TECHNOLOGIES AND COSTS FOR
^CONTROL OF DISINFECTION BY-PRODUCTS
STANDARDS AND RISK REDUCTION BRANCH
STANDARDS AND RISK MANAGEMENT DIVISION
OFFICE OF GROUND WATER AND DRINKING WATER
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C
PROJECT OFFICER: WILLIAM HAMELE
OCTOBER 1998
INTERNATIONAL CONSULTANTS, INC.
' 260 Northland Boulevard
Suite 119
Cincinnati, Ohio, 45246
MALCOLM PIRNHC, INC.
432 N. 44th Street
Suite 400
Phoenix, Arizona, 85008-7603
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ACKNOWLEDGEMENTS
The Office of Ground Water and Drinking Water, Standards and Risk Reduction'Branch,
Standards and Risk Management Division prepared this document. The Task Order Project
Officer was Mr. William Hamele of the U.S. EPA.
Technical consultants played a significant role in the preparation of this document. The
primary technical consultant was Malcolm Pirnie, Inc. under .subcontract to International
Consultants, Inc. The project manager was Timothy E. Soward of International Consultants.
Members of the Malcolm Pirnie technical support team included Doug Owen,' Zaid Chowdhury,
Arun Gera, Alan Gelderloos and Anne Jack. Members of the International Consultants technical
support team included Christopher Hill and Michael f. Cowles. Summers and Hooper, Inc.
provided technical assistance in document production. Members of the Summers and Hooper
technical support team were Stuart Hooper arid Malcolm Hooper. Technical assistance was also
provided via telecon or E-mail by Philip Singer, University of North Carolina , Stuart Krasner,
Metropolitan Water District of Southern California, Hiba. Shukairy, U.S. EPA and R. Scon
Summers, University of Cincinnati. Mark Thompson of Malcolm Pirnie also provided valuable
council. Special thanks to peer reviewers: John Dyksen, David J. Hiltebrand and Joe Jacangelo
for their excellent reviews and valuable comments on the draft manuscript. Finally, thanks to the
Washington Office of the American Water Works Association for their review and comments on
the draft manuscript.
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TABLE OF CONTENTS
EXECUTIVE SUMMARY . . . ............. ...................... ...... ES-1
Background ......... .......................... ....... .......... ES-1
DBF Properties and Treatment Alternatives ............................... ES-3
Removal of DBF Precursors ................. ......................... ES-4
Alternative Disinfectants .............. , .............................. ES-5
Removal of DBFs After Formation ........................ ES-8
Development of Design Criteria and Upgrade Costs ......................... ES-9
1.0 INTRODUCTION .............. M
1 ,1 Background .............................. ...................... !!
1.2 Purpose [[[ I"5
1.3 Document Organization ............................... 1-6
1.4 References ......................... . ---- ..................... I'8
2.0 DISINFECTANT AND DISINFECTION BY-PRODUCTS 2-1
2.1 Introduction .................................................. -2-1
2.2 DBFs Proposed for Stage 1 D/DBP Rule ............... , . ............ 2-1
2.2. 1 Introduction .......... . .................................. 2-1
2.2.2 Maximum Contaminant Levels ... .......................... 2-1
2.2.3 Total Trihalomethanes (TTHM) ............................. 2-2
2.2.4 Haloacetic Acids (HAA5) .................................. 2-4
2.2.5 Chlorite ............... . / ................ .............. 2-5
2.2.6 Bromate .......................................... - ---- 2-5
2.3 DBFs in the ICR Monitoring ...... ....... . ........................ 2-6
2.3.1 Introduction . ........................................ 2-6
2.3.2 Halogenated Organic By-Products ........ .................... 2-7
2.3.2.1 Total Organic Halide (TOX) .......... '. . : 2-7
2.3.2.2 Trihalomethanes ................................. 2-8
2.3.2.3 Haloacetic Acids (HAA6 or HAA9) ................. 2-8
2.3.2.4 Haloacetonitriles ..................... 2-9
2.3.2.5 Haloketones ................................ 2-10
2.3.2.6 Chloral Hydrate 2-
2.3.2.7 Chloropicrin ,- 2-
2.3.2.8 Cyanogen Chloride 2-
2.3.3 Non-halogenated Organic Oxidation By-Products 2-
2.3.3.1 Introduction ' 2-
2.3.3.2 Aldehydes - 2-12
2.3.3.3 Assimilable Organic Carbon (Optional for ICR) 2-14
2.3.3.4 Biodegradable Dissolved Organic Carbon (Optional for
ICR) 2-15
2.3.4 Inorganic By-Products '' 2-16
2.3.4.1 Bromate '. 2-16
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24 Other DBFs ................ ' ......... 2'16
2.4 1 Carboxylic Acids ....... ..... 2'16
2 4.2 Chlorophenols ....................... 2'17
2.4.3 MX .................................... 2'17
2 5 Other Inorganic DBFs .................................... . 2'19
2.5.1 Introduction ................ . ......................... 2'19
2.5.2 lodate ................................ . .......... 2'19
2.5.3 Hydrogen Peroxide .................................... 2'19
2.5.4 Ammonia .......................................... ' ,2'19
2.6 Disinfectant Residuals ..................................... ..... 2'20
2.6.1 Maximum Residual Disinfectant Levels ...................... 2'2l
2.7 Summary [[[ 2-24
2.8 References [[[ 2'25
3.0 TECHNOLOGIES AVAILABLE FOR DBF CONTROL 3-1
3.1 Introduction ............................................... 3~|
3.2 Coagulation/Filtration ...................................... 3'1
3.3 Precipitative Softening ................................... .- 3^
1 3 4 Adsorption Process .......................................... ~
3.4.1 Granular Activated Carbon ................................ 3'5
3.4.2 Activated Carbon Filters ................................. 3-9
3.4.3 Powdered Activated Carbon .............................. 3'9
3.4.4 Alternative Adsorbents/Ion Exchange .................... 3'10
3.5 Oxidation Processes ......................................... 3'1 J
3.5.1 Ozone ..................... . ........ - .............. 3-
3.5.2 Chlorine Dioxide .................................. 3'12
3.5.3 Potassium Permanganate .............................. 3'12
3.5.4 Chlorine ............... ............................. 3'^
3.5.5 Chloramines ....................................... 3'1:
3.5.6 Advanced Oxidation Processes 3'^
3.6 Air Stripping . .- ................................ 3~1^
3.6.1 Packed Column Air Stripping ....................... *'u
3.6.2 Diffused Air Stripping ................................ 3" ฐ
3.7 Membrane Processes ..................... ................ 3'[*
3.7.1 Important Factors for Membrane Performance ' 3-18
3.8 Reduction Processes ................................... ^[
3.8.1 Sulfur Dioxide ..'. ................................. ;*'-'
3.8.2 Sulfite Compounds ..... . ............................... 3'^
3 9 Biological Processes ......................................... 3"22
3.10 References ...............................................
4.0 TECHNOLOGIES FOR DBF PRECURSOR REMOVAL 4-1
4.1 Introduction "
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4 3 1 Introduction - 4'^
4.3 2 Total and Dissolved Organic Carbon ; 4-5
4 3.3 Ultraviolet Light Absorbance at 254 nm . . 4-6
434 Specific Ultraviolet Light Absorbance 4-6
4.3.5 DBF Formation Tests ' .- 4'7
4.3.5.1 Formation Potential (FP) Tests 4-7
4.3.5.2 Simulated Distribution System Test . ..: 4-8
4.3.5.3 Uniform Formation Conditions Test 4-8
4.3.6 Summary 4'9
4.4 Coagulation/Filtration , 4-9
4.4.1 Introduction 4-9
4.4.2 Removal Mechanisms 4-11
4.4.3 . Relationships Between Physicochenucal Characteristics of Natural
Organic Matter and Coagulation/Filtration Performance 4-12
4.4.3.1 Molecular Weight 4-12
4.4.3.2 - Charge 4'13
4.4.3.3 Solubility : - 4-13
4.4.3.4 Aromatic Content 4-14
4.4.3.5 Specific Ultraviolet Light Absorbance 4-14
4.4.4 Coagulant Dose and pH Impacts 4-14
4.4.5 Impacts of Temperature and Time of Year 4-19
4.4.6 Comparison between THMFP Removal and TOC Removal 4-19
4.4.7 Comparison between THMFP Removal and DBPFP Removal 4-20
4.4.8 Impacts of Preoxidation 4-21
4.4.8.1 Introduction 4-21
4.4.8.2 Chlorine 4'21
4.4.8.3 Chloramines 4'23
4.4.8.4 Ozone 4'23 -
4.4.8.5 Chlorine Dioxide 4'25_
4.4.9 Precoat Filters with Amendments 4'25
4.4.10 Impacts of PAC Addition 4'25
4.4.11 Membrane Processes with Coagulant Addition 4-2&
4.4.12 Summary ' 4'28
* " A **O
4.5 Precipitative Softening 4o"
4.5.1 Introduction 4'30
4.5.2 Relationships Between Physicochemical Characteristics of Natural
Organic Matter and Performance of Precipitative Softening 4-30
4.5.2.1 Molecular Weight 4-31
4.5.2.2' Charge - 4'31
4.5.2.3 Solubility .. -. ' 4'32
4.5.2.4 Other Factors 4'32
4.5.3 Water Quality and Chemical Dose Impacts 4'32
4.5 4 DBPFP Removal 4'3*
4.5.5 Summary 4'3ฐ
4.6 Granular Activated Carbon "
in
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4.6. 1 Introduction .................................. 4'36
4.6.2 pH Impacts ....................................... 4'37
4.6.3 Impacts of Pretreatment with Coagulation/Filtration ........ 4-38
464 Impacts of Preozonation ...................... 4'39
4.6.5 Impacts of GAC Type ............................... 4-40
4.6.6 Impacts of Empty Bed Contact Time ................ 4-41
4.6.7 Impacts of Blending ................................... 4-42
4.6.8 Comparisons of Case Studies ............................... I-43
4.6.9 Summary .............................................. 4~44
4.7 Powdered Activated Carbon ...................................... 4-45_
4.7. 1 PAC with Conventional Treatment ........................... 4-45
4.7.2 PAC with Membrane Treatment ............................. 4-46
4.8 Resin Absorbents .............................................. 4'48
4.8.1 NOM Removal ......................................... 4'4.8
4.8.2 Bromide Removal ................ . ..................... 4'5_ฐ
4 9 Oxidation Processes .......................................... 4"^
4.9.1 Ozone .................. ........................... *'*ป
4.9.2 Chlorine Dioxide ............. ......................... . ' 4'^2
4.9.3 Potassium Permanganate ............................. 4'53
4.9.4 Advanced Oxidation Processes ........................... 4'55
4.9.5 Photoassisted Heterogeneous Catalytic Oxidation 4-56
4.9.6 Summary .......................................... 4'^
4.10 Membrane Processes .......................................... 4"^
4.10.1 Introduction ............................................ 4'^
4.10.2 Review of Treatability Studies ............................ 4o9
4.10.2.1 NOM Removal ........................... 4'59
4.10.2.2 Bromide Removal
4.10.3 Summary .......................
4 1 1 Biological Degradation ---- .
4.11.1 Introduction ...........................................
4.11.2 Biological Treatment on Non-Adsorptive Media ........... 4-ฐ4.
4.11.3 Biological Treatment on Granular Activated Carbon .......... 4-65
4.11.4 Summary ....................................... ^
4.12 Summary ...... ........................ ' .................... "
4.13 References ................................................
5.0 ALTERNATIVE DISINFECTION TECHNOLOGIES 5-1
5.1 Introduction ................................................ ^"
5.2 Disinfection Alternatives ....................................... ?"
5.2.1 Primary Disinfection
5.2.2 Secondary Disinfection
5.2.3 Disinfection Strategies
5.3 DBP Formation by Alternative Disinfectants
5.3.1 Introduction
5.3.2 Ozonation DBFs ............ ,
IV
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5.3.3 Chlorine Dioxide DBFs 5-9
5.3 4 Chloramination DBFs 5-10
5.4 Impact of Alternative Disinfection Strategies 5-11
5.4.1 Introduction .: 5-11
5.4.2 Moving the Point of Chlorination 5-11
5.4.3 Switching to Ozone as Primary Disinfectant 5-12
5.4.3.1 Introduction 5-12
5.4.3.2 Utility 19 5-12
5.4.3.3 Utility 7 5-14
5.4.3.4 Utility 6 5-16
5.4.4 Switching to Chorine Dioxide as a Primary Disinfectant 5-17
5.4.4.1 Introduction 5-17
5.4.4.2 Utility 16 5-17
5.4.4.3 Evansville, Indiana 5-18
5.4.4.4 Chester Metropolitan Water District, South Carolina . . 5-20
5.4.4.5 Louisville, Kentucky 5-21
5.4.5 Switching to Chloramines as Secondary Disinfectant 5-22
. 5.4.5.1 Introduction 5-22
5.4.5.2 Metropolitan Water District of Southern California 5-22
5.4.5.3 Kentucky-American Water Company 5-23
5.4.5.4 Tampa Water Department, Tampa, Florida 5-24
5.4.5.5 Utility? 5-25
5.5 Summary 5-26
5.6 References 5'28
6.0 DISINFECTION BY-PRODUCT REMOVAL AND CONTROL OF
DISINFECTANT RESIDUALS : 6'r
6.1 Introduction 6'1
6 2 GAC Adsorption 6'2
6.2.1 Adsorption Capacity , 6-2
6.2.2 Removal of Trihalomethanes 6-3
6.2.3 Removal of Inorganic By-Products and Disinfectant Residuals 6-16
6.2.4 Summary of GAC Adsorption 6-19
6.3 Air Stripping 6'20
6.4 Conventional Treatment . .6-21
6.5 PAC Adsorption 6'22
6.5.1 Summary 6'25
6.6 Oxidation Processes " 6-25
6.6.1 Chlorination By-Products : > 6-25
6.6.2 Ozonation 6'26
6.6.3 Advanced Oxidation Processes 6'27
6.6.4 Summary of Oxidation Processes 6-29
6.7 Membrane Processes -f *'2
6 8 Reduction Processes
6.8.1 Chlorination By-Products
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6.8.2 Chlorine Dioxide By-Products 6.-34
6.8.3 Summary of Reduction Processes .. .. 6-37
6 9 Biological Removal 6-38
6.9.1 Introduction ...- 6-38
6 9.2 Removal of BDOC -. 6-38
6.9.3 Removal of Other DBPs , 6-39
- 6.9.4 Summary' of Biological Processes 6-43
6.10 Summary of DBP Removal 6-43
6.10.1 Inorganic By-Products , 6-43
6.10.2 Organic Oxidation By-Products 6-46
6.10.3 Halogenated Organic By-Products 6-46
6.11 References 6-47
7.0 DEVELOPMENT OF DESIGN CRITERIA AND UPGRADE COSTS
FOR DISINFECTION BY-PRODUCT CONTROL 7-1
7.1 Introduction 7'!
' 7.2 Treatment Upgrades 7'2
7.3 Overview of Previous Approach 7-4
7.4 Basis for Cost'Estimates 7'1!
7.5 Cost Escalation Factors 7'23
7.5.1 Capital Cost Escalation . ." 7-23
7.5.2 Operation & Maintenance Cost Escalation - 7-24
7.6 Design Criteria and Estimated Costs for Treatment Upgrades 7-25
7.6.1 ' Base Treatment Plant , 7-25
7.6.2 Move Point of Chlorination 7-27
7.6.3 Switching to Chloramines as a Secondary Disinfectant 7-27
7.6.4 Increased Coagulant Dosage 7-29
7.6.5 Enhanced Precipitative Softening 7-34
7.6.6 Switching to Ozone for Primary Disinfection 7-34
7.6.7 Switching to Chlorine Dioxide as Primary Disinfectant 7-44
,7.6.8 Installation of GAC Adsorption : . 7-55-
7.6.9 Addition of Membrane Filtration 7-62
7.6.9.1 'Large Systems : 7-63
7.6.9.2 Small Systems : : 7-66
7.7 Greenfield Adjustment Factors 7-68
7.8 Interest Rate Sensitivity Analysis 7-69
7.9 References -. ' 7'70
VI
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LIST OF TABLES
Table Following
No. Description . . ฃงฃ?.
ES-1 Primary and Secondary Disinfection Alternatives r ES-6
ES-2 Design Criteria and Key Assumptions ES-12
ES-3 EPA Flow Categories ' ES'13
ES-4 Estimated Base Plant Costs -, ES'14
1-1 Disinfectants/Disinfection By-Products I.'7
2-1 (a) Non-Enforceable Health Goals (MCLGs) for D/DBP Rule 2-2
2-l(b) Maximum Contaminant Levels for D/DBP 2-2
2-l(c) Physicochemical Properties of Trihalomethanes 2-3
2-l(d) Physicochemical Properties of Haloacetic Acids (HAAS) 2-4
2-l(e) Physicochemical Properties of Haloacetic Acids (HAA6 or HAA9) 2-8
2-l(f) Physicochemical Properties of Haloacetonitriles 2-9
2-l(g) Physicochemical Properties of Haloketones 2-10
2-l(h) Physicochemical Properties for Various .Aldehydes 2-13
2-l(i) Physicochemical Properties of Carboxylic Acids 2-16
2-l(j) Physicochemical Properties of Chlorophenols 2-17
2-l(k) Conventional Treatment Plant Disinfectants 2-18
2-1(1) Raw Water and Finished Water Disinfection Schemes 2-18
2-l(m) Physicochemical Properties of Inorganic DBFs 2-19
2-l(n) Physicochemical Properties of Disinfectant Residuals 2-21
2-l(o) Non-Enforceable Health Goals For D/DBP 2-21
vn
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2-l(p) Maximum Residual Disinfectant Levels for D/DBP ........... 2-22
2-1 Impacts of Disinfection Practice on DBF Formation .......... Following 2-29
2-2 Impacts of pH on Organic Halogen Formation ............ Following Table 2-1
3-1 Candidate DBF Control Processes ................................ 3-2
3-2 Typical Recovery for Membrane Processes ......................... 3-19
4-1 Characteristics of JMM/MWD Alum Plant Database .................. 4-16
4-2 Summary of Equation Constants for TOC Removal by Coagulation 4-18
4-2(a) Impact of Moving Preoxidation Application Point ...................... 4-23
4-3 Effect of Sludge Recycle Ratio on TOC Removal .................... 4-33
4-4 TOC Prediction Equations for Lime Softening ........................ 4-34
4-5 Average Removal of NOM by PAC .............................. 4-47
4-6 Equilibrium Capacity of Adsorbents ........................... : 4-49
4-7 Effectiveness of CL02 on THMFP and TOXFP 4-53
4-8 Removal Results for 7-day CHC13FP .......................... 4-54
4-8(a) Membrane Process Versus Pore Size Range 4-58
4-10 Impact of Ozonation on TOC Removal by GAC 4-67
4- 1 1 Process Summary for Removal of Disinfection By-Products Precursors 4-70
5-l(a) National Survey of Bromide in Drinking Water ................. . >7
5-1 DBFs after Switching from Chlorine/Chlorine Disinfection to
Ozone/Chlorine Disinfection ............................ . ......... 5'15
.5-2 Residential Times of Disinfectants ---- ......................... 5'16
5-3 ' Disinfectant Residuals ............................ . ......... >17
5-4 Contaminant Exposures ................................. >18
5-5 Distribution System Average Concentration
viii
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5-6 Disinfectants Versus Residence Time 3-26
6-1 Freundlich Isotherm Parameters for Activated Carbon Adsorption 6-4
6-2 Summary of TTHM Adsorption on Virgin GAC _ -6-6
6-3 Performance Level of GACs for Chloroform Removal 6-9
6-4 THM andTHMFP Removal with Calgon F-400 GAC 6-10
6-5 . Influent Water Quality Parameters 6-11
6-6 Removal of THMs by GAC . ...- . . 6-13
6-7 THM Removal with GAC 6'15
6-8 THM Removal with GAC ' '6'15
6-9 Summary of GAC Study 6-17
6-10 Chlorite Removal with GAC 6'18
6-11 Chlorine Dioxide Removal GAC 6'19
6-12 Chloroform Removal with Conventional Treatment >.. 6-21
6-13 THM Removal by PAC from Louisville. Kentucky Tap Water 6-23
6-14 Formaldehyde, Acetaldehyde and Hexanoic Acid Removal with GAC ..: . .6-24
6-15 Bromoform, Dichlorobromomethane and Dibromochloromethane
Removal with Ozone . 6'26
6-16 DBP Removal by Ozonation 6'27
6-17 .THM Removal with RO 6'29
6-18 THM Removal with RO " - 6'30
6-19 THM Removal withNF 6'30
6-20 Bromoform Removal with RO
6-21 Predicted Half-Lives and Removal Times for Chlorite Ion by Sulfur
Dioxide-Sulfite Ion in the Absence of Oxygen 6'37
IX
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6-22 AOC Removal with Ozonation and Biological Filtration 6-39
6-23 Ammonia Removal with BEAC 6-41
6-24 Aldehyde Removal with Ozonation and GAC 6-42
*
6-25 Effectiveness of Treatment Technologies for the Removal and Control
of DBFs 6'44
7-1 Updated Water Quality Distributions 7'7
7-2 EPA Flow Categories 7-1ฐ
7-2(a) Small System Labor Costs 7'12
7-3 Basis for Cost Estimates for DBF Control-Small Systems 7-13
7-4 Basis for Cost Estimates for DBF Control Large Systems 7-16
7-5 Cost Allowance .Factors 7'21
7-6 Indices used in the Escalation of Costs 7'24
7-7 Estimated Base Plant Costs 7'26
7-7(a) Median Design Criteria via WTP Model 7'27
7-8 Estimated Upgrade Costs for Additional Contact Basin Size (X$ 1000) 7-28
7-8(a) Median Design Criteria for Alum Dosage 7'31
7-9 - Estimated Upgrade Costs for Chloramines as Secondary Disinfectant 7-31
7-10 Estimated Upgrade Costs for Increasing Coagulant Dosage 7-33
7-11 Estimated Upgrade Cost for Enhanced Precipitative Softening "7-35
7-12 Estimated Installation and Upgrade Costs for Ozone as Primary .
Disinfectant 7"38
7-13 Estimated Installation and Upgrade Costs for Chlorine Dioxide as Primary
Disinfectant 7~45
7-13(a) Costs for GAC 10 and GAC20 Technology 7'58
7-14 Estimated Installation and Upgrade Costs GAC Adsorption 7'59
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7-14(a) Escalation Factor for Cost of GAC in Small Systems . . .7-61
7-14(b) Escalation Factor for Cost of GAC in Large Systems 7-61
7-15(aj Nanofiltration Costs for Source Water at 20"C 7-65.
7-15(b) Nanofiltration Costs for Source Water at 10ฐC 7-66
7-15(c) Small Systems Costs from 1994 RIA 7-67
7-15(d) Small Systems Costs June 1997 : 7-67
7-16 Greenfield Adjustment Factors 7-68
7-16 Summary of Interest Rate Sensitivity Analysis 7-70
XI
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LIST OF FIGURES
Figure Following
No. Description Page
J^-l ' Upgrade Costs for Improved NOM Removal ES-16
ES-2 Upyiiป-~ vosis roi * ~..~" ^infection Fig. ES-16
2-1 Trihalomethanes ^ 2'3
2-2 Haloacetic Acids 2-4
2-3 Inorganic By-Products 2'5
2-4 . Haloacetic Acids 2'8
2-5 Haloacetonitriles 2'9
2-6 Haloketones 2'10
2-7 Miscellaneous Halogenation By-Products Fig. 2-6
2-8a Aldehydes : 2'12
2-8b Aldehydes '. .- Fi8- 2'8a
2-9 Chlorate -. FiS 2'8b
2-10 Carboxylic Acids 2'15
2-11 Chlorophenols 2'16
2-12 MX - 2'17
2-13 Inorganic By-Products 2'19
2-14 Disinfixtant Residuals 2'20
3-1 Coagulation/Filtration Treatment Plant ; 3'2
3-2 Lime Softening Plant Treatment Plant 3'3
3-3 Typical GAC Contactors 3'6
3-4 Typical Ozone Oxidation Process 3'12
3-5 Typical Ozone/Peroxide Process 3'15
xii
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3-6 Typical Packed Column Air Stripper x- 3-17
3-7 Diffused Air Stripping Alternative F'g- 3'6
3-8 Typical Membrane Filtration Process : , 3'21
4-1 . Total Organic Carbon Occurrence in United States Water Supplies 4-1
4-2 Comparison of Fax Survey TOC Data with GWSS Data ....: Fig. 4-1
4-3 Comparison of Fax Survey TOC Data with WIDE Data -Fig 4-2
4-4 Removal of NOM During Coagulation/Filtration : 4-12
4-5 Removal ofTTHMFP During Coagulation/Filtration Fig. 4-4
4-6 Alum Coagulation Treatment Plant Locations 4'15
4-7 Impact of Coagulation pH on TOC Removal by Alum
Coagulation/Filtration Table 4'J
4-8 Impact Raw-Water TOC pn TOC Removal by Alum
Coagulation/Filtration F|S= 4'6
4-9 Residual Probability Plot of TOC Removal .- 4-17
4-10 Summary Raw-Water Statistics for Enhanced Coagulation Database Fig. 4-9
4-11 TOC vs. Coagulant Dose ! 4'18
4-12 Removal of Surrogate Parameters in an Alum Coagulation/Filtration
Plant 4'19
4-13 Alum Dose Versus Removal of Different Surrogate Parameters . 4-20
4-14 Removal of DBP Formation Potential by Alum Coagulation/Filtration Fig. 4-13
4-15 Impact of Magnesium on Removal of TOC by Precipitative Softening ..4-33
4-16 Summary Raw-Water Statistics for Enhanced Coagulation Database 4-34
4-17 TOC vs. Coagulant Dose Fl8 4'16
4-18 Removal of DBP Formation Potential by Precipitative Softening 4-35
.4-19 Impact of Alum Coagulation on GAC Adsorption 4-38
4-20 Impact of GAC type on TOC Removal
Xlll
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4-21 Impact of EBCT on GAC Adsorption of THMFP -.-., . Fig. 4-20
4-22 Impact of EBCT on GAG Adsorption of TOC Fig 4-21
4-23 Impact of EBCT on GAC Adsorption of THMFP 4-42
4-24 Impact of EBCT on GAC Adsorption of TOC Fig. 4-23.
4-25 Blended GAC Effluent from Multiple Contractors Operated in Parallel Fig. 4-24
4-26 Effect of Blending on TOC Breakthrough for Passaic River Water Fig. 4-25
4-27 Running Average TOC Removal by GAC 4-56
4-28 Removal of Natural Organic Parameters by Ozone Oxidation Fig. 4-27
4-29 Removal of THMFP by Oxidation ..... 4-57
4-30 Impact of MWC on DOC Removal in Membrane Processes 4-58
4-31 Impact of MWC on THMFP Removal in Membrane Processes Fig. 4-30
4-32 Impact of MWC on TOXFP Removal in Membrane Processes Fig. 4-31
t
5-1 .Comparison of DBP Formation at Utility 19 (A) 5-15
5-2 Comparison of DBP Formation at Utility 19 (B) Fig. 5-1
5-3 Comparison of DBP Formation at Utility 7 ......' Fig. >2
5-4 Comparison of DBP Formation at Utility 6 . 5'17
5-5 Comparison of DBP Formation at Utility 16
(Dist. Sys. Residence Time = 45 Minutes) Fig 5-4
5-6 Comparison of DBP Formation at Utility 16
(Dist. Sys. Residence Time = 160 hrs) Fig. so
7-25
7-1 Alum Coagulation/Filtration Base Plant :
7-2 Aliim Coagulation/Filtration System Upgraded with Chlonne/Chloramine
Disinfection .' , 7"27
7-3 Alum Coagulation/Filtration System Upgraded with Ozone/Chloramine
Disinfection .. _ , 7"J
7-4 Alum Coagulation/Filtration Systems Upgraded with GAC Adsorption 7-56
7-5 Membrane Capital Cost at 20. degrees C for Nanofiltration 7-66
xiv -
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7.-6 Membrane Capital Costs at 10 degrees C for Nanofiltration Figure 7-5
xv
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EXECUTIVE SUMMARY
BACKGROUND
The 1986 Amendments to the Safe Drinking Water Act (SDWA) required the United
i
States Environmental Protection Agency (EPA) to set maximum contaminant level goals
(MCLGs) for many contaminants found in drinking water. These MCLGs must provide an
adequate margin of safety from contaminant concentrations that are known or anticipated to
induce adverse effects on human health. For each contaminant, EPA must establish either a
treatment technique or a maximum contaminant level (MCL) that is as close to the MCLG
as is feasible with the use of best available technology (BAT).
Acting on the 1986 Amendments, EPA developed a list of disinfectants and
disinfection by-products (D/DBPs) for possible regulation after several rounds of stakeholder
comments. The course of the D/DBP regulation was decided by regulatory negotiation which
took place among stakeholders in 1992-93. Following the negotiation, EPA proposed three
regulations: the D/DBP Rule, the Interim Enhanced Surface Water Treatment Rule
(IESWTR) and the Information Collection Rule (the ICR); the ICR will provide occurrence
data for DBPs and precursors, microbials, water quality parameters, and treatment plant
parameters. This data will be used to develop the Stage 2 D/DBP and Long Term 2
Enhanced Surface Water Treatment Rule (LT2) rules. The first stage of the D/DBP Rule
includes MCLs for TTHMs, the sum of five haloacetic acids (HAAS), chlorite, and bromate.
Maximum residual disinfectant levels (MRDLs) are included for chlorine, chloramines, and
chlorine dioxide. A TOC removal treatment technique is included for conventional treatment
plants with sedimentation and filtration and precipitative softening plants with filtration.
Recent developments include the 1996 Amendments to the SDWA and the start of the
ICR monitoring. As the start of the ICR has been,delayed by three years, ICR data will not
be available for development of the Stage 1 D/DBP and IESWTR rules which are to be
promulgated in November 1998.
Total trihalomethanes (TTHMs) is the only contaminant currently regulated; the MCL
for TTHMs is 100 ug/L This MCL applies to the sum of the four chlorinated and/or
ES-1
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brominated THMs (chloroform, bromodichloromethane, dibromochloromethane, and
bromoform) .
The purpose of this document is to characterize the feasibility of treatment for DBF
control and to estimate costs for treatment alternatives that can then be used by utilities to
meet national regulations. Design criteria and upgrade costs were previously presented in the
1992 version of this document for selected DBF control technologies. Treatment criteria were
developed through various means including the use of a Water Treatment Plant (WTP)
simulation model for parameters critical to disinfection and DBF control, vendor-provided
information, engineering judgement, and recent published research.
The WTP simulation model was developed in the late '80s and early '90s to assist
EPA in developing a regulatory impact analysis for DBFs, in addition to being used as a basis
for design criteria for the DBF Technology and Cost Document. The DBF T & C document
was originally submitted in December 1992 and the upgrade costs were peer-reviewed and
accepted for the RIA. When it became necessary to update the document to support the
FACA process in 1997 before the D/DBP Rule became final in November 1998, USEPA
consulted with AWWA and other stakeholders involved in the 1992-1993. regulatory
negotiation and determined that costs should be modifiedpnly for those processes which may
have had significant changes in unit costs as a result of technology development; namely .
i ,'
chlorine dioxide (which was not included in the first document), ozone, and membranes. It
was agreed that other costs for 1992 would only be updated to current costs based upon
available indices. Therefore, while it is recognized that the WTP simulation model is now
being updated by EPA to reflect more recent input, peer-reviewers (AWWA) agreed that it
was not necessary to modify the method by which costs were developed for many of the
technologies. The WTP simulation model predicts DBF formation based on source water
quality and operational parameters for unit treatment processes. The model predicts the
removal of DBF precursors through treatment processes, and DBF formation upon
chlorination. Processes for DBF precursor removal that can be simulated include coagulation,
granular activated carbon (GAC) adsorption, and membrane filtration; precipitative softening
is currently being developed. The WTP simulation model can only predict the formation of '
\
THMs and HAAs at this time. Limited verification has been performed on the WTP model
ES-2
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predictions
The design criteria established were used to develop treatment costs for DBF control
These costs will be used by EPA to determine national costs for various potential DBF
regulatory scenarios.
DBF PROPERTIES AND TREATMENT ALTERNATIVES
This document includes a description of the chemical, structures and physical/chemical
characteristics of those disinfectants and DBFs that are being considered by EPA for possible
regulation. DBF formation depends on many factors including the type(s) of disinfectants,
disinfectant dosages, and water quality chaVacteristics such as pH and concentration of natural
organic matter (NOM). DBF formation also depends on other factors including bromide
levels in the raw water and the size and characteristics of the distribution system, especially
with respect to residence time in the system.
Research has identified the following generic treatment alternatives for control of
D/DBPs-
Removal of NOM prior to disinfection;
Use of alternative oxidants or disinfectants that do not create DBFs at levels
considered adverse to human health; and
Removal of DBFs after they are formed.
/
Because of the uncertainty relative to the occurrence and health risk for DBFs from
alternative oxidants and disinfectants, the first alternative listed above is considered the safest
for controlling DBFs.
Further, the use of alternative disinfectants may decrease some DBFs while increasing
other DBFs through the reaction of the alternative disinfectant with precursors present in the
raw water. Therefore, the impacts of treatment process modifications and water quality
characteristics on DBFs must be viewed in terms of potential risk trade-offs. The risk trade-
off becomes especially difficult since little is known about the health effects of many D/DBPs.
A major concern in the water industry is how to provide adequate disinfection to
ES-3
-------
inactivate microorganisms while minimizing DBF formation. In addition, it is important to'
control known DBFs without increasing risks from, as yet, undefined DBFs -This document
discusses the following technologies available for D/DBP control:
Coagulation/filtration
Precipitative softening
Adsorption processes
. Oxidation processes
Air stripping
Membrane processes
Reduction processes
Biological processes
i
REMOVAL OF DBF PRECURSORS ^
NOM . is a generic term for naturally occurring organic material that contains
precursors which react with disinfectants to form DBFs. NOM consists of (organic)
intermediates from the breakdown of living matter and their reaction products. NOM has
been shown to bind with metals and synthetic organic chemicals (SOCs), thereby allowing
these contaminants to proceed through treatment processes not designed for NOM removal
However, NOM levels can contribute to the following:
Increased disinfectant demand, requiring higher disinfectant dosages;
Increased DBF formation
Increased substrate for microorganism growth in distribution systems;
t
Higher coagulant dosages.
Greater competition .with SOCs for activated carbon adsorption sites
Because the characteristics of NOM are widely varied on a chemical and physical
basis, surrogate parameters must, be used to measure'NOM levels. Commonly used
ES-4
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surrogates to measure NOM concentration include
Total and dissolved organic carbon (TOC and DOC)
Ultraviolet absorbance at a wavelength of 254 nm(UV-254)
Uniform formation conditions (UFC)
Another more direct method of assessing DBF precursors is to measure their
formation under specific reaction conditions such as formation potential (FP), simulated
distribution system (SDS) and uniform formation conditions (UFC). Historically THMFP
has been used. More recently, however, the SDS and UFC conditions have been used to
represent conditions of disinfection practice. These surrogates may be used to screen raw
water sources for DBF precursor content to determine the performance of unit processes for
the removal of DBF precursors. The following processes were evaluated as technologies for
NOM (DBF precursor) removal:
Coagulation/filtration and precipitative softening;
Adsorption processes such as granular activated carbon (GAC), powdered
activated carbon (PAC) and resin adsorbents;
Oxidation processes such as ozone and chlorine dioxide;
Membrane processes; and
Biological degradation. .
Based on the evaluations in this document, the following processes are considered most
effective for NOM removal:
Coagulation/filtration, particularly at low pH and high coagulant dosages;
Precipitative softening, particularly at high pH.
GAC adsorption; and
Membrane processes
ALTERNATIVE DISINFECTANTS
ES-5
-------
In addition to treatment technologies to remove MOM, alternative disinfectants were
evaluated for D/DBP control. Any disinfection alternative implemented at a treatment plant
should:
Provide adequate disinfection to control pathogens at the treatment plant
and in the distribution system;
Limit the formation of regulated DBFs to concentrations lower than the
MCL;
^
Limit the formation of unregulated DBFs to concentrations lower than those
of potential concern; and
Achieve adequate color removal, iron oxidation, and taste and odor control.
The most prevalent disinfectants for primary disinfection (pathogen inactivation) in the
United Sates include chlorine (C12), chlorine dioxide (CIO,) and Ozone (O3). Secondary
disinfection is provided by maintaining a disinfectant residual throughout .the distribution
system; candidate secondary disinfectants in the.United States include C12, monochloramine
(NH2C1)4 and C1O2.
To achieve both primary and secondary disinfection, utilities may use a combination
of disinfectants. Primary and secondary disinfectant combinations that are capable of meeting
the Surface Water Treatment Rule (SWTR) are summarized in Table ES-1.
TABLE ES-1
PRIMARY AND SECONDARY DISINFECTION ALTERNATIVES
ES-6
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Although the SWTR does not specify primary disinfection credit for the
ozone/hydrogen peroxide process, the process can be used as a primary disinfectant if the,
utility can demonstrate that adequate levels of primary disinfection are-maintained. The
combination of ozone and chlorine dioxide is not commonly, used in the United States,
however, such uses are often seen in Europe. Primary disinfection credit can also be
achieved with chloramines, however, few utilities can use chloramines in this capacity because
of the relatively poor disinfecting capacity and large CT values (the product of disinfectant
concentration in mg/L and disinfection contact time in minutes) required by the SWTR In
some systems, primary disinfection is achieved with beta free chlorine followed by chloramine.
Because ozone does not maintain a residual in the distribution system over time, another
disinfectant must be applied to achieve secondary disinfection. The presence of disinfectant
residual continues the formation of DBFs in the distribution system, the extent of which
depends on the type of disinfectant and treated water characteristics.
In the United States, the combination of disinfectants most commonly used are
chlorine/ chlorine and chlorine/chloramine for primary/secondary disinfection. Some water
treatment plants that continue to use chlorine as the primary disinfectant have found that
moving the point of chlorination after a portion of the NOM removal occurs or eliminating
prechlorination if multiple application location are used can be effective if reducing DBFs.
The impact of this change on disinfection must be carefully considered before implementation.
Many utilities, particularly in the southeast, midwest and Texas, have pursued the use
of chlorine dioxide as a primary disinfectant. Utilities typically have used chlorine or
chloramines as a secondary disinfectant when chlorine dioxide is used as a primary
disinfectant. Ozone is increasing in popularity as a primary disinfectant in the United States.
Free chlorine and more commonly, chloramines, are typically used as secondary disinfectants
following ozonatidn. In a few cases ozonation could be followed by chlorine dioxide as a
secondary disinfectant.
Each of these disinfectant combinations produce DBFs. Therefore, the use of
alternative disinfectants requires considerable care. A modified disinfection scheme may
decrease the formation of some DBFs while increasing the presence of others. As previously
indicated, the rate and extent of DBF formation is strongly related to the type, concentrations,
ES-7
-------
and characteristics of the NOM present, the type of disinfectant, the locations of disinfectant
application, residence time in the system and other water quality characteristics, such as pH,
temperature, and bromide concentration.
REMOVAL OF DBFs AFTER FORMATION
Removing DBFs before the finished water enters the distribution system is the
remaining DBF control strategy discussed in this document. The strategy for removing DBFs
after their formation is limited by the following factors:
The amount of DBFs formed in the treatment plant relative to the amount
formed in the distribution system; and
Costs for the required treatment.
the following technologies may be applicable for removing DBFs:
GAC adsorption;
PAC adsorption;
Air stripping;
Conventional treatment;
Oxidation;
Membranes;
Reducing agents; and
Biological treatment.
For this approach to be feasible from a.process standpoint, a significant proportion of
the DBFs must be formed before the water leaves the treatment plant. In addition, the
addition of a given technology may be specific to only a small portion of the DBFs and
therefore, is relatively costly compared to removing precursors for a wide range of DBFs.
ES-8
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DEVELOPMENT OF DESIGN CRITERIA AND UPGRADE COSTS
The overall approach for the development of design criteria and upgrade costs for DBF
control alternatives assumes that there are six basic types of treatment practiced in the United
States at the present time:
Surface waters
- Coagulation/filtration systems
- Precipitatiye softening systems
- Unfiltered systems (including those that will be required to .filter under the
SWTR)
- Membrane treatment
Ground Waters
- Unfiltered systems
- Precipitative softening systems .
- Membrane treatment
i
For the analysis presented in this document, only the surface water,
coagulation/filtration category was evaluated. This category was analyzed first because. 1)
surface water systems are generally more sensitive to DBF formation than ground waters,
i
except for some areas such as Florida, where grouhdwaters are sensitive to DBF formation
because of high TOC concentrations, and 2) this category represents the largest population
served.
As stated previously in this section, the three basic alternatives for control of D/DBPs
are.
, Removal of NOM prior to disinfection;
Use-of alternative disinfectants; and
Removal of DBFs after formation.
Design criteria and upgrade costs were developed for specific treatment schemes
employing the first two control alternatives. Costs for removal of DBFs after formation were
ES-9
-------
not developed because it is almost always more cost efficient to remove the precursors before
they are formed.
Based on overall effectiveness, expected economic feasibility and practical full-scale
experience, the most promising and effective processes for the removal of NOM are
Increasing the coagulant dosage (only for coagulation/filtration systems),
Enhanced precipitative softening at high pH.
Installing GAC adsorption; and
Installing membrane filtration
For the use of alternative disinfectants, only two primary disinfectants were considered;
CU and 03. The most applicable secondary disinfection alternatives for the control of DBFs
are C12 and NH2C1. Treatment plants may require one, or a combination of, the NOM
removal processes or alternate disinfectants listed above in order to meet future D/DBP
standards. As a result, this document provides costs for the following NOM removal and
alternate disinfection processes:
Using monochloramine (as opposed to free chlorine) as a secondary disinfectant
Increasing coagulant dosage to improve NOM removal
Enhanced precipitativei softening to improve NOM removal
Using ozone as a primary disinfectant and monochloramine as a secondary
disinfectant
Installing post-filter GAC adsorption , . .
Installing membrane filtration (retrofit to the. base plant)
A summary of the key design criteria and assumptions used to develop upgrade costs
are presented in Table ES-2. As shown in Table ES-2, design criteria and upgrade costs for
membrane filtration were based on nanofiltration. Nanofiltration is capable of achieving
significant removals of NOM as well as providing excellent disinfection.
Upgrade cost .estimates were prepared for each control alternative for water supply.
systems of several sizes, based on the EPA's 12 flow categories. An additional large system
flow category was added for this document (design flow = 520 mgd). These categories were
divided into two groups; small systems having design flow of less'than 1 mgd and large
systems having design flow greater than 1 mgd. The median population served, average flow
ES-10
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and design capacity for each flow category is presented in Table ES-3
For these systems, the cost presented .in this document apply separately to each
treatment facility within a given water system. For example, some large systems have.
treatment facilities at. multiple locations. The total costs for such a system can be obtained
by adding together the costs for each individual treatment facility. .
Estimated costs were developed using models such as the Water model for small
systems and the WATERCOST model for large systems and information obtained from
utilities, vendors, trade groups, and literature. Estimated total upgrade costs consist of
operation and maintenance (O&M) and annual debt service on capital cost (i.e., 10 percent
interest, 20-year design life). The cost basis is July, 1997. The cost basis in the
accompanying RIA is June 1998. An interest rate sensitivity analysis indicated that the .
change in interest rate from 10 percent to 7 percent significantly affects overall costs.
ES-11
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TABLE ES-2
DESIGN CRITERIA AND KEY ASSUMPTIONS
Control Alternative
Using Chloramines
Increase Coagulant Dose
Practice Enhanced
Precipitative Softening
Using Ozone/Chloramines
Using ClOz/Clj
Install GAC Adsorption
Install Membranes
_
Desicn Criteria and Key Assumptions
.4:1 chlorine residual to ammonia ratio.
0.8 mg/L ammonia dose.
Alum as coagulant.
Increase dosage to 50 mg/L from 10 mg/L.
Lagoons used for dewatering.
Land for additional lagoons available on site.
Based on a 25% cost increase over enhanced
coagulation.
Ozone doses assumed to achieve CT required for
1, 3, and 5 log inactivation ofGiardia.
Ozone generation system and contact chamber
sized for design flow.
4. 1 chlorine residual to ammonia ratio.
0.8 mg/L ammonia dose.
Chlorine dioxide dosage of 0.5, 1, 1 mg/L for 1,
3, 5 log inactivation ofGiardia with contact basin
residence time of 60, 60, 120 minutes.
EBCTs of 10 and 20 minutes.
1 80-day regeneration frequency.
Replacement of GAC for Flow Categories 1 to
On-site GAC regeneration for Flow Categories 7
to 12(I>.
Nanofiltration assumed.
Sized for water production at design flow
(assuming 85 percent recovery rate).
Molecular weight cutoff = 200.
Operating pressure = 80 psi. 1
Note:
(1) See Table ES-3 for Flow Category description.
1 ES-12
-------
Table ES-4 summarizes the cost of the base plant for various flow categories.
TABLE ES-3
EPA FLOW CATEGORIES
EPA Flow
. " A , f . Vf*
: Categories 5.-^
'. " . -:--'-
',;; ., .x- .-'. . > .. '-';
'*. *,-' s .'' ' .'^.'^
' ''"'.": '."" "
Medran Copulation -
'"- ' . x'.. . ป ..
. Served
:. . Average Flow
' 1 mgd
5
6
7
8
9
10
11
12
12A
5,500
15,000
35,000
60,000
88,000
175,000
730,000
1,550,000
NA
0.70
2.1
5.0
8.8
13
27
120
270
350
1.8
4.8
11
18
26
51'
210
430
520
Upgrade costs are shown graphically in Figures ES-1 and ES-2. Figure ES-1 shows
upgrade costs for NOM removal strategies (i.e., increasing coagulant dosage, enhanced
precipitative softening, installing GAC and installing membrane filtration). Figure ES-2 shows
ES-13
-------
upgrade costs for alternate disinfection strategies (i.e., switching to chloramines as a
secondary disinfectant, switching to ozone as a primary disinfectant and switching to chlorine
dioxide as a primary disinfectant).
. TABLE ES-4
ESTIMATED BASE PLANT COSTS1
SMALL SYSTEMS
Design. FloW.
O&MCost
Total Costฎ 10%
0.024
0.63
600
4233
0.087
0.86
188
1343
0.27
1.4
90
605
0.65
2.0
56
330
LARGE SYSTEMS
Design Mwjr\J
1.8
48
11
18
26
51
210
430
520
1 1991 Capital Costs escalate
; Opal Cost "'
4.3
7.3
12
17
22
36
120
230
380
d based upon a factor of 1 .23
" :- O&MCost,-' ...
'' Vi ""'
74
47
39
36
35
33
32
31
26
======
derived from the ENR BCI.
^ ^^SSS
^^^^^^^^^^^^^^^^^^^^^^^^
" TotdtCosf
'.:' V '''
272
159.
118
98
89
76
65
59
61
J===5=====!J
ES-14
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The upgraded costs presented in this document are used as the basis to generate
national costs for compliance with different disinfection/disinfection by-product goals
Through the development of design criteria and upgrade costs for DBF control alternatives,
it was found that the upgrade costs for different combinations of alternatives was nearly equal
to the sum of the individual costs for each upgrade. For example, the costs for installing GAC
adsorption and switching to chloramines was nearly equal to the sum of individual upgrade
cost for adding GAC and the upgrade cost for switching to chloramines. As a result, only
costs for individual control alternatives.are presented in this document.
Upgrade costs for each D/DBP control alternative are designed to represent the costs
for an existing plant to improve treatment to meet potential D/DBP standards. For the
purpose of this evaluation, an existing treatment plant without D/DBP control, also referred
to as a "base plant", is assumed to be a facility which utilizes a Cy C12 disinfection strategy
and which currently meets the requirements of the SWTR. Upgrade costs were calculated
by either escalating the costs from the previous version of the document (EPA, 1992) based
on inflation, or by developing new or completely revised costs. New costs were developed
for chlorine dioxide, which was not included in the 1992 version of the document. Revised
costs were generated for ozone and membrane filtration because of recent advances in
technology and/or increase usage in the water treatment industry.
For the 1992 version of this document, the Water Treatment Plant (WTP) simulation
model and cost models were used to develop design criteria and cost respectively. In general,
the approach consisted of programming the WTP model to generate design criteria for each
treatment technology under a wide range of raw water qualities and under specified treatment
assumptions and constraints. Predicted design criteria from the model and other design
criteria based on engineering judgement were input into cost models. From these cost models,
upgrade costs were calculated for EPA's 13 flow categories by subtracting the total cost of
a treatment plant with the upgrade from the total cost of a baseline plant.
> ป *
It is the intent of USEPA that there be no significant reduction in microbial protection
as the result of modifying disinfection practices to meet maximum contaminant levels (MCLs)
for TTHM and HAAS. A microbial benchmark may need to be established for systems
moving the point of chlorination or changing disinfectants so that the modified treatment
ES-15
-------
scheme will provide a similar level of primary disinfection. At this time, the microbial
benchmark being provided by these systems is not known and, therefore, the level of
disinfection required for treatment upgrades is not known. As a result, a range of disinfection
levels are provided for technologies such as ozone and chlorine dioxide, and the appropriate
costs can be used once additional information is obtained for the actual benchmarking studies.
"ES-16
-------
FIGURE ES-1
UPGRADE COSTS FOR IMPROVED NOM REMOVAL
SMALL SYSTEMS
2,000
en
ฐ> 1,500
o
o
o
00
o
O
"co
i3
500
250
^^200
03
05
O
O
ฐ-150
5-
"w
o
O 100
~03
50
Treatment Upgrade
Increased Cqaaulant Dosage
Addition of GACJEBCT= 10 min)
..^..
Addition of GAC/EBCT = 20 min)
Addition pf^nofiltration
/FT"
Addition of CIO2 (log 3, auto generation)
...
0.03 0.05 0.1 0.2
Design Flow (mgd)
LARGE SYSTEMS
0.3
0.5
.1 . 'j*, i
N. . \
>. "ซ
> '. '
^ ^ ^ V .
! | -,tfx:
,-fflJx, *'-.
Treatment Upgrade
Increased Coaaulant Dosage
Addition of GACJEBCT- 10 min^
Addition of GAcTEBCT = 20 min)
Addition of^Janofiltration
Addition of CIO2 (log 3, auto generation)
^^ "* --...
4. I * *'
fo r .....'^. - - -^
10 20 50 100
Design Flow (mgd)
200
500 1.00C
-------
FIGURE ES-2
UPGRADE COSTS FOR ALTERNATE DISINFECTION
3600
:=> 3000 -
03
O)
O
O
O
2400 -
5* 1800 -
8
o
ซ 1200 -
c
600 -
0.02
40
35
ro 30
O)
O
O 25
O
O
c
< 10
0.03
SMALL SYSTEMS
NH2CI as Secondary
O3 as Primary Disinfectant
Addition of CKD2 (log 3
auto generation)
0.05
0.1 0.2 0.3
Design Flow (mgd)
LARGE SYSTEMS
w^^
,
.
"*ป.,
**ป,,
>
k
%
%
i *
X^
\
4-
- - -'^k
^*
--
V
SK^
"^"**a
K-,
'"- ^.
Treatment Upgrade
NH2CI as Secondary
O3 as Primary Disinfectant
Addition of CKD2 (log 3
auto generation)
""
**ซซ(.
4. A.
* +
^ ป
10 20 50 100
Design Flow (mgd)
200
500 1.00C
-------
1.0 INTRODUCTION
1.1 BACKGROUND
The use of disinfection to reduce waterborne disease in drinking water is one of the
greatest public health success stories in the history of mankind. As a result, 'disinfectants --
primarily chlorine - have been used relatively liberally to ensure that drinking water is safe
from pathogens Unfortunately, research in the latter part of the twentieth century has
indicated that these disinfectants can form undesirable organic and inorganic by-products
through oxidation/reduction and substitution reactions in natural waters. These DBFs can
have long-term' adverse health effects (e.g., cancer) and also may have short-term effects
. Consequently, the EPA has been searching since the mid-1970's for effective ways to control
the formation of DBFs while- ensuring that disinfection practices are adequate.
Concern about the human health impacts of DBF formation began in the early 1970s
when trihalomethanes (THMs) were first identified in public drinking water supplies (Rook,
1974; Bellar, etaL 1974; Symons, etaL 1975). In 1979, a MCL for the sum of four THMs
(chloroform, bromodichloromethane, dibromochloromethane .and bromoform). was
promulgated at 0. 10 mg/L (100 ng/L). At the same time, EPA identified the following as
generally available technologies for control of THM formation (USEPA, 1979):
1 \,
Use of chloramines as an alternate or supplemental disinfectant.
Use of chlorine dioxide as an alternate or supplemental disinfectant or oxidant
Improved coagulation for THM precursor reduction.
Moving the point of chlorination to reduce THM formation and, where
necessary, replacing the .use of chlorine as a pre-oxidant with chloramines,
chlorine dioxide or potassium permanganate.
Use of powdered activated carbon on a seasonal or intermittent basis for THM
precursor or THM reduction at dosages not to exceed 10 mg/L on an annual
average basis.
1-1
-------
if none of the above treatment methods was considered effective for a given system,
then that system could apply for a' variance from the regulation EPA recommended,
however, that those systems receiving a variance should determine whether the following '
methods permitted the system to comply with the THM MCL in a technologically and
economically feasible manner.
Introduction of off-line water storage for THM precursor reduction.
Aeration for THM reduction, where : geographically and environmentally
appropriate.
Introduction of coagulation where not currently practiced.
Consideration of alternative sources of raw water.
Use of ozone as an alternate or supplemental disinfectant or oxidant.
Systems receiving a variance were.required to install or use one of these treatment
methods in connection with a compliance schedule if the Primacy Agency determined that
treatment method to be feasible.
Water systems that modified their plants to comply with the THM Rule were also
required to monitor microbiological parameters to assure that the modification did not
compromise microbiological quality of the distributed water. In addition, EPA recommended.
that states require monitoring of chlorine dioxide, chlorite and chlorate for those systems
installing chlorine dioxide. A recommended limit of 1 mg/L was established for the sum of
these three oxidants.
In 1986 Congress passed an Amendment to the SDWA, requiring the EPA to set
MCLGs for many contaminants found in drinking water. These MCLGs must provide an
adequate margin of safety from contaminant concentrations that are known or anticipated to
induce adverse effects on human health. For each'contaminant, EPA must establish a MCL
that is as close to the MCLG as is feasible with the use of best available technology (BAT).
Although the BAT identified for each contaminant must be an economically feasible and
proven technology under field conditions, systems are not required to install BAT for
purposes of meeting a corresponding MCL. If analytical techniques are not economically or
1-2
-------
technologically feasible for a given contaminant, then EPA must set a treatment technique for
that contaminant in lieu of an MCL. The treatment technique must, in EPA's judgement, be
capable of providing economically feasible reduction of human health risks.
^
Acting on the 1986 Amendments, EPA developed a list of disinfectants and disinfection
by-products for possible regulation. This list was further refined based upon available data
indicating the potential of specific DBFs to pose significant health risk at levels that occur in
drinking waters. EPA released an Overview of Anticipated General Requirements and Major
Issues for the D/DBP Rule on June 21,1991. That document provided a list of DBPs which
could be regulated with MCLs, including trihalomethanes, haloacetic acids, chloral hydrate,
bromate, chlorate and chlorate. Disinfectants were also listed, including chlorine, chloramines
and .chlorine dioxide.
Three options were considered for THM regulation; 1) MCLs for each of the four
THM species, 2) a MCL for TTHMs, and 3) a MCL for each of the THMs and a MCL for
total'THMs (TTHMs - which may be different from the sum of the individual, species).
Similarly, three options considered for HAA regulation.
Industry comment on the 1991 strawman was significant and prompted EPA to
conduct a regulatory negotiation, which took place among stakeholders in 1992-93.
Following the negotiation, EPA proposed the D/DBP Rule and the IESWTR. Development
of these rules was originally dependent upon conducting additional DBP and microbial
occurrence studies through the ICR. The first stage of the D/DBP Rule includes MCLs for
TTHMs, HAAS, chlorite and bromate. Maximum residual disinfectant levels (MRDLs) were
also proposed for chlorine, chloramines and chlorine dioxide (USEPA, 1994). A treatment
technique was. also proposed for conventional treatment plants with sedimentation and
filtration as well as precipitative softening plants with filtration.
In 1996 Congress further amended the SDWA, thereby changing the number of
contaminants which must be regulated, the manner in which regulations are set, and providing
direction for water utility initiatives such.as providing consumer confidence reports and
focusing on watershed management. The standard setting process was modified to consider
cost-benefit analysis, in an attempt to better quantify the value of the regulatory process
Consequently, EPA was forced to move forward without the ICR data and an
agreement in principle was negotiated in 1997 under the Federal Advisory Committee Act
1-3
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(FACA) The Stage 1 D/DBP Rule and ESWTR negotiated under the FACA are to be
promulgated in November 1998. ' .
Various treatment strategies are available to address D/DBP regulations, including
modification of existing treatment systems, and installation of new treatment systems
Communities must consider the following factors when selecting a DBF compliance strategy:
Quality of the water source, particularly concentrations of those species that
exert an.oxidant demand or require disinfection (e.g., NOM, microbiological
contaminants, bromide, reduced metals and odor causing contaminants).
Impacts of the strategy on microbiological quality, in the plant and in the
distribution system. .
i
Impacts of the strategy on other treatment processes (e.g., filtration).
Economies of scale and the economic stability of the community being served.
i
Waste disposal requirements.
The selection of a compliance strategy may require engineering studies and/or pilot-plant
, ' r
investigations to determine the level of DBF control provided by various alternatives
Research into DBF control methods has identified three generic treatment strategies
for control of organic DBFs. These alternative strategies are as follows:
Remove as much NOM as feasible prior to the addition of chemical oxidants or
disinfectants.
Use alternative oxidants or disinfectants that do not create DBFs at levels
considered adverse to human health.
' Remove DBFs after they are formed.
Of these generic alternatives, the first is considered the most effective for controlling
organic DBFs. Use of the second alternative may reduce the formation of some DBFs while
increasing the formation of other DBFs. One thing is certain at this time; there is no currently
known chemical disinfectant of any significant strength that kills microbes without producing
DBFs (Moser, 1991). Some technologies used for the third alternative, such as aeration, may
1-4
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adequately remove some DBFs but no.t necessarily all DBFs of concern If the third
alternative is used without a NOM removal step, then NOM can react with the secondary
disinfectant to produce DBFs in the distribution system.
1.2 PURPOSE
The purpose of this document is to determine treatment costs for DBF control
alternatives. These costs can subsequently be used by EPA in evaluating the national
treatment costs for compliance with various D/DBP regulatory scenarios (Wade Miller
Associates, Inc., 1994).
Process criteria for unit treatment processes were either based upon a WTP simulation
model prepared for EPA as a part of this effort or best engineering judgement. The WTP
simulation model predicts the formation of DBFs based upon source water quality and
operational parameters for unit treatment processes. The removal of NOM (as DBF
precursors) through unit treatment processes such as coagulation, GAC adsorption, and
membrane filtration is predicted with the model. DBF formation as a result of the reaction
* ' '
between chlorine and NOM surrogates also is predicted. This model was used in the
regulatory negotiation to assist industry experts in evaluating the compliance with various
regulatory alternatives.
At this time, only THM and HAAS formation can be predicted with the model. The
formation of brpmate and bromoform upon ozonation of bromide-containing waters is
currently being evaluated. The removal of NOM by precipitative softening also is being
developed at this time. A detailed; description of the model is provided elsewhere (USEPA,
1992).
Using the treatment criteria, costs were developed using the WATER and
WATERCOST model, together with manufacturers quotations for selected equipment and
recent literature. Unit prices and cost indices for model input were based upon prevailing
rates and published values in the trade literature (e.g., Engineering News Record, Bureau of.
Labor Statistics). These costs were peer-reviewed by water industry and 'manufacturer
representatives through the American Water Works Association.
1-5
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1.3 DOCUMENT ORGANIZATION
This document contains the following sections:
Section 1: Describes background of the DBF issue and discusses the purpose
and scope of the document, defines technology categories and presents the
organization of the document.
Section 2: Presents, chemical structures, physicochemical properties and
formation characteristics of the DBFs listed in Table 1 -1.
Section3: Presents process descriptions of candidate technologies to be used
for DBF control.
Section 4: Summarizes research on the performance of alternative technologies
for removal of natural organic matter.
Section 5: Summarizes research on the use of alternative oxidation/disinfection
strategies for DBF control.
Section 6: Reviews research on the removal of DBFs after their formation and
the control of disinfectant residuals.
Section 7: Identifies process trains which are expected to meet the anticipated
disinfection requirements while providing feasible DBF control.
The costs presented in the last section are being used by EPA to determine the'national
treatment costs of the M/DBP Rule.
. 1-6
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TABLE 1-1
DISINFECTANTS/DISINFECTION BY-PRODUCTS
PROPOSED FOR REGULATION ' '
Organic DBFs
THM4 - Chloroform, Bromodichloromethane, Dibromochloromethane. Bromoform
HAA5 - Monochloroacetic Acid, Dichloroacetic Acid. Trichloroacetic Acid,
Mbnobromoacetic Acid, Dibromoacetic Acid
Inorganic DBFs
Bromate
Chlorite
Disinfectant Residuals
Chlorine
Chloramine
Chlorine Dioxide
INCLUDED IN ICR MONITORING
Halogenated Organic DBFs
Trihalomethanes (THM4)
Haloacetic Acids (HAA6) - HAAS compounds listed above plus Bromochloroacetic acid.
Monitoring of the other three species (Bromodichloroacetic acid, Chlorodibromoacetic
acid, Tribromoacetic acid) is optional.
, Haloacetonitriles - Dichloroacetonitrile, Bromochloroacetonitrile. Dibromoacetonitrile.
Trichloroacetonitrile
Haloketones - 1,1-Dichloropropanone, 1,1,1-Trichloropropanone
Chloral Hydrate
Chloropicrin
Cyanogen Chloride
TOX
Chlorite
Chlorate
Bromate
Non-Halogenated Organic DBFs
Aldehydes - Formaldehyde, Acetaldehyde. Hexanal. Heptanal
AOC/BDOC
OTHER ORGANIC DBFs
Carboxylic Acids - Hexanoic Acid, Heptanoic Acid
Chlorophenols - 2-Chlorophenol, 2,4-Dichlorophenol. 2,4;6-Trichlorophenol
MX
OTHER INORGANIC DBFs
lodate
Hydrogen Peroxide
Ammonia
1-7
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1.4 REFERENCES
Bellar, T A., Lichtenberg, J. J., Kroner, R C. (1974). "The Occurrence of Organohalides in
Chlorinated Drinking Water." J. AWWA. 66(12) p. 703.
Moser R. H. (1991). " Overview of the Disinfection By-Product Problem." Proceedings.
1991 AWWA Annual Conference, Philadelphia, PA.
Rook, J. J. (1974) "Formation of Haloforms During Chlorination of Natural Waters "
Water Treatment & Examination. 23(2) p. 234.
Symons, J. M., et al. (1975). "National Organics Reconnaissance Survey for Halogenated
Organics." IAWWA 67(11) p. 634.
USEPA (1979). Federal Register, No. 49:231, 6824-68689, November 29, 1979.
USEPA (1992). "Water Treatment Planlt Simulation Program User's Manual." Prepared
Office of Ground Water and Drinking Water Resource Center. Washington, D.C.
USEPA. EPA-811-8-B-92-001.
s i
USEPA (1994). National Primary Drinking Wataer Regulations: Disinfctants/Disinfection
By-Products Proposed Rule Fed Reg., 59:145:38667.
Wade Miller Associates, Inc. (1994). Regulatory Impact Analysis for the National Primary
Drinking Water Regulations: Disinfectants/Disinfection By-Products Rule. Prepared
for USEPA, May 25, 1994. .
1-8
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2.0 DISINFECTANT AND DISINFECTION
BY-PRODUCT PROPERTIES
2.1 INTRODUCTION
Both disinfection and oxidation are necessary to ensure production of high quality drinking
water. Disinfection is required for inactivation of any microbiological contaminants not removed
by prior treatment steps and is, therefore, essential from a health effects standpoint. Oxidation is
primarily used to control aesthetic and, more recently, synthetic organic contaminants in drinking
water. Iron, manganese, sulfide, color, and taste/odor causing compounds can all be removed to
some extent by oxidation. While removal of such parameters may not be necessary from a health
effects standpoint, their removal improves the aesthetic qualities of a water and customers often
perceive the presence of such parameters as an indicator of contamination.
While the use of chemical disinfectants and oxidants are considered essential in drinking
water treatment, disinfectants and oxidants are known to react with NOM present in water
supplies. These reactions produce incomplete oxidation by-products which may pose a public
health risk. In addition, the disinfectants themselves may pose a public health risk at high
concentrations.
i
This chapter describes the properties of those disinfectants and disinfection by-products
(DBFs) considered for regulation under Stage I of the D/DBP Rule, those included in the
Information Collection Rule (ICR) and other known DBFs. The properties discussed in this chapter
include chemical structure, physicochemical characteristics, and generarformation characteristics.
2.2 DBFs PROPOSED FOR STAGE I OF THE D/DBP RULE '
2.2.1 ' Introduction .
The D/DBP rule introduces specific limits for certain disinfectants and disinfection by-
products in drinking water. As proposed, it reduces the maximum contaminant level (MCL) for
' t
trihalomethanes (TTHMs) and sets MCLs for additional DBFs (HAAS, chlorite and bromate).
2.2.2 Maximum Contaminant Levels
Congress has given EPA broad authority to establish National Primary Water Regulations,
(NPDWRs) and to publish Maximum Contaminate Level Goals (MCLGs). The MCLGs are
developed as non-enforcable health goals. As defined in 40CFR 141.2, the MCLG is set "at the
2-1
-------
level at which no known or anticipated adverse effect on -?:e health of the person would occur, and
which allows an adequate margin of safety". EPA policy is to establish MCLGs for suspected
human carcinogens at zero. MCLs are the legally enforceable standard, and the MCL is set to be
as close to the MCLG as practical and feasible, taking technology and cost into account. The
MCLGs for the D/DBP rule are as follows:
TABLE 2-l(a)
NON-ENFORCEABLE HEALTH GOALS (MCLGs) FOR D/DBP RULE
/" ." -,"'"'-. -' "" ' "-. -' -
, Vr***;V--- - -
Bromoform
Chloroform
Bromodichloromethane
Dibromochloromethane
Dichloroacetic acid
Trichloroacetic acid
Bromate
Chlorite
Chloral Hydrate
. . : MCLGs (rog/L)
- " . " ; "; D/DBP RULE ; / "'; ".
0
0
0
0.06
0
0.3
0
0.08
0.04
The MCLs for the Stage 1 D/DBP Rule are presented in the following table:
TABLE 2-l(b)
MAXIMUM CONTAMINANT LEVELS FOR D/DBP
.- '.' V c^M ..--:.- ..
Total Trihalomethanes (TTHMs)
Haloacetic Acids
(HAAS)
Bromate
Chlorite
STAGE! D/DBP RULE
0.080
i
0.060
0.010
- 1.0
2.2.3 Total Trihalomethanes (TTHM)
The specific THMs of concern include:
Chloroform;
Bromodichloromethane;
Dibromochloromethane; and
Bromoform.
2-2
-------
The structural formulas of these four THMs are illustrated in Figure 2-1 while physicochemical
properties are summarized as follows (Weast, 1982-1983; Windholz, 1983):
TABLE 2-l(c)
PHYSICOCHEMICAL PROPERTIES OF TRIHALOMETHANES
Compound
Chloroform
Bromodichloromethane
Dibromochloromethane
Bromoform
Molecular
Weight
119.4
163.8
208.3
252.8
Solubility
Ong/L)
8200 @ 20ฐC
'NA
4400 @ 22ฐC
3190@30ฐC
Melting
. Point (ฐC)
-63.5
-57.1
-20.0
8.3
Boiling
Point (ฐC)
61.7
90.0
119.0
149.5
Vapor
Pressure
-------
FIGURE 2-1
TRIHALOMETHANES
Cl
Cl
CHLOROFORM
Cl
Cl
BROMODICHLOROMETHANE
Br
Br
DIBROMOCHLOROMETHANE
Br
Br
BROMOFORM
-------
account for a significant portion of chloroform formation. Ozonation can decrease the levels of
some chloroform precursors; however, the formation of other precursors such as 1,1,1-
trichloropropanone can increase (Reckhow and Singer, 1985).
2.2.4 Haloacetic Acids (HAAS)
The specific haloacetic acids (HAAs) of concern include
Monochloroacetic Acid (MCAA)
Dichloroacetic Acid (DCAA)
Trichloroacetic Acid (TCAA)
Monobromoacetic Acid (MBAA)
Dibromoacetic Acid (DBAA)
The structural formulas of these five HAAs are illustrated in Figure 2-2 while physicochemical
* properties are summarized as follows (Weast, 1982-1983; Windholz, 1983):
TABLE 2-l(d)
PHYSICOCHEMICAL PROPERTIES OF HALOACETIC ACIDS (HAAS)
Compound
Monochloroacetic Acid
Dichloroacetic Acid
Trichloroacetic Acid
Monobromoacetic Acid
Dibromoacetic Acid
Molecular
: -.-Weight
94.5
128.9
163.4
139
217.9
'. Solubility
-------
FIGURE 2-2
H
HALOACETIC ACIDS
H OH
Cl '
H
Cl OH
c:
Cl
MONOCHLOROACETIC ACID DICHLOROACETIC ACID
Cl OH
Cl!
Cl
TRICHLOROACETIC ACID
H
DIBROMOACETIC ACID
MONOBROMOACETIC ACID
-------
Stevens, et_aL (1988), evaluated the impacts of pH on the formation of HAAs during
chlorination. Trichloroacetic acid formation was shown to decrease with increasing pH at pH
levels higher than 7.0. However, trichloroacetic acid formation was not affected by pH levels
lower than 7.0. Dichloroacetic acid formation was not observed to be affected by pH. Other
HAAs were at or below detection limits and pH impacts on their formation could not be identified.
While chlorination generally produces the greatest quantity of HAAs, ozone can produce the
brominated species when water contains high levels of bromide. An ozone dose of 2 mg/L
produced 17 ug/L of dibromoacetic acid in a water containing 2 mg/L of bromide (McGuire, et
aL, 1990).
Reckhow and Singer (1985) showed that chlorination and hydrolysis of other DBFs can
lead to HAA formation. Dichloroacetonitrile hydrolyzes slowly at pH 7.0 and may produce
dichloroacetic acid. Trichloroacetic acid is a possible product of the decomposition of
dichloroacetonitrile in the presence of aqueous chlorine. In addition, chloral hydrate reacts slowly
with chlorine to form trichloroacetic acid, however, this intermediate does not account for a
significant quantity of trichloroacetic acid formation.
2.2.5 Chlorite
The structural formula of chlorite, molecular weight 67.4. is illustrated in Figure 2-3.
Chlorite formation is principally due to reduction of chlorine dioxide. Research has shown that 0 7
mg of chlorite is generally formed for each mg of chlorine dioxide consumed (Werdehoff and
Singer, 1987). At low and neutral pH values, chlorite can react with chlorine either to produce
chlorate or to regenerate chlorine dioxide. However, the reaction between chlorite and chlorine at
high pH is believed to produce chlorate only (Aieta and Roberts, 1986). Research has shown
chlorate to be the only product of this reaction in organic free water at pH 7.0 (Singer and O'Neil,
1987). However, the products of this reaction in the presence of NOM have yet to be studied.
2.2.6 Bromate
The structural formula of bromate, molecular weight 127.9 is illustrated in Figure 2-3.
Under typical water treatment conditions, ozone can oxidize bromide to .free bromine
(hypobromous acid and hypobromite).. Ozone can further oxidize hypobromite to bromate and
another species which regenerates bromide. Bromate concentration is a function of pH, the ratio of
ozone to bromide and the presence of NOM (Glaze, 1988; Haag and Hoigne, 1983). Pilot studies
demonstrated that an ozone dose of 2 mg/L produced 0.07 mg/L of bromate in a water containing 2
mg/L of bromide (McGuire, gLal, 1990).
2-5
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FIGURE 2-3
INORGANIC BY-PRODUCTS
-------
2.3 DBPs IN THE ICR MONITORING
2.3.1 Introduction
The ICR involves the monitoring of the source water and drinking water for general water
quality characteristics, DBPs, surrogates for DBPs, surrogates for DBP precursors, and the
collection of treatment plant operational data. The agency has expanded the list of the Stage I
D/DBP Rule DBPs in the monitoring for the Information Collection Rule. The preamble to the
proposed ICR rule discussed difficulties in the preservation of samples for the determination of
haloacetonitriles, haloketones, chloropicrin, and chloral hydrate concentrations in drinking water. In
the interim between proposal and promulgation, EPA developed a preservation technique for these
samples and a revised method. Because the new version of the method (EPA Method S31.1)
addresses a problem that was of concern to both EPA and many commenters, EPA promulgated
551.1 instead of EPA Method 551 for the compounds listed above (EPA 814-B-96-002, April
1996). TTHMs can also be analyzed by this method.
EPA also developed a new method for measuring HAA concentrations in drinking water
during the period between proposal and promulgation. EPA Method 552.2 combines the positive
aspects of the two methods that were included in the proposal and eliminates some of the concerns
i
expressed by the laboratory community regarding proposed methods. Therefore, EPA decided to
list method 552.2 as an additional improved method for performing HAA analyses (EPA 814-B-
96-002, April 1996). This method increases the HAA5 list to HAA9 and provides improved
variability for waters containing competing ions.
Bromate is the ozonation by-product that has generated a great deal of concern about
potential adverse health effects. As a result, bromate is being proposed at a level of 0.01 rng/L in
Stage I D/DBP rule. EPA has recently developed a new method for the analysis of bromate in
drinking water (EPA method 300.1). This ion chromatography method offers a significant
improvement over the detection limit for bromate in EPA method 300. Detectectable levels of
bromate in high ionic strength waters at levels of 0.00128 ug/L have been obtained by EPA method
300.1.
2-6
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2.3.2 Halogenated Organic By-Products
Organic halogens are formed when NOM reacts with free chlorine or free bromine The
most significant quantities of organic halogens are produced by the addition of free chlorine for
disinfection in drinking water treatment. In practical treatment situations, however, free chlorine
may also be present in limited quantities whenever chlorine dioxide or chloramine. disinfection
practices are used. For chloramine disinfection, free chlorine may be present for a short period of
time when chlorine and ammonia are simultaneously added at one point in the treatment process.
This is primarily due to the inability.of the mixing process to bring all of the free chlorine into
contact with ammonia before the free chlorine reacts with something else. In addition,
monochloramine slowly hydrolyzes to free chlorine in aqueous solution. Thus, the occurrence of
halogenatipn reactions exists even when monochloramine is formed prior to addition in the
treatment process (Rice and Gomez-Taylor, 1986). It should be noted that during the Surfece
Water Treatment Rule meetings in Washington, DC in May 1988, there was a consensus among
the group chaired by the late Dr. Olivieri that the addition of ammonia should always follow
breakpoint chlorination. This is due to the fact that, prior to reaching breakpoint, it is possible that
some of the combined chlorine residual detected was in reality an organochloramine complex that
was not a true disinfectant. For chlorine dioxide disinfection, free chlorine may be present because
it is used to generate chlorine dioxide from chlorite. Free bromine can be formed in drinking water
treatment whenever bromide is oxidized by strong oxidants such as ozone, chlorine and chlorine
dioxide. The level of brominated by-products formed during oxidation is dependent on the
concentration of bromide in the raw water, source and the relative amount of bromide present in
comparison to organic precursor levels.
Most of the existing information on organic halogens has focused on THMs while only
limited data are available on the health, effects, chemistry and occurrence of the other organic
halogens. Research efforts have only recently shifted to the other organic halogens, hence, our
knowledge of these by-products is much less definitive than it is for THMs.
2.3.2.1 TOX
Total organic halide (TOX) is a surrogate measure of the total amount of
dissolved halogenated organic matter in a water sample. Since known DBFs account for less than
50 percent of organically-bound halide as measured by TOX (Reckhow and Singer, 1985),
monitoring TOX during drinking water treatment is a useful surrogate parameter to determine the
2-7
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control of total halogenated DBF formation.
2.3.2.2 Trihalomethanes
As required under stage 1 of the D/DBP Rule, THMs are also required under
the ICR A discussion of trihalomethanes is found in section 221
2.3.2.3 Haloacetic Acids (HAA6 or HAA9)
The haloacetic acids required under the ICR include HAA5 plus
bromodichloroacetic acid (HAA6). A discussion of HAA5 is found in section 2.2.2. Three
additional haloacetic acids (HAA9) are optional under the ICR.
The specific haloacetic acids of interest include:
HAAS
Bromochloroacetic acid (HAA6)
Bromodichloroacetic acid *
Chlorodibromoacetic acid *
Tribromoacetic acid *
41 Optional analytes under the ICR (HAA9)
The structural formulas of HAA6 and HAA9 are illustrated in Figure 2-4
while physicochemical properties are summarized as follows (H. Zimmer et. al, 1990):
TABLE 2-l(e)
PHYSICOCHEMICAL PROPERTIES OF HALOACETIC ACIDS (HAA6 OR HAA9)
1 '.
Compound
Bromochloroacetic acid
Bromodichloroacetic
acid
Dibromochloroacetic
acid
Tribromoacetic acid
. Molecular
Weight
173.8
207.83
252.29
296.74
Solubility
(mg/L)
V Soluble
NA
NA
NA
Melting
Point (ฐC)
31.5
78-80
108-110
132
Bolting
Point (ฐC)
215
NA
NA
245
Vapor
Pressure
(mmHg)
NA
NA
NA
NA
2-8
-------
FIGURE 2-4
HALOACETIC ACIDS
Br O
Cl O
Cl
Cl
BROMOCHLOROACETIC ACID BROMODICHLOROACETIC ACID
Br O
Br
Br O
CHLORODIBROMOACETIC ACID TRIBROMOACETIC ACID
-------
A study by Pourmoghaddes et al (1993) investigated the impact of bromide ion, pH.
reaction time, and chlorine dose on the formation and speciation of the nine HAA species.
Concentrations of BCAA, BDCAA, CDBAA and TBAA increased with increasing bromide
concentration and decreased with increasing pH. Cowman and Singer (1996) showed that the mole
fraction distribution of mono-, di-, and trihalogenated species remained fairly constant over a range
(0-2000 ug/L) bromide concentration.
2.3.2.4 Haloacetonitriles
The specific haloacetonitriles (HANs) of concern include:
Trichloroacetonitrile (TCAN);
Dichloroacetonitrile (DCAN);
Bromochloroacetonitrile (BCAN); and
Dibromoacetonitrile (DBAN).
The structural formulas of these four HANs are illustrated in Figure 2-5 while
physicochemical properties are summarized as follows (Weast, 1982-1983; Windholz, 1983):
TABLE 2-1(0
PHYSICOCHEMICAL PROPERTIES OF HALOACETONITRILES
Compound
Tnchloroactonitrile
Dichloroacetonitnle
Bromochloroacetonitrile
Dibromoacetonitrile
Molecular
Weight f
144.9
109.9
153.4
196.9
Solubility. .
(wg/LJ
NA
NA
NA
NA
. Melting
Point CQ
-42
NA
NA
NA
Boiling
Point {"C)
85.7
112
NA
NA.
Vapor
Pressure
(nunHg)
741@84.6ฐC
NA
NA
NA
Chlorination alone generally produces the greatest yield of HANs In a survey
of finished waters from 35 utilities (Krasner, etal.. 1989), dichloroacetonitrile was found to be the
most significant species followed by bromochloroacetonitrile and dibromoacetonitrile. Raw water
bromide levels affect the distribution of these species. Trichloroacetonitrile was generally found in
insignificant quantities (Krasner, etal.. 1989).
Dichloroacetonitrile formation decreases with increasing pH (Stevens, et al..
1988; USEPA, 1988). The remaining HANs were present at or below detection levels and.
therefore, pH impacts on the formation of these species could not be determined in this study
2-9
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FIGURE-2-5
HALOACETONITRILES
ci
ci
TRICHLOROACETONITRILE
CI
N
CI
DICHLOROACETONITRILE
CI
Br
Br
Br
BROMOCHLOROACETONITRILE
DIBROMOACETONITRILE
-------
Reckhow and Singer (1985) studied the hydrolysis and chlorination of
dichloroacetomtrile This compound was observed to undergo base catalyzed hydrolysis and was
considered to be a long-lived intermediate at neutral pH rather than a true end product of
chlorination of natural organics. Dichlqroacetonitrile was also observed to react with aqueous
chlorine, possibly leading to the formation of trichloroacetonitrile and trichloroacetic acid.
2.3.2.5 Haloketones
The specific haloketones (HKs) of concern include:
1,1 -Dichloropropanone, and
1,1,1-Trichloropropanone.
