EPA/625/R-92/004
September 1992
Manual
Guidelines for Water Reuse
U.S. Environmental Protection Agency
Office of Water
Office of Wastewater Enforcement and Compliance
Washington, DC
Office of Research and Development
Office of Technology Transfer and Regulatory Support
Center for Environmental Research Information
Cincinnati, Ohio
U.S. Agency for International Development
Washington, DC
Printed on Recycled Paper
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Notice
This document has been reviewed in accordance with the U.S. Environmental Protection Agency's peer and
administrative review policies and approved for publication. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use.
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Contents
Chapter
Page
1 INTRODUCTION 1
1.1 Objectives of the Guidelines 1
1.2 Water Demands 1
1.3 Source Substitution , 2
1.4 Pollution Abatement 3
1.5 Treatment and Water Quality Considerations 3
1.6 Overview of the Guidelines 4
1.7 References 5
2 TECHNICAL ISSUES IN PLANNING WATER REUSE SYSTEMS 7
2.1 Planning Approach 7
2.1.1 Preliminary Investigations 7
2.1.2 Screening of Potential Markets 8
2.1.3 Detailed Evaluation of Selected Markets 9
2.2 Potential Uses of Reclaimed Water 10
2.2.1 National Water Use 10
2.2.2 Potential Reclaimed Water Demands , 12
2.2.3 Reuse and Water Conservation 14
2.3 Sources of Reclaimed Water 14
2.3.1 Locating the Sources 14
2.3.2 Characterizing the Sources 15
2.4 Treatment Requirements for Water Reuse 18
2.4.1 Health Assessment of Water Reuse 19
2.4.2 Treatment Requirements 29
2.4.3 Reliability in Treatment 36
2.5 Seasonal Storage Requirements 43
2.5.1 Identifying the Operating Parameters 43
2.5.2 Storage to Meet Irrigation Demands 44
2.5.3 Storage to Prevent Surface Water Discharge 46
2.5.4 Partial Commitments of Supply 47
2.6 Supplemental Water Reuse System Facilities 48
2.6.1 Conveyance and Distribution Facilities 48
2.6.2 Operational Storage 54
2.6.3 Alternative Disposal Facilities 56
2.7 Environmental Impacts 59
2.7.1 Land Use Impacts 59
2.7.2 Stream Flow Impacts 60
2.7.3 Hydrogeological Impacts 60
2.8 References 60
iii
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Contents (continued)
Chapter Page
3 TYPES OF REUSE APPLICATIONS 67
3.1 Introduction 67
3.2 Urban Reuse 67
3.2.1 Reclaimed Water Demand .....68
3.2.2 Reliability and Public Health Protection 69
3.2.3 Design Considerations 69
3.3 Industrial Reuse 72
3.3.1 Cooling Water 72
3.3.2 Boiler-Feed Water 75
3.3.3 Industrial Process Water 75
3.4 Agricultural Irrigation 76
3.4.1 Estimating Agricultural Irrigation Demands 79
3.4.2 Reclaimed Water Quality 81
3.4.3 Other System Considerations 86
3.5 Habitat Restoration/Enhancement and Recreational Reuse 90
3.5.1 Natural and Manmade Wetlands 90
3.5.2 Recreational and Aesthetic Impoundments 91
3.5.3 Stream Augmentation ; 92
3.5.4 Other Recreational Uses 93
3.6 Groundwater Recharge 93
3.6.1 Methods of Groundwater Recharge 94
3.6.2 Fate of Contaminants in Recharge Systems 97
3.6.3 Health and Regulatory Considerations 100
3.7 Augmentation of Potable Supplies 102
3.7.1 Water Quality Objectives for Potable Reuse 102
3.7.2 Indirect Potable Water Reuse 103
3.7.3 Groundwater Recharge for Potable Reuse 103
3.7.4 Direct Potable Water Reuse 104
3.8 Case Studies 107
3.8.1 Pioneering Urban Reuse for Water Conservation: St. Petersburg,
Florida .107
3.8.2 Meeting Cooling Water Demands with Reclaimed Water: Palo Verde Nuclear
Generating Station, Arizona 108
3.8.3 Agricultural Reuse in Tallahassee, Florida 109
3.8.4 Seasonal Water Reuse Promotes Water Quality Protection: Sonoma County,
California 109
3.8.5 Combining Reclaimed Water and River Water for Irrigation and Lake
Augmentation: Las Colinas, Texas 110
3.8.6 Integrating Wetlands Application with Urban Reuse: Hilton Head
Island, South Carolina 112
3.8.7 Groundwater Replenishment with Reclaimed Water: Los Angeles
County, California 113
3.8.8 Aquifer Recharge Using Injection of Reclaimed Water: El Paso, Texas 114
3.8.9 Water Factory 21 Direct Injection Project: Orange County, California 115
3.9 References 117
4 WATER REUSE REGULATIONS AND GUIDELINES IN THE U.S. 123
4.1 Inventory of Existing State Regulations 123
4.1.1 Reclaimed Water Quality and Treatment Requirements 126
4.1.2 Reclaimed Water Monitoring Requirements 130
4.1.3 Treatment Facility Reliability 130
IV
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Contents (continued)
Chapter
Page
4.1.4 Minimum Storage Requirements 131
4.1.5 Application Rates 131
4.1.6 Groundwater Monitoring 131
4.1.7 Setback Distances for Irrigation 131
4.2 Suggested Guidelines for Water Reuse 132
4.3 References 140
5 LEGAL AND INSTITUTIONAL ISSUES 141
5.1 Identifying Legal Issues . 141
5.2 Federal Legal Issues 142
5.3 State Legal Issues 142
5.3.1 State Water Rights 142
5.3.2 State Liability Laws 144
5.3.3 State Franchise Law 144
5.3.4 State Case Law ; 145
5.4 Local Legal Issues 145
5.4.1 Reuse Ordinance 145
5.4.2 User Agreements , 146
5.4.3 Institutional Structures 146
5.5 Institutional Inventory and Assessment. '. 147
5.6 Guidelines for Implementation 147
5.7 Case Studies '. 149
5.7.1 1979 Wyoming Case: Thayervs. City of Rawlins 149
5.7.2 1989 Arizona Case: Arizona Public Service vs. Long 150
5.8 References 150
6 FUNDING ALTERNATIVES FOR WATER REUSE SYSTEMS 151
6.1 Decision Making Tools 151
6.2 Externally Generated Funding Alternatives 152
6.2.1 Municipal Tax-Exempt Bonds 152
6.2.2 Grant and State Revolving Fund Programs 152
6.2.3 Capital Contributions 154
6.3 Internally Generated Funding Alternatives 154
6.3.1 Operating Budget and Cash Reserves 154
6.3.2 Property Taxes and Existing User Charges 155
6.3.3 Special Assessments or Special Tax Districts 155
6.3.4 Connection Fees 156
6.3.5 Reuse User Charges 156
6.4 Incremental Versus Proportionate Share Costs 156
6.4.1 Incremental Cost Basis 155
6.4.2 Proportionate Share Cost Basis 157
6.5 Phasing and Participation Incentives 158
6.6 Sample Rates and Fees 158
6.6.1 Connection Fees , 158
6.6.2 User Fees 158
6.7 Case Studies ......159
6.7.1 Financial Incentives for Water Reuse: Los Angeles County, California 159
6.7.2 The Economics of Urban Reuse: Irvine Ranch Water District, California 160
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Contents (continued)
Chapter
Page
6.7.3 Determining the Financial Feasibility of Reuse in Florida .-.161
6.7.4 An Innovative Funding Program for an Urban Reclaimed Water
System: Boca Raton, Florida 163
6.8 References 163
7 PUBLIC INFORMATION PROGRAMS 165
7.1 Why Public Participation? 165
7.1.1 Source of Information 165
7.1.2 Informed Constituency 165
7.2 Defining the "Public" 166
7.3 Overview of Public Perceptions 166
7.4 Involving the Public in Reuse Planning 168
7.4.1 General Requirements for Public Participation 169
7.4.2 Specific Customer Needs 170
7.4.3 Agency Communication 171
7.5 Case Studies ! 172
7.5.1 Using Public Surveys to Evaluate Reuse: Venice, Florida 172
7.5.2 Having the Public Evaluate Reuse Alternatives: San Diego, California 174
7.5.3 Accepting Produce Grown with Reclaimed Water: Monterey, California 175
7.5.4 Water Independence for Cape Coral-An Implementation Update 176
7.6 References 176
8 WATER REUSE OUTSIDE THE U.S 179
8.1 Water Reuse in Other Countries 179
8.1.1 Planning Water Reclamation Projects 180
8.1.2 Technical Issues 182
8.1.3 Institutional and Legal Issues 188
8.1.4 Economic and Financial Issues 190
8.1.5 Implementation of Reuse in Developing Countries 191
8.2 Examples of Reuse Programs Outside the U.S 191
8.2.1 Argentina 192
8.2.2 Brazil 192
8.2.3 Chile 193
8.2.4 Cyprus 193
8.2.5 India 193
8.2.6 Israel 194
8.2.7 Japan 194
8.2.8 Kuwait 195
8.2.9 Mexico 195
8.2.10 People's Republic of China 195
8.2.11 Peru 197
8.2.12 Republic of South Africa 197
8.2.13 Saudi Arabia 197
8.2.14 Singapore 198
8.2.15 Sultanate of Oman 198
8.2.16 Tunisia 199
8.2.17 United Arab Emirates 199
8.3 References 200
VI
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Contents (continued)
Chapter
APPENDIX A
APPENDIX B
Page
STATE REUSE REGULATIONS AND GUIDELINES 203
ABBREVIATIONS AND ACRONYMS 245
VII
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Tables
Table Page
1 Infectious Agents Potentially Present in Untreated Domestic Wastewater 20
2 Infectious Doses of Selected Pathogens 22
3 Microorganism Concentrations in Raw Wastewater 22
4 Typical Pathogen Survival Times at 20-30 °C 23
5 Inorganic and Organic Constituents of Concern in Water Reclamation
and Reuse 27
6 Typical Composition of Untreated Municipal Wastewater 28
7 Typical Constituent Removal Efficiencies for Primary Treatment 30
8 Typical Percent Removal of Microorganisms by Conventional Wastewater
Treatment 30
9 Applicability of Alternative Disinfection Techniques 32
10 Typical Filtration Process Removal 34
11 Coagulation-Sedimentation Typical Constituent Removals 35
12 Summary of Class I Reliability Requirements 38
13 Recommended Cooling Water Quality Criteria for Make-Up Water
to Recirculating Systems 74
14 Recommended Industrial Boiler-Feed Water Quality Criteria 76
15 Industrial Process Water Quality Requirements 77
16 Industrial Water Reuse Quality Concerns and Potential Treatment Processes 77
17 Crop Salt Tolerance 84
18 Salinity of Applied Water 85
19 Recommended Limits for Constituents in Reclaimed Water for Irrigation 87
20 Summary of Facilities and Management Practices for Percolation Recharge 96
21 Water Quality at Phoenix, Arizona SAT System 97
22 Results of Test Basin Sampling Program at Whittier Narrows, California 100
23 Factors that May Influence Virus Movement in Groundwater , 101
24 Isolation of Viruses Beneath Land Treatment Sites 101
25 Test Results, Denver Potable Water Reuse Demonstration Project 105
26 Summary of State Regulations and Guidelines 125
27 Number of States with Regulations or Guidelines for Each Type of
Reuse Application 126
28 Suggested Guidelines for Water Reuse 133
29 User Fees for Existing Urban Reuse Systems 159
30 Percentage of Respondents Opposed to Various Uses of Reclaimed Water
in General Opinion Surveys 167
31 The Tools of Public Participation 169
32 Extent of Water and Sanitation Services in Urban Areas of Developing
Countries 182
33 Recommended Microbiological Quality Guidelines for Wastewater Use
in Agriculture ; 185
34 Expected Removal of Excreted Microorganisms in Various Wastewater
Systems 186
35 Quality Criteria of Treated Wastewater Effluent to be Reused for
Agricultural Irrigation in Israel 187
viii
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Tables (continued)
Table Page
36 Typical Land Area Required for Pond Treatment Systems and Secondary
Treatment Plants 188
37 Uses of Reclaimed Water in Japan 195
38 Uses of Reclaimed Water in Dual Systems in Japan 195
39 Types of Buildings Using Reclaimed Water in Japan 195
40 Reclaimed Water Criteria in Japan 196
41 Reclaimed Water Standards in Kuwait 196
42 Reclaimed Water Guidelines in South Africa 197
43 Reclaimed Water Standards for Unrestricted Irrigation in Saudi Arabia 198
44 Maximum Concentrations for Reclaimed Water Reused in Agriculture
in Tunisia ; 199
A-1 Unrestricted Urban Reuse 204
A-2 Restricted Urban Reuse 210
A-3 Agricultural Reuse — Food Crops 218
A-4 Agricultural Reuse — Non-Food Crops 227
A-5 Unrestricted Recreational Reuse 237
A-6 Restricted Recreational Reuse 239
A-7 Environmental Wetlands 241
A-8 Industrial Reuse 242
B-1 Abbreviations for Units of Measure 246
B-2 Acronyms/Abbreviations 247
IX
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Figures
Figure
1 Actual and Projected World Population 1
2 Growth of Cities of >1 Million Population 2
3 Phases of Reuse Program Planning 8
4 U.S. Fresh Water Demands by Major Uses, 1985 10
5 Total Treated Wastewater Design Flows by State 11
6 Total Fresh Water Demands by State, 1985 11
7 Average Residential Water Usage by Type of Use 12
8 Average Daily Residential Water Usage Comparison: National,
Pennsylvania, & California 13
9 Estimated Potable Water Conservation Achieved Through Urban Reuse,
City of St. Petersburg, Florida 15
10 Three Configurations Alternatives for Water Reuse Systems 16
11 Reclaimed Water Supply vs. Irrigation Demand 17
12 Generalized Flow Sheet for Wastewater Treatment 29
13 Average Monthly Rainfall and Pan Evaporation 44
14 Average Pasture Irrigation Demand and Potential Supply 45
15 Estimated Storage Required to Commit All Available Reclaimed Water
for Pasture Irrigation (Average Condition) 46
16 Required Storage Capacity to Meet Irrigation Demands vs. Percent of Supply
Committed 47
17 Example of Multiple Reuse Distribution System 49
18 Florida Separation Requirements for Reclaimed Water Mains 52
19 City of St. Petersburg Customer Connection Protocol 55
20 Anticipated Daily Reclaimed Water Demand Curve vs. Diurnal Reclaimed Water
Flow Curve 56
21 Hydrograph for Diurnal Flows 56
22 TDS Increase Due to Evaporation for One Year as a Function of Pond Depth 57
23 Potable and Nonpotable Water Use Monthly Historic Demand Variation
Irvine Ranch Water District 69
24 Potable and Total Water Use Monthly Historic Demand Variation
St. Petersburg, Florida 69
25 Typical Water Reclamation Plant Process for Urban Reuse 71
26 Comparison of Agricultural Irrigation, Public/Domestic, and Total Fresh
Water Withdrawals 78
27 Agricultural Reuse Categories by Percent in California 78
28 Assessing Crop Sensitivity to Salinity for Conventional Irrigation 82
29 Divisions for Classifying Crop Tolerance of Salinity 83
30 Schematic of Soil-Aquifer Treatment Systems 98
31 Number of Drinking Water Contaminants Regulated by the U.S. Government 102
32 Denver Potable Reuse Demonstration Treatment Processes 106
33 Public Participation Program Required for Water Reuse System Planning 169
34 Changes In Urban and Rural Populations in Latin America, Africa, and Asia 180
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Acknowledgments
Guidelines for Water Reuse was prepared by Camp Dresser & McKee Inc. (COM) under the direction of Mr. Robert
L. Matthews, Officer-in-Charge. Principal authors were Dr. James Crook (Project Director), David K. Ammerman
(Project Manager), and Dr. Daniel Okun (Technical Consultant). Contributing authors were Jeffrey F. Payne, Diane
C. Kemp, Patrick E. Gallagher, Eric M. Etters, Raymond C. Murphy, Konstandinos Kalimtgis, and Michael G. Heyl.
Marlene A. Hobel edited the document and prepared the graphics. The assistance of Denise M. Cormier and Trade
A. Vann is gratefully acknowledged.
Preparation of the Guidelines was jointly funded by the U.S. Environmental Protection Agency (EPA) and the U.S.
Agency for International Development (AID) through AID'S Water and Sanitation for Health (WASH) Contract No.
DPE-5973-Z-00-8081 -00, Project No. 836-1249. The WASH project is sponsored by AID'S Office of Health, Bureau
for Research and Development and is managed by Camp Dresser & McKee International, a COM subsidiary.
We wish to acknowledge the direction, advice, and suggestions of the sponsoring agencies, notably: Mr. Robert K.
Bastianwith EPA; Dr. John Austin and Dr. Rita Klees with AID; and J. Ellis Turner, Eduardo Perez, and RickMattson
with the AID/WASH Project.
The following individuals served on an advisory committee during development of the document and provided
valuable information and substantive suggestions for improving its focus and content. Their assistance is greatly
appreciated. Their review does not necessarily signify endorsement.
Dr. Sergio A.S. Almeida
Multiservice Engenharia Ltda.
Rio de Janeiro, Brazil
Dr. Julian Andelman
University of Pittsburgh
Pittsburgh, Pennsylvania
Tokuji Annaka
Ministry of Construction
Ibaraki-ken, Japan
Richard P. Arber
Richard P. Arber Associates, Inc.
Denver, Colorado
Peter M. Archuleta
Eastern Municipal Water District
San Jacinto, California
Dr. Takashi Asano
University of California at Davis
Davis, California
Akissa Bahri
Ministere De L'Agriculture
Ariana, Tunisia
Rodger B. Baird
Sanitation Districts of Los Angeles County
Whittier, California
Dr. Ursula J. Blumenthal
London School of Hygiene & Tropical Medicine
London, England
Dr. Herman Bouwer
U.S. Department of Agriculture
Phoenix, Arizona
Dr. William H. Bruvold
University of California at Berkeley
Berkeley, California
Dr. Robert C. Cooper
University of California at Berkeley
Berkeley, California
Ronald W. Crites
Nolle & Associates
Sacramento, California
Ing. Fulvio Grace
Servizi di Ingerieria
Palermo, Italy
John Grossman
U.S. Bureau of Reclamation
Denver, Colorado
Salvatore D'Angelo
Boyle Engineering Corporation
Orlando, Florida
Dr. Robert A. Gearheart
Humboldt State University
Arcata, California
Dr. Charles P. Gerba
University of Arizona
Tucson, Arizona
Dr. Adnan Gur
World Health Organization
Amman, Jordan
Dr. Ivanildo Hespanhol
World Health Organization
Geneva, Switzerland
XI
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Dr. Wiley Home
Metropolitan Water District of Southern California
Los Angeles, California
Robert H. Hultquist
California Dept. of Health Services
Berkeley, California
John L. Irwin
Thetford Systems Inc.
Ann Arbor, Michigan
William D. Johnson
City of St. Petersburg
St. Petersburg, Florida
Richard J. Karlin
AWWA Research Foundation
Denver, Colorado
James M. Kelly
Central Contra Costa Sanitary District
Martinez, California
John W. Kluesener
Bechtel Corp.
San Francisco, California
Dr. Rafael Mujeriego
Universidad Politecnica de Cataluna
Barcelona, Spain
Ken Murakami
Ministry of Construction
Tokyo, Japan
Dr. Eva C. Nieminski
Utah Department of Health
Salt Lake City, UT
Peter E. Odendaal
Water Research Commission
Pretoria, South Africa
Nagaharu Okuno
Tokyo Metropolitan Government
Tokyo, Japan
Dr. Alan Overman
University of Florida
Gainesville, Florida
Sherwood C. Reed
Environmental Engineering Consultant
Norwich, Vermont
Dr. Martin G. Rigby
Orange County Water District
Fountain Valley, California
Millard Robbins
Upper Occoquan Sewage Authority
Centreville, Virginia
Jean Robertson
South Valley Water Reclamation Facility
Midvale, Utah
Dr. Joan B. Rose
University of South Florida
Tampa, Florida
Dr. Richard Sakaji
East Bay Municipal Utility District
Oakland, California
Dr. Saqer Salem Al Salem
Water Authority
Amman, Jordan
Dr. M.I. Shaikh
World Health Organization
Alexandria, Egypt
Dr. Gedaliah Shelef
Technion - Israel Inst. of Tech.
Haifa, Israel
Hillel Shuval
The Hebrew University of Jerusalem
Jerusalem, Israel
Robert C. Siemak
James M. Montgomery Consulting Engineers
Pasadena, California
Dr. Charles A. Sorber
University of Pittsburgh
Pittsburgh, Pennsylvania
Martin Strauss
International Reference Centre for Waste Disposal
Duebendorf, Switzerland
Dr. Fabian A. Yanez
Sanitary Engineer
Quito, Ecuador
Dr. David W. York
Florida Dept. of Environmental Regulation
Tallahassee, Florida
Ronald E. Young
Irvine Ranch Water District
Irvine, California
xii
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The following individuals also provided review comments:
Frank Bell - EPA Office of Water/Office of Science and Technology, Washington, D.C.
Paul S. Berger - EPA Office of Water/Office of Ground Water & Drinking Water, Washington, D.C.
Dale Bucks - U.S. Department of Agriculture, Agricultural Research Service, Washington, D.C.
William J. Carmack - U.S. Department of Agriculture, Soil Conservation Service, Washington, D.C.
Cindy Dyballa - EPA Office of Policy, Planning, Evaluation/Office of Policy Analysis, Washington, D.C.
Joe Karnak - U.S. Department of Agriculture, Soil Conservation Service, Washington, D.C.
A.W. Marks - EPA Office of Water/Office of Ground Water & Drinking Water, Washington, D.C.
Mark J. Parrotta - EPA Office of Water/Office of Ground Water & Drinking Water, Washington, D.C.
Rao Surampali - EPA Region 7, Kansas City, Kansas
Bryan Yim - EPA Region 10, Seattle, Washington
Peer Reviewers:
Alan Hais - EPA Office of Water/Office of Science and Technology, Washington, D.C.
James F. Kreissl - EPA Office of Research and Development/ Center for Environmental Research Information,
Cincinnati, Ohio
Harold Thompson - EPA Region 8, Denver, Colorado
Dr. David W. York - Florida Dept. of Environmental Regulation, Tallahassee, Florida
XIII
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CHAPTER 1
Introduction
With many communities throughout the world
approaching or reaching the limits of their available water
supplies, water reclamation and reuse has become an
attractive option for conserving and extending available
water supplies. Water reuse may also present
communities an opportunity for pollution abatement when
it replaces effluent discharge to sensitive surface waters.
Water reclamation and nonpotable reuse only require
conventional water and wastewater treatment technology
that is widely practiced and readily available in countries
throughout the world. Furthermore, because properly
implemented nonpotable reuse does not entail significant
health risks, it has generally been accepted and endorsed
by the public in the urban and agricultural areas where it
has been introduced.
1.1 Objectives of the Guidelines
Water reclamation for nonpotable reuse has been
adopted in the United States and elsewhere without the
benefit of national or international guidelines or
standards. However, in recent years, many states in the
U .S. have adopted standards or guidelines, and the World
Health Organization (WHO) has published guidelines for
reuse for agricultural irrigation. The primary purpose of
this document is to present guidelines, with supporting
information, for utilities and regulatory agencies in the
U.S. In states where standards do not exist or are being
revised or expanded, the Guidelines can assist in
developing reuse programs or appropriate regulations.
The Guidelineswlll also be useful to consulting engineers
and others involved in the evaluation, planning, design,
operation, or management of water reclamation and
reuse facilities. In addition, a section on reuse
internationally is offered to provide background and
discuss relevant issues for authorities in other countries
where reuse is being considered. The document does
not propose standards by either the U.S. Environmental
Protection Agency (EPA) or the U.S. Agency for
International Development (AID). In the U.S., water
reclamation and reuse standards are the responsibility of
state agencies.
These guidelines primarily address water reclamation for
nonpotable urban, industrial, and agricultural reuse,
about which little controversy exists. Also, attention is
given to augmentation of potable water supplies by
indirect reuse. Because direct potable reuse is not
currently practiced in the U.S., only a brief overview is
provided.
1.2 Water Demands
Demands on water resources for household, commercial,
industrial, and agricultural purposes are increasing
greatly, and the situation is exacerbated by growing
urbanization. According to a United Nations report (United
Nations, 1989), while world population will have grown
150 percent over the second half of the 20th century, the
urban population will have grown 300 percent, with almost
half the total population living in cities by the year 2000
(Figure 1).
Figure 1. Actual and Projected World Population
9000
8000
7000
| 6000
& 5000 4-
.9
Ij 4000
Q.
£
Total Population
Urban Population
Fl
1950 1960 1970 1980 1990 2000 2025
Source: UN, 1989.
1
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Also, the number of large cities is growing rapidly (Figure
2). While fewer than 80 cities exceeded 1 million in
population in 1950, by 1990 the number had grown to
almost 300 and was projected to exceed 400 by the end
of the century (United Nations, 1985).
Although rural populations can usually find the waterthey
need locally, urban populations need to draw water from
large drainage areas or extensive aquifers. Most cities
have already fully exploited the readily available water
resources and are now obliged to develop and treat
sources of lower quality or go long distances to develop
new supplies, both costly options.
Figure 2. Growth of Cities of >1 Million Population
700 T
600
I 500..
o
"o 4004-
"I 300--
z
200--
100 X
0
1950 1960 1970 1980 1990 2000 2025
Source: UN, 1985.
Furthermore, while people in rural communities can often
dispose of their wastewaters satisfactorily on site, cities
must generally discharge their wastewaters into nearby
water courses, which requires adequate wastewater
treatment prior to disposal to prevent water quality
degradation and protect public health.
1.3 Source Substitution
The use of reclaimed water for nonpotabie purposes
offers the potential for exploiting a "new" resource that
can be substituted for existing sources. By "source
substitution" — replacing the potable water used for
nonpotabie purposes — an increased population can be
served from an existing source.
Source substitution is not a new idea. In 1958, the United
Nations Economic and Social Council enunciated a policy
that "No higher quality water, unless there is a surplus of
it, should be used for a purpose that can tolerate a lower
grade" (United Nations, 1958). With the growth and
increased density of populations, few cities now enjoy a
surplus of high quality water; if they do, this surplus can
be expected soon to be exhausted.
Many urban residential, commercial, and industrial uses
can be satisfied with water of less than potable water
quality: irrigation of lawns, parks, roadway borders and
medians; air conditioning and industrial cooling towers;
stack gas scrubbing; industrial processing; toilet and
urinal flushing; construction; cleansing and maintenance,
including vehicle washing; scenic waters and fountains;
and environmental and recreational purposes.
Customarily, public water supplies are designed to
provide water of potable quality to serve all these
purposes.
EPA policy states that "Because of human frailties
associated with protection, priority should be given to
selection of the purest source" (EPA, 1976). When the
demand exceeds the capacity of the purest source, and
additional sources are unavailable or available only at a
high cost, a lower quality water can be substituted to serve
the nonpotabie purposes. In some coastal cities, such as
Hong Kong, seawater has been substituted for high
quality fresh water for toilet flushing. In the British
midlands, highly polluted Trent River water has been
used for industrial purposes in place of high quality
sources. In many instances, however, treated wastewater
from the city to be served, or a nearby city, may provide
the most economical and/or available substitute source.
Understandably, the construction of reclaimed water
transmission and distribution lines to existing users in
large cities is likely to be expensive and disruptive. When
retrofitting an urban area for water reuse, supplying large
users can reduce system development costs. In
Baltimore, Maryland, for example, a water reuse system
was built in 1936 to serve a single large user, the
Sparrows Point steel plant of the Bethlehem Steel
Company. In 1942, 4.5 mi (7.3 km) of 96-inch (244 cm)
pipeline was built from the Baltimore Back River activated
sludge plant to the steel plant to provide 100 mgd (4,380
Us) of waterthat would otherwise have come from a fresh
water supply source (Okun, 1990).
Once established, reuse programs initially developed for
large users may be extended to serve a more diverse
customer base. Such was the case in St. Petersburg,
Florida, where the reclaimed water lines were initially
installed in 1977 to serve the irrigation needs of large
commercial customers. By 1990, however, the reclaimed
water system had grown to serve more than 6,000 single-
family residential customers. The conservation benefits
of source substitution are clearly underscored by the
St. Petersburg system; the city has experienced about
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10 percent population growth since 1976 without
substantial increase in potable water demand (Eingold
and Johnson, 1984).
The economics of source substitution with reclaimed
water are site specific, depending on the marginal costs
of new sources of high quality water and the costs of
treatment and disposal of wastewaters. The reclamation
and reuse of wastewaters will likely be most attractive in
serving new residential, commercial, and industrial areas
of a city, where the installation of dual distribution mains
and dual building services would be far more economical
than in already developed areas.
Reuse of reclaimed water for agricultural purposes near
urban areas can also be economically attractive.
Agricultural users are usually willing to make long-term
commitments, often for as many as 20 years, to use large
quantities of reclaimed water instead of fresh water
sources.
One potential scenario is to provide a new reclaimed
water system to serve agricultural needs outside the city
with the expectation that when urban development
replaces agricultural lands in time, reclaimed water use
can be shifted from agricultural to urban needs. For
example, in Orange County, California, the Irvine Ranch
Water District currently provides reclaimed water to
irrigate urban landscape and mixed agricultural lands. As
agricultural land use is displaced by residential
development in this growing urban area, the district has
the flexibility to convert its reclaimed water service from
agricultural to urban irrigation (Parsons, 1990).
Under the Safe Drinking Water Act, EPA has established
maximum contaminant limits (MCLs) to control organic,
inorganic, microbiological and radioactive contaminants
in public drinking water supplies and is obliged to add
about 25 more every three years. Also, most MCLs are
becoming even more stringent over time. The costs to
supply water for drinking and other potable uses will
increase in the future to the point that economic analyses
for specific locales may dictate changes in the way that
nonpotable uses are satisfied, (i.e., by reclaimed water in
dual distribution systems).
1.4 Pollution Abatement
While the need for additional water supply has indeed
been the impetus for numerous water reclamation and
reuse programs in arid and semi-arid areas, many
programs inthe U.S. were initiated in response to rigorous
and costly requirements for effluent discharge to surface
waters, particularly the removal of nitrogen and
phosphorus. By eliminating effluent discharges for all or
even a portion of the year through water reuse, a
municipality may be able to avoid or reduce the need for
the costly advanced wastewater treatment processes.
For most nonpotable reuse applications, nutrient removal
is unnecessary and actually contraindicated for irrigation.
The purposes and practices may differ between water
reuse programs developed strictly for pollution abatement
and those developed for water resources or conservation
benefits. When systems are developed chiefly for the
purpose of land applicationforwastewatertreatment and/
or disposal, the objective is to dispose of as much effluent
on as little land as possible; thus, application rates are
often greater than irrigation demands. On the other hand,
when the reclaimed water is considered a valuable
resource, the objective is to apply the water according to
irrigation needs.
Differences are also apparent in the distribution of
reclaimed water for these different purposes. Where
disposal is the objective, meters are difficult to justify, and
reclaimed water is often distributed at a flat rate or at
minimal cost to the users. Where reclaimed water is
intended to be used as a water resource, however,
metering is appropriate to provide an equitable method
for distributing the resource, limiting its waste, and
recovering the costs. In St. Petersburg, Florida, where
disposal was the original objective, the reclaimed water
became an important resource and meters, which were
not provided initially, are now being installed to prevent
waste of the reclaimed water.
Naturally, a water reuse program can easily serve both
water conservation and pollution abatement purposes.
However, the scope of the Guidelines has focused on
water reuse programs for resource management. Ample
other sources exist for designing land treatment systems;
most notably, EPA's Process Design Manual on Land
Treatment of Municipal Wastewater (EPA, 1981 and
1984) provides a complete discussion of the design
requirements for such systems.
1.5 Treatment and Water Quality
Considerations
The overriding consideration in developing a reuse
system is that the quality of the reclaimed water be
appropriate for its intended use. Higher level uses, such
as irrigation of public-access lands or vegetables to be
consumed without processing require a higher level of
wastewater treatment prior to reuse than will lower level
uses, such as pasture irrigation.
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In urban settings, where there is a high potential for
human exposure to reclaimed water used for landscape
irrigation, industrial purposes, toilet flushing, and many
other purposes, there must be minimum hazard.
According to Okun (1990), the most important water
quality objective for such uses is that the water be
adequately disinfected and that a chlorine residual be
maintained in the distribution system. The reclaimed
water must be clear, colorless, and odorless to ensure
that it is aesthetically acceptable to the users and the
public at large. Research by the Sanitation Districts of
Los Angeles County (1977) has demonstrated that a high-
quality secondary effluent, treated with small doses of
either coagulant, polymer, or both; direct conventional
sand filtration; and chlorine disinfection can easily and
continuously provide a satisfactory product.
Several states have published standards or guidelines
for one or more types of water reuse (See Section 4.1).
Some of these states require specific treatment
processes, others impose effluent quality criteria, and
some require both. All of the states that have water
reclamation criteria require disinfection for high-level uses
and limits for either total or fecal coliform organisms (See
Tables A-1 to A-8 in Appendix A).
Many states also include requirements for treatment
reliability to prevent the distribution of any reclaimed water
that may not be adequately treated because of a process
upset, power outage, or equipment failure. Reliability
requirements typically include provisions for alarms,
standby power supplies, multiple or standby unit
treatment processes, emergency storage or disposal
provisions, and standby replacement equipment. A strict
industrial pretreatment program is also necessary to
ensure the reliability of the biological treatment processes
by excluding potentially toxic levels of pollutants from the
sewer system. Wastewater treatment facilities receiving
substantial amounts of high-strength industrial wastes
may be limited in the number and type of suitable reuse
applications.
Dual distribution systems (i.e., reclaimed water
distribution systems that parallel a potable water system)
must also incorporate safeguards to prevent cross
connections of reclaimed water and potable water lines
and misuse of reclaimed water. For example, piping,
valves, and hydrants are marked or color-coded to
differentiate reclaimed water from potable water,
backf low prevention devices are installed, and hose bibbs
on reclaimed water lines may be prohibited to preclude
the likelihood of incidental human contact.
1.6 Overview of the Guidelines
This document, the Guidelines for Water Reuse, is an
update of the Guidelines for Water Reuse developed for
EPA by Camp Dresser & McKee Inc. (COM) in 1980.
Funded under the co-sponsorship of EPA and the U.S.
Agency for International Development (AID) through its
global Water and Sanitation for Health (WASH) program,
the updated and expanded guidelines reflect the
significant technical and institutional developments in
water reuse over the last decade and include
consideration of the special needs for water reuse
applications in other countries.
The Guidelines provide information for evaluating the
requirements and potential benefits of water reuse
systems, covering the key issues needed to evaluate
water reclamation and reuse opportunities, assess the
costs and benefits for reuse alternatives, and plan and
implement a water reuse system. Major technical and
non-technical issues are identified and discussed,
drawing upon the experiences of those with water reuse
programs.
The document has been arranged by issues, devoting
separate chapters to each of the key technical, financial,
legal and institutional, and public involvement
considerations that a reuse planner might face. A
separate chapter has also been provided to discuss reuse
applications in other countries. These chapters are:
Q Chapter 2, Technical Issues in Planning Water
Reuse Systems - An overview of the potential
uses of reclaimed water, the sources of reclaimed
water, treatment requirements, seasonal storage
requirements, and supplemental system
facilities, including conveyance and distribution,
operational storage, and alternative disposal
systems.
Q Chapter 3, Types of Reuse Applications -
Urban, industrial, agricultural, recreational and
habitat restoration/enhancement, groundwater
recharge and augmentation of potable supplies.
Direct potable reuse is also briefly discussed.
Q Chapter 4, Water Reuse Regulations and
Guidelines in the U.S. - Existing U.S.
regulations, state standards and guidelines, and
recommended guidelines.
Q Chapter 5, Legal and Institutional Issues -
Reuse ordinances, user agreements, water
rights, franchise law, and case law.
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Q Chapter 6, Funding Alternatives - Funding
and cost recovery options for reuse system
construction and operation. Management issues
for utilities.
Q Chapter 7, Public Information Programs -
Strategies for educating and involving the public
in water reuse system planning and reclaimed
water use.
Q Chapter 8, Water Reuse Outside the U.S. -
Water reuse systems in other countries, with an
assessment of the differences between practices
in the U.S. and elsewhere. Examples from a
wide variety of countries are presented.
1.7 References
Eingold, J.C.; Johnson, W.C., 1984. St. Wastewater
Reclamation and Reuse Project - Eight Years Later. In:
Proceedings of the Water Reuse Symposium HI, August
26-31, 1984, San Diego, California, AWWA Research
Foundation, Denver, Colorado.
Los Angeles County Sanitation Districts. 1977. Pomona
Virus Study, Final Report. California State Water
Resources Control Board, Sacramento, California.
Okun, D.A. 1991. Water Reuse: Potable or Nonpotable?
There is a Difference! Water Environment & Technology,
3(1):66.
Okun, D.A. 1990. Realizing the Benefits of Water Reuse
in Developing Countries. Water Environment &
Technology, 2(11):78-82.
Parsons, J. 1990. Irvine Ranch's Approach to Water
Reclamation. Water Environment & Technology, 2(12):
68-71.
U.S. Environmental Protection Agency. 1984. Process
Design Manual for Land Treatment of Municipal
Wastewater, Supplement on Rapid Infiltration and
Overland Flow. EPA 626/1-81-013a, EPA Center for
Environmental Research Information, Cincinnati, Ohio.
U.S. Environmental Protection Agency. 1981. Process
Design Manual, Land Treatment of Municipal
Wastewater. EPA 625/1-81-013, EPA Center for
Environmental Research Information, Cincinnati, Ohio.
U.S. Environmental Protection Agency. 1976. National
Interim Primary Drinking Water Regulations. EPA 570/
9-76-003, Washington, D.C.
United Nations. 1989. World Population Prospects.
Department of International Economic and Social Affairs.
United Nations, New York, New York.
United Nations. 1985. Estimates and Projections of
Urban, Rural, and City Populations, 1950 to 2025: The
1982 Assessment. Department of International Economic
and Social Affairs. United Nations, New York, New York.
United Nations. 1985. Water for Industrial Use. UN Report
No. E/3058ST/ECA/50, Economic and Social Council.
United Nations. New York, New York.
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CHAPTER 2
Technical Issues In Planning Water Reuse Systems
The technical issues involved in planning a water reuse
system include:
Q The identification and characterization of
potential demands for reclaimed water;
Q The identification and characterization of
existing sources of reclaimed water to determine
their potential for reuse;
Q The treatment requirements for producing a safe
and reliable reclaimed water that is suitable for
its intended applications;
Q The storage facilities required to balance
seasonal fluctuations in supply with fluctuations
in demand;
Q The supplemental facilities required to operate
a water reuse system, such as conveyance and
distribution networks, operational storage
facilities, and alternative disposal facilities; and
Q The potential environmental impacts of
implementing water reclamation.
The technical issues in this section apply broadly to most
reuse applications. Technical issues of concern in
specific reuse applications are discussed in Chapter 3,
'Types of Reuse Applications."
2.1 Planning Approach
One goal of the Guidelines for Water Reuse is to outline
a systematic approach to planning for reuse, so that
planners can make sound preliminary judgments about
the local feasibility of reuse-taking into account the full
range of important issues that have been addressed in
implementing earlier programs or that might be
encountered in future programs.
Figure 3 illustrates a three-phased-approach to reuse
planning that groups reuse planning activities into
successive stages of preliminary investigations,
screening of potential markets, and detailed evaluation
of selected markets. Through all of these stages, public
involvement efforts provide guidance to the planning
process, and from the very outset steps will be taken
that will support project implementation should reuse
prove to be feasible. Each stage of activity builds on
previous stages until enough information is available to
develop a conceptual reuse plan and to begin negotiating
the details of reuse with selected users.
2.1.1 Preliminary Investigations
This is a fact-finding phase, meant to rough out physical,
economic, and legal bounds to the water reuse plan.
The primary task is to locate all potential sources of
effluent for reclamation and reuse and all potential
markets for this reclaimed water. It is also important to
identify institutional constraints and enabling powers that
might affect reuse. This phase should be approached
with a broad view. Exploration of all possible options at
this early stage in the planning program will both
establish a practical context for the plan and help to
avoid creating dead-ends in the planning process.
The questions to be addressed in this phase include:
Q What local sources of effluent might be suitable
for reuse?
Q What are the potential local markets for
reclaimed water?
Q What public health considerations are
associated with reuse, and how can these be
addressed?
Q What are the potential environmental impacts of
water reuse?
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Figure 3.
Phases of Reuse Program Planning
Public Involvement and Steps Toward Implementation
i
4
i
Preliminary
Investigations
>.
Screening of
Potential Markets
>.
Detailed Evaluation
of Selected Markets
Q How would water reuse "fit in" with present uses
of other water resources in the area?
Q What are the present and projected user costs
of fresh water in the area?
Q What existing or proposed laws and regulations
affect reuse possibilities in the area?
Q What local, state or federal agencies must
review and approve implementation of a reuse
program?
Q What are the legal liabilities of a purveyor or user
of reclaimed water?
Q What sources of funding might be available to
support the reuse program?
Q What reuse system would attract the public's
interest and support?
The major task of this phase involves preliminary market
assessment, as represented in the second question
above. This involves defining the water market, probably
through discussions with water wholesalers and retailers,
and identifying major water users in the market. Initial
contact by telephone and follow-up letter will probably
be necessary to determine what portion of total water
use might be satisfied by reclaimed water, what quality
of water is required for each type of use, and how use of
reclaimed water might affect the user's operations or
discharge requirements.
Obviously, it will be important, even at this early stage, to
develop good working relationships among wastewater
managers, water supply agencies, and potential
reclaimed water users. Potential users will be concerned
with the quality of reclaimed water and reliability of its
delivery; they will also want to know state and local
regulations that apply to use of reclaimed water, and
constraints such as hookup costs or additional
wastewater treatment costs that might affect their ability
to use the product.
2.1.2 Screening of Potential Markets
The essence of this phase is a comparison between the
unit costs of fresh water to a given market and the unit
costs of reclaimed water to that same market. On the
basis of information gathered in preliminary
investigations, one or more "intuitive projects," may be
developed that are obvious possibilities or that just
"seem to make sense." For example, if a large water-
using industry is located next to a wastewater treatment
plant, there exists a strong potential for reuse: the
industry has a high demand for water, and costs of
conveying reclaimed water would be. low. But the value
of reclaimed water—even to such an "obvious" potential
user — will depend on:
Q The quality of water to be provided, as compared
to the user's requirements;
Q The quantity of water available, and the ability to
meet fluctuating demand;
Q The effects of laws that regulate this reuse, and
the attitudes of agencies responsible for
enforcing applicable laws; and
Q The present and projected future cost of fresh
water to this user.
These questions all involve detailed study, and it lies
beyond the capacities of most public entities to apply the
required analyses to every reuse possibility in their
areas. A useful first step is to identify a wide range of
candidate reuse systems that might be suitable in the
area and then to "screen" these alternatives down to a
handful of promising project alternatives for detailed
evaluation. In order to establish the most complete list of
reuse possibilities, not only the different types of reuse
that could improve use of water resources should be
considered, but also such factors as:
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Q Different levels of treatment — if advanced
wastewater treatment (AWT) is currently
required prior to discharge of effluent, there
might be cost savings available if a market exists
for secondary effluent.
Q Different project sizes — the scale of reuse can
range from conveyance of reclaimed water to a
single user to the general distribution of
reclaimed water for a variety of nonpotable uses;
Q Different conveyance networks — different
distribution routes will have different
advantages, taking better advantage of existing
rights-of-way, for example, or serving a greater
number of users.
In addition to a comparison of the overall costs estimated
for each alternative, several other criteria can be factored
into the screening process. The East Bay Dischargers
Authority in Oakland, California, used demonstrated
technical feasibility as one criterion, and the comparison of
estimated unit costs of reclaimed water with unit costs of
fresh water, as another (Murphy and Lee, 1979). East Bay
Municipal Utility District, also of Oakland, used an even
more complex screening process (East Bay Municipal
Utility District, 1979) that included comparison of weighted
values for a variety of objective and subjective factors,
such as:
Q How much flexibility would each system offer for
future expansion or change?
Q How much use of fresh water would be replaced
by each system?
Q How complicated would program
implementation be, given the number of
agencies that would be involved in each
proposed system?
Q To what degree would each system advance the
"state-of-the-art" in reuse?
Q What level of chemical or energy use would be
associated with each system?
Q How would each system affect land use in the
area?
Review of user requirements could enable reduction of
the list of potential markets to a few selected markets for
which reclaimed water could be of significant value.
2.1.3 Detailed Evaluation of Selected Markets
The evaluation steps contained in this phase represent
the heart of the analyses necessary to shape a reuse
program. Following the screening steps above, a ranking
of "most-likely" projects will be established, and the
present fresh water consumption and costs for selected
potential users will be known. In this phase, by looking in
more detail at the conveyance routes and storage
requirements of each selected system, the preliminary
cost estimates for delivering reclaimed water to these
users can be refined. Funding options can be compared,
user costs developed, and a comparison made between
the unit costs of fresh water and of reclaimed water for
each selected system. It will be possible also to evaluate
in more detail the environmental, institutional and social
aspects of each project. Questions that may need to be
addressed include the following:
Q What are the specific water quality requirements
of each user? What fluctuation can be tolerated?
Q What is the daily and seasonal water use
demand pattern for each potential user?
Q Can fluctuations in demand best be met by
pumping capacity or by storage? Where would
storage facilities best be located?
Q If additional treatment of the effluent is required,
who should own and operate the additional
treatment facilities?
Q What costs will the users in each system incur in
connecting to the reclaimed water delivery
system?
Q Will industrial users in each system face
increased treatment costs for their waste
streams as a result of using reclaimed water? If
so, is increased internal recycling likely, and how
will this affect their water use?
Q Will water customers in the service area allow
project costs to be spread overthe entire service
area?
Q What interest do potential funding agencies
have in supporting each type of reuse program
being considered? What requirements would
they impose on a project eligible for funding?
Q Will use of reclaimed water force agricultural
users to alter irrigation patterns or to provide
better control of return flows?
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Q What payback period is acceptable to users who
must invest in additional facilities for onsite
treatment, storage or distribution of the
reclaimed water?
Q What are the prospects of industrial source
control measures in your area, and would
institution of such measures reduce the
additional treatment steps necessary to permit
reuse?
Q How "stable" are the potential users in each
selected candidate reuse system? Are they
likely to remain in their present locations? Are
process changes being considered that might
affect their ability to use reclaimed water?
As is apparent, many of these questions can be
answered only after further consultation with water
supply agencies and prospective users. Both groups
may seek more detailed information as well, including
the preliminary findings made in the first two phases of
effort.
The detailed evaluations should lead to a preliminary
assessment of technical feasibility and costs.
Comparison among alternative reuse programs will be
possible, as well as preliminary comparison between
these programs and alternative water supplies, both
existing and proposed. In this phase, economic
comparisons, technical optimization steps, and
environmental assessment activities leading to a
conceptual plan for reuse might be accomplished by
working in conjunction with appropriate consulting
organizations.
2.2 Potential Uses of Reclaimed Water
Urban public water supplies are treated to satisfy the
requirements for potable use. However, potable use
(drinking, cooking, bathing, laundry and dishwashing)
represents only a fraction of the total daily residential
use of treated potable water. The remainder may not
require water of potable quality. In many cases, water
used for nonpotable purposes, such as irrigation, may
be drawn from the same ground or surface source as
municipal supplies, creating an indirect demand on
potable supplies. The Guidelines examine opportunities
for substituting reclaimed water for potable water or
potable supplies for uses where potable water quality is
not required. Specific water use categories where reuse
opportunities exist include:
Q Urban
Q Industrial
Q Agricultural
Q Recreational
Q Habitat restoration/enhancement, and
Q Groundwater recharge.
The technical issues associated with the implementation
of each of these reuse alternatives are discussed in detail
in Chapters. The use of reclaimed water to provide both
direct and indirect augmentation of potable supplies is
also presented in Chapter 3.
2.2.1 National Water Use
Figure 4 presents the national pattern of water use
according to the U.S. Geological Survey (Solley et al.,
1988). The largest water demands are associated with
agricultural irrigation and thermoelectric generation,
representing 40 percent and 39 percent respectively of
the total water use in the United States. Public and
domestic water users constitute 12 percent of the total
demand. The remainder of the water use categories are
industrial and commercial with 8 percent of the demand
and livestock with 1 percent of the demand.
Figure 4. U.S. Fresh Water Demands by Major Uses,
1985
Public & Domestic
12%
Thermoelectric
39%
Industrial &
Commercial
Agricultural
Irrigation
Livestock
1%
Source: Solley et al., 1988.
Figure 5 shows estimated wastewater effluent produced
daily in each state, representing the total potential
reclaimed water supply from existing wastewater
treatment facilities. Figure 6 shows the estimated water
demands by state in the United States. Areas of high
water demands might benefit by augmenting their
existing water supplies with reclaimed water.
Municipalities in coastal and arid states, where water
10
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Figure 5. Total Treated Wastewater Design Flows by State
Range in mgd
I 1 0 - 200
f I 200 - 400
FQ 400-1000
H|{$ 1000-2000
1H 2000 - 3500
Source: EPA, 1991.
Figure 6. Total Fresh Water Demands by State, 1985
Range in mgd
CU 0-400
I 1400-1200
EH 1200-4000
mi 4000-12000
• 12000-25000
Source: Adapted from Solley etal., 1988
11
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demands are high and fresh water supplies are limited,
appear to have a reasonable supply of wastewater
effluent that could, through proper treatment and reuse,
greatly extend their water supplies.
