally this means that 0.3 mg/1 of chlorine must be added (the balance
being residual ozone).
The plant follows a strict schedule of thorough cleaning of the
ozonators after every 2500 hours of operation. In addition, the intermit-
tent operation of the units has lead to considerable other maintenance,
mainly fuse and gasket replacement. Tube leakage, however, has not occurred
on either unit to date. There is an ozone detector in the ozonator room —
the presence of ozone starts an automatic ventilator fan and another ozone
detector with an alarm is placed between the ozone generation room and the
contactor.
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The raw and finished waters are tested for pH, turbidity, aluminum,
calcium, copper, iron, magnesium, manganese, potassium, sodium, zinc,
sulfates, chlorides, fluoride, hardness and alkalinity at the plant.
Bacteriological samples are taken at 5 points in the distribution system
and analyzed by an outside laboratory. Finished water at the plant is not
normally analyzed for bacteriological water quality.
SHERBROOKE, QUEBEC, CANADA
The Sherbrooke, Quebec, Canada water treatment plant is a new facility
(which had just been turned over to the city about a month before the plant
visitation was made) incorporating some equipment from an older plant of
the same name. Raw water, pumped from Lake Memphremagog eighteen miles
away, passes through microstrainers for algae removal (three new ones in
operation and three old ones currently being refurbished). Prechlorination
is used when the temperature of the raw water increases or when algae
problems appear. The microstrained water (16 mlgd at the time of the
visit) flows through the ozone contactors, described below, to a twenty
million Imperial gallon reservoir located under an adjacent athletic
field. As water is withdrawn from the reservoir, it is chlorinated at a
dosage of 1.4 mg/1 prior to entering the distribution system. The extremity
of the water system is 3.5 to 4 miles from the plant. The average residence
time in the distribution system is approximately 24 hours but the system
has dead ends in it. Chlorine residuals are monitored at 6 of the 19 pump
stations in the system. Water quality samples are taken three times per
week for analysis at the Provincial Government Laboratory in Quebec City.
Air Preparation System
The air preparation system was the only one observed which utilizes
pressure swing or heatless (desiccant) driers which operate at 100 psi, and
one of two to utilize a concept called Ozonazur by the manufacturer,
Degremont, that incorporates an air drier, ozone generator, and controls on
a single skid mounted unit (see Figure B-ll). The ozonation system was
designed and manufactured in Canada by Degremont Infilco Ltd.
Four Gardner-Denver "Electro Screw" compressors, located in a separate
room, discharge 100 psi air to four water cooled heat exchangers. High
noise levels exist in the compressor room.
Ozone Generators
The cooled air passes to the four modular drier/ozone generator units.
Air enters the pressure swing desiccant driers through a filter at 87 psi
and leaves at 85 psi. Activated alumina is used as the desiccant material.
A dew point of minus 40°C was estimated for the gas under pressure but no
dew point monitor or hygrometer was installed. A pressure reducing valve
is provided to reduce the pressure of the air entering the ozone generators
to 12 psi. At this pressure, the dew point of the gas becomes lower.
Ozonized air pressure leaving the ozone generators was 10.5 psi. Inlet air
temperature was 31°C and the exit ozonized air temperature 45°C, with
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AIR IN CQMP WATER COOLED HEAT
D "
AIR FILTER
AIR IN
ID-
MR FILTER
EXCHANGER
AIR
COMP WATER COOLED HEAT
EXCHANGER
AIR
AIR IN COMP WATER COOLED HEAT
AIR FILTER EXCHANGER
AIR IN COMP WATER COOLED HEAT
AIR FILTER EXCHANGER
DESICCANT
DREI
DESICCANT
DRIER
DESICCANT
DRIER
OZONE
GENERATOR
OZONE
GENERATOR
OZONE
GENERATOR
R
*
t
e FLOW t
METER
FIGURE B-l I OZONATION SYSTEM SCHEMATIC AT
SHERBROOKE, QUE BEC, CANADA
FLOW
METER
OFF-GAS
OZONE CONTACTOR
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cooling water temperature of 24°C. Ozone generators are constructed
entirely of 316L stainless steel except for the bubbler heads which are
constructed of type 304L. The heads do not come into contact with cooling
water. Each ozone generator contains 126 tubes. Cooling water is finished
water which is discharged from the ozone generator to the head of the
plant.
Ozone Contacting
Each pair of ozone generators discharges to one of the two ozone
contactors through gas flowmeters to porous tubes at a water depth of
sixteen feet. Each contactor consists of two compartments operating in the
countercurrent mode. A contact time of eight minutes at the design flow
rate is provided. Residual ozone levels in solution are monitored at the
exit from compartment No. 1 and at the exit from compartment No. 2. The
ozone dosage is controlled automatically by the residual ozone monitor
reading at the exit of compartment No. 1, while the second monitor is
programmed to sound an alarm if the residual ozone level at the exit from
compartment No. 2 drops below 0.4 mg/1 ozone. The ozone analyzers were
Amperazur, amperometric analyzers, Type 5, Series 3, manufactured by Degre-
mont, France. The signal from the Amperazur is compared to a predetermined
set point and the voltage of the ozonator is increased or decreased appropria-
tely to correct the ozonator output. One residual ozone meter was indicating
0.03 mg/1 and the other indicated zero. It was not clear whether the units
were properly calibrated or not. It is known that the ozone demand of the
water is higher than was originally predicted.
Contactor off-gas is discharged to the atmosphere through four roof-
top vents. Ozone could be smelled in the vicinity of the plant. There are
no ambient ozone monitors in the ozone generator room.
Four, skid mounted, oil filled transformers (one for each ozone gene-
rator) are situated in a lower level room that is accessible only from the
outside through a door that is normally kept locked. The room temperature
was approximately 95 to 100°F.
PIERREFONDS, QUEBEC, CANADA
The Pierrefonds, Quebec, Canada plant draws water from Riviere des
Prairies 200 feet off-shore through 1100 feet of 36 inch diameter intake
pipe by means of four 7000 U.S. gpm pumps. The design capacity is 42 mlgd
but current production is approximately 21 mlgd. The plant began operating
in late 1976.
Raw water passes through a magnetic flow meter to a screening room to
pass through one of two screens. Prechlorination is used when considered
to be required, more frequently in summer than in winter. Screened water
passes through a flash mixing chamber to a ribbon type walking beam floc-
culator. Chemical clarification is provided in two Pulsator units* with
See description of Tailfer plant (Brussels, Belgium) for discussion of
operating characteristics of Pulsator.
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activated silica, caustic soda and alum. Provision is made to add chemicals
at the intake pipe, in the flash mixing chambers or later in the system.
During the visit, chemicals were being added at the mixing chamber.
The clarified effluent proceeds to 6 older single filter units and 4
newer double filter units so that there is the equivalent of 14 single
filters. Each filter medium consist of 24 inches of anthracite coal,
supported by 6 inches of sand and 6 inches of support gravel. The filter
rate ranges from 2 Imperial gpm per sq ft to 4 Imperial gpm per sq ft. The
filters are backwashed every 125 hours, when the filtrate turbidity reaches
0.6 JTU, or if the head loss is greater than 0.15 meters. The backwash
cycle includes air wash, surface wash, and water backwash. The filtered
water passes to the two ozonation contactors for organics oxidation and
disinfection. Ozonated water flows to a three million gallon reservoir.
Caustic soda (pH adjustment), fluoride and chlorine are added to the water
as it is drawn from the reservoir by four finished water pumps, having a
maximum combined capacity of 25,000 Igpm.
Approximately 1.0 mg/1 of chlorine is added to finished water at
Pierrefonds. Water is pumped to the Dolar reservoir that is eight miles
from the plant. Chlorine residual at the Dolar reservoir is maintained at
approximately 0.4 mg/1, which maintains the chlorine residual level in the
distribution system at approximately 0.2 mg/1. There are approximately 23
miles of 24 inch and 36 inch diameter distribution pipes in the system.
Average residence time of water in the system is approximately 3 days.
Ozonation System
The Pierrefonds ozonation system is illustrated in Figure B-12.
Blowers, water cooled heat exchangers and refrigerant coolers are located
in a lower floor room, apparently to isolate the blowers and refrigerant
coolers from the remainder of the plant. The rotary valve blowers take
suction from the interior of the room through individual inlet filter-
silencers. The blowers also are equipped with discharge silencers and were
selected for a minimum rotational speed to minimize noise generation.
Three blowers are fixed speed (750 RPM) and one variable speed (up to 1400
RPM). Air temperature leaving the air blowers is at 100°C. Four water
cooled heat exchangers are provided to reduce the air temperature from the
blowers to 24°C. Finished water from the high pressure pumps is used for
cooling. Two refrigerant (glycol) driers are used to reduce the air tempera-
ture to the desiccant driers to 8°C.
The cooled air passes upward to the ozone generator room which also
houses the desiccant driers. Two dual-cell, silica gel desiccant driers
discharge gas at approximately 28°C and at an equivalent dew point of minus
80°C (2 to 3 mg/1 of moisture measured by hygrometer). The dried air is
fed to three Trailigaz, water cooled, horizontal tube ozone generators.
Each generator contains 240 tubes. Cooling water is supplied from the
discharge side of the high pressure pumps and returned upstream of the
gravity filters. Cooling water is approximately 1°C in winter and as high
as 24°C in summer.
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AW IN AIR
COMPRESSOR
AIRFttTER
AM IN
WATER COOLED
HEAT
EXCHANGE*
AM
AIR FILTER
AIR IN
WICTER COOLFD
HEAT
EXCHANGER
AM FILTER
All IN
WTCR COOLED
HEAT
AMFNTCJt
VKTER COOLED
HEAT
EXCHANGER
REFRIGERANT
COOLED DRIER
6AS OFF
PRV
:ANT
REFRMERANT
COOLED DMCR
PRV
OZONE
GENERATOR
OZONE
GENERATOR
OZONE
GENERATOR
OZONE CONTACTOR
FIGURE BH2
OZONATION SYSTEM SCHEMATIC
P1ERREFONDS WATER TREATMENT PLANT QUEBEC,CANADA
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Two ozone contactors are provided with a water depth of approximately
18 feet. Each contactor has two ozonation compartments, the first with
countercurrent ozonation and the second with cocurrent ozonation. A third
compartment is provided for degassing. 1.6 mg/1 of ozone is added to the
first chamber and 0.3 mg/1 is added to the second chamber. A total ozone
dosage of 1.5 to 2.0 mg/1 ozone is required to maintain a residual of 0.4
mg/1. The ozone residual in the treated water is measured by equipment
supplied by Chloro Residual Co. of Milano, Italy (Chloresiduometro -Chlorosis
Breyatato - Sis, Milano). The monitor indicated a residual of 0.47 mg/1
during the plant visit. The unit is recalibrated every two weeks by using
ozone-free water to establish a zero point.
The ozone contactor off-gases are discharged to a rooftop stack
without complaints from the neighbors in the rural surroundings. No off-
gas monitoring is used. Dasibi (Model 1003AH) ambient air ozone monitors
were installed in both the blower room and the generator room. The monitors
in the generator room were not in service. They had just returned from
repair as they had become plugged with paint when the room had been spray
painted. The alarm was set for 0.08 mg/1 ozone. The Dasibi monitor samples
ambient air every 20 seconds and provides an instantaneous digital reading.
The Dasibi monitor in the blower room indicated 0.07 to 0.08 mg/1 during the
plant visit.
The ozonation system has been in operation only since 1976 but the
plant manager plans once per year maintenance of the system. Three to four
dielectric tubes were broken during start-up but none in subsequent operation
so far. The plant manager has ordered 10 tubes as spare parts. Dielectric
tubes cost approximately $120 each, or $200 for each unit complete with
high tension connection. A feature of this plant was the provision of
three mobile carts for tube storage. Each wheeled cart has 64 vertical
spaces to provide tube storage during generator servicing.
QUEBEC CITY
Introduction and Overview
The Quebec City water treatment plant is located adjacent to the St.
Charles River, approximately 8 miles north of the city. The plant was
designed to treat 220,000 cu m/day (58 mgd); it can be readily expanded to
264,000 cu m/day (72 mgd). It is semi-automated and is operated by 14
people. Raw water is pumped from the river and prechlorinated to 1 mg/1
with 181 kg/day of chlorine, followed by chemical addition. After flash
mixing, the water is flocculated, clarified and filtered. Ozonation follows
filtration and the treated water is stored in 4 reservoirs totalling 31,820
cu m of storage capacity.
The first Quebec water works was built in 1840 and pumped essentially
untreated water a distance of 18 miles to the city. Chiorination was
instituted in 1930, but no other treatment was used until 1969 when the
present plant came on line.
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The plant tests daily for COD, turbidity, color, pH, chlorine residual,
alkalinity and hardness. Bacteriological tests are not performed at the
plant, but rather are checked at 14 points (including the plant) and analyzed
at a laboratory in Quebec City.
Pretreatment, Coagulation, Flocculation and Sedimentation
Processing of the raw water at the Quebec City plant begins with
addition of 0.5 to 1.5 mg/1 (depending on season; higher in summer) of
chlorine, used specifically to kill the larvae of river flies. This is
followed by the addition of lime and alum coagulants. Flash mixing of the
chemicals is carried out in 6 flash mixing basins of 1 minute detention
time, based on design flow. Polyelectrolyte is added after flash mixing
and the water then is flocculated in 7 ribbon flocculator equipped basins.
Sedimentation is carried out in 4 circular basins with 4 hour retention
time, based on design flow, prior to filtration. Water treatment sludges
are returned to the river. Chlorine in the amount of 0.1 mg/1 is also
added prior to filtration.
Filtration
Sixteen multimedia rapid sand filters of 65 sq m surface area are
provided for filtration. Bed design is 61 cm of anthracite (0.9 to 1.2 mm)
over 15 cm of sand (0.75 to 0.55 mm) with 30 cm of graded rock and gravel
on the bottom. Design flow rate in treatment is 9 m/hr (9 cu m/sq m/hr)
and backwash rate is 36 m/hr with clear water only. No air washing is used
at this plant. Backwash times average 7 minutes and approximately 273 cu m
are consumed with each washing. Backwash water is returned to the river.
Better raw water conditions in winter often allow filtration rates exceeding
18 to 20 m/hr during winter months.
Ozonation
Ozonation at Quebec City is provided by 12 Otto plate ozone generators,
in banks of 3 each. The units are water cooled (37 cu m/hr total air
flow), and air is filtered and dried by two parallel air treatment trains,
one operating and one on standby. Air is filtered, compressed, dried in
silica gel columns and then fed to the ozonators. Four sets of silica gel
beds are provided, two for each treatment train. The desiccators are
regenerated each 8 hours with hot air at 220°C. Output humidity is monitored
after the desiccators with a lithium bromide relative humidity meter. The
unit will sound an alarm and shut the ozonator down when its set point is
exceeded.
Negative pressure is maintained in the ozonators to reduce leakage,
which has been a problem. At the time of the plant visit, the ambient
ozone level in the ozone room read 0.78 mg/1 and was strongly noticeable.
This level dropped to 0.15 mg/1 later in the visit.
Ozone is generated in a voltage range of 9,000 to 15,000 volts, adjusted
in a stepwise manner. Normally, the units are set at 11,500 volts. Total
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installed power for the 12 ozonators is 760 kw and the plant normally draws
300 to 350 kw. Ozone residual in the contact chamber is 0.4 mg/1 after 4
minutes which appears as 0.2 mg/1 at the sampling point in the laboratory.
The ozone is contacted with the water supply for 6 to 8 minutes. The
contacting is done in an injector system which contacts the ozone with a
small portion of the water flow, then reinjects it into a down-flowing
tube. The system is similar to those at DUsseldorf and Konstanz (Germany)
plants. Ozone is drawn into the water flow through a venturi under negative
pressure, hence maintaining a slightly negative pressure on the ozonators.
Off-gases from the contact basin are vented untreated to the atmosphere.
In general, the ozonation equipment has performed satisfactorily.
Maintenance problems arise from the non-continuous operations of the
ozonator as they are only operated 18 hours per day. It has been found
necessary to flush an ozonator for at least 1 hour with dried gas after
maintenance prior to restarting at the lowest voltage setting.
Final Chiorination
Following processing, the treated water is dosed with 0.5 to 1.0 mg/1
of chlorine (more in summer) and stored in two on-site 3-day retention
reservoirs. As needed, additional chlorine is added to the reservoirs to
maintain a residual of 0.6 mg/1. The overall operational objective is to
maintain a minimum residual of 0.15 mg/1 at a distance 7 miles from the
plant. Lime and polyelectrolytes are also added after ozonation for pH
adjustment and corrosion control in the distribution system.
445
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APPENDIX C
FIGAWA TECHNICAL PAPERS ON OZONE TECHNOLOGY
Page
Technical Report #1: Ozone in Water Treatment . 449
Technical Report #2: Ozone and Corrosion -
Protective Systems ... 457
Technical Report #3: Ozone Generators for
Water Treatment 463
446
-------
In this Appendix we are including translations of three documents
developed in Germany by collaboration of the FIGAWA and the DVGW.
FIGAWA is the Technischen Vereinigung der Firmen im Gas- und Wasserfach,
founded in 1926 and headquartered in Kttln, Federal Republic of Germany
(Marienburger Strasse 15; 5000 KOln 51). Its members are equipment supplier
companies who market to gas and water works.
The DVGW (Deutscher Verein des Gas- und Wasserfaches e.V.) is a technical-
scientific organization, founded in 1859 and located in Eschborn, Federal
Republic of Germany (DVGW-HauptgeschaftsfUhrung; Postfach 5240, Frankfurter
Allee 27; 6236 Eschborn 1). Members of DVGW are scientists, engineers and
organizations in the fields of gas, water or wastewater treatment.
The three technical documents included in this appendix are:
(1) Ozone in Water Treatment (May, 1975), which discusses the use of ozone
in drinking water treatment, swimming pools and wastewater.
(2) Ozone and Corrosio'n - Safeguard Systems (July, 1975), which discusses
the methods of protecting treatment plant materials and components.
(3) Ozone Production Plants for Water Treatment (December, 1976), which
contains minimum requirements for the structure, operation and safety
equipment for ozonation systems used in water treatment plants.
We are including these documents because they represent the experiences
and considered opinions of organizations who have been involved with the
generation and application of ozone in water treatment for many years.
447
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FIGAWA
Technical Report #1
Ozone in Water Treatment (May, 1975)
Recently papers were compiled in the work groups of FIGAWA which deal
with special and actual technical problems in the different research areas
and in which material collected by members of these groups concerning these
questions are contained. As is the practice of FIGAWA, these papers are
given to the appropriate committee of experts of DVGW for further revision.
There they serve as a basis for discussion for the compilation of DVGW work
and information papers. In that these documents deal with actual technical
questions and that FIGAWA is constantly asked for such information, the
results of this work should be published as "technical reports" in the
group's journal. This would occur only as these papers become available.
The FIGAWA "Ozone" work group is now offering technical report #1
"Ozone in Water Treatment". This information was collected over a period
of two years and contains basic information concerning the use of ozone in
different areas of water treatment such as drinking water, swimming pool
water, and treatment of wastewater. It is the basis of discussion in the
newly formed DVGW "Ozone" work group. In connection with this research,
other types of papers are being developed which will deal with the question
of corrosion in regard to the use of ozone. Suggestions and improvements
are greatly appreciated by the management of FIGAWA.
The following firms participated in the compilation of the FIGAWA
"Ozone" work group.
1. Akdolit-Werk GmbH, 5605 Hochdahl
2. Bamag-Verfahrenstechnik GmbH, 6308 Butzbach
3. Benckiser Wassertechnik, 6905 Schriesheim
4. Chenrie und Filter GmbH, 6900 Heidelberg-Wieblingen
5. Clouth-Gummiwerke AG, 5 KOln 60
6. DEMAG-Metallgewinnung, 41 Duisburg
7. Th. Goldschmidt AG, 68 Mannheim 81
8. Gebr. Herrmann, 5 KOln 30
9. Lechler Chemie GmbH, 7 Stuttgart 40
10. Messer-Griesheim, 4 Stuttgart 1
11. Secova GmbH, 504 Bruhl
12. Dr. Starck & Co., 52 Siegburg
13. Philipp Muller, 7 Stuttgart 1
14. WABAG, 865 Kulmbach
448
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OZONE IN WATER TREATMENT
1. Ozone
1.1 Definition
The term "ozone" is understood to be the triatomic modification of
oxygen and is designated by the formula 03 with a molecular weight of
47.998. Three oxygen atoms form a triangle in the ozone molecule with an
angle of 127° in which the invervals between the atoms amount to 1.26-1.26-
2.26 10-1! m.
Under normal conditions (p = 1.012 bars and T = 0°C) ozone is a
distinctly blue-colored gas with the following constants:
Boiling Point (Kp) = -110.5°C
Melting Point (Fp) = -251.4°C
Density (L) = 2.144 g/1
With regards to the equation:
03 + 2H+ + 2e > 02 + H20
it yields a normal potential of Eo = 2.07 v. Ozone is, therefore, one of
the strongest means of oxidation. Ozone decays very rapidly at room tempera-
ture, but it decays much slower at this temperature in gas mixtures which
are produced by normal ozone producing equipment. The decay rate is in-
creased by traces of particular elements such as silver, platinum and
manganese oxides. The decay of ozone in liquid solutions is accelerated at
higher pH values.
1.2 Formation and Production
The formation of ozone is obtained by numerous processes: such as
electrolysis of sulfuric acid and by the decomposition of oxygen-rich
mixtures such as permanganates or dichromates. Of the others, ozone is
formed by energy-rich radiation of air. Therefore the earth is surrounded
by an ozone layer at an altitude of approximately 15 to 30 km which is
formed there by the unimpaired ultraviolet rays of the sun. The maximum
levels of ozone contained in air are found at an altitude of approximately
22 km and amount to approximately 10~6 volume parts.
For the production of greater ozone quantities one must make use of
the silent electric discharge as the only efficient and acceptable method.
Werner Siemens' principle of the so called "ozone canal" (tube, pipe,
shaft) developed over one hundred years ago still has value for us today.
The electrical discharge devices were, in the course of development,
simplified and their performances improved so that today one has available
tubular and plate discharge elements. There is a principle common to all
449
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such units by which two metal electrodes (non-corrosive metal) are separated
from one another by a dielectric medium as well as an air gap or space.
High tension alternating current of an appropriate frequency is conducted
to the electrodes whereby the dielectric serves the purpose of a series
resister, thereby hindering the direct charge flow from electrode to electrode
leading to a short circuit. Within the air gap there is, with the transmis-
sion of an oxygen-containing gas, silent electric discharge which results
in ozone formation.
Ozone is formed according to these equations:
AH = + 59.1 Kcal
0 + Oo^^Oo AH = - 24.6 Kcal
AH = + 34.5 Kcal
The process is endothermic, which depends upon the use of a relatively
large quantity of energy. Therefore, a large part of the conducted energy
is released in the form of heat. The latter is removed by a suitable means
of cooling because it influences in a negative manner the performance
efficiency of an ozone generator.
The equilibrium is influenced by the moisture content of the oxygen-
containing gas to be injected into the ozone generator so that desiccation
is necessary. Thereby a dewpoint of under -45°C for the desiccated gas is
necessary in order to prevent the formation of nitrogen oxides and ultimately
nitrogen oxide acids which damage the construction elements of the ozone
generator.
The energy consumption of modern ozone generators for the production
of 1 g of ozone lies between the following values:
a. with the introduction of pure oxygen 7 to 15 watt hours
b. with the introduction of desiccated atmospheric air
15 to 30 watt hours
The actual energy required depends on different construction parameters as
well as desired ozone concentration.
1.3 Reactions
In Section 1.1 the oxidation capacity of ozone was indicated, character-
ized by its normal potential of 2.07 V. It follows that all reactions with
ozone are oxidative. Reactions are possible with all materials which are
accessible to corrosion due to determined functional groups or by a low
valence state (capable of combining with oxygen).
The effect of ozone takes place mostly with reactions with inorganic
materials through the utilization of an oxygen atom. The reaction with
450
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organic materials in water is dependent upon the structure of the organic
substances as well as the pH value. The employment of ozone in water
treatment techniques has acquired a wider range. In this area its intro-
duction as a means of disinfection has developed to a large and varied
importance.
It is employed today for:
- separation and precipitation of heavy metal ions such as iron and
manganese
- decomposition of odor and taste elements
- elimination of colors
- eradication of toxic materials
- flocculation of colloids
The action of ozone on organic substances is designated as "ozonating";
analogous to the terms "chlorination" and "chlorinating".
1.4 Physiological effect
Ozone is detectable by its characteristic odor even in the smallest
concentrations (greatly diluted). The odor threshold lies at 0.02 mg/1 =
0.04 mg ozone/cu m air.
Physiologically ozone affects one as an irritant and it has a general
anesthetizing effect. Particular weak points for acute effects are the
mucous membranes of the eyes, nose and lungs. Long periods of exposure in
an atmosphere with an ozone concentration above 0.2 mg ozone/cu m will
cause coughing; higher than 0.2 mg ozone/cu m will cause chest and head
pains, and at even greater concentrations, circulatory disturbances and
salivation.
The Accident Prevention Ordinances (Professional Society of Gas and
Water Works, DUsseldorf) allows a maximum concentration at a work location
(MAK value) of 0.1 mg/1 = 0.2 mg ozone/cu m air. More detailed information
may be obtained from the named organization.
2. Effect On Elements Found In Water
2.1 Microorganisms
The introduction of ozone for the destruction of microorganisms
(disinfection) has been recognized for years. Through work carried out in
recent times the bactericidal and, above all, the virucidal effects were
reconfirmed. Ozone is discussed accordingly with all the other disinfection
means found in water chemistry and the following table will make points of
comparison clear:
451
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DISINFECTION EFFICIENCY OF OZONE VS. CHLORINE
Germ Count
60,000
coli forms/ml
350 spores
of B. subtil is/ml
PM-Virus strains
MV and Le Virus
suspension 1:1000
Means of Disinfection
chlorine
ozone
chlorine
ozone
chlorine
ozone
Add mq/1
0.1
0.1
1.4
0.05
0.25-1.0
0.05-0.46
Lethal Effect/sec
15,000
5
9,000
30
180*
2*
From Bringman [Z. Hyg. Infektionskronkh. 139:130 (1954); 139:333-337 (1954)]
With regard to French work, it is further recognized that a residual
of 0.4 mg/1 ozone over a period of four minutes produces a sufficient
assurance for the inactivating of polio virus. This result also applies to
river water from various sources as well as to variable levels of contami-
nation. A residual of ozone is needed for a guaranteed disinfection of the
water in which the bactericidal and viricidal effects extend themselves
over a wide range of pH values.
2.2 Heavy Metals
Heavy metals such as iron and manganese+are transformed by ozone into
their highest valence. The oxidation of Fe and Mn ions occurs in
accordance with the following equations:
2Mn2+ +
50
+ 02 + (OH)'
2MnO + 50 + 6H
The employment of ozone for removal of iron and manganese is applicable
especially in the case of waters found difficult to treat; for example in
the presence of protective colloids (humus elements). In accordance with
the first equation iron is in the form, after ozonizing, of ferric oxide
hydrate, e.g., a form capable of filtration. Its precipitation occurs in a
suitable filter. The permanganate ion formed in the second equation can be
reduced, insofar as it is not converted in the water treatment process, in
activated carbon and disposed of. These reactions are continuously dependent
upon pH value which is especially important for the removal of heavy metals
from weakly acidic water.