The structural formulas of these two HKs are illustrated in Figure 2-6 while
physicochemical properties are summarized as follows (Weast, 1982-1983; Windholz, 1983):
TABLE 2-l(g)
PHYSICOCHEMICAL PROPERTIES OF HALOKETONES
- V ;- .:"-.;::."; ;- - :
- . Compound .
1 , 1 -Dichloropropanone
1,1,1-
Trichloropropanone
Molecular
-Weight
127
161.4
Solubility
/
-------
FIGURE 2-6
HALOKETONES
Cl O H
I
Cl
H
H
1,1 -DICHLORQPROPANONE
Cl
O
H
Cl
H
Cl
H
1,1,1 -TRICHLOROPROPANONE
-------
FIGURE 2-7
MISCELLANEOUS HALOGENATION
BY-PRODUCTS
Cl
Cl
CHLOROPICRIN
Cl OH
"
. Cl OH
CHLORAL HYDRATE
CYANOGEN CHLORIDE
-------
2.3.2.6 Chloral Hydrate -
Chloral hydrate occurs primarily as a result of chlonnation although
ozonation followed by chlorination has been observed to increase levels beyond those observed
w,th chlonnation only (Jacangelo, tfjL 1989). Chloral hydrate undergoes base-catalyzed
hydrolysis and is considered to be a long-lived intermediate rather than an end product of
chlorination of natural organics (Reckhow and Singer, 1985). Chloral hydrate formation increases
with increasing PH; however, .the rate of hydrolysis also increases with increasing pH and is greater
than the rate of formation at a value of 9.4 (Stevens, etaL 1989; USEPA, 1988). The structural
formula for chloral hydrate is illustrated in Figure 2-7.
2.3.2.7 Chloropicrin
Chlorppicrin is produced by the chlorination of humic materials in the
presence of nitrite ion (Duguet, et_aL 1985; Thibaud, *jL 1987). Ozonation followed by
chlorination or chloramination can increase chloropicrin levels above those observed with
' chlorination or chloramination alone (Jacangelo, et_aL 1989). The structural formula for
chloropicrin is illustrated in Figure 2-7.
%
2.3.2.8 Cyanogen Chloride
Cyanogen chloride generally occurs at highest levels in systems using
chloramination (Krasner, AjL 1989) although ozonation followed by chloramination has.beeh
observed to increase levels beyond.those" observed with chloramination only (Jacangelo, ajL
1989) However, cyanogen chloride has also been found to occur at higher levels as a result of
pre- and post-chWination when compared to other alternatives such as pre-chlorination/post-
ammoniation (Jacangelo, *jL .1989). Cyanogen bromide, the brominated analog of cyanogen
chloride, has been detected after ozonation of a water containing high bromide levels (McGuire, et
al, 1990). The structural formula for cyanogen chloride is illustrated in Figure 2-7.
23>3 NQN-HALOGENATED ORGANIC OXIDATION BY-PRODUCTS
2.3.3.1. Introduction
Organic oxidation by-products are formed by reactions between NOM and all
oxidizing agents'added during drinking water treatment.' Some of these by-products are
halogenated as discussed in the previous section, while others are not. 'This section focuses on the
2-11
-------
non-halogenated by-products. The types of organic oxidation by-products produced and the extent
to which they are formed varies according to the type and dosage of the oxidant(s) being used,
i
chemical characteristics and concentration of the NOM being oxidized and other factors such as
pH and temperature. Research has only recently begun to examine the characteristics of these by-
products and much less is known about these by-products than the organic halogens.
2.3.3.2 Aldehydes
The specific aldehydes of concern include:
Formaldehyde
Acetaldehyde
Propanal
Butanal
Pentanal
Hexanal*
Heptanal*
Octanal*
Benzaldehyde*
Nonal*
Decanal*
Glyoxal
Methyl Glyoxal
* Compounds are optional under the ICR
The structural formulas for aldehydes are illustrated in Figures 2-8 (a and b)
while physicochemical properties are summarized as follows (Weast, 1982-1983; Windholz,
1983):.
Jacangelo, et_aL (1989), studied the occurrence of formaldehyde and acetaldehyde in
systems employing a number of alternative disinfection schemes. In general, ozonation followed by
chlorination was found to yield the highest levels of these two aldehydes. In addition, ozonation
prior to chloramination was shown to produce more of these aldehydes than chloramination alone.
Chlorine has also been observed to form aldehydes without prior ozonation (Jacangelo, et al..
1989).
2-12
-------
FIGURE 2-8a
ALDEHYDES
H
H
H '
H
H1
FORMALDEHYDE
H H
I I
HC CC
I I I
H H H
PROPANAL
H
ACETALDEHYDE
O O .
GLYOXAL
H
H
H-
H H H O
III II
CC CC
I I I I
H H H H
H
H
] I I
rn
H H H
-------
FIGURE 2-8b
ALDEHYDES
HH-HHHHHQ
I I I I I I I II
HCC C C C C CC H
I I I I I I I I
HH H H H -H H H
OCTANAL
H-H H H H H H H O
I I I I I I I I II
HC CCC-^C CCCCH
I I I I I I I I I
HHHHHHHHH
NONAL
HHHHHHHHHQ
H-Ll-!-!-!-!-!-!-!-"
H i I i i i I I r i i
HH H HH H H H H H
DECANAL
BENZALDEHYDE
-------
FIGURE 2-9
-------
TABLE 2-1(h>
PHYSICOCHEMICAL PROPERTIES FOR VARIOUS ALDEHYDES
Compound
:ormaldehyde
Acetaldehyde
Propanal
Butanal
'entanal
iexanal
ieptanal
Dctanal
Nonal
Decanal
Glyoxal
Methyl Glyoxal
Molecular
Weight
30.1
44.1
58.08
72.10
NA
100.2
114.2
NA
NA
156
58.04
NA
Solubility .
(mg/L)
NA
NA
160,000
71,000
NA
NA
NA
NA
NA
NA
15
NA
Melting
Point (ฐC)
-92
-121
-81
-99
NA
-56
-43.3
NA
NA
213
51
NA
Boiling
point :eฐc)
-21
20.8
49
74.8
NA
128
152.8
NA
NA
213
NA
NA
Vapor
Pressure
(mmHg)
400 @ -33 ฐC
740 @ 20 ฐC
NA
NA
NA
10 @ 20 ฐC
3 @ 25 ฐC
NA
NA
NA
NA
NA
Glaze and co-workers have identified numerous aldehydes in finished waters from
treatment plants employing ozonation (Glaze, et al.. 1989a; Glaze, et al.. 1989b; Glaze, et al..
1989c). Aldehydes identified thus far include, but are not limited to, the four aldehydes noted
above as well as propanal, butanal, pentanal, octanal, nonanal and decanal.
According to Glaze (1988), formaldehyde yields are apparently an order of
magnitude higher than the yield of higher molecular weight aldehydes and may continue to increase
hours after ozonation is completed, especially at elevated temperatures. The molar yield of
heptanal, one of the most prevalent organic ozone by-products, appears to be on the order of 0.016
percent of the molar dissolved organic carbon (DOC) concentration in the water. This is about an
order of magnitude lower than the most prevalent chlorination by-products (THMs). Hexadeca-9-
enoic acid has been identified as a naturally occurring organic precursor of heptanal. Glaze et_al.
(1991) indicated that the origin of the ozonated by-product's is not known, but it is presumed. They
are formed by the addition of ozone to either unsaturated side chains or aromatic functionality's of
natural organic matter, which has a multiplicity of organic structural units. Aldehydes may. be
viewed as surrogates for very large numbers of polar organics that are formed at low levels when
ozone is used in water treatment.
2-13
-------
Among the major ozonation by-products, aldehydes and carboxylic acids have
the highest concentrations (Glaze and Weinberg, 1993). The dialdehyde, glyoxal (Figure 2-8a) ,s
also found in drinking water treated with ozone
2.3.3.3 Assimable Organic Carbon (Optional under the ICR)
Assimilable organic carbon (AOC) is not a specific organic contaminant but is a
generally used surrogate measure of water's ability to provide a carbon food source for
microorganisms. AOC is comprised of many chemical species, including the aldehydes and
carboxylic acids noted above. Because AOC is not a specific chemical contaminant, there are no
specific chemical related health effects that can be ascribed to AOC. However, since AOC is a
surrogate measure of bacterial re-growth potential, it can be used to indicate the potential for re-
growth of opportunistic pathogens in distribution systems. Research has shown that re-growth of
heterotrophic bacteria is limited when AOC levels are less than 10 ug of acetate carbon equivalents
per liter. However, strong bacterial re-growth has been observed when AOC levels are greater
than 50 ug of acetate carbon equivalents per liter. The following briefly describes the general
procedure used to determine the AOC concentration of given water:
. Allow the selected microorganism to be grown on the water sample of interest.
This selection is important since one -microorganism may grow at a faster rate
than another microorganism on one substrate while growing at a slower rate on
another substrate. If several tests are run, each with a different microorganism.
then the results may provide some indication of the chemical distribution of the
AOC. . .
. Once the microorganism is selected, allow the microorganism species to grow in
a known volume of the water of interest.
. After some period of time, measure the number of microorganisms that grew in
the sample.
. Compare the number of microorganisms grown in the water sample>th the
maximum yield of that microorganism species on a known substrate. The value
of AOC for the water sample of interest is then given as the equivalent
concentration of the known substrate.
For example, one researcher may elect to determine the AOC content of a water
sample by examining the growth of Psendomonas fluorescens strain PIT. After some specified
time period, the researcher finds that X microorganisms grew in the water sample. The researcher
2-14
-------
then elects to compare that growth with the growth of Pseudomonas fluorescens strain PI7 in an
aqueous solution of acetate. The maximum yield'is given as Y microorganisms grown per ug of
acetate carbon-consumed. The AOC of the sample is obtained from the ratio X:Y and is given in
Hg of acetate carbon equivalents per liter.
All of the following information on AOC was obtained from .a report released by
the American Water Works Research Foundation (AWWARF) (AWWARF, 1988).
AOC formation studies,' primarily performed in the Netherlands, have shown
that both ozonation and chlorination can yield increased levels of AOC. This is believed to be the
result of oxidizing high molecular weight organics to much smaller and more readily bioassimilable
molecules. Field scale surveys have shown an AOC (measured through the use of Pseudomonas
fluorescens strain P17) increase of 200 to 1000 percent after ozonation at dosages of 2.0 to 3.5
mg/L. Other full scale surveys have shown that chlorination at dosages of 0.4 to 3.0 mg/L can
increase AOC anywhere from 0 to 140 percent. Other tests have also indicated that AOC may be
increased by chlorine dioxide oxidation.
"
2.3.3.4 Biodegradable Dissolved Organic Carbon (Optional for the ICR)
Biodegradable dissolved organic carbon (BDOC) is the fraction of organic
matter available to microorganisms as substrate. BDOC can be measured by bio-mass-based or
DOC (dissolved organic carbon based methods) Langlais et al. (1991); Huck, (1990). DOC-based
methods determine the amount of organic matter available as nutrients to bacteria by measuring the
amount of (DOC) in a water sample, inoculating the sample (Allgeier et al., 1996). The sample
can be inoculated with a suspension of bacteria or with sand that has been colonized by bacteria.
\
Biomass based methods estimate BDOC by measuring the growth of organisms over time in a
given water sample and obtaining the BDOC value by correlation. Either known organisms or a
mixture of naturally-occuring organisms are utilized. Several BDOC methods are .summarized by
Huck (1990) and Allgeier etal. (1996).
The removal of BDOC during drinking water treatment can yield a more
biologically stable water, reduce disenfectant demand, and help control DBP formation. BDOC
can also be used to gauge the efficiency of biological treatment for DOC removal.
2-15
-------
FIGURE 2-10
CARBOXYLIC ACIDS
HEPTANOIC ACID
-------
2.3.4 Inorganic By-Products
2.3.4.1 Bromate
Bromate is also regulated under Stage I of the D/DBP rule (ref section 226)
2.3.4.2 Chlorate/Chlorite
Chlorite is also regulated under Stage I of the D/DBP rule (ref. section 2.2.5) Chlorate, molecular
weight 83.4, is produced by ozonation of chlorite, chlorine dioxide and hypochlonte (Rice and
Gomez-Taylor, 1986). Therefore, if chlorate formation is not desirable, carrying a free chlorine,
chlorite or chlorine dioxide residual into an ozone contactor is not recommended. The structural
formula of chlorate is found in Figure 2-9.
2.4 OTHER DBFs
2.4.1 Carboxylic Acids
The specific carboxylic acids of concern include:
Hexanoic Acid, and
Heptanoic Acid.
The structural formulas of these two carboxylic acids are illustrated in Figure 2-10 while
physicochemical properties are summarized as follows (Weast, 1982-1983; Windholz, 1983):
TABLE 2-l(i)
PHYSICOCHEMICAL PROPERTIES OF CARBOXYLIC ACIDS
Compound
Hexanoic Acid
Heptanoic Acid
: Molecular
Weight
116.2
130.2
Solubility
(mg/L)
11,000@
20ฐC
2,410@20ฐC
V %
. Melting
Point (ฐC)
-2
-7.5
Boiling
Point (ฐC)
205
223
Vapor
Pressure
(mmHg)
0.2 @ 20ฐC
10(งjll3.2ฐC
Glaze, et al. (1989b), have also identified numerous carboxylic acids, including the two
noted above, in finished waters from several treatment plants employing ozonation. Oxidation of
previously formed aldehydes to carboxylic acids is a probable mechanism, adding small molecular
2-16
-------
FIGURE 2-11
CHLOROPHENOLS
2,4-DICHLOROPHENOL
2-CHLOROPHENOL
2,4,6-TRICHLOROPHENOL
-------
weight fatty acids to the naturally occurring fatty acids that are found in natural waters (Glaze.
1988).
2.4.2 Chlorophenols
The specific chlorophenols of concern include:
2-Chlorophenol;
2,4-Dichlorophenol, and
2,4,6-Trichlorophenol.
The structural formulas of these three chlorophenols are illustrated in Figure 2-11
while physicochemical properties are summarized as follows (Weast, 1982-1983;
Windholz, 1983):
* TABLE 2-l(j)
PHYSICOCHEMICAL PROPERTIES OF CHLOROPHENOLS
-
t
Compound
2-Chlorophenol
2,4-Dichlorophenol
2.4,6-Trichlorophenol
Molecular
Weight
128.6
163.0
197.4
Solubility
(mg/L)
28,500 @
20ฐC
4,600 @ 20ฐC
800 @ 25ฐC
Melting
Point (ฐC)
9
45
69.5
Booting
Point (ฐC)
174.9
210
246
Vapor
Pressure
(mmHg)
10@56ฐC
110@146ฐC
NA
Field studies suggest that the three chlorophenols listed above rarely occur at detectable
concentrations in finished waters entering the distribution system (Krasner, et al.. 1989).
2.4.3 MX
MX, 3-chloro-4-(dichloromethyl)-4-oxobutenoic acid is a very potent mutagen and
. has been identified in disinfected drinking waters in Finland, the United States and Great
Britain. A survey of 26 utilities in Finland found MX concentrations ranging from 0-67
nanograms per liter (ng/L) in finished water samples (Kronberg and Vartianinen, 1989).
MX concentrations in finished waters from conventional treatment plants were dependent
on the disinfection scheme employed. The following results were observed for
2-17
-------
FIGURE 2-12
MX
(Closed Form)
-------
conventional treatment plants using surface water sources.
TABLE 2-l(k)
CONVENTIONAL TREATMENT PLANT DISINFECTANTS
Disinfectants Used
Pre and Post Chlorination
Post Chlorination
Chlorine Dioxide/Chlorine
Ozone/Chloramine
Average MX
Concentration
. (ftg/L)
48
20
18
Not
Detected
Std. Dev.
(ng/L)
25
15
8
~
Range
(ng/L)
11-67
0-46
12-24
"
.Number of
Observations
4
14
2
1
Average raw and finished water TOC levels were similar for each disinfection scheme.
The study also determined that MX was responsible for 15-57 percent of the mutagenic
activity in the samples where MX was found.
A survey of three finished waters in the United States also identified MX in each of
the three waters (Coleman, etal.. 1989). The following results were observed:
TABLE 2-1(1)
RAW WATER AND FINISHED WATER DISINFECTION SCHEMES
Typical
Raw Water
20-25
23
1-3
TOC Ranges
-------
2.5 OTHER INORGANIC DBFs
2.5.1 Introduction
The specific inorganic DBFs of concern include.
lodate;
Hydrogen peroxide; and
Ammonia.
The structural formulas of these three inorganic DBFs are illustrated in Figure 2-13
while physicochemical properties are summarized as follows (Weast, 1982-1983;
Windholz, 1983):
TABLE 2-l(m)
PHYSICOCHEMICAL PROPERTIES OF INORGANIC DBPs
Compound
Molecular
Weight ,
.Point.CC)
Point (ฐC)
Vapor
Pressure
(mmHg)
NA
lodate
174.9
NA
NA
Hydrogen peroxide
34
-0.41
150.2
NA
Ammonia
17.0
-77.7
-33.5.
0.33
2.5.2 lodate
The chemical structure of iodate is illustrated in Figure 2-13.
2.5.3 Hydrogen Peroxide
Hydrogen peroxide is a by-product of water treated by ozone (Glaze and Weinberg,
1993) and is being considered for regulation in Europe. The chemical structure of
hydrogen peroxide is illustrated in Figure 2-13.
2.5.4 Ammonia
Ammonia is present in many water supplies, particularly those downstream of
municipal wastewater treatment plant discharges. Ammonia is also introduced to drinking
water supplies through chloramination practices. Chloramines are formed by the reaction
2-19
-------
FIGURE 2-13
INORGANIC BY-PRODUCTS
HYDROGEN PEROXIDE
CHLORITE
H
H H
AMMONIA
BROMATE
IODATE
-------
of free, chlorine and ammonia. Because dichloramine and trichloramine lead to taste and
odor problems, excess amounts of ammonia are often added to favor the formation of
monochloramine. If the mass ratio between free chlorine and ammonia is less than 5:1,
then ammonia will be present in the finished drinking water. In most drinking water
treatment situations, the ammonia is present in the form of the ammonium ion however,
ammonia is most toxic in its unionized form.
In addition to any chemical health effects which may be associated with ammonia,
ammonia is also responsible for the growth of autotrophic ammonia oxidizing bacteria.
According to several-reports (Ike, et_aL 1988; Wolfe, et_aJL, 1989) these bacteria oxidize
ammonia to nitrite and nitrate and fix carbon dioxide to fulfill energy and carbon needs.
the formation of nitrite and nitrate is accompanied by a rapid disappearance of the
chloramine residual and a rapid increase in heterotrophic bacteria plate count (HPC). .
Under such conditions, systems may have difficulty meeting disinfectant residual
requirements in the Surface Water Treatment Rule. In addition, if ammonia is present at
concentrations greater than or equal to 1 mg/L as nitrogen, nitrite formation could
conceivably exceed a proposed nitrite MCL of 1 mg/L as nitrogen. The chemical structure
of ammonia is illustrated in Figure 2-13.
2.6 DISINFECTANT RESIDUALS
The specific disinfectant residuals of interest include:
Chlorine
Hypochlorous acid
Hypochlorite ion
Chloramines
Monochloramine
Dichloramine
Trichloramine (Nitrogen Trichloride)
Chlorine Dioxide
The structural formulas of these disinfectant residuals are illustrated in Figure 2-14 while
/
2-20
-------
FIGURE 2-14
DISINFECTANT RESIDUALS
CHLORINE
HYPOCHLOROUS ACID HYPOCHLORITE ION
CHLORAMINES
Cl Cl ci
H H H Cl Cl Cl
MONOCHLORAMINE DICHLORAMINE . TRICHLORAMINE
CHLORINE DIOXIDE
-------
physicochemical properties are
1983).
summarized as follows (Weast, 1982-1983; Windholz,
TABLE 2-l(n)
PHYSICOCHEMICAL PROPERTIES OF DISINFECTANT RESIDUALS
Compound
Molecular
: y *-
Weight
Solubility
(mgfl>)
Melting
MtfPQi'
Vapor^
.Pressure
(mm Eg)
2 6 1 Maximum Residual Disinfectant Levels
similar to MCLGs, Maximum Residual Disinfectant Level Goals (MRDLGs) are a
health goal and are not legally enforceable. The MRDLGs for the Stage I regulation are
presented as follows:
TABLE 2-l(o)
NON-ENFORCEABLE HEALTH GOALS (MRDLGs) FOR D/DBP
Chlorine Dioxide (as C1O2)
Under this region, Maximum Residua. Disinfectant Levels (MRDLs) are established
for ,he most commonly used disinfectants and are enforceable .units, similar to MCLs. The
MRDLS for Stage 1 of the D/DBP Rule are presented as follows.
2-21
-------
TABLE 2-l(p)
MAXIMUM RESIDUAL DISINFECTANT LEVELS FOR D/DBP
Compound
Chlorine (as Cl2)
Chloramine (as Cl2)
Chlorine Dioxide (as C1O2)
MRDLs
STAGE I D/DBP RULE
4.0 mg/L
4.0mg/L
0.8 mg/L
When chlorine gas is dissolved in water, it reacts to form hypochlorous (HOC1) acid and
hydrochloric (HC1) acid as follows:
ci2 + H2o --> HOCI + H* + cr
The dilution of commercially available sodium hypochlorite in water also results in the production
of hypochlorous acid.
NaOCl + H20 > HOCI + Na+ + OH
Hypochlorous acid dissociates to form hypochlorite and hydrogen ions:
HOCI ~> FT + OC1
Hypochlorous acid and hypochlorite ions occur in equal concentrations at pH 7.6 at 25ฐC (Stumm
and Morgan, 1981). As pH falls below this level, hypochlorous acid predominates. As pH rises
above this level, hypochlorite ion predominates, with virtually no hypochlorous acid present at pH
levels above 9. The relative fractions of hypochlorous acid and hypochlorite ion are also dependent
on temperature. At a fixed pH, the fraction of hypochlorous acid decreases as temperature
increases .(White, 1986). Although both hypochlorous acid and hypochlorite ions are strong
oxidizing agents, hypochlorous acid is the stronger of the two. As a result, oxidation reactions and
disinfection reactions are more effective during conditions when hypochlorous acid predominates.
2-22
-------
Chloramines are formed by the reaction of chlorine and ammonia, and' can exist as
monochloramine, dichloramine, or trichloramine. The formation reactions are as follows:
Monochloramine: NH3 + HOC1 > NH2C1 + H20
Dichloramine: NH2C1 + HOC1 > NHC12 + H20
Trichloramine: NHC12 + HOC! > NC13 + H20
The particular form of chloramine is dependent on several factors including the ratio of
chlorine to ammonia, temperature and pH. It should be noted that organic chloramines
may form during chloramination. These can often erroneously been measured as free
chlorine, however, have no substantial disinfection capability.
,Wheri the ratio of chlorine to ammonia is equimolar (5:1 by weight) or less,
monochloramine is preferentially produced. The fastest conversion of free chlorine to
monochloramine occurs at a pH of 8.3. This reaction rate also decreases with decreasing
temperature.
Dichloramine forms when chlorine to ammonia ratios are between 5:1 and 10:1 on a
weight basis. This reaction may take an hour or more at pH 7 and above, however, the
reaction rate increases markedly as the pH approaches 5. Like monochloramine,
dichloramine reaction rates are affected by decreasing temperatures. Dichloramine
produces a noticeable taste and odor problem (White, 1986).
Dichloramine is unstable and reacts quickly with itself to form nitrogen gas in
accordance with the following reaction (Isaac and Morris, 1983):
s
2NHC12 + H2O > N2 + HOC! + 3H* + 3 CT
j
In most cases applicable to drinking water treatment, the decomposition of dichloramine
to nitrogen gas is favored over the formation of trichloramine. Because of this reaction,
monochloramine is the predominant chloramine in most cases, particularly when pH is
greater than 7.
2-23 '
-------
Chlorine to ammonia ratios greater than 7.5:1 on a weight basis may result in the
formation of trichloramine. Trichloramine is most readily formed at pH levels below 5,
however, if the chlorine to ammonia ratio is significantly high, trichloramine can be
maintained at higher pH levels (White, 1986).
Chlorine dioxide can be generated from sodium chlorite (NaClO2) and chlorine gas
as follows:
2NaC102 + C12 > 2C102 + 2NaCl
Chlorine dioxide may dissociate to chlorite and chlorate at high pH levels. It also reacts
readily with reduced species in solution to form chlorite.'
2.7 SUMMARY
*
DBF formation depends on many factors including .the type of disinfection strategy
employed, disinfectant dosages and water quality characteristics, such as pH and
concentrations of NOM. Table 2-1 provides a summary of fiill scale and pilot scale
evaluations that examined DBF formation before and after a modification in disinfectionr
practice (JacangelOi etal.. 1989). Most modifications were found to decrease some DBFs
while increasing other DBFs. In general, strategies incorporating free chlorine as 'both a
primary and secondary disinfectant produced the highest quantities of THMs, HAAs and
HANs. However, the application .of ozone as. a primary disinfectant prior to the
application of chlorine as a secondary disinfectant may increase THM levels above those
reached by chlorination alone. This has primarily been observed when chlorination is
performed at elevated pH levels (Reckhow, etal.. 1986).
When ozone was introduced as a> primary disinfectant, aldehyde levels were
increased in all cases. Ozone was also observed to increase haloketone, chloropicrin and
chloral hydrate formation in several cases. The most significant quantities of cyanogen
chloride were generally produced by chloramination strategies. .
Table 2-2 shows a summary of pH impacts on the formation of organic halogens
.2-24
-------
(Stevens, et al.. 1988). While it isVwidely recognized that THM formation increases with
increasing pH, Table 2-2 shows that the formation of several other organic halogens
decreases with increasing pH. This has important implications for utilities that wish to use
increased pH levels as a.strategy for controlling corrosion in distribution systems.
The impacts of treatment process modifications and water quality characteristics on
DBF formation must be viewed in light of human health risks. EPA is currently developing
several human health effects documents scheduled for completion in November 1998.
2.8 REFERENCES :
A. 'Adin, J. Katzhundler, D. Alkaslassy and Ch. Rav-Acha (1991) "Trihalomeihane
Formation in Chlorinated Drinking Water: A Kinetic Model." Water Research
Vol. 25 No. 7 p. 797.
E. M. Aieta and P. V. Roberts (1986). "Kinetics of the Reaction between Molecular
Chlorine and Chlorite in Aqueous Solution." Environ. Sci. Technol.. 20(1), p. 50.
S C Allgeier, R. S. Summers, J. G. Jacangelo, V. A. Hatcher, D. M. Moll, S. M: Hooper,
J. W. Swertfeger, and R. B. Green (1996). "A Simplified and Rapid Method for
Biodegradable Dissolved Organic Carbon Measurement." Proceedings of the 1996
AWWA Water Quality Technology Conference, Boston, MA.
American Water Works Association Research Foundation and Keuringsinstituut voor
Waterleidingartikelen (1988). The Search for a Surrogate. AWWA, Denver, CO.
G L Amy, L. Tan and M. K. Davis (1991) "The Effects of Ozonation and Activated
Carbon Adsorption On Trihalomethane Speciation." Water Research 25 (2) p. 191
G. L. Amy, P. A. Chadik and Z. K. Chowdury '(1987). "Developing Models for Predicting
Trihalomethane -Formation Potential and Kinetics." J. AWWA. 79(7), p. 89..
W E Coleman J. W. Munch, P. A. Hodakievic, F. C. Kopfler, J. R. Meier, R. P.
Streicher and H. Zimmer (1989). "GC/MS Identification of Mutagens in Aqueous
Chlorinated Humic Acid and Drinking Waters Following HPLC Fractionation of
Strong Acid Extracts." In Rioha^rds of Drinkinp Water Treatment. R. A. Larson
(ed.), Lewis Publishers, Chelsea, MI, page 107.
Q A Cowman and P.C. Singer (1996), Effect of Bromide Ion on Haloacetic Acid
Speciation Resulting from Chlorination and Chloramination of Aquatic Humic
substances . Env. Sci & Tech.
Vol. 30, No 1. ' '
2-25
-------
J P. Duguet, Y. Tsutsumi, A. Bruchet and J. Mallevialle (1985). "Chloropicrin in Potable
Water: Conditions of Formation and Production During Treatment Processes "
Water Chlorination: Chemistry. Environmental Impact and Health Effects vol 5
Lewis Publishers, p. 1201.
EPA 814-B-96-002 (1996) DBP/ICR Analytical Methods Manual
W. H. Glaze (1988). "Summary of Ozone Byproducts Workshop." Held at UCLA on
Jan. 13-15, 1988. Memo dated Mar. 18, 1988.
W. H. Glaze, M. Koga, E. C. Ruth and D. Cancilla (1989a). "Application of Closed-Loop
Stripping and XAD Resin Adsorption for the Determination of Ozone By-Products
from Natural Water." in Biohazards of Drinking Water Treatment R. A Larson
(ed.), Lewis Publishers, Chelsea, MI, p. 201.
W. H. Glaze, M. Koga, D. Cancilla, K. Wang, M. J. McGuire, S. Liang, M. K. Davis C
H. Tate and E. M. Aieta (1989b). "Evaluation of Ozonation By-Products from
Two California Surface Waters." J. AWWA. 81(8), p. 66.
W. H. Glaze, M. Koga and D. Cancilla (1989c). "Ozonation By-Products. 2.
Improvement of an Aqueous-Phase Deriyitization Method for the Detection of
Formaldehyde and Other Carbonyl Compounds Formed by the Ozonation of
Drinking Water." Environ. Sci. TechnoL 23, p. 838.
W H. Glaze, H.S. Weinburg, S.W. Krasner and M. J. Selimenti (1991) "Trends In
Aldehyde Formation and Removal Through Plants Using Ozonation and Biological
Active Filters" presented at the 1991 Annual AWWA Conference, Philadelphia,
PA. -
W. H. Glaze, H.S. Weinburg (1993) Identification and Occurrence of Ozonation By-
Products in Drinking Water, American Water Works Association Research
Foundation: Denver, CO.
W.H. Glaze, H.S. Weinberg, and I.E. Cavanagh. (1993; Evaluating the Formation of
Brominated DBFs during Ozonation, Jour. AWWA 85( 1 )96.
W. R. Haag and J. Hoigne (1983). "Ozonation of Bromide Containing Waters: Kinetics
of Formation of Hypobromous Acid and Bromate." Environ. Sci. Technol.. 17(51
p. 261. ...
P; M. Huck (1990). "Measurement of Biodegradable Organic Matter and Bacterial
Growth Potential in Drinking Water." J. AWWA. 82(7), p. 78.
2-26
-------
N R Ike R L Wolfe and E. G. Means (1988). "Nitrifying Bacteria in a Chloraminated
Driving Water System." Water Sci. Tech.. 20(1 1), p. 441 .
R A Isaac and J.C. Morris (1983). "Modeling of Reactions Between Aqueous Chlorine
and Nitrogenous Compounds." In Water Chlorination- Environmental Impact and
Health Effects. Vol. 4, Lewis Publishers, p. 63. ;
J G Jacangelo, N. L. Patania, K. M. Reagan, E. M. Aieta, S. W. Krasner and M. J
McGuire (1989) "Impact of Ozonation on the Formation and Control of
Disinfection By-Products in Drinking Water." J. AWWA. 81(8). p. 74. .
S W Krasner M J McGuire, J. G. Jacangelo, N. L. Patania, K. M. Reagan and E. M.
' ' Aieta (1989). "The Occurrence of Disinfection By-Products in U.S. Drinking
Water." J. AWWA. 81(8), p. 41.
T Kronbere and T Vartiainen (1989). "Ames Mutagenicity and Concentration of the
. sStutagen ^3-CW0ro-4-(c^
Geometric Isomer E-2-Chloro-3-(dichloromethylH-oxo-butenoic Acid in Drinking
Water." Submitf"* tn Mutation Research. ,
B Langlais, D...A. Reckhow, and D.R. Brink (eds.) 1991. Ozone in V***
frr,L^ ,nH Fleering. Cooperative Research Report AWWA Research
Foundation and Compagnie Generate des Faux, Lewis Publ., Chelsea, MI.
M J McGuire, S.W. Krasner and J. T. Gramith (1990). "Comments on Bromide Levels
in State Project Water and Impacts on Control of Disinfection By-Products.
H Pourmoghaddas, A.A. Stevens,- R.N. Kinman, R.C. Dressman, LA. Moore,. J.C.
IrTnd (1993) Effect of Bromide Ion on Fromation of HAAs During Chlonnation.
Jour AWWA 85 (1) 82.
D A Reckhow (1988) "Control of Disinfection Byproducts: Current Knowledge and
ResSS " Prepared for inclusion in AWWARF report Research Status of
Disinfection Byproducts. Nov. 1988.
D. A. Reckhow, B. Legube and P. C. Singer (1986). ^ ฐซ*ป
Precursors: Effect of Bicarbonate." Water Research. 20 (8), p. 987.
D A Reckhow and P.C. Singer (1985). "Mechanisms of Organic Hajide Formation
During Fulvfc ^Acid Chlorination and Implications with Respect to Preozonation
watปr rhlnrination- rhftmistrv. Environmental Impact and Health Effects., vol. 3,
Lewis Publishers, p. 1229.
2-27
-------
R. G. Rice and M. Gomez-Taylor (1986). '.-'Occurrence of By-Products of Strong
Oxidants Reacting with Drinking Water Contaminants - Scope of the Problem."
Environ. Health Perspectives. Vol. 69, p. 31.
P. C. Singer and W. K. (Weil (1987). "Technical Note: The Formation of Chlorate From
the Reaction of Chlorine and Chlorite in Dilute Aqueous Solution " J AWWA,
. 79(11), p. 75.
A. A. Stevens, L. A. Moore and R. J. Miltner (1988). "Formation and Control of Non-
Trihalomethane By-Products." Proceedings of the 1988 AWWA Water Quality
Technology Conference, St. Louis, MO.
R.S. Summers, M.A. Benz, H.M. Shukairy and L. Cummings. (1993) Effect of Separation
Processes on the formation of Brominated THMs, Jour AWWA 85(1)88.
W. Stumm and J. J. Morgan (1981). Aquatic Chemistry. 2nd Edition, John Wiley & Sons,
New York, NY.
H. Thibaud, J. DeLaat and M. Dore (1988). "Effects of Bromide Concentration on the
Production of Chloropicrin During Chlorination of Surface Waters: Formation of
Brominated Trihalonitromethanes." Water Research. 22(3), p. 381.
H. Thibaud, J. DeLaat, N. Merlet and M. Dore (1987). "Chloropicrin Formation in
Aqueous Solution: Effect of Nitrites on Precursors Formation During the Oxidation
of Organic Compounds." Water Research. 21(7), p. 813.
United States Environmental Protection Agency (1992). Draft Discussion of Possible
MCLGs for Disinfectants and Disinfection By-Products. Office of Science and
Technology.
United States Environmental Protection Agency (1988). In-House Pilot Studies for
Control of Chlorination Bv-Products. Organics Control Branch, Drinking Water
Research Division, Risk Reduction Engineering Laboratory, Cincinnati, OH.
R. C. Weast, ed. (1982-1983). CRC Handbook of Chemistry and Phvsics. 63rd Edition,
CRC Press, Inc., Boca Raton, Florida.
K. S. Werdehoff, and P. C. Singer (1987). "Chlorine Dioxide Effects on THMFP,
TOXFP, and the Formation of Inorganic By-Products." J. AWWA. 79(9), p. 107.
G. C. White (1986). Handbook of Chlorination. 2nd Ed, Van.Nostrand Reinhold
Company, Inc.
M. Windholz (1983). The Merck Index and Encyclopedia of Chemicals and Drugs. 10th
Edition, Merck & Company, Inc., Rahway, New Jersey.
2-28
-------
R. L Wolfe, N. I. Lieu, G. Izaguirre and E. G. Means (1989). "Ammonia Oxidizing
Bacteria in a Chloraminated Distribution System: Seasonal Occurrence,
Distribution and Disinfection Resistance." , Submitted to Applied Environ.
Microbiology, unpublished.
R. L. Wolfe, E. G. Means, M. K. Davis and S. E. Barrett (1988). "Biological Nitrification
in Covered Reservoirs Containing Chloraminated Water." J. AWWA, 80(9), p.
109.
H. Zimmer et. al., (199,0) Anal. Lett. Vol 23
2-29
-------
TABLE 2-1
IMPACTS OF DISINFECTION PRACTICE ON DBP FORMATION
(AFTER JACANGELO, ET AL.; REF. 5)
Disinfection By-Prodซc$ -
&^
Ozone/Cnforamlnes
Utility #36
Total Trihalomethanes
Tatar Hafeacgte Acids'^
Total Hatoacetonitriles
Total Aldehydes
Chtofoptorltt -
Chloral Hydrate
Cvwrogen CMorfete
decrease
"' {te$f^8Se ,
decrease
; &&ft&ซ >
not analyzed
fป-"dttซn0B-';
decrease
decrease
^"
-------
TABLE 2-2
IMPACTS OF pH ON ORGANIC HALOGEN FORMATION
(AFTER STEVENS. MOORE AND MILTNER; REF. 12)
;Hatogen
S.O
7.0
9.4
3tal Trihalomethanes
higher formation
efic Ackf
Dichloroacetic Acid
similar formation - perhaps slightly higher at pH 7
concentrations. betowS ug/i. ttencte^cKKjerrdbte.
itonocntoroaoctic Actet
Jibromoacetic Acid
concentrations below 1 pg/L. trends not discernible
cntaral Hydrate
i famSsafr.
concentrations below 1
, trends not discernible
concentrations below 2 gg/L trends not djscemlble
"'m^^ttattoteiX^O.S tidgL1ป>araaMiBiปHi'.
Trichtoroacetonitrile
1 ,1 .t^
-------
3.0 TECHNOLOGIES AVAILABLE FOR DBF CONTROL
3.1 INTRODUCTION
The central question in the water industry at the present time is how to attain turbidity
goals less than 0.1NTU, minimize exposure to Giardia and Crvptosporidium. and at the same
time limit DBFs.
As discussed in Chapter 1, three general approaches to DBF control are as follows:
Remove NOM prior to disinfection and/or oxidation.,
Use an alternative primary/secondary disinfection scheme that does not form
DBFs at levels considered adverse to human health.
Remove DBFs after they are formed.
Technologies available for DBF control are identified in this chapter. Table 3-1 lists
the unit processes generally considered for DBF control. A more detailed description of these
technologies and other water treatment can be found in AWWA (1990), Montgomery (1985),
and Sontheimer et. al. (1988). General descriptions of the unit processes considered in this
document are provided in this section. More detailed discussions of the unit processes that
are relevant to the above three types of control technologies could be found in subsequent
chapters.
3.2 COAGULATION/FILTRATION
_. *.-
*.
Coagulation/filtration is a treatment process by which the physical or chemical
properties of dissolved colloidal or suspended matter are altered such that agglomeration is
enhanced to an extent that the resulting particles will settle out of solution by gravity or will
be removed by filtration. Coagulants change surface charge properties of solids to allow
agglomeration and/or to enmesh particles into a precipitate. In either case, the final products
are larger agglomerated particles, or floe, which more readily filter or settle under the
influence of gravity.
3-1
-------
Table 3-1
CANDIDATE DBF CONTROL PROCESSES
Conventional Processes
. - Alum Coagulation / Filtration
. - Ferric Coagulation / Filtration
- Precipitative Softening
AHcnrptinn Processes
- Granular Activated Carbon
- Powdered Activated Carbon
- Resin Asorbents
Oxidation an** nuinff^rtinn Processes
- Ozone
- Chlorine Dioxide
- Potassium Permanganate
- Chlorine
- Chloramines
- Advance Oxidation Processes
A grot inn ProCCSSCS
- Packed Column Aeration
- Diffused Aeration
The coagulation/filtration process has traditionally been used to remove solids from
drinking water supplies. However, the process is not restricted to the removal of particles
Coagulants render some dissolved species (e.g., NOM, inorganics and hydrophobe SOCs)
insoluble and the metal hydroxide particlesi product by the addition of metal sal. coagulants
Onto* aluminum sulfate and ferric chloride or ferric sulfete) am adsorb other d-ssolved
species Major components of a basic coagulation/filtration' facility, as shown in Fซure 3-1,
.include chemical feed systems, mixing equipment, basins for rapid mix, floccubuon, setting,
3-2
-------
COAGULATION/FILTRATION TREATMENT PLANT
COAGULANT
AND
POLYMER
FEEDERS
ALKALINITY
FEEDER
FILTRATION
CLEARWELL
STORAGE
db
SEDIMENTATION
/v
/
RAW WATER
PUMPING
RAPID
MIX
FLOCCULATION
TO
DISTRIBUTION
SYSTEM
FILTER
BACKWASH
PUMP
FILTER BACKWASH
WASTE WATER
TO WASTE TREATMENT
AND DISPOSAL
tป
SEDIMENTATION BASIN SLUDGE
-n
O
C
31
m
-------
filter media, sludge handling equipment and filter backwash'facilities Settling may not be
necessary in situations where the influent particle concentration is very low. Treatment plants
without settling are known as direct filtration plants.
Variations in coagulation/filtration include the use of dissolved air floatation (DAF) in
lieu of sedimentation basins or solids contact clarifiers, and the use of coagulants in
conjunction with membrane processes such as microfiltration and ultrafiltration. Other
variations in coagulation/filtration include upflow solids contact units, patented processes and
adsorption clarifiers. Full scale DAF plants are still rare in the United States; however, there
is a heightened level of interest in this technology due to its promise of improved removals
of protozoan cysts.
A typical DAF treatment scheme includes coagulant addition, rapid mixing,
flocculation, followed by a floatation tank and filtration. Minute air bubbles, are introduced
into the flocculation tank by dissolving air under pressure into a recycle stream and releasing
the pressure using nozzles or needle valves. Solids are floated to the top and can be scraped
periodically. The typical DAF loading rates of (4 to 6 gpm/ft2) are an order of magnitude
higher than those practiced in conventional sedimentation basins, while the DAF detention
times (5 to 15 minutes) are an order of magnitude lower. The DAF process is very effective
in the removal of low density solids, such as algae, bacteria, protozoan cysts, and precipitated
metallic hydroxides of humic material; solids which are difficult to.remove with conventional
sedimentation. In addition, the use.of DAF can result in air stripping of volatile organic
compounds and compounds that cause taste and odor. Membranes could be used as the final
filtration steo after DAF.
The use of coagulants with low-pressure membrane processes such as microfiltration
- and ultrafiltration can result in a slightly improved NOM removal in addition to significant
paniculate removal. The membrane process replaces traditional media filters for paniculate
removal and coagulant addition improves NOM removal.' As the use of low-pressure
. membranes for paniculate removal increases, this variation of coagulation/filtration could
become more widespread.
3-3
-------
LOW LIFT PUMP
LIME SOFTENING TREATMENT PLANT
\ | LIME FEED
t-| I SODA ASH FEED (OPTIONAL)
POLIMER FEED
RECARBONATION BASIN
(OPTIONAL) FILTER
CLEARWELL
HIGH LIFT PUMP
UPFLOW
SOLIDS
CONTRACTOR
TO
DISTRIBUTION
SYSTEM
CARBON DIOXIDE FEED
(OPTIONAL)
FILTER BACKWASH PUMP
FILTER BACKWASH
WASTEWATER
TO WASTE
TREATMENT
DISPOSAL
CLARIFIER SLUDGE
TO WASTE
TREATMENT
NO DISPOSAL
O
C
31
m
CJ
I
M
-------
3.3 PRECIPITATIVE SOFTENING/FILTRATION
The precipitative softening process is used to remove hardness from raw drinking water
sources. In most waters, hardness is primarily due to the presence of calcium and magnesium.
The American Water Works Association (AWWA, 1968) recommends that finished water
hardness levels not exceed 80 mg/L as calcium carbonate (CaC03). The precipitative
softening process removes hardness by producing a shift in carbonate equilibrium conditions.
This shift is obtained by raising pH to convert bicarbonate ions to carbonate ions and to
minimize the solubility of calcium carbonate. The addition of lime (cafcium hydroxide) or
caustic (sodium hydroxide) is commonly employed to achieve the pH increase. Soda ash
(sodium carbonate) is added if insufficient carbonate is present to precipitate calcium to the
desired level. .Softening for calcium removal is usually operated in a pH range between 9.0
and 9.5.
For magnesium removal, excess lime is added beyond the point of calcium carbonate
precipitation in order to precipitate magnesium hydroxide. Magnesium removal is usually
achieved in sufficient quantities if pH levels are greater than 10.5.
Adjustment of pH is required if the softened water pH level is too high for potable use
or if the finished water remains supersaturated with respect to calcium. The most common
form of pH adjustment in softening plants is recarbonation with carbon dioxide.
Lime, caustic and/or soda ash dosages are dependent on several raw water quality
parameters including hardness, alkalinity, pH, temperature and total dissolved solids. A
typical softening plant is illustrated in Figure 3-2. Major components of this process include
the following:
Lime or caustic feed system.
Polymer feed system.
i
Soda ash feed system (optional).
k. Upflow solids clarification.
*
Carbon dioxide feed -system (optional).
3-4
-------
Recarbonation basin (optional).
Filtration.
i
Metal salt coagulants, typically ferric chloride, are added for surface waters with
appreciable amounts of particles.
3.4 ADSORPTION PROCESS
3.4.1 Granular Activated Carbon
The application of granular activated carbon (GAC) adsorption for drinking water
treatment involves the following major process design considerations:
Empty bed contact time (EBCT, volume of empty contactor divided by
flowrate).
Reactivation interval or frequency.
GAC usage rate (pounds of GAC used per gallon of water treated).
. Pretreatment.
Contactor configuration (e.g., downflow versus upflow, pressure Versus gravity,
single-stage versus multi-stage or parallel, filter adsorber versus post-filter GAC
contactor).
. . " /
Method of GAC reactivation (e.g., on-site versus off-site).
i
The EBCT provides an indication of the quantity of GAC on-line at any, one time, and
thus reflects the capital cost for the system. The EBCT is an important design parameter and
may have some impact on the GAC usage rate for removal of NOM.
GAC adsorption, as practiced in water treatment, is an unsteady state process, with the
effluent concentration increasing with time. Once the effluent concentration meets the
maximum allowable concentration for a contaminant, the GAC column must be taken offline >
and the GAC replaced with reactivated or fresh GAC. The operation time to this maximum
effluent concentration is termed the reactivation interval.
3-5
-------
The GAC usage rate provides an indication of the rate at which the GAC is exhausted
or replaced and, therefore, primarily affects the operating cost of the GAC treatment system
For a full scale GAC. installation, the GAC usage rate often dictates the choice between
providing an on-site reactivation system or replacing the spent GAC with virgin GAC. It also
affects the costs of GAC handling (i.e. storage, dewatering, attrition losses and
transportation). ' .
GAC systems may require some kind of pretreatment to prevent clogging of the GAC
bed, to minimize the organic loading on the GAC and to improve cost effectiveness.
Clogging of the GAC bed could be caused by suspended solids in the raw water or by
precipitation of calcium carbonate, iron and manganese on the GAC. Suspended solids
typically cause problems in surface water systems while carbonate 'sealing, iron and
manganese precipitation may occur in both surface and ground waters. When the GAC bed
life is long, clogging may also be caused by biological growths. Pretreatment methods include
coagulation, filtration or softening ahead of the GAC system. Conventional coagulation,
clarification and filtration processes may be optimized for organics removal to reduce natural
organic loading to the GAC bed.
Based oh the estimates of GAC usage rate-and contact time, a conceptual process
design can be developed by evaluating various contactor configurations. The two basic
modes, of contactor operation are downflow and upflow. Upflow beds typically have been
applied to situations where very long contact times (greater than 120 minutes) are required
and/or where the level of suspended solids is high. Downflow fixed bed contactors offer the
simplest and most common contactor configuration for drinking water treatment. The
contactors can be operated either under pressure or by gravity.
The choice of pressure or gravity is generally dependent upon the hydraulic constraints
of a given system. Pressure, contactors may be more applicable to groundwater systems
because pumping of the groundwater is required. Gravity contactors are generally more
suitable for surface water systems if sufficient head is available. Gravity contactors, when
used, are typically placed downstream of surface water filtration systems. Figure 3-3 displays
typical pressure and gravity contactors.
3-6
-------
FIGURE 3-3
TYPICAL GAC CONTACTORS
RAW RAW WATER INLET . TOP BAFFLE
SURFACE WASHER
APPROX. 50% FREEBOARD
FILTERED WATER OUTLET
LATERALS
SUPPORT LAYERS
CONCRETE SUB-FILL
SUPPORTS
PRESSURE CONTACTOR
SURFACE WASHERS
NORMAL WORKING LEVEL
SUPPORT LAYERS-
WASH TROUGH
GAC BED
OPERATING FLOOR
INLET
BACKWASH OUTLET
BOTTOM CONNECTION
GRAVITY CONTACTOR
-------
GAC contactors may be operated in a series or parallel configuration. In series
configuration, GAC in the first contactor is reactivated when the effluent of the second
contactor no longer meets the, treatment objective. Once the GAC ,in the first contactor is
replaced, the roles of the two contactors may be reversed where the second contactor
becomes the first contactor and vice versa. NOM is a mixture of unknown compounds which
separate along the bed in a manner proportional to their adsorption potential. Weakly
adsorbing components of NOM may irreversibly preload the GAC at the downstream end of
the bed and may, therefore, reduce the capacity of the bed for stronger adsorbing components
at the end of the bed.
In parallel operation, multiple GAC beds can be operated in a staggered pattern such
that effluents from beds with breakthrough concentrations higher than the treatment objective
are blended with effluents from beds with little or no breakthrough. In this manner, the
combined effluent concentration from the GAC beds can be kept less than the specified
treatment objective and exhausted beds would be reactivated in a staggered manner.
The choice between a single contactor and contactors in series or parallel is site specific
and depends on the type and concentration of the contaminant to be removed and its rate of
adsorption. This choice also depends on the types, concentrations and adsorption .rates of
competing contaminants. Furthermore, ah economic analysis should be performed based on
site specific data to decide on an optimal contactor configuration.
GAC contactors should be used when longer EBCTs are required while sand filters
with a GAC cap, where the top portion of the sand is replaced by GAC, can be used when
shorter EBCTs are feasible. These GAC capped filters are often called filter-adsorbers. -Filter
-adsorbers can also be filtration units which contain GAC alone. Because of their shorter
EBCTs, filter-adsorbers meet desired water quality goals for a much shorter period of time
than GAC contactors.. For treating seasonal changes in water quality or contaminant shock
loads, filter-adsorbers may have an economic advantage over post-filter GAC contactors.
/
One disadvantage of filter-adsorbers is that GAC losses are high during backwashing and
reactivation, and equipment separating GAC from sand may be required before reactivation.
An economic analysis considering GAC usage rate and treatment goals should be performed
h
to decide between GAC contactor and filter-adsorber modes of operation.
3-7
-------
Another consideration in the design of a GAC system is the method of GAC
reactivation. The two basic approaches to regenerating GAC are:
Off-site disposal or reactivation.
- On-site reactivation.
Based on information from GAC manufacturers, on-site reactivation does not generally
appear economical for systems where the GAC usage rate is less than 2,000 Ib/day.
Under the throwaway concept of off-site disposal, virgin GAC is generally purchased
in bags or drums. Once the GAC becomes exhausted, it is generally slurried by gravity to a
draining bin where the free water is removed and returned for treatment. The drained GAC
is then manually drummed'and shipped for landfilling or incineration.
The advantages to this approach lie mainly in its technical simplicity. It is a sound
approach for applications requiring a relatively small GAC usage rate, generally less than 500
Ib/day. The need to dispose of the spent GAC, however, is a definite drawback, especially
if testing demonstrates that the spent GAC is considered a hazardous waste. If this occurs,
it may become necessary to consider incineration of the spent GAC prior to disposal in a
landfill. Alternatively, a hazardous waste landfill could be used at increased cost.
The off-site reactivation approach is somewhat similar from a GAC handling standpoint
to the throwaway concept; however, it begins to assume some of the economies associated
with GAC reuse. When compared to other alternatives, however, the number of handling
steps and resulting GAC losses are a major disadvantage. The off-site reactivation approach
has generally proven most cost effective in applications.where the GAC usage rate falls in the
500 to 2,000 Ib/day range (Komegay, 1979).
The major equipment typically found in a GAC installation includes:
GAC Contactors - either common wall concrete orlined steel vessels. In either
case, provisions for underdrainage, backwashing, and removing the spent GAC
must be made.
GAC Storage - additional storage facilities may be required for handling of
virgin, reactivated and spent GAC, depending on the type and size of the facility.
GAC Transport Facilities - includes piping, valves and pumps.
3-8
-------
GAC Fill - the actual initial GAC charge depends on the type and volume of
GAC required for treatment.
3.4.2 Activated Carbon Fibers
One of the problems encountered in the use of GAC is that a number of large-scale
adsorption facilities are usually needed to treat a large quantity of water, since the adsorption
rate to GAC is very slow due to the diffusion resistance within GAC particles. Adsorbents
having both large adsorption capacity and adsorption rate are preferable. According to
Sakoda, etal. (1991) recently developed adsorbent, activated carbon fiber (ACF),. produced
by carbonizing and activating various raw materials such as rayon, phenol resins etc., may
satisfy this demand and may be promising material for future application. Evaluation of ACF
using isotherms and packed columns (Sakoda, etal.: 1991) concluded the following:
Trihalomethane adsorption capacities of ACFs investigated were comparable
with or slightly larger than those of conventional GACs usually used for the
THM control in drinking water. .
The breakthrough curve for single component THM adsorption was successfully
predicted using a mathematical model assuming that the adsorption equilibrium
is instantaneously established when a THM solution .contacts the ACF.
The rapid removal of THMs from drinking water was carried out in practice
using the ACF packed beds. The ACF having only small micropores was found
to be suitable for this purpose.
Though the price of AC^Fs is several times higher than that of GACs in terms of price
per unit weight, Sakoda etal.. (1991) indicate that the advantages in the ACF adsorption,
\ '
particularly the rapid adsorption rate which results in smaller adsorption bed, may suggest the
promising feasibility of the ACF as a new material for controlling THMs in drinking water.
3.4.3 Powdered Activated Carbon
Powdered activated carbon (PAC) has traditionally been used in water treatment plants
for removing trace organic compounds associated with taste and odor problems. PAC
requires the same facilities as conventionalcoagulation, clarification and filtration processes
3-9
-------
feed equipment, mixing chambers, settling basins and filters. In addition, the use of PAC
entails additional sludge handling. More stringent sludge disposal requirements may apply
depending on whether or not any toxic or hazardous organic materials are being adsorbed
onto the PAC.
The application of PAC for removal of NOM from drinking water supplies involves the
following major process design considerations:
PAC usage rate
Contact time
PAC Disposal
Under typical treatment conditions, PAC is added concurrently or slightly before
coagulants. The growth of floe around PAC particles may block adsorption onto PAC to
some degree. When PAC is added ahead of settling basins most PAC tends to settle rapidly,
thereby decreasing the contact time. However, lighter grades of PAC can be used so that the
PAC will travel further into the settling basin before settling, thereby providing longer contact
time and better use of the carbon.
3.4.4 Alternative Adsorbents/Ion Exchange
The resin adsorption process is essentially the-same as GAC adsorption with a synthetic
resin replacing GAC. Synthetic resins have been developed that effectively adsorb low
molecular weight organics from water. One such resin, Ambersorb XE-340, has been
designed to remove nonpolar, low molecular weight organics such as the halogenated
organics sometimes found in groundwater aquifers. The major disadvantages of using
synthetic resins are the high cost of the resins ($10 per pound compared to $1 per pound for
GAC) and the unproven technology (especially on a full scale) associated with regenerating
resins in-situ with low temperature steam. Strong base anion exchange resins have been
shown to be effective for the removal of the negatively charged fraction of NOM. This
fraction tends to be hydrophilic and is not well removed by GAC. The disposal of waste
stream generated from the regeneration process of either resins further limits the use of these
technologies.
3-10
-------
3.5 OXIDATION PROCESSES
3.5.1 Ozone
Ozone was originally installed at a water treatment plant in France for disinfection
purposes at the beginning of the 20th century. Since then, the number of ozone facilities for
drinking water has increased to about 3,000 worldwide in 1987. Although ozone has been
employed for miany years in Europe to improve drinking water quality, ozone technology in
the United States is only just beginning to gain acceptance as a viable water treatment option.
According to the International Ozone Association (IOA, 1997) approximately 192 water
treatment plants in the United States currently use ozone for disinfection, color removal, taste
and odor control or DBF control. As of May 1997, another 19 ozone plants are under
construction and an additional 30 plants are in the design stage.
Ozone is one of the most powerful oxidants available for water treatment (second only
to the hydroxyl free radical). Because ozone reacts with hydroxide ions to form hydroxyl free
radicals, the pH of the water during ozonation is a very important parameter in determining
the degrees and rates of contaminant oxidation. Oxidation with ozone is also influenced by
other water quality characteristics such as temperature, alkalinity and the concentration of
reduced chemical species, such as bromide. Other important considerations include ozone
dose and contact time.
' -/
The major components of an ozone oxidation system, as shown in Figure 3-4, include
air compressors, after coolers (optional), refrigerant dryers, desiccant dryers, air filters, ozone
generators, contact basins, demisters, ozone off-gas destruct units and exhaust blowers. The
feed gas may be either air or oxygen. According to the IOA, most of the recently constructed
i
ozonation plants use oxygen as the feed gas. Liquid oxygen is often the simplest (e.g. no air
preparation equipment) and cheapest to use, and yields a higher ozone concentration than
does air as a feed gas. Feed gas pretreatment provides the ozone generators with a clean,
dry gas stream with a dew-point between -60ฐ and -50ฐC. Contact basins are designed in
terms of flow rates, ozone mass transfer and required detention time. Ozone off-gas destruct
units are installed to destroy any excess ozone that has not reacted in the contact basins prior
to discharge into the atmosphere. . .
3-11
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TYPICAL OZONE OXIDATION PROCESS
VENT
WATER
OZONE
OFF-GAS
t
f ! I
ป
?
.0
'0
OP
ปd
0 i
"6
DLH
i
0 f
OZONA1E
WATER
OZONE EXHAUST
DESTRUCT BLOWER
OZONE
AIR
COMPRESSOR
AMERCOOK.R
(OPMONAI)
REFRIGERANT
DRYER
DESICCANI
DRYER
AIR
FILTER
OZONE
GENERATOR
o
c
m
OJ
I
*>
-------
3.5.2 Chlorine Dioxide
\
Chlorine dioxide cannot be transported because of its instability and explosiveness.
Therefore, it is generated at the site of application. The most common method for producing
chlorine dioxide is by mixing a high strength chlorine solution with a high/strength sodium
chlorite solution. The reaction between, chlorine and chlorite is typically allowed to proceed
in a PVC chamber, filled with porcelain rings, designed for a detention time on the order of
0.2 minutes. Generally, 1.7 pounds of sodium chlorite are required for each pound of chlorine
dioxide to be generated. Chlorine is normally used at a 1:1 molar ratio with sodium chlorite
to ensure completion of the reaction and to lower the pH to 4. Chlorine dioxide dosages are
constrained by the limits on the production of by-products such as chlorite, chlorate, and
chlorine dioxide residual.
Typical equipment requirements for chlorine dioxide generation include sodium chlorite
mixing and metering systems, chlorine dioxide generators and other miscellaneous storage,
mixing and metering systems. Chlorine dioxide may also be generated by acidifying solutions
of sodium chlorite and sodium hypochlorite. This method is only applicable for small systems
where little operator time is available.
3.5.3 Potassium Permanganate
Potassium permanganate while a good oxidant under specific conditions is generally
considered a poor disinfectant. The most common uses for potassium permanganate include
oxidation of reduced metals, particularly iron and manganese, and trace organic compounds
associated with taste and odor problems. Potassium permanganate may be added at several
different points in drinking water treatment facilities. However, this chemical must be used
prior to a paniculate removal step, such as settling or filtration, because the permanganate ion
forms insoluble manganese dioxide when it oxidizes chemical species in the water source.
Additional sludge handling is necessary as a result of manganese dioxide formation. Caution
must also be exercised with potassium permanganate dosages since overdosing produces an
* easily detected pink color to finished waters. This-condition must be avoided from a customer
relations standpoint. Potassium permanganate'is usually delivered to treatment plants in dry
.3-12
-------
form and is typically mixed into solution on-site. Equipment needs include miscellaneous
storage, mixing and metering systems.
3.5.4 Chlorine
Chlorine is used extensively in the United States for oxidation/disinfection purposes.
Its feed systems may be divided into four basic types:
Direct solution or dry chemical feed systems.
Gas-to-solution systems.
Direct gas injection.
On-site generation.
Direct solution or dry chemical feed systems use sodium hypochlorite or calcium
hypochlorite which are available commercially. Gas-to-solution systems are the most
commonly used for chlorine disinfection. The basic system may include one or more chlorine
cylinders, evaporators, chlorinators and injectors, plus a piping system. Direct gas injection
into the main flow is possible but is not a common procedure. Chlorine may also be
generated on-site by electrolysis of brine or salt, at sites where chemical supply is not reliable
or where local codes do not permit the transportation of chlorine. However, this practice is
not very common in drinking water treatment.
Important practical design factors for chlorination facilities include:
Method of chlorine addition and provision of mixing,
Design of chlorine contact basin,
Provision for bypassing the chambers or a portion of it,
Sampling and monitoring, of the chlorine residual in the water, and
Safety precautions.
3-13
-------
3.5.5 Chloramines
\
For disinfection using chloramines, the addition of ammonia is required to form
monochloramine from free residual chlorine (if significant levels of ammonia do not exist in
the raw water). The formation of chloramines during water treatment can be performed by
several alternatives: 1) simultaneous addition of chlorine and ammonia; 2) addition of
ammonia after chlorine addition; 3) addition of ammonia prior to chlorine addition; and 4)
preformed chloramines. The choice of alternative depends, to a large, degree, upon'the need
to provide adequate primary disinfection and the need to limit DBF formation. Because of
its relative ineffectiveness as a primary disinfectant, chloramines are primarily used for
secondary disinfection. The most common alternatives are simultaneous addition of chlorine
and ammonia (after primary disinfection using chlorine or ozone) and the addition of ammonia
after chlorine addition. Theaddition of ammonia prior to chlorine and the use of preformed
chloramines are used primarily by systems that need'to limit DBF formation.because free
chlorine contact time is significantly reduced or eliminated (depending on mixing conditions
. and pH levels).
Ammonia is commercially available in four forms: anhydrous ammonia, which is
commonly stored and transported as a liquid in pressure vessels; aqua ammonia, most
commonly a 20 to 30 percent solution of ammonia in deionized or softened water; ammonium
sulfate and ammonium chloride, both of which come in granular form.
Anhydrous ammonia is the least expensive of the four ammonia forms to purchase, 'but
it requires pressurized storage tanks which are relatively expensive. Aqua ammonia is more
expensive than anhydrous ammonia, but the storage tanks are somewhat less expensive.
Because aqua ammonia can be stored in nonpressurized or low-pressure tanks, it is less
hazardous to handle than anhydrous ammonia. In addition, aqua ammonia feeding equipment
is less expensive than anhydrous ammonia feeders.
The salts of ammonia are the most expensive forms. Ammonium sulfate, which is
* I
cheaper than ammonium chloride, is the typically preferred salt. Ammonium sulfate and
ammonium chloride both involve feeding a dry material through feeders which require
frequent maintenance. The salts are extremely hygroscopic and tend to cake up, causing
3-14
-------
problems with feed equipment. Because of these problems and the higher chemical costs,
they are not used in water treatment.
3.5.6 Advanced Oxidation Processes
Advanced oxidation processes (AOPs) are defined as those oxidation processes which
involve the generation of hydroxyl free radicals in sufficient quantity to impact water
purification. Examples of AOPs include ozone at high pH levels, ozone/hydrogen peroxide
and either ozone or hydrogen peroxide with other free radical initiators such as ultraviolet
(UV) light, metals and metal oxides. The hydroxyl free radical has a higher oxidation
potential and frequently reacts at 'faster rates than more conventional oxidants such as
chlorine, permanganate, chlorine dioxide and ozone. In some situations, AOPs may be
reasonably cost effective. As a result, AOPs show promise for removal of a variety of
contaminants which were previously not treatable with more conventional oxidation
processes. The ozone/hydrogen peroxide AOP process essentially requires the same
equipment as the ozone process, except that hydrogen peroxide feed equipment is also
necessary (see Figure 3-5).
3.6 AIR STRIPPING
Air stripping has been used effectively in water treatment to reduce the concentration
of some taste and odor producing compounds/and certain organic compounds. Air stripping
may be described as the transfer of a substance from solution in a liquid phase to solution in
a gas phase. The driving force for transfer is a concentration gradient of the substance across
the boundary between the liquid and gas phases. A concentration gradient tends to move the
substance in such a direction as to equalize concentrations and, thereby, destroy the gradient.
The driving force for mass transfer is the difference between actual conditions in the
air stripping unit and conditions associated with equilibrium between the gas and liquid
phases. The equilibrium concentration of a solute in air is directly proportional to the
concentration of the solute in water at a given temperature. This equilibrium is in accordance
with Henry's Law, which states that the amount of solute that dissolves in a given quantity
3-15
-------
FIGURE 3-5
TYPICAL OZONE/PEROXIDE PROCESS
WELL
RAW WATER
OZONE DESTRUCTION EQUIPMENT
BAFFLES
AIR
r
\
ซ
4
Q
r
^
n
~j
n
n
V *
n
-.
h
OZONE
OZONE CONTACT BASIN
OZONE GENERATION
EQUIPMENT
TO DISTRIBUTION SYSTEM
BOOSTER
PUMPS
QJ
-------
of liquid, at constant temperature and total pressure, is directly proportional to the partial
pressure of the solute above, the solution. Thus, Henry's Law Coefficients describe the
relative tendency for a compound to separate between the gas and liquid phases. Henry's Law
Coefficients can be used to give a preliminary indication of how well a contaminant can be
removed from water via air stripping.
The magnitude of the coefficient for a compound is a function of its solubility in the
liquid phase and its volatility. A high Henry's Law Coefficient indicates equilibrium favoring
the gaseous phase; i.e., the compound is more easily stripped from water than one with a
lower Henry's Law Coefficient. .
Air stripping may result in certain secondary effects. These effects may be considered
beneficial or adverse and include the following:
Beneficial
Removal of hydrogen sulfide or carbon dioxide.
Oxidation of iron and manganese.
Removal of VOC's.
Decreased corrosivity from removal of carbon dioxide.
Introduction of dissolved oxygen into the water.
Adverse
Potential air quality concerns.
Increased corrosivity from higher dissolved oxygen levels.
Excessive calcium carbonate scaling.
Air stripping can be carried out in various configurations. The most common methods
are
Packed Tower.
Diffused Air.
3-16
-------
In designing an air stripping system the following factors must be considered:
Air: Water Ratio.
Contact Time.
Available area for mass transfer.
Physical chemistry of the contaminant.
Percent removal desired.
, Temperature.
While the first three factors may be cpntrolled in the air stripper, the last three are set for a
specific water supply.
Detailed descriptions of the above methods are presented in the following sections.
3.6.1 Packed Column Air Stripping
In a packed column air stripping system, the contaminated water is pumped to the top
of a column. It flows downward by gravity and is counter-currently met by air blown upward
from the bottom of the column. Packing materials are placed within the column to effect a
continuous and thorough mixing between the water and air.
The air flow requirements for a packed column depend on the Henrys Law Coefficient
for the particular compound(s) to be removed from the water. In an ideal air stripping
system, the minimum air/water ratio which achieves complete removal of a contaminant is
proportional to the reciprocal of the Henry's Law Coefficient. The greater the Henry's Law
*
Coefficient, the less air is required to remove the compound from water.
In selecting the packing material, a mass transfer.coefficient is used to relate the driving
force (concentration gradient) to the actual contaminant quantity transferred from water to
air. The mass transfer coefficient is a function of the physical/chemical properties of an
individual contaminant, the type of packing material used, and the gas and liquid loading rates.
Typically, the best packing materials provide high void volumes and high surface area.
3-17
-------
FIGURE 3-6
TYPICAL PACKED COLUMN AIR STRIPPER
OEMISTER MAT
CONTAMINATED
INFLUENT
EXIT AIR
AND SOC
n n *-\
/ A
ORIFICE PLATE DISTRIBUTOR
~- PACKING MATERIAL
SUPPORT PLATE
INCOMING AIR
BLOWER
PACKING MATERIAL
EFFLUENT
PACKED COLUMN
-------
FIGURE 3-7
DIFFUSED AIR STRIPPING ALTERNATIVE
AIR SUPPLY
INFLUENT
DIFFUSE* GBID_L_L-
EFFLUENT
SINGLE COMPARTMENT BASIN
INFLUENT
DIFFUSER
J.1
AIR SUPPLY
EFFLUENT
STAGED BASIN
-------
A'diagram of a typical packed tower installation is shown on Figure 3-6 and consists
of the folio wing:
Packed Tower: Metal (steel or aluminum), plastic, fiberglass or concrete is used
for the outer shell. Internals (packing, supports, distributors, mist eliminators)
are generally made of metal or plastic.
Blower: Typically centrifugal type, either metal or plastic construction. Noise
control may be required depending on the size and system location.
Effluent Storage: Generally provided as a concrete clearwell below the packed
tower.
.>
Effluent Pumping: Generally required because effluent is usually at atmospheric
pressure. Vertical turbine pumps mounted on clearwell are typical.
3.6.2 Diffused Air Stripping
Diffused air stripping is accomplished by injecting air bubbles (usually compressed air)
into the water by means of submerged diffusers or porous plates. A schematic of a typical
diffused air stripping unit is shown on Figure 3-7. Ideally, diffused air stripping is conducted
counterflow with the untreated water entering the top, and the fresh air entering through the
bottom. This type of air stripping technique may be adapted to existing storage tanks and
basins. The air diffusers may be placed on the side of the tank to further induce turbulence
s
and assist in gas transfer.
An alternative approach would be utilization of a staged basin producing a plug flow
system. Counterflow as previously described would still be utilized and the flow between
compartments would be through openings in the dividing walls. Each compartment would
receive compressed air through a separate set of submerged diffusers. A schematic of this
system is presented on Figure 3-7.
3.7 MEMBRANE PROCESSES
3.7.1 Important Factors for Membrane Performance
Commercial pressure-driven membranes are available in many types of.material and in
various configurations. The chemistry of the membrane material, in particular surface charge
3-18
-------
and hydrophobicity, play an important role in rejection characteristics since membranes can
also remove contaminants through adsorption. Membrane configuration and molecular
weight cut-off (MWCO), i.e. pore size, also influence rejection properties, as well as
operational properties, to a .great extent. These options must be chosen appropriately
depending on source water characteristics and removal requirements.
Source water quality is also important in the selection of a membrane process. Water
quality can have significant effects on membrane operation and rejection. Water temperature
is very important to all membrane processes. Lower water temperatures will decrease the flux
at any given pressure. To compensate, additional membrane area and/or higher feed pressures
must be provided to maintain equivalent production at lower temperatures. Depending on
'source water quality, pretreatment is often necessary, particularly with the high-pressure
processes. The small pore size of NF and RO membranes makes them more prone to fouling
than UF or MF membranes. The application of NF and RO for surface water treatment is
generally not accomplished without extensive pretreatment for particle removal and possibly
. pretreatment for dissolved constituents. The rejection of scale-causing ions, such as calcium,
can lead to precipitation on the membrane surface. Organic compounds and metal
compounds, such as iron and manganese, can promote fouling as well. Precipitation can
result in irreversible fouling and must be avoided by appropriate pretreatment, including anti-
scaling chemical and/or acid to the feed water.
The percentage of product water that can be produced from the feed water is known
as the recovery. Recovery for MF and UF is typically higher than recovery for RO and NF.
The recovery is limited by the characteristics of the feed water and membrane properties.
Typical recoveries for membrane processes are given in Table 3-2.
TABLE 3-2
Typical Recovery for Membrane Processes
Membrane Process
MF
UF
NF
, RO
PercentRecovery
90 to 97
85 to 97
75 to 85
70 to 80
3-19
-------
Pressure driven membrane operations were initially used for removing total dissolved
solids (TDS) from brackish water sources. Lately, pressure driven membrane operations
have found increasing acceptance as a method for removal of hardness and DBF precursors.
An important parameter which controls removal of most contaminants from drinking water
sources is the nominal molecular weight cutoff (MWC) of the membrane. The MWC
provides an indication of the molecular size that a given membrane rejects at some
predetermined efficiency. Membranes with lower MWC values should be capable of rejecting
a wider range of chemical species than membranes with higher MWC values. However,
MWC is not a standardized measurement and is usually provided by the membrane
manufacturer. Two membranes with the same reported MWC may also have different pore
size distributions and, therefore, may not necessarily perform in a similar manner.
Pressure driven membrane operations are.commonly divided into the following
categories:
Reverse osmosis (RO).
Nanofiltration (NF).
Ultrafiltration (UF).
Microfiltration (MF).
MWC values for NF membranes generally range from 200 to 1000 daltons while
MWC values for UF membranes are generally greater than 500. MF membranes have a MWC
one order of magnitude greater .than UF membranes. RO membranes have the greatest
rejection potential since MWC values for RO are generally considered to be lower than those
for NF. Lower MWC values are also accompanied by higher operating pressure
requirements. Thus, membrane systems have tradeoffs between operating costs and process
performance.
In terms of contaminant rejection, depending on the mechanism of rejection the
performance of a membrane with a given MWC may be influenced by the operating pressure
/
and percent recovery.. Percent recovery is the ratio between the product water flow rate and
3r20
-------
the feed water flow rate. Contaminant rejection generally increases with increasing operating
pressure and with decreasing percent recovery. Thus, rejection can be enhanced by changing
operating parameters but not .without increased operating costs. To increase recovery,
membranes are often staged, i.e. the concentrate of one stage of membranes is treated by
another stage of membranes. Two to three stages are common. Staging is also used to keep
the fluid velocity across the membranes at a specified rate. The maximum attainable percent
recovery is usually governed by the degree to which the water can be concentrated without
the occurrence of precipitation..Contaminant rejection that are sieving controlled are not
influenced by pressure and recovery.
Membrane performance, particularly in terms of product water flux, is also influenced
by temperature, In the temperature range of 15 to 3Q6C, the water flux increases
approximately 3.5 percent for each degree of temperature increase (Weber, 1972). .Thus,
membrane plants in colder climates must install larger systems than membrane plants in
V.
warmer climates, however in many plants, an impact of temperature is negated by the lower
water demand in colder months.
The major components of a typical membrane filtration treatment system for
groundwater include chemical feed systems for pH adjustment and scale inhibition, cartridge
filters, high pressure feed pumps, membrane modules, a degassification system and a
concentrate disposal system, as shown on Figure 3-8. A surface water system would require
substantially greater pretreatment. Concentrate disposal regulations may present serious
limitations on the availability of membrane systems for general use.
3.8 REDUCTION PROCESSES
Reducing agents have been used in potable water and wastewater practices
predominantly for dechlorination purposes. As described in Chapter 6, sulfur based reducing
agents have been evaluated for control of chlorine dioxide by-products. These processes are
described below.
3.8.1 Sulfur Dioxide
3-21
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TYPICAL MEMBRANE FILTRATION PROCESS
SULFURIC ACID
- SCALE INHIBITOR
CONCENTRATE
UME
TO
DISTRIBUTION
SYSTEM
CARTRIDGE
FILTER
HIGH PRESSURE
FEED PUMPS
MEMBRANE
ASSEMBLY
DEGASSER
(FOR RO
SYSTEMS ONLY)
CUEARWELL
HIGH LIFT
PUMP
O
C
33
m
u
-------
Sulfur dioxide storage and feed systems are similar to chlorination systems because
sulfur dioxide equipment is interchangeable with .chlorination equipment. Sulfur dioxide is
r
available in ton containers or tank trucks. Due to the low vapor pressure of sulfur dioxide,
special precautions must be taken when using ton containers to prevent reliquification. The
key control parameters for this process are:
. Maintaining proper dosages.
Adequate mixing at the point of application.
3.8.2 Sulfite Compounds
Sulfite compounds are used in solution and are primarily for smaller installations where
feed rates for sulfur dioxide are less than 100 Ib/day (White, 1986). Sulfites are also used on
large installations where storage of .sulfur dioxide might be considered a^hazard. .These
solutions are applied with metering pumps. Feed rate control and process monitoring of these
systems need more attention and require more complex instrumentation than sulfur dioxide
systems.
Four sulfur compounds are available as alternative chemicals to sulfur dioxide as a
reducing agent: sodium sulfite, sodium bisulfite, sodium metabisulfite, and sodium
thiosulfate. Sodium sulfite is available only as a white powder or crystals. The dry form is
extremely difficult to handle because it is hygroscopic and, therefore, it is rarely used as a
dechlorinating agent. Sodium thiosulfate is used in solution, but almost entirely as a
laboratory chemical. It is not a satisfactory dechlorinating agent for treatment plant use
because it is not amenable to metering control situations. Therefore, only sodium bisulfite and
sodium metabisulfite are considered practical alternatives to sulfur dioxide.
3.9 BIOLOGICAL PROCESSES
In drinking water treatment biological activity occurs whenever a disinfectant residual
is not maintained throughout a given treatment process. Biological processes are generally
considered to include those processes which foster the growth of microorganisms and thus
3-22
-------
enhance the biodegradation of organic compounds .The most common biological processes
are:
Biological rapid media (e.g. sandy, anthracite) filters.
Slow sand filters.
Biological GAC filter-adsorbers.
Biological GAC post filter adsorbers.
j
With the exception of slow sand filters, most biological processes are developed around
existing unit processes. Many treatment facilities already contain some of these unit
processes. Alterations to existing operational procedures or modifications to the existing
process could promote the conditions necessary for biological activity to prosper. For
instance, relocating the point of chlorination to the filter effluent can allow microbiological
activity to develop within filter beds. Some period of time, weeks to months, may be required
to allow the microorganisms to acclimate to the contaminants of interest.
Oxidation ofbackground organic matter, especially by ozonation, may produce smaller
compounds which are degraded more readily than the parent organic matter. These more
readily degradable compounds provide a carbon food source necessary for cell maintenance
and reproduction. Increased biodegradation reduces organic loading on downstream
processes such as GAC and,'if used after ozonation, increased biodegradation would decrease
the concentration, of biodegradable organic matter, e.g., AOC, entering the distribution
system. By reducing the level of organic matter entering the finished water, a reduced
disinfectant residual in the distribution system may be implemented, in turn lowering DBF
formation.
3-23.
-------
3.10 REFERENCES
AWWA(1990). Water Quality and Treatment: A Handbook of Community Water Supplies.
American Water Works Association, fourth edition, McGraw-Hill, New York, NY,
1990.
Montgomery (1985). Water Treatment Principles and Design. James M. Montgomery,
Consulting Engineers, Inc., John Wiley & Sons, New'York, NY.
Sontheimer et al. (1988). Sontheimer, H., Crittenden, J. C. and Summers, R. S. Activated
Carbon for Water Treatment. 2d ed., DVGW-Forschungstelle am Engler-Bunte-
Institut der Universitat Karlsruhe, Karlsruhe, West Germany,' 1988.
AWWA (1968). Quality Goals for Potable Water: A Statement of Policy Adopted by the
AWWA Board of Directors on January 28,1968. Based on the Final Report of Task
Group 2650P - Water Quality Goals, Elwood L. Bean, Chairman," Journal AWWA,
vol.60, 1968, p. 1317.
IQA, 1997. Information on Drinking Water Treatment Plants Currently Using Ozone.
Submitted to the USEP A for the D/DBP Stage 1 and Interim Enhanced Surface Water
Treatment Rule by Michael Dimitriou of International Ozone Association, June 1997.
Komegay, B. H. .(1979). "Control of Synthetic Organic Chemicals of Activated Carbon -
Theory, -Application and Regeneration Alternatives." Presented at the Seminar on
Control of Organic Chemicals in Drinking Water, sponsored by USEP A, Feb. 13-14;
1979.
i
James M. Montgomery, C.E., Inc., Water Treatment: Principles and Design,
. Wiley-Interscience, New York, NY, 1985.
Sakoda, A., Suzuki, M., Krai, R. and Kawazoe, K .(1991). "Trihalomethane Adsorption
on Activated Carbon Fibers." Water Research. 25(2) p. 219.
Sontheimer H., Crittenden J.C., Summers R.S.: Activated Carbon For Water
Treatment, 2nd Edition, DVWG Forschungsstelle, Karlsruhe, Germany: (1988):
722pp. ,
Weber, W. J.'(1972). Phvsicochemical Processes for Water Quality Control. John Wiley &
Sons, New York, NY.
White, G. C (1986). Handbook of Chlorinatioh. Second Edition, Van Nostrand Reinhold
Company, Inc., New York, NY.
3-24
-------
4.0 TECHNOLOGIES FOR DBF PRECURSOR REMOVAL
4.1 INTRODUCTION
Natural organic matter (NOM), is ubiquitous in surface and ground water sources.