The arid states of the southwestern United States are
obvious candidates for wastewater reclamation, and
indeed significant reclamation projects are underway
throughout this region. However, this macroscopic view
can obscure local opportunities that may exist for a given
municipality to benefit from reuse by: (1) extending local
water supplies, and/or (2) reducing or eliminating surface
water discharge. For example, the City of Atlanta,
located in the relatively water-rich southeast, has
experienced water restrictions as a result of recurrent
droughts. In south Florida, subtropical conditions and
almost 55 in/yr (140 cm/yr) of rainfall suggest an
abundance of water; however, cultural practice and
regional hydrogeology combine to result in frequent
water shortages and restrictions on water use. Thus
opportunities for water reclamation and reuse must be
examined on a local level to judge their value and
feasibility.
2.2,2 Potential Reclaimed Water Demands
The average total water usage in an urban potable water
system is approximately 180 gal (680 L)/capita/d, of
which 120 gal (450 L)/capita/d is for combined residential
and public uses (Grisham and Fleming, 1989). This
includes potable-quality water used extensively for
purposes not requiring this high quality, such as toilet
flushing, vehicle washing, industrial process and cooling
water, general washdown, and landscape irrigation.
Depending on the location of a community, the actual
potable water requirement may range from 11 percent to
60 percent of the total water demand (American Water
Works Association, 1983).
Residential water demand can further be categorized as
indoor use, which includes toilet flushing, cooking,
laundry, bathing, dishwashing and drinking, or outdoor
use, which consists primarily of landscape irrigation.
Outdoor use accounts for approximately 32 percent of
this residential demand, while indoor use represents
approximately 68 percent. (Sanders and Thurow, n.d.).
Figure 7 presents the average residential water use by
category. It should be noted that these are national
averages and few residential households will actually
match these figures. These estimates also show that the
potable use (cooking, drinking, bathing, laundry and
dishwashing) represents only about 40 percent of the
total average residential demand. Reclaimed water could
be used for the remaining 60 percent.
Figure 7. Average Residential Water Usage
by Type of Use
Bathing
23%
Cooking &
Drinking 3%
Laundry &
Dishes 14%
Outdoor Use
32%
Toilet Flushing
28%
Source: Sanders and Thurow, n.d.
Outdoor residential water usage varies widely depending
on the geographical area and season. On an annual
average basis, outdoor use in the arid West and
Southwest represents a much higher percentage of the
total residential demand than in areas of the Midwest or
East. Figure 8 compares the national average interior/
exterior residential water usage to that for Pennsylvania
and California. On an average daily basis, outdoor
residential water use amounts to approximately 7
percent of the total residential demand in Pennsylvania
and 44 percent in California (American Water Works
Association, 1983). The largest portion of this use is for
landscape irrigation. Since potable quality water is not
required for outdooruse, reclaimed water can be used to
meet this demand.
The need for irrigation is highly seasonal. In the North
where turf goes dormant, irrigation needs will be zero in
the winter months. However, irrigation demand may
represent a significant portion of the total potable water
demand in the summer months. In coastal South
Carolina, winter irrigation use on the potable system is
estimated to be less than 10 percent of the total demand.
This increases to over 30 percent in the months of June
and July. In Denver, during July and August when
temperatures exceed 90°F (32°C), approximately 80
percent of all potable water is used for irrigation of
bluegrass lawns. On these days, Denver residents
consume 500 gal (1,900 L)/capita/d compared to their
annual average of 150 gal (570 L)/capita/d (Sanders
and Thurow, n.d.). Given the seasonal nature of urban
irrigation, eliminating this demand from the potable
system through reuse will result in a net annual reduction
in potable demands and, more importantly, may also
significantly reduce peak month potable water demands.
12
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Figure 8. Average Daily Residential Water Usage Comparison: National, Pennsylvania, & California
National Average Pennsylvania California
Outdoor Use
32%
Outdoor Use
7%
Indoor Use
68%
Sources: Sanders and Thurow, n.d.
AWWA, 1983
Outdoor Use
44%
Indoor Use
93%
Indoor Use
56%
It is not surprising then that landscape irrigation currently
accounts for the largest urban use of reclaimed water in
the United States. This is particularly true of urban areas
with substantial residential areas and a complete mix of
landscaped areas ranging from golf courses to office
parks to shopping malls. In a "typical" American city, 70
percent of the landscaped areas surround residential
properties, primarily single-family homes (University of
California Division of Agricultural and Natural Resources,
1985). The urban areas also have schools, parks, and
recreational facilities which require regular irrigation.
Within Florida, for example, studies of potable water
consumption have shown that 50 to 70 percent of all
potable water produced is used for outside purposes,
principally irrigation. These studies also show that more
than half of the potable water demand in urban areas is
used by single-family homes.
The irrigation demand for reclaimed water generated by
a particular urban area system can be estimated from an
inventory of the total irrigable acreage to be served by
the reuse system and the estimated weekly irrigation
rates, determined by factors such as local soil
characteristics, climatic conditions, and type of
landscaping. In some states, recommended weekly
irrigation rates are available from water management
agencies, county or state agricultural agents, and
irrigation specialists. Reclaimed water demand
estimates should also take into account any other
proposed uses for reclaimed water within the system,
such as industrial cooling and process water, decorative
fountains, and other aesthetic water features.
Agricultural irrigation, representing 40 percent of the total
water demand nationwide, presents another significant
opportunity for water reuse, particularly in areas where
agricultural sites are near urban areas and can easily be
integrated with urban reuse applications. Such is the
case in Orange County, California, where the Irvine
Ranch Water District currently provides reclaimed water
to irrigate approximately 2,000 ac (800 ha) of urban
landscape and 1,000 ac (400 ha) of mixed agricultural
lands (orchards and vegetable row crops). As agricultural
land use is displaced by residential development in this
growing urban area, the district has the flexibility to
convert its reclaimed water service to urban irrigation
(Parsons, 1990).
In Manatee County, Florida, agricultural irrigation is a
significant component of a county-wide water reuse
program. During 1990, the county's three subregional
water reclamation facilities, with a total treatment
capacity of 28.8 mgd (1,260 Us), provided about 21 mgd
(920 Us) of reclaimed water for a combination of uses
that includes irrigation of golf courses, parks, a 1,500-ac
(600-ha) gladioli farm, and about 6,000 ac (2,400 ha) of
mixed agricultural lands (citrus, ridge and furrow crops,
sod farms, and pasture). The reuse agreements with the
agricultural users are for 20 years, ensuring a long-term
commitment for reclaimed water with a significant water
conservation benefit. The urban reuse system has the
potential to grow as development grows; the county
estimates that it can provide another 16 mgd (700 Us) of
reclaimed water to irrigate the lawns and landscaping of
approximately 24,000 homes as wastewater flows
increase with increased development (Ammerman and
Heyl, 1991).
A detailed inspection of existing or proposed water use
is essential for planning any water reuse system. This
information is often available through municipal billing
records or water use monitoring required through local
13
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or regional water management agencies. In other cases,
predictive equations may be required to adequately
describe water demands. Defining water needs for
various reuse alternatives is explored further in Chapter
3.
2.2.3 Reuse and Water Conservation
The need to conserve the potable water supply is
becoming an increasingly important part of urban and
regional planning. For example, the Metropolitan Water
District of Southern California has predicted that by the
year 2010 water demands will exceed reliable supplies
by approximately 326 billion gal (1,200 x 109 m3) annually
(Adams, 1990). To help conserve the potable water
supplies, the Metropolitan Water District has developed
a multi-faceted program that includes conservation
incentives, groundwater storage, water exchange
agreements, reservoir construction, and reclaimed water
projects. Urban reuse of reclaimed water is an essential
element of the program. In 1990, approximately 88 billion
gal (330 x 106 m3) of reclaimed water was used in
Metropolitan's service area for groundwater recharge,
landscape irrigation, and agricultural, commercial and
industrial purposes. It is estimated that more than 195
billion gal (740 x 106m3) of reclaimed water will be
reused by the Year 2010.
Perhaps the greatest benefit of urban reuse systems is
their contribution in delaying or eliminating the need to
expand potable water supply and treatment facilities.
The City of St. Petersburg, Florida, has experienced
about a 10 percent population growth since 1976 without
any significant increase in potable water demand
because of its urban reuse program. Prior to its reuse
system, the average residential water demand in a study
area in St. Petersburg was 435 gal (1,650 L)/d. After
reclaimed water was made available, the potable
demand was reduced to 220 gal (830 L)/d (Johnson and
Pamell, 1987). The estimated potable water savings for
the City of St. Petersburg since the implementation of its
urban reuse program is shown in Figure 9.
Currently, 25 percent of all water supplied by the Irvine
Ranch Water District in southern California is reclaimed
water. Total water demand is expected to reach 51 mgd
(2,235 Us) in Irvine by the Year 2000 (Irvine Ranch
Water District, 1991). By the Year 2000, Irvine expects
to provide approximately 13 mgd (570 L/s of this demand
with reclaimed water (Parsons, 1990). Altamonte
Springs, a fast-growing city in central Florida, expects to
stabilize potable water consumption by 1995 through
implementation of its comprehensive urban water reuse
system (Howard Needles Tammen & Bergendoff, 1986).
2.3 Sources of Reclaimed Water
Under the broad definition of water reclamation and
reuse, sources of reclaimed water may range from
industrial process waters to the tail waters of agricultural
irrigation systems. For the purposes of these guidelines,
however, the sources of reclaimed water are limited to
the effluent generated by domestic wastewater treatment
facilities (WWTFs).
Treated municipal wastewater represents a significant
potential source of reclaimed water for beneficial reuse.
As a result of the Federal Water Pollution Control Act
Amendments of 1972, the Clean Water Act of 1977 and
its subsequent amendments, centralized wastewater
treatment has become commonplace in urban areas of
the United States. In developed countries it is estimated
that approximately 73 percent of the population is served
by wastewater collection and treatment facilities. It is
estimated that only 7 percent of the population of
developing countries is served by wastewater collection
and treatment facilities. (Van Leeuwen, 1988). Within
the United States, the population generates an estimated
31 billion gal/d (1.4 x 106 Us) of potential reclaimed water
(SoIIey, et al., 1988). As the world population continues
to shift from rural to urban, the number of centralized
wastewater collection and treatment facilities will also
increase, creating significant opportunities to implement
water reuse systems to augment water supplies and, in
many cases, improve the quality of surface waters.
2.3.1 Locating the Sources
In areas of growth and new development, completely
new collection, treatment, and distribution systems may
be designed from the outset with water reclamation and
reuse in mind. In most cases, however, existing facilities
will be incorporated into the water reuse system. In areas
where centralized treatment is already provided, the
existing WWTFs are potential sources of reclaimed
water.
In the preliminary planning of a water reuse system
incorporating existing facilities, the following information
is needed for the initial evaluation:
Q Residential areas and their principal sewers,
Q Industrial areas and their principal sewers,
Q Wastewater treatment facilities,
Q Areas with combined sewers,
Q Existing effluent disposal facilities,
Q Areas and types of projected development, and
14
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Figure 9. Estimated Potable Water Conservation Achieved Through Urban Reuse
City of St. Petersburg, Florida
Reclaimed Water
| | Potable Water
Projected Potable Use
w/o Reclaimed Water
1985
1990
Source: Johnson, 1992.
Q Locations of potential reclaimed water users.
For economy, the wastewater treatment facilities ideally
should be located near the major users of the reclaimed
water. However, in adapting an existing system for water
reuse, other options are available. For example, if a trunk
sewer bearing flows to a WWTF passes through an area
of significant potential reuse, a portion of the flows can
be diverted to a new reclamation facility to serve that
area. The sludge produced in the reclamation facility
can be returned to the sewer for handling at the WWTF.
By this method, odor problems may be reduced or
eliminated at the reclamation facility. However, the
effects of this practice can be deleterious to both sewers
and downstream treatment facilities. Alternatively, an
effluent outfall passing through a potential reuse area
could be tapped for some or all of the effluent, and
additional treatment could be provided, if necessary, to
meet reclaimed water quality standards. These
alternative configurations are illustrated in Figure 10.
2.3.2 Characterizing the Sources
Existing sources must be characterized to roughly
establish the effluent's suitability for reclamation and
reuse. To compare the quality and quantity of available
reclaimed water with the requirements of potential users,
information on the operation and performance of the
existing WWTF and related facilities must be examined.
Important factors to consider in this preliminary stage of
reuse planning are:
Q Level of treatment (e.g., primary, secondary,
advanced) and specific treatment processes
(e.g., ponds, activated sludge, filtration,
disinfection, nutrient removal, disinfection);
Q Effluent water quality;
Q Effluent quantity (daily and season average,
maximum, and minimum flows);
Q Indu strial wastewater contributions to flow;
Q System reliability; and
15
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Rgura 10. Three Configuration Alternatives
for Water Reuse Systems
A. Central Treatment Near Reuse Site(s)
Collection
Reclaimed
Water to
Reuse Site(s)
a Reclamation of Portion of Wastewater Flow
Reclaimed Water
to Reuse Site(s)
Diversion
of Portion
of Influent
Collection
T
Water
Reclamation
Facility
Return c
Iidge
^
Trunk Sewer ~~
if
Central
Wastewater
Treatment
Facility
Effluent
Disposal
0. Reclamation of Portion ol Effluent
Collection
Central
Wastewater
Treatment
Facility
>
^
k
Effluent Disposal
Div
OfP
ofE
Return of
Sludge
<
=rsion
ortion
ffluent v
f
Water
Reclamation
Facility
1
Sludge Treatment
and Disposal
Reclaimed Water
to Reuse Site(s)
Q Supplemental facilities (e.g., storage, pumping,
transmission).
2.3.2.1 Level of Treatment and Processes
Because meeting all applicable treatment requirements
for the production of safe, reliable reclaimed water is one
of the keys to operating any water reuse system, careful
analysis of applicable requirements and provision of all
necessary process elements are critical in designing a
reuse system. At the early stage of planning, however,
only a preliminary assessment of the compatibility of
treatment facilities with potential reuse applications is
needed. A detailed discussion of treatment requirements
for water reuse applications is provided in Section 2.4.
Knowledge of the level of treatment and the treatment
processes provided is important in evaluating the
WWTF's suitability as a water reclamation facility and
determining the possible reuse applications. An existing
plant providing at least secondary treatment, while not
originally designed for water reclamation and reuse, can
be upgraded by modifying existing processes or adding
new process units to the existing train to supply
reclaimed water for most uses. For example, with the
addition of chemicals, filters, and other facilities to ensure
reliable disinfection, most secondary effluents can be
enhanced to provide a source of reclaimed water suitable
for unrestricted urban reuse. In Manatee County, Florida,
filtration, additional disinfection and pumping facilities
were constructed as part of a WWTF expansion. The
design capacity of these units processes matched the
identified reclaimed water irrigation demand of public
access sites but was less than the total WWTF capacity.
The unf iltered chlorinated reclaimed water was used for
the irrigation of gladiolus on a restricted access site.
Some existing processes necessary for effluent disposal
practices may no longer be required for water reuse. For
example, an advanced wastewater treatment plant
designed to remove nitrogen and/or phosphorus would
need little or no nutrient removal for agricultural or urban
irrigation, the nutrients in the reclaimed water being
beneficial to plant growth.
2.3.2.2 Effluent Water Quality
Effluent water quality sampling and analysis are required
as a condition of WWTF discharge permits. The specific
parameters tested are those required for preserving the
water quality of the receiving water body, [e.g.,
biochemical oxygen demand (BOD), suspended solids
(SS), conforms (or other indicators), nutrients, and
sometimes toxic organics and metals]. This information
is useful in the preliminary evaluation of the potential
utility of a source of reclaimed water. For example, as
noted earlier, the nitrogen and phosphorus in reclaimed
water represents an advantage for certain irrigation
applications. For industrial reuse, however, nutrients
may encourage biological growths that could cause
fouling. Where the latter uses are a small fraction of the
total use, the customer may be obliged to remove the
nutrients or blend reclaimed water with other sources.
The decision is based on case-by-case assessments.
In some cases, the water quality data needed to assess
the suitability of a given source are not included in the
WWTF's existing monitoring requirements and will have
to be gathered specifically for the reuse evaluation. For
example, coastal cities may experience saltwater
infiltration of the sewer system, resulting in elevated
chloride concentrations in the effluent. Chloride levels
16
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are of concern in irrigation because high levels are toxic
to many plants. However, chloride levels at WWTFs are
not typically monitored. Even in the absence of saltwater
infiltration or industrial contributions, practices within the
community being served may adversely impact
reclaimed water quality. For example, the widespread
use of water softeners may increase the concentration
of salts to levels making the reclaimed water unusable
for some applications.
The urban reuse system in the City of St. Petersburg,
Florida, provides an example of the importance of
reclaimed water quality. Between 1981 and 1991, the
city substantially increased its residential irrigation
customer base from approximately 20 percent of total
connections to more than 95 percent of the 7,000 total
reclaimed water service connections (Crook and
Johnson, 1991). In 1985, the city received a significant
number of complaints of damage to ornamental foliage
from reclaimed water. The problem was traced to
elevated chlorides in the reclaimed water. The chlorides
had not been a problem when the customer base was
dominated by golf course irrigation because turf grass
has a high tolerance for chlorides. While efforts are being
made to reduce saltwater infiltration to the sewerage
system, residents are cautioned to plan their landscaping
around salt-tolerant species (Johnson and Parnell,
1987). A case study of the St. Petersburg program is
provided at the end of Chapter 3.
For the purpose of reuse planning, it is best to consider
reclaimed water quality from the standpoint of a water
supply, i.e., what quality is required for the intended use.
Where a single large customer dominates the demand
for reclaimed water, the treatment selected may suit the
major customer. An example is Pomona, California,
where activated carbon filters were used in place of
conventional sand filters in the reclamation plant to serve
paper mills that require low color in their water supply.
Industrial reuse might be precluded if high levels of
dissolved solids, dissolved organic material, chlorides,
phosphates, and nutrients are present, unless additional
treatment is provided by the industrial facility.
Recreational reuse might be limited by nutrients, which
might result in unsightly and odorous algae blooms.
Trace metals in high concentrations might restrict the
use of reclaimed water for agricultural and horticultural
irrigation.
2.3.2.3 Effluent Quantity
Just as the water purveyor must meet the diurnal and
seasonal variations in demand for potable water, so too
must the purveyor meet such variations in demand for
reclaimed water. Diurnal and seasonal fluctuations in
supply and demand must be taken into account for both
elements of a dual system. Diurnal variations in sources
of reclaimed water are much more variable than in
sources of potable water supplies.
For example, WWTF flows are low at night, when urban
irrigation demand is high. Seasonal flow fluctuations may
occur in resort areas subject to a periodic influx of
tourists, and seasons of high flow do not necessarily
correspond with seasons of high irrigation demand.
Figure 11 illustrates the fluctuations in reclaimed water
supply and irrigation demand in a southwest Florida
community. Treatment facilities serving college
campuses, resort areas, etc. also experience significant
fluctuations in flow throughout the year.
Figure 11. Reclaimed Water Supply vs. Irrigation Demand
1.4.
1.2-
1.0.
0.6.
0.4.
0.2-
0-
Reclaimed Water
Residential Irrigation
Demand
Send to Storage |—| Retrieve from Storage
FMA
I
M
I I I 1 I I
JJASOND
Where collection systems are prone to infiltration and
inflow, significant fluctuations in flow may occur during
the rainy season. A 1981 report on agricultural reuse
systems in California cited a Lake County system where
the dry season reclaimed water supply of 0.7 mgd (31 U
s) rose to 1.8 mgd (79 Us) in the wet season due to
groundwater infiltration (Boyle Engineering Corporation,
1981). In a 1990 study of rainfall induced infiltration, a
review of ten systems documented a peak wet weather
flow ranging from 3.5 to 20 times the average dry
weather flow (EPA, 1990).
Information on flow quantities and fluctuations is critical
in sizing the storage facilities necessary to balance
supply and demand in water reuse systems. A complete
discussion of seasonal storage requirements is provided
in Section 2.5. Operational storage requirements to
balance diurnal flow variations are detailed in Section
2.6.2.
2.3.2.4 Industrial Wastewater Contributions
Industrial waste streams differ from domestic wastewater
in that they may contain relatively high levels of elements
17
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and compounds which may be toxic to plants and
animals or may adversely impact treatment plant
performance. Where industrial wastewater flow
contributions to the WWTF are significant, reclaimed
water quality may be affected. The degree of impact will,
of course, depend on the nature of the industry. A
rigorous pretreatment program is required for any water
reclamation facility that receives industrial wastes to
ensure the reliability of the biological treatment
processes by excluding potentially toxic levels of
pollutants from the sewer system. Planning a reuse
system around a WWTF with substantial industrial flows
will require identification of the constituents that may
interfere with particular reuse applications, and
appropriate monitoring for parameters of concern is
prudent. Wastewater treatment facilities receiving
substantial amounts of high-strength industrial wastes
may be limited in the number and type of suitable reuse
applications.
2.3.2.5 System Reliability
Reliability requirements for reclaimed water production
go beyond EPA Class I reliability (EPA, 1974), which
provides redundant facilities to prevent treatment upsets
during power and equipment failures, flooding, peak
loads, and maintenance shutdowns. Reliability for water
reuse includes, in addition:
Q Strict operator training and certification to ensure
that qualified personnel are operating the
WWTF;
Q Instrumentation and control systems for on-line
monitoring of treatment process performance
and alarms for process malfunctions;
Q A comprehensive quality assurance program to
ensure accurate sampling and laboratory
analysis protocol;
Q Adequate emergency storage to retain
reclaimed water of unacceptable quality for re-
treatment or alternative disposal;
Q Supplemental storage to ensure that the
quantity of the supply is adequate to meet the
user's demands; and
Q A strict industrial pretreatment program and
strong enforcement of sewer use ordinances to
prevent illicit dumping of hazardous materials
into the collection system.
Reliability and quality assurance are discussed in greater
detail in Section 2.4.3.
2.3.2.6 Transmission and Distribution Facilities
Apart from facilities specifically associated with
treatment, facilities for storage, transmission, and
distribution must also be considered. Will the available
pumping capacity of existing facilities be adequate to
meet expected reclaimed water demands? Can existing
lagoons be converted to operational storage facilities?
When the City of Venice, Florida, constructed a 2.1-mgd
(92-L/s) water reclamation facility in the eastern portion
of the city to reduce flows to an overloaded WWTF on
the west side, the western WWTF remained in service to
treat only about 0.3 mgd (13 Us) to provide irrigation
water for an adjacent golf course. At this reduced flow,
however, significant volumes of storage and treatment
capacity remained unused at the western site much of
the year. To take advantage of these facilities, provisions
were made in the wastewater collection system to divert
flows from selected lift stations to either WWTF, allowing
the city to balance supplies, demands, and storage
needs as conditions warrant (Ammerman and Moore,
1991).
2.4 Treatment Requirements for Water
Reuse
One of the most critical objectives in any reuse program
is to assure that health protection is not compromised
through the use of reclaimed water. Other objectives,
such as preventing environmental degradation, avoiding
public nuisance, and meeting user requirements, must
also be satisfied in implementing a successful reuse
program, but the starting point remains the safe delivery
and use of properly treated reclaimed water.
Protection of public health is achieved by: (1) reducing
concentrations of pathogenic bacteria, parasites, and
enteric viruses in the reclaimed water; (2) controlling
chemical constituents in reclaimed water; and/or (3)
limiting public exposure (contact, inhalation, ingestion)
to the reclaimed water. Where human exposure is likely
in a reuse application, reclaimed water should be treated
to a high degree prior to its use. Conversely, where
public access to a reuse site can be restricted so that
exposure is unlikely, a lower level of treatment may be
satisfactory, provided worker safety is not compromised.
Providing the necessary treatment for the intended reuse
application requires an understanding of the constituents
of concern in wastewater and the levels of treatment and
processes applicable for removing these constituents to
achieve the desired reclaimed water quality.
18
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2.4.1 Health Assessment of Water Reuse
The presence of toxic chemicals and pathogenic
microorganisms in untreated wastewater creates the
potential for adverse toxicological health effects and
disease transmission where there is contact, inhalation,
or ingestion of the chemical or microbiological
constituents of health concern. Control measures include
elimination or reduction in concentration of these
constituents in reclaimed water and, where appropriate,
practices to prevent or limit direct and indirect contact
with the reclaimed water.
Health significant microorganisms and chemical
constituents clearly are present in untreated wastewater
and, thus, justifiably present a health concern. It is also
clear that for most uses of reclaimed water, conventional,
widely practiced water and wastewater treatment
processes are capable of reducing these hazardous
constituents to acceptable levels or virtually eliminating
them from the water. For some uses, (e.g., indirect
potable reuse), advanced treatment processes may be
necessary to accomplish this task.
2.4.1.1 Pathogenic Microorganisms and Health
Risks
The principal infectious agents that may be present in
raw wastewater can be classified into three broad
groups: bacteria, parasites (protozoa and helminths),
and viruses. Table 1 lists many of the infectious agents
potentially present in raw domestic wastewater.
a. Bacteria
One of the most common pathogens found in municipal
wastewater is the genus Salmonella. This group contains
a wide variety of species that can cause disease in man
and animals. The three distinct forms of salmonellosis in
humans are enteric fevers, septicemias, and acute
gastroenteritis. The most severe form of salmonellosis is
the typhoid fever caused by Salmonella typhi. The
Salmonella septicemias are not particularly common in
human populations. The third form of salmonellosis,
acute gastroenteritis, is the form in which the Salmonella
are most commonly encountered. In excess of 1,500
different serotypes have been identified.
A less common genus of bacteria that has been isolated
from wastewater is Shigella, which produces an intestinal
disease known as bacillary dysentery or shigellosis.
Waterborne outbreaks of shigellosis have been reported
where wastewater has contaminated wells used for
drinking water (National Communicable Disease Center,
1969 and 1973). The survival time of Shigella in
wastewater is relatively short, and shigellosis appears to
be spread primarily by person-to-person contact.
However, Shigella is the leading cause of recreational
waterborne outbreaks in lakes and rivers.
There are a variety of other bacteria of lesser importance
that have been isolated from raw wastewater. These
include Vibrio, Mycobacterium, Clostridium, Leptospira
and Yersinia species. While these pathogens may be
present in wastewater, their concentrations are usually
too low to initiate disease outbreaks. Vibrio cholerae is
the disease agent for cholera, which is not common in
the United States but is still prevalent in other parts of
the world. Man is the only known host, and the most
frequent mode of transmission is through the water route.
Mycobacterium tuberculosis has been found in
wastewater (Greenberg and Kupka, 1957), particularly
where an institution treating tuberculosis patients is
involved or where industries such as dairies and
slaughterhouses handling tubercular animals discharge
to a municipal sewerage system. Outbreaks among
persons swimming in water contaminated with
wastewater have been reported (California Department
of Health and Cooper, 1975).
Waterborne gastroenteritis of unknown cause is
frequently reported, with the suspected agent being
bacterial. One potential source of this disease is certain
gram-negative bacteria normally considered to be
nonpathogenic. These include enteropathogenic
Escherichia coli and certain strains of pseudomonas
which may affect the newborn. Waterborne
enterotoxigenic E. coli have been implicated in
gastrointestinal disease outbreaks (National
Communicable Disease Center, 1975).
Campylobacter coli has been identified as the cause
of a form of bacterial diarrhea in man. While it has
been well-established that this organism causes
disease in animals, it has also been implicated as the
etiological agent in human waterborne disease
outbreaks (Craun, 1988).
In recognition of the many constraints associated with
analyzing wastewater for all of the potential pathogens
that may be present, it has been common practice to use
a microbial indicator or surrogate to indicate fecal
contamination of water. Bacteria of the coliform group
have long been considered the prime indicators of fecal
contamination and are the most frequently applied
indicators of water quality by state regulatory agencies.
The coliform group is made up of a number of bacteria,
including the genera Klebsellia, Citribacter, Escherichia,
Serratia, andEnterobacteria. The total coliform group are
all gram-negative aspogenous rods and are found in
feces of warm-blooded animals and in soil. Fecal
coliform bacteria are restricted to the intestinal tract of
19
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Table 1.
Infectious Agents Potentially Present in Untreated Domestic Wastewater
Pathogen
Disease
Protozoa
Entamoeba histolyllca
Giardia lamblia
Balantldium coll
Ciyptosporidium
Helminths
Ascaris lumbricoides (roundworm)
Ancylostoma duodenale (hookworm)
Nacator americanus (roundworm)
Ancylostoma (spp.) (hookworm)
Strongloides starcoralis (threadworm)
Trichuris trichiura (whipworm)
Taenia (spp.) (tapeworm)
Enterobius vermicularis (pinworm)
Echinococcus granulosus (spp.) (tapeworm)
Bacteria
Shlgella (4 spp.)
Salmonella typhi
Salmonella (1700 serotypes)
Vibro cholerae
Escherichla coli (enteropathogenic)
Yersinia entarocolitica
Leptospira (spp.)
Legionella
Campylobacter jejune
Viruses
Enteroviruses (72 types) (polio, echo,
coxsackie, new enteroviruses)
Hepatitis A virus
Adenovirus (47 types)
Rotavirus (4 types)
Parvovirus (3 types)
Norwalk agent
Reovirus (3 types)
Astroviais (5 types)
Calicivirus (2 types)
Coronavirus
Amebiasis (amebic dysentery)
Giardiasis
Balantisiasis (dysentery)
Cryptosporidiosis, diarrhea, fever
Ascariasis
Ancylostomiasis
Necatoriasis
Cutaneous larva migrams
Strongyloidiasis
Trichuriasis
Taeniasis
Enterobiasis
Hydatidosis
Shigellosis (dysentery)
Typhoid fever
Salmonellosis
Cholera
Gastroenteritis
Yersiniosis
Leptospirosis
Legionnaire's disease
Gastroenteritis
Gastroenteritis, heart anomolies,
meningitis, others
Infectious hepatitis
Respiratory disease, eye infections
Gastroenteritis
Gastroenteritis
Diarrhea, vomiting, fever
Not clearly established
Gastroenteritis
Gastroenteritis
Gastroenteritis
Source: Adapted from Sagikef a/., 1978; Hurst era/., 1989.
warm-blooded animals and comprise a portion of the
total coliform group. Escherichia coli and enterococci
are sometimes used as indicators of bacteriological
contamination in recreational waters. Coliform
organisms are used as indicators because they occur
naturally in the feces of warm-blooded animals in higher
concentrations than pathogens and are easily and
unambiguously detectable, exhibit a positive correlation
with fecal contamination, and generally respond similarly
to environmental conditions and treatment processes as
many bacterial pathogens. However, coliform bacteria
determinations, by themselves, do not adequately
predict the presence or concentration of pathogenic
viruses or protozoa.
b. Protozoa
There are a number of protozoan and metazoan agents
that are pathogenic to humans and that occur in
municipal wastewater. Probably the most important of
the parasites is the protozoan Entamoeba histolytica,
which is responsible for amoebic dysentery and amoebic
hepatitis. The amoeba is found in sewage in the form of
cysts, which are excreted by infected humans. The cysts,
upon entering a susceptible host by contaminated food
or water, germinate in the gut and can initiate infection.
The diseases are worldwide, but in the U.S., Entamoeba
histolytica has not been an important disease agent
since the 1950s.
20
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Waterborne disease outbreaks around the world have
been linked to the protozoans Giardia lamblia and
Cryptosporidium, although no Giardia or
Cryptosporidium cases related to water reuse practices
have been reported. The flagellate Giardia lamblia is the
cause of giardiasis, which is responsible for
gastrointestinal disturbances, diarrhea, and general
discomfort, and is emerging as a major waterborne
disease. Infection is caused by ingestion of Giardia cysts.
Cryptosporidium cause diarrhea! disease, with oocysts
being the infectious stage (Rose, 1986).
c. Helminths
There are several helminthic parasites that occur in
wastewater. The most important are intestinal worms,
including the stomach worm Ascaris lumbricoides, the
tapeworms Taenia saginata and Taenia solium, the
whipworm Trichuris trichirar, the hookworms
Ancylostoma duodenia and Necator americanus, and
the threadworm Strongyloides stercoralis. Many of the
helminths have complex life cycles, including a required
stage in intermediate hosts. The infective stage of some
helminths is either the adult organism or larvae, while
the eggs or ova of other helminths constitute the infective
stage of the organisms. The free living nematode larvae
stages are not pathogenic to human beings. The eggs
and larvae are resistant to environmental stresses and
may survive usual wastewater disinfection procedures,
although eggs are readily removed by commonly used
wastewater treatment processes, such as
sedimentation, filtration, or stabilization ponds.
d. Viruses
Over 100 different enteric viruses capable of producing
infections or disease are excreted by humans. Enteric
viruses are those which multiply in the intestinal tract
and are released in the fecal matter of infected persons.
Not all types of enteric viruses have been determined to
cause waterborne disease.
The most important human enteric viruses are the
enteroviruses (polio, echo, and coxsackie), rotaviruses,
reoviruses, parvoviruses, adenoviruses, and hepatitis A
virus (Hurst, etal., 1989; WPCF, 1989). The reoviruses
and adenoviruses, which are known to cause respiratory
illness, gastroenteritis, and eye infections, have been
isolated from wastewater. Of the viruses that cause
diarrheal disease, only the Norwalk virus and rotavirus
have been shown to be major waterborne pathogens
(Rose, 1986). Hepatitis A, the virus causing infectious
hepatitis, is a virus frequently reported to be transmitted
by water.
There is no evidence that the human immunodeficiency
virus (HIV), the pathogen that causes the acquired
immunodeficiency syndrome (AIDS), can be transmitted
via a waterborne route (Riggs, 1989). The results of one
laboratory study (Casson et al., 1992), where primary
and undisinfected secondary effluent samples were
inoculated with HIV (Strain IIIB) and held for up to 48
hours at 25°C (77°F), indicated that HIV survival was
significantly less than poliovirus survival under similar
conditions.
It has been reported that viruses and other pathogens
that may be present in wastewater used for irrigation do
not readily penetrate fruits or vegetables unless the skin
is broken (Bryan, 1974). In one study where soil was
inoculated with poliovirus, viruses were detected in the
leaves of plants only when the plant roots were damaged
or cut (Shuval, 1978). Although absorption of viruses by
plant roots and subsequent acropetal translocation has
been reported (Murphy and Syverton, 1958), it probably
does not occur with sufficient regularity to be a
mechanism for transmission for interepidermic survival
of viruses. Therefore, the likelihood of translocation of
pathogens through trees or vines to the edible portions
of crops is extremely low, and the health risks are
negligible.
The study of low level or endemic occurrence of
waterborne virus diseases has been virtually ignored for
several reasons:
Q Current virus detection methods are not
sufficiently sensitive to accurately detect low
concentrations of viruses even in large volumes
of water.
Q Enteric virus infections are often not apparent,
thus making it difficult to establish the endemicity
of such infections.
Q The apparently mild nature of most enteric virus
infections preclude reporting by the patient or
the physician.
Q Current epidemiological techniques are not
sufficiently sensitive to detect low level
transmission of viral diseases through water.
Q Illness due to enteroviral infections may not
become obvious for several months or years.
Q Once introduced into a population, person-to-
person contact becomes a major mode of
transmission of an enteric virus, thereby
obscuring the role of water in its transmission.
21
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2.4.1.2 Mechanism of Disease Transmission
Diseases can be transmitted to humans either directly
by skin contact, ingestion, or inhalation of infectious
agents in water, or indirectly by contact with objects
previously contaminated. The following circumstances
must occur for an individual to become infected from
exposure to reclaimed water: (a) the infectious agent
must be present in the community and, hence, in the
wastewater from that community; (b) the agents must
survive all the wastewater treatment processes to which
they are exposed; (c) the individual must either directly
or indirectly come in contact with the reclaimed water;
and (d) the agents must be present in sufficient numbers
to cause infection at the time of contact.
Whether illness occurs depends on a series of complex
interrelationships between the host and the infectious
agent. Specific variables include: the numbers of the
invading microorganism (dose); the numbers of
organisms necessary to initiate infection (infective dose);
the organism's ability to cause disease (pathogenicity);
and the relative susceptibility of the host. The infectious
dose of some organisms may be lower than the dose
required to cause overt symptoms of the disease.
Infection may be defined as an immunological response
to pathogenic agents by a host without necessarily
showing signs of a disease.
Table 3.
Microorganism Concentrations in
Raw Wastewater
Table 2.
Infectious Doses of Selected Pathogens
Organism
Escherichia coli (enteropathogenic)
Clostridium perfrlngens
Salmonella typhi
Vibrio cholerae
Shlgalta flexneri2A
Entameoba histolytica
Shigella dysentariae 1
Giardia lamblia
Viruses
Ascaris lumbricoides
Infectious Dose
106-1010
1x1010
104-107
103-107
180
20
10
<10
1-10
1-10
Organism
Concentration
(number/100 mL)
Fecal Coliforms
Fecal streptococci
Shigella
Salmonella
Helminth ova
Enteric virus
Giardia lamblia cysts
Entamoeba histolytica cysts
104-109
104-106
1 - 1,000
400 - 8,000
1-800
100-50,000
50-104
0-10
Source: Adapted from Feachem era/., 1981 and Feachem etal., 1983.
Susceptibility is highly variable and dependent upon both
the general health of the subject and the specific
pathogen in question. Infants, elderly persons,
malnourished persons, and persons with concomitant
illness are more susceptible than healthy adults. The
infectious doses of selected pathogens are presented in
Table 2.
The large variety of pathogenic microorganisms that may
be present in raw domestic wastewater is derived
principally from the feces of infected human and animal
hosts. There are occasions when host infections cause
passage of pathogens in urine. The three principal
infections leading to significant appearance of pathogens
in urine are: urinary schistosomiasis, typhoid, and
leptospirosis. Coliform and other bacteria may be
numerous in urine during urinary tract infections, but
they constitute little public health risk in wastewater.
Microbial agents resulting from venereal infections can
also be present in urine, but they are so vulnerable to
conditions outside the body that wastewater is not an
important vehicle of transmission (Feachem etal., 1983).
2.4.1.3 Presence and Survival of Pathogens
The occurrence and concentration of pathogenic
microorganisms in raw wastewater depends on a
number of factors, and it is not possible to predict with
any degree of assurance what the general
characteristics of a particular wastewater will be with
respect to infectious agents. Important variables include
the sources contributing to the wastewater, the general
health of the contributing population, the existence of
"disease carriers" in the population, and the ability of
infectious agents to survive outside their hosts under a
variety of environmental conditions.
22
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Table 4. Typical Pathogen Survival Times at 20-30 °C
Pathogen
Fresh Water & Sewage
Survival Time idavsi
Crops
Soil
Viruses3
Entero viruses'5
Bacteria
Fecal coliforms3
Salmonella spp.3
Shigella spp.3
Vibrio choleras0
Protozoa
Entamoeba
histolytica cysts
Helminths
Ascaris
lumbricoides eggs
<120 but usually <50
<60 but usually <30
<60 but usually <30
<30 but usually <10
<30 but usually <10
<30 but usually <15
Many months
<60 but usually <15
<30 but usually <15
<30 but usually <15
<10 but usually <5
<5 but usually <2
<10 but usually <2
<60 but usually <30
<100 but usually <20
<70 but usually <20
<70 but usually <20
<20 but usually <10
<20 but usually <10
Many months
a In seawater, viral survival is less, and bacterial survival is very much less, than in fresh water.
b Includes polio-, echo-, and coxsackieviruses.
c V. cholerae survival in aqueous environments is a subject of current uncertainty.
Source: Adapted from Feacham etal., 1983.
Table 3 illustrates the variation and order of magnitude
of the concentration of certain organisms that may be
present in raw wastewater. Bradley and Hadidy (1981)
reported that raw sewage in Aleppo, Syria, contained
1,000 to 8,000 Ascaris eggs/L, due to an estimated 42
percent of the population excreting an average of
800,000 eggs/person/day. Salmonella may be present
in concentrations up to 10,000/L. The excretion of
Salmonella typhi by asymptomatic carriers may vary
from 5 x 103 to 45 x 106 bacteria/g of feces (Drexel
University, 1978).
Enteroviruses are not normally excreted for prolonged
periods by healthy individuals, and their occurrence in
municipal wastewater fluctuates widely. Virus
concentrations are generally highest during the summer
and early autumn months. Viruses shed from an infected
individual commonly range from 1,000 to 100,000
infective units/g of feces, but may be as high as
1,000,000/g of feces (Feachem etal., 1983). Viruses as
a group are generally more resistant to environmental
stresses than many of the bacteria, although some
viruses persist for only a short time in municipal
wastewater. In water-short areas such as Israel where
per capita water use is relatively low, virus
concentrations have been reported to range from 600 to
approximately 50,000 plaque-forming units per 100
milliliters (pfu/100 mL) (Buras, 1976). This is in contrast
to virus levels in the U.S. which have been reported to
be as high as 700 virus units/100 mL but are typically
less than 100 pfu/100 mL (Melnick et al., 1978; EPA,
1979).
Under favorable conditions, pathogens can survive for
long periods of time on crops or in water or soil. Factors
that affect survival include number and type of organism,
soil organic matter content (presence of organic matter
aids survival), temperature (longer survival at low
temperatures), humidity (longer survival at high
humidity), pH, amount of rainfall, amount of sunlight
(solar radiation detrimental to survival), protection
provided by foliage, and competitive microbial fauna and
flora. Survival times for any particular microorganism
exhibit wide fluctuations under differing conditions.
Typical ranges of survival times for some common
pathogens on crops and in water and soil are presented
in Table 4.
2.4.1.4 Aerosols
Aerosols are particles less than 50 urn in diameter that
are suspended in air. Viruses and most pathogenic
bacteria are in the respirable size range; hence, a
possible direct means of human infection by aerosols is
by inhalation. Bacteria and viruses have been found in
aerosols emitted by spray irrigation systems using
untreated and poorly treated wastewater (Camann and
23
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Guentzel, 1985; Camann and Moore, 1988; Teltsch et
al., 1980).
The concentration of pathogens in aerosols is a function
of their concentration in the applied wastewater and the
aerosolization efficiency of the spray process. During
spray irrigation, the amount of water that is aerosolized
can vary from less than 0.1 percent to almost 2 percent,
with a mean aerosolization efficiency of 1 percent or less
(Johnson et al., 1980a, 1980b; Bausum et al., 1983;
Camann et al., 1988). Infection or disease may be
contracted indirectly by deposited aerosols on surfaces
such as food, vegetation, and clothes. The infective dose
of some pathogens is lowerfor respiratory tract infections
than for infections via the gastrointestinal tract; thus, for
some pathogens, inhalation may be a more likely route
for disease transmission than either contact or ingestion
(Hoadley and Goyal, 1976).
A comprehensive evaluation of viruses indicated that a
number of waterborne viruses are capable, if
aerosolized, of producing respiratory tract infections and
disease (Sobsey, 1978). The infectivity of an inhaled
aerosol depends on the depth of the respiratory
penetration and the presence of pathogenic organisms
capable of infecting the respiratory system. Aerosols in
the 2 to 5 um size range are primarily removed in the
respiratory tract, some to be subsequently swallowed.
Thus, if gastrointestinal pathogens are present, infection
could result. A considerably greater potential for infection
occurs when respiratory pathogens are inhaled in
aerosols smallerthan 2 um in size, which pass directly to
the alveoli of the lungs (Sorber and Guter, 1975).
in general, bacteria and viruses in aerosols remain viable
and travel farther with increased wind velocity, increased
relative humidity, lower temperature, and lower solar
radiation. Other important factors include the initial
concentration of pathogens in the wastewater and
droplet size. Aerosols can be transmitted for several
hundred meters under optimum conditions. Some types
of pathogenic organisms, e.g., enteroviruses and
Salmonella, appear to survive the wastewater
aerosolization process much better than the indicator
organisms (Teltsch et al., 1980).
One study found that coliforms were carried 295 to 425 ft
(90 to130 m) with a wind velocity of 3.4 mph (1.5 m/s),
and H was estimated that fine mist could be carried 1000-
1300 ft (300-400 m) with an 11 mph (5 m/s) wind (Sepp,
1971). Another study found that the mean net bacterial
aerosol levels, i.e., the observed minus the simultaneous
mean upwind value, were 485 colony-forming units
(CFU)/ma at a distance of 70-100 ft (21-30 m) from the
most downwind row of sprinkler heads in a spray field
and 37 CFU/m3 at 660 ft (200 m) downwind (Bausum et
al., 1983). The sprayed wastewater had received
treatment in stabilization lagoons before disinfection with
chlorine.
During a study in Israel, echovirus 7 was detected in air
samples collected at 130 ft (40 m) downwind from
sprinklers spraying undisinfected secondary effluent
(Teltsch and Katzenelson, 1978). Aerosol
measurements at Pleasanton, California, where
undisinfected secondary effluent was sprayed, indicated
that the geometric mean aerosol concentration of
enteroviruses obtained 165 ft (50 m) downwind of the
wetted spray area was 0.014 pfu/m3 (Johnson et al.,
1980b). This concentration is equal to one virus particle
in 2,500 cu f (71 m3) of air.
One of the most comprehensive aerosol studies, the
Lubbock Infection Surveillance Study (Camann et al.,
1986), monitored viral and bacterial infections in a mostly
rural community surrounding a spray injection site near
Wilson, Texas. The source of the irrigation water was
undisinfected trickling filter effluent from the Lubbock
Southeast water reclamation plant. Spray irrigation of
the wastewater significantly elevated air densities of
fecal coliforms, fecal streptococci, mycobacteria, and
coliphage above the ambient background levels for at
least 650 ft (200 m) downwind. The geometric mean
concentration of enteroviruses recovered 150-200 ft (44
- 60 m) downwind was 0.05 pfu/m3, a level higher than
that observed at other wastewater aerosol sites in the
U.S. and in Israel (Camann era/., 1988). While disease
surveillance found no obvious connection between the
self-reporting of acute illness and the degree of aerosol
exposure, serological testing of blood samples indicated
that the rate of viral infections was slightly higher among
members of the study population who had a high degree
of aerosol exposure (Camann era/., 1986).
For intermittent spraying of disinfected reclaimed water,
occasional inadvertent contact should pose little health
hazard from inhalation. Aerosols from cooling towers
which issue continuously may present a greater concern
if the water is not properly disinfected. For example,
Legionella pneumophila, the bacterium that causes
Legionnaire's Disease, is present in many types of water
and proliferates in some cooling water systems, thus
presenting a potential health hazard regardless of the
source of the water. The concentration of pathogens in
the recirculated waters of cooling towers using reclaimed
water is reduced somewhat by the treatment to prevent
biofouling, which is generally by the addition of chlorine.
On the other hand, the evaporation in cooling towers
concentrates contaminants in the water, and the water
in the tower and in aerosols or windblown spray may
24
-------
contain pathogen concentrations little different from the
reclaimed water. Although a great deal of effort has been
expended to quantify the numbers of fecal conforms and
enteric pathogens in cooling tower waters, there is no
evidence that they occur in large numbers, although the
numbers of other bacteria may be quite large (Adams
and Lewis, n.d.).
Because there is limited information available regarding
the health risks associated with wastewater aerosols,
health implications are difficult to assess. Several studies
in the U.S. have been directed at residents in
communities subjected to aerosols from sewage
treatment plants (Camann et at., 1979; Camann etal.,
1980; Fannin etal., 1980; Johnson etal., 1980a). These
investigations have not detected any definitive
correlation between exposure to aerosols and disease.
Although some studies have indicated higher incidences
of respiratory and gastrointestinal illnesses in areas
receiving aerosols from sewage treatment plants than in
control areas, the elevated illness rates were either
suspected to be the result of other factors, such as
economic disparities, or were not verified by antibody
tests for human viruses and isolations of pathogenic
bacteria, parasites, or viruses (Fannin et al., 1980;
Johnson et al., 1980a).
There have not been any documented disease
outbreaks resulting from the spray irrigation of
disinfected reclaimed water, and studies indicate that
the health risk associated with aerosols from spray
irrigation sites using reclaimed water is low (EPA,
1980b). However, until more sensitive and definitive
studies are conducted to fully evaluate the ability of
pathogens contained in aerosols to cause disease, the
general practice is to limit exposure to aerosols produced
from reclaimed water that is not highly disinfected
through design or operational controls. Emission of
aerosols or windblown spray from cooling towers
receiving reclaimed water also may warrant attention.
2.4.1.5 Infectious Disease Incidence Related to
Wastewater Reuse
Epidemiological investigations directed at wastewater-
contaminated drinking water supplies, use of raw or
minimally-treated wastewater for food crop irrigation,
health effects to farmworkers who routinely contact
poorly treated wastewater used for irrigation, and the
health effects of aerosols or windblown spray emanating
from spray irrigation sites using undisinfected
wastewater have all provided evidence of infectious
disease transmission from such practices (Lund, 1980;
Feachem etal., 1983; Shuval etal., 1986).
However, epidemiological studies of the exposed
population at water reuse sites receiving disinfected
reclaimed water treated to relatively high levels are of
limited value because of the mobility of the population,
the small size of the study population, the difficulty in
determining the actual level of exposure of each
individual, the low illness rate—if any—resulting from
the reuse practice, insufficient sensitivity of current
epidemiological techniques to detect low-level disease
transmission, and other confounding factors. It is
particularly difficult to detect low-level transmission of
viral disease because many enteric viruses cause such
a broad spectrum of disease syndromes that scattered
cases of acute illness would probably be too varied in
symptomoldgy to be attributed to a single etiological
agent.
The limitations of epidemiological investigations
notwithstanding, water reuse in the U.S. has not been
implicated as the cause of any infectious disease
outbreaks (WPCF, 1989).