2.3 Organic substances
The substances of an organic nature found in water are identified in
only a few cases. Therefore one is assured that substances which impair
the odor and the taste of water (to yield turbid colored water) are pre-
452
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dominantly organic in nature. Ozone is effective here too for the breaking
down of these substances. The basic investigations of Harries, Rieche,
Staudinger and Criegee are gathered for the reaction mechanism. The
existence of "ozonides" is accepted by many authors who support the treat-
ment effect of oxidizing and disinfecting. These assumptions are contested
because the reaction mechanism of ozonation requires, for the formation of
ozonides, water free solution.
For the reaction of, for example, phenol (carbolic acid) with ozone in
an aqueous solution, the intermediate products of pyrocatechol (catechol,
pyrocatechin), o-quinone, and muconic acid are produced as well as the end
products maleic acid, fumaric acid and oxalic acid.
CHCOOH
CHCOOH COOH
phenol pyro- muconic maleic oxalic
catechin acid acid acid
Generalizing, one can say that the reaction of ozone with organic
materials found in water leads to the destruction of the original molecule,
whereby, in many cases, the reaction product results in a lower molecular
weight. This deals also with carcinogens and polycyclics which are trans-
formed into non-carcinogenic forms.
By the oxidation process with ozone certain organic substances may
become toxic or increase, at least their virulence, as is the case with
pesticides such as Aldrin and Parathion which are to be removed through
further treatment.
3. Areas of Application (techniques)
3.1 Regarding the provisions of DIN 2000, drinking water must be free of
all disease agents and is not permitted to contain elements dangerous to
health. Along with elements allowed in the Drinking Water Treatment
Ordinance (TAV) in toxicologically harmless concentrations, ozone represents,
as is described in section 2.1, an effective means of disinfection. Further,
ozone serves as a means of disinfection for water difficult to treat as
described in sections 1.3, 2.2, 2.3.
The ozone requirement is dependent upon the type and quantity of the
material contained in water. If the occasion arises, the necessary treatment
steps are to be added to the ozone treatment.
453
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3.2 Mineral water
Ozone has proven itself for the treatment of mineral water. In
essence, the provisions of Section 3.1 are to be fulfilled. Fundamentally
the table water ordinance (TWV) is to be followed.
The effects of ozone are dealt with in sections 1.3, 2.1, 2.2 and 2.3.
Particular attention applies to the content of bromides and/or iodides
which are oxidized by ozone. With a combination of ozone and ultraviolet
it is to be observed that ozone can be subjected to decay by photochemical
reactions.
3.3 Swimming Pool Water
The experiences of ozonizing drinking water have also been applied to
swimming pool water since the middle of the 1960s. The following is the
goal of the sixties:
- breaking up of produced organic material
- breaking up of the components of urine
- destruction of disease agents
At the same time the typical odor of the indoor swimming pool is eliminated
by ozone input, as oxygen deficit is replenished and a visual improvement
of the water is noted.
The redox potential is presented as a criterion for the effect of
ozonizing in the area of swimming pool water. A smaller surplus of ozone
produces a redox potential of E = +800 mV [against saturated calomel
(mercurous chloride)] electrodes with a pH of 7. With this potential,
disease agents are eliminated in the shortest amount of time (inactivated)
(see section 2.1).
An average input of 0.5 to 1.5 g ozone into each cubic meter of water
is sufficient for the treatment (of the water).
Because organic contaminations are continually eliminated and/or
flocculated by ozone, the addition of flocculating agents as well as the
quantity of chlorine needed for the assurance of good water can be reduced.
A reduction of the latter (chlorine) results in a decreased formation of
chlorine substitution products which are responsible for the irritation of
the mucous membrane and for the typical odors of the indoor swimming pool.
Following the guiding principle for "Water Treatment for Swimming Pool
Water, June, 1972", ozone, due to toxicological reasons, is not permitted
to be present in pool water. With the addition of suitable reducing agents,
a content of residual ozone is avoided. For the treatment of thermal and/-
or salt water a content of bromides and iodides is, with the addition of an
ozone stage (of treatment), to be taken into account (see Section 3.2).
454
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3.4 Wastewater
The oxidation strength of ozone allows for a widespread input when
treating wastewater. Because of the relatively large amounts of ozone
necessary for this process it is seldom employed.
The advantages of ozonizing for the decoloration, deodorizing, and
reduction of concentrations of organic substances as well as disinfection
are also to be applied, as they were in previous paragraphs, to wastewater.
A particular equation is the decontamination of cyanide:
2KCN + H20 + 503 >2KHC03 + N£ + 502
Further, the oxidation of nitrite and sulfite is known to follow the equations:
N02" + 03 —>N03" + 02
so32 + o3 —>so;j2 + o2
The possible elimination of phenols already was discussed in Section 2.3.
In conclusion, one may say that ozone may be employed in wastewater
techniques. Here too, investigations are necessary which:
a) have as their goal the effective reduction of ozone requirement
b) eliminates a possible toxicity of wastewater treated with ozone
(see Section 2.3).
455
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FIGAWA
Technical Report #2
Ozone and Corrosion - Protective Systems (July, 1975)
Once the technical report #1 of FIGAWA was presented as publication 5
May 1975, the FIGAWA "Ozone" work group today submits, in reference to the
forward of bbr 5/75, Technical Report #2, "Ozone and Corrosion - Protective
Systems". The information was collected after more than two years of work
and contains the most up-to-date information on this subject. It is the
basis of discussion by the committee of experts of the DVGW "Internal
Corrosion-Water" group. Suggestions and improvements are greatly appreciated
by the management of FIGAWA.
The following participated in the compilation of this report by the
FIGAWA "Ozone" work group:
1. Akdolit-Werk GmbH, 5605 Hochdahl
2. Bamag-Verfahrenstechnik GmbH, 6308 Butzbach
3. Benckiser Wassertechnik, 6905 Schriesheim
4. Chemie und Filter GmbH, 6900 Heidelberg-Wieblingen
5. Clouth-Gummiwerke AG, 5 Kflln 60
6. DEMAG-Metallgewinnung, 41 Duisburg
7. Th. Goldschmidt AG, 68 Mannheim 81
8. Gebr. Herrmann, 5 KOln 30
9. Lechler Chemie GmbH, 7 Stuttgart 40
10. Messer-Griesheim, 4 Stuttgart 1
11. Philipp Muller, 7 Stuttgart 1
12. Secova GmbH, 504 BrUhl
13. Dr. Starck & Co., 52 Siegburg
14. WABAG, 865 Kulmbach
456
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OZONE AND CORROSION - PROTECTIVE SYSTEMS
1. Definition
The behavior of diluted liquid ozone solutions makes the safeguarding
of metallic plant materials necessary; particularly the unalloyed carbon
steels used in many types of equipment.
Ozone, in smaller concentrations in a liquid phase, acts as a depolar-
izer much like oxygen in a water solution, i.e., in one way it is able to
form protective oxide films quickly. Corrosion affects unalloyed steel to
a particular degree. This steel is used primarily for the water area of
the container. For this reason the safeguarding of these structured
elements by the use of coating systems is necessary.
Metallic substances are not the only substances which are affected by
corrosion. Non-metallic substances are also affected; of the latter, those
with double bonds are most endangered. The presence of water causes an
accelerated corrosion. The Dechema material table "Ozone" (ref. 21 of this
document) offers a survey of this point.
The mode of operation of a corrosion-resistant coating system is
divided into four sections:
—It must adhere well to the undercoating
—It must demonstrate a great resistance capability against corroding
materials - ozonizing water - and against mechanical effects
—It must be absolutely safe in a physiological sense. In drinking
water it is not permitted to emit either taste, odor, or colour or
materials dangerous to health or hygiene (in suspicious amounts).
Algoid formation and bacteria growth are not to take place in this
water.
--Along with a high diffusion resistance it must possess pore
"freedom" in order to also prevent local corrosion.
2. Area of Application and Requirements
The protective systems employed due to the input of ozone during water
treatment must be absolutely safe in a physiological sense corresponding to
recommendation XXXI of the commission dealing with synthetics (of the EGA),
i.e., they must possess the quality of food. Its safeness is to be proven.
Its resistance capability must extend to aqueous ozone concentrations in
the area of 0.5 of 3.0 mg/1 of ozone.
The amount of suitable coating materials is dependent upon:
--materials contained in water and their concentration, for example
carbonic acids, salts
457
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~pH value
--temperature
The safeguard systems must possess a sufficient mechanical stability
in the pressure area up to 16 bars and resist abrasion, for example, the
filter material in the backwashing of a filter.
Additional requirements for the protective systems are:
--ordering possibility of the materials in question; in particular
metallic, but also those of concrete
—adequate adhesion to the undercoating
—sufficient diffusion resistance to the medium used in the operation
—ability to test for coating defects
—ability to repair mechanical defects
3. Protective Systems
The following described systems serve as a safeguard against the
corrosion of metallic and non-metallic materials. Consideration (of these
systems) depends on the present state of technology.
3.1 Thin Coating Systems
Included here are such systems which are applied in one or more coats
and have a dry coating thickness up to 160 urn.
3.2 Thick Coating Systems
One understands these systems which are applied in one or more coats
and has a dry coating thickness over 160 um.
3.3 Foil Containing Systems
Foil coatings (linings) are prefabricated and attached to the material
to be safeguarded.
With respect to their resistance against ozonized water, various
coating materials (found in 3.2 and 3.3) have proven themselves in practice.
These are systems that have been proved:
--chlorinated rubber
--mixed polymers of polyvinylidiene chlorides/polyvinychloride
—unsaturated polyester
458
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4. Performance
The protecting value of a coating system depends not only on its
quality but to a great degree on the following factors:
—pre-treatment and condition of the surface material to be protected
—conditions of the environment during the coating procedure
—post-handling of the protective casing
4.1 Pre-treatment
Metallic surfaces are to be sand-blasted to metallic sheen with a
quality ASa3, BSa3, or GSa3 (following the Swedish standard SIS 055900).
Surfaces with a quality DSa3 are excluded for use as plant parts.
Washed quartz sand with a grain size of 0.5 to 1.2 mm, sharp-edged
steel grain with a grain size between 0.5 and 0.75 mm (No. 34 - No. 24) or
corundum with a grain size of 0.5 to 1.2 mm are recommended as sand blasting
materials.
The sand blasting material must be dry and is not permitted to contain
an "aggressive" component.
After the sand blasting the dust is to be removed from the surfaces.
4.2 Surface Condition
The rough depth of the metallic surface to be protected should amount
to between 30 and 50 ym. In such a condition the surface is not permitted
to exhibit any evidence of rust and no "aggressive" qualities are to be
displayed.
4.3 Environmental Conditions
During the preparation of the protective systems the temperature
(metal and air) should be between 10° and 30°C. The dew point of the air
must be at least 5° lower than the surface temperature of the material to
be protected and the apparatus used in the process (of baking).
The environment must be free of "aggressive" gases or dust (for
example: salt dust).
4.4 Preparation and Post-Handling
The preparation and post-handling of the protective system depend on
special qualities. The recommendations of the manufacturer are to be
followed.
459
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The one applying the coating must be continuously careful not to
contaminate the cleansed undercoating (hand sweat may be removed with pure
Xytol whereby the solution must be allowed to vaporize from the surface).
5. Testing
Concerning non-destructive tests the following are considered:
--measuring coating thickness magnetic, electro-magnetic, eddy
current, capacitive, & -rays
—pore examination high voltage, electrolytic
These examinations can be combined.
6. Transport and Storage
These depend upon the special qualities of the coating system. The
regulations of the manufacturer are to be followed.
Thermoplastics should be transported only at temperatures above +5°C
due to the danger of tearing. During storage the temperature is not
permitted to go below 0°C.
STANDARDS, REGULATIONS AND RECOMMENDATIONS
1. DIN 18 364 Efforts dealing with the protection of steel
(VOB-Part C) surfaces
2. DIN 50 902 Handling of metal surfaces for protecting
against corrosion
3. DIN 53 151 Testing of coating materials-barbed wire test
4. DIN 53 210 Demonstration of rust percentage of coating
5. DIN 55 928 Protective coating of steel structures
6. SIS 055900 Rust percentage of steel surface and materials
used in the preparation of steel surfaces for rust
preventative coating
7. VDI 2532 Form and performance of structures to be protected
8. VDI 2533 Surface protection with organic materials
9. VDI 2535 Surface protection with organic materials in
liquid form
10. VDI 2537 Surface protection with strips of natural and
synthetic (India) rubber
460
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STANDARDS, REGULATIONS AND RECOMMENDATIONS (continued)
11. AGI Work
Report K 20
12. Report concern-
ing use of steel
Nr. 269
13. DB DV 807
(rust)
14. Report concern-
ing use of steel
Nr. 197
15. Report concern-
ing use of steel
Nr. 329
16. British Standard
Code of Practice
CP 2008
17. SSPC-Steel
Structure
Protection of steel constructions (Arbeitsgemein-
schaft Industriebau eV)
Surface protection of steel by coating
Technical regulations for rust protection of steel
structures of the German Federal Railroad
Flaming steel structures
Surface protection by flame and coating
Protection of iron and steel structures from
Corrosion
U.S. Regulations for the handling of undercoating
and recommendations of Painting Council coating
systems
18. Report - official report of the BMV, volume 6/1965: Regulations for
the performance and characteristics of rust preventive coatings for
steel structures
19. Wastewater - technical cleansing (ATV -Essen): Regulations for the
protective coating of iron components in canalization and cleansing
plants
20. Comit§ Europeen des Associations des fabrikants de peintures et
d'encres d'imprimerie
21. Dechema - materials table "Ozone"
461
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FIGAWA
Technical Report #3
Ozone Generators for Water Treatment December 15, 1976
Since November, 1975 the FIGAWA "Ozone" work group has dealt with the
drafting of a standard for ozone generators. This outline should contain
the minimum requirements for structure, operation and safety equipment of
such generators.
The representatives of well-known manufacturers of ozone generators,
as well as those who employ ozone, worked together with the FIGAWA "Ozone"
work group, in particular the following:
Mr. Blankenfeld Mr. Kurzmann, Chairman
Mr. Bredtmann Dr. Leitzke
Mr. Bttrgel Dr. Roennefahrt
Mr. Ensenauer Mr. Suppan
Mr. Goslau Mr. Voss
Mr. Hoelscher Mr. Btihme, group leader
Mr. Koepf
Through the work dealing with analysis of ozone in the gas phase by
the DVGW "Ozone" work group (Chairman, Dr. Maier) drafting of the standard
can be correspondingly expanded so that the now existing uncertainties in
this area can be removed.
This outline which is now presented for public consideration was
discussed with the representatives of those who employ "ozone" who do not
belong to the aforementioned work groups.
We also extend our thanks to Dr. Geiner and Dr. Wolf.
FIGAWA "Ozone" work group
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OZONE GENERATORS FOR WATER TREATMENT
1. Scope of Investigation
This standard applies TO ozone GENERATORS which employ the principle
of the silent electric discharge and which are employed for the treatment
of water (drinking water, industrial water, pool water, wastewater).
2. Goal
The ozone gas mixtures produced in the ozone production plants are
employed for the oxidation of inorganic and organic materials as well as
for the elimination of microorganisms.
3. Definition
Ozone is created by the effect of a silent electric discharge on
oxygen or oxygen-containing gases. The electric discharge results in a
"gas space" between two electrodes which are separated from each other by
a dielectric medium. One electrode is connected to high voltage while the
opposing electrode is connected to a grounded return line to the source of
the high voltage or to earth potential.
The gas employed in ozone production must be mechanically purified and
"dried" to a dew point under 228°K. At this dew point an economic operation
free from disturbance is produced.
4. Terminology
Ozone production element: plant unit in which oxygen or oxygen-containing
gases are exposed to a silent electric discharge.
Ozone generator: plant unit in which the ozone production elements are
formed.
Ozone generator: complete operation which is necessary for the
production of ozone.
5. Characteristics of the Ozone Generator
Ozone generators are distinguished by the following characteristics:
5.1 Generators of a compact or separated construction style;
i.e., spatially grouped or separate placement of structure groups
(see Section 7).
5.2 Form of the ozone generating elements:
Tubular or pi ate-type form of ozone generating elements.
463
-------
5.3 Working pressure
with negative pressure or positive pressure ozone generators.
5.4 Working frequency
Ozone generators operating with line frequency (50/60 Hz) or higher
frequencies.
6. Technical Data of the Ozone Generator
The ozone generator is to be characterized by the statement of the
following technical data which are to be presented in the operational
instructions:
—manufacturer, type and year of construction of the ozone generator.
—gas used (composition), i.e., gas added.
--ozone production in grams per hour (0, g/hr) at a concentration of 03
g/cu m related to a pressure of 1013 mbar and a temperature of 0°C (See
Section 12).
--volume flow in cu m/hr under operational conditions.
--working pressure of the ozone generator and the highest allowable negative
pressure or excess pressure in bars.
--working pressure of the air preparation system and highest allowable
pressure in bars.
--connection value of the ozone generator in volts (V), amperes (A),
and hertz (Hz).
--working frequency in the ozone generator element in hertz.
--maximum voltage in the ozone generator element in kV (kilovolts).
--energy requirement for the ozone generator in kW.
—connection value of ozone generator in kVA.
—cooling agent.
—volume flow of the cooling agent in cu m/hr.
--entrance temperature of the cooling agent in degrees Kelvin (°K).
—maximum and minimum pressure of the cooling agent in bars.
—dimensions of the plant in meters (length, width, height).
464
-------
--space requirement for the generator in cu m.
—operational weight of the generator in kg.
7. Structure groups, construction, and materials of the ozone generator
The following components belong to an ozone generator in the meaning
of this standard and independent of the "form" of the ozone production
elements and the spatial placement of structure groups:
—equipment for the supply of gas added during production of ozone
—ozone generators
—electrical equipment for the production of high voltage
—equipment for the operation and supervision (of the plant).
Besides this, the necessary safety equipment stated in Section 8 must
be present.
7.1 Equipment for the Supply of Necessary Gas
7.1.1 Construction
The equipment needed is established by the type and condition of the
gas to be used in the ozone production. Usually this structure group
encompasses the use of air, a double absorption system which is filled with
a desiccant and through which the gas to be used is directed, whenever the
occasion arises, during the insertion of a cooling aggregate.
The regeneration of the absorbent occurs according to the type of
drying system with dry and/or warm gas. For an operation with dry oxygen
(dew point 228°K) without circulation control, a drying unit is not necessary.
According to the construction of the ozone generator, this plant unit
is operated with negative or positive pressure, whereby the gas production
equipment is stipulated.
7.1.2 Materials
These are governed by the type and condition of gas to be used in the
ozone production.
During the employment of oxygen as the gas to be used for ozone
production, the safety regulations for oxygen (VBG 62) are to be observed.
7.2 Ozone Generators
465
-------
7.2.1 Construction
The ozone generator elements are to be ordered In a vertical or hori-
zontal manner within a closed container (ozone generator). Cooling equip-
ment is necessary for the removal of heat produced during the production of
ozone whereby the removal of this heat can be effected by gases or liquids.
7.2.2 Materials for the Parts Affected by Ozone
Stainless steel (for example material #1,4571), aluminum (Al 99.8),
suitable synthetic materials (PTFE-Teflon), ceramics and glass.
7.3 Electrical Equipment for the Production of High Voltage
The electrical equipment must correspond to the VDE regulations.
High voltage transformers and, when the occasion arises, throttle
valves and the corresponding regulatory apparati, serve for the production
of high voltage. For frequencies higher than the line frequency an acceptable
transducer is needed in the primary circuit.
7.4 Equipment for Operation and Supervision
The control equipment for the operation of an ozone generator is to be
easily accessible as well as arranged. The control panel for control and
supervision must contain everything necessary for the safe operation of the
switch, regulatory, guidance, measurement and control parts of the generator.
The primary voltage contained in the high voltage transformer must be
adjustable for the control of the ozone production. Voltage and current
intensity are indicated visibly on the appropriate measuring instruments.
This also applies for generators with frequencies higher than the line
frequency. If the ozone production is regulated by frequency, this too is
to be indicated.
A flow and pressure indicator must be built into the gas control
system so that the present operating conditions are readily evident.
8. Safety Equipment
The safety equipment must shut off or prevent the initiation of
operation of any ozone generator whose particular limit values are either
exceeded or, on the other hand, not attained.
To this end, the following safety equipment is necessary:
The protection or safety of:
—gas control (quantity and/or pressure)
--cooling (pressure, quality and/or temperature)
466
-------
--high voltage source (over-current and/or temperature)
Further the following items should be present:
—ozone gas warning indicator
—operational hours counter
—dew point indicator
--high voltage indicator
--ozone concentration indicator
The safety equipment are to correspond with the most up-to-date VDE
and DIN regulations. For the connection of the ozone generator with
circuitry, one must follow the regulations for the operation of a high
voltage production plant of the conditional electricity maintenance under-
taking (EVU). Electrical indicators and/or machines which are easily
accessible and whose locations do not occasion the need for a greater
degree of safety are to at least carry out a system of safety in regard to
IP 23 (see DIN 40 050, part one, safety types: contact, foreign body, and
water protection for electrical operations; definition and application
August, 1970). If these indicators and/or machines are not easily accessible,
a safety type such as IP 00 (see part one of DIN 40 050) will suffice
whenever the VDE regulations for this area are carried out.
9. Location
Different types of electrical machines and/or indicators are located
in the ozone generator which necessitate certain minimum requirements as to
location (of these machines, etc.). The arrangement necessitates the type
of safety system for the installed electric machines and/or indicators (see
Section 8). For the protection of a measured life span of the electrical
equipment a temperature above 303°K and a relative humidity over 60% is not
permissible and it is suggested that the manufacturer of the ozone generator
add additional treatment. The location should be continuously dust free
(maximum dust content in the air: 2.5 mg/cu m).
Unstable gases and contaminants which oxidize, such as chlorine,
sulfuric acid, and carbon monoxide, etc., are not permitted to be present
in the environment.
For ventilation, the environment's air is to be changed at least ten
times per hour whereby this ventilation must be allowed to operate outside
of the danger zone (MAK value for Oj = 0.1 ppm). (See the publication
concerning the employment of ozone as a means of water sterilization;
published as UVV of the Professional Society of Gas and Water Works, DUssel-
dorf, 1970). In order to avoid damage to a water-cooled ozone generator, a
frost-free location is necessary.
467
-------
The location's area should be designed so that maintenance and repair
work can be carried out without any hindrance.
10. Cooling Water
The water should not surpass a temperature of 293°K when an ozone
concentration of over 20 g/cu m is to be produced (with a pressure of 1013
bar and a temperature of 273°K).
The following standard values apply (methods for the determination of
the standard value followed by the DEV — Deutschen Einheitsverfahren):
pH value over 6.5
content of displaced materials under 0.1 ml/I
content of iron (Fe) under 5 mmole/cu m
content of manganese (Mn) under 2 mmole/cu m
The employment, by the manufacturer of the generator, of stainless
steel applies for the additional chlorine content.
With the employment of aluminum as a material to be in contact with
the water, its solubility with a pH value greater than 7.5 is to be indicated.
Recycling or reuse of the cooling water is possible.
11. Operating Information
For the operation of an ozone generator, the technical data as well as
information concerning installation, servicing and maintenance by the
manufacturer are necessary.
After the start of operation of an ozone generator, evidence of its
performance must be gathered by way of testing the ozone product in the
manner stated in Sections 12 and 13.
This performance evidence applies as part of the sample testing. This
is to be carried out by competent personnel. A contract agreement for
maintenance work is recommended. The necessary data concerning operation
is to be entered into an operations book on a daily basis.
12. Determination of Ozone Concentration
The following described methods for the determination of the ozone
concentration and, therefore, the ozone production per unit time, relate to
the input gas.
12.1 Titrimetric determination following the potassium iodide method (see
article 10, October 1976).
468
-------
12.1.1 Theory
The reaction of ozone with potassium iodide takes place only in a
neutral buffered aqueous solution (pH = 7) in a stoichiometric manner
following the equation:
0 + 21
H20
2(OH)
The liberated iodine is titrated by the acidified sodium thiosulfate:
V
12.1.2 Indicators and equipment
—means of transmission
—wash bottles
--three way spigot
--membrane pump
—gas meter
—barometer
—stop watch
—general accessories
.-2
•21% (S406)
-2
high quality steel, glass or PTFE
(Teflon)
500 ml content after Muenke
with plugs out of PTFE (Teflon)
ozone tight [necessary only in plants
employing low pressure (negative
pressure)]
wet design with needle counter as well
as thermometer fittings for gas and
liquid, consumption performance per drum
revolution: 1 liter
glass beads, used tubing out of PE or
PVC for short elastic connections
—retort stand WE 500 (DIN 12 835)
—graduated cylinder 250 (DIN 12 680)
—burette S25 x 0.05 A (DIN 12 700)
—pipettes VPA 1 and VPA 5 (DIN 12 690)
(recommended: magnetic stirrer with stirring rod made of PTFE—
Teflon).
469
-------
12.1.3 Chemicals
Potassium iodide solution:
Sodium thiosulfate solution:
Sulfuric acid, diluted:
20.0 g Potassium iodide (KI), 7.3 g
di sodium hydrogen phosphate (Na^HPO.-
x2H20) and 3.5 g potassium dihyarogen
phosphate (KHLPO*) are dissolved in
1000 ml of double distilled water.
0.1N standardized titrimetrically
25 ml sulfuric acid (HgSO
=1.84 are carefully aade
double distilled water and
well
, d
to
mixed
Zinc iodide-starch solution:
4 g starch are triturated with a
little distilled water and
added to a simmering solution of 20
g zinc chloride in 100 ml of water.
The solution is boiled until it
becomes clear by the restoration of
the evaporated water, diluted,
displaced with 2 g zinc iodide,
filled up to 1000 ml and filtered.
The solution is stored in a brown
bottle; it is not permitted to turn
blue after dilution with 50 times
the volume of water during acidifi-
cation with diluted sulfuric acid.
12.1.4 Construction
The structure of the regulating area (of the plant) is represented in
Illustration 1 (not included in publication). The gas feeder [A] should be
as short as possible and connected directly to the ozone generator.
All parts of the measuring apparatus which come into contact with the
gas mixture containing ozone are not permitted to exhibit any type of ozone
consumption. Necessary elastic tube connections are to be as short as
possible. Every other wash bottle (placed one after the other) is supplied
with 200 ml of potassium iodide solution each and employed corresponding to
the experimental set-up in the gathering of samples with regard to Figure
1. Both of the three-way spigots are to be set up next so that the gas
used in the experiment is directed through the by-pass area. In this
position the flow speed of the measuring gas is adjusted by the throttling
valve so that the volume flow is fed through at approximately 1 liter/ min.
During the switching over of the three-way spigot in the measuring
area the location of the indicator needle of the gas meter should be watched.
A renewed measuring time during the measuring is not necessary because the
tolerance in the inserted flow speed of ± 20% can be accepted without
hesitation. The total input of gas volume should amount to more than 1
470
-------
liter, but not more than 5 liters, and is determined exactly. After the
completion of the measuring the gas flow is switched again to the by-pass
area and the measuring is repeated. During the gathering of samples the
barometric levels and measuring gas temperature should be read off.
The freed iodine is titrated with 0.1 N sodium thiosulfate solution
after acidification with 5 ml of diluted sulfuric acid. At the conclusion
of the titration 1 ml zinc iodide-starch solution is added to the bright
yellow colored solution and titrated until it is colorless. Both wash
bottles are to be considered, particularly with high concentrations of
ozone.
12.1.5 Evaluation
1 ml 0.1 N sodium thiosulfate corresponds to 2.4 mg ozone (03).