Figure 4-1 shows the occurrence of TOC in surface and ground water systems as presented
in a Natural Organics Reconnaissance Survey funded by USEPA (Symons et al. 1975).
Results of more recent surveys of utilities affected by the Information Collection Rule (ICR)
are presented in Figures 4-2 and 4-3 (McGuire, 1997). In these figures, TOC levels of 95
groundwater (GW) and 217 surface water (SW) ICR plants are compared with the TOC
levels in other databases (Ground Water System Survey and Water Industry Database). The
GW survey consists of 216 data points and the SW survey consists of 576 data points
collected during the months of September, October and November. According to any of the
probability distributions shown on these figures, a majority of the treatment plants in the US
treat raw surface water with TOC levels greater than 2.0 mg/L.
NOM consists of humic substances, amino acids, sugars, aliphatic acids, aromatic
acids and'a large number of other organic molecules. Although interest in NOM research and
removal has primarily revolved around the reactions between NOM and chemical
disinfectants, a water system should consider optimizing existing treatment practices for
removal of NOM for several other reasons. NOM has been shown to bind with harmful'
metals and synthetic organic chemicals (SOCs), thereby allowing these contaminants to
proceed through treatment processes not designed to remove NOM. In addition, NOM
creates a disinfectant demand and forces systems to use higher disinfectant dosages to
maintain an adequate residual in water distribution systems. Some NOM components may
also provide nutrients for microorganisms in these distribution systems allowing regrpwth.
NOM also competes with SOCs for adsorption sites on activated carbon and hinders the
coagulation process by stabilizing dispersed and colloidal particles.
This chapter focuses on treatment technologies that have been evaluated for their
ability to remove NOM. However, the characteristics and measures of NOM have important
4-1
-------
FIGURE 4-1
TOTAL ORGANIC CARBON OCCURRENCE
IN UNITED STATES WATER SUPPLIES
(AFTER SYMONS, ET AL., 1975)
CD
E
O
CO
CJ
O
1
a:
o
20
7.4
2.7
1.0
0.37
0.14
0.05
SURFACE WATERS
GROUNDWATERS
0.1 1 5 20 50 80 95 99
CUMULATIVE FREQUENCY OF OCCURRENCE
99.9
-------
Figure 4-2 Comparison of Fax Survey TOO Data with GWSS Data
100.0%
90.0%
0.0%
GWSS w/ Soft
* 'GWSS w/0 Soft
" * Fax Survey
-------
Figure 4-3 Comparison of Fax Survey TOC Data with WIDB Data
100%
90%
WIDB CI2
WIDB NH2CI
Fax Survey
10
-------
implications with regard to the performance and evaluation, respectively, of these processes.
Therefore, this chapter begins with two sections summarizing these characteristics and
measures. This chapter describes process evaluations listed below. A classification of those
processes considered most applicable for NOM removal is proposed at the end of the chapter.
Precipitation/filtration processes such as coagulation and softening.
Adsorption processes such as granular activated carbon (GAC), powdered
activated carbon (PAC), and resin adsorbents.
Oxidation processes such as ozone and chlorine dioxide.
Other processes such as membranes and biological degradation.
4.2 CHARACTERISTICS OF NATURAL ORGANIC MATTER
NOM characteristics vary considerably and have important implications for drinking
water treatment processes. Of those constituents which comprise NOM, humic substances
have arguably received the largest amount of research. Humic substances comprise about 50
percent of the dissolved organic carbon (DOC) in surface waters, but this percentage can vary
considerably and may be as high as 80 percent in some colored waters (MacCarthy and Suffet,.
1989). These substances are formed by the biodegradation of plant and animal tissue in both
soil and aquatic environments and may be fractionated into humic acids and fulvic acids.
**
Humic substances vary widely in chemical and physical characteristics but can generally be
classified as large polyelectrolytic macromolecules. Chemical composition of humic
substances ranges by weight from 40 to 60 percent carbon, 30 to 50 percent oxygen, 3 to 6
percent hydrogen and 1 to 4 percent nitrogen (MacCarthy and Suffet, 1989; Steinberg and
Muenster, 1985). In addition, the major functional groups on these polyelectrolytes are
carboxyl, phenolic hydroxyl and alcoholic hydroxyl compounds. Typical average molecular
weight for aquatic humic substances varies between 800 and 3,000 daltons, while average
molecular weight for soil humic acids can be greater than 100,000 Daltons (MacCarthy and
Suffet, 1989)
4-2
-------
The chemical and physical nature of humic substances is dependent on the pH and ionic
i
strength of the water. The most thermodynamically stable form of ah uncharged
macromolecule is that of the random coil. However, when the macromolecule contains
negatively charged functional groups as humic substances do, electrostatic repulsions force
the configuration of the molecule to become more linear. If the pH of solution is lowered
beyond the acidity constant of a'given functional group, then a hydrogen ion may bind with
and neutralize the negative charge on that functional group. In addition, when the
concentration of positively charged ions; such as calcium and sodium, is increased in the
background aquatic environment, these electrostatic repulsions are reduced by the
accumulation of cations around the negatively charged functional groups. These two
conditions allow the humic macromolecule to adjust to a more coiled and compact state.
Thus, a simple decrease in pH or increase in cation concentration can lead to both decreased
negative charge and decreased molecular size of humic macromolecules. This phenomenon
was demonstrated by Ghosh and Schnitzer (1980) for a soil humic acid and a soil fulvic acid.
" ' i
Although this phenomenon may not apply to all components of NOM, it still has important
implications for the removal of NOM by water treatment processes. The size and solubility
(hydrophobicity) of NOM have proven to be important factors in NOM removal through
coagulation and adsorption as discussed in Section 4.4.3.3,
4.3 SURROGATE PARAMETERS FOR NOM (DBF PRECURSOR) REMOVAL
i
4.3.1 , Introduction
Because NOM characteristics are widely varied on a chemical and physical basis, no
single analytical technique is. available to characterize NOM. As a result, surrogate
parameters such as organic carbon content must be used to describe generalized NOM
characteristics. The use of surrogate parameters for monitoring plant performance and
measuring water quality is not new to the water industry. Turbidity, for example, is widely
used for controlling and monitoring the operation -of treatment plants for the removal of
particulate matter. Other surrogates currently used are color (as a measure of NOM) and
c'oliform bacteria (as a measure of pathogen presence).
4.-3
-------
An ideal surrogate parameter should possess the following qualities:
Can be measured rapidly
Does not require sophisticated equipment or special training
Permits accurate estimation of target parameter
Commonly used surrogate measures of NOM concentration include:
Total and dissolved organic carbon (TOC and DOC)
Ultraviolet (UV) absorbance at a wavelength of 254 nm (UV-254)
Another more direct method of assessing DBF precursors is to measure their formation
I . C
under specific reduction.conditions such as formation potential (FP), simulated distribution
system (SDS) and uniform formation conditions (UFC). Historically THMFP has been used.
More recently, however, the SDS and UFC conditions have been used to represent conditions
of disinfection practice. These conditions often more adequately predict the impact of
bromide on DBF formation compared to FP conditions. DBF surrogates (i.e. TOC, DOC and
UV-254), however, can adequately screen raw water sources for DBF precursor content and
to determine the performance of unit treatment processes for removal of DBF precursors.
The following sections briefly summarize those NOM characteristics that the above
surrogates measure and some of the limitations associated with each. An excellent review of
the status of many surrogate parameters was published in 1988 by a joint effort of AWWARF
and the Keuringsiristituut voor Waterleidingartikelen (AWWARF and KIWA, 1988). In
addition, an AWWARF-sponsored project studied the characteristics of NOM and its
relationship to treatability (Owen et al., 1993). The reader is referred to these reports for an
in-depth discussion of the analytical methods and application of surrogate measures for NOM.
4-4
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4.3.2 Total and Dissolved Organic Carbon
Several methods are available for measuring the TOC of a water sample; proper use
of alternative methods can be assumed to produce directly comparable results. Most of the
TOC results reported in the drinking water literature may be assumed as representative of the
non-purgeable organic fraction of the water being measured. Typically, purgeable organic
carbon is only a minor fraction of TOC.
Although TOC is a direct measure of a water's organic carbon content, it is not
necessarily a consistent measure of DBF precursor concentrations. One plausible explanation
for this observation is that TOC does not provide an indication of the aromaticity, aliphatic
nature, functional group chemistry or chemical bonding associated with natural organic
molecules. The reactivity of chemical bonds and functional groups is likely to.be a significant
factor in explaining why different waters with the same TOC concentration will form different
' f
DBF concentrations under identical disinfection conditions and bromide levels. Although
Summers et al. (1996) have shown that when chlorinated under identical conditions, uniform
formation conditions (UFC), the coefficient of variation (standard deviation divided by the
mean) of the DBF yield (DBP/TOC) of 12 waters was less than 20% for TOX, TTHM and
HAAS.
DOC is also a commonly used surrogate measure of DBF precursor concentrations.
DOC is operationally defined as that portion of TOC which passes through a 0.45 urn
membrane filter. Therefore, DOC measures the amount of organic carbon dissolved in a
given water. Dissolved phase organics may be more reactive than paniculate phase organics.
Thus, the ratio of DOC to TOC may also be considered an important factor in explaining why
different waters having the same TOC concentration will form different DBF concentrations
under identical disinfection conditions and bromide levels. DOC is often about 90 percent of
the TOC (Owen et. ,al., 1993).
If the DOC/TOC ratio is relatively low, that is a large amount of organic material is in
paniculate form, physical processes such as sedimentation and filtration can be expected to
4
remove a significant fraction of the NOM. On the other hand, relatively high DOC/TOC
ratios indicate that much of the NOM is in soluble form. Therefore other processes such as
enhanced coagulation, GAC adsorption, and membrane filtration are required to achieve
4-5'
-------
significant removal. After filtration there is usually less than a five percent difference between
TOC and DOC.
4.3.3 Ultraviolet Light Absorbance at 254 nm
One of the most commonly used surrogates in drinking water research has been the
measurement of a water's ability to absorb ultraviolet light at a wavelength of 254 nm (UV-
254). UV-254 absorbance indicates the concentration of organic molecules with aromatic
groupings or extended conjugation. Interstudy comparisons of unit process performance for
UV-254 reduction may be limited to some extent because UV-254 results are dependent on
the pH and turbidity of the water being tested. Recent reports suggest that the pH should be
standardized for UV-254 measurements and that prewashed 0.45 urn membrane filters be
used to remove paniculate matter prior to UV-254 analysis (Owen et.al., 1993; AWWARF
and KIWA, 1988). According to Standard Methods, there is no recgmmendation as to the
standard pH for the measurement of UV-254. According to Edzwald(l 985) UV absorbance
remains constant in fulvic acid solutions between pH 4 and 10!
Other limitations may also affect the use of UV-254 as an indicator of unit process
performance for DBF precursor removal. These limitations primarily result from interference
of inorganic species (e.g. iron) that also absorb ultraviolet light at wavelengths near 254 nm.
For instance, monochloramine and dissolved ozone absorb ultraviolet light at wavelengths of
243 nm and 260 nm, respectively. Evaluations of unit process performance for reduction of
UV-254 should recognize these potential interferences.
j
4.3.4 Specific Ultraviolet Light Absorbance
Specific ultraviolet light absorbance (SUVA) has proven to be a good indicator of the
humic content of a water (Edzwald and Van Benschoten, 1990). SUVA is defined as UV-
/
254 (measured in m-1) divided by the DOC concentration (in mg/L), resulting in SUVA units
of L/mg-m. SUVA values of less than about 3 L/mg-m signify a water containing mostly
nonhumic material. SUVA values of 4 to 5 L/mg-m are typical of waters containing primarily
humic material (Edzwald and Van Benschoten, 1990).
_4-6
-------
SUVA can also be predictive of the removal capability accomplished with enhanced
coagulation practices. Several studies (Krasner et.al., 1996, Cowman et.al., 1996,
Chowdhury et.al., 1997) reported that waters with a high SUVA value exhibited large
reductions in SUVA as a result of enhanced coagulation, indicating an overall substantial
removal of NOM. Waters with low SUVA values; however, exhibited relatively low
reductions in SUVA, indicating an overall insignificant removal of NOM.
4.3.5 DBF Formation Tests
DBF formation is a measure of a water's potential to form DBFs under specified
chlorination conditions. Depending on the chlorination conditions, formation tests can be
classified into: (1) Formation Potential (FP) test, (2) Simulated Distribution.System (SDS)
test, or (3) the Uniform Formation Conditions (UFC) test. .A brief description of each of
these testing protocol are included here.
The value of the DBF formation tests is that they can provide an indirect measure of
DBF precursor removal across a unit treatment process. As shown in subsequent sections
of this chapter, removal of TOC may be quite different from the removal of DBF precursors.
Such a result may indicate that DBF precursor molecules are preferentially removed over
other natural organic molecules, or vice versa. This type of information can be critical when
evaluating unit process performance and, despite its limitations, the DBF formation tests
should be included as an integral part of evaluating treatment processes for removal of DBF
precursors.
The formation concept was developed to study THM precursors. The concept has
been extended by several researchers to.other DBFs including HAAs, HANs and TOX.
(McGuire, et al..' 1989; Stevens, et al.. 1989; Reckhow and Singer, 1984). - However, the
majority of the research to date has evaluated THMFP.
4.3.5.1 Formation Potential (FP) Test
The FP test determines the potential to form DBFs under relatively extreme
chlorination conditions. The test is done by measuring the concentration of DBFs at the time
of sampling (Inst-DBP) and the concentration of DBFs after the collected sample has been
4-7
-------
subjected to chlorination (Term-DBF). DBPFP is defined as the difference between Term-
DBF and Inst-DBP. If.there is no chlorine in the sample at the time of collection, Inst-DBP
will be close to zero and Term-DBF will be equivalent to DBPFP. If chlorine is present at
the time of sampling, the difference between Term-DBF and Inst-DBP becomes DBPFP.
The recommended (Standard Methods, 1995) chlorination conditions for DBPFP tests
include an incubation time of seven days with a free chlorine residual of 3 to 5 mg/L at the
end of incubation period. The recommended incubation temperature is 25 ฑ 2ฐC and the
\
recommended pH is 7.0 ฑ 0.2 (with phosphate buffer).
Researchers have measured DBPFP by using a wide range of pH conditions, chlorine
dosages and contact times. Therefore, when summarizing research work, it is necessary to
report.the conditions under which DBPFP was measured. Unfortunately, direct quantitative
interstudy comparisons of DBPFP removal across unit processes cannot be performed if
different procedures were used to determine DBPFP.
4.3.5.2 Simulated Distribution System Tests
Simulated Distribution System (SDS) test for DBFs is a modification of the DBPFP
test described above (McGuire, et al.. 1989; De Marco, et al.. 1983; Standard Methods,
1995). In SDS tests, chlorine dosages, pH conditions, and incubation times are selected to
be more representative of actual conditions in the distribution system. While SDS tests may
provide more accurate indications of actual distribution system DBF levels, SDS test results
f i
must also be reported with their accompanying test conditions.
4.3.5.3 Uniform Formation Conditions Test
The DBPFP test described above portrays DBF formation under extreme conditions.
As a result of these extreme chlorination conditions, the distribution of DBF between the
chlorinated and brominated species become skewed and often do not represent actual
conditions in operating systems. The SDS test does not have the limitation of the FP test,
since more realistic chlorination conditions are used. SDS tests from one utility, however,
cannot be compared with SDS tests from another utility because of differing chlorination
4-8
-------
conditions. A set of uniform formation conditions was proposed to overcome these
limitations.
The proposed protocol (Summers et al., 1996) for UFC condition include an incubation
period of 24 ฑ 1 hour at a temperature of 20 ฑ 1.0ฐC and at a pH of 8.0 ฑ 0.2. The target
chlorine residual after the incubation period is 1.0 ฑ 0.3 mg/L. It is noteworthy that a pH of
8.0 will favor the formation of THMs over the formation of HAAs.
These conditions were developed by conducting a survey of 318 utilities across the
nation. This protocol allows DBF formation to be analyzed under representative formation
conditions and directly compare DBF formation between waters under similar conditions.
This test can also be used to analyze how treatment conditions;affect DBF formation. The
. test can be used to assess how seasonal variability in water quality can affect DBF formation.
4.3.6 Summary \ . ,
Surrogate parameters must be used to describe NOM .because no single analytical
technique is capable of measuring the widely varied characteristics of NOM. Commonly used
surrogate measures of NOM include TOC, DOC and UV-254. The use of NOM surrogates
to represent DBF precursors is limited. A better, but more involved, approach, is the use of
DBF formation tests. Each parameter has advantages and disadvantages as discussed above.
TOC is used in this chapter to quantitatively compare the results of different studies to
determine relationships between operational practice and process performance. However,
DBF formation removals are also presented to highlight any differences between TOC
removal and DBF formation removal.
4.4 COAGULATION/FILTRATION
4.4.1 Introduction
Coagulation/filtration is a process by which the physical or chemical properties of
dissolved, colloidal or suspended matter are destabilized so that agglomeration is enhanced
to an extent that the resulting solids can be removed by other processes i.e settling,
4-9
-------
floatation, and filtration. Coagulants change surface charge properties of solids to allow
agglomeration and/or enmeshment of particles into floes. The larger agglomerated particles,
or floe, are then removed.
The coagulation/filtration process has traditionally been used to remove solids from
drinking water supplies. This process is not restricted, however, to the removal of particles.
Coagulants render some dissolved species (e.g., NOM, inorganics and hydrophobic SOCs)
insoluble and therefore removable. Metal hydroxide particles produced by the addition of
metal salt coagulants can adsorb yet other dissolved species. The degree of removal of NOM
by coagulation/filtration depends on a number of factors including but not limited to the
following:
Nature and concentration of NOM entering the process.
Water quality characteristics such as pH, hardness, ionic strength and
temperature.
Treatment processes, such as oxidation, used prior to the process.
Type and dose of the coagulant being used.
Coagulants are selected based upon their ability to destabilize particles and create a floe
that can be removed by subsequent physical processes. NOM removal, cost, residuals
handling and disposal are also important factors. Aluminum and iron salts are typically used
as primary coagulants because their trivalent ions form positively charged species that can
neutralize the negative charge of naturally occuring particles (charge neutralization), and
precipitate NOM. They also form insoluble hydroxides that remove paniculate and dissolved
material by enmeshment, coprecipitation or adsorption. Both charged and uncharged
polymers are also used as coagulant aids for destabilization and particle bridging to improve
the development and subsequent removal of floe. Polymerized forms of aluminum, such as
polyaluminum chloride (PAC1), also can be used as a primary coagulant in low turbidity
waters. Because of the relatively low dosages used in water treatment, however, PAC1
typically does not remove significant amounts of NOM.
4- 10
-------
Filtration is also important in NOM removal. Solids removal during granular media
filtration is a two-step process. During the initial step, particles are transported to the surface
of media grains or previously captured floe. Transport is believed to be largely a result of
hydrodynamic forces, with contact occurring as streamlines converge in pore restrictions.
The second step is attachment of the particles to either grain or floe surfaces. Electrokinetic
and molecular forces are responsible for the adherence of the particles on the surfaces within
the bed. Physical straining is generally a minor means of solids removal in granular media
filters.
In traditional water treatment practice, biological activity within a filter is discouraged
through the,addition of a disinfectant (e.g., chlorine) prior to filtration. However, in many
systems in Europe, particularly those using ozone as a preoxidant, biological activity is
encouraged in filtration as a means to stabilize biodegradable organic matter and thereby
reduce the concentration of NOM. In systems which want to reduce DBF formation by
moving the point of chlorination further into the treatment train, even as far as the filter
effluent, biological activity in filtration can provide some steady-state removal of NOM. The
extent is dependent upon the concentration of biodegradable organic material in the filter
influent. Some plants are currently using chlorination ahead of filtration to control manganese.
, /
' Section 4.11 discusses biofiltration in more detail.
4.4.2 Removal Mechanisms
Overall, coagulation/filtration, processes remove NOM from drinking water sources by
several mechanisms (Dempsey, etal.. 1984; Sinsabaugh, etal.. 1986a; Randtke, 1988). While
these mechanisms can be very complex on a microscopic level, the removal of NOM by
coagulation/filtration can be generalized into the following two basic steps at a macroscopic
level:
'Convert some NOM from the dissolved phase to the paniculate phase during
coagulation and flocculation stages. . .
Remove particulates, including those containing NOM, during clarification and
filtration stages.
4-11
-------
Because some NOM is in the paniculate phase prior to the coagulation stage, the first step
is used to agglomerate these particles into a state that is more readily settled or filtered.
This process is illustrated in Figures 4-4 and 4-5 for TOC and THMFP, respectively.
These figures show field-scale data from a treatment plant in Newport News, Virginia
(Malcolm Pimie,. 1988). THMFP tests were run with a chlorine dose of 20 mg/L for a period
of 7 days at pH 8 and a temperature of 20ฐC. The treatment scheme included alum
coagulation at a dose of 52 mg/L. Lime was added with the alum to maintain a settled water
pHof.6.1.
As shown by Figures 4-4 and 4-5, a 25 percent conversion of organic carbon and a 30
percent conversion of THMFP from the dissolved phase to .the paniculate phase occurred
during the initial coagulation step. Additional conversion took place during the flocculation
process; however, the extent of the conversion process appeared to be complete by the end
of that stage. Clarification and filtration provided for the removal of paniculate phase NOM.
However, these processes did not provide any appreciable removal of the dissolved NOM.
4.4.3 Relationships Between Physicochemical Characteristics of Natural
Organic Matter and Coagulation/Filtration Performance
Several bench-scale studies have demonstrated the impacts of NOM characteristics on
the performance of the coagulation/filtration process. Some of these characteristics evaluated
to date include molecular weight, charge, solubility (hydrophobicity), aromatic content,
SUVA and UV-272. Each of these is discussed subsequent sections.
4.4.3.1 Molecular Weight
NOM can be classified into molecular weight (MW) fractions or size ranges.
Although the molecular weight of NOM is a specifically defined value, in practice, the term
carries the connotation simply of relative size. Although it is important to categorize NOM
into certain size ranges, the usefulness of the measurement is found in the relative comparison
of higher versus lower MW material.
4-12
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O)
- 4
z
o
CD
o:
< 3
O
o
o
o:
o
o
REMOVAL OF NOM DURING COAGULATION/FILTRATION
NEWPORT NEWS, VIRGINIA
PARTICULATE PHASE
rrteo
31
o
c
7J
m
-------
NOM removal during coagulation is not consistent for all molecular weight
ranges. Owen et. al. (1993) found that coagulation preferentially removes higher MW
compounds over lower MW compounds. They found that the majority of DOC removal was
a result of reductions in larger and medium size range NOM (>1K). Furthermore, they
documented NOM increases in the smallest MW range (<0.5 K) upon ozonation. This
indicates a breakdown of some higher MW NOM compounds during ozonation.
Semmens and Staples (1986) studied changes in the molecular weight
distribution of NOM from Mississippi River water at Minneapolis, Minnesota. According to
these researchers, small NOM molecules (MW <1,000) were not removed by either coagulant
under the coagulation conditions used in this study. Larger molecules, particularly those with
molecular weights greater than 10,000, were readily removed. Similar results were reported
other researchers as well (Semmens and Ayers, 1985; Semmens, etaL 1986; Sinsabaugh, et
al, 1986a; Sinsabaugh, et_al., 1986b; Knocke, etaL 1986; AWWARF, 1992; Chadik and
Amy, 1986; Collins, gLal., 1985; Vik,-et_aL, 1985). Dryfuse et al. (1995) showed that
increased coagulant doses led to near complete removal of the large (> 3K) fraction and over
50 percent removal of the intermediate (0.5 - 3K) fraction. The results of these studies
suggest that coagulation/filtration processes may remove a greater percentage of NOM when
used for treatment of waters containing higher percentages of large NOM molecules.
4.4.3.2 Charge
Studies have also evaluated the influence of molecular charge distributions
on NOM removal by coagulation/filtration processes. Using statistical methods, Sinsabaugh,
et al.. (1986a), found molecular charge distribution to be .second only to molecular weight
distribution as a factor influencing removal of NOM molecules. Acidic and basic molecules
were removed effectively while neutral molecules tended to remain'in solution.
4.4.3.3 Solubility
Sinsabaugh, etal.. (1986a) also found solubility distribution to be important.
Hydrophilic and hydrophobic molecules were more readily removed than mesic molecules.
The authors suggested that the more polar hydrophilic molecules may react directly with the
4-13
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REMOVAL OF TTHMFP DURING COAGULATION/FILTRATION
NEWPORT NEWS, VIRGINIA
~o> 500
ro.
PARTICULATE PHASE
*ป *ฃ!ป#*>
***
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-------
coagulant to form'precipitates while the less polar hydrophobic molecules may adsorb to non-
polar domains on the precipitate. Semmens and Staples (1986) found hydrophobic molecules
to be more readily removed than hydrophilic molecules. Dryfuse et al. (1995) found that at
conventional coagulation doses the hydrophobic fraction is easily removed and at increased
doses, 20 to 60 percent of the hydrophilic fraction could be removed. '
/
4.4.3.4 Aromatic Content
(
High aromatic content has typically been associated with high humic content.
Humic substances comprise about SO percent of the DOC in surface waters, but this
i
percentage can vary considerably and may be as high as 80 percent in some colored surface
waters (MacCarthy and Suffet, 1989). The humic fraction of NOM has typically been found
to be more instrumental in DBF formation than the non-humic fraction. Owen et. al. (1993)
found that the humic fraction of several source waters contained the majority of constituents
that adsorb UV light or fluoresce, reflecting the potential for DBF formation.
4.4.3.5 SUVA
Specific ultraviolet light absorbance has proven to be a good indicator of the
humic content of a water (Edzwald and Van Benschoten, 1990). SUVA can .also be
predictive of the removal capability accomplished with enhanced coagulation practices.
Several studies (Krasner et.al., 1996, Cowman et.al., 1996, Chpwdhury et.al., 1997) reported
that waters with a high SUVA value exhibited large reductions in SUVA as a result of
enhanced coagulation, indicating an overall substantial removal of NOM. Waters with low
SUVA values, however, exhibited relatively low reductions in SUVA, indicating an overall
insignificant removal of NOM.
4.4.4 Coagulant Dose and pH Impacts
Many investigators have evaluated the impacts of coagulant dose and coagulation pH
on NOM removal at a bench-scale level (Kavanaugh, 1978; Young and Singer, 1979;
Semmens and Field, 1980; Chadik and Amy, 1983; Knocke, et al.. 1986; Hubel and Edzwald,
1987; James M. Montgomery, 1992). In general, these studies'have found that the removal
4-14
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of NOM can be optimized by maintaining certain pH ranges during coagulation, flocculation
and sedimentation. 'For alum coagulation, the optimal pH for NOM removal generally occurs.
in the range of pH 5 to pH 6. The optimal pH for ferric coagulation generally occurs in the
pH 4 to pH 5 range.
James M. Montgomery (1992) studied the effects of coagulation arid ozonation on the
formation of DBPs for the AWWA for eighteen raw waters from utilities across the United
States. The results, of this study indicate the following:
s
Coagulation removed between 0 and 75 percent of THM and HAA
precursors, depending on water quality.
The majority of waters had less than 30 percent TOC removal.
Removal of organic matter' by coagulation resulted in increasing
bromide/TOC ratio and shifting the THM and HAA speciation towards the
brominated species.
' From these results, James M. Montgomery concluded that modified coagulation may
be applicable for minimizing DBFs in finished water depending on. water quality and MCL
values set by the EPA. .
In a field-scale assessment of pH and coagulant dose.impacts James M. Montgomery
and the Metropolitan Water District (1989) gathered data from 14 alum coagulation/filtration
plants across the United States. TOC and UV-254 levels were evaluated for raw, filter
influent and finished waters at each plant. This information was combined with data from two
similar .evaluations (Edzwald, 1984; Singer, 1988). This database includes 45 data points
obtained from the 17 treatment plants shown in Figure 4-6. Characteristics of the database
are given in Table 4-1.
4-15
-------
100
Q
LU
O
^
LU
O
O
80
60
40
20
IMPACT OF RAW WATER TOC ON TOC REMOVAL
BY ALUM COAGULATION / FILTRATION
o Li
Raw Water TOC
1.1 mg/L
Coagulation pH = 7.15
Raw water TOC values are the minimum, median
and maximum values in the field-scale database.
10
20 30 40
ALUM DOSE (mg/L)
50
60
c
m
ฃ.
CXI
-------
ALUM COAGULATION TREATMENT PLANT LOCATIONS
Contra Costa County, CAj^sacramentb, CA ;
San Francisco, CA^ast Bay MUD, CA
Santa Clara Valley, CA
4cAurbra, CO
MWD - Mills WTP, CA*MWD - Weymouth Wf, CA
Big Spring,
| 4o_ittle Rock, AR
ifcArlington, TX j (
^Canton, NY
40neida, NY
t)l)jl*iiorwich, CT
^Mackensack, NJ
4^JNewport News, VA
...%..'
onroe, NC
REFERENCES
^Edzwald, 1984 BSinger, 1988 ^JMM and MWD, 1989
T]
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7)
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-------
100
ฃ
Q
LJJ
O
^
LLJ
(Z
O
O
IMPACT OF COAGULATION pH ON TOC REMOVAL BY
ALUM COAGULATION/FILTRATION
Coagulation pH values are the minimum, median
and maximum values in the field-scale database
20 30 40
ALUM DOSE (mg/L)
o
c
Zl
m
-------
TABLE 4-1
Characteristics of JMM/MWD Alum Plant Database
Raw Water Quality
TOC (mg/L)
UV-254 (cnV1)
Alkalinity (mg/L as CaCO3)
Hardness (mg/L as CaCO3)
Temperature (ฐC)
Turbidity (NTU)
Chloride (mg/L)
pinished Water Quality
TOC (mg/L)
UV-254 (cm'1)
Turbidity (NTU)
| Coagulation pH
|| Alum Dose
===
u
3)
.^_-_^
D
=
Distribution
lognormal
lognormal
normal
lognormal
lognormal
normal
lognormal
lognorma
lognorma
lognorma
lognorma
normal
lognorma
Range
1.11-12.1
0.019 - 0.84
6.3-9.0
5.8 -149
10 - 550
2-31
0.4 - 26
1-640'
0.78 - 6.3
0.002 - 0.095
0.04 - 0.61
5.5-8.0
1.5-55
Median
2.78
0.111
7.7
52
93
18
2.4
20
1.98
0.037
0.16
7.15
11
As indicated by the above data, a wide range of water quality was included in the database.
Median TOC and UV-254 removals in this database were 26 and 68 percent, respectively.
Equation 4-1 was developed based on this database. The adjusted R2 for this analysis was
0.968, indicating a high quality of fit.
ln(TOCf) = 0.1639 + 1.159[ln(TOC0)] - 0.4458[ln(alum dose)]
-0.06982[ln(TOC0)][ln(alum dose)] + 0.05666(pHe)[ln(alum dose)] (Eq. 4-1)
Where TOCf = Finished water TOC
TOC0 = Raw Water TOC
pH,. = Coagualtion pH
" A sensitivity analysis of the above equation is shown in Figures 4-7 and 4-8. These
figures indicate the following:
4-16
-------
TOC removal increases with increasing alum dose, however, the size of the
. increase becomes smaller as alum dose increases. This is typical of bench scale
observations in the literature.
TOC removal increases with decreasing coagulation pH in the coagulation pH
range of 5,5 to 8.0. This is also in agreement with the literature, however, the
range of coagulation pH levels, in the database did not allow for the
determination of an optimal coagulation pH.
At alum dosages greater than 10 mg/L, TOC removal increases with increasing
raw water TOC levels.
An analysis was also performed to determine the differences between finished water
TOC levels predicted by the above equation and those observed in the 17 treatment plants.
Figure 4-9 shows that 60 and 90 percent of the predicted finished water TOC levels were
within 0.2 and 0.4 mg/L, respectively, of the observed level. In addition, 90 percent of the
predicted values differed from observed values by less than 12 percent. This deviation needs
to be compared with the accuracy of measuring TOC:
As part of the reg-neg process for the D/DBP rule, Malcolm Pirnie, as part of an
AWWA funded project, assembled a national database containing coagulation and softening
experiments. The data were gathered from utilities, researchers and consultants from around
the United States. The database initially included 3500 records, however, by eliminating
those data with PAC1, extremely low pH and no TOC and by averaging experiments
performed on identical source waters, the database was pared down to 1286 records
performed on 127 different waters. The raw water quality data contained in this database are
summarized in Figure 4-10. As. shown, all waters were divided into 9 subsets of raw water
quality, which correspond to the alkalinity and TOC ranges selected for the proposed
requirements.
Using the coagulation data included in each subset, empirical models were formulated
which predict precursor removal as a function of coagulant dose. For each subset, the data
were considerably scattered, probably a result of varying TOC nature and analytical
discrepancies. A decision was made to use the 90th percentile of TOC levels at discrete
coagulant doses. The 90th percentile data points were.used to develop the equations The
,4-17
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99.9
99
95
80
50
20
0.1
RESIDUAL PROBABILITY PLOT OF TOO REMOVAL
-0.7
O
o
O"
o
-0.6 -0.5 -0.4 -0.3 -0.2 -0.1
0.1 0.2 0.3 0.4 0.5 0.6 0.7
(OBSERVED EFFLUENT TOG) - (PREDICTED EFFLUENT TOC)
T]
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-------
Summary Raw-Water-Statistics for Enhanced Coagulation Database
Figure 4-10
2.0 < TOC=<4.0
4.0 < TOC=<8.0
TOO 8.0
Percentile
Rank
10th
50th
90th
10th
SOth
90th
10th
SOth
90th
A
Alkalinity
11 .
52
60
n
20
27
45
12
16
28
Ikalini
TOC
2.2
2.7
3.6
= 20
. \
5.3
6.0
7.0
n = 6
13.2
16.0
23.5
ty=<60
UV-254
0.069
0.090
0.127
(149)
0.142
0.229
0.288
(77)
0.595
0.747
1.258
SUVA
2.84
3.38
3.97
2.38
329
4.79
4.33
486
5.45
n = 6 (102)
t
l
' !
;
i ,
! .'
'', '
60 <
Alkalinity
74
85
113
i
70
96
110
n
86
'87
88
Alkalinity =<1 20
TOC iivjj** cuv.4
2.4
2.8
3.5
i = 30
;
4.1
59
6.4
= 14
, if
15.1
ni
.1
19.0
0.054
0.077
0.103
(283)
0.087
01 on
. I JU
0.217
(172)
i'!'i
0.674
0x0*7
.oy/
0.719
n=2 (44)
2.03
2.73
3.09
1.93
2AO
.48
3.83
3.80
4ซ f
.15
4.49
~ ~
!
1 '
1 .
i
^M
Allrnli.*:*.
Alkalinity
126
141
214
^MMKa^_^^ป^^^
128
146
202
i
137
218
227
^^^^^ ^ ซ^ซ
Alkalinity > 120
1UC
2.3
3.0
3.5
n- 2
4.1
4.8
6.5
n = 1
8.6
10.3
133
n-
UV-^34
0.039
0.053
0.104
2 (197)
0.067
0.092
0.142
8 (169)
0.203
0.252
0357
9 (93)
SUVA
1 43
1.74
J.<55
1.64
1.90
301
2.22
2.60
3.17
--
Units: Alkalinity mg CaCO3/L; TOC mg/L; UV-2S4 cm'1; SUVA L/mg-m Note:
1 number of raw water (number of datapoints).
-------
90th percentile was used because the EPA requirements were meant to be easily accomplished
by 90 percent of'the affected utilities. Figure 4-11 shows an example of the equation for one
of the nine subsets. Table 4-2 summarizes the constants for all nine subsets.
This database proved to be important towards determining TOC percent removal
requirements under the enhanced coagulation portion of the D/DBP rule. Modifications will
be made to the proposed rule according to these data.
/Table 4-2
Summary of Equation Constants for TOC Removal by Coagulation
4-18
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4.0
3.5
3.0
Figure 4-11
0.00
TOC = 1.42 + 2.04 e-715*Dose
(Alkalinity: 0 to 60 mg/L, TOO 2 to 4 mg/L)
0.10 0.20 0.30 0.40 0.50
Coagulant Dose (mmoles/L)
0.60
-------
4.4.5 Impacts of Temperature and Time of Year
Knocke, et a]., (1986), used bench-scale studies to evaluate the impacts of temperature
on removal of NOM from two southeastern waters. Coagulation/filtration experiments were
conducted with alum and ferric sulfate at temperatures of 2ฐC and 22ฐC. The authors
concluded that water temperature did not have a significant impact on removal of TOC or
THMFP from these two waters. However, turbidity removal was significantly impaired at the
low temperature condition.
4.4.6 Comparisons Between THMFP Removal and TOC Removal
Many NOM surrogate parameters exist, each characterizing NOM in a particular way.
Differences in the removal of these parameters, THMFP and TOC for example, are indicative
of the fact that many organic molecules can be converted, or oxidized, into new organic
molecules with different characteristics.
Several bench-scale studies have suggested that THM precursors, as measured by
THMFP, are removed to a more significant extent than the overall organic carbon content
(Babcock and Singer, 1979; Johnson and Randtke, 1983; Sinsabaugh, et al., 1986b). Another
study (James M. Montgomery, 1992) indicated that the average percent reduction of THM
levels (measured under simulated distribution system conditions) was comparable to the
removal of TOC. Data collected at a Newport News, Virginia treatment plant suggests that
this observation may depend on the measure of THMFP being used (Malcolm Pirnie, 1988).
Figure 4-12 compares the removal of several different THMFP measurements with the
removal of both UV-254 and DOC. All of the parameters shown in this figure apply to the
dissolved phase NOM present in raw and finished waters. For this particular treatment plant,
1-hour THMFP was removed to the largest extent while 7-day THMFP was removed to the
smallest extent. These results demonstrate that THMFP test conditions can influence the
.conclusions developed from a particular study. .In addition, the results point out the
difficulties involved in making quantitative interstudy comparisons with THMFP.
Figure 4-12 also shows that UV-254 removal is similar to the removal of 1-hour
THMFP. This is not surprising because UV-254 measures the concentration of chemical
bonds that generally react quickly with free chlorine Removal of DOC is similar to removal
4-19
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ง
o
^
111
10
o
ALUM COAGULATION / FILTRATION PLANT
NEWPORT NEWS, VIRGINIA
ooc
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-C-
-------
of 5-day and 7-day THMFP. Again, this is not surprising since DOC is representative of all
the organic material available for reaction with free chlorine. These results should be
confirmed by studies at other plants.
4.4.7 Comparisons Between THMFP Removal and DBPFP Removal
A limited number of studies have evaluated the removal of other DBF precursors by
alum coagulation. Figure 4-13 shows the results of a bench-scale evaluation of NOM removal
by alum coagulation. A lake from Chapel Hill, North Carolina was used as the raw water
source and coagulation was performed at pH 5.5 (Reckhow and Singer, 1990). Formation
potential tests were run for 3 days at 20ฐC, pH 7 and a chlorine dose of 20 mg/L. In general,
trichloropropanone formation potential (TCPKFP) was the most difficult fraction of organic
matter to remove. Dichloroacetonitrile formation potential (DC ANFP) was more readily
removed than the other fractions. This figure demonstrates that some DBF precursors may
ป
be removed to a more significant extent than other DBF precursors.
Pilot-scale coagulation/filtration tests were also performed to evaluate the removal of
different DBF precursors from Ohio River water at Cincinnati, Ohio (USEPA, 1988; Stevens,
et al, 1989). Figure 4-14 shows removals obtained with an alum .dose of 40.5 mg/L at a
coagulation pH of 5.8. Chlorine dosages were applied in accordance with the standard
method for THMFP (Clesceri; et al., 1989). The temperature of the chlorination period was
maintainedat 25ฐC. In general, TCPKFP appeared to be the most difficult fraction of organic
matter to remove. However, the authors concluded that raw water and treated water
TCPKFP values were too close to the detection limit to conclude that TCPKFP removal was
significantly different from THMFP removal. Based on the data presented in Figure 4-14, the
authors.concluded that DBPFP removal and THMFP removal were the same. Figure 4-14
also shows that removal of organics leading to rapid THM formation was greater than the
removal of organics leading to long-term THM formation, confirming the results shown in
Figure 4-12. James M. Montgomery (1992) found that the percent reduction of HAAS levels
(measured under simulated distribution system conditions) was approximately equal to the
percent reduction of TOC by alum and ferric chloride coagulation. These results were similar
to those found for THM and TOC reduction. Dryfuse et al. (1995) found that TOC was a
4-20
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100
Q
LLJ
>
o
LU
0
ALUM DOSE VERSUS REMOVAL OF
DIFFERENT SURROGATE PARAMETERS
UNIVERSITY LAKE - CHAPEL HILL, NC
INITIAL TOG = 6.8 rng/L
COAGULATION pH = 5.5
10
20 30
ALUM DOSE (mg/L)
50
TRICHLOROACETONE
FORMATION POTENTIAL
DICHLOROACETONITRILE
FORMATION POTENTIAL
TRIHALOMETHANE
FORMATION POTENTIAL
TOTAL ORGANIC
CARBON
DICHLOROACETIC ACID
FORMATION POTENTIAL
UV-254
TRICHLOROACETIC ACID
FORMATION POTENTIAL
TOTAL ORGANIC HALIDE
FORMATION POTENTIAL
T]
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m
f-
-------
REMOVAL OF DBP FORMATION POTENTIAL BY
ALUM COAGULATION / FILTRATION
OHIO RIVER PILOT PLANT AT CINCINNATI, OHIO
100
8
O
S
m
o:
CHLQRINATION CHLORINATION
" pH = 7.0 PH = 94
4 HOURS 2 DAYS 6 DAYS
4 HOURS 2 DAYS 6 DAYS
CHLORINE REACTION TIME
4 HOURS 2 DAYS 6 DAYS
TRIHALOMETHANE
FORMATION POTENTIAL
CHLOROPICRIN
FORMATION POTENTI>
HALOACETIC ACID
FORMATION POTENTIAL
1,1,1-T-jjpCHLOROPROPANONE
FORMATION POTENTIAL
HALOACETONITRILE
FORMATION POTENTIAL
CHLORAL HYDRATE
FORMATION POTENTIAL
AVERAGE ALUM DOSE = 40.5 mg/L
AVERAGE SETTLED WATER pH = 5.8
RAW WATER TOC = 2.5 mg/L
* NOT DETECTED IN RAW OR FINISHED WATER
NOT DETECTED IN FINISHED WATER
o
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m
-e*
-------
conservative indicator for THM, HAA6, TOX, trihaloacetylnitrile (THAN), chloral hydrate
(CH) and 1,1,1-trichloropropanone (TCP) under UFC chlorination conditions for the
conventional and optimized coagulation of three waters. They also found this to be true for
the molecular size and humic/non-humic fractions.
4.4.8 Impacts of Preoxidation
4.4.8.1 Introduction
Preoxidation can influence the NOM removal performance of coagulation/filtration in
a few ways. First, NOM molecules that are precursors to a given DBP can be oxidized to
molecules that are not precursors to that DBP. Conversely, NOM molecules that are not
precursors to a given DBP can be oxidized to molecules that are precursor to that DBP. In
effect, some DBP precursors are destroyed while others are created. If the destruction of
organic precursors for a given DBP exceeds the creation of new organic precursors for that
DBP, then oxidation may be considered a precursor removal process for that DBP. Second,
preoxidation can influence NOM removal by decreasing the size of NOM molecules and by
increasing the charge on NOM molecules. In some cases, however, preoxidation may
increase the size of NOM molecules through polymerization reactions (Grasso and Weber,
1988). As noted in Sections 4.4.3.1 and 4.4.3.2, coagulation/filtration processes appear to
preferentially remove NOM molecules having high molecular weight and high charge density.
Therefore, preoxidation could either inhibit or enhance NOM removal.
;.. 4.4.8.2 Chlorine
Chlorine is widely used throughout the United States for
oxidation/disinfection purposes. Prechlorination is often used to minimize operational
problems associated with biological growth on filters, pipes or tanks. However with recent
concerns over DBP formation, prechlorination is being avoided when possible without
compromising microbiological quality of the treated water. Prechlorination may impact NOM
removal. Bench-scale studies conducted by Johnson and Randtke (1983) indicate that
\ "
prechlorination will reduce the amount of NOM removal achieved with coagulation. In these
studies a surface water and a groundwater were both treated with chlorine at chlorine to TOC
4-21
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ratios of 7 and 5.2 for 48 hours prior to alum coagulation. For both these waters,
prechlorination significantly reduced NOM removal capabilities as compared to coagulation
without prechlorination. For example, at an alum dose of 60 mg/L the groundwater TOC
removal was reduced from 55 to 40%.
Recently prechlorination has come under scrutiny due to its potential to
increase DBF levels during enhanced coagulation. Many plants, however, rely on
prechlorination to help solve many operational problems including, taste & odor control,
\
turbidity control, algae growth control, inorganic oxidation .and microbial inactivation.
Initially the EPA did not plan to allow disinfection credit prior to enhanced coagulation.
Recent research (Summers et al.. 1997) and .the input received from utilities during the
Technologies Working Group, convinced EPA to allow disinfection credit prior to enhanced
coagulation.
A survey of 329 surface water treatment plants found that 80% use prechlorination,
many of these for multiple reasons. Further investigation showed that the majority of utilities
f
would need to provide additional contact time for microbial protection if predisinfection credit
were not given. Additionally, a majority of utilities would still need to predisinfect for reasons
other than microbiological control,(i.e. taste & odor control, inorganic oxidation). The end
result would be an increase in DBF levels. Moreover, a study performed' by Summers et_al
\
(1991) examined the effects of enhanced coagulation and predisinfection application point on
DBF levels. He found that enhanced coagulation, even with predisinfection, reduces DBF
levels by about 20% as long as the point of predisinfection is within 3 minutes of the rapid
mix. For this reason, enhanced coagulation is believed to provide substantial benefit even
with prechlorination. These results led the EPA to revisit the proposed predisinfection credit
limitations. In the absence of ICR data and in the effort not to increase microbial risk, the
EPA has decided to allow disinfection credit prior to enhanced coagulation.
The table below shows the effect of moving the point of chlorination on DBFs during
conventional and enhanced coagulation. In this table, percent benefit is based on the decrease
in DBF concentration compared to baseline coagulation when pre-rapid mix is the point of
chlorination. As-shown in these tables, the benefit increases significantly as the point of
4-22
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chlorination is moved farther from the pre-rapid mix. Also, a minimum benefit of about 4%
was seen even if the point of chlorination was prior to the rapid mix.
TABLE 4-2(a)
IMPACT OF MOVING PREOXIDATION APPLICATION POINT
Pre-RM
Post-RM
Mid-Floe
Post-Sed
Median Benefit (%)
TOX(n=7)
Baseline Enhanced
Coagulation Coagulation
11
0.3 10
3.9 23
11 40
TTHM (n=9)
Baseline Enhanced
Coagulation Coagulation
17
1.6 21
8.7 . 36
21 48
HAAS (n=6)
Baseline Enhanced
Coagulation Coagulation
4.7
5.3 21
14 36
35 61
4.4.8.3 Chloramines
Limited research has been performed on the effectiveness of chloramines for
removal of THMFP and TOXFP. Chloramines used as a preoxidant along with coagulation,
however, can be an option for DBP control. Reed (1983) conducted pilot studies which
showed that prechloramination is just as effective as prechlorination for the removal of DBP
precursors. Other studies (Kirmeyer et al., AWWARF, 1993) also indicate that chloramines
are no more effective than any other preoxidant for precursor removal.
4.4.8.4 Ozone
Studies on ozone for removal of DBPFP (Chang and Singer, 1991; Singer
and Chang, 1988; Reckhow and Singer, 1984) concluded the following:
4-23
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Although preozonation alone has an almost negligible impact on i
the overall TOC concentration of raw water, the organic material
is altered such that the color and UV absorbance of the water are
reduced.
Preozonation alone can lower THMFP by about 10 percent at the
\
ozone dosages commonly used in water treatment practice. With
regard to THM control, the principal benefit derived from
employing preozonation in place of prechlorination is that chlorine
can be added later in the treatment train.
Hardness and TOC have a major impact on the stability of
paniculate material. The aggregation rate of suspended
paniculate matter was very sensitive to the hardness-to-TOC ratio
of the non-ozonated raw water.
<
When used as a preoxidant in water treatment, ozone can
destabilize paniculate material. The optimal dosage of ozone for
this benefit depends on the hardness and TOC concentration of the
water. Optimal ozone-induced coagulation occurs in waters with
hardness-to-TOC ratios >25 mg CaCOj/mg TOC and ozone doses
of about 0.4-0.8 mg Oj/mg TOC.
Work by Edwards et. ai. (1993) found conflicting effects of preozonation
at a full-scale plant for two source waters. Preozonation improved NOM removal by directly
removing organic matter through mineralization, volatilization and/or stripping. However,
preozonation also reduced NOM removal by decreasing the surface charge of floe, and
therefore hindered adsorptive removal of organic matter. .The relative magnitude of each of
these effects would determine the overall effect. The researchers determined that in a
majority of utilities, preozonation would have a negative effect at ozone doses above 0.7 mg
4-24
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O3/mg TOC. For higher concentrations of organic matter (i.e. less than 0 7 mg O3/mg TOC),
however, NOM removal may be enhanced
\
4.4.8.5 Chlorine Dioxide
Limited research has been performed on the impact of chlorine dioxide on
coagulation. Lykins and Griese (1986) studied the use of chlorine dioxide in a field-scale
alum coagulation/filtration plant treating water from the Ohio River at Evansville, Indiana.
The treatment plant had two parallel process trains, one of which was treated with 1.4 mg/L
of chlorine dioxide as a preoxidant. The other train was not treated with an oxidant prior to
coagulation. Both trains received the same level of alum treatment followed by the same level
of chlorination. Although the removal of TOC or THMFP was not reported, filter effluent
instantaneous THM levels were 32 percent lower in the train treated with chlorine dioxide.
Chlorine residuals at the points of THM measurement were not reported. Chlorine demand
may have been exerted by chlorite and, therefore, would have reduced the amount of chlorine
'available for THM formation.
4.4.9 Precoat Filters with Amendments
A study was performed to evaluate precursor removal using precoat filters with
crushed GAC and powdered anionic resin (Spencur and Collins, 1990). The results of the
study concluded that amending diatomaceous earth with a strong base anionic resin in the
precoat and body feed steps allowed the removal of dissolved organic precursors from a
synthetic raw water source. The combination removed 66 percent of the UV-254.and 51
percent of the incoming non-purgeable DOC. The combination also produced effluent
turbidities that started the run at .0.80 NTU and improved to 0.20 NTU by run termination
and gave acceptable headlosses of 12 to 14 psi over the 4 hour runs.
4.4.10 Impacts of PAC Addition
PAC addition may impact coagulation processes in several ways. With the addition of
PAC, particle loading will increase. The system must now remove the PAC particles through
coagulation/filtration in addition to the natural turbidity in the source water. This may lead
to a need for increased coagulant doses and more frequent filter backwashes. Also, at
4-25
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increased PAC doses the chance of carbon fines leaving the filters increases. This provides
the potential for bacterial growth problems in the distribution system. Coagulation may also
affect PAC adsorption. Floe particles can clog small pores in the PAC particles. Effective
PAC adsorption relies heavily on the full utilization of the porous carbon (i.e. large surface
area). If floe particles clog PAC pores, adsorbable contaminants cannot diffuse into the PAC
particles and the- effectiveness of the PAC is reduced.
In some eases, such as> waters containing only small amounts of particles, the additional
(PAC) particles may actually be beneficial for the coagulation/flocculation process (i.e.
increased floceulation efficiency). Also, since PAC is reduced carbon, it can exert an oxidant
demand. In addition, in recent years, it has been observed that any PAC that gets to a filter
(i.e. not removed during the clarification process) will go through a filter and is often not
picked up by the turbidimeter (although they are detected by particle counters) because of the
PAC's ability to absorb light as opposed to scattering light. This passage of PAC into the
finished water has been observed by a number of utilities which have filtered 3 to 4 L samples
of finished water through either 1 Aim glass fiber filters or 0.45 ^m membrane filters during
the periods when they are feeding PAC. The passage of PAC through granular media filters
is likely due to the surface chemistry of the PAC. The passage of these particles in the finished
water poses a challenge when it comes to water quality control in the distribution system.
With the ability to settle out in quiescent or low velocity areas, they provide attachment points
for organics and bacterial growth.
4.4.11 Membrane Processes with Coagulant Addition
Low-pressure membrane processes, such as microfiltration (MF) and ultrafiltration
(UF), have recently become popular in the drinking water industry because they have become
cost competitive with traditional treatment processes. MF and UF provide excellent particle
removal and there by offer excellent protozoan removal (e.g. Gardia and Cryptosporidmm).
However, due to relatively large pore size, these processes are only mildly effective in NOM
and DBP precursor removal. For this reason, MF and UF have often been combined with
pretreatment options such as coagulation to remove organic material which would otherwise
pass through the membrane pores.
Unfortunately, because the technology is still new, there is only a small body of work
on coagulation/membrane systems. In addition to this, the effect of coagulation on a
membrane system will be site specific, depending on factors such as water quality, membrane
4-26
-------
material, membrane configuration and coagulant type and dose.' This makes it difficult to
generalize the effect of coagulation on membrane processes. However, several studies are
presented here to give an indication of some of the advantages and disadvantages associated
r
with these combined processes.
Fu et al. (1997) studied the effects of alum coagulation with crossflow and deadend UF
at several doses and pHs during short-term bench-scale tests. Amicon PM-10 membranes
(MWCO 10,000) were used during testing. These membranes are made from hydrophobic,
polysulfone material which does not adsorb inorganic molecules, but has a tendency to adsorb
some organic macromolecules. Coagulant dose and pH strongly affected fulvic acid and TOC
removal, flux decline and flux recovery. At both pH of 7.2 and 6.0, fulvic acid removal
increased with increasing alum dose (dosed from 30 to 210 mg/L). TOC removal, however,
was a more complicated function of pH and removal varied (between about 55 and 85
percent) depending on pH and alum dose. 15-20 percent of this removal, however, was
attributed to adsorption on the membrane. Flux decline decreased as alum dosed increased
at both pHs. At a pH of 6.0, however, the flux decline was generally less severe (10-20
percent as opposed to 10-60 percent decline).'
Jacangelo et al. (1994) also studied the operational effects of in-line alum coagulation
on crossflow UF at pilot-scale for two surface waters. An alum dose of 50 mg/L was tested
at pH 7.7 and pH 6.5. Testing was performed with Aquasource hollow fiber membranes
(MWCO 100,000, cellulose acetate). Severe fouling was observed for both source waters.
Lowering the pH did not alleviate membrane fouling. Flux declined about 64 percent after
only 800 hours of operation for one water. During testing with the other water, flux decline
was so severe that a chemical cleaning was necessary to continue operation after only 334
hours.
i
Some researchers, however, have found benefits and experience little fouling during
membrane/coagulation processes. Laine et al. (1990) found that flux could be enhanced with
aluminum chloride doses of 60 mg/L when treating a surface water with crossflow UF
(MWCO 100,000, hydrophilic and hydrophobic polymeric membranes). These tests,
however, were conducted at bench-scale and long-term fouling was not examined. Laine et.
al. also found 70 percent reduction in UV-254 and 53-63 percent reduction in TOC when a
60 mg/L aluminum chloride dose was used.
Although Jacangelo et al. (1994) previously experienced severe fouling of Aquasource
membranes when in-line alum coagulation was used, Laine (1997) has obtained preliminary
4-27
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data which attest to the feasible operation of Aquasource UF on settled alum coagulated
water. For a 1.5 month period operating UF on an alum settled water, no flux decline was
observed! Laine (1997) has also obtained preliminary data using a ferric based coagulant with
Aquasource UF. During initial testing, no operational losses were seen when in-line ferric
chloride coagulation was used. Jack (1997) also experience promising results when using in-
line ferric chloride coagulation with an Aquasource UF pilot system. No loss in flux was
observed over a 144 hour operation period when the coagulant was dosed at 14 mg/L. In
addition to this ferric chloride addition, PAC was also added at 10 mg/L. TOC reductions
of 25-30 percent were seen during this testing (raw water TOC was 5 mg/L). TOC
reductions with only PAC addition averaged 27 percent indicating that ferric chloride addition
did not aid significantly in TOC removal while PAC was used. Oliveri et al. (1991), however,
found that THMFP removal of a surface water could be increased from 15 to 60 percent
when a 10-15 mg/L ferric chloride dose was used in conjunction with MF.
\
4.4.12 Summary
Coagulation/filtration processes can achieve significant levels of NOM' removal.
Taking alum dose and coagulation pH into account, NOM removal is influenced by initial
TOC levels and by the characteristics of the NOM. Higher NOM removals could be achieved
by decreasing coagulation pH levels and increasing alum dosages beyond those currently
used. NOM removal .is also dependent on its molecular size. Higher MW NOM is typically
easier to remove than lower MW NOM. .
It is believed that through judicial use of polymers, high levels of TOC removal can be
achieved while maintaining low finished water turbidity levels. However, the impacts of'
increasing alum dose and decreasing coagulation pH levels may complicate sludge handling.
Using a hurnic acid extract as the source of organic material, Dulin and Knocke (1989)
reported that the rate and extent of alum sludge dewatering was impaired as more organic
matter was incorporated into the sludge. Thickening rates were also reduced. Therefore,
increased NOM removal will increase sludge handling costs through increased quantities of
sludge, and may also increase costs as a result of decreased thickening and dewatering rates,
'and decreased dewaterability.
4-28
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TOC removal was frequently found to be a conservative indicator of DBF precursor
removal. Therefore, removal of DBF precursors may exceed the 50 to 60 percent maximum
removal of TOC in many instances. With the potential exception of TCPKFP, the removal
of THMFP by alum coagulation/filtration generally provided a conservative indication of the
removal of other DBF precursors.
Some studies have shown preoxidation enhances NOM removal by alum
coagulation/filtration; however, because of the reduction in NOM molecule size, preoxidation
could inhibit NOM removal. While results are site-specific, preoxidation is not a generally
recommended strategy from a NOM removal perspective. This strategy may be more
appropriate for other applications such as iron and manganese removal and oxidation of taste
and odor compounds.
Finally, it should be recognized that the extent of improvement in TOC, THM and
other DBF removals by modifying coagulation conditions is highly dependent upon the source
water characteristics. The removal of TOC is strongly related to pH, and therefore the extent
to which pH can be depressed during coagulation will have a profound effect on NOM
removal. For example, higher coagulant dosages will depress pH significantly in poorly-
buffered waters with low alkalinity. Waters with higher alkalinity (>80 to 100 mg/L as
CaC03) will resist pH depression by coagulant addition alone, and therefore removal of NOM
will likely be 'less than in low alkalinity waters for a given coagulant dosage. Also, the
addition of acid to reduce pH in these waters may increase costs and facility requirements
substantially. These costs may be greater than the costs associated with sludge handling
(Malcolm Pirnie, Inc., 1989; James M. Montgomery, 1992).
Further, the potential for improving NOM removal in plants which provide direct
filtration will be mitigated, because coagulant dosages cannot be increased above some level
at which filtration efficiency will be compromised. Therefore, the greatest potential for
substantially improving coagulation exists in conventional treatment plants with raw water
sources of moderate to low alkalinity, although increasing coagulant dosages in all waters
likely will improve the removal of NOM and reduce the formation of DBFs upon subsequent
disinfection.
4-29
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4.5 PRECIPITATIVE SOFTENING
4.5.1 . Introduction
Lime softening is typically not thought of as an organics removal process.
However, lime softening removes NOM by the same mechanism as coagulants and can
remove NOM to a significant degree in some cases. The primary differences between
softening and metal-salt coagulation are that CaC03 solids, unlike iron or alum hydroxides,
have a small surface area and a negative charge. Coagulants-typically have a larger surface
area and a neutral or positive charges and therefore have a higher affinity for the negatively
charge NOM. However, because calcium has an affinity for certain functional groups (mainly
carboxylic acids), some NOM removal will be possible. Also, when MgOH is precipitated -
with high pH; significant NOM removal can be anticipated. This is because MgOH acts very
much like a coagulant and is an effective absorbent for NOM (Randtke, 1988).
The degree of removal of NOM by precipitative softening depends on a
number of factors including the following:
Nature and concentration pf NOM entering the process.
Other water quality characteristics including calcium hardness and
magnesium hardness. ...
Treatment processes, such as oxidation, used prior to the
precipitative softening process.
- Type and dose of the chemical being used for hardness removal.
In many cases of softening of surface water, a metal salt coagulant (ferric) is
often used. The following sections briefly describe some key results observed in several
precipitative softening studies.
452 Relationships Between Physicochemical Characteristics of Natural
Organic Matter and Performance of Precipitative Softening
NOM removal during precipitative softening will depend on many factors, both process
and non-process related. Physicochemical characteristics of the NOM will greatly affect the
4-30
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ability of a softening process to remove adsorbable organics. Many of the important
characteristics include charge, molecular weight, functionality, solubility, degree of
polymerization and molecular geometry. These are discussed below.
4.5.2.1 Molecular Weight
Semmens and Staples (1986) reported that larger molecules, particularly
those with molecular weights greater than 10,000, were readily removed by precipitative
softening. However, an increased level of TOC was observed for the fraction containing
molecules with molecular weights less than 1,000. According to the authors, this observation
may have resulted from hydrolytic decomposition of large molecules at the high pH levels
used in the process. Changes in water chemistry may have also affected the rejection
efficiency of the membranes used for fractionation. El-Rehaili and Weber (1987) also
reported that larger organic molecules were preferentially removed by precipitative softening.
Liao and Randtke (1985) also found during bench-scale tests that most of the removable
NOM was the high molecular weight fraction. They also found that polymers of organic
substances were much more likely to be removed than their monomeric analogs.
4.5.2.2 Charge
CaCO3 precipitates are negatively charged. Therefore, electrostatic
adsorption of only positively charged contaminants is anticipated. Since most NOM is
negatively charged, adsorption will not occur unless sufficient chemical interaction is available
to overcome the charge repulsion. Although electrostatic forces are weak compared to
chemical interactions, if a positively charged contaminant is sufficiently polymerized,
electrostatic adsorption could be substantial. This presumption was confirmed by Liao and
Randtke (1985) by comparing removal of simple and polymeric ammonia salt. The influence
of molecular charge distributions on NOM removal by precipitative softening was also
evaluated by Semmens and Staples (1986). They found that acidic molecules were poorly
removed while neutral and basic molecules were effectively removed.
4-31
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4.5.2.3 Solubility
According to Liao and Randtke (1985), for a compound to adsorb to CaCO3
precipitates, it must be slightly hydrophilic. If a compound is too hydrophilic, it will remain
in the aqueous phase, however, if it is too hydrophobic it will not have the charge or the
functional groups necessary to adsorb. Therefore compounds with solubility distribution
extremes will probably not be readily removed.
The influence of organic matter solubility on NOM removal by precipitative
softening was also evaluated by Semmens and Staples (1986). This study found, however,
that hydrophobic molecules were more.readily removed than hydrophilic molecules.
4.5.2.4 Other Factors
The type of functional group on a compound will affect its completion
with CaCO, precipitates. Calcium will preferentially bond with oxygen-containing species
(Liao and Randtke, 1985). As a result, NOM with oxygenated functional groups may be
more easily removed. Additionally, alteration of the functional groups upon disinfection may
also aid in NOM removal. Jekel and Ernst (1981) found that ozonation increased the
adsorption of NOM during lime softening.
Molecular geometry is also'an important'factor towards the ability of a
compound to bind to a solid. Geometry affects whether an NOM substance will be adsorbed
and if so, to what extent the NOM will be adsorbed. Molecular deformability and degree of
hydration also affect the adsorption of organic compounds (Liao and Randtke, 1985).
4.5.3 Waterpuality and Chemical Dose Impacts
Several reports in the literature have described the performance of .precipitative
softening for NOM removal at a bench-scale level (Johnson and Randtke, 1983; Liao and
Randtke 198,5; Semmens and Staples, 1986; Jodellah and Weber, 1985; Weber and Jodellah,
1985; Collins, et al, 1985; El-Rehaili and Weber, 1987; Randtke, et al., 1982). The most
extensive evaluations of NOM removal by precipitative softening were performed by Randtke
and co-workers.- Using fulvic acid isolated from an Illinois groundwater, Liao and Randtke
(1985) reported that NOM removal in the precipitative softening process was primarily
4-32
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achieved by adsorption onto calcium carbonate and magnesium hydroxide. Therefore, NOM
removal depends'on the amounts of calcium carbonate and magnesium hydroxide produced
in the softening process. The amount of calcium carbonate produced depends on raw water
calcium and carbonate concentrations, the amounts of calcium and carbonate added to the
process, and the pH of the softening process. The amount of magnesium hydroxide produced
depends on raw water magnesium concentration and the pH of the softening process.
In addition, when the ratio of raw water magnesium to total calcium was increased, the
removal of NOM also increased (Randtke, et a]., 1982 and Liap and Randtke, 1985). Total
calcium refers to the sum of raw water calcium and the calcium added by lime addition.
Figure 4-15 shows results reported by Randtke, et a]., (1982), for a fulvic acid isolated from
an Illinois groundwater. These results suggest that magnesium hydroxide adsorbs NOM to
a stronger degree than calcium carbonate.
Liao and Randtke (1985) also demonstrated that NOM removal is influenced by the
manner in which calcium carbonate is precipitated. NOM removal was enhanced by the
formation of finely divided calcium carbonate with poor crystallinity. Because of this, NOM
removal is inhibited by processes that favor the rapid formation of large calcium carbonate
particles. Such conditions are present when softening plants recycle sludge to increase the
rate and extent of hardness removal. Using the groundwater fulvic acid described above and
a softening pH of 11, results given in Table 4-3 were reported.
TABLE 4-3
Effect of Sludge Recycle Ratio on TOC Removal
Ratio of Recycled
Solids to Solids
Precipitated
0
1
2
TOC Removed
(percent)
35
31
23
4-33
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100
IMPACT OF MAGNESIUM ON REMOVAL OF
TOG BY PRECIPITATIVE SOFTENING
FULVIC ACID ISOLATED FROM ILLINOIS GROUNDWATER
200 400 600
TOTAL HARDNESS PRECIPITATED (mg/L as Calcium Carbonate)
800
FIGURE
5
-------
In addition, NOM removal was enhanced when calcium was in excess with respect to
carbonate In contrast, hardness removal .is enhanced when an excess supply of carbonate is
available. Therefore, NOM removal appears to be favored by conditions that inhibit
satisfactory removal of hardness (e.g., no sludge recycle and excess calcium). The authors
suggest a two-stage process be used to effectively remove both NOM and hardness. These
stages are as follows:
Stage 1: Optimize NOM removal by adding excess lime to elevate pH and
calcium levels.
Stage 2: Optimize hardness removal by adding carbonate alkalinity and by
recycling sludge. ' '
For plants using both lime and soda ash in a single stage process, the authors suggest
delaying the addition of soda ash for several minutes after lime addition.
During earlier work, Randtke et. al. (1982) found that the removal of humic substances
during lime-soda softening was increased with increasing pH, increasing precipitate formation
and decreased TOC concentrations. Also, they found that organics removal was enhanced
by the presence of magnesium or phosphate.
Using the softening data contained in an AWWA database (see section 4.4.4), empirical
models were formulated which predict precursor removal as a function of lime/soda dose..
Table 4-4 gives the equations for each TOC range. In developing these equations, cases with
high ferric dose' (> 10 mg/L) were excluded. Figure 4-16 gives the water quality data
collected for the softening plants.
TABLE 4-4
TOC Prediction Equations for Lime Softening
TOC Range
2 < TOC <, 4
4 < TOC S 8
8
-------
Summary Raw-Water-Statistics for Enhanced Coagulation Database
4.0 120
Ikalinity
126
141
214
TOC
2.3
3.0
3.5
UV-254
0.039
0.053
0.104
SUVA
143
1.74
3.68
'197)
n = 18 (169)
128
146
202
4.1
4.8
6.5
0.067
0.092
0.142
1.64
1.90
' 3.01
137
218
227
8.6
10.3
73.3
0.203
0.252
0.357
2.22
2.60
3.77
n = 9 (93)
Note: n = number of raw water (number of datapoints)
-------
O
O
1.0
0.5
0.0
Figure 4-17
TOC = 1.30 +2.30 eฐ12*Dose
(TOC 2 to 4 mg/L)
0.00 2.00 4.00 6.00 8.00 10.00 12.00
Coagulant Dose (mmoles/L)
-------
Field-scale data from eight softening plants (Montgomery and Metropolitan, 1989,
Singer, 1988) showed that precipitative softening plants can achieve1 the same level of NOM
removal as alum coagulation/filtration .plants. TOC removal in these plants ranged from 12
to 88 percent while UV-254 removal ranged from 44 to 96 percent. Median removals of
TOC and UV-254 were 37 and 76 percent, respectively. It should be noted that in full-scale
softening plants, alum or ferric chloride addition is also practiced. Lime addition often creates
small particles that are difficult to filter; plants often add coagulants to remove these particles.
Coagulants are also combined with lime softening to remove precursor material not removed
by softening. A significant amount of TOC removal can be attributed to the addition of
coagulant.
i t'
ป
4.5.4 DBPFP Removal
Pilot-scale softening tests were performed to evaluate the removal of different DBF
precursors from Ohio River water at Cincinnati, Ohio (USEPA, 1988; Stevens, et aj., 1989).
Figure 4-18 shows removals and test conditions for this evaluation. Chlorine dosages were
applied in accordance with the standard method for THMFP (Clesceri, et al., 1989). The
temperature of the chlorination period was maintained at 25ฐC.
In general, DBPFP removals ranged from 30 to 60 percent under the conditions used
in this evaluation. The data do not clearly show which precursor fractions are least readily
removed. HAAFP appeared to be removed to a greater extent than THMFP; however, the
authors concluded that DBPFP and THMFP removals were essentially the same.
The pilot plant also achieved 39. percent removal of TOC. In most cases, this level of
removal was lower than the removals of THMFP, HAAFP and HANFP. Thus, TOC removal
may be a conservative.indicator of the.removal of THM, HAA and HAN precursors.
Johnson arid Randtke (1983) examined the removal TOC during bench-scale lime
softening for several different source waters. Softening with postchlorination resulted in TOC
reductions of 14 and 32% for a river water and groundwater, respectively. Softening with
postchlorination of a fulvic acid solution resulted in TOC reductions of 46, 85 and 92 percent
for lime doses of 100, 200 and 300 mg/L, respectively.
4-35
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Q
LU
>
O
^
LJJ
cr
100
80
60
40
20
0
REMOVAL OF DBP FORMATION POTENTIAL BY
PRECIPITATIVE SOFTENING
OHIO RIVER PILOT PLANT AT CINCINNATI, OHIO
CHLORINATION
pH = 5,0
CHLORINATION
pH=7,0.
CHLORINATION
4 HOURS 2 DAYS 6 DAYS
4 HOURS 2 DAYS 6 DAYS
CHLORINE REACTION TIME
4 HOURS 2 DAYS 6 DAYS
TRIHALOMETHANE
FORMATION POTENTIAL
CHLOROPICRIN
FORMATION POTENTIAL
HALOACETIC ACID
FORMATION POTENTIAL
111-TRICHLOROPROPANONE
FORMATION POTENTIAL
HALOACETONITRILE
FORMATION POTENTIAL
CHLORAL HYDRATE
FORMATION POTENTIAL
LIME DOSE = 186 mg/L
SODA ASH DOSE = 117 mg/L
SOFTENING pH = 10.8
RAW WATER TOC = 2.3 mg/L
RAW WATER CALCIUM = 144 mg/L
RAW WATER MAGNESIUM = 91 mg/L
+ NOT DETECTED IN FINISHED WATER
* NOT DETECTED IN RAW OR FINISHED WATER
# DATA NOT SUFFICIENT FOR ANALYSIS
3J
O
c
m
-&.
oo
-------
4.5.5 Summary
1 Precipitative softening can achieve the same range of TOC removal as achieved by
alum coagulation/filtration processes. Field-scale data from eight softening plants showed
that these plants were achieving TOC removals of 12 to 88 percent and UV-254 removals of
44 to 96 percent. Pilot-scale studies with Ohio River water showed that TOC removal may
be a generally conservative indicator of THMFP, HAAFP and HANFP removal.
Like coagulation/filtration, processes, the precipitative softening process can be
modified to increase NOM removal. In general, NOM removal is enhanced by conditions that
favor the formation of magnesium hydroxide and small calcium carbonate particles. These
conditions are achieved by:'
Elevating pH to approximately 10.8 or higher.
Delaying carbonate addition for several minutes..
Delaying sludge recycling.
The latter two modifications inhibit the removal of hardness. Thus, process modifications
> '
should be implemented in a cautious manner. For systems employing a multi-staged process,
satisfactory NOM and hardness removal might be achieved by the two-stage process noted
above. In many full-scale cases, alum or ferric coagulants are also added to softening plants.
4.6 GRANULAR ACTIVATED CARBON
s
4.6.1 Introduction
" ซ i
The removal of NOM by GAC adsorption depends on a large number of
factors including the those listed below. This section briefly describes some key results
observed in several continuous flow GAC studies.
Molecular size, polarity and concentration of NOM entering the GAC
process.
Other water quality characteristics such as pH and ionic strength.
Treatment processes used prior to the GAC process.
4-36
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GAC characteristics such as pore size distribution and surface chemistry.
Operational characteristics such as EBCT and GAC usage rate.
4.6.2 pH Impacts
The impacts of pH on adsorption of NOM and humic extracts have been well
i
documented in equilibrium studies using powdered activated carbon (Weber, et a]., 1983;
Randtke and Jepsen, 1982; McCreary and Snoeyink, 1980; Summers, 1986). All of these
studies showed increased removal of TOC with decreased pH levels. Unfortunately, some
of the work has been done with different initial TOC concentrations, TOC,,, and the increased
performance attributed to low pH may be because of the lower TOCo. A relationship between
the relative adsorption capacity for TOC at the same TOC0 and pH has been established for
13 different source waters and a bituminous coal-based GAC (Hooper et al., 1996b). Within
the pH range of 5 to 10, a decrease in the pH of one unit yielded a 6 % increase in adsorption
capacity. However, the number of continuous flow evaluations of pH impacts is limited.
In a pilot-scale evaluation of treatment alternatives for the City of San Diego, Malcolm
Pimie (1990) used rapid small scale column tests (RSSCT) downstream of a continuous flow
pilot plant to evaluate the effect of lower pH on GAC adsorption. Pretreatment at the pilot
plant included ferric chloride coagulation (15 mg/L) at two alternative pH values of 7.3 and
6.5. GAC adsorption at EBCTs of 10 and 20 minutes were simulated. GAC usage rates of
500 Ibs/MG was observed for pH 7.3 to reach a target THM level of 25 ug/L. The usage rate
decreased to 200 Ibs/MG at pH of 6.5 to achieve the same THM target.
In a bench-scale^study Semmens, et a]., (1986) examined the impacts of pH on
adsorption of NOM from the Mississippi River at Minneapolis, Minnesota. Prior to
adsorption, the water was treated with alum coagulation, flocculation, sedimentation and
filtration. The alum dose was 100 mg/L and the pH of coagulation was 5. Columns were
packed with Westvaco Nuchar WV-G GAC and flow rates were maintained to produce an
average EBCT of 1.15 minutes. They reported increased adsorbability of TOC with
decreased pH levels. The most substantial increase was observed for a pH change from 7.0
to 6.1. For treatment objectives in the range of 50 to 70 percent TOC removal, this pH
4-37
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change increased the GAC bed life by 85 to 100 percent. The study klso showed increased
reduction of THMFP and UV-254 with decreased pH levels.
4.6.3 Impacts of Pretreatment with Coagulation/Filtration
The impacts of coagulation on NOM adsorption have also been well documented in
batch experiments studying adsorption equilibria (Weber, et al., 1983; Randtke and Jepsen,
1981; Lee, et al.; 1981; El-Rehaili and Weber, 1987; Harrington and DiGiano, 1989).
Coagulation processes, as a pretreatment to GAC, can. both reduce influent TOC
concentration and decrease the influent pH to the adsorber, thus leading to improved GAC
performance.
A study by Semmens, et al., (1986) showed that coagulation pretreatment to GAC
increases the run time of the contactor, and that further improvement in GAC run time can
be achieved at higher coagulant doses, In this study, Mississippi River water at Minneapolis,
Minnesota (raw water TOC of 5.4 mg/L) was treated with alum at pH 5 and alum dosages
of 25, 50 and 75 mg/L. These alum dosages achieved TOC removals of 16, 33 and 38
percent, respectively. Figure 4-19 shows the TOC breakthrough profiles for air three
coagulated waters at an EBCT of 1.15 minutes and an adsorption pH of 5. The initial
breakthrough of TOC was observed at 1,000, 2,000, and 4,000 bed volumes with the
alternative coagulation pretreatments using 25, 50, and 75 mg/L alum. Similar results were
observed for removal of THMFP and UV-254.
In another study by Hooper et al. (1996a), conventional coagulation pretreatment and
optimized coagulation pretreatment were compared prior to GAC adsorption for three waters
1) Salt River, Arizona, 2) Ohio River, Ohio and 3) Harsha Lake, Ohio. In this study,
optimized coagulation was defined as coagulation at a dose beyond which marginal TOC
removal were not measurable. Consequently, optimized coagulation resulted in rather large
alum dosages'(70 to 90 mg/L for optimized coagulation compared to 8 to 44.mg/L in
conventional coagulation). The effluent from the GAC contactors were characterized for
various DBFs and precursor material. The GAC run time increased by a factor of 2 to 3 as
a result of optimized coagulation pretreatment. The increase in treatment cost due to
coagulation optimization (under the extreme conditions of this study) was found to offset the
4-38
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IMPACT OF ALUM COAGULATION ON
GAC ADSORPTION
MINNEAPOLIS, MN
ALUM DOSE = 25 mg/L
Init. TOG = 4.55 mg/L
ALUM DOSE = 50 mg/L
Init. TOO = 3.62 mg/L
ALUM DOSE = 75 mg/L
Init. TOG = 3.36 mg/L
0
2,000 4,000
6,000 8,000 10,000
BED VOLUMES FED
12,000 14,000 16,000
Q
c
m
-tx
-------
reduction in GAC costs. Under more realistic enhanced coagulation conditions, however, the
increase in cost for coagulation optimization is expected to be less than the decrease in cost
for GAC adsorption.
Several investigators have reported better GAC performance for TOC control after
coagulation or after increasing the coagulant dose, i.e., enhance coagulation. Hooper et al.
(1996a; 1996b; 1996 c) have shown that the increase in GAC run time after enhanced
coagulation can be attributed to the lower pH and lower initial TOC concentration associated
i
with the enhanced coagulated water.
*
4.6.4 Impacts of Preozonation
Several studies have examined the impacts of ozonation on the GAC adsorption of
NOM (Huber, 1984; Benedek, ej al., 1979; Chen, et al, 1987; Kaastrup, 1985; Somiya, et
al., 1986; Harrington and DiGiano, 1989; Malcolm Pirnie, 1990; Summers et al., 1997).
These studies demonstrated that the impacts of ozonation on adsorption of NOM can be
highly variable. These widely varying results can be attributed to the following:
Ozone can increase adsorbability of NOM by reducing the overall molecular size
of NOM molecules.
Ozone can decrease adsorbability of NOM by forming highly polar, hydrophilic
molecules. , '
i
In addition, the overall impact of ozone on NOM removal by GAC is described by changes
in both adsorbability and biodegradability. The difference between NOM removal by
adsorption and NOM removal by bibdegradation is'difficujt to quantify. In light of these
difficulties, this section focuses on the overall impact of ozonation on the GAC process while
Section 4.11.2 focuses on the differences between the two NOM removal mechanisms.
Several continuous flow studies have been designed to evaluate the impacts of
ozonation prior to the GAC process. In one of these studies, pilot-scale investigations were
. conducted on Delaware River water in Philadelphia, Pennsylvania (Maloney, et al., 1985;
Neukrug, et al., 1983). The pilot-scale GAC columns (EBCTs of 15 and 30 minutes) were
set up to receive pretreated water with and without ozonation. Pretreatment included
4-39
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coagulation with ferric chloride, sedimentation and filtration. The results indicated that the
breakthrough of TOC and THMFP were slower for the ozonated process trains compared to
the unozonated trains. In another study, Cross Lake water from Shreveport," Louisiana
(Glaze and Wallace, 1984; Glaze, et a]., 1982) was pretreated with alum coagulation,
flocculation, sedimentation and filtration and applied to pilot-scale GAC columns'with 12 and
24 minute EBCTs. TOC and THMFP breakthrough did not show any significant difference
as a result of ozonation. In a City of San Diego study, Malcolm Pirnie (1990) observed
results which were similar to the Shreveport studies. A small difference, however, was
observed in this study which indicated a slightly earlier breakthrough of SDS-THMs in
ambient pH experiments with ozonated process train.