Reasonable standards of personal hygiene, e.g., use of
protective clothing, change of clothing at the end of the
work period, avoiding exposure to reclaimed water
where possible, and care in handwashing and bathing
following exposure and prior to eating, appear to be
effective in protecting the health of workers at water
reuse sites, regardless of the level of treatment provided.
Protective measures may be relaxed at sites where
reclaimed water has received a high level of treatment
and disinfection.
The use of pathogen risk assessment models to assess
health risks associated with the use of reclaimed water
is a relatively new concept. Risk analysis has been used
as a tool in assessing relative health risks from
microorganisms in drinking water (Gerba and Haas,
1988; Regli etal., 1991; Rose etal., 1991) and reclaimed
water (Asano and Sakaji, 1990; Rose and Gerba, 1991).
Risk analyses require several assumptions to be made,
e.g., minimum infectious dose of selected pathogens,
concentration of pathogens in reclaimed water, quantity
of reclaimed water (or pathogens) ingested, inhaled, or
otherwise contacted by humans, and probability of
infection based on infectivity models. Operation and
management practices, such as treatment reliability
features and use area controls, play an important role in
reducing estimated health risks. At the present time, no
reclaimed water standards or guidelines in the U.S. are
based on risk assessment using microorganism
infectivity models.
25
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2.4.1.6 Chemical Constituents
The chemical constituents potentially present in
municipal wastewater are a major concern when
reclaimed water is used for potable reuse and may also
affect the acceptability of reclaimed water for other uses
such as food crop irrigation. The mechanisms of food
crop contamination include: physical contamination,
where evaporation and repeated application may result
in a buildup of contaminants on crops; uptake through
the roots from the applied water or the soil; and foliar
uptake. With the exception of possible inhalation of
volatile organics from indoor exposure, chemical
concerns are less important where reclaimed water is
not to be consumed. Chemical constituents are also a
consideration when reclaimed water percolates into
groundwater as a result of irrigation, groundwater
recharge, or other uses. These practices are covered in
Chapter 3. Some of the inorganic and organic
constituents of importance in water reclamation and
reuse are listed in Table 5.
a. Inorganics
In general, the health hazards associated with the
ingestion of inorganic constituents, either directly or
through food, are well-established (EPA, 1976), and EPA
has set maximum contaminant levels (MCLs) for drinking
water. The concentrations of inorganic constituents in
reclaimed water depend mainly on the source of
wastewater and the degree of treatment. Residential use
of water typically adds about 300 mg/L of dissolved
inorganic solids, although the amount added can range
from approximately 150 mg/L to more than 500 mg/L. As
indicated in Table 5, the presence of total dissolved
solids, nitrogen, phosphorus, heavy metals, and other
inorganic constituents may affect the acceptability of
reclaimed water for different reuse applications.
Wastewater treatment generally can reduce many trace
elements to below recommended maximum levels for
irrigation and drinking water with existing technology
(Gulp, et al., 1980).
b. Organics
The organic makeup of raw wastewater includes
naturally occurring humic substances, fecal matter,
kitchen wastes, liquid detergents, oils, grease, and other
substances that one way or another become part of the
sewage stream. Industrial and residential wastes can
contribute significant quantities of synthetic organic
compounds.
The need to remove organic constituents is related to
the end use of reclaimed water. Some of the adverse
effects associated with organic substances include:
Q Aesthetically displeasing: they may be
malodorous and impart color to the water.
Q Nuisance: deposits of organic matter may
present vector control and eventually health
problems.
Q Clogging: paniculate matter may clog sprinkler
heads or accumulate in soil and affect
permeability.
Q Oxygen consuming: organic substances upon
decomposition deplete the dissolved oxygen
content in streams and lakes, thus negatively
impacting aquatic life which depends upon this
supply of oxygen for survival.
Q Use limiting: many industrial applications cannot
tolerate water high in organic content.
Q Disinfection effects: organic matter can interfere
with chlorine, ozone, and ultraviolet disinfection,
thereby making them less available for
disinfection purposes.
Q Health effects: ingestion of water containing
certain organic compounds may result in acute
or chronic health effects.
The health effects resulting from organic constituents
are of primary concern for indirect or direct potable reuse
but, as with certain inorganic constituents, may also be
of concern where reclaimed water is utilized for food
crop irrigation, where reclaimed water from irrigation or
other beneficial uses reaches potable groundwater
supplies, or where the organics may bioaccumulate in
the food chain, e.g., in fish-rearing ponds. The effects
may be manifested from short-term exposure or become
apparent only after years of exposure. Although drinking
water standards contain MCLs for some organic
contaminants, compliance with existing standards alone
would not assure that reclaimed water is safe for potable
reuse.
Traditional measures of organic matter such as BOD,
chemical oxygen demand (COD), and total organic
carbon (TOC) are widely used as indicators of treatment
efficiency and water quality for many nonpotable uses of
reclaimed water, but they have only indirect relevance to
toxicity and health effects evaluation. The identification
and quantification of extremely low levels of organic
constituents in water is possible using sophisticated
analytical instrumentation such as gas chromatography/
mass spectrometry (GC/MS) interfaced with computers.
GC/MS analyses are costly and may require extensive
26
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Table 5. Inorganic and Organic Constituents of Concern in Water Reclamation and Reuse
Constituent
Measured
Parameters
Reason for Concern
Suspended Solids
Biodegradable
Organics
Nutrients
Stable
Organics
Suspended solids (SS),
including volatile and
fixed solids
cause plugging in irrigation systems.
Biochemical oxygen
demand,
Chemical oxygen
demand,
Total organic carbon
Nitrogen,
Phosphorus,
Potassium
Specific compounds
(e.g., pesticides,
chlorinated
hydrocarbons)
Organic contaminants, heavy metals, etc. are adsorbed on
particulates. Suspended matter can shield microorganisms
from disinfectants. Excessive amounts of SS
Aesthetic and nuisance problems. Organics provide food for
microorganisms, adversely affect disinfection processes,
make water unsuitable for some industrial or other uses,
consume oxygen, and may result in acute or chronic
effects if reclaimed water is used for potable purposes.
Nitrogen, phosphorus, and potassium are essential
nutrients for plant growth, and their presence normally
enhances the value of the water for irrigation. When discharged
to the aquatic environment, nitrogen and phosphorus can lead
to the growth of undesirable aquatic life. When applied at
excessive levels on land, nitrogen can also lead to nitrate
build-up in groundwater.
Some of these organics tend to resist conventional methods
of wastewater treatment. Some organic compounds are
toxic in the environment, and their presence may limit
the suitability of reclaimed water for irrigation or other uses.
Hydrogen Ion
Concentration
Heavy Metals
Dissolved
Inorganics
Residual
Chlorine
PH
Specific elements (e.g.,
Cd, Zn, Ni, and Hg)
Total dissolved solids,
electrical conductivity,
specific elements (e.g.,
Na, Ca, Mg, Cl, B)
Free and combined
chlorine
The pH of wastewater affects disinfection, coagulation,
metal solubility, as well as alkalinity of soils. Normal range in
municipal wastewater is pH = 6.5 - 8.5, but industrial waste
can alter pH significantly.
Some heavy metals accumulate in the environment and are
toxic to plants and animals. Their presence may limit the
suitability of the reclaimed water for irrigation or other uses.
Excessive salinity may damage some crops. Specific ions
such as chloride, sodium, boron are toxic to some crops.
Sodium may pose soil permeability problems.
Excessive amount of free available chlorine (>0.05 mg/L)
may cause leaf-tip burn and damage some sensitive crops.
However, most chlorine in reclaimed water is in a
combined form, which does not cause crop damage. Some
concerns are expressed as to the toxic effects of
chlorinated organics in regard to groundwater ontamination.
Source: Adapted from Pettygrove and Asano, 1985.
and difficult sample preparation, particularly for
nonvolatile organics.
In addition, organic compounds in wastewater can be
transformed into chlorinated organic species where
chlorine is used for disinfection purposes. To date, most
attention has focused on the trihalomethane (THM)
compounds, a family of organic compounds typically
occurring as chlorine or bromine substituted forms of
methane. Chloroform is the most prevalent THM
compound and has been implicated in the development
of cancer of the liver and kidney.
Although a large number of specific organic constituents
have been identified in wastewater, about 90 percent of
the residual organic fraction remains unidentified.
Toxicological testing of reclaimed water organic
residuals using the Ames Salmonella Microsome
Mutagen Assay and the Mammalian Cell Transformation
Assay have indicated mutagenicity, cytotoxicity, and
27
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Table 6, Typical Composition of Untreated Municipal Wastewater8
Concentration Range"
Constituent
Solids, total:
Dissolved, totar
Rxed
Volatile
Suspended
Rxed
Volatile
Settleable solids, mL/L
Biochemical oxygen demand,
5-day 20°C
Total organic carbon
Chemical oxygen demand
Nitrogen (total)
Org-N
NH3-N
NOg'N
NOs'N
Phosphorus (total)
Organic
Inorganic
Chloridesd
Alkalinity (as CaCOs)d
Grease e
Total coliform bacteria
(#/100mL)
Fecal coliform bacteria9
(#/100mL)
Viruses, PFU/100 ml_a
a All values are expressed
b After Metcalf & Eddy, Inc
c Gulp et a/., 1979.
Strong Medium
1,200
850
525
325
350
75
275
20
400
290
1,000
85
35
50
0
0
15
5
10
100
200
150
—
~~~
in mg/L, except as noted.
., 1979.
720
500
300
200
220
55
165
10
220
160
500
40
15
25
0
0
8
3
5
50
100
100
—
~
Weak
350
250
145
105
100
20
80
5
110
80
250
20
8
12
0
0
4
1
3
30
50
50
—
U.S.
Average0
—
—
—
192
—
—
—
181
102
417
34
13
20
—
0.6
9.4
2.6
6.8
—
211
—
22x1 O6
8x1 06
500
d Values should be increased by amount in domestic water supply.
e Geldreich, 1978.
f Most probable number/1 00 mL of water sample.
g Plaque-forming units.
carcinogenicity in in vitro cellular assays (Nellor, et al.,
1984). However, these in v/fro lexicological evaluations
cannot be relied on by themselves to provide proof of
carcinogenic activity. The only way to address the
question of whether the unknown aggregated trace
organic substances in reclaimed water would cause any
meaningful risk to populations consuming the water is
by whole animal tests on mixture concentrates and by
retrospective surveillance of the population. State-of-the-
art toxicology studies on animals provide the only
recognized method for evaluating risk prior to public
exposure (State of California, 1987).
Results of epidemiological studies of populations
receiving drinking water considered to contain significant
quantities of organic compounds have been
inconclusive, although positive correlations'were found
in several studies. Causal relationships could not be
proven on the basis of the results of the studies. The
National Academy of Sciences (1983) concluded that
the associations were small and had a wide margin of
error, which could be attributed to the methodological
difficulties inherent in most epidemiological studies
(National Academy of Sciences, 1983). NAS also
concluded that, when viewed collectively, the
epidemiological studies provided sufficient evidence for
maintaining the hypothesis that there may be a potential
health risk.
While technology regarding trace organics has advanced
substantially in the last decade, uncertainties persist
regarding the range of compounds, additive, synergistic
or antagonistic effects, and the total health significance
of trace organics in drinking water. The ability to identify
and quantify low levels of contaminants in water has
outstripped our capability to evaluate and interpret the
significance of the levels measured in assessing
potential health effects.
28
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Figure 12. Generalized Flow Sheet for Wastewater Treatment
Preliminary
Primary
Secondary
Advanced
Effluent
Effluent
stabilization ponds
aerated lagoons
High-Rate Processes
activated sludge
trickling filters
RBCs
(Secondary
Sedimentation
>
( Sludge Processing ))
V ,—^
j
ISpOE
Disposal
Source: Adapted from Pettygrove and Asano, 1985.
Nitrogen Removal
nitrification - denitrification
selective ion exchange
breakpoint chlorination
gas stripping
overland flow
Phosphorus Removal
chemical precipitation
biological
Suspended Solids Removal
chemical coagulation
filtration
\*»
Organics & Metals Removal
carbon adsorption
chemical precipitation
Dissolved Solids Removal
reverse osmosis
electrodialysis
distillation
ion exchange
2.4.2 Treatment Requirements
Raw municipal wastewater may include contributions
from domestic and industrial sources, infiltration and
inflow from the collection system, and, in the case of
combined sewer systems, urban stormwater runoff. The
quantity and quality of wastewater derived from each
source vary among communities depending upon the
number of commercial and industrial establishments in
the area and the condition of the sewer system. Table 6
presents the typical composition of untreated municipal
wastewater.
Levels of wastewater treatment are generally classified
as preliminary, primary, secondary, and advanced. A
generalized flow sheet for municipal wastewater
treatment is given in Figure 12.
2.4.2.1 Preliminary Treatment
Preliminary treatment of wastewater consists of the
physical processes of screening or comminution and grit
removal. Coarse screening is generally the first
treatment step employed and is used for the removal of
large solids and trash that may interfere with downstream
treatment operations. Comminution devices have been
29
-------
Table 7. Typical Constituent Removal Efficiencies for
Primary and Secondary Treatment
Average Percent Removal*
Constituent
BOD
COD
TSS
NH3-N
Phosphorus
Oil and grease
Arsenic
Cadmium
Chromium
Copper
Iron
Lead
Manganese
Mercury
Selenium
Silver
Zinc
Color
Foaming agents
Turbidity
TOG
Primary
Treatment
42
38
53
18
27
65
34
38
44
49
43
52
20
11
0
55
36
15
27
31
34
Activated
Sludge
89
72
81
63
45
86
83
28
55
70
65
60
58
30
13
7
75
55
—
—
~
Trickling
Filters
69
58
63
—
—
—
—
—
5
19
56
46
40
16
0
—
55
56
—
—
~
* Note: Actual percent removal will vary.
Source: Adapted from WPCF, 1989, and other sources.
Table 8. Typical Percent Removal of Microorganisms by
Conventional Wastewater Treatment*
Infectious Agent
Secondary Treatment
Primary Activated Trickling
Treatment Sludge Filter
Fecal coliform
Salmonella
Mycobactaiium fufeercu/os/s
Shigalla
Entamoeba histolytica
Helminth ova
Enteric viruses
<10
0-15
40-60
15
0-50
50-98
Limited
0-99
70-99+
5-90
80-90
Limited
Limited
75-99
85-99
85-99+
65-99
85-99
Limited
60-75
0-85
*Not including disinfection.
Source: Crook, 1990.
used with limited success to cut up solids into a smaller
uniform size to improve downstream operations. Grit
chambers are designed to remove material such as
sand, gravel, cinders, eggshells, bone chips, seeds,
coffee grounds, and large organic particles, such as food
wastes. Settling of most organic solids is prevented in
the grit chamber due to the high flow velocity of
wastewater through the chamber. Other preliminary
treatment operations can include flocculation, odor
control, chemical treatment, and pre-aeration.
2.4.2.2 Primary Treatment
Primary treatment is a physical treatment process to
remove settleable organic and inorganic solids by
sedimentation and floating materials by skimming. This
process also is effective for the removal of some organic
nitrogen, organic phosphorus and heavy metals, but
does little for the removal of colloidal and dissolved
constituents. Additional phosphorus and heavy metal
removal can be achieved through the addition of
chemical coagulants and polymers. Average constituent
removal efficiencies for primary treatment processes are
given in Table 7.
Primary treatment has little effect on the removal of most
biological species present in the wastewater. However,
some protozoa and parasite ova and cysts will settle out
during primary treatment, and some particulate-
associated microorganisms may be removed with
settleable matter. Primary treatment does not effectively
reduce the level of viruses in sewage. Typical
microorganism removal efficiencies of primary treatment
are shown in Table 8. Generally, primary treatment by
itself is not considered adequate for reuse applications.
2.4.2.3 Secondary Treatment
Secondary treatment follows primary treatment where
the latter is employed and utilizes an aerobic biological
treatment process for the removal of organic matter and,
in some cases, nitrogen and phosphorus. Aerobic
biological treatment occurs in the presence of oxygen
whereby microorganisms oxidize the organic matter in
the wastewater. Several types of aerobic biological
treatment are utilized for secondary treatment, including:
activated sludge, trickling filters, rotating biological
contactors (RBCs), and stabilization ponds. Typical
microorganism and other constituent removal
efficiencies for selected secondary treatment processes
are presented in Tables 7 and 8.
The activated sludge, trickling filter, and other attached
growth processes are considered high-rate biological
processes due to the high concentrations of
microorganisms utilized for the metabolization of organic
matter. These processes accomplish biological oxidation
30
-------
in relatively small basins and utilize sedimentation tanks
(secondary clarifiers) after the aerobic process to
separate the microorganisms and other settleable solids
from the treated wastewater.
In the activated sludge process, treatment is provided in
an aeration tank in which the wastewater and
microorganisms are in suspension and continuously
mixed through aeration. Trickling filters utilize media
such as stones, plastic shapes or wooden slats in which
the microorganisms become attached. RBCs are similar
to trickling filters in that the organisms are attached to
support media, which in this case are partially
submerged rotating discs in the wastewater stream.
These high-rate processes are capable of removing up
to 95 percent of BOD, COD, and SS originally present in
the wastewater and significant amounts of many (but not
all) heavy metals and specific toxic organic compounds.
Trickling filters are not as effective as activated sludge
processes in removing soluble organics because of less
contact between the organic matter and microorganisms.
Activated sludge treatment can reduce the soluble BOD
fraction to 1 to 2 mg/L while the trickling filter process
typically reduces the soluble BOD to 10 to 15 mg/L.
Biological treatment, including secondary sedimentation,
typically reduces the total BOD to 15 to 30 mg/L, COD to
40 to 70 mg/L, and TOC to 15 to 25 mg/L. Very little
dissolved minerals are removed during conventional
secondary treatment.
Stabilization ponds require relatively large land areas
and are most widely used rural areas and in warm
climates and/or where land is available at reasonable
cost. They are often arranged in a series of anaerobic,
facultative, and maturation ponds with an overall
hydraulic detention time of 10-50 days, depending on
the design temperature and effluent quality required
(Mara and Cairncross, 1989). Most organic matter
removal occurs in the anaerobic and facultative ponds.
Maturation ponds, which are largely aerobic, are
designed primarily to remove pathogenic
microorganisms following biological oxidation processes.
Well-designed stabilization pond systems are capable of
reducing the BOD to 15-30 mg/L, COD to 90-135 mg/L,
and SS to 15-40 mg/L (Shuval et al., 1986).
Stabilization ponds utilize algae to provide oxygen for
the system. This process is considered a low-rate
biological process. However, stabilization ponds are
capable of providing considerable nitrogen removal
under certain conditions, e.g., high temperature and pH
and long detention times. Stabilization ponds are
effective in removing microorganisms from wastewater.
Well designed and operated pond systems are capable
of achieving a 6-log reduction of bacteria, a 3-log
reduction of helminths, and a 4-log reduction of viruses
and cysts (Mara and Cairncross, 1989).
Conventional secondary treatment processes reduce the
concentration of microorganisms by predation or
adsorption to particulates that are subsequently removed
by sedimentation. Biological treatment is capable of
removing over 90 percent of the bacterial organisms and
viruses. Removal by lagoon systems can be erratic, but
stabilization pond systems having long retention times
can effectively reduce pathogen concentrations to very
low levels.
Secondary treatment may be acceptable for reuse
applications where the risk of public exposure to the
reclaimed water is low, such as in irrigation of non-food
crops as well as landscape irrigation where public access
is limited.
2.4.2.4 Disinfection
The most important process for the destruction of
microorganisms is disinfection. In the United States, the
most common disinfectant for both water and
wastewater is chlorine. Ozone and ultraviolet light are
other prominent disinfectants used at wastewater
treatment plants. Factors that should be considered
when evaluating disinfection alternatives include
disinfection effectiveness and reliability, capital and
operating and maintenance costs, practicality (e.g., ease
of transport and storage or onsite generation, ease of
application and control, flexibility, complexity, and
safety), and potential adverse effects such as toxicfty to
aquatic life or formation of toxic or carcinogenic
substances. The predominant advantages and
disadvantages of disinfection alternatives are well know
and have been summarized by EPA in its design manual
on municipal wastewater disinfection (EPA, 1986). Table
9 presents information to help assess chlorination,
chlorination followed by dechlorination, ozonation, and
ultraviolet radiation with respect to non-monetary factors.
Some of these factors are further discussed below.
The efficiency of disinfection with chlorine is dependent
upon the water temperature, pH, degree of mixing, time
of contact, presence of interfering substances,
concentration and form of the chlorinating species, and
the nature and concentration of the organisms to be
destroyed. In general, bacteria are less resistant to
chlorine than are viruses, which in turn are less resistant
than parasite ova and cysts.
The chlorine dosage required to disinfect a wastewater
to any desired level is greatly influenced by the
constituents present in the wastewater. Some of the
31
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Table 9. Applicability of Alternative Disinfection Techniques
Consideration
Size of plant
Applicable level of
treatment prior to
disinfection
Equipment
reliability
Process control
Relative complexity
of technology
Safety concerns
in transportation
Safety concerns
onsite
Bactericidal
Viruclda!
Fish toxicity
Hazardous
byproducts
Persistent
residual
Contact time
Contributes
dissolved oxygen
Reacts with
ammonia
Color removal
Increased
dissolved solids
pH dependent
O&M sensitive
Corrosive
Source: EPA. 1986.
^^••^•H
Chlorination
all sizes
all levels
good
well
developed
simple to
moderate
yes
substantial
good
poor
toxic
yes
long
long
no
yes
moderate
yes
yes
minimal
yes
mi^^mm^m
Chlorination/
Dechlorination
all sizes
all levels
fair to
good
fairly well
developed
moderate
yes
substantial
good
poor
non-toxic
yes
none
long
no
yes
moderate
yes
yes
minimal
yes
32
Ozone
medium to
large
secondary
fair to
good
developing
complex
no
moderate
good
good
none
expected
none
expected
none
moderate
yes
yes (high
pH only)
yes
no
slight
(high pH)
high
yes
Ultraviolet
small to
medium
secondary
fair to
good
developing
simple to
moderate
no
minimal
good
good
non-toxic
no
none
short
no
no
no
no
no
moderate
no
-------
interfering substances are organic constituents, which
consume the disinfectant; particulate matter, which
protects microorganisms from the action of the
disinfectant; and ammonia, which reacts with chlorine to
form chloramines, a much less effective disinfectant
species than free chlorine. In practice, the amount of
chlorine added is determined empirically, based on
desired residual and effluent quality. Chlorine, which in
low concentrations is toxic to many aquatic organisms,
is easily controlled in reclaimed water by dechlorination,
typically with sulfur dioxide.
Ozone (O3), is a powerful disinfecting agent and a
powerful chemical oxidant in both inorganic and organic
reactions. Due to the instability of ozone, it must be
generated onsite from air or oxygen carrier gas. Ozone
destroys bacteria and viruses by means of rapid
oxidation of the protein mass, and disinfection is
achieved in a matter of minutes. Some disadvantages
are that the use of ozone is relatively expensive and
energy intensive, ozone systems are more complex to
operate and maintain than chlorine systems, and ozone
does not maintain a residual in water. Ozone is a highly
effective disinfectant for advanced wastewater treatment
plant effluent, removes color, and contributes dissolved
oxygen.
Ultraviolet (UV) is a physical disinfecting agent.
Radiation at a wave length of 254 mm penetrates the
cell wall and is absorbed by the cellular nucleic acids.
This can prevent replication and cause death of the cell.
UV radiation is receiving increasing attention as a means
of disinfecting reclaimed water because it may be less
expensive than disinfection with chlorine, it is safer to
use than chlorine gas, and—in contrast to chlorine—it
does not result in the formation of chlorinated
hydrocarbons. The effectiveness of UV radiation as a
disinfectant (where fecal coliform limits are on the order
of 200/100 ml_), has been well established as evidenced
by its use at more than 120 small- to medium-sized
wastewater treatment plants in the United States (EPA,
1986). Little information is available on the ability of UV
disinfection to achieve high levels of disinfection;
however, in one pilot plant study, a UV dose of 60 mw-s/
cm2 or greater consistently disinfected unfiltered
secondary effluent to a total coliform level of 23/100 ml_
or less, and a UV dose of at least 97 mw-s/cm2
consistently disinfected filtered secondary effluent to a
total coliform level of 2.2/100 ml_ or less (Snider et al.,
1991). The study also indicated that filtration, which was
effective in removing significant amounts of SS and
providing an effluent with a turbidity of less than 2 NTU,
enhanced the performance of the UV disinfection.
Other disinfectants, such as gamma radiation, bromine,
iodine, and hydrogen peroxide, have been considered
for the disinfection of wastewater but are not generally
used because of economical, technical, operational, or
disinfection efficiency considerations.
2.4.2.5 Advanced Wastewater Treatment
Advanced wastewater treatment processes are
generally utilized when a high quality reclaimed water is
necessary, such as for the irrigation of urban landscaping
and food crops eaten raw, contact recreation, and many
industrial applications. Individual unit processes capable
of removing the above mentioned constituents are
shown in Figure 12.
The principal advanced wastewater treatment processes
for water reclamation are:
Q Filtration - Filtration is a common treatment
process used to remove particulate matter prior
to disinfection. Filtration involves the passing of
wastewater through a bed of granular media,
which retain the solids. Typical media include
sand, anthracite, and garnet. Removal
efficiencies can be improved through the
addition of certain polymers and coagulants.
Table 10 presents average constituent removal
efficiencies for filtration.
Q Nitrification - Nitrification is the term generally
given to any wastewater treatment process that
biologically converts ammonia nitrogen
sequentially to nitrite nitrogen and nitrate
nitrogen. Nitrification does not remove
significant amounts of nitrogen from the effluent;
it only converts it to another chemical form.
Nitrification can be done in many suspended
and attached growth treatment processes when
they are designed to foster the growth of
nitrifying bacteria. In the traditional activated
sludge process it is accomplished by designing
the process to operate at a solids retention time
that is long enough to prevent the slow-growing
nitrifying bacteria from being wasted out of the
system. Nitrification will also occur in trickling
filters that operate at low BOD/TKN ratios either
in combination with BOD removal, or as a
separate advanced process following any type
of secondary treatment. A well designed and
operated nitrification process will produce an
effluent containing 1.0 mg/L or less ammonia
nitrogen. Ammonia nitrogen can also be
removed from effluent by several chemical or
physical treatment methods such as air
stripping, ion exchange, RO and breakpoint
33
-------
Table 10. Typical Filtration Process Removal
Constituent
Average Performance (%)*
Following Biological Following Physical-
Secondary Treatment3 Chemical Treatment"
BOD
COD
TSS
NHo-N
N03N
Phosphorus
Alkalinity
Arsenic
Cadmium
Chromium
Iron
Lead
Manganese
Mercury
Selenium
Color
Turbidity
TOC
39
34
73
33
56
57
83
67
32
53
56
16
SO
33
90
31
71
33
36
22
42
—
—
—
—
0
38
9
—
26
—
0
0
—
31
26
Note: Actual percent removal will vary.
Values given in terms of percent removal from secondary effluent.
Values given in terms of percent removal from chemically clarified
secondary effluent.
Source: Adapted from WPCF, 1989.
chlorination. However, these methods have
generally proven to be uneconomical or too
difficult to operate for ammonia removal in most
municipal applications. Ammonia removal may
be required for discharges to surface waters for
any of three basic reasons. These are the
toxicity of ammonia to aquatic organisms, the
relatively high biological oxygen demand of
ammonia, and its value as an aquatic plant
nutrient. It is also the necessary first step for
biological denitrification.
Q Denitrification - Denitrification is any wastewater
treatment method that completely removes total
nitrogen. As with ammonia removal,
denitrification is usually best done biologically
for most municipal applications, in which case it
must be preceded by nitrification. In biological
denitrification, nitrate nitrogen is used by a
variety of heterotrophic bacteria as the terminal
electron acceptor in the absence of dissolved
oxygen. In the process, the nitrate nitrogen is
converted to nitrogen gas which escapes to the
atmosphere. A carbonaceous food source is
also required by the bacteria in these processes.
Denitrification can be done using many
alternative treatment processes. These include
variations of many common suspended growth
and some attached growth treatment processes
provided they are designed to create the proper
microbial environment. The denitrification
reactor must contain nitrate nitrogen, a carbon
source and facultative heterotrophic bacteria in
the absence of dissolved oxygen. Biological
denitrification processes can be designed to
achieve effluent nitrogen concentrations
between 2.0 mg/L and 12 mg/L nitrate nitrogen.
The effluent total nitrogen will be somewhat
higher depending on the concentration of VSS
and soluble organic nitrogen present.
Denitrification may be necessary where
reclaimed water reaches potable water supply
aquifers. It may also be required prior to using
effluent for agricultural irrigation of certain crops
during specific times in their growing cycle (such
as sugar cane and corn).
Q Phosphorus Removal - Phosphorus can be
removed from wastewater by either chemical or
biological methods, or a combination of the two.
The choice of methods will depend on site
specific conditions, including the amount of
phosphorus to be removed and the desired
effluent phosphorus concentration. Chemical
phosphorus removal is done by precipitating the
phosphorus from solution by the addition of iron,
aluminum or calcium salts. Biological
phosphorus removal relies on the culturing of
bacteria that will store excess amounts of
phosphorus when exposed to anaerobic
conditions followed by aerobic conditions in the
treatment process. In both cases, the
phosphorus is removed from the treatment
process with the waste sludge. Chemical
phosphorus removal can attain effluent
orthophosphorus concentrations less than 0.1
mg/L, while biological phosphorus removal will
usually produce an effluent phosphorus
concentration between 1.0 and 2.0 mg/L.
Q Coagulation-Sedimentation - Chemical
coagulation with lime, alum, or ferric chloride
followed by sedimentation removes SS, heavy
metals, trace substances, phosphorus, and
turbidity. Table 11 presents average constituent
removal efficiencies for the coagulation-
sedimentation process.
34
-------
Q Carbon Adsorption - One of the most effective
advanced wastewater treatment processes for
removing biodegradable and refractory organic
constituents is granular activated carbon.
Carbon adsorption can reduce the levels of
synthetic organic chemicals in secondary
effluent by 75 to 85 percent. The basic
mechanism of removal is by adsorption of the
organic compounds onto the carbon. Carbon
adsorption preceded by conventional secondary
treatment and filtration can produce an effluent
with a BOD of 0.1 to 5.0 mg/L, a COD of 3 to 25
mg/L, and a TOC of 1 to 6 mg/L.
Carbon adsorption treatment will remove
several metal ions, particularly cadmium,
hexavalent chromium, silver, and selenium.
Activated carbon has been used to remove un-
ionized species, such as arsenic and antimony,
from an acidic stream, and it also decreases
mercury to low levels, particularly at low pH
values.
Q Other Processes - Other advanced wastewater
treatment processes of constituent removal
include ammonia stripping, breakpoint
chlorination for ammonia removal, selective ion-
exchange for nitrogen removal, and reverse
osmosis for TDS reduction and removal of
inorganic and organic constituents.
Advanced wastewater treatment processes such as
chemical coagulation, sand or mixed media filtration, and
ion exchange are not designed to remove many organic
substances, particularly soluble organics. When these
processes follow conventional secondary treatment, they
typically remove 40 to 85 percent of the total BOD, COD,
and TOC.
Advanced treatment by chemical coagulation,
sedimentation, and filtration unit processes has been
demonstrated to remove more than 2 logs (99 percent)
of seeded poliovirus (Sanitation Districts of Los Angeles
County, 1977). This treatment chain reduces the turbidity
of the wastewater to very low levels, thereby enhancing
the efficiency of the subsequent disinfection process.
Chemical coagulation and sedimentation alone can
remove up to 2 logs (99 percent) of the viruses, although
the presence of organic matter can significantly decrease
the amount of viruses removed. Direct filtration, that is,
chemical coagulation and filtration, has also been shown
to remove up to 2 logs (99 percent) of seeded poliovirus
(Sanitation Districts of Los Angeles County, 1977). In
one study, sand and dual media filtration of secondary
effluent, without coagulant addition prior to filtration, did
Table 11. Coagulation-Sedimentation Typical Constituent
Removals
Averaae Performance (%¥
Constituent
BOD
COD
TSS
NHa-N
Phosphorus
Alkalinity
Oil & grease
Arsenic
Barium
Cadmium
Chromium
Copper
Fluoride
Iron
Lead
Manganese
Mercury
Selenium
Silver
Zinc
Color
Foaming agents
Turbidity
TOC
Alum
Addition
65
69
70
—
78
16
89
83
—
72
86
86
44
83
90
40
24
0
89
80
72
55
86
51
Lime
Addition
65
52
70
22
91
—
40
6
61
30
56
55
50
87
44
93
0
0
49
78
46
39
70
73
Ferric
Addition
62
61
67
14
71
36
91
49
—
68
87
91
—
43
93
—
18
0
89
72
73
42
88
66
'Values given in terms of percent removal from secondary effluent.
Note: Actual percent removal will vary.
Source: Adapted from WPCF, 1989.
not significantly reduce enteric virus levels (Noss et al.,
1989). The primary purpose of the filtration step is not to
remove viruses but to remove floe and other suspended
matter, which coincidentally may contain adsorbed or
enmeshed viruses, thereby making the disinfection
process more effective.
Chemical coagulation and filtration followed by chlorine
disinfection to very low total coliform levels can remove
or inactivate 5 logs (99.999 percent) of seeded poliovirus
through these processes alone and subsequent to
conventional biological secondary treatment can
produce effluent essentially free of measurable levels of
pathogens (Sanitation Districts of Los Angeles County,
1977; Sheikh, et al., 1990). This abbreviated treatment
chain, in conjunction with specific design and operational
controls has been shown to produce reclaimed water
free of measurable levels of viruses. Based in part on
the two studies cited above, the State of California
developed a policy statement that includes the following
design and operational controls for direct filtration
facilities producing reclaimed water for uses where an
35
-------
essentially virus-free water is deemed necessary (State
of California, 1988):
Q Coagulant addition unless secondary effluent
turbidity is less than 5 NTU,
Q Maximum filtration rate of 12 m/h (5 gpm/sq ft),
Q Average filter effluent turbidity of 2 NTU or less,
Q High-energy rapid mix of chlorine,
Q Theoretical chlorine contact time of at least 2
hours with an actual modal contact time of at
least 90 minutes,
Q Minimum chlorine residual of 5 mg/L after the
required contact time,
Q Chlorine contact chamber length to width or
depth ratio of at least 40:1,
Q 7-day median number of total coliform
organisms in the effluent of 2.2/100 mL or less,
not to exceed 23/100 mL in any sample.
Virus inactivation under alkaline pH conditions can be
accomplished using lime as a coagulant, but pH values
of 11 to 12 are required before significant inactivation is
obtained. The mechanism of inactivation under alkaline
conditions is caused by denaturation of the protein coat
and by disruption of the virus.
The removal of biological contaminants by advanced
treatment processes designed to remove either inorganic
or organic constituents is incidental and, generally, not
too efficient. An exception is reverse osmosis, which can
be very effective in removing most viruses and virtually
all larger microorganisms. Activated carbon adsorption
has been shown to adsorb some viruses from wastewater,
but the adsorbed viruses can be displaced by organic
compounds and enter the effluent.
2.4.3 Reliability tn Treatment
A high standard of reliability is required at water
reclamation plants. Because there is potential for harm
in the event that improperly treated reclaimed water is
delivered to the use area, water reuse requires strict
conformance to all applicable water quality parameters.
The need for reclamation facilities to reliably and
consistently produce and distribute reclaimed water of
adequate quality and quantity is essential and dictates
that careful attention be given to reliability features during
the design, construction, and operation of the facilities.
A number of fallible elements combine to make up an
operating water reclamation system. These include the
power supply, individual treatment units, mechanical
equipment, the maintenance program, and the operating
personnel. There is an array of design features and non-
design provisions which can be employed to improve
the reliability of the separate elements and the system
as a whole. Backup systems are important in maintaining
reliability in the event of failure of vital components.
Particularly critical units include the disinfection system,
the power supply, and the various treatment unit
processes.
For reclaimed water production, EPA Class I reliability is
recommended. Class I reliability requires redundant
facilities to prevent treatment upsets during power and
equipment failures, flooding, peak loads, and
maintenance shutdowns. Reliability for water reuse
should also consider:
Q Operator certification to ensure that qualified
personnel operate the water reclamation and
reclaimed water distribution systems.
Q Instrumentation and control systems for on-line
monitoring of treatment process performance
and alarms for process malfunctions.
Q A quality assurance program to ensure accurate
sampling and laboratory analysis protocol.
Q Adequate emergency storage to retain reclaimed
water of unacceptable quality for re-treatment or
alternative disposal.
Q Supplemental storage to ensure that the supply
can match the user's demands.
Q An industrial pretreatment program and
enforcement of sewer use ordinances to prevent
illicit dumping of hazardous materials into the
collection system.
2.4.3.1 EPA Guidelines for Reliability
EPA, under its predecessor agency the Federal Water
Quality Administration, recognized the importance of
treatment reliability more than 20 years ago, and issued
guidelines entitled "Federal Guidelines: Design,
Operation and Maintenance of Waste Water Treatment
Facilities" (Federal Water Quality Administration, 1970).
These guidelines provided an identification and
description of various reliability provisions and included
the following concepts or principles regarding treatment
plant reliability:
36
-------
a. All water pollution control facilities should be
planned and designed to provide for maximum
reliability at all times.
b. The facility should be capable of operating
satisfactorily during power failures, flooding,
peak loads, equipment failure, and maintenance
shutdowns. A minimum of primary treatment
may be required where necessitated by the uses
of the receiving waters.
c. Such reliability can be obtained through the use
of various design techniques which will result in
a facility which is virtually "failsafe" (Federal
Water Quality Administration, 1970).
The following are the more specific subjects for
consideration in the preparation of final construction
plans and specifications which will aid in accomplishing
the above principles:
The following design features were defined as necessary
for ensuring reliability:
Q Duplicate sources of electric power.
Q Standby power for essential plant elements.
Q Multiple units and equipment.
Q Holding tanks or basins to provide for
emergency storage of overflow and adequate
pump-back facilities.
Q Flexibility of piping and pumping facilities to
permit rerouting of flows under emergency
conditions.
Q Provision for emergency storage or disposal of
sludge (Federal Water Quality Administration,
1970).
The non-design reliability features in the federal
guidelines include provisions for qualified personnel, an
effective monitoring program, and an effective
maintenance and process control program. In addition
to plans and specifications, the guidelines specify
submission of a preliminary project planning and
engineering report which will clearly indicate compliance
with the guideline principles.
In summary, the federal guidelines identify eight design
principles and four other significant factors which appear
appropriate to consider for reuse operations:
Design factors
Duplicate power sources
Standby power
Multiple units and equipment
Emergency storage
Piping and pumping flexibility
Dual chlorination
Automatic residual control
Automatic alarms
Other factors
Engineering report
Qualified personnel
Effective monitoring program
Effective maintenance and process control program
EPA subsequently published "Design Requirements for
Mechanical, Electric, and Fluid Systems and Component
Reliability" in 1974 (EPA, 1974). While the purpose of
that publication was to provide reliability design criteria
for wastewater treatment facilities seeking federal
financial assistance under PL 92-500, the criteria are
useful for the design and operation of all wastewater
treatment plants. These requirements established
minimum standards of reliability for wastewater
treatment works. Other important reliability design
features include on-line monitoring, e.g., turbidimeters
and chlorine residual analyzers, and chemical feed
facilities.
Table 12 presents a summary of the equipment
requirements under the EPA guidelines for Class I
reliability treatment facilities.
As given in Table 12, the integrity of the treatment system
is enhanced by providing redundant or oversized unit
processes. This reliability level was originally specified
for treatment plants discharging into water bodies that
could be permanently or unacceptably damaged by
improperly treated effluent. Locations where Class I
facilities might be necessary are given as facilities
discharging near drinking water reservoirs, into shellfish
waters, or in proximity to areas used for water contact
sports (EPA, 1974).
Given the original intent of a Class I reliability
requirements, similar requirements for water reclamation
facilities are often desirable. For example, chemical
addition facilities are a desirable reliability design feature.
These facilities can provide greater operational flexibility
by assisting during treatment plant upsets. In addition to
unit processes, storage facilities may also be required to
provide assurance that the product will be available in
adequate supply to meet demand.
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Table 12. Summary of Class I Reliability Requirements
Unit
Class I
Requirement
Mechanically-Cleaned
Bar Screen
Pumps
Comminution Facilities
Primary Sedimentation Basins
Filters
Aeration Basins
Mechanical Aerator
Chemical Flash Mixer
Final Sedimentation Basins
Flocculation Basins
Disinfectant Contact Basins
A backup bar screen shall be provided (may be manually cleaned).
A backup pump shall be provided for each set of pumps which performs the same function. Design flow
will be maintained with any one pump out of service.
If comminution is provided, an overflow bypass with bar screen shall be provided.
There shall be sufficient capacity such that a design flow capacity of 50 percent of the total
capacity will be maintained with the largest unit out of service.
There shall be a sufficient number of units of a size such that a design capacity of at least 75 percent of
the total flow will be maintained with one unit out of service.
At least two basins of equal volume will be provided.
At least two mechanical aerators shall be provided. Design oxygen transfer will be maintained with one
unit out of service.
At least two basins or a backup means of mixing chemicals separate from the basins shall be provided.
There shall be a sufficient number of units of a size such that 75 percent of the design capacity will be
maintained with the largest unit out of service.
At least two basins shall be provided.
There shall be sufficient number of units of a size such that the capacity of 50 percent of the total design
flow may be treated with the largest unit out of service.
Source: Adapted from U.S. Environmental Protection Agency, 1974.
2.4.3.2 Design Elements of Reliability
a. Power Supply
A standby power source should be provided at all water
reclamation plants, except those few that operate entirely
by gravity and have no critical processes relying on
electric power (restricted to primary treatment and pond
systems).
The standby power source should be of sufficient
capacity to provide necessary service during failure of
the normal power supply. Standby sources typically
include gasoline or diesel operated generators or
connections to another completely separate power
system. Separate transformers should be provided for
each power source. Many reclamation plants provide
standby power with fuel-driven generators that require
manual starting. Added reliability is attained by installing
battery-operated switchover mechanisms together with
an automatic starter. Standard operating procedure
should require testing all of the equipment at least once
a week.
It may be necessary for the primary power source to
sustain only the critical loads in the standby or
emergency mode of operation. These include pumps,
important unit processes, instrumentation and controls,
and critical lighting and ventilation. A single source of
electrical power should normally be sufficient to provide
for the needs of non-critical operations.
Power distributed to main control centers or control
panels within the plant for the critical loads should be
supplied from motor control centers connected to in-
plant unit substations. Substations and feeders to motor
control centers should be redundant. Critical in-plant
power loads should be divided within the motor control
center by tie breakers. The motor control center should
be supplied with power at all times to treat the reclaimed
water. Instrumentation and control panels associated
with the operation of process critical loads should be
provided with similar redundancy.
It may be acceptable to connect non-critical process
loads to only one power source. However, non-critical
loads within a unit operation should be divided as equally
38
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as possible between motor control centers so that a
single failure will not result in complete unit operation
loss.
b. Multiple Units and Equipment
When process units are taken out of service for
maintenance, repair, or unanticipated breakdown,
multiple units or standby unit processes should be
available to continue treatment.
Multiple units means two or more process units such as
tanks, ponds, compartments, blowers, or chemical
feeders which are needed for parallel operation. The
multiple units are a part of the normal treatment system
and the total should be of sufficient capacity to enable
effective operation with any one unit out of service. For
example, with several aeration basins operated in
parallel, it may be quite possible to continue to provide
effective biological treatment while one basin is shut
down for maintenance. A duplicate of the largest unit is
usually provided for multi-unit pumping or chemical feed
equipment.
A standby unit process means a complete unit process,
such as a primary treatment system, a filtration system,
or a disinfection system, which is maintained in operable
condition and is capable of successfully replacing the
usually operated system.
2.4.3.3 Additional Requirements for Reuse
Applications
Different degrees of hazard are posed by process
failures. From a public health standpoint, it is logical that
a greater assurance of reliability should be required for a
system producing reclaimed water for uses where direct
or indirect human contact with the water is likely than for
one producing water for uses where the possibility of
contact is remote. Similarly, where specific constituents
in reclaimed water may affect the acceptability of the
waterforany use, e.g., industrial process water, reliability
directed at those constituents is important.
A unit process may be deficient in different degrees and
for many reasons, including operational and mechanical
deficiencies over- and under-loading, toxic substances,
and breakdown of individual components. There are
usually several alternatives available to meet reliability
provisions. For example, California's Wastewater
Reclamation Criteria (State of California, 1978) require
that a biological treatment unit process be provided with
any one of the following reliability factors:
Q Alarm and multiple biological treatment units
capable of producing oxidized wastewater with
one unit not in operation;
Q Alarm, short-term retention or disposal
provisions, and standby replacement
equipment;
Q Alarm and long-term storage or disposal
provisions; or
Q Automatically actuated long-term storage or
disposal provisions.
Standby units or multiple units should be encouraged for
the major treatment elements at all reclamation facilities.
For small installations, the cost may be prohibitive and
provision for emergency storage or disposal is a suitable
alternative.
a. Piping and Pumping Flexibility
Process piping, equipment arrangement, and unit
structures should allow for efficiency and ease of
operation and maintenance and provide maximum
flexibility of operation. Flexibility should permit the
necessary degree of treatment to be obtained under
varying conditions. All aspects of plant design should
allow for routine maintenance of treatment units without
deterioration of the plant effluent.
No pipes or pumps should be installed that would
circumvent critical treatment processes and possibly
allow inadequately treated effluent to enter the reclaimed
water distribution system. The facility should be capable
of operating during power failures, peak loads,
equipment failures, treatment plant upsets, and
maintenance shutdowns. In some cases, it may be
necessary to divert the wastewater to emergency
storage facilities or discharge the wastewater to
approved, non-reuse areas. During power failures or
equipment failure, standby portable diesel driven pumps
can also be utilized.
b. Emergency Storage or Disposal
The term "emergency storage or disposal" means a
provision for the containment or alternative treatment
and disposal of reclaimed whenever the quality is not
suitable for use. It refers to something other than the
normal operational or seasonal storage which may be
provided for reclaimed water until it is needed for use.
Provisions for emergency storage or disposal may be
considered to be a basic reliability provision for
reclamation facilities. Where such provisions exist, they
may substitute for multiple or standby units and other
specific features.
Provisions for emergency storage or disposal may
include:
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Q Holding ponds or tanks.
Q Approved alternative disposal provisions such
as percolation areas, evaporation-percolation
ponds, or spray disposal areas.
Q Pond systems having an approved discharge to
receiving waters or discharge to a reclaimed
water use area for which the lower quality water
is acceptable.
Q Provisions to return the wastewater to a sewer
for subsequent treatment and disposal at the
reclamation or other facility.
Q Any other facility reserved for the purpose of
emergency storage or disposal of untreated or
partially treated wastewater.
Automatically actuated emergency or disposal provisions
should include all of the necessary sensors, instruments,
valves, and other devices to enable fully automatic
diversion of the wastewater in the event of failure of a
treatment process and a manual reset to prevent
automatic restart until the failure is corrected. For either
manual or automatic diversion, all of the equipment other
than the pump back equipment should either be
independent of the normal power source or provided with
a standby power source. Irvine Ranch Water District in
California automatically diverts its effluent to a pond when
it exceeds a turbidity of 2 NTU and subsequently
recirculates it to the reclamation plant influent. The City of
St. Petersburg diverts its effluent to deep wells for
disposal when the chlorine residual is less than 4 mg/L,
turbidity exceeds 2.5 NTU, TSS exceeds 5 mg/L or
chlorides exceed 600 mg/L.
Where emergency storage is to be utilized as a reliability
feature, storage capacity is an important consideration.
Short-term retention capacity in holding facilities for 24
hours is often provided in systems depending on a single
power source. This short-term provision is also suitable
for situations where reserve parts and replacement are
immediately available and corrective actions would take
no longer. Such is not always the case, and where it is
not, the emergency storage capacity should be 20 days
or longer for effective plant reliability. This would allow
sufficient time to carry out almost any necessary
corrective measure. Where corrective measures cannot
be accomplished by plant personnel, provisions for a
pre-arranged repair service may be made. In any case,
as the emergency storage capacity is increased, so is
the reliability.
In Florida, a separate, off-line system for storage of reject
water is required, unless another permitted reuse system
or effluent disposal system is capable of discharging the
reject water (Florida Department of Environmental
Regulation, 1990). The minimum allowable reject water
storage capacity is a volume equal to one day's flow at
the average daily design flow of the treatment plant or
the average daily permitted flow of the reuse system,
whichever is less. In addition, provisions are necessary
to recirculate the reject water for further treatment.
c. Disinfection
An undisinfected effluent may be suitable for certain
limited uses of reclaimed water or where stabilization
pond systems effectively reduce pathogen
concentrations in the effluent to a level deemed
acceptable for many nonpotable uses. For uses where
direct or indirect human contact with reclaimed water is
likely provisions for adequate and reliable disinfection
are the most essential features of the reclamation
process.
Chlorination, the most widely used disinfection process,
can be interrupted by various causes, e.g., exhaustion
of the chlorine supply, chlorinator failure, water supply
failure, and most commonly, power failure. A variety of
features can be implemented to .provide chlorine
disinfection systems with increasing degrees of
reliability. These features include:
Q Standby chlorine cylinders,
Q Chlorine cylinder scales,
Q Manifold systems,
Q Alarm systems,
Q Automatic cylinder changeover,
Q Standby chlorinators,
Q Multiple-point Chlorination,
Q Automatic control of chlorine dosage, and
Q Automatic measuring and recording of chlorine
residual.