Calculation is possible following the formula:
G = 2.4af(l + 0.00367t)(1013)
bp
G = content of ozone (03) in g/cu m under normal conditions (273°K, 1013
mbar)
a = consumption of 0.1 N sodium thiosulfate solution in ml
b = gas volume which was fed through (in liters)
t = temperature of measured gas in °C
p = air pressure at measuring location in mbar
f = normality factor of the sodium thiosulfate solution
The results are rounded off to the next whole number.
12.1.6 Errors
The sum of errors is to be estimated with the ± 5% (relative error) of
the measured values.
12.2 Information Concerning Further Methods of Determination Dependent Upon
Calibration
12.2.1 Photometric Determination in the UV Region
Ozone exhibits a wide absorption band between 200 and 300 nm (known as
the Hartley Band). At 253.7 nm the absorption coefficient of ozone passes
through a maximum. The principle of the method is based on the measurement
of the optical absorption of a monochromatic ray with a wave length of
253.7 nm within a gas absorption bulb with quartz glass windows.
12.2.2 Caloric Determination by the Measurement of Enthalpy Decay
During the decay of ozone, the release of heat quantities of 144.41
KJoule per mole of ozone represents a measurement of the ozone concentration
of an ozone-containing gas. The principle of the method is based on the
exact measurement of a temperature difference between gas containing ozone
471
-------
and gas free of ozone which is brought about by the released heat quantities
(through catalytic ozone decay) depending on the ozone concentration of the
gas which was fed through.
13. Performance of the Ozone Generator
The performance of the ozone production plant is worked out by the
following formula:
A = G x QL
where:
A = performance of the ozone production plant in g 03/hr
G = g 03/cu m (after section 12.1.5)
Q. = volume flow in cu m/hr (after section 12.1.5)
The result is influenced above all by the variation of:
--volume flow
--net primary voltage and frequency
--cooling water temperature
—multiplication factor
472
-------
APPENDIX D
OZONE QUESTIONNAIRE SUMMARY TABLES
Table Page
D-l. European Plants 475
D-2. Canadian Plants 515
473
-------
This appendix provides summary tables drawn from the ozone questionnaire
responses from Europe and Canada. The data reported herein are as provided
by the individual plants. "NA" signifies "Not Available", and that the
respondant did not provide data for the specific question.
The tables are arrayed on two pages and read from left to right. The
treatment process is described in order of the design, beginning with the
first process step. Data are provided for ozone dosage, power consumption,
and chlorine or chlorine dioxide use in final disinfection. The reader is
cautioned, however, that the bases on which some of these data have been
reported are not always known; hence, data which vary widely from the norm
should be discounted. In particular, power consumption data were not always
adequately defined by the responding plants, and very low or very high data
can be misleading.
474
-------
TABLE D-l. EUROPEAN OZONE QUESTIONNAIRE SUMMARY
Ozone
Generation
Capacity
(kg/day)
Plant, Location, Water Design
Source & Year Ozone Capacity
Installed (cu m/day)
Treatment Process
Purpose(s)
of
Ozonatlon
Type of
Contacting
en
Tullich Treatment Works, 10,000
Oban, Scotland
Loch River (1977)
Loch Turret Treatment 81,800
Works, Crieff, Scotland,
Sunnyhurst Treatment 5,000
Plant, Blackburn,
Great Britain (1969)
Watchgate Treatment 450,000
Plant, Kendal,
Great Britain,
Haweswater Lake (1971)
Barmby Treatment Works, 55,000
near Howdcn, North Humber-
side, England, Derwent River
(to begin in 1978)
Durleigh Filter Station, 30,000
Ourleigh Surface Reservoir
1974
(continued)
72 microstraining, ozonation, filtration
ozonation, chlorination, pH adjust-
ment
168 microstraining, prechlorination,
ozonation, post-chlorination
14.4 lime treatment, slow sand
filtration, ozonation,
chlorination
800 microstraining, prechlorination,
rapid sand/anthracite flltrat'on,
ozonation, lime addition, chlori-
nation, sulphur dioxide for
dechlorinatlon
288 rapid gravity filtration, ozonation,
slow sand filtration, chlorination
192 microstraining, chlorination, ozona-
tion (3 stapes), coagulation,
chlorination, pressure filtration
Color removal; addi-
tional benefits are
Fe & Mn removal,
viral inactivation,
& bacterial disin-
fection
Color removal,
bacterial disin-
fection
Color removal
Color removal
Color removal
Iron & manganese,
color, taste &
odor removal
3 sparger contactors,
2 stages, 11 min
total contact time
7 units, single stage,
contacting by injectors,
5
1 unit, single stage,
sparger
9 units, single stage,
injector, 30 minute
contact time
3 units, single stage,
submerged turbine
3 units (number of
stages unknown),
diffusers, 1-5 min
contact time
-------
TABLE D-1 (continued)
Plant Name
Tulllch
Loch Turret
Sunny hurst
Watchgate
Barmby
Durlelgh
Ozone Dosage
plant has not
begun operation
2.5
1.5 to 2.0
up to 3.0,
avg. 1.25
not yet 1n
operation
4
Energy Demand,
Kwh/kg
23 estd.
37 total
2 air prep
22.6 generation
6.6 contacting
5.3 03 destruction
not available
(NA)
25.5
27 estd.
36 total
Contactor off-gas Type of
Treatment Generators
relnjected at plant Tralllgaz tube type,
Inlet water cooled
thermally des- CEO Tralllgaz,
troyed at 300°C Hollow Plate, water-
cooled
none Tralllgaz tube type,
water cooled
activated carbon, Tralllgaz, tube type,
vent gas absorber water cooled
catalytic des- Gebruder Herrmann tube,
truction water cooled
activated carbon, Trail igaz tube type,
Conjunctive Use of Clg or C10? 1n
Pretreatment Pofit-treatment
Cl* used, concentration
unKnown
0.7 mg/1 Cl~ applied;
0.1 mg/1 free residual
In plant effluent
0.2 to 0.3 mg/1 C12
added at plant outfet
CU added, up to 0.4
ing/l
C12 to be used when
plant begins operation
4 mg/1 residual 1n plant
12 for air prep-
aration
18 for genera-
tion,
6 for contacting
destruction units
to be added In
1977
water cooled
effluent 1s 1.0 mg/1
(continued)
-------
TABLE 0-1 (continued)
Plant, Location, Water
Source & Year Ozone
Installed
Hondsweg Onddorp,
Netherlands Haringvllet
Water (surface), 1976
Design
Capacity
(cu m/day)
15,000
Ozone
Generation
Capacity
(kg/day)
44
Treatment Process
ground infiltration (60 days retention
time), sand filtration, ozonation,
dual media filtration (coal, sand),
hypochlorite disinfection
Purpose(s)
of
Ozonation
color, taste &
odor, organics
removal
Type of
Contacting
2 submerged turbine
contactors; 10-20 min
contact time; stages of
contactor unknown
Noordendijk Dordrecht, 28,800
The Netherlands
Rhine River, 1968
Engelse Werk Zwalle, 30,000
Netherlands, ground-
water plus bankflltrate,
1972
Provincial Amsterdam, 82,200
Netherlands
Bethunepolder,
December 1976
Pumpstation Buren, Buren 1,080
(The Isle of Ameland)
Netherlands
86.4 breakpoint chlorination, coagulation,
upflow filtration, downflow filtra-
tion, ozonation, chlorination
river sand bank filtration, dry
filtration, deacidification tower,
filtration, ozonation
600 coagulation, settling, rapid filtra-
tion, ozonation, coagulation, rapid
filtration, slow filtration,
chlorination
rapid filtration, slow sand filtra-
tion, ozonation, holding basin,
rapid sand filtration
taste & odor
removal, color
removal
taste removal
taste, color,
organic com-
pound removal,
viral inactiva-
tlon, bacterial
disinfection
iron removal,
color removal
6 units, single stage,
dispersion by rotating
cavitatlng pumps; 10 min
contact time
1 unit, single stage,
dispersion by Injector;
5 sec contact time
1 unit, 3 stages dispersion
by sparger; 4 min
contact time
1 unit, single stage,
dispersion by submerged
turbine; contact time of
6-18 sees; detention time
in holding basin of
40-115 min
(continued)
-------
TABLE D-1 (continued)
oo
Energy Demand, Contactor off-gas Type of Conjunctive Use of C10 or C100 In
Plant Name Ozone Dosage
Hondsweg Onddorp 3 (av)
Noordendijk Dordrecht "2
Kwh/kg Treatment Generators Pretreatment
17-20 thermal destruction Kerag tube type,
water cooled
35 thermal destruction Kerag tube type, breakpoint
water cooled chloHnatlon
Post-Treatment
sodium hypochlorite
added at concentration
of 0.2 mg/1
chlorine added at 1.0
mg/1 concentration; 0.4
mg/1 free residual In
effluent; 0.05 mg/1 at
extremity of distribution
system
Engelse Werk Zwalle 0.23
(0.2 kg/hr)
Amsterdam
Pumpstation Buren
2.5
50
25
NA
destruction by
activated carbon
treatment
Argentox tube type,
water cooled
none
thermal destruction TrailIgaz tube type,
water cooled
none
Kerag tube type,
water cooled
none
Cl~ applied as terminal
step at concentration of
0.4 mg/1. Free residual
of 0.1 mg/1 obtained In
plant effluent
none
(continued)
-------
TABLE D-l (continued)
Plant, Location, Water Design
Source & Year Ozone Capacity
Installed (cu m/day)
Cantineweg, Katwijk aan 70,000
de Rign, Netherlands,
1972
Ozone
Generation Purpose(s)
Capacity Treatment Process of
(kg/day) Ozonation
120 aeration, rapid sand filtration, taste, odor,
ozonatlon, slow sand filtration color & organic
compound re-
moval
Type of
Contacting
1 unit, dispersion by
submerged turbine; 2 min
contact time
Schaardljk, 150 Rotterdam, 210,000
Netherlands, Meuse (3
months storage) 1977
Stadtbetriebe Linz G.m.b.h. 26,000
Linz a.d., Donau, Austria,
1972
Pumpwerk Seibersdorf, 4,320
Sudstadtzentrum, Austria,
horizontal filtered well,
1972
Stadtwerke, St. POlten, 8,640
St. Pfllten (Wellfield 3,
Well equipment 16, 17)
Austria, Groundwater (well)
1972
Stadtwerke St. POlten, 8,640
St. Polten (Wellfield 3,
Well equipment 14) Austria,
Groundwater (well) 196.5
576 coagulation, ozonatlon, secondary co-
agulation, filtration, activated
carbon, chlorination
27.36 ozonatlon, degasing
5.04 ozone 1s added by injector 1n a
partial stream for sterilization.
This 1s only treatment.
10.8 ozonatlon, hypochlorite
8.64 ozonatlon
taste, odor & 6 unit, single stage,
color removal, submerged turbine; 4 min
bacterial dis- contact time
infection,
turbidity removal,
viral inactivatlon,
filtration aid
bacterial disin- 4 units, single stage,
fection, viral dispersion by injector;
Inactivatlon 10 min contact time
bacterial dis-
infection
bacterial dis-
infection
bacterial dis-
infection
1 unit, dispersion by
injector
1 unit, 10 min contact
time, schwimmbegaser
1 unit, 10 min contact
time, schwimmbegaser
(continued)
-------
TABLE 0-1 (continued)
Energy Demand,
Kwh/kg
Contactor off-gas
Treatment
Type of Conjunctive Use of Cl, or CIO., In
Generators Pretreatment Post-Tr6atment
Plant Name
Ozone Dosage
Cantineweg
Schaardljk
2.4 24.5 total,
3.0 air prepara-
tion, 21 0,
generation; 0.6
contacting
3.0 26
thermal destruction
at 300°C
combination of
thermal destruc-
tion plus catalyst
Linz
Seibersdorf
St. Pfllten
St. POlten
(continued)
0.06 45 total, 14
air preparation
21 generation,
10 contacting
Not given 40 total ,
20 air prep-
aration,
20 generation
0.37-0.56 16
0.17-0.21 16
partial reinject
activated carbon
filter
surface area
vacuum pump
surface area
vacuum pump
Trailigaz tube type,
water cooled
Kerag tube type,
water cooled
Sauter plate type,
water cooled
Tralligaz plate type,
water cooled
Kerag tube type,
•water cooled
Kerag tube type,
water cooled, 1 unit
None
1 mg/1 C12 In
summer; total resid-
ual of 0.3-0.6 mg/1
in plant effluent
Not necessary
None
0.8 mg/1 of hypo-
chlorite applied
None
-------
TABLE D-l (continued)
•e*
CO
Plant, Location, Water
Source & Year Ozone
Installed
Salzburger, Stadtwerke-
Deslgn
Capacity
(cu m/day)
58,000
Ozone
Generation
Capacity
(kg/day")
3.6
Treatment Process
ozonation, holding tank, distribution
Purpose(s)
of
Ozonatlon
color removal, bac-
Type of
Contacting
9 units, dispersion by
Wasserwerk, Salzburg,
Austria, deep wells with much
Intermediate dilution of high
quality groundwater
Seewasserwerk Riet,
St. Gall en, Switzerland,
Lake of Constance
1968
60,000
City of Bern Waterworks, Bern, 24,000
Switzerland, Wellwater, 1955
Waterworks Arbon, Arbon, 30,000
Switzerland,
Lake of Constance, 1964
Waterworks Ronrschach, 15,000
Rohrschach, Switzerland,
raw water source unknown
1969
288 neutralization, flocculation, 2-stage
rapid filtration, slow sand filtra-
tion, ozonation, activated carbon
filtration, chlorine dioxide
21.4 filtration, ozonation, reservoir,
residual ozone measurement,
chlorine dioxide addition
30 prechlorination, filtration, ozonation
activated carbon, chlorination
35 prechlorination, filtration,
ozonation, chlorination
terial disinfection
organics removal,
viral 1nact1vat1on
color removal,
taste & odor remov-
al , bacterial disin-
fection, organics
removal, viral in-
activation
odor removal,
bacterial disin-
fection
taste & odor re-
moval , bacterial
disinfection,
viral inactivation
bacterial, disin-
fection, viral
Inactivation,
taste removal
injector; 4 min con-
tact time; 3 injectors
per chamber
8 submerged turbines;
27-50 min contact time
(Includes time in
piping after contact
chamber & until reach-
ing GAC filter)
1 unit, dispersion by
injection; 5-8 min
contact time
1 unit, dispersion by
injector, contact time
unknown
3 units, single stage,
injector-, 10 min
contact time
(continued)
-------
TABLE D-1 (continued)
Plant Name
Salzburger
Energy Demand,
Ozone Dosage Kwh/kg
1.2 55
Contactor off-gas Type c
Treatment General
None Argentox
)f Conjunctive
:ors Pretreatment
tube type, —
Use of C10 or CIO, In
"Post-Treatment
chlorine used only 1f
00
PO
Riet, St. Gallen 0.3 - 0.58
Bern Waterworks 0.3 - 0.5
Waterworks Arbon ca. 0.8
Waterworks Rohrschach 0.3
26.7
81.1 total,
24.1 for air
preparation,
25.1 generation,
30.9 contacting
17
(ozone generation
only)
NA
thermal destruction
None
None
None
water cooled,
3 generators
Kerag tube type,
water cooled,
4 generators of
3 kg/hr capacity
Welsbach & Degr€mont/
van der Made; tube
type, water cooled,
6 generators
CEO TraiHgaz plates,
water cooled, 5
generators
Sauter plate type,
water cooled, 3
generators of 0.6
kg/hr capacity
the ozone equipment 1s
not 1n service;
0.5 mg/1
ClOp added as terminal
step 1n concentration
of 0.10 to 0.15 mg/1
ClOo added at
reservoir outlet In
0.04 mg/1 concentra-
tion
prechlorinatlon C12 added after acti-
vated carbon, 0.1 mg/1
prechlorinatlon Cl? added at reservoir
outlet, 0.2 mg/1
(continued)
-------
TABLE D-l (continued)
Plant, Location, Water
Source & Year Ozone
Installed
Waterworks B1el, Biel,
Switzerland, Bieler Lake
(38 m deep)
Waterworks Thai, Kauton,
St. Gall en, Switzerland,
Lake of Constance, 1967
-P»
00
co
Waterworks Altstatten,
Altstatten, Switzerland,
well water
Villingen, Baden-
Wdrttemberg, Federal
Republic of Germany (F.R.G.),
well water, 1974
SUsel, Schleswig Holstein,
FRG, groundwater, 1969
Solingen, Nordrhein-Westfaien
Bank filtrate from Ruhr River
Design
Capacity
(cu in/day )
36,000
12,000
2,500
13,000
30,000
, 2,000
»
Ozone
Generation
Capacity
(kg/day)
130
(based on 20
hr/day opera-
tion). Total
capacity Is
155.5
27
3.79
26
20
48
Treatment Process
prechlorinatlon, alum coagulation, dual media
(pumice, sand) filtration, ozonation, activated
carbon/sand filtralton, pH adjustment with
NaOH, chlorine dioxide addition
filtration, chlorination, ozonation, chlorine
dioxide addition
ozonation only
ozonation, flocculation, filtration, chlorine
dioxide addition
ozonation, double layer filtration, (activated
carbon/sand)
aeration, softening, double layer filter,
ozonation, filtration plus flocculation,
Purpose(s)
of
Ozonation
taste & odor
removal , color
removal ,
organics re-
moval , viral
inactivatlon
taste & odor
removal, bac-
terial disin-
fection, viral
inactivation
bacterial dis-
infection,
organics re-
moval
bacterial dis-
infection
iron removal
organics re-
moval
organics
removal
Type of
Contacting
36 units, 2 stages,
dispersion by
sparger; 10 min con-
tact time
3 units, dispersion
by turbine
1 unit, single stage,
mixing by turbine
injector
Wabag contactor, 1
min contact time,
type of unit unknown
washer w/Raschig
rings
1977
(continued)
activated carbon, chlorine dioxide
-------
TABLE 0-1 (continued)
Energy Demand,
Plant Name Ozone Dosage Kwh/kg
Biel 1.6 23 total, 2.3 air
preparation, 17
generation, 3.7
contacting
Thai NA 20
CO Altstatten NA NA
J>
VIlHngen 0.3 NA
SUsel 2.0 NA
Soltngen 0.4-0.8 50
Contactor off-gas
Treatment
dilution with air
none
withdrawn by
suction pump
destruction by
activated carbon
none
NA
Type of Conjunctive Use of Cl
Generators Pretreatment
Sauter plate type, prechlorlnatlon
water cooled, 6
generators of 1 .08
kg/hr capacity
Kerag tube type, chlorination, prior to
water cooled, 3 ozonatlon
generators of
6.375 kg/hr
capacity
Kerag tube type, —
water cooled, 1
generator of 0.158
kg/hr capacity
unknown —
Herrmann tube type, none
water cooled;
2 units
tube type, water —
cooled, manufacturer
0 or CIO, 1n
"Post-Treatment
C102 added, 0.18
mg/T
C102 post-treat-
ment
Clo equipment
available
CIO, added, 0.3
mg/T
_ — -
CIO, added, 0.2
mg/f
(continued)
-------
TABLE 0-1 (continued)
00
en
Plant, Location, Mater
Source & Year Ozone
Installed
Sieqburg, Nordrhein-
Westfaien, wells, 1968
Osterode, Niedersachsen,
FRG, wellwater, 1972
Design
Capacity
(cu m/day)
70,000
119
Ozone
Generation
Capacity
(kg/day)
48
0.24
Treatment Process
aeration, filtration, ozonation, activated
carbon, chlorination
ozonation only
Purpose(s)
of
Ozonation
organics re-
moval, color,
taste & odor
removal
bacterial
disinfection
Type of
Contacting
Injector, 1 column
injector
DUren, Nordheim, Westfaien,
FRG, Ruhr River water, 1970
Duisburg, Nordheim,
Westfaien, FRG, Rhine River
1966-72
Diez/Lahn, Rheinland, Pfalz,
FRG, groundwater, 1966
Wieslautern/Dahn, Rheinland,
Pfalz, FRG, groundwater 1975
Bad Neustadt, Bavaria, FRG,
groundwater, 1965
36,000
72,000
2,000
1,500
9,000
18 microstraining (5u), ozonation, granular
activated carbon, softening
192 sand bank filtration, ozonation, granular
activated carbon, chlorine dioxide,
softening
1.0 ozonation, hypochlorination
1.5 ozonation
4.8 ozonation
Fe, Mn removal 2 Frings mixers; 4
disinfection, min detention
organics re-
moval
disinfection, 2 packed columns;
taste & odor 6 min detention,
removal, oxy- Wabag
genation, color
removal, viral
inactivation,
Mn removal,
organics removal
disinfection
2 injectors; 30 min
detention
disinfection 1 injector
disinfection
1 injector;
5 min detention
(continued)
-------
TABLE D-l (continued)
CO
Plant Name Ozone Dosage
Siegburg 4-5
Osterode 57
DUren 0.3
Duisburg 2.0
Dlez/Lahn 0.15
Wieslautern/Oahn 0.3
Bad Neustadt 0.25
(continued)
Energy Demand,
Kwh/kg
20
28
30
13
100
20
TOO
Contactor off-gas
Treatment
treated, method un-
known
none
activated carbon
recycling
none
yes
none
Type of Conjunctive
Generators Pretreatment
Herrmann tube type,
water cooled
Kluber tube type, —
water cooled;
1 generator
Herrmann tube type, none
water cooled;
1 generator
Dercag tube type, —
water cooled;
4 generators
Benckiser tube type, —
water cooled;
2 generators
Schade tube type, none
water cooled;
3 generators
Kluber tube type, none
water cooled;
10 generators
Use of Cl, or CIO, In
""Post-Treatment
C12 added, 0.3
mg71
none
none
chlorine dioxide
0.5 mg/1
hypochlorination
0.25 mg/1
none
none
-------
TABLE D-l (continued)
CO
Plant, Location, Water
Source & Year Ozone
Installed
Bad Honnef, Nordheim,
Design
Capacity
(cu m/day)
13,000
Ozone
Generation
Capacity
(kg/day)
24
Treatment Process
river sand bank filtration, ozonation,
Purpose(s)
of
Ozonation
taste 4 odor con-
Type of
Contacting
1 Ozotech injector;
Westfaien, FRG,
Rhine River water, 1975
Annweiler, Rheinland, Pfalz, 480
FRG, groundwater, 1977
Albstadt, Baden-WUrttemberg, 18,000
FRG, groundwater, 1976
Neustadt/Sisch, Bavaria, 2,600
FRG, wellwater, 1959
Neuffen, Baden-WUrttemberg, 1,600
FRG, wellwater, 1970
filtration, chlorine dioxide
MU1helm/Ruhr, Nordrhein-
Westfaien, FRG, Ruhr River
1977
50,000
0.5 ozonation
40 preozonation, C02 degassing, double layer
filtration, granular activated carbon,
chlorine dioxide
2.6 ozonation only
1.56 flocculatlon, sand filtration, ozonation
192 preozonation, flocculation, sedimentation,
ozonation, filtration, carbon adsorption,
biological filtration, ground passage,
chlorination
trol, disinfec-
tion, organics
removal, viral
inactivation
disinfection
10 min detention
injector
disinfection, 2 Sauter gas turbines;
viral Inactive- 8 min detention
tion, taste & odor,
turbidity & organics
removal
bacterial
disinfection
bacterial disin-
fection, organics,
turbidity, viral
inactivation
color & turbidity
removal, Fe & Mn
removal, taste &
odor control,
flocculation, dis-
infection & viral
inactivation
turbulence chamber
w/rotor; 20 min
contact time
Argentox injector;
14 min contact time
2 diffuser systems;
1 turbine system
(continued)
-------
TABLE D-l (continued)
Plant Name
Bad Honnef
Annweller
Albstadt
.£»
Co
00
Neustadt
Neuffen
Mtll helm/Ruhr
(continued)
Ozone Dosage
3.0
0.3
0.8
2.0
0.4
4.0
Energy Demand, Contactor off -gas
Kwh/kq Treatment
catalytic
20 yes
catalytic
78 none
107 none
catalytic
Type of Conjunctive Use of
Generators Pretreatment
Herrmann tube type,
water cooled;
2 generators
Schade tube type, none
water cooled
Sauter plate type, —
water cooled;
1 generator
Kerag tube type, none
water cooled;
1 generator
Argentox tube type, none
water cooled;
1 generator
Trail Igaz tube type,
water cooled;
2 generators
Cl, or C100 In
"Post-Treatment
chlorine dioxide
0.1 mg/1
none
chlorine dioxide
0.3 mg/1
none
none
0.3 mg/1 C12
-------
TABLE D-l (continued)
Ozone
Generation
Capacity
(kg/day)
Plant, Location, Water Design
Source & Year Ozone Capacity
Installed (cu m/day)
Treatment Process
Purpose(s)
of
Ozonation
Type of
Contacting
00
Munchengladback, Nordrhein- 20,000
Westfaien, FRG, groundwater,
1965
Lindau, Bavaria, FRG. 20,000
Lake of Constance, 1972
Limberg, Hessen, FRG, 7,700
groundwater, 1969
Gruiistedt, Rheinland Pfalz, 240
FRG, wellwater, 1970
DUsseldorf, Nordheim, 403,000
Westfalen, FRG, Rhine River,
sandbank, 1969-77
Aachen, Nordheim, Westfaien, 7,200
FRG, groundwater, 1968
Bodensee Wasserversorgung
(SippHnger Berg), Baden-
Wurttemberg, FRG, Lake of
Constance water, 1969
650,000
14.4 preaeration, gravel filtration, ozonation,
hypochlorination
44 micros training, ozonation, filtration, final
chlori nation
2.4 ozonation
0.4
874
3.6
780
disinfection,
taste control
Argentox injector;
3-5 min detention
disinfection, 2 VAR injectors;
organics removal, 10 min detention
turbidity
ozonation
disinfection
disinfection
1 injector
1 injector
sand bank filtration, ozonation, prefiltration, Fe, Mn removal, 1 injector; 5 min
granular activated carbon, softening, chlorine taste & odor con- detention plus 20
dioxide trol, organics min holding tank
removal, disin-
fection
ozonation, filtration, chlorine dioxide
mlcrostraitnng, ozonation, filtration,
chlorine dioxide
taste, Fe & Mn, Uabag packed column;
color, turbidity, 3.7 min detention
disinfection
taste & odor, Wabag packed column;
disinfection & 12 min detention
viral inactivation,
micro-flocculation,
organics removal
(continued)
-------
TABLE D-l (continued)
Plant Name Ozone Dosage
MUnchengladback 0.9
Lindau 0.4
Umberg 2.7
vo
o
Grunstedt 0.3
DUsseldorf 3.0
Aachen 0.35
Sipplinger Berg 1.0
(continued)
Energy Demand,
Kwh/kg
30
--
28
30
30
30
29.5
Contactor off-gas
Treatment
none
none
yes
yes
activated
carbon &
catalytic
none
activated
carbon
Type of
Generators
Argentox tube type,
water cooled;
12 generators
CEO plate type,
water cooled;
2 units
Benckiser tube type,
water cooled;
2 units
Schade tube type,
water cooled;
1 unit
Herrmann tube type,
water cooled;
28 generators
Herrmann tube type,
water cooled;
1 generator
Herrmann tube type,
water cooled;
6 generators
Conjunctive Use of C10 or CIO-
in
Pretreatment "Post-Treatment
0.1 mg/1
0.2 mg/1
none none
none none
— chlorine
0.2 mg/1
— chlorine
0.3 mg/1
— chlorine
NaOCl
C12
dioxide
dioxide
0.6 mg/1
-------
TABLE D-l (continued)
Plant, Location, Water Design
Source 4 Year Ozone Capacity
Installed (cu m/day)
Ozone
Generation
Capacity
(kg/day)
Treatment Process
Purpose(s)
of
Ozonation
Type of
Contacting
Wuppertal, Nordheim, 150,000
Westfaien, FRG, Rhine River,
1967
KOnigswinter, Nordheim, 4,800
Westfaten, FRG, Rhine River,
1962
Altheimingen, Rheinland Pfalz, 400
FRG, groundwater, 1964
Oberhessen, Hessen, FRG, 50,000
groundwater, 1970
Floremberg, Hessen, FRG, 2,500
groundwater, 1970
Friedrichshafen, Baden- 30,000
WUrttemberg, FRG, Lake of
Constance water, 1970
Meersbury, Baden-WUrttemberg, 4,000
FRG, Lake of Constance water,
1969
360 sand bank filtration, aeration, ozonation, gravel
filtration, granular activated carbon, chlorine
dioxide
5.6 sand bank filtration, granular activated carbon,
ozonation, granular activated carbon, chlorl-
nation
•i.