If biological treatment, either within the GAC column or ahead of the GAC column,
is not effective in removing the hydrophillic NOM, then these weakly adsorbing compounds
can have a negative impact on the overall GAC performance. Solarik et al. (1996) and
Summers et al. (1997) systematically evaluated the impact of ozonation and biotreatment on
subsequent GAC performance for five waters. They showed that ozonation and biotreatment
decreased the humic and intermediate molecular size fractions, which are the most strongly
adsorbing fractions. They found that the early part of the breakthrough was GAC dominated
by the relative increase in the weakly adsorbing fraction which in some cases led to earlier
breakthrough, while the overall lower initial TOC dominated the latter portion of the
breakthrough curve which always led to longer run times.
4.6.5 Impacts of GAC Type
The relationship between GAC pore size distribution and NOM molecular size
distribution has been shown to be important by several investigations (Summers and Roberts,
1988; Lee, et aj., 1983; Semmens and Staples, 1986; El-Rehaili and Weber, 1987; Chadik and
Amy, 1987). In general, investigators have found the GAC process to favor removal of NOM
molecules of low to moderate molecular size even though the adsorption process should favor
removal of large molecules. This phenomenon takes place because, small GAC pores
physically exclude large NOM molecules from adsorbing. Thus, GACs having a greater
4r40
-------
quantity of large pores can be expected to remove more NOM than GACs having a smaller
1
quantity of large pores.
Continuous flow, bench-scale experiments were used to study the impacts of GAC type
on removal of TOC (Lee, et aL, 1983). The tests studied the adsorption of organic material
obtained from a fulvic acid extract of peat soil. Despite differences between peat fulvic acid
and aquatic NOM, the results can be generally applied to practical situations. Three GAC
columns, each with an EBCT of 7.5 minutes, received untreated fulvic acid and were packed
with Westvaco Nuchar WV-G, Westvaco Nuchar WV-W and ICI America's HD-3000. The
total GAC pore volume was greatest for the column containing WV-G and was smallest for
the column containing WV-W. Figure 4-20 shows TOC breakthrough curves, for each
column and indicates that increased pore volume resulted in longer column runs. Because the
density of each GAC and influent TOC were different, this figure cannot be used to conclude
that mass based GAC usage rates were decreased with increased pore volume. pH levels
during adsorption were not reported.
' 4.6.6 Impacts of Empty. Bed Contact Time
The impacts of EBCT on GAC usage rate for NOM removal have been studied in
numerous continuous flow evaluations. In one study, pilot-scale columns containing
Westvaco Nuchar WV-G were set up to receive treated water from the Ohio River water in
Cincinnati, Ohio (Miller and Hartman, 1982). The pilot-scale unit consisted of three columns
in series to simulate EBCTs of 2.8,12 and 15.2 minutes. THMFP tests were run with a
chlorine dose of 15 mg/L for a period of 7 days at pH 9.5 and a temperature of 29.4ฐC..
THMFP and TOC breakthrough profiles are presented in Figures 4-21 and 4-22, respectively.
These breakthrough profiles indicate that the GAC usage rate was significantly decreased by
an increase in EBCT from 2.'8 to 15.2 minutes.
Pilot-scale studies were also conducted on Colorado River water by the Metropolitan
Water District of Southern California (McGuire, et a]., 1989). Treatment prior to GAC
adsorption included preoxidation with chlorine dioxide, alum coagulation, flocculation, setting
and dual media filtration. Pilot-scale GAC columns (containing Calgon F-400 GAC) were
set up in series to simulate EBCTs of 7.5, 15, 30, and 60 minutes. The pH of the adsorption
4-41
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IMPACT OF GAG TYPE ON TOC REMOVAL
PEAT FULVIC ACID
GAG = WV-W
Init. TOC = 4.09 mg/L
GAC = HD-3000
Init. TOC = 3.98 mg/L
GAC = WV-G
Init. TOC = 3.56 mg/L
0
50
100 150
BED VOLUMES FED
200
250
300
T]
Q
C
;o
m
O
-------
IMPACT OF EBCT ON GAC ADSORPTION OF THMFP
CINCINNATI, OH
EBCT = 15.2 min EBCT = 7.2 min EBCT = 2.8 min
10,000
BED VOLUMES FED
-------
1.0
O 0.8
O
ill
Z)
O
O
I-
ill
ID
_1
U_
LL
0.6
0.4
o.2
0.0
IMPACT OF EBCT ON GAG ADSORPTION OF TOC
CINCINNATI, OH
0
EBCT =15.2 min EBCT = 7.2 min EBCT = 2.8 min
ป
ป
0
*ปปปซป ^
* *^mป
5,000
10,000
BED VOLUMES FED
15,000
20,000
m
-N
ro
-------
step was approximately 8 Figures 4-23 arid 4-24 show breakthrough profiles for TOC and
SDS THM levels, respectively. These figures show that GAC usage rate decreased with an
increase in EBCT from 7.5 to 30 minutes. However, a further increase in EBCT from 30 to
60 minutes did not influence the GAC usage rate.
Summers et aj., (1997) evaluated EBCTs of 10 and 20 minutes for a number of water
sources and summarized that, EBCT had a definite effect in prolonging the life of a GAC
i
contactor, however, the carbon usage rate was relatively unaffected by EBCTs at the ranges
evaluated. They also noted that the balance between EBCT and the frequency of GAC
ป ' * '
replacement or reactivation is primarily a choice between larger capital investment (longer
EBCTs) and greater operational complexities (more frequent reactivation).
4.6.7 Impacts of Blending
In most GAC applications of any significant size, multiple contactors are operated in
a parallel configuration and the number of contactors depend on the plant size. Parallel GAC
contactors are operated in a staggered mode wherein each, contactor is in operation for
different lengths of time. In this mode of operation, one contactor at a time is taken off-line
when the blended effluent exceeds the target effluent concentration and a column with fresh
or reactivated GAC is then placed on-line. This will cause the blended effluent concentration
to temporarily decrease as illustrated in Figure 4^25. The effluent from the contactor in
operation the longest can be higher than the target breakthrough concentration, as it is
blended with water from the contactors that have effluent concentrations much lower than the
target concentrations. Consequently, the effluent of parallel contactors are blended prior to
disinfection. Thus, parallel operation in a multiple contactor configuration will result in
longer GAC bed-life and the time between reactivation will be longer. Under ideal conditions,
staged blending with multiple parallel contactors leads to near steady-state effluent
concentratipn (Roberts and Summers 1982).
Experimental and modeling methods for predicting the blended effluent concentration
, from GAC. contactors are developed by Summers et al., (1997). Figure 4-26 shows an
example of single contactor and blended effluent concentrations from a GAC contactor
derived from these modeling efforts- It was observed during this study that the time to GAC
- 4-42 .
-------
IMPACT OF EBCT ON GAC ADSORPTION OF THMFP
METROPOLITAN WATER DISTRICT
OF SOUTHERN CALIFORNIA
o.o
1,000
2,000
BED VOLUMES FED
3,000
4,000
2]
c
;o
m
-t"
CO
-------
IMPACT OF EBCT ON GAC ADSORPTION OF TOC
METROPOLITAN WATER DISTRICT
OF SOUTHERN CALIFORNIA
1.0
EBCT = 7.5 min EBCT = 15 min EBCT = 30 min EBCT = 60 min
0.6
LU
0.2
0.0
J.
0
1,000
2,000
BED VOLUMES FED
3,000
4,000
a
c
m
f-
-------
FIGURE 4-25
BILENDED GAC EFFLUENT FROM MULTIPLE CONTACTORS
OPERATED IN PARALLEL
o
'ซ*-ซ
ro
ง
o
start-up
plant effluent criterion
normal operation
t
Time
Figure 6.20 Blended GAC effluent from multiple contactors operated
in parallel
REFERENCE: SUMMERS et al. (1997)
-------
FIGURE 4-26
EFFECT OF BLENDING ON TOC BREAKTHROUGH
FOR PASSAIC RIVER WATER
2.5
i
o
2.0 -
1.5 -
ง 1-0 H
o
O
0.5
0.0
TOC
EBCT= 15 min
Logistic Model
Predicted Blended Effluent
Discrete effluent samples 3.0
Blended effluent samples 3.0
100 150 200
Scaled operation time (days)
250
Figure 6.21 Effect of blending on TOC breakthrough for Passaic River
water
REFERENCE: SUMMERS et al. (1997)
-------
performance goals can be significantly extended by blending the effluent from multiple
contactors For the three waters examined, blending increased the run time by an average of
150 percent for both TOC and UFC-TTHM. .
4.6.8 Comparisons of Case Studies
Eight pilot-scale GAG studies (Neukrug, et aL, 1983; Glaze, et a]., 1982; Miller and
Hartman, 1982; McGuire, et a]., 1989; Wood, gt aj., 1980; Koffskey, 1987; Kittridge, et a].,
1983; CH2MHU1, 1986) were evaluated to determine the capabilities of GAC for removing
TOC under the following conditions:
Reactivation frequency of 180 days.
EBCTs of 15 and 30 minutes.
Of the above eight studies, only five evaluated GAC adsorbers run for a period of more than
180 days. The water sources for these five studies were:
Ohio River at Cincinnati, Ohio.
Mississippi River at Jefferson Parish, Louisiana.
Colorado River at Metropolitan Water District, California.
Delaware River at Philadelphia, Pennsylvania.
Cross Lake at Shreveport, Louisiana.
In all five cases, the water was coagulated, clarified and filtered prior to GAC contact.
Because DBP regulations are based on a running annual average, the average amount
of TOC removed over the 180 day period was evaluated rather than the minimum amount of
TOC removed on the 180th day. In those cases where EBCTs of 15 and 30 minutes were not
studied, projections were established, for these EBCTs by using procedures discussed by Clark
(1987). Projections could not be established for the Ohio River at an EBCT of 30 minutes.
4-43
-------
The results of this analysis are presented in Figure ,4-27 Using these five waters and a
reactivation interval of 180 days, the average TOC removals were 55 and 75 percent at
EBCTs of 15 and 30 minutes, respectively. If data for the other three waters had been
developed and used in this analysis, the averages just noted would have been lowered to some
extent.
Summers and coworkers (Summers et al.,' 1994; Hooper et al., 1996c), have
summarized the impact of initial TOC concentration, TOC0, on the run time to a 50 % TOC
breakthrough, measured as. bed volumes, BV50, for a wide range of source waters (bed
volumes = run time / EBCT). The relationship can be expressed as
BV50=18,000/TOC0.
Twenty-eight case studies of GAC bench; pilot,and full-scale contactors from 21 different
source waters were evaluated. All systems utilized bituminous coal based GAC and the
influent pH was between 7 and 8 for the river, lake and groundwaters examined. The
relationship was verified by five GAC runs of the same isolated NOM, but diluted to different
concentrations. Part of the variability of the data around the regression line is likely due to
differences in the adsorbabilty of the NOM caused by pretreatment and different sources.
4.6.9 Summary
In many circumstances, GAC is an effective process for removal of NOM from drinking
water sources. With an EBCT of 15 minutes and a reactivation interval of 180 days, GAC
can remove 35 to 70 percent of the influent TOC on a running average basis:. Running
average TOC removals of 55 to 85 percent can be achieved with an EBCT of 30 minutes and
a reactivation interval of 180 days. ,
The case studies described above demonstrate how the performance of GAC systems
can be influenced by many process variables. In general, the process can be modified to
provide the same level of NOM removal at lower GAC usage rates by the following:
Maintaining low pH conditions through the process.
4-44
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Increasing NOM removal in processes that precede GAC adsorption, such as
coagulation/filtration.
Using an EBCT greater than or equal to 10 minutes.
Ozonation prior to GAC does not guarantee improved NOM removals because it can either
decrease or increase the adsorbability and increase the biodegradability of NOM. The overall
impact of preozonation on NOM removal in GAC contactors depends on the efficiency of
biotreatment to remove the weakly adsorbing hydrophilic fraction.
4.7 POWDERED ACTIVATED CARBON
4.7.1 PAC with Conventional Treatment
PAC has been successfully used for taste and odor control in many water treatment
facilities. PAC can also be used to remove NOM. Many studies have indicated that PAC
capacity for NOM increases with contact time up to 7 days or longer. In typical water
treatment situations, PAC is added at the rapid mix stage and settles out in the sedimentation
/
stage. Therefore, the contact time in conventional settling basins is limited to several hours
and may not be long enough to produce effective removal of NOM by PAC.
Two different PACs, Westvaco Aqua Nuchar and Westvaco Nuchar SA, were studied
for precursor removal in conjunction with alum coagulation (Malcolm Pirnie, 1988). Results,
shown in Table 4-5, indicate that alum coagulation alone achieved ah average 55 percent
reduction of THMFP. Alum coagulation combined with Aqua Nuchar dosed at 25 mg/L
(0.21 la/1,000 gal) reduced THMFP .by 70 percent with preozonation (0.05 to 0.2 mg Oj/mg
TOC) and 60 percent without preozonation. Alum coagulation combined with Nuchar SA
dosed at 16 to 21 mg/L (0.13 to 0.18 lb/1,000 gal) reduced THMFP by 75 percent with
preozonation and 70 percent without preozonation. These dosages are significantly higher
than those typically used in drinking water treatment and represent a significant increase in
sludge production. With these relatively high dosages, PAC enhanced TOC removal by 10
to 20 percent and THMFP removal by 0 to 20 percent.
4-45
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TWO-additional applications of PAC in water treatment include- 1) prior to ah upflow
solids contact clarifier and 2) in conjunction with Jow pressure membranes. An upflow solids
contact clarifier may retain PAC in the sludge blanket, significantly increasing PAC contact
time and capacity for NOM removal beyond that seen when PAC is simply added to a point
in the treatment train. Kassam et al. (1989) reported mean carbon residence times in contact
recirculating clarifiers from 9 hours to 8.5 days. Hoehn et al. (.1987) and Najm et al. (1989)
documented the addition of PAC to pilot-scale floe blanket reactors and found PAC retention
times of between 9 hours and 2 days. Increasing PAC retention time can significantly
decrease the required dose. PAC dose was reduced by 25-40% for the adsorption of a
detergent (Najm et al., 1991).
4.7.2 PAC with Membrane Treatment
Combining PAC with membrane filtration improves process performance in two ways:
1) organics removal is increased and 2) membrane fouling by organic absorption is decreased.
Typically, low-pressure membrane processes, such as MF and UF, cannot remove a
substantial amount of organic material due to their relatively large pore size. PAC addition
improves NOM removal by associating NOM, which alone would pass through the pores,
with the filterable paniculate phase. PAC combined with crossflow membrane processes can
also greatly increase the PAC detention time by recycling PAC through the membrane fibers.
Many PAC/UF studies have evaluated organic carbon removal (Anselme and Charles, 1990;
Laine et al., 1990, Heneghan and Clark, 1991, Adham et_al., 1991, Adham et al., 1993,
Jacangelo et al., 1995, Marriott et al., 1996, Jack, 1997). TOC removals between 13 and 85
. percent and DOC removals between 13 and 76 percent have been documented. It is important
to note that PAC concentrations > 200 mg/L are required to obtain these percent removals.
4-46
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TABLE 4-5
AVERAGE REMOVAL OF NOM BY PAC
PILOT SCALE UPFLOW SOLIDS CONTACT CLARIFffiR
NEWPORT NEWS, VIRGINIA
Treatment Scheme
TOC Removal
THMFP Removed
Without
Preozonation
With
Preozonation
Without
Preozonation
With
Preozonation
Coagulation Only
Coagulation + Aqua
Nuchar PAC
Coagulation + Nuchar SA
PAC
40
50
60
45
55
60
55
55
70
55
70
75
Average Test Conditions: ' >
Alum Dose = mg/L
Coagulation pH = 6.0
Aqua Nuchar PAC Dose = 25 mg/L
Nuchar SA PAC Dose = 20 mg/L
Initial TOC = 6.4 mg/L
Initial THMFP = 360 pg/L
THMFP Test Conditions
pH = 7.0
Temperature = 20 ฐC
' Contact Time = 7 days
Ratio of Chlorine Dose to TOC = 3:1
PAC can also reduce membrane fouling by preventing organics from adsorbing to the
.membrane surface. This enhances membrane flux, reduces the frequency of chemical
cleanings and prolongs the life of the membrane (Laine et al., 1990, Marriott et al., 1996,
Henegan and Clark, 1991, Jacangelo et al., 1995).
4-47
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4.8 RESIN ADSORBENTS
4.8.1 NOM Removal
Anion exchange is an effective method for removal of DBF precursors.
NOM can be removed from surface waters and.groundwaters by using macroporous anion
exchangers in the chloride form (Clifford, 1990). The primary sorption mechanism for DOC.
removal is ion exchange, with a very small DOC percentage removed through adsorption (Fu
and Symons, 1988). Generally, hydrophobic polyacrylic resins have shown superior
performance in DOC removal compared to hydrophilic polystyrene resins. Macroporous
resins have performed better than the gel types for DOC removal. Research has shown that
the greater the resin porosity, the better the DOC removal (Clifford, 1990). Literature on the
subject is limited, however, available case studies and information is summarized here.
A bench-scale study was conducted in Dade County, Florida to evaluate two synthetic
resins for their ability to remove NOM and several SOCs (Wood, etal., 1980). One resin,
Ambersorb XE-340, is a polymeric carbonaceous adsorbent while the other resin, IRA-904,
is a strong basic cationic adsorbent. Both resins are manufactured by Rohm and Haas
Company. The performance of each resin was compared with the performance of Calgon F-
400 GAC. An organic groundwater (TOC = 8.6 to 9.8 mg/L) contaminated with several
SOCs was the source water for this study. One set of columns was used to evaluate the
adsorption of NOM from the raw water while another set was used to evaluate the adsorption
of NOM from coagulated, chlorinated and sand filtered water. Each column was operated
at an EBCT of 6.1 minutes. The equilibrium capacity of each adsorbent is given in Table 4-6.
These results show that GAC was more effective for removing.NOM from both waters than
. either resin.
4-48
-------
TABLE 4-6
Equilibrium Capacity of Adsorbents
Equilibrium TOC
Capacity
(mg TOC/100 g
adsorbent)
Water Source
Raw Water
Coagulated/Filtered
GAC
7.5
5.5
XE-
340
1.1
1.0
IRA-
904
3.8
4.6
Equilibrium THFMP
Capacity
(mg THFMP/100 g
adsorbent)
GAC
1.18
0.13
XE-340
0.80
0.07
ERA-
904
0.44
0.08
Kim and Symons (1991) studied the effect of anion exchange on removal of TOC and
THMFP by GAC as part of a larger investigation at a water treatment facility in Houston,
Texas. Filtered water was passed through mini-columns containing Rohm and Haas IRA-958
anion exchange resin, Calgon F-400 GAC, and a combination of the two. Flow rates were
adjusted to provide an EBCT of 10 minutes. For the column containing GAC only, TOC
breakthrough approached 40 percent of influent concentration at about 2000 bed volumes.
When used with the anion exchange resin, this breakthrough remained below 10 percent
through 4,000 bed volumes, or 4 weeks of operation. Kim and Symons (1991) further
estimated, based on an influent THMFP of 266 ug/L, effluent THMFP concentration to be
6.5 ug/L at 4000 bed volumes.
Kim and Symons (1991) attributed this improvement to the removal of larger molecular
weight organics by the anion resin. Water typically contains organics with a wide range of
molecular weights. When applied to a GAC bed, the larger molecular weight organics
compete successfully against the smaller molecular weight organics for adsorption sites,
causing breakthrough to occur more rapidly. The anion resin successfully removes the larger
weight organics, resulting in less competition in the GAC bed, and prolonging breakthrough.
Two full-scale anion exchange processes used for DOC removal have been
documented. Kolle (1984) documents the use of a macroporous polystyrene resin for
4-49
-------
treatment of a highly colored groundwater (initial TOC was 6.5 mg/L). DOC removal fell
from about 85 percent to 50 percent during a cycle until breakthrough was reached. Over a
period of 2 years, process efficiency was reduced by only 10 percent due to resin fouling and
losses. Brattebo et al. (1987) have documented a similar system used to remove DOC from
a highly colored surface water. DOC removals up to 80 percent were seen.
4.8.2 Bromide Removal
Anionic exchange can be effective in bromide removal. Some resins will have a higher
affinity for bromide than others. Resins for bromide removal should be selected on the basis
of high bromide and bromate selectivity (as opposed to low chloride and fluoride selectivity).
This typically reduces process costs (Amy and Siddiqui, 1997). In work by Amy and Siddiqui
(1997), resins types were selected for'bromide removal. These included three chloride resins
manufactured by Mitsubishi Kasei: 1) PA 308, 2) SA 10A and 3) PA 408. The capacity of
each of these resins for bromide was 4.0,3.4 and 3.3 meq/g, respectively. Complete removal
of bromide, bromate and chloride was seen for NOM-free waters. The presence of NOM,
however, prevented complete removal. Bromide removal capacity in a natural, water
(California State Project Water) ranged from 100 to 359 mgBKVg resin.
Summers and co-workers (Summers et al, 1990; Benz et al., 1992; Koechling et al.,.
1997) have evaluated the use of macroporous strong base resins alone and as a pretreatment
to GAC for the removal of NOM and THM precursors. They found that while in most cases
' GAC alone out performed the resins alone, the combined resin/GAC systems at the same
EBCTs as the GAC alone yielded better performance. This was attributed to the removal by
resins of NOM fractions that are weakly adsorbed to the GAC (Koechling et al., 1997).
4.9 OXIDATION PROCESSES .
Oxidation processes are not traditionally considered NOM removal processes because
complete oxidation of NOM to carbon dioxide and water is highly impractical. During an
oxidation process, NOM molecules are converted into other organic forms which could alter
their reaction in subsequent disinfection processes. Oxidation can also alter NOM so that
4-50
-------
some compounds'become more biodegradable. Increasing biodegradability is harmful from
the standpoint that it provides opportunity for regrowth in the distribution system. It could
be beneficial, however, if oxidation is followed by biological filtration. In this'respect NOM
f
removal would be further increased. For example, Speitel et al. (1993) found that
preozonation followed by biodegradation (biofilm on filter media) removed up to 50% of
THM precursors and up to 70% of HAA precursors. Most of the research to date has
examined the impacts of oxidation on TOC, UV-254 and THMFP while little information is
available on other precursors.
4.9.1 Ozone
Reckhow and Singer (1984) conducted bench-scale tests using fulvic acid extracted
from Black Lake, North Carolina. The results of their study indicate, for this fulvic acid, that
TOC was removed to a lesser extent than CHC13FP, TCAAFP, DCANFP, TOXFP and UV-
254. However, TCPKFP substantially increased with increasing ozone consumption and
DCAAFP was not changed.
The effect of bicarbonate ions on the performance of ozone was studied by Reckhow,
et al., (1986). Because bicarbonate ions act as free radical scavengers, the authors
hypothesized that increasing bicarbonate concentration would shift the ozone oxidation
pathway towards direct oxidation and away from hydroxyl free radical oxidation. la this
research, increased removals of THMFP and TOXFP were obtained by increasing the
concentration of bicarbonate ions, even though ozone consumption was lower. This indicates
that, oxidation by molecular ozone may be more conducive to the destruction of these
precursors than hydroxyl free radical oxidation. The authors indicated that this result also
applied to the destruction of TCAA, DCAA, TCAK and DCAN precursors. Singer and
Chang (1988) tested the performance of ozone oxidation for NOM removal at five utilities
with preozpnation facilities. They observed less than 10 percent TOC removal during
ozonation at the dosages used by these utilities.
Kusakabe eta!. (1990) studied the use of ozone in combination with UV irradiation as
a method for the.removal of THM precursors. This study found that the destruction of
dissolved organic substances using the combination of UV/ozone proceeds at least 10 times
4-51
-------
faster than that of ozonation alone. This study concluded that the use of UV irradiation
greatly enhanced the TOC destruction rate and that TOX concentration was momentously
decreased with increasing ozone dosage in the presence of UV irradiation.
Chang and Singer (1991) studied the impact of ozonation on particle stability, the
removal of TOC and the removal of THM precursors. They concluded that preozonation can
only remove small fractions of TOC and THMFP while large decreases in UV-254 and color
v
could be achieved.
Work by Edwards et al. (1993) found conflicting effects of preozonation at a full-scale
plant for two source waters. Preozonation improved NOM removal by directly removing
organic matter through mineralizatibn, volitilization and/or stripping. However, preozonation
also reduced NOM removal by decreasing the surface charge of floe, hindering adsorptive
removal of organic matter. The relative magnitude of each of these effects would determine
the overall effect. The researchers determined that in a majority of utilities, preozonation
would have a negative effect at ozone doses above 0.7 mg Oj/mg TOC. For higher
concentrations of organic matter(i.e. less than 0.7 mg O3/mg TOC), however, NOM removal
may be enhanced.
/
4.9.2 Chlorine Dioxide
The effectiveness of chlorine dioxide for removal of THMFP and TOXFP was
evaluated at bench-scale with fulvic acid extracted from Lake Drummond, Virginia
(Werdehoff and Singer, 1987). All oxidation tests were performed at PH 7 with varying
chlorine dioxide dosages and varying initial TOC levels. Formation potential tests were run
for 7 days at pH 7, 20ฐC and a chlorine dose of 20 mg/L. Results are given in Table 4-7.
These removals were similar to those observed from ozone oxidation when compared on a
mass ratio of oxidant applied to initial TOC. However, none of the chlorine dioxide dosages
noted above were capable of producing any removal of TOC.
4-52
-------
TABLE 4-7
Effectiveness of CLO2 on THMFP and TOXFP
Chlorine Dioxide
Dose
(mg CI02/mg
TOC)
0.44
0.55
1.11
Initial TOC
(mg/L)
4.5
1 1.8
1.8
Removal (%)
THMFP
13
, 19
33
TOXFP
14
17
30
4.9.3 Potassium Permanganate
The ability of potassium permanganate to remove NOM was evaluated on a bench-
scale level for raw water from University Lake, North Carolina and for settled water from
Lake Michie, North Carolina (Singer, etal.. 1980). The study evaluated changes in TOC
CHCljFP resulting from permanganate dosages in the 0 to 10 mg/L range. CHC13FP tests
were run for several contact times (ranging from 2 hours to 7 days) at room temperature, pH
7 and chlorine dosages of 15 to 20 mg/L. Table 4-8 shows the results for removal of 7-day
CHCljFP. The results indicate that removal of CHC13FP exceeds 10 percent when
permanganate consumption reaches a range of 0.4 to 0.5 mg of permanganate consumed per
mg of initial TOC. However, none of the permanganate dosages were capable of producing
a detectable change in TOC.
Similar studies were performed with a fiilvic acid extract from Lake Drummond,
Virginia and a commercial humic acid extract (Colthurst and Singer, 1982). Permanganate
oxidations were performed at pH 7 with dosages in the 0 to 10 mg/L range. CHC13FP tests
were run for 7 days at room temperature, pH 7 and a sufficient chlorine dose to ensure the
presence of a free chlorine residual throughout the 7-day period. The results, also shown in
Table 4-8, indicate that CHC13FP was harder to remove in these humic extracts than it was
in the raw and settled waters evaluated in the previous study. A 10 percent removal was
obtained when permanganate consumption was in the 0.6 to 1 mg KMnO4/mg TOC range.
Again, TOC removal was generally found to be insignificant although 10 percent removals
4-53
-------
TABLE 4-8
Removal Results for 7-day CHCI3FP
Water Source
Initial
TOC
(mg/L) ,
^^^^^^^^^^^^==S=
University Lake T 89
University Lake
University Lake
Univeniiy Lake
University Lake
University Lake
University Lake
University Lake
University Lake
University Lake
University Lake
' University Lake
University Lake
University Lake
University Lake
Lake Miehie (Settled) .
Lake Miehfe (Settled)
FulvieAcid'
Fulvic Acid
Fulvic Acid
Fulvic Acid
Fulvic Acid
Humic Acid
Humic Acid
Humic Acid
Humic Acid
Humic Acid
Humic Acid
Humic Acid
II Humic Acid
89
89
65
65 .
65
65
62
62
62
62
56
5.6
5.6
L 56
56
67
67
6.7
2.9
2.9
29
11 1
11.1
11 1
4.8
4.8
- 23
2.3
2.3
77
7.7
77
41
41
41
. 20
20
' Potassium
Permanganate
Potassium Permanganate
Consumed (mg/mg TOC)
Dmt Oxidation
|- t>H=6.S \ PH=7.0
!^=^=^=^=^=^^=^=
,022 | 022
056 1
1.12
0.08
015
031
046
008
016
032 .
0.48
0.09
0.18
0.27
036
0.54
0.30
0.75
149
069 .
172
345
UN/A
#N/A
ปN/A
0N/A
0N/A
*N/A
0N/A
0N/A
ปN/A
ซN/A
0N/A
MM/A
#N/A
tfN/A
' ปN/A
tfN/A
II HumicAeid 1 20 I OVA
051
070
008
015
030
046
008
016
0.32
048
009
0.18
027
0.36
0.54
WJ/A
DM/A
0N/A
044
0.50
061
DM/A
*N/A
#N/A
#N/A
tfN/A
*N/A
tfN/A
tfN/A
ปN/A
*N/A
#N/A
#N/A
tfN/A
tfN/A
"0N/A
0N/A
#N/A
^^^^^^=
tfN/A
ซN/A
ซN/A
tfN/A
ปN/A
W4/A
#N/A
- 'tfN/A
tfN/A
#N/A
tfN/A
#N/A
#N/A
#N/A
tfN/A
#N/A .
tfN/A
#N/A
tfN/A
#N/A
#N/A
#N/A
018
0.45
0.90
0.42
1.17
0.61
0.78
109
0.26
065
0.81.
0.41
049
088
055
0.95
pH-lOJ
tfN/A
ซN/A
tfN/A
tfN/A -
tfN/A
' #N/A
#N/A
tfN/A
tfN/A
tfN/A
.#N/A
tfN/A
. #N/A
m/A
#N/A
tfN/A
0.30
0.74
1.13
'0.68
1.28
1.41
tfN/A .
tfN/A
tfN/A
tfN/A
#N/A
tfN/A
#N/A
tfN/A
tfN/A
ซN/A
tfN/A
tfN/A
tfN/A
tfN/A
tfN/A
tfN/A
- 130 1 *N/A
Percent Removal
of 7-day CHCUFP
pH=6.S
-24
133
221
4.8
-15
11.5
22.1 '
-2.0
-1.0
6.2
112
15
15
5.0
74
83
tfN/A
tfN/A
tfN/A
169
23.0
29.1
tfN/A
tfN/A
tfN/A
#N/A
tfN/A
#N/A
#N/A
tfN/A
tfN/A
#N/A
tfN/A
tfN/A '
#N/A
tfN/A
tfN/A
#N/A
tfN/A
Oxidation
pH=7.0
tfN/A .
#N/A
tfN/A
tfN/A
tfN/A
#N/A
tfN/A
tfN/A
0N/A
tfN/A
, tfN/A
tfN/A
tfN/A
ซN/A
tfN/A
tfN/A
0N/A
tfN/A
tfN/A
ซN/A
tfN/A
#N/A
0.0
2.0
110
90
180
120
140
220
10
10
100
50
40
60
40
9.0
130
pH=10J
#N/A
ซN/A
ซN/A
#N/A
tfN/A
, #N/A
.ซN/A
*N/A
tfN/A
' *N/A
ซN/A
*N/A
*N/A
*N/A
#N/A
#N/A
85
153
. 27.5
179
314
336
#N/A
ซN/A
*N/A
#N/A
#N/A
.ซN/A
#N/A
*N/A
tfN/A
tfN/A
0N/A
#N/A
#N/A
x #N/A
#N/A
tfN/A
tfN/A II
4-54
-------
were achieved for the fulvic acid extract when permanganate consumption exceeded 1 mg
. KMnO4/mg TOC.
4.9.4 Advanced Oxidation Processes
Advanced oxidation processes (AOPs) are defined as those oxidation processes which
\
involve the generation of hydroxyl free radicals in sufficient quantity to impact water
purification. Examples of AOPs include ozone at high pH levels, ozone/hydrogen peroxide
and either ozone or hydrogen peroxide with other free radical initiators such as ultraviolet
(UV) light, metals and metal oxides. The hydroxyl free radical has a higher oxidation
potential and frequently reacts at faster rates than more conventional oxidants such as
chlorine, permanganate, chlorine dioxide and ozone. In some situations, AOPs may be
reasonably cost effective. As a result, AOPs show promise for removal of a variety of
contaminants which were previously not treatable with more conventional oxidation
processes. The ozone/hydrogen peroxide AOP process essentially requires the same
equipment as the ozone process, except that hydrogen peroxide feed equipment is also
necessary.
Research has demonstrated that advanced oxidation processes may increase DBPFP
at lower ozone dosages typical of water treatment, but can reduce DBPFP at higher dosages
(Wallace, et_ai., 1988; Duguet, et_al., 1985). The use of AOPs in combination with
chloramines can successfully reduce the formation of DBFs as alternative oxidants rather than
DBF precursor removal processes (Gromith etal.. 1991). .
Wallace, et al (1988), used alum coagulated and settled water from Cross Lake,
Louisiana, to evaluate ozone and several advanced oxidation processes (AOPs) for removal
of THMFP. In this study with the ozone only strategy, THMFP increased at all ozone
dosages. The AOP strategies (using H2O2 and/or UV radiation) were also found to increase
THMFP at most of the conditions evaluated.
Duguet, et aL (1985), used bench-scale studies to determine the performance of the
ozone plus hydrogen peroxide (H2O2) process on THMFP removal from two natural waters.
Like the Louisiana case noted above, ozone alone increased the level of THMFP in three
out of four cases. The AOP process was also observed to increase THMFP at the lowest
4-55
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ozone dose. The AOP process-achieved significant reductions in THMFP at higher ozone
dosages (higher than the dose typically applied at the plant).
4.9.5 Photoassisted Heterogeneous Catalytic Oxidation
Hand, et al. (1991) evaluated the technical and economic feasibility of using
photoassisted heterogeneous catalytic oxidation (PHCO) process for the destruction of DBF
precursors. The PHCO technique involves the use of photoactive n-type semiconductor
powders (e.g., titanium dioxide). When these powders are illuminated with near-UV light in
an oxygenated aqueous suspension, they can produce a sufficient redox environment to
mineralize organic compounds. Hand, et al. (1991) listed the following potential and current
advantages and disadvantages.
Hand, etal. (1991) selected two surface waters for their study; Hillsborough River,
(Tampa, Florida) and Sacramento - San Joaquim Estuary, (Antioch, California). The
conclusions for the study presented in Hand, etal. (1991) are as follows:
NPOC and DBP precursors can be mineralized using the PHCO process with
reasonable contact times. _ . '
For the two alum coagulated surface waters and contact times between 15 and
60 minutes, NPOC removals ranged from 42 to 70 percent and THMFP
removals ranged from 41 to 80 percent.
Sunlight can be used to activate the Ti02'catalyst.
4.9,6 Summary
The tests described above demonstrate that the oxidation of NOM primarily results
in an alteration of organic material rather than a removal of organic material. A summary of
TOC and UV-254 removal data is shown in Figure 4-28 for.the ozonation process. The data,
obtained from three different bench-scale studies, (Singer and Chang, 1988; Stephenson, et
al, 1979; Gilbert, 1988) represent oxidation of organics from seven natural waters and one
aquatic fulvic acid solution. As noted earlier, the removal of UV-254 is significantly greater
than removal of DOC. DOC removal is normally less than 10 percent at ozone dosages
4-56
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D)
E
Q3
LLJ
o
LJJ
o: 2
o
o
LJJ
ฐi
LU
0
RUNNING AVERAGE TOC REMOVAL BY GAC
REGENERATION FREQUENCY = 180 DAYS
1234
AVERAGE INFLUENT TOC (mg/L)
o
C
;o
m
ro
-------
REMOVAL OF NATURAL ORGANIC PARAMETERS
BY OZONE OXIDATION
1 UU :
90 -
80 -
-Trt -
f(J '*
Q
UJ en -
> ou
0
m 40 -
n
DOC
) !> UV-254
A
*
^> 0
6
*
* " "
U -' * '' ป' ป. v - i 1 1 "f
0 2 46 8 10 12
OZONE DOSE (mg ozone /mg DOC)
-n
c
m
N)
on
-------
considered typical of water treatment practice (0.5 to 2 mg O3/mg TOC). Even the high
j
ozone dose of approximately 10 mg O3/mg TOC could not remove more than 30 percent of
the DOC present in the original water.
Werdehoffand Singer (1987) compared the performance of ozone (Reckhow and
Singer, 1984), chlorine dioxide (Werdehoffand Singer, 1987) and potassium permanganate
(Colthurst and Singer, 1982) for removal of THMFP from fulvic acids extracted from Lake
Drummond, Virginia. This comparison (see Figure 4-29) shows that ozone and chlorine
dioxide perform similarly when oxidant dose is expressed as a mass ratio of oxidant applied
to initial TOC. Potassium permanganate is somewhat less effective. It is important to stress
that neither oxidant achieved more than a 5 percent removal of TOC at the dosages shown
in this figure.
The results presented above indicate that oxidation cannot be relied upon to remove
DBF precursors in a uniform manner. While some DBF precursors are destroyed by
oxidation, other DBF precursors are produced by the process. The primary reason for this
i
observation appears to be that oxidation does not remove NOM to a significant degree but
converts the organic molecules comprising NOM into other, more highly oxidized, organic
molecules. These new organic molecules are available for reaction with disinfectants applied
later in the treatment process. Therefore, the use of oxidation as a DBF precursor removal
process should be secondary to the use of oxidation as a means of removing reduced metals
or taste and odor compounds. The results of the PHCO process appear promising to date,
however, additional research is needed to confirm this method.
4.10 MEMBRANE PROCESSES
i
4.10.1 introduction
Membrane processes can remove DBF precursors through filtration and
adsorption of organics. If NOM molecules are larger than the membrane pores, NOM will
be rejected and DBPFP will be reduced. Size, however, is only one factor which influences
NOM rejection. Shape and chemical characteristics of organic compounds also play
important roles in the permeation of NOM through a membrane (Buckley and Hurt, 1996).
4-57
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MembranesmayalsoremoveNOMthroughadsorpuonoforganicsonthemembranesurface
Adsorption depends on the chemical characteristics,, particular., charge and hydrophobe,
of both the membrane material and organic compounds. Unfortunate,,, organic adsorpfon
is undesirable since it has proven to be a primary cause of irreversible fouhng
Pressure^ membrane processes are typically categorized into microfiltratton
(MF) ultraffltrationCUFXnanofitotionCNFJ^^erse osmosis (RO). High-pressure
pro^sse* (i.e. NF and RO) have a relative!, smaller pore size aUowing significant DBF
precursor removal. Low-pressure processes (U. MF and UF), however, have a re.aซ,vdy
targer pore size and cannot remove NOM substantially without pretreatment means.
TABLE 4-8(a)
MEMBRANE PROCESS VERSUS PORE SEE RANGE
I Ilil ffrTlMllHffi^
2-0.1
_ซ^ป
1-0.002
0.01-0.001
Microfiltration
Ultrafiltration
Nanofiltration
Rgverse Osmosis
Table Reference:
DBF precursor removal will be a Junction of the type of membrane process,
membrane material characteristics, and water quaUty characteristics (i.e. NOM
characterization and concentration, pH). Some major design considerations for the use of
membrane9for*eremovalofDBPprecursorsinclude*efonpWing(Carlson,1991).
Removal efficiency of NOM.
Feed water recovery.
Degree of membrane fouling
4-58
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REMOVAL OF THMFP BY OXIDATION
FULVIC ACID SOLUTIONS - LAKE DRUMMOND, VA
(AFTER WERDEHOFF & SINGER, J. AWWA, 9/87)
40
30
Q
ฃ20
O
^
til
10
0
POTASSIUM
PERMANGANATE
CHLORINE
DIOXIDE
0.0
0.2
0.4 0.6 0.8
OXIDANT DOSE (mg/mg TOC)
1.0
1.2
o
c
rn
-i^
i
CD
-------
100
80
Q 60
LU
O
LJJ
K.
O
O
Q
40
20
30
IMPACT OF MWC ON DOC REMOVAL
IN MEMBRANE PROCESSES
100
300 1,000 3,000 10,000
NOMINAL MOLECULAR WEIGHT CUTOFF
30,000
100,000
o
c
m
.^
o
-------
100
IMPACT OF MWC ON THMFP REMOVAL
IN MEMBRANE PROCESSES
100
300 1,000 3,000 10,000
NOMINAL MOLECULAR WEIGHT CUTOFF
30,000
100,000
o
c
70
m
-------
IMPACT OF MWC ON TOXFP REMOVAL
IN MEMBRANE PROCESSES
300 1,000 3,000 10.0JQO
NOMINAL MOLECULAR WEIGHT CUTOFF
o
c
;o
m
CO
M
-------
4.10.2 Review of Treatability Studies
4.10.2.1 NOM Removal
Without pretreatment, membrane processes remove NOM to varying
degrees. NOM removal will also depend on the characteristics of the membrane, including
MWCO and hydrophobicity, characteristics of the NOM, and membrane system operating
parameters. MF and UF removals typically range between about 5 and 30 percent.
Typically NF and RO removals are on the order of 50 to 99 percent. Several studies on
NOM removal by membrane processes are presented in Table 4-9. These studies are
discussed as follows.
Bench-scale studies have examined the impact of MWCO on removal of
NOM from four Florida drinking water sources (Taylor, et a]., 1987; Taylor, et aj., 1989a)
and two Arizona waters (Amy, ej al., 1990). In one Florida study, THMFP and TOXFP
tests were run for a period of 4 days at pH 8 and 23ฐC (Taylor, et aj., 1987). Figures 4-
30, 4-31 and 4-32 present the removal of DOC, THMFP and TOXFP, respectively, as a
function of MWCO. The larger variation in THMF.P and TOXFP removal may, in part, be
related to the variability associated with the formation potential test. The data indicate
that MWCs of 100 to 500 are needed to achieve DOC removals of at least 90 percent. A
50 percent removal of DOC may be achieved with a range of MWCs between 1000 and
3000..'
Pilot-scale studies were used to evaluate the impacts of operating pressure and
percent recovery on removal of NOM from two of the water sources noted above (Taylor,
et_a}., 1987). Both pilqt studies used a two stage membrane system containing spiral.
' wound Filmtec N50 membranes. These membranes were rated with a nominal MWC of
400. In both cases, operating pressure and recovery had negligible impact on the removal
of all NOM parameters tested. However, total hardness and TDS rejections were
significantly increased by an increase in operating pressure and/or a decrease in recovery.
In another application of the pilot-scale system noted above, rejection of DOC
averaged 88 percent while permeate waterTHMFP averaged 27 ug/L. Although the
authors did not report a raw water THMFP, they noted that the permeate THMFP was at
4-59
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least 90 percent lower than THM concentrations in the extremities of the distribution
system. Product water flux declined at an average rate of 0.44 gpd/stfday.
A ground water source for the ACME Improvement District, Florida, was tested
with the same membrane system for 1,018 hours over a 78-day period. Average operating
conditions for the entire test included a raw water DOC of 16 mg/L, an operating pressure
of 98 psi, a product water flux of 16.4 gpd/sf and a recovery of 79 percent. Rejection of
DOC. averaged 85 percent while permeate THMFP averaged 43 ug/L. Raw water
THMFP and THMFP removals were not reported. Product water flux declined at an
average rate of 0.06 gpd/sffday. This flux decline was considerably lower than that shown
above. The difference is believed to be caused by biological fouling.
' A pilot-scale system was also used to evaluate NOM removal from a groundwater
, source at Flagler Beach, Florida (Taylor, sLal., 1989b). This pilot study used a three-
stage system containing spiral wound Filmtec N70 membranes. These membranes were
rated with a nominal MWC of 300. The system was operated for 5,098 hours over a 364-
day period. Under normal conditions, the plant was operated 16 hours each day. Average
operating conditions for the entire test included an operating pressure of 141 psi, a
product water flux of 13 gpd/sf and a recovery of 76 percent. Feedwater THMFP,
TOXFP and DOC averaged 403 ug/L, 1017 ug/L and 11.5 mg/L, respectively. Rejection
of DOC, THMFP and TOXFP averaged 86,95 and 97 percent, respectively. Permeate
THMFP averaged 20 ug/L. Flux decline was not reported for this pilot test.
The same pilot-scale system was used to evaluate NOM removal from a surface
water source at Punta Gorda, Florida (Taylor, et aj., 1989a). The system was evaluated
*
with sand filtered raw water and with coagulated and sand filtered water. Sand filtered
raw water was processed for 2,642 hours with an average product water flux of 8T.9 gpd/sf
and an average flux decline of 0.12 gpd/sfi'day. During this period, feedwater THMFP,
TOXFP, and DOC approximately average 900 ug/L, 3500 ug/L and 20 ug/L, respectively.
Coagulated and sand filtered water was processed for 4,034 hours with an average
product water flux of 8.2 gpd/sf and an average flux decline of 0.10 gpd/stfday. During
this period, feedwater THMFP, TOXFP and DOC approximately averaged 400 ug/L,
1800 ug/L and 7 mg/L, respectively. The entire 6,676-hour test period was conducted
4-60
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over 365 days and characterized by an average operating pressure of 154 psi, an average
flux of 8.6 gpd/sf and an average recovery of 50 percent. Rejection of DOC, THMFP and
TOXFP averaged 95, 94 and 98 percent, respectively. Permeate THMFP averaged 37
ug/L. The study concluded that operation of a membrane system for an organic surface
water would require more frequent cleaning, more extensive pretreatment, lower flux and
lower recovery than for a groundwater.
i
Conlon and McClellan (1989) reported NOM removals achieved by field-scale
systems in Loxahatchee Groves and West Jupiter, Florida. Both systems used the Filmtec
NF-70 membrane at 75 percent recovery. The Loxahatchee Groves system-was operated
at 100 psi while the West Jupiter system was operated at 90 psig. Formation potentials
were evaluated with a chlorine contact time of 7 days. Other formation potential test
conditions were not reported. Organics removals greater than 90 percent were achieved,
as shown in Table 4-9.
Dunkelberger and Beaudet (1991) reported on the performance of low pressure
membranes in the nanofilter category for the removal THM precursors. The basis of this
report waste results from pilot plant studies and full scale operations at the Palm Beach.
County Water Utilities Plant. Membranes utilized at the facilities were of the spiral wound
thin film composite type termed "softening membranes." The report indicated color and
TOC were both rejected by the membranes to levels of analytical detection. In summary,
the authors stated, the pilot and full scale plant analysis for DBPs for softening membrane
technology proposed in this case shows THMFP levels below 50 ppb in all circumstances'
evaluated. Actual THM levels would be significantly lower with the use of chloramines
and of contact times of less than 7 days. When the cost of the membrane technology was
'compared to a lime softening plant with ozonation and granular activated carbon,
membrane technology is.the most cost effective alternative in this particular case.
Allgeier and Summers (1995) evaluated the use of NF to reject NOM and DBP
(UFC) precursors for five waters using a bench-scale system. They found that TOC and
i
precursors for TTHM, HAA6 and chloral hydrate were all rejected by 66 to 97 percent.
The level of rejection was water source dependent and TOC was a good surrogate
4-61
-------
indicator. THAN precursor rejection was lower for all five waters and ranged from 25 to
90 percent. ,
Laine, et al. (1990) evaluated the use of pretreatment processes consisting of
various combinations of coagulation-flocculation and powdered activated carbon
adsorption prior to ultrafiltration (UF) for removal of THMFP. The results of this
evaluation indicated that pretreatment appears to be necessary to significantly reduce the
organic matter passing through UF membranes. UF with activated carbon pretreatment
showed the most promise for optimization of organic carbon and THMFP removal.
Previous studies have indicated the main cause of irreversible membrane fouling of UF
membranes is the adsorption of organic matter on the membrane. The study reported by
Laine, etal. concluded that pretreatment using coagulation-flocculation, powdered
activated carbon or both reduced irreversible membrane fouling by removing the organic
\.
foulant. This study also concluded that with proper pretreatment, low-pressure membrane
processes like UF can remove not only the majority of particular matter but also a large
fraction of dissolved organic matter and THMFP.
As demonstrated here, NF and RO processes can remove significantly more
organic matter than MF and UF. In fact, NF, traditionally a softening processes, is gaining
\
popularity as a DBP removal processes since production costs are comparable with
competing processes (Buckley and Hurt, 1996). If TOC reductions of more than 30
percent are required, NF or RO would be needed or MF or UF in conjunction with a
pretreatment system would be necessary. Pretreatment can help MF and UF processes
remove more organic matter. Discussion of these and their capabilities are given in
Sections 4.4.10 and 4.7.2. Of importance as well, however, is the decrease in fouling
which results from PAC'or coagulant addition.
4.10.2.2 Bromide Removal
MF and UF are not suitable for removal of bromide due to their large pore
sizes. NF and RO, however, are capable of significant bromide removal. Nanofiltration
membranes have demonstrated chloride removals between 60 and 70 percent, with
bromide removal expected to be nearly identical (Conlon and McClellan, 1989, Taylor et
i
4-62
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al., 1989 a,b). Investigations by Amy and Siddiqui (draft 1997) found bromide removals
for NF (MWCO 150 - 300) between 38 and 41 percent. Prados et al. (1993) found
bromide removal up to 63 percent with an NF-45 membrane on a surface water spiked
with 300 mg/L of bromate. Removal of bromide with RO processes would be even more
effective, depending on pore size, charge and the type of membrane selected. Overall,
however, bromide removal using NF or RO would probably not be cost effective if used
only for that purpose. If the processes were incorporated into a treatment train and used
for other contaminant removal, though, membrane removal of bromide may, become cost
effective (Amy and Siddiqui, 1997). It is important to note that if bromide is not removed
sufficiently and TOC levels are removed, the TOC to bromide ratio will increase
considerably and will cause, in the least, a net shift in speciation of DBFs to the more
brominated compounds. In the worst case, such a scenario could cause a net increase in
the absolute level of brominated DBFs after chlprination at least for bromoform(as
compared to chlorination of the feedwater).
4.10.3 Summary
Membranes, particularly those with MWCOs in the 100 to 500 range, appear to be
very effective as a means of DBF precursor removal. TOC, THMFP and TOXFP
removals of 70 to 95 percent are commonly achieved in systems using such membranes.
These processes can effectively remove bromide as well. Larger MWCO membranes,
however, will not be as effectively for these removals.
While MWCO is an important indicator of process performance, it is also an
important indicator of process costs. Systems using membranes with higher MWCOs are
likely to achieve higher product'water flux and operate at lower pressures (and lower
costs) than those using membranes with lower MWCOs. In effect, improved effluent
water quality is traded for higher costs. Higher MWCO membranes can be combined with
PAC or coagulations to allow substantial DBF precursor removal. This increases costs as
well. However, with recent advances in membrane technology, increasing popularity and
the threat of stricter regulations, membranes are becoming cost .competitive with
traditional processes.
4-63
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4.11 BIOLOGICAL DEGRADATION
,4.11.1 . Introduction
Use of a biological process can increase NOM removal and decrease DBF
formation. Biomass will remove NOM by using it as substrate. Biological treatment can
also aid performance when used after disinfection. Some NOM will be altered during
disinfection and become more easily biodegradable. Removing this biologically can help
prevent biological growth in the distribution system.
A common form, of biological treatment are biofilters. Biofilm is allowed to
grow on filtration media such as sand or activated carbon. Biological treatment is then
accomplished as water permeates through the filter. Although biomass can grow
.throughout the depth of the filter, biomass accumulation decreases as filter depth increases
(Wang et al., 1995). Therefore most biological removal will be accomplished near the top
of the biofilter.
4.11.2 Biological Treatment on Non-Adsorptive Media
Many studies have evaluated biological activity on adsorptive media such as GAC.
However, quantifying the removal of NOM due to biodegradation is difficult to separate
from that due to adsorption. Therefore, this section focuses on biodegradation of NOM
through filters containing non-adsorptive media such as sand and anthracite. A discussion
of GAC and biological treatment is presented in the following section.
Using bench-scale tests, Maloney, et al. (1984), demonstrated the impacts of
temperature on biological removal of TOC in sand filters. Two sand filters, each with ah
EBCT of 15 minutes and a 36-inch sand depth, received coagulated, clarified, filtered and
ozonated water from the Delaware River. One sand filter was operated at a water
- temperature of 5ฐC to 11 ฐC while the other was operated at a water temperature of 15ฐC
to20ฐC. Ozone dosages were not reported. Over a period of 60 days, TOC removals
averaged 15.7 and 8.5 percent under warm and cold water conditions, respectively.
The impact of maintaining a chlorine or chloramine residual through a sand filter
on biological removal of TOC has not been extensively reported. Thereis little question,
however, that this condition would inhibit biological growth and eliminate or reduce TOC
4-64
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removal. At least one report has shown substantially decreased biological activity in sand
filters operated with a residual compared to parallel sand filters operated with no residual
(Lykins, et al., 1986). One study by Miltner et al. (1995) analyzed the effect of
chlorinated versus non-chlorinated backwashing on biofilter performance. By
backwashing the dual-media (sand and anthracite) filter with chlorinated water, biomass
accumulation was reduced and TOC and DBF precursor removal was reduced. Although
some biomass loss occurred immediately after backwashing, the biomass concentration
returned to normal by the end of the filter run.
Little information is available to demonstrate direct differences in NOM removal
on sand filters receiving water ozonated to different degrees. However, numerous
investigators have reported increased biodegradability of NOM with increasing ozone
dose (Harrington and DiGiano, 1989; Somiya, et al., 1986; van der Kooij, et al., 1989;
Stephenson, elaj., 1979). Lykins, et a]. (1986), observed a 16 percent removal of TOC
through a sand filter after ozonation and no removal of TOC when no disinfectant was
applied. These results indicate that increased ozone dosages prior to sand filtration can be
expected to improve the removal of NOM by biodegradation. Chlorinated backwashing
may also impact ozone DBF formation. Miltner et al. (1995) found a decrease in ozone
DBFs when chlorinated (versus non-chlorinated) backwashing was used for a dual-media
(sand and anthracite) biofilter.
4.11.3 Biological Treatment on Granular Activated Carbon
Numerous reports have been published regarding NOM removal in biologically
active GAC contactors. However, few investigators have attempted to quantify the
removal due to biodegradation and that due to adsorption. Maloney, et aj. (1984), used
bench-scale tests at different temperatures to demonstrate that the rate of biological
removal of TOC was statistically the same in sand columns as it was in GAC columns.
Both sand and GAC columns received coagulated, clarified, filtered and ozonated water
from the Delaware River. They attributed the better performance of GAC to adsorption.
Wang et al. (1995), however, found that GAC media were able to accumulate more
biomass which could also account for superior GAC performance.
4-65
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Lykins, et al. (1986), compared biological activity in pilot-scale sand filters and in
pilot scale GAC filters operated in parallel. In those cases when a disinfectant residual
was not present in the feed stream, biological activity in sand filters was higher than or
similar to the biological activity in GAC. Qn the other hand, when chlorine, chloramine or
chlorine dioxide were present in the feed stream, biological activity was greater in GAC
than in sand. In fact, biological activity in GAC was relatively independent of the presence
of a disinfectant residual. This was probably due to rapid removal of any residual
disinfectant within the GAC. While biological activity is not a direct measurement of
NOM removal, these results give indirect evidence that:
Biological removal of NOM in GAC filters may not be inherently superior to
biological removal of NOM in sand filters.
Carrying a disinfectant residual into a GAC filter may not inhibit biological
removal of NOM. This is contrary to expectations with sand filters and is the
result of GAC's ability to remove disinfectant residuals.
' i
Despite the above findings, Bouwer and Crowe (1988) noted that several
investigators found evidence of higher biological removals of NOM on GAC than on sand.
They stated that "reported increases in biodegradation rates on GAC relative to
nonadsorbing media may be due to utilization of adsorbed substrate, higher surface area,
or a more favorable acclimation environment."
Glaze, et al. (1986), evaluated the impact of ozonation on removal of TOC in
GAC adsorbers. The Shreveport, Louisiana, pilot plant described in Section 4.6.4 was
used for this analysis. After 83 weeks of operation, the cumulative removal of TOC was
recorded as given in Table 4-10.
4-66
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TABLE 4-10
Impact of Ozonation on TOC Removal by GAC
EBCT (min)
11.75
23.5
Cumulative TOC Removal (%) *
Unozonated
Stream
26.1
44.5
Ozonated
Stream
28.5
47.8
The average ozone dose over the 83-week period was approximately 3.0 mg/L. The
results indicate that ozone had little or no impact on the overall removal of TOC within
the GAC adsorbers. However, with the aid of bench-scale isotherm and kinetic data, the
authors used a homogeneous surface diffusion model to simulate TOC removal due to
adsorption. If the results of the simulation are interpreted as representative of actual
adsorption conditions in the pilot plant, the simulation indicates:
Ozone enhanced the removal of TOC by biodegradation
Ozone inhibited the removal of TOC by adsorption
The combination of these impacts resulted in the observation that little change in overall
TOC removal resulted from ozonation.
DeWaters arid DiGiano (1990) studied biodegradation and adsorption of NOM in
a laboratory-scale GAC reactor and concluded that ozonation of the NOM used in this
study at a dose of 1 mg Oj/mg TOC increased biodegradation and encouraged biofilm
growth in the GAC bed. This achieved a substantial steady-state reduction in TOC were
within a relatively short EBCT in the presence of this actively growing biofilm. This
significant removal or organic matter within a short EBCT implies that biological activity
has the potential for reducing the necessary size of a GAC facility, thereby reducing capital
cost. This study also concluded that the biofilm grown on ozonated NOM readily
4-67
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degraded trace concentrations of phenol The evalu?.tors further concluded that this shift
in the removal pathway for phenol removal from adsorption to biodegradation which
indicates a biological activity provided by a readily available substrate (ozonated NOM).
can effectively remove not only the bulk substrate but trace synthetic organics as well.
Removal of degradable SOCs through biodegradation means that the sorptive capacity of
the GAC bed will be preserved for contaminants that are less susceptible to biodegradation
and therefore increase the service time of the GAC column, reducing the operating cost
associated with GAC reactivation.
4.11.4 Summary
It is evident from these studies that the type of filter media plays an important role
in biodegradation. Although both sand and GAC will sustain biological growth and
remove NOM to comparable levels, GAC media may be capable of larger biomass
accumulation and may be able to accomodate disinfectants better. Based on the evidence
published to date, the use of biological degradation for DBF precursor removal is also
enhanced by the use of ozone prior to a granular media barrier. Disinfectant residuals
must be eliminated prior to or immediately within the granular media barrier in order for
the process to work effectively. Additionally, chlorinated backwashes could reduce
biomass and hinder NOM removal.
Even when biological processes are operating effectively, the removal of TOC
directly by biodegradation appears to be less than 20 percent in most cases. This removal,
however, may be limited by the ozone dosages typically employed in current water
treatment practice. Nevertheless, the removal of NOM by biodegradation is significantly
lower than removals achieved for biodegradable organic matter (BDOC) (see Chapter 6).
Biological treatment should, therefore, be used primarily as a means to remove BDOC T
the biodegradable fraction of NOM.
4-68
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4.12 SUMMARY
As stated in the introduction to this chapter, the removal of NOM from drinking
water sources is important for a number of reasons. In the context of this.document,
NOM removal is important because of its ability to react with oxidizing agents to form by-
products that may be harmful to humans. This chapter provided a summary of NOM
removal strategies that may be employed in drinking water treatment.
Carlson (1991) reviewed several technologies for DBF precursor removal based
on process experience, important considerations, expected performance and limitations. A
comparison of the technologies in order of general feasibility established is presented in
Table 4-11. Carlson indicated that the order of technologies are somewhat arbitrary,
positions may change depending on site specific conditions and major technologies may
become more feasible as improvements are made.
Based on the information presented in this chapter, the following processes are
considered most effective for NOM removal:
. Coagulation/filtration, particularly at low pH
Precipitative softening, particularly at high pH
GAC adsorption
Membrane processes
These processes were selected for this classification because of their ability to remove a
wide range of DBF precursors to an extent greater than 40 percent. These conclusions
were based on technological feasibility only and a cost feasibility analysis may alter them.
4-69
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TABLE 4-11
Process Summary for Removal of Disinfection By-Products Precursors
Process
Coagulation/Flocculation
for DBF-precursor removal
- Inexpensive
- Easily implemented
- Extensive experience
- Obvious first step
- 30-50 percent removal
- Concurrent turbidity
removal
- 30-50 percent removal
may not be enough
- Residual disposal
Powered activated carbon
Relatively inexpensive
Extensive experience
- Concurrent removal of
taste and odor compounds
- Limited effectiveness
especially without floe
blanket
. 0-30 percent removal
Granular activated carbon
Very effective
50-70 percent removal
Considered BAT (1)
Good experience
especially in Europe
Concurrent removal of
taste and odor compounds
and organic contaminants
- Costly option
- Less expensive in United
States
- Pilot testing usually
required
-GAC regeneration
Membranes
- Most effective
- 80-90 percent removal
- Considered BAT
- Good experience in
Florida ground waters
- Concurrent removal of
calcium and magnesium
- Technology improving
- Costly option
- Uncertain pretreatment
requirements for surface
waters
- Pilot testing required
- Concentrate disposal
- Technology not mature
f 1) BAT = Best available technol
4-70
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Substances in Lakewater," in Humic Substances in Soil. Sediment, and Water:
Geochemistry. Isolation and Characterization. G.R. Aiken, et al.. (eds.), Wiley-
Interscience, New York, NY.
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Stephenson, P., Benedek, A., Malaiyandi, M. and Lancaster, E. A. (1979). "The Effect of
Ozone on the Biological Degradation and Activated Carbon Adsorption of Natural
and Synthetic Organics in Water. Part I. Ozonation and Biodegradation."
Ozone Sci. Ener., 1 (3), page 263.
Stevens, A. A., Moorek, L. A. and Miltner, R. J. (1989). "Formation and Control of
Non-Trihalomethane By-Products." J. AWWA. 81 (8), Page 54.
Stukenburg, J. R. and Hesby, J. C. (1991). "Pilot Testing of the Heberer Process in the
United States." J. AWWA. 83(a), Page 90.
Summers, R.S. et al (1997), "Removal of DBP Precursors by Granular Activated Carbon
Adsorption," Amer. Water Works Assoc. Research Foundation, Denver, CO
(1997).
Summers, R. S., DiCarlo, D., Palepu, S .S.: "GAC Adsorption in the Presence of
Background Organic Matter: Pretreatment Approaches and Attenuation of Shock
Loadings," Proc., Amer. Water Works Assoc. Conference, Cincinnati, OH (1990).
Summers, R. S., Hong, S., Hooper, S., Solarik ,G.: "Adsorption of Natural Organic
Matter and Disinfection By-Product Precursors," Proc. Amer. Water Works
Assoc. Annual Conference, New York, NY (1994).
Summers, R. S., Hooper, S., Shukairy, H., Solarik, G., Owen, D. M.: "Assessing DBP.
Yield: Uniform Formation Conditions," J. Amer. Water Works Assoc., 88 (6)
(1996): 80-93.
Summers, R. S. (1986). Activated Carbon Adsorption of Humic Substances: Effect of
Molecular Size and Heterodisoersitv. Ph.D Dissertation, Stanford Univ., Stanford,
CA.
Summers, R. S. and Roberts, P. V. (1988). "Activated Carbon Adsorption of Humic
Substances. EL Size Exclusion and Electrostatic Interactions." Jour. Colloid
Interface Sci.. 122(2), Page 382.
Summers, R. S. and Roberts, P. V. (1982). "Performance of Granular Activated Carbon
for Total Organic carbon Removal. J. AWWA.. 74 (2), Page 113-118
Symons, J. M., Bellar, T. A., Carswell, J. K., DeMarco, J., Kropp, K. L., Robeck, G. G.,
Seeger, D. Ri, Slocum, C. J., Smith, B. L. and Stevens, A. A. (1975). "National
Organics Reconnaissance Survey for Halogenated Organics." J AWWA, 67( 11),
Page 634. ' .
i
Tan, L. and Amy, G. L. (1991) "Comparing Ozonation and Membrane Separation for
'' Color Removal and Disinfection By-product Control," JAWWA. 83(5), page 74.
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Taylor, J S., Mulford, L. A., Barrett, W. M, Duranceau, S. J. and Smith, D. K.
(1989a). Cost and Performance of Membranes for Organic Control in Small
Systems: Flagler Beach and Punta Gorda. Florida. USEPA Risk Reduction
Engineering Laboratory, Cincinnati, OH.
Taylor, J. S., Mulford, L. A.,.Duranceau, S. J. and Barrett, W. M. (1989b). "Cost and
Performance of a Membrane Pilot Plant." J.AWWA. 81(11), Page 52.
Taylor, J. S., Thompson, D. M. and Carswell, J. K. (1987). "Applying Membrane
Processes to Groundwater Sources for Trihalomethane Precursor Control" L
AWWA. 79 (8), Page 72.
United States Environmental Protection Agency (1988). In-House Pilot Studies for
Control of Chlorination Bv-Products. Organics Control Branch, Drinking Water
Research Division, Risk Reduction Engineering Laboratory, Cincinnati, OH.
van der Kooij, D., Hijnen, W. A. M. and Kruithof, J. C. (1989). "The Effects of
Ozonation, Biological Filtration and Distribution on the Concentration of Easily
Assimilable Organic Carbon in Drinking Water." Ozone SciEng 11(31 Page
297.
i
Vik, E. A., Carlson, D. A., Eikum, A. S. and Gjessing, E. T. (1985). "Removing Aquatic
Humus from Norwegian Lakes." LAWWA, 77(3), Page 58.
i
Wallace, J. L., Vahadi, B., Fernandes, B. L. and Boyden, B. H. (1988). "The
Combination of Ozone/Hydrogen Peroxide and Ozone/UV Radiation for
Reduction of Trihalomethane Formation Potential in Surface Water."
Ozone Sei. Eng.. 10(1), Page 103.
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Relationships to Biomass," J.AWWA. 87(12), Page 55.
Weber, W J. and A. M. Jodellah (1985). " Removing Humic Substances by Chemical
Treatment and Adsorption." J.AWWA. 77 (4), Page 132.
Weber, W. J., Voice, T. C. and Jodellah, A. (1983). "Adsorption of Humic Substances:
The Effects of Heterogeneity and System Characteristics." J.AWWA. 75(12),
Page 612.
\
Werdehoff, K. S. and Singer, P. C. (1987). "Chlorine Dioxide Effects on THMFP,
TOXFP, and the Formation of Inorganic By-Products." J.AWWA. 79(9), page
107.
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Westerhoff, P., G. Amy., R. Song., R. Minear., "Evaluation of Bromate Formation
and Ozone Decomposition Kinetics", Disinfection By-Products in Water
Treatment. Chapter 11, ed. R. Minear and G. Amy, CRC Press, Inc.,
Page 255-281, 1996. ,
Wood, P. R., Jackson, D. F, Gervers, J. A., Waddell, D. H. and Kaplan, L. (1980)
Removing Potential Organic Carcinogens and Precursors From Drinking Water.
USEPARpt. No. EPA/600/2-80/130 Cincinnati, OH.
Young J S and Singer, P. C. (1979). "Chloroform Formation in Public Water Supplies:
'A Case Study." J AWWA. 71(12), Page 87.
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5.0 ALTERNATIVE DISINFECTION TECHNOLOGIES
5.1 INTRODUCTION
Objectives of disinfection in water treatment are two fold:
To achieve inactivation of disease-causing microbes (primary disinfection)
whose'presence is ubiquitous in natural surface waters, and
To maintain conditions in the distribution system which prevent regrowth of
such organisms (secondary or residual disinfection). .
Chemical disinfection is achieved in water treatment through the use of chemical oxidizing
agents which are referred to as disinfectants. As discussed in Section 4, these disinfectants
form DBFs. Given a single water source, the quantities and types of DBFs formed during
water treatment and distribution is related to the disinfection strategy used. DBFs produced
by one disinfection strategy may be minimized by using an alternative strategy. However,
changing from one disinfection strategy to another may also increase other DBFs. Any
alternative disinfection strategy selected for implementation at a treatment plant should:
i
Adequately meet treatment objectives that include disinfection, and may also
include color removal, iron oxidation and taste and odor control;
Limit the formation .of regulated DBFs to concentrations lower than the
maximum contaminant level (MCL); and
Limit the formation of unregulated DBFs to concentrations lower than those of
potential concern.
This chapter presents a summary of the available alternative primary and secondary
disinfectants and the known by-products formed by each. Case studies from pilot-scale and
from implementation of alternative disinfection strategies in full-scale treatment operations
are also presented. Changes in disinfection strategy include changes in the types of
disinfectants and" in the location of disinfectant application.
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5.2 DISINFECTION ALTERNATIVES
.5.2.1 Primary Disinfection.
A relatively strong oxidizing agent is typically applied to achieve primary disinfection.
The most, prevalent disinfectants used for primary disinfection in the United States include:
Chlorine
Ozone
Chlorine Dioxide
Chlorine is not considered an alternate disinfectant. Some water treatment plants that
ป . *
continue to use chlorine as the primary disinfectant, however, have found that moving the
point of chlorination after a portion of the NOM removal occurs or eliminating
prechlorination if multiple application location are used can be effective in reducing DBFs.
The impact of this change on disinfection must be carefully considered before implementation.
Ozone is one of the most powerful oxidizing agents that is available for water
/
treatment practices. As such, it is used for many other purposes other than, or in addition to,
disinfection, including oxidation of organic material, taste and odor removal, color removal,
removal of iron and manganese, and enhanced coagulation. The use of ozone has increased
substantially in the last 10 years with over 158 known water treatment plants using ozone in
1996 for at least one of the purposes listed above (Dimitriou, 1997). The principle benefit
derived by using ozone for .controlling THM formation is that it allows chlorine to be applied
. later in the treatment process after precursors have been removed. A drawback of using
ozone as a disinfectant is that it is chemically unstable and short-lived and therefore can only
be used as a primary disinfectant. Ozone does not produce chlorinated DBFs, however, it
does oxidize bromide to hypobrbmous acid leading to the formation of bromoform, bromate
and other brominated DBFs when ozonation is utilized on bromide-containing waters. By-
products of ozonation are discussed in greater detail in Section 5.3.2. In addition, ozonation
'5-2
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of natural waters produces formaldehyde, other aldehydes and other types of biodegradable
organic material which must be adequately controlled.
Chlorine dioxide (ClOj) is an effective primary disinfectant that is typically used in the
midwest, southeast, and in Texas for 1) reduction of taste arid odor-causing compounds, and
2) THM control (Aieta and Berg, 1986; Lykins and Griese, 1986; Myers etal., 1986; Walker
et al.. 1986; Griese et al.. 1991; Lykins, 1992). Interest in chlorine dioxide increased since
the promulgation of the THM Rule in 1979 because it produces significantly lower
chlorination DBFs, including THMs and HAAs, and it has been shown to be an effective
disinfectant for some chlorine-resistant pathogens. A major problem associated with the use
of this disinfectant, however, is the by-product formation of chlorite ion (C102") and chlorate
iori (C103"). Section 5.3.3 discusses this issue in greater detail. In contrast to chlorine,
chlorine dioxide remains in molecular form as C102 in the pH range typically found in most
natural waters and does not react, with ammonia or nitrogenous compounds. Furthermore,
in contrast to ozone, high-purity chlorine dioxide does not oxidize bromide ion to brorhate
ion, unless photolyzed, and it does not produce appreciable amounts of aldehydes, ketones,
or other by-products associated with ozonation of organic matter. Because it is explosive as
a gas at elevated temperatures and is highly unstable, chlorine dioxide is almost always
generated at the point of use prior to application.
It should be noted that primary disinfection credit can be achieved with cnloramines,
t
although few utilities have continued to use chloramines in this capacity because of the
relatively poor disinfecting capacity and .large CT values required by the Surface Water
Treatment Rule (SWTR). For this reason, chloramine is-not considered as an alternative
primary disinfectant.
Advanced oxidation processes (AOPs) are those that couple with other treatment such
as hydrogen peroxide and ultraviolet irradiation, or peroxide in combination with ultraviolet
* . s
irradiation to generate a hydroxyl radical, which serves as a strong, non-selective, broad-
based, and rapid oxidant of organic contaminants. A significant issue with regard to AOPs,
especially those involving ozone, is that at,present, no disinfection credit is given unless a
dissolved molecular ozone residual can be measured. AOPs are not considered as primary
disinfectants in this document.
5-3
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5.2.2 Secondary Disinfection
Secondary disinfection is achieved by maintaining a residual of the oxidizing agent
throughout the distribution system. Most commonly, treatment plants operate to maintain
a target concentration of residual disinfectant in the water entering the distribution system,
and utilities serving large areas often have the capability to add additional disinfectant in the
distribution system in order to maintain a residual at remote locations. Chemicals typically
used for secondary disinfection in the United States include:
Chlorine
. Chloramine
Because ozone does not maintain a residual in the distribution system over time,
another disinfectant must be applied to achieve secondary disinfection.
Chloramination involves the addition of both chlorine and ammonia, either sequentially
or simultaneously. Chloramine is a much weaker oxidant than chlorine; however, for this
reason it tends to be more persistent in the distribution system, making it an ideal secondary
disinfectant. This persistence makes Chloramine slightly more effective in controlling biofilms
than chlorine. Compared to chlorine, the application of chloramines produces significantly
lower concentrations of chlorination by-products. The effectiveness of chloramines to control
DBF production depends upon a variety of factors, notably the chlorine to ammonia ratio, the
point of ammonia addition relative to that of chlorine, the extent of mixing and pH, These
issues are discussed in greater detail in Section 5.3.4.
5.2.3 Disinfection Strategies
Utilities may use any combination of the above disinfectants to achieve primary and
secondary disinfection. In the United States, the combination of disinfectants most commonly
used are chlorine/chlorine and chlorine/chloramine for primary/secondary disinfection. Ozone
is increasing in popularity as a primary disinfectant in the United States. Free chlorine, and
5-4
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more commonly chloramines, are used as secondary disinfectants. Other utilities, particularly
in the southeast, midwest and Texas, have pursued the use of chlorine dioxide as a primary
disinfectant. Although its use as a secondary disinfectant has been reported (Myers et al..
1986), utilities typically have used chlorine or chloramines as a secondary disinfectant when
chlorine dioxide is used as a primary disinfectant.
Section 5 A presents the results of various case studies of systems that have evaluated
or implemented changes in primary and secondary disinfection strategies.
5.3 DBP FORMATION BY ALTERNATIVE DISINFECTANTS
5.3.1 Introduction
As stated previously, all of the disinfection alternatives to chlorine considered in this
section can form DBFs. The following sections describe the DBFs formed by these
disinfectants and factors that influence their formation.
5.3.2 Ozonation DBFs
Ozone is an extremely strong oxidant that reacts with organic and inorganic material
in natural water. For waters containing bromide, ozonation leads to the formation of
hypobromous acid (HOBr), hypobromite (OBr"), bromate (BrO3~), and brominated organic
/
by-products. Haag and Hoigne (1983) have shown that ozone oxidizes bromide to form
HOBr/OBr under water treatment conditions. Hypobromite was found to be further oxidized
to bromate or to a species that regenerates bromide, whereas HOBr reacted with NOM to
.-
form brominated organic by-products. The principle organic DBFs identified are bromoform,
dibromoacetonitrile, dibromoacetic acid, cyanogen bromide, bromopicrin, 1,1-
dibromoacetone, other bromoacetic acids, and bromohydrins (Cooper et al, 1986, Weinberg,
et al, 1993, and Cavanagh et al, 1992). Mass balances between total organic bromide and
individual brominated organics indicate that these DBFs represent only a small portion (10
to 33 percent) of the total organic bromide (Glaze, et al, 1993). This indicates that other
brominated DBFs exist which are not yet identified.
5-5
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The formation of ozonation by-products is dependent upon numerous water quality
parameters, including bromide ion concentration, the source and concentration of NOM, pH,
ozone dosage, temperature, and alkalinity. Several studies have examined the effect of some
or all of these parameters on various water supplies. Siddiqui and Amy (1993) performed an
extensive bench-scale evaluation of two surface waters and two groundwater sources. The
surface waters in this study included California state project water and water from the Contra
Costa Water District, both of which were taken from the Sacramento-San Joaquin River Delta
and are subject to saltwater intrusion. The groundwater sources included a well in Orange
County, CA and water from the Biscayne Aquifer in Florida. Glaze, et.al (1993) conducted
bench-scale testing of surface water from University Lake, Orange County, NC. with the
purpose of evaluating the formation of brominated compounds during ozonation. Shukajry,
et al (1994) performed similar investigation of Ohio River water at various ozone dosages and
bromide concentrations. Finally, Krasner, et al (1993) evaluated the occurrence and control
of bromate from three major studies. One of the studies performed extensive bench-scale
tests to evaluate the water quality and ozonation parameters that affect and control bromate.
Although much knowledge ,has been gained recently, it was noted by these researchers
that the ozone-to-bromide-to-TOC system is extremely complex and that more study is
needed to better understand the effects of water quality variables on the formation of
brominated by-products! The following paragraphs describe some of the general factors
influencing production of ozonation DBFs in waters containing bromide.
At common drinking water pH levels, HOBr is in equilibrium with OBr' (pK, is 8.8
at 20ฐC). Changes in pH can have a dramatic effect on the concentration of HOBr and OBf
and therefore, the species of by-products formed. Increases in pH result in increased bromate
1 \ '
formation. This increase may be because of a shift in equilibrium to OBr' (the precursor of
bromate) or because of the more .rapid bromate formation kinetics at higher pH through a
hydroxyl radical pathway (Siddiqui and Amy, 1993). While a reduction in pH results in a
reduction in bromate, the lower pH enhances formation of bromoform and other organic
\
brominated DBFs. This result is likely attributable to the predominance of HOBr over OBr'
at lower pH levels (Siddiqui and Amy, 1993).
5-6
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/
The pH also affects ozone decay rates, with lower pH extending the half-life of ozone
Krasner et al (1993) noted that as the pH of ozonation was lowered, the ozone dosage to
meet CT requirements to meet the SWTR dropped and less bromate was formed. For one
of the waters evaluated during bromide spiking, bromate concentrations were reduced from
24-68 ug bromate/L at pH 8 to as low as <5-7 ug/L at pH 6.
Formation of ozonation by-products increases with increased levels of bromide ions
in the water supply. This is a particular concern for coastal water supplies which may be
influenced by salt water intrusion. Bromide levels of at least 0.18 mg/L were necessary to
produce measurable levels of bromate when using ozone for primary disinfection purposes
for the waters evaluated by Krasner et al (1993). In other studies (Siddiqui and Amy, 1993),
bromide levels above 0.25 mg/L were required to produce measurable levels of bromoform.
These threshold values are based on the specific test conditions (i.e., ozone dosage/DOC
ratio, pH, etc.); however, they provide an approximate level of concern. For reference, the
following table 5.3.2 contains results of national surveys of bromide in drinking water
supplies: %
TABLE 5-l(a)
National Survey of Bromide in Drinking Water
Source
Rivers
Lakes
Groundwaters
Coastal Areas
Numberof =-
.-Sources "
35
29
34-.v.
37
11
= Range of Br-
:lpvmg/L--";A:-
0.01-3.0
0.003-0.426
0.003-0.322
0.002-0.429
0.05-0.40
Average Br-
mg/L
o.np
0.101
0.038
0.096
0.210
"Reference
Krasner, et al (1989)
Amy, etal( 1993)
Amy, et al (1993)
Amy, et al (1993)
Amy, etal( 1993)
As shown in this table, coastal waters have the highest average bromide
concentrations. Furthermore, all of the categories have some sources with bromide levels
which exceed the approximate threshold values described.
5-7
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Ozone dosage also plays a critical role in the formation of ozonation by-products.
The selected ozone dosage for a particular water treatment system will depend on many site-
specific characteristics, including ozone demand of the natural water and the intended purpose
of ozone (i e disinfection or oxidation). For systems using ozone for primary disinfection,
an ozone residual is required to meet'the CT requirements of the SWTR. Krasner eLal,
(1989) found that an ozone residual was necessary to produce detectable levels of bromate.
Siddiqui and Amy (1993) found that the bromoform concentration first increased, then
diminished at higher dosages. A decrease in aldehydes at high ozone dosage is indicative of
this because aldehydes are a precursor of bromoform.
To meet the CT requirements of the SWTR, Song, et al (1995), demonstrated that
lower ozone dosage and longer contact time should produce less bromate than higher dosages
and shorter contact times.
Temperature and alkalinity also affect formation of by-products during ozonation.
Increased temperatures will increase the levels of bromate, bromoform and total organic
bromide. It also increases the decomposition of ozone. On the other hand, increasing
alkalinity has been shown to reduce the formation of bromoform and total organic bromide
and increase the formation of bromate. Bicarbonate scavenges OH radicals, suggesting that
-the OH radical may play a role in the formation of brominated species.by affecting the level
of HOBr, which is presumed to be active species for total organic bromide formation (Glaze,
etal, 1993). . ,
Ammonia addition has been used to limit the formation ozonation by-products.