Spare cylinders should be available if continuous
Chlorination is to be provided. Scales are necessary to
identify the amount of chlorine remaining in a cylinder so
that the need for changeover to a full cylinder can be
anticipated. A manifold system allows a rapid
changeover to a full cylinder can be anticipated. It also
40
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provides a greater chlorine reserve and greater intervals
between cylinder changes. Automatic cylinder
changeover devices on the manifold system provide for
uninterrupted chlorination without operator attention,
particularly where there is not full-time plant supervision.
An effective alarm system can minimize interruptions in
the disinfection process. At a facility which received full-
time operator attention, a simple visual-audio alarm
which sounds at the plant and warns of malfunction is
adequate. Where there is only part-time attendance at
the plant, it is necessary to have an alarm system which
will sound a warning at a continuously staffed location,
such as a police or fire station.
d. Alarms
Alarm systems should be installed at all conventional
water reclamation plants, particularly at plants that do
not receive full-time attention from trained operators. If a
critical process were to fail, the condition may go
unnoticed for an extended time period, and an
unsatisfactory reclaimed water would be produced for
use. An alarm system will effectively warn of an
interruption in treatment.
Minimum instrumentation should consist of alarms at
critical treatment units to alert an operator of a
malfunction. This concept requires that the plant either
be attended constantly or that an operator be on call
whenever the reclamation plant is in operation. In the
latter case, a remote sounding device would be needed.
If conditions are such that rapid attention to failures
cannot be assured, automatically actuated emergency
control mechanisms should be installed and maintained.
Requirements for warning systems should specify the
measurement to be used as the control in determining a
unit failure, e.g., dissolved oxygen in an aeration
chamber, or the requirements could be general and
merely specify the units or processes which should be
included in a warning system. The latter approach
appears more desirable because it allows more flexibility
in the design. Alarms could be actuated in various ways,
such as failure of power, high water level, failure of
pumps or blowers, loss of dissolved oxygen or chlorine
residual, loss of coagulant feed, high head loss on filters,
high effluent turbidity, or loss of chlorine supply.
It is axiomatic that along with the alarm system there
must be means available to take corrective action for
each situation which has caused the alarm to be
activated. As noted above, provisions must be available
to otherwise treat, store, or dispose of the wastewater
until the corrections have been made. Alternative or
supplemental features for different situations might
include an automatic switch-over mechanism to
emergency power and a self-starting generator, or an
automatic diversion mechanism which discharges
wastewater from the various treatment units to
emergency storage or disposal.
e. Instrumentation and Control
Major considerations in developing an instrumentation/
control system for a reclamation facility include:
Q Ability to analyze appropriate parameters,
Q Monitoring and control of treatment of process
performance,
Q Monitoring and control of reclaimed water
distribution,
Q Methods of providing reliability, and
Q Operator interface and system maintenance.
The potential uses of the reclaimed water determine the
degree of instrument sophistication required in a water
reuse system. For example, health risks may be
insignificant for reclaimed water used for non-food crop
irrigation. On the other hand, if wastewater is being
treated for indirect potable reuse via groundwater
recharge, risks are potentially high. Consequently, the
instruments must be highly sensitive, so that even minor
discrepancies in water quality are detected immediately.
Selection of monitoring instrumentation is governed by
the following factors: sensitivity, accuracy, effects of
interferences, frequency of analysis and detection,
laboratory or field application, analysis time, sampling
limitations, laboratory requirements, acceptability of
methods, physical location, serviceability, and reliability
(WPCF, 1989). Each water reclamation plant is unique
and has its own requirements for an integrated
monitoring and control instrumentation system. The
process of selecting monitoring instrumentation should
address aspects as frequency of reporting, parameters
to be measured, sample point locations, sensing
techniques, future requirements, availability of trained
staff, frequency of maintenance, availability of spare
parts, and instrument reliability (WPCF, 1989). Such
systems should be designed to detect operational
problems during both routine and emergency operations.
If an operating problem arises, activation of a signal or
alarm permits personnel to correct the problem before
an undesirable situation is created.
System control methods should provide for varying
degrees of manual and automatic operation. Functions
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of control include the maintenance of operating
parameters within preset limits, sequencing of physical
operations in response to operational commands and
modes, and automatic adjustment of parameters to
compensate for variations in quality or operating
efficiency.
System control may be manual, automated, or a
combination of manual and automated systems. For
manual control, the operations staff members are
required to physically carry out all work tasks such as
closing and opening valves and starting and stopping
pumps. For automated control no operator input is
required except for the initial input of operating
parameters into the control system. In an automated
control system, the system automatically performs
operations such as the closing and opening of valves
and the starting and stopping of pumps. These
automated operations can be accomplished in a
predefined sequence and time frame and can also be
initiated by a measured parameter.
Automatic controls can vary from simple float switches
that start and stop pumps to highly sophisticated
computer systems that gather data from numerous
sources, compare the data to predefined parameters,
and initiate actions in order to maintain system
performance within required criteria. For example, in the
backwashing of a filter, instrumentation that monitors
head loss across a filter signals the automated control
system that a predefined head loss value has been
exceeded. The control system, in turn, initiates the
backwashing sequence through the opening of valves
and starting of pumps.
2.4.3.4 Operator Training and Competence
Regardless of the automation built into a plant,
mechanical equipment is subject to breakdown, and
qualified, well-trained operators are essential to insure
that the reclaimed water produced will be acceptable for
the intended uses. The facilities operation should be
based on detailed process control with recording and
monitoring facilities, a strict preventive maintenance
schedule, and standard operating procedure
contingency plans to assure the reliability of the product
water quality.
The plant operator is held by many to be the most critical
reliability factor in the wastewater treatment system. All
available mechanical reliability devices and the best
possible plant design are to no avail if the operator is not
capable and conscientious. There are three particular
considerations relative to operating personnel which
influence reliability of treatment: operator attendance,
operator competence, and operator training provisions.
Most regulatory agencies require operator certification
as a reasonable means of assuring competent operation.
Operator competence is enhanced by frequent training
via continuing education courses or other means.
2.4.3.5 Quality Assurance in Monitoring
Quality assurance in monitoring of a reclamation
program includes: (1) selecting the appropriate
parameters to monitor, and (2) handling the necessary
sampling and analysis in an acceptable manner.
Sampling techniques, frequency, and location are critical
elements of monitoring and quality assurance. Standard
procedures for sample analysis may be found in the
following references:
Q Standard Methods for the Examination of Water
and Wastewater (American Public Health
Association, 1989).
Q Handbook for Analytical Quality Control in Water
and Wastewater Laboratories, (EPA, 1979a).
Q Methods for Chemical Analysis of Water and
Wastes (EPA, 1979b).
Q Handbook for Sampling and Sample
Preservation of Water and Wastewater (EPA,
1982).
Typically, the quality assurance (QA) plan associated
with sampling and analysis is a defined protocol that
sets forth data quality objectives and the means for
developing quality control data that serve to quantify
precision, bias, and other reliability factors in a
monitoring program. Strict adherence to written
procedures ensures that the results are comparable, and
that the level of uncertainty is verifiable.
Quality assurance plans and quality control procedures
are well documented in the referenced texts. QA/QC
measures should be dictated by the severity of the
consequences of acting on the "wrong answer" or on an
"uncertain" answer. QA/QC procedures are often
dictated by the regulatory agencies, and do constitute
necessary operation overhead. For reuse projects, this
overhead may be greater than for wastewater treatment
and disposal.
Sampling parameters required for reclamation extend
beyond those common to wastewater treatment. For
example, turbidity measurements are sometimes
required for reclamation, but not for treatment and
disposal. Monitoring for chlorides may be necessary for
reuse in coastal communities.
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Keeping adequate records of operation is an essential
part of the overall monitoring program. It is reasonable
and compatible with usual practice and requirements to
require routine reporting of plant operation and
immediate notification of emergency conditions.
2.5 Seasonal Storage Requirements
Managing and allocating reclaimed water supplies may
be significantly different from the management of
traditional sources of water. For example, a water utility
currently drawing from groundwater or surface
impoundments uses the resource as source and storage
facility. If all of the yield of the source is not required, the
water is simply left for use at a later date. In the case of
reuse, reclaimed water is continuously generated and
what cannot be used immediately must be stored or
disposed of in some manner.
Depending on the volume and pattern of the projected
reuse demands, seasonal storage requirements may
become a significant design consideration and have a
substantial impact on the capital cost of the system.
Seasonal storage systems will also impact operational
expenses. This is particularly true if the quality of the
water is degraded in storage by algae growth and
retreatment is required to maintain the desired or
required water quality.
The need for seasonal storage in reclaimed water
programs generally results from one of two
requirements. First, storage may be required during
periods of low demand for subsequent use during peak
demand periods. Second, storage may be required to
reduce or eliminate the discharge of excess reclaimed
water into surface water. These two needs for storage
are not mutually exclusive, but different parameters are
considered in developing an appropriate design for each.
Where resource management rather than pollution
abatement is the primary consideration, the reclaimed
water supply and user demands must be calculated, and
the most cost effective means of allocating that resource
must be determined. When reclaimed water is viewed
as a resource or commodity, the users' needs must be
anticipated and accommodated in a similar manner to
potable water supplies. In short, the supply must be
available when the consumer demands it.
While the concept of "safe yield" is commonly applied to
surface water bodies in assessing available potable
water supplies, the determination of the "safe yield" of a
reclaimed water source is somewhat new. Typically,
reuse agreements with individual customers and reuse
ordinances for urban irrigation systems have avoided a
guarantee on continuous delivery, primarily to allow for
the interruption of service in the event of treatment plant
upsets, but allowances for shortages have also been
included. With water reuse assuming a greater role in
conserving potable supplies, reclaimed water becoming
a commodity, and water reuse systems emerging as a
new utility, the considerations of safe yield indeed
become necessary.
Where water reuse is being implemented to reduce or
eliminate wastewater discharges to surface waters, state
or local regulations usually require that adequate storage
be provided to retain excess wastewater under a specific
return period of low demand. In some cold climate states,
storage volumes may be specified according to projected
non-application days due to freezing temperatures.
Failure to retain reclaimed water under the prescribed
weather conditions may constitute a violation of an
NPDES permit and result in penalties.
A method for preparing storage calculations under low
demand conditions is given in the EPA Process Design
Manual: Land Treatment of Municipal Waste water (EPA,
1981 and 1984). In many cases, state regulations will
also include a discussion on the methods to be used for
calculating storage required to retain water under a given
rainfall or low demand return interval.
The remainder of this section discusses the design
considerations for both types of seasonal storage
systems. For the purposes of discussion, the projected
irrigation demands of pasture grass in a hot, humid
location (Florida) and a hot, arid location (California) are
used to illustrate storage calculations. Irrigation demands
were selected for illustration because irrigation is a
common use of reclaimed water and irrigation demands
exhibit the largest seasonal fluctuations, which can affect
system reliability. However, the general methodologies
described in this section can also be applied to other
uses of reclaimed water and other locations as long as
the appropriate parameters are defined.
2.5.1 Identifying the Operating Parameters
The primary factors controlling the need for supplemental
irrigation are evapotranspiration and rainfall.
Evapotranspiration is strongly influenced by temperature
and will be lowest in the winter months, highest in mid-
summer. The magnitude of the evapotranspiration will
vary according to local conditions, but a bell-shaped
curve peaking in the summer months is common for all
locations where seasonal changes in temperature occur.
The need for irrigation at a specific location is a function
of the vegetative cover receiving irrigation, stage of
growth, irrigation system, and local rainfall patterns, all
of which may vary considerably from site to site.
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Figure 13. Average Monthly Rainfall and Pan Evaporation
California
10-
Potential
Evaporation
Florida
I I I I I I I
In many cases, a water reuse system will provide
reclaimed water to a diverse customer base. Urban
reuse customers typically include golf courses and parks
and may also include commercial and industrial
customers. Such is the case in both the City of St.
Petersburg and Irvine Ranch reuse programs, which
provide water for cooling, wash down, and toilet flushing
as well as for irrigation. Each water use has a distinctive
seasonal demand pattern and thereby impact the need
for storage.
Where uses other than irrigation are being investigated,
other factors will be the driving force on demand. For
example, demand for reclaimed water for industrial reuse
will depend on the needs of the specific industrial facility.
These demands could be estimated based on past water
use records, if data are available, or a review of the
water use practices of a given industry. When
considering the demand for water in a man-made
wetland, the system must receive water at the necessary
time and rate to ensure that the appropriate hydroperiod
is simulated. If multiple uses of reclaimed water are
planned from a single source, the factors affecting the
demand of each should be identified and integrated into
a composite system demand.
Figure 13 presents the average monthly potential
evaporation and average monthly rainfall in southwest
Florida and Davis, California (Pettygrove and Asano,
1985). The average annual rainfall is approximately 52
in (132 cm)/yr, with an average annual potential
evaporation of 71 in (180 cm)/yr in Florida. The average
annual rainfall in Davis, California is approximately 17 in
(43 cm)/yr with a total annual average potential
evaporation rate of approximately 52 in (132 cm)/yr. In
both locations, the shape of the potential evaporation
curve is similar over the course of the year.
The distribution of rainfall at Florida and California sites
differs significantly. In California, rainfall is restricted to
the late fall, winter, and early spring, and little rainfall can
be expected in the summer months when evaporation
rates are greatest. The converse is true for the Florida
location, where the major portion of the total annual
rainfall occurs between June and September.
2.5.2 Storage to Meet Irrigation Demands
Once seasonal evapotranspiration and rainfall have
been identified, reclaimed water irrigation demands
throughout the seasons can be estimated. The expected
fluctuations in the monthly need for irrigation of grass in
Florida and California are presented in Figure 14. The
figure also illustrates the seasonal variation in
wastewater flows, the potential supply of irrigation water
for both locations. In both locations the potential monthly
supply and demand are expressed as a fraction of the
average monthly supply and demand.
Defining the expected fluctuations in the supply of
reclaimed water at the Florida site is accomplished by
averaging the historic flows for each month from the
available data. A long record of data is desirable for
developing this average. However, the user must also
be careful to select data representative of future
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Figure 14. Average Pasture Irrigation Demand and Potential Supply
California
3.0-
o
II 2.0.
as-S
« S
ro o
Irrigation Demand
Reclaimed
Water Supply
JFMAMJ JASOND
Florida
3.0"-
2.0-
1.0-
Irrigation Demand
Reclaimed
Water Supply
rrrnrmr
O N D
conditions. The fractional monthly reclaimed water
supply for the Florida example indicates elevated flows
in the late winter and early spring with less than average
flows in the summer months, reflecting the region's
seasonal influx of tourists. The seasonal irrigation
demand for reclaimed water in Florida was calculated
using the Thornthwaite equation. (Withers and Vipond,
1980). It is interesting to note that even in months where
rainfall is almost equal to the potential evapo-
transpiration, a significant amount of supplemental
irrigation may still be required. This occurs as a result of
high intensity short duration rainfalls in Florida coupled
with the relatively poor water holding capacity of the
surficial soils.
The average monthly irrigation demand for California,
shown in Figure 14, is based on data developed by Pruitt
and Snyder (Pettygrove and Asano, 1985). Because
significant rainfall is absent through the majority of the
growing season, the seasonal pattern of supplemental
irrigation for the California site is notably different from
that of Florida. For the California example it has been
assumed that there is very little seasonal fluctuation in
potential supply of reclaimed water.
If the expected annual average demands of a reclaimed
water system are approximately equal to the average
annual available supply, storage is required to hold water
for peak demand months. Using monthly supply and
demand factors, the required storage can be obtained
from the cumulative supply and demand. The cumulative
supply and demand for Florida and California are
illustrated in Figure 15. The results of this analysis
suggest that to make beneficial use of all available water
under average conditions, the Florida reuse program will
require approximately 90 days of storage, while 150 days
will be needed in California.
These calculations are based on only the estimated
consumptive demand of the turf grass. In actual practice,
the estimate would be refined based on site-specific
conditions. Such conditions may include the need to
leach salts from the root zone or the intentional over-
application of water as a means of disposal. The
vegetative cover receiving irrigation will also impact the
condition under which supplemental water will be
required. Drought conditions will result in an increased
need for irrigation. The requirements of a system to
accommodate annual irrigation demands greater than
the average expected demands should also be
examined.
Where reclaimed water serves to provide irrigation,
periodic shortages may be tolerable. In general, the level
of assurance should be established in discussions with
the customers. Depending on the nature of the customer
base, storage considerations must include non-
application periods associated with system maintenance
and harvest.
2.5.3 Storage to Prevent Surface Water Discharge
In cold climate states, storage volumes may be specified
based primarily on the projected non-application days
due to freezing temperatures and frozen ground
45
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Rgure 15. Estimated Storage Required to Commit All Available Reclaimed Water for Pasture Irrigation (Average Condition)
California
365.
Florida
300 —
200 —
100—
Irrigation Demand
Reclaimed —v; • -r-
Water Supply ^ J^' |
-'' Maximum A = 90 Days
F M A M i ! I 4 A I 4
conditions. The state of Illinois, for example, requires a
minimum of 150 days of storage at design average flow
for all reuse irrigation projects.
In many subtropical or warm climate states, however,
storage volumes are calculated based on a specified
return period of low demand. In the case of an irrigation
program, this demand return interval is based on rainfall.
For example, Florida and Missouri require storage
volumes to be determined based on a 1 -in-10 year return
period of low demand, while Georgia requires storage
volumes be determined on a 1-in-5 year monthly return
of low demand.
Using a methodology similar to that defined by EPA
(EPA, 1981 and 1981b), information regarding supply
and demand factors can be used to analyze storage
needs under a low demand event with a given
probability. For the purposes of illustration, a 1-in-10
year low demand probability has been selected. The
calculation is accomplished by reducing the monthly
irrigation demand by the fraction associated with a 90
percent probability low demand year. By selecting this
probability, it is assumed that the resulting storage will
be able to retain all reclaimed water generated 9 out of
10 years.
Using the monthly demands associated with the Florida
and California sites, the reduction in demand associated
with the 1-in-10 year event is distributed to each month
according to the average monthly distribution of demand.
The calculated storage for a 1-in-10 year low demand
event forthe Florida example is approximately 140 days
or 50 days greater than the projected storage
requirements under average conditions (Figure 15). The
results of the calculated storage required for California
for a 1-in-10 year low demand event indicate
approximately 190 days of storage are required or 40
days greater than projected under average conditions.
Results of a similar analysis for the Lakeway Municipal
Utility District in Texas indicated 100 days of storage
would be required to prevent discharge (Mullarkey and
Hall, 1990). The Lakeborough, California Wastewater
Management Plan studied reclaimed water use under 1-
inch, 10-year rainfall conditions and estimated 144 days
of storage would be required to prevent a discharge
(Nolte and Associates, 1990). In describing the
methodology used in the design of reclaimed water
reservoirs under adverse weather conditions for the
California Regional Water Quality Control Board, it was
estimated that approximately 118 days of storage would
be required to prevent discharge (Clow, 1992). In
general, the estimate storage quantities in the examples
cited are on the order of the 140 and 190 days calculated
in the hypothetical Florida and California examples.
However, specific consideration must be made
according to actual site conditions. For example, in the
Lakeborough project, a 10 percent increase in the
calculated irrigation rate was included as a leaching
requirement. This adjusted application rate (ET +
leaching) was then divided by 0.80 reflecting the
anticipated irrigation efficiency of the application system.
Additional information on leaching requirements and
irrigation efficiency is given in Section 3.4 Agricultural
Irrigation.
Several alternative means of modeling storage
requirements are available. The EPA manual Land
Treatment of Municipal Wastewater (EPA, 1981 and
46
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1984) also presents the use of the 1-in-5 year return
period low demand month to develop a composite year.
Summing the individual 1-ln-5 year return months is,
according to the EPA manual, equivalent to modeling on
the 1-in-10 year return period. Pruitt and Snyder
(Pettygrove and Asano, 1985) recommend synthesizing
a 1-in-10 year event from normal year data using a
coefficient for the spring and fall transition months (April
and October) and a second coefficient for the dry
summer months. In some cases, modelers have relied
on actual weather data in estimating storage
requirements. Buchberger and Mardment (1989a,
1989b) suggest the use of the Monte Carlo simulation,
borrowed from stochastic reservoir analysis, as an
appropriate means of sizing reclaimed water storage
facilities. No single methodology will be adequate for all
conditions and sites. Calculating storage requirements
using a number of different methods is recommended.
2.5.4 Partial Commitments of Supply
Water reuse programs based on the need for disposal
and requiring only a partial use of the resource are more
common than a total use of the resource. As the
reclaimed water becomes more valuable, this is
expected to change.
A partial reuse strategy is intended to reduce pollutant
loading in critical periods of the year and discharge all or
a portion of the effluent in periods when it can be
assimilated without water quality degradation. Programs
of this nature are intended primarily for pollution
abatement and may have applications in locations where
discharge is undesirable in certain times of the year.
This strategy, in many cases, offers an alternative to
developing the higher levels of treatment required for a
year-round discharge.
A partial commitment of reclaimed water may also have
applications in the following situations:
Q The cost of providing storage for the entire flow
is prohibitive,
Q Sufficient demand for the total flow is not
available,
Q The cost of developing transmission facilities for
the entire flow is prohibitive, and
Q Total abandonment of existing disposal facilities
is not cost effective.
The volume of storage required to facilitate a partial
commitment of reclaimed water varies according to the
fraction of reclaimed water intended for beneficial use.
As illustrated in Figure 16, a reuse commitment of 60
percent of the available reclaimed water requires
approximately 12 days of storage for the Florida location
and 32 days for the California site.
Figure 1 6.
160
Required Storage Capacity to Meet Irrigation
Demands vs. Percent of Supply Committed
Reuse Commitment
{% of Available Reclaimed Water)
Systems designed to use only a portion of the reclaimed
water supply are plentiful. The City of Modesto,
California, has developed an agricultural irrigation
program designed to eliminate effluent discharge in the
summer months (Jenks, 1991). In a similar system in
Santa Rosa, California, discharges are restricted to a
percentage of the receiving water body flows (Fox et al.,
1987). The City of St. Petersburg, Florida, provides no
significant seasonal storage for its urban reuse system.
Underground storage by creating a reclaimed water
lense on top of a saline aquifer, to be withdrawn in peak
demand periods, was intended at the outset, but has not
been developed. St. Petersburg is using approximately
half of the total reclaimed water supply available. Excess
reclaimed water is disposed of through a series of deep
wells without any recovery.
The Irvine Ranch Water District reclamation program
provides another illustration of the impacts storage has
on the operation of a reuse system. Abandoned irrigation
reservoirs currently provide seasonal storage for the
system. The storage facilities do not have sufficient
capacity to retain all excess reclaimed water. Because
of this limited storage capacity, it is necessary to
discharge reclaimed water in the low demand winter
months. In addition, the seasonal storage facilities do
not retain enough reclaimed water to assure that peak
47
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summer demands can be met and supplemental sources
of water are required.
The use of open ponds to provide seasonal storage
represents the only cost effective means of retaining
large volumes of reclaimed water. However, water
placed into such facilities will undergo quality
degradation. The most common problem is the growth
of algae. While such growth will occur in any exposed
water body, the nutrients in reclaimed water tend to
accelerate this process. The net result is that reclaimed
water placed into seasonal storage may not meet water
quality criteria when it is retrieved from storage. In
general, reclaimed water quality criteria difficulties
related to long-term storage will fall into the categories
given below:
Q Regulatory - many states specify water quality
requirements for various uses. The growth of
algae may result in a SS level in excess of a
regulatory limit.
Q Aesthetic - excessive algae growth may result
in a product that is not aesthetically suitable for
the intended use. Difficulties may include
degradation in both appearance and odor.
Q Functional - quality degradation may result in
operational difficulties in downstream units. For
example, sprinkler clogging in St. Petersburg
was traced to the introduction of seeds in the
open storage facilities.
The solution to water quality degradation as a result of
storage varies according to local conditions. In St.
Petersburg, the absence of seasonal storage results in a
decreased ability to meet peak seasonal demands and
permits a reuse commitment of less than 50 percent of
the available water. At the Irvine Ranch Water District,
reclaimed water is refiltered and chlorinated prior to
introduction to the distribution network. The need to
provide retreatment will vary with the intended use of the
water, but the cost of such retreatment should be
included in any present worth analysis.
Strategies for alternative disposal systems required
where there is a partial commitment of the reclaimed
water are discussed in Section 2.6.3.
2.6 Supplemental Water Reuse System
Facilities
2.6.1 Conveyance and Distribution Facilities
The distribution network includes pipelines, pump
stations, and storage facilities. No single factor is likely
to influence the cost of water reclamation more than the
conveyance or distribution of the reclaimed water from
its source to its point of use. The design requirements of
reclaimed water conveyance systems vary according to
the needs of the users. The design requirements will
also be affected by the policies governing the
reclamation system (e.g., what level of shortfall, if any,
can be tolerated). Where a dual distribution system is
created, the design will be similar to that of a potable
system in terms of pressure and volume requirements.
However, if the reclaimed water distribution system does
not provide for an essential service such as fire
protection or sanitary uses, the reliability of the
reclamation system need not be as stringent. This, in
turn, would reduce the need for backup systems, thereby
reducing the cost of the system. In addition, an urban
reuse program providing primarily for irrigation will
experience diurnal and seasonal flows as well as peak
demands that have differing design parameters than the
fire protection requirements generally used in the design
of potable water systems.
The target customer for many reuse programs may be
those traditionally not part of municipal water/wastewater
systems. Such is the case of agricultural and large green
space areas such as golf courses that often rely on wells
to provide for nonpotable water uses. Even where these
sites are not directly connected to municipal water
supplies, reclaimed water service to these sites may be
desirable for the following reasons:
Q The potential user currently draws water from
the same source as that used for potable water
creating an indirect demand on the potable
system.
Q The potential user has a significant demand for
nonpotable water and may provide a cost
effective means of reducing or eliminating
reliance on existing effluent disposal methods.
Q The potential user is seeking reclaimed water
service to enhance the quality or quantity (or
both) of the water available.
Q A municipal supplier is seeking an exchange of
nonpotable reclaimed water for raw water
sources currently controlled by the prospective
customer.
The conveyance and distribution needs of these sites
may vary widely and be unfamiliar to a municipality. For
example, a golf course may require flows of 500 gpm (38
L/s) at pressures of 120 psi (830 kPa). However, if the
golf course has the ability to store and repump irrigation
48
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Figure 17. Example of a Multiple Reuse Distribution System
SPECIAL NEED CUSTOMERS
In-Line Booster
URBAN REUSE
Customer
Requiring
Pressure >
System Pressure
Industrial
Use
Commercial
Customers
Single- & Multi-
FarniTy Customers
Sprinkler
Irrigation
fT~1 >• Repump to
VX. Golf Course
!•— Irrigation System
Onsite Storage
AGRICULTURAL REUSE
Microjet Citrus
Irrigation
Onsite Well
(Supplemental)
OpenChamel
Conveyance &
Flood Irrigation
water, as is often the case, reclaimed water can be
delivered at atmospheric pressure to a pond at
approximately one-third the instantaneous demand.
Where frost-sensitive crops are served, an agricultural
customer may wish to provide freeze protection through
the irrigation system. Accommodating this may increase
peak flows by an order of magnitude. Where customers
that have no history of usage on the potable system are
to be served with reclaimed water, detailed investigations
are warranted to ensure that the service provided will be
compatible with the user needs. These investigations
should include an interview with the system operator as
well as an inspection of the existing facilities.
Figure 17 provides a schematic of the multiple reuse
conveyance and distribution systems that may be
encountered. The actual requirements of a system will
be dictated by the final customer base and are discussed
in Chapter 3. The remainder of this section discusses
issues pertinent to all reclaimed water conveyance and
distribution systems.
Clustering or concentration of users results in lower unit
costs than a delivery system to dispersed users. Initially
a primary skeletal system is generally designed to serve
large institutional users who are clustered and closest to
the treatment plant. A second phase may then expand
the system to more scattered and smaller users which
receive nonpotable water from the central arteries of the
nonpotable system. Such an approach was successfully
implemented in the City of St. Petersburg, Florida. The
initial customers were institutional (e.g. schools, golf
courses, urban green space, and commercial). However,
the lines were sized to make allowance for future service
to residential customers. The growth of the St.
Petersburg system was and continues to be service to
residential customers who are supplied from major trunk
mains which were installed as part of the skeletal system.
As illustrated in St. Petersburg, and elsewhere, once
reclaimed water is made available to large users, a
secondary customer base of smaller users often seek
service. To ensure that, expansion can occur to the
projected future markets, the initial system design should
49
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model sizing of pipes to satisfy future customers within
any given zone within the service area. At points in the
system where future network of connections is
anticipated, such as a neighborhood, turnouts should be
installed. Pump stations and other major facilities
involved in conveyance should be designed to allow for
planned expansion. Space should be provided for
additional pumps, or the capacities of the pumps may be
expanded by changes to impellers and motor size.
Increasing a pipe diameter by one size is economically
justified since over half the initial cost of installing a
pipeline is for excavation, backfill and pavement. Some
thought should also be given to modifications in the
delivery system that may be needed as the water use
changes. This could include the need to improve system
pressures as the customer base shifts from flood
irrigation to sprinkler irrigation or quality improvements
that may be required as customers shift to drip irrigation
systems, for example.
A potable water supply system is designed to provide
round-the-clock, "on-demand" service. Some nonpotable
systems allow for unrestricted use (City of St.
Petersburg), while others place limits on the hours when
service is available. A decision on how the system will
be operated will significantly affect system design.
Restricted hours for irrigation (i.e. to evening hours) may
shift peak demand and require greater pumping capacity
than if the water was used over an entire day or may
necessitate a programmed irrigation cycle to reduce
peak demand. The Irvine Ranch Water District, though it
is an "on-demand" system, restricts landscape irrigation
to the hours of 9 p.m. to 6 a.m. to limit public exposure.
Due to the automatic timing used in most applications,
the peak hour demand was found to be six times the
average daily demand and triple that of the domestic
water distribution system (Young, etal., 1988). As noted
previously, attributes such as freeze protection may
result in similar increases in peak demands of
agricultural systems.
System pressure should be adequate to meet the user's
needs within the reliability limits specified in a user
agreement or by local ordinance. The Irvine Ranch
Water District runs its system at a minimum of 90 psi
(600 kPa). The City of St. Petersburg currently operates
its system at a minimum pressure of 60 psi (400 kPa).
However, the City of St. Petersburg is recommending
users to install low-pressure irrigation devices which
operate at 50 psi (340 kPa) as a way of transferring to a
lower pressure system in the future to reduce operating
costs.
When there are significant differences in elevations
within the service area, the system should be divided
into pressure zones. Within each zone, a maximum and
minimum delivery pressure is established. Minimum
delivery pressure may be as low as 10 psi (70 kPa) and
maximum delivery pressure may be as high as 150 psi
(1,000 kPa) depending on the primary uses of the water.
Several existing guidelines recommend that operating
the nonpotable system at pressures lower than the
potable (10 psi, 70 kPa lower) in order to mitigate any
cross connections (American Water Works Association,
1989). If the system is operated as a low pressure
system (below 40 psi, 280 kPa) standards have to be set
forthe userto install only low-pressure irrigation devices.
In turn this requires coordination with plumbers and
irrigation vendors to ensure that the proper devices are
installed from the outset.
2.6.1.1 Public Health Safeguards
The major concern which guides design, construction,
and operation of a reclaimed water distribution system is
the prevention of cross-connections. A cross connection
is a physical connection between a potable water system
used to supply water for drinking purposes and any
source containing nonpotable water through which
potable water could be contaminated.
Another major concern is to prevent improper use or
inadvertent use of reclaimed water as a potable water.
To protect the public health from the outset, a reclaimed
water distribution system should be accompanied by
health codes, procedures for approval (and
disconnection) of service, regulations governing design
and constructions specifications, inspections and
operation and maintenance staffing. Among some of the
public health protection measures that have been
identified (American Water Works Association, 1983)
and should be addressed in the planning phase are:
Q Establish that public health is the overriding
concern.
Q Devise procedures and regulations to prevent
cross connections.
Q Develop a uniform system to mark all
nonpotable components of the system.
Q Prevent improper or unintended use of
nonpotable water.
Q Provide for routine monitoring, and surveillance
of the nonpotable system.
Q Establish special staff responsible for
operations, maintenance, inspection, and
approval of reuse connections.
50
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Q Develop construction and design standards.
Q Provide for the physical separation of the
potable water, reclaimed water, and sewer lines
and appurtenances.
The following are some of the steps which have been
successfully implemented to achieve these measures.
a. Identification of Pipes and Appurtenances
All components and appurtenances of the nonpotable
system should be clearly and consistently identified
throughout the system. Identification should be through
color coding and marking. The nonpotable system
(pipes, pumps, outlets, valve boxes, etc.) should be
easily set apart from the potable system. The methods
most commonly used are: unique colorings, labeling,
and markings.
At the Irvine Ranch Water District, nonpotable piping
and appurtenances are painted purple (American Water
Works Association. California-Nevada Section, 1989) or
can be integrally stamped or marked "CAUTION NON-
POTABLE WATER - DO NOT DRINK" or "CAUTION:
RECLAIMED WATER - DO NOT DRINK", or the pipe
may be wrapped in purple polyethylene vinyl wrap. The
City of St. Petersburg uses brown coloring to distinguish
reclaimed water piping.
Another identification method is marking pipe with
colored marking tape or adhesive vinyl tape. When tape
is used, the letters (e.g., "CAUTION: RECLAIMED
WATER - DO NOT DRINK") should be equal to the
diameter of the pipe and placed longitudinally at 3-ft
(0.9- m) intervals. Other methods of identification and
warning are: stenciled pipe with 2-3-in (5-8 cm) letters
on opposite sides, every 3-4 ft (0.9-1.2 m); for pipe less
than 2-in (5 cm), lettering should be at least 5/8-in (1.6
cm) at 1-ft (30 cm) intervals); plastic marking tape (with
or without metallic tracer) with lettering equal to the
diameter of pipe, continuous over the length of pipe at
no more than five ft (1.5 m) intervals; vinyl adhesive tape
may be placed at the top of the pipe for diameters 2.5 to
3 in (6-8 cm) and along opposite sides of the pipe for
diameters 6 to 16-in (15-40 cm), and along both sides
and on top of the pipe for diameters of 20-in (51 cm) or
greater (American Waterworks Association, 1983).
Valve boxes for hydraulic and electrical components
should be colored and warnings should be stamped on
the cover. The valve covers for nonpotable transmission
lines should not be interchangeable with potable water
covers. Blow off valves should be painted and carry
markings similar to other system piping. Irrigation and
other control devices should be marked both inside and
outside. Any constraints or special instructions should
be clearly noted and placed in a suitable cabinet. If fire
hydrants are part of the system, they should be painted
or marked and the stem should require a special wrench
for opening.
b. Horizontal and Vertical Separation of Potable
from Nonpotable
The general rule is that a 10-ft (3-m) horizontal interval
and a 1 -ft (0.3-m) vertical distance should be maintained
between potable (or sewer) lines and nonpotable lines
that are parallel to each other. When these distances
cannot be maintained, special authorization may be
required, though a minimum lateral distance of 4 ft (1.2
m) (St. Petersburg) is generally mandatory. The State of
Florida specifies a 5-ft (1.5-m) separation between
reclaimed water lines and water or force mains, with a
minimum of 3 ft (0.9 m) separation from pipe wall to pipe
wall (Florida Department of Environmental Regulation,
1990). This arrangement allows for the installation of
reclaimed water lines between water and force mains
that are separated by 10 ft (3 m). The potable water
should be placed above the nonpotable if possible.
Under some circumstances, using a reclaimed water
main of a different depth than that of potable or force
mains might be considered to provide further protection
from inadvertent cross-connection. Nonpotable lines are
usually required to be at least 3 ft (90 cm) below ground.
Figure 18 illustrates Florida's separation requirements
for nonpotable lines.
c. Prevent Onsite Ability to Tie into Reclaimed
Water Line
The Irvine Ranch Water District has regulations
mandating the use of special quick coupling valves for
onsite irrigation connections. For reclaimed water these
valves are operated by a key with an Acme thread. This
thread is not allowed for the potable system. The cover
on the reclaimed water coupler is different in color and
material from that used on the potable system. Hose
bibbs are generally not be permitted on nonpotable
systems because of the potential for incidental use and
possible human contact of the reclaimed water (Parsons,
1989). Below ground bibbs in a locking box or requiring
a special tool to operate are allowed by Florida
regulations (Florida Department of Environmental
Regulation, 1990).
d. Backflow Prevention
Except in special cases, some form of backflow
prevention is needed to protect potable water line in
areas where reclaimed water is used. As an example of
when backflow prevention devices are not required, the
State of California will waive its backfiow prevention
device requirements"... when rules of service that are
51
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Figure 18. Florida Separation Requirements for Reclaimed Water Mains
Finished Grade
• S'VVS'S'SSS'S'Sl' XX
''X'X'x'N's'X'x's'sV
.-'Potable Water'Maif»/x'
x'x'x'x'x'x'x'x'x'x'x'
X X X _X _X X X X X X X
S S
\: •
"x"
V
Reclaimed Water Main
'x'x'x'x'x* 41 m'n-
Sanitary Sewer/ \"^ ZffSi—
Force Main _^'"*3^
Finished Grade
X X X X X X x'
Raw Water or \
Water Main
XX XX X X X X X X
X X X X X X X '
Sanitary .V
acceptable to the Department are incorporated, and
when either of the following conditions can be satisfied:
1. The potable water and the reclaimed water
systems are underthe control of the water supplier
and the following requirements are met:
a. Only the water supplier or others approved by
the water supplier are allowed to work on
either the potable water or the reclaimed water
system piping, and
b. The reclaimed water system conforms to
AWWA California-Nevada Section's
Guidelines' for Distribution of Nonpotable
Water, and
c. The water supplier conducts annual cross-
connection surveys to assure conformance
with the rules of service, or
2. The potable water and the reclaimed water piping
are horizontally separated by a minimum distance
of 200 ft, and the water supplier conducts annual
cross-connection surveys to assure conformance
with the rules of service." (California Department
of Health Services, 1990).
Where the possibility of cross-connection between
potable and reclaimed water lines does exist, backflow
prevention devices should be installed onsite when both
potable and reclaimed water services are provided to a
user. The backflow prevention device is placed on the
potable water service line to prevent potential backflow
from the reclaimed water system into the potable water
system if the two systems are illegally interconnected.
Accepted methods of backflow prevention include:
Q Air gap,
Q Reduced-pressure principal backflow
prevention assembly,
Q Double-check valve assembly,
Q Pressure vacuum breaker and,
Q Atmospheric vacuum breaker.
The AWWA recommends the use of a reduced-pressure
principal backflow prevention assembly where reclaimed
water systems are present. However, many communities
have successfully used double-check valve assemblies.
The backflow prevention device will prevent water
expansion into the water distribution system. At some
residences, the tightly closed residential water system
can create a pressure buildup that causes the safety
relief on a water heater to periodically discharge. This
problem was solved by the City of St. Petersburg by
providing separate pressure release valves which allow
for release of water through an outdoor hose bibb.
If potable water is used as make up water for lakes or
reservoirs, there should be a physical break between
the potable water supply pipe and a receiving reservoir.
The air gap separating the potable water from the
reservoir containing nonpotable water should be at least
two pipe diameters. There should never be any
52
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permanent connection between nonpotable and potable
lines in the system.
In most cases, backflow prevention devices are not
provided on the reclaimed water system/However,
where a reclaimed water user wishes to inject chemicals
into the reuse irrigation system, provisions for backflow
prevention may be warranted.
e. Safeguards when Converting Existing Potable
Lines to Nonpotable Use
In cases where the parts of the system are being
upgraded and some of the discarded potable water lines
are transferred over to the nonpotable system, care must,
be taken to prevent any cross connection. As each
section is completed, the new system should be shut
down and drained and each water user checked to
ensure that there are no connections. Additionally a
tracer, such as potassium permanganate may be
introduced into the nonpotable system to test whether
any of it shows up at any potable fixture.
In existing developments where an in-place irrigation
system is being converted to carry reclaimed water, the
new installation must be inspected and tested with
tracers or some other method to ensure separation of
the potable from the nonpotable supply.
2.6.1.2 Operations and Maintenance
The maintenance requirements for the nonpotable
components of the reclaimed water distribution system
are often the same as those for the potable. As the
system matures, any disruption of service due to
operational failures will upset the users. From the outset,
such items as isolation valves, which allow for repair on
parts of the system without affecting a large area, should
be designed into the nonpotable system. Flushing the
line after construction should be mandatory to prevent
sediment from accumulating and hardening and
becoming a serious future maintenance problem.
Differences in maintenance procedures for potable and
nonpotable cannot generally be forecast prior to the
operation of each system. The City of St. Petersburg, for
instance, flushes its nonpotable lines twice a year during
the off season months. The amount of water used in the
flushing is equal to a day's demand of reclaimed water.
The IRWD reports no significant difference in the two
lines, though the reclaimed lines are flushed more
frequently (every 2-3 years vs. every 5-10 for potable)
due to suspended matter and sediment picked up in lake
storage.
a. Blow Offs
Even with sufficient chlorination, residual organics and
bacteria may grow at dead spots in the system. This
may lead to odor and clogging problems. Blow-off valves
and blow-off periodic maintenance of the system can
significantly allay the problem. In most cases, the blow-
off flow is directed into the sewage system.
b. Flow Recording
Even when a system is unmetered, accurate flow
recording is essential to manage the growth of the
system. Flow data are needed to confirm total system
use and spatial distribution of water supplied. Such data
_allow for. efficient management of the reclaimed water
pump stations and formulations of policies to guide
system growth. Meters placed at the treatment facility
may record total flow and flow monitoring devices may
be placed along the system particularly in high
consumption areas.
c. Permitting and Inspection
The permitting process includes plan and field review
followed by periodic inspection of facilities. The oversight
includes inspection of both onsite and offsite facilities.
Onsite facilities are the user's nonpotable water facilities
downstream from the reclaimed water meter. Offsite
facilities are the agency's nonpotable water facilities up
to and including the reclaimed water meter.
Though inspection and review regulation vary from
system to system, the basic procedures are essentially
the same. The steps are:
(1) Plan Review: A contractor (or resident) must
request service and sign an agreement with the
agency or department responsible for permitting
reclaimed water service. Dimensioned plans and
specifications for onsite facilities must conform to
regulations. Usually the only differences from
normal irrigation equipment will be identification
requirements and special appurtenances to
prevent cross connections. Some systems,
however, require that special strainer screens be
placed before the pressure regulator for protection
against slime growths fouling the sprinkler system,
meter, or pressure regulator.
The plans are reviewed and the agency works with
the contractor to make sure that the system meets
all requirements. Systems with cross-connections
to potable water systems must not be approved.
Temporary systems should not be considered.
Devices for any purpose other than irrigation
should be approved by special procedures.
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Installation procedures called out on the plan
notes are also reviewed because they provide the
binding direction to the landscape contractor. All
points of connection are reviewed for safety and
compatibility. The approved record drawings ("as
builts") are kept on file. The "as-builts" include all
onsrte and offsite nonpotable water facilities as
constructed or modified and all potable water and
sewer lines.
(2) Field Review: Field review is generally conducted
by the same staff involved in the plan review.
Improper connections, identification, insufficient
depth of pipe installation are reviewed and
corrected. There is a cross-connection control test
and finally the actual onsite irrigation system is
operated to ensure that overspraying and
overwatering is not occurring. There are usually
follow-up inspections and in some cases fixed
interval (e.g. semi-annual) inspections and
random inspections.
(3) Monitoring: Among the items monitored are:
Q Ensuring that landscape contractors or irrigation
contractors provide minimal education to their
personnel so that they are familiar with the
regulations governing reclaimed water
installations.
Q All modifications to approved facilities should be
submitted to and approved by the responsible
agency.
Q Detection of any breaks in the transmission
main.
Q Random inspection at user sites to detect any
faulty equipment, or violation or irrigation
schedule.
Q Installation of monitoring stations throughout the
system for testing of pressure, chlorine residual,
and other water quality parameters.
The procedures for connecting residential customers in
St. Petersburg are illustrated in Figure 19. A reclaimed
water supplier should reserve the right to withdraw
service for any offending condition subject to correction
of the problem. Such rights are often established as part
of a user agreement or a reuse ordinance. Chapter 5
provides a discussion of the legal issues associated wjth
reclaimed water projects.
2.6.2 Operational Storage
As with potable water distribution systems, a reclaimed
water system must provide sufficient operational storage
to accommodate diurnal fluctuations in demand and
supply. The volume required to accommodate this task
will depend on the interaction of the supply and demand
over a 24-hour period.
Designs are dependent on assessments of the diurnal
demand for reclaimed water. Such assessments, in most
cases, require a detailed investigation of the proposed
user or users. When possible, records of actual historical
use should be examined as a means of developing
demand requirements. Where records are absent, site-
specific investigations are in order. In some cases, pilot
studies may be warranted prior to initiating a full-scale
reuse program.
Figure 20 presents the anticipated diurnal fluctuation of
supply and urban irrigation demand for a proposed
reclaimed water system in Boca Raton, Florida (Camp
Dresser & McKee Inc., 1991). This information was
developed based on the historic fluctuations in
wastewater flow experienced in Boca Raton and the
approximate fluctuations in the reclaimed water urban
irrigation demand experienced in the St. Petersburg,
Florida urban reuse program. A hydrograph of the
cumulative supply and demand is presented in Figure
21, indicating the system will require approximately 5
million gal (19 x 103m3) of storage. In this example, the
diurnal storage volume required is equal to 30 to 35
percent of the daily flow. Actual service storage needs of
a reclamation system reflect the final uses of the water.
Operational storage may be provided at the reclamation
facility, as remote storage out in the system, or a
combination of both. For example, the City of Altamonte
Springs, Florida, maintains ground storage facilities at
the reclamation plant and elevated storage tanks on the
reclaimed water system. The selection of this
configuration was based on a cost analysis of the
transmission and pumping requirements for a variety of
storage schemes (Howard Needles Tammen &
Bergendoff, 1986). Large sites, such as golf courses,
commonly have onsite ponds capable of receiving water
throughout the day. Such onsite facilities reduce
operational storage requirements that need to be
provided by the utility. In the City of Naples, Florida,
where reclaimed water is provided to nine golf courses,
remote booster pumping stations deliver reclaimed water
to the users from a covered storage tank located at the
reclamation plant (Camp Dresser & McKee Inc., 1983).
Operational storage facilities are generally covered tanks
or open ponds. Covered storage in ground or elevated
tanks is used for unrestricted urban reuse where
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Figure 19. City of St. Petersburg Customer Connection Protocol
Send Application
Package to Citizen
V
Endorsed Package
Returned to Citizen
Perform Preliminary
Inspection
V
Send Connection Fee
Letter to Citizen
V
Send Application
to Customer Service
Receive Work Order
From Customer Service
Citizen Ready for
Final Inspection?
Perform Final
Inspection
Return Completed Work
Order to Customer Service
Turn On
Service
aesthetic considerations are important. Ponds are less
costly, in most cases, but generally require more land
per gallon stored. Where property costs are high or
sufficient property is not available, ponds may not be
feasible. Open ponds also result in water quality
degradation from biological growth, and a chlorine
residual is difficult to maintain, as noted previously in the
discussion on seasonal storage. Ponds are appropriate
for onsite applications such as agricultural irrigation and
golf courses.
When providing reclaimed water to large users such as
golf courses or parks, it is often possible to deliver water
to onsite ponds over a 24-hour period. The user would
then withdraw water for irrigation with an onsite pumping
system over a 4 to 6 hour period at night. Under these
conditions, the operational storage needs of the large
customer are addressed onsite. However, as with
seasonal storage ponds, onsite impoundments may
result in a degradation of water quality. The most
common form of degradation is increased algae growth
due to nutrients. In the case of ponds located in highly
maintained areas such as golf courses, it is not
uncommon for owners to experience aesthetic problems
prior to and apart from the storage of reclaimed water.
Where irrigation systems have historically used water
55
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Figure 20. Anticipated Daily Reclaimed Water Demand Curve vs.
Diurnal Reclaimed Water Flow Curve
I1 24.
•o
I 20-J
Q
16
E
"o
12:00
AM
Wastewater
Diurnal Flow Curve
Reclaimed Water
Demand
4:00
AM
8:00
AM
12:00
PM
4:00
PM
8:00
PM
12:00
AM
withdrawn from onsite successfully, the introduction of
reclaimed water into the pond would not be expected to
significantly increase operational problems (i.e., clogging
of sprinkler heads).
Figure 21. Hydrograph for Diurnal Flows
Cumulative Irrigation
Demand
Cumulative Reclaimed
Water Supply
Required Equalization
Volume
12:00 4:00 8:00
AM AM AM
12:00 4:00 8:00
PM PM PM
12:OC
AM
12.00
AM
Apart from the biological aspects of storing reclaimed
water in onsite impoundments, the concentration of
various constituents due to surface evaporation may
present a problem. Reclaimed water often has a more
elevated concentration of TDS than other available
sources of water. Where evaporation rates are high and
rainfall is low, the configuration of onsite storage ponds
was found to have significant impacts on water quality in
terms of TDS (Chapman and French, 1991). Shallow
ponds with a high area-to-volume ratio will experience
greater concentrations of dissolved solids due to surface
evaporation. Dissolved solids increase in all ponds, but
deeper ponds can serve to mitigate the problem. Figure
22 summarizes the expected concentration of TDS with
pond depth for reclaimed water of 1,112 mg/L and 1,500
mg/L of TDS, assuming water is lost from a storage
through evaporation only.