0.9 ozonation
32.4 ozonation, chlorination
1.2 ozonation
52.4 ozonation, flocculation, granular activated
carbon over sand filter, chlorination
9.0 microstraining, ozonation, sand filtration,
chlorination
Fe, Mn remov-
al , taste 4
organics re-
moval , viral
inactivation
spray tower within
filter
Fe, Mn removal, injector,
taste removal 40 min detention
disinfection injector
disinfection, VAR injectors,
viral inacti- 7 min detention
vation
disinfection Argentox injector
taste removal, VAR injectors,
disinfection, 4-8 min detention
organics &
turbidity removal
color, taste & 1 injector, 1 rotor,
odor removal, VAR
disinfection
(continued)
-------
TABLE 0-1 (continued)
ro
Plant Name
Wuppertal
KOnlgswInter
Al theimlngen
Ozone Dosage
0.8-1.0
0.2
0.3
Energy Demand,
Kwh/kg
35
--
50
Contactor off-gas
Treatment
none
none
none
Type of
Generators
Herrmann tube type,
water cooled
Demag tube type,
water cooled
Schade tube type,
Conjunctive
Pretreatment
---
—
none
Use of C10 or ClOo in
-Post-Treatment
chlorine dioxide
chlorine dioxide
none
Oberhessen 0.6
Floremberg 0.35
Friedrlchshafen 0.8
Meersburg 1.6
35
22.5
none
none
activated
carbon
activated
carbon
water cooled;
2 generators
VAR plate type,
water cooled;
2 generators
Argentox,
water cooled
TraiHgaz plate type,
water cooled;
3 generators
VAR Sauter plate,
water cooled;
1 generator
chlorine 0.08 mg/1
chlorine dioxide
0.3 mg/1
chlorine 0.4 mg/1
(continued)
-------
TABLE D-1 (continued)
VO
CO
Plant, Location, Water
Source & Year Ozone
Installed
Bad Mergentheim, Bad-
UUrttemberg. FRG, 1976
Mat hay, Commune de Mat hay,
France. Doubs River
Alencon, France, surface
water, 1965
Usine Francois Duroy,
Louvigny-Caen, France,
Orne River, 1976
Design
Capacity
(cu m/day)
6,000
75,000
20,000
Avg Daily Flow
30,000
Ozone
Generation
Capacity
(kg/day)
6
270
80
108
Treatment Process
flocculation, filtration, ozonation.
filtration, chlorlnation
prechlorination, coagulation, sedimentation,
filtration, ozonation, chlorlnation
prechlorination, coagulation, sedimentation,
filtration, ozonation, chlorine dioxide
sodium hypochlorite, coagulation,
sedimentation, powd. act. carbon, filtration,
ozonation, chlorlnation
Purpose(s)
of
Ozonation
disinfection
color, taste &
odor, bacterial
disinfection,
turbidity, viral
Inactlvation
taste & odor,
color removal
taste & odor,
color, organ ics
removal, bacter-
ial disinfection,
turbidity reduction
viral Inactlvation
Type of
Contacting
2 injectors,
Schneider, 10 min
detention
porous plate
diffuser, 2 compart-
ments per chamber
2 units, 3 stages,
porous plate diffuser
2 units, porous plate
diffusers, 10 min
contact
,
Le Mans, France, river water 30,000
1970
240 prechlorination. coagulation, sedimentation,
filtration, ozonation, chlorine dioxide
iron oxidation, 3 units, 15 min
taste & odor con- contact time, porous
trol, organics tubes
removal, bacterial
disinfection, viral
inactivation
(continued)
-------
TABLE D-l (continued)
Plant Name Ozone Dosage
Bad Nergenthelm 0.6
Mat hay 1.5
Alencon 3
Louvigny-Caen 1.3
Le Mans 3 to 4
Energy Demand,
Kwh/kq
--
21.9
NA
18-20
24
Contactor off -gas
Treatment
yes
none
therman des-
truction at
220°C
none
dilution &
ventilation
Type of
Generators
Argentox tube type,
water cooled;
1 generator
Degr&nont tube type,
water cooled;
3 generators of
3.75 kg/hr
Degr&nont-Wel sbach
Degr&nont tube type,
water cooled; 2
generators of 2.25
kg/hr capacity
TraHigaz tube type,
water cooled; 4
Conjunctive Use. of
Pretreatment
---
prechlorlnatlon
prechlorlnatlon
sodium hypochlorite
addition
prechlorlnatlon
C10 or C10? in
"Post-Triatment
chlorine dioxide
0.1 mg/1
Cl, added, 0.3 to
0.5 mg/1. 0.2 mg/1
free residual at
plant exit
C102 added, 0.2
mg/f
Cl, added, 0.15
chlorine dioxide;
1.0-1.5 mg/1
generators--2 of 1.5
kg/hr & 2 of 4.5
kg/hr capacity
(continued)
-------
TABLE 0-1 (continued)
Plant, Location, Water Design
Source & Year Ozone Capacity
Installed (cu in/day)
Ozone
Generation
Capacity
(kg/dayl
Treatment Process
Purpose(s)
of
Ozonatlon
Type of
Contacting
Rosporden, France, river 3,600
plus spring water, 1974
7.2 prechlorlnatlon, coagulation with alum,
sedimentation, filtration, ozonation, lime
addition, chlorination
Langres, France, water
from dam, 1958
1,200 avg dally 4.56
production
Saint-Charles Waterworks, 140,000 187.2
Nancy, France, Moselle
River, 1935
Du Rupt du Mad Water- 90,000 199.68
works, Metz, France,
1971
Planques Waterworks, 19,200
Montauban, river water
plus spring water, 1973
Toulon, Perigueux, springs 30,000 36
of Cluzeau and Abime, 1971
bacterial disin- 1 unit, porous tubes,
fection, organics, 5.5 min contact time
taste, turbidity
reduction
prechlorinatlon, alum coagulation sedimen-
tation, ozonation
prechlorlnatlon, coagulation, sedimentation,
filtration, Hrne addition, chlorination,
ozonation
prechlorination, coagulation, sedimentation,
filtration, ozonation, post-chlorination
4.8 prechlorlnation, coagulation, sedimentation,
filtration, ozonation
coagulation, sedimentation, filtration,
ozonation
bacterial disin-
fection, viral
inactivation
bacterial disin-
fection
taste & odor re-
moval , bacterial
disinfection,
Mn removal
bacterial disin-
fection
taste & odor,
organics,
turbidity reduc-
tion, bacterial
disinfection
1 unit, dispersion by
injector, 2 stage
contactor
dispersion by
injector
1 unit, porous tubes,
ZO min contact time
2 units, porous tubes,
7 min maximum
contact time
porous tubes, 10 min
contact time
(continued)
-------
TABLE D-1 (continued)
VD
o*
Plant Name
Rosporden
Langres
Saint-Charles
(Nancy)
Ozone Dosage
NA
1.2
NA
Energy Demand,
Kwh/kg
NA
23.85
NA
Contactor off-gas
Treatment
none
none
none
Type of
Generators
Trail igaz tube type,
water cooled
CEO Trail Igaz plate
type, water cooled,
2 generators
CEO Trail Igaz plate
type, water cooled,
Conjunctive Use
Pretreatment
prechlorl nation
prechlorl nation
prechlorl nation
of Cl, or CIO, In
Post-Treatment
Cl, added at 0.4
mg/1 maximum
none
Cl- added prior to
ozonation
Du Rupt du Mad
Planques
Toulon
NA
NA
0.30 to 0.50
NA
NA
none
thermal
destruction
47 total; thermal
11 air preparation destruction
26 generation
12 thermal destruc-
tion
11 generators
Degrfimont tube type,
water cooled, 1
generator of 0.2
kg/hr capacity
Degr€mont tube type,
water cooled, 4
generators of 2.08
kg/hr capacity
Decrement tube type,
water cooled, 1
generator
prechlorl nation
prechlorlnatlon
prechlorination
none
0.1 mg/1 free Cl-
residual at plant
exit
0.15 to 0.20 mg/1
C12 added
(continued)
-------
TABLE D-l (continued)
Plant, Location, Water
Source & Year Ozone
Installed
Anglet, France, 25
le Nive River, 1967
Les Vans, France
le Chassezac River,
1973
Pont Aven, France (Moelan-
sur-Mer), 1 'Aven River,
Design
Capacity
(cu m/day)
,000 avg dally
production
4,320
2,000
Ozone
Generation
Capacity
(kg/day)
50.4
8.2
3.6
Treatment Process
prechlorination coagulation, sedimentation,
filtration, ozonatlon
prechlorination, alum and lime coagulation,
sedimentation, filtration, ozonation,
sodium carbonate
chlorine dioxide, coagulation, sedimentation,
filtration, ozonatlon, chlorine dioxide
Purpose(s)
of
Ozonation
bacterial disin-
fection
bacterial disin-
fection
bacterial disin-
fection
Type of
Contacting
2 spray tower units,
5 minute contact time
dispersion by a sub-
merged tube
dispersion by spray
tower
1976
Pont Aven, France (Route 4,800 24
de Bannalec), 1974
Barrage des RivlSres, 8,000 18
le Longeron, raw water
from dam, 1952
Annet-sur-Marne, France, 25,000 162
Marne River, 1973
chlorine dioxide, coagulation, sedimentation, bacterial disin-
filtration, ozonatlon, chlorine dioxide fection,
organlcs removal
chlorine/activated carbon, lime and alum co- bacterial disin-
agulation, sedimentation, sand filtration, fection, viral
ozonatlon, chlorination, lime addition inactivation
prechlorination, coagulation, sedimentation,
ozonatlon, chlorine dioxide
taste & odor
removal,
bacterial disin-
fection, viral
inactivation
porous tubes
porous tubes, 1
chamber, single
stage, 6 mln contact
time
3 units, porous
tubes, 7 min contact
time
(continued)
-------
TABLE D-1 (continued)
<£>
CO
Energy Demand
Plant Name Ozone Dosage Kwh/kg
Anglet 10 NA
Les Vans NA 9.4
Pont Aven (Moelan-sur- 0.3 NA
Mer)
Pont Aven (Route de NA NA
Banna lee)
Barrage des Rivieres 1 to 2.5 105
Annet-sur-Marne 2 NA
, Contactor off-gas Type of
Treatment Generators
none CEO Trail Igaz plate
type, water cooled
none Welsbach-Degremont
tube type, water
cooled, 1 generator
none OegrSmont tube type,
water cooled,
1 generator
none Degr&nont tube type,
water cooled,
1 generator
none Degr&nont tube type,
water cooled,
1 generator
recycling TraIHgaz tube type,
water cooled, 3
Conjunctive Use of C10 or
Pretreatment
prechl or 1 nation
prechlori nation
C102 addition
C102 addition
prechlorination
prechlorlnation
CIO,, in
^•Post^TrBatment
none
none
cio2
cio2
1.0
ci2
addition
addition
to 1 .5 mg/1
added
0.5 mg/1 C10?
added
generators of 2.25
kg/hr capacity
(continued)
-------
TABLE D-l (continued)
Plant, Location, Water Design
Source & Year Ozone Capacity
Installed (cu m/day)
Ozone
Generation
Capacity
(kg/day)
Treatment Process
Purpose(s)
of
Ozonation
Type of
Contacting
Chattellerault, France, 23,000
Vienna River, 1925
72 coagulation, sedimentation, filtration,
ozonation
taste & odor, color, 2 chambers,. 4 injec-
bacterial disinfec- tors, 6 min contact
tion, organics re-
moval , viral in-
activation
time, 3 stages per
chamber
10
10
Aubusson, France, 2,880
dam water, 1974
Bourbon Lancy, France 4,800
water from alluvial water
table of the Loire River,
1974
Gueugnon (Saone et Loire), 8,000
France, Arroux River, 1976
Ste. Cecile, France, 1970 2,400
Lescure D'Alb1geo1s, France, 3,350
groundwater from alluvial
water table of Tain River
9.9
15
coagulation, sedimentation, filtration,
ozonation
ozonation plus filtration (for demangani-
zation), neutralization, chlorination
taste & odor, color, 2 chambers, single
bacterial disinfec- stage, injector, 8
tion, organics re- min contact time
moval, viral in-
activation
iron & manganese 1 chamber, dispersion
oxidation, bacterial by injector, 8 min
disinfection contact time
prechlorlnation, coagulation, sedimentation, taste removal, 1 chamber, dispersion
filtration, ozonation, chlorination bacterial disinfec- by injector, 8 min
tion
3.96 prechlorlnation, coagulation, sedimentation, taste & color re-
filtration, ozonation, chlorination moval, bacterial
(intermittent) disinfection
contact time
2 chambers, porous
diffusers
NA
ozonation only
bacterial disinfec- 1 chamber, porous
tion, viral inacti- diffusers
vation (sterilization)
(continued)
-------
TABLE 0-1 (continued)
Energy Demand,
Plant Name Ozone Dosage Kwh/kg
Chattellerault 3 18
Aubusson 2 14
en
o
o _ , ...
, Contactor off -gas Type of Conjunctive Use
Treatment Generators Pretreatment
none CEO Trailigaz plate none
type, water cooled,
3 generators of
1.2 kg/hr capacity
none CEO Trailigaz plate none
type, water cooled,
2 generators of
0.18 kg/hr capacity
PI f. + t Kn +,,r,o nr.no
of Cl, or C100 in
"Post-Treatment
none
none
n c mn/i n *AA^A
Gueugnon
Ste. Cecile.
Lescure D'Albigeois
tratlon of manganese
in the raw water
0.8 NA
0.2 NA
NA NA
none
none
none
water cooled
Degr£mont tube type,
water cooled
Degr&nont tube type
water cooled
Degr&nont tube type,
water cooled
prechlorination
prechlorination
none
dp added, approxi-
mately 0.1 mg/1 free
residual at plant
exit
C1? added intermit-
tently
none
(continued)
-------
TABLE D-l (continued)
Ozone
Plant, Location, Water Design Generation
Source & Year Ozone Capacity Capacity Treatment Process
Installed (cu ra/day) (kg/day)
Ste.-Maries-de-la-Mer, 3,600
France, river water
Saint Gllles du Gard, 4,800
France, river water, 1970
Ul
2 La Roche waterworks, Nantes, 240,000
France, Loire River, 1975
Villeneuve-la-Garonne, 40,000 max
France, well water, 1970 daily pro-
duction
Flins, France, well water, 120,000
1968
Le Pecq, France, well water, 30,000
1967
15 prechlorlnation, coagulation, sedimentation,
filtration, ozonation
5.8 prechlorlnation, coagulation, sedimentation,
filtration, ozonation
720 3 to 17 tng/1 chlorine, alum and sodium
silicate coagulation, sedimentation with
pulsators, filtration, ozonation, chlorination
96 nltrlflcatlon/deferrizatlon, filtration,
ozonation
264 coagulation, powd. act. carbon, sedimentation,
ni tr1 f 1 cation/def err i za ti on , ozona ti on ,
chlorination
36 nltrificatlon/deferrization, filtration,
ozonation
Purpose(s)
of
Ozonation
taste A odor,
color, bacterial
disinfection,
viral Inactivation
taste & odor,
color, bacterial
disinfection,
viral inactivation
taste & odor,
color, bacterial
disinfection,
organics removal,
viral inactivation
bacterial disin-
infection
bacterial disin-
fection
bacterial disin-
fection
Type of
Contacting
2 chambers, porous
diff users, 4 m1n
contact time
2 chambers, porous
tube, 5 rain contact
time
3 chambers, 2 stages,
porous tube diffusers,
8 min contact time
1 chamber, 2 stage,
injector, 15 min
contact time
1 chamber, 2 stage,
porous tubes, 15 min
contact time
1 chamber, 2 stage,
porous tubes, 15
min contact time
(continued)
-------
TABLE D-l (continued)
Plant Name Ozone Dosage
Ste.-Maries-de- 0.6
la-Mer
Saint Gllles du Gard 0.5
La Roche 1.5
en
o
ro
V1lleneuve-la-Garonne 1
Fllns 1
Energy Demand,
Kwh/kg
31.6
32
50
30 total
12 air prep-
aration,
18 generation
30 total
12 air prep-
aration,
IS generation
Contactor off-gas Type of
Treatment Generators
none
recycled
thermal
destruction
NA
thermal
destruction
Trail Igaz tube type,
water cooled
Trail Igaz tube type,
water cooled, 1
generator of 0.240
kg/hr capacity
DegrSmont tube type,
water cooled, 6
generators of 5
kg/hr capacity
Degremont tube type,
water cooled, 2
generators of 2
kg/hr capacity
Degr&nont*tube type,
water cooled, 1
generator of 11
kg/hr capacity
Conjunctive Use of Cl, or CIO,, 1n
Pretreatment "Post-Trfeatment
prechloHnatlon none
prechloHnatlon none
prechlorlnatlon 0.5 to 2 mg/1 Cl?
3 to 17 mg/1 added
NA none
none 0.2 mg/1 C12 added
Le Pecq
30
NA
CEO plate type,
water cooled, 1
generator of 1.5
kg/hr capacity
NA
none
(continued)
-------
TABLE 0-1 (continued)
Plant, Location, Water
Source & Year Ozone
Installed
en
O
CO
Croissy, France,
well water, 1975
Huez-en-Oisans,
Lake Blanc
Clalrfont Plant,
France, Garonne
1970
Nerls Les Bains,
France, surface
France,
Toulouse,
River,
Marcoing,
water (dam),
Design
Capacity
(cu m/day)
30,000
2,500
110,000
780
Ozone
Generation
Capacity
(kg/day)
72
7
216
8.2
Treatment Process
nltriflcation/deferrization, filtration,
ozonatlon
mineralization (carbon dioxide gas addition),
filtration, ozonatlon, sodium carbonate
neutralization
chlorine dioxide, coagulation, double
sedimentation, sand filtration, ozonatlon,
lime/sodium silicate addition
prechlorination, coagulation, settling,
filtration, ozonation, final chlorination
Purpose(s)
of
Ozonatlon
bacterial
disinfection
bacterial
disinfection
taste, odor,
organics, bacterial
disinfection, viral
inactlvation
bacterial
disinfection
Type of
Contacting
4 chambers,
porous tubes
contact time
1 chamber, 2
porous tubes
contact time
4 chambers,
porous tubes
contact time
diffuser
2 stage,
, 15 min
stage,
, 8 min
4 stage,
, 8 min
1974
Aubagne, France, Marseille 25,000
Canal (Purance River), 1967
Marseille, France, 90,000
Provence Canal (Verdon
River), 1976
20.4 prechlorination, coagulation, settling,
filtration, ozonation, final chlorination
200 prechlorination, coagulation, filtration,
ozonatlon, final chlorination
bacterial disin-
fection, viral
inactivation
4 diffusers, 20 nrln
detention
taste & odor, 4 diffusers, 20 min
organics, bacterial detention
disinfection, viral
inactlvation
(continued)
-------
TABLE D-l (continued)
Plant Name Ozone Dosage
Crolssy 1
Huez-en-Olsans 0.7
en
o
*" Clalrfont 1.8
Nerls Les Bains 1-2
Aubagne 0.9
Marseille 1.0
Energy Demand,
Kwh/kg^
30
20
43
NA
NA
NA
Contactor off-gas
Treatment
thermal
destruction
none
cycled Into
dlesel gener-
ators
none
none
none
Type of
Generators
Degr&nont tube type,
water cooled, 1
generator of 1 .5
kg/hr capacity
Degr&nont tube type,
water cooled, 1
generator of 0.342
kg/hr capacity
Trail 1gaz tube type,
water cooled, 4
generators of 2.25
kg/hr capacity
Degremont tube type,
water cooled
2 tube type, water
cooled
Degremont tube type,
Conjunctive
Pretreatment
NA
none
C102 added
yes
chlorine
chlorine
Use of Cl, or CIO., In
"Post-Treatment
none
none
none
chlorine, 0.5
chlorine, 0.4
chlorine, 0.2
mg/1
mg/1
mg/1
water cooled, 2
units
(continued)
-------
TABLE D-l (continued)
Plant, Location, Water Design
Source & Year Ozone Capacity
Installed (cu m/day)
Ozone
Generation
Capacity
(kg/day)
Treatment Process
Purpose(s)
of
Ozonation
Type of
Contacting
en
o
tn
Annecy-le-Vieux, France, 7,500
Lake of Annecy, 1975
Ferel, France, river water, 30,000
1971
St. Jean-sur-Mayenne, France, 2,400
Mayenne River, 1976
Ferel, France, river water, 30,000
1971
Couesmes-en-Froulay, France,
river water, 1973
600
15 NA
60 prechlorination, coagulation, settling, filtra-
tion, ozonation, chlorine dioxide
2.7 prechlorinatlon, coagulation, settling, filtra-
tion, ozonation, final chlorinatlon
120 prechlor1 nation, coagulation, settling, filtra-
tion, ozonation, chlorine dioxide
1.2 prechlorination, coagulation, settling, filtra-
tion, ozonation, neutralization, final
chlorinatlon
taste & odor, 3 diffusers
organics,
bacterial disinfec-
tion, viral inacti-
vation
taste & odor, 2 diffusers,
organics, viral 15 min detention
inactivation,
bacterial disin-
fection
taste & odor,
organics, viral
inactivation,
bacterial disin-
fection
taste & odor,
organics,
bacterial disin-
fection, viral
inactivation
1 diffuser
2 diffusers,
15 min detention
Fe removal, color, 1 diffuser
taste & odor,
bacterial disinfec-
tion, viral inacti-
vation
(continued)
-------
TABLE D-l (continued)
en
o
Plant Name Ozone Dosage
Annecy-le-V1eux NA
Ferel 2.0
St. Jean-sur-Mayenne 2.0
Ferel 2.0
Couesmes-en-Froulay 3.0
Energy Demand,
Kwh/kg
29
25
NA
25
NA
Contactor off-gas
Treatment
thermal
destruction
none
none
none
none
Type of
Generators
Degremont tube type,
water cooled, 2
units
Welsbach, tube type,
water cooled, 4
units
Degr&nont tube type,
water cooled, 12
units
Welsbach, tube type,
water cooled, 4
units
Degrfiinont tube type,
Conjunctive
Pretreatment
NA
ciz
ci2
ci2
ci2
Use of Cl, or Cl00 in
Post-Treatment
0.1 mg/1 C12
2 mg/1 C102
0.5 mg/1 C12
2 mg/1 C102
0.5 mg/1 C12
units
(continued)
-------
TABLE D-l (continued)
Plant, Location, Water
Source & Year Ozone
Installed
Port Brillet, France, lake
water, 1975
Ancteville, France, river
water, 1970
Le Poiroux, France
Coutances, France,
river water
Design
Capacity
(cu m/day)
2,400
1,000
16,000
2,000
Ozone
Generation
Capacity
(kg/day)
6.0
2.0
32
7
Treatment Process
prechlorination, coagulation, settling, filtra-
tion, ozonatlon, neutralization, final
chlorination
prechlorination, coagulation, settling, filtra-
tion, ozonaticn, final chlorination
prechlorination (chlorine dioxide), KMnO.
addition, coagulation, settling, filtration,
ozonatlon, neutralization, chlorination
chlorine dioxide, coagulation, settling, filtra-
tion, ozonation, chlorine dioxide
Purpose(s)
of
Ozonatlon
taste removal,
bacterial disin-
fection, viral
inactivation
bacterial disin-
fection, viral
inactivation
taste, odor,
color, bacterial
disinfection, viral
inactivation, tur-
bidity, organics
taste removal ,
viral inactiva-
tion, bacterial
disinfection
Type of
Contacting
2 diff users
1 plate column,
20 sec
diff user
1 plate column,
20 sec
Pinel Hauterive (Lot et 7,200
Garrone) Lot River, 1968
Crissey, France, 7,200
groundwater, 1974
12 prechlorination, flocculation, settling, filtra-
tion, ozonatlon
34 ozonatlon, coagulation, filtration
organics removal, 2 injectors,
viral inactiva- 4 min detention
tion, bacterial
disinfection
iron & manganese diffuser
(continued)
-------
TABLE D-l (continued)
Plant Name Ozone Dosage
Port BHllet 0.15
Anctevllle 1.6
Le Polroux NA
Coutances 3.4
Pinel HauteHve 1.0
Crlssey 0.3-0.5
Energy Demand,
Kwh/kg
20-30
20-30
NA
20-30
NA
48
Contactor off-gas
Treatment
none
none
NA
none
none
thermal
destruction
Type of
Generators
Degremont tube type,
water cooled, 7
units
Degremont tube type,
water cooled, 5
units
Degremont tube type,
water cooled, 2
units
Degremont, 19 units,
water cooled
Otto plate type,
water cooled, 2
units
Degremont tube type.
water cooled, 2
Conjunctive
Pretreatment
C12
ci2
£.
CIO,
£.
CIO,
£
ci2
f.
none
Use of Cl, or C10,
In
"Post-Treatment
1.4 mg/1
0.2 mg/1
ci2
a
0.2 mg/1
none
none
C12
C,
cu
£.