Lower concentrations of organic by-products were.produced when ammonia was added to
some waters. In one study, (Siddiqui and Amy, 1993) bromoform concentrations decreased
by about 30 percent on adding a ratio of NH3 to ozone of 0.25 mg/mg. The reason for this
reduction is because HOBr reacts with ammonia to form bromamines, presumably making
HOBr unavailable for reaction with NOM. Conflicting results of ammonia addition on
bromate formation have been observed. Glaze et al (1993) found that bromate production
was reduced to below detection limits with specified ammonia concentrations; however,
Krasner et al (1993) found that bromate production was not minimized at similar ammonia
levels.
5-8
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Although less of a regulatory focus, it should be noted that ozone can increase the
concentration of biodegradable organic carbon (BDOC), which can encourage microbial
regrowth in a distribution system if not properly stabilized through treatment processes
These by-products of NOM oxidation include various aldehydes and ketones. The use of
biologically active filters, maintained by discontinuing the application of a disinfectant to the
filters, have been shown to successfully remove aldehydes and other compounds representing
a portion of the BDOC in a water (Bablon et al, 1988; Rittman, 1990; Reckhow et al, 1992,
Shukairy et al, 1995).
5.3.3 Chorine Dioxide DBFs
Chlorate ion and chlorite ion are the main by-products of chlorine dioxide use.
According to Hoehn et al, 1996, the chlorate ion by-product derives from three principal
sources, the most significant of which is the oxidation of chlorine dioxide by excess chlorine
during generation or by oxidant addition to the chlorine-dioxide treated water. The other
sources are sodium chlorate impurity in the sodium chlorite feedstock that is carried through
the.generator, and photolysis. Some chlorite ion by-product comes from unreacted sodium
chlorite feedstock that passes through the generator, but the major source of chlorite ion in
the distribution system is the reduction of chlorine dioxide in its action on target compounds.
Hoehn et al, 1996, suggest that chlorate ion production can be prevented to a
significant extent through careful feedstock handling procedures and by frequent generator
tuning to avoid excess chlorine. Further actions that can prevent chlorate formation involve
avoiding mixing chlorine dioxide with other oxidants (e.g., ozone or chlorine) and protecting
the chlorine dioxide from light. Chlorite ion can also be prevented by feedstock control and
by frequent generator tuning; however, the chlorite ion resulting-from chlorine dioxide
reactions will still be present, especially in high demand waters. Two chemical processes have
been developed for chlorite removal: reduced iron and sulfite ion addition. These removal
processes are described in greater detail in Section 6.
5-9
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5.3.4 Chloramination DBPs
Numerous studies have demonstrated that chloramines produce much lower levels of.
DBFs than does free chlorine (AWWARF 1993 and Symons 1996). Symons et al (1996)
demonstrated that even preformed chloramines produced measurable amounts of by-products.
The by-products formed by chloramination, for the most part, are identical to those produced
during chlorination and include THMs, HAAs, haloacetonitriles and cyanogen chloride. With
the possible exception of cyanogen chloride, chloramination does not preferentially form any
of the halogenated DBFs.
The formation of DBFs resulting from chloramination is influenced by the following
treatment variables (AWWARF 1993):
Point .of ammonia application
Chloramine dosage
i
pH
Temperature
i Chlorineiammohia-nitrogen ratio
Mixing and reaction time for chloramine formation
The point of ammonia application after chlorine addition generally impacts the length
of time free chlorine reacts with NOM. For most plants using chlorine as a primary
disinfectant, the point of ammonia application depends on disinfection requirements and goals.
Once ammonia is added, the rate of DBF formation is significantly reduced.
Increases in temperature increase the rate of DBF formation. Within the range of
chloramine residuals commonly used in the water industry (1 to 5 mg/L), chloramine dosage
does not appear to be a significant factor in DBF formation; rather, it is the chloramine:
ammonia-nitrogen ratio used that is more significant. TTHMs remain quite low at chlorine
to ammonia weight ratios less than 5:1, then increase dramatically above the 5:1 ratio
(AWWARF 1993). . Most "utilities use chlorine uTammonia weight ratios of 3:1 to 5:1
5-10
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because dichloroamine and nitrogen trichloride can be formed at ratios higher than 5.1.
These compounds cause tastes and odors and are unstable compounds.
Good mixing can reduce the time free chlorine has to react with NOM. Assuming
complete mixing, at neutral pHs of 7,to 9 and temperatures of 20 to 25ฐC the reaction of
ammonia and chlorine to form monochloramine takes from 0.07 to about 3 seconds, almost
immediately eliminating the free chlorine and reducing the potential for DBF formation.
As noted above, pH is important for rapid formation of chloramines. Symons (1996).
showed that DBF formation decreased with increasing pH. Exceptions to the trend were
noted in some instances at pH 8, where Symons noted the complexity of chloramine chemistry
may cause water-specific responses. Regardless of the cause, the DBFs formed were much
less the proposed MCLs.
5.4 IMPACT OF ALTERNATIVE DISINFECTION STRATEGIES
5.4.1 Introduction . '
The promulgation of a TTHM standard in 1979 prompted some utilities to evaluate
and implement changes in disinfection practices. The following sections present the result of
studies evaluating disinfection alternatives. Some of the results presented are from a 2-year
study, funded by EPA and the Association of Metropolitan Water Agencies (AMWA)
(Metropolitan and Montgomery, 1989). This study surveyed 35 water treatment facilities
throughout the United States to evaluate the occurrences of DBFs. Seven facilities were used
*
to evaluate the impact of changes in oxidation/disinfection practices on the formation of
DBFs. Six full-scale and two pilot-scale studies were conducted at selected sites. The
following summary is not intended to be an exhaustive review, but rather to provide examples
of changes in DBF formation that are effected by modifying disinfection strategies.
5.4.2 Moving the Point of Chlorination
As discussed in Section 4.4, the THMFP is reduced after the coagulant addition.
Thus, plants that prechlorinate and are capable of moving the point of chlorination after rapid
mix or after sedimentation can reduce the amount of chlorination by-products formed in the
5-11
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distribution system. After the promulgation of the THM Rule in-1979, many utilmes
examined their existing disinfection practices. Some of these utilities were able to meet the
THM standard of 0.10 mg/L by modifying their chlorination practices by moving the point
of chlorination, reducing the chlorine dose, and/or eliminating prechlorination.
More recently, Summers (1997) evaluated the impact of moving the point of
chlorination on the formation of TOX, TTHM and HAAS on 16 waters representing a wide
distribution of raw water quality. In bench-scale tests, chlorine was added to four parallel jars
at four different times during coagulation, flocculation, and sedimentation. For TOX and the
specific by-products, moving the point of chlorination downstream in the coagulation,
flocculation, and sedimentation process decreased DBF formation and the chlorine demand
by providing additional time for the NOM removal before chlorine could react with the NOM
to fomi DBFs. In general, moving the point of chlorination resulted in a percent decrease in
. DBF formation that was equivalent of or greater than the percent TOC removal achieved.
5.4.3 Switching to Ozone as Primary Disinfectant
5.4.3.1 Introduction .
Recognizing the strong oxidation capacity of ozone, many utilities have investigated
the use of ozone as a.primary disinfection alternative to chlorine. Free chlorine or
chloramines are used as secondary disinfectants.
5.4.3.2 Utility 19
The following alternative disinfection schemes were evaluated atthis utility's full-scale
treatment plant (Metropolitan and Montgomery, 1989; Jacarigelo, gtal., 1989):
- . rhiorine/Chlorine: 1.8 mg/L of chlorine, was added to the raw water and 0.3
mg/L was added to the filtered water.
. O^one/CWorine: Ozone was applied at a dosage of 1.1'mg/L-to the raw water
and 15 mg/L chlorine was added to the filtered water for residual disinfection.
5-12
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In-plant samples were collected after the clearwell and distribution system samples
were collected at points representing detention times of 4.3 and 11 hours. TOC levels in the
clearwell effluent were 1.2 mg/L for both disinfection strategies.
DBF concentrations in the 11 hour distribution system samples are shown in Table 5-1
and Figures 5-2 and 5-3. As shown in the table, the replacement of pre-chlorination with pre-
t
ozonation resulted in decreased concentrations of chloroform, brqmodichloromethane,
dichloroacetic acid and trichloroacetic acid. Decreases in dichloroacetonitrile and
bromochloroacetonitrile were also observed, however, these changes occurred at
concentrations near 1 ug/L. Replacing pre-chlorination with pre-ozonation increased the
concentrations of dibromochloromethane and chloral hydrate. Increases in the concentrations
of bromoform, dibromoacetic acid, 1,1-dichloropropanone, dibromoacetonitrile and
chloropicrin were also observed, however, these concentrations occurred at concentrations
near 1 ug/L.
Several items listed below should be considered when evaluating the data shown in
Table 5-1:
Moving the point of chlorine addition after the coagulation and filtration should
reduce chlorinated DBFs. However, an assessment of the precursor removals
achieved at this plant was not performed.
The combination of implementing pre-ozonation and moving the point of
chlorination resulted in a 0.6 mg/L reduction in the overall chlorine dosage.
This should also reduce the chlorinated DBFs.
In the ozone/chlorine alternative, chlorine contact time was equivalent to 11
hours plus the contact time in the clearwell. With chlorine/chlorine disinfection,
chlorine contact time was 11 hours plus the contact time in the plant's
flocculators, filters and clearwell. The shorter chlorine contact time with ozone/
chlorine should also reduce chlorinated DBFs.
If ozonation increases the precursor concentration of some chlorinated DBFs,
this effect would not be evident unless the increase caused by ozonation was
large enough to offset the decreased precursor concentrations caused by
coagulation/filtration.
5-13
-------
In the ozone/chlorine strategy, bromine has the opportunity to react through the
ozone contactor, the flocculators and the filters without kinetic competition
'from chlorine. This would favor the brominated by-products over the
chlorinated by-products.
The results presented in table 5-1 indicate that the molar quantity of bromine
incorporated into the trihalomethanes was 10 percent higher with ozone/chlorine
than with chlorine/chlorine. Bromide concentrations were not reported for
either alternative; therefore, the cause of the higher levels of brominated DBFs
cannot be attributed to either increased bromide levels or to the non-competitive
reactive period prior to chlorine addition.
Temperatures with ozone/chlorine were 3 to 4ฐC higher than those with
chlorine/chlorine. Therefore, the rates of DBF formation and decay would likely
be faster with ozone/chlorine than with chlorine/chlorine.
5.4.3.3 Utility?
Two of the disinfection alternatives evaluated at Utility 7 were (Metropolitan and
Montgomery, 1989):
Chlorine/Chlorine: 2.3 mg/L of chlorine was applied to the raw water and 1.1
mg/L was applied to the settled water.
Qzone/Chloramine: Ozone was applied at 2 mg/L prior to rapid mix. Ammonia
and chlorine were applied simultaneously to the filtered water at 0.5 mg/L and
1.5 mg/L, respectively. Therefore, the alternative also employed a chlorine to
ammonia ratio of 3:1 by weight.
Finished water was collected for each alternative and held for 2 hours and 24 hours
under conditions representative of the utility's distribution system. DBF concentrations from
these alternatives are summarized in Figure 5-1.
s
Compared to chlorine/chlorine, ozone/chloramine formed lower concentrations of
most of the halogenated DBFs. Cyanogen chloride was higher with ozone/chloramine at 2
hours but was approximately the same for both alternatives at 24 hours. The concentration
of 1,1-dichloropropanone increased at both residence times, however, this concentration was
below 1 ug/L in both instances.
5-14
-------
TABLE 5-1
DBFs After. Switching from Chlorine/Chlorine
to Ozone/Chlorine Disinfection
(Jacangela, et al., 1989)
;-. . ..-.:-.. ' i ... .
vi <-- <'.. ;.:..
Disinfection By-Product
(All conceptions in ug/L) ^
v' '/' :. ' :ฃ-*':' ,
Trihalomethanes
Chloroform
Bromodichloromethane
Dibromochloromethane
Bromoform
Total Trihalomethanes
Haloacetic Acids
Monochloroacetic Acid
Dichloroacetic Acid
Trichloroacetic Acid
Monobromoacetic Acid
Dibromoacetic Acid
Haloacetic Acids (5)
Haloketones
1 , 1 -Dichloropropanone
1,1,1- Trichloropropanone
Total Haloacetonitriles
Haloacetonitriles
Trichloroacetonitrile
Dichloroacetonitrile
Bromochloroacetonitrile
Dibromoacetonitrile
Total Haloacetonitriles
Miscellaneous
Chloropicrin
Chloral Hydrate
Cyanogen Chloride
.- \
- Clitorine ,
"' 'Qdate-
19
10
3.8
0.3
33
<1.0
9.4
7.4
<0.5
0.7
18
0.16
1.1
1.2
<0.012
2
1
0.41
3.4
0.073
6.3
0.1
tfti&ii-. ปซ'
. Utfltty 19
...%.!.
"'" t .-f -f
Ozone and
?: taubiiM';'.'
6.1
6.4
6.1
1.1
20
1.1
4.7
1.3
<0.5
1.7
8.8
0.25
1.1
1.4
<0.012
u, 0.72
0.69
0.79
2.2
0.49
8.6
NA
- " " :
Change (%)
-68
-36
61
267.
-39
-50
-82
143
-51
56
0
17
-64
-31
93
-35
571
37
NA = Not Analyzed
5-15
-------
COMPARISON OF DBP FORMATION AT UTILITY 19
35
30
O)
25
O
F 20
ai
O 15
Z
O
O
0.
g 10
OZONE/CHLORINE
CHLORINE/CHLORINE
TTHM
HAA
DBP CLASS
Reference: Metropolitan and Motgomery (1989)
01
-------
COMPARSION OF DBP FORMATION AT UTILITY 19
O)
n.
Z
a:
LU
o
z
o
o
Q_
m
Q 1
OZONE/CHLORINE
CHLORINE/CHLORINE
HAN
HK CHP
DBP CLASS
CNCI
NA: NOT ANALYZED
Reference: Metropolitan and Montgomery (1989)
O
c
m
m
CJl
ru
-------
COMPARISON OF DBP FORMATION AT UTILITY 7
200
B)150
3.
Z
I
z
111
o
100
o
o
CL
ED 50
O
1 2
XDBPsum
CHLORINE/CHLORINE
CHLORINE/CHLORAMINE
OZONE/CHLORAMINE
1 2
2,4-DCP
DIST. SYS. RESIDENCE TIME (t)
1:t = 2HRS. 2:t = 24HRS.
* BELOW MDL
DBP CLASS
Reference: Metropolitan and Montgomery (1989)
O
c
Zl
rn
Ul
OJ
-------
In addition to the DBFs, the disinfectant residuals were as follows:
TABLE 5-2
RESIDENTIAL TIMES.OF DISINFECTANTS
Disinfectant
Chlorine (Free C12)
Chloramines (Total C12 - Free C12)
Res. Time = 2 hr
C12/CI2
1.1.
0.2
CI2/NH2CI
<0.1
1.4
Res. Time - 24 hr,
C12/CI2
0.3
NA
C12/NH2C1
NA
1.3
With the chlorine/chlorine, the consumer is exposed to a chlorine residual, while with
~>
ozone/chloramine, the consumer is exposed to a chloramine residual. As discussed in
Chapter. 2, a chloramine residual may be a more significant health concern than a chlorine
residual.
5.4.3.4 Utility 6
During the course of this study, Utility 6 converted from chlorine/chloramine to
ozone/chloramine as follows (Metropolitan and Montgomery, 1989):
Chlorine/Chloramine: Chlorine was added to the plant influent, flocculator
influent, filter influent and filtered water. Ammonia was added to the filtered
water. Chemical dosages were not reported.
Ozone/Chloramine: Ozone was applied to the plant influent and the plant
was modified to a direct filtration process. Chlorine was applied to the filter
influent and ammonia to the filtered water. This new practice reduced the
amount of contact time for free chlorine. Chemical dosages were not
reported. ~ -
Figure 5-4 summarizes the DBF concentrations observed under these disinfection
conditions. These samples were collected from the distribution system at a point
approximately 7 hours from the treatment plant. As noted in the figure, most of the
halogenated DBFs decreased. However, the concentration of 1,1-dichloropropanpne
increased. Utility 6 was operated at a pH ranging from 7.5 to 8.0.
In addition to the DBFs, the disinfectant residuals after 7 hours were as follows:
5-16
-------
TABLE 5-3
DISINFECTANT RESIDUALS
[Disinfectant
Chlorine (Free C12)
Chloramines (Total
C12 - Free C12) .
Clj/NHjCl
NA '
>2.0
Q3/NH3a
ND
2.0,
5.4.4 Switching to Chlorine Dioxide as a Primary Disinfectant
5.4.4.1 Introduction
As stated previously, many utilities in the southeast, midwest and Texas have
implemented the use of chlorine dioxide as a primary disinfectant in lieu of chlorine. This
modification often has been made to address taste and odor problems, as well as THM
formation, and is a less expensive alternative compared to ozone. Further, this strategy
does not generate brominated by-products to the same extent as ozone in bromide:
containing waters, although other inorganic by-products (i.e. chlorite and chlorate) are
formed. .
5.4.4.2 Utility 16
Normal operations at this facility include the use of chlorine/chlorine disinfection.
(Metropolitan and Montgomery, 19S9). Periodically, chlorine dioxide/chlorine is used to
control taste and odor events. The two disinfection alternatives studied at this facility
were as follows:
Chlorine/Chlorine: Chlorine was applied to the raw water and the filtered
water at 2.0 and 1.0 mg/L, respectively.
Chlorine Dioxide/Chlorine: Chlorine dioxide was applied at 0.5 mg/L to the
raw water and chlorine was applied at 1.9 mg/L to the filtered water. The
chlorine dioxide to TOC ratio was 0.19 and the chlorine to TOC ratio was
0.71.
i ' - , '
The concentration of DBFs 45 minutes after filtration and 160 hours into the. distribution
system are presented in Figures 5-5 and 5-6, respectively. Chlorine dioxide/chlorine
produced higher total aldehyde concentrations and lower concentrations of TTHMs and
5-17
-------
COMPARISON OF DBP FORMATION AT UTILITY 6
140
120
en
100
O
!< 80
a:
O
en
60
O
O
0_ 40
CD
Q
20
CHLORINE/CHLORAMINE
OZONE/CHLORAMINE
XDBPsum
THM
HAN HK
DBP CLASS
HAA
ALD
DIST. SYS. RESIDENCE TIME (t) = 7 MRS.
* TCAN BELOW MDL ** MBAA BELOW MDL
NA: NOT ANALYZED
Reference : Metropolitan and Montgomery (1989)
Tj
O
c
;o
m
01
-------
COMPARISON OF DBP FORMATION AT UTILITY 16
(Distribution System Residence Time = 45 Minutes)
CHLORINE/CHLORINE
CHLORINE DIOXIDE/CHLORINE
XDBPsum
THM
HAN HK
DBP CLASS
HAA
ALD
Reference: Metropolitan and Montgomery (1989)
O
c
TO
m
en
cn
-------
70
60
250
O
40
O 30
O
O
Si20
D
10
COMPARISON OF DBP FORMATION AT UTILITY 16
(Distribution System Residence Time = 160 Hours)
CHLORINE/CHLORINE
CHLORINE DIOXIDE/CHLORINE
XDBPsum
THM
HAN HK
DBP CLASS
HAA
ALD
NA: Not Analyzed
Reference: Metropolitan and Montgomery (1989)
a
c
;o
m
en
en
-------
tota! ha.oace.ic acids a, 45 minu.es after filtration. However, a, .he end of 160 hours, .he
TfHMs were higher for chlorine dioxide/chlorine. In addition, .he concen.rav.ons of
chlorine, chlorine dioxide, chlorite and chlorate were observed as follows:
rONTAMINANT EXPOSUKES
Sample Location 2
Consumer exposure .0 chlorine was essentially .he same under dtar disinfection
alternative. However, chlorine dioxide, chlorite and chlorate were not detected wrth
chlorine/chlorine.
Several items listed.below should be considered when evaluating this data.
observed in DBF formation.
overall chlorine dosage.
5.4.43 Evansville, Indiana
The Evansville Filtration Plant initially used chlorine/chlorine for disinfection
purposes Based on .he results of a pilot sซ,dy (Lykins and Griese, J986), which showed
marked'reduc,ion in .he THM formation wi.h the application of chlorine dioxide as a
primary disinfectant, this utility implemented chlorine dioxide in .heir rull-scale facihry. In
this smdy, .he fuH-scale .rea.men. plan, was run wM, chlorine/chlorine disinfection whue a
5-18
-------
pilot-scale treatment plant was operated with chlorine dioxide/chlorine disinfection. The
characteristics of the two trains were as follows:
Chlorine/Chlorine: A chlorine dose averaging 6 mg/L was applied prior to
alum coagulation and sedimentation. A sample of filtered water was
collected, chlorinated and held at ambient temperature and pH 8.0 for 3 days
to simulate the Evansville distribution system.
Chlorine Dioxide/Chlorine: A chlorine dioxide dose averaging 1.1 mg/L was
applied prior to alum coagulation and sedimentation. A sample of filtered
water was collected, chlorinated and held at ambient temperature and pH 8.0
for 3 days to simulate the Evansville distribution system.
The use of chlorine dioxide/chlorine reduced TTHMs by 60 percent in the simulated
distribution system samples.
Several items should be considered when evaluating the TTHM results:
The point of chlorine addition was moved to a point after coagulation and
filtration. In the chlorine/chlorine case, chlorine was initially applied to a
water containing 3 to 5 mg/L of TOC. In the chlorine dioxide/chlorine case,
chlorine was initially applied to a water containing 2 to 3 mg/L of TOC.
An analysis of the pilot plant chlorine dioxide feed stream showed that the
feed stream was 64 percent chlorine dioxide, 30 percent chlorite and 6
percent chlorine.
If excess chlorine was not fed into the plant with the chlorine dioxide,
chlorine contact time through the flocculators, sedimentation basins and
filters would be eliminated.
A brief, full-scale study was conducted to determine the effect the coagulation,
sedimentation and filtration on the observed decrease in TTHMs. One side of the
treatment plant was operated with chlorine dioxide pre-oxidation at 1.4 mg/L and with
chlorine applied at a point between sedimentation and filtration. The other side of the
plant was operated with no pre-oxidant and with chlorine applied at a point between
sedimentation and filtration. TOC removals and chlorine dosages were the same on both
sides of the plant. When compared with the chlorine/chlorine side of the plant, TTHMs
5-19
-------
averaged 30 percent lower in the filtered water on the chlorine dioxide/chlorine side of the
plant. Distribution system concentrations, either real or simulated; were not determined
for either process train.
5:4.4.4 Chester Metropolitan Water District, South Carolina
In 1984, the Chester Metropolitan Water District changed their pre-oxidation from
chlorine to chlorine dioxide (Singer, 1988). Raw water quality at this source is highly
seasonal, with the raw water.TQCs varying from4.1 to 13.5 mg/L between March 1984
and July 1985 The plant is located downstream of a paper mill waste discharge and the
raw water contained up to 400 ug/L of total organic halides (TOX). However, none of
the THMs were detected.
This plant employs conventional alum coagulation for water clarification. Alum
coagulation is carried out at pH values of 5.5 to 6.0 and more than 50 percent removal of
TOC and THM precursors were observed at this plant.
The following disinfection alternatives were evaluated in this study:
. rhinrine/Chlorine: A total dosage of 1 1 mg/L was applied, on average, at
the treatment plant with most of the chlorine applied to the raw water. The
free chlorine residual in the distribution system was 1 to 1.5 mg/L.
. OKWJ- n^ide/Chlorine: Pre-oxidation with ^ chlorine dioxide at 0 ,7 mg/L
was practiced with chlorine applied on top of the filters at 35 to 4 mg/L.
e free chlorine residual in the distribution system was 0.4 to 0.5 mg/L.
hoSflneS^ Chlorine was substantially lower than the pnorpracnce,
unts or ositive coliform was observed.
thone
no indication of high plate counts or positive coliform was observed.
With chlorine/chlorine, TTHMs in the distribution system ranged from 1 10 to 300 ug/L
and averaged 200 ug/L. After changing to chlorine dioxide/chlorine, TTHMs in the
distribution system ranged from 54 to 120 ug/L with an average of 90 ug/L. In addmon,
the concentrations of chlorine, chlorine dioxide, chlorite and chloratefor chlorine flood*
chlorine disinfection were observed as follows:
5-20
-------
TABLE 5-5
DISTRIBUTION SYSTEM AVERAGE CONCENTRATION
Distribution System
Average Concentration (mg/L)
Contaminant
Chlorine
Chlorine Dioxide
Chlorite
Chlorate
cicyci,
0.34 -
0.02
0.24
NR
Consumer exposure to chlorine, chlorine dioxide, chlorite and chlorate were not reported
for chlorine/chlorine. However, chlorine dioxide and chlorite would not be expected with
chlorine/chlorine..
Again, several items should be considered when evaluating the TTHM results.
The point of chlorine addition was moved to a point after coagulation and
clarification. With chlorine/chlorine, chlorine was initially applied to a water
containing 4 to 14 mg/L of TOC. With chlorine dioxide/chlorine, chlorine
was initially applied to a water containing 2.5 to 6 mg/L of TOC.
The use of chlorine dioxide as a preoxidant allowed for a reduction in the
. free chlorine dose.
Chlorine dioxide is generated on-site by the reaction between hydrochloric
acid and chlorite. An analysis of the chlorine dioxide feed stream showed
that the feed stream was 88 percent chlorine dioxide, 8 percent chlorite and 4
percent chlorine (as C12). The chlorine "dose" applied by the chlorine dioxide
feed was not likely to be significant in terms of THM formation. In fact,
settled water THMs concentrations averaged less than 3 ug/L.
If excess chlorine was not fed into the plant with the chlorine.dioxide,
chlorine contact time through the flocculators, sedimentation basins and
filters was eliminated, which should reduce chlorinated DBFs.
Studies were not conducted to determine the relative importance of these items.
N " m
5.4.4.5 Louisville, Kentucky
This study focused on a Louisville treatment plant which practiced alum
coagulation followed by lime softening. In an effort to limit THM formation, the
5-21
-------
Louisville Water Company studied the following disinfection alternatives (Hubbs, et_al.,
1981):
Chlorine/Chloramines: Chlorine,was applied to a rapid mix unit and
ammonia was added 6 hours later in the process. Additional amounts of
chlorine and ammonia were added after filtration, as needed to maintain
residual in the distribution system. Chlorine and ammonia dosages were not
reported.
Chlorine Dioxide/Chloramines: Chlorine dioxide was applied to a rapid mix
unit at 0.6 to 0.8 mg/L and ammonia was applied 10 minutes later in the
process. Chlorine, was added to the filtered water to form chloramines prior
to distribution. Chlorine and ammonia dosages were not reported.
i
Running annual average TTHMs approached 100 .ug/L with chlorine/chloramine. The
modification to chlorine dioxide/chloramine limited TTHM production to less than 5 ug/L..
The TOC concentration of the raw water was not reported.
5.4.5 Switching to Chloramines as Secondary Disinfectant
5.4.5.1 Introduction
Information presented in this section was obtained from a publication by the
American Water Works Association Research Foundation (AWWARF, 1993). This
reference supplies additional information on the reason(s) for switching to chloramines and
contains information on chloramination changeover and start-up procedures, nitrification,
and impact on taste and odor, where available, for each of these utilities.
5.4.5.2 Metropolitan Water District of Southern California
MWD is a municipal corporation that wholesales drinking water to southern
California's 15 million residents through 27 cities and water districts of member agencies.
MWD is the second largest water supplier in the United States.
Water for the MWD supply system is imported into the area from two separate
sources - rivers in northern California and the Colorado River. Raw water quality differs
significantly between the two sources. Water is treated at fiye filtration plants owned and
5-22
-------
operated by MWD, which have a combined capacity of 1,595 mgd. Blending of these'
sources depends upon demand and operating conditions and may vary widely at various
plants and in many areas of the distribution system.
In 1979, when USEPA first promulgated the 0.10-mg/L THM standard and MWD
officials realized that the utility and its member agencies might have difficulty meeting this
regulation, an intensive effort was carried out to reduce THMs. After two years of field
and laboratory studies, MWD was able to implement modifications to its chlorine
treatment program that reduced THM levels in the distribution system from a running
annual average of more than 0.90 mg/L in 1981 to less than 0.70 mg/L by 1984. Several
i
of the municipal agencies continued to have elevated THM levels in their systems,
however, and chloramination was implemented in 1985 to provide better THM control
throughout the service area.
MWD's. average THM levels in water leaving the treatment facilities were not
significantly reduced after chloramination start-up in 1985. This lack of reduction has
been attributed to the need to prechlorinate plant influents to control taste and odors. The
change to chloramination, however, did reduce THM levels in the systems of MWD's.
member agencies, enabling them to comply with the THM regulation.
5.4.5.3 Kentucky-American Water Company
The Kentucky-American Water Company (KAWC) provides retail and wholesale
water service to a population of 225,000.in the Lexington area of north-central Kentucky.
Approximately 75 percent of the water serving the KAWC system comes directly from the
Kentucky River and is treated at the 40-mgd Kentucky River Station, a filtration facility
located 12 mi southeast of downtown Lexington. The remaining 25 percent is drawn, from
Jacobson Reservoir, located within the Lexington city limits, and is treated at the
Richmond Road Statipn, a conventional 20rmgd filtration plant. Water supply from
Jacobson Reservoir is supplemented during periods of peak .demand with raw water
pumped directly from the Kentucky River. . .
Since the THM standard of 0.10 mg/L was promulgated in 1979, KAWC has
sought to reduce THM concentrations in its distribution system. Kentucky River water
5-23
-------
contains bromide ion in concentrations that have seasonally exceeded 1.0 mg/L. These
concentrations are attributed to discharge of oil drilling brines in the watershed.
In December 1983, prechlorination was replaced with chlorine dioxide to reduce
THM formation. The introduction of chlorine dioxide as the primary disinfectant, coupled
with postchlorination to'maintain a free chlorine residual, resulted in an immediate 60.
percent reduction in THM levels in water discharged from the plant. As a result of
problems with the chlorine dioxide system, its application was limited to only those
quarters of the year with the highest THMFP. Continued studies and process
modifications were carried out to eliminate chlorine dioxide problems. These evaluations
included investigation of alternative disinfectants, and in the fall of 1987 the decision was
made to switch from chlorine dioxide to post chloramination.
Distribution system THM levels have been well within the regulatory limit since
the changeover, despite the fact that KAWC must average results from samples collected
in its system with those of its bulk customers. THM concentrations in the distribution
system of one of these bulk customers were so high before the switch that the customer
found it necessary to remove the THMs by air stripping. Air stripping by that customer is
no longer practiced. Running annual average THMs have been about 0.075 mg/L since
1987.
5.4.5.4 Tampa Water Department, Tampa, Florida
The City of Tampa Water Department is a retail supplier providing water to more
than 475,000 customers in Hillsborough County, Fla. Most of the city's water is drawn
from the Hillsbororogh River, which originates approximately 50 mi to the northeast in the
Green Swamp. Humic and fulyic acids in the surface water source result in high color
levels in the water arriving at the Hillsborough Treatment Plant, a 100-mgd facility. Color
in the source water varies.on a seasonal basis, ranging from as low as 25 pcu during dry
weather to 350 pcu during periods of heavy precipitation. TOC levels in the raw water
range from 4 to 40 mg/L. .
Studies concluded in 1980 indicated that the most cost-effective method for
controlling TTHMs was to use short-term chlorination in the plant to achieve primary
5-24
-------
disinfection and a combined residual in the distribution system. In 1980, before
chloramine treatment, only 10 percent of the THM samples met MCL requirements. In -
198l[ THM levels were even higher, and none of the samples met the MCL. After
chloramination began in 1982 and other treatment adjustments were made, including
improved precursor removal and modifications to optimize primary disinfection
conditions, the level of THMs in the distribution system steadily decreased. Since 1985,
all THM samples have been found to be less than the 0.10 mg/L standard, and as of 1991,
total THMsfor 1990 and 1991 averaged 0.075 mg/L.
5.4.5.5 Utility 7
The following disinfection alternatives, were among those evaluated at this utility-
(Metropolitan and Montgomery, 1989): -
Chlorine/Chlorine: 2.3 mg/L of chlorine was applied to the raw water and 1.1
mg/L was applied to the settled, water.
Chlorine/Chloramine: 2.3 mg/L of chlorine was applied to the raw water and
0.6 mg/L was applied to the settled water. Ammonia was added to the
filtered water at 0.5 mg/L (as NH3-N). With a free chlorine residual of 1.5
mg/L at the point of ammonia addition, the chlorine to ammonia ratio was
3:1 by weight.
Finished water was collected for each alternative, and held for 2 hours and 24 hours under
conditions representative of the utility's distribution system. DBF concentrations from
these two strategies are summarized in Figure 5-1.
Compared to chlorine/chlorine,'chlorine/chloramine formed lower concentrations
of most of the halogenated DBFs. Cyanogen chloride was higher with
chlorine/chloramine at 2 hours but was approximately the same for both alternatives at 24
hours. The concentration of 1,1-dichloropropanone increased at both residence times,
however, this concentration was below 1 ug/L in both strategies. Utility 7 was near the
optimal pH condition with a pH of 8.2.
.In addition to the DBFs, the disinfectant residual concentrations were as follows:
5-25
-------
TABLE 5-6
DISINFECTANTS VERSUS RESIDENCE TIME
Chloramines (Total C12 -FreeCl2)
With chlorine/chlorine, the consumer is exposed to a chlorine residual. Hoover, with
chlorine/chloramine, the consumer is exposed to a chloramine residual. As discussed in;
Chapter 2, a chloramine residual may be a more significant health concern than a chlonne
residual.
SUMMARY
.
Today's water treatment uses several disinfection alternatives, each of which
-produces certain DBFs.. The types and concentrations of the DBFs formed during
disinfection are dependent on:
The disinfection scheme used during treatment
Water quality at the points of application of disinfectant
The applied dosages of the particular disinfectant.
Alternative strategies can be used to control DBFs associated with a particular
disinfectant. The modified disinfection scheme can increase the formation of other DBFs,
which should be considered prior to selecting a new disinfectant.
In general, raw water chlorination, applied prior to a NOM removal unit process,
combined with chlorination for residual disinfection produces the highest level of
halogenated DBFs. The studies show that oxidation/disinfection of raw water with ozone
chlorine dioxide can reduce the formation of halogenated DBFs because of the
or
following reasons:
5-26
-------
.Ozone changes the characteristics of the NOM which may reduce the
concentration of reactive sites on the NOM and thus reduce the available
precursors,
Ozonation allows for a shift in the point of chlorine application from raw
water to settled or filtered water.
The case studies presented in this chapter evaluated the effect of moving the point
of disinfectant application further into the process along with other changes in the
disinfection scheme, such as different combinations of primary and secondary
disinfectants. The utilities evaluated these alternatives to identify appropriate treatment
strategies to supply adequately disinfected water to the consumers while minimizing
DBFs.
The use of chloramines for secondary disinfection minimizes the formation of many
halogenated DBFs primarily because it limits free chlorine contact time to that at the .
treatment plant. However, the health effects of a chloramine residual may be a concern.
Ozone is being used more frequently as a primary disinfectant and for other
purposes that utilize its strong oxidation capabilities. An ozone/chloramines disinfection
strategy produces much lower DBF concentrations than most chlorine/chlorine or
chlorine/chloramine strategies. Because ozone oxidizes some of the NOM to BDOC,
biologically active filters are required to reduce the potential for regrowth in the ~
distribution system.
While the formation of halogenated DBFs can often be reduced through use of an
alternative disinfection strategy, some caution must be exercised regarding the formation
;
of other DBFs.' The addition of ozone to a treatment process can lead to increases in
aldehyde formation and frequently leads to increased levels of haloketones and halopicrins.
The addition of chlorine dioxide to a treatment process will produce chlorite and chlorate.
Chlorine dioxide addition may also enhance the formation of some halogenated DBFs, as
exhibited by Utility 16.
The use of an alternative disinfection strategy may prove to be an effective
approach to DBF control in many situations. The impact of alternate disinfectants on the
5-27
-------
microbial and chemical quality of the water, however, must be well understood before
implementation. ,
5.6 REFERENCES
Aieta E. M. and Berg, J. D. (1986). "A Review of Chlorine Dioxide in Drinking Water
' Treatment." J. AWWA. 78(6), p. 62.
Amy, G., et al., (1993). National Survey of Bromide in Drinking Waters", Proc. 1993
AWWA Ann. Conf, San Antonio, TX.
AWWARF (1993). Optimizing Chloramine Treatment. American Water Works
Association
Bablon, G. P., Ventresque, C. and Aim, R. B. (1988). "Developing a Sand-GAC Filter to
Achieve Higli-Rate Biological Filtration," J. AWWA. 80(12), p. 47.
*W-
Cavanagh J E (1992) "Ozonation By-products: Identification of Bromohydnns From
the Ozofiation of Natural Water with Enhanced Bromide Levels", Hnvir. Sci. and
TechnoL 26 (8) 1658.
Cooper W J (1986). "Bromoform Formation in Ozohated Groundwater Containing
Bromide and Humic Substances", Ozone- Sci. and Engin.. 8 (1) 63.
Dimitriou, M. A. (1997). "Ozone Cost Review", White Paper for M/DBP FACA
Committee and Technical Work Groups.
Glaze W.H.,Weinberg,H.S.and Cavanagh, J. E. (1993). Evaluating the Formation of
' Bromlnated DBFs During Ozonation", J. AWWA, 85(1), p. 96.
i
Griese M H Hauser, K., Berkmeier M. and Gordon G. (1991). "Using Reducing
Agents to Eliminate Chlorine Dioxide and Chlorite Ion Residuals in Drinking
Water " J AWWA. 83(5). p. 56.
Haag W R and HoigneJ. (1983). Ozonation of Bromide-Containing Waters: Kinetics of
' Formation of Hypobromous Acid and Bromate, Fnvir Sci. andTechnol..
R.'c.2 Rosenblatt, A. A. and Gates, D. J. (1996). UCฐ*ซfo*CUo,
Dioxide Treatment of Drinking Water", Proc. WQTC, Boston, MA, Nov; 1996.
Hubbs S. A.', Amundsen, D. and Olthius, P. (1981). "Use of Chlorine Dioxide,
' Chloramines and Short-Term Free Chlorination as Alternative Disinfectants.
J. AWWA. 73(2), p. 97.
5-28
-------
Jacangelo, J. G., Patania, N. L., Reagan, K. M., Aieta, E. M., Krasner, S W and
McGuire, M. J. (1989). "Ozonation: Assessing Its Role in the Formation and
Control of Disinfection By-Products." J. AWWA. 81(8), p. 74.
Krasner, S. W., Glaze, W. H, Weinberg, H. S., Daniel, P. A. and Najm, I. N. (1993).
"Formation and Control of Bromate During Ozonation of Waters Containing
Bromide", J. AWWA. 85(1), p. 73.
Krasner, S. W., et al., (1989). "The Occurrence of Disinfection By-Products in U.S.
Drinking Water", J. AWWA, 81(8), p. 41.
Lykins, B. W. and Griese, M. H. (1986). "Using Chlorine Dioxide for Trihalomethane
Control." J. AWWA. 78(6), p. 88.
Lykins, B. W. (1992). "Practical Applications of Chlorine Dioxide/Field Data."
Proceedings. Second International Symposium on Chlorine Dioxide: Drinking
Water Issues, Houston, TX, May, 1992.
Metropolitan Water District of Southern California and James M. Montgomery Consulting
Engineers (1989). Disinfection By-Products in United States Drinking Waters.
. Volume 1. United States Environmental Protection Agency and Association of
Metropolitan Water Agencies. Cincinnati, OH and Washington, DC.
\
Myers, G. L.Jhompson, A., Owen, D. M. and Baker, J. M. (1986). "Control of
rihalomethanes and Taste and Odor at the Galveston County Water Authority."
Presented at the 1986 Annual AWWA Conference, Denver, CO.
Reckhow, D. A., Tobiason, J. E., Switzenbaum, M. S., McEnroe, R., Xie,Y., Zhou, X.,
McLaughlin, P. and Dunn, H. J. (1992). "Control of Disinfection Byproducts and
AOC by Pre-Ozonation and Biologically-Active In-Line Direct Filtration,"
Proceedings, 1992 Annual AWWA Conference, Vancouver, B.C., June, 1992.-
Rittman, B. E. (1990). "Analyzing Biofilm Processes Used in Biological Filtration," I_
AWWA. 82(12), p. 62.
Shukairy, H. M., Miltner, R. J. and Summers, R. S. ft 995). "Bromide's Effect on DBP
Formation, Speciation, and Control: Part 2, Biotreatment", J. AWWA. 87(10),
p,71.
Shukairy, H. M., Miltner, R. J. and Summers, R. S. (1994). "Bromide's Effect on DBP
Formation, Speciation, and Control: Part 1, Ozonation", J. AWWA. 86(6), p. 72.
5-29
-------
Siddiqui M S. and Amy, G. L. (1993). "Factors Affecting DBF Formation During Ozone
- Bromide Reactions", J. AWWA. 85 (1) 63.
Singer P C (1988). 'Alternative Qxidant and Disinfectant Treatment Strategies for
. ' Controlling Tphalnmethane Formation. USEP A Risk Reduction Engineering
Laboratory, Cincinnati, OH. Kept. No. EPA/600/2-88/044, NTIS Publ. No.
PB88-238928.
Song R Minear, R., Westerhoff, P. and Amy, G. (1995). '-'Bromate Formation, and
Minimization in Water Treatment", Proc WOTC. New Orleans, LA.
Summers R S (1997) "Evaluation of DBP Formation from Prechlorination and
Coagulation with Jar Testing", M/DBP NODA Package, US Environmental
Protection Agency. (
Symons, J. M., Speitel, G. E., Hwang, C. J., Krasner, S.W., Barrett, S. E., Diehl, A. C.
and Xia,R. (1996). "Factors Affecting Disinfection By-Product Formation During
Chloramination", Proc. WOTC. Boston, MA.
Walker, G. S., Lee, F. P. and Aieta, E. M. (1986). "Chlorine Dioxide for Taste and
Odor Control." J. AWWA. 78(3), p. 84. .
Weinberg,H. S., et al., (1993). "Identification and Occurrence of Ozonation By-products
in Drinking Water", AWWA Research Foundation.
5-30
-------
6.0 DISINFECTION BY-PRODUCT REMOVAL
AND CONTROL OF DISINFECTANT RESIDUALS
6.1 INTRODUCTION
Removing DBFs before the finished water enters the distribution system is the final
DBF control strategy discussed in this document. Several treatment, methods are available to
i
remove these chemical species. However, the feasibility of this strategy is limited by the
following two factors:
Rate of formation of DBFs, tliat is, the amount of DBFs formed in the
treatment plant relative to the amount formed in the distribution systems.
Costs for providing additional treatment
For this strategy to be feasible from a process standpoint, a significant portion of the
DBFs should be formed before the water leaves the treatment plant. For example, ozone is
useful only as a primary disinfectant or preoxidant and the same is likely to be true for
chlorine dioxide. Therefore, most of the DBFs formed by these two oxidants will be
generated in the treatment plant and not in the distribution system? On the other hand,
secondary disinfectants such as chlorine will continue to form DBFs throughout the
distribution system. In many cases, only a small portion of the final THMs may be formed
within the treatment plant.
The costs associated with providing additional treatment to remove DBFs could also
limit the application of this strategy. The costs for this strategy should be compared with
those for the other control strategies discussed in Chapters 4 and 5.
In general, the following technologies may be applicable for removing various DBFs.
Performance of these processes for removing various DBFs, are discussed in the following
sections.
GAC adsorption
Packed column aeration
6-1
-------
Diffused aeration
Conventional treatment
PAC adsorption
Oxidation .
Membrane filtration
Reducing agents
Biological treatment
6.2 GAC ADSORPTION
GAC adsorption is a proven technology for removing, a wide range of organic
contaminants from water. In addition, GAC can remove inorganic oxidants present in the
water! Therefore, this treatment method could be appropriate for removing several DBFs. At
present, treatability studies on the performance of GAC adsorption for removing DBFs are
limited to THMs, and certain inorganic oxidants.
6.2.1 Adsorption Capacity
The adsorption capacity for many DBFs can be estimated from their single solute
isotherm data. Isotherms are developed from bench-scale experiments in which dosages of
activated carbon are equilibrated with a known concentration of a solute in batch reactors of
known volume. Using solute concentrations at equilibrium conditions arid simple mass balance
calculations solute surface loadings on activated carbon can be determined. Table 6-1
summarizes the available information on Freundlich isotherm parameters for DBFs in distilled
' water. The Freundlich isotherm is given by qe - KCe"ป where q. is the mass of solute
adsorbed to the activated carbon at equilibrium (mg solute/mg Action Carbon), Ce is the
solution concentration of adsorbate at equilibrium in (mg/L), and K and 1/n are constants.
The adsorption potential of a DBF increases with increasing Freundlich K value. Knowing
these parameters, mathematical models can be used to estimate activated carbon usage rates
for the GAC and PAC processes. Isotherm constants are "available mostly for halogenated
DBFs.
6-2
-------
The presence of other competing contaminants and background organic matter in the
water matrix can adversely impact the adsorption of contaminants of interest. Because the
isotherm constants presented in Table 6-1 were developed for single solute systems, their use
may not be appropriate for drinking water treatment situations. Generally, weakly adsorbing
contaminants, such as THMs, are more affected by the presence of strongly adsorbing
compounds, whereas, strongly adsorbing compounds, such as chlorophenols, are.more
affected by fouling of GAC with background organic matter.
/
The isotherm parameters for some compounds in Table 6-1 were predicted using
Polanyi Potential Theory. This theory, based on thermodynamic principles, requires physical
properties of the compound and GAC to predict the isotherm parameters (Greenbank and
Manes, 1981; Speth, 1986).
^
'6.2.2 Removal of Trihalomethanes
Symons, et al. (1981), summarized the performance of several pilot and full scale
GAC installations from around the country for removing THMs from filtered water. The GAC
installations included:
Cincinnati, Ohio
Mt. Clemens, Michigan
. Miami, Florida
Evansville, Indiana
Little Falls, New Jersey
Philadelphia, Pennsylvania
Newport, Rhode Island
Huntingdon, West Virginia
Beaver Falls, Pennsylvania .
Jefferson Parish, Louisiana
6-3
-------
TABLE 6-1
Freundlich Isotherm Parameters for Activated Carbon Adsorption
Bromodichloromethane
Dibromochloromethane
Bromoform
Dichloroacetic Acid
Trichloroacetic Acid
2-Chlorophenol
2,4-Dichlorophenol
2,4,6- Trichlorophenol
Chloropicrin
Hexanoic Acid
Heptanoic Acid
MX
163.8
208.3
252.8
128.9
163.4
12S.6
163.0
197.5
164.4
1162
130.2
217.4
6.4
6.7
6.8
7.3
6.6
6.6
6.8
7.0
5.3
6.8
6.9
6.9
6.9
5.3
6.6
6.8
6.8
6.8
NA
NA
3-9
5.3
7.0
9.0
3.0
6.0
9.0
NA
NA
NA
6.5
F-400
CECA
MOO
F-300
F-300
CECA
F-400
F-400
F-300
F-400
F-300
CECA
F-400
F-300
F-400
F-400
F-300
CECA
F-400
F-400
F-300
F-300
F-300
F-300
F-300
F-300
F-300
F-400
F-400
F-400
F-400
0.77
0.70
0.67
0.66
0.61
0.57
0.68
0.66
0.34
0.52
0.60
0.59
0.59
0.52
0.56
0.49
0.56
0.54
0.52
0.43
0.41
0.15
0.35
0.29
0.29
0.40
0.39
0.43
0.35
030
0.21
3
12
10
16
14
27
18
21
23
5
40
51
38
41
20
78
85
86
66
5
35
51
157
147
141
219
. 155
130
77
46
108
53
5
19
19
32
28
55
40
38
43
14
86
95
72
78
38
142
172
157
125
35
99
185
734
478
511
693
411
350
218
186
456
176
Dobbs& Cohen (1980)
Andrews etal. (1987)
Andrews etal (1987)
Spethatal.(1990)
Andrews etal. (1987)
Andrews etal. (1987)
Andrews etal. (1987)
Andrews etal. (1987)
Spethatal. (1990)
Dobbs& Cohen (1980)
Spethatal. (1990)
Andrews etal. (1987)
Andrews etal. (1987)
Andrews etal. (1987)
Dobbs& Cohen (1980)
Andrews etal. (1987)
Spethatal. (1990)
Andrews etal. (1987)
Andrews etal. (1987)
Polanyi Potential Pred.
Polanyi Potential Pred.
Dobbs& Cohen (1980)
Dobbs& Cohen (1980)
DobbsA Cohen (1980)
DobbsA Cohen (1980)
Dobbs& Cohen (1980)
Dobbs& Cohen (1980)
Dobbs& Cohen (1980)
Polanyi Potential Pred.
Polanyi Potential Pred
Polanyi Potential Pred.
Andrews etal. (1987)
6-4
-------
Kansas City, Missouri
The performance of different GACs at varying EBCTs and the use of post-filter and filter-
adsorber contactors were evaluated. Influent concentrations of total THMs during these tests
varied widely from 0.7 to 156 ug/L. The test conditions and results of these studies are
summarized in Table 6-2. The study indicated the following:
Time for GAC breakthrough ranged from three to greater than 26 weeks.
Time for breakthrough increased with longer EBCTs and lower influent THM
concentrations.
Time for breakthrough was lower for waters with higher Chloride: bromide
ratios, indicating that chlorinated THMs were more poorly adsorbed than
brominated THMs. This trend is comparable to the trend exhibited by the
isotherm parameters shown in Table 6-1.
The presence of background prganics, indicated in Table 6-2 by THMFP, and
other specific organic chemicals in the water matrix adversely affected the
adsorption of THMs.
The study concluded that GAC bed life for the control of formed THM was typically a few
weeks, primarily because of the weak adsorption potential of chloroform, the predominant
THM in many low-bromide waters.
Blanck (1979) evaluated the performance of filter-adsorbers in Davenport, Iowa on
Mississippi River water. The filters were capped with Calgon's F-400 GAC and operated at
a typical filter loading rate of 2 gpm/sf, for an EBCT of 7.5 minutes. Filter influent THM
concentrations ranged between 97 and 109 ug/L and THMFP concentrations in the settled
water varied from 26 to 87 ug/L. The following filter performance was reported:
THM reductions of 23 to 31 percent were obtained with GAC on line for 28
months of filter operation.
Upon changing the GAC in the filters, THM reductions varied from 29 to 60
, percent for similar influent THM concentrations.
6-5
-------
TABLE 6-2
Summary of TTHM Adsorption on Virgin GAC
&,*'*
ซ-'ปJf
Cincinnati, OH WVG 12x40
Cincinnati, OH
Cincinnati, OH
Cincinnati, OH
Mt. Clemens, MI
Mt. Clemens, Ml
Miami, FL
Evansville, IN
Huntington, WV
Cincinnati, OH
1
1 Cincinnati, OH
Cincinnati, OH
Cincinnati, OH
Philadelphia, PA
Little Falls, NJ
Little Falls, NJ
Little Falls, NJ
Cincinnati, OH
Newport, RI
11 Cincinnati. OH
HD 10x30
WVG 12.40
Filtrasoib 40 .
HD3000
HD3000
Filtrasoib 40
HD 10x30 .
WVW 14x40
HD 10x30
WVG
WVG 20x50
WVG 12x40
NA
HD 10x30
WVW
Filtrasoib 40
HD 10x30
Filtrasoib 40
Filtrasoib 20
PC/PAs
PC/PA
FS/SRs
PC/PA
FS/SR
FS/SR
PC/PA
PC/PA
FS/SR
PC/PA
PC/PA
FS/SR
FS/SR
PC/PA
FS/PA
FS/PA
FS/PA
PC/PA
PC/PA
PC/PA
i==
r 3.2
3.2
4.5
5.0
5.8
2.8
6.2
6.6
7.1
7.5
7.5
7.5
7.5
7.5
8.0
8.0
8.0
9.0
9.0
9.0
^=^=s=z
2.3
1.9
2.3
2.3
4.4
4.6
1.8
13.2
11.3
2.9
3.8
4.1
2.3
NA
12
52
12
3
6.1
6.3 I
...GAC Usage
Rateฎ
Notes:
FS - Full Scale PC - Pilot Plant NA - Not Available PA - Post Filter Adsorber
SR-Sand Replacement
6-6
-------
TABLE 6-2 (cont)
Summary of TTHM Adsorption on Virgin GAC
>. :/.: ^ . . , >^. *
^" . " " "
f A - . V % %
*" w- J . i4-_ <! " '
,v^v^ .^f j<.r
Cincinnati, OH
Evansville, IN
Cincinnati, OH
Cincinnati, OH
Cincinnati, OH
Beaver Falls, PA
Jeff. Parish, LA
Kansas City, MO
Kansas City, MO
Kansas City, MO
Kansas City, MO
Kansas City, MO
Jeff. Parish, LA
Beaver Falls, PA
Beaver Falls, PA
Cincinnati, OH
Cincinnati, OH
Miami, FL
Jeff. Parish, LA
Jeff. Parish, LA
'ฃ' ''*.
5y$&MWC$.
v" ฃ v. ' : " :.
.j v ff 4sf$f:^
WVG 12x40
HD 10x30
Filtrasorb 40
PICA-A
PICA-B
Filtrasorb C.
Filtrasorb 40
WVG
HD 10x30
LCK
Norit ROW
Filtrasorb C
WVG
Filtrasorb 40
HD8xl6
WVG
HD 10x30
Filtrasorb 40
WVG
WVG
A^.'iS.S"'
&$$':
PC/SR
PC/PA
PC/PA
PC/PA
PC/PA
FS/SR
PC/PA
PC/PA
PC/PA
PC/PA
PC/PA
PC/PA
PC/PA
FS/SR
FS/SR
PC/PA
PC/PA
PC/PA
FS/SR
FS/SR
%
' K,;:s*
*_;_?___3fc.__S..^S
9.4
9.6
10
10
10
10.1
10.9
11
11
11
11
11
11.2
11.3
11.4
11.8
11.8
12.4
13.6
14
. '*'*'*.$&'
v- ^v.ivSKf ,
:*$ปฃ;;
U.&5&&V
?siir,'-J*-:
3.4
19.9
2.3
0.72
1.8
7.2
30
11.7
4.6
5
5.5
5.1
54.5
6.4
6.4
4.7
3
3.6
5.7
12.2
,;ฅ ..
^'linflwot .
i:^UH&'ซf "4
.:.-. llfcซ^^
57
0.7
97
48
49
45
3.5
14
18
29
29
18
5
67
63
8.7
17
155
6.6
7.5
,.: ..,;.Itinu'ent .
^'.tmm ,.;
244
58
137
NA
NA
110
NA
NA
NA
NA
NA
NA
NA
110
110
230
281
NA
281
319
Time to
;; Exhaustion
(wซซla)
22
19
0
12
13
15
8
12
12
12
12
13
7
10
9
16
17
17
18
13
GAC Usage
Rateฎ
: ^duration
Ob/Keal)
0.15
1.19
0.31
0.31
0.28
0.25
0.50
0.34
0.34
0.34
0.34
0.31
0.59
0.42
0.47
0.27
0.25
0.27
028
0.40
Notes:
FS - Full Scale
PC - Pilot Plant NA - Not Available PA - Post Filter Adsorber SR-Sand Replacement
6-7
-------
TABLE 6-2 (cont)
Summary of TTHM Adsorption on Virgin GAC
I Cincinnati, OH
Cincinnati, OH
Jeff. Parish, LA
Jeff. Parish, LA
Jeff. Parish, LA
Jeff. Parish, LA
Jeff. Parish, LA
Jeff. Parish, LA
Jeff. Parish, LA
Jeff. Parish, LA
Jeff. Parish, LA
Jeff. Parish, LA
Jeff. Parish, LA
Jeff. Parish, LA
Jeff. Parish, LA
Jeff. Parish, LA
Jeff: Parish, LA
Jeff. Parish. LA
Notes:
WVG
HD 10x30
WVG
WVG
WVG
Filtrasorb 40
WVG .
Filtrasoib 40
Filtrasorb 40
Filtrasoib 40
WVG
Filtrasoib 40
WVG
WVG
WVG
Filtrasoib 40
WVG
Filtrasoib 40
^f^f"
PC/PA
PC/PA
PC/SR
FS/PA
FS/SR
FS/PA
FS/PA
PC/PA
PC/SR
FS/SR
PC/PA
PC/PA
PC/PA
FS/PA
PC/PA
PC/PA
PC/PA
PC/PA
MM
B^^^^=
17
17
5
6.4
6.1
3.3
6.1
2.4
3.8
2.4
4.3
5.5
4.4
4
3
3.6
NA
NA
=-==5S2
E^^^S^^i^^^s^-^^"
230
259
319
NA
192
365
NA
NA
343
NA
NA
365
NA
NA
NA
365
NA
253
======1
GACUsage
' Rateฎ
Bxhaution
i^^^^"^
n
17
16
18
12
14
15
14
15
14
16
14
18
>25
26
18
>26
>26
0.35
0.35
0.39
0.36
0.55
051
0.49
056
0.53
0.58
0.5 i
0.6
0.52
<0.38
0.46
0.71
<0.62
0.60
i^g gas
FS - Full' Scale PC - Pilot Plant NA - Not Available PA - Post Filter Adsorber SR-Sand Replacement
6-8
-------
Wood and DeMarco (1975) conducted bench-scale studies to evaluate DBF and DBF
precursor removal on a Florida groundwater after lime softening. Breakpoint chlorination
was practiced with a chlorine dose of approximately 18 mg/L. The groundwater had a TOC
of about 10 mg/L and a THMFP of 650 to 950 ug/L. GAC adsorption was studied in bench-
scale columns for removal of halogenated SOCs, THMs, TOC and THMFP. The study
evaluated.four GACs:
'
CalgonF-400
Westvaco WV-G
ICIHydrodarcol030
Witco Chemical Corporations Witcarb 950 .
The columns operated at 3 gpm/sf for an FJBCT of 6.2 minutes. Total THMs and
chloroform in the column influent were .150 and 67 ug/L, respectively. The performance
levels of the different GACs with respect to chloroform breakthrough of 25 and 50 ug/L were
as shown in Table 6-3.
TABLE 6-3
Performance Level of GACs for Chloroform Removal
GAC Type
Witcarb 950
Calgon F-400
Hydrocarb 1030
Westvaco WV-G
GAC Usage Rate (lb/1,000 Gal)
Chloroform Concentration
25 ug/L
0.38
0.60
0.69
0.67
50 ug/L
0.27
0.46
0.34
0.53
Witcarb 950 provided the best removal of chloroform, but the lowest removal of
THMFP. Similar results were observed for the removal ofchloroform and THMFP for all
the other GACs. These inconsistencies in performance may be attributed to the pore size
distribution in each type of GAC. Witcarb 950, with its smaller pore size distribution,
6-9
-------
performed better than the other GACs for removing low molecular weight THMs but did not
perform as well as the other GACs for removing high molecular weight NOM.
The study also reported THM and THMFP removals given in Table 6-4 for Calgon
F-400 GAC with longer EBCTs of 18.6 and 24.8 minutes. The results indicate that the GAC
usage rate for adsorption of instantaneous THMs decreases with increasing EBCT.
TABLE 6-4
THM and THMFP Removal with Calgon F-400 GAC
GAC Usage
Rate
(lbs/1000 gal)
Muffins, &Jl (1981), conducted a bench-scale GAC study on tap water from the
Louisville Water Company. They compared the performance of the following eight GACs for
THM control:
Calgon F-400
Witcarb 950
Westvaco WV-W
Westvaco WV-G
Hydrodarco 1030
Columbia LCK
Bameby-Cheney PC-1
the columns were operated at 4.2 gpm/sf for an EBCT of 2.7 minutes. The mesh size for
each GAC was 16x20. Influent water quality parameters varied through the study period as
shown in Table 6-5.
6-10
-------
TABLE 6-5
Influent Water Quality Parameters
Parameter
pH
Temperature
Chlorine Residual
TOC
Chloroform
Bromodichloromethane
Value
7.9-8.8
19.0 - 30ฐC
0.9-3.1mg/L
2.5 - 8.2 mg/L
40.0 - 140 ug/L
8.0 - 28 ug/L
For 10 and 50 percent breakthrough of chloroform and bromodichloromethane,
respectively, Witco 950 and Barneby-Cheney PC-1 provided the longest bed lives. However,
the study estimated a GAC bed life of only one to two weeks for 50 percent removal of
chloroform. This short bed life was probably caused by the short EBCT used in this study.
Maloney, et al. (1985), evaluated the impacts of prechlorination, with and without
post-ozonation, on the removal of THMs by GAC adsorption following conventional
treatment of Delaware River water. Four contactors were installed, each to test one of the
following conditions:
Coagulated, settled and filtered water (no disinfection used)
Chlorinated, coagulated, settled, filtered water
Coagulated, settled, ozonated, filtered water
Chlorinated, coagulated, settled, ozonated, filtered water
Contactor were operated at 2 gpm/sf, for an EBCT of 15 minutes. The GAC usage rates
required to meet different THM treatment objectives are summarized in Table 6-6. With
prechlorination, implementing post-ozonation shortened.the bed life by one week for initial
chloroform breakthrough. The earlier breakthrough of chloroform when using post-
ozonation ,was due to greater competition between chloroform and background organic
6-11
-------
compounds formed upon ozbnation. This indicated that the chlorinated background organics
were more strongly adsorbed after ozonation than before ozonation.
Kruithof (1986) reviewed a number of GAC installations in the Netherlands for
removal of THMs. The raw water was chlorinated at a dose of 5.5 mg/L and the GAC
adsorber had an EBCT of 13 minutes. The initial breakthrough for chloroform; at an average
influent concentration of 35 ug/L, was experienced after approximately 18 days. After 8,000
bed volumes a GAC usage rate of 0.47 lb/1,000 gallon, the following removals were obtained
for THMs in Table 6-7.
6-12
-------
TABLE 6-6
Removal of THMs by GAC
Location
Type
of
GAC
EB.CT
(min)
Influent
THM
(ug/L)
Influent
TOC
(mg/L)
TIME (days) TO REACH NOTED TTHM
BREAKTHROUGH
5 ug/L
10 ug/L
25 ug/L
50 ug/L
USAGE RATE (lb/1000 gal) REQUIRED TO
REACH NOTED THM BREAKTHROUGH
5 ug/L
10 ug/L
25 ug/L | 50ug/l.
COMPOUND : CHLOROFORM
Dade Co., FL
GW
Cincinnati, OH
SW
Philadelphia.PA
SW.CI2
Philadelphia,PA
SW.C12 + O3
Waterworks
at Rotterdam
F-400
WVG
F-400
F-400
NA
6.1
12.2
18.4
24.5
7.2
15.2
IS
30
IS
30
13
67.3
24
99
66
35
5.4
2.0
2.6
2.4
NA
10
32
54
78
57
144
50
95
40
86
22
12
34
56
.80
87
157
53
97
45
92
34
14
37
62
86
145
174
58
102 -
55
97
77
21
46
67
88
NA
NA
66
104
64
103
NA
1.59'
0.99
088
081
0.32
0.27
0.78
0.82
0.97
0.90
1.54
1.35
0.93
085
0.79
0.21
0.25
073
0.80
0.87
084
0.99
1.13
085
0.77
074
0.12
022
0.67
076
071
0.80 -
0.44
0.75
069
071
072
NA
NA
059
075
061
075
NA
COMPOUND : DffiROMOCHLOROMETHANE
Dade Co., FL
Water Works at
Rotterdam
F-400
NA
6.1
12.2
13
336
11.5
5.4
NA
32
80
124
s
43
94
NA
83
NA
NA
NA
NA
NA
0.49
0.39
0.27
036
0.33
NA
0.19
NA
NA
NA
NA
NA
6-13
-------
TABLE 6-6 (cont)
Removal of THMs by GAC
Location
COMPOUND : BF
Dade Co., Fl
Philadelphia.PA
SW.C12 . .
Philadelphia,PA
SW, C12 + O3
Water Woiks
at Rotterdam
Type
of
GAC
tOMODI
F-400
\
F-400
F-400
NA
^=:^=
EBCT
(min)
CHLORO
=^^=
6.1
12.2
18.4 '
24.5
15
30
15
30
13
5==^=:
Influent
THM
(ug/L)
^^^^a*^^^*B
METHANE
s===
47
21
15
24
Influent
TOC
(mg/L)
.5.4
2.6
2.4
NA
TIME (days) TO REACH NOTED
TTHM BREAKTHROUGH
5 ug/L 1
S^^^SS^^SE
17
49
85
122
71
152
83
148
55
10 ug/L |
^BESSES
20
54
92
NA
95
174 .
97
158
94
25 ug/L 1 50 ug/L
SSSESSSSS=5=5=5E3SSSS
31
68
112
NA
113
NA
136
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA .
NA
USAGE -RATE (lb/1000 gal) REQUIRED
TO REACH NOTED THM
BREAKTHROUGH
5 ug/L
s^^^sss
0.93
0.63
0.56
0.52
0.55
0.51
0.47
0.52
0.61
10 ug/L .
0.79
0.58
0.52
NA
0.41
0.44
0.40
0.49
0.36
25 ug/L
^^^^^^^^^
0.51
0.46
0.42
- NA
0.34
NA
0.28 '
NA
NA
50 ug/L
NA
NA
NA
NA
NA .
NA
NA
NA
NA
6-14
-------
TABLE 6-7
THM Removal with GAC
THM
Chloroform
Dichlorobromomethane
Dibromochloromethane
Bromoform
Total THMs
Average Influent
Concentration
Oig/L)
35
24
12
2
73
Removal
(%)
30
65
80
No Breakthrough
53
At an approximate throughput of 17,000 bed volumes, chlorination was stopped and influent
THM concentrations declined to zero. Chloroform was still present at low concentrations in
the adsorber effluent up to 9,000 bed volumes later because of its desorption.
The Provincial Waterworks of North Holland in Andjek uses two-stage GAC
adsorption with EBCTs of 20 to 30 minutes following conventional treatment. Chloroform
and bromodichloromethane were immediately 'present in the effluent of the first stage
adsorber, while appreciable reductions of dibromochloromethane and bromoform were
obtained. On a weight basis, 70 percent of the THMs were removed for a period of 1 year.
Average removal of individual THMs for one year are shown in Table 6-8.
TABLE 6-8
THM Removal with GAC
THM
Chloroform
Dichlorobromomethane
Dibromochloromethane
Bromoform
Influent (ug/L)
27
29
23
4
Effluent (ug/L)
15
7
1
0
6-15
-------
Kruithof concluded that THMs can be removed by GAC adsorption only to a limited degree.
Initial breakthrough for chloroform and dichlorobromomethane can be expected after a short
period while dibromochloromethane and bromoform are relatively better adsorbed.
Koffesky and Brodtmann (1983) compared the performance of filter-adsorbers with
post-filtration adsorbers (parallel and series) for removal of THMs formed upon disinfection
with chloramines. ,Two different GACs were studied: Westvaco WV-G and Calgon F-400.
The results, summarized in Table 6-9, show that adsorbers performed better than filter-
adsorbers and that Westvaco WV-G performed better than Calgon F-400. Average THM
\
removal, however, at breakthrough was low.
6.2.3 Removal of Inorganic By-Products and Disinfectant Residuals
Thompson and Ashe (1990) conducted studies to determine the removal of total
oxidant species of chlorine dioxide disinfection by-products (chlorate and chlorite) by GAC.
The results of this study indicated that GAC may be a viable means for the removal of chlorite
and chlorine dioxide but not for chlorate. It is apparent from the study that the EBCT, the
level of oxidants applied, and the age of the GAC are factors which must be given
consideration.
Dixon and Lee (1990) studied the use of GAC for the removal of chlorite in pilot and
full-scale facilities operated by the American Water Works Service Company. The authors
concluded: >
m The adsorptive capacity of GAC for chlorite diminishes rapidly, and EBCT
significantly influences the degree of adsorption/reduction of chlorite.
Preloading of the GAC with NOM adversely affects chlorite removal.
Chlorite is oxidized to chlorate on the GAC.by free chlorine present in the
1 water - The GAC usage requirements and formation of chlorate call into
question the technical and economic viability of GAC as a chlorite treatment
strategy.
Steinbergs (1986) reported the following removal of chlorite by GAC adsorption
.using a 6.4 minute EBCT column at a pH of 7.0 tp 7.5. GAC A, manufactured from peach
6-16
-------
TABLE 6-9
Summary of GAC Study
Contactor
Filter-Adsorber
Adsorber
Filter-Adsorber
Adsorber
Filter-Adsorber
Adsorber
Filter-Adsorber
Adsorber
Adsorber
Adsorber
Type
of GAC
WVG
WVG
WVG
WVG
WVG
WVG
F*H)0 .
F-400
WVG
F-400
Average
Influent
THM (ug/L)
12.8
7.6
4.7
4.6
8.5
8.2
3.5
3.9
8
6.2
EBCT (min)
,
21
23.2
16
23.7
14
18.3
21.9
19.3
10.4
20.7
31.4
43.5'
11
22.6
34.9
46.3
Time to
Saturation
(Days)
58
88
89
160
114
128
91
91
46
128
>180
>180
68
98
119
>180
Average
Removal
(%)
44
70
38
62
51
57 '
74
72
NA
NA
NA
NA
NA
NA
NA
NA
NOTE:
(1) Reference: Koffesky and Brodtmann (1983)
(2) NA : Not Available
6-17
-------
pits; was supplied by Carbon Co of Tacoma, WA while GAC. B, manufactured from
bituminous coal, was supplied by Ceca Inc. of Tulsa, OK. Results are shown in Table 6-10
TABLE 6-10
Chlorite Removal with GAC
GAC
A
B
Days In
Operation
57
92
30
51
GAC Usage Rate
Ob/1,000 gal)
0.29
0.18
0.55
0.33
Influent
Concln (mg/L)
0.48+/-0.13
0.25 +/- 0.00
0.28 +/- 0.05
0.39 +/- 0.10
Removal
(%).
87 +/- 6
84 +/- 0
82+/-0.
87 +/- 13
GAC A was unable to reduce the chlorite concentration to below the detection limit of 0.016
mg/L. Further, at an average influent concentration of 0.29 mg/L of chlorite, neither of the
GACs produced a chlorite free water. Chlorate (0.05 to 0.68 mg/L) was not detected in the
effluent from the GAC contactors. .
Based on pilot-scale studies, McGuire, etal. (1989), reported a removal of 14.6 mg
of chlorite per gram of GAC, with EBCTs of 7.5 and 15 minutes. The raw water chlorine
dioxide dose varied from 0.3 to 1.0 mg/L all of which was reduced to chlorite ion before
entering the GAC columns. The chlorite removal for this study was much less than the
removal of 80 to 90 mg of chlorite per gram of GAC reported by Voudrias (1983). The
authors attributed the differences to the impact of background humic matter present in the
McGuire study.. A comparison of pH condition was not performed.
Thompson (1988) reported complete removal of chlorine dioxide and.chlorite by GAC
adsorption at an EBCT of 10 minutes with up to 2 mg/L of chlorine dioxide. This result was
confirmed in a full-scale study, when virgin GAC completely removed chlorine dioxide and
its by-products up to an applied chlorine dioxide dose of 2.68 mg/L. Time to breakthrough
was not evaluated.
The second study reported by Thompson (1988) showed removal of chlorine dioxide
and its by-products by GAC used in different configurations given in Table 6-11.
6-18
-------
TABLE 6-11
Chlorine Dioxide Removal with GAC
GAC Contacting
Mode
Filter-Adsorber
Post-Filter Adsorber
Post-Filter Adsorber
EBCT
(Min.)
5
2.2
6
Oxidants1 Removal
(%)
20 to 50
60 to 90
100
Note: 1 Includes chlorine dioxide, chlorite, chlorate and chlorine.
Amy and Siddiqui (AWWARF, 1997) studied the use of GAC for the removal of
bromate. It was found that the bromate removal was a two step process: adsorption followed
by chemical reaction. Bromate reduction by GAC was improved by decreasing pH and
dissolved organic carbon (DOC). More effective removal of bromate was observed at higher
EBCTs. The carbon characteristics affected significantly the removal of bromate. An inverse
trend was observed between the inorganic composition (concentration of metals) on the
surface of the carbon and the percentage removal of bromate. GAC with higher isoelectric
points (pH^: zero-point charge) demonstrated the best removal of bromate. Results from
pilot-scale studies indicated that GAC provided effective bromate removal over approximately
5,000 bed volumes in the presence of natural organic matter (NOM). While the pilot testing
was not long enough to ascertain the effects of biological/biofilm activity, ozonation reduced
the adsorption of DOC and hence lowered the adverse effects of DOC on bromate removal.
Rapid small-scale column tests (RSSCTs) conducted under this study indicated that this
approach underestimated the pilot-scale performance. The RSSCT testing demonstrated the
superior performance of the catalytic (Centaur) GAC over other types of GAC; moreover,
this carbon was more selective in removing bromate than DOC.
i
6.2.4 Summary of GAC Adsorption
Based on the above studies, GAC usage rates for THM adsorption are typically high.
Table 6-6 presented the GAC usage rates for different breakthrough concentrations of
6-19
-------
chloroform, dichlorobromomethane and dibromochloromethane. The usage rates were based
on reported bed-lives. While no studies have generated usage rates for the removal of
bromoform, it is more strongly adsorbed than the other THMs and, therefore, will have
relatively lower usage .rates than the other three THMs. GAC adsorption of THMs can be
affected by numerous factors. Following are a list of factors that serve to delay time of THM
breakthrough and increase bed life.
Increase in the EBCT of the adsorption column.
Decrease in applied THM concentration.
Decrease in chlorine:bromide ratio.
Decrease in background organics.
Decrease in pore size distribution of GAC.
Existing information indicates that chlorite is removed by GAC via two mechanisms;
adsorption on the surface or reduction to chlorate on the surface. The effectiveness of these
two processes depends on various water quality parameters (such as TOC, hardness etc.) and
operational parameters (such as applied dose, EBCT etc.).
The removal of bromate using GAC is affected by EBCT, characteristics and type of
carbon, pH, and level of DOC. Existing research indicated that RSSCT testing
underestimates pilot-scale performance for bromate removal.
6.3 AIR STRIPPING
Packed tower air stripping appears to be an effective treatment method for removing
THMs from water supplies. Bilello and Singley (1986) report that greater than 95% removal
of THM can be achieved with packed tower air stripping regardless of the initial THM
concentration, provided that sufficient packing depths and air to water ratios are .designed.
Diffused air stripping could be less efficient than packed tower air stripping for removal of
THMs. THM removal increased with air to water ratios. Many of the DBFs of concern are
far less volatile than the THMs and may be much nrore difficult to remove by this process.
. 6-20
-------
Like packed column air stripping, the usefulness of this process may be limited by continued
formation of THMs in the distribution system. Case studies on the removal of other DBFs
are currently not available.
6.4 CONVENTIONAL TREATMENT
Little information is available in the literature regarding the conventional treatment
removal of pre-formed DBFs from drinking water. Literature reports have indicated that
removal of DBFs by conventional treatment is only to. the extent of the removal of NOM acts
as a precursor to DBFs. Baird, et al. (1989), performed pilot tests with a secondary
wastewater effluent, to evaluate the removal of chloroform using conventional treatment and
direct filtration. The treatment conditions and removals given in Table 6-12 were reported
for the two alternatives.
TABLE 6-12
Chloroform Removal with Conventional Treatment
nfluent Flow (gpm)
Alum Dose (mg/L)
Polymer Dose (mg/L)
Chloroform:
Influent Cone (ug/L)
Removal (%)
Conventional Treatment
40.0
150.0
0.2
1.8
39.0
Direct Filtration
25.0
5.0
0.06
1.2
-25.0 .
Because the influent concentrations of chloroform in this study were near the detection limit,
it is uncertain if any reliable chloroform removals were demonstrated.
6-21
-------
6.5 PAC ADSORPTION
PAC adsorption is generally used along with conventional treatment for the removal
of taste and odor compounds. PAC can also be used for the removal of DBFs. The required
PAC dose depends on the contaminant and its concentration, the type and concentrations of
other competing contaminants, contact time and the chemical properties of the water matrix.
It is important to note that when using high dosages of PAC, there is a significant potential
for an increase of carbon fines passing through the filters and entering the distribution system.
Initial estimates for PAC dosages for DBP control can be estimated from the single solute
isotherm parameters presented in Table 6-1. Single-solute isotherms can, however, greatly
underestimate the required PAC dosages in a real system because of the presence of
competing organic compounds in the water matrix. In addition, many water treatment plants
do not have the contact time necessary to reach the equilibrium conditions represented by the
isotherm. Also, the addition of PAC at the rapid mixer would preclude the use of
prechlorination, since chlorine is also removed by PAC.
As shown in Table 6-13, Weil (1979) showed that a minimum PAC dose of SO mg/L
and a contact time of 30 minutes was needed to reduce total THM concentrations by SO
percent. Chloroform, the most weakly adsorbed THM, was removed to a lesser extent at
S ' ,
different PAC doses and contact times than dichlorobromomethane and
dibromochloromethane. This would be expected based on the isotherm parameters shown
in Table 6-1. Volatilization of THMs during the tests was not considered. Therefore, the
tests may have underestimated the actual PAC doses. Hoehn, et al. (1978) also showed
t
significant improvements in chloroform removal by increasing PAC doses up to SO mg/L.
Singley, et al. (1981), found that PAC dosages from 7 to 27 mg/L reduced total
THMs by approximately 10 percent. However, a reduction of approximately 80 percent was
observed at a PAC dose of 15 mg/L for three of the THMs with initial concentrations of
approximately 140 ug/L. The presence of TOC and competing organic chemicals may have
adversely affected the adsorption of the THMs.
Snoeyink, etal. (1977), conducted isotherm tests on 2,4-dichlorophenol (2,4-DCP)
and 2,4,6-trichlorophenol (2,4,6-TCP) using a pulverized form of Calgon's F-400 GAC. In
6-22
-------
TABLE 6-13
THM Removal by PAC from Louisville, Kentucky Tap Water (1)
v*&^
ATV*?. ป.f
i\>^':. > : :'*' -\ '^
0
(Control)
25
50
v
100
^i*^
.: v TV* J;
;?:'t(iปin^:. .
0
5
15
30
60
0
5
15
30
60
0
5
15
30
60
0
5
15
30
60
:. -!PPฎ*\:J
48.2
41.7
42.7
41.4
38.6
48.2
33.8
30.3
28.7
23.2
48.2
30.1
21.3
20.5
17.7
48.2
20.3
14.6
11.1
10.5
'*.* ,T ">ปซซ
^.pB|%L*
35.2
30.3
31.8
30.2
29.4
35.2
26.3
24.1
23.2
19.2
35.2
25
18.1
17.7
15.5
35.2
17.4
13.2
10.1
9.7
ซ*$^lf*''
12.3
10.3
10.2
10.5
8.7
12.3
7.2
5.9
5.3
3.9
12.3
4.9
3.1
2.7
2.1
12.3
2.8
1.4
1
0.8
*'^ir
iHJ|r2Clvc
0.7
1.1
0.7
0.7
0.5
0.7
0.3
0.3
0.2
0.1
0.7
0.2
0.1
0.1
0.1
0.7
0.1
0
0
0
f2^:f ฃv :ฃป*ซic%) r.
^-Wpwy^
.
_
_
-
0
19
29
31
40
0
28
50
50
54
0
51
66
73
73
? ฃHG3$
-
0
13
24
23
35
0
17
43
41
47
0
43
58
67
67
'> V
CHBrCIZ
.
^
-
0
30
42
50
55
0
52
70
74
76
0
73
86
90
91
Note:
CHBr2Cl
.
-
0
73
57
71
80
0
82
86
86
80
0
91
100
100
100
( 1 ) Reference : Weil ( 1 979)
6-23
-------
order to study the effect of pH on.adsorption of chlorinated phenols, single solute and
bisolute isotherms were conducted at pHs of 5.2, 7.0 and 9.1, The tests indicated the
following:
2,4-DCP and 2,4,6-TGP adsorbed best when the water pH was less than or
equal to their pKa values. Significant reductions in adsorption capacities were
observed when the water pH exceeded pKa values for the chlorinated phenols
indicating that the anionic species of these compounds are more poorly
adsorbed than the non-ionic species.
Phenols with a larger number of chlorine atoms had increased absorbability.
The adsorption equilibrium for 2,4-DCP and 2,4,6-TCP were described by a
second order polynomial because Langmuir isotherm expressions could not
describe the equilibrium.
t
Competition between 2,4-DCP and 2,4,6-TCP, in bisolute experiments,, was
dependent on pH and the relative concentration of each.
Adsorption capacities were adversely impacted'by the presence of humic
substances, commercial humic acid, leaf fill vie acid and soil fulvic acid in the
test water.
Giusti, et'al. (1974), conducted single dose equilibrium tests for formaldehyde,
acetaldehyde and hexanoic acid using pulverized Westvaco WV-G GAC. The following test
results were reported as shown in Table 6-14.