2.6.3 Alternative Disposal Facilities
While water reclamation and reuse often provide the
secondary benefit of reducing the water quality impacts
of effluent discharge, reuse of 100 percent of the effluent
may not always be feasible. In such cases, some form of
alternative use or disposal of the excess water is
necessary.
Where reclamation programs incorporate existing
WWTFs, an existing disposal system will likely be in
place and can continue to be used for partial or
intermittent disposal. Common alternative disposal
systems include surface water discharge, injection wells,
land application, and wetlands application.
2.6.3.1 Surface Water Discharge
An intermittent surface water discharge may represent
an acceptable method for the periodic disposal of excess
reclaimed water. While demand for reclaimed water
normally declines during wet weather periods, surface
56
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waters are then generally more able to assimilate the
nutrients in reclaimed water without adverse water
quality impacts. Conversely, during the warm summer
months when surface water bodies are often most
susceptible to the water quality impacts of effluent
discharges, the demand for irrigation water is high and
an excess of reclaimed water is less likely. Thus, the
development of water reuse program with intermittent
discharge can reduce or eliminate wastewater
discharges during periods when waters are most
sensitive to nutrient concentrations while allowing for a
discharge in periods where adverse impacts are less
likely. By eliminating discharges for a portion of the year
through water reuse, a municipality may also be able to
avoid the need for the costly AWT nutrient removal
processes often required for a continuous discharge.
Figure 22. TDS Increase Due to Evaporation for
One Year as a Function of Pond Depth
7000
f; 6000 -
J 5000 -
•g 4000 -
I
j| 3000 -
,2 2000 -
1000 .
0
influent salinity, 1,112 mg/l
influent salinity, 1,500 mg/l
0 2 4 6 8 10 12 14 16 18
Pond Depth (ft)
Source: Chapmen and French, 1991.
The City of Santa Rosa, California, developed an
agricultural reuse program in response to a permit
limiting discharge of wastewater to a percentage of the
base stream flow, with discharge prohibited for stream
flows of less than 1,000 cfs [28 m3/s) (Donald et a/.,
1987). The City of Modesto, California, utilizes a winter
discharge to the San Joaquin River as part of an
agricultural reuse program. The Lodi, California reuse
program includes a 150-d/yr maximum allowance for
discharge to White Slough (Boyle Engineering
Corporation, 1981).
According to the Florida Department of Environmental
Regulation (1990), allowing limited discharge of excess
reclaimed water during wet weather periods will facilitate
implementation of reuse projects. Florida's reuse
regulations allow for limited wet weather discharge to
surface waters with minimal water quality review under
restricted conditions. Discharge normally is limited to a
maximum of 25 percent of the year as long as required
dilution ratios are maintained. Dilution requirements are
based on the frequency of discharge, quality of reclaimed
water produced, and travel time to sensitive, downstream
water bodies.
2.6.3.2 Injection Wells
Injection wells, which convey reclaimed water into
subsurface formations, are also used as an alternative
means of disposal. In some cases, the injection of
reclaimed water may even be considered reuse when
intended to create a barrier to saltwater intrusion.
According to EPA (n.d.), technical requirements for
injection wells include:
Q Wells are sited to inject into a formation which is
beneath the lower-most formation containing an
underground source of drinking water.
Q It is demonstrated through hydrogeological
investigations that the injection zone is
separated from potable aquifers or aquifers that
may serve as a source of potable water by an
impermeable formation.
Q The injection well is constructed such that it will
not allow the movement of water between
isolated formations.
Q Ongoing monitoring of the appropriate formation
is required to ensure system integrity.
Injection wells are a key element of the urban reuse
program in City of St. Petersburg, Florida (Waller and
Johnson, 1989). The city operates 10 wells which inject
excess reclaimed water into a saltwater aquifer at depths
between 700 and 1,000 ft (210 and 300 m) below land
surface. Approximately 50 percent of the available
reclaimed water is disposed of through injection. While
the primary use of the wells is for the management of
excess reclaimed water, the wells are also employed to
dispose of any reclaimed water not meeting water quality
standards.
Under suitable circumstances, excess reclaimed water
can be stored in aquifers. This has an advantage over
surface storage in that little or no reclaimed water quality
degradation occurs.
57
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2.6.3.3 Land Application
In water reuse irrigation systems, reclaimed water is
applied in quantities to meet an existing water demand;
in land treatment systems, effluent may be applied in
excess of the needs of the crop. Land application may
have a reuse benefit, as irrigation and/or where
beneficial groundwater recharge is achieved. However,
in many cases the design of land application systems is
concerned with avoiding the detrimental impacts on
groundwater resulting from the application of nutrients
or toxic compounds.
In some cases, a site may be amenable to both reuse
and "land application." Such are the conditions of the
Tallahassee, Florida sprayfield system. The system is
located on a sand ridge, where only drought-tolerant
flora survives without irrigation. By providing reclaimed
water for irrigation, the site is made suitable for
agricultural production and has been leased by a farmer
for that use. However, because of the extreme infiltration
and percolation rates, it is possible to apply up to 3 in/
week of reclaimed water without significant detrimental
impacts to the crop (Allhands and Overman, 1989).
The City of Santa Maria, California, operates a similar
agricultural reuse program where the lease farmer is
required to take all of the water generated. An inspection
of this facility in 1981 indicated that the reuse site was
experiencing operational difficulties due in part to an
over-application of irrigation water (Boyle Engineering
Corporation, 1981).
Where some form of land application is used as
alternative disposal, it is common to have separate sites
dedicated to reuse and land application. The City of
Santa Rosa, California, developed an agricultural reuse
program with a conditional seasonal discharge. When
unable to meet its surface water discharge permit
conditions, the City expanded the reuse irrigation
capacity, requested a less restrictive discharge permit,
and developed dedicated land application areas where
application rates could be maximized (Donald et al.,
1987). The Cities of Apopka and Venice, Florida, have
also established dedicated land application sites as part
of their urban reuse programs (Godlewski et al., 1990;
Ammerman and Moore, 1991).
A joint water reuse program between the City of Orlando
and Orange County, Florida, provides reclaimed water
for citrus irrigation with a system of 60 rapid infiltration
basins for land application of excess reclaimed water.
The basins provide some reuse benefit through
groundwater recharge. With the decline in citrus acreage
resulting from a series of severe freezes in the late
1980s, this land application back-up system has become
critical to the reuse program. New irrigation customers
and crop diversification are being investigated to reduce
reliance on the land application system (Ammerman and
Hobel, 1991).
The City of Fresno, California, provides reclaimed water
for irrigation to leased and private farming operations. If
required, the total volume of reclaimed water generated
may be diverted to a series of percolation beds. The
percolation site includes a series of extraction wells
which ultimately discharge into the Fresno Irrigation
District's agricultural supply system, thus allowing for
the recovery and additional treatment of the reclaimed
water (Boyle Engineering Corporation, 1981).
The use of land application as an alternative means of
disposal is subject to hydrogeological considerations.
The EPA manual Land Treatment of Municipal
Wastewater(EPA, 1981) provides a complete discussion
of the design requirements for such systems. The use of
land application systems for wet weather disposal is
limited unless high infiltration and percolation rates are
possible, such as rapid infiltration basins or manmade
wetlands.
In cases where manmade wetlands are created,
damaged wetlands are restored, or existing wetlands
are enhanced, wetlands application may be considered
a form of water reuse, as discussed in Section 3.5.1.
Partial or intermittent discharges to wetlands systems
have also been incorporated as alternative disposal
means in water reuse systems, with the wetlands
providing additional treatment through filtration and
nutrient uptake.
In 1978, the creeks and canals in the vicinity of Hilton
Head Island, South Carolina, were closed to shellfishing
by the State Department of Health. In 1982, a
moratorium on new or expanded wastewater treatment
was imposed. In response, the resort community initiated
an urban reuse program to serve local golf courses and
landscaped areas. The selected means of alternative
disposal for this program was the development of a
discharge to wetlands so that additional treatment of the
excess reclaimed water is achieved as it passes through
the wetlands system (Hirsekorn and Ellison, 1987). A
similar wetlands discharge is used in Orange County,
Florida, where a portion of the reclaimed water
generated by the Eastern Service Area WWTF is reused
for power plant cooling and the remainder is discharged
by overland flow to a system of manmade and natural
wetlands. Application rates are managed to simulate
natural hydroperiods of the wetland systems (Schanze
and Voss, 1989).
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2.7 Environmental Impacts
Elimination or reduction of a surface water discharge by
reclamation and reuse generally reduces adverse water
quality impacts to the receiving water. However, moving
the discharge from a disposal site to a reuse system
may have secondary environmental impacts. An
environmental assessment may be required to meet
state or local regulations and is required wherever
federal funds are used. Development of water reuse
systems may have secondary environmental impacts
related to land use, stream flow, and groundwater
quality. Formal guidelines for the development of an
environmental impact statement (EIS) have been
established by the EPA. Such studies are generally
associated with projects receiving federal funding or new
NPDES permits and are not specifically associated with
reuse programs. Where an investigation of
environmental impacts is required, it may be subject to
state policies.
The following conditions are given as those that would
induce an EIS in a federally funded project:
Q The project may significantly alter land use;
Q The project is in conflict with any land use plans
or policies,
Q Wetlands will be adversely impacted;
Q Endangered species or their habitat will be
affected;
Q The project is expected to displace populations
or alter existing residential areas;
Q The project may adversely affect a flood plain or
important farm lands;
Q The project may adversely affect park lands,
preserves or other public lands designated of
scenic, recreational, archaeological or historical
value;
Q The project may have a significant adverse
impact upon ambient air quality, noise levels,
surface or groundwater quality or quantity; and
Q The project may have adverse impacts on water
supply, fish, shellfish, wildlife and their actual
habitats.
The types of activities associated with federal EIS
requirements are outlined below. Many of the same
requirements are incorporated into environmental
assessments required under state laws.
In addressing the requirements of the EIS, the purpose
and need of the proposal action is to be stated. A
thorough evaluation of the alternative under
consideration, including required facilities, capital and
operating costs and the anticipated environmental
impacts of the project, is to be presented. In addition, the
EIS process is open to public and agency review and
comment as the study progresses. This process includes
the submittal of the appropriate documentation to the
affected parties and the presentation of workshops open
to the public.
A formal EIS may be a very involved process and in
most cases will not be required of reclamation projects.
This does not mean, however, that the potential
environmental issues associated with reuse can be
neglected. The more common environmental impacts
associated with reuse projects are discussed below.
2.7.1 Land Use Impacts
Water reuse can induce land use changes that could be
considered either beneficial or detrimental. If a
community's growth had been limited by the capacity of
the water supply, and if, through water reuse, the portion
of the potable supply available to residents were
increased, then development that had previously been
excluded could occur. In most cases, the decision-
making process involved in implementing reclamation
and reuse also impels examination of community goals.
In Westminster, Colorado, for example, a water-
exchange program between the city and area farmers
were tied directly into a comprehensive six-point growth
and resource-management plan that includes
establishment of land-use priorities, fiscal impact
planning, and conservation programs (Thurber, 1979).
Water reuse can encourage a more intensive use of
land in a municipality. For example, parks or golf courses
can be developed on previously undeveloped land. In a
developed urban environment, landscaping of green
space may be enhanced. A water reuse program might
result in a more dramatic change in land use. For
example, a small manufacturing facility, attracted by the
availability of water, might be developed on a site not
previously dedicated to industrial use. The availability of
reclaimed water can also provide an opportunity for new
residential development by extending potable supplies.
In some cases, more intensive use can be made of
agricultural land by virtue of having more irrigation water
59
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available. A farmer may be able to extend planting from
one crop season to two crop seasons or plant a higher
value crop.
2.7.2 Stream Flow Impacts
In the past, leaving water in a stream was considered a
waste of a resource, and most states did not regulate in-
stream flows for the maintenance of habitat. Today,
however, in-stream flows are considered valuable to the
environmental system (National Research Council,
1989). Where wastewater discharges have occurred
over an extended period of time, the indigenous flora
and fauna have adapted and, in some cases, become
dependent on that water. In some cases, water reuse
projects have been halted over concerns related to water
rights because the elimination of an existing discharge
was expected to result in a decreased volume of water
available to downstream users.
In developing an urban reuse plan around an existing
12.5-mgd (548 Us) WWTF, the City of Altamonte
Springs, Florida, intends to commit 10 mgd (438 Us) of
the available reclaimed water to urban use, greatly
reducing the hydraulic and nutrient loadings into the Little
Wekiva River from its previous practice of effluent
discharge. However, the remaining 2.5 mgd (110 Us will
receive advanced treatment and continue to be
discharged to the river to maintain a minimum hydraulic
input to the system. In periods of low reclaimed water
demand, the entire flow may be discharged, providing
the reclaimed water meets water quality standards
(Howard, Needles, Tammen & Bergendoff, 1986).
The City of Phoenix has reuse agreements with the Palo
Verde nuclear power plant and with irrigation customers
downstream of the WWTF's discharge into the Salt
River. Reclaimed water is delivered to the power plant
through a reuse main. The irrigation water is conveyed
to the users through the natural river channel. Future
plans call for a halt to all surface water discharges and
the construction of a reuse main to the irrigation
customers. Any excess reclaimed water would be
diverted to a proposed groundwater recharge project.
Environmental groups have expressed concern over
adverse impacts on the habitat the withdrawal of the
discharge may cause. However, previous rulings in
Arizona have designated that reclaimed water is the
property of producer and may be discharged or not as
the producer wishes.
2.7.3 Hydrogeologlcal Impacts
As a final environmental consideration of water reuse,
the groundwater quality effects of the reclaimed water
for the intended use must be reviewed. The exact
concerns of any project are evaluated on a case-by-
case basis. One of the better known sources of potential
groundwater pollution is nitrate, which may be found in
or result from the application of reclaimed water.
However, additional physical, chemical, and biological
constituents found in reclaimed water may pose an
environmental risk. In general, these concerns increase
when there are significant industrial wastewater
discharges to the water reclamation facility.
The impacts of these constituents are influenced by the
hydrogeology of the reuse application site. Where karst
conditions exist, for example, there is a potential for
constituents within the reclaimed water to ultimately
reach the aquifer. Irrigation with Reclaimed Municipal
Wastewater: A Guidance Manual (Pettygrove and
Asano, 1985) provides chapters on the fate of nutrients,
trace elements, pathogens, and trace organics in the
soil.
In many reclaimed water irrigation programs, a
groundwater monitoring program is required to detect
the impacts of reclaimed water constituents, but such
programs will also detect other sources of pollution. For
example, the monitoring program forthe reclaimed water
agricultural irrigation system in Tallahassee, Florida,
detected elevated nitrates in the groundwater. Ultimately,
a nutrient balance of the system indicated the cause of
the nitrates was fertilizer applications to the site (Allhands
and Overman, 1989). The city was able to coordinate
with the farmer to address this issue. It is interesting to
note, however, that such a problem may have gone
undetected were it not for the reuse program and the
associated monitoring plan.
2.8 References
When an NTIS number is cited in a reference, that
reference is available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
(703) 487-4650
Adams, A.P., and B.G. Lewis, n.d. Bacterial Aerosols
Generated by Cooling Towers of Electrical Generating
Plants. Paper No. TP-191 -A, U.S. Army Dugway Proving
Ground, Dugway, Utah.
Adams, D.L. 1990. Reclaimed Water Use in Southern
California: Metropolitan Water District's Role. In: 1990
Biennial Conference Proceedings, National Water Supply
Improvement Association, Vol. 2. August 19-23, 1990.
Buena Vista, Florida.
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Allhands, M.N. and A.R. Overman. 1989. Effects of
Municipal Effluent Irrigation on Agricultural Production
and Environmental Quality. Agricultural Engineering
Department, University of Florida, Gainesville, Florida.
American Public Health Association. 1989. Standard
Methods for the Examination of Water and Wastewater,
17th Edition. [Clesceri, L.S.; A.E. Greenberg; and R.R.
Trussed (ed.)]. American Public Health Association,
Washington D.C.
American Water Works Association. 1990.
Recommended Practice for Backflow Prevention and
Cross-Connection Control, AWWA M14, Denver,
Colorado.
American Water Works Association. 1983. Dual Water
Systems. AWWA Manual M24, Denver, Colorado.
American Water Works Association. California-Nevada
Section. 1989. Guidelines for Distribution of Nonpotable
Water.
Ammerman, O.K., and M.G. Heyl. 1991. Planning For
Residential Water Reuse in Manatee County, Florida.
Water Environment & Technology, 3(11).
Ammerman, O.K., and M.A. Hobel. 1991. Managing
Reclaimed Water as a Resource. Florida Water
Resources Journal, August 1991.
Ammerman, O.K., and R.D. Moore. 1991. The City of
Venice Urban Reuse Program. In: Proceedings of the
ASCE Environmental Engineering 1991 Specialty
Conference.
Asano, T. and R.H. Sakaji, 1990. Virus Risk Analysis in
Wastewater Reclamation and Reuse. In: Chemical Water
and Wastewater Treatment, pp. 483-496, H.H. Hahn and
R. Klute (eds.), Springer-Verlay, Berlin.
Bausum, H.T., S.A. Schaub, R.E. Bates, H.L. McKim,
P.W. Schumacher, and B.E. Brockett. 1983.
Microbiological Aerosols From a Field-Source
Wastewater Irrigation System. Journal WPCF, 55(1): 65-
/ o.
Boyle Engineering Corporation. 1981. Evaluation of
Agricultural Irrigation Projects Using Reclaimed Water.
Office of Water Recycling, California State Water
Resources Control Board, Sacramento, California.
Bradby, R.M. and S. Hadidy. 1981. Parasitic Infestation
and the Use of Untreated Sewage for Irrigation of
Vegetables with Particular Reference to Aleppo, Syria.
Public Health Engineer, 9:154-157.
Bryan, F.L. 1974. Diseases Transmitted by Foods
Contaminated by Wastewater. In: Wastewater Use in the
Production of Food and Fiber, EPA-660/2-74-041, U.S.
Environmental Protection Agency, Washington, D.C.
Buchberger, S.G. and Mardment, D.R. 1989a. Design of
Wastewater Storage Ponds at Land Treatment Sites, I:
Parallels With Applied Reservoir Theory. American
Society of Civil Engineers Journal of Environmental
Engineering, 115 (4): 689-703.
Buchberger, S.G. and Mardment, D.R. I989b. Design of
Wastewater Storage Ponds at Land Treatment Sites, II:
Equilibrium Storage Performance Functions. American
Society of Civil Engineers Journal of Environmental
Engineering, 115 (4): 689-703.
Buras, N. 1976. Concentration of Enteric Viruses in
Wastewater Effluent: A Two-Year Study. Water Res.,
10(4): 295-298.
California Department of Health and R.C. Cooper. 1975.
Wastewater Contaminants and Their Effect on Public
Health. In: A "State-of-the-Art" Review of Health Aspects
of Wastewater Reclamation for Groundwater Recharge,
pp. 39-95, State of California Department of Water
Resources, Sacramento, California.
California Department of Health Services. 1990.
Guidelines Requiring Backflow Protection for Reclaimed
Water Use Areas. California Department of Health
Services, Office of Drinking Water, Sacramento,
California.
Camann, D.E., R.J. Graham, M.N. Guentzel, H.J.
Harding, K.T. Kimball, B.E. Moore, R.L. Northrop, N.L.
Altman, R.B. Harrist, A. H. Holguin, R.L. Mason, C.B.
Popescu and C.A. Sorber. 1986. The Lubbock Land
Treatment System Research and Demonstration Project:
Volume IV. Lubbock Infection Surveillance Study. EPA-
600/2-86-027d, U. S. Environmental Protection Agency,
Health Effects Research Laboratory, Research Triangle
Park, North Carolina. NTIS No. PB86-173622.
Camann, D.E. and M.N. Guentzel. 1985. The Distribution
of Bacterial Infections in the Lubbock Infection
Surveillance Study of Wastewater Spray Irrigation. In:
Future of Water Reuse, Proceedings of the Water Reuse
Symposium III, pp. 1470-1495, AWWA Research
Foundation, Denver, Colorado.
Camann, D.E., D.E. Johnson, H.J. Harding, and C.A.
Sorber. 1980. Wastewater Aerosol and School
Attendance Monitoring at an Advanced Wastewater
Treatment Facility: Durham Plant, Tigard, Oregon. In:
Wastewater Aerosols and Disease, pp. 160-179, H.
Pahmer and W. Jakubowski (eds.), EPA-600/9-80-028,
NTIS No. PB81-169864, U.S. Environmental Protection
Agency, Cincinnati, Ohio.
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Camann, D.E. and B.E. Moore. 1988. Viral Infections
Based on Clinical Sampling at a Spray Irrigation Site. In:
Implementing Water Reuse, Proceedings of Water Reuse
Symposium IV, pp. 847-863, AWWA Research
Foundation, Denver, Colorado.
Camann, D.E., B.E. Moore, H.J. Harding and C.A. Sorber.
1988. Microorganism Levels in Air Near Spray Irrigation
of Municipal Wastewater: the Lubbock Infection
Surveillance Study. Journal WPCF, 60:1960-1970.
Camp Dresser & McKee Inc. 1991. Boca Raton Reuse
Master Plan. Prepared forthe City of Boca Raton, Florida,
by Camp Dresser & McKee Inc., Ft. Lauderdale, Florida.
Camp Dresser & McKee Inc. 1990. The City of Venice
Reuse Master Plan. Prepared for the City of Venice,
Florida by Camp Dresser& McKee lnc.,Sarasota, Florida.
Camp Dresser & McKee Inc. 1987. Reclaimed Water
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CHAPTER 3
Types of Reuse Applications
3.1 Introduction
While Chapter 2 provides a discussion of the key
elements of water reuse common to most reuse projects
(i.e., supply and demand, treatment requirements,
storage, distribution), this chapter provides information
specific to the major types of reuse applications:
Q Urban
Q Industrial
Q Agricultural
Q Recreational
Q Habitat restoration/enhancement
Q Groundwater recharge
Q Augmentation of potable supplies
Quantity and quality requirements are considered for
each reuse application, as well as any special
considerations necessary when reclaimed water is
substituted for traditional sources of water. A brief
discussion of potable reuse is also presented. Case
studies of reuse applications are provided in Section 3.8.
3.2 Urban Reuse
Urban reuse systems provide reclaimed waterfor various
nonpotable purposes within an urban area, including:
Q Irrigation of public parks and recreation centers,
athletic fields, school yards and playing fields,
highway medians and shoulders, and
landscaped areas surrounding public buildings
and facilities.
Q Irrigation of the landscaped areas of single-family
and multi-family residences, general washdown,
and other maintenance activities.
Q Irrigation of landscaped areas surrounding
commercial, office, and industrial developments.
Q Irrigation of golf courses.
Q Commercial uses such as vehicle washing
facilities, window washing, mixing water for
pesticides, herbicides, and liquid fertilizers.
Q Ornamental landscape uses and decorative
water features, such as fountains, reflecting
pools and waterfalls.
Q Dust control and concrete production on
construction projects.
Q Fire protection.
Q Toilet and urinal flushing in commercial and
industrial buildings.
Urban reuse can include systems serving large users,
such as parks, playgrounds, athletic fields, highway
medians, golf courses, and recreational facilities; major
water-using industries or industrial complexes; and a
comprehensive combination of residential, industrial, and
commercial properties through "dual distribution
systems."
In dual distribution systems, the reclaimed water is
delivered to the customers by a parallel network of
distribution mains separate from the community's potable
water distribution system. The reclaimed water
distribution system essentially becomes a community's
third water utility (wastewater, potable water, reclaimed
water) and is operated, maintained, and managed in a
manner similar to the potable water system. The oldest
municipal dual distribution in the U.S., in St. Petersburg,
Florida, has been in operation since 1977. The system
provides reclaimed water for a mix of residential
properties, commercial developments, industrial parks, a
resource recovery power plant, a baseball stadium, and
schools.
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During the planning of an urban reuse system, a
community must decide whether or not the reclaimed
water system will be interruptible. Generally, unless
reclaimed water is utilized as the only source of fire
protection in a community, an interruptible source of
reclaimed water is acceptable. The City of St. Petersburg,
Florida, for example, decided that an interruptible source
of reclaimed water would be acceptable, and that
reclaimed water would be utilized only as a backup for
fire protection. If a community determines that a non-
interruptible source of reclaimed water is needed, then
reliability must be provided to ensure a continuous flow
of reclaimed water. Reliability might include more than
one water reclamation plant supplying the reclaimed
water system, as well as additional storage to provide for
fire protection needs in the case of a plant upset.
Retrofitting a developed urban area with a reclaimed
water distribution system can be expensive; in some
cases, however, the benefits of conserving potable water
may justify the cost. For example, the water reuse system
may be cost-effective if it eliminates or forestalls the need
to obtain additional water supplies from considerable
distances or to treat a raw water supply source of poor
quality.
In newly developing urban areas, substantial cost savings
may be realized by installing a dual distribution system as
an integral part of the utility infrastructure as the area
develops and by stipulating connection to the system as
a requirement of the community's land development
code. For example, in 1984 the City of Altamonte Springs
enacted as part of its land development code the
requirement fordevelopersto install reclaimed water lines
so that all properties within the development are provided
service. The section of the code further states that: 'The
intent of the reclaimed water system is not to duplicate
the potable water system, but rather to complement each
other and thereby provide the opportunity to reduce line
sizes and looping requirements of the potable water
system" (Howard, Needles, Tammen, and Bergendoff,
1986a).
The Irvine Ranch Water District in California studied the
economic feasibility of expanding its urban dual
distribution system to provide reclaimed water to high-
rise buildings for toilet and urinal flushing. The study
concluded that use of reclaimed water was feasible for
flushing toilets and urinals and priming floor drain traps
for buildings of six stories and higher (Young and
Holliman, 1990). Following this study, an ordinance was
enacted requiring all new buildings over 55 ft (17 m) high
to install a dual distribution system for flushing in areas
where reclaimed water is available (Irvine Ranch Water
District, 1990).
3.2.1 Reclaimed Water Demand
The daily irrigation demand for reclaimed water
generated by a particular urban system can be estimated
from an inventory of the total irrigable acreage to be
served by the reclaimed water system and the estimated
weekly irrigation rates, determined by such factors as
local soil characteristics, climatic conditions, and type of
landscaping. In some states, recommended weekly
irrigation rates may be available from water management
agencies, county or state agricultural agents, and
irrigation specialists. Reclaimed water demand estimates
must also take into account any other permitted uses for
reclaimed water within the system.
An estimation of the daily irrigation demand of reclaimed
water can also be made by evaluating local water billing
records. For example, in many locations, second water
meters measure the volume of potable water used
outside the home, primarily for irrigation. An evaluation of
the water billing records in Manatee County, Florida, has
shown that the average irrigation demand measured on
the residential second meters is approximately 660 gpd
(2.5 m3/d), compared to 185 gpd (0.7 m3/d) on the first
meter, which measures the amount of water for in-house
uses (COM, 1990b). Using these data to estimate the
daily demand for reclaimed water for residential use
indicates that a 78-percent reduction in residential
potable water demand could be accomplished in
residential areas served by a dual distribution system for
residential irrigation in Manatee County.
Water use records can also be used to estimate the
seasonal variation in reclaimed water demand. Figure 23
shows the historic monthly variation in the potable and
reclaimed water demand for the Irvine Ranch Water
District, while Figure 24 shows the historic monthly
variation in the potable and nonpotable water demand for
St. Petersburg, Florida. Although the seasonal variation
in demand is different between the two communities, both
show a similar trend in the seasonal variation between
the potable and nonpotable demand. Figures 23 and 24
illustrate how fluctuations in potable water demand may
be influenced by nonpotable uses such as irrigation, even
where a significant portion of the potable demand is met
by an alternate source of water.
For potential reclaimed water users such as golf courses
that draw their irrigation water from onsite wells, an
evaluation of the permitted withdrawal rates can be used
to estimate the reclaimed water demand.
In assessing the reuse demand for an urban reuse
system, demands for uses other than irrigation must also
be determined. Demands for industrial users, as well as
commercial users such as car washes, can be estimated
68
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from water use or billing records. Demands for
recreational impoundments can be estimated by
determining the volume of water required to maintain a
desired water elevation in the impoundment.
Figure 23. Potable and Nonpotable Water Use
Monthly Historic Demand Variation
Irvine Ranch Water District
2.0-
!„
0.5-
£
Nonpotable
(1982-89
Avg.)
I I I I I I I I I I I I
JFMAMJJASOND
Source: Irvine Ranch Water District, 1991.
Figure 24. Potable and Nonpotable Water Use
Monthly Historic Demand Variation,
St. Petersburg, Florida
Nonpotable
Demand
(1984-87 Avg.)
Potable
Demand
(1984-87 Avg.)
0.8
n i I i i I I I I I i r
JFMAMJJASOND
Source: Camp Dresser & McKee Inc., 1990b.
For those systems using reclaimed water for toilet
flushing as part of their urban reuse system, water use
records can again be used to estimate this demand.
According to Grisham and Fleming (1989) toilet flushing
can account for up to 45 percent of the indoor residential
water demand. A study conducted by the Irvine Ranch
Water District in 1987 on commercial high-rise water
usage showed that 70 to 85 percent of the water used in
an office high-rise is used for toilet and urinal flushing
(Young and Holliman, 1990).
3.2.2 Reliability and Public Health Protection
In the design of an urban reclaimed water distribution
system, the most important considerations are the
reliability of service and protection of public health.
Treatment to meet appropriate water quality and quantity
requirements and system reliability are addressed in
Section 2.4. The following safeguards must be
considered during the design of any dual distribution
system:
Q Assurance that the reclaimed water delivered to
the customer meets the water quality
requirements for the intended uses,
Q Prevention of improper operation of the system,
Q Prevention of cross connections with potable
water lines, and
Q Prevention of improper use of nonpotable water.
To avoid cross connections, all equipment associated
with reclaimed water systems must be clearly marked.
National color standards have not been established, but
accepted practice by manufacturers and many cities is
purple. A more detailed discussion of distribution
safeguards and cross connection control measures is
presented in Section 2.6.1, Conveyance and Distribution
Facilities.
3.2.3 Design Considerations
Urban water reuse systems have two major components:
Q Water reclamation facilities for reclaimed water
production;
Q Reclaimed water distribution system, including
operational storage and high-service pumping
facilities.
3.2.3.1 Water Reclamation Facilities
Water reclamation facilities must provide the required
treatment to meet appropriate water quality standards for
the intended use. In addition to secondary treatment,
69
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filtration and disinfection are generally required for reuse
in an urban setting. Because urban reuse usually involves
irrigation of properties with unrestricted public access or
other types of reuse where human exposure to the
reclaimed water is likely, reclaimed water must be of a
higher quality than may be necessary for other reuse
applications. On the other hand, where a large customer
needs a higher quality reclaimed water than afforded by
this treatment, the customer may have to provide the
additional treatment onsite, as is commonly done with
potable water. Treatment requirements are presented in
Section 2.4. Figure 25 is aflowdiagramforatypical water
reclamation plant in the reuse system of the Sanitation
Districts of Los Angeles County. Secondary treatment,
filtration, and disinfection are provided, and the sludge is
returned to the trunk sewer for processing at a central
wastewater treatment plant.
3.2.3.2 Distribution System
Operational storage facilities and high-service pumping
are usually located at the water reclamation facility.
However in some cases, particularly for large cities,
operational storage facilities may be located at
appropriate locations on the system and/or near the
reuse sites, and the latter may be provided by the utility or
the customer. When located near the pumping facilities,
ground or elevated tanks may be used; when located
within the system, operational storage is generally
elevated.
Sufficient storage to accommodate diurnal flow variation
is essential in the operation of a reclaimed water system.
The volume of storage required can be determined from
the daily reclaimed water demand and supply curves.
Reclaimed water is normally produced 24 hours/d in
accordance with the diurnal flow at the water reclamation
plant and may flow to ground storage to be pumped into
the system or into a clear well for high-lift pumping to
elevated storage facilities. Covered storage is preferred
to preclude biological growth and maintain a chlorine
residual. Refer to Section 2.6.2 for a discussion of
operational storage.
Since variations in the demand of reclaimed water also
occurseasonally, large volumes of seasonal storage may
also be necessary if all available reclaimed water is to be
used, although this may not be economically practical.
The selected location of the seasonal storage facility will
also have an effect on the design of the distribution
system. A detailed discussion of seasonal storage
requirements is given in Section 2.5.
The design of an urban distribution system is similar in
many respects to that of the municipality's potable water
distribution system, and the use of materials of equal
quality for construction is recommended. System integrity
should be assured; however, the reliability of the system
need not be as stringent as potable water system unless
reclaimed water is being used as the only source of fire
protection. No special measures are required to pump,
deliver, and use the water. Also, no modifications other
than identification of equipment or materials are required
because reclaimed water is being used. However for
service lines in urban settings, different materials may be
desirable for more certain identification.
The design of distribution facilities is based on
topographical conditions as well as reclaimed water
demand requirements. If topography has wide variations,
multi-level systems may have to be used. Distribution
mains must be sized to provide the peak hourly demands
at a pressure adequate for the user being served.
Pressure requirements for a dual distribution system vary
depending on the type of user being served. Pressures
for irrigation systems can be as low as 10 psi (70 kPa) if
additional booster pumps are provided at the point of
delivery, and maximum pressures can be as high as 100
to 150 psi (700 to 1,000 kPa).
The peak hourly distribution mains rate of use, which is a
critical consideration in sizing the delivery pumps and
distribution mains, may best be determined by observing
and studying local urban practices and considering time
of day and rates of use by large users to be served by the
system. The following design peak factors have been
used in designing urban reuse systems:
System Peaking Factor
Altamonte Springs, Florida (HNTB, 1986a) 2.90
Apopka, Florida (Godlewski, etal., 1990) 4.00
Aurora, Colorado (Johns era/., 1987) 2.50
Boca Raton, Florida (COM, 1990a) 2.00
Irvine Ranch Water District (IRWD, 1991)
- Landscape Irrigation 6.80
- Golf Course and Agricultural Irrigation 2.00
Sea Pines, S. C. (Hirsekorn and Ellison, 1987) 2.00
St. Petersburg, Florida (COM, 1987) 2.25
For reclaimed water systems that include fire protection
as part of their service, fire flow plus the maximum daily
demand should be considered when sizing the
distribution system. This scenario is not as critical in sizing
the delivery pumps since it will likely result in less pumping
capacity, but is critical in sizing the distribution mains
because fire flow could be required at any point in the
system, resulting in high localized flows.
The Irvine Ranch Water District Water Resources Master
Plan recommends a peak hourly use factor of 6.8 when
reclaimed water is used for landscape irrigation and a
peakfactorof 2.0 for agricultural and golf course irrigation
70
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Figure 25. Typical Water Reclamation Plant Process for Urban Reuse
Primary
Settling
Tank
To Water
Reuse Sites
To Wastewater Treatment
& Disposal
Wastewater Trunk Sewer
systems (IRWD, 1991). The peak factor for landscape
irrigation is higher because reclaimed water use is
restricted to between 9 p.m. and 6 a.m. This restriction
does not apply to agricultural or golf course use.
Generally, there will be "high-pressure" and "low-
pressure" users on an urban reuse system. The high-
pressure users receive water directly from the system at
pressures suitable for the particular type of reuse.
Examples include residential and landscape irrigation,
industrial process and cooling water, car washes, fire
protection, and toilet flushing in commercial and industrial
buildings. The low-pressure users receive reclaimed
water into an onsite storage pond to be repumped into
their reuse system. Typical low-pressure users are golf
courses, parks, and condominium developments which
utilize reclaimed water for irrigation. Other low pressure
uses include delivery of reclaimed water to landscape or
recreational impoundments.
Typically, urban dual distribution systems operate at a
minimum pressure of 50 psi (350 kPa), which will satisfy
the pressure requirements for irrigation of larger
landscaped areas such as multi-family complexes and
offices, commercial and industrial parks. Based on
requirements of typical residential irrigation equipment, a
minimum delivery pressure of 30 psi (210 kPa) is used for
the satisfactory operation of in-ground residential
irrigation systems. A minimum pressure of 50 psi (350
kPa) should also satisfy the requirements of car washes,
toilet flushing, construction dust control, and some
industrial users.
For users who operate at higher pressures than other
users on the system, additional onsite pumping will be
required to satisfy the pressure requirements. For
example, golf course irrigation systems typically operate
at higher pressures (100-200 psi [700 kPa-1,400 kPa]),
and if directly connected to the reclaimed water system,
will likely require a booster pump station. Repumping may
be required in high-rise office buildings using reclaimed
water for toilet flushing. Additionally, some industrial
users may operate at higher pressures.
The design of a reuse transmission system is usually
accomplished through the use of computer modeling, with
portions of each of the sub-area distribution systems
representing demand nodes in the model. The demand
of each node is determined from the irrigable acreage
tributary to the node, the irrigation rate, and the daily
irrigation time period. Additional demands for uses other
than irrigation, such as fire flow protection, toilet flushing,
and industrial uses must also be added to the appropriate
node.
The two most common methods of maintaining system
pressure under widely varying flow rates are (1) constant-
speed supply pumps and system elevated storage tanks,
which maintain essentially consistent system pressures,
or (2) constant-pressure, variable-speed, high-service
supply pumps, which maintain a constant system
pressure while meeting the varying demand for reclaimed
water by varying the pump speed. While each of these
systems has advantages and disadvantages, either
system will perform well and remains a matter of local
71
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choice. The dual distribution system of the City of
Altamonte Springs, Florida, operates with constant-
speed supply pumps and two elevated storage tanks,
and pressures range between 55 and 60 psi (380 kPa
and 410 kPa). The urban system of the Marin Municipal
Water District, in California, operates at a system
pressure of 50 to 130 psi (350 kPa and 900 kPa),
depending upon elevation and distance from the point of
supply, while Apopka, Florida, operates its reuse system
at a pressure of 60 psi (410 kPa).
The system should be designed with the flexibility to
institute some form of usage control when necessary and
provide for the potential resulting increase in the peak
hourly demand. One such form of usage control would be
to vary the days per week that schools, parks, golf
courses and residential areas are irrigated. In addition,
large users, such as golf courses, will have a major impact
on the shape of the reclaimed water daily demand curve
and hence on the peak hourly demand, depending upon
how the water is delivered to them. The reclaimed water
daily demand curve may be "flattened" and the peak
hourly demand reduced if the reclaimed water is
discharged to golf course ponds over a 24-hour period or
during the daytime hours when demand for residential
landscape irrigation is low. These methods of operation
can reduce peak demands, thereby reducing storage
requirements.
3.3 industrial Reuse
Industrial reuse represents a significant potential market
for reclaimed water in the U.S. and other developed
countries. Although industrial uses accounted for only
about 8 percent of the total U.S. water demands in 1985,
in some states, industrial demands accounted for as
much as 43 percent of a state's total water demands.
Reclaimed water is ideal for many industries where
processes do not require water of potable quality. Also,
industries are often located near populated areas where
centralized wastewater treatment facilities already
generate an available source of reclaimed water.
Reclaimed waterfor industrial reuse may be derived from
in-plant recycling of industrial wastewaters and/or
municipal water reclamation facilities.
Recycling within an industrial plant is usually an integral
part of the industrial process and must be developed on
a case-by-case basis. Industries, such as steel mills,
breweries, electronics, and many others, treat and
recycle their own wastewater either to conserve water or
to meet or avoid stringent regulatory standards for effluent
discharges. This document does not discuss in-plant
recycling; however, ample information and guidelines are
available from industrial associations and regulatory
authorities.
Industrial uses for reclaimed water include:
Q Evaporative cooling water,
Q Boiler-feed water
Q Process water, and
Q Irrigation and maintenance of plant grounds.
Of these uses, cooling water is currently the predominant
industrial reuse application. In most industries, cooling
creates the single largest demand for water within a plant.
According to Keen and Puckorius (1988), a small
petroleum refinery (40,000 barrels/d) or a 250-MW utility
power plant will need about 1 to 2 mgd (44-88 Us) of
makeup water for a recirculating cooling system.
Worldwide, the majority of industrial plants using
reclaimed water for cooling are utility power stations.
3.3.1 Cooling Water
3.3.1.1 Once-Through Cooling Systems
Once-through cooling systems use water to cool the
process equipment and then discharge the heated water
after a single use. Because once-through cooling
systems use such large volumes of water, reclaimed
water is rarely considered afeasible source. For instance,
flow for a once-through cooling system at a typical 1,000-
MW fossil fuel power plant would be approximately 650
mgd (28,500 Us), as compared to recirculating systems,
such as wet towers and cooling ponds that would use
approximately 9 and 6.5 mgd (395 and 285 Us),
respectively (Breitstein and Tucker, 1986).
In the largest single industrial reuse project in the U.S.,
the Bethlehem Steel Company in Baltimore, Maryland,
uses approximately 100 mgd (4,380 L/s) of treated
wastewater effluent from Baltimore's Back River WWTF
for processing and cooling in a once-through system
(Water Pollution Control Federation, 1989). Generally,
however, once-through cooling systems require too large
a volume of water to rely on public water supplies.
Because water quality requirements for these cooling
systems are generally not restrictive, large lakes, rivers,
and even saltwater can be used, in some cases with little,
if any, treatment.
3.3.1.2 Recirculating Cooling Systems
Recirculating cooling systems use water to absorb
process heat, then transfer the heat from the water by
evaporation, and recirculate the water for additional
cooling cycles. This recirculating cooling process may
employ cooling towers or cooling ponds.
72
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a. Cooling Towers
Cooling towers are designed to take advantage of the
water's high heat of evaporation, i.e., one volume of
evaporated water will cause 100 volumes to drop in
temperature by approximately 10°F. Dry air is brought
through the sides or bottom of the tower while water is
pumped to the top of the tower's packing material. The
water is broken into droplets to increase air/water contact,
and then brought into contact with the upcoming air, which
causes a portion of the water to evaporate. The cooled
water droplets collect at the bottom of the tower and then
are recycled.
Evaporation and wind action at the top of the tower (drift)
result in a water loss that must be replaced. To prevent
an unacceptable build-up of salt contaminants due to
evaporation, a portion of the recirculating water is also
continuously wasted as "blowdown," and a source of
make-up water is required. Makeup water must be of high
quality since any contaminants in the water are
concentrated many times during the cooling cycle (Asaho
and Mujeriego, 1988).
Cooling tower make-up water constitutes a large
percentage of the total water used (from 25 to 50 percent)
in such industries as electric power stations, chemical
plants, metal factories, and oil refineries. The cooling
tower recirculating water system is almost always a
closed loop system that is operated as a separate process
with its own characteristic water quality requirements.
The water quality is determined by ascertaining the
concentration of the potential precipitants within the
make-up.
The cycles of concentration, which is defined as the ratio
of a concentration of a given ion or compound in the
blowdown cooling waterto the concentration in the make-
up water, is indicative of the number of times that the
cooling water is recirculated. According to Keen and
Puckorius (1988), most cooling systems are operated in
the range of 5 to 10 cycles of concentration. Above this
range, the small amount of water conserved is rarely
justified by the increased risk of scaling and SS
deposition.
Regulatory constraints on waste discharges often require
treatment of the blowdown water. Treatment methods
vary according to the specific discharge standards and
may include temperature and pH adjustments and ion
exchange for metals removal. The discharge limits and
the costs of removing the contaminants can place limits
on the cycles of concentration.
b. Cooling Ponds
Cooling ponds may also be used as closed recirculating
cooling systems. The pond water serves as the source of
cooling water, and surface evaporation from the pond is
the mechanism for cooling the heat-exchanged water.
The critical parameter in pond design is the surface area
required for cooling the heated water. The approximation
used for power plant cooling ponds is 1 to 3 ac (2.5-7.5
ha)/MW of generated electricity (Gehm, 1976). Cooling
ponds are attractive because of their low capital costs,
large storage capacity, and ability to function without
makeup water for extended periods. However, their
drawbacks include potential groundwater contamination,
large land requirements, and maintenance problems
involving algae and weeds.
The City of Fort Collins, Colorado, supplies reclaimed
water to the Platte River Power Authority for cooling the
250-MW Rawhide energy station (Fooks et a/., 1987).
The recirculating cooling system includes a 5.2-billion gal
(20 million m3) cooling pond to supply 170,000 gpm
(10,700 L/s) to the condenser and auxiliary heat
exchangers. The water reclamation facility provides
complete-mix activated sludge treatment with provisions
for polymer addition, followed by final clarification,
chlorination, and dechlorination with sulfur dioxide.
Additional treatment for phosphorus removal is provided
at the energy station to deliver a maximum phosphorus
concentration of 0.2 mg/L. After about 2 years of
operation, the cooling lake deteriorated in aesthetic
appearance and chemical quality, and a limnological
management program was instituted to provide aeration
and minnow control in the cooling lake.
3.3.1.3 Cooling Water Quality Requirements
The most frequent water quality problems in cooling water
systems are scaling, corrosion, biological growth, fouling,
and foaming. These problems arise from contaminants in
potable water as well as reclaimed water, but the
concentrations of some contaminants in reclaimed water
may be higher. Table 13 lists water quality criteria for
cooling water supplies.
In Burbank, California, about 5 mgd (219 L/s) of municipal
secondary effluent has been successfully utilized for
cooling water make-up in the city's power generating
plant since 1967. The effluent is of such good quality that
treatment consisting of additional chlorine, acid, and
corrosion inhibitors makes the reclaimed water nearly
equal in quality to fresh water.
The City of Las Vegas and Clark County Sanitation
District used 90 mgd (3,940 L/s) of secondary effluent to
supply 35 percent of the water demand in power
generating stations operated by the Nevada Power
73
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Table 13. Recommended Cooling Water Quality Criteria for
Make-Up Water to Reclrculating Systems
Parameter3
Cl
TDS
Hardness
Alkalinity
pHc
COD
TSS
Turbidity0
BOD°
Organics°
NH4 - N°
PO4C
SiOg
Al
Fe
Mn
Ca
Mg
HCO3
SO4
Recommended
Limit5
500
500
650
350
6.9-9.0
75
100
50
25
1.0
1.0
4
50
0.1
0.5
0.5
50
0.5
24
200
UAH values in mg/L except pH.
"Water Pollution Control Federation, 1989.
0 From Goldstein era/., 1979.
°Methylene blue active substances.
Company. The power company provides additional
treatment consisting of two-stage lime softening, filtration,
and chlorination priorto use as cooling tower make-up. A
reclaimed water reservoir provides backup for the water
supply.
In Odessa, Texas, three industries have used
approximately 2.5 mgd (110 L/s) of municipal effluent for
cooling tower make-up and boiler feed for over 20 years.
Secondary effluent is treated by cold lime softening
followed by filtration prior to use by the industries. This
water is used directly for cooling tower make-up; water
use for boiler feed is treated by two-bed demineralization
before use (Water Pollution Control Federation, 1989).
a. Scaling
The cooling water must not lead to the formation of scale,
i.e. hard deposits. Such deposits reduce the efficiency of
the heat exchange. The principal causes of scaling are
calcium (as carbonate, sulfate, and phosphate) and
magnesium (as carbonate and phosphate) deposits.
Scale control for reclaimed water is achieved through
chemical means and sedimentation. Acidification or
addition of scale inhibitors can control scaling. Acids
(sulfuric, hydrochloric, and citric acids and acid gases
such as carbon dioxide and sulfur dioxide) and other
chemicals (chelants such as EDTA and polymeric
inorganic phosphates) are often added to increase the
water solubility of scale-forming constituents, such as
calcium and magnesium (Strauss and Puckorius, 1984).
Lime softening, commonly used to treat reclaimed water
for cooling systems, significantly increases the cycles of
concentration. The lime removes carbonate hardness
and the soda ash removes the noncarbonate hardness.
Other methods used to control scaling are alum treatment
and sodium ion exchange, but the higher costs of these
processes limit their use.
b. Corrosion
The recirculated water must not be corrosive to metal in
the cooling system. High total dissolved solids (TDS)
promotes corrosion by increasing the electrical
conductivity of the water. The concentrations of TDS in
municipally treated reclaimed water, generally two to five
times higher than in potable water, can increase electrical
conductivity and promote corrosion. Dissolved gases and
certain metals with high oxidation states also promote
corrosion.
Corrpsion may also occur when acidic conditions develop
in the cooling water. The Jones Station power plant in
Lubbock, Texas, reported that the ammonia present in
reclaimed water was converted to nitrates in the
recirculating cooling water, resulting in a lowering of the
pH from a range of 7.4 to 7.9 to a value of 6.5 or less. The
pH was adjusted by adding carbon dioxide to increase
the bicarbonate alkalinity of the cooling water (Treweek
etal., 1981).
Corrosion inhibitors such as chromates, polyphosphates,
zinc, and polysillicates can also be used to reduce the
corrosion potential of the cooling water. These
substances may need to be removed from the blowdown
priorto discharge. The alternative to chemical addition is
ion exchange or reverse osmosis, but high costs limit
their use (Strauss and Puckorius, 1984).
c. Biological Growth
Reclaimed water used in cooling systems must not supply
nutrients or organics [biochemical oxygen demand
(BOD)] that promote the growth of slime-forming
organisms. The moist environment in the cooling tower is
conducive to biological growth. Microorganisms can
significantly reduce the heat transfer efficiency, reduce
water flow, and in some cases generate corrosive by-
products (Troscinski and Watson, 1970; California State
Water Resources Control Board, 1980; Goldstein etal.,
1979).
74
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The reduction of BOD and nutrients during treatment
reduces the potential of the reclaimed water to sustain
microorganisms. Chlorine is the most common biocide
used to control biological growth because of its low cost,
availability, and ease of operation. Chlorination is also
used as a disinfectant to reduce potential pathogens in
the reclaimed water. Frequent Chlorination and shock
treatment is generally adequate. Chlorine gas (purchased
as liquid chlorine) is used most often, but it may also be.
applied as sodium hypochlorite as a liquid or solid.