CIO-
£
units
(continued)
-------
TABLE 0-1 (continued)
Plant, Location, Mater
Source & Year Ozone
Installed
Bonnetable, France, 1948
Gueret, France, 1967
01
o Tlntry Pont Duroi , France,
river water, 1973
Branden, France,
lake water, 1967
Blanzy, France,
lake water, 1974
Design
Capacity
(cu m/day)
2,000
2,500
7,500
10,000
10,000
Ozone
Generation
Capacity
(kg/day)
3
12.0
14.0
12.0
30.0
Treatment Process
prechlorlnation, coagulation, settling, filtra-
tion, ozonation, final chlorination
chlorine dioxide, coagulation, settling, filtra-
tion, ozonation
chlorine dioxide, coagulation, settling, pre-
ozonation, filtration, ozonation
chlorine dioxide addition, coagulation,
settling, preozonation, filtration, final
ozonation
chlorine dioxide, coagulation, settling, pre-
ozonation, filtration, ozonation
Purpose(s)
of
Ozonation
bacterial disin-
fection, viral
inactlvation
color, taste,
odor, organics,
bacterial dis-
infection
bacterial disin-
fection, viral
inactivation
Fe, Mn removal ,
bacterial dis-
infection, viral
inactivation
Fe, Mn removal,
color removal ,
bacterial dis-
infection
Type of
Contacting
2 injectors,
detention
diff users
4 diff users,
detention
2 diff users,
12 min
diffusers, 12
detention
5 min
6 min
min
Salgues, (Aveyron), NA
France, river water, 1977
(continued)
NA chlorine dioxide, coagulation, settling, fil-
tration, ozonation, chlorine dioxide & poly-
phosphate addition
color, taste, odor, NA
turbidity, organics,
bacterial disinfection
-------
TABLE D-l (continued)
Plant Name
Bonnetable
Gueret
2 Tlntry Pont Durol
o
Branden
Blanzy
Salgues (Aveyron)
Ozone Dosage
0.15
0.5
0.2
NA
1.8
NA
Energy Demand,
Kwh/kg
21.3
NA
20
20
17
NA
Contactor off-gas Type of
Treatment Generators
none CEO TralUgaz plate
type, water cooled,
10 units
none Trail Igaz tube type,
water cooled, 1
unit
none TralUgaz tube type,
water cooled, 7
units
none TralUgaz tube type,
water cooled, 2
units
none TralUgaz tube type,
water cooled, 1
unit
NA Trail Igaz tube type,
Conjunctive Use of
Pretreatment
ci2
cio2
chlorine dioxide
chlorine dioxide
chlorine dioxide
chlorine dioxide
Cl, or ClOo in
"Post-Trfeatment
1 mg/1 C12
none
chlorine dioxide
(as needed)
none
chlorine dioxide
(as needed)
chlorine dioxide
water cooled
(continued)
-------
TABLE D-l (continued)
Plant, Location, Water
Source & Year Ozone
Installed
Morsang-sur-Se1ne, France,
Seine River, 1970
Oll'loules, France,
Verdon River, 1976
Chalon/Saone, France,
1972
Design
Capacity
(cu m/day)
150,000
37,000
21,600
Ozone
Generation
Capacity
(kq/day}
316.8
58
32
Treatment Process
prechlorlnatlon, coagulation, settling, filtra-
tion, ozonation, granular activated carbon
filtration, final chlorination
prechlorination, coagulation, settling, filtra-
tion, ozonation, final chlorination
preozonation, filtration, final ozonation,
neutralization
Purpose(s)
of
Ozonation
color, taste,
odor, bacterial
disinfection
turbidity, odor,
organics, bac-
terial disinfec-
tion, viral
1nact1vat1on
Fe, Mn, taste,
odor, organics,
bacterial dis-
infection
Type of
Contacting
4 diff users,
10 min detention
diffuser
diffuser, injector
V1lleneuves/Lot, France, 10,000
Lot River, 1971
Penne d'Argenais, France 1,200
Lot River, 1972
21 chlorine dioxide, rapid mixing, coagulation,
settling, filtration, ozonation, chlorine
dioxide
prechlorination, pulsator, filtration, ozona-
tion, chlorination
color, odor,
taste, organics,
viral inactlva-
tion, bacterial
disinfection
color, odor,
taste removal,
bacterial dis-
infection, viral
inactlvation
1 diffuser,
11 min detention
1 diffuser,
15 min detention
(continued)
-------
TABLE D-l (continued)
Plant Name Ozone Dosage
en
ro
Morsang-sur-Selne
Oll'loules
Chalon/Saone
Villeneuves/Lot
2.85
NA
NA
2.0
Energy Demand
Kwh/kg
37.5
NA
NA
NA
, Contactor off-gas Type of
Treatment Generators
thermal
destruction
recycling
NA
none
Wei sbach-Degr&nont
tube type, water
cooled, 4 units
tube type, water
cooled
tube type, water
cooled
Trail igaz tube type,
Conjunctive Use of
Pretreatment
chlorine
chlorine
NA
chlorine dioxide
C10 or ClOo
In
"Post-Treatment
0.2 mg/1
chlorine
NA
chlorine
chlorine
dioxide
Penne d'Argenais
2.0
NA
none
water cooled, 2
units
Traillgaz tube type, chlorine
water cooled, 1
unit
0.2 mg/1
chlorine dioxide
0.2 mg/1
(continued)
-------
TABLE D-l (continued)
Plant, Location, Water Design
Source & Year Ozone Capacity
Installed (cu m/day)
Ozone
Generation
Capacity
(kg/day)
Treatment Process
Purpose(s)
of
Ozonation
Type of
Contacting
Muret, France (Haute 10,000
Garonne), Garonne River,
1970
Buzet-sur-Tarn, France, 4,800
Tarn River, 1968
in Blagnac, France, 4,800
~J Garonne River, 1969
Vichy, France 22,000
Mougins, France, (Alpes 100,000
Marltimes), river water,
1959
Moulin de Ferguilyen, 3,000
Bodilis, France
20 prechloHnatlon, coagulation, settling, filtra-
tion, ozonation
9.6 prechlor1 nation, coagulation, settling, filtra-
tion, ozonation
24 settling, filtration, ozonation
96 prechlorinatlon, chlorine dioxide, coagulation,
settling, filtration, ozonation, chlorine
dioxide
129.6 coagulation, settling, filtration, ozonation
4.8 prechlorination, coagulation, settling, filtra-
tion, ozonation, final chlorinatlon
color, odor,
taste removal,
bacterial dis-
infection, viral
inactivation
1 diffuser,
14 min detention
taste & odor, 1 plate column,
bacterial dis- 15 min detention
infection, viral
inactivation
taste, odor,
color removal,
viral inactiva-
tion, bacterial
disinfection
NA
1 diffuser
2 diffusers,
8 min detention
organics remov- 2 injectors,
al, bacterial 4 min detention
disinfection,
turbidity removal
color, odor, 2 diffusers,
taste, turbidi- 8 min detention
ty, organics re-
moval, viral inacti-
vation, bacterial
disinfection
(continued)
-------
TABLE D-l (continued)
Plant Name Ozone Dosage
Muret
Buzet-sur-Tarn
<£] Blagnac
-P*
Vichy
Mouglns
Moulin de Fergullyeri
2.0
0.4
3.0
0.4
0.3-0.4
1.2-1.5
Energy Demand,
Kwh/kg
28
NA
NA
NA
26
NA
, Contactor off-gas Type of
Treatment Generators
none Trail igaz tube type,
water cooled, 2
units
none tube type, water
cooled, 1 unit
none TraiHgaz tube type,
water cooled
NA Welsbach, DegnSmont
tube type, water
cooled, 2 units
none CEO, plate type,
water cooled, 12
units
NA Welsbach-DegrSmont,
tube type, water
Conjunctive Use of Cl, or C109 In
Pretreatment
chlorine
chlorine
none
prechlorlnatlon/
chlorine dioxide
none
chlorine
"Post-Tr&atment
none
none
none
chlorine dioxide
none
0.6-0.8 mg/1
chlorine
cooled, 1 unit
-------
TABLE D-2. CANADIAN OZONE QUESTIONNAIRE SUMMARY
en
Plant, Location, Water
Source & Year Ozone
Installed
Design
Capacity
Ozone
Generation
Capacity
capacity capacity
(cu in/day) (kg/day)
Treatment Process
Purpose(s)
of
Ozonation
TAssomption, 9,988
Riviere 1'Assomption,
1966
Buckingham, 18,900
Riviere du Ligvre,
1976
Drummondville, 54,000
Riviere St. -Francois,
1966
1'Epiphanie, 4,540
Rivi&re 1 'Achigan,
1962
He Perrot, 6,800
Lac St.-Louis,
1963
Lac Etchemin, 2,383
Northern part of Lake,
1966
NA screening, chlorination, coagulation,
sedimentation, filtration, ozonation,
post-chlorination, pH adjustment
28.6 prechlorination, lime, alum + poly-
electrolyte, coagulation, sedimentation,
filtration, caustic soda, reservoir,
ozonation, chlorination
40.8 prechlorination, coagulation, sedimen-
tation, filtration, ozonation, post-
chlorination
NA screening, chlorination, coagulation,
sedimentation, filtration, chlorination,
ozonation, adjust pH
9 chlcrination, alum, SiOp, coagulation,
sedimentation, filtration, ozonation,
lime, fluoride
7.2 microstraining, ozonation, chlorination
odors, tastes,
phenols, organics,
bacterial disin-
fection, viral
inactivation
tastes & odors
tastes & odors
throughout winter
tastes, odors,
phenols, organics,
bacterial disin-
fection, viral
inactivation
color, tastes &
odors, bacterial
disinfection
color, tastes,
odors, "sterili-
zation"
Type of
Contacting
injector (no contact
time given)
porous diffuser (5-10
min)
injector (3-5 min)
injector
submerged turbine (20
min)
injector
(continued)
-------
TABLE D-2 (continued)
en
Plant Name Ozone Dosage
TAssomption NA
Buckingham 1-2 mg/1
Drummondville 0.6 mg/1
1'Epiphanie NA
He Perrot 0.8-1.0 mg/1
Energy Demand, Contactor off-gas Type of
Kwh/kg Treatment Generators
NA none
24 total none
22 total ; none
2.2 air preparation;
15.4 0,;
4.4 contacting
NA none
45 total ; none
9 air preparation;
Trailigaz, plate type,
water cooled, 1 unit.
Degr&nont horizontal
tube, water cooled,
1 unit
Trailigaz, plate type,
water cooled, 3 units
Trailigaz, plate type,
water cooled, 1 unit
Welsbach, horizontal
tube, water cooled,
Conjunctive Use of Cl, or CIO,, in
Pretreatment
0.5 mg/1
NA
1.5-3.2 mg/1
NA (8 Ibs/day
total)
1.3 mg/1 at co-
agulation basin
PoSt-Treatfnent
0.4 mg/1
1 mg/1 dosage; 0.2
mg/1 at plant exit;
0.02 mg/1 at extremi-
ty of distribution
system
0.2-0.3 nig/1 dosage;
0.2-0.3 at plant exit;
0.1 mg/1 at extremity
of distribution system
3 mg/1 at plant exit,
0 at extremity of
distribution system
trace of Cl? leaving
the plant
Lac Etchemin
21
15 contacting
28 total
none
1 unit
Trailigaz, plate type,
water cooled, 1 unit
none
5 Ibs/day; 0.1 mg/1
at plant exit, 0 at
extremity of distri-
bution system
(continued)
-------
TABLE 0-2 (continued)
in
Plant, Location, Water
Source & Year Ozone
Installed
Laval (Pont Viau),
RiviSre des Prairies,
1957
Laval (Ste-Rose),
Riviere des Mille-Iles,
1961, 1968
Oka, Lac des
Deux-Montagnes,
1958
Design
Capacity
(cu m/day)
95,850
25,560
2,192
Ozone
Generation
Capacity
(kg/day)
72
48
0.3
Treatment Process
Si02 + alum, coagulation, sedimentation,
filtration, reservoir, ozonation (2
stages), lime, fluoride, chlorination
SiOo + alum, coagulation, sedimentation,
filtration, reservoir, ozonation, lime,
fluoride, chlorination
prechlorination, lime, alum, coagulation,
sedimentation, filtration, reservoir,
ozonation, lime. No chlorine residual
Purpose(s)
of
Ozonation
tastes, odors,
bacterial disin-
fection, viral
inactivation
tastes, odors,
bacterial disin-
fection, viral
inactivation
tastes, viral in-
activation,
bacterial disin-
Type of
Contacting
injector (b-10 min)
injector (2-5 min)
injector (5 min)
Pierrefonds, 95,500 250
Rivi6re des Prairies,
1976
Quebec City, 218,000 360
Riviere St.-Charles,
1969
Repentigny, 22,730 45.5
RiviSre 1'Assomption,
1973
soda, chlorine, (NH.)pSO,, Na silicate,
alum, rapid mixing, ffocculation,
decantation (pulsator), filtration, ozona-
tion, chlorination
prechlorination, coagulation, floccu-
lation, sedimentation, filtration, ozona-
tion, post-chlorination, pH adjustment
screening, prechlorination, coagulation,
sedimentation, filtration, ozonation,
adjust pH, post-chlorination. If ozone
generators don't work, then PAC, not Cl
fection
tastes, odors,
bacterial disin-
fection
tastes, organics,
viral inactiva-
tion, bacterial
disinfection
tastes, organics,
viral inactiva-
tion, bacterial
disinfection
porous diffusers
(4 min)
injector (pulveriza-
tion column) (4 min)
porous diffusers
(continued)
-------
TABLE D-2 (continued)
en
03
Plant Name
Laval (Pont Viau)
Laval (Ste-Rose)
Oka
Pierrefonds
Quebec City
Ozone Dosage
1.5-2 mg/1
1.5-2 mg/1
2 mg/1
2 mg/1
1.3 mg/1
Energy Demand,
Kwh/kg
21.4 total
(6 kw/ralg)
13.3 total
(5 kw/mlg)
23.3 total
18 total;
6 air pretreatment
12 03
30 total
Contactor off-gas Type of
Treatment Generators
none Trailigaz, plate type,
water cooled, 12 units
none Trailigaz, plate type,
water cooled, 3 units
none Trail 1gaz, plate type,
water cooled, 1 unit
none Trailigaz, horizontal
; tube type, water cooled,
2 units
none Trailigaz, plate type,
Conjunctive Use
Pretreatment
none
none
NA
0.8 mg/1
1.2-2.4 mg/1
of Cl, or CIO,, In
PoSt-Treatfttent
3 mg/1 dosage; 0.3
mg/1 at plant exit;
trace at extremity of
distribution system
0.85 mg/1 dosage;
0.?5 mg/1 at plant
exit; trace at extrem-
ity of distribution
system
none
0.5 mg/1 dosage;
0.5 mg/1 at plant exii
0.35 mg/1 at plant
Repentigny
(continued)
NA
NA
none
water cooled, 12 units
Trailigaz, horizontal yes, but NA
tube, water cooled,
1 unit
exit; 0.1 mg/1 at
extremity of dis-
tribution system
0.83 mg/1 total (pre
post) dosage. 0 mg/1
at plant exit
-------
TABLE 0-2 (continued)
tn
Plant, Location, Water
Source & Year Ozone
Installed
RiviSre du Loup,
RiviSre du Loup,
1977
Roberval ,
Lac St. -Jean,
1971
St. Denis,
RiviSre Richelieu,
1972
St. Eustache,
Rividre des Mille-Iles;
Lac des Deux-Montagnes,
1957
Sherbrooke,
Lac Memphremagog,
1965, 1977
Design
Capacity
(cu m/day)
15,120
7,715
27,300
1,060
98,262
Ozone
Generation
Capacity
(kg/day)
36
43.18
28
NA
163
Treatment Process
prechlorination, rapid mixing, coagula-
tion, sedimentation, filtration,
ozonation, chlorination
ozonation, coagulation, filtration, ozona-
tion, chlorination. During period when raw
water is colored, but low turbidity, ozona-
tion, filtration, ozonation, chlorination
prechlorination, coagulation, sedimen-
tation, filtration, ozonation, post-
chlorination
coagulation, sedimentation, filtration,
ozonation, chlorination
occasional prechlorination, micro-
straining, ozonation, chlorination
Purpose(s)
of
Ozonation
tastes & odors
color
tastes, odors,
bacterial dis-
infection
tastes & odors
tastes, odors,
bacterial dis-
infection
Type of
Contacting
porous diffusers
porous diffusers
porous diffusers
injector (20 min)
porous diffusers
Terrebonne,
Rivi&re des mi lie-lies,
1963
15,120 28.5 prechlorination, alum, polyelectrolyte,
coagulation, sedimentation, filtration,
fluoride, reservoir, ozonation,
chlorination, lime
tastes, odors, injector (5-10 min)
viral inactivation,
bacterial disin-
fection
-------
TABLE D-2 (continued)
Plant Name
Ozone Dosage
Energy Demand, Contactor off-gas Type of
Kwh/kg Treatment Generators
Conjunctive Use of Clg or ClOp in
Prelreatment Post-Treatment
Riviere du Loup 1 ir.g/1
en
ro
o
Roberval
St. Denis
St. Eustache
Sherbrooke
Terrebonne
4.5 mg/1
0.6 mg/1 and
less
NA
2 mg/1
1.15 mg/1
25.3 total
NA
NA
NA
(144 kg/day, total)
29.1 total
7.9 air treatment,
21.2 0,
23.3 total
catalytic PCI-Ozone, horizontal 2.5 mg/1
tube, water 8 oil
cooled, 1 unit
none Welsbach, horizontal none
tube, water cooled,
1 unit
none PCI-Ozone, horizontal 1.0 mg/1
tube, water & oil
cooled, 2 units
none Trailigaz plate type, none
water cooled, 3 units
none Degr&nont, horizontal NA
tube, water cooled,
4 units
none Trailigaz, plate type, NA
2 units
5 Ibs/day dosage; 0.3
mg/1 at plant exit. NA
at extremity of dis-
tribution system
3.1 mg/1 dosage; 0.4
mg/1 at plant exit;
0.05 mg/1 at extremity
of distribution system
0.2-0.3 mg/1 dosage;
0.1 mg/1 at plant
exit; trace at extrem-
ity of distribution
system
2 mg/1 dosage; 0.7
mg/1 at plant exit;
trace at extremity of
distribution system
about 88 kg/day total
dosage; 0.2 mg/1 at
plant exit; none at
extremity of distri-
bution system
2 mg/1 dosage at
entrance to reservoir;
0.4 mg/1 at plant exit;
0.2 mg/1 at extremity
of distribution system
-------
APPENDIX E
DESCRIPTIONS OF SELECTED U.S.A. DRINKING WATER TREATMENT
PLANTS USING CHLORINE DIOXIDE
Plant Page
Columbus, Ohio 522
Newark, Ohio 524
Bethesda, Ohio 525
Hamilton, Ohio 527
Toledo, Ohio 529
Atlanta, Georgia
(Chattahoochee Plant) 531
Atlanta, Georgia
(Hemphill Plant) 533
Carroll ton, Georgia . 534
Fayetteville, Georgia 536
Marietta, Georgia
(Wykoff Plant) 537
Wheeling, West Virginia 539
Covington, Kentucky 541
Ann Arbor, Michigan 543
521
-------
COLUMBUS, OHIO
The 35 million gallon per day (mgd) (133,000 cu m/day) plant at
Columbus uses C10? seasonally for the control of taste and odor problems
which are generally caused by phenols and algae (70% natural and 30%
industrial). The industrial sources are identified as highway runoff and
washdown wastes from a nearby railroad switching yard. The plant obtains
its raw water from the Scioto River through a series of two surface
reservoirs. The ClOo operation began in 1975 and has since solved the
taste and odor (T/0) problem.
The Columbus plant (Dublin Road) has the following process steps:
• chemical addition - lime/alum
- KMn04 (optional)
• flocculation
• sedimentation
• prechlorination - chlorine
t softening - Na2C03
• recarbonation
t chemical addition - fluoride
- sequestration
• filtration
• chemical addition - chlorine dioxide
• clearwell - distribution system
The C10? is generated by mixing aqueous Clg and 37% aqueous NaC102 in
the ratio ofi:l by weight. The addition of C102 is seasonal. Liquid
chlorine is delivered to the plant in one ton (900 kg) cylinders. The
NaC102 is shipped to the site in a 4,000 gallon (15.2 cu m) tank truck and
pumpea into two 1,300 gallon (4.94 cu m) fiberglass storage tanks. These
containers are located inside a large room which adjoins the chlorine
storage room. The NaC10? room is heated in the cold months because of the
relatively high freezing point of 37% concentrated NaC102 (49°F). 01 in
Corporation manufactures the NaC102 but an area distributor delivers the
chemical to the plant.
The C102 generation system consists of one Fischer and Porter C102
reactor vessel, two BIF proportional metering pumps for NaC102 feed (one as
standby), and one Fischer and Porter chlorinator. A chlorine sensor is
located inside the clearwell to measure the chlorine residual which results
from the addition of C102 to the finished plant water. A signal is trans-
mitted to the chlorinator for purposes of increasing or decreasing the
522
-------
chlorine feed. A set point establishes the desired chlorine residual in
the finished water. Because the chlorine feed may vary whereas the NaClCL
feed is constant, the 1:1 ratio may not always be achieved. It was stated
however, that the chlorine feed does not vary appreciably and there are
rarely "spikes" in the feed rates. Piping for the C102 system is schedule
80 PVC except for the chlorine gas piping which is black steel.
The chlorine room contains the plant chlorinators, one ton (900 kg)
chlorine cylinders and the CIO,, reactor vessel. A Fischer and Porter
chlorine leak detection system automatically activates the exhaust fan
system if a leak occurs inside the room. The air is sampled for chlorine
every 60 seconds. The two exhaust fans appear to be adequately sized for
the 40 ft x 80 ft (12 m x 24 m) room. The entrance doors have glass
panels for visual inspection of the room interior. Entrance to the chlorine
room is through an interior wall only -- there is no exterior entrance to
the chlorine room. The one ton (900 kg) chlorine cylinders are delivered
to the chlorine storage room through a common overhead door which opens to
the adjoining NaClOp room. The overhead crane carries the ton cylinders
from the loading platform outside the NaC102 room to the chlorine room.
The Nad02 room has no forced exhaust system, although the exterior
windows provide ventilation during warmer months. The area surrounding the
NaC102 storage tanks is bordered by a 12 inch high (0.3 m) concrete step.
If the tanks or transfer pipes develop a rupture, the liquid NaC102 is
momentarily contained. The liquid chemical is emptied through the floor
drain and directed into the plant coagulation basin. The NaC102 feed pumps
have a similar retaining wall and drainage system.
The production of C102 is monitored visually by the color that is
generated inside the C102 reactor vessel. A site glass mounted at the
discharge port of the opaque reactor allows the operator to inspect the
C102 color. Plant personnel also monitor the taste and odor of the finished
water every two hours as a means of evaluating the ClOo performance. When
the C102 unit is operating, the average concentration of NaC102 in the
plant water is 0.4 to 0.5 mg/1.
Plant supervisors expressed a concern for toxic effects of chlorite
ions in the finished water. Although C102 is used sparingly because of its
high cost, the supervisor is considering replacing chlorine in the prechlori-
nation process with C1Q2.
The chemical cost for chlorine is $0.086/pound ($0.191/kg). The cost
for NaCIO- was not immediately available. Costs for the NaC102 tanks and
chemical Teed pumps have been promised. Chemical costs for the production
of finished water were not available at the time of this writing.
The plant expects to install temperature probes in its largest water
surface reservoir in order to determine seasonal turnovers. This, in turn,
can assist the plant in predicting a possible rise in algae or manganese
concentration.
523
-------
NEWARK, OHIO
The 10 mgd (38,000 cu m/day) plant at Newark uses C102 to control the
presence of phenols and magnesium In Its raw water source ~ the Licking
River. Taste and odor problems, which are attributed to phenols, were at
their peak in the early 1960s, but the origin of the phenols was never
determined. The plant subsequently began adding C102 in 1964 as a "pre-
chlorination" step, and the process and has worked well since.
The Newark plant has the following process steps:
t raw water intake - chlorine dioxide
• chemical addition - lime/alum
- powdered activated carbon
• flash mix
» flocculation
• sedimentation
t recarbonation/excess lime for iron removal
t filtration
• chemical addition - chlorine
- fluoride
• clearwell - distribution system
Water quality data for both raw and finished water have been obtained.
C109 is generated by mixing aqueous Cl? and aqueous NaC102 in the
ratio or4.18:l by weight [100 pounds (45 kg) Cl2/day and 24 pCunds (10.8
kg) NaC102/day]. This is a constant feed dosageT Post-chlorination requires
about 40 pounds/day of chlorine. Technical grade anhydrous NaC102 is
delivered in 100 pound (45 kg) drums. The NaC102 is manufactured fay 01 in
Corporation and distributed by a local retailer.
The C102 generation system is Wallace and Tiernan equipment: one
reactor vessel for C10? production, one diaphragm pump for NaC102 feed and
one chlorinator. There is also a W&T chlorinator for the post- chlorination
step. The piping is schedule 80 PVC except for the chlorine gas line which
is black steel. The C102 generating equipment is housed within the plant
building, but in a room with an outside entrance. The room where the one
ton (900 kg) chlorine cylinders are stored adjoins the C102 room. The
entrance to this room is also from the exterior wall of the building.
Both rooms have forced exhaust systems which are installed at floor
level. The capacity of the units appears adequate. The switches for
524
-------
both the lights and fans are located on the exterior wall of the entrance
doorways. There are floor drains in the CICU room which empty into french*
drains beneath the building. An ammonium hyaroxide bottle has been placed
inside the chlorine room for emergency neutralization. Both entrance doors
have glass panels for inspection of the room interior. There are ABC fire
extinguishers in both rooms and two self-contained breathing apparatuses in
the main control room about 75 feet (22.5 m) away.
Production of ClOp is monitored visually by the color that appears
inside the reactor vessel. The chemical feed rates of G12 and NaClCL also
are checked daily. The effectiveness of CIO,, is measured by the absence of
T/0 problems in the finished water. The concentration of magnesium in the
raw water can jump to above 25 mg/1 while the finished water may contain 10
to 12 mg/1. The estimated concentration of NaClCL in plant water is around
0.3 to 0.4 mg/1. The C102 dosage remains constant year-round.
Oxidants in the finished water are analysed by the DPD method. The
total chlorine residual leaving the plant is 0.1 to 0.2 mg/1. The extremi-
ties of the distribution system have a total chlorine residual of 0.1 to
0.05 mg/1.
The chemical cost of NaCIO- is $83/100 pounds ($1.84/kg). Chlorine
costs 9
-------
• prechlori nation - chlorine
• chemical addition - lime/alum
- powdered activated carbon
(optional)
t flash mix
t flocculation
• sedimentation
t chemical addition - sodium tripolyphosphate
blended with KMnO, (1% by
weight of chemical feed)
• chemical addition - chlorine dioxide
• filtration
• clearwell - distribution system
Manganese (Mn) in the raw water averages 0.7 mg/1 while iron (Fe)
averages about 0.6 rng/1. The finished water has only trace amounts of Mn
but 0.4 mg/1 Fe. The reservoir is seasonally treated with copper sulfate
(CuSOj for control of algae growth. There are no immediate records for
loading rates for the past five years.
p is generated by mixing aqueous NaCIO? and aqueous Clo in the
ratio or5.6:l by weight [20 pounds (9 kg) NaCnWday and 3.6 pounds CWday
(1.62 kg)]. Total C12 consumption, including prechlori nation, is approxi-
mately five pounds per day. The concentration of NaC102 in the plant water
is 17.4 mg/1. Plant personnel feel that this is a desirable dosage to
prevent T/0 complaints. The NaClOo is manufactured by 01 in Corporation and
delivered to the plant by an area distributor. The anhydrous NaClOn is
technical grade and is supplied in 100 pound (45 kg) drums. The chlorine
gas is supplied to the plant in 150 pound (67.5 kg) cylinders.
The C102 generation system consists of one Wallace and Tiernan reactor
vessel for CiO? production, one Gorman-Rupp bellow pump and one Wallace and
Tiernan chlorinator. The piping for the NaC102 and ClOo solution is schedule
80 PVC. The chlorine gas is piped to the chlorinator with black steel.
The tubing from the chlorinator to the C102 reactor vessel is a flexible
plastic pipe of unknown specifications. Several of the joints are secured
with hose clamps. There have been no reports of chemical leakage. The
Cl2/NaC102 chemical feed equipment and C102 reactor unit are housed in one
building separate from the plant.
The building has no forced exhaust system. There is also no alarm
system or a chlorine gas leak detection system (a bottle of ammonium
hydroxide solution for detecting chlorine gas was not present). There are,
however, windows in this 10' x 20' (3 m x 6 m) building that offer some
526
-------
ventilation. The entrance door has a glass panel for easy inspection of
the room interior. A light switch is located on the inside wall beside the
doorway. There are no floor drains inside the chemical equipment room.
The production of C102 is monitored visually by the color that appears
inside the reactor vessel and also by checking the NaC102/Cl2 feed rates
daily. C102 is generated seasonally when the need arises. The effectiveness
of C102 is evaluated by the absence of T/0 problems in the finished water.