TABLE 6-14
Formaldehyde, Acetaldehyde and Hexanoic Acid Removal with GAC
Compound
Formaldehyde
Acetaldehyde
Hexanoic Acid
Concentration (pg/L)
Initial
1,000
1,000
' 1,000
Final
964
881
30
Removal
(Percent)
3.6
11.9
97.0
Carbon Usage
(gm/gm GAC)
0.018
0.022
0.194
6-24
-------
Based on these test results, both formaldehyde and acetaldehyde appear to be poorly
adsorbed, even at high initial concentrations.
6.5.1 Summary
In summary, PAC addition has not been reputed as an effective process for the
removal of formed DBFs such as THMs. The biggest drawback with the use of PAC to
remove DBPs is the need for a settling process to remove the PAC, and the likelihood that
sufficient DBPs may not have been formed at this point in the process. On the other hand, it
could be an effective technology for the removal of some strongly adsorbed halogenated
phenols. Adsorption on PAC may be affected by several factors including PAC type, PAC
dosage, PAC contact time, presence of other competing organics, chemical properties of the
contaminant and the water matrix.
6.6 OXIDATION PROCESSES
6.6.1 Chlorination By-Products
Oxidation with chlorine can remove some of the inorganic DBPs such as chlorite and
ammonia. Chlorine oxidizes chlorite ion to chlorine dioxide or chlorate according to the
following equations:
1/2 ei2 + cio2- > cr + cio2
C12+ CI02- + H20 > 2IT + 2C1' + C103-
Because chlorine dioxide can be reformed in the distribution system, the combined use of
chlorine dioxide and chlorine has been recommended for some waters (Noack, etal. 1985).
However, the formation of chlorate limits the usefulness of chlorine for the purpose of
chlorite removal. Ammonia can also be oxidized by chlorine to form chloramines. Chlorine
also reacts with hydrogen peroxide present in the water.
6-25
-------
6.6.2 Ozonation
Lee and Hunter (1985) evaluated the use of ozone for removing EPA Priority
Pollutants from a treated wastewater. The tested pollutants included several DBPs. Results
of this study are summarized in Table 6-16. As indicated in the table, ozone provided
moderate removals of chloroform and bromoform, while bromodichloromethane and
dibromochloromethane were poorly removed. Chlorophenols were almost completely
removed by ozonation at dosages greater than 25 mg/L. The pH of ozonation was not
reported.
The effectiveness of ozone for removing bromoform, dichlorobromomethane and
dibromochloromethane was tested by Fronk (1987). Results of the pilot-study, conducted
with spiked distilled water at neutral pH, are summarized in Table 6-15 for various applied
ozone dosages.
TABLE 6-15
Bromoform, Dichlorobromomethane and Dibromochloromethane
Removal with Ozone
Dichlorobromomethane
Dirbomochloromethane
As indicated above, these DBPs were impervious to ozonation at neutral pH, even at applied
ozone dosages of 20 mg/L. Also, because ozone d6se had no effect on the destruction of
these DBPs, the reactions appear to be rate limited at neutral and probably low pH.
Duguet, etal. (1987), studied the removal of phenols from petrochemical and coking
wastewater. They spiked 2,4 dichlorophenol (DCP) in the wastewater at concentrations of
1 and 100 mg/L. At a pH of 7.5 to 8, an ozone dose of 1 mg O3/mg C (2 moles of O^mole
of 2,4 DCP) was reported to remove more than 90 percent of 2,4 DCP.
6-26
-------
TABLE 6-16
DBF Removal by Ozonation (1)
DBF
Chloroform
Bromodichlorpmethane
Dibromochloromethane
Bromoform ,
2-Chlorophenol
2,4-Dichlorophenol
2,4,6-Trichlorophenol
DBF
Cone.
(mg/L)
10
10
10
.10
10
10 .
10 "
Ozone
Dose
(mg/L
7.5
i
7.5
7.5
7.5
28.2
28.2
28.2
Reduction (%)
. Time (Hr.)
0.25
1
7
0
11
. 100
100
97
6.5
12
11
8
11
100
100
97
1
15
10
' 5
27
100
100
97
2
16
10
5
28
100
100
97
3
17
7
4
30
100
100
97
Note:
(1) Reference: Lee and Hunter (1985) .
6.6.3 Advanced Oxidation Processes
Prengle, et al. (1976), studied the oxidation of several chlorinated compounds by
ozone/UV irradiation. They examined the oxidation rates of five chlorinated compounds,
including' chloroform. Their test results confirmed that chloroform was removed more
effectively by ozone/UV than by ozone alone. They predicted that the chlorine atom in
chloroform was probably transformed to the chlorine molecule and then to hypochlorous acid.
No evidence was given to verify the formation of free chlorine.
Glaze, etal. (1980), conducted an extensive study to evaluate the use of ozone/UV
irradiation for the removal of several refractory organics including chloroform and
bromodichloromethane. The following results were observed:
6-27
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The odd orders of dose rate dependence for chloroform indicated that its
reaction was kinetically very complicated.
' At the end of 100 minutes, only 18 percent of the chloroform was removed
by ozone at pH 7, while a similar dosage at a pH of 10 removed 56 percent.
With ozone/UV irradiation, at the end of 120 minutes, about 88 percent of the
chloroform was removed at pH 9.8 while more than 97 percent was removed
at pH 6.5 in only 15 minutes.
Bromodichloromethane was removed much more quickly at pH 10 than at pH
3.2 and pH 6.5. Experiments in which no UV or ozone was present showed
that basic hydrolysis of bromodichloromethahe occurred at pH 10, but it was
not fast enough to contribute appreciably to the rate of removal.
I
The removal of Bromodichloromethane by ozone/UV was enhanced by low
pH. .
The products resulting from ozone/UV treatment of chloroform were also analyzed
Chloroform was completely broken down into hydrogen ion, chloride and water.
Siddiqui et al.. (1996) studied the bromate destruction by UV irradiation. Medium
pressure mercury lamps which emit radiation in the 200-300 nm range (energy input of 394
mW/cm2) and low pressure mercury lamps at 254 nm (energy input of 2.5 mW/cm2) were
evaluated for bromate destruction. The effect of two different quartz types (Quartz A : <200
i i
nm, Quartz B : 254 nm) was also evaluated. Results indicated that medium pressure lamps
were more effective -in destroying bromate, than low pressure lamps because of higher energy
input. However, a low pressure lamp was more effective than a medium pressure lamp for
similar dosages. The dose required to destroy about 40% of bromate from an initial
concentration of 50 ug/L using a low pressure lamp was 250 mW/cm2 as opposed to 550
*
mW/cm2 using a medium pressure lamp. The UV dosage required for 50% destruction of
initial bromate ion (50 ug/L) using Quartz A was 245 mW/cm2 and the UV dosage required
using Quartz B was 500 mW/cm2. Bromate destruction was not affected by pH using low
and medium pressure lamps. However, the bromate destruction efficiency was dependent on
the water temperature. Also, the presence of DOC decreased bromate removal efficiency.
6-28
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6.6.4 Summary of Oxidation Processes.
THMs are impervious to ozonation alone at neutral or low pH, however, removal by
ozone is enhanced at higher pH or with UV. While AOPs (including UV radiation) may be
useful for removing THMs entering a treatment plant, they are not likely to be applicable in
many water treatment situations for the purpose of removing THMs. Chlorination may be
effective for removal of certain inorganic DBFs, however, its use could be limited due to the
formation of other DBFs. Existing information indicates that UV irradiation is an effective
technology for bromate destruction.
6:7 MEMBRANE PROCESSES
Reinhard, etal. (1986) and Argo (1984) reported on the removal of specific organics
by membrane processes at Water Factory 21 in Orange County, California. The results of
reverse osmosis (RO) membrane operation at a pressure of 460 psi, a pH of 5.8, and a
recovery of 85 percent is summarized in Table 6-17.
TABLE 6-17
THM Removal with RO
Compound
Chloroform
Bromodichloromethane
Dibromochloromethane
Bromoform
2,4,6-Trichloropropanane
Concentration (fig/L)
Feed
4.5
6.1
5.7
2.4
0.22
Permeate
4.1
5.7
5.3
2.3
0.13
Brine
6.6
8.5
7.7.
3.0
0.72
Removal
.(%)
8
7 .
6
4 -
40
The results of another RO membrane test at a pressure of 250 psi, a pH of 5.6 to 5.8,
and recoveries of 52 and 67 percent are shown in Table 6-18. These results indicate that
removal of THMs is sensitive to the recovery levels.
6-29
-------
TABLE 6-18
THM Removal with RO
1=========
Compound
Chloroform
Bromodichloromethane
Dibromochloromethane
Bromoform
2,4,6-Trichloropropanane
Heptanal
=====
Recovery
(%)
52
67
52
'67
52
67
52
67
52 ,
67
52
Concentration (ug/L)
Feed
3.1
0.52
0.53
0.32
0.49
0.02
Permeate
0.89
2.4
0.11 .
0.42
0.11
0.45
<0.20
0.22
ND
0.20
ND
=============
Brine
4.4
4.9
1.1
0.94
1.0
0.90
0.56
0.55
1.1
1.3
0.12
=====
Removal
(%)
71
23
79
19
79
-15
>67
31
100
59
100
Conian and McClellan (1989) reported on the performance 'of a full-scale membrane
softening plant located in West Jupiter, Florida. The 0.18 mgd plant utilizes a polyamide thin-
film composite membrane and operates at a: feed pressure of 90 psi and a recovery of 75
percent. The following results were reported in Table 6-19.
TABLE 6-19
THM Removal with NF
=====
Concentration (ug/L)
Compound
Feed
Permeate,
Removal
Chloroform
222
4,3
98
Dibromochloromethane
142
<1
>99
Bromodichloromethane
Bromoform
60
^^^^
5.1
>98
>80
6-30
-------
The results indicate that softening membranes can successfully remove THMs from potable
water. However, process components or sampling points were not discussed. Samples taken
downstream from any post-membrane degassifiers would reflect concentration reductions
resulting from air-stripping in the degassifier.
Chang and Singer (1984) studied the performance of various RO membranes in
removing bromoform from seawater at a pilot-scale desalination facility in Wrightsville Beach,
North Carolina. Pretreatment consisted of prechlorination, coagulation, sedimentation and
pressure filtration. Post-chlorination was practiced on chlorine-resistant membranes in order
to control microbiological growth on the membrane. The following results were reported in
Table 6-20.
TABLE 6-20
Bromoform Removal with RO
Compound
Bromoform
Membrane
Type
CA
TFC
TFC
TFC
Concentration (ug/L)
Feed
40
40
35
35
Permeate
51
2.5
5.0
2.0
Brine
29
54
53
36
Removal
(%)
94
86
94
Note:
CA = cellulose acetate membrane
TFC = thin-film composite membrane
The results indicated that thin-film composite membranes provided good removal of
bromoform from seawater, although the recoveries were very low. Cellulose acetate
membranes did not appear to be effective. A cellulose acetate membrane was also tested with
an alternate pretreatment system consisting of ultrafiltration. Bromoform concentrations
actually increased across the membrane, from 83 ug/L in the feed to 127 ug/L in the
permeate, which is similar to the results for the other cellulose acetate membrane. The poor
6-31
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performance of the cellulose acetate membranes was attributed to poor bromoform rejection
by the membrane compounded by the higher solubility of bromoform in freshwater.
Steinbergs (1986) evaluated the removal of chlorine dioxide by-products using reverse
osmosis at a dialysis clinic in Alameda County, California. The clinic's 4 gpm treatment system
provided additional purification of the potable water supplied by the Del Valle water
treatment plant. Pretreatment for the reverse osmosis system consisted of GAC adsorption,.
cation exchange, pH adjustment, and cartridge filtration. The hollow fiber polyamide
membranes were operated at a pressure of 150 psi, a pH not more that 7V.5, and a recovery
of 38 percent. The membranes obtained an average chlorite removal of 68 percent. The
investigator concluded that greater removals could have been obtained if the membranes were
operated at their rated pressure of 400 psi.
In summary, current literature indicates that membrane processes provide variable
performance with regards to the removal of organic DBFs. In general, higher removals of
DBFs were achieved at lower recoveries indicating that, for the membranes evaluated, the
' - i
mechanism for removal of.DBPs may be controlled by diffusion rather than molecular size
exclusion. However, removal may be DBF dependent.
6.8 REDUCTION PROCESSES ^^_
6.8.1 Chlorination By-products
Several studies indicate that reducing agents lower the mutagenic activity of
chlorinated waters, probably by destroying mutagenic species. Cheh, etal. (1980), found that
a small excess of sodium sulfite over that required to quench the residual chlorine could lead
to a 40 to 80 percent reduction in the mutagenic activity (Ames test) of chlorinated natural
waters at pHs of 7.5 to 8.7. Wilcox and Denny (1985) noted that partial dechlorinatipn was
only marginally successful at destroying mutagens. This indicates that the reaction between
sulfite and residual chlorine is faster than reactions between organic mutagens and sulfite. >
They rechlorinated the water samples that were treated with sulfite, and retested for Ames
mutagenicity. Results indicated that "zero to 50 percent of the original mutagenicity was
regenerated upon rechlorination.
6-32
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Little information is available describing the use of sulfite to remove specific
compounds in drinking water. Trehy and Bieber (1981) showed that dihaloacetonitriles and
a variety of unsaturated alkyl halides can readily undergo dehalogenation reactions with
sodium sulfite.
Croue and Reckhdw (1989) evaluated the performance and kinetics for the reaction
of sodium sulfite with organohalides formed during the chlorination of dilute solutions of
aquatic fulvic acid. The experiments were performed at various pHs and in the presence or
absence of bromide. Removal performance and reaction kinetics were determined for
'ป
chloropicrin, trichloroacetonitrile, dichloroacetonitrile, dibromoacetonitrile, 1,1,1-
trichloropropanone and MX (3-Chloro-4 (dichloromethyl)-5-hydroxy-2(5H)-Furanone).
Chloropicrin was reduced by sulfite to dichloronitromethane. The rate of
decomposition of chloropicrin increases with higher pHs. In the absence of sulfite, loss of
chloropicrin was observed to be less than 10 percent after three hours, regardless of pH. The
researchers concluded that the hydrolysis rate was insignificant when compared with the
overall removal rate. Tests on the reaction kinetics indicated that decomposition of
chloropicrin was first order in total sulfite.
In contrast to chloropicrin, trichloroacetonitrile showed a significant rate of hydrolysis
in the absence of sulfite. The final degradation products, although not identified in these tests,
were expected to be naloacetamides and, ultimately, haloacetic acids. In the presence of
sulfite,-accelerated decomposition of trichloroacetonitrile was observed with the formation
of dichloroacentonitrile at pH 6.1. As with chloropicrin, the decomposition rate increased
with increasing pH.
In order to verify that trichloracentionitrile did not reform from its primary
degradation products, an additional experiment was performed. 100 ug/L solutions of
dichloroacetonitrile were chlorinated and analyzed over a period of eight hours. The absence
ป
of trichloroacetonitrile in the quenched solutions indicated that Trichloroacetonitrile could not
be formed by this route under conditions typical of drinking water treatment.
The researchers observed that dichloroacetonitrile underwent base-catalyzed
decomposition. Although hydrolysis rates noted in the study were small, the value at pH 8.5
6-33
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was significantly higher than the one determined at pH 7.2. No significant additional -
decomposition was observed in .the presence of sulfite.
Dibromoacetonitrile was found to undergo very slow base-catalyzed hydrolysis in
water. The product of hydrolysis in the presence of sulfite was bromoacetohitrile. The rate
of hydrolysis of dibromoacetonitrile increased with increasing pH. 1,1,1 -Trichloropropanone
showed a significant decomposition rate at pH of 8.5. However, no additional loss could be
detected at that pH in the presence of sulfite. The base-catalyzed reaction rate was observed
to be second-order. Experiments run at pH 6.1 and.pH 7.2 in the presence of sulfite showed
only a very slight loss of 1,1,1,-trichloropropanone. The loss was probably caused by the
slow hydrolysis expected at these pHs.
Slow hydrolysis of MX was found to take place at a pH of 7.0. The addition of sulfite
increased the rate of decomposition, although at a much lower rate than observed for
chloropicrin, trichloroacetonitrile and dibromoacetonitrile. Little or no hydrolysis of MX was
observed at a pH of 6.0. Because MX has been shown to contribute a significant fraction of
mutagenicity to chlorinated waters, the researchers noted that the low reactivity of MX was
surprising in light of the work of Cheh, et_al., (1980), who reported significant reduction in
the mutagenicity from dechlorination with sulfite. The apparent anomaly suggested that
compounds other than MX were responsible for the drop in mutagenicity as water was
dechlorinated. .
In addition to those discussed above, chloral, 2,3,6-tricnloroanisole and 1,1-
dichloropropanone were tested for decomposition in the presence of sulfite. None of these
by-products were reduced by sulfite within the conditions used by this research.
Based on the results of these experiments, Croue and Reckhow (1989) provided a
method to calculate the removal of chloropicrin, trichloroacetonitrile, and dibromoacetonitrile
as a function of sulfite dose and contact time.
i
6.8.2 Chlorine Dioxide By-Products
When chlorine dioxide is used in water treatment, chlorite ions (C1O2') and chlorate
ions (C1O30 are always potential byproducts. Gordon, etal. (1990), evaluated the use of
sulfite ion chemistry to quantitatively remove chlorite ion to below 0:1 mg/L level. The
i
6-34
-------
results of this experiment indicated that sulfite ion will remove chlorite ion in the pH 4.0 to
7.5 range. The reaction in this pH range is described by the following equation:
cio2- -ป> 2 so42- + cr
The reaction corresponds to a stoichiometry of two moles of SO32" consumed for every mole
of C1O2~ removed. The researchers noted that at pH 8 and above, in the. presence of air, the
overall stoichiometry appeared to deviate from this requirement, most probably because of
an increase in the rate of competing sulfite ion-oxygen reaction.
The rate of reaction was demonstrated to be first order in chlorite ion, second order
in sulfite ion, and at least first order in hydrogen. A summary of the predicted half-lives for
the removal of various levels of chlorite ion at different pH levels at 22 ฐC is shown in Table
6-21 along with the predicted time for greater than 99 percent removal of the total chlorite
ion. The results establish that the sulfite ion-chlorite ion reaction is greater than 90 percent
effective. Furthermore, with a tenfold excess of sulfur dioxide-sulfite ion and with chlorite
ion at the 0.5 to 7 mg/L level, the removal of chlorite ion is complete in less than one minute
at pH 5 and below, and complete in 15 minutes or less at pH 6.5.
The researchers also noted that chlorate ion was not removed by sulfur dioxide-sulfite
ion under the conditions tested. The calculated half-life for the removal of chlorate ion at the
milligram-per-liter level with excess sulfur dioxide-sulfite ion is on the order of months.
Much of the above work was performed in distilled water in the absence of oxygen.
Recent studies demonstrate that sulfite may catalyze the formation of chlorate from the
reaction of chlorite with oxygen (Gilbert, 1990; Dixon and Lee, 1990). Studies evaluating
the use of sulfur dioxide/sulfate (Griese 1991) confirmed the formation of chlorate in
oxygenated water supplies. Furthermore, this process has not yet been demonstrated at the
field scale level.
Griese, etal. (1991) studied the use of reducing agents to remove Chlorine Dioxide
and Chlorite from drinking water. The researchers thoroughly investigated the application
of a variety of reducing agents to waters pretreated with Chlorine dioxide. The researchers
have also in addition to the conclusion noted previously, concluded:
6-35
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. Sodium thiosulfate as a reducing agent for Chlorite appears to be unaffected
by the presence of dissolved oxygen but is highly dependent on pH and
contact time and only minimal Chlorite was formed.
Ferrous iron appears to be extremely effective for removing undesirable
Chlorine dioxide and Chlorite residuals in finished water. Both oxidants were
eliminated from the water in minutes at pH 6.0-7.0 and preliminary results
indicate that excess reductant maybe easily controlled by prefilter
chlorination. Coupled with control of Chlorate formation by optimizing
Chlorine dioxide generator efficiency, the use of ferrous iron following
Chlorine dioxide treatment will greatly minimize residual oxidants levels in the
finished water.
.
latrou and Knocke (1991) studied the effect of ferrous iron on chlorite removal.
Based on the results of this study, the following conclusions were formulated:
s
The ferrous iron - chlorite reaction is kinetically rapid over the pH 5.0-7.0
range, with complete chlorite reduction occurring in reaction times as short
as 3-5 seconds.
Stoichiometric ferrous iron dosages of 3 mg Fe/mg CIO/ were found to be
effective for chlorite reduction. This stoichiometry reasonably predicts
chloride ion (CIO as the by-product of the chlorite reduction.
<
Excess dosages of reduced iron could be removed by reaction with oxygen
under neutral pH conditions. However, stability of soluble iron may-be a
problem with excess ferrous iron dosages under acidic pH conditions.
Oxygen was ineffective for iron oxidation for pH values below 6.3.
There was no evidence of chlorate formation as a by-product of the ferrous
iron-chlorite reaction, suggesting that chlorate-formation should not be a
problem, in water treatment facilities that utilize this chlorite removal
technique.
No significant coagulative benefits were noted regarding the by-product ferric
hydroxide formed during the chlorite reduction reaction. However, the
presence of such ferric solids did riot adversely affect the performance of alum
as a primary coagulant for turbidity and DOC removal.
6-36
-------
TABLE 6-21
Predicted Half-Lives and Removal Times for Chlorite Ion
By Sulfur Dioxide-Sulflte Ion in the Absence of Oxygen (1)
pH
5
5.5
5.5
6.5
6.5
7.5
7.5
8.5.
Chlorite (mg/L)
0.5
, 0.5
1
1
1
1
1
, 0
Sulfite (mg/L)
5
5
10
10
20
10
100
100
Half-Life (sec)
2.9
38
9.5
130
' 32.6
8,020
80.2
40,000
99% Removal of
Chlorite Ion
0.34 min
. 4.4 min
1.1 min
15.2 min
3. 8 min
15.6 min
9.4 min
3 2 days
Note;
( 1 ) Reference: Gordon et al., (1990)
6.8.3 Summary of Reduction Processes
Chlorination byproducts including chloropicrin, trichlaroacetonitrile and
dibromoacetonitrile can be rapidly destroyed with small doses of sulfite. However, the potent
mutagen MX decomposes slowly over several days. Increases in pH were found to increase
the rate of destruction and the level of removal of chlorinated byproducts. The major
degradation products of the reaction between chlorinated byproducts and sulfite are partially
dehalogenated species including dichloronitromethane, dichloroacetonitrile and
bromoacetonitrile. It is unclear whether these species are more or less desirable than the
. original species. The primary degradation products do not appear to reform the original
chlorinated byproducts upon rechlorination.
6-37
-------
Reducing agents, such as sulfites, sulfur dioxide and ferrous salts, are effective in
controlling the concentration of chlorine dioxide residual and chlorite ion at pH values of 5
to 7. The presence of oxygen in natural waters may decrease the rate of removal. For many
systems with moderate to high alkalinity, in which pH depression to a value of 6.0 may not
be practical, reducing agents may not offer a feasible solution for removal of chlorite.
6.9 BIOLOGICAL REMOVAL
'
i , '
6.9.1 Introduction
- Biological processes are generally considered to include those processes which foster
the growth of microorganisms and, therefore, enhance the biodegradation of organic
.compounds. Rapid sand filters, slow sand filters and-GAC adsorbers found in many treatment
facilities can be converted to biologically active unit processes.
6.9.2 Removal of BDOC
As discussed in Chapter 2, the biodegradable portion of the background organic
matter in a water matrix is often measured as a surrogate parameter termed assimilable
organic carbon (AOC) or biodegradable organic carbon (BDOC), The 'concentration of this
parameter is an indicator of biological regrowth potential. Significant quantities of AOC and
BDOC .are formed during ozonation but can also be formed by chlorine and chlorine dioxide.
Leinhard and Sontheimer (1979), Gurol and Singer (1983), Staehelin and Hoigne (1983,
1985) and other researchers have shown that ozonation may convert complex organic
molecules to simpler molecules which are more biodegradable than the original molecules.
Bouwer and Crowe (1988) summarized the performance of biological processes
currently in use in drinking water treatment, primarily in Europe. Reductions ranging
between 3 and 84 percent were repeated for influent AOC concentrations of 23 to 500 ug/L.
Van der Kooij, etal. (1989), evaluated the effects of ozonation and biological processes upon
AO.C concentrations in two full-scale plants in the Netherlands. Both plants utilized dune-
infiltrated Rhine River water as their source of supply. The results are summarized below in
Table 6-22.
6-38
-------
TABLE 6-22
AOC Removal with Ozonation and Biological Filtration
Compound
Plant
Ozone
(mg/L)
Effluent Concentration (fig Acetate eq/L)1
Rapid Sand
Filters
Ozonation
Biological
GAC/Sand
Filters
Remova
AOC
A
B
7.2
13
55
59
Plant A had a raw water DOC concentration of 5.7 mg/L. Ozonation increased the AOC
portion of the DOC from 0.15 percent prior to ozonation to 2.4 percent following ozonation.
Subsequent biological activity reduced this ratio to 1 percent. DOC data was unavailable for
Plant B. Although biodegradation reduced AOC levels by 50 to 60 percent, plant effluent
AOC levels exceeded plant influent levels because of AOC formation during ozonation.'
. 6.9.3 Removal of Other DBFs
Speitel, etal. (1989), conducted batcK and fixed-bed column studies to evaluate the
removal of chloroform using biologically enhanced activated carbon (BEAC). Complete
biodegradation of chloroform to carbon dioxide by methanotrophs was reported after 12 days
in batch-scale experiments. The initial concentration of chloroform was 40 ug/L. In a fixed-'
bed column experiment containing glass beads with an EBCT of 70 minutes and an initial
chloroform concentration of 100 ug/L, no statistically significant difference was observed
between the influent and effluent concentrations of chloroform. Low removal was attributed
to the slow biodegradation kinetics of chloroform and to the occurrence of channeling.
Neukrug, et_al. (1984), evaluated the removal of natural and synthetic organics by
BEAC in pilot studies following conventional treatment of a Delaware River water. Filtered
water was ozonated at a dosage of 0.3 mg/L. Contactors and retention tanks provided a
contact time of 47 minutes during and after ozonation. The GAC pilot contactors were
6-39
-------
operated at a surface loading rate of 2 gpm/sf for an EBCT of 15 minutes. Although
ozonation increased the steady-state-removal of TOC in the GAC contactors, performance
with respect to THM removal was not improved. Steady-state removal of chloroform,
bromodichloromethane and dibromochloromethane did not occur in the GAC contactors
regardless of whether ozone was applied.
Speitel, etal. (1989), evaluated the biodegradation of 2,4-dichlorophenol (DCP) in
a pilot study using ozonation and GAC following conventional treatment of a lake water.
Filtered water was spiked with DCP at a concentration of 10 ug/L and ozone was added at
a dosage of 0.95 mg O^mg TOC. . Two treatment trains were evaluated: 1) GAC
adsorption only and 2) GAC preceded by ozonation. The GAC column was operated at an
EBCT of 0.4 minutes. Significant biodegradation occurred after five weeks of operation
reducing DCP in the effluent from 5 ug/L at the onset of biological activity to less than 2
ug/L at steady state. Although ozone enhanced the adsorption of DCP, biodegradation of
DCP was greater without the addition of ozone. However, little bioregeneration of the GAC
occurred, indicating that DCP was irreversibly adsorbed and biodegradation of sorbed DCP
was insignificant.
Wang, et al. (1989), operated two pilot- and one full-scale biofilters to evaluate
ammonia removal. The first pilot plant included facilities for preozonation, rapid sand
filtration (RSF), and BEAC. Three process trains were evaluated: (1) BEAC; (2) ozone-
BEAC; (3) ozone-RSF. The raw water supply contained ammonia levels of 0.3 to 0.6 mg as
nitrogen/L and ozone was applied at a dosage of 4 to 5 mg/L over a contact time of 3 to 5
minutes. The RSFs were operated at an EBCT between 7.3 to 9.8 minutes. The BEAC
columns were also operated at an EBCT of 7 to 10 minutes. The BEAC, ozone-BEAC, and
ozone-RSF processes showed ammonia removals of 61, 87, and 52 percent, respectively.
Biodegradation seemed to be the primary mechanism for removal since previous studies had
indicated that ammonia was not adsorbable. The ozone-BEAC process was the most efficient
because it fostered the greatest amount-of biological activity, evidenced by the highest effluent
microbial concentration. , , .
The second pilot plant consisted of ozonation and BEAC. BEAC was evaluated with
and without preozonation dosed at 2 to 4 mg/L. High ammonia removals were reported for
6-40
-------
both process trains,' with removals ranging between 60 and 100 percent. The best removals
were obtained at the end of the study period as biological activity increased. As with the
previous pilot study, the ozone-BEAC process was more efficient than BEAC alone in
reducing ammonia concentrations.
A 0.13 mgd full-scale plant was also evaluated. Treatment consisted of alum
coagulation, dual-media microflocculation/direct filtration, and BEAC. The pressure filters
were operated at an EBCT of 8 to 11 minutes. The BEAC pressure contactors were operated
at an EBCT of 12 to 17 minutes. The results of these three studies indicate that biological
treatment, especially ozone-BEAC, can successfully remove ammonia from drinking water.
The results are given in Table 6-23.
TABLE 6-23
Ammonia Removal with BEAC
Compound
Ammonia
Influent
(mg/L)
1.0
Filter
Effluent
(mg/L)
0.28
BEAC
Effluent
(mg/L)
0.17
Removal (%)
Filter
72
BEAC
39
Cumulative
83
Miltner, etal (1990), evaluated the effect of ozone following conventional treatment
on the formation and control of DBFs. Three parallel pilot plants were used to evaluate the
following oxidation schemes to treat river water seeded with.sewage (to add microbial
indicators).
-<.i
Pre-ozonation with post-chlorination,
Pre-ozonation with post-chloramination, and
Post-chlorination.
Chlorine doses in the post chlorination streams resulted in free residuals of 0.2 to 0.25 mg/L
at 25ฐ C after 3 days. Chloramination was achieved by adding ammonium hydroxide following
6-41
-------
chlorination and resulted in monochloramine residuals of 0.7 mg/L at 25ฐ C after 3 days. The
ozone dose was based on an ozone/TOC ratio of 0.8.
After ozonation, formaldehyde levels reached 26 ng/L and AOC levels reached 200
Hg/L of acetate carbon equivalents. Biodegradation of formaldehyde and AOC was observed
during the sedimentation and filtration processes. After rapid sand filtration, formaldehyde.
levels were reduced to 4 ug/L and AOC levels were reduced to 70 ug/L of acetate carbon
equivalents. Thus, formaldehyde and AOC removals of 85 and 65 percent, respectively, were
obtained through the rapid sand filtration-process. While these ozone by-products were
effectively removed by biodegradation, subsequent chlorination increased formaldehyde levels
to 10 ug/L and AOC levels to 200 ug/L of acetate carbon equivalents.
Huck, etal. (1990), reported the formation and removal of aldehydes in a pilot plant
incorporating conventional treatment, ozonation and GAC adsorption for treatment of a river
water. The average raw water acetaldefode, formaldehyde and propionaldehyde
concentrations were 8 ug/L, 1.2 ug/L and 1.1 ug/L, respectively. Ozonation at doses of 0.5
and 1 mg 0,/mg TOC increased the average formaldehyde concentrations by 1 and 2 ug/L,
respectively! Ozonation did not increase the concentrations of acetaldehyde. The percent
removal for formaldehyde with different ozone doses and hydraulic loadings, after dual-media
filtration and GAC adsorption are summarized in Table 6-24. Dual-media filtration and GAC
adsorption did not remove acetaldehyde.
TABLE 6-24
Aldehyde Removal with Ozonation and GAC
lemoval of Formaldehyde,
Dual-Media Filtration
GAC Adsorotion
6-42
-------
McGuire, etal. (1989), reported that an ozone dose of 2 mg/L resulted in formation
of formaldehyde at an approximate concentration of 15 ng/L at a conventional treatment
plant. Disinfection with chloramines (1.5 mg/L) before filtration did not allow any
formaldehyde removal in the filters. However, approximately 90 percent of the formaldehyde
was removed across the filter when chloramines were added after the filter. This removal was
attributed to biodegradation of formaldehyde in the filter.
Shukairy and Summers (1990) studied methods of reducing the.formation of DBFs
as measured by TOX and purgeable organic halide (POX). One of the methods studied was
the use of biodegradation after preozonation. The results of this study indicated that using
ozone followed by biotreatment and then chlorination would be a good method to effect
reduction in organic halides, while still maintaining a residual in the distribution system.
6.9.4 Summary of Biological Processes
Recent research has shown that biological processes hold a promising future In water
treatment. In a water, AOC content can be increased by oxidation before its application to
biological treatment processes. Post- disinfection may be necessary after such processes.
DBPs such as chloroform, formaldehyde and chlorophenols have been shown to degrade
under specific environmental conditions. Many of these studies were conducted in laboratory
controlled conditions. Studies have also shown successful removal of ammonia using
biological processes.
6.10 SUMMARY OF DBP REMOVAL
Effectiveness of treatments discussed for removals of disinfection by products and
residuals are summarized in Table 6-25-.
6.10.1 Inorganic By-Products
Chlorite can be removed with treatment by GAC adsorption, however, the GAC usage
rates necessary to achieve effective removal of chlorite needs to be better defined. Preloading
6-43
-------
TABLE 6-25
Effectiveness of Treatment Technologies for
the Removal and Control of DBFs -
DBFs
DISINFECTANT RESIDUALS
Free Chlorine
- Hypochlorous Acid
- Hypochlorite Ion -
Chloramines
Dichloreminc
- Trichloramine . .
INORGANIC BY-PRODUCTS
Chlorate
Chlorite
Bromate
lodate
Hydrogen Peroxide
.ORGANIC OXIDATION
BY-PRODUCTS
Aldehydes
- Formaldehyde
-Acetaldehyde
-Hexanal
-Heptanal .
Carboxyl Acids
- Hexanoic Acid
- Heptanoic Acid
AOC
Notes: G = Good Removal / '.
GAC
Adsorption*
G
G .
G
G
G.
G
P
G
NA
NA
NA
NA
P '
P
NA
NA
M
M
NA
Packed Tower
. Aeration
P
P
P
P
P
P
P
.P
P .
P
P
P
NA
NA
NA
NA
NA
NA.
'NA
Diffused
Aeration
P
P
P
P
P
P
P
P
P
P .
P
P
NA
NA
NA
NA.
NA
NA
NA
Cbnv.
.Treatment
P
P
P
P
P .
P
P
P
P
P
P
P
NA
NA
NA
NA
NA
NA
NA
PAC
Adsorption
Q-
O
G
G
G
G
P
G
NA
NA
NA
NA .
P
P
NA
NA
M
M
NA
Oridatfon
P
P
G
G
G
P
P
M
NA
NA -
G
G
NA
NA
NA
NA
NA
NA
NA
Membrane
Filtration
NA
NA
NA
NA
NA
M
M
M
NA
NA
NA-
NA
NA
NA
NA
G
NA
NA
NA
Reducing
Agents
G
G
NA
NA
NA
G
P
G
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Biological
Treatment
P
P
P
P
P
P
NA
NA
NA
NA
NA
G
-NA
NA
NA
NA
NA
NA
M/G
M - Moderate Removal / P = Poor Removal / . NA = Information Not Available
6-44
-------
TABLE 6-25 (cont)
Effectiveness of Treatment Technologies for
the Removal and Control of DBFs
DBFs
HALOCENATED ORGANIC BY-
PRODUCTS
Trihalomethanes
- Chloroform
- Bromofoim
Haloacclic Acid
- Monochloroacetic Acid
- Dichloroacelic Acid
- Trichloroacetic Acid
- Dibromoacetic Acid
Haloacetonitriles
- Dichloroacetonitrile
- Bromochloroacelonitrile
- DibromoacetonHrile .
- Trichloroacetonitrile
Haloketones
- 1 , 1 -Dichloropropanone
Chlorophenols
- 2-Chlorophenol
2,4-Dichlorophenol
- 2.4,6-Trichlorophenol
Chloropicrin
Chloral Hydrate
Cyanogen Chloride
N-Organochloramines
MX
GAC
Adsorption
'
P
P
P
M
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
M
G
G
NA
NA
NA-
NA
M
Packed Tower
Aeration
G
G
G
G
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Dittoed
G
G
G
G
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Conv.
P
P
P
P
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
PAC
P
P
P
M
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA ;
M
O
G ,
NA
NA
NA
NA
M
Oxidation
M
M
M
M
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
G
G
0
NA
NA
NA
NA
NA
Membrane
G
G
G
G
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
G
NA
NA
NA
NA
NA
Reducing
NA
NA
NA
NA
NA
NA
NA
NA
M
NA
G
G
NA
P
NA
NA
NA
G
NA
NA
NA
M
Biological
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA'
NA
NA
G
NA
NA
NA
NA
NA
NA
Notes: O - Good Removal / M = Moderate Removal / P ฐ Poor Removal / NA = Information Not Available
6-45
-------
of GAC with NOM, however, adversely affects chlorite removal. In addition, chlorite may
be oxidized to chlorate by free chlorine present in treated water applied to the GAC. Recent
research indicates that sulfur may not be'adequate for chlorite removal in real treatment
conditions. However, preliminary results indicate that ferrous reducing agents may be
promising, depending upon the treated water pH. Hydrogen, peroxide and ammonia are
effectively removed by oxidation with chlorine. In addition, ammonia is also easily
biodegraded. Most effective technologies for bromate removal include UV radiation,.GAC
adsorption and chemical reduction. Of the technologies reviewed, only membrane filtration
appears to provide moderate removal of chlorate.
6.10.2 Organic Oxidation By-Products
Little treatability information is available on the removal of most aldehydes and
carboxylic acids to define the applicable technologies for these DBFs. Membrane processes
appear to provide good removal of heptahoic acid. Adsorption with GAC and PAC could
remove carboxylic acids. Biological processes could be most applicable for the removal of
formaldehyde and AOC. However, this strategy may be limited in. situations where chlorinev
is used as the secondary disinfectant.
Glaze, et al. (1980) indicated that aldehyde formation is quite prolific during
ozonation with the dialdehydes glyoxal and methyl glyoxal being most abundant among them.
Filtration following ozonation seems to be effective in the removal of a large percentage of
these aldehydes when operating in a biological mode. However, there is no firm evidence to
show that either preozonation or subsequent filtration can completely remove the precursor
' j
to their formation by post-disinfection.
i
6.10.3 Halogenated Organic By-Products
The DBF removal strategy may have limited application to chlorinated by-products,
as many of them continue to form in the distribution system. THMs are most effectively
removed by aeration and membrane filtration. Moderate removals of bromoform can be
achieved with GAC or PAC adsorption. Due to inadequate treatability information for most
6-46
-------
of the haloacetic acids, haloacetonitriles apd haloketones, applicable technologies cannot be
defined at present.
AOPs appear to provide good removals of 2-chlorophenol, 2,4-dichlorophenol and
2,4,6-trichlorophenol. In addition, 2,4-dichlorophenol and 2,4,6-trichlorophenol are well
removed by GAC and PAC adsorption. Sulfite reduction may be an applicable treatment
method for removing chloropicrin, however, this process has not been demonstrated at the
field-scale level. Currently no treatability information is available to define treatment
technologies for removing chloral hydrate, cyanogen chloride, N-organochloramines and MX.
Sulfite reduction appears to have limited application for MX removal.
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Andrews, R. C., Daignault, S. A., Loverdure, C., Williams, D. T. and Hack, P. M. (1989).
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Argo, D. R. (1984). "Use of Lime Clarification and Reverse Osmosis in Water
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Bablon, G. P., Ventreseque C. and Ben Aim, R. (1988). "Developing a Sand GAC Filter to
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Baird, R., Selna, M, Raskins, J. and Chappelle, D. (1989). "Analysis of Selected Trace
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^ -
Bilello, L. J. and Singley, J. E. (1986). "Removing Trihalomethanes by Packed-Column and
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Blahck, C. A. (1979). "Trihalomethane Reduction in Operating Water Treatment Plants."
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Bouwer, E. J. and Crowe, P. B. (1988). "Biological Processes in Drinking Water
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Chang, N. W. and Singer, P. C. (1984). "Formation and Fate of Bromoform During
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Cheh, A. M., Skochdopak, J., Doski, P. and Cole, L. (1980). Science, 207, p. 90.
Conlon, W. J. and McClellan, S. A. (1989). "Membrane Softening: A Treatment Process
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Croue, J. P. and Reckhow, D. A. (1989). "Destruction of Chlorination Byproducts with
' Sulfite." Environ. Sci. Technol.. 23(2), p. 1412. ' .
DeLuca, S. J., Chao,. A. C. and Smallwood, C. (1983). "Removal of Organic Priority
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Dixon, K. L. and Lee, R. G. (1990). "Chlorite and Chlorate Removal in Water Treatment
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Dobbs, R. A. and Cohen, J. M. (1980). Carbon Adsorption Isotherms for Toxic Organics.
MERL, ODW, USEP A, Cincinnati, OH. EPA-600/8-80-023. .
Duguet, J. P., Dussert, B., Mallevialle, J. and Fiessinger, F. (1987). "Polymerization Effects
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Frank, C. A. (1987). "Destruction of Volatile Organic Contaminants in Drinking Water By
Ozone Treatment." Ozone Sci. Ene.. Vol. 9, p. 265.
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Glaze, W H , Peyton, G. R, Huang; F Y., Burleson, J. L. and Jones, P. C (1980)
Oxidation of Water Supply Refractory Species By Ozone With Ultraviolet Radiation.
USEPA, Cincinnati, OH, EPA-600/2-80-110
Gordon, G. (1990). "The Removal of Chlorite Ion from Drinking Water After Treatment
with Chlorine Dioxide." Proceedings of the 1990 AWWA Conference, Cincinnati,
Ohio.
Gordon, G., Slootmaekers, B., Tachiyashiki, S. and Wood, D. W. (1990). "Minimizing
Chlorite Ion and Chlorate Ion in Water Treated with Chlorine Dioxide." J. AWWA.
82(4), p. 160.
Greenbank, M. and Manes, M. (1981). "Application of the Polyanyi Adsorption Potential
Theory to Adsorption from Solution on Activated Carbon. H. Adsorption of Organic
Liquid Mixtures from Water Solution." J. Phvs. Chem.. 85(21), p. 3050.
Griese, M. H., Houser, K., Berkumeier, M. and Gordon, G. (1991). "Using Reducing Agents
to Eliminate Chlorine Dioxide and Chlorate Ion Residents in Drinking Water," I
AWWA, 83C5), p. 56-61.
Griese, M. H. (1991)." Pilot Plant Optimization Of The Chlorine Dioxide Treatment Process
'por Disinfection By-Product Reduction," 1991 AWWA Annual Conference,
Philadelphia, Pennsylvania.
Guisti, D. M., Conway, R. A. and Lawson, C. T. (1974). "Activated Carbon Adsorption of
Petrochemicals." J. AWWA. 46(5), p. 947-965.
' Gurol, M. D. and Singer, P. C. (1983). "Dynamics of Ozonation of Phenol. I. Experimental
' Observations." Water Res.. 17(9). p. 1173.
Gurol, M. D. and Singer, P. C. (1983). "Dynamics of Ozonation of Phenol. II. Mathematical
Simulation." WaterRes,, 17(9), p. 1173.
Hoehn, R. C., Randall, C. W., Groode, R. P. and Shaffer, P. T. B. (1978). "Chlorination and
Water Treatment for Minimizing Trihalomethanes in Drinking Water." in Water
Chlorination: Environmental Impact and Health Effects. Volume 2. R. L. Jolley, H.
Gorchev and H. D. Hamilton (Eds). Ann Arbor Science Publishers, Ann Arbor,
Michigan, p. 519.
Huck, P. M., Anderson, W. B., Rowley, S. M. and Daignault, S. A. (1990). "Formation and
Removal of Selected Aldehydes in a Biological Drinking Water Treatment Process."
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Shreveport, Louisiana.
.6-49
-------
latrou, A. and Knocke, W. R. (1991) "Chlorite Removal By The Addition Of Ferrous Iron,"
1991 AWWA Annual Conference, Philadelphia, Pennsylvania.
/
Lykins Jr., B. W., Koffskey, W. E. and Griese, M. H. (1991). " Controlling Disinfection By-
Products With Alternative Disinfectants," 1991 AWWA Annual Conference,
Philadelphia, Pennsylvania.
Koffesky, W. E. and Brodtman, N. V. (1983). Organic Contaminant Removal in Lower
Mississippi River Drinking Water bv Granular Activated Carbon Adsorption.
USEPA, Cincinnati, OH, EPA-600/2-83-032.
Kruithof, J. C. (1986). Chlorination Bv-Products: Production and Control. KIWA,
Communication # 74, AWWA Research Foundation, Denver, CO.
LeLacheur, R. M., Singer, P. C. and Charles, M. J. (1991)" Disinfection By-Products In
New Jersey Drinking Waters," Presented at the 1991 AWWA Annual Conference,
Philadelphia, PA.
i '
Lamarchek, P. and Droste, R. L. (1989). "Air-Stripping Mass Transfer Correlations for
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\
Maloney, S. W., Suffet,.I. H., Bancroft, K. and Neukrug, H. M. (1985). "Ozone-GAC
Following Conventional US Drinking Water Treatment." J. AWWA. 77(8), p. 66.
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McGuire, M. J., Davis, M. K., Liang, S., Tate, C. H., Aieta, E. M., Wallace, I. E., Wilkes,
D. R., Crittenden, J. C. and Vaith, K. (1989). Optimization and Economic
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Miltner, R, Rice E. W. and Stevens! A A. (1990). "A Study of Ozone's Role in Disinfection
By-Product Control." Presented at the 1990 Spring Conference of the International
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Mullins, R. L., Zogorski, J. S., Hubbs, S. A. and Allgeier, G. D. (1981). "The Effectiveness
of Several Brands of Granulated Activated Carbon for the Removal of
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Neukrug, H. M. Smith, M. G., Maloney, S. W. and Suffet, I. H. (1984). "Biological
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Mixtures Thereof with Humic Acid: An Interim Report." in Water Chlorination:
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Compounds in Water." presented at the International Ozone Institute Forum on
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Research Needs." Draft chapter prepared for inclusion in the AWWA Research
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\
Reinhard, M., Goodman, N. L., McCarthy, P. L. and Argo, D. G. (1986). "Removing Trace
Organics by Reverse Osmosis Using Cellulose Acetate and Polyamide Membranes."
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Shukairy, H. M. and Summers, R. S. (1990) "The Impact of Preozonation and
Biodegradation on the Formation of Halogehated Organic Compounds After
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Soeitel G E Turakhia, M. H. and Lu, C. J. (1989). "Initiation of Micropollutant
P Bfode^adation ir! Virgin GAC Columns." LAWWA, 81(4), p. 168.
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-
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6-53
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7 0 DEVELOPMENT OF DESIGN CRITERIA AND UPGRADE
COSTS FOR DISINFECTION BY-PRODUCT CONTROL
7.1 INTRODUCTION
One of the primary objectives of this document is to determine estimated costs for
disinfection by-product control to assist the EPA in generating national costs. The purposes of this
chapter are to:
i
. Identify DBF control alternatives for which upgrade costs will be generated;
Develop design criteria associated with these control alternatives; and
. Estimate upgrade costs for the selected DBF control alternatives.
Chapters 4 through 6 focused on the following three basic alternatives for DBF control:
.Remove NOM prior to disinfection;
Use of alternative disinfectants that do hot form DBFs at levels considered
adverse to human health; and ป
Remove DBFs after they are formed.
The treatment upgrades considered in this section focus on the first two control strategies.
Removal of DBFs after formation was not developed since it is more efficient to remove the
precursors before DBFs are formed.,
Design criteria and upgrade cost information were previously presented in the 1992
' version of this document for selected DBF control technologies. For some technologies, costs have
increased nearly proportional to inflation since 1992. This document presents the approbate
inflationary factors to be applied to each of these technologies. Por other technologies, costs have
not increased proportional to inflation because of recent advances in the technology and increased
use in the water treatment industry. This document presents the approach used to generate rev,sed
7-1
-------
costs for these technologies. Furthermore, this document provides costs for technologies hot
included in the previous version.
For the 1992 version of this document, the Water Treatment Plant (WTP) simulation
model (EPA, 1992) and cost models were used to develop design criteria and cost, respectively. In
general, the approach consisted of programming the WTP model to generate design criteria for each
treatment technology under a wide range of raw water qualities and under specified treatment
assumptions and constraints. Predicted design criteria from the model and other design criteria based
on engineering judgement were input into cost models. From these cost models, upgrade costs were
calculated for EPA's 13 flow categories by subtracting the total cost of a treatment plant with the
upgrade from the total cost of a baseline plant.
Because of limitations of the WTP model and other project constraints, the WTP model
approach is not used in this document to develop design criteria for those technologies requiring new
or revised costs, namely ozone, membranes and chlorine dioxide. It was felt the existing facility cost
data would be more accurate than the WTP model and the WTP model does not represent current
knowledge. Rather, design criteria are predicted using best engineering judgement and a review of
existing facilities. For cost estimates, recent manufacturer costs and surveys of existing facilities
were evaluated for those technologies that did not increase proportional to inflation. The
development of design criteria and estimated costs for each technology is presented in Section 7.6.
A more detailed discussion of the approach used in the 1992 version of this document is provided in
Section 7.3.
7.2 TREATMENT UPGRADES
As stated in Section 7.1, treatment upgrades for DBP control focused on NOM removal
prior to disinfection and use of alternative disinfectants.
In Chapter 4 a wide spectrum of treatment processes for the removal of NOM were
examined. The evaluation of DBP precursor removal processes was summarized in Section 4.12.
A comparison of relevant technologies and their general feasibility are presented in Table 4-5. Based
on overall effectiveness, expected economic feasibility, and practical full-scale experience, the most
promising and effective processes for the removal of DBP precursors are:
7-2
-------
-Improved coagulation/filtration;
Membrane separation;
' GAC adsorption; and
Improved precipitative lime softening.
In a similar fashion, Chapter 5 examined the effects of alternative disinfection strategies
for the control of DBFs. Considerable care must be taken when evaluating any alternative
disinfection strategies. A modified disinfection scheme may decrease the formation of some DBFs
while increasing the presence of others and result in diminished protection from pathogenic
organisms. Major findings of Chapter 5 are summarized in Section 5.5.
Two alternative primary disinfectants listed in Section 5.2 are considered in the treatment
upgrades; ozone (O3) and chlorine dioxide (ClOj). Based on a review of the most recent literature
findings, the most applicable alternative secondary disinfectant for the control of DBFs is
monochloramine (NH2C1) and this is the only alternative secondary disinfectant considered in this
chapter.
In addition, to precursor removal and alternate disinfectants, some systems may be able
to control DBFs to a specified level by moving the point of chlorination. According to some surveys
of treatment practices (Haas, 1991), between one-half to two-thirds of plants in this category may
apply chlorine prior to sedimentation. Moving the point of chlorination after sedimentation would
reduce the level of NOM available to react with chlorine and thus reduce levels of DBFs in the
distribution system. Systems that move the point of chlorination further into the treatment process,
however, must compensate for the disinfection provided through sedimentation.by either increasing
the chlorine contact time after filtration and/or increasing the post-filter chlorine dose.
At this time, design criteria and estimated upgrade costs have been developed for seven
DBF control strategies, including:
Switching to monochloramine as a secondary disinfectant;
Increasing coagulant dosage to improve NOM removal;
7-3
-------
Increasing lime dosage to improve NOM removal,
Switching to ozone as a primary disinfectant;
Switching to chlorine dioxide as a primary disinfectant;
Adding post-filter GAC adsorption; and
Adding membrane separation.
Although design criteria are not provided for systems that move the point of chlorination, upgrade
costs for installing additional contact time are provided in Section 7.6.
It is the intent of USEPA that there be no significant reduction in microbial protection as
the result of modifying disinfection practices to meet maximum contaminant levels (MCLs) for
TTHM and HAAS. A microbial benchmarking procedure will be established in the Interin Enhanced
Surface Water Treatment Rule (IESWTR) for systems moving the point of chlorination or changing
disinfectants so that the modified treatment scheme will not result in a reduction in microbial
protection. The actual requirements and applicability are found in the final IESWTR and in the
Disinfection Benchmarking Guidance Document issues by EPA in November of 1998 (EPA, 1998).
7.3 OVERVIEW OF PREVIOUS APPROACH
As discussed in Section 7.1, the Water Treatment Plant (WTP) simulation model was
used extensively to develop design criteria for the selected DBP control technologies in the 1992
version of this document. The WTP model was developed specifically for EPA in support of the
M/DBP Rule. Equations in the model simulate the removal of NOM, the formation of DBFs and
disinfection levels in water treatment plants and distribution systems based on specified inputs
including raw water quality, treatment process characteristics and chemical dosages. Design criteria
predicted by the WTP model for this analysis included: 1) chemical dosages; 2) contact basin size;
and 3) solids production.
7-4
-------
Because raw water quality plays a key role in the feasibility of any DBF control
alternative, this computer model allowed for the evaluation.of various raw water qualities. The
following parameters were considered:
Concentration and type of NOM and surrogate parameters such as TOC and
UV-254;'
Concentration of pathogenic microbiological organisms such as Giardia,
i
Alkalinity;
pH;
Calcium hardness;
Total hardness;
Turbidity;
Temperature;
- Bromide; and
Ammonia.
The overall approach used by EPA to evaluate the effects of the DBF Rule assumed that
there are five basic types of treatment practiced in the United States at the present time. The five
treatment categories are assumed to be the following:
Surface Waters
Coagulation/filtration, systems;
Precipitative softening systems; and .
Unfiltered systems (including those that will be required to filter under the
SWTR).
7-5
-------
Ground Waters
Unfiltered systems; and
Precipitative.softening systems.
Membrane filtration
From extensive surveys of water treatment systems, raw water quality distributions were
generated. Distributions presented in the 1992 version of the document are shown in Table 7-1 for
four treatment categories (unfiltered surface waters are not shown) From distributions similar to
these, 100 raw water quality sets were generated to represent the different raw water qualities across
the United States. These 100 simulated data sets were analyzed using the WTP model to develop
design criteria for the various treatment upgrades. Although raw water quality distributions were
generated for four of the five treatment categories, design criteria and upgrade costs were generated
for only one treatment category: surface waters using coagulation and filtration. The surface water
category was analyzed initially because surface water systems: 1) are generally much more sensitive
to DBF formation than ground waters as a result of source water NOM "(excluding Florida
groundwaters)" and; 2) serve a much larger segment of the overall population.
To develop realistic design criteria from the WTP model, certain treatment constraints
were programmed into the model. These constraints included 1) TTHM constraints (HAAs
were not evaluated); 2) primary and secondary disinfection constraints; and 3) pH constraints for
corrosion control in the distribution system. .
7-6
-------
TABLE 7-1
UPDATED WATER QUALITY DISTRIBUTIONS
Parameter
Mean
Standard
Deviation
Minimum
25th
Percentile
Median
75th
Percentile
Maximum
N Count'
COAGULATION/FILTRATION SURFACE WATERS
TOC (mg/L)
UV-254(l/cm)
pH
Alkalinity (mg/L
as CaCO3)
Total Hardness
(mg/L as CaCO3)
Calcium Hardness
(mg/L as CaCOS)
Turbidity (NTU)
Bromide (mg/L)
Ammonia (mg/L)
Temperature (C.C)
average
Temperature (ฐC)
minimum
5.291
0150
7.57
75^52
122.81
92.11
15.10
0.32 N
0.11
14.47
4.41
489 .
0.163
0.52
82.85
157.48
. 118.11
21.56
0.83
0.16
3.66
3.52
0.39
0.001
6.06
8.06
11.20
8.40
0.17
0.00
0.00
4.93
0.26
2.10
0.045
>7.30
28.77
35.12
26.34
3.12
0.02
0.03
11.91
2.02
3.89
0.094
7.51
46.75
70.97
53.23
7.91
0.08
0.05
14.52
3.30
5.60
0.185
7.90
79.39
125.97
94.48
16.95
0.22
0.13
17.45
5.45
26.39
0.812
9.06
573.22
778.82
584.12 '
121.43
5.00
i.42
21.47
20.33
61
30
226
225
217
NA
' 224
30
12
215
219
PRECIPITATIVE SOFTENING SURFACE WATERS x
TOC (mE/L)
UV-254(l/cm) -
PH
Alkalinity (mg/L
as CaCO3)
Total Hardness
(mg/L as CaCO3)
Calcium Hardness
(mg/L as CaCOS)
Turbidity (NTU)
Bromide (mg/L)
Ammonia (mg/L)
Temperature (CC)
average
Temperature (ฐC)
minimum
8.01
0.216 .
7.75
.121.81 .
200.54
150.40
54.75
0.24
0.44
15.46
4.04
11.15
0.255
0.49
1 154.18
. 217.46
163.09
96.58
0.38
0.66
3.69
3.32
0.10
0.001
6.78
10.68
5.00
3.75
0.20
0.00
0.00 .
5.04
0.67
1.71
0.037
7.44
43.93
59.79
44.84
7.30
0.06 .
0.05
12.61
1.91
4.42'
0.117
7.68
70.91
123.97
92.98
17.43
0.14
0.16
15.26
2.87
10.22
0.312
' 8.00
. 130.05
243.64
182.73
58.53 -
0.28
0.54
18.10
5.21
60.00
1.000 .
9.19
1000.0
1000.0
750.0 .
,602.44
3.22
400
,25.09
24.48
21
30
. 66
65
65
NA
65
30
12
63
65
7-7
-------
TABLE 7-1 (Con't)
UPDATED WATER QUALITY DISTRIBUTIONS
Parameter
Mean
Standard
Deviation
Minimum
25th
Percentiie
Median
75th
Percentiie '
Maximum
N Count*
COAGULATION/FILTRATION GROUNDWATER
TOC (mg/L)
UV-254(l/cm)
pH
Alkalinity (mg/L
as CaCO3)
Total Hardness
(mg/L as CaCO3)
Calcium Hardness
(mg/L as CaCO3)
Turbidity (NTU)
Bromide (mg/L)
Ammonia (mg/L)
Temperature (ฐC)
average
Temperature (ฐC)
minimum
234
0.065
7.35
18144
'l81.71
136.28
1.30
0.13
0.090
17.31
14.18
4.62
0.144
0.70
140.14
193.84
145.38
2.80
0.31
0.130 .
4.87
4.13'
0.10
0.001
5.65
22.88
15.40
11.55 '
0.01
0.01
0.000
8.99
5.64
0.24
0.001
6.93
81.57
59.87
% 44.91
0.12
0.03
0.030
13.66
11.52
0.82
0.012
7.34
151.51
114.78
86.09
0.30
0.06
0.060
17.12
14.66
226
- 0.071
7.77
224.76
236.95
177.71
0.93
0.11
0.100
20.60
17.05
3394'
1.000
922
67087
1000.0
750.0
18.60
2.30
0890
30.0
23.69
11
30
- 124
123
124
NA
15.
40
14
96
90
PRECIPITATIVE SOFTENING GROUNDWATER
TOC (mg/L)
UV-254(l/cm)
PH
Alkalinity (mg/L
as CaCO3)
Total Hardness
(mg/L as CaCO3)
Calcium Hardness
(ma/L as CaCO3)
Turbidity (NTU)
Bromide (mg/L)
Ammonia (me/L)
Temperature (ฐC)
average
Temperature (ฐC)
350
0.087
7.36
24245
286.69
. 215.02
0.99
0.11
0.85
17.43
1521
7.18
0168
0.32
60190
82.45
61.83
roo
010
0.77
5.03
5.52
010
0.001
6.48
86.86
75.76
56.82
0.05
0010
0.12
7.69
0.20
0.61
0.001
7.18
202.98
237.05
177.78
0.32
0.04
0.35
13.96
12.08
1.28
0.022
7.34
233.41
276.54
207.40
0.62
0.07
0.61
17.10
15.76
3.18
0.091
7.57
277.50
344.49'
258.36
1.28
0.13
1.01
19.98
18.44
60.0
1.000
8.27
385.56
491.00
368.26
4.93
0.45
40
30.0
26.32
11
30
32
32
32
NA
15
40
9
29'
22
7-8
-------
The design criteria predicted by the WTP model.using the approach described above
represented realistic values for the various treatment upgrades when compared to existing facilities.
However, the impact of using a wide range of raw water quality (i.e., 100 simulated systems) was
minimized because design criteria were chosen to be the median value of only those systems that met
the DBF constraints, these systems tended to have better raw water quality than those that did not
meet the model constraints. The greatest impact of using the raw water quality distributions is in
estimating the percentage of systems installing a given DBF control technology. Based on the
realistic design criteria predicted by the WTP model, it is appropriate to continue to use the predicted
design criteria for cost estimating purposes. It was felt the existing facility cost data would be more
accurate than the WTP model and the WTP model does not represent current knowledge. However,
because of project constraints, it was not possible to use the WTP model to develop design criteria
for those systems with revised costs in this document. For these systems, design criteria was
determined using best engineering judgement and a review of design criteria of existing facilities.
For cost estimating purposes, EPA's 13 flow- categories (shown in Table 7-2) were
divided into two groups: Flow Categories 1 through 4, with design flows less than 1 mgd, are
classified as small systems; and Flow Categories 5 through 12a, with design flows greater than 1 mgd,
are classified as large systems. The upgrade costs for each flow category and for each treatment
upgrade are provided in the respective subsections of Section 7.6.
For these systems, the cost presented in this document apply separately .to each treatment
facility within a given water system. For example/some large systems provide treatment facilities at
multiple locations. The total costs for .such a system can be obtained by adding together the costs of
the individual treatment facility.
- In the 1992 version of this document, estimated capital, operation and maintenance
(O&M), and total .costs were computed using the WATER model (USEPA and Gulp, Wesner, Gulp,
1984) for small systems and the WATERCOST model (USEPA, et_al., 1986) for large systems.
Where necessary, a GAG cost model (Adams and Clark, 1990) and vendor costs were used to
supplement the WATER and WATERCOST models. In these models, information from existing
7r9
-------
plants and manufacturers was used to .determine the cost of equipment, supplies and operating
requirements.
TABLE 7-2
EPA FLOW CATEGORIES
EPA FLOW
CATEGORIES
MEDIAN
POPULATION
SERVED
AVERAGE FLOW
(mgd)
DESIGN
CAPACITY
(mgd)
SMALL SYSTEMS - DESIGN FLOW < 1 MGD
1
2
3
4
57
225
750
1,910
0.0056
0.024
0.086
0.23
0.024
0.087
0.27
0.65
LARGE SYSTEMS - DESIGN FLOW > 1 MGD
5
6
7
8
9
10
11
12'
12a
5,500
15,000
35,000
60,000
88,000
175,000
730,000
1,550,000
N/A
0.70
2.1
5.0
8.8
13
27
120
270
350
1.8
. 4.8
11
18
26
51
210
430
520
The WATER model was developed for small systems serving up to 1 mgd. It is
appropriate to distinguish costs for small and large systems because small systems are generally
remote and seldom operated on a full-time basis. Small system technology is also amenable to a
complete "package" treatment system supplied by a manufacturer. This tends to generalize the
specific design parameters to fit the unit instead of having them engineered specific to the application.
In past documents, the logical break between small and large system has been with the first four
system sizes as shown in Table 7-2.
7-10
-------
7.4 BASIS FOR COST ESTIMATES
One of the purposes of this chapter is to provide the costs for treatment upgrades to
existing water treatment plants. As such, assumptions must be made regarding the type and level of
treatment provided by the existing plant, also referred to as the base plant. A base plant is defined
as a representative treatment plant that does not include any of the DBF control alternatives discussed
in Section 7.2. , '
For the surface waters using coagulation and filtration, the base plant consists, of rapid
mixing, flocculation, sedimentation, filtration, contact basin, and finished water storage as shown
schematically in Figure 7-1. Although not shown in the figure, solids handling facilities consist of
dewatering lagoons. The disinfection strategy is chlorine/chlorine (primary disinfection/secondary
disinfection).. The plant meets the primary disinfection requirements of the Surface Water Treatment
Rule (SWTR) by providing at least a 3-log reduction (inactivation and removal) ofGiardia, As noted
in Section 7.2, ,a microbial benchmark may need to be established for this system before changes to
the disinfection scheme are made. The plant also meets the secondary disinfection requirements of
the SWTR by providing a detectable chlorine residual throughout the distribution system. The
process shown in Figure 7-1 is assumed to achieve the filtered water turbidity levels required by the
SWTR. .
Chemical feeds include alum, caustic soda, and chlorine. Alum is added at a specified
dosage at the rapid mix stage to coagulate turbidity and convert dissolved NOM to the paniculate
phase for subsequent removal in the sedimentation and filtration processes that follow. Caustic is
added for corrosion control after the contact basin to achieve a desired distribution system PH of at
least 8.2 throughout the distribution system. Chlorine is added prior to filtration to provide the
necessary primary and secondary disinfection. It is assumed that multiple points of chlorination will
have a negligible effect on upgrade costs when compared to the costs of other technologies for DBF
control The adjustment of PH was not specifically modeled for DBF control. A procedure to
calculate the optimum chlorine dose and contact time is presented in the 1992 Technology and Cost
Document.
7-11
-------
To calculate the total costs for the base treatment plant, design criteria and general
engineering assumptions are required. The WTP model was used to determine chemical dosages and
contact basin size. Examples of additional design criteria include clarifier overflow rates and filtration
rates. Examples of general engineering assumptions include the type of baffling for clearwells. The1
design criteria and general engineering assumptions for the base plant are presented in Tables 7-3 and
7-4 for small and large systems, respectively.
For small'systems, labor costs for operation and equipment maintenance can have a
significant impact on the projected annualized and unit costs (S/MG). It is recognized that many
small systems, particularly the very small systems, do not have full-time operators and such plants are
frequently operated by an outside contractor. Therefore, labor costs for small systems were
calculated based upon three levels of operator attention (low, medium and high). The annual labor
costs presented for the different levels of attention assume a S-day/week operation and are shown
below.
_ TABLE 7-2(a)
SMALL SYSTEM LABOR COSTS
Operation (hrs/day)
Maintenance (hrs/wk)
Total Labor (hrs/yr)
Annual Labor Cost1
Low Attention
0.5
1.0
182
$3,290
Medium Attention
1.0
2.0
364
$6,582
High Attention
2.0
4.0
728
$13,163
1 1991 Costs escalated based on factor of 1.23 derived from ENR BCI
The high level of attention approximates the total number hours estimated by
manufacturers for each individual unit process. For a small system treatment plant where these unit
processes are combined, the efficiency of operation increases, thus decreasing the level of attention.
Based on experience with some small systems, the low level of attention may more closely
approximate labor costs.
The small system labor costs, presented above, were developed by EPA in a draft
document for very small systems, (USEPA, 1992d), because EPA recognizes that the WATER model
may overestimate small system costs. EPA also recognizes that some of the cost allowance factors
7-12
-------
TABLE 7-3
BASIS FOR COST ESTIMATES FOR DBF CONTROL
SMALL SYSTEMS
Process
Package Raw Water
Pumping
Package Complete
Treatment Plant
Hypochlorite Solution
Chlorination Svstem
WATER Model
Assumptions
Premanufactured packaged pumping station using submersible pump
contained in a 20 fl deep steel" pump sump.
Manifold piping, sump intake valve, pump check valves, and electrical
controls.
Total dynamic head is SO ft. -
Pump and motor efficiencies are 80 and 90%, respectively.
Coagulation, flocculation, sedimentation, and filtration equipment provided
including tube settlers rated at 1,500 gpd/sf, mixed media filters with
application rates of 2 to 5 gpm/sf and media depth of 30 in.
Chemical feed facilities include storage tanks and feed pumps.
Filter backwash pumps and, where applicable, surface wash water pumps.
Flow measurement and control devices, pneumatic air supply (for 200 gpm
or larger plants), effluent pumps, and building. ' '
Solution tanks, mixers, and metering pumps
Melerine oumos. PVC Dices, valves and controls are included.
Engineering
Assumption
Sodium hypochlorite dose of 2.4 mg/L
determined by WTP model.
7-13
-------
TABLE 7-3
BASIS FOR COST ESTIMATES FOR DBP CONTROL
SMALL SYSTEMS
Process
Sodium Hydroxide Feed
System
Alum Feed System
Package High Service
Pump Station
Clearwell Storage Above
Ground
Sludge Dewatering
Lagoons *
Dewatered Sludge
Hauling
WATER Model
Assumptions
Storage tanks, heater, manual transfer pump, mixers, feed tanks and
metering pumps are included.
PVC pipes, valves and control are also included.
Solution tanks, mixers, and calibrated metering pumps are included.
PVC pipes, valves and controls are also included.
Includes 2 or 3 centrifugal pumps, pressure sensing, flow control valves,
instrumentation and equipment.
Pumps provide a maximum output of 70 psi.
Above ground, steel tanks including instrumentation and control of
clearwell water level and instrumentation for turbidity and residual
monitoring is provided.
Unlined lagoon and inlet, outlet structures are provided.
2 ft freeboard, 3:1 side slopes, 5 ft depth are also provided. .
Loading facilities including sludge conveyer, hopper, and hopper enclosure
are provided.
1 pnath nf haul ic 70 milcc nnp-vuay -
Engineering
Assumption
Alum dose is determined by DBP control
alternatives.
Clearwell size is based on storage of 25%
the daily operating flow.
of
Sizing of lagoons is based on solids content
of 5%.
Sludge is thickened to a solids concentration
of 30%.
(
7-14
-------
TABLE 7-3 (cont.)
Process
Contact Basin
BASIS FOR COST ESTIMATES FOR DBF CONTROL
__ SMALL SYSTEMS
WATER Model
Assumptions
Engineering
Assumption
Below ground tanks without repumping are
assumed.
Size of basin is 60 minutes, as determined
by the WTP model.
The well baffled tanks are assumed to
provide actual contact time of 0.7 times the
theoretical according to the SWTR
Guidance Manual.
O&M costs were unpredictable and. were
assumed to be negligible.
7-15
-------
TABLE 7-4
BASIS FOR COST ESTIMATES FOR DBF CONTROL
LARGE SYSTEMS
Process
WATER Model
Assumptions
Engineering
Assumption
Raw Water Pumping
Total dynamic head 100 ft
Manifold piping velocity
Standby pump, manifold piping, and instrumentation are provided
Alum Feed System
Diaphragm metering pumps, steel storage hoppers with dust collector, and
mechanical weight belt feeders
Commercial alum density 60 Ib/cu ft
Dissolving tank detention time 5 min with 2 gal of water per Ib of dry alum
added
Maximum hopper volume 6.000 cu ft with fifteen days of storage
Alum dose is determined by DBF
control alternatives
Rapid Mix
Vertical shaft, variable speed turbine mixers with stainless steel shafts and
paddles and TEFC motors
Maximum basin capacity 2,500 cu ft
Water temperature 15ฐ C
Overall mechanism efficiency 70% ;
G = 900/sec
Detention time is I min at design flow
7-16
-------
TABLE 7-4
BASIS FOR COST ESTIMATES FOR DBF CONTROL
LARGE SYSTEMS
Process
WATER Model
Assumptions
Engineering
Assumption
Flocculalion (Horizontal
Paddle)
Rectangular-shaped, reinforced concrete basins with 12 ft depth, 4:1 length to
width ratio, and 12,500 cu ft individual maximum basin size
Variable speed drive units requiring IS min/day routine O&M and an oil change
every 6 months requiring 4 hrs of labor
Overall mechanism efficiency 60% -
G = 50/sec
Detention time is 30 min at design flow
Rectangular Clarifiers
Chain and flight collector with drive mechanism, sludge pumps, reinforced
concrete structure, and withdraw pumps are included
Side wall depth =12 ft
Overflow rate = 1,000 gpd/sq ft
Maximum number of units is 2
Maximum basin area = 20,000 sq fl
Gravity Filtration
' Systems
Filter structure, underdrains, wash water troughs, pipe gallery piping and valves,
instrumentation, control panel, and filter housing are provided
Filter box depth = 16 ft
Maximum filter size = 1.275 sq ft ' '
Minimum 4 filters per plant
Filter loading rate = 4 gpin/sq ft
Filtration Dual Media
20 in of 1.0 to 1.2 mm effective size anthracite coal (UC = 1.7)
10 in of 0.42 to O.S2 mm effective size silica sand (UC - 1.6)
IJ in iinHprrirainc MpHia pnngjgfino nf d civpc t\f cilira
7-17
-------
TABLE 7-4 (cont.)
BASIS FOR COST ESTIMATES FOR DBF CONTROL
LARGE SYSTEMS
Process
WATER Model
Assumptions
Engineering
Assumption
Backwash Pumping
Facilities
All required pumps and motors, flow control, sequencing control, valves and
backwash headers are included
Pumping head = 50 ft
Overall mechanism efficiency 70% ,_
Backwash rate = 18 gpm/sq ft
One filter is backwashed at a time with
each filter backwashed approximately
every two days
Wash Water Surge
Basins'
Below ground, reinforced concrete basins and level control instrumentation
provided
Sized to store a 20 min volume or
backwash water at design flow
Unthickened Sludge
Pumping
Variable speed, centrifugal pumps, piping and valves, electrical equipment
housing, dry well, and a wet well are included
Pipe velocity = 5 ft/sec
Total dynamic head = 30 ft
Overall pump-motor efficiency = 65%
Unthickened sludge solids
concentration = 1%
12 hr/day of sludge pumping
Sludge Dewatering
Lagoons
Unlined lagoon and inlet and outlet structures are provided
2 ft freeboard, 3:1 side slopes, and 10 ft depth are also provided
Solids production is determined by
WTP model
Sludge is thickened to a solids
concentration of 30%
Sizing of lagoons is based on a solids
content of 5%.
7-18
-------
TABLE 7-4 (cont.)
BASIS FOR COST ESTIMATES FOR DBF CONTROL
LARGE SYSTEMS
Process
WATER Model
Assumptions
Engineering
Assumption
Dewatered Sludge
Hauling
Loading facilities including sludge conveyor, hopper, and hopper enclosure are
provided ' .
Length of haul is 20 miles one-way
Dewatered sludge has a solids content
of 30% . .
In-plant Pumping
Constant speed, vertical turbine pumps, pump motor, wet well, and piping and
valves are included
Pipe velocity = S ft/sec
Total dynamic head = 50 ft
Chlorine Feed Facilities
Chlorinator, standby chlorinator, cylinder scales, .evaporators, residual analyzers
with flow proportioning device injector pumps, and housing to include 30 days of
cylinder storage are provided
Injector pumps deliver water at 25 psi to allow production of 3,500 mg/L
solution . ~~
Chlorine dose is 2.4 mg/L as
determined by WTP model
Sodium Hydroxide Feed
System
Storage tanks, heater, manual transfer pump mixers, feed tanks and metering
pumps are included
"v
PVC pipes, valves and controls are also included '
Sodium hydroxide dose is 16 mg/L as
determined by WTP model
Finished Water
Pumping
Vertical turbine pumps powered by constant speed motors, electrical equipment
instrumentation, valves, and manifolds are provided
Total dynamic head is 300 ft .
StanHhv nnmn if
7-19
-------
TABLE 7-4 (cont.)
BASIS FOR COST ESTIMATES FOR DBF CONTROL
LARGE SYSTEMS
Process
WATER Model
Assumptions
Engineering
Assumption
Clearwell Storage Below
Ground
Control and instrumentation of clearwell, level and instrumentation for turbidity
and chlorine measurement is included
Size of cleanvells is based on storage of
10% of operating (low and 5% of
design flow for one day
Contact Basin
Contract basin size determined by WTP
model
For capacities <30,000 gallons: below
ground tanks without repumping are
assumed
For capacities >30,000 gallons and < 10
million gallons: ground level tanks with
distribution and center baffles are
assumed
For capacities > 10 million gallons:
multiple tanks with distribution but
without center baffles are assumed
The well baffled tanks are assumed to
nrtwiHp arh.al rnntart tinuป
7-20
-------
for small systems (discussed below and presented in Table 7-5) may overestimate upgrade costs.
However, the cost-allowance factors presented in the very small system document were not used in
this analysis.
Capital costs for each treatment upgrade .include cost -allowance factors. These include
sitework, interface piping, subsurface considerations, standby power, contractors overhead and profit,
engineering interest during construction, and legal, fiscal and administrative fees. The factors used
for these allowances are provided in Table 7-5 for small,and large systems.
TABLE 7-5
COST ALLOWANCE FACTORS
Small Systems
Water Model
10
Item
=^^
Site work and Interface
Piping
Subsurface Considerations
Standby Power
General Contractors
Overhead and Profit
10
12
Large Systems
WATERCOST Model(%)
15
10
12
Engineering
Legal", Fiscal and
Administration fees
IS"'- ,
5to6<ป
lsn
9 tollฎ
Notes:
0)Percentages added to estimated construction cost plus.estimated cost for other
allowances factors.
"Percentages added to estimated construction cost <
7-21
-------
The capital cost estimates are based on "greenfield" construction; that is, construction that
is not hindered by site constraints, does not require the acquisition of land, and that can be easily
interfaced with existing facilities without demolition. Estimates of greenfield adjustment factors
are provided in Section 7.7.
. O&M costs were computed.on an annual basis and include the costs for materials, labor,
and chemicals. As noted above, labor costs for small systems was calculated assuming a "medium"
level of attention. .
Total costs include the annual O&M costs and the annual debt service on the facilities at
t
10 percent for 20 years. These costs are combined on an annual basis and converted to a total cost
per 1,000 gallons.
The following units are used for chemical dosages and treatment residuals throughout this
chapter:
Chemical Units
Alum mg/LasAl2(SO4)3ป14H2O
Caustic mg/L as NaOH (100 percent)
Chlorine - mg/L as C12
, Ammonia mg/L as N
Ozone mg/L as 03
Alum Sludge mg/L as dry solids
When costs are developed for different forms of these chemicals, such as dry alum
versus liquid alum or chlorine versus sodium hypochlorite, the appropriate conversion factors are
applied. All estimated chemical dosages are based on the volume of water treated. Similarly,
sludge production estimates are given as milligrams of dry solids produced per liter of raw water
treated.
7-22
-------
7.5 COST ESCALATION FACTORS
i
7.5.1 Capital Cost Escalation
Capital costs from the 1992 Technologies and Costs document were expressed in Fall
1991 dollars. The Engineering News Record's (ENR) Building Cost Index (BCI) was used to
i
escalate the cost estimates to Summer 1997 dollars. The decision to use the BCI as the basis for
escalation came after an extensive analysis of many different indices including the following:
ENR's Construction Cost Index (CCI), Bureau of Labor Statistics (BLS) Producer Price Index
(PPI) for Finished Goods, Materials and Components for Construction and individual BLS indices
for general purpose machinery, concrete, steel, pipe and valves, and electrical. The analysis
demonstrated a significant disparity between the BLS indices and the ENR's indices. The decision
to base the escalation factor for capital cost on one of the ENR indices was made because this
method reduces the chance of error in developing an overall weighted average of individual -
indices. Both the CCI and BCI contain the necessary, components in the estimation of capital costs
including the following: the use 25 cwt (hundred weight) of fabricated standard steel (based on
a 20-city average); 1,128 tons bulk portland cement; and 1,088 board-feet of 2"x 4" lumber. The
major difference and the basis for the elimination of the CCI from use as the basis of escalation is
i
in the content and type of labor. The CCI includes in its index 200 hours of common labor versus
the BCI's 68.38 hours of skilled labor. The CCI's labor content was considered to be too high
for use as the basis for capital escalation. The use of the BCI as the capital cost escalation factor,
due largely to its lower content of labor, provides a more realistic estimation of cost movement
over the last several years. As shown in Table 7-6, the ENR BCI indicates an escalation factor of
23 percent from Fall 1991 to Summer 1997. This escalation factor was applied to the following
technologies:
Base Plant (Table 7-7);
""
Chloramines as a secondary disinfectant (Table 7-9);
Increasing coagulant dosage (Table 7-10); ,
7-23
-------
Enhanced precipitative softening (Table 7-11);
Installation of GAC adsorption (Table 7-14); and
Installation of membrane filtration systems, small systems only (Table 7-15).
TABLE 7-6
INDICES USED IN THE ESCALATION OF COSTS
DESCRIPTION
Building Cost Indei
Chemical & Allied Products
Skilled Labor
Materials
Utility Natural 17aซ
INDEX
REFERENCE
ENR1
BLS2
ENR1 .
ENR1
RI <\ flSS 2
NUMERICAL
VALUE .
3391.86
147.2
5231.35
2268.57
1111
ESCALATION
VALUE
1.23
1.19
1.178
1.328
1 A7O
Engineering News Record (July, 1997)
2 Bureau of Labor Statistics (March, 1997)
7.5.2 Operation & Maintenance Cost Escalation
Operation and maintenance (O&M) costs in the 1992 Technologies and Costs document
were expressed in Fall 1991 dollars. The BLS Chemical and Allied Products Index was used as
the basis for the escalation cost estimates for the following technologies:
Base Plant costs (Table 7-7);
Chloramines as a secondary disinfectant (Table 7-9);
Increasing coagulant dosage (Table 7-10); and
Enhanced precipitative softening (Table 7-11).