Chlorine dioxide is also frequently used.
At the City of Lakeland, Florida, which uses reclaimed
water from a secondary treatment facility for power plant
-cooling, the system design of four to six cycles was
reduced significantly due to biological growth and fouling
of the cooling tower. Biological mass accumulated in the
tower to such an extent that structural stability was
threatened. The problem was solved by instituting a
pretreatment program to reduce BOD, phosphorus, and
SS (Libey and Webb, 1985).
On the other hand, the Orlando (Florida) Utilities
Commission has reported no biological accumulation or
fouling problems in the cooling system of the C.H. Stanton
energy facility, which uses approximately 5 mgd (219 U
s) of highly treated reclaimed water (5 mg/L BOD, 5 mg/
L TSS, 2 mg/L TN and 1 mg/L P) from an Orange County
WWTF. Prior to use, the energy facility also provides pH
adjustment, rechlorination, scale inhibitors, and anti-
foaming agents.
In Hillsborough County, Florida, a municipal water
reclamation facility provides reclaimed water for cooling
a 1,200-ton/d, waste-to-energy facility and treats the
blowdown water wasted from the cooling towers. The
reclaimed water from the advanced treatment system
meets the following water quality standards: BOD, 20
mg/L; TSS, 5 mg/L; total nitrogen, 20 mg/L;fecal coliform,
<1/100 mL; and pH, 6 to 8.5. The reclaimed water is
treated with additional chemicals at the waste-to-energy
facility to prevent algae growth and biological buildup in
the cooling system. Approximately 330,000 gpd (14 L/s)
of used cooling water is discharged back to the
wastewater treatment plant (Tortora and Hobel, 1990).
d. Fouling
Fouling is controlled by preventing the formation and
settling of paniculate matter. Chemical coagulation and
filtration during the phosphorus removal treatment phase
significantly reduce the contaminants that can lead to
fouling. Chemical dispersants are also used as required.
3.3.2 Boiler-Feed Water
The use of reclaimed water differs little from the use of
conventional public supplies for boiler-feed water; both
require extensive additional treatment. Quality
requirements for boiler-feed make-up water are
dependent upon the pressure at which the boiler is
operated as shown in Table 14. Generally the higher the
pressure, the higher the quality of water required. Very
high pressure boilers require makeup water of distilled
quality.
In general, both potable water and reclaimed water used
for boiler water makeup must be treated to reduce the
hardness of the boiler-feed water to close to zero.
Removal or control of insoluble-salts of calcium and
magnesium and control of silica and aluminum are
required since these are the principal causes of scale
build-up in boilers. Depending on the characteristics of
the reclaimed water, lime treatment (including
flocculation, sedimentation, and recarbonation) might be
followed by multi-media filtration, carbon adsorption, and
nitrogen removal. High purity boiler-feed water for high-
pressure boilers might also require treatment by reverse
osmosis or ion exchange. High alkalinity may contribute
to foaming, resulting in deposits in superheater, reheater,
and turbines. Bicarbonate alkalinity, under the influence
of boiler heat, may lead to the release of carbon dioxide,
which is a source of corrosion in steam-using equipment.
The considerable treatment and the relatively small
amounts of makeup required, make boiler-feed a poor
candidate for reclaimed water.
3.3.3 Industrial Process Water
The suitability of reclaimed water for use in industrial
processes depends upon the particular use. For example,
the electronics industry requires water of almost distilled
quality for washing circuit boards and other electronic
components. On the other hand, the tanning industry can
use relatively low-quality water. Requirements fortextiles,
pulp and paper, and metal fabricating are intermediate.
Thus, in investigating the feasibility of industrial reuse
with reclaimed water, the potential users must be
contacted to determine specific requirements for process
water. Table 15 presents industrial process water quality
requirements for a variety of industries. Table 16
summarizes some of the water quality concerns for
industrial water reuse and potential treatment processes.
3.3.3.1 Pulp and Paper
Reuse of reclaimed water in the paper and pulp industry
is a function of cost and grade of paper. The higher the
quality of paper, the more sensitive to water quality.
Impurities found in water, particularly certain metal ions
and color bodies, can cause the paper produced to
change color with age.
75
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Table 14. Recommended Industrial Boiler-Feed Water Quality Criteria
Parameter*
Silica
Aluminum
Iron
Manganese
Calcium
Magnesium
Ammonia
Bicarbonate
Sulfate
Chloride
Dissolved solids
Copper
Zinc "
Hardness
Alkalinity
pH, units
Methylene blue active substances
Carbon tetrachloride extract
Chemical oxygen demand
Hydrogen sulfide
Dissolved oxygen
Temperature, °F
Suspended Solids
Low
Pressure
(<150 psig)
30
5
1
0.3
**
**
0.1
170
**
**
700
0.5
0.01
350
350
7.0-10.0
1
1
5
**
2.5
**
10
Intermediate
Pressure
(150-700 psig)
10
0.1
0.3
0.1
0.4
0.25
0.1
120
**•
**
500
0.05
0.01
1.0
100
8.2- 10.0
1
1
5
**
0.007
**
5
High
Pressure
(>700 psig)
0.7
0.01
0.05
0.01
0.01
0.01
0.1
48
**
**
200
0.05
0.07
40
8.2 - 9.0
0.5
0.5
1.0
**
0.0007
0.5
* Recommended limits in mg/L except for pH (units) and temperature (°F).
Accepted as received (if meeting other limiting values); has never been a problem at concentrations encountered.
Source: EPA, 1980b.
Major considerations associated with the use of
reclaimed water in the pulp and paper industry include
(Camp Dresser & McKee, 1982):
Q Biological growth may cause clogging of
equipment and odors and may affect the texture
and uniformity of the paper. Chlorination (3 mg/
L residual) has been found adequate to control
micro-organisms.
Q Corrosion and scaling of equipment may result
from the presence of silica, aluminum, and
hardness.
Q Discoloration of paper may occur due to iron,
manganese, or micro-organisms. Suspended
solids may decrease brightness of paper.
3.3.3.2 Chemical Industry
The water quality requirements for the chemical industry
vary greatly according to production requirements.
Generally, waters in the neutral pH range (6.2 to 8.3),
moderately sort, with low turbidity, SS, and silica are
required; dissolved solids and chloride content are not
critical (Water Pollution Control Federation, 1989).
3.3.3.3 Textile Industry
Waters used in textile manufacturing must be
nonstaining; hence, they must be low in turbidity, color,
iron, and manganese. Hardness may cause curds to
deposit on the textiles and may cause problems in some
of the processes that use soap. Nitrates and nitrites may
cause problems in dyeing.
3.3.3.4 Petroleum and Coal
Processes for the manufacture of petroleum and coal
products can usually tolerate water of relatively low
quality. Waters generally must be in the 6 to 9 pH range
and have moderate SS of no greater than 10 mg/L.
3.4 Agricultural Irrigation
Agricultural irrigation represents a significant fraction of
the total demand forf resh water. As discussed in Chapter
2, agricultural irrigation is estimated to represent 40
percent of the total water demand nationwide (Solley et
al., 1988). In western states with significant agricultural
production, the percentage of fresh water used for
irrigation is markedly greater. For example, Figure 26
illustrates the total daily fresh water withdrawals, public
water supply, and agricultural irrigation usage for
76
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Table 15. Industrial Process Water Quality Requirements
Parameter*
Cu
Fe
Mn
Ca
Mg
Cl
HC03
NO3
S04
SiO2
Hardness
Alkalinity
IDS
TSS
Color
PH
CCE
Pulp & Paper
Mechanical Chemical,
pulping unbleached
0.3 1 .0
0.1 0.5
20
12
1 ,000 200
50
100
10
30 30
6-10 6-10
Textiles
Pulp & Paper,
bleached
0.1
0.05
20
12
200
50
100
10
10
6-10
Chemical
0.1
0.1
68
19
500
128
5
100
50
250
125
1,000
5
20
6.2-8.3
Petrochem.
& coal
0.05
1.0
75
30
300
350
1,000
10
6-9
Sizing
suspension
0.01
0.3
0.05
25
100
5
5
Scouring,
bleach & dye
0.1
0.01
25
100
5
5
Cement
2.5
0.5
250
250
35
400
600
500
6.5-8.5
1
*AII values in mg/L except color and pH.
Source: Water Pollution Control Federation, 1989.
Table 16. Industrial Water Reuse Quality Concerns and Potential Treatment Processes
Parameter
Potential Problem
Advanced
Treatment Process
Residual organics
Ammonia
Phosphorus
Suspended solids
Calcium, magnesium,
iron, and silica
Bacterial growth, slime/scale
formation, foaming in boilers
Interferes with formation of free
chlorine residual, causes stress
corrosion in copper-based alloys,
stimulates microbial growth
Scale formation, stimulates
microbial growth
Deposition, "seed" for
microbial growth
Scale formation
Nitrification, carbon
adsorption, ion exchange
Nitrification, ion
exchange, air stripping
Chemical precipitation,
ion exchange, biological
phosphorus removal
Filtration
Chemical softening,
precipitation, ion exchange
Source: Water Pollution Control Federation, 1989.
77
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Irrigation Demand
Public/Domestic Supply
I I Other
Montana, Colorado, Idaho, and California. These states
are the top four consumers of water for agricultural
irrigation, which accounts for more than 90 percent of
their total water demand.
Figure 26. Comparison of Agricultural Irrigation,
Public/Domestic, and Total Freshwater
Withdrawals
40.000
30,000-
20,000_
10.000-
dontana Colorado Idaho California
Source: Solleyefa/., 1988.
The total area in agricultural production in the United
States and Puerto Rico is estimated to be approximately
3.6 billion ac (1.5 billion ha), of which approximately 605
million (245 million ha) are irrigated. Worldwide it is
estimated that irrigation water demands exceed any other
category of use by a factor of 10 (Pair era/., 1983).
A significant portion of existing water reuse systems
supply reclaimed water for agricultural irrigation. In
Florida, agricultural irrigation accounts for approximately
34 percent of the total volume of reclaimed water used
within the state (Florida Department of Environmental
Regulation, 1990). In California, agricultural irrigation
accounts for approximately 63 percent of the total volume
of reclaimed water used within the state (California State
Water Resources Control Board, 1990). Figure 27 shows
the percentages of the types of crops irrigated with
reclaimed water in California.
In California, Florida, and Texas, the following volumes
of reclaimed water are being used for agricultural
irrigation.
State
Agricultural Reuse
mgd m3/s
California
Florida
Texas
150
90
290*
570 x103
340 x103
1.100 X103*
* This is based on the design flow of the WWTP providing water
and may exceed actual use.
Given the high water demands for agricultural irrigation,
the significant water conservation benefits of reuse in
agriculture, and the opportunity to integrate agricultural
reuse with other reuse applications, planning water reuse
programs will often involve the investigation of agricultural
irrigation.
This section discusses the considerations specific to
water reuse programs for agricultural irrigation:
Q Agricultural irrigation demands
Q Reclaimed water quality for agricultural irrigation
Q System design considerations
The technical issues common to all reuse programs are
discussed in Chapter 2, and the reader is referred to the
following subsections for this information: 2.4 - Treatment
Requirements, 2.5 - Seasonal Storage Requirements,
2.6 - Supplemental Facilities (conveyance and
distribution, operational storage, and alternative
disposal).
Figure 27. Agricultural Reuse Categories
by Percent in California
Food Crops
2%
Mixed or
Unknown
44%
Harvested Feed,
Fiber & Seed
37%
Nursery & Sod
2%
Orchards &
Vineyards
Pasture 3%
12%
Source: California State Water Resources
Control Board, 1990.
78
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3.4.1 Estimating Agricultural Irrigation Demands
Because crop water requirements vary with climatic
conditions, the need for supplemental irrigation will vary
from month to month throughout the year. This seasonal
variation is a function of rainfall, temperature, crop type,
and stage of plant growth, and other factors depending
on the method of irrigation being used.
The supplier of reclaimed water must quantify these
seasonal demands, as well as any fluctuation in the
reclaimed water supply, to assure that the demand for
irrigation water can be met. Unfortunately, the agricultural
user is often unable to provide sufficient detail on irrigation
demands for design purposes. The user's seasonal or
even annual water use is seldom measured and
recorded, even where water has been used for irrigation
for a number of years. Expert guidance, however, is
usually available through state colleges and universities
and the local soil conservation service office.
Nevertheless, to assess the feasibility of reuse, the
reclaimed water supplier must be able to reasonably
estimate irrigation demands and reclaimed water
supplies. To make this assessment in the absence of
actual data on an agricultural site's water use,
evapotranspiration, percolation and runoff losses, and net
irrigation must be estimated, often through the use of
predictive equations. As discussed in Section 2.5
(Seasonal Storage), predictive equations may also be
required to model periods of low demand for the purpose
of sizing storage facilities.
Irrigation Requirement
= Evapotranspiration -
precipitation +
surface runoff +
percolation losses +
conveyance and
distribution losses
3.4.1.1 Evapotranspiration
Evapotranspiration is defined as water either evaporated
from the soil surface or actively transpired from the crop.
While the concept of evapotranspiration is easily
described, quantifying the term mathematically is difficult.
It has been suggested that the study and restudy of
evapotranspiration is one of the most popular subjects in
hydrology and irrigation (Jensen etal., 1990).
Evaporation from the soil surface is a function of the soil
moisture content at or near the surface. As the top layer
of soil dries, evaporation decreases. Transpiration, the
water vapor released through the plants' surface
membranes, is a function of available soil moisture,
season, and stage of growth. The rate of transpiration
may be further impacted by soil structure and the salt
concentration in the soil water. Primary factors affecting
evaporation and transpiration are relative humidity, wind,
and solar radiation.
In water-critical regions, the use of weather stations to
generate real-time (daily) estimates of evapotranspiration
is becoming more common. The state of California has
developed the California Irrigation Management
Information System (CIMIS), which allows growers to
obtain daily reference evapotranspiration information
through a computer dial-up service. Data are made
available for numerous locations within the state
according to regions of similar climatic conditions. State
publications provide coefficients for converting these
reference data for use on specific crops, location, and
stages of growth, allowing users to refine irrigation
scheduling and conserve water.
Numerous equations and methods have been developed
to define the evapotranspiration term. A variety of
methods currently used to calculate evapotranspiration
are briefly described below. The reader is referred to
appropriate references for specific equations and more
information on applying these methods.
a. The Penman Equation (Jones et al., 1984;
Withers and Vipond, 1980; Pair et al., 1983,
Jensen et al., 1990)
The Penman equation combines an energy balance with
an experimentally derived aerodynamic equation as a
means of calculating potential evapotranspiration.
Because there is general agreement that the Penman or
a modified form of the Penman equation provides the
most reliable means of estimating evapotranspiration, the
Penman equation is recommended when possible.
However, it is often difficult to obtain the meteorological
data required to calculate this equation. For example,
dew point temperatures are not available in many
locations. In addition, wind speed is normally not
measured at 2 m above a grassed surface at most U.S.
weather stations as required forthis method. Even where
the required data are available, the period of record may
be insufficient to generate a data base sufficient for
statistical analysis.
b. Pan Evaporation Method (Pettygrove and
Asano, 1985; Jones et al., 1984; Withers and
Vipond, 1980; Pair et al., 1983)
An open pan is currently the most widely used method of
estimating evapotranspiration. In addition, there are
numerous locations throughout the U.S. and the world
where pan evaporation data are available for a long
period of record.
The concept of the pan station is straightforward. A pan
of standard dimensions is filled with water and exposed
79
-------
io the atmosphere. The resulting water loss through
evaporation can be measured and, in turn, related to the
consumptive use of a crop under similar conditions. The
advantages of the pan method are simplicity and taw cost.
However, the user must exercise caution in the use of
pan data. A number of different standard pans are now in
use throughout the world, each differing in construction
and each with a different pan coefficient. In addition, pans
are relatively sensitive to location; a pan located within a
large expanse of turf will have significantly lower potential
evaporation than one surrounded by bare soil.
c. Empirical Evaluations of Evapotranspiration
(Jones et al., 1984; Withers and Vipond, 1980;
Pairetal., 1983)
Many empirical methods have been developed to
estimate evapotranspiration. The advantages of these
methods are that they require only commonly measured
data, such as temperature, and most are relatively simple
to calculate. However, the use of a simplified equation to
evaluate the complex process of evapotranspiration has
inherent limitations. When selecting an appropriate
empirical method, the user should identify equations
developed in a similar climate. If possible, the user should
re-evaluate coefficients using local data. In general,
empirical equations using only temperature as a means
of calculating evapotranspiration are not adequate for arid
and semiarid regions (Jensen et al., 1990).
The Thornthwaite and Blaney-Criddle methods of
estimating evapotranspiration are two of the most cited
methods in the literature. The Blaney-Criddle equation
uses percent of daylight hours per month and average
monthly temperature. The Thornthwaite method relies
on mean monthly temperature and daytime hours. In
addition to specific empirical equations, it is quite common
to encounter modifications to empirical equations for use
under specific regional conditions. In selecting an
empirical method of estimating evapotranspiration, the
potential user is encouraged to solicit input from local
agencies familiar with this subject.
3.4.1.2 Effective Precipitation, Percolation and
Surface Water Runoff Losses
Traditionally, the design of land application systems has
attempted to account for the movement of water into and
out of the application site. This approach is oriented to
maximizing hydraulic capacity and, in turn, minimizing
the land required for a given disposal capacity. It is quite
common to find crop selection for land application sites
based on the crop's ability to tolerate extended periods of
excessive soil moisture. Under disposal-oriented design,
as specified in most state regulations, the application of
effluent in a manner resulting in surface runoff is
discouraged or prohibited. However, the designer
typically provides for runoff of rainfall. In many cases,
runoff losses are assumed to be a fixed percentage of
total rainfall throughout the year based on Soil
Conservation Service (SCS) runoff coefficients for a
specific soil type and ground cover.
Percolation losses are generally based on site-specific
investigation of the hydrogeologic conditions of the
selected land application site. The EPA manual Land
Treatment of Municipal Wastewater (EPA, 1981)
recommends that the system percolation losses be
estimated between 4 to 10 percent of the minimum soil
permeability encountered on the site.
The allowable percolation loss from a land application
site is not specifically regulated, but may be indirectly
controlled by groundwater quality regulations. While the
parameters related to maintenance of groundwater
quality may vary from state to state, most areas
specifically require nitrate levels of less than 10 mg/L,
mainly to minimize the possibility of methemoglobinemia
or "blue baby syndrome," which could result from
consumption of groundwater containing elevated levels
of nitrate. This water quality requirement is applicable to
almost all land application systems using municipal
wastewater effluents due to the nitrogen content of the
reclaimed water.
The approach for the beneficial reuse of reclaimed water
will, in most cases, vary significantly from land treatment.
Specifically, the reclaimed water is treated as a resource
to be used judiciously. The prudent allocation of this
resource becomes even more critical in locations where
reclaimed water is assigned a dollar value, thereby
becoming a commodity. Where there is a cost associated
with using reclaimed water, the recipient of reclaimed
water would seek to balance the cost of supplemental
irrigation against the expected increase in crop yields to
derive the maximum economic benefit. Thus, percolation
losses will be minimized because they represent the loss
of water available to the crop and wash fertilizers out of
the root zone. An exception to this occurs when the
reclaimed water has a high salt concentration, and excess
application is required to prevent the accumulation of salts
in the root zone (see Section 3.4.2).
In evaluating the need for supplemental irrigation, it is
desirable to estimate that fraction of the precipitation
which actually becomes available to the crop, called
"effective rainfall." The amount of effective rainfall will be
influenced by rainfall intensity, soil infiltration rates, soil
water storage capacity, management of irrigation water,
and rooting depth of the crop. As with methods of
estimating evapotranspiration, a precise calculation of
effective rainfall is not possible. The SCS has developed
80
-------
an empirical method (USDA, 1967) that provides a
reasonable estimate of effective rainfall; however, site-
specific information should be used if available.
Irrigation demand is that water required to meet the needs
of the crop and overcome system losses. System losses
will consist of percolation, surface water runoff, as well as
transmission and distribution losses. In addition to the
above losses, the application of waterto crops will include
evaporative losses or losses due to wind drift. These
losses may be difficult to quantify individually and are
often estimated in a single system efficiency. The actual
efficiency of a given system will be site specific and will
vary widely depending on management practices
followed. Irrigation efficiencies typically range from 35 to
90 percent (Pettygrove and Asano, 1985). A general
range by type of irrigation system is as follows:
Q Surface (flood) irrigation - 50 - 70 percent
Q Sprinkler irrigation - 65 - 70 percent
Q Drip/trickle irrigation - 85 - 90 percent
Combining the various losses, the net irrigation may also
be written as:
Total Irrigation Demand = (ET - effective rainfall)/
system application efficiency
When using closed pipes to transmit reclaimed water,
water system losses will be similar to those observed in
potable distribution systems and, in most cases, should
not represent a significant portion of the net demand.
System losses may become significant when unlined,
open channels are used to transmit water.
Since there are no hard and fast rules for selecting the
most appropriate methods for projecting irrigation
demands and establishing parameters for system
reliability, it may be prudent to undertake several of the
techniques and to verify calculated values with available
records. In the interest of developing the most useful
models, local irrigation specialists should be consulted.
3.4.2 Reclaimed Water Quality
General treatment requirements to ensure a reliable
reclaimed water suitable for the various reuse
applications are presented in Section 2.4. There are also
some constituents in reclaimed water that have special
significance in agricultural irrigation.
The constituents in reclaimed water of concern for
agricultural irrigation are salinity, sodium, trace elements,
excessive chlorine residual, and nutrients. Sensitivity is
generally a function of a given plant's tolerance to these
constituents encountered in the root zone or deposited
on the foliage. Reclaimed water tends to have higher
concentration of these constituents than the groundwater
or surface water sources from which the water supply is
drawn.
The types and concentrations of constituents in reclaimed
wastewater depend upon the municipal water supply, the
influent waste streams (i.e., domestic and industrial
contributions), amount and composition of infiltration in
the wastewater collection system, the wastewater
treatment processes, and the type of storage facilities. In
most cases, the reclaimed water is of acceptable quality
if the municipal potable source is acceptable. Conditions
which can have an adverse impact on reclaimed water
quality may include:
Q Elevated TDS levels.
Q Industrial discharges of potentially toxic
compounds into the municipal sewer system.
Q Saltwater (chlorides) infiltration into the sewer
system in coastal areas.
3.4.2.1 Salinity
Salinity is the single most important parameter in
determining the suitability of a water for irrigation
(Pettygrove and Asano, 1985). The tolerance of plants to
salinity varies widely. Crops must be chosen carefully to
ensure that they can tolerate the salinity of the irrigation
water, and even then the soil must be properly drained
and adequately leached to prevent salt buildup.
Leaching is the deliberate over-application of irrigation
water in excess of crop needs to establish a downward
movement of water and salt away from the root zone.
The formula for leaching requirement is:
(U.S. Bureau of Reclamation, 1984)
LR = ECiw/ECdwx100
where: ECiw = electrical conductivity of irrigation
water
ECdw = electrical conductivity of drainage
water and is determined by the salt
tolerance of the crop to be grown
The extent of salt accumulation in the soil depends on the
concentration of salts in the irrigation water and the rate
at which it is removed by leaching. Salt accumulation can
be especially detrimental during germination and when
81
-------
plants are young (seedlings), even at relatively low
concentrations. Salinity is usually determined by
measuring the electrical conductivity of the water, yet
salinity may also be reported as TDS. Electrical
conductivity of a water is a quick measure of its total
dissolved salt concentration and is commonly expressed
as ds/m or mmho/cm (Pettygrove and Asano, 1985). The
TDS is commonly expressed as mg/L, a ratio of the weight
of dissolved solids contained in one liter of solution.
The values for electrical conductivity (EC) and TDS are
interchangeable within an accuracy of about +10 percent
(Pettygrove and Asano, 1985). The equations used to
convert EC to TDS is:
TDS (mg/L) x 0.00156 == EC (mmho/cm)
The EC is used as an expression of salinity in the irrigation
water (ECiw), salinity in the saturated extract (ECe), and
salinity in the soil solution (ECss). To determine the ECe,
demineralized water is added to soil until the solid paste
glistens and flows slightly. The soil paste is then filtered
under suction and the solution is obtained and analyzed
for electrical conductivity (Tanji, 1990). Crops are divided
into the four major groups, shown in Figure 28, based on
tolerance to irrigation salinity, leaching fraction, and the
respective root zone salinity (ECe). Note that the leaching
fraction is determined by measuring water infiltration and
estimating evapotranspiration.
Figure 28.
Assessing Crop Sensitivity to
Salinity for Conventional Irrij
Irrigation
•5- 10
9
8
7
6
5
4
1
6
,1?
I
Threshold
Tolerance
of Crops
0.05
Leaching Fraction
0.1 0.2 0.3
(Moderately Tolerant)
(Moderately Sensitive) —
(Sensitive)
I I I I
2 4 6 8 10
Electrical Conductivity of Irrigation Water
(ds/m)
12
Source: Tanji, 1990.
The following is a description of the irrigation water quality
as it relates to salinity for each of the crop groups:
Q Sensitive Crops - The water can be used for
irrigation of most crops on most soils with little
likelihood that soil salinity will develop. Some
leaching is required, butthis occurs under normal
irrigation practices, except in soils of extremely
low permeability.
Q Moderately Sensitive Crops - The water can be
used if a moderate amount of leaching occurs.
Plants with moderate salt tolerance can be grown
in most cases without special practices for
salinity control.
Q Moderately Tolerant Crops - The water cannot
be used on soils with restricted drainage. Even
with adequate drainage, special management
for salinity control may be required, and plants
with good salt tolerance should be selected.
Q Tolerant Crops - The water is not suitable for
irrigation under ordinary conditions, but may be
used occasionally under very special
circumstances. The soils must be permeable,
draining must be adequate, irrigation water must
be applied in excess to provide considerable
leaching, and very salt-tolerant crops should be
selected (Pair etal., 1983).
Figure 29 shows the various crop divisions with a
relationship of percent crop yield to the salinity of
saturated soil extract taken from the root zone (ECe).
Table 17 divides the types of crops into their respective
groups based on salt tolerance at the root zone (ECe). In
addition, a study in St. Petersburg, Florida, found that of
the 205 species of landscape plants reviewed in a
homeowner study, 55 were highly tolerant to reclaimed
water, 108 were tolerant, 39 were found to need extra
maintenance with reclaimed water, and only three
species were not recommended (Parnell, 1987).
The concerns with salinity are its influence on: (1) the
soil's osmotic potential, (2) specific ion toxicity, and (3)
degradation of soil physical conditions that may occur.
These conditions may result in reduced plant growth
rates, reduced yields, and, in severe cases, total crop
failure.
Salinity reduces the water uptake of plants by lowering
the osmotic potential of the soil. This, in turn, causes the
plant to use a large portion of its available energy on
adjusting the salt concentration within its tissue to obtain
adequate water, resulting in less energy available for
82
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plant growth. The problem is greater under hot and dry
climatic conditions, because of greater plant water usage,
and is even more severe when irrigation is inadequate.
Figure 29. Divisions for Classifying Crop
Tolerance of Salinity
100
--80
60
g
JS
&
40
20
Yields Unacceptable
for Most Crops
Sensitive \Moderately\Moderately \ Tolerant
Sensitive \ Tolerant
10
' Source: Tanji, 1990.
15 20 25 30 35
ECe (ds/m)
The concentration of specific ions may cause one or more
of these trace elements to accumulate in the soil and
plant, and long-term buildup may result in animal and
human health hazards or phytotoxicity in plants. When
irrigating with municipal reclaimed water, the ions of most
concern are sodium, chloride, and boron. Household
detergents are usually the source of boron, and water
softeners contribute sodium and chloride. Plants vary
greatly in their sensitivity to specific ion toxicity. Toxicity is
particularly detrimental when crops are irrigated with
overhead sprinklers during periods of high temperature
and low humidity. Highly saline water applied to the
leaves results in direct absorption of sodium and/or
chloride and can cause leaf injury.
3.4.2.2 Sodium
The potential influence sodium may have on soil
properties is indicated by the sodium-adsorption-ratio
(SAR), which is based on the effect of exchangeable
sodium on the physical condition of the soil. The
concentration of sodium in water relative to calcium and
magnesium is expressed as SAR and is calculated as
follows:
SAR =
Na
where ion concentrations, Na, Ca and Mg are
expressed in meq/L
For reclaimed water, it is recommended that the SAR be
adjusted for alkalinity to include a more correct estimate
of calcium in the soil water following irrigation, specifically
adj RNa. The adjusted value is calculated as:
Na
adj
where the Cax value can be determined from
Table 18.
Note that the calculated (adj RNa) is to be substituted for
the SAR value (Pettygrove and Asano, 1985).
Sodium salts influence the exchangeable cation
composition of the soil, which lowers the permeability and
affects the tilth of the soil. This usually occurs within the
first few inches of the soil and is related to high sodium or
very low calcium content in the soil or irrigation water.
Studies have also shown that in soils groups with a very
high amount of organic matter or oxides show little loss of
hydraulic conductivity when saturated with Na and
equilibrated to very low levels of salinity (Tanji, 1990).
Sodium hazard does not impair the uptake of water by
plants but does impair the infiltration of water into the soil.
The growth of plants is thus affected by an unavailability
of soil water (Tanji, 1990). Calcium and magnesium act
as stabilizing ions in contrast to the destabilizing ion (Na)
in regard to the soil structure. They offset the phenomena
related to the distance of charge neutralization for soil
particles caused by excess sodium. Sometimes the
irrigation water may dissolve sufficient calcium from
calcareous soils to decrease the sodium hazard
appreciably. Leaching and dissolving the calcium from
the soil is of little concern when irrigating with reclaimed
water because it is usually high enough in salt and
calcium. Reclaimed water, however, may be high in
sodium relative to calcium and may cause soil
permeability problems if not properly managed.
3.4.2.3 Trace Elements
Trace elements in reclaimed water normally occur in
concentrations less than a few mg/L, with usual
concentrations less than 100 jig/L (Pettygrove and
Asano, 1985). Some are essential for plants and animals
but all can become toxic at elevated concentrations or
doses (Tanji, 1990).
A study in California (Engineering Science, 1987) was
performed to determine if a higher concentration of heavy
83
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Table 17. Crop Salt Tolerance
Sensitive
Bean
Paddy Rice
Sesame
Carrot
Okra
Onion
Parsnip
Pea
Strawberry
Almond
Apple
Apricot
Avocado
Blackberry
Boysenberry
Cherimoya
Sweet Cherry
Sand Cherry
Currant
Gooseberry
Grapefruit
Lemon
Lime
Loquat
Mango
Orange
Passion Fruit
Peach
Pear
Persimmon
Plum; Prune
Pummelo
Raspberry
Rose Apple
White Sapote
Tangerine
Moderately
Sensitive
Broad Bean
Corn
Flax
Millet
Peanut
Sugarcane
Sunflower
Alfalfa
Bentgrass
Angleton Bluestem
Smooth Brome
Buffelgrass
Burnet
Alsike Clover
Ladino Clover
Red Clover
Strawberry Clover
White Dutch Clover
Corn (forage)
Cowpea (forage)
Grass dallis
Meadow Foxtail
Blue Grama
Love Grass
Cicer Milkvetch
Tall Oat Grass
Oats (forage)
Orchard Grass
Rye (forage)
Sesbania
Sirato
Sphaerophysa
Timothy
Big Trefoil
Common Vetch
Broccoli
Brussel Sprouts
Cabbage
Cauliflower
Celery
Sweet Com
Cucumber
Eggplant
Kale
Kohlrabi
Lettuce
Muskmelon
Pepper
Potato
Pumpkin
Radish
Spinach
Scallop Squash
Sweet Potato
Tomato
Turnip
Watermelon
Castorbean
Grape
Moderately
Tolerant
Cowpea
Kenaf
Oats
Safflower
Sorghum
Soybean
Wheat
Barley (forage)
Grass Canary
Hubam Clover
Sweet Clover
Tall Fescue
Meadow Fescue
Harding Grass
Blue Panic Grass
Rape
Rescue Grass
Rhodes Grass
Italian Ryegrass
Perennial Ryegrass
Sundan Grass
Narrowleaf Trefoil
Broadleaf Trefoil
Wheat (forage)
Durum Wheat (forage)
Standard Crested Wheat Grass
Intermediate Wheat Grass
Slender Wheat Grass
Beardless Wild Rye
Canadian Wild Rye
Artichoke
Red Beet
Zucchini Squash
Fig
Jujube
Papaya
Pomegranate
Tolerant
Barley
Cotton
Guar
Rye
Sugar Beet
Triticale
Semi-dwarf Wheat
Durum Wheat
Alkali Grass
Nuttail Alkali
Bermuda Grass
Kallar Grass
Desert Salt Grass
Wheat Grass
Fairway Wheat
Crested Wheat
Tall Wheat Grass
Altai Wild Rye
Russian Wild Rye
Asparagus
Guayule
Jojoba
Source: Tanji, 1990.
84
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Table 18. Salinity of Applied Water (ECW)
(mmho/cm or dS/m)
co
8
Ratio of
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.75
1.0
1.25
1.50
1.75
2.00
2.25
2.50
3.00
3.50
4.00
4.50
5.00
7.00
10.00
20.00
0.1
13.20
8.31
6.34
5.24
4.51
4.00
3.61
3.30
3.05
2.84
2.17
1.79
1.54
1.37
1.23
1.13
1.04
0.97
0.85
0.78
0.71
0.66
0.61
0.49
0.39
0.24
0.2
13.61
8.57
6.54
5.40
4.65
4.12
3.72
3.40
3.14
2.93
2.24
1.85
1.59
1.41
1.27
1.16
1.08
1.00
0.89
0.80
0.73
0.68
0.63
0.50
0.40
0.25
0.3
13.92
8.77
6.69
5.52
4.76
4.21
3080
3.48
3.22
3.00
2.29
1.89
1.63
1.44
1.30
1.19
1.10
1.02
0.91
0.82
0.75
0.69
0.65
0.52
0.41
0.26
0.5
14.40
9.07
6.92
5.71
4.92
4.36
3.94
3.60
3.33
3.10
2.37
1.96
1.68
1.49
1.35
1.23
1.14
1.06
0.94
0.85
0.78
0.72
0.67
0.53
0.42
0.26
0.7
14.79
9.31
7.11
5.87
5.06
4.48
4.04
3.70
3.42
3.19
2.43
2.01
1.73
1.53
1.38
1.26
1.17
1.09
0.96
0.87
0.80
0.74
0.69
0.55
0.43
0.27
1.0
15.26
9.62
7.34
6.06
5.22
4.62
4.17
3.82
3.53
3.29
2.51
2.09
1.78
1.58
1.43
1.31
1.21
1.12
1.00
0.90
0.82
0.76
0.71
0.57
0.45
0.28
2.0
15.91
10.02
7.65
6.31
5.44
4.82
4.35
3.98
3.68
3.43
2.62
2.16
1.86
1.65
1.49
1.36
1.26
1.17
1.04
0.94
0.86
0.79
0.74
0.59
0.47
0.29
3.0
16.43
10.35
7.90
6.52
5.62
4.98
4.49
4.11
3.80
3.54
2.70
2.23
1.92
1.70
1.54
1.40
1.30
1.21
1.07
0.97
0.88
0.82
0.76
0.61
0.48
0.30
4.0
17.28
10.89
8.31
6.86
5.91
5.24
4.72
4.32
4.00
3.72
2.84
2.35
2.02
1.79
1.62
1.48
1.37
1.27
1.13
1.02
0.93
0.86
0.80
0.64
0.51
0.32
5.0
17.97
11.32
8.64
7.13
6.15
5.44
4.91
4.49
4.15
3.87
2.95
2.44
2.10
1.86
1.68
1.54
1.42
1.32
1.17
1.06
0.97
0.90
0.83
0.67
0.53
0.33
6.0
19.07
12.01
9.17
7.57
6.52
5.77
5.21
4.77
4.41
4.11
3.14
2.59
2.23
1.97
1.78
1.63
1.51
1.40
1.24
1.12
1.03
0.95
0.88
0.71
0.56
0.35
8.0
19.94
12.56
9.58
7.91
6.82
6.04
5.45
4.98
4.61
4.30
3.28
2.71
2.33
2.07
1.86
1.70
1.58
1.47
1.30
1.17
1.07
0.99
0.93
0.74
0.58
0.37
Source: Adapted fromSuarez, 1981.
metals could be found in plots irrigated with reclaimed
water vs. well water. After a 5-year period, it was
determined that there were no increasing trends with the
exception of copper, which rose for all water types, yet
still well below the average of California soils. It was
determined that concentrations were so low (below
detection for the most part), that irrigationfor much longer
periods would lead to the same conclusion as the 5-year
test with the exception of iron and zinc (two essential
plant and animal micronutrients). It was found that iron
was more concentrated in plots irrigated with well water
and zinc was greater with the reclaimed water. However,
at the levels found for either, the uptake by plants would
be greater than the accumulation from irrigation input.
In addition, it was found that the input of heavy metals
from commercial chemical fertilizer impurities was far
greater than that contributed by the reclaimed water.
The elements of greatest concern at elevated levels are
cadmium, copper, molybdenum, nickel, and zinc. Nickel
and zinc are of a lesser concern than cadmium, copper
85
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and molybdenum because they have visible adverse
effects in plants at lower concentrations than the levels
harmful to animals and humans. Zinc and nickel toxicity
reduces as pH increases. Cadmium, copper, and
molybdenum, however, can be harmful to animals at
concentrations too low to affect plants.
Copper is not toxic to monogastric animals, but may be
toxic to ruminants. However, theirtolerance increases as
available molybdenum increases. Molybdenum can also
be toxic when available in the absence of copper.
Cadmium is of particular concern as it can accumulate in
the food chain. It does not adversely affect ruminants in
the small amounts they ingest. Most milk and beef
products are also unaffected by livestock ingestion of
cadmium because it is stored in the liver and kidneys of
the animal rather than the fat or muscle tissues.
Table 19 shows EPA's recommended limits for
constituents in irrigation water.
The recommended maximum concentrations for "long-
term continuous use on all soils" are set conservatively,
to include sandy soils that have low capacity to leach with
(and so to sequester or remove) the element in question.
These maxima are below the concentrations that produce
toxicity when the most sensitive plants are grown in
nutrient solutions or sand cultures to which the pollutant
has been added. This does not mean that if the suggested
limit is exceeded that phytotoxicity will occur. Most of the
elements are readily fixed or tied up in soil and
accumulate with time. Repeated applications in excess
of suggested levels might induce phytotoxicity. The
criteria for short-term use (up to 20 years) are
recommended for fine-textured neutral and alkaline soils
with high capacities to remove the different pollutant
elements (EPA, I980b).
3.4.2.4 Chlorine Residual
Free chlorine residual at concentrations less than 1 mg/
L usually poses no problem to plants. However, some
sensitive crops may be damaged at levels as low as 0.05
mg/L. Some woody crops, however, may accumulate
chlorine in the tissue to toxic levels. Excessive chlorine
has a similar leaf-burning effect as sodium and chloride
when sprayed directly on foliage. Chlorine at
concentrations greater than 5 mg/L causes severe
damage to most plants.
3.4.2.5 Nutrients
The nutrients most important to a crop's needs are
nitrogen, phosphorus, potassium, zinc, boron and sulfur.
Reclaimed water usually contains enough of these
nutrients to supply a large portion of a crop's needs.
The most beneficial nutrient is nitrogen. Both the
concentration and form of nitrogen need to be considered
in irrigation water. While excessive amounts of nitrogen
stimulate vegetative growth in most crops, they may also
delay maturity and reduce crop quality and quantity. In
addition, excessive nitrate in forages can cause an
imbalance of nitrogen, potassium, and magnesium in the
grazing animals and is a concern if the forage is used as
a primary feed source for livestock; however, such high
concentrations are usually not expected with municipal
reclaimed water.
The nitrogen in reclaimed water may not be present in
concentrations great enough to produce satisfactory crop
yields, and some supplemental fertilizer may be
necessary. This is the case in Tallahassee, Florida, where
a farmer leases city-owned land supplied with reclaimed
water via a center-pivot irrigation system. Even though
the irrigation rate exceeds the crops'consumptive needs,
the dilute nature of the nitrogen (approximately 18 mg/L)
requires supplemental fertilizers at certain times of the
year (Allhands and Overman, 1989).
Soils in the western U.S. may contain enough potassium,
while many sandy soils of the southern U.S. do not, yet in
either case, the addition of potassium with reclaimed
water has little effect on the crop. Phosphorus contained
in reclaimed water is usually too low to meet a crop's
needs; yet overtime it can build up in the soil and reduce
the need for phosphorus supplementation. Excessive
phosphorus does not appear to pose any problem to
crops, but can be a problem in runoff to surface waters.
Numerous site specific studies have been conducted
regarding the potential water quality concerns associated
with reuse irrigation. A survey of agricultural systems
operating in California found no indications that crop
quality or quantity had deteriorated as a result of
reclaimed water irrigation. In fact, several of the farmers
using reclaimed water felt that crop production had been
enhanced as a result of nutrients in the water (Boyle
Engineering Corporation, 1981). Studies of the
Tallahassee, Florida spray irrigation system noted that
after 5 years of irrigation, steady state conditions with
respect to ionic species on soils exchange site had not
come to a steady state, but no adverse impacts on
agricultural production were expected (Payne and
Overman, 1987). These and other investigations suggest
that reclaimed water will be suitable for most agricultural
irrigation needs.
3.4.3 Other System Considerations
In addition to irrigation supply and demand and reclaimed
water quality requirements, there are other
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Table 19. Recommended Limits for Constituents in Reclaimed Water for Irrigation
TRACE HEAVY METALS
Constituent
Long-Term Use Short-Term Use
(mg/L) (mg/L)
Remarks
Aluminum
Arsenic
Beryllium
Boron
Cadmium
Chromium
Cobalt
Copper
Fluoride
Iron
Lead
Lithium
Manganese
Molybdenum
Nickel
Selenium
5.0
0.10
0.10
0.75
0.01
0.1
0.05
0.2
1.0
5.0
5.0
2.5
0.2
0.01
0.2
0.02
Tin, Tungsten, & Titanium —
Vanadium 0.1
Zinc 2.0
OTHER PARAMETERS
20 Can cause nonproductivity in acid soils, but soils at pH 5.5 to 8.0 will precipitate the ion and
eliminate toxicity.
2.0 Toxicity to plants varies widely, ranging from 12 mg/L for Sudan grass to less than 0.05 mg/L for
rice.
0.5 Toxicity to plants varies widely, ranging from 5 mg/L for kale to 0.5 mg/L for bush beans.
2.0 Essential to plant growth, with optimum yields for many obtained at a few-tenths mg/L in nutrient
solutions. Toxic to many sensitive plants (e.g., citrus) at 1 mg/L. Usually sufficient quantities in
reclaimed water to correct soil deficiencies. Most grasses relatively tolerant at 2.0 to 10 mg/L.
0.05 Toxic to beans, beets, and turnips at concentrations as low as 0.1 mg/L in nutrient solution.
Conservative limits recommended.
1.0 Not generally recognized as essential growth element. Conservative limits recommended due
to lack of Knowledge on toxicity to plants.
5.0 Toxic to tomato plants at 0.1 mg/L in nutrient solution. Tends to be inactivated by neutral and
alkaline soils.
5.0 Toxic to a number of plants at 0.1 to 1.0 mg/L in nutrient solution.
15.0 Inactivated by neutral and alkaline soils.
20.0 Not toxic to plants in aerated soils, but can contribute to soil acidification and loss of essential
phosphorus and molybdendum.
10.0 Can inhibit plant cell growth at very high concentrations.
2.5 Tolerated by most crops at up to 5 mg/L; mobile in soil. Toxic to citrus at low doses -
recommended limit is 0.075 mg/L.
10.0 Toxic to a number of crops at a few-tenths to a few mg/L in acid soils.
0.05 Nontoxic to plants at normal concentrations in soil and water. Can be toxic to livestock if forage
is grown in soils with high levels of available molybdenum.
2.0 Toxic to a number of plants at 0.5 to 1.0 mg/L; reduced toxicity at neutral or
alkaline pH.
0.02 Toxic to plants at low concentrations and to livestock if forage is grown in soils with low levels
of added selenium.
— Effectively excluded by plants; specific tolerance levels unknown
1.0 Toxic to many plants at relatively low concentrations.
10.0 Toxic to many plants at widely varying concentrations; reduced toxicity at
increased pH (6 or above) and in fine-textured or organic soils.
Constituent
Recommended Limit
Remarks
pH
TDS
Free Chlorine Residual
6.0
500-2,000 mg/L
< 1 mg/L
Most effects of pH on plant growth are indirect (e.g., pH effects on heavy metals' toxicity
described above).
Below 500 mg/L, no detrimental effects are usually noticed. Between 500 and 1,000 mg/L, TDS
in irrigation water can affect sensitive plants. At 1,000 to 2,000 mg/L, TDS levels can affect
many crops and careful management practices should be followed. Above 2,000 mg/L, water
can be used regularly only for tolerant plants on permeable soils.
Source: Adapted from EPA, 1973.
87
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considerations specific to agricultural water reuse that
must be addressed. Both the user and supplier of
reclaimed water may have to consider modifications in
current practice that may be required to use reclaimed
water for agricultural irrigation. The extent to which
current irrigation practices must be modified to make
beneficial use of reclaimed water will vary on a case-by-
case basis. This requires that those investigating
reclaimed water programs have a working knowledge of
the appropriate regulations, crop requirements, and
means of application. Important considerations include:
Q System reliability,
Q Site use control,
Q Monitoring requirements,
Q Runoff controls,
Q Marketing incentives, and
Q Irrigation equipment.
3.4.3.1 System Reliability
Two basic issues are involved in system reliability. First,
as in any reuse project, when irrigation is implemented as
a means of reducing or eliminating surface water
discharge, the treatment and distribution facilities must
operate reliably to meet permit conditions. Second, the
supply of reclaimed water to the agricultural user must be
reliable in quality and quantity for successful use in a
farming operation.
Reliability in quality involves providing the appropriate
treatment forthe intended use, with special consideration
of crop sensitivities and potential toxicity effects of the
constituents in reclaimed water (see Sections 2.4 and
3.4.2) Reliability in quantity involves balancing supply
with irrigation demand, largely accomplished by providing
sufficient operational and seasonal storage facilities (see
Sections 2.5 and 2.6.2).
It is also necessary to ensure that the irrigation system
itself can reliably accept the intended supply to minimize
the need for discharge or alternate disposal. In 1985 in
Santa Rosa, California, the city exceeded its effluent
discharge limits in part because the irrigation systems on
the private farms were not able to distribute sufficient
f lows (Fox et a/., 1987).
In some cases, provisions may have to be made to
supplement reclaimed water with another source to
ensure that adequate supplies are available for peak
demands. For example, to meet the occasional peak
water demands associated with freeze protection of 27
citrus groves in the joint Orange County/Orlando, Florida
Conserv II, water reuse program, 23 back-up irrigation
wells were constructed, providing a peak well water flow
of 51,000 gpm (3,220 Us) (Cross etal., 1992). The Walnut
Valley Water District water reuse system in California also
provides back-up wells to ensure demands can be met.
As an interim solution until the wells went on line, two
connections to the potable system were provided for
emergency use (Cathcart and Biederman, 1984).
3.4.3.2 Site Use Control
Many states require a buffer zone around areas irrigated
with reclaimed water. The size of this buffer zone is often
associated with the level of treatment the reclaimed water
has received and the means of application. Additional
controls may include restrictions on the times irrigation
can take place and restrictions on the access to the
irrigated site. Such use area controls may require
modification of existing farm practices and limit the use of
reclaimed water to areas where required buffer zones
can be provided. See Chapter 4 for a discussion of the
different buffer zones and use controls specified in state
regulations. Signs specifying that reclaimed water is
being used may be required to prevent accidental contact
or ingestion.
3.4.3.3 Monitoring Requirements
Monitoring requirements for reclaimed water use in
agriculture differ by state (see Chapter 4). In most cases,
the supplier will be required to sample the reclaimed water
quality at specific intervals for specific constituents at the
water reclamation plant and, in some cases, in the
distribution system.
Groundwater monitoring is often required at the
agricultural site, with the extent depending on the
reclaimed water quality and the hydrogeology of the site.
Groundwater monitoring programs may be as simple as
a series of surficial wells to a complex arrangement of
wells sampling at various depths. In locations of karst
topography, where reclaimed water may percolate into
underground sources of drinking water, reuse may be
limited and in some cases prohibited.
Monitoring must be considered in estimating the capital
and operating costs of the reuse system, and a complete
understanding of monitoring requirements is needed as
part of any cost/benefit analysis.
3.4.3.4 Runoff Controls
Some irrigation practices, such flood irrigation, result in a
discharge of irrigation water from the site (tail water).
Regulatory restrictions of this discharge may be few or
none when using surface water or groundwater sources;
however, when reclaimed water is used, runoff controls
88
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may be required to prevent discharge or a National
Pollutant Discharge Elimination System (NPDES) permit
may be required for a discharge to a surface water.
3.4.3.5 Marketing Incentives
In many cases, an existing agricultural site will have an
established source of irrigation water, which has been
developed by the user at some expense (e.g.,
engineering, permitting and construction). In some
instances, the user may be reluctant to abandon these
facilities for the opportunity to use reclaimed water.
Reclaimed water use must then be economically
competitive with existing irrigation practices or must
provide some other benefits. For example, reclaimed
water may extend an agricultural user's supply, allowing
the user to expand production or plant a more valuable
crop. Where irrigation is restricted as a water
conservation measure in arid climates and during drought
in other regions, reclaimed water can provide a
dependable source for irrigation. Reclaimed water may
also be of better quality than that water currently available
to the farmer, and the nutrients may provide some
fertilizer benefit.