The DPD method is used to check chlorine residual for the state, but the
OTA method is used around the plant for "spot checking" chlorine residual
in the process water. The finished water has a combined chlorine residual
of 2.5 mg/1 (1.8 mg/1 free chlorine). At the extremity of the distribution
system, there is a combined chlorine residual of 0.82 mg/1 (0.63 mg/1 free
chlorine).
The cost of NaC102 is $105/100 pounds ($2.33/kg). Chlorine costs are
not available. The overall chemical cost for plant water is about 43^/1000
gallons (11.3
-------
pound (67.5 kg) cylinders. Aqueous NaClOo is manufactured by 01 in Corporation
and shipped to the site by an area distributor. Each drum contains 200
pounds (9 kg) of 37% aqueous NaC102.
The ClOo generation system consists of one plant fabricated reactor
vessel for CTOo production, one BIF peristaltic pump for liquid NaC102 and
two Fischer ana Porter chlorinators with one serving as a standby. Two 150
pound (67.5 kg) liquid chlorine cylinders are positioned next to the chlori-
nators. One is in service while the other serves as a backup. The weight
of the chlorine cylinder contents is measured by a scale. Switchover from
one tank to the other is manual. Fischer and Porter specifies schedule 80
PVC tubing for the line between the chlorinator and the reactor vessel.
Heavy Tygon* tubing is used for transporting the liquid NaC102 from the
drum to a small plastic day tank and to the reactor vessel. The Tygon
tubing reportedly loses its rigidity after a month's use and is subsequently
replaced. The semi-transparent day tank allows visual inspection of the
level of liquid NaClOo and thereby enables the operator to maintain an
acceptable suction head on the peristaltic pump.
The C102 reactor vessel is made from what appears to be schedule 80
polyvinyl chloride (PVC) pipe material — 18 inches (45.7 cm) high and
approximately 6 inches (15.2 cm) in diameter. The vessel is filled with 1
inch (2.54 cm) diameter rings of PVC pipe. The chamber is opaque except
for the sight glass which is mounted "in-line" on the discharge piping. A
white card is placed behind the sight glass for proper inspection of the
C102 color.
The ClOo generation equipment is housed in a room with no direct
access to the outside, A corridor connects the room to the outside where
150 pound (67.5 kg) chlorine cylinders are stored. The cylinders are
protected from direct sunlight. There is an exhaust fan system in the C102
room. There is no chlorine leak detector in the room. Both entrance doors
to the C102 room have glass panels for visual inspection of the room interior.
Production of C102 is monitored visually by the color of the C102 that
appears inside the reactor vessel. Chemical feed rates for NaC102 ana C12
are also checked to ensure the proper mix of chemicals for C102 production.
Both color and feed rates are checked hourly.
The effectiveness of C102 is determined by bacteriological tests and
the absence of T/0 problems in the finished water. Plant water is analyzed
three times daily and once daily in the distribution system. The C102 in
the finished water is measured speetrophotometrically to levels of less
than 0.2 mg/1 as C102. It was noted that the H-acid method requires a
higher level of skiIT than other tests such as OTA or DPD. The concentration
in the plant water is 0.2 mg/1 as C102. The C102 feed concentration generally
is constant year-round. The C102 residual leaving the plant is 0.15 mg/1
and the residual at the extremities of the distribution system is 0.10 mg/1
C102.
Tygon is a registered trademark of the Dupont Company.
528
-------
The cost for ClO^ addition is about 3.6<£/capita/year (1977). Chlorine
and NaClCL together cost about $6,540/year (1977). Chemical costs for
finished water average 19
-------
• chemical addition - fluoride
- chlorine
- chlorine dioxide
t clearwell - distribution system.
The C102 is generated by mixing aqueous C12 and aqueous NaC10? in the
approximate ratio'of 6.5:1 by weight [935 pounds (421 kg) CU/day and 147
pounds (66 kg) NaC102/day]. Liquid chlorine is supplied to the plant in
one-ton (900 kg) cylinders. The anhydrous NaC102 is supplied as technical
grade in 100 pound (45 kg) drums. Toledo formerly purchased the NaClO^
from France through a United States distributor (named Pettibone) located
in Chicago. The chemical was marketed under the name of "Cloritane" and
was packaged in 50 and 80 kg containers (110.25 and 176.4 pounds, respec-
tively). The NaClOo used at the plant presently is manufactured by Olin
Corporation and distributed by a local retailer. The plant is scheduled to
switch to aqueous NaC102 because of the potential flammability of NaClOo in
the flake form. Delivery of the aqueous NaC107 will be made by tank truck.
The C102 generation system consists of four plant fabricated C102
reactor vessels (two serve as standby), four Wallace and Tiernan chlori-
nators (two serve as standby) and two BIF proportional feed pumps. The
standby chlorinators are rotated periodically with the operating chlori-
nators in order to equalize wear on the equipment. Piping is schedule 80
PVC except for black steel pipe which is used for the transport of chlorine
gas from the ton cylinders to the chlorinators. Most of the PVC joints
[sizes 2" (7.08 cm) and smaller] are sealed with Teflon tape. There was no
report of chemical or water leakage from the piping system. The NaC102 and
ClOo chemical equipment are housed in one room whereas the chlorine cylinders
are stored in an adjoining room.
Both the ClOn and C12 rooms have forced air exhaust systems mounted at
floor level. The switches for both the exhaust system and lights are
located next to the entrance door on the outside of each room. Only the
chlorine room has an exit to the outside of the building. This is an
overhead door which provides access to the ton cylinder storage area from
the delivery yard outside. The other doors have glass panels for visual
inspection of the room interior. There are no chlorine leak detectors in
either room, although one is being considered for the chlorine room. There
are two MSA gas masks and four self-contained breathing apparatuses located
throughout the plant building. The two MSA masks are located in the hall
corridor outside the C102 room. Any chemicals that spill onto the floor
are washed into the floor drains which are in each room. The drains feed
into the sanitary sewer system.
Production of C102 is monitored visually by the color of CIO- that
appears in each reactor vessel. The NaClCL/Clp chemical feed rates also
are checked periodically. Finished water is analyzed hourly by the threshold
odor test. The plant uses powdered activated carbon at the raw water lift
station to reduce the carry-over of T/0 problems into the plant. Chlorine
residual is analyzed by the DPD method and in the future will be measured
530
-------
by the amperometric method. The total chlorine residual (chlorine + 0102)
in the finished water is 1 mg/1 (0.4 mg/1 free chlorine) and a 0.1 mg/1
free chlorine residual in the distribution system. The average concentration
of NaC102 in the plant water is 0.23 mg/1. The C^ is manually proportioned
to plant flow and is added year-round.
The chemical cost for solid NaC102 is $72/100 pounds ($1.60/kg). The
cost for the "chloritane" brand was $65.75/100 pounds ($l,46/kg). The
French product apparently has dropped from the area market for reasons not
immediately known. Chlorine costs $0.09/pound. The 0/M costs for C^
production are nominal and are not considered in the plant budget.
ATLANTA, GEORGIA (CHATTAHOOCHEE PLANT)
The 110 mgd (418,000 cu m/day) Chattahoochee plant at Atlanta uses
ClOp for seasonal problems due to iron and manganese. The plant obtains
its raw water from the Chattahoochee River which flows from a surface
reservoir 50 miles (80 km) upstream. C102 has performed satisfactorily
since its first operation in 1960.
The Atlanta plant has the following process steps:
• chemical addition - chlorine
raw water intake - lime
- powdered activated carbon
(optional)
• chemical addition - chlorine
at plant - chlorine dioxide (optional)
- lime
- powdered activated carbon
- alum
• flash mix
• flocculation
• sedimentation
• filtration
• chemical addition - chlorine
- lime
- fluoride
• clearwell - distribution system
The C10~ is generated by mixing aqueous Clo and aqueous NaC102-
Chlorine feea rates for C10? production were not readily available because
ClOo was not being added at the time of the visit. The anhydrous NaClO- is
a technical grade manufactured by 01 in Corporation. A local distributor
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delivers the 100 pound (45 kg) drums to the plant. Liquid chlorine is
delivered in one-ton (900 kg) cylinders.
The C102 generation system consists of Wallace and Tiernan equipment:
two reactor vessels for C^ production, two plunger pumps and two chlori-
nators. One C102 reactor serves as a backup unit to the C102 reactor that
is operating. Tne piping from the NaClOp mixing tanks to the chemical feed
pumps is'Tygon tubing.* The remaining piping of the ClOo system is schedule
80 PVC. The only exception is the piping from the one-ton (900 kg) chlorine
cylinders to the chlorinators, which is black steel. There is ample floor
space around the mixing tanks, pumps and C102 reactors. The equipment area
is serviced by floor drains which empty into the municipal sanitary sewer
system. The NaC102 mixing tanks are one floor below the C102 reactors, all
of which are located in the filtration building. Piping is exposed along
the walls and ceilings for easy inspection and maintenance.
The chlorine storage room is also part of the filtration building.
Approximately 16 one-ton (900 kg) chlorine cylinders are housed in this
room whereas 24 one-ton (900 kg) cylinders are stored in the chlorine
building at the raw water intake. Both facilities have forced exhaust
systems with motor operated dampers. Exhaust systems are mounted at floor
level and the switches for these units (and for the lights) are mounted on
the wall outside the entrance doorway. The doors have glass panels for
visual inspection of the room interior. Each chlorine storage room has a
Wallace and Tiernan leak detector. Air samples are monitored for chlorine
gas continuously.
The production of C102 is monitored by the color of C102 that appears
inside the transparent reactor vessel. Chemical feed rates are closely
checked during each shift. The efficiency of C102 performance is evaluated
hourly by measuring the concentration of iron and manganese in the plant
effluent. The plant adds C102 only when chlorination does not satisfac-
torily reduce the levels of iron and manganese in the finished water. For
a typical summer day, the plant uses approximately 800 to 1,000 pounds (360
to 450 kg) of chlorine at the raw water intake, another 250 pounds (112.5
kg) at the plant for prechlorination and another 210 pounds (94.5 kg) of
chlorine for post-chlorination. Residual chlorine is measured at six
different locations throughout the treatment works. A 0.5 mg/1 free
chlorine residual is maintained at the raw water lift station.
The plant uses the amperometric technique for analyzing chlorine
residual. The DPD method is used to measure chlorine residual in the water
distribution system. The finished water has a 1.5 mg/1 free chlorine
residual, whereas the extremities of the distribution system have a 0.5
mg/1 free chlorine residual.
The cost of chlorine is 8^/pound (17.8<£/kg). Anhydrous technical
grade NaC102 costs $70/100 pounds ($1.55/kg).
The Chattahoochee plant has a well developed watershed monitoring
program which was implemented in 1963. There are 8 sampling stations
upstream of the plant which have in-line sensors for determining the
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following river quality parameters: pH, electrical conductance, turbidity,
dissolved oxygen, temperature and water stage height. There are 50 other
stations along the river where grab samples are taken and analyzed for
additional water quality data. This monitoring program alerts the plant to
any adverse quality river water that is flowing toward the plant intake.
The addition of ClOp is used primarily to supplement the other chemicals
when the river water quality becomes very poor.
ATLANTA, GEORGIA (HEMPHILL PLANT)
The 70 mgd (266,000 cu m/day) Hemphill Plant at Atlanta uses C102 to
control the presence of manganese in its raw water supply. Water from the
Chattahoochee River is diverted into two reservoirs which in turn supply
the Hemphill treatment works. C102 has been employed since the 1960s.
The Atlanta plant has the following process steps:
• chemical addition - lime/alum
- chlorine
- chlorine dioxide
• flash mix
• chemical addition - powdered activated carbon
• flocculation
• sedimentation
• filtration
• chemical addition - lime
- chlorine
- fluoride
- sodium tripolyphosphate
• clearwell - distribution system.
CIO? is generated by mixing aqueous C12 and aqueous (29%) NaC102 in
the ratio of 0.75:1 by weight [400 pounds (T80 kg) of chlorine per day and
524 pounds (236 kg) of NaC10? per day]. Liquid chlorine is delivered in
one-ton (900 kg) cylinders; aqueous NaClOo is delivered to the plant by
4,000 gallon (15.2 cu m) tank trucks and pumped to an 8,000 gallon (30.7 cu
m) storage tank inside the chemical feed building. The 29% NaC102 is
manufactured and delivered by 01 in Corporation.
The CIO? generation system consists of two Wallace and Tiernan C102
reactor vessels, one Wallace and Tiernan chlorinator and two Wallace ana
Tiernan diaphragm pumps. Piping is schedule 80 PVC except for the feed
line to the chlorinator; this pipe material is black steel. The C102
reactors are wall-mounted one floor above the NaC102 chemical feed pumps.
The ton cylinders of chlorine are stored in a separate room.
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Inside the chlorine storage room are two exhaust fans mounted at floor
level. Switches for both the exhaust system and the ceiling lights are
located just inside the doorway. The room has two chlorine leak detectors
positioned on opposite sides of the room. The air is monitored for chlorine
gas every 30 to 60 seconds. The chlorine gas sensors are mounted on the
side of a channel drain which runs below the metal floor grating. Two
self-contained breathing apparatuses are stored outside the chlorine room.
The floor drains inside the chlorine room as well as the floor drains
around the NaC102 tanks empty into the municipal sanitary sewer system.
The production of C102 is monitored visually by the color that appears
inside the C102 reactor vessel. Chemical feed rates also are checked
during the dayf The efficiency of C102 addition is monitored by the absence
of manganese in the finished water. Wnen C102 is being generated, the
estimated concentration of NaC102 in the plant water is 0.9 mg/1.
Chlorine residual in the plant water is analyzed by the amperometric
method. Field checks along the distribution system are performed more
frequently with the OTA than by the DPD method. The finished water leaving
the plant has a free chlorine residual of 1.3 mg/1. The ends of the distri-
bution system have free chlorine residuals of 0.5 mg/1.
The chemical cost for 29% aqueous NaC102 is $74.59/100 pounds ($1.66
per kg). Chlorine costs $0.076/pound when delivered in one-ton cylinders.
For the month of August 1977, the plant was generating C102 to control a
high concentration of manganese in the raw water supply. Chemical costs
for that month were as follows: NaC10? - 47,869 pounds (21,541/kg) @
$20,780; C12 - 60,391 pounds (27,176 kg) @ $4,590. The latter figures are
for the entire use of chlorine at the plant. A breakdown of C12 for C102
production for the month of August was not available.
The plant operator is satisfied with the performance of C102- The
plant had tried KMnO* but the high chemical costs and chemical feed problems
persuaded management to discontinue its use. The C102 reportedly removes
the manganese early in the treatment process and the manganese is almost
totally absent at the sedimentation tanks. Chlorine was found to be not
effective for removing manganese, thus the plant began adding C^.
CARROLLTON, GEORGIA
The 4.5 mgd (17,034 cu m/day) plant at Carroll ton uses C102 for the
removal of iron and manganese. The raw water supply is the Little Tulla-
poose River. Since 1953, C102 has been used at the plant, although potassium
permanganate was used on a trial basis for replacing C102. The KMn04 did
not perform satisfactorily.
The Carroll ton plant has the following process steps:
• chemical addition - chlorine dioxide
- lime
- alum
- powdered activated carbon
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• flash mix
t coagulation
t sedimentation
• filtration
• chemical addition - chlorine
- lime
- fluoride
• clearwell - distribution system.
C102 is generated by mixing aqueous Cl? and aqueous NaC10? in the
ratio of 4.7:1 by weight [280 pounds (126 kg) of CWday and 60 pounds (27
kg) of NaC102/day]. This is a constant feed year-round. Liquid chlorine
is delivered to the site in one-ton (900 kg) cylinders. Technical grade
NaClOo is manufactured by 01 in Corporation and delivered to the site by an
area Distributor. Anhydrous NaC102 is shipped in 100 pound (45 kg) drums.
The C102 generation system uses Wallace and Tiernan equipment. There
are two ClOo reactor vessels, two diaphragm pumps and two chlorinators.
There is also a standby chlorinator. The piping from the ton cylinders to
the chlorinators is black steel. The remaining chemical feed piping is
schedule 80 PVC. Tygon tubing is used for the suction line from the
diaphragm pumps to the two NaC102 day tanks. There are reportedly no
problems with the pumps or piping. The chemical feed system for C102
generation is located in the chlorine storage room.
There is a motor operated damper unit inside the chlorine room for
forced ventilation. The exhaust fan is mounted at floor level. The
switch to activate the exhaust system and the interior lights are located
outside the doorway. A glass panelled door provides for visual inspection
of the room interior. There is no chlorine gas leak detector inside the
room. A MSA mask is stored outside the chlorine room along with a chlorine
ton cylinder emergency repair kit. A self-contained breathing apparatus is
located in the main control room.
Production of C102 is monitored visually by the color of CIO, that
appears inside the reactor vessel. Chemical feed rates of C12 ana NaC102
also are checked. The efficiency of C102 is evaluated by the absence of Fe
and Mn in the finished water. Typical concentrations in the raw water are
1 to 1.5 mg/1 for iron and 0.5 mg/1 for manganese. The estimated concentra-
tion of NaC102 (as dosed) in the plant water is 1.6 mg/1.
The concentration of chlorine in the finished water is measured
hourly using a "color wheel". Finished water has a free chlorine residual
of 1.5 mg/1 while the extremities of the distribution system have 0.5 mg/1
free residuals.
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The operator is concerned about the high cost of chlorine dioxide.
NaCKL costs $103/100 pounds (46<£/kg) delivered whereas chlorine costs
und when delivered in ton cylinders.
The operator is pleased with the secondary benefits from using
for disinfection and T/0 control, but despite the success of ClO^, he is
still considering using KMnO* in place of CIO? for a second trial period.
Since the plant was redesigned in 1971, he believes that KMnO^ may perform
better than it did before.
FAYETTEVILLE, GEORGIA
The 0.15 mgd (570 cu m/day) plant at Fayetteville uses ClO^ as the
sole chemical oxidant in the treatment process. Although excess chlorine
is added for ClOo production, the ClO^ is used for disinfection and also to
reduce manganese, color and T/0 problems. The source of raw water supply
is Ginger Lake Creek. The plant has been adding C10? since the early
1960s.
The Fayetteville plant has the following process steps:
t chemical addition - chlorine dioxide
- lime
- alum
• coagulation
• sedimentation
t filtration
• chemical addition - chlorine dioxide (optional)
0 clearwell - distribution system
C1CL is generated by mixing aqueous C12 and aqueous NaC102 in the
ratio of^2:l by weight [10 pounds (4.5 kg) CWday and 5 pounds (2.25 kg)
NaC102/day]. This is a constant dosage year-round. Liquid chlorine is
supplied in 150 pound (67.5 kg) cylinders. Technical grade NaClOp is
manufactured by Olin Corporation and delivered in 100 pound (75 kg) drums
by an area distributor.
The ClOp generation system consists of Wallace and Tiernan equipment.
There is one ClOp reactor vessel, one chlorinator and one diaphragm plunger
pump. The piping from the chlorine tank to the ejector is black steel.
Heavy gauge rubber tubing is used between the ejector and the C102 reactor
vessel as well as from the reactor vessel to the discharge point in the
chemical addition chamber. The NaC102 pump suction line is Tygon tubing
and the discharge line is of a heavier gauge rubber of undetermined specifi-
cations. The 150 pound (67.5 kg) chlorine tanks, NaC102 drums and mixing
tank are located in the small, crowded C102 room.
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The C102 room has two windows but no air exhaust system. The room has
a solid wood door which opens only to the filtration gallery. The switch
for the interior lights is located inside the C102 room. There is no
chlorine leak detector inside. There are several holes that have been
chiseled into the concrete floor which allow wash down water to drain from
the C102 room to the service pump room below. No floor drains were noted
in the pump room.
The piping for the C102 generation system appears disorganized and
disjointed. The operator reported that some of the piping has been patched
and replaced with material around the plant. The present piping arrangement,
however, reportedly presents no operational problems.
The mixing tank for NaC102 is a plastic 30 gallon (114 liter) drum.
Mixing is provided by opening a water spigot and using the plant water
pressure to mix the chemical. There is evidence of "caking" around the
periphery of the tank. The hose from the spigot is submerged in the
NaC102 solution. No back flow prevent valve was noted on the plant water
line.
There is no flow meter for the finished water discharge pumps. The
operator therefore approximates the flow through the plant (presumably)
using pumping curves provided by the manufacturer). Based on a reported
flow rate of 0.15 mgd (520 cu m/day) and a range of NaC102 addition from 5
to 22 pounds (2.25 to 9.2 kg) per day, the plant water has an estimated
concentration of NaC102 from 4 mg/1 to 17.6 mg/1. The plant operates 16
hours a day (at a constant flow rate), and shuts down the remaining 8 hours.
The production of C102 is monitored visually by the color of ClOp that
appears in the CIO? reactor vessel. The chemical feed rates of the C?2/NaC102
systems are also checked periodically. Manganese is monitored in the
finished water every 2 hours. The concentration of manganese in the raw
water may range from 1.5 to 3.0 mg/1; iron concentration is negligible. The
finished water has a manganese concentration of 0.1 mg/1 or less. Both
manganese and chlorine are analyzed colorimetrically.
The free chlorine residual in the chemical addition tank is maintained
at 1.2 to 2.0 mg/1, while the finished water has a concentration of 1.0 to
1.4 mg/1. The OTA method is used to analyze for chlorine residual. (It
was noticed that there is an area of concentrated bubbling inside the
chemical addition tank. Presumably this is due to poor hydraulics in the
tank and an excessive volume of chlorine gas entering the tank. The smell
of chlorine was sharply noticeable at the chemical addition tank.)
MARIETTA, GEORGIA (WYKOFF PLANT)
The 22 mgd (83,600 cu m) plant at Marietta uses CIO? primarily for
removal of iron and manganese from its raw water. Lake Allatoona, which is
fed by the Etowah River, is the raw water supply for the plant. C102 is
used also for disinfection and abatement of T/0 problems. The plant has
been using C102 since 1958.
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The Marietta plant has the following process steps:
• raw water lift station - chlorine
• chemical addition - chlorine dioxide
- lime
- alum
• flash mix
• coagulation
* sedimentation
t filtration
• chemical addition chlorine
- lime
- fluoride
• clearwell - distribution system.
The C102 is generated by mixing aqueous C12 and aqueous NaC102 in the
approximate ratio of 1.24:1 by weight [80 pounds (36 kg) of chlorine per
day and 64 pounds (28.8 kg) of NaC102 per day]. The Cl2/NaC102 ratio can
increase to as high as 7.8:1 depending upon the quality of water that is
pumped to the filtration plant. C102 is used to pretreat the water before
chemical coagulation in a constant feed system. Liquid chlorine is delivered
to the site in one-ton cylinders. Technical grade NaC102 is manufactured
by 01 in Corporation and delivered by an area distributor in 100 pound
drums.
The C102 generation system consists of equipment manufactured by
Wallace and Tiernan. There is one C102 generator, one plunger pump and one
chlorinator. NaC102 is mixed in a large holding tank in a room above the
C102 generation room. The NaC102 day tank in the C102 room is gravity
fined each day from the larger NaC102 tank. Anhydrous NaC102 is stored on
the floor above along with the larger NaClOo mixing tank. Piping from the
chlorine tanks to the ejector is black steef; piping from the ejector to
the C102 reaction vessel is a heavy gauge rubber hose. The NaC102 chemical
system piping from the large mixing tank to the day tank one floor below is
schedule 80 PVC. The suction line from the NaC102 plunger pump is Tygon
tubing; the discharge pipifig from the pump to the C102 reactor vessel is a
heavy gauge rubber hose - supplied by the manufacturer. The chlorinators
and the one ton (960 kg) chlorine cylinders are located in separate rooms
next to the C102 generation room.
The chlorine storage room has forced ventilation by way of a motor
generated damper unit. The exhaust fan is mounted at floor level and
appears to provide for adequate circulation. The switches for the exhaust
system as well as for the ceiling lights are located outside the entrance
doorway to the chlorine room. The door, which opens to the outside grounds,
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has a glass panel for visual inspection of the room interior. The room
where the chlorinators are located is provided with the same general equipment.
The chlorinator room adjoins the chlorine storage room and has an exit to
the outside yard. There are no chlorine leak detectors. There are,
however, gas masks positioned outside of these rooms in the hallway.
The CICL generation room houses the C102 reaction vessel, the NaC102
feed pumps and day tank. The room has a floor drain that connects to the
local municipal sewer system. There are spigots and hoses for washdown.
The day tank consists of a plastic 40 to 50 gallon (152 to 190 liter) tank
supported inside a metal 55 gallon (209 1) drum. The tank has a plastic
lid that fits securely on top to prevent spills. The plastic tanks are
replaced every 4 to 5 years for aesthetic purposes. The metal drum has a
one-inch open slit along the side to allow the operator to see the liquid
level of NaClOo inside the day tank. The volume is measured in gallons as
determined by the markings painted along the open slit.
Production of C102 is monitored visually by the color of ClOo that
appears inside the reactor vessel. Chemical feed rates of C12 ana NaC102
also are checked. The efficiency of C102 addition is evaluated hourly by
confirming the absence of iron and manganese in the finished water. The
typical influent concentrations of these metals during the late summer is
0.15 mg/1. The approximate concentration of NaC102 in the plant water is
0.35 mg/1.
The concentration of free chlorine in the finished water is 1 mg/1.
The free chlorine residual before the flash mix ranges from 0.1 to 0.75
mg/1. Chlorine residual is measured frequently.by the OTA method, but when
recording information for State files, the DPD method is employed. The
plant supervisor noted that the DPD method produces values consistently
higher than the OTA method (i.e., 1.45 mg/1 DPD and 1.25 mg/1 OTA).
Chemical costs for C102 production are incomplete. The cost of
NaC109 is $103/100 pounds ($2.29/kg) and the estimated chemical cost for
producing C10? per 1,000 gallons of water is $0.002 (0.06£/cu m). The 0/M
costs are reportedly negligible. The plant sells the finished water to
county customers at $0.35/1,000 gallons ($0.09/cu m).
WHEELING, WEST VIRGINIA
The 10 mgd (38,000 cu m) plant at Wheeling uses C102 primarily for the
control of phenolic compounds in its raw water source ~ the Ohio River.
Iron and manganese also pose problems. The source of the phenols, iron and
manganese are attributed to both natural and industrial origin. The C102
addition has been in operation since 1951.
The Wheeling plant has the following process steps:
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t pre-settling
t aeration
• chemical addition - lime/ ferric sulfate
• prechlori nation - chlorine
• flash mix
• flocculation
• sedimentation
• chemical addition - sodium tripolyphosphate
t filtration
• chemical addition - sodium silicofluoride
- chlorine dioxide
• clearwell - distribution system.
C10? is generated by mixing aqueous Cl? and aqueous NaC102 in the
ratio of 5:1 by weight [500 pounds (225 kg) of CWday and 100 pounds (45
kg) of NaCl Do/day], This is a constant feed dosage year-round. The
relatively high dosage of chlorine in the CIO? reactor reportedly is
achieved to maintain a low pH for efficient CTOp production. Liquid
chlorine is supplied to the site via rail tank car. The NaClO^ is a
technical grade manufactured by 01 in Corporation and distributed by a local
retailer. The anhydrous NaCl02 is shipped in 100 pound (45 kg) drums.
The ClOp generation system consists of one Fischer and Porter reactor
vessel for CT02 production, one Wallace and Tiernan diaphragm pump, NaC102
feed, and one Fischer and Porter gas evaporator and chlorinator. The
piping for the aqueous NaClO^ and C^ presumably is schedule 80 PVC as
specified by Fischer and Porter. The piping for both the liquid and
gaseous chlorine is black steel. No leaks have been reported with the
tubing materials. The Clo/NaClO^ chemical feed equipment and ClOn reactor
unit are housed in a separate building which adjoins the rail siding.