The driving component of O&M costs in the preceding technologies was considered to be
the chemicals used in each process. Additional O&M cost components include: materials, power,
and labor but are less weighted in the overall O&M process. The decision' to use the BLS's
7-24
-------
Chemical and Allied Products Index was based on this determination. Further, the Chemical and
Allied Products Index provides a conservative estimate of O&M cpsts.
The method used to develop an escalation factor for GAC O&M costs is provided in the
discussion of GAC upgrade costs (Section 7.6.8).
7.6 DESIGN CRITERIA AND ESTIMATED COSTS FOR TREATMENT
UPGRADES
7.6.1 Base Treatment Plant .
As described'in Section 7.3, a base treatment plant is used to generate the baseline
i
treatment costs from which all the treatment upgrade costs will be computed. The base plant is
/
represented by a conventional treatment plant using a chlorine/chlorine disinfection strategy. A
schematic of the base plant was shown in Figure 7-1. For this system, an alum dose of 30 mg/L
was assumed. This alum dose does not necessarily represent current conditions; but rather'was
chosen in order to simplify the cost analysis. The design criteria and general engineering
assumptions for the base plant were presented in Tables 7-3 and 7-4 for small and large systems,
respectively.
Estimated capital, O&M and total costs per 1,000 gallons are shown in Table 7-7 for EPA's
13 flow categories and divided into small and large systems. These costs represent the baseline
total costs from which upgrade costs for DBF control alternatives will be generated.
7-25
-------
FIGURE 7-1
ALUM COAGULATION / FILTRATION BASE PLANT
Rapid
Mix
Flocculation
& Clarification
Filtration Contact Storage
Basin
-------
TABLE 7-7
ESTIMATED BASE PLANT COSTS
SMALL SYSTEMS
Design
Flow
(mgd)
0.024
0.087
0.27
Capital
Cost1
($M)
0.63
0.86
1.4
O&M
Cost2
ซ/1000 eal)
600
188
90
Costฎ 3%
ft/1000 gal)
2672
848
390
Costฎ 7%
ft/1000 gal)
3509
1115
496
Cost @ 10%
ft/1000 aal)
4233
1343
605
========
Design
Flow
(mgd)
1.8
4.8
11
18 .
26
51
210
430
520
sss^sssss^sss^sss^^sss:^si
Capital
Cost1
KM)
4.3
7.3
. 12
17
22
36
120
230
iซn
LARGE SYSTEMS
O&M
Cost2
ft/1000 gaD
74
47
39
36
35
33
32
31
Total
Costฎ 3%
ft/1000 eal)
187
111
83
72
66
58
50
47
i*
Total
Costฎ 7%
(#1000 gal)
233
137
102
86
78
68
58
53
54
Total
Costฎ 10%
ft/1000 gal)
272
159
118
98
89
76
65
59
1 6j D
j[ ~yj I VsVJOl WOWCUCILWW isM0**w **!*%*ป ซป. - - -
21991 Cost escalated based upon a factor of 1.19 derived from the BLS Chemical and
Allied Products Index
7-26
-------
7.6.2 Move Point of Chlorination
The schematic of the base plant in Figure 7-1 assumes that point of chlorination has already
been moved. A plant practicing pre-chlorination (not shown schematically) would most likely apply
chlorine to the rapid mix basin. Systems that move the point of chlorine addition further into the
treatment plant must compensate for the disinfection that had been achieved in the sedimentation
basin by increasing the chlorine contact time after the filters and/or increasing the post-filter chlorine
dose.
Design criteria are not provided for this DBF control alternative; however, upgrade costs for
different sizes of contact basins are shown in Table 7-8. The basins are assumed to be well-baffled.
7.6.3 Switching to Chloramines as a Secondary Disinfectant
The only difference between this alternative and the base plant is the ammonia feed system
located after the contact basin (see Figure 7-2). Ammonia is added after primary disinfection is
achieved with free chlorine. A residual chlorine to ammonia ratio of 4:1 was selected to:
Reduce the amount of excess ammonia entering the distribution system thereby
controlling the growth of nitrifying bacteria; and
Reduce the formation of dichloramine and trichloramine which lead to taste and odor
complaints.
A pH of 8.2 used in the distribution system is considered to be suitable for rapid formation
of monochloramine. The median design criteria predicted by the WTP model and used to develop
upgrade costs for switching to chloramines are shown below:
TABLE 7-7(a)
MEDIAN DESIGN CRITERIA VIA WTP MODEL
Predicted Design Criteria
Chlorine Dose
(mt
Ammonia Dose
Caustic Dose
(mR/L)
Contact Basin
Size(min)
Solids Production
(mg/L)
7-27
-------
FIGURE 7-2
ALUM COAGULATION / FILTRATION SYSTEM
UPGRADED WITH
CHLORINE/ CHLORAMINE DISINFECTION
Alum
Caustic
Ammonia
Rapid Flocculation
Mix & Clarification
Rltration Contact Storage
Basin
CHLORAMINATION PROCEDURE
Ammonia Dose Based on 4:1 Chlorine Residual to Ammonia Ratio
-------
TABLE 7-8
ESTIMATED UPGRADE COSTS
FOR ADDITIONAL CONTACT BASIN SIZE (x $1000)'
DESIGN
FLOW
0.024
0.087
0.27
0.65
1.8
4.8
11
18
26
51
210
430
s?n
30 min
14
25
52
77
197
274
432
611
815
1,454
5514
11,132
n i7d
60 min
21
34
80
112
244
396
713
1,070 .
1,478
2,755
10,876
22,112
7ฃ A7Q
Chlorine Contact Basin Time
120 min
26
66
103
218
335
642
1,274
1,990
2,807
5,360
21,600
44,071
51 99d
180 min
28
76
140
251
427
887
1,836
2,909
4,135
7,965
32,324
- 66,031
70 78 S
240 min
38
82
180
284
519
1,132
2,399
3,828
5,462
10,569
43,050
87,991
IftA 1^0
300 min
46
84
220
317
611
1,376
2,961
4,748
6,791
13,175
53,774
109,951
1*31 1 O*3
360 min
55
100
234
351
702
1622
3521
5667
8118
15,778-
64,499
131,910
1 &O Aซ
ivy i tx>st escalated based upon a actor of 1.23 derived from the ENR BCI
7-28
-------
It is important to note that the median contact basin size predicted by the WTP model for
this treatment system was 30 minutes; however, a 60-minute contact basin size is used for cost
purposes The 30-minute contact basin represented the actual median value predicted by the
-modeling analysis while 60 minutes represents the basin size used in the base plant .analysis. The
predicted basin size was smaller for this alternative because a higher chlorine residual was maintained
through the contact basin, before ammonia addition, in order to meet a 2 mg/L chloramine residual
constraint at the end of the distribution system. As a result of the higher chlorine residuals, the
predicted contact times necessary to meet primary disinfection requirements were lower for this
disinfection alternative. Because monochioramine reduces the rate of TTHM formation in the
distribution system, these higher residuals are feasible with CyNH2Cl disinfection but are not feasible
with C12/C12 disinfection. .
The 60-miriute basin size'is used to generate capital and total costs so that upgrade costs
only reflect those costs associated with the addition of the ammonia feed system. Because upgrade
costs are calculated by subtracting total costs of the upgraded plant from the base plant, the smaller
basin size would reduce the cost of the upgrade. In order to. eliminate this effect, the contact time
for this alternative is the same as the base plant.
For small systems, the ammonia feed system is based on the use of ammonium sulfate. The
1 *
system includes 10-day storage tanks, dissolving and mixing tank, metering pumps, piping, valves,
electrical and instrumentation. For large systems the ammonia feed system is based on the use of
aqua ammonia. The system includes usable storage for ten days, piping, valves, metering pumps,
electrical and instrumentation. Aqua ammonia is stored in a horizontal pressure vessel with
i
length/width ratio of 3:1. . . ,
The upgrade costs for EPA's 13 flow categories are provided in Table 7-9. Generally,
these upgrade costs represent the costs for an ammonia feed system and chemical costs for ammonia
s
and additional chlorine. .
7.6.4 Increased Coagulant Dosage
Enhanced coagulation is a regulatory-based definition for improving the removal of TOC
and DBF precursors through coagulation, flocculation and sedimentation processes. There are many
methods to improve removals in coagulation, such as changing the coagulant type (e.g., from alum
7-29
-------
to ferric chloride), increasing coagulant dosages, and lowering the pH of coagulation For the
purpose of this'document, costs were only developed for increasing the coagulant dosage. This was
done because this is typically the method of operation a utility would consider first when attempting
to improve organic removal by coagulation. .Other alternatives will be evaluated as different
constraints (e.g., sludge disposal option) become limiting. Secondary effects of enhanced softening
are being addressed in detail in another EPA document currently in progress entitled, "Guidance
Manual for Enhanced Coagulation and Enhanced Precipitative Softening."
Enhanced coagulation was modeled by increasing the coagulant dosage to improve NOM
removal. For this analysis, upgrade costs for increasing the alum dosage by 40 mg/L were generated.
Because design criteria and treatment costs had been generated before this analysis at alum dosages
of 10, 30 and 50 mg/L, it was decided that upgrade costs would be generated using the total costs
computed for the 10 mg/L and 50 mg/L dosages. In order to generate costs with these two dosages,
the 10 mg/L alum dosage is assumed to be the base plant in this analysis. Upgrade costs then
represent the difference in total costs between an alum dose of 10 and 50 mg/L, or an increase of 40
mg/L. The Water Industry Database (AWWA, 1992) indicates an average alum dose of
approximately 15 mg/L.
The 40 mg/L increase in alum dosage used in this document for cost purposes is likely a
conservative case. Many recent studies (Malcolm Pimie, Inc., 1997) indicate that lower incremental
dosages are required by utilities, or that utilities can use smaller dosage increases together with
reducing pH at lower total costs than those associated with increasing the dosage by 40 mg/L.
Therefore, these costs may ne slightly conservative, but provide a reasonable upper estimate for
enhanced coagulation.
A schematic of this treatment upgrade is not shown because the only difference between
this system and -the base plant (see Figure 7-1) is the increased alum dosage.
The median design criteria used to develop upgrade costs for increasing alum dosages are
shown below:
7-30
-------
Alum Dosage
(me
Design
Flow
Chlorine Dose
(ml
Caustic Dose
(me
Contact Basin
Size (min)
Solids
Production
(me
TABLE 7-9
ESTIMATED UPGRADE COSTS FOR
CHLORAMINES AS SECONDARY DISINFECTANT
Capital
Cost1
SMALL SYSTEMS
Total
Costฎ 3%
O&M
Cost2
Total
Costฎ 7%
LARGE SYSTEMS
Total
Costฎ 3%
Allied Products Index
7-31
-------
As shown above the contact basin size is the same for both alum dosages. It should be noted
that the predicted basin size for an alum dosage of 50 ma/L was 45 minutes; however, 60 minutes is
used for the same reason cited in the previous section. The smaller basin size for the higher alum
dosage is a result of removing more of the chlorine demand so that higher residuals can be maintained
at the end of the contact basin.
As expected, solids production increases from an alum dose of 10 to 50 mg/L. Additionally,
because alum consumes alkalinity, thus lowering the pH, a greater caustic dosage is required for
increased alum dosages in order to raise the pH to meet the distribution.system pH requirements
Table 7-10 shows the upgrade capital, O&M and total costs for systems using an increased
alum dosage for EPA's 13 flow categories.
As noted in Section 7.3, every system utilizes thickening/dewatering lagoons for solids
handling. A survey (AWWA, 1992) supports this assumption with about 68 percent of surface water
plants (serving greater than 10,000 people) reporting the use of lagoons for either thickening and/or
dewatering. It is difficult, however, to predict how systems would handle additional solids production
because of site-specific conditions, namely the availability of land for additional lagoons. For this
analysis, it is assumed that necessary land is available at the existing solids handling location. As a
result, upgrade costs include the expansion of the existing lagoons, disposal of additional solids, and
additional alum and caustic usage.
If additional land is not- available, plants would be required to add mechanical
thickening/dewatering devices such as gravity thickeners and centrifuges or filter presses. The total
cost of this modification could be significant, particularly if a plant must discontinue the use of the
dewatering lagoons and implement mechanical dewatering.
7-32
-------
TABLE 7-10
ESTIMATED UPGRADE COSTS FOR
INCREASING COAGULANT DOSAGE
SMALL SYSTEMS
Design
Flow
(med)
0.024
0.087
0.27
OfiS
Capital
Cost1
(SM)
0.001
0.003
0.006
nmi
O&M
Cost2
ft/1000 eal)
10
10
10
10
Total
Cost @ 3%
(tf/1000 eal)
13
12
11.3
100
Total
Costฎ 7%
tf /1000 eaD
15
13
12
ll
Total
Cost @ 10%
tt/1000 eal)
16
14
13
19
LARGE SYSTEMS
Design
Flow
(med)
1.8
4.8
11
18
26
51
210
430
S90
Capital
Cost1
(San
0.08
0.14
0.18
0.26
0.36
0.64
1.4
2.7
*ฃ
O&M
Cost2
(01000 eal)
6.3
5.9
5.8
5.7
5.7
5.7
5.6
5.6
Sfi
Total
Costฎ 3%
tt/1000 eal)
8.4
7.1
6.5
6.2
6.2
6.1
5.8
5.8
SR
Total
C08t@ 7%
ซ/1000eaI)
9.1
7.7
7.0
6.8
6.7
6.6
6.3
6.3
61
Total
Cost @ 10%
(#1000 eal)
9.8
8.1
7.2
7.0
6.9
6.8
6.4
6.3
fiT
1 1991 Cost escalated based upon a factor of 1.23 derived from the ENR BCI
21991 Cost escalated based upon a factor of 1.19 derived from the BLS Chemical and
Allied Products Index
7-33
-------
7.6.5 Enhanced Precipitative Softening
Costs for precipitative softening were not provided in the 1992 version of this document
because a sufficiently-refined treatment simulation model for such systems was not available to
provide input to developing national costs. During regulatory negotiations, it was understood that
costs were necessary because the .number of individuals served by systems that use lime softening is
not insignificant. As a result, the Technologies Working Group developed costs for this upgrade, as
discussed in this section.
t
As with systems that use conventional coagulation, costs will vary significantly according to
the type of softening performed (e.g. magnesium versus calcium removal), the manner in which lime
is handled (e.g. purchased in bulk versus recalculated) and the method of sludge disposal. For the
purposes of determining national costs, it was assumed that the costs for enhancing TOC removal by
precipitative lime softening was 25 percent greater than for enhanced coagulation, to account for the
increased cost in chemical addition (i.e., lime, soda ash, and potentially metal coagulants) and sludge
handling. Capital, O&M and total upgrade costs for enhanced precipitative softening are presented
in Table 7-11.
7.6.6 Switching to Ozone for Primary Disinfection
This treatment alternative is shown schematically in Figure 7-3. The difference between this
alternative and the base plant is the replacement of chlorine by ozone as the primary disinfectant and
the replacement of chlorine by chloramines as the secondary
7-34
-------
Design
Flow
TABLE 7-11
ESTIMATED UPGRADE COSTS FOR
ENHANCED PRECIPITATiV E SOFTENING
SMALL SYSTEMS
Capital
Cost1
(SM)
O&M
Cost2
(#1000 gal)
Total
Costฎ 3%
(#1000 gal)
Total
Costฎ 7%
K/lOOOgal)
LARGE SYSTEMS
Total .
Cost @ 10%
tt/lOOOgal)
=^=:^
Design
Flow
(mgd)
1.8
4.8
11
18
26
51
210
430
L52Q
Capital
Cost1
(SM)
0.10
0.16
0.23
0.33
0.45
0.80
1.7
3.4
I 40
O&M
Cost2
tt/1000 gal)
7.5
7.5
7.5
7.5
7.5
7.5
7.5
7.5
L=^5
=====1
Total
Costฎ 3%
tt/1000 gal)
10
8.9
8.4
8.2
8.1
8.0
7.8
7.7
7 7
Total
Costฎ 7%
tt/1000 gal)
11
9.6
8.7
8.4
8.4
8.3
7.9
7.8
1 78
_ TTVTD TS/"
-------
disinfectant The location of primary disinfection for this model system is between sedimentation and
filtration The purpose of providing filtration after ozonation is to allow biological removal of
. biodegradable dissolved organic carbon (BDOC) within the filters. As noted in Chapters 2 and 6,
ozone can significantly increase the BDOC content of a given water.
Costs for ozone system installation and upgrade were developed using data from a 1997
International Ozone Association (IOA) survey of water treatment plants currently utilizing or
constructing ozone systems and from Langlais et al. (1991).
Design criteria presented in this discussion are based upon three specific treatment scenarios.
Giardia log-inactivation was the primary factor considered in developing design criteria. A summary
of each design scenario is presented below.
Giardia log-inactivation of 1, consisting of a theoretical hydraulic detention time
of 10 minutes, and an ozone dosage of 2 mg/L;
Giardia log-inactivation of 3, consisting of a theoretical hydraulic detention time
of 10 minutes, and an ozone dosage of 5 mg/L; and
Giardia log-inactivation of 5, consisting of a theoretical hydraulic detention time
of 10 minutes, and an ozone dosage of 7 mg/L.
Design criteria were specified for each of the 13 EPA flow categories and were based
upon typical operating scenarios presented in the IOA survey and Langlais, et al. (1991). For
each scenario evaluated, the following assumptions were made:
All estimates are assumed for oxygen-based systems;
At design flow, ozone generators are operated at 75% of maximum capacity;
Design temperature is 5ฐ C; and
Two parallel contactors are utilized, each treating one-half the design flow.
Costs were developed for each of the 13 EPA flow categories. Larger systems (>1 mgd)
capital and O&M costs were developed using estimation techniques presented by Langlais, et al.
(1991). Small systems (<1 mgd) capital and operation and maintenance (O&M) costs were
7-36
-------
developed using data from a 1997 International Ozone Association (IOA) survey of water treatment
plants currently using or constructing an ozone system. All capital costs are based on design-flows
and dosages
Capital costs for large systems include equipment costs for ozone generation equipment
(including air preparation system), ozone destruction equipment (thermal unit with heat recovery),
piping, valves, instrumentation, disc-type diffusers, control system, and installation. All systems
evaluated by Langlias, et al. (1991) used air-based generation equipment. Costs for the ozone
diffusion system and control systems have been estimated at 5 and 20 percent of the total cost,
respectively. Capital costs also include contactor basin equipment costs. The systems include two
basins constructed in parallel, each designed to treat one-half of the design flow. .Contactor costs
include estimates for both contactors, concrete support structures, stainless steel piping and
installation, drains, baffles and other miscellaneous expenses. Finally, capital costs include equipment
i
housing costs. Surveys indicate there is a wide range of unit area for a given ozone production rate,
due to engineer design or owner preference rather than equipment need. Based upon survey results,
the average housing size for various levels of ozone production (i.e. ft2/lb ozone produced) was used
to develop housing costs. A national average of $50 per square foot was used. Capital cost estimates
for large systems can be found in Table 7-12.
Estimation techniques for small systems have not yet been refined. For these systems, IOA
survey data was utilized. A range of capital costs for a variety of small systems was presented in the
i
IOA survey results. A conservative approach was taken and the maximum capital cost for a given
flow was used for estimating purposes.. All systems evaluated by the IOA used oxygen-based
generation equipment. Table 7-12 presents capital cost estimates for small systems.
7-37
-------
FIGURE 7-3
ALUM COAGULATION / FILTRATION SYSTEMS
UPGRADED WITH
OZONE/CHLORAMINE DISINFECTION
- Caustic
Chlorine
Ammonia
Rapid Flocculation
Mix & Clarification
Ozone
Filtration
Storage
CHLORAMINATION PROCEDURE
Free Chlorine Contact for 1 Minute at
Peak Hourly Flow Prior to Ammonia Addition
Ammonia Dose Based on 4:1 Chlorine Residual to Ammonia Ratio
-------
TABLE 7- 12
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR OZONE AS PRIMARY DISINFECTANT - SMALL SYSTEMS
Design
Flow
(mgd)
0.024
0.086
0.27
0.65
=====
Design
Flow
(mgd)
0.024
0.086
0.27
0.65
Log Inactivation = 1
Upgrade
Capital
Cost
($M)
0.22
0.24
0.29
0.39
Upgrade
O&M
Cost
(eVIOOOgal)
161
38
10
3.9
1
Total
Upgrade
Costฎ 3%
(#1000 gal)
885
222
72
35
L^^^^s^s^s
MBซB ซJ^ ^ ^^^ fc
Log Inactivation ซ1
Upgrade
Capital
Cost
($M)
0.22
0.24
0.29
0.39
Upgrade
O&M
Cost
(#1000 gal)
161
38
10
3.9
^^ ^ ^
Total
Upgrade
Costฎ 7%
(#1000 gal)
1177
297
97
48
Log Inactivation = 3
Upgrade
Capital
Cost
(SM)
0.23
0.28
0.40
0.64
!===i
Upgrade
O&M
Cost
Of/1000 gal)
322
75
21
7.8
!==5=d
Total
Upgrade
Costฎ 3%
(#1000 gal)
1078
290
107
59
Log Inactivation * 3
Upgrade
Capital
Cost
(SM)
0.23
0.28
0.40
0.64
Upgrade
O&M
Cost
(#1000 gal)
322
75
21
7.8
Total
Upgrade
Costฎ 7%
(#1000 gal)
1384
377
145
81
Log Inactivation =
Upgrade
Capital
Cost
($M)
0.24
0.30
0.47
0.80
Upgrade
O&M
Cost
(#1000 gal)
644
150
42
16
Log Inactivation !
Upgrade
Capital
Cost
(SM)
0.24
0.30
0.47
0.80
Upgrade
O&M
Cost
(#1000 gal)
644
150
42
16
= 5
Total
Upgrade
Cost @ 3%
(ft/1000 gal)
1433
380
143
80
= 5
Total
Upgrade
Costฎ 7%
(#1000 gal)
1752
473
183
106
7-38
-------
TABLE 7- 12 (cont)
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR OZONE AS PRIMARY DISINFECTANT - SMALL SYSTEMS
Design .
1ft mv
(ragd)
0.024
0.086
0.27
0.6S
Log Inactivation =
Upgrade
Capital
Cost
($M)
0.22
. 0.24
0.29
0.39
Upgrade
O&M
Cost
(eVIOOO gal)
161
38
10
3.9
= 1
Total
Upgrade
Cost @ 10%
(eVIOOO gal)
1442
361
119
59
Log Inactivation = 3
Upgrade
Capital
Cost
(SM)
0.23
0.28
0.40
0.64
Upgrade
O&M
Cost
(CV1000 gal)
322
75
21
7.8
Total
Upgrade
Cost @ 10%
(eVIOOO gal)
1661
445
170
98
Log Inactivation = 5
Upgrade
Capital
Cost
<$M)
0.24
0.30
0.47
080
Upgrade
O&M
Cost
(eVIOOO gal)
644
150
42
16
Total
Upgrade
Cost @ 10%
(eVIOOO gal)
2023
551
217
128
7-39
-------
TABLE 7- 12 (cont.)
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR OZONE AS PRIMARY DISINFECTANT
LARGE SYSTEMS
Log Inactivation
Loglnactivation
Log Inactivation
Total
Upgrade
Cost @ 3%
(if/1000 gal)
Upgrade
O&M
Cost
(l/1000gal)
Upgrade
Capital
Cost
Total
Upgrade
Upgrade
O&M
Cost
(it/1000 gal)
Upgrade
Capital
Cost
Upgrade
Costฎ 3%
(#1000 gal)
7-40
-------
TABLE 7- 12 (cont.)
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR OZONE AS PRIMARY DISINFECTANT
LARGE SYSTEMS
Design
Flow
(mgd)
1.8
.4.8
11
18
26
51
210
430
520
Loglnactivatton<=l
Upgrade
Capital
Cost
(SM)
0.89
1.5
. . 1.9
2.4
2.6
3.8
9.2
16.5
20
Upgrade
O&M
Cost
0/1000 gal)
1.8
1.8
1.8
1.8
1.8
1.8
1.8
1.8-
1.8
Total .
Upgrade
Costฎ 7%
0/1000 gal)
35
21
12
8.9
7.2
5.6
4.0
3.6
3.4
Log Inactivation = 3
Upgrade
Capital
Cost
(SM)
1.5
1.9
2.6
3.0
3.9
6.2
18
35
42
Upgrade
O&M
Cost
ft/1000 gal)
4.4
4.4
4.4
4.4
4.4
4.4
4.4
4.4
4.4
Total
Upgrade
Costฎ 7%
0/1000 gal)
58
28
17
13
12
10
7.8
7.4
6.1
Log Inactivation = 5
Upgrade
Capital
Cost
(SM)
1.4
2.0
2.8
3.7
4.8
7.4
24
47
57
Upgrade
O&M
Cost
0/1000 gal)
6.3
6.3
6.3
6.3
6.3
6.3
6.3
6.3
6.3
Total
Upgrade
Cost @ 7%
0/1000 gal)
56
31
'21
17
15
13
11
11
10
7-41
-------
TABLE 7- 12 (cont.)
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR OZONE AS PRIMARY DISINFECTANT
LARGE SYSTEMS
=====
Design
Flow
(mgd)
1.8
4.8
11
18
26
SI
210
430
520
1 = =
Loglnactivation=l
Upgrade
Capital
Cost
(SM)
0.89
1.5
1.9
2.4
2.6
3.8
9.2
16
20
=====
Upgrade
O&M
Cost
(eVIOOOgal)
1.8
1.8
1.8
. 1.8
1.8
1.8
1.8
1.8
1.8
======
Total
Upgrade
Cost $10%
(eVIOOOgal)
43
26
14
11
8.4
6.5
4.5
4.0
3.6
=====
LogInactivatfonB3
Upgrade
Capital
Cost
(SM)
1.5
1.9
2.6
3.0
3.9
6.2
18
35-
42
1==
Upgrade
O&M
Cost
(eVIOOOgal)
4.4
4.4
4.4
4.4
4.4
4.4
4.4
4.4
4.4
=====
Total
Upgrade
Costฎ 10%
(>t/1000 gal)
72
34
21
15
14
11
8.7
8.2
8.2
Log Inactivation -
Upgrade
Capital
Cost
(SM)
1.4
2.0
2.8
3.7
4.8
7.4
24
47
57
Upgrade
O&M
Cost
tf/1000 gal)
6.3
6.3
6.3
6.3
6.3
6.3
6.3
6.3
6.3
= 5
Total
Upgrade
Cost @ 10%
(#1000 gal)
69
37
24
20
18
15
12
12
10
7-42
-------
O&M costs for both large arid small systems were developed based upon the annual average
flow for each of the EPA flow categories, and annual average ozone dose (assumed to be the design
dosage for estimation purposes). A list of O&M cost assumptions for large systems is presented
below.
Giardia log-inactivation values of 1, 3 and 5;
Estimated system specific energy is 10 kWh/lb;
\
Energy cost is assumed $0.07/kWh (Energy Information Administration
1997);
Energy costs account for 65% of total O&M costs (Langlais, et al.); and
"Other O&M Costs" including labor, equipment maintenance, etc. make
up the remaining 35% of total O&M costs (Langlais, et al.).
Note that "Other O&M Costs" for large systems are typically 25 to 35 percent of total O&M
costs. For the purpose of this document, a conservative estimate of 3 5% hais been used. O&M cost
i
estimates for large systems are presented in Table 7-12.
For small systems, O&M cost estimates were calculated in the exact manner as large
systems. These results were evaluated against IOA survey data, and deemed comparable. In all
cases, the calculated O&M cost estimate was more conservative, yet reasonably close to the survey
data. Because O&M cost estimates for small systems are so modest, the more conservative,
calculated estimates are presented here. O&M cost estimates for small systems are included, along
with the large system estimates, in Table 7-12.
Cost estimates for large systems generated using the method described in Langlais, et al.
(1991) were compared with IOA survey data. It was found that the calculated estimates fell within
the range of actual costs presented in the IOA survey. The most important factors affecting this
estimation technique are detention time and ozone dosage, which are based upon desired level of
disinfection. These design parameters are significantly influenced by pH and temperature because
they affect the ozone decay rate. Increases in temperature and pH generally cause more rapid decay
of ozone, thus affecting its disinfection capabilities.
7-43
-------
The accuracy of small systems cost estimates is largely dependent upon the completeness
of the 10 A survey data. Omissions by respondents to the survey are considered to be negligible,
and when taken as a whole have no significant impact on the estimation techniques utilized in this
document.
7.6.7 Switching to Chlorine Dioxide as Primary Disinfectant
' Chlorine dioxide is an effective oxidant/disinfectaht frequently used to control THM
concentration. However, controlling the formation of both chlorite and chlorate ions presents
considerable obstacle in chlorine dioxide treatment implementation. To control byproduct
formation, the chlorine dioxide dosage was limited to 1 mg/L.
Typically, chlorine dioxide is produced by mixing a high strength chlorine solution with a
high strength sodium chlorite solution. The reaction generally takes place in a PVC chamber, filled
with porcelain rings, and designed for a detention type of approximately 0.2 minutes. 1.7 pounds
of sodium chlorite are required for each pound of chlorine dioxide to be generated.
Typical requirements of a chlorine dioxide generation system include sodium chlorite mixing
and metering systems, chlorine dioxide generators, and other miscellaneous storage, mixing and
metering systems.
The design criteria for which the capital and O&M costs have been developed are based
upon three specific treatment scenarios. Giardia log-inactivation was the primary factor considered
in developing these design criteria. A summary of each scenario is presented below:
. Giardia log-inactivation of 1, involving a theoretical contact time of 60 minutes (included
in Base Plant) and a chlorine dioxide dosage of 0.5 mg/L;
. Giardia lo^inactivation of 3, involving a theoretical contact time of 60 minutes (included
in Base Plant) and a chlorine dioxide dosage of 1.0 mg/L; and
. Giardia log-inactivation of 5, involving a theoretical contact time of 120 minutes (60
minutes in addition to the Base Plant) and a chlorine dioxide dosage of 1.0 mg/L.
7-44
-------
TABLE 7-13
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR CHLORINE DIOXIDE AS PRIMARY DISINFECTANT
(MANUAL GENERATOR)
SMALL SYSTEMS
Design
Flow
(mgd)
0.024
0.087
0.27
Oฃ*
Design
Flow
(mgd)
0.024
0.087
0.27
(\M
Lo2 Inactivatio
Upgrade
Capital
Cost*"
(SM)
0.10
0.10
0.10
n in
Upgrade
Capital
Cost'"
(SM)
0.10
0.10
0.10
n in
Upgrade
O&M
Cost
(eVIOOOeal)
1929
452
128
4Q
Total
Upgrade Cost
@ 3%
(tYlOOOEal)
2258
529
149
S7
LOB Inactivation ป 1
Upgrade
O&M
Cost
ftVlOOOeal)
1929
452
128
4Q
Total
Upgrade Cost
@7%
(tVlOOOeal)
2391
560
158
fin
Lo
Upgrade
Capital
Corf"
(SM)
0.10
0.10
0.10
n in
Lot
Upgrade
Capital
Cost0'
(SM)
0.10
0.10
0.10
n in
e Inactivation * 3
Upgrade
O&M
Cost
ft/lOOOeal)
1934
456
132
ซ
E Inactivation =
Upgrade
O&M
Cost
(^/lOOOean
1934
456
132
s?
Total
Upgrade
Costฎ 3%
tf/lOOOeal)
2263
533
153
60
ป3
Total
Upgrade
Cost @ 7%
(eVlOOOeal)
2396
564
162
M
LOB Inactivation = 5
Upgrade
Capital
Cost
(SM)
0.13
0.15
0.22
njปs
. Lc
Upgrade
Capital
Corf"
(SM)
0.13
0.15
0.22
098
Upgrade
O&M
Cost
(ฃY1000eaD
1934
456
132
S7
Total
Upgrade
Cost @ 3%
(1/lOOOgal)
2362
571
179
74
te Inactivation = 5
Upgrade
O&M
Cost
(l/lOOOeal)
1934
456
132
S7
Total
Upgrade
Costฎ 7%
(eVIOOOeal)
2534
618
198
ft\
7-45
-------
TABLE 7-13 (cont)
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR CHLORINE DIOXIDE AS PRIMARY DISINFECTANT
(MANUAL GENERATOR)
SMALL SYSTEMS
Design
Flow
(mgd)
Upgrade
Capital
Cost
($M)
Upgrade
O&M
Cost
Wit
1929
452
128
Total
Upgrade Cost
@ 10 %
Upgrade
Capital
Cost**
Upgrade
O&M
Cost
Total
Upgrade
Costฎ 10%
Upgrade
Capital
Corf"
Upgrade
O&M
Cost
(eVIOOOgal)
Total
Upgrade
Cost @ 10%
rt/lpOOgal)
7-46
-------
TABLE 7-13 (cont.)
' ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR CHLORINE DIOXIDE AS PRIMARY DISINFECTANT
(AUTOMATIC GENERATOR)
SMALL SYSTEMS
Design
Flow
(mgd)
0.024
0.087
0.27
n*s
Design
Flow
(mgd)
0.024
0.087
0.27
OfiS
Upgrade
Capital
Cost">
(SM)
0.33 .
0.33
0.33
n n
Upgrade
Capital
Cost"*
(SM)
0.33
0.33
0.33
oil
-02 Inactivation
Upgrade
O&M
Cost
(eVlOOOeal)
1548
364
104
40
Loe Inactivation
Upgrade
O&M
Cost
(eVlOOOeal)
1S48
364
104
An
ซ1
Total
Upgrade
Costฎ 3%
{eVlOOOeal)
2633
617
175
f.f.
= 1
Total
Upgrade
Costฎ 7%
(eVlOOOeal)
3072
720
203
77
Lo
Upgrade
Capital
Cost*0
(SM)
0.33
0.33
0.33
n 11
e Inactivation B 3
Upgrade
O&M
Cost
(eVlOOOeal)
1552
367
107
41
Total
Upgrade
Cost @ 3%
(eVlOOOeal)
2637
620
178
69
Lop Inactivation ป 3
Upgrade 1 Upgrade
Capital
Cost"'
(SM)
0.33
0.33
0.33
n 11
O&M
Cost
(eVlOOOeal)
1552
367
107
di
Total
Upgrade
Costฎ 7%
(eVlOOOeal)
3076
723
206
80
LOB Inactivation = 5
Upgrade
Capital
Cost
(SM)
0.37
0.39
0.47
n s?
Upgrade
O&M
Cost
(eVlOOOeal)
1552
367
107
41
total
Upgrade
Cost @ 3%
(eVlOOOgal)
2769
666
208
xs
Loe Inactivation = S
Upgrade
Capital
Cost"'
(SM)
0.37
0.39
0.47
0 S9
Upgrade
O&M
Cost
(eVlOOOeal)
1552
367
107
41
Total
Upgrade
Costฎ 7%
(cVlOOOeal)
3261
787
248
101
7-47
-------
Design
Flow
(mgd)
TABLE 7-13 (cent.)
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR CHLORINE DIOXIDE AS PRIMARY DISINFECTANT
(AUTOMATIC GENERATOR)
SMALL SYSTEMS
Upgrade
Capital
Cost0'
Upgrade
O&M
Cost
($M) (tVlOOOgal)
Total
Upgrade
Costฎ 10%
feVlOOOgal) (SM)
Upgrade
Capital
Cost<'>
Upgrade
O&M
Cost
tf/lC
Total
Upgrade
Costฎ 10%
Upgrade
Capital
Corf"
(SM)
Upgrade
O&M
Cost
(tVlOOOgal)
Total
Upgrade
Cost @ 10%
(eVIOOOgal)
(1)ฐ Cost were adjusted to account for an increase in basin contact time from the information reported in Table 7-10
7-48
-------
TABLE 7-13 (cont.)
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR CHLORINE DIOXIDE AS PRIMARY DISINFECTANT
(MANUAL GENERATOR)
LARGE SYSTEMS
Design
Flow
(mgd)
1.8
4.8
11
18
26
51
210
430
570
Upgrade
Capital
Cost*1'
(SM)
0.10
0.10
0.10
0.20
0.20
0.28
0.29
0.35
n is
Loe Inactivation - 1
Upgrade
O&M
Cost
(eVIOOOeal)
18
7.4
4.3
3.8
3.2
2.4
1.8
1.6
1 4
Total
Upgrade
Costฎ 3%
tt/IOOOttl)
20.6
8.3
4.7
4.2
3.5
2.6
1.8
1.6
i d
Loi
Upgrade
Capital
Cost">
(SM)
0.10
0.10
0.10
0.20
0.20
0.28
0.29
0.35
nis
ป Inactivation - 3
Upgrade
O&M
Cost
feVlOOOeal)
20
9.6
6.5
5.8
5.1
4.6
3.6
3.2
? d.
Total
Upgrade
Costฎ 3%
ซ/!OOOaaO
22.6
10.5
6.9
6.2
5.4
4.8
3.6
3.2
7 4
Lo
Upgrade
Capital
COST
(SM)
0.50
0.75
1.3
3.7
5.1
9.4
36
73
80
e. Inactivation - 5
Upgrade
O&M
Cost
(eVIOOOeal)
20
9.6
6.5
5.8
5.1
4.6
3.6
3.2
9
Total
Upgrade
(eVIOOOgal)
33
16
11.3
13.5
12.3
11
9.1
8.2
7 1
7-49
-------
TABLE 7-13 (cont.)
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR CHLORINE DIOXIDE AS PRIMARY DISINFECTANT
(MANUAL GENERATOR)
LARGE SYSTEMS
7-50
-------
TABLE 7-13 (cont.)
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR CHLORINE DIOXIDE AS PRIMARY DISINFECTANT
(MANUAL GENERATOR)
LARGE SYSTEMS
Design
Flow
(mgd)
1.8
4.8
11
18
26
51
210
430
S90
Loe Inactivation
Upgrade
Capital
Costป>
(SM)
0.10
0.10
0.10
0.20
0.20
0.28
0.29
0.35
01S
Upgrade
O&M
Cost
(eYlOOOeal)
18
7.4
4.3
3.8
3.2
2.4
1.8
1.6
1 4
= 1
Total
Upgrade
Cost @ 10%
K/lOOOeal)
22
8.8
4.9
4.5
3.7
2.8
1.9
1.7
1 4
Lo
Upgrade
Capital
Cost<ป
(SM)
0.10
0.10
0.10
0.20
0.20
0.28
0.29
0.35
nis
E Inactivation = 3
Upgrade
O&M
Cost
tf/lOOOeal)
20
10
6.5
5.8
5.1
4.3
3.5
3.2
? A
Total
. Upgrade
Costฎ 10%
(l/lOOOeal)
25
11
7.1
6.5
5.6
4.6
3.6
3.2
> S
Lc
Upgrade
Capital
Cost
(SM)
0.50
0.75
1.3
3.7
5.1
9.4
36
73
80
e Inactivation = 5 '
Upgrade
O&M
Cost
(1/lOOOeal)
20
10
6.5
5.8
5.1
4.3
3.5
3.2
) d
Total
Upgrade
Cost @ 10%
(l/lOOOgal)
43
21
15
19
18
15
13
12
1 1
(l> Cost were adjusted to account for an increase in basin contact time from the information reported in Table 7-10
7-51
-------
TABLE 7-13 (cont.)
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR CHLORINE DIOXIDE AS PRIMARY DISINFECTANT
(AUTOMATIC GENERATOR)
LARGE SYSTEMS
7-52
-------
TABLE 7-13 (cont.)
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR CHLORINE DIOXIDE AS PRIMARY DISINFECTANT
(AUTOMATIC GENERATOR)
LARGE SYSTEMS
Design
Flow
(mgd)
1.8
4.8
11
18
26
SI
210
430
S70
L
Upgrade
Capital
Corf"
($M)
0.33
0.33
0.33
0.68
0.68
0.76
0.77
0.83
ft Q1
on Inactivation = 1
Upgrade
O&M
Cost
(eVlOOOsal)
IS
6.3
3.9
3.3
2.9
2.3
1.8
1.6
i i
Total
Upgrade
Costฎ 7%
(eVIOOOeal)
27
10
5.7
5.0
4.4
2.7
2.2
2.1
JLd
Lo
Upgrade
Capital
Cost*"
(SM)
0.33
O.J3
0.33
0.68
0.68
0.76
0.77
0.83
ft Q1
> Inactivation = 3
Upgrade
O&M
Cost
U/lOOOeal)
17
8.6
6.0
5.3
4.8
4.1
3.5
3.1
t s
Total
Upgrade
Costฎ 7%
tt/lOOOeal)
29
13
7.7
7.0
6.4
4.7
4.2
3.1
7 6
Lo
Upgrade
Capital
Cost*"
(SM)
0.74
0.99
1.5
4.2
5.6
10
37
74
Qft
e Inactivation =
Upgrade
O&M
Cost
(c/lOOOeal)
17
8.6
6.0
5.3
4.8
4.1
3.5
3.1
9 S
= 5
Total
Upgrade
Costฎ 7%
tt/10008al)
44
21
14
17
16
13
12
10
Q 1
(l) Cost were adjusted to account for an increase in basin contact time from the information reported in Table 7-10
7-53
-------
TABLE 7-13 (cont.)
ESTIMATED INSTALLATION AND UPGRADE COSTS
FOR CHLORINE DIOXIDE AS PRIMARY DISINFECTANT
(AUTOMATIC GENERATOR)
LARGE SYSTEMS
Design
Flow
(mgd)
L8
4.8
11
18
26
51
210
430
S90
(l) Cost w
Upgrade
Capital
Cos*1'
(SM)
0.33
0.33
0.33
0.68
0.68
0.76
0.77
0.83
n 01
sre adjusted t<
Upgrade
O&M
Cost
(eVlOOQeal)
IS
6.3
3:9
3.3
2.9
2.3
1.8
1.6
i i
D account for an
Total
Upgrade
Cost @ 10%
(eVIOOOeal)
30
11
6.1
5.5
4.7
2.9
2.2
2.1
1 4
increase in basin
Upgrade
Capital
Cost*0
(SM)
0.33
0.33
0.33
0.68
0.68
0.76
0.77
0.83
n 01
contact time froi
z Inactivation = 3
Upgrade
O&M
Cost
tt/lOOOeal)
17
8.6
6.0
5.3
4.8
4.1
3.5
3.1
9 s
m the informatii
Total
Upgrade
Costฎ 10%
tt/iooosai)
32
14
8.1
7.5
6.7
4.9
4.2
3.1
Lo
Upgrade
Capital
Corf"
(SM)
0.74
0.99
1.5
4.2
5.6
10
37
74
on reported in Table 7-10
glnactivation
Upgrade
O&M
Cost
(tflOOOsal)
17
8.6
6.0
5.3
4.8
4.1
3!
3.1
-5
Upgrade
Cost @ 10%
tf/lOOOaal)
51
24
16
21
I'1..
16
13
12
7-54
-------
The cost information presented in Table 7-13 for chlorine dioxide as a primary disinfectant
/
during water treatment were developed using information presented in a Chlorine Dioxide Cost
Project (1997). The cost assumptions used for all flow categories are presented below.
The building costs for chlorine dioxide systems were estimated to be $75 per square foot.
Building size is dependent upon the generation equipment necessary to produce the design levels
of chlorine dioxide. Capital, O&M, and Total Cost were developed for both manual and
automatic systems. All cities with a median population above 50,000 (beginning with EPA Flow
Category 8), were assumed to require an additional system. Further cost assumptions are
presented below.
0.5 Ib. of chlorine is required to produce one pound of chlorine dioxide;
5.4 Ib. of 25% sodium chlorite is required to produce one pound of chlorine dioxide;
Storage equivalent to a thirty-day supply of chlorine and sodium chlorite is provided;
Costs for building to house chlorine dioxide feed and storage facilities included; and
Chlorine dioxide equipment costs are amortized over five years, building costs are
amortized over 20 years;
Generator maintenance is assumed to be 4 hours per week for automatic generators,
and 11.5 hours per week for manual generators;
Analytical and technical support is assumed to be'$20,000 per year (approximately
50% of the cost of one technical person); and
Material costs are $0.26 per pound chlorine, and $0.41 per pound sodium chlorite
(assumes 4,000 pound bulk purchase).
7.6.8 Installation of GAC Adsorption
The major difference between a system with GAC and the base plant is the insertion of
GAC adsorption between filtration and the contact basin, as shown in Figure 7-4. The point of
chlorination is also moved from pre-filtration to post adsorption. This treatment scheme further
7-55
-------
reduces the amount of dissolved NOM available for TTHM formation. The design criteria in the
1992 version of this document included two definitions of post-filter absorbers.
Empty bed contact time (EBCT) of 15 minutes at average flow and regeneration
frequency of 180 days; and .
EBCT of 30 minutes at average flow and regeneration frequency of 180 days.
GAC replacement is assumed for flow categories 1 through 6 and on-site regeneration
for flow categories 7 through 12a. The flow category at which oh-site generation becomes cost-
effective will depend upon the GAC regeneration frequency (i.e., usage rate). The more frequent
the regeneration (and, hence, the higher the carbon usage rate), the lower the flow at which on-
site regeneration is cost effective. For the purposes of this document, the "break even" point
between flow categories 6 and 7 was based upon manufacturers' experience and a typical
regeneration frequency of 180 days. .
When GAC was applied to either small or large systems, it was assumed that the entire
plant flow would be applied to the GAC process. Bypassing a portion of the flow to achieve a
desired finished water quality by blending was not considered and was beyond the scope of this
effort. It is recognized, however, that bypassing a portion of the flow to achieve a desired
finished water quality by blending will reduce the overall cost of the GAC installation for a given
system size.
Upon review by the Technologies Working Group, it was determined that it would be
desirable to establish GAC definitions that more broadly encompassed a feasible range of GAC
treatment performance and costs. The TWG was formed by the Advisory Committee to provide
technical analysis of regulatory options identified by the Advisory Committee. The TWG
consisted of technical representatives from all interested organizations represented on the
Advisory Committee. As such, the WTP simulation model was used to evaluate performance
criteria for a range of EBCTs and regeneration frequencies. Four hypothetical source waters
were selected for evaluation. The treatment scheme shown in Figure 7-4 was assumed.
7-56
-------
FIGURE 7-4
ALUM COAGULATION / FILTRATION SYSTEMS
UPGRADED WITH GAG ADSORPTION
Alum
Chlorine r- Caustic
Rapid Floccuiation
Mix & Clarification
Filtration GAG Contact Storage
Adsorption Basin
-------
The objectives of the evaluation were to determine-
. Performance criteria for a contactor with 10 minutes EBCT and regeneration
frequency of 180 days; and, ,
Design criteria (i.e., EBCT and regeneration frequency) to achieve a TTHM
concentration in the OAC contactor effluent that represented a 90 percent
reduction of that predicted in the raw water.
These objectives encompassed the range of statutory interpretations for GAC treatment
at that time.
The surrogate for NOM content in the hypothetical source waters included TOC
concentrations of 2.7,3.9,6.5, and 8.4 mg/L. The two lower TOQvalues (i.e., 2.7 and 3.9 mg/L
represent the 50th percentile of the population-based and system based TOC concentrations,
respectively, from the Water Industry Data Base (AWWA, 1992). The two higher TOC values
(i.e., 6.5 and 8.4 mg/L represent the 90th percentile values for the population-based and system-
based.TOC concentrations, respectively.
Based upon the modeling results, theTollowing design criteria were selected to meet the
objectives:
EBCT of 10 minutes at average flow and a regeneration frequency of 180 days
(carbon usage rate of 144 lbs/MG>treated); and
EBCT of 20 minutes at average flow and a regeneration frequency of 60 days
(carbon usage rate of 866 Ibs/MG treated).
These systems associated with the criteria above were defined as GAC10 and GAC20,
respectively.
It may be possible for systems to install GAC 10 in a filter absorber arrangement as a
media replacement. The GAC20 definition is associated with post-filter contactors.
7-57
-------
Rather than using costs from the Adams and Clark (1990) cost model, actual construction
costs from a large, operating GAC installation were used Capital and O&M costs from the full-
scale facility were reduced to the following unit costs.
contactors, capital cost: $24,000/mgd per minute of EBCT;
on-site regeneration, capital cosf $160 per Ib/day of GAC regenerated,
on-site regeneration, O&M cost: $0.18 per Ib/day of GAC regenerated; and
O&M costs for the contactors were considered negligible.
The flow rate for the full-scale GAC facility used to develop these costs was similar to
EPA Flow Category 11. Based .upon these factors, the costs presented in the table below were
developed' for GAC 10 and GAC20.
TABLE 7-13(a)
COSTS FOR GAC10 AND GAC20 TECHNOLOGY
Technology
GAC 10
GAC20
Upgrade
Capital Cost
(MS)
34
87
^ Upgrade
O&M Cost
(#1000 gal)
. 2.5
15.5
Upgrade
Annualized Cost
(#1000 gal)
12
39
Because the size of the facility used to develop the costs approximated flow category
11 (average and design flow of 120 mgd and 210 mgd, respectively), it was recognized that these
costs contained the benefits of economies of scale. Therefore, the Technologies Working Group
recommended that the costs for the other flow categories be based upon the relative costs for
GAC presented in the 1992 version of this document. In other words,-the relative proportion
of capital and O&M costs, as determined by the previous cost models, were calculated for all
flow categories using the Category 11 model estimate as a basis. These proportions were then
applied to the capital and O&M costs estimates developed from the full-scale operating plant.
Based on this methodology, Table 7-14 summarizes the capital, O&M and annualized costs for
GAC 10 and GAC20 for EPA's 13 flow categories
7-58
-------
TABLE 7-14
ESTIMATED UPGRADE COSTS FOR
INSTALLATION OF GAC ADSORPTION
SMALL SYSTEMS
Minutes EBCT
10 Minutes EBCT
Total
Cost @ 3%
ft/1000 gal)
Capital
Cost1
Total
Costฎ 7%
(t/1000 gal)
O&M
Cost
(eVlOOO gal)
Capital
Cost1
(4/1000 gaD
32
Total
Costฎ 10%
(it/1000
Capital
Cost1
O&M
Cost
4/1000 gal)
[ | f\^ _^^_^^^_^JJ^^^^^^^^-^^^^^^^^^^^^*^ggg^^^^^^^^^S^^^^^^a^^^^^^B^^^a^^^^^^^^^
1991 Cost escalated based upon a factor of 1.23 derived from the ENR BCI
7-59
-------
TABLE 7-14 (cont.)
ESTIMATED UPGRADE COSTS FOR
INSTALLATION OF GAC ADSORPTION
LARGE SYSTEMS
Total
Costฎ 3%
(4/1000 gal)
Capital
Cost1
O&M
Cost
(#1000
Capital
Cost1
(SM)
0.95
Design
Flow
(mgd)
Total
Costฎ 7%
(4/1000 eal)
O&M
Cost
tf/1000
84
Capital
Cost1
Capital
Cost1
(SM)
Design
Flow
(mgd)
Total
Costฎ 10%
Capital
Cost1
Total
Costฎ 10%
Capital
Cost1
1991 Cost escalated based upon a factor of 1.23 derived from the ENR BCI
7-60
-------
The costs associated with the O&M of GAC systems include the following. GAC, power,'
materials, and labor (skilled). The escalation factor for O&M cost for GAC was developed based
on a weighted average of the following indices:
Vendor Data for GAC Costs ;
BLS 055 Utility Natural Gas (100 % Natural Gas assumed);
ENR's Materials Index; and
ENR's Skilled Labor Index.
The overall weights of each O&M component were determined by the breakdown of cost
information presented in Adams and Clark (1990). The cost information was presented in Table
5 of the report detail costs associated with on-site reactivating. The escalation factor for small
systems was calculated based upon a lower overall weight applied to the cost of GAC. In
contrast, the escalation factor for large systems was calculated based upon a higher weight given
to the cost of GAC. The overall escalation factors were calculated as follows:
TABLE 7-14(a)
ESCALATION FACTOR FOR COST OF GAC IN SMALL SYSTEMS
Component
GAC
POWER
MATERIALS
LABOR
Percentage Increase
0.14869
0.16789
0.3284748
0.1782798
Weight
0.32
0.22
0.1
0.36
O&M F^calatinn Factor1
;
0.04758
0.03694
0.03285
0.06418
n IK
TABLE 7-14(b)
ESCALATION FACTOR FOR COST OF GAC IN LARGE SYSTEMS
Component
GAC
POWER
MATERIALS
LABOR
Percentage Increase
0.14869
0.16789
0.3284748 '
0.1782798
Weight .
0.54
0.16
0.09
0.21
O&M Fsealatinn Factor*
0.08029
0.02686
0.02956
0.03744
0 17
7-61
-------
7.6.9 Addition of Membrane Filtration
Membrane systems can be very effective for the removal of NOM, as discussed in Chapter
4 This section presents costs for nanofiltration (NF) systems. NF systems typically consist of spiral-
wound NF membrane elements assembled in a parallel formation on skids. NF is a diffusion-
controlled process capable of removing divalent salts, as well as turbidity and pathogens (Taylor and
Jacobs, 1996). NF systems typically operate at feed pressures between 70 and 150 psi, and reject
over 90 percent of hardness-forming ions and between SO to 70 percent of dissolved solids NF
membranes are also effective in removing disinfection by-product precursors.
NF is often used in combination with other treatment techniques. Physical pretreatment,
including microfiltration and multi-media filters, is often used to reduce influent paniculate
concentration and to protect the NF membranes. Chemical pretreatment, including anti-sealants and
coagulants, is also often employed. Some groundwaters and most surface water systems will require
pretreatment to control fouling. In some cases extensive pretreatment (i.e. coagulation and filtration)
may be needed prior to NF. These pretreatment costs will be in addition to the NF costs presented
here.
Although costs are presented for nanofiltration, other membrane processes, including
ultrafiltration (UF) and reverse osmosis (RO), may be feasible DBF control alternatives for some
source waters. The effectiveness of ultrafiltration as a control alternative is highly contingent upon
the MWCO of the membrane. High MWCO UF membranes, on the order of 10,000 Daltons and
larger, remove very little organic matter (less than 20 percent). However, low MWCO UF
membranes (less than 10,000 Daltons) may remove significant amounts of organic material. RO
membranes are very effective for the removal of organic matter. However, because of the higrrlevel
of salts removed during RO (greater than 98 percent), an unstable, corrosive product water often
results. This may require a utility to by-pass a portion of raw water to blend with the finished water
to meet acceptable water quality goals.
The costs presented here consider NF as an 'add-on' technology to a conventional plant.
Capital and O&M costs for large and small systems are given in Tables 7-lS.a and 7-15b for source
7-62
-------
water temperatures of 20 degrees and 10 degrees Celsius, respectively Descriptions of how these
costs were determined for large and small systems are given in the following sections.
\
7.6.9.1 Large Systems
Capital and O&M cost estimates for large systems, i.e. greater than 1 mgd, were developed
from NF cost data presented in a NF plant survey conducted by Bergman (1996). Costs presented
in this survey were escalated to 1997 using the 1997 and 1995 ENR Building Cost Indices. Capital
and O&M costs presented here were derived from cost data submitted by existing plants, the
Bergman survey, however, presented capital cost and O&M cost data obtained between 1988 and
1996. It is recognized that spiral-wound membrane modules; which include the majority of NF
membranes, have decreased in cost significantly in recent years. Based on vendor information, costs
for spiral-wound membrane modules have been reduced^ approximately 50 percent over the past
five years. For this reason, costs for membrane modules presented in the above reference obtained
between 1988 and 1995 were reduced by 50 percent.. The reduced cost items'included new
membrane capital costs and q&M membrane replacement costs.
The costs given in the Bergman survey consist solely of nanofiltration costs from Florida
plants. The source waters treated by these plants are warm, resulting in higher membrane flux values
than potential flux values for lower temperature waters of comparable quality. As a result, the costs f
presented in these references may not be representative of costs for all areas of the country. For this
reason, the costs were, adjusted to equivalent costs at 20 degrees Celsius and 10 degrees Celsius
This was accomplished by assuming atemperature of 25 degrees Celsius for the Florida plants and
adjusting the membrane capital costs.and O&M membrane replacement costs to account for the
additional membrane area that would be required at the lower temperatures: The temperature
correction equation for permeate flux VJ^l .03 was used for these calculations (Wiesner and
Aptel, 1996). ' - .
Best-fit curves were generated for capital and O&M costs. Capital costs were separated into
membrane module costs and facility costs. As indicated by Bergman (1996) the membrane system
costs included:
7-63
-------
supply and installation of pretreatment chemical pumps and day tanks
cartridge filters
feedwater booster pumps
membrane modules
pressure vessels and support skids and racks
control system
The facility cost components included:
buildings
degasifiers
clearwells
transfer pumps
high service pumps
bulk storage
stand-by power
yard piping
site development
Using the Bergman survey data, the average facility cost was found to be between two and
three times the cost for membrane equipment. However, capital and operational costs for clearwells
and high service pumping will not be required in a retrofit situation. Subtracting the capital costs for
these two components results in a fector of 1.5 to 2.0 for facility costs when compared to membrane
system costs. For this reason, facility costs used in determining the best-fit equation were calculated
by multiplying the membrane cost for each plant by two (a conservative estimate). It should be noted
that Bergman (1996) did not provide itemized costs for clearwells and'high service pumping. Costs
for these items were calculated by the WatercoSt model (large systems model) with the assumption
that the clearwell volume will be 20 percent of the design flow. The membrane module cost curves
for 20 and 10 degrees C are given in Figures 7-5 and 7-6, respectively. It should be noted, that these
7-64
-------
curves end'at 12 or 14 mgd, capacities corresponding to the largest plants surveyed Since at the
present time very few facilities above this capacity exist. there is no way to accurately judge the
economies-of-scale that may be seen beyond this point. For this reason, it was conservatively
assumed that no economies-of-scale would exist beyond 14 mgd.
The curves in Figures 7-5 through 7-7 were used to produce the final capital and Q&M costs
for each flow category, including both small and large systems. The final capital and O&M
nanofiltration costs for large systems are given in Tables 7-15a and 7-15b for source water
temperatures of 20 degrees and 10 degrees, respectively.
TABLE 7-lSa
NANOFILTRATION COSTS FOR SOURCE WATER AT 20ฐ C
LARGE SYSTEMS
-------
TABLE 7-15b
NANOFBLTRATION COSTS FOR SOURCE WATER AT 10ฐ C
LARGE SYSTEMS
Design
Flow
(mgd)
1.8
4.8
. 11
. 18
26
51
210
430
520
Capital
Cost
(SM)
3.20
6.30
11,3 .
18.0
26.0
54.0
240
538
698
O&M
Cost
(0/1000 eal)
84
64
51
48
48
48
48
48
48
Total
Cost @ 3%
tf/lOOOgal)
168
120
93
85
85
85
85
85
85
Total
Cost @ 7%
(tf/1000 gal)
202
142
110
99
99
99
99
99
99
Total
Cost @ 10%
(0/1000 eal)
230
161
124
112
112
112
.112
112
112
7.6.9.2 Small Systems
Peer reviewer comments on the June, 1997 Draft Technologies and Costs D/DBP document
indicated that the nanofiltration costs for the four smallest flow categories may have been over
estimated. The costs in the 1997 Draft were developed by extrapolating the large system
nanofiltration costs derived from the Bergman survey. Note that the Bergman paper did not provide
cost data for systems with plant flows below 1 mgd.; thus the extrapolation was required. It was
concluded that the extrapolation did not provide reliable cost estimates for the four smallest flow
categories. Therefore, the nanofiltration presented in this document for the four smallest flow
t ,
categories were developed from the 1994 D/DBP RIA cost estimate. The 1994 RIA cost estimate
was developed with vendor supplied information, and they provide a more accurate estimate than the
extrapolation procedure. For reference purposes, the 1994 RIA costs appear in Table 7-15c. The
escalated, 1997 dollar value of these nanofiltration costs appears in Table 15d.
7-66
-------
Figure 7-5: Membrane Capital Costs at 20 degrees C for Nanofiltration
a
t/5
*-s
U
o
ts
o
U
1.8
6 8 10 12
Design Flow (mgd)
-------
Figure 7-6: Membrane Capital Costs at 10 degrees C for Nanofiltration
8 10
Design Flow (mgd)
-------
TABLE 7-15c
SMALL SYSTEMS COSTS
FROM 1994 RIA
Design
Flow
(mgd)
0.024
0.087
0.27
065
Capital
Cost
($M)
0.029
0.148
0.527
1 150
O&M
Cost
(#1000 gal)
172
151
145
108
Total
Costฎ 10%
(#1000 gal)
339
349
342
269
Design
Flow
(mgd)
Capital
Cost
(SM)
TABLE 7-15d
SMALL SYSTEMS
NANOFBLTRATION COSTS
JUNE 1997
O&M
Cost
(#1000 gal)
Total
Costฎ 3%
(If/1000 gal)
Total
Costฎ 7%
(#1000 gal)
Total
Cost @ 10%
(#1000 gal)
0.024
0.087
0.27
0.65
0.032
0.160
0.570
1.244
186
163
157
117
289
287
279
217
332
336
328
257
367
378
370
291
7-67
-------
7.7 GREENFIELD ADJUSTMENT FACTORS
As noted previously, the costs presented in Section 7 6 are Greenfield costs and do not reflect
potential costs for site constraints, land acquisition, or interfacing with other unit processes. Based
upon experience in the construction and operation of treatment facilities, the Technologies Working
Group (a working group of water industry professionals formed during the Regulatory Negotiation
Proceedings) recognized that these site-oriented factors should be considered. The Technologies
Working Group concluded that the multiplicative factors presented in the table below were
representative site of contingencies that should be applied to the greenfield cost estimates. These
factors were not applied to the costs presented in this document; however, they were applied to
subsequent cost analysis performed by others.
These factors range between 1.0 (no increased contingency) for ammonia feed systems to 2.0
for chlorine contact basins. Ammonia feed systems require little space and can be easily retrofitted
into an existing facility. Chlorine contact basins, on the other hand, require significant area and must
either be constructed withing existing hydraulic constraints or be subject to repumping prior to
distribution. Greenfield adjustment factors for the remaining technologies were estimated between
1.1 and 1.5, depending upon the relative complexity of the technology and the extent to which the
technology has been implemented at full-scale facilities.
TABLE 7-16
Greenfield Adjustment Factors
Technology
Ammonia Addition
GAC10
Enhanced Coagulation
Ozone Addition
GAC20
Nanofilters
Chlorine Contact Basins
Adjustment Factor
1.0
1.1
1.2
1.2
1.3
1.5
2.0
7-68
-------
It is recognized that these factors were hypothesized in 1993 and the adjustment factors c'an
* '
be lower as the industry becomes more familiar with- the technology, particularly in the case of
membranes. Systems should consider their own individual circumstances when applying these factors.
7.8 INTEREST RATE SENSITIVITY ANALYSIS
An analysis was performed to determine interest rate sensitivity of the estimated upgrade
costs for each of the technologies presented in Section 7.6. The analysis consisted of determining the
relative percent difference (RPD) between the total cost calculated for each technology based on 10
% amortization over 20 years .and 7% amortization over. 20 years. The amortization factors for these
two scenarios are presented here:
0.11746 for 10% over 20 years; and
0.09439 for 7% over 20 years.
i i
Total unit costs for these two interest rates were presented in the corresponding upgrade
cost tables in Section 7.6. Table 7-17 shows the range of differences for each upgrade over 13 EPA
flow categories.
Generally, a larger percent difference exists with those flow categories or technologies
in which the capital costs are a much more significant portion of the total unit costs.
7-69
-------
TABLE 7-17
SUMMARY OF INTEREST RATE SENSITIVITY ANALYSIS
Technology
Switch to Chloramines
Increased Coagulant Dosage
Enhanced Precipitative Softening
Switch to Ozone .(log 3)
Switch to Chlorine Dioxide (log 3
and automatic generator)
Add G AC 10
Add GAC20
Add Membranes
Relative Percent Difference
Avg. flow - 0.0056
xngd
(Category 1)
14.6
' 7.2
7.2
16.4
10.8
18.8
16.1
7.6
Avg. Flow = 5
ragd
(Category 7)
11.7
3.2
3.2
1S.8
5.1
14.3
11.4
9.1
Avg. Flow = 270
xngd
(Category 12)
5.5
1.0
1.0
10.0
0.6
15.0
11.3
6.1
7.9
REFERENCES
Adams, J. Q. andR. M. Clark (1990). "Cost Estimates for GAC Treatment Systems." J.
AWWA, 81(1), page 35.
American Water Works Association (AWWA) (1992). The Water Industry Database (Update
October, 1992).
Bergman, Robert A. (1996). "Cost of Membrane Softening in Florida." J. AWWA, May 1996,
Page 32
Clark, Robert M., Adams, Jeffery Q., and Lykins, Benjamin W. (1994). "DBF Control in
Drinking Water: Cost and Performance." J. Environmental Engineering, 120 (4), Page 759
Energy Information Administration (1997), Survey results United States Electric Utility Average
Revenue per Kilowatt hour by Sector, 1987 Through April 1997.
7-70
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Haas, C N (1991) "Final Report of the 1990 AWWA Disinfection Study, AWWA Disinfection
Committee."
Lanlais, B., D.A. Reckhow and D.R. Brink (,1991). Ozone in Water Treatment: Application
and Engineering. Page 491-520.
Taylor, J. and E. Jacobs (1996). "Water Treatment Membrane Processes". AWWARF,
Lyonnaise des Eaux, Water Research Commission of S. Africa, Ed. J. Mallevialle, P
Odendaal, M. Wiesner, McGraw-Hill. Chapter 9
Tooker, Dale and Robinson, Larry (1996). Clifton Water District, Clifton, Colorado.. American
Water Works Association Annual Conference, Toronto, Ontario, Canada. "Nanofiltration as
a Post-Treatment at a Conventional Water Treatment Plant".
USEPA (1992). "Water Treatment Plant Simulation Program User's Manual." Developed by
Malcolm Pirnie, Inc. for USEPA. EPA-811-8-B-92-001. Diskette for P.C. EPA 81l-C-92-
92-001'
USEPA/Culp, Wesher,' Gulp and Technicomp, Inc. (1986), WATERCQST - A Computer
Program For Estimating Water and Wastewater Treatment Costs.
USEPA/Culp, Wesner, Gulp (1984). WATER - Estimation of Small System Costs. USEPA
600/2-84-184a.
Wiesner, M. and P. Aptel (1996): "Water Treatment Membrane Processes". AWWARF,
' Lyonnaise des Eaux, Water Research Commission of S. Afiiqa, Ed. J. Mallevialle, P.
Odendaal, M. Wiesner, McGraw-Hill. Chapter 4 .
7-71
-------
NOTICE
All cost calculations contained in this Appendix were based on the water
treatment plant model and were completed for the 1992 version of this document.
These costs are in 1992 dollars andjojiot reflect current upgrade costs for the
technologies covered. The costs contained here were used as a baseline from
which new cost estimates (see Section 7.4) were calculated by using escalation
factors to account for 'inflation.
The following costs were included as an historical reference and to -
demonstrate the methodology used for the 1992 calculations. -Again, these costs do
not reflect current upgrade costs.
-------
APPENDIX A
EXAMPLE COST CALCULATIONS AND COST TABLES
FOR SMALL SYSTEMS
This section provides example cost calculations and cost tables for the base plant and
each treatment improvement defined in Section 7.5. As discussed in Chapter 7, cost
estimates were prepared for each treatment process at TTHM limits of 50 of 100 /tg/L and
considering Giardia inactivations of 0.5, 1.5 and 2.5 logs. For every cost table, design
criteria predicted by the WTP model are provided. These predicted design criteria and
assumed design criteria based on engineeringjudgement are used to generate capital, O&M,
and total costs using the WATER cost model and, where necessary, a GAG, cost model and
vendor costs.
The costs shown in these tables present the costs for constructing and operating a
completely new treatment. Using the base plant as a baseline, the upgrade-cost for each
treatment alternative can be computed. These upgrade costs are presented in separate
tables in Section 7.11.
This section contains the cost tables for the following treatment systems:
Treatment Alternative
Base plant
Base plant and chloramines as secondary
disinfectant
Base plant and increased coagulant
dosage
Based plant and ozone/chloramines as
primary /secondary disinfectants
Base plant and GAC adsorption
Base plant and nanofiltration
Table No.
A-l
A-2
V
A-3
A-4
A-5
A-6
Example calculations for each treatment upgrade for Flow Category 2 are provided
prior to each cost table.
-------
EXAMPLE CALCULATIONS FOR TABLE A-l
ESTIMATED CAPITAL, O&M AND TOTAL COSTS FOR
BASELINE TREATMENT PLANT
I. BREAKDOWN OF CAPITAL AND O&M COSTS FOR CATEGORY 2
Design Flow = 0.087 mgd
Average Flow ป 0.024 mgd
A. . PACKAGE TREATMENT PLANT (WATER Process 66)
A package plant is assumed to be a conventional plant including alum feed,
mixing, flocculation, settling and filtration. For these plants, an alum dosage
of 30 mg/L is assumed.
Design Flow:
= (dose in mg/L) x 8.34 x (design flow in mgd)
30 mg/L x 834 x 0.087 mgd = 21.5 Ib/day
Filtration: Assume a 2 gpm/ft2 loading' rate.
Design Flow:
*
= 0.087 mgd x 10* gal x dav
. 2 gpm/ft2 x MG x 1440 min
29.9 ft2
Average Flow:
0.024 mgd x 10* gal x dav
2 gpm/ft2 x MG x 1440 min
8.3ft2
. Total Capital Costs = $376,800
O&M Costs = 69.8e/1,000 gal
Al-l
-------
B. PACKAGE RAW WATER PUMPING (WATER Process 31)
Total Capital Costs = $61,100
O&M Costs . = 3.4C/1,000 gal
C. SODIUM HYPOCHLORTTE FEED SYSTEM (WATER Process 25)
Chlorine Required: Assume a, chlorine dosage of 2.4 mg/L.
Design Flow:
- = (dosage in mg/L) x 8.34 x (design flow in mgd)
2.4 mg/L x 8.34 x 0.087 mgd = 1.7 Ib/day
Average Flow:
2.4 mg/L'x 8.34 x 0.024 mgd = 0.48 Ib/day
Total Capital Costs = $34,500
O&M Costs . = 12.4C/1.000 gal
D. SODIUM HYDROXIDE FEED SYSTEM (WATER Process 81)
Caustic Required: Assume a caustic dosage of 16 mg/L.
Design Flow:
(dosage in mg/L) x 8.34 x (design flow in mgd)
= -16 mg/L x 8.34 x 0.087 mgd = 11.5 Ib/day
Average Flow:
16 mg/L x 8.34 x 0.024 mgd = 3.2 Ib/day
Total Capital Costs = $4,200
O&M Costs = 4.3ซ/1,000 gal
Al-2
-------
E. CONTACT BASIN
Volume (MG) at Average Flow:
= , contact time (min) x flow (mgd) / 1440 (min/day)
60 min x 0.024 mgd / 1440 (min/day)
0.001 MG
The following equation for contact basin costs was developed from
manufacturer quotes:
Cost ($) = 697,500 x volume (MG) + 123,000
$123,700
Total Capital Cost = $123,700
O&M Costs = Negligible
F. PACKAGE FINISHED WATER PUMPING (WATER Process 30)
Design Flow = 0.087 mgd
Average Flow = 0.024 mgd
Total Capital Costs = $ 33,600
O&M Costs = 7.0e/1,000 gal
G. GROUND LEVEL CLEARWELL (WATER Process 59)
Assume clearwell sized for 25 percent of daily operating flow.
Volume:
0.024. mgd x 0.25 x day
0.006 MG = 6,000 gallons
Total Capital Costs = $ 27,500
O&M Costs = Negligible
Al-3
-------
H. SOLIDS DEWATERING LAGOONS (WATER Process 86)
Assume: 12 percent solids concentration (120 g/L) to size the lagoons and
solids production of 18 mg/L of total plant flow.
Volume (ftj/yr) at design flow:
18 mg/L x 0.087 med x 365 dav x IP6 gal x vd3 x ft3
120 g/L x 103 mg/g x 7.48 gal x MG
630 ft3/yr
Vplume required (ft'/yr) at Average Flow:
18 mg/L x O.Q24 mad x 365 days x 10* gat x ft3
120 g/L x 10s mg/g x 7.48 gal x MG
ISOftVyr
Total Capital Costs = $2,200
O&MCost = 0.32C/1.000 gal
I. DEWATERED SOLIDS HANDLING (WATER Process 100)
Assume 30 percent (300 g/L) dewatered solids concentration
Volume of solids (yds/yr) at design flow:
. = 18 mg/L x 0.087 med x 365 days x 106 gal x vd1 x ftj
300 g/L x 103 mg/g x 7.48 gal x 1 yr x MG x 27 ft3
9.6.yd3/yr
Volume of solids (yd3/yr) at average flow:
18 mg/L x O.Q24 mgd x 365 days x 10* gal x yd3 x ft3
300 g/L x 103 mg/g x 7.48 gal x 1 yr x MG x 27 ft3
2.7 yd3/yr
Total Capital Costs = $ 36,100
O&M Costs = 0.09
-------
II. CAPITAL, O&M AND TOTAL COSTS
Sum of Capital Costs = j699 70Q
Sum of O&M Costs (Without' Labor) = 97.2c/l,000 gal
Total Labor (Medium-Level) = 61.1c/l,000 gal
Total O&M Costs . 158.4^/1,000. gal
Total Costs:
= (Capital cost ft) x amortisation factor * mn?/f + O&M (c/1,000 gal)
Average flow (mgd) x 1,000 KG/MG x 365 days/yr
= f699.700* 011746* mm + 158.4
0.024 x 1,000 x 365
= 1,0970/1000 gal
Al-5
-------
TABLE A-1
SMALL SYSTEMS
BASE PLANT DESIGN CRITERIA AND
TREATMENT COSTS
TTIIM LIMIT OF 100/xg/L
-
Giardia Inactivalion (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact ( min)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
PREDICTED DESIGN CRITERIA
0.5 (1)
30
2.4
16
18
60
70
1.5
30
2.5
16
18
170
70
2.5
30
2.5
16
18
70
ESTIMATED COSTS
DESIGN
FLOW
0.024
0.087
0.27
0.65
CAPITAL
COST
MILLION S
0.514
0.700
1.12
1.59
O&M TOTAL
COST COST
c/lOOOgal
504
158
75.3
47.1
3.459
1.097
496
269
CAPITAL
COST
MILLION S
0.515
0.701
1.13
1.60
O&M TOTAL
COST COST
c/lOOOeal
504
158
75.3
47.1
3.461
1,098
497
271
CAPITAL O&M
COST COST
MILLION S c/1
0.515 504
0.702 '158
1.13 75.3
1.61 47.1
TOTAL
COST
3.463
1,100
499
TTIIM LIMIT OF 50>ig/L
Giardia loactivation (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (min}
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
PREDICTED DESIGN CRITERIA
0.5
30
2.4
16
18
60
58
1.5
30
2.4
16
18
170
58
2.5
30
2.5
16
18
280
58
OSTI MATED COSTS
DESIGN
FLOW
med
0.024
O.OS7
0.27
065
CAPITAL
COST
MILLION S
0514
0.700
1.12
1.59
O&M TOTAL
COST COST
c/1000Ra!
504
158
753
47.1
3.459
1.097
496
269
CAPITAL
COST
MILLION $
0.515
0.701
1.13
1.60
O&M TOTAL
COST COST
C/lOOOeal
504
158
75.3
47.1
3.461
1.098
497
271
CAPITAL O&M
COST COST
MILLION J c/1
0.515 504
0.702 158
1.13 75.3
1.61 47.1
TOTAL
COST
aOQgal
3.463
1.100
499
273
(1) Noie. The design criicna and estimated costs for these ircaimenl conditions were used lo represent the
"Base Plant* from which all ihe upgrade costs were developed
-------
EXAMPLE CALCULATIONS FOR TABLE A-2
I. BREAKDOWN OF CAPITAL AND O&M COSTS FOR FLOW CATEGORY 2
1. Capital and O&M costs for a completely new treatment plant utilizing chloramines
c ^ dismfectant are identical to the base plant for the following Unit
-
A. Package treatment plant.
B. Package raw water pumping.
C. Sodium hydroxide feed system.
D. Contact basin.
E. Finished water pumping.
F. Ground-level storage.
G. Solids dewatering lagoons.
H. Dewatered solids handling.
'
Total Capital Cost = $665,200
O&M Cost = 84.9C/1.000 gal
Note that although the contact basin size predicted for a plant utilizing chloramines
(shown in Table A-2) is 30 minutes and the base plant basin sizeiTfo mSH
is assumed that the basin size for this plant is the same as the base PSnt?h
ฐf ซ" ^ade ซ when the
2. Capital and O&M costs are required for the Mowing additional unit process:
SODIUM HYPOCHLORITE FEED SYSTEM (WATER Process 25)
Chlorine Required: Assume chlorine dosage of 3.8 mg/L
Design Flow:
= (dosage in mg/L) x 8.34 x (design flow in mgd)
= 3.8 mg/L x 8.34 x 0.087 mgd = 2.7 Ib/day
Average Flow:
= 3.8 mg/L x 8.34 x 0.024 mgd = 0.76 Ib/day
Total Capital Costs = $34,500
O&M Costs = 12.6c/l,000 gal
A2-1
-------
3. Capital and O&M costs are required for the following additional unit process:
AMMONIA FEED SYSTEM (WATER Process 79)
Ammonia Required: Assume ammonia dosage of 0.8 mg/L and dry ammonium sulfate
is used. Stoichiometrically, 2.8 mg/L of ammonium sulfate is equivalent to 0.8 mg/L
ammonia.
Design Flow:
= (Dosage in mg/L) x 8.34 x (design flow in mgd)
= 2.8 mgd x 8.34 x 0.087 mgd = 2.0 Ib/day
Average Flow:
= 2.8 mg/L x 8.34 x 0024 mgd = .0.56 Ib/day
Total Capital Costs = $10,000 '
O&M Costs = 4.40/1,000 gal
x
II. CAPITAL, O&M, TOTAL AND UPGRADE COSTS
\ ' '
Sum of Capital Costs = $709,700
Sum of O&M Costs (Without Labor) = 101.90/1,000 gal
Total Labor (Medium-Level) = 61.1&/1.000 gal
Total O&M Costs . = 162.9C/1,000 .gal
Total Cost:
= (Capital ($~) x amortization factor x IQQg/S) + O&M (c/1,000 gal)
0.024 x 1,000 x 365
= (709.700 x 0.11746 x 1001 + 162.9
0.024 x 1,000 x 365
= 1,115ซ/1,000 gal
Upgrade Cost for Switching to Chloramines:
= Total cost for chloramine plant - total cost for base plant
= 1,115- 1,097 = 18s/1,000 gal
A2-2
-------
TABLE A-2
SMALL SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS FOR SYSTEMS
SWITCHING TO CMLORAMINES AS SECONDARY DISINFECTANT
TTIIM LIMIT OF 100jig/L
PREDICTED DESIGN CRITERIA . 1
Giardia Inaclivation (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Ammonia Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (mla)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5 (1)
30
3.8
0.8
16
18
30
100
.
DESIGN
FLOW
med
0.024
0.087
0.27
0.65
1.5
30
3.9
0.8
15
18
110
98
ESTIMATED COSTS
CAPITAL O&M TOTAL
COST COST COST
MILLION J c/lOOOeal
0.523 522
0.7JO 163
1.14 76.9
1.60 47.9
3J28
1.115
502
272
2.5
30
4.0
0.8
16
18
180
98
CAPITAL O&M TOTAL
COST COST COST
MILLIONS c/iooooni
0.523
0.711
1.14
1.61
322 3.529
163 1.H6
76.9 503
47.9 273
^ _ _
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/lP '
0.524 522
0.712 163
1.14 76.9
1.62 47.9
3.531
1.118
505
275
TTIIM UMITOF50/tg/L
PREDICTED DESIGN CRITERIA
Giardia Inactivalion (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Ammonia' Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (m\a)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5
30
3.8
0.8
16
18
30
97
1.5
30
3.9
0.8
15
18
110
90
2.5
30
3.9
0.8
15
18
mo
90
ESTIMATED COSTS
DESIGN
FLOW
med
0.024
0.087
0.27
0.65
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/lOOOeal
0.523 522
0.710 163
1.14 76.9
1.60 47.9
3.528
1.115
502
272
CAPITAL
COST
MILLION S
0.523
0.7J 1
1.14
1.61
O&M TOTAL
COST COST
c/IOOOeal
522
163
76.9
47.9
3.529
1.116
503
CAPITAL O&M
COST COST
0.524 522
0.712 163
1.14 769
TOTAL
COST
3.531
1.118
505
(1) Noic: The design criteria and estimated costs for these treatment conditions were used to estimate upgrade costs
for switching to chloramincs as a secondary disinfectant.
-------
EXAMPLE CALCULATIONS FOR TABLE A-3
ESTIMATED CAPITAL. O&M AND TOTAL COSTS FOR
PLANTS INCREASING COAGULANT DOSAGE
Upgrade costs for this DBF control alternative were developed using the total costs for an
alum dose of 10 and 50 mg/L with total costs for an alum dose of 50 mg/L subtracted from
the total costs for an alum dose of 10 mg/L. In the calculations shown below, capital
O&M, and total costs are calculated for a plant with an alum dose of 10 mg/L. Then costs
are generated for an alum dose of 50 mg/L.