In some instances, the supplier of reclaimed water may
find it cost effective to subsidize reclaimed water rates to
agricultural users if reuse is allowing the supplierto avoid
higher treatment costs associated with alternative means
of disposal. Rates and fees for reuse systems are
discussed in Chapter 6.
Agricultural users will also expect assurance that
reclaimed water will be beneficial to their crops and
capable of producing a wholesome and valuable product.
In some cases, a pilot project may be in order.
In the early 1980s, the Irvine Ranch Water District in
Orange County, California, investigated the use of
reclaimed water for the irrigation of strawberries. Field
studies indicated that over the course of the season,
yields for test and control plots were similar. However,
the elevated concentrations of sodium and chloride in the
reclaimed water resulted in reduced yields early in the
season. Early season berries were being sold as fresh
fruit for approximately $8.60/tray. The late season berries
typically were frozen and sold for approximately $3.60/
tray. Even with equal yield forthe total season, the shifting
of berry production from early to late season posed a
marketing problem forthis application (Hyde and Young,
1984).
3.4.3.6 Irrigation Equipment
By and large, few changes in equipment are required to
use reclaimed water for agricultural irrigation. There are,
however, some considerations for certain irrigation
systems.
As previously noted, surface irrigation systems (ridge and
furrow, graded borders) normally result in the discharge
of a portion of the irrigation water from the site. Where
discharge is not permitted with reclaimed water, some
method of tailwater return or pump back may be required.
In sprinkler systems, dissolved salts and paniculate
matter may cause clogging, depending on the
concentration of these constituents and the nozzle size.
Studies in the Napa Sanitation District, California,
indicated plugging of nozzles as small as 5/32-in (4-mm)
diameter was not a serious problem with reclaimed water
from an oxidation pond (Thornton et al., 1984). In the
Lubbock, Texas land treatment system, the use of a
storage reservoir prior to irrigation greatly reduced nozzle
clogging from trickling filter effluent. The quiescent
reservoir allowed plastic fragments and other solid
particles to settle out prior to irrigation. An unfortunate
side effect of using the storage pond, however, was the
loss of approximately 71 percent of the nitrogen value of
the water (George et al., 1984).
Because water droplets or aerosols from sprinkler
systems are subject to wind drift, the use of reclaimed
water may necessitate the establishment of buffer zones
around the irrigated area. In some types of systems (i.e.,
center pivots), the sprinkler nozzles may be dropped
closer to the ground to reduce aerosol drift and thus
minimize the buffer requirements. In addition, sprinkler
irrigation of crops to be eaten raw is restricted by some
regulatory agencies as it results in the direct contact of
reclaimed water with the fruit.
Micro-irrigation systems apply water at slow rates
frequently, on or beneath the soil surface. Water is
applied as drops, minute streams, or miniature sprays
through closely spaced emitters attached to water
delivery lines or via miniature spray nozzles. The conduits
on which the emitters or miniature sprinklers are mounted
are usually on the soil surface within the diameter of the
root zone. The conduits may be buried at shallow depths
or attached to trees for certain applications such as
orchards. An extremely efficient form of irrigation, micro-
irrigation systems are usually used in areas where water
is scarce or expensive; soils are sandy, rocky, or difficult
to level; or where crops require a high degree of soil
moisture control.
When reclaimed water is used in a micro-irrigation
system, a good filtration system is required to prevent
complete orpartial clogging of emitters, and close, regular
inspections of emitters are required to detect emitter
89.
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clogging. In-line filters of a 80 to 200 mesh are typically
used to minimize clogging. In addition to clogging,
biological growth within the transmission lines and at the
emitter discharge may be increased by nutrients in the
reclaimed water. Due to low volume application rates with
micro-irrigation, salts may accumulate at the wetted
perimeterof the plants and then be released attoxic levels
to the crop when leached via rainfall.
3.5 Habitat Restoration/Enhancement
and Recreational Reuse
Uses of reclaimed water for recreational and
environmental purposes range from the maintenance of
landscape ponds, such as water hazards on golf course
fairways, to full-scale development of water-based
recreational sites for swimming, fishing, and boating. In
between lies a gamut of possibilities that includes
ornamental fountains, snowmaking, rearing of freshwater
sport fish, and the creation of marshlands to serve as
wildlife habitat and refuges. As with any form of reuse, the
development of recreational and environmental water
reuse projects will be a function of a water demands
coupled with a cost-effective source of reclaimed water
of suitable quality.
As discussed in Chapter4, many states have regulations
specifically addressing recreational and environmental
uses of reclaimed water. For example, California's
recommended treatment train for each type of
recreational water reuse is linked to the degree of body
contact in that use (that is, to what degree swimming and
wading are likely). Secondary treatment and disinfection
to 2.2 total coliforms/100 mL is required for recreational
water bodies where fishing, boating, and other non-body
contact activities are permitted. And, for nonrestricted
recreational use that includes wading and swimming,
treatment of secondary effluent is to be followed by
coagulation, filtration and disinfection to achieve 2.2 total
coliforms/100 mL and a maximum of 23 total conforms/
100 mL in any one sample taken during a 30-day period.
The primary purpose of the coagulation step is to reduce
SS and, thereby, to improve the efficiency of virus
removal by chlorination.
In California, approximately 7 percent of the total reuse
within the state was associated with recreational and
environmental reuse in 1987 (California State Water
Resources Control Board, 1990). In Florida,
approximately 9 percent of the reclaimed water currently
produced is being used for environmental enhancements,
all for wetlands restoration (Florida Department of
Environmental Regulation, 1990).
The remainder of this section provides an overview of the
following environmental and recreational uses:
Q Creation or enhancement of wetlands habitat
Q Recreational and aesthetic impoundments
Q Stream augmentation
Q Other recreational uses
The objectives of these reuse projects are typically to
create an environment in which wildlife can thrive and/or
to develop an area of enhanced recreational or aesthetic
value to the community through the use of water.
3.5.1 Natural and Manmade Wetlands
Over the last 200 years, approximately 50 percent of the
wetlands in the continental United States have been
destroyed for such diverse uses as agriculture, mining,
forestry, and urbanization. Approximately 109 million ac
(44 million ha) of the original 215 million ac (87 million ha)
of wetlands have been destroyed with an additional
370,000 to 555,000 (150,000 to 225,000 ha) destroyed
each year (Hammer, 1989). Wetlands provide many
worthwhile functions, including flood attenuation, wildlife
and waterfowl habitat, productivity to support food chains,
aquifer recharge, and water quality enhancement. In
addition, the maintenance of wetlands in the landscape
mosaic is important for the regional hydrologic balance.
Wetlands naturally provide water conservation by
regulating the rate of evapotranspiration and in some
cases by providing aquifer recharge. The deliberate
application of reclaimed water to wetlands can be a
beneficial use (and therefore reuse) because the
wetlands are maintained so that they may provide these
valuable functions.
Reclaimed water has been applied to wetlands for three
main objectives:
Q To create, restore, and/or enhance wetlands
systems;
Q To provide additional treatment of reclaimed
water prior to discharge to a receiving water
body; and
Q To provide a wet weather disposal alternative for
a water reuse system (see Section 2.6.3).
For wetlands that have been altered hydrologically,
application of reclaimed water serves to restore and
enhance the wetlands. New wetlands can be created
through application of reclaimed water, resulting in a net
gain in wetland acreage and functions. In addition,
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manmade and restored wetlands can be designed and
managed to maximize habitat diversity within the
landscape.
The application of reclaimed water to wetlands is a good
example of providing for compatible uses. Wetlands are
often able to enhance the water quality of the reclaimed
water without creating undesirable impacts to the
wetlands system, thereby enhancing downstream natural
water systems and providing concomitant aquifer
recharge.
Water quality enhancement is provided by transformation
and/or storage of specific components within the wetland.
The maximum contact of reclaimed water within the
wetland will ensure maximum nutrient assimilation. This
is due to the nature of the assimilation process. If optimum
conditions are maintained, nitrogen and BOD assimilation
in wetlands will occur indefinitely, as they are primarily
controlled by microbial processes. In contrast,
phosphorus assimilation in wetlands is finite and is related
to the adsorption capacity of the soil. The wetland will
provide additional water quality enhancement to the high
quality reclaimed water product.
In most reclaimed water to wetlands projects described
in the literature, the primary intent is to provide additional
treatment of effluent prior to discharge. However, this
focus does not negate the need for design considerations
that will maximize wildlife habitats, thereby resulting in an
environmentally valuable system. Appropriate plant
species should be selected based on the quality and
quantity of reclaimed water applied to the wetland system.
A salinity evaluation on any created wetlands should also
be performed since highly saline wetlands often exhibit
limited vegetative growth. Such design considerations
will seek to balance the hydraulic and constituent loadings
with the needs of the ecosystem. Protection of
groundwater quality should also be considered.
Wetlands enhancement systems developed to provide
wildlife habitats as well as treatment are illustrated by
Arcata, California, and Orlando, Florida. In the Arcata
program, one of the main goals of the project was the
enhancement of the beneficial uses of the downstream
surface waters. A wetlands application system was
selected because the wetlands: (1) serve as nutrient sinks
and buffer zones, (2) have aesthetic and environmental
benefits, and (3) can provide cost-effective treatment
through natural systems. The Arcata wetlands system
was also designed to function as a wildlife habitat. The
Arcata wetland system, consisting of three 10-ac (4-ha)
marshes, has attracted more than 200 species of birds,
provided a fish hatchery for salmon, and was a direct
contributor to the development of the Arcata Marsh and
Wildlife Sanctuary (Gearheart, 1988).
Due to a 20-mgd (877 Us) expansion of the City of
Orlando Iron Bridge Regional Water Pollution Control
Facility in 1981, a wetland system was created to handle
the additional flow. Since 1981, reclaimed water from the
Iron Bridge Plant has been pumped 16 mi (20 km) to the
wetland that was created by diking approximately 1,200
ac (480 ha) of improved pasture. The system is further
divided into smaller cells forf low and depth management.
The wetland consists of three major vegetative areas.
Thefirst area, approximately 420 ac (170 ha), is a shallow
marsh consisting primarily of cattails and bulrush and with
nutrient removal as the primary function. The second area
consists of 380 ac (150 ha) of a variety of mixed marsh
species utilized for nutrient removal and wildlife habitat.
The final area, 400 ac (160 ha) of hardwood swamp,
consists of a variety of tree species providing nutrient
removal and wildlife habitat. The reclaimed water then
flows through approximately 600 ac (240 ha) of natural
wetland priorto discharge to the St. Johns River (Lothrop,
n.d.)
A number of states provide regulations which specifically
address the use of reclaimed water in wetlands systems,
including Arizona, Florida, and South Dakota. Where
specific regulations are absent, wetlands have been
constructed on a case-by-case basis. In addition to state
requirements, natural wetlands, which are considered
waters of the United States, are protected under EPA's
NPDES Permit and Water Quality Standards programs.
The quality of the reclaimed water entering natural
wetlands is regulated by federal, state and local agencies
and must be treated to at least secondary treatment levels
or greater to meet water quality standards. Constructed
wetlands, on the other hand, which are built and operated
for the purpose of treatment only, are not considered
waters of the United States. As a result, the application of
primary effluent discharge into constructed wetlands to
meet secondary effluent standards has been utilized in
some instances.
3.5.2 Recreational and Aesthetic Impoundments
For the purposes of this discussion, an impoundment is
defined as a manmade water body. The use of reclaimed
water to augment natural water bodies is discussed in
Section 3.5.3. Impoundments may serve a variety of
functions from aesthetic, non-contact uses, to boating
and fishing, to swimming. As with other uses of reclaimed
water, the required level of treatment will vary with the
intended use of the water. As the potential for human
contact increases, the required treatment levels increase.
The appearance of the reclaimed water must also be
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considered when used for impoundments, and treatment
for nutrient removal may be required as a means of
controlling algae. Without nutrient control there is a high
potential for algae blooms, resulting in odors, an unsightly
appearance, and eutrophic conditions. Phosphorous is
generally the nutrient limited as a means of controlling
algae in fresh water impoundments (Water Pollution
Control Federation, 1989).
Reclaimed water impoundments can be easily
incorporated into urban developments. For example,
landscaping plans for golf courses and residential
developments commonly integrate water traps or ponds.
These same water bodies may also serve as a storage
facilities for irrigation water within the site.
In Las Colinas, Texas, the design for a 12,000-ac (4,800
ha) master planned development included a series of
manmade lakes [19 lakes covering 270 ac (110 ha)] for
aesthetic enhancement. Lake levels are maintained with
reclaimed water supplemented by water from the Elm
Fork of the Trinity River. Six fountain type aerators were
installed to enhance and maintain water quality (Smith et
a/., 1990)
In Santee, California, reclaimed water has been used to
supply recreational lakes for boating and fishing since
1961. Five lakes are served with reclaimed water with a
total surface area of approximately 30 ac (12 ha). High
nutrient levels in the reclaimed water promote algae and
aquatic weed growth in the first two lakes; however, algae
and other plant control through chemicals and
mechanical harvesting is practiced. The lakes have
become a part of a widely used and popular recreational
area for local residents (Water Pollution Control
Federation, 1989).
In Lubbock, Texas, approximately 4 mgd (175 Us) of
reclaimed water is used for recreational lakes in the
Yeltowhouse Canyon Lakes Park (Water Pollution
Control Federation, 1989). The canyon, which was
formerly used as a dump, was restored through the use
of reclaimed waterto provide water-oriented recreational
activities. Four lakes, which include man-made waterfalls,
are utilized forfishing, boating and water skiing; however,
swimming is restricted.
The Tillman Water Reclamation Plant in Los Angeles,
California is providing 8 mgd (350 L/s) of reclaimed water
to fill the 26-ac (11-ha) Sepulveda Wildlife Lake. The
Sepulveda Lake was created to provide a way station for
migratory birds that travel through the Los Angeles area.
A walking path has also been provided along the lake for
wildlife viewing. Once the lake is filled, the amount of
reclaimed water provided to the lake is reduced to 5 mgd
(219 L/s) (Office of Water Reclamation - City of Los
Angeles, 1991).
3.5.3 Stream Augmentation
Stream augmentation is differentiated from a surface
water discharge in that augmentation seeks to
accomplish a beneficial end, whereas discharge is
primarily for disposal. Stream augmentation may be
desirable to maintain stream flows and to enhance the
aquatic and wildlife habitat as well as to maintain the
aesthetic value of the watercourses. This may be
necessary in locations where a significant volume of
water is drawn for potable or other uses, significantly
reducing the downstream volume of water in the river.
As with impoundments, the water quality requirements
for stream augmentation will be based upon the
designated use of the stream as well as the aim to
maintain an acceptable appearance. In addition, there
may be an emphasis on creating a product that can
sustain aquatic life. To achieve aesthetic goals, studies
in Kawasaki City, Japan, suggest that both phosphorus
removal and high-level disinfection are required.
However, to ensure that aquatic life is maintained, ozone
is used in place of chlorine as a disinfectant (Kuribayashi,
1990).
In Japan, an appreciable amount of reclaimed water is
being used for augmenting streams in urban areas and
for creating ornamental streams and lakes (Murakami,
1989). Many streams and channels within urbanized
Japanese cities dry up periodically as a result of changes
in surrounding land use. Restoring these streams to
productive water bodies has become important as people
within the cities place more importance on a better
environment. A typical project of this kind is illustrated by
the restoration of the Nobidome and Tanagawa channels
in metropolitan Tokyo. Originally constructed for water
supply in the 17th century, these channels have lost all or
most of their flow as a result of modern water
transportation systems. The discharge of filtered
secondary reclaimed water was begun in the early 1980s
as a means of restoring these streams. Maintenance of
the channels, primarily cleaning out trash and fallen
leaves, is performed in cooperation with the local
residents. The Nobidome receives approximately 4 mgd
(175 L/s) and the Tanagawa approximately 3.5 mgd (153
L/s). Reaction from the surrounding urban population has
been quite favorable (Murakami, 1989).
Several agencies in southern California are evaluating
the process in which reclaimed water would be delivered
to streams in order to maintain a constant high-quality
flow of water for the enhancement of the aquatic and
wildlife habitat as well as to maintain the aesthetic value
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of the streams. Reclaimed water delivered to these
streams would also receive the benefit of additional
treatment through natural processes (Crook, 1990).
3.5.4 Other Recreational Uses
Other recreational uses of reclaimed water that are
beginning to gain recognition include the rearing of
freshwater sport fish and snowmaking. Commercial fish
production in reclaimed water impoundments is a widely
used practice in Israel and China (Crook, 1990). Large-
scale fish production with reclaimed water is currently
being investigated in the United States and has the
potential of providing a significant future use. Most
recreational impoundments that utilize reclaimed water
in the United States currently allow the use of fishing
within the impoundment. When fish taken from an
impoundment comprised entirely of reclaimed water are
used for human consumption, the quality of the reclaimed
water should be thoroughly assessed (chemical and
microbiological quality) for possible bioaccumulation of
toxic contaminants through the food chain.
The use of reclaimed waterf or snowmaking was originally
studied as a means of storing effluent during winter when
land application was not feasible. A study conducted at
Steamboat Springs, Colorado, showed that snowmelt
from reclaimed water has exhibited a substantial
reduction in BOD and TSS (Smith, 1986). Reclaimed
water for artificial snowmaking has been proposed as a
method of supplementing snowmaking at ski resorts
throughout New England. In Vermont, several
experiments with using reclaimed water for snowmaking
have been conducted; however at this time, no full-scale
projects have been approved.
3.6 Groundwater Recharge
This section addresses planned groundwater recharge
with reclaimed water with the specific intent to replenish
groundwater. Although practices such as irrigation may
contribute to groundwater augmentation, the
replenishment is an incidental byproduct of the primary
activity and is not discussed in this section.
The purposes of groundwater recharge using reclaimed
water include: (1) to establish saltwater intrusion barriers
in coastal aquifers, (2) to provide further treatment for
future reuse, (3) to augment potable or nonpotable
aquifers, (4) to provide storage of reclaimed water, or (5)
to control or prevent ground subsidence.
Pumping of groundwater aquifers in coastal areas may
result in seawater intrusion into the aquifers, making them
unsuitable as sources of potable supply or for other uses
where high salt levels are intolerable. A battery of injection
wells and extraction wells can be used to create a
hydraulic barrier to maintain intrusion control. Reclaimed
water can be injected directly into a confined aquifer and
subsequently extracted, if necessary, to maintain a
seaward gradient and thus prevent inland subsurface
seawater intrusion.
Infiltration and percolation of reclaimed water takes
advantage of the subsoils' natural ability for
biodegradation and filtration, thus providing additional in
s/fc/treatment of the wastewater and additional treatment
reliability to the overall wastewater management system.
The treatment achieved in the subsurface environment
may eliminate the need for costly advanced wastewater
treatment processes, depending on the method of
recharge, hydrogeological conditions, requirements of
the downstream users, and otherfactors. In some cases,
the reclaimed water and groundwater blend and become
indistinguishable.
Groundwater recharge helps provide a loss of identity
between reclaimed water and groundwater. This loss of
identity has a positive psychological impact where reuse
is contemplated and is an important factor in making
reclaimed water acceptable for a wide variety of uses,
including potable water supply augmentation.
Groundwater aquifers provide a natural mechanism for
storage and subsurface transmission of reclaimed water.
Irrigation demands for reclaimed water are often
seasonal, requiring either large storage facilities or
alternative means of disposal when demands are low. In
addition, suitable sites for surface storage facilities may
not be available, economically feasible, or
environmentally acceptable. Groundwater recharge
eliminates the need for surface storage facilities and the
attendant problems associated with uncovered surface
reservoirs, such as evaporation losses, algae blooms
resulting in deterioration of water quality, and creation of
odors. Also, groundwater aquifers serve as a natural
distribution system and may reduce the need for surface
transmission facilities.
While there are obvious advantages associated with
groundwater recharge, there are possible disadvantages
to consider (Oaksford, 1985):
Q
Q
Extensive land areas may be needed for
spreading basins.
Energy and injection wells for recharge may be
prohibitively costly.
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Q Recharge may increase the danger of aquifer
contamination. Aquifer remediation is difficult,
expensive, and may take years to accomplish.
Q Not all added water may be recoverable.
Q The area required for operation and maintenance
of a groundwater supply system (including the
groundwater reservoir itself) is generally larger
than that required for a surface water supply
system.
Q Sudden increases in water supply demand may
not be met due to the slow movement of
groundwater.
Q Inadequate institutional arrangements or
groundwater laws may not protect water rights
and may present liability and other legal
problems.
3.6.1 Methods of Groundwater Recharge
Recharge can be accomplished by riverbank or dune
filtration, surface spreading, or direct injection.
3.6.1.1 Riverbank or Dune Filtration
Recharge via riverbank or sand dune filtration is practiced
in Europe as a means of indirect potable reuse. It is
incorporated as an element in water supply systems
where the source is a contaminated surface water,
usually a river. The contaminated water is infiltrated into
the groundwater zone through the riverbank, percolation
from spreading basins, or percolation from drain fields of
porous pipe. In the latter two cases, the river water is
diverted by gravity or pumped to the recharge site. The
water then travels through an aquifer to extraction wells
at some distance from the riverbank. In some cases, the
residence time underground is only 20 to 30 days, and
there is almost no dilution by natural groundwater
(Sontheimer, 1980). In the Netherlands, dune infiltration
of treated Rhine River water has been used to restore the
equilibrium between fresh and saltwater in the dunes (Piet
and Zoeteman, 1980), while serving to improve water
quality and provide storage for potable water systems.
Dune infiltration also provides protection from accidental
spills of toxic contaminants into the Rhine River.
3.6.1.2 Surface Spreading
Surface spreading is adirect method of recharge whereby
the water moves from the land surface to the aquifer by
infiltration and percolation through the soil matrix.
An ideal soil for recharge by surface spreading would
have the following characteristics:
Q Rapid infiltration rates and transmission of water;
Q No clay layers or other layers that restrict the
movement of water to the desired unconfined
aquifer;
Q No expanding-contracting clays that create
cracks when dried that would allow the reclaimed
water to bypass the soil during the initial stages
of the flooding period;
Q Sufficient clay contents to provide large
capacities to adsorb trace elements and heavy
metals and to provide surfaces on which
microorganisms decompose organic
constituents; and
Q A supply of available carbon that would favor
rapid denitrification during flooding periods,
support an active microbial population to
compete with pathogens, and favor rapid
decomposition of introduced organics (Pratt ef
a/., 1975). BOD and TOG in the reclaimed water
will also be a carbon source.
Unfortunately, some of the above characteristics are
mutually exclusive. The importance of each soil
characteristic is dependent on the purpose of the
recharge. For example, adsorption properties may be
unimportant if recharge is primarily for storage.
After the applied recharge water has passed through the
soil zone, the geologic and subsurface hydrologic
conditions control the sustained infiltration rates. The
following geologic and hydrologic characteristics should
be investigated to determine the total usable storage
capacity and the rate of movement of water from the
spreading grounds to the area of groundwater draft:
Q Physical character and permeability of
subsurface deposits;
Q Depth to groundwater;
a Specific yield, thickness of the deposits, and
position and allowable fluctuation of the water
table;
Q Transmissivity, hydraulic gradients, and pattern
of pumping; and
Q Structural and lithologic barriers to both vertical
and lateral movement of groundwater.
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Although reclaimed water typically receives secondary
treatment and disinfection (and in some cases, advanced
wastewater treatment by filtration) prior to surface
spreading, other treatment processes are sometimes
provided. Depending on the ultimate use of the water and
otherfactors (dilution, thickness of the unsaturated zone,
etc.), additional treatment may be required. In soil-aquifer
treatment systems where the extracted water is to be
used for nonpotable purposes, satisfactory water quality
has been obtained at some sites using primary effluent
for spreading (Carlson etal., 1982; Lance, etal., 1980;
Rice and Bouwer, 1984).
For surface spreading of the reclaimed water to be
effective, the wetted surfaces of the soil must remain
unclogged, the surface area should maximize infiltration,
and the quality of the reclaimed water should not inhibit
infiltration.
Operational procedures should maximize the amount of
water being recharged while optimizing reclaimed water
quality by maintaining an unsaturated (vadose) zone to
take maximum advantage of treatment through the soil
matrix. If infiltration is intended to improve water quality,
as with rapid infiltration land treatment systems (EPA,
1981), the depth to the groundwater table should be deep
enough to ensure continuous and effective removal of
chemical and microbiological constituents.
Techniques for surface spreading include surface
flooding, ridge and furrow systems, stream channel
modifications, and infiltration basins. The system used is
dependent on many factors such as soil type and porosity,
depth to groundwater, topography, and the quality and
quantity of the reclaimed water.
a. Flooding
Reclaimed water is spread over a large, gently sloped
area (1 to 3 percent grade). Ditches and berms may
enclose the flooding area. Advantages are low capital
and O&M costs. Disadvantages are large areal
requirements, evaporation losses, and clogging.
b. Ridge and Furrow
Water is placed in narrow, flat-bottomed ditches. Ridge
and furrows are especially adaptable to sloping land, but
only a small percentage of the land surface is available
for infiltration.
c. Stream Channel Modifications
Berms are constructed in stream channels to retard the
downstream movement of the surface water and, thus,
increase infiltration into the underground. This method is
used mainly in ephemeral or shallow rivers and streams,
where machinery can enter the stream beds when there
is little or no flow to construct the berms and prepare the
ground surface for recharge. Disadvantages may include
a frequent need for replacement due to washouts and
possible legal restrictions related to such construction
practices.
d. Infiltration Basins
Infiltration basins are the most widely used method of
groundwater recharge. Basins afford high loading rates
and relatively low maintenance and land requirements.
Basins consist of bermed, flat-bottomed areas of varying
sizes. Long, narrow basins built on land contours have
been effectively used. Basins constructed on highly
permeable soils to achieve high hydraulic rates are called
rapid infiltration basins.
Rapid infiltration basins require permeable soil for high
hydraulic loading rates, yet the soil must be fine enough
to provide sufficient soil surfaces for biochemical and
microbiological reactions, which provide additional
treatment to the reclaimed water. Some of the best soils
are in the sandy loam, loamy sand, and fine sand range.
When the reclaimed water is applied over to the spreading
basin, the water percolates through the unsaturated zone
to the saturated zone of the groundwater table. The
hydraulic loading rate is preliminarily estimated by soil
studies, but final evaluation is done by operating in situ
test pits or ponds. Hydraulic loading rates for rapid
infiltration basins vary from 65 to 500 ft (20 to 150 m)/yr,
but are usually less than 300 ft (90 m)/yr (Bouwer, 1988).
Though management techniques are site specific and
vary accordingly, some common principles are practiced
in most systems. A wetting and drying cycle with periodic
cleaning of the bottom is used to prevent clogging by
accumulated SS, maintain a high rate of infiltration,
maintain microbial populations to consume organic
matter and help reduce levels of microbiological
constituents in the reclaimed water, and promote
nitrification and denitrification processes for nitrogen
removal. The loading rates are usually higher when
nitrogen removal is not a concern.
Spreading grounds can be managed to avoid nuisance
conditions such as algae growth and insect breeding in
the percolation ponds. Generally, a number of basins are
rotated through filling, draining, and drying cycles. Cycle
length is dependent on both soil conditions and the
distance to the groundwater table and is determined on a
case-by-case basis from field testing. Algae can clog the
bottom of basins and reduce infiltration rates. Algae
further aggravate soil clogging by removing carbon
dioxide, which raises the pH, causing precipitation of
calcium carbonate. Reducing the detention time of the
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Table 20. Summary of Facilities and Management Practices for Percolation Recharge
Location
Load Rate
(MG/ac/yr)
Perc. Rate
(ft/d)
Load
Schedule
Soil Type
Spreading Area
Maintenance
Camp Pendelton, CA N/A
Hemet, CA 29
Oceanside, CA 47
Phoeniz.AZ 137
San Ctemente, CA 140
St Croix. Virgin Is. 36
Whittier, CA 46
8 As water becomes available Coarse sand
2.5 Fill 1 day (2.5-ft depth),
drain 2 days, dry 1 day
4.5 Fill to 3-ft depth,
drain & dry, refill
2.5 Fill 10 days,
dry 14 days
5-10 Continuous
1-2 Fill 18 days,
dry 30 days
5-10 Fill 7 days (4-ft. depth),
drain 7 days, dry 7 days
Medium &
coarse sand
Coarse sand
Loamy sand surface,
coarse sand & gravel
Coarse sand & gravel
Silt, sand & clay
Sandy loam
Berm redevelopment,
remove surface solids
every other year
Periodic rototilling
of basins
Basins scarified
periodically
Closely maintain flooding
schedule, periodic scarifying
None
Basins scarified periodically
Source: EPA, 1977.
reclaimed water within the basins minimizes algal growth.
Also, scarifying, rototilling or discing the soil following the
drying cycle can help alleviate clogging potential,
although scraping or "shaving" the bottom to remove the
clogging layer is more effective than discing it. Table 20
summarizes facilities and management practices for
surface spreading operations at some sites in the U.S.
3.6.1.3 Soil-Aquifer Treatment Systems
Where hydrogeologic conditions permit groundwater
recharge with surface infiltration facilities, considerable
improvement in water quality may be obtained by
movement of the wastewater through the soil,
unsaturated zone, and aquifer. Table 21 provides an
example of improvement in the quality of secondary
effluent in a groundwater recharge soil-aquifer treatment
(SAT) system. These data are the results of a
demonstration project in the Salt River bed west of
Phoenix, Arizona (Bouwer and Rice, 1984). The cost of
SAT has been shown to be less than 40 percent of the
cost of equivalent above-ground treatment (Bouwer,
1991).
SAT systems usually are designed and operated such
that all of the infiltrated water is recovered via wells,
drains, or seepage into surface water. Typical SAT
recharge and recovery systems are shown in Figure 30.
SAT systems with infiltration basins require unconfined
aquifers, vadose zones free of restricting layers, and soils
that are coarse enough to allow high infiltration rates but
fine enough to provide adequate filtration. Sandy loams
and loamy orfine sands are the preferred surface soils in
SAT systems.
In the U.S., municipal wastewater usually receives
conventional primary and secondary treatment prior to
SAT. However, since SAT systems are capable of
removing more BOD than is in secondary effluent
(Bouwer, 1991), secondary treatment may not be
necessary where the wastewater is subjected to SAT and
subsequently reused for nonpotable purposes. The
higher organic content of primary effluent may enhance
nitrogen removal by denitrification in the SAT system
(Lance et a/., 1980) and may enhance removal of
synthetic organic compounds by stimulating greater
microbiological activity in the soil (McCarty et al, 1984). A
disadvantage of using primary effluent is that infiltration
basin hydraulic loading rates may be lower than if higher
quality effluent is used. This would require more frequent
cleaning of the basins and increase the cost of the SAT,
but not necessarily the total system cost.
Other methods of pretreatment prior to SAT may include
lagoons or stabilization ponds, overland flow, or "natural"
methods such as wetlands treatment. However, some of
these low cost treatment methods may create infiltration
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Table 21. Water Quality at Phoenix, Arizona SAT
System
Total dissolved solids
Suspended solids
Ammonium nitrogen
Nitrate nitrogen
Organic nitrogen
Phosphate phosphorus
Ruoride
Boron
Biochemical oxygen demand
Total organic carbon
Zinc
Copper
Cadmium
Lead
Fecal coliforms/100 mLa
Viruses, pfu/100mLb
Secondary
effluent
mg/L
750
11
16
0.5
1.5
5.5
1.2
0.6
12
12
0.19
0.12
0.008
0.082
3500
2118
Recovery well
samples
mg/L
790
1
0.1
5.3
0.1
0.4
0.7
0.6
<1
1.9
0.03
0.016
0.007
0.066
0.3
<1
a Chlorinated effluent
b Undisinfected effluent
Source: Adapted from Bouwerand Rice, 1984.
problems if the water contains significant amounts of
algae. The algae can form a filter cake or clogging layer
on the bottom of the infiltration basins. To help alleviate
this problem, the SAT infiltration basins should be shallow
enough to avoid compaction of the clogging layer and to
promote rapid turnover of the waterin the basins (Bouwer
and Rice, 1989).
3.6.1.4 Direct Injection
Direct injection involves the pumping of reclaimed water
directly into the groundwaterzone, which is usually a well-
confined aquifer. Direct injection is used where
groundwater is deep or where hydrogeological conditions
are not conducive to surface spreading. Such conditions
might include unsuitable soils of low permeability,
unfavorable topography for construction of basins, the
desire to recharge confined aquifers, or scarcity of land.
Direct injection into a saline aquifer can create a
freshwater "bubble," from which water can be extracted
for reuse. Direct injection is also an effective method for
creating barriers against saltwater intrusion in coastal
areas.
Direct injection requires water of higher quality than
surface spreading because of the absence of soil matrix
treatment afforded by surface spreading and the need to
maintain the hydraulic capacity of the confined aquifer.
Treatment processes beyond secondary treatment that
are used prior to injection include disinfection, filtration,
air stripping, ion exchange, granular activated carbon,
and reverse osmosis or other membrane separation
processes. Using these processes, or various subsets in
appropriate combinations, it is possible to satisfy all
present water quality requirements for reuse.
For both surface spreading and direct injection, locating
the extraction wells as great a distance as possible from
the recharge site increases the flow path length and
residence time in the underground, as well as the mixing
of the recharged water with the natural groundwater
(Todd, 1980).
Ideally, an injection well will recharge water at the same
rate as it can yield water by pumping. However, conditions
are rarely ideal. Though clogging can easily by remedied
in a surface spreading system by scraping, discing, drying
and other methods, remediation in a direct injection
system can be costly and time consuming. The most
frequent causes of clogging are accumulation of organic
and inorganic solids, biological and chemical
contaminants, and dissolved air and gases from
turbulence. Very low concentrations of SS, on the order
of 1 mg/L, can clog an injection well. Even low
concentrations of organic contaminants can cause
clogging due to bacteriological growth near the point of
injection.
There are many criteria specific to the quality of the
reclaimed water, the groundwater, and the aquifer
material that have to be taken into consideration prior to
construction and operation. These include possible
chemical reactions between the reclaimed water and the
groundwater, iron precipitation, ionic reactions,
biochemical changes, temperature differences, and
viscosity changes (O'Hare, 1986). Most clogging
problems are avoided by proper pretreatment and proper
operation.
3.6.2 Fate of Contaminants in Recharge Systems
The fate of contaminants is an important consideration
forgroundwater recharge systems using reclaimed water.
Contaminants in the subsurface environment are subject
97
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Figure 30. Schematic of Soil-Aquifer Treatment Systems
A. Drainage of Reclaimed Water into
Stream, Lake, or Low Area
C. Infiltration Area in Two Parallel Rows and
Line of Wells Midway Between
Source: Bouwer, 1991.
B. Collection of Reclaimed Water
by Subsurface Drain
Impermeable
Ti7TTT& TTT
D. Infiltration Areas in Center Surrounded by a
Circle of Wells
to processes such as biodegradation by microorganisms,
adsorption, filtration, ion exchange, volatilization, dilution,
chemical oxidation and reduction, chemical precipitation
and complex formation, and photochemical reactions (in
spreading basins) (Roberts, 1980; EPA, 1989). For
surface spreading operations, most of the removals of
both chemical and microbiological constituents occur in
the top 6 ft (2 m) of the vadose zone at the spreading site.
3.6.2.1 Paniculate Matter
Particles larger than the soil pores are strained off at the
soil-water interface. Paniculate matter, including some
bacteria, is removed by sedimentation in the pore spaces
of the media during filtration. Viruses are mainly removed
by adsorption. The accumulated particles gradually form
a layer restricting further infiltration. Suspended solids
that are not retained at the soil-water interface may be
effectively removed by infiltration and adsorption in the
soil profile. As water flows through passages formed by
the soil particles, suspended and colloidal solids far too
small to be retained by straining are thrown off the
streamline through hydrodynamic actions, diffusion,
impingent on, and sedimentation. The particles are then
intercepted and adsorbed onto the surface of the
stationary soil matrix. The degree of trapping and
adsorption of suspended particles by soils is a function of
the SS concentration, soil characteristics, and hydraulic
loading (Chang and Page, 1979). Suspended solids
removal is enhanced by longer travel distances
underground.
For dissolved inorganic constituents to be removed or
retained in the soil, physical, chemical, or microbiological
reactions are required to precipitate and/or immobilize
the dissolved constituents. In a groundwater recharge
system, the impact of microbial activity on the attenuation
of inorganic constituents is thought to be insignificant
(Chang and Page, 1979). Chemical reactions that are
important to a soil's capability to react with dissolved
inorganics include cation exchange reactions,
precipitation, surface adsorption, chelation,
complexation, and weathering (dissolution) of clay
minerals.
While inorganic constituents such as chloride, sodium,
and sulfate are unaffected by ground passage, many
other inorganic constituents exhibit substantial removal.
For example, iron and phosphorus removals in excess of
90 percent have been achieved by precipitation and
adsorption in the underground (Sontheimer, 1980;
Idelovitch, etal., 1980), although the ability of the soil to
remove these and other constituents may decrease over
time. Heavy metal removal varies widely forthe different
elements, ranging from 0 to more than 90 percent,
depending on speciation of the influent metals.
Trace metals which normally occur in solution as anions
(e.g., silver, chromium, fluoride, molybdenum, and
selenium) are strongly retained by soil (Chang and Page,
1979; John, 1972). Boron, which is mainly in the form of
undissociated boric acid in soil solutions, is ratherweakly
adsorbed and, given sufficient amounts of leaching water,
most of the adsorbed boron is desorbed (Rhoades etal.,
1979). There are indications that once heavy metals are
adsorbed, they are not readily desorbed, although
desorption depends, in part, on buffer capacity, salt
98
-------
concentrations, and reduction-oxidation potentially
(Sontheimer, 1980).
For surface spreading operations where an aerobic zone
is maintained, ammonia is effectively converted to
nitrates, but subsequent denitrification is dependent, in
part, on anaerobic conditions during the flooding cycle
and is often partial and fluctuating unless the system is
carefully managed.
3.6.2.2 Dissolved Organic Constituents
Dissolved organic constituents are subject to
biodegradation and adsorption during recharge.
Biodegradation mainly occurs by microorganisms
attached to the media surface. The rate and extent of
biodegradation is strongly influenced by the nature of the
organic substances and by the presence of electron
acceptors such as dissolved oxygen and nitrate. There
are indications that biodegradation is enhanced if the
aquifer material is finely divided and has a high specific
surface area, such as fine sand or silt. However, such
conditions can lead to clogging by bacterial growths.
Coarser aquifer materials such as gravel and some sands
have greater permeability and, thus, less clogging, but
biodegradation may be less rapid and perhaps less
extensive (Roberts, 1980). The biodegradation of easily
degradable organics occurs a short distance (few meters)
from the point of recharge.
The end products of complete degradation under aerobic
conditions include carbon dioxide, sulfate, nitrate,
phosphate, and water, and the end products under
anaerobic conditions include carbon dioxide, nitrogen,
sulfide, and methane. The mechanisms operating on
refractory organic constituents over long time periods
typical of groundwater environments are not well
understood. The degradation of organic contaminants
may be partial and result in a residual organic product
that cannot be further degraded at an appreciable rate.
Adsorption of organic constituents retards their
movement (they can desorb and move
chromatographicaily in the underground) and attenuates
concentration fluctuations. Attenuation is a measure of
the damping of organic constituent concentration
fluctuations. The degree of attenuation increases with
increasing adsorption strength, increasing distance from
the recharge point, and increasing frequency of input
fluctuation (Roberts, 1980). Recharged water may be free
of many chemicals when it first appears at an extraction
well, but the chemicals may begin to appear much later.
Thus, chemical retardation needs to be evaluated when
determining the effectiveness of contaminant removal in
a recharge system (Bouwer, 1991).
Adsorption of uncharged organic compounds is believed
to be related to the hydrophobic nature of compounds;
highly chlorinated hydrocarbons are strongly adsorbed
onto soils and, undertypical recharge conditions, may be
retained for many years (Roberts, 1980). Data reported
by Sontheimer (1972) for riverbank infiltration along the
Rhine River indicate that organic removal efficiency in
bank filtration decreased as the relative amount of
chlorine in the molecule increased. Studies involving
sand dune filtration in the Netherlands indicated that the
haloforms and organic nitrogen compounds were readily
removed during passage through the dunes (Piet and
Zoeteman, 1980).
In one study involving rapid infiltration of secondary
effluent, nonhalogenated aliphatic and aromatic
hydrocarbons and the priority pollutants ethylbenzene,
napthalene, phenanthene, and diethylphthalate exhibited
a concentration decrease between 50 and 99 percent
during soil percolation, but many of the compounds could
still be detected in the underlying groundwater (Bouwer,
et a/., 1984). Smaller reduction in concentrations of the
halogenated organic compounds and organic
substances represented by total organic halogen were
observed with soil passage compared to the specific
nonhalogenated organic compounds found in the basin
water. Another study indicated that nonvolatile organic
halogens in injected reclaimed water were not retarded
during passage through the ground, but that 50 percent
were removed, presumably due to microbial degradation
(Reinhard, 1984). Table 22 indicates the variability in
different constituent removals after 2.5 m (8 ft) of
percolation at a spreading basin.
3.6.2.3 Microorganisms
The survival or retention of pathogenic microorganisms
in the subsurface is dependent on several factors,
including climate, soil composition, antagonism by soil
microflora, flow rate, and type of microorganism. At low
temperatures (below 4°C [39°F]) some microorganisms
can survive for months or years. The die-off rate is
approximately doubled with each 10°C rise in
temperature between 5 and 30°C (41 and 86°F) (Gerba
and Goyal, 1985). Rainfall may mobilize bacteria and
viruses that had been filtered or adsorbed and thus
enhances their transport (Wellings et a/., 1975).
The nature of the soil affects survival and retention. For
example, rapid infiltration sites at which viruses have
been detected in groundwater were located on coarse
sand and gravel types. Infiltration rates at these sites were
high, and the ability of the soil to adsorb the viruses was
low. Generally, coarse soil does not inhibit virus migration
(EPA, 1981). Other soil properties, such as pH, cation
concentration, moisture holding capacity, and organic
99
-------
Table 22. Results of Test Basin Sampling Program at Whittter Narrows, California
Total hardness
(mg CaCOa/L)
Total dissolved
solids (mg/L)
Ammonia (mg/L)
Nitrate (mg/L)
Nitrite (mg/L)
COD (mg/L)
TOG (mg/L)
Methylene chloride
(HO/L)
Chloroform (jig/L)
Trichloroethylene
(Mfl/U
Tetrachloroethylene
(MS/U
Average Concentration
At Surface At 8 ft (2.5m)
202
516
14.6
0.91
0.86
29.3
10.15
16.9
5.2
2.7
2.3
373
703
0.25
8.52
0.02
12.3
3.43
1.9
2.5
3.8
1.0
Trend
Increasing
Increasing
Decreasing
Increasing
Decreasing
Decreasing
Decreasing
Decreasing
Decreasing
Increasing
Decreasing
Significance3
<0.001
<0.001
<0.001
0.009
<0.001
<0.001
<0.001
0.026
0.008
NSb
0.019
aLevel of significance based on two-tailed f-test.
bNot significant (p>0.05)
Source: Nellor etal., 1985.
matter affect the survival of bacteria and viruses in the
soil (Gerba and Lance, 1980). Resistance of
microorganisms to environmental factors depends on the
species and strains present.
Drying of the soil will kill both bacteria and viruses.
Bacteria survive longer in alkaline soils than in acid soils
(pH 3 to 5) and when large amounts of organic matter are
present (Gerba, Wallis, and Melnick, 1975). In general,
increasing cation concentration and decreasing pH and
soluble organics tend to promote virus adsorption.
Bacteria and larger organisms associated with
wastewater are effectively removed after percolation
through a short distance of the soil mantle. Factors that
may influence virus movement in groundwater are given
in Table 23. Viruses have been isolated by a number of
investigators examining a variety of recharge operations,
after various migration distances. These are summarized
in Table 24. Propertreatment (including disinfection) prior
to recharge, site selection, and management of the
surface spreading recharge system can minimize or
eliminate the presence of microorganisms in the
groundwater.
3.6.3 Health and Regulatory Considerations
The constraints on recharge are conditioned by the use
to which the abstracted water will be put, and include
health concerns, economic feasibility, physical
limitations, legal restrictions, water quality constraints,
and reclaimed water availability. Of these constraints, the
health concerns are the most important as they pervade
almost all recharge projects. Where there is to be
ingestion of the reclaimed water, health effects due to
prolonged exposure to low levels of contaminants must
be considered as well as the acute health effects from
pathogens or toxic substances. [See Section 2.4 Health
Assessment and Section 3.7 Augmentation of Potable
Supplies.]
One problem with recharge is that boundaries between
potable and nonpotable aquifers are rarely well definec
Some risk of contaminating high quality potablo
groundwater supplies is .often incurred by recharging
"nonpotable" aquifers. The recognized lack of knowledge
about the fate and long-term health effects o!
contaminants found in reclaimed water obliges a
conservative approach in setting water quality standards
for groundwater recharge. In light of these uncertainties,
some states, have set stringent water quality requirements
and require high levels of treatment—in some cases
organics removal processes—where recharge affects
potable aquifers:
3.7 Augmentation of Potable Supplies
100
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Table 23. Factors that May Influence Virus Movement to Groundwater
Factor .___ Comments
Soil type Fine-textured soils retain viruses more effectively than light-textured soils. Iron oxides increase the adsorptive
capacity of soils. Muck soils are generally poor adsorbents.
pH Generally, adsorption increases when pH decreases. However, the reported trends are not clear-cut due to
complicating factors.
Cations Adsorption increases in the presence of cations (cations help reduce repulsive forces on both virus and soil
particles). Rainwater may desorb viruses from soil due to its low conductivity.
Soluble organics Generally compete with viruses for adsorption sites. No significant competition at concentrations found in
wastewater effluents. Humic and fulvic acids reduce virus adsorption to soils.
Virus type Adsorption to soils varies with virus type and strain. Viruses may have different isoelectric points.
Flow rate The higher the flow rate, the lower virus adsorption to soils.
Saturated vs. Virus movement is less under unsaturated
unsaturated flow flow conditions.
Source: Gerba and Goyal, 1985.
Table 24. Isolation of Viruses Beneath Land Treatment Sites
Maximum Distance of
Virus Migration (m)
Site Location
St.. Petersburg, FL
Gainesville, FL
Lubbock, TX
Kerrville.TX
Muskegon, Ml
San Angelo, TX
East Meadow, NY
Holbrook.NY
Sayville, NY
12 Pines, NY
North Masapequa.NY
Babylon, NY
Ft. Devens, MA
Vinelartd, NJ
Lake George, NY
Phoenix, AZ
Dan Region, Israel
Site Type3
S
S
S
S
S
S
R
R
R
R
• R
'*' R
R
R
R
R
R
Depth
6.0
3.0
30.5
1.4
10.0
27.5
11.4
6.1
2.4
6.4
9.1
22.8
28.9
16.8
45.7
18.3
31-67
Horizontal
7
—
—
—
—
3.0
45.7
3
—
—
408
183
250
400
3
60-270
aS = Slow-rate infiltration, R = Rapid infiltration.
Source: Adapted from Gerba and Goyal, 1985.
101
-------
Water is a renewable resource. It is cleansed and reused
continually, powered by solar energy in the hydrological
cycle. The distillate produced, rainfall, is pure, until it picks
up contaminants as ft falls through the atmosphere and
flows over and through the ground and in rivers and lakes
polluted by urban, industrial, and agricultural discharges.
A principle that has guided the development of potable
water supplies for almost 150 years was stated in the
1962 Public Health Service Drinking Water Standards:
"... water supply should be taken from the most desirable
source which is feasible, and efforts should be made to
prevent or control pollution of the source." This was
affirmed by EPA (1976) in its Primary Drinking Water
Regulations:"... priority should be given to selection of
the purest source. Polluted sources should not be used
unless other sources are economically unavailable..."
This section discusses indirect potable reuse, where
treated wastewater is discharged into a water course or
underground and withdrawn downstream or
downgradient at a later time for potable purposes, and
direct potable reuse, where the reclamation plant effluent
is piped into the potable water system. Both such sources
of potable water are, on their face, less desirable than
using a higher quality source for drinking.
3.7.1 Water Quality Objectives for Potable Reuse
Whereas the water quality requirements for nonpotable
urban reuse are quite tractable and treatment
requirements are not likely to change significantly in the
future, drinking water quality standards will become more
rigorous in the future, requiring more and more treatment
forpotable reuse. The number of contaminants regulated,
by the Public Health Service until 1974 and subsequently
by the EPA, has grown from a handful in 1925 to a target
of more than 100 as shown in Figure 31. Not only are the
numbers of contaminants to be monitored increasing, but,
for many of them, the maximum contaminant limits
(MCLs) are decreasing. For example, the MCL for lead
was reduced in 1992 from 50 ug/Lto an action level of 15
ug/L. The health effeejs for many of the individual
regulated contaminants are not well established.
*•
It is estimated that only about 10 percent by weight of the
organic compounds in drinking water have been identified
(National Research Council, 1980) and the health effects
of only a few of the individual identified compounds have
been determined (National Research Council, 1980). The
health effects of mixtures of two or more of the hundreds
of compounds in any single source of drinking water
drawn from wastewater will not be easily characterized.
Health effects studies for reuse are applicable only to the
specific situation, as the contaminant mix varies from city
to city. Also, for any one city, it is likely that the
contaminants will change over the years.