The building has a motor operated damper (MOD) exhaust system located
at floor level. The air change rating is unknown but the unit appears to
be of sufficient size. Makeup air is supplied through a louver on the
opposite side of the room. The switches for the fan and interior lights
are located on the exterior wall next to the door. An alarm switch is
located on the interior wall inside the building. (The plant alarm system
is tied into the city's fire station which is one block away.) The second
of four alarm switches is located inside the entrance doorway. The
chlorine leak detector, an ammonium hydroxide bottle, is located on
540
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top of a chlorinator. The entrance door has a glass window for visual
inspection of the room interior. There are no floor drains inside the
building.
The production of CICL is monitored by the color of C102 that appears
inside the reactor vessel. Chemical feed rates of C12 and NaCIO? are also
checked. The Fischer and Porter reactor vessel also nas a sampling port on
the immediate discharge port of the vessel. The plant does not analyze the
C102 product from the reactor vessel. Efficiency of C1CL addition is
evaluated by the absence of taste and odor problems in tne finished water.
If the T/0 problems persist, the NaC102 feed rate is increased, not the C12
feed rate. Exact quantities or ranges of chemical feed for the operation
of the C102 generator are not available. The estimated concentration of
NaC102 in the plant water is 1.2 mg/1.
The concentration of chlorine in the finished water is analyzed
hourly by the laboratory. The plant uses the DPD method for the analysis
of combined and free chlorine. Finished water has a free chlorine residual
of 3 mg/1 while the free chlorine residual at the extremities of the
distribution system ranges from 0.5 to 1 mg/1.
The operator is concerned about the high cost of NaC102 as well as the
potential hazard of storing dry NaC102. He is otherwise satisfied with the
use of C109 and intends to continue using it. The plant spends over $18,000/
year for cniorine and $8,048/year for NaC102 (1976).
COVINGTON, KENTUCKY
The 10 mgd (38,000 cu m/day) Fort Thomas plant at Covington uses C102
for control of taste and odor problems in its raw water source—the Ohio
River. The cause of these taste and odor bodies is unknown. Addition of
CIO- has been in operation since the early 1950s, although during the
1960s, the plant added ammonia with chlorine and discontinued C102. Since
1972, the plant has resumed the addition of C102 together with chTorine and
terminated the use of ammonia because the chloramines were not holding the
desired residual across the treatment basins. Chlorine has always been
added to the plant water.
The Covington plant has the following process steps:
t chemical addition - lime/alum
- chlorine - an injection point
separate from the C102
point of addition
- chlorine dioxide
0 flash mix
• coagulation
• sedimentation
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• filtration
• chemical addition - chlorine
- sodium silicofluoride
• clearwell - distribution system
The Covington plant pumps Ohio River water to two raw water reservoirs.
During the warmer months, copper sulfate (CuSO.) is added at the raw water
station at approximately 200 pounds (90 kg) per day. C102 is generated by
mixing aqueous Cl? and 37% aqueous NaC102 in the ratio of 1.5:1 by weight
[75 pounds (33.75 kg) of C12 per day and 50 pounds (22.5 kg) of NaCIO, per
day]. The aqueous NaC102 is manufactured by 01 in Corporation and delivered
in 55 gallon dry weight arums by an area distributor. Chlorine is supplied
in one ton (900 kg) cylinders.
The C102 generation system consists of one Fischer and Porter C1CL
reactor, one Fischer and Porter chlorinator and one Wallace and Tiernan
diaphragm pump for liquid NaC102. The operator reported that the diaphragm
pump develops cracks inside the plastic diaphragm casing. This causes the
suction head to decrease and reduces the NaClOg feed rate. The reason for
the cracks was not known. A second Fischer ana Porter chlorinator is used
for feeding chlorine into the plant water - separate from the C102 feed
system. Both C12 and C102 have the same application point in the chemical
addition chamber. Piping from the NaC102 drum to the C102 reactor vessel
is Tygon tubing. Black steel pipe is used for conveying gaseous chlorine
from the one ton (900 kg) cylinders to the chlorinator. A heavy-walled
rubber hose is used for transporting aqueous chlorine from the chlorinator
to the C102 reactor. The same black rubber material is used for piping the
C102 product to the plant water. There were no reports of leakage from any
of the piping material. The C102 generation equipment as well as the
lime/ferric feed equipment are located in one building. The one-ton (900
kg) chlorine cylinders are housed in a separate building.
Aqueous NaC102 is stored in 55 gallon (209 1) drums in the same room
as the liquid alum feed equipment. There is no air exhaust system in this
room although there are eight windows on the exterior wall. The floor
drains inside this room empty to a french drain which empties beneath the
building. NaClOp solution is fed undiluted from the drum to the C102
reactor. When tne NaC102 level is low, the operator removes the Tygon
tubing from the spent drum and places it inside a full drum. Any NaC102
spills that occur are washed down the floor drain. This is done to prevent
any potential fire hazard due to dry NaC102 that may remain on the floor.
The working area around the NaC102 equipment is very close.
The chlorine storage room has a large exhaust fan mounted at floor
level. Makeup air is provided by opening the entrance door or by an
opened window. The switches for the exhaust fan and the ceiling lights
542
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are located on the interior wall next to the doorway. The entrance door
has a glass panel for visual inspection of the room interior. The only
leak detector for chlorine gas consists of two ammonium hydroxide bottles
that are located in the center of the estimated 20' x 50' building. There
is no alarm system on the plant grounds. Two self-contained breathing
apparatuses and one MSA mask are stored in the control building — about
125 feet away.
Production of ClO^ is monitored visually by the color that appears
inside the C1CL reactor. The chemical feed rates are also checked.
Efficiency of C102 production is monitored by the absence of T/0 problems
in the finished water. The estimated concentration of NaClCL in the plant
water is 0.6 mg/1.
Chlorine in the plant water is analyzed by the DPD and the amperometric
method. Free chlorine residual in the finished water varies from 2.5 to 4
mg/1 but reportedly has been as high as 6 mg/1. The chlorine residual at
the extremities of the distribution system at the plant was not immediately
known. The State has required breakpoint chlorination since 1974. The
plant reportedly uses at least one ton of chlorine every 2 to 3 days for
water treatment (8 to 12 mg/1 chlorine).
Chemical costs for the CIC^ system were not available.
ANN ARBOR, MICHIGAN
The 16 mgd (60,800 cu m/day) plant at Ann Arbor uses C102 for control
of taste and odor problems in its raw water source -- the Huron River.
Well water is used as an auxiliary source. The reported cause of the T/0
problems is actinomycetes and is a year-round problem. The addition of
has been in service since 1974.
The Ann Arbor plant has the following process steps:
• prechlorination - chlorine
• chemical addition - lime/soda ash
0 flash mix
• coagulation
• sedimentation
• recarbonation
• chemical addition - powdered activated carbon
- lime
• flash mix
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0 coagulation
• sedimentation
• chemical - chlorine dioxide
• filtration
• chemical addition - chlorine
- fluoride
• clearwell - distribution system
C102 is generated by mixing aqueous NaC102 and hydrochloric acid in
the ratio of 6.1:1 by weight [32 pounds (14.4 Kg) of NaC102 per day and
5.24 pounds (2.36 kg) of HC1 per day dry weight]. HC1 is aelivered in 150
pound (67.5 kg) carboys as non-inhibited muriatic acid. The anhydrous
NaClCL is delivered in 100 pound (45 kg) drums. 01 in Corporation manufactures
the technical grade NaClOo and an area distributor delivers the chemical to
the plant.
Ann Arbor changed to HC1 as a reagent for C102 production because of
the high costs of using liquid chlorine. The HC1 also offers more reliable
pH control than chlorine. Solution pH is measured periodically from the
sample port on the discharge side of the reactor vessel.
The ClOp generation system consists of two Wallace and Tiernan ClOo
reactor vessels (one as a standby) and one Wallace and Tiernan diaphragm
pump for each of the HC1 and NaClO^ feed systems. There are also two
plastic day tanks for liquid chemical feed storage. Plant personnel have
installed a sampling port on the discharge end of the C102 reactor.
Heavy-walled Tygon tubing is used to transport liquid chemicals from the
day tanks to chemical feed pumps. A semi-rigid plastic pipe carries the
chemical reagents from the pumps to the reactor. On the C102 unit, the
effluent piping begins as schedule 80 PVC but then joins a semi-rigid
plastic pipe which carries the aqueous C102 product to the sedimentation
tanks. The sampling valve on the C102 unit is a PVC material. The piping
network reportedly has had no problems with leakage. The plastic drums
need replacing every two years or so; the Tygon tubing for the feed systems
is replaced more frequently. The ClOo generation equipment is located in a
hallway inside the filter gallery, which exits to the outside where the
liquid HC1 is stored in drums. NaClOo drums are stored along the wall of
the hall. There are no floor drains immediately around the C102 generation
equipment.
Production of C102 is monitored visually by the color that appears
through the transparent reactor vessel. The CIO, solution had the richest
red-brown color witnessed while visiting the various water plants, indicating
that a higher concentration of C102 is produced at Ann Arbor by the acid
technique. Effluent from the C102 reactor vessel is periodically analyzed
for pH. The chemical feed pumps are also checked for proper feed rates.
544
-------
Efficiency of ClOp addition is measured by the absence of taste and odor in
the finished water.
The cost of HC1 is approximately 28
-------
APPENDIX F
CHLORINE DIOXIDE QUESTIONNAIRE SUMMARY TABLES
Table Page
F-1. United States C102 Questionnaire Summary. . 548
European C102 Questionnaire Summaries
F-2. Great Britain C102 Questionnaire Summary. . 559
F-3. French and Austrian C102 Questionnaire
Summary 560
F-4. German C102 Questionnaire Summary 564
546
-------
These tables summarize the questionnaire responses from the U.S. and
Europe regarding use of chlorine dioxide in water treatment. As is the case
with the ozone questionnaires, these data are reported as provided by the
responding plants, without interpretation. In some cases, data were
reported in incomplete form in a given category. Consequently, the reader
is cautioned to discount data which vary widely from the norm, as the
bases for those data may differ from the general case.
Also, note that Hamilton, Indiana is the only U.S. plant using C102
strictly for residual disinfectant, even though other plants indicated this
application on their questionnaire responses.
A process description is provided for each plant, beginning with the
first process step and terminating at the clearwell. The method of C102
preparation is also provided, where known.
In considering the dosages and/or residuals of ClO^ reported, the
reader should be aware that whenever excess chlorine is added to sodium
chlorite, and the "chlorine dioxide" is measured by the OTA, DPD or
amperometric titration methods, total oxidant is measured. This consists of
chlorine plus chlorine dioxide, and the amount of chlorine present will
depend upon the amount of excess chlorine added originally.
Many U.S. plants report dosages of ClO^ as the amount of NaCK^ added,
and assume that it is all converted to 01 Op with sufficient excess chlorine.
In the tables, the following abbreviations are used:
NA = not available
I = intermittent C102 dosage
C = continuous dosage
sed. = sedimentation
exp. = expansion
W&T = Wallace & Tiernan
F&P = Fischer & Porter
T/0 = taste and odor
GAC = granular activated carbon
PAC = powdered activated carbon
547
-------
TABLE F-l. UNITED STATES C102 QUESTIONNAIRE SUMMARY
ui
-P»
00
Plant Name
Hartford, CT
Design Plant
Capacity (MGD)
NA
Year C10-
Use *•
Initiated
NA
Process Description
NA
Purposes of CIO,
Use
have capability
Average
, Dosaqe
(mg/l)
to NA
Residual
in Dist.
System
(mg/1)
NA
Method of
Preparation
NA
Lebanon, CT
Hamburg, NY
9.5
2.0
Blnghamton, NY 2.0
Tonawanda, NY 24.0
New Brighton, PA 6.0
NA coagulation, sedimentation,
filtration, chlorination
NA air mixing, primary sed.,
secondary mixing, floccu-
latlon, secondary sed.,
filtration, storage
1956
use CIO, but have
not usea it to date
odor removal
taste, odor, organlcs I
removal 1 0
C102 addition
NA
odor removal
phenols
1969 mixing, flocculatlon, primary odor, organics,
settling, mixing, secondary taste removal
settling, filtration,
chlorlnatlon
NA NA
NA CIO, fed before primary
sed. or after filtration
as needed. C10» from
gaseous chlorine & NaCIO-.
C102 is discharged into
clearwell or at raw water
mixing chamber. Mathieson
C109 generator
1951 coagulation, sed., filtration, disinfection, taste, C 0.03
CIO, fed into finished
water. CIO, generated by
gaseous chlorine & NaC102
NA NA CIO, generated with gaseous
chlBrine & NaC102- W&T C102
system
I NA ClOo produced from gaseous
0.18 chlorine & NaClOo. W&T
C102 system
(continued)
-------
TABLE F-l (continued)
01
-P*
Plant Name
Year CIO
Design Plant Use
?
Process Description
Capacity (MGD) Initiated
Oakmont, PA
Midland, PA
10.0 1948
expd. 1974
4.4 1946
chemical addition, rapid mixing,
slow mixing, flocculation,
settling, filtration, post
chlorination & C102 addition
rapid mix, coagulation, sedimen-
tation, filtration
Average
Purposes of C109 Dosage
Use c
disinfection, odor
taste, organics
removal
NA
(mg/1)
C
0.1-
0.2
C
0.4
Residual
in Dist.
System Method of
(mg/1) Preparation
NA C10? produced from gaseous
chlorine & NaClOp. C102
added before clearwell.
W&T C102 system
0.15 ClOn produced from gaseous
chlorine & NaCIO,. C10~
Pittsburgh, PA
(Becks Rd.)
Charleroi, PA
Penn Hills,
Wilksburg, PA
McKeesport, PA
(continued)
52.9
10.0
275.0
10.0
NA
1975
1947
1967
chemical addition, rapid mixing, odor, taste, organics I
recarbonation, sedimentation, removal 0.15
activated carbon filtration
NA
flash mixing, powdered acti-
vated carbon, flocculation,
settling, chlorination,
filtration
alum, lime, carbon, C102 addi-
tion, flocculation, settling,
chlorination, filtration
odor, taste removal C
0.023
odor, taste, organics C
removal 0.1-
0.15
NA
NA
NA
added before clearwell.
Mathieson C102 generator
CIO/, produced from gaseous
chlorine &
C10
odor, taste, organics I, but NA
removal NA
added before clearwell. pH
of C12 solution is adjusted
to 3.5. W&T C102 system
W&T C102 system
CIO,, produced from gaseous
chlorine & NaC102 & in-
jected before clearwell*
W&T C102 system
C10? produced from gaseous
chlorine & NaC102 & in-
jected as needed before
flocculation.
system
W&T C100
-------
TABLE F-l (continued)
tn
tn
o
Plant Name Design Plant
Capacity (MGD)
Washington, PA 5.2
Charlottesvllle, VA 4.0
Wheeling, WV 10.0
Newman, GA 4.5
Roswell, GA 0.6
Year C10?
Use
Initiated
1973
1966
1951
1957
1936
Process Description
aeration, coagulation, pre-
chloHnatlon, settling, filtra-
tion, post chlorlnatlon, C10~
addition
aeration, CIO, addition, flash
mix, coagulation, settling,
filtration, chlorlnatlon
presettllng, aeration, chemical
addition of Hme & ferric sul-
fate, prechlorlnatlon, flash
mixing, flocculatlon, settling,
chemical addition of sodium tri-
polyphosphate, filtration,
chemical addition of sodium
sllicofluorlde, C102 addition
C10o addition, flash mixing,
flocculatlon, settling, filtra-
tion, chlorlnatlon
ClOo addition, coagulation,
settling, filtration
Purposes of CIO,
Use i
odor, taste
removal
odor, taste
removal
organics, Fe & Mn
control , taste &
odor removal
Fe, Mn removal
Mn, taste removal ,
chlorine residual
Average
Dosage
{•ng/1 )
Residual
In Dist.
Sys tern
(mg/1 )
C NA
0.20
I,
NA
C
3.0
C,
NA
C,
NA
but NA
1.0
but NA
but 0.5
Method of
Preparation
C10? is produced from
chlorine & NaC10? & added
before clear-well 7 F&P C102
generator
CIO, produced from gaseous
chlorine & NaC102 & added
as needed before flash
mixing. W&T C102 system
C10? produced from gaseous
chlOrine & NaClOp & added
before clearwell
C10? produced from gaseous
chlOrine & NaC102. W&T
C102 system
C10? produced from gaseous
chlorine & NaC10?. W&T
C102 system
(continued)
-------
TABLE F-l (continued)
en
en
Year C102
Plant Name Design Plant Use Process Description
Capacity (MGD) Initiated
Marietta, GA 24.0
Lincolnton, GA 0.375
Forsyth, GA 1 .0
Atlanta, GA 80.0
(Boulton Rd.)
1958 C102 addition, coagulation,
settling, filtration, floccu-
lation, chlorination, pH
adjustment
1971 ClOp addition, rapid mixing,
flocculation, settling, filtra-
tion, C102 addition
1974 C102 addition, coagulation,
settling, C19 addition, filtra-
tion i
1960 prechlorination (at intake),
pH adjust, (lime), powd. act.
Residual
Average in Dist.
Purposes of C102 Dosage System Method of
Use (nig/1 ) (nig/1) Preparation
Fe, Mn, taste
& odor removal ,
disinfection
Mn removal
Mn, taste removal ,
chlorine residual
Mn, Fe removal
C 0.5
0.32
I, but NA
NA
NA NA
I, but NA
NA
C10? produced from gaseous
chlorine & NaC102. W&T
C102 system
C10? produced from gaseous
chlSrine & NaClOo. W&T
C102 system
ClOo produced from gaseous
chlorine & NaClO-. W&T
C102 system
C102 from gaseous chlorine
& NaC102. W&T C102 system
Griffin, GA
carbon (as needed), chlorination,
C102 (as needed) addition. pH
control (lime), PAC addition,
alum coagulation, settling, filtra-
tion, post chlorination, lime
addition for corrosion control,
fluoride addition
8.0
1966
ClOp addition, coagulation,
settling, filtration, post
chlorination
Mn removal
NA NA C109 produced from gaseous
chlorine & NaC102. W&T C102
system
(continued)
-------
TABLE F-l (continued)
in
en
no
Year C102
Plant Name Design Plant Use Process Description Purposes of CIO,
Capacity (MGD) Initiated Use
Carrollton, GA 8.0
Monroe, GA 4.0
1953 C102 addition, rapid mixing. Fe, Mn removal
coagulation, settling, filtra-
tion, post chlorlnatlon, lime
addition, fluoride addition
1959 C102 addition, flash mixing, Mn removal
coagulation, sedimentation,
Residual
Average in Dist.
Dosage System Method of
(mg/1) (mg/1) Preparation
C, but
NA
C, but
NA
NA CIO? produced from gaseous
ch!5rine & NaCIO-. W&T
CIO, system
£.
NA NaC102 dissolved in water
& pumped Into chlorinated
East Point, GA 12.0
Fayetteville, GA 0.2
Warrenton, GA 0.75
Bremen, GA
(continued)
0.8
filtration, post chlorlnatlon
1963 prechlorlnatlon, CIO? addition,
coagulation, settling, filtra-
tion, post chlorlnatlon
NA prechlorlnatlon, C102 addition,
coagulation, settling, filtra-
tion, post chlorination
1970 C10- addition, coagulation,
settling, filtration,
chlorination
NA C102 addition, flash mixing,
alum & Hme coagulation,
settling, filtration, post
chlorlnatlon, C12 residual
Fe, Mn, taste
removal
C
0.5
Fe, color, Mn, C
odor, taste re- 1.4
moval, disinfection,
chlorine residual
Fe, odor, color, I
Mn, taste removal 10.0
Mn, odor, taste C
removal, disin- 4.0-9.0
fectlon
water line; average 70 Ibs
chlorine to 14 Ibs NaC10?.
W&T C102 system
NA C10? produced from gaseous
chlorine & NaC102. W&T
C102 system
0.5 C109 produced from gaseous
chlfcrine & NaC102. W&T
C102 system
NA C10? produced from gaseous
chlorine & NaC102. W&T
C102 system
NA CIO? produced from gaseous
chlorine & NaCIO?. W&T
CIO- system
-------
TABLE F-l (continued)
Plant Name Design Plant
Capacity (MGD)
Bur ford, GA 1.0
Monticello, GA 0.5
Buchanen, GA 2.5
in
in
00
McDonald, GA 1.0
Waynesboro, GA 1.2
Year CIO.,
Use i
Initiated
1967
1946
1975
1959
1972
Process Description
C102 addition, flash mixing,
flocculation, settling, filtra-
tion, chlorination
C10o addition, flash mixing,
flocculation, settling,
filtration
C102 addition, flash mixing,
flocculation, settling,
filtration, chlorination
C10? & Cl? addition, coagula-
tion, settling, filtration,
pH adjust.
C102 addition, flash mixing,
coagulation, settling, filtra-
Purposes of C10?
Use
Fe, Mn, odor,
taste removal
disinfection
Fe, Mn removal ,
disinfection,
chlorine residual
Fe, odor removal
Fe, color, odor,
organics, Mn,
taste removal ,
disinfection,
chlorine residual
scale control ,
corrosion control ,
Average
Dosage
(mg/1 )
C
0.5
C, but
NA
C
2.0
C
5-6
C, but
NA
Residual
in Dist.
System
(mg/1)
NA
1.0
NA
0.8
0.5
Method of
Preparation
ClOo produced from gaseous
chlorine & NaClO-. W&T
C102 system
ClOn produced from gaseous
chlorine & NaC102. W&T
C102 system
CIO, produced from gaseous
chlorine & NaClOo. W&T
ClOp system
ClOo produced from gaseous
chlOrine & NaC102. W&T
C102 system
CIO- from gaseous chlorine
& N3C10?. W&T C10? system
Louisville, KY
(continued)
NA
tion, final chlorination
1965 coagulation, settling, filtra-
tion, post chlorination &
C102 addition (as needed)
disinfection
organic removal
chlorine residual
NA NA ClOo use discontinued in
1968. Generated from
gaseous chlorine & NaC10?.
W&T CIO, system
-------
TABLE F-l (continued)
01
01
Plant Name Design Plant
Capacity (MGD)
Covington, KY 18.0
(Ft. Thomas)
Portsmouth, OH 16.0
Campbell, OH 3.8
Oregon, OH 0.8
ElyHa, OH NA
Year CIO,
Use
Initiated
1972
1950
1975
1964
NA
Process Description
C102 t C12 addition, lime +
alum addition, coagulation,
settling, filtration, final
chlorlnatlon, fluoride
addition
prechlorinatlon, chemical
addition (alum + KMnOj,
flash mixing, coagulation,
settling, chemical addition,
(alum + lime), flash mixing,
settling, filtration, final
chlorlnatlon (C12/C102)
chemical addition, flash mixing,
coagulation, settling, filtra-
tion, C12/C102 addition Into
clearwel T
NA
NA
Purposes of CIO,
Use i
odor, organics,
taste removal
odor, taste
removal
taste, odor re-
moval, disin-
fection
taste, odor re-
moval
haven't used in
Average
Dosaqe
(mg/1)
C
0.6 as
NaCIO,
t
C
0.21
C
0.60
C
0.1
9 NA
Residual
1n Dist.
System
(mg/1)
NA
0.3
total;
0 as
free
chlorine
NA
NA
NA
Method of
Preparation
CIO, from gaseous chlorine
& N5C10,
C.
C10? from gaseous chlorine
and NaC102. W&T C102 system
CIO, from gaseous chlorine
and NaCIO,. W&T CIO, system
C. £.
CIO, from gaseous chlorine
& N5C10,. W&T C10? system
with PVC header/dfffuser
NA
yrs-was used for
phenols but phenol
problem now 1s
corrected
(continued)
-------
TABLE F-1 (continued)
Year CIO,
Plant Name Design Plant Use Process Description
Capacity (MGD) Initiated
Ironton, OH 5.0 1919 NA
WellsvHle, OH 2.2 1937 chemical addition (lime, alum,
KMnO.), CIO, addition, carbon
addition, flash mixing, coagu-
lation, settling, filtration
Napolean, OH 4.5 1966 chemical addition (alum +
in lime), flash mixing, coagula-
££ tlon, settling, chemical
addition (soda ash + KMnO.),
flash mixing, coagulation,
settling, prechlorlnatlon,
filtration, C102 addition
Manawa, MI 8.5 NA NA
Steubenville, OH 12.0 1954 prechlorination, coagulation,
settling, filtration, post
chlorlnatlon, C102 addition
Defiance, OH 5.0 1971 chemical addition, coagulation,
settling, recarbonation,
filtration, CIO, addition
t
Purposes of CIO,
Use *
taste, odor re-
moval , chlorine
residual , disin-
fection
Mn, taste, odor
removal
taste, odor re-
moval, C12
residual , disin-
fection
taste, odor re-
moval , ci2
residual, disin-
fection
taste, C12 resid-
ual , disinfection
taste, odor,
organic com-
pounds removal
Average
Dosage
(rag/1)
C
2 mg/1
C
0.50
C 0.25
I 0.5
C
1.2-1.5
C
5.6
I
0.5-2.0
Residual
in Dist.
System Method of
(mg/1) Preparation
NA CIO, from gaseous chlorine
& N5Cio2
NA CIO, from gaseous chlorine
& N5C10?
2.0 CIO, from gaseous chlorine
& N5C102. C102 added
before clearwell
0.2 C10? from gaseous chlorine
free & NaCIO,. C102 added into
clearwefl; contact 20 to
30 minutes
0.3 CIO, from gaseous chlorine
& N5C102; added at clear-
wel 1 entrance
NA ClOo from gaseous chlorine
& NSC100; added at clear-
(used twice well entrance
since 1971)
(continued)
-------
TABLE F-1 (continued)
Plant Name Design Plant
Capacity (MGO)
Escanaba, HI 1.5
Rogers City. HI 1.5
U1
en
en
Henominee, HI 4.5
Ontonagon, MI 0.3
Narquette, MI 3.5
Gladstone, MI 3.0
Year CIO,
Use
Initiated
1970
1955
1971
1967
1945
1972
Process Description
pre CIO- addition, carbon
addition, chemical addition
(alum), flash mixing, floccu-
lation, settling, chemical
addition, filtration, CIO,
addition into clearwell, final
C102 addition
NA
carbon addition, chemical
addition, coagulation,
settling, C10? addition,
filtration
chemical addition, coagulation,
settling, filtration, CIO,
addition Into clearwell
chlorine, CIO, addition Into
clearwell
chlorine addition, coagulation,
settling, filtration, CIO,
Purposes of CIO,
Use *
taste, odor,
organic compound
removal, disinfec-
tion, Cl, residual
taste, odor, color
taste, odor removal
Cl, residual
L.
taste, odor, color
removal, Cl, resid-
ual , disinfection
taste, odor removal
Average
Dosage
(mg/1)
I
1-2
C
6
I
C
1.6
C
Residual
in Dist.
System
(mg/1)
NA
NA
NA
NA
NA
2.5 Ibs/day
taste, odor removal
I
0.5
NA
Method of
Preparation
CIO, from gaseous chlorine
& NSC10,
£.