I. BREAKDOWN OF COSTS FOR FLOW CATEGORY 2 AND ALUM DOSE OF 10 mg/L
A. Capital and O&M costs for a plant utilizing a 10 mg/L alum dose are identical to the
base plant (30 mg/L_alum dose) for the following unit processes.
1. Package Raw Water Pumping.
2. Contact Basin.
3. Package Finished Water Pumping.
4. Ground Level Clearwell.
Total Capital Cost = . $245,900
O&M Cost = 10.3c/l,000 gal
Note that although the contact basin size predicted for a plant utilizing a 10 mg/L
alum dose (shown in Table A-3) is 90 minutes and the base plant basin size is 60
minutes, it is assumed that the basin size for this plant is the same as the base plant.
This assumption provides for a more accurate calculation of upgrade costs associated
with the different alum dosages.
B. Capital and O&M costs for a plant utilizing a 10 mg/L alum are modified for the
following unit processes:
1. PACKAGE TREATMENT PLANT (WATERCOST PROCESS 66)
/
Alum Required: Assume an alum dosage of 10 mg/L.
a. Design Flow:
= (dosage in mg/L) x 8.34 x (design flow in mgd)
= 10 x 8.34 x 0.087 = 72 Ib/hr
b. Average Flow:
= 10 x 8.34 x 0.024 = 2.0 Ib/day
A3-1
-------
Filtration: Assume 2 gpm/ft2 loading rate.
a. Design Flow:
= FlowYmgcH x 10* gal/MG x day
loading rate (gpm/ft2) x 1440 min
= 0.087 x 10* = 29.9 ft2
. 2 x 1440
b. Average Flow:
= 0.024 x 1Q6 = 8.3 ft2
2 x 1440
Total Capital Costs - = ' $376,800
O&M Costs = 67;3e/1,000 gal
2. SODIUM HYPOCHLORTTE FEED SYSTEM (WATERCOST PROCESS 25)
Chlorine Required: Assume a chlorine dosage of 2.6 mg/L.
a. Design Flow:
= (dosage in mg/L) x 8.34 x (design flow in mgd)
ซ 2.6 mg/L x 8.34 x 0.087 mgd = 1.86 Ib/day
b. Average Flow:
i
= 2.6 mg/L x 8.34 x 0.024 mgd = 0.52 Ib/day
Total Capital Costs = $34,500
O&M Costs . = 12.3C/1,000 gal
/ " f
3. SOLIDS DEWATERING LAGOONS (WATERCOST PROCESS 32)
Assume solids concentration 12 percent (120 g/L) to size the lagoon and solids
production of 10.6 mg/L of total flow
Design Flow
Volume (ft'/yr) at design flow:
= Solids fmg/LVx flow in mgd x 365 day x 106 gal
120 g/L x 1,000 mg/g x 7.48 gal/ft2 x MG x yr
A3-2
-------
- 10.6 x 0.087 y 365 x 10*
120x1,000x7.48
= 370ft3/yr '
Average Flow
Volume (ftYyr) at average flow:
= 10.6 mg/L x Q.Q24 x 365 Y 1flซ
120 x 1,000 x 7.48
= 103ft3/yr
Total Capital Costs = $1,700
ฐ&M Costs .= o.2 c/1,000 gal
4. DEWATERED SOLIDS HAULING (WATER PROCESS 100)
Assume 30 percent dewatered solids concentration
Volume of solids (yd'/yr) at design flow:
" *ฐ-6 mg/L x 0.087 mgd Y ft' y 365 dav Y mซ **} v v^3
300 g/L x 1,000 mg/g x 7.48 gal x 27 ft3 -
- 0.77yd3/yr
Volume of solids (yd3/yr) at average flow:
10-6'mg/L Y Q.Q24 mgd Y ft3 x 365 davs x 1Q6 gal
. 300 g/L x 1,000 mg/g x 7.48 gal x 27 ft3
Y
= 0.21yd3/yr
Assume 50 percent ownership of a regional facility. Also, one truck is used.
Total Capital Costs = $36,100
' O&M Costs = 0.09
-------
5. SODIUM HYDROXIDE FEED SYSTEM (WATER PROCESS 81)
Assume caustic dosage of 7.8 mg/L
Design Flow:
= Dosage mg/L x 8.34 x flow mgd
= 7.8 x 8.34 x 0.087 = 5.6 Ib/day
Average Flow:
= 7.8 x 8.34 x 0.024 = 1.6 Ib/day
Total Capital Costs = $3,500
. O&M Costs . = 2.5e/1,000 gal
II. CAPITAL, O&M AND TOTAL COSTS FOR AN ALUM DOSE OF 10 mg/L
Sum of Capital Costs = $698,500
Sum of O&M Costs (Without Labor) = 92.70/1,000 gal
Labor Costs (Medium-Level) = 61.10/1,000 gal
Total O&M Costs = 153.80/1,000 gal
Total Cost
rCapital cost (S) x amortization factor x 10Qg/$^ + O&M (c/1,000 gal)
Average flow (mgd) x 1,000 KG/MG x 365 days/yr
= (698.500 x 0.11746 x 100^ + 153.8
0.024 x 1,000 x 365
= 1.090C/1,000 gat
A3-4
-------
! Um
a 10 mg/L dose for the following unit processes.
1. Package Raw Water Pumping.
2. Package Finished Water Pumping.
3. Ground Level Clearwell.
4. Contact Basin.
Total Capital Costs = $245,900
O&M Costs = 10.30/1,000 gal
estimate of upgrade costs when the total costs are calculated
B. The following unit processes must be modified at an alum dose of 50 mg/L.
1. PACKAG&TREATMENT PLANT (WATER PROCESS 66)
Alum Required: Assume alum dosage of 50 mg/L.
a. Design Flow:
- dosage mg/L x 8.34 x (design flow in mgd)
= 50 x 8.34 x 0.087 = 36.3 Ib/day
b. Average Flow:
. = 50x8.34x0.024= 10.1 Ib/day
Filtration: Assume 2 (gpm/ft2) loading rate
a. Design Flow:
Flow (mpd\ x 1Q6 f>al/un v
Loading Rate (gpm/ft2) x 1440 min
= 0.087 x 10" = 30.2 ft2
2 x!440
b.- Average Flow:
= 0.024 x 10* = 8.3 ft2
2 x 1440
A3-5
-------
. Total Capital Costs = $377,100
. O&M Costs = 72.4C/ 1,000 gal
2. SODIUM HYPOCHLORTTE FEED SYSTEM (WATER PROCESS 25)
Assume dosage of 2.4 mg/L.
Design Flow:
= Dosage (mg/L) x 8.34 x flow (mgd)
= 2.4 x 8.34 x 0.087 = 1.74 Ib/day
Average Flow:
= Dosage (mg/L) x 8.34 x flow (mgd)
= 2.4 x 8.34 x 0.024 = 0.48 Ib/day
l
Total Capital. Costs = $34,500
O&M Costs = 12.3(5/1,000 gal
3. SOLIDS DEWATERING LAGOON (WATER PROCESS 86)
Assume solids concentration of 12 percent (12 g/L) to size the lagoon and solids
production of 25.9 mg/L of total flow.
Design Flow:
Volume (ft3 at design flow)
Solids-rmg/L> x Flow fmgd^ x 365 d/vr x 10* gal/MG
120 g/L x 103 mg/g x 7.48 gal/ft3
= - 25.9 x 0.087 x 365 x 106 = 905.8 ft3
120 x 103 x 7.48
Average Flow:
= 25.9 x 0.024 x 365 x 106 = 252.7 ftj/yr
120 x 103 x 7.48
Total Capital Costs = $2,500
O&M Costs = 0.4e/ 1,000 gal
A3-6
-------
4. DEWATERED SOLIDS HAULING (WATER PROCESS 100)
Assume 30 percent dewatered solids concentration.
Volume (yd3/yr at design flow)
= Solids fmg/LI x Flow (m?d) x 365 d/v x 10* gal/MG Y yip/n W
Solids x 103 mg/g x 1440 min/day
= 25.9 x 0.087 x 365 x 1Q6 = 1.9 yd1
300 x 103 x 1440
Also assume: 50 percent ownership of the regional facility
Total Capital Costs = $36,100
O&M Costs = 0.090/1,000 gal
5. SODIUM HYDROXIDE FEED SYSTEM (WATER PROCESS 81)
Assume caustic dosage of 23.1 mg/L.
Design Flow:
= Dosage (mg/L) x 8.34 x Flow (mgd)
= 23.1 x 834 x 0.087 = 16.6 Ib/day
Average Flow:
= 23.1 x 8.34 x 0.024 = 4.6 Ib/day
Total Capital Costs = $4,700
O&M Costs = 6.0c/l,000 gal
IV. CAPITAL, O&M AND TOTAL COSTS FOR AN ALUM DOSE OF SO mg/L
Sum of Capital Costs = $700,800
Sum of O&M Costs (Without Labor) = 101.5c/1,000 gal
Labor Costs (Medium-Level) = 61.1c/l,000 gal
Total O&M Costs = 162.6*/1,000 gal
A3-7
-------
Total Cost:
fCapital cost ($1 x amortization factor x 10Qg/$ + O&M Ul 1,000 gal)
Average flow (mgd) x 1,000 KG/MG x 365 days/yr
= (700.800 x Q.I 1746 x 1001 + 162.6
0.024 x 1,000 x 365
= l,102c/i,000 gal
V. UPGRADE COSTS FOR INCREASING COAGULANT DOSAGE
Upgrade Costs = (Total cost for 50 mg/L - Total Cost for 10 mg/L)
- $1,102 - $1,090
= 12e/l,000gal
A3-S
-------
TABLE A-3
SMALL SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS
FOR SYSTEMS WITH ALUM DOSE OF 10 mg/l
TTHM LIMIT OF 100;ig/L
PREDICTED DESIGN CRITERIA 1
Giardia Inaclivatioo (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (m\a)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5 (I)
10
2.6
7.8
11
90
40
DESIGN
FLOW
m^d
0.024
0.087
0.27
1.5
10
2.7
7.8
11
210
40
ESTIMATED COSTS
CAPITAL O&M TOTAL
COST COST COST
MILLION S c/lOOOeal
0.514 800
0.699 238
1.12 107
1-58 59.8
3.753
1.175
526
281
CAPITAL
COST
MILLION S
0.514
0.700
1.13
1.59
O&M
COST
c/lOt
800
238
107
59.8
2.5
10
2.8
7.8
11
iin
TOTAL
COST
Wgal
3.754
1,176
528
283
CAPITAL
COST
MILLION S
0.514
0.701
1.13
L61
40
-
-
O&M TOTAL
COST COST
800
238
107
59.8
3.756
1,178
529
284
TTHM LIMIT OF 50 /ig/L
Giardia Inactivation (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (mini
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
PREDICTED DESIGN CRITERIA
0.5
10
2J
7.8
11
77
30
1
DESIGN
FLOW
0.024
0.087
0.27
06S
CAPITAL
COST
MILLION S
0.514
0.699
1.12
1.58
1.5
10
2.6
7.8
11
200
30
ESTIMATED COSTS
O&M TOTAL
COST COST
c/lOOOgal
800
238
107
59.8
3.753
1.175
526
281
CAPITAL
COST
MILLION S
0.514
0.700
1.13
1.59
O&M
COST
c/lOC
800
238
107
59.8
2.5
10
2.7
7.8
11
330
30
TOTAL
COST
Ogal
3.754
1.176
528
283 1
CAPITAL O&M TOTAL
COST COST COST
MILLION S c/lOO"--1
0.5 U 800
0.701 238
1.13 107
1.61 59 S
3.756
1.178
529
2S.'S
(1) Note- ll,c design criteria and estimated costs were used .o estimate upgrade costs for increasing the alum dose
from I Oio 501115/1.
-------
TABLE A-3 (confd)
SMALL SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS
FOR SYSTEMS WITH ALUM DOSE OF 50 mg/l
TTHM LIMIT OF 100/ig/L
PREDICTED DESIGN CRITERIA
Uiardia Inactivalion (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (min)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5 (1)
50
2.4
23
26
44
82
|
DESIGN
FLOW
0.024
0.087
0.27
0.65
ESTIMATED COSTS
CAPITAL O&M TOTAL
COST COST COST
MILLION J c/lOOOeal
0.515 809
0.701 247
1.13 113
1.59 68.6
3,767
1,187
534
291
CAPITAL
COST
MILLION $
0.515
0.702
1.13
1.60
1.5
50
2.4
23
26
150
82
O&M
COST
c/HX
809
247
113
68.6
2.5
50
2.5
23
26
82
TOTAL
COST
Xfeal
3,768
1,189
536
293
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/lOOOgal
0.515 809 3,770
0.703 247 1,190
1.13 113 537
L61 68.6 295
TTHM LIMIT OF SOpg/L
PREDICTED DESIGN CRITERIA
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
1 Disinfection Contact faring
i
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5
50
2.3
23
26
42
72
DESIGN
FLOW
0.024
0.087
0.27
0.65
1.5
50
2.4
23
26
140
ESTIMATED COSTS
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/IOOOqal
0.515 809
0.701 247
1.13 113
Lซ> 68.6
3.767
1.187
534
291
CAPITAL
COST
MILLION S
0.515
0.702
1.13
1.60
72
...
2.5
50
2.4
23
26
JA(\
72
O&M TOTAL
COST COST
c/lOOOeal
809
247
113
68.6
3.768
1.189
536
293
CAPITAL O&M TOTAL
COST COST COST
MILLIONS c/100n"-'
0.515 809
0.703 247
1.14 113
1.62 686
3.771
1.190
537
295
(I) Note. The design criteria and estimated costs were used to est
from
imate upgrade costs for increasing the alum dose
-------
EXAMPLE CALCULATIONS FOR TABLE A-4
ESTIMATED CAPITAL. O&M AND TOTAL COSTS FOR
OZONE AS A PRlk\RY DISINFECTANT AND
CHLORAMINES AS A SECONDARY DISINFECTANT
I. BREAKDOWN OF CAPITAL AND O&M COSTS FOR FLOW CATEGORY 2
A. Capital and O&M costs for a completely new treatment plant utilizing O3/NH,C1 are
identical to the base plant for the following unit processes:
1. Package treatment plant.
2. Package raw water pumping.
3. Sodium hydroxide feed system.
4. Contact basin.
5. Finished water pumping.
6. Ground-level storage.
7. Solids dewatering lagoons.
8. Dewatered solids handling.
Total Capital Cost = $665,200
" O&M Cost = 84.9^/1000 gal
Note that although the chlorine contact basin size is not needed for a system
utilizing ozone for primary disinfection, the contact basin is assumed to be identical
to the base plant. This assumption provides for a more accurate estimate of
upgrade costs when the total costs are calculated.
B. Capital and O&M costs are modified for the following unit processes:
1. SODIUM HYPOCHLORTTE FEED SYSTEM (WATER Process 25)
Chlorine Required: Assume chlorine dosage of 3.0 mg/L
a. Design Flow:
= (dosage in mg/L) x 8.34 x (design flow in mgd)
= 3.0 mg/L x 8.34 x 0.087 mgd = 2.2 Ib/day
b. Average Flow:
= 3.0 mg/L x 8.34 x 0.024 mgd = 0.60 Ib/day
Total Capital Costs = $34,500
O&M Costs = i2.6e/1,000 gal
A4-1
-------
C. Capital and O&M costs are required for the following additional unit process:
1. AMMONIA FEED SYSTEM (WATER Process 79)
Ammonia Required: Assume ammonia dosage of 0.8 mg/L. Also assume dry
ammonium sulfate is used. Stoichiometrically, 0.8 mg/L of ammonia is equal
to 2.8 mg/L of ammonium sulfate.
a. Design Flow:
= (Dosage in mg/L) x 8.34 x (design flow in mgd)
= 2.8 mg/L x 8.34 x 0.087 mgd = 2.0 Ib/day
b. Average Flow:
= 2.8 mg/L x 8.34 x 0.024 mgd = 0.56 Ib/day
Total Capital Costs = $10,000
O&M Costs = 4.4c/1,000 gal
2. OZONE FEED SYSTEM
Costs for Flow Categories 1 and 2 were developed from manufacturer quotes.
The ozone feed system costs include the generation system and the contact
chamber.
a. Ozone Required: Assume ozone dosage of 5.0 mg/L.
b. Design Flow:
= (dosage in mg/L) x 8.34 x (design flow in mgd)
= 5.0 x 8.34 x 0.087 mgd = 3.6 Ib/day
c. Average Flow:
= 5.0 x 8.34 x 0.024 mgd = 1.0 Ib/day
Total Capital Costs = $60,000
- O&M Costs = 63.6C/1,000 gal
A4-2
-------
II. CAPITAL, O&M, TOTAL AND UPGRADE COSTS
Sum of Capital Costs = $769,700
Sum of O&M Costs (Without Labor) = 165.5c/l,000 gal
. Labor Costs (Medium-Level) = 61.6c/l,000 gal
Total O&M Costst = 226.5c/l,000 gal
Total Cost
(Capital r$1 x amortization factor x IQQg/S) + O&M (ซ/1,000 gal)
0.024x1,000x365
= (769.700 x 0.11746 x 100^ + 226.5
0.024 x 1,000 x 365
= l,259e/l,000 gal
Upgrade Cost for Switching to O3/NH2C1
= Total cost for O3/NH2C1 plant - Total cost for base plant
= 1,259 - 1,097 = 162e/l,000 gal
A4-3
-------
TABLE A-4
SMALL SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS
FOR SYSTEMS SWITCHING TO OZONE/CII LOR AMINES
TTIIM LIMIT OF 100/ig/L
PREDICTED DESIGN CRITERIA
Giardia Inaciivalion (Log)
Alum Dose (mg/L)
Ozone Dose (mg/L)
Chlorine Dose (mg/L)
Ammonia Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (mia)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5 (1)
30
5.0
3.0
0.8
15
18
0
100
1.5
30
5.0
3.0
0.8
15
18
0
100
2.5
30
5.0
3.0
0.8
15
18
0
100
ESTIMATED COSTS
DESIGN
FLOW
med
0.024
0.087
0.27
0.65
CAPITAL O&M TOTAL
COST COST COST
MILLION S c/lOOOeal
0.563 749
0.770 227
1.31 96.9
1.86 60.2
3.985
1.259
585
320
CAPITAL
COST
MILLION S
0.563
0.771
1.31
1.87
O&M TOTAL
COST COST
c/lOOOual
749
227
96.9
60.2
3.987
1.260
587
322
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/lOOOgal
0.564 749 3.990
0.773 227 1,264
1.32 96.9 590
1.90 60.2 3Z5
TTIIM LIMITOFSOjig/L
PREDICTED DESIGN CRITERIA
Giardia Inaclivation (Log)
Alum Dose (mg/L)
Ozone Dose (mg/L)
Chlorine Dose (mg/L)
Ammonia Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (m\n)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5
30
5.0
3.0
0.8
15
18
0
98
1.5
30
5.0
3.0
0.8
15
18
0
98
2.5
30
5.0
3.0
0.8
15
18
0
98
ESTIMATED COSTS
DESIGN
FLOW
mgd
0.024
O.OS7
027
0.65
CAPITAL O&M TOTAL
COST COST COST
MILLION S c/lOOOgal
0563 749
0.770 227
1.31 969
1.86 602
3.985
1.259
585
320
CAPITAL
COST
MILLION S
0.563
0.771
1.31
1.87
O&M TOTAL
COST COST
c/lOOOgal
749 3.987
227 1.260
96.9 587
60.2 32'
CAPITAL O&M TOTAL
COST COST COST
MILLION S c/lOOOcal
0 564 749
0.772 227
1 31 96.9
1.88 602
3.989
1.262
589
324
(1) Note: The design criteria and estimated costs for these conditions were used to estimate upgrade costs for
switching to O7one/chlorainincs
-------
EXAMPLE CALCULATIONS FOR TABLE A-5
ESTIMATED CAPITAL, O&M AND TOTAL COSTS FOR
INSTALLATION OF GAC ADSORPTION (EBCT = 15
I. BREAKDOWN OF CAPITAL AND O&M COSTS FOR FLOW CATEGORY 2
*
1- Package treatment plant.
2. Package raw water pumping.
3. Sodium hydroxide feed system.
4. Sodium hypochlorite feed system.
5. Contact basin.
6. Finished water pumping.
7. Ground-level storage.
8. Solids dewatering lagoons.
9. Dewatered solids handling.
Total Capital Cost = $699,700
O&M Cost = 97.3e/1000gal
B. Capital and O&M costs are required for the following additional unit process:
I. GAC CONTACTORS
h~d ~ the Adams an
Total Capital Costs = $213,000
Costs = 17.1c/l,000gal
A5-1
-------
II. CAPITAL, O&M, TOTAL AND UPGRADE COSTS
Sum of Capital Costs = $912,700
Sum of O&M Costs (Without Labor) = 114.4c/1,000 gal
Labor Costs (Medium-Labor) = 61.1ซ/1,OGO gal
Total O&M Costs = 175.5e/1,000 gal
Total Cost
= (Capital ($) x amortization factor x IQQg/S) + O&M (e/1,000 gal)
0.024 x 1,000 x 365
= (912.700 x 0.11746 x 1001 + 175.5
0.024 x 1,000 x 365
= l,399e/1,000 gal
Upgrade Cost for Installation of GAC
= Total cost for GAC plant - Total cost for base plant
= 1,399 - 1,097 = 302e/l,000 gal
A5-2
-------
TABLE A-5
SMALL SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS
FOR SYSTEMS ADDING GAC
(EBCT = 15 minutes)
TTHM LIMIT OF 100/ig/L
PREDICTED DESIGN CRITERIA " 1
Giardia Inaciivation (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (min}
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5
30
2.3
16
18
60
96
DESIGN
FLOW
i mxd
0.024
0.087
0.27
1.5
30
2.3
16
18
180
ESTIMATED COSTS
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/lOOOotl
0.651 1.010
0.913 309
1-47 138
2.17 84.6
4,748
1.533
690
388
CAPITAL
COST
MILLION $
0.651
0.914
1.48
2.18
96
O&M
COST
c/lW
1.010
309
138
84.6
2.5
30
2.4
16
18
inn
TOTAL
COST
Ogal
4.749
1.534
691
389
CAPITAL-
COST
MILLION $
0.652
0.915
1.48
.119
96
O&M
COST
j./1/V
1.010
309
138
84.6
~
TOTAL
COST
Ogal
4.751
1,536
693
391
TTHM LIMIT OF 50/ig/L
Giardia Inactiyation (Log)
Alum Dose (mg/L) '
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (mm)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5
30
2.3
16
18
60
92
DESIGN
FLOW
mj>d
0.024
0087
0.27
0.6S
1-5
-.'so ;.'.;
2.3
16
18
180
ESTIMATED COSTS
CAPITAL O&M TOTAL
COST COST COST
MILLION S c/lOOOeal
0.651 ! 1.010
0913,' 309
M71 13$
2.17| 84.6
4.748
1.533
690
388
CAPITAL
COST
MILLION S
0.652
0.914
1.48
2.18
92
O&M
COST
c/lOC
1.010
309
138
84.6
^~ ^ .
TOTAL
COST
Xfeal
4.749
1.534
691
389
2.5
\ '' V- . 30
2.4
16
18
300
92
CAPITAL O&M TOTAL
COST COST COST
MILLIONS c/lOO""-1
0.652 1.010
0.915 309
1.48 138
2.19 84.6
1.751
1.536
693
391
(1) Noic: Used 10 CSIIMUIC costs for adding GAC with a 15 minute EBCT
-------
TABLE A-5 (conI'd)
SMALL SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS
FOR SYSTEMS ADDING GAC
(EBCT = 30 minutes)
TTHM LIMIT OF 100/ig/L
Giardia Inactivation (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact ( min)
Percent of Systems Meeting
[Constraints Listed ;n Sect. 7.4
1 . PREDICTED DESIGN CRrmmT '
__
|
DESIGN
FLOW
mgd
0.024
0.087
0.27
0-65
CAPITAL
COST
MILLIONS
0.687
0.984
1.65
2.43
0.5 (1)
22
&mtf
16
IK
10
61}
_ mj
100
^-^
O&M
COST
c/10
1.010
305
135
80.9
ESTIMAj
TOTAL
COST
4.950
1.625
754
421
*
CAPITAL
COST
MILLION S
0.687
0.985
1.66
2.44
1.5
30
2.2
16
18
180
100
_
O&M
COST
C/lOj
1,010
305
135
S0.9
~
TOTAL
COST
IQgal
4.952
L626
755
422
2.5
30
2.2
16
18
300
-
~~
CAPITAL
COST
MILLION $
0.687
0.986
1.66
2.45
100
~ _
-
O&M
COST
c/lOt
1,010
305
135
80.9
TOTAL
COST
Ogal
1,628
757
4241
TTHM LIMIT OF 50/ig/L
I
Giardia Inaclivalioo (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (min)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
O&M TOTAL
COST COST
c/lOt
1.010
305
135
80.9J
Xfcal
4.952
1,626
755
422
CAPITAL O&M TOTAL
COST COST COST
MILLIONS c/ionop,.-,!
0.687
0.986
1.66
2.45
1.010
305
135
80.9
4.954
1.62S
757
124
(1) Noie: Used ,o ซi,,,u,c cos.s for addmg GAC with a 30 ,,,i,,u(e EBCT
-------
EXAMPLE CALCULATIONS FOR TABLE A-6
ESTIMATED CAPITAL, O&M AND TOTAL COSTS FOR
INSTALLATION OF NANOFILTRAT1ON
I. BREAKDOWN OF CAPITAL AND O&M COSTS FOR FLOW CATEGORY 2
A. Capital and O&M costs for a completely new treatment plant utilizing
coagulation/filtration with membrane filtration are identical to the base plant for the
following unit processes:
1. Package treatment plant.
2. Package raw water pumping.
3. Sodium hydroxide feed system.
4. Sodium hypochlorite feed system.
5. Contact basin.
6. Finished water pumping.
7. Ground-level storage.
8. Solids dewatering lagoons.
9. Dewatered solids handling.
Total Capital Cost = $699,700
O&M Cost = 97.30/1000 gal
B. Capital and O&M costs are required for the following additional unit process:
1. MEMBRANE SYSTEM
Costs for membrane systems were obtained from two different vendors and
averaged based on a molecular weight cutoff (MWC) of 200, 80 psi operating
pressure and 85 percent recovery. The vendors also provided data for
development of cost estimates for buildings, recovery rate, reject disposal
electrical, chemical maintenance and labor requirements.
Total Capital Cost = $340,000
O&M Cost = 160.8c/1,000 gal
A6-1
-------
II. CAPITAL, O&M, TOTAL AND UPGRADE COSTS
Sum of Capital Costs = $1,039,700
Sum of O&M Costs (Without Labor) = 258.1c/l,000 gal
Labor Costs (Medium-Level) = 6l.lซ/l,000 gal
Total O&M Costs = 319. lc/1,000 gal
Total Cost
= fCapital m x amortization factor x lOQe/SI + O&M (c/1,000 gal)
0.024x1,000x365
= (1.039.700 x 0.11746 x Wff\ + 319.1
0.024 x 1,000 x 365
= 1.713C/1.000 gal
Upgrade Cost for Installation of Nanofiltration
= Total cost for nanofiltration plant - Total cost for base plant
= 1,713 - 1,097 = 616C/1.000
A6-2
-------
TABLE A-6
SMALL SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS
FOR SYSTEMS ADDING NANOFILTRATION
TTIIM LIMIT OF 100/tg/L
PREDICTED DESIGN CRITERIA
Giardia Inactivalion (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (mia)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5
30
2.1
12
18
60
(I)
100
1.5
30
2.1
12
18
180
100
2.5
30
2.5
12
18
300
100
ESTIMATED COSTS
DESIGN
FLOW
med
0.024
0.087
0.27
0.65
CAPITAL O&M
COST COST
TOTAL
COST
MILLION $ c/lOOOeal
0.734 803
1.04 319
1.65 194
2.67 150
5.023
1.713
813
523
CAPITAL
COST
MILLION S
0.735
1.04
1.66
2.68
O&M
COST
TOTAL
COST
c/lOOOeal
803
319
194
150
5.025
1,715
815
524
CAPITAL
COST
MILLION $
0.735
1.04
1.66
2.69
O&M
COST
TOTAL
COST
c/lOOOeal
803
319
194
150
5.026
1,716
816
526
TTIIM LIMIT OF 50/ig/L
PREDICTED DESIGN CRITERIA
Giardia Inactivation (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact fmio)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5
30
2.1
12
18
60
100
1.5
30
2.1
12
18
180
100
2.5
30
2.2
12
18
300
100
ESTIMATED COSTS
DESIGN
FLOW
mRd
0.024
0.087
0.27
0.65
CAPITAL
COST
MILLION $
0.734
1.04
1.65
2.67
O&M TOTAL
COST COST
c/lOOOgal
803
319
194
150
5.023
1.713
813
523
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/lOOOeal
0.735 803
1.04 319
1 66 194
2.68 150
5.025
1.715
815
524
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/lOOOeal
0.735 803
1.04 319
1.66 194
2.69 150
5.027
1.717
817
526
(1) Noic. The design criteria and estimated costs for these treatment conditions were used to estimate upgrade costs
for adding nanofillralion.
-------
APPENDIX B
EXAMPLE COST CALCULATIONS AND COST TABLES
FOR LARGE SYSTEMS
This section provides example cost calculations and cost tables for the base plant and
each treatment improvement defined in Section 7.5. As discussed in Chapter 7, cost
estimates were prepared for each treatment process at TTHM limits of 50 of 100 /ig/L and
considering Giardia inactivations of 0.5, 1.5 and 2.5 logs. For every cost table, design
criteria predicted by the WTP model are provided. These predicted design criteria and
assumed design criteria based on engineeringjudgement are used to generate capital, O&M,
and total costs using the WATERCOST model and, where necessary, a GAC cost model and
vendor costs.
The costs shown in these tables present the costs for constructing and operating a
completely new treatment. Using the base plant as a baseline, the upgrade cost for each
treatment alternative can be computed. These upgrade costs are presented in separate
tables in Section 7.11.
This section contains the cost tables for the Mowing treatment systems:
Treatment Alternative
Base plant
Base plant and chloramines as secondary
disinfectant
Base plant and increased coagulant
dosage
Based plant and ozone/chloramines as
primary /secondary disinfectants
Base plant and GAC adsorption
Base plant and nanofUtration
Table No.
B-l
B-2
B-3
B-4
B-5
B-6
Example calculations for each treatment upgrade for Flow Category 9 are provided
prior to each cost table.
-------
EXAMPLE CALCULATIONS FOR TABLE B-l
ESTIMATED CAPITAL, O&M AND TOTAL COSTS FOR
BASELINE TREATMENT PLANT
I. BREAKDOWN OF CAPITAL AND O&M COSTS FOR FLOW CATEGORY 9
Design Flow = 26 mgd
Average Flow = 13 mgd
A. RAW WATER PUMPING (WATERCOST Process 96)
Total Capital Cost = $841,300
O&M Cost = 3.85e/l,000 gal
B. ALUM FEED SYSTEM (WATERCOST Process 35)
Alum Required: Assume alum dosage of 30 mg/L.
1. Design Flow:
= (dose in mg/L) x 8.34 x flow in mgd
= 30 mg/L x 8.34 Y ?fi m?H = 270 Ib/hr
24 hr/day
2. Average Flow:
= 30 mg/L x 8 34 v n mgH = 136 lb/hr
24 hr/day
Total Capital Costs = $148,200
' O&M Cost = 1.93c/l,000 gal
C. RAPID MIX (WATERCOST Process 106)
G = 900 sec'1
Volume (ft3): Assume 1-minute detention time at design flow.
= 1 min x 26 mgd x 1 day x 1Q6 t>al x 1 ft3
1440 min x MG x 7.48 gal
2,410 ft3
Bl-l
-------
Total Capital Cost = $206,400
- O&MCost = 0.9C/1.000 gal
D. FLOCCULATION (WATERCOST Process 71)
G = 50 sec'1
Volume (ft1): Assume 30-minute detention time at design flow.
= 30 min x 26 mgd x 1 dav x 106 gal x 1 ft3
1440 min x MG x 7.48 gal
72,400 ft3
Total Capital Cost = $822,600
- O&MCost = 0.20
-------
2. Average Flow:
= 2.4 mg/L x 8.34 x 13 mgd
= 2601b/day
Total Capital Costs = $167,600
O&M Costs = 0.66c/1,000 gal
G. FILTER MEDIA - DUAL (WATERCO$T Process 56)
Area: Assume 4 gpm/ft2 loading rate:
= 26 mgd x 10* pal x 1 dav
4 gpm/ft2 x MG x 1440 min
= 4,510ft2
Total Capital Cost = $266,800
O&M Cost = Negligible
H. GRAVITY FILTER STRUCTURE (WATERCO$T Process 54)
Area: Same as for filter media:
4,510 ft2
Assume four filters at 1,130 ft2 each
Total Capital Cost = $4,134,500
. O&M Cost = 2.2e/l,000
I. BACKWASH PUMPING FACILITIES ((WATERCO$T Process 58)
Capacity: Assume 18 gpm/ft2 backwash rate and one filter is backwashed at a time.
Area Backwashed = 1,130 ft2
= 18 gpm/ft2 x 1,130 ftYfilter
= 20,340 gpm
Total Capital Cost = $593,600
- O&M Cost = 0.16C/1,000 gai
Bl-3
-------
J. IN-PLANT PUMPING (WATERCO$T Process 97)
Assume total dynamic head is 50 ft and two units installed at different locations of
process train.
Design Flow = 26 mgd
Average Flow = 13 mgd
Total Capital Cost = $1,710,600
O&M = 4.82C/1.000 gal
K. SURFACE WASH WATER BASINS (WATERCOST Process 61)
Assume basins sized for 20 minutes detention time at design flow.
Volume = 26 mgd x 1 day x 20 min x 10* gal
1,440 min x MG
= 362,000 gallons
Total Capital Costs = $1,320,700
O&M Costs = Negligible
L. HYDRAULIC SURFACE WASH SYSTEM (WATERCO$T Process 59)
Area: Same as filter area
= 4,510ft2
Total Capital Cost = $399,400
O&M Cost = 0.13e/1,000 gal
M. SODIUM HYDROXIDE FEED SYSTEM (WATERCO$T Process 45)
Caustic Required: Assume caustic dosage of 16 mg/L
1. Design Flow:
= 16 mg/L x 8.34 x 26 mgd = 3,470 Ib/day
2. Average Flow:
= 16 mg/L x 8.34 x 13 mg/L = 1,730 Ib/day
Bl-4
-------
Total Capital Cost = $118,000
O&M Costs = 2.21e/l,000 gal
N. CONTACT BASIN
Volume (MG) at Average Flow:
= contact time (min) x flow (mgd)/1440 (min/day)
= 60 min x 13 mgd/1440 (min/day)
= 0.54 MG
The following equation was developed from manufacturer quotes for contact basin
sizes less than 1 MG:
Cost ($) = 697,500 x volume (MG) + 123,000
= $499,700
Total Capital Cost = $499,700
O&M Costs = Negligible
Note: For contact basins larger than 1 MG, the following equation was developed from
manufacturer quotes:
Costs ($) = 483,300 x volume + 365,500
O. CHEMICAL SOLIDS PUMPING (WATERCO$T Process 101)
Assume solids concentration of 1 percent
1. Design Conditions:
Solids Production:
= 18 mg/L x 8.34 x 26 mgd
= 3,900 Ib/day
Bl-5
-------
Solids Flow (gpm):
= 3.900 Ib/day x 10* gal
8.34 Ib/MG x 10,000 mg/L x 1440 min
mg/L
= 32 gpm
2. Average Conditions:
Solids Production:
= 18 mg/L x 8.34 x 13 mgd
= 1,950 Ib/day
Solids Flow (gpm):
= 1.950 Ib/dav x 106 gal
8.34 Ib/MG x 10,000 mg/L x 1440 min
mg/L
= 16 gpm
Total Capital Costs = $103,000
O&M Costs = 0.13C/1,000 gal
P. SOLIDS DEWATERING LAGOONS (WATERCOST Process 132)
Assume: 12 percent solids concentration (120 g/L) to size the lagoons and solids
production of 18 mg/L of total plant flow.
Volume (ft3/yr) at design flow:
= 18 mg/L x 26 mgd x 365 day x 10a gal x vd3 x ft3
120 g/L x 103 mg/g x 7.48 gal x MG
= 196,400 ftj/yr
Bl-6
-------
Volume required (ft3/yr) at Average Flow:
= 18 mg/L x 13 mgd x 365 davs x 1Q6 pal y ft3
120 g/L x 10J mg/g x 7.48 gal x MG
= 98,200 ft'/yr
Total Capital Costs = $105,200
. O&MCost = 0.25C/1.000 gal
Q. DEWATERED SOLIDS HAULING (WATERCOST Process 135)
Assume 30 percent (300 g/L) dewatered solids concentration
Volume of solids (yd3/yr) at design flow:
= 18 mg/L x 26 mgd x 365 davs x 10* pal x vd3 x ft3
300 g/L x 103 mg/g x 7.48 gal x 1 yr x MG x 27 ft3
= 2,910 yd'/yr
Volume of solids (yd3/yr) at average flow:
= 18 mg/L x 13 mgd x 365 davs x 10* gal x vd3 Y ft*
300 g/L x Iff mg/g x 7.48 gal x 1 yr x MG x 27 ft3
= 1,460 ydj/yr
Total Capital Costs = $195,600
O&M Costs = 0.140/1,000 gal
R. CLEARWELL STORAGE - BELOW-GROUND (WATERCO$T Process 150)
Assume clearwell sized for 10 percent of design flow per day and 5 percent of
average flow per day.
Volume at design flow:
= 26 mgd x 0.10 day
= 2.6 MG = 2,600,000 gal
Bl-7
-------
Volume at average flow:
= 13 mgd x 0.05 x day
= 2.6 MG = 2,600,000 gal
Total Capital Costs = $1,352,700
- O&M Costs = Negligible
S. FINISHED WATER PUMPING (WATERCO$T Process 98)
Design Flow = 26 mgd
Average Flow = 13 mgd
Total Capital Costs = 1,440,800
O&M Cost = 10.90/1,000 gal
II. CAPITAL, O&M AND TOTAL COSTS
Sum of Capital Costs = $17,796,700
Sum of O&M Cost = 29.0e/ 1,000 gal
Total Cost:
= rCapital cost (to x amortization factor x IQQg/SI + O&M (ซ/l,000 gal)
Average flow (mgd) x 1,000 KG/MG x 365 days/yr
= ( 17.796.700 x 0.11746 x IQQI + 29.0
13 x 1,000 x 365
= 73. lc/ 1,000 gal
Bl-8
-------
TABLEB-l
LARGE SYSTEMS
BASE PLANT DESIGN CRITERIA
AND TREATMENT COSTS
TTHM LIMIT OF lOOjig/L
Giardia laactivalion (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (rain)
Percent of Systems Meeting
Constraints Listed in SecL 7.4
DESIGN
FLOW
mad
1.8
4.8
11
18
26
51
210
430
PREDICTED DESIGN CRITERIA
0.5(1)
30
2.4
16
18
60
70
1.5
30
2.5
16
18
170
70
ESTIMATED COSTS
CAPITAL . . 0AM .TOTAL
COST COST COST
MILLION $
3.50
5.95
10.0
13.8
17.8
29.5
101
189
. c/lOOOgal
61.9
. 39.2
32.4
30.0
29.0
'27.7
26.5
262
223
130
96.9
.80.7
73.1
* .62*
53.4
48.7
CAPITAL OAM TOTAL
COST COST COST
MILLION $ c71000ซl
3.54
..:6.06
10.3
14.4
18.4
30.5
105
199
61.9
39.2
32.4
30.0
29.0
; 27.7
26.5
225
132
98.5
82.5
74.6
64.0
54.6
._ 49.9
2.5
30
7 S
16
18
270
7(1
CAPITAL OAM TOTAL
COST COST COST
MILLION S e/lOOOeal
3.57
6.16
10.5
17.6
18.8
31.4
109
208
61.9
39.2
32.4
30.0
29.0
27.7
26.5
226
134
100
84
76
65
56
TTHM LIMIT OF 50/ig/L
PREDICTED DESIGN CRITERIA
Giardia Inactivation (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact ( mm)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5
30.
2.4
16
18
60
58
1.5
30
2.4
16
18
170
58
2.5
30
2.5
16
18
280
58
ESTIMATED COSTS
DESIGN
FLOW
med
1.8
4.8
11
18
26
51
210
430
CAPITAL OAM TOTAL
COST COST COST
MILLION S c/lOOOeal
3.50
5.95
10.0
13.8
17.8
29.5
101
189
61.9
39.2
32.4
30.0
29.0
27.7
26.5
26.2
223
130
96.8
80.7
73.1
618
53.4
48.7
CAPITAL OAM TOTAL
COST COST COST
MILLION S c/lOOOeal
354
6.06
10.3
14.3
18.4
30.5
105
199
61.9
39.2
32.4
30.0
29.0
27.7
26.5
26.2
215
132
98.5
815
74.6
64.0
54.6
49.9
CAPITAL OAM TOTAL
COST COST COST
MILLION S c/lOOOeal
357
6.16
10.5
14.6
18.8
31.4
109
208
61.9
39.2
32.4
30.0
290
27.7
265
26.2
226
13-1
100
83.5
756
6-i.l
557
510
(1) Note. The design criteria and estimated costs for these treatment conditions were used to represent the 'Hasc Plant'
from which all the upgrade costs were developed.
-------
EXAMPLE CALCULATIONS FOR TABLE B-2
ESTIMATED CAPITAL, O&M AND TOTAL COSTS FOR
CHLORAMINES AS A SECONDARY DISINFECTANT
I. BREAKDOWN OF CAPITAL AND O&M COSTS FOR FLOW CATEGORY 9
1. Capital and O&M costs for a completely new treatment plant utilizing chloramines
as a secondary disinfectant are identical to the base plant for the1 following unit
processes:
A. Raw water pumping.
B. Alum feed system.
C. Rapid mix.
D. Flocculation.
E. Clarification.
F. Filter media.
G. Gravity filter structure.
H. Backwash pumping facilities.
I. In-plant pumping.
J. Surface wash water basins.
K. Hydraulic surface wash system.
L. Sodium hydroxide feed system.
M. Contact basin.
N. Chemical solids pumping.
O. Solids dewatering.
P. Dewatered solids hauling.
Q. Clearwell storage.
R. Finished water pumping.
Total Capital Costs . = $17,629,100
O&M Costs = 28.4C/1.000 gal
Note that although the contact basin size predicted for a plant utilizing chloramines
(shown in Table A-2) is 30 minutes and the base plant basin size is 60 minutes, it
is assumed that the basin size for this plant is the same as the base plant. This
assumption provides for a more accurate estimate of the upgrade costs when the
total costs are calculated.
2. Capital and O&M costs are modified for the following unit process:
CHLORINE GAS FEED SYSTEM (WATERCOST Process 48)
Chlorine Required: Assume chlorine dosage of 3.8 mg/L
B2-1
-------
Design Flow:
= (dosage in mg/L) x 8.34 x (design flow in mgd)
= 3.8 mg/L x 8.34 x 26 mgd = 824 Ib/day
Average Flow:
= 3.8 mg/L x 8.34 x 13 mgd = 412 Ib/day
Total Capital Costs = $246,400
ฐ&M Costs a 0.92c/1,000 gal
3. Capital and O&M costs are, required for the following additional unit process:
AMMONIA FEED SYSTEM (WATERCOST Process 38)
Ammonia Required: Assume ammonia dosage of 0.8 mg/L
Design Flow:
= (Dosage in mg/L) x 8.34 x (design flow in mgd)
= 0.8 mgd x 8.34 x 26 mgd ซ 173 Ib/day
Average Flow:
^
= 0.8 mg/L x 8.34 x 13 mgd = 87 Ib/day
Total Capital Costs = $86,900
- O&M Costs = 0.05s/1,000 gal
II. CAPITAL, O&M, TOTAL AND UPGRADE COSTS
i
Sum of Capital costs = $17,962,400
Sum of O&M Costs = 29.3
-------
Upgrade Cost for Switching to Chloramines:
= Total cost for chloramine plant - total cost for base plant
= 73.8 - 73.1 = 0.70/1,000
B2-3
-------
TABLE B-2
LARGE SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS FOR SYSTEMS
SWITCHING TO CHLORAMINES AS SECONDARY DISINFECTANT
TTHM LIMIT OF 100 /ig/L
PRDICTTED DESIGN CRITERIA
GiardU Inactivation (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Ammonia Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (rain)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5 (1)
30
3.8
0.8
16
18
30
100
U
30
3.9
0.8
16
18
110
98
2.5
30
4.0
.0.8
16
18
180
98
ESTIMATED COSTS
DESIGN
FLOW
mgd
1.8
4.8
11
18
26
51
210
430
CAPITAL O&M TOTAL
COST COST COST
MILLION S c/lOOOsal
3.54
6.00
10.1
14.0
18.0
29.8
101
.189
63.1
39.8
3X8
30.4
293
27.9
26.7
265
226
132
97.8
8L5
815
73*
63.4
49.0
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/lOOOgal
3.57
6.12
10.4
14.5
18.6
30.7
105
199
63,1
39.8
32.8
30.4
293
'27.9
26.7
26.5
227
134
99.5
833
753
64.6
55.0
50.2
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/lOOOgal
3.61
6.22
10.6
14.8
19.0
^ 31.7
109
208
63.1
39.8
32.8
30.4
293
27.9
26.7
265
229
135
101
84.3
76.4
65.7
56.0
513
TTHM LIMIT OF 50 pg/L
. . : PREDICTED DESIGN CRITERIA .
Giardia Inactivation (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Ammonia Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (mm)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.3
30
3.8
0.8
16
18
30
97
1.5
30
3.9
0.8
16
18
110
90
2.5
30
3.9
0.8
16
18
180
90
ESTIMATED COSTS
DESIGN
FLOW
mgd
1.8
4.8
11
IS
26
51
210
430
CAPITAL O&M TOTAL
COST COST COST
MILLION S c/lOOOgal
3.54
6.00
10.1
14.0
18.0
29.8
101
189
63.1
39.8
32.8
30.4
29.3
27.9
26.7
26.5
226
132
97.8
81.5
73.8
63.4
537
49.0
CAPITAL O&M TOTAL
COST COST COST
MILLION S c/lOOOgal
3.57
6.12
10.4
14.5
18.6
30.8
105
199
63.1
39.8
32.8
30.4
29.3
27.9
26.7
26.S
227
134
99.5
83.3
75.3
64.6
54.9
50.2
CAPITAL
COST
MILLION S
3.61
6.23
10.6
14.8
19.0
31.7
110
209
O&M
COST
TOTAL
COST
c/lOOOsal
63.1
39.8
32.8
30.4
293
27.9
26.7
265
229
135
101
845
76 S
65 S
56 1
51.4
(1) Nolc: The dcsicn criteria and estimated costs Tor these treatment conditions were used to estimate upcr.ulc
costs Tor switching to chloramines as secondary disinfectant.
-------
EXAMPLE CALCULATIONS FOR TABLE B-3
ESTIMATED CAPITAL, O&M AND TOTAL COSTS FOR
PLANTS INCREASING COAGULANT DOSAGE
Upgrade costs for this DBF control alternative were developed using the total costs for an
alum dose of 10 and 50 mg/L with total costs for an alum dose of 50 mg/L subtracted from
the total costs for an alum dose of 10 mg/L. In the calculations shown below, capital,
O&M, and total costs are calculated for a plant with an alum dose of 10 mg/L. Then costs
are generated for an alum dose of 50 mg/L.
I. BREAKDOWN OF COSTS FOR FLOW CATEGORY 9 AND ALUM DOSE OF 10 mg/L
A. Capital and O&M costs for a plant utilizing a 10 mg/L alum dose are identical to the
base plant (30 mg/L alum dose) for the following unit processes.
1. Raw water pumping.
2. Rapid mix.
3. Flocculation.
4. Clarification.
5. Filter media.
6. Gravity filter structure.
7. Backwash pumping facilities.
8. In-plant pumping.
9. Surface wastewater basins.
10. Hydraulic surface wash system.
11. Contact basin.
12. Clearwell storage.
13. Finished water pumping.
<
.' Total Capital Costs = $16,959,100
- O&M Costs = 23.7e/l,000 gal
Note that although the contact basin size predicted for a plant utilizing 10 mg/L alum
dose (shown in Table A-3) is 90 minutes and the base plant basin size is 60 minutes,
it is.assumed that the basin size for this plant is the"same as the base plant. This
assumption provides for a more accurate comparison of cost associated with the
different alum dosages.
B. Capital and O&M costs for a plant utilizing a 10 mg/L alum are modified for the
following unit processes:
. 1. ALUM FEED SYSTEM (WATERCOST PROCESS 35)
Alum Required: Assume an alum dosage of 10 mg/L.
B3-1
-------
a. Design Flow:
= (dosage in mg/L) x 8.34 x (design flow in mgd)
= 10 mg/L x 8.34 x 76 mpd = 90 Ib/hr
24 hr/day
b. Average Flow:
= 10 mff/L x 8.34 x 13 mgd = 45 Ib/day
, , 24 hr/day
Total Capital Costs = $97,600
O&M Costs = 0.67C/1.000 gal
2. CHLORINE GAS FEED SYSTEM (WATERCOST PROCESS 48)
Chlorine Required: Assume a chlorine dosage of 2.6 mg/L.
a. Design Flow:
' = (dosage in mg/L) x 8.34 x (design flow in mgd)
= 2.6 mg/L x 8.34 x 26 mgd - 564 Ib/day
b. Average Flow:
= 2.6 mg/L x 8.34 x 13 mgd = 282 Ib/day
Total Capital Costs ' . = $173,800
O&M Costs = 0.690/1,000 gal
3. CHEMICAL SOLIDS PUMPING (WATERCO$T PROCESS 101)
Assume solids concentration of 1 percent.
a. Design Conditions:
Solids Production:
= 11 mg/L x 8.34x26 mgd
= 2,390 Ib/day .
B3-2
-------
Solids Flow
2.390 Ib/davir 1flซgg|
8.34 Ib/MG x 10,000 mg/L x 1,440 min.
mg/L ,
20gpm
b. Average Conditions:
Solids Production:
= 1 1 mg/L x 8.34 x 13 mgd
= 1,190 Ib/day
Solids Flow fgpm):
= - 1.190 lb/davYinซgal _
8.34 Ib/MG x 10,000 mg/L x 1440 min
mg/L
= lOgpm
Total Capital Costs = $94,400
0&M Costs = 0.13C/1.000 gal
4. SOLIDS DEWATERING LAGOONS (WATERCOST PROCESs'32)
to s
Design Flow
Volume (ftj/yr) at design flow:
= 10.6 mg/T. Y ?.6 mgd x ft3 Y 365 dav * in8 pa
120 g/L x 1,000 mg/g x 7.48 gal x MG x yr
= 1 12,000 ft'/yr
B3-3
-------
Average Flow
Volume (ft3/yr) at average flow:
= 10.6 mg/L x 13 mgd x ft3 x 365 day x 10* gal
120 g/L x 1,000 mg/gx 7.48 gal x MG xyr
= 56,000 ft3/yr
I
Total Capital Costs =$66,100
O&M Costs = 0.15e/1,000 gal
5. DEWATERED SOLIDS HAULING
Assume 30 percent dewatered solids concentration
Volume of solids (yd3/yr) at design flow:
= 10.6 mg/L x 26 mgd x ft3 x 365 day x 10* gal x yd3
300 g/L x 1,000 mg/g x 7.48 gal x 27 ft3
= 4,150 yd3/yr
Volume of solids (yd3/yr) at average flow:
= 10.6 mg/L x 13 mgd x ft3 x 365 davs x 10* gal x vd3
300 g/L x 1,000 mg/g x 7.48 gal x 27 ft3
= 2,080 ydj/yr
Total Capital Costs = $168,800
. O&M Costs = 0.12e/1,000 gal
:
6. SODIUM HYDROXIDE FEED SYSTEM (WATERCO$T PROCESS 45)
Assume caustic dosage at 7.8 mg/L
Design Flow
= Dosage mg/L x 8.34 x flow mgd
. = 7.8 x 8.34 x 26 = 1,690 Ib/day
B3-4
-------
Average Flow
= 7.8 x 8.34 x 13 = 845 Ib/day
Total Capital Costs = $78,400
O&M Costs . = 1.138/1,000 gal
II. CAPITAL, O&M AND TOTAL COSTS FOR AN ALUM DOSE OF 10 mg/L
Sum of Capital Costs = $17,638,500
Sum of O&M Costs = $26.6e/l,000 gal
Total Cost
= (Capital cost ($1 x amortization factor x mng/.|) + o&M (0/1,000 gal)
Average flow (mgd) x 1,000 KG/MG x 365 days/yr
(17.638.500 x 0.11746 x IQm + 26.6
13 x 1,000 x 365
= 70.30/1,000 gal
B3-5
-------
III. BREAKDOWN OF CAPITAL AND O&M COSTS FOR FLQW CATEGORY 9 AND
ALUM DOSE OF 50 mg/L.
i
A. Capital and O&M costs for a plant utilizing a 50 mg/L alum dose are identical to a
plant utilizing a 10 mg/L dose for the following unit processes.
1. Raw water pumping.
2. Rapid mix.
3. Flocculation.
4. Clarification.
5. Chlorine gas feed system.
6. Filter media.
7. Gravity filter structure.
8. Backwash pumping facilities.
9. In-plant pumping.
10. Surface wastewater basins.
11. Hydraulic surface wash system.
12. Contact basin.
13. Clearwell storage.
14. Finished water pumping.
Total Capital Costs = $17,132,900
O&M Costs = 24.4e/l,000 gal
Note that although the contact basin size predicted for a plant utilizing a 50 mg/L
alum dose (shown in Table A-3) is 45 minutes ,and the basin size for a plant utilizing
a 10 mg/L alum dose is assumed to be 60 minutes, the basin size for a 50 mg/L alum
dose is assumed to be 60 minutes. This assumption provides for a more accurate
estimate of upgrade costs when the total costa are calculated.
B. The following unit processes must be modified at an alum dose.of 50 mg/L.
1. ALUM FEED SYSTEM (WATERCOST PROCESS 35)
Alum Required: Assume alum dosage of 50 mg/L.
i
a. Design Flow:
= 50 mg/L x 8.34 x 26 mgd = 10,840 Ib/day
b. Average, Flow:
= 50 mg/L x 8.34 x 13 nigd = 5,420 Ib/day
Total Capital Costs = $190,900
. O&M Costs = 3.18ซ/1,000 gal
B3-6
-------
2. CHEMICAL SOLIDS PUMPING (WATERCOST PROCESS 101)
Assume solids concentration of 1 percent.
a. Design Conditions:
Solids Production-
= 26 mg/L x 8.34 x 26 mgd
= 5,640 Ib/day
Solids Flow (gpm)-
5.640 Ib/davx in6 gal
8.34 Ib/MG x 10,000 mg/L x 1,440 min.
mg/L
= 47 gpm
b. Average Conditions:
Solids Production:
= 26 mg/L x 8.34 x 13 mgd
= 2,810 Ib/day
Solids Flow
2.810 Ib/dav x 1Qซ gal
8.34 Ib/MG x 10,000 mg/L x 1440 min
mg/L
= 23 gpm
Total Capital Costs = $105,700
O&M Costs = 0.14c/l,000 gal
3. SOLIDS DEWATERING LAGOONS (WATERCOST PROCESS 32)
Assume solids concentration 12 percent (120 g/L) to size the lagoon and a solids
production of 25.9 mg/L of total flow.
B3-7
-------
Design Flow
Volume (ftYyr) at design flow:
= 25.9 mg/L x 26 mgd x ft3 x 365 day x 10* gal
300 g/L x 1,000 mg/g x 7.48 gal
= 273,800 ftYyr
Average Flow
Volume (ft3/yr) at average flow:
= 25.9 mg/L x 13 mgd x ft3 x 365 dav x 10" gal
300 g/L x 1,000 mg/g x 7.48 gal
= 136,900 ftj/yr
Total Capital Costs = $136,900
O&M Costs = 0.35e/l,000 gal
4. DEWATERED SOLIDS HAULING
Assume 30 percent dewatered solids concentration
Volume of solids (yd3/yr) at design flow:
= 25.9 mg/L x 26 mgd x ft3 x 365 dav x 1Q6 gal x vd3
300 g/L x 1,000 mg/g x 7.48 gal x 27 ft3
= 10,140yd3/yr
Volume of solids (yd'/yr)1 at average flow:
= 25.9 mg/L x 13 mgd x ft3 x 365 dav x 10" gat x vd3
300 g/L x 1,000 mg/g x 7.48 ft3 x 27 ft3
= 5,070 yd3/yr
Total Capital Costs . = $211,000
. O&M Costs - = 0.16
-------
5. SODIUM HYDROXIDE FEED SYSTEM (WATERCOST PROCESS 45)
Assume caustic dosage of 23.1 mg/L
Design Flow
= Dosage (mg/L) x 8.34 x Flow (mgd)
= 23.1 x 8.34 x 26 = 5,000 Ib/day
Average Flow
= 23.1 x 8.34.x 13 = 2,500 Ib/day
Total Capital Costs = $148,400
- O&M Costs = 3.2C/1.000 gal
IV. CAPITAL, O&M AND TOTAL COSTS FOR AN ALUM DOSE OF 50 mg/L
Sum of Capital Costs = $17,925,800
Sum of O&M Costs = 31.40/1,000 gal
Total Cost:
= (Capital cost (ft x amortization factor x IQQe/S) + O&M (c/1,000 gal)
Average flow (mgd) x 1,000 KG/MG x 365 days/yr
= ri7.925.8QQ x 0.11746 x 100^ + 31.4
13 x 1,000 x 365 , .
= 75.8
-------
TABLE B-3
LARGE SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS
FOR SYSTEMS WITH ALUM DOSE OF 10 mg/1
TTHM LIMIT OF
Giardia Inaclivatioo (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact fmuO
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
'
! DESIGN
FLOW
mud
1.8
4.8
11
18
26
51
210
430
PREDICTED DESIGN CRITERIA
0.5 (1)
10
2.6
7.8
11
90
40
1.5
10
2.7
7.8
11
210
40
2.5
10
2.8
7.9
11
330
40
ESTIMATED COSTS
CAPITAL O&M TOTAL
COST COST COST
MILLIONS c/lOOOeal
3.46
5.88
9.93
13.7
17.7
29.2
99.9
187
59.2
. 36.7
29.9
27.6
26.6
25.3
24.1
23.9
219
127
93.8
77.8
70.3
.60.1
50.9
46.2
CAPITAL O&M TOTAL
COST COST COST
MILLION S c/lOOOeal
3.50
5.99
10.1
14.2
18.3
, 30.2
104
197
59.2
36.7
29.9
27.6
26.6
.25.3
24.1
23.9
220
129
95.5
79.6
71.8
613
52.0
47.4
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/lOOOeal
3.54
6.09
10.4
14.5
18.7
31.1
108
206
59.2
36.7
29.9
27.6
26.6
25.3
24.1
23.9
222
130
97.1
80.7
72.9
613
53.1
48.5
PREDICTED DESIGN CRITERIA
Giardia Inactivation (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact fmin)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5
10
2.5
7.8
11
90
30
1.5
10
2.6
7.8
11
200
30
2.5
10
2.7
7.8
11
330
30
ESTIMATED COSTS
DESIGN
FLOW
med
1.S
48
11
IS
26
51
210
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/lOOOgal
3.46
5.8S
9.93
13.7
17.7
29.2
999
430 187
59.2
36.7
29.9
27.6
26.6
25.3
24.1
23.9
219
127
93.8
77.8
70.3
60.1
50.9
46.2
CAPITAL O&M TOTAL
COST COST COST
MILLION S c/lOOOul
3.50
5.99
10.2
14.2
18.3
30.2
104
197
59.2
36.7
29.9
27.6
26.6
25.3
24.1
23.9
220
129
95.5
79.6
71.8
61.3
520
47.4
CAPITAL
COST
MILLION S
3.54
6.10
105
14.6
18.7
31.2
109
207
O&M TOTAL
COST COST
c/IOOOeal
59.2
36.7
29.9
27.6
266
25.3
241
23.9
222
130
97.2
SOS
730
62.5
53.2
486
(1) Note: The design criteria and estimated costs Tor these treatment conditions were used to estimate upcrade cost*
Tor increasing the alum dose from 10 to 50 ing/I.
-------
TABLE B-3 (conI'd)
LARGE SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS
FOR SYSTEMS WITH ALUM DOSE OF 50 mg/I
TTHM LIMIT OF 50/tg/L
Giardia loactivatioo (Log)
Alum Dose (mg/L)
Chloripe Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (mln)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
DESIGN
FLOW
nucd
1.8
4.8
11
.18
26
51.
210
430
PREDICTED DESIGN CRITERIA
0.5(1)
50
2.4
23
26
45
82
1.5
50
24
23
26
150
82
ESTIMATED COSTS
CAPITAL O&M TOTAL
COST COST COST
MILLIONS c/lOOOeal
3.53
5.99
10.1
14.0
17.9
29.7
101
190
64.5
41.7
34.8
32.4
31.4
30.0
28.8
28.6
227
134
99.7
83.4
75.8
65.5
55.9
51.1
CAPITAL O&M TOTAL
COST COST COST
MILLIONS C/lOOOeal
3.57
. 6.10
10.3
14.4
18.6
30,7
106
200
64.5
41.7
34.8
32.4
31.4
30.0
28.8
28.6
229
135
101
85.2
773
66.7
57.0
523
2.5
-------
EXAMPLE CALCULATIONS FOR TABLE B-4
ESTIMATED CAPITAL, O&M AND TOTAL COSTS FOR
OZONE AS A PRIMARY DISINFECTANT AND
CHLORAMINES AS A SECONDARY DISINFECTANT
I. BREAKDOWN OF CAPITAL AND O&M COSTS FOR FLOW CATEGORY 9
1. Capital and O&M costs for a completely new treatment plant utilizing O3/NH2C1 are
identical to the base plant for the following unit processes:
A. Raw water pumping.
B. Alum feed system.
C. Rapid mix.
D. Flocculation.
E. Clarification.
F. Filter media.
G. Gravity filter structure.
H. Backwash pumping facilities.
I. In-plant pumping.
J. Surface wash water basins.
K. Hydraulic surface wash system.
L. Sodium hydroxide feed system.
M. Contact basin.
N. Chemical solids pumping. v
O. Solids dewatering.
P. Dewatered solids hauling.
Q. Clearwell storage.
R. Finished!water pumping.
Total Capital Costs ' = $17,629,100
O&M Costs = 28.4C/1.000 gal
Note that although a chlorine contact basin is not needed for a system utilizing
ozone for primary disinfection, the contact basin is assumed to be identical to the
base plant. This assumption provides for a more accurate estimate of upgrade costs
when the total costs are calculated.
2. Capital and O&M costs are modified for the following unit processes:
CHLORINE GAS FEED SYSTEM (WATERCOST.Process 48)
Chlorine Required: Assume chlorine dosage of 3.0 mg/L
B4-1
-------
Design Flow:
= (dosage in mg/L) x 8.34 x (design flow in mgd)
= 3.0 mg/L x 8.34 x 26 mgd = 650 Ib/day
. Average Flow:
= 3.0 mg/L x 8.34 x 13 mgd = 330 Ib/day
Total Capital Costs = $193,900
O&M Costs = 0.77e/1,000 gal
3. Capital and O&M costs are required for the following additional unit process:
AMMONIA FEED SYSTEM (WATERCOST Process 38)
Ammonia Required: Assume ammonia dosage of 0.8 mg/L
Design Flow:
= (Dosage in mg/L) x 8.34 x (design flow in mgd)
= 0.8 mg/L x 8.34 x 26 mgd = ,173 Ib/day
Average Flow:
= ,-0.8 mg/L x 8.34 x 13 mgd = 87 Ib/day
Total Capital Costs .. = $86,900
O&M Costs = O.OSc/1,000 gal
\ i
OZONE FEED SYSTEM (WATERCO$T Process 83 and 84)
Costs include generation system and contactor.
Ozone Required: Assume ozone dosage of 5.0 mg/L.
Design Flow:
= (dosage in mg/L) x 8.34 x (design flow in mgd)
= 5.0 x 8.34 x 26 mgd = 1,080 Ib/day
B4-2
-------
Average Flow:
= 5.0 x 8.34 x 13 mgd = 540 Ib/day
Total Capital Costs = $3,356,000
O&M Costs = 3.70/1,000 gal
II. CAPITAL, O&M, TOTAL AND UPGRADE COSTS
Sum of Capital Costs = $21,265,900
Slim of O&M Costs = 32.9C/1,000 gal
Total Cost:
= (Capital m x amortization factor x IQOe/S) + O&M (c/1,000 gal)
13 x 1,000 x 365
= (21.265.900 x 0.11746 x 1001 + 32.9
13 x 1,000 x 365
= 85.5C/1.000 gal
Upgrade Cost for Switching to O3/NH,C1:
= Total cost for O3/NH2C1 plant - Total cost for base plant
= 85.5 - 73.1 = 12.4c/l,000 gal
B4-3
-------
TABLE B-4
LARGE SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS
FOR SYSTEMS SWITCHING TO OZONE/CHLORAMINES
TTHM LIMIT OF 100/ig/L
~
Giardia Inactivatioo (Log)
Alum Dose (mg/L)
Ozone Dose (mg/L)
Chlorine Dose (mg/L)
Ammonia Dose (mg/L)
Caustic Dose (mg/L)
'Solids Production (mg/L)
Disinfection Contact (min
I Percent of Systems Meeting
I Constraints Listed in Sect. 7.4
-ฐg)
L)
din)
:ling
xl. 7.4
^ >^M^^_
_
DESIGN
FLOW
1.8
11
' 18
26
51
210
430
CAPITAL
COST.
MILLION S
4.08
7.15
113
16.7
21.3
34.8
120
226
0-5(1)
30
5.0
3.0
0.8
15
18
0
100
O&M
COST
c/10
70.6
45.0
363
34.0
319
31.0
29.6
293
*ป ซv*n vปi\i i
-
" ^ ^
^ ^-*-v^_
ESTIMATED COSTS
TOTAL
COST
258
.155
115
95.2
85.5
7Z5
61.8
5&3
CAPITAL
COST
MILLIONS
4.12
7.26
116
17.2
21.9
35.8
124
236
CK1A
1
1.5
30
5.0
7 A
-XU
0.8
15
18
0
100
O&M
COST.
C/101
70.6
45.0
36.3
34.0
319
.31.0
29.6
2.5
30
5.0
3.0
0.8
15
18
0
100
' .
TOTAL
COST
Xlgal
260
156
117
97.0
87.0
73.6
63.0
57.4
CAPITAL
COST
MILLIONS
4.15
7.36
118
. 17.5
213
36.7
128
245
-
.
O&M TOTAL
COST COST
c/lOOOeal
70.6
45.0
36.3
34.0
319
31.0
29.6
29.3
262
158
119
98.1
.88.1
74.7
64.0
58.5
-
Giardia Inactivation (Log)
Alum Dose'(mg/L)
Ozone Dose (mg/L)
Chlorine Dose (mg/L)
Ammonia Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (mm\
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
TTHM LIMIT OF 50 /tg/L
PREDICTED DESIGN CRITERIA
0.5
30
5.0
3.0
0.8
15
18
_0_
98
98
DESIGN
FLOW
mgd
1.8
4.8
11
18
26
51
210
430
CAPITAL
COST
MILLIONS
4.08
7.15
12.?
16.7
21.3
34.8
120
226^
ESTIMATED COSTS
O&M
COST
c/1
70.6
45.0
36.3
34.0
32.9
31.0
296
29.3
TOTAL
COST
jgal
258
155
115
95.2
85.5
715
61.8
56.3
CAPITAL
COST
MILLION S
4.12
7.26
12.6
17.2
21.9
35.8
124
. 236
O&M TOTAL
COST COST
c/10j
70.6
45.0
36.3
34.0
32.9
31.0
29.6
29.3^
Mgal
260
156
117
97.0
87.0
73.6
63.0
57.4
CAPITAL
COST
MILLION S
4.15
7.36
12.8
17.5
22.3
367
12S
2-j.s
-------
EXAMPLE CALCULATIONS FOR TABLE B-5
ESTIMATED CAPITAL, O&M AND TOTAL COSTS FOR
INSTALLATION OF GAC ADSORPTION (EBCT = 15 MINUTES)
I. BREAKDOWN OF CAPITAL AND O&M COSTS FOR FLOW CATEGORY 9
1. Capital and O&M costs for a completely new treatment plant utilizing
coagulation/filtration and GAC adsorption at a 15 minute empty-bed contact time
are identical to -the base plant for the following unit processes:
A. Raw water pumping.
B. Alum feed system.
C. Rapid mix.
D. Flocculation.
E. Clarification.
F. Chlorine gas feed system.
G. Filter media.
H. Gravity filter structure. .
I. Backwash pumping facilities.
, J. In-plant pumping.
. K. Surface wash water basins.
L. Hydraulic surface wash system.
M. Sodium hydroxide feed system.
N. Contact basin. "
O. Chemical solids pumping.
P. Solids dewatering.
Q. Dewatered solids hauling.
R. Clearwell storage.
S. Finished water pumping.
Total Capital Costs = $17,796,700
O&M Costs . = 29.00/1,000 gal
2. Capital and O&M costs are required for the following additional unit process:
GAC CONTACTORS
Costs were developed based on the Adams and Clark cost model using an EBCT of
15 minutes.
Total Capital Costs = $9,780,000
- O&M Costs = 5.1c/l,000gal
B5-1
-------
II. CAPITAL, O&M, TOTAL AND UPGRADE COSTS
Sum of Capital Costs = $27,576,700
Sum of O&M Costs = 34. lc/1,000 gal
Total Cost:
" (Capital/I) x amortization factor x lOQc/S^t + o&M (0/1,000 gal)
13 x 1,000 x 365 v / . g i;
= r27.576.7QQx 0.11746 x mm +34.1
13 x 1,000 x 365
= 102.4e/l,000 gal
Upgrade Cost for Installation of GAG:
= Total cost for GAG plant - Total cost for base plant
= 102.4 - 73.1 = 29.3c/l,000,gal .
B5-2
-------
TABLE B-5
LARGE SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS
FOR SYSTEMS ADDING GAC
(EBCT = 15 Minutes)
TTHM LIMIT OF 100/ig/L
Giardia Inactivation (Log)
Alum Dose (mg/L) '
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (tain)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
._'
DESIGN
FLOW
1.8
4.8
11
18
26
51
210
i 430
PREDICTED DESIGN CRITERIA
0-5(1)
30
2.3
.16
18
60
96
1.5
30
2.3
16
18
180
96
.1
ESTIMATED COSTS
CAPITAL
COST
MILLION $
4.54
8.29
14.4
20.5
27.6
. 45.0
146
270
O&M TOTAL
COST COST
c/1000eal .
77.5
52.2
4Z7
40.2
34.1
3L8
29.7
29.2
286
179
135
115
102
. 85.4
69.0
61.5
CAPITAL
COST
MILLION S
4.6
8.4
14.6
21.1
28.2
46.0
151
280
O&M ' TOTAL
COST .COST
c/lOOOeal
77.5
52.2
42.7
- 40.2
34.1
31.8
29.7
29.2
288
181
137
117
104
86.6
70.1
62.7
2.3
30
2.4
16
18
96
^_
^ ___
CAPITAL O&M TOTAL
COST COST COST
Mirjf ION t -xnnn
4.6
8.5
14.9
21.3
28.6
46.9
155
. 289
77.5
52.2
42.7
40.2
34.1
31.8
29.7
'29.2
2S9
183
139
118
105
.87.7
71.2
63.7
TTHM LIMIT OF 50 jig/L*
Giardia Inactivation (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (mini
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
rKiiuiuJtiU D
0.5
30
2.3
16
18
60
92
ESIGN CRIT
^^ ^^^^^ป^^
ESTIMATED COSTS
DESIGN
FLOW
1.8
4.8
11
18
26
51
210
. 430
CAPITAL O&M TOTAL
COST COST COST
MILLION J c/lOOOeal
4.54
8.29
14.4
20.5
27.6
45.0
146
270
77.5
52.2
42.7
40.2
34.1
31.8
29.7
292
286
179
135
115
102
85.4
69.0
61.5
CAPITAL
COST
MILLION S
4.58
8.40
14.6
21.0
28.2
46.0
151
280
SRIA
Ts
30
2.3
16
18
180
92
..
_
2.5
30
2.4
16
18
92
O&M TOTAL
COST COST
c/lOOOeal
77.5
52.2
42.7
40.2
341
31.8
29.7
29.2
288
181
137
117
104
86.6
70.1
62.7
CAPITAL O&M
COST COST
MILLIONS -/fn(
461
8.50
14.9
21.4
28.7
47.0
155
290
77.5
52.2
42.7
40.2
3-4.1
31 S
29.7
29.2
TOTAL
COST
)Ooil
290
1S3
139
IIS
10?
87.S
713
63 S
(1) Noio. Used 10 estimalc cosis for adding GAC with a 15 minute EHCT
-------
TABLE B-5 (coofd)
LARGE SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS
FOR SYSTEMS ADDING GAG
(EBCT = 30 Minutes)
TTHM LIMIT OF 100/ig/L
Giardia loactivatioo (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Causiic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (mitO
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
DESIGN
FLOW
m^d
1.8
4.8
11
18
26
51
210
. 430
PREDICTED DESIGN CRITERIA ~
0.5 (1)
30
2.2
16
18
60
100
1 5
3O
2 2
16
18
180
inn
ESTIMATED COSTS
CAPITAL
COST
MILLION $
5.34
10.3
17.3
25.3
32.3
54.9
180
- 326
O&M TOTAL
COST COST
c/lOOOaal
73.2
47.9
38.5
35.9
34.7
30.8
28.9
28 J
319
206
150
128
115
96.2
77.1
673
CAPITAL O&M TOTAL
. COST COST COST
MILLIONS c/ioonซi
5.38
10.4
17.6
25.8
319
55.8
184
. 336
73.2
47.9
38.5
35.9
34.7
30.8
28.9
28.5
321
208
152
130
116
97.4
78.3
68.5
T- -
2.5
30
2.2
16
18
300
100
CAPITAL O&M TOTAL
COST COST COST '
MILLION $ ซ-/innn...i
5.42
10.5
17.8
26.1
33.3
56.8
188
345
73.2
47.9
38.5
35.9
34.7
30.8
28.9
28.5
322
210
153
131
117
98.5
794
69.6
TTHM LIMIT OF 50/ig/L
Giardia Inactivation (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact ( mia)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
DESIGN
FLOW
mRd
1.8
4.8
11
18
26
51
210
430
PREDICTED DESIGN CRITERIA
0.5
30
2.2
17
18
60
98
1 <
2 2
18
180
Q8
ESTIMATED COSTS
CAPITAL
COST
MILLIONS
5.34
10.3
17.3
25.3
32.3
54.9
180
326
O&M TOTAL
COST COST
c/lOOOgal
73.2
47.9
38 5
35.9
34.7
308
28.9
28.5
319
206
150
128
115
96.2
77.1
67.3
CAPITAL O&M TOTAL
COST COST COST
MILLION S c/1000ซl
5.38
10.4
17.6
25.8
32.9
55.8
184
336
73.2
47.9
38.5
35.9
34.7
30.8
28.9
28..'5
321
208
152
130
116
97.4
78.3
68.5
2.5
30
2.2
17
18
300
98
CAPITAL O&M TOTAL
COST COST COST
MILLIONS .-/innno.,1
5.42
10.6
17.8
26 1
33.3
56.8
1S9
73.2
47.9
3S.5
35.9
34.7
30.8
2S.9
322
210
153
131
117
9S6
TO 5
(1) Noic Ustd 10 estimate cosis for adding GAC with a 30 rninuic EBCT
-------
EXAMPLE CALCULATIONS FOR TABLE B-6
ESTIMATED CAPITAL, O&M AND TOTAL COSTS FOR
INSTALLATION OF NANOFILTRATTON
I. BREAKDOWN OF CAPITAL AND O&M COSTS FOR FLOW CATEGORY 9
1. Capital and O&M costs for a completely new treatment plant utilizing
coagulation/filtration with membrane filtration are identical to the base plant for the
' following unit processes:
A. Raw water pumping.
B. Alum feed system.
C. Rapid mix.
D. Flocculation.
E. Clarification.
F. Chlorine gas feed system.
G. Filter media.
H. Gravity filter structure.
I. Backwash pumping facilities.
J. In-plant pumping.
K. Surface wash water basins.
L. Hydraulic surface wash system.
M. Sodium hydroxide feed system.
N. Contact basin.
O. Chemical solids pumping.
P. Solids dewatering.
Q. Dewatered solids hauling.
R. Clearwell storage.
S. Finished water pumping.
Total Capital Cost = $17,796,700
O&M Cost = 29.00/1000 gal
2. Capital and O&M costs are required for the following additional unit process:
MEMBRANE SYSTEM
Costs for membrane systems were obtained from two different vendors and
averaged based on a molecular weight cutoff (MWC) of 200, 80 psi operating
pressure and 85 percent recovery. The vendors also provided data for
development of cost estimates for buildings, recovery rate, reject disposal;
electrical, chemical maintenance and labor requirements.
^
Total Capital Cost , = $20,820,000
O&M Cost = 56.0c/l,000 gal
B6-1
-------
II. CAPITAL, O&M, TOTAL AND UPGRADE COSTS
Sum of Capital Costs = $38,616,700
Sum of O&M Costs = 85.0c/1,000 gal
Total Cost:
= rCapital m x amortization factor x IQOe/t) + .O&M (c/1,000 gal)
13 x 1,000 x 365
= f38.57Q.QQQ x 0.11746 TC 100) + 85.0
13 x 1,000 x 365
= 180e/1,000 gal
Upgrade Cost for Installation of Nanofdtration:
/
= Total cost for nanofiltration plant - Total cost for base plant
= 180 - 73.1 = 107(8/1,000
B6-2
-------
TABLE B-6
LARGE SYSTEMS
DESIGN CRITERIA AND TREATMENT COSTS
FOR SYSTEMS ADDING NANOFILTRATION
TTHM LIMIT OF lOOjig/L
Giardia Inactivalioo (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (tain)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
DESIGN
.FLOW
mgd
1.8
4.8
11
18
26
51
210
' 430
PREDICTED DESIGN CRITERIA
0.5(1)
30
2.1
12
18
60
100
1.5
30
2.1
12
18
180
100
ESTIMATED COSTS
CAPITAL O&M TOTAL
COST . -COST COST- .-
MILLION $ c/lOOOxal
5.90
11.1
20.3
29.3
38.6
68.9
263
524
178
112
98.4
88.0
85.0
78.7
TLS
71.2
449
283
229
195
181
161
143
134
CAPITAL O&M : TOTAL
COST COST COST
MILLION $ c/1000ซl
5.94
11.2
20.6
29.8
39.2
69.9
267
534
178
112
98.4
88.0
85.0
78.7
72.5
71.2
451
284
231
197
182
162
144
^135
2.5
30
2 5
12
1R
300
100
CAPITAL O&M TOTAL
COST COST COST
MILLIONS e/innriMi .
5.97
11.3
20.8
30.1
39.7
70.9
271
543
178
112
98.4
8S.O
85.0
78.7
72.5
71.2
453
2S6
232
198
183
163
145
136
TTHM LIMIT OF 50/ig/L
PREDICTED DESIGN CRITERIA
Giardia Inactivation (Log)
Alum Dose (mg/L)
Chlorine Dose (mg/L)
Caustic Dose (mg/L)
Solids Production (mg/L)
Disinfection Contact (min)
Percent of Systems Meeting
Constraints Listed in Sect. 7.4
0.5
30
2.1
12
18
60
100
1.5
30
2.1
12
18
180
100
2.5
30
2.2
12
18
300
100
ESTIMATED COSTS
DESIGN
FLOW
med
1.8
4.8
11
18
26
' 51
210
430
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/1000Kal
5.90
11.1
203
29.3
38.6
68.9
263
524
178
112
98.4
8S.O
85.0
78.7
72.5
71.2
449
283
229
195
181
161
143
134
CAPITAL O&M TOTAL
COST COST COST
MILLION $ c/IOOOeal
5.94
11.2
20.6
29.8
39.2
69.9
267
534
178
112
98.4
88.0
85.0
78.7
72.5
71.2
451
284
231
197
182
162
144
135
CAPITAL O&M TOTAL
COST COST COST
MILLION $ r/lfWIonl
5.98
11.4
20.9
30.1
39.7
71.0
272
544
178
112
98.4
88.0
85.0
78.7
72.5
71.2
453
2S6
232
I9S
183
163
145
136
(1) NOIC- The design crilcna and estimated cosls for these treatment conditions wore used to estimate upgrade costs
for adding naiiofiltratioii.
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