Figure 31. Number of Drinking Water Contaminants
Regulated by the US. Government
*From this date, requirements of Safe Drinking
Water Act and its amendments
Some organic compounds, particularly chlorinated
species, are known or suspected carcinogens. Many
epidemiological studies have been conducted to assess
the potential health effects associated with drinking water
derived from sources containing significant amounts of
wastewater. The results have generally been
inconclusive, although they provided sufficient evidence
for maintaining a hypothesis that there may be a health
risk (National Research Council, 1980). One study,
conducted by the National Cancer Institute, indicated an
increased incidence of bladder cancer in people who
drank chlorinated surface water as compared to those
who drank unchlorinated groundwater (Cantor ef a/.,
1987). Recognizing the limitations of epidemiological
studies because of the many compounding variables,
these studies — and the earlier research on drinking
water taken from the Mississippi River that led to initial
passage of the Safe Drinking Water Act — do provide a
basis for concern where water that may contain significant
levels of organic constituents is subsequently chlorinated
and distributed for potable use. In general, the poorerthe
102
-------
raw water quality, the more chlorine is required and the
greater is the resulting risk.
Quality standards have been established for- many
inorganic constituents and treatment and analytical
technology has demonstrated our capability to identify,
quantify, and control these substances. Similarly,
available technology is capable of eliminating pathogenic
.agents from contaminated waters. However, unanswered
questions remain with organic constituents, due mainly
to their potential large number and unresolved health risk
potential resulting from long-term exposure to extremely
low considerations.
3.7.2 Indirect Potable Water Reuse
Many cities have elected in the past to take water from
large rivers that receive substantial wastewater
discharges because of the assurance that conventional
filtration and disinfection will eliminate the pathogens
responsible for water-borne infectious disease. These
supplies were generally less costly and were more easily
developed than upland supplies orunderground sources.
Such large cities as Philadelphia, Cincinnati, and New
Orleans, drawing water from the Delaware, Ohio and
Mississippi Rivers, respectively, are thus practicing
indirect potable water reuse, the many cities upstream
of their intakes can be characterized as providing water
reclamation in their wastewater treatment facilities,,
although they were not designed, nor are they operated,
as potable water sources. NPDES permits for these
discharges are intended to make the rivers "fishable and
swimmable," and generally do not reflect potable water
requirements downstream. These indirect potable reuse
systems originated at a time when the principal concern
for drinking water quality was the prevention of enteric
infectious diseases. Nevertheless, most cities do provide
water of acceptable quality that meets current drinking
water regulations.
More recent indirect potable reuse projects are
exemplified by the Upper Occoquan Sewage Authority
(UOSA) treatment facilities an northern Virginia, which
discharge reclaimed water into the Bull Run just above
Occoquan Reservoir, a source of water supply for Fairfax
County, Virginia, and the Clayton County, Georgia,
project where wastewater, following secondary
treatment, undergoes land treatment, with the return
subsurface flow reaching a stream used as a source of
potable water. The UOSA plant provides AWT (Robbins
and Ehalt, 1985) that is more extensive than required
treatment for nonpotable reuse and accordingly provides
water of much higher quality for indirect potable reuse
than is required for nonpotable reuse.
While UOSA now provides a significant portion of the
water in the system, varying from an average of about 10
percent of the total flow to as much as 40 percent in low
flow periods, most surface indirect potable reuse projects
have been driven by requirements for wastewater
disposal and pollution control; their contributions to
increased public water supply were incidental. In a
comprehensive comparative study of the Occoquan and
Clayton County projects, the water quality parameters
assessed were primarily those germane to wastewater
disposal and not to drinking water (Reed and Bastian,
1991). Most discharges that contribute to indirect potable
water reuse, especially via rivers, are managed as
wastewater disposal functions and are handled in
conformity with practices common to all water pollution
control efforts. The abstraction and use of the reclaimed
water is almost always the responsibility of a water supply
agency that is not at all related politically, administratively
or even geographically, except for being downstream, to
the wastewater disposal agency.
While direct potable reuse is not likely to be adopted soon,
indirect potable reuse via surface waters has been, and
will continue to be, practiced widely. Issues evolving from
these practices are the substance of extensive studies of
water pollution control and water treatment, resulting in a
large number of publications and regulations that do not
require elucidation, in this document. Indirect potable
reuse via groundwater recharge is being practiced to a
lesser extent.
3.7.3 Groundwater Recharge for Potable Reuse
As mentioned in Section 3.6.1., Methods of Groundwater
Recharge, groundwater recharge via riverbank or sand
dune filtration, surface spreading, or injection has long
been used to augment potable aquifers. Riverbank or
dune filtration of untreated surface water is distinctly
different from recharge of highly treated wastewater, but
the health concerns associated with this practice are
similar to those for potable reuse generally. Riverbank or
dune filtration includes infiltrating river water into the
groundwater zones through the riverbank, percolation
from spreading basins, or percolation from drain fields or
porous pipe. In the latter two cases, the river water is
diverted by gravity or pumped to the recharge site. The
water then travels through an aquifer to extraction wells
at some distance from the riverbank. In some cases, the
residence time underground is only 20 to 30 days, and
there is almost no dilution by natural groundwater
(Sontheimer, 1980). In the Netherlands, dune infiltration
of treated Rhine River water has been used to restore the
equilibrium between fresh and saltwater in the dunes (Piet
and Zoeteman, 1980), while serving to improve water
quality and provide storage for potable water systems.
103
-------
Dune infiltration also provides protection from accidental
spills of toxic contaminants into the Rhine River.
Although both planned and unplanned recharge into
potable aquifers has occurred for many years, few health-
related studies have been undertaken. The most
comprehensive health effects study of an existing
groundwater recharge project was carried out in Los
Angeles County in response to uncertainties about the
health consequences of recharge for potable use raised
by a California Consulting Panel in 1975-76.
In 1978, the Sanitation Districts of Los Angeles County
initiated a 5-year, $1.4 million, study of the Montebello
Forebay Groundwater Recharge Project at Whittier
Narrows that had been replenishing groundwater with
reclaimed water since 1962. Three water reclamation
plants provide water for the spreading operation. The
plants provide secondary treatment (activated sludge),
dual-media filtration (Whittier Narrows and San Jose
Creek) or activated carbon filtration (Pomona),
disinfection with chlorine, and dechlorination. By 1978,
the amount of reclaimed water spread averaged about 9
billion gal/yr (34 x 103 mVyr) or 16 percent of the total
inflow to the groundwater basin with no more than about
8 billion gal (42 x 106x m3) of reclaimed water spread in
any year. The percentage of reclaimed water contained
in the extracted potable water supply ranged from 0 to 11
percent on a long-term (1962-1977) basis (Crook et a/.,
1990).
Historical impacts on groundwater quality and human
health and the relative impacts of the different
replenishment sources-reclaimed water, stormwater
runoff, and imported surface water-on groundwater
quality were assessed after conducting a wide range of
research tasks, including:
Q Water quality characterizations of groundwater,
reclaimed water, and other recharge sources in
terms of their microbiological and inorganic
chemical content;
Q Toxicological and chemical studies of
groundwater, reclaimed water and other
recharge sources to isolate and identify health-
significant organic constituents;
Q Percolation studies to evaluate the efficacy of
soil in attenuating inorganic and organic
chemicals in reclaimed water;
Q Hydrogeological studies to determine the
movement of reclaimed water through
groundwater and the relative contribution of
reclaimed water to municipal water supplies;
and,
Q Epidemic logical studies of populations ingesting
reclaimed water to determine if their health
characteristics differ significantly from a
demographically similar control population.
The study's results indicated that the risks associated
with the three sources of recharge water were not
significantly different and that the historical proportion of
reclaimed water used for replenishment had no
measurable impact on either groundwater quality or
human health (Nellor, et al., 1984). The health effects
study did not demonstrate any measurable adverse
effects on the area's groundwater or the health of the
population ingesting the water. The cancer-related
epidemiological study findings are somewhat weakened
by the fact that the minimal observed latency period for
human cancers that have been linked to chemical agents
is about 15 years, and may be much longer. Because of
the relatively short time period that groundwater
containing reclaimed water has been consumed, it is
unlikely that examination of cancer mortality rates would
have detected an effect of exposure to reclaimed water
resulting from the groundwater recharge operation, even
if an effect were present (State of California, 1987).
Groundwater recharge has inherent disadvantages not
present with indirect surface water reuse. If water of poor
quality is discharged to a river, the river can be expected
to be cleansed when the pollution is stopped. If poor
quality water is charged into an aquifer and found later to
be troublesome, cleansing the aquifer will be costly and
difficult.
3.7.4 Direct Potable Water Reuse
Pipe-to-pipe water reclamation and direct potable reuse
is currently practiced in only one city in the world,
Windhoek, Namibia, and there only intermittently. In the
U.S., the most extensive research focusing on direct
potable reuse has been conducted in Denver, Colorado;
Tampa, Florida; and San Diego, California. A
considerable investment in potable reuse research has
been made in Denver, Colorado, over a period of more
than 20 years, which included operation of a 1-mgd (44-
L/s) reclamation plant in many different process modes
over a period of about 10 years (Lauer, 1991). The
product water was reported to be of better quality than
many potable water sources in the region and certainly
better than what is produced by many purveyors of
drinking water elsewhere in the country who use run-of-
river sources. Table 25 illustrates the high quality of the
product water produced by the demonstration plant, to
the extent revealed by the parameters monitored. Health
104
-------
Table 25. Test Results, Denver Potable Water Reuse Demonstration Project
(Geometric Mean Values, Jan. 9 to Dec. 31,1989)
'arameter
mg/l unless indicated)
Seneral
Total Alkalinity
Hardness
TSS
TDS
Specific Conductance (umhos/cm)
JH
Temperature - °C
Turbidity - NTU
TOC
Particle Size > 128 iim (count/50 ml)
Particle Size 64-128 jim (count/50 ml)
Particle Size 32-64 fim (count/50 ml)
Particle Size 16-32 (im (count/50 ml)
Particle Size 8-16 |im (count/50 ml)
Particle Size 4-8 urn (count/50 ml)
Asbestos - million fibers/I
hAD AC
Mono
TOX
Radiological
Gross Alpha - pCi/l
Gross Beta - pCi/l
Radium 228 - pCi/l
Radium 226 - pCi/l
Tritium - pCi/l
Radon - pCi/l
Plutonium - pCi/l
Microbiological
m-HPC (count/ml)
Total Coliform (count/100 ml)
Fecal Strep (count/100 ml)
Fecal Coliform (count/100 ml)
Snigella
Salmonella
Clostridium
Campylobacter
Coliphage B (pfu/100 ml)
Coliphage C (pfu/100 ml)
Giardia (cysts/I)
Endamoeba coli (cysts/I)
Nematodes (count/I)
Algae (count/ml)
Enteric Virus
Entamoeba histolytica (cysts/I)
Cryptosporidium (oocysts/l)
Inorganic
Aluminum
Arsenic
Boron
Bromide
Cadmium
Calcium
Chloride
Chromium
Copper
Cyanide
Fluoride
Iron
Potassium
Magnesium
Manganese
Mercury
Molybdenum
TKN
Ammonia-N
Nitrate-N
Nitrite-N
Nickel
MCL
500
6.5-8.5
15
7
n f\
U.9
15
50
5
5
20,000
—
1
—
—
—
—
—
—
—
—
0.05
0.01
250
0.05
1
0.2
2
0.3
—
0.05
0.002
—
10
1
0.1
RO
3
6
*
18
67
6.6
8.3
21
0.06
*
*
1.2
58
147
219
*
*
8
*
*
.
*
*
*
*
*
*
*
*
*
*
*
*
•
*
0.2
I
1
19
*
0.009
*
*
0.02
0.7
0.1
*
it
5
5
0.1
*
*
UF
166
108
352
648
7.8
6.9
21
0.2
0.7
* '
18
100
448
1290
*
23
6
*
37
•
350
*
*
*
*
*
*
*
*
*
*
0.3
•
38
96
*
0.01
0.03
0.78
0.07
9.1
1.8
*
0.004
19
19
0.3
*
Parameter
mg/l unless indicated)
Inorganic (continued)
Total Phosphate-P
Selenium
Silica
Strontium
Sulfate
Lead
Uranium
Sodium
Lithium
Titanium
Barium
Silver
Rubidium
Vanadium
Iodine
Antimony
Thallium
Test Method
EPA 502.2
Grob Closed Loop Stripping
GC/MS (EPA 8270)
Carbamate Pesticides
(EPA -531)
Pesticides
(EPA 508) + (EPA 608)
Herbicides
(EPA 51 5.1)
Polychlorinated Biphenyls
(EPA 504)
Polynuclear Aromatic
Hydrocarbons (EPA 610)
Base Neutral & Acid
Extractables (EPA 625)
Haloacetic Acids"
Pentane Extractable
Disinfection Byproducts"
Aldehydes"
MCL
0.01
250
0.05
5
1.0
0.05
0.002
Number of Tests
UF
47
44
2
5
3
3
3
3
3
2
RO
53
48
2
5
3
3
4
4
4
2
RO
0.02
*
2
*
1
0006
48
UF
0.05
*
8.8
0.13
58
*
*
0.016
78
0.014
0.035
0.003
*
0.002
*
Comments
No compounds detected
No compounds detected
No compounds detected
No compounds u6t6ci60
No compounds detected
No compounds detected
No compounds detected
No compounds detected
No compounds detectet
No compounds detected
UF contained:
7 |ig/l acetaldehyde am
1 3 |ig/l formaldehyde
RO contained:
no aldehydes
NOTES:
MCL = EPA Maximum Contaminant Level for drinking water at time
of testing.
RO = Reuse product treated by processes in Figure 32 including
reverse osmosis.
UF = Reuse product treated by processes in Figure 32 including
ultra filtration.
— = No MCL established at time of testing.
* = More than 50% of data below detection limit.
" = Montgomery Laboratory Methods (Pasadena, California).
Source: Hamaan etal., 1992.
105
-------
Figure 32. Denver Potable Reuse Demonstration Treatment Processes
Unchtorinsled
Secondary
Effluent
Source: Adapted from Lauer, 1991.
effects and toxicity studies were also carried out, but the
results are not yet available. Field work was completed in
1990, but there are no immediate plans to implement
direct or indirect potable reuse in Denver.
Representative of the treatment train required for direct
potable reuse Fs that developed in Denver. It includes,
after secondary treatment, the following processes, as
shown in Figure 32:
Q High-pH lime clarification,
Q Recarbonation,
Q Multimedia filtration,
Q Ultraviolet disinfection (as an option),
Q Activated carbon adsorption,
Q Reverse osmosis or ultraf iltration (as alternative
options),
Q Air stripping,
Q Ozonation, and
Q Chlorination
Most of these unit processes are well understood and
their performance can be expected to be effective and
reliable in large, well-managed plants. However, the
heavy burden of sophisticated monitoring for trace
contaminants that is required for potable reuse may be
beyond the capacity of smaller enterprises.
Despite the generally excellent results achieved in Denver,
there are no immediate plans to implement potable reuse
there. The implementation of direct, pipe-to-pipe, potable
reuse is not likely to be adopted in the foreseeable future
in the U.S. or elsewhere for several reasons:
Q Many attitude surveys show that the public will
accept and endorse many types of nonpotable
reuse while being reluctant to accept potable
reuse. In general, the public's reluctance to
support reuse increases as the degree of human
contact with the reclaimed water increases.
Section 7.3 includes a discussion of public
perceptions about reuse.
Q Indirect potable reuse is more acceptable to the
public than direct potable reuse because the
water is perceived to be "laundered" as it moves
in a river, lake, or aquifer. Whittier Narrows and El
106
-------
Paso are examples. Indirect reuse, by virtue of
the residence time in the water course, reservoir
or aquifer, often provides additional treatment
and offers an opportunity for monitoring the
quality and taking appropriate measures before
the water is abstracted for distribution. In some
instances, however, water quality may actually be
degraded as it passes through the environment.
3.8 Case Studies
Direct potable reuse will seldom be necessary.
Only a small portion of the water used in a
community needs to be of potable quality. While
high quality sources will often be inadequate to
serve all urban needs inthe future, the substitution
of reclaimed water for potable quality water now
used for nonpotable purposes would release
more of the high quality water service for potable
purposes.
3.8.1 Pioneering Urban Reuse for Water
Conservation: St. Petersburg, Florida
The City of St. Petersburg, Florida, is recognized as a
pioneer in urban water reuse. Faced with the alternatives
of ceasing effluent discharges to Tampa Bay or upgrading
to advanced wastewater treatment, the city council
adopted a policy of "zero discharge" in 1977, and in 1978
St. Petersburg began distributing reclaimed water for
nonpotable uses via an urban dual distribution system.
Today, St. Petersburg operates one of the largest urban
reuse systems in the world, providing reclaimed water to
more than 7,000 residential homes and businesses. In
1991, the city provided approximately 21 mgd (920 Us) of
reclaimed water for irrigation of individual homes,
condominiums, parks, school grounds, and golf courses;
cooling tower make-up; and supplemental fire protection.
Four wastewater treatment plants, with a total combined
capacity of 68.4 mgd (3,000 Us), provide activated sludge
secondary treatment, followed by alum coagulation,
filtration, and disinfection.
The dual distribution system comprises an extensive
network of more than 260 mi (420 km) of pipe ranging in
diameter from 2 to 48 in (5 to 122 cm). The system
incorporates five city-owned and operated, and four
privately-owned and operated booster pump stations.
Operational storage is provided in covered storage tanks
at the treatment facilities; however, no seasonal storage is
provided. Instead, 10 deep wells inject excess reclaimed
water into a saltwater aquifer approximately 1,000 ft (300
m) below the land surface. On a yearly average,
approximately 60 percentof the reclaimedwaterproduced
is injected into the deep wells.
Criteriafordelivery of reclaimed watertothe system include
chlorine residual, turbidity, SS, and chloride concentrations.
Reclaimed water is rejected for reuse and diverted to the
deep wells if the chlorine residual is less than 4.0 mg/L,
turbidity exceeds 2.5 nephelometric turbidity units (NTU),
SS exceed 5 mg/L rejected water, or chloride
concentrations exceed 600 mg/L.
While the initial impetus forthe reuse system was pollution
abatement, its greatest benefit has been water
conservation. By providing reclaimed water for urban
irrigation and other nonpotable uses, St. Petersburg has
been able to meet the community's rising potable water
demands without increasing supplies, despite a 10
percent population growth. Since procuring additional
potable supplies from an inland source would be
prohibitively expensive, water reuse has also made
economic sense for St. Petersburg.
Source: Johnson, 1990; COM 1987.
City of St. Petersburg Reclaimed Water Delivery Criteria
Source: Johnson, 1990.
107
-------
3.8.2 Meeting Cooling Water Demands with
Reclaimed Water: Palo Verde Nuclear
Generating Station, Arizona
The Palo Verde Nuclear Generating Station (PVNGS) is
the largest nuclear power plant in the nation, with a
generating capacity of 3,810 MW. The plant is located in
the desert, approximately 55 mi (89 km) west of Phoenix,
Arizona. The facility utilizes reclaimed water for cooling
purposes, and has zero discharge. The sources of the
cooling water for PVNGS are two wastewater treatment
plants in Phoenix and Tolleson, which provide secondary
treatment. The reclaimed water receives additional
treatment at the power plant to meet water quality
requirements.
PVNGS initially investigated alternative cooling systems
in conjunction with the available sources of cooling water
in the surrounding area. PVNGS first investigated once-
through cooling and found that the high demand could
not be met by any water bodies in the surrounding area.
PVNGS then decided to utilize cooling towers which
would only require an outside source to provide enough
water lost through evaporation and for blowdown water
to control salt content. This make-up demand of
approximately 37,000 gpm (2,330 Us), based on 75
percent annual average station capacity factor, still posed
obstacles in locating a source of water that could meet
this delivery rate and the quality requirements for coolant
water.
The Colorado River, located 100 mi (160 km) to the west,
was the first choice; however, the competition for the
water from several states eliminated that alternative.
Groundwaterwas also eliminated as an alternative due
[o quantity and quality concerns. It was then determined
that of the 150 mgd (6,575 L/s) of secondary quality
effluent being produced by the 91st Avenue WWTP in
Phoenix, only 35 mgd (1,530 L/s) was committed to other
users and the remaining 115 mgd (5,000 Us) was being
discharged to the normally dry Salt River. In addition, the
Tolleson WWTP, located only 1 mile from the 91st
Avenue plant, produced 17.5 mgd (767 Us) of effluent
that was also being discharged into the Salt River.
The combined available flow from the two plants, 132.5
mgd (5,800 L/s), was determined to more than adequately
meet the PVNGS flow demand and was selected as the
cooling water source. The transmission system from the
WWTPs to PVNGS consists of 28 mi (45 km) of gravity
pipeline, ranging from 114 in (290 cm) to 96 in (244 cm)
in diameter, and 8 mi (13 km) of 66-in (168.cm) diameter
pressurized force main.
Two 467-ac (189-ha) evaporation ponds were
constructed to dispose of liquid waste from blowdown.
The number of cycles of concentration was determined
to be 15 without any scale formation, so long as the
reclaimed water from the WWTP was f urthertreated prior
to use. A 90-mgd (3,940 L/s) tertiary wastewater
reclamation facility (WRF) was constructed at PVNGS.
The treatment process includes trickling filtration, cold
lime/soda ash softening, and gravity filters.
The trickling filtration reduces influent ammonia, which
causes metal corrosion, from 18-25 mg/L (As N) to less
than 5 mg/L. The filters provided a second benefit of
reducing alkalinity, thereby lowering the lime softening
demand. Cold lime/soda ash softening reduces scaling
and corrosive components such as calcium, magnesium,
silica and phosphate. Lastly, gravity filters deliver a
filtered effluent of less than 10 mg/L TSS.
108
-------
3.8.3 Agricultural Reuse In Tallahassee, Florida
The Tallahassee agricultural reuse system is a
cooperative operation in which the city owns and
maintains the irrigation system, while the farm is leased to
commercial enterprise. During evolution of the system
since 1966, extensive evaluation and operational flexibility
have been key factors in its success.
The City of Tallahassee was one of the first cities in Florida
to utilize reclaimed water for agricultural purposes. Spray
irrigation of reclaimed water from the City's secondary
wastewater treatment plant was initiated in 1966.
Detailed studies of this system in 1971 showed that the
system was successful in producing crops for agricultural
use. The study also concluded that the soil was effective
at removing SS, BOD, bacteria, and phosphorus from the
reclaimed water.
Until 1980, the system was limited to irrigation of 120 ac
(50 ha) of land used for hay production. Based upon
success of the early studies and experience, a new
sprayfield was constructed in 1980 southeast of
Tallahassee.
The Southeast Sprayfield has been expanded twice since
1980 to a total area of approximately 1,750 ac (700 ha).
The permitted application rate of the site is 3.16 in (8 cm)/
week, for a total capacity of 21.5 mgd (942 Us).
Sandy soils account for the high application rate. The soil
composition is about 95 percent sand, with a clay layer at
a depth of approximately 33 ft (10 m). The sprayfield has
gently rolling topography with surface elevations ranging
from 20 to 70 ft (6 to 21 m) above sea level.
Secondary treatment is provided the city's Thomas P.
Smith wastewater renovation plant. The reclaimed water
produced by this 17.5-mgd (767 L/s) activated sludge
plant meets waterquality requirements of 20 mg/LforBOD
and TSS and 200/100 ml for fecal coliform.
Reclaimed water is pumped approximately 8.5 mi (13.7
km) from the treatment plant to the sprayfield and
distributed via 13 center-pivot irrigation units.
The major crops produced include corn, soybeans,
coastal bermuda grass, and rye. Corn is stored as high-
moisture grain prior to sale, and soybeans are sold upon
harvest. Both the rye and bermuda grass are grazed by
cattle. Some of the bermuda grass is harvested as hay
and haylage.
Sources: Payne eta/., 1989; Overman and Leseman, 1982.
3.8.4 Seasonal Water Reuse Promotes Water
Quality Protection: Sonoma County,
California
Faced with a "no discharge" requirement in accordance
with the San Francisco Bay Regional Water Quality
Control Board's 1982 Basin Plan, the Sonoma Valley
County Sanitation District investigated the diversion of
approximately 3 mgd (131 Us) of effluent during the dry
weather months of May through October. The receiving
water, Schell Slough, is a tidal estuary less than 150 ft (46
m) wide and less than 10 ft (3m) deep at high tide. The
slough is particularly sensitive to water quality impacts
during the dry season, from May to October, when fresh
water flows in the slough cease and the water body
becomes a dead end slough flushed only by limited tidal
action. Dry weather dye studies indicated limited flushing
in the dry season. Based on these studies, the "no
discharge" directive forthe district was modified to prohibit
discharge only from May to October 31 of each year, with
discharge allowed during the rainy season.
Instead of discharging to the slough during the dry
season, local vineyards are irrigated with reclaimed
water. While the nutrient content of reclaimed water is
often viewed as a benefit, in this application there was a
concern that the nitrogen would produce excessive
foliage growth at the expense of grape production. As a
condition of use, the farmers required denitrification of
the reclaimed water. Nitrogen removal is achieved by
denitrification on an overland flow field. Cheese whey is
added to the reclaimed water prior to overland flow as a
substitute for growth of the denitrification
microorganisms. A backup means of avoiding discharge
to Schell Slough between May and October has been
developed for periods of high wastewater flows and/or
low irrigation demands. Excess reclaimed water is spray
irrigated and flows through a wetlands into Huderman
slough. Huderman Slough has greater dilution flows than
Schell Slough in dry weather, resulting in reduced impacts
when and if a discharge is required.
109
-------
3.8.5 Combining Reclaimed Water and River Water
for Irrigation and Lake Augmentation: Las
Collnas, Texas
Advanced secondary treated effluent and raw water from
the Elm Fork of the Trinity River are used to irrigate golf
courses, medians and greenbelt areas, and to maintain
water levels at.the Las Colinas development in Irving,
Texas. Las Colinas is a 12,000-ac (4,800 ha) master
planned development that features exclusive residential
areas, high-rise offices, luxury hotels, and four
championship golf courses. The drought-proof supply of
reclaimed water and river water, known as the Raw Water
Supply Project (RWSP), delivers irrigation water to 550
ac (220 ha) of landscaped areas and provides water to 19
lakes to make up evaporative losses from their 270-ac
(110 ha) total surface area.
Schematic of the Las Colinas Raw Water Supply Project
HackborryCr.
Country Club
Irrigation
Pump Station
Median
Irrigate:
if •*t$ggf*' xc^2t^^
i Lake 4 i LakeSA LakeSB
n A A
m I -1-
^-\-
Median Irrigation (2 Locations)
Exxon (4 Locations)
L. Remle Pump
Station No. 2
Central
Regional WWTP
HackbonyCr.
LSogment III
L. Remle Pump
Station No. 1
Elm Fork
Pump Station
Urban Center
Pump Stations
Elm Fork of
Trinity River
Las Colinas Sports Club
Irrigation Pump Station No. 1
Las Colinas Sports Club
Irrigation Pump Station No. 2
Las Colinas Sports Club
Irrigation Pump Station No. 3
Medians,
Greonbelt
Irrigation
(13 Location:)
Cottonwood Cr.
L. Segment I
Seg. II Seg. Ill Seg. IV Seg.V Seg. VI Seg. VII Cottonwood Valley
L. Segment I
Cottonwood
Pump Station
Las Colinas Sports Club
Irrigation Pump Station
Decker L Wlngren L.
L Seaman! V ^BES*" ^tgg&r ^qgszr ^
'^ CononwoodCr. Texas Green Texas Green
L. Seg. VIII L. Seg. I L. Seg. II
Beaver Cr. Beaver Cr. Beaver Cr. A Beaver Cr.
L. Seg. I L. Seg. II L. Seg. Ill ^L Seg. IV
1_ o _>.
Median Irrigation
(4 Locations)
GTE (9 Locations)
Res. RBS. Res. Res. i Rochelle [,Rclct',elle0 A Rochelte
SSatunga No., 10 No. 5 No. 6 No. 4 No. 3 A Res. No. 1 Res-No-3 A Res.No.2
Lake
I J- n
Rochelte
Pump Station
Median Irrigation
(8 Locations)
110
-------
The RWSP was initiated in July 1987. The reclaimed
water originates from the 115-mgd (5,040 Us) Central
Regional wastewater treatment plant (CRWWTP).
Reclaimed water is available year-round but is limited to
the pumping system's capacity of 16.4 mgd (719 Us).
Reclaimed water is pumped 11 mi (18 km) through a 30-
in (76-cm) diameter pipeline to Lake Remle. A portion of
the water is then pumped to a storage lake for irrigation at
one country club, and a portion is pumped to Lake Carolyn
where it is mixed with river water. A pump station on the
Elm Fork can deliver up to 4.6 mgd (202 Us) of river water
through a 16-in (41-cm) diameter pipeline to Lake
Carolyn. All water from the Elm Fork and the CRWWTP
blends with water in at least one lake before distribution
to 23 discharge points. The lakes are designed to allow
water to spill from lake to lake within the development
thereby controlling water surface elevations and
enhancing circulation. A schematic of the distribution
system is presented below.
Treatment processes at the CRWWTP consist of primary
clarification, equalization, activated sludge, secondary
clarification, filtration, activated carbon (as needed), and
disinfection by chlorination. The reclaimed water
discharged into Lake Remle has consistently met
discharge permit requirements of no more than 10 mg/L
BOD and 15 mg/LTSS. In addition, water quality samples
are collected from the Elm Fork and at selected lakes to
assess the water's irrigation, aesthetic, and recreational
quality.
The parameters monitored include BOD, TSS, fecal
coliform, dissolved oxygen, Secchi depth, pH, sodium
adsorption ratio (SAR), salinity, ortho-phosphorus, and
algae. Mixing the reclaimed waterwithriverwaterin lakes
reduces the SAR value of the reclaimed water from 3.85
to less than 2.0 in Lake Carolyn. A SAR value of 3.0 was
established as an acceptable limit to irrigate golf courses
at Las Colinas. The concentration of ortho-phosphorus
has increased at sampling locations in Lake Remle and
Lake Carolyn since the RWSP began. However,
accelerated eutrophication of lakes has not been noticed,
and the lake maintenance program for aquatic weeds
and algae was not altered.
Six fountain aerators were installed in lakes to increase
their assimilative capacity and to improve lake
appearance. In general, water quality in the Las Colinas
lakes remains acceptable subsequent to delivery of
reclaimed water. The success of the program is attributed
to the excellent quality of the reclaimed water; the
significant dilution which occurs as the reclaimed water,
river water and natural drainage blend during progression
through the system; and the flexibility to manage the
system by blending waters and promoting circulation
through the lakes, as required, to maintain water quality.
Sources: Water Pollution Control Federation, 1989; Smith
efa/., 1990.
111
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3.8.6 Integrating Wetlands Application with Urban
Reuse: Hilton Head Island, South Carolina
Hilton Head Island, located off the southeastern shore of
South Carolina, is plagued by poor soil conditions and
saltwater intrusion. The island is resort-oriented with
several golf courses and a booming population. Because
of the soil conditions and the increasing population,
wastewatertreatment and effluent disposal have become
an Increasing concern.
In 1982, a wastewater management plan was developed
with the goal of maximizing water reuse on the island. In
1983, the Hilton Head Island Utility Committee was
created to coordinate the efforts of the various agencies
involved in implementing the plan. The island-wide plan
called for upgrading all wastewater treatment plants to
tertiary treatment in order to minimize nutrient
concentrations in the reclaimed water and allow for
discharge when reuse demand is not sufficient. The
treatment levels can remain at the advanced secondary
treatment levels for golf course irrigation. In addition to
managing and coordinating the island-wide wastewater
treatment and reuse program, the Hilton Head Island
Utility Committee also developed guidelines for reuse.
These guidelines contain information regarding the
approved uses of reclaimed water, design criteria, and
administrative and hook-up procedures.
Golf courses have been irrigated with reclaimed water on
Hilton Head Island since 1973, when the Sea Pines and
Forest Beach Public Service Districts began irrigating the
Club Course at Sea Pines Plantation. In 1985, the Sea
Pines Public Service District upgraded and expanded the
existing wastewatertreatment plant to 5 mgd (219 Us).
The reclaimed water transmission system was also to be
upgraded and expanded in two phases. The Phase I
expansion includes service to approximately 150 ac (60
ha) of commercial and multi-family residences in addition
to the existing and new golf course irrigation. The entire
system, once completed, will include approximately 13
linear mi (20 km) of new reuse piping.
To serve the expanded irrigation system, a new 10-mgd
(438 Us) effluent pumping station has been constructed,
but is not yet fully operational. In addition, a 5-million gal
(19-million _) storage tank has been constructed.
Because the demand for reclaimed water decreases
during the rainy season, an alternative disposal system is
required. Several alternatives were studied, with the most
environmentally sound being the use of existing wetlands
on the island.
The use of reclaimed water to supplement wetlands
systems is ideal. The demand for reuse among the
connected customers decreases in the wet winter months
and increases in the summer. Due to the natural cycling,
wetlands typically are drier in the summer and wet in the
winter. This is the exact opposite of the reuse demand
and makes a perfect complement to the irrigation system.
Boggy Gut wetland in the Sea Pines Forest Preserve was
selected for a 3-year pilot study beginning in 1983. The
study called for an increase in the discharge from 0.3
mgd (13 Us) to 1.0 mgd (44 Us) over the entire study
period. No observable detrimental impacts on
groundwaterwere noted, and the pilot study was deemed
a success. It has since become fully operational.
The Sea Pines Public Service District Wetlands Program
has been expanded to include the White Ibis Marsh,
which recently began to receive reclaimed water. The
conceptual plan is to enhance the performance of both
wetland cells by stopping service to one cell every 5 years
and allowing the built up organics to oxidize. Service will
once again be returned to the renewed cell and the same
process repeated for the next cell.
The second project of interest is the Hilton Head
Plantation treatment plant and reuse system, located in
the northern portion of the island. The AWT plant serves
a private residential area, with golf course irrigation as
the primary means of reuse. The wet weather back-up to
the system is discharge to two wetlands: the Whooping
Crane Conservancy and the Cypress Conservancy.
Prior to wet weather discharge, both of these wetlands
areas had been drying due to changes in water flow
patterns resulting from development in the area. The
Nature Conservancy worked with the Hilton Head
Plantation in an effort to mutually benefit both institutions.
Hilton Head Plantation was granted a wet weather
discharge back-up to the golf course irrigation system,
and the Whooping Crane and Cypress conservancies
were given much needed water to help restore their
natural flow patterns.
Since wet weather discharge has begun to these two
wetlands areas, there has been a revival of wildlife.
Wading birds have increased in the conservancies, and
they are once again in their rookery states.
Both of these projects on Hilton Head Island are using
reclaimed water for recreational benefit by golf course
irrigation and are providing enhancement to area
wetlands by wet weather discharge.
Source: Hirsekorn and Ellison, 1987.
112
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3.8.7 Groundwater Replenishment with Reclaimed
Water: Los Angeles County, California
In south-central Los Angeles County, replenishment of
groundwater basins is accomplished by artificial recharge
of aquifers in the Montebello Forebay area. Waters used
for recharge via surface spreading include local storm
runoff, imported water from the Colorado River and state
project, and reclaimed water. The latter has been used
as a source of replenishment water since 1962. At that
time, approximately 12,000 ac-ft/yr (15 x 106 m3/yr) of
disinfected, activated sludge secondary effluent from the
Sanitation Districts of Los Angeles County Whittier
Narrows water reclamation plant (WRP) was spread in
the Montebello Forebay area of the Central groundwater
basin, which has an estimated usable storage capacity of
780,000 ac-ft (960 x 106 m3). In 1973, the San Jose Creek
WRP was placed in service and also supplied secondary
effluent for recharge. In addition, effluent from the
Pomona WRP that is not reused for other purposes is
discharged into San Jose Creek, a tributary of the San
Gabriel River, and ultimately becomes a source for
recharge in the Montebello Forebay.
In 1978, all three reclamation plants were upgraded to
provide secondary treatment, dual-media filtration
(Whittier Narrows and San Jose Creek WRPs) or
activated carbon filtration (Pomona WRP), and
chlorination/ dechlorination. In 1990, 50,000 ac-ft (62 x
106 m3/yr.)of reclaimed water was recharged, or
approximately 30 percent of the total inflow to the
Montebello Forebay.
The replenishment program is operated by the Los
Angeles County Department of Public Works (DPW),
while overall management of the groundwater basin is
administered by the Central and West Basin Water
Replenishment District. DPW has constructed two
spreading areas designed to increase the indigenous
percolation capacity. The Rio Hondo spreading basins
have a total of 427 ac (173 ha) available for spreading,
and the San Gabriel River spreading grounds have 224
ac (91 ha). The Rio Hondo and San Gabriel River
spreading grounds are subdivided into individual basins
that range in size from 4 to 20 ac (1.5 to 8 ha).
Under normal operating conditions, batteries of the
basins are rotated through a 21-day cycle consisting of:
Q A 7-day flooding period during which the basins
are filled to maintain a constant 1.2-m (4-ft)
depth;
Q A 7-day draining period during which the flow to
the basins is terminated and the basins are
allowed to drain; and
Q A 7-day drying period during which the basins
are allowed to thoroughly dry out.
This wetting/drying operation serves several purposes,
including maintenance of aerobic conditions in the upper
soil strata and vector control in the basins.
The reclaimed water produced by each reclamation plant
complies with primary drinking water standards and
meets total coliform and turbidity requirements of less
than 2.2/100 mL and 2 NTU, respectively. Reclaimed
water and groundwater quality data are given in the
following table.
1988-1989 Results of Reclaimed Water Analyses for the
Montebello Forebay Groundwater Recharge
Project3
Constituent
San Jose
WRPb
Whittier Narrows
WRP
Pomona Discharge
WRP Limits
Arsenic (mg/L) 0.005 0.004 <0.004 0.05
Aluminum (mg/L) <0.06 <0.10 <0.08 1.0
Barium (mg/L) 0.06 0.04 0.04 1.0
Cadmium (mg/L) NDC ND ND 0.01
Chromium (mg/L) <0.02 <0.05 <0.03 0.05
Lead (mg/L) ND ND <0.05 0.05
Manganese (mg/L) <0.02 <0.01 <0.01 0.05
Mercury (mg/L) <0.0003 ND <0.0001 0.002
Selenium (mg/L) <0.001 0.007 <0.004 0.01
Silver (mg/L) <0.005 ND <0.005 0.05
Lindane (ug/L) 0.05 0.07 <0.03 4
Endrin(ug/L) ND ND ND 0.2
Toxapene (ug/L) ND ND ND 5
Methoxyclor (ug/L) ND ND ND 100
2,4-D(ug/L) ND ND ND 100
2,3,5-TP (ug/L) <0.11 ND ND 10
SS(mg/L) <3 <2 <1 15
BOD (mg/L) 7 4 4 20
Turbidity (TU) 1.5 .1.6 1.0 2
Total Coliform (#/100 mL)<1 <1 <1 2.2
TDS(mg/L) 598 523 552 700
Nitrite + Nitrate (mg/L) 1.55 2.19 0.69 10
Chloride (mg/L) 123 83 121 250
Sulfate (mg/L) 108 105 82 250
Fluoride (mg/L) 0.57 0.74 0.50 1.6
Average of samples collected from October 1988 through
September 1989. Sampling frequency varied from daily to
bimonthly depending on constituent.
WRP - Water reclamation plant
ND - Not detected.
Source: Sanitation Districts of Los Angeles County, 1989.
113
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3.8.8 Aquifer Recharge Using Injection of
Reclaimed Water: El Paso, Texas
El Paso, Texas has injected reclaimed wastewater from
the Fred Hervey water reclamation plant into the Hueco
Bolson aquifersince June 1985. The Hueco Bolson aquifer
is an unconf ined aquiferthat supplies about 65 percent of
the water supply needs of El Paso. The reclaimed water is
transported from the treatment plant 1 mile (1.6 km) to a 3-
mile (4.8 km) long series of 10 injection wells. Each well is
16-in (41 cm) diameter and is screened from about 350 ft
(107 m) deep to a completed depth of 800 ft (244 m) below
ground.
The Hueco Bolson aquifer recharge was selected as a
demonstration study for the High Plains Reuse Project.
The 4-year study, siatedto be completed by October 1992,
is sponsored by the U.S. Bureau of Reclamation, El Paso
Water Utility, and the U.S. Geological Survey. The study
investigates the impacts of using reclaimed water to
recharge a water supply aquifer and evaluates
effectiveness and reliability of treatment processes in the
plant.
As part of the study, a groundwater flow and solute
transport model was used to calculate the residence time
of injected reclaimed water in the aquifer before it is
pumped out at production wells located from 0.25 mi (0.4
km) to 4.5 mi (7.2 km) distant from the injection wells. The
Liquid Treatment Train for Groundwater Recharge, El Paso, Texas
model results indicate that the representative residence
time is approximately 5 to 15 years.
The reclaimed water must meet drinking water standards
before it is injected to the aquifer. The effluent maintains
a free chlorine residual of about 0.3 mg/L as it leaves the
treatment train. The chlorine residual is needed to prevent
bacterial growth in the storage tank before the reclaimed
water is injected. The concentrations of trihalomethanes
(THMs) in the effluent is less than 50 ug/L (microgram per
liter). Groundwater samples collected from monitor wells
near the injection site have had elevated concentrations of
THMs, but always less than 30 ug/L.
The demonstration study includes a full evaluation of the
reliability of the water reclamation plant and identification
of the role played by each treatment step in achieving the
drinking water quality objectives established for the
effluent. The plant reliability review involves analyses of
priority pollutants and THMs in water samples taken from
the treatment train, THM-precursor analysis at the
granular activated carbon and ozonation treatment
stages, and evaluations of biotoxicity and pathogen
removal.
The Fred Hervey Water Reclamation Plant has a
maximum capacity of about 12 mgd (526 Us). Its 10-step
treatment train begins with primary treatment to allow
Primary
Screen.^ Degrit Settling
1st
Stage
Contact si
•Aeration ch
_f
Denitrification
Ml
2nd
Stage
Clarifier
Lime Sand GAC
Coagulation Recarbonatlon Filtration Disinfection Filtration
Clear Well Effluent
Storage Pumps
To Injection
Wells &
Industry
114
-------
screening, degritting, sedimentation and flow equalization.
The primary effluent enters a two-stage biophysical
process which combines activated sludge with powdered
activated carbon adsorption (PACT™ system). This step
of the treatment is designed for organic removal,
nitrification and denitrificatfon. Methanol is added to the
second stage to provide a carbon source for the
denitrifiers. Waste secondary sludge and spent carbon
are processed in a wet air regeneration (oxidation) unit
which destroys the sludge and regenerates the carbon for
reuse in the PACT system. The wastewater effluent
advances to a lime treatment step to remove phosphorus
and heavy metals, to kill viruses, and to soften the effluent.
Turbidity removal is provided by sand filters and
disinfection is provided by ozonation. The final product
water is passed through a granular activated carbon filter
to provide final polishing before release to storage.
Between 1985 and 1990, approximately 7.5 billion gal (28
x 106 m3) of reclaimed water have been injected to
recharge the Hueco Bolson aquifers. The current price of
treating and injecting the water is about $2.00/gal (up from
$1.55/1,000 gal in 1986).
Before the aquifer recharge project was initiated, water
levels in the Hueco Bolson aquifer declined at a rate of 2
to 6 ft (0.6 to 1.8 m)/yr because groundwater was
withdrawn 20 times fasterthan the aquifer's natural rate of
recharge. Groundwater model results indicate that
groundwater levels in 1990 are 8 to 10 ft (2.4 to 3.0 m)
higherthan what theywould have been withoutthe aquifer
recharge project.
Sources: Knorr, 1985, Knorref a/., 1987.
3.8.9 Water Factory 21 Direct Injection Project:
Orange County, California
A project involving groundwater recharge by the injection
of reclaimed water is operated by the Orange County
Water District (OCWD) in Fountain Valley, California.
OCWD first began pilot studies in 1965 to determine the
feasibility of using tertiary wastewater treatment in a
hydraulic barrier system to prevent saltwater
encroachment into potable water supply aquifers.
Construction of a tertiary treatment facility, known as
Water Factory 21 Treatment Processes
Water Factory 21, was started in 1972, and injection
operations began in 1976.
Water Factory 21 has a design capacity of 15 mgd (657
Us) and treats activated sludge secondary effluent from
the adjacent Orange County Sanitation District's (OCSD)
wastewater treatment plant by the following unit
operations: lime clarification for removal of SS, heavy
metals, and dissolved minerals; air stripping (not currently
in service) for removal of ammonia and volatile organic
Influent
Mixing
Flocculation
CtarflSflon
Chlorine
Disinfection
Filtration
Injection
Carbon
Reverse
Osmosis
Extraction
Source: Adapted from Water Pollution Control Federation, 1989.
115
-------
compounds; recarbonation for pH control; mixed-media
iitration for removal of SS; granular activated carbon
adsorption for removal of dissolved organics; reverse
osmosis (RO) for demineralization; and chlorination for
biological control and disinfection.
Due to atotal dissolved solids limitation of 500 mg/L prior
:o injection, RO is used to demineralize up to 5 mgd (219
Js) of the reclaimed water used for injection. The
feedwater to the RO plant is effluent from the mixed-
media filters. Effluent from the carbon adsorption
process is disinfected and blended with RO-treated
water. Activated carbon is regenerated onsite. Solids
rom the settling basins are incinerated in a multiple-
nearth furnace from which lime is recovered and reused
n the chemical clarifier. Brine from the RO plant is
pumped to OCSD's facilities for ocean disposal.
Reclaimed water produced at Water Factory 21 is
injected into a series of 23 multi-casing wells, providing
81 individual injection points into four aquifers to form a
seawater intrusion barrier known as the Talbert injection
barrier (Argo and Cline, 1985). The injection wells are
located approximately 3.5 mi (5.6 km) inland from the
Pacific Ocean. There are seven extraction wells (not
currently being used) located between the injection wells
and the coast. Before injection, the product water is
blended 2:1 with well water from a deep aquifer not
subject to contamination. Depending on basin
conditions, the injected water flows toward the ocean
forming a seawater barrier, flows inland to augment the
potable groundwater supply, or flows in both directions.
Water Factory 21 reliably produces high-quality water.
No coliform organisms were detected in any of 179
samples of the reclaimed water during 1988. A virus
monitoring program conducted from 1975 to 1982
demonstrated to the satisfaction of the state and county
health agencies that Water Factory 21 produces
reclaimed water that is essentially free of measurable
levels of viruses (McCarty et. al., 1982). The average
turbidity of filtereffluent was 0.22 FTU and did not exceed
1.0 FTU during 1988.
The average COD and TOC concentrations for 1988
were 8 mg/L and 2.6 mg/L, respectively. The
effectiveness of Water Factory 21 's treatment processes
for the removal of inorganic and organic constituents is
shown in the following tables.
Water Factory 21 Injection Water Quality
Constituent
Discharge Limits Injection Water*
Concentration in mg/L
Sodium 115
Sulfate 125
Chloride 120
IDS 500
Hardness 180
pH (units) 6.5-8.5
Ammonia Nitrogen —
Nitrate Nitrogen —
Total Nitrogen 10
Boron .05
Cyanide 0.2
Fluoride 1.0
MBAs 0.5
Concentration in ua/L
Arsenic 50
Barium 1,000
Cadmium 10
Chromium 50
Cobalt 200
Copper 1,000
Iron 300
Lead 50
Manganese 50
Mercury 2
Selenium 10
Silver 50
82
56
84
306
60
7.0
4-7
0.4
5.8
0.4
<0.01
0.5
0.5
<5.0
18
0.6
4.7
33
<1.0
4.3
<0.5
<5.0
3.3
*After blending 2:1 with deep well water.
Source: Wesner, 1989.
Water Compounds Detected in Water Factory 21
Injection Water0
Constituent
Injection Water *•* (ug/L)
Methylene Chloride
Chloroform
Dibromochloromethane
Chlorobenzene
Bromodichloromethane
Bromoform
1,1,1-Trichlorethane
1.0
5.4
1.1
TRC
3.7
0.8
TR
Fifty-three specific volatile organic compounds were reported
as undetected in the sample.
After blending 2:1 with deep well water.
TR = Trace. Concentration was below reportable detection
limit.
Source: Orange County Water District, 1989.
116
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Leseman. 1989. Operational Characteristics of a
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Piet, G.J., and B.C.J. Zoeteman. 1980. Organic Water
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122
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CHAPTER 4
Water Reuse Regulations and Guidelines in the U.S.
Most reuse programs operate within a framework of
regulations that must be addressed in the earliest stages
of planning. A thorough understanding of all applicable
regulations is required to plan the most effective design
and operation of a water reuse program and to streamline
implementation.
Currently, there are no federal regulations directly
governing water reuse practices in the United States.
Water reuse regulations have, however, been developed
by many of the states. These regulations vary
considerably from state to state. Some states, such as
Arizona, California, Florida, and Texas, have developed
regulations that strongly encourage water reuse as a
water resources conservation strategy. These states
have developed comprehensive regulations specifying
water quality requirements, treatment processes, or both
for the full spectrum of reuse applications. The objective
in these states is to derive the maximum resource benefits
of the reclaimed water while protecting the environment
and public health. Some states have developed water
reuse regulations with the primary intent of providing a
disposal alternative to discharge to surface waters,
without considering the management of reclaimed water
as a resource.
This section provides an inventory of the various state
water reuse regulations throughout the U.S. and
introduces recommended guidelines that may aid in the
development of more comprehensive state or even
federal standards for water reuse. Water reuse outside
the U.S. is discussed in Chapter 8.
4.1 Inventory of Existing State
Regulations
The following inventory of state reuse regulations is
based on a survey of all states conducted