CIO, from gaseous chlorine
& NaCIO,; added into distM
bution system
CIO, from gaseous chlorine
& N5C102. C102 unit fabri-
cated by water treatment
plant
CIO, from gaseous chlorine
& N3C 10,
{,
CIO, from gaseous chlorine
& N5C102
CIO, from gaseous chlorine
& N5C10-
Adrian. HI
(continued)
10.0
addition Into clearwell
1949 coagulation, CIO, addition, taste removal
filtration, final chlorination
NA CIO, from gaseous chlorine
& N3C102
-------
TABLE F-1 (continued)
and
lime addition, settling, recar-
bonation, C12 addition, filtration,
C102 addition Into clearwell
120.0 1942 carbon addition, lime/soda taste, odor removal
softening, settling, recarbo- disinfection
nation, filtration, fluoride,
ClOp/Cl- addition
Residual
Average in Dist.
Dosage System Method of
(mg/1) (mg/1) Preparation
NA 0.15 ClOp from gaseous
at plant & N5C10-,
0.10
in system
, I NA CIO- from gaseous
2.3-10.0 & N5C10,
£.
C NA CIO, from gaseous
0.40 & NSC10,
t
, C NA C109 from gaseous
0.2 & NaCIO,
£
, C NA C109 from gaseous
0.2 & NaClOp
(ranges from
0.2-0.4)
chlorine
chlorine
chlorine
chlorine
chlorine
(continued)
-------
TABLE F-l (continued)
Year CIO-
Plant Name Design Plant Use
Capacity (MGD) Initiated
Process Description
Residual
Average in Dist.
Purposes of CIO? Dosage System Method of
Use (rng/1) (mg/1) Preparation
en
en
oo
Ann Arbor, MI
Midland, TX
Augusta, KS
50.0
12.0
2.0
Greenville, OK 3.0
Bowling Green, OH 6.0
tas^e, odor removal
C
0.24
1939 prechlorlnatlon, lime/soda
softening, settling, recarbo-
natlon, carbon addition, coagu-
lation, settling, CIO- addition,
filtration, post chlorination,
fluoride addition
1970 CIO, addition when needed, co- taste, odor removal
agination, settling, filtration
1976 addition of alum, Hme, Cl- & taste, odor, C
C10?, coagulation, settling, organlcs removal, 0.12 as
filtration, final chlorination disinfection, NaC102
chlorine residual,
decrease C12 demand
1967 coagulation, settling, filtra- taste, odor removal C
tlon, C102/C12 addition 0.5
1951 coagulation, settling, recarbo- taste removal I
nation, filtration, chlorination 0.25
NA
NA
NA
NA
NA
ClOp from hydrochloric
acia & NaC102
CIO, equipment installed
but^never used. W&T C102
system
CIO, from gaseous chlorine
& N5C102. F&P C102 system
ClOp from gaseous chlorine
& NSC10-. Herberg Chemical
C102 system
CIO, used very infrequent-
i
-------
TABLE F-2. GREAT BRITAIN C102 QUESTIONNAIRE SUMMARY
Design Plant
Plant Name Capacity
cu m/day
Chester, G.B., 288,000
(Huntington Plant)
River Dee
Great Sutton, G.B., 64,000
(Sutton Hall Treat-
cn ment works) River
S Dee
Surham, G.B. , 45.000
(Rochester), Kent
River Midway
Egham, G.B., North 44,000
Surrey Water Co. ,
River Thames
Southampton, G.B. , 44,500
Testwood Pumping
Year CIO,
Use
Initiated
1970
1961
1975
1966
1968
Process Description
chemical addition, (lime,
alum C12, ClOo), flash mix-
ing, settling, sand filtra-
tion, pH adjustment & final
chlori nation
chemical addition (alum poly-
electrolyte), mixing, set-
tling, filtration, lime &
C102, S02 addition
prechlorination, coagulation,
sedimentation, filtration,
pH adjustment, C102 addition
prechlorination, coagulation
settling, filtration, chlori-
nation, C102 addition
prechlorination, coagulation,
settling, C10? addition,
Purposes of C102
taste & odor con-
trol , bacterial
disinfection,
chlorine residual
taste & odor re-
moval , bacterial
disinfection,
residual oxidant
taste & odor re-
moval , bacterial
disinfection,
chlorine residual
bacterial disin-
fection, chlorine
residual, preven-
tion of nuisance
growth
bacterial disin-
fection, phenolic
Average
Dosage
(mq/1)
C
0.2-0.4
C
0.3-0.4
C
0.05-0.1
C
0.3
C
0.2-0.5
Residual
in Dist.
System
(mq/1 )
NA
NA
NA
0.05
NA
Method of
Preparation
gaseous chlorine + sodium
chlorite. Excess of
chlorine
gaseous chlorine + sodium
chlorite. Excess of
chlorine
gaseous chlorine + sodium
chlorite
gaseous chlorine + sodium
chlorite combined in a
Raschlg ring reactor
gaseous chlorine + sodium
chlorite, mixed in reactor
Station, River Tert
filtration
taste
-------
TABLE F-3. FRENCH AND AUSTRIAN C102 QUESTIONNAIRE SUMMARY
Residual
Average 1n Dist.
Dosage System
(mg/1) (mg/1 )
Plant Name
Design Plant
Capacity
cu m/day
Year CIO,
Use c
Initiated
Process Description
Purposes of CIO,
Method of
Preparation
ui
o
St. Oven 1'Aumone, 2,400
France, river
water
Vichy, France, NA
river water
V1ry-Chat1ll1on
France
100,000
Toulouse, France, 110,000
surface water
reservoir
Rennes, France, 24,000
surface water
reservoir
Vlgneux-sur-Seine 57,600
France, Seine
River
Vienna, Austria, 230,000
Ubergangskainmer II
1976
NA
1951
1970
prechlorlnation, coagulation, bacterial dlslnfec- C
settling, act. carbon flltra- tlon, viral Inacti- NA
tlon, final C102 addition vatlon
NA
MA
prechlorlnatlon, coagulation, color, taste re-
settling, filtration, C102 moval, bacterial
addition disinfection
C
0.2-0.3
pre-CIO, addition, coagulation color, odor, taste, C
settling, filtration, 0,, organlcs removal, 0.8
sodium silicate addition bacterial disin-
fection
1977 03, C102 addition
1959 prechlorlnatlon, coagulation,
settling, filtration, final
C102 addition
1973 NA
bacterial d1s1n-
fection
color, taste re-
moval , bacterial
disinfection
bacterial disin-
fection, chlorine
residual
C
NA
C
0.2-0.25
C
0.25
0.2 gaseous chlorine + sodium
chloMte-CIFEC "B1oxy"
system
NA used for pre CIO, addition
and final C102 aadltlon.
Only Information given
NA gaseous chlorine + sodium
chlorite, Degr&nont system
NA gaseous chlorine + sodium
chlorlte-CIFEC "Bloxy"
system
0.25 gaseous chlorine + sodium
chlorlte-CIFEC system
NA gaseous chlorine + sodium
chlorite. Degr&nont system
0.08 reaction of chlorine and
sodium chlorite
(continued)
-------
TABLE F-3 (continued)
Plant Name
Vienna, Austria,
ground waterworks
Nussdorf
Design Plant
Capacity
cu in/day
100,000
Les Rousses, 5,000
France, lake water
Year CIO,
Use *
Initiated
1967
1959
Process
Description
NA
pre-CTOp addition as
settling, filtration
chlorlnatlon
needed,
, final
Purposes of C102
bacterial disin-
fection, chlorine
residual
odor, organlcs re-
moval, bacterial
disinfection
Average
Dosage
(mg/1)
C
0.25
C
1.0
Residual
in Dist.
System
(mg/1 )
not
measured
0.1
Method of
Preparation
reaction of chlorine
sodium chlorite
and
chlorine + sodium chlorite
Degr&nont equipment
Le Mans (Sarthe), 60,000
en France, river
O"> water
Suresnes, France, 112,000
Seine River
Porticclo, France, 25,300
river water
Bellerive-sur-
Allier, France
(continued)
6,600
1970 prechlorlnation, coagulation,
settling, filtration, C10?
addition, 0,, final C10?
addition J e~
NA line iCl-chemical addition,
powd. act. C., settling, fil-
tration, C102 addition, hypo-
chlorjte addition, line # 2-
prechlorlnation, alum, powd.
act. C., coagulation, set-
tling, filtration, CIO-
addition
1966 coagulation, settling, fil-
tration, C102
NA Clo, coagulation, sedimenta-
tion, filtration, 0,, Cl,/
C102 J i
color, organics, odor, C
taste removal, bac- 2-3
terial disinfection, (total)
viral inactivation
bacterial disinfec-
tion, chlorine
residual
NA
trace
NA
chlorine + sodium chlorite
CIFEC system
hypochlorite + sodium.
chlorite
bacterial disinfec-
tion
disinfection
NA
C
0.1-0.2
0.1
NA
gaseous chlorine + sodium
chlorite
C12 + NaC102
-------
TABLE F-3 (continued)
Design Plant
Plant Name Capacity
cu in/day
Le Potroux, 16,000
Aurllle, France
Chalandry, 10,000
El a 1 re, France
on
ro Warcq, France 8,400
Communante 600,000
Urbalne de Lyon,
France
Marseille, 100,000
France
Villefranche- 28.000
sur-Saone, France
Year CIO-
Use Process Description
Initiated
NA KMnO.. C102, C12, coagulation,
sedimentation, filtration, 0,,
neutralization, Cl,
1975 C1?/C10?, coagulation, sedi-
mentation, filtration, 0.,,
CU 3
Z
1973 C12/C)0?, coagulation, sedi-
mentation, filtration, 0,,
C12 3
£
1977 NA
1953 Clo/C10?, coagulation, sedi-
mentatiCn, filtration, C1,/
cio2
1975 CWC10- addition only
£ •£
Residual
Average In Dlst.
Purposes of C109 Dosage System
c (mq/1) (mg/1)
Fe, color, odor,
taste, organlcs,
Mn removal ,
bacterial disin-
fection
Fe, Mn, color, odor,
taste, organics re-
moval, bacterial
disinfection, viral
inactivation
Fe, Mn, taste, odor,
taste, color.
organics removal ,
disinfection, viral
Inactivation
disinfection
taste, odor, organics
removal, disinfection
viral inactivation
taste, odor removal ,
disinfection, prevent
formation of chloro-
phenols
1.0 C 0
(dislnf)
8.0 I
(T/0)
0.13 C NA
(T/0)
"trace"
(dislnf)
"traces" NA
(dislnf)
0.2 C as
C12 (T/0)
C 0
0.075
NA NA
9
C 0
0.15
(disinf)
0.25
(T/0)
Method of
Preparation
C12.+ NaC102, CIFEC system
Cl, + NaCIO,, CIFEC system
C. C.
C19 + NaCIO,, CIFEC system
£, £
Clo + NaC102, Degremont
system
Cl? + NaC10? (pretreatment
byTIFEC) *
Cl, + NaCIO,, CIFEC system
£ t
-------
TABLE F-3 (continued)
Plant Name
Paray le Monial,
Design Plant
Capacity
cu in/day
6,000
Year C10?
Use
Initiated
1969
France, river water
St. Etienne,
France, lake water
Carcassone, France
river water
tn
o^
CO
La Ferte,
Bernard, France
Agon Coutaimville,
France
Coutances, France
20,000
16,000
8,000
1,000
1,600
1972
1946
NA
1972
1957
Process Description
prechlorination, coagulation,
flocculatlon, settling, fil-
tration, C102 addition
NA
settlinq, filtration, C10?
addition
prechlorination, coagulation,
sedimentation, filtration,
cio2
CIO,, coagulation, sedimen-
tation, filtration, 0,,
CIO,
L.
CIO,, coagulation, sedimen-
tation, filtration, 0,,
CIO- J
c.
Purposes of ClOp
taste removal ,
bacterial dis-
infection
bacterial disinfec-
tion
organics, taste,
odor removal ,
bacterial disinfec-
tion
color, taste, odor
removal , disinfec-
tion
Fe, color, odor,
organics, Mn,
taste, turbidity
removal, bacterial
disinfection, viral
inactivation
Fe, color, odor,
organics, Mn,
taste, turbidity
removal, bacterial
Average
Dosage
(mg/1)
C
1.3
C
0.3
C
0.3-0.5
0.7 C
(disinf)
Residual
in Dist.
System
(n.g/1)
0.1
0.02
0
0
Method of
Preparation
gaseous chlorine + sodium
chlorite, Degremont equip-
ment
gaseous chlorine + sodium
chlorite, CIFEC system
gaseous chlorine + sodium
chlorite. CIFEC system
Cl, + NaCIO, (Degremont)
L. L
1.0 (T/0)
0.2 C
(disinf)
0.3 C
(disinf)
1.6 I
(T/0)
0
0
Cl, + NaC109 (Degremont)
C £.
Cl, + NaClO,
L. £.
disinfection
(continued)
-------
cn
TABLE F-4. GERMAN ClOg QUESTIONNAIRE SUMMARY
Design Plant
Plant Name Capacity
cu m/day
Einhausen 50,000
(Hessen), Germany
Wasserwerk III- 72,000
Wittlaer,
Duisburg, Germany
Dulsburg (46 18,000
plant), Germany
Dulsburg (14 22,000
plant), Germany
Year C102
Use Process Description
Initiated
1963 aeration, KMnO. addition, fil-
tration, C102 addition
1962 03, filtrat1on(anthracite and
GAC), C102 addition, neutrali-
zation
1968 pumping, pH adjustment, CIO-
addition
1968 prechlorlnation, mixing basin
pH adjustment, storage tank,
Average
Purposes of CIO? Dosage
(mg/1 )
chlorine NA
residual
chlorine C
residual 0.20
bacterial disinfec- C
tion 0.4
bacterial disinfec- C
tion 0.4
Residual
in Dist.
System Method of
(mq/1) Preparation
NA prepared by reacting
NaC102 + chlorine gas
0 prepared by reacting
NaC102 + chlorine gas &
water
0.02 prepared by reacting
NaC10? + Cl? gas &
water
0.02 prepared by reacting C12
gas plus water + NaC10?
Karlsruhe Water- 104,500
works, Germany
MUlheim, Germany 60,000
(Styrum)
Wolfsburg City
Works, Gem.
Sassenburg, Germany
15,500
1977
1955
1967
C102 addition
aeration, coagulation, filtra- bacterial disinfec- C 0
tion, C102 addition tion 0.20
river sand bank filtration, taste & odor removal C 0.1
storage well, C102 addition bacterial disinfec- 0.4-0.5
tion, chlorine
residual
coagulation, filtration, C10? chlorine residual NA NA
addition
prepared by reacting
NaCIO/, gas; capacity of
4.0 kg/day
prepared by reacting
NaC102 + C12 in a 1:1
ratio; analyze for the
sum of C1
C10
NA
(continued)
-------
TABLE F-4 (continued)
Plant Name
Mainz City Works,
Mainz, Germany
City Works Mainz
AG, Mainz, Germany
Dr. Friedrich-
g? Kirchhoff Street
ui Plant
City Works Mainz
AG, Wormser Street
Plant, Mainz,
Germany
Pforzheim City
Works, Pforzheim,
Germany
DUsseldorf
City Works,
Germany
Design Plant
Capacity
cu in/day
25,000
3,200
2,700
24,000
403,000
Year C10?
Use
Initiated
1958
1960
1967/
1972
1962
1961-67
Process Description
aeration, KMnO. addition, fil-
tration, C102 addition
C102 addition 1s only treat-
ment
C102 addition is only treat-
ment
wells, C102 addition,
holding tank, distribution
river sand bank filtration,
0,, filtration thru pre-
activated carbon, GAC filtra-
Purposes of C102
organics, taste &
odor removal , bac-
terial disinfection
chlorine residual
organics, taste &
odor removal , bac-
terial disinfection
chlorine residual
Residual
Average in Dist.
Dosage System
(n.g/1) (mg/1)
C <0.1
0.6
,
C <0.1
0.3
I
organics, taste A C <0.1
odor removal , 0.3
bacterial disinfec-
tion, chlorine residual
bacterial disinfec-
tion
bacterial disinfec-
tion, chlorine
residual
C NA
0.25
C <0.1
0.1-0.2
Method of
Preparation
prepared by reacting
NaC102 + chlorine gas
prepared by reacting
NaC102 + C12 gas
prepared by reacting
chlorine gas +• NaC102
prepared by reacting
NaC102 + chlorine gas;
(Degussa-Chlorite system)
C102 capacity is 415 kg/
day. Prepared by reacting
chlorine gas + NaClOo,
tion, neutralization (NaOH),
C102 addition
0.25 kg Clp/1000 cu m
0.68 kg NaC10?/1000 cu m
(continued)
-------
TABLE F-4 (continued)
Plant Name
Wasserwerk das
krelas, Aachen,
Germany
Wuppertal City
Works, DUsseldorf-
Benrath, Germany
en
g* Berlin, West
Germany
(Jungfernherde
Plant)
Augsburg City
Works, Bavaria,
Germany
Design Plant
Capacity
cu nt/day
172,800
150,000
170,000
100,000
Year CIO,
Use i
Initiated
1962
1967
1975
1963
Process Description
NA
river sand bank filtration,
aeration, 03, sand filtra-
tion, activated carbon,
C102 addition
groundwater, aeration, fil-
tration, C10?, clean water
holding tank; C102 measure-
ment
CIO- addition only
£
Purposes of CIO,
taste & odor removal
bacterial disinfec-
tion
bacterial
disinfection
bacterial
disinfection
bacterial disinfec-
tion, prevention of
bacterial regrowth
Average
Dosage
(mg/1)
, c
0.1
C
0.2
I
0.20
NA
Residual
in Dist.
System
(mg/1 )
NA
0.1
0
NA
in distribution system
Groundwater Pump-
works, Deggendorf,
60,000
1970
magnesium & iron precipita-
tion, filtration, C10,
chlorine
residual
C
0.3
0.05-0.10
Method of
Preparation
C102 capacity is 180 kg/
day prepared by reacting
50 kg of NaCIO, with 50 kg
chlorine on a flaily basis
CIO, capacity is 72 kg/
day prepared by reacting
sodium chlorite +• chlorine
gas and water
prepared by reacting 30%
sodium chlorite +• chlorine
gas; capacity of 17.3 kg/
day
capacity of 740 kg/day.
Prepared by reacting NaCIO,
+ C19 gas
L
prepared by reacting
chlorine gas + NaC102
Germany
Neuss City Works. 43,000
Neuss, Germany
NA
C102 addition only
taste & odor removal, C
bacterial disinfec- 0.1
tion
0.0 prepared by reacting NaClOj
and chlorine gas
(continued)
-------
TABLE F-4 (continued)
en
Plant Name
Albstadt City
Works, Albstadt,
Germany
Stolberger Water-
works, Stolberg,
Germany
Ansbach City
Works (1),
Ansbach, Germany
Ansbach City
Works (2),
Ansbach, Germany
Wittlich City
Works, Wittlich,
Germany
Zweckverband
Keckquellen,
Deisslingen,
Germany
Design Plant
Capacity
cu m/day
18,000
30.000
10,000
10,000
10,000
12,960
Year CIO-
Use "
Initiated
1977
1970
1973
1967
1967
1974
Process Description
pre-Oo, reaction tank, C02
stripping, two stage filtra-
tion, activated carbon, C102
addition
C102, aeration, filtration,
activated carbon filtration,
C102 addition
aeration, iron & manganese
filtration, C102 addition
aeration, iron & manganese
filtration, C102 addition
NA
0,, coagulation, filtration,
CT02 addition
Purposes of C102
chlorine residual
Fe, Mn removal .bac-
terial disinfection
chlorine residual
taste removal , bac-
terial disinfection
taste removal , bac-
terial disinfection
chlorine residual
post-chlorination
Average
Dosage
(mg/1)
C
0.3
C
, 0.01
C
0.3
C
0.30
C
0.2
C
0.3
Residual
in Dist.
System
(mg/1)
0.1
0.0-0.02
0.1
0.10
0.05
0.2
Method of
Preparation
prepared by reacting
gas & NaC102
prepared by reacting
WaC102 with C12 gas
prepared by reacting
NaC102 + C12 gas
ci2
30%
prepare C10? by reacting
30% NaC102 T C12 gas
prepared by reacting
gas + NaClOp
prepared by reacting
NaC102 with chlorine
Cl,
gas
(continued)
-------
TABLE F-4 (continued)
en
Design Plant
Plant Name Capacity
cu m/day
Vallena Water- 5,700
works, Vallendar,
Germany
Wasserverband 8,000
Dlllkrels-Sud,
Germany
L1nn1ch City 7,200
Waterworks,
Unnlch, Germany
Llchtenfels City 4,500
Works, Llchtenfels,
Germany
Herborn City 2,500
Works, Herborn,
Germany
Eberbach City 3,970
Works, Eberbach,
Germany
Solingen City 3,000
Works, Solingen,
Year C102
Use Process Description
Initiated
1964 prechlorlnation (low dosage),
oxygen addition, neutraliza-
tion, activated carbon, C102
addition, reaction basin
1975 ozonation, neutralization,
C102. addition
1969 groundwater, ClOp addition
ground storage
1965 C102 addition only
1973 aeration, filtration, CIO.,
addition
1977 C102 addition, neutralization
1965 C0? addition, KMnO. addi-
tion, 2-stage filtration,
Residual
Average In Dist.
Purposes of CICU Dosage System Method of
(mg/1) (mg/1) Preparation
taste & odor remov- C 0.0 prepare C102 in two ways:
al, bacterial disin- 0.1 NaClO- * Cl? gas and
fection, chlorine (disinf) NaCIO- + HCT in 2 sets of
residual I 0.3 equipment
(I/O)
bacterial dislnfec- NA NA NA
tlon
bacterial disinfec- C 0 prepared by C12 gas re-
tion 0.1 action + NaC102
bacterial disinfec- C 0.04 NA
tion 0.2
iron & manganese re- C 0 prepared by reacting C12
moval, bacterial dis- 0.5 gas + NaC102
infection, to satisfy
oxygen demand
bacterial disinfec- C 0.02 prepared by reacting C12
tion, chlorine 0.16 gas + NaC102
residual
chlorine residual C NA prepared by reacting Cl?
0.1 gas + NaC10?
Germany
(continued)
C102 addition
-------
TABLE F-4 (continued)
Plant Name Design Plant
Capacity (MGD)
Plochingen City 1,800
Works, Plochingen,
Germany
Spaichingen City 1,500
Works, Spaichingen,
Germany
Baumberg Water- 2,000
jj, works, Solingen,
cr> Germany
vo
Braunschweig, 24,000
Germany
Neumarkt, 2,000
Germany
Lohr on Main City 5,200
Waterworks, Lohr
on Main, Germany
Wollsteln, Germany 1,200
(continued)
Year C102
Use Process Description
Initiated
1959 NA
1969 flocculation, C10? addition,
filtration
1977 aeration, softening, double
filtration, 0,, filtration plus
flocculation, activated carbon,
C102 addition
1963 aeration, filtration, C10?
addition
1974 C102 addition only
1975 0,, sedimentation, filtration,
CT02 addition
1976 C102 addition only
Residual
Average in Dist.
Purposes of C102 Dosage System Method of
Use (mg/1) (nig/1) Preparation
odor removal ,
bacterial disin-
fection
bacterial disinfec-
tion, chlorine
residual
chlorine residual
bacterial disinfec-
tion
bacterial disinfec-
tion
NA
bacterial disinfec-
tion
C
0.2-0.3
C
0.30
C
0.1
C
0.1
C
0.15
C
0.05
C
0.3
0.03 prepared by reacting
gas + NaC102
ci2
0.1 prepared by mixing bleach
(sodium hypochlorite solu-
tion) and NaC102
NA prepared by reacting
gas * NaC102
trace prepared by reacting
NaC102 + C12 gas
0.1 prepared by reacting
gas and NaC102
0.02 NA
0.1 NA
ci2
ci2
-------
TABLE F-4 (continued)
Year ClOg
Plant Name Design Plant Use Process Description
Capacity (MGD) Initiated
Ludwlgsburg, 12,000
Germany
Kitzingen Water- 20,000
works. Kitzingen,
-j Germany
O
Friedsrlchshafen, 30,000
Germany
Ammerbuch- 16,000
Poltrlngen,
Germany
Bad Mergenthelm, 6,050
Germany
Schwabisch Hall 8,600
City Works,
Germany
1965
1961,
1966,
1967
1971
1967
1976
1969
2 split streams: first stream
1s aerated, combined w/second
stream in a holding basin prior
to CIO, addition. Second stream
1s aerated and has biological
removal of ammonia, Fe, Mn on a
media filter of quartz, sand
CIO, addition only
£.
0,, alum flocculatlon, 2-stage
ffltratlon (sand, activated
carbon), C102 addition
NA
flocculation, pre-filtration,
0,, post filtration, C10?
addition
CIO, addition, flocculation,
filtration, spraying, post-
filtration, C10- addition
Residual
Average 1n 01st.
Purposes of C102 Dosage System Method of
Use (ntq/1) (mg/1) Preparation
bacterial disinfec- C 0.05
tion, chlorine 0.12
residual
bacterial disinfec- C 0.04
tion 0.15
bacterial disinfec- C 0
tion 0.18
bacterial disinfec- C NA
tion 0.25
chlorine residual C 0
0.1
chlorine residual C 0.05
0.4-0.6
prepared by reacting
NaCIO, + Cl, gas
£ £
prepared by reacting
NaC102 + C12 gas
prepared by reacting
NaC102 with C12 gas
prepared by reacting
NaC102 + C12 gas
30% NaC10? reacted +•
C12 gas
prepared by reacting
NaC102 + C12 gas
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
1. REPORT NO.
EPA-600/2-78-147
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
5. REPORT DATE
AN ASSESSMENT OF OZONE AND CHLORINE DIOXIDE
TECHNOLOGIES FOR TREATMENT OF MUNICIPAL WATER SUPPLIES
August 1978 (Issuing Date")
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
G. Wade Miller, Rip G. Rice, C. Michael Robson,
Ronald L. Scull in, Wolfgang KUhn, and Harold Wolf
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Public Technology, Incorporated
1140 Connecticut Avenue, NW
Washington, D.C. 20036
10. PROGRAM ELEMENT NO.
1CC614
11. CONTRACT/GRANT NO.
R804385-01
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory--Cin.,OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: J. Keith Carswell (513) 684-7228
16. ABSTRACT
This research program and technology transfer effort was initiated in response to
growing national concern about the generation of toxic and carcinogenic compounds in
current U.S. drinking water treatment practices. The principal focus of this report
is a review of the pertinent international technology of ozonation and chlorine
dioxide usage.
Questionnaires were mailed to water treatment plants in the U.S., Canada, and Europe,
requesting detailed data on use of ozone and/or chlorine dioxide. The questionnaires
were supplemented by a detailed literature survey, a survey of the principal manufac-
turers of ozone and C102 equipment, and telephone contact with many water treatment
plants. The project team also conducted on site surveys at 23 treatment plants in
Europe, 7 water treatment plants in Canada, and 13 water treatment plants in the U.S.
On site data for engineering design of systems, and for procedures and results of water
quality analysis were emphasized. The organic oxidation products resulting from
chlorine dioxide and ozone application are covered in considerable detail.
Significant advances in the technology and engineering of water supply treatment
equipment and systems were identified by this study and are discussed in detail herein.
The Biological Activated Carbon (BAC) process, recently discovered and tested full
scale in Germany, is also discussed in great detail because of its potential impact on
the present high cost of activated carbon treatment.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Ozone, Water supply, Water treatment
devices, Engineering costs
Chlorine dioxide,
Oxidation products,
Drinking water treatment,
Engineering design, Bio-
logical activated carbon,
Canada, Western Europe,
United States
13B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS {This Report)
Unclassified
21. NO. OF PAGES
585
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77)
571
4 U.S. GOVERHMBtTPRIKT1NG OFFICE: 1978—7 57 -140/1375
------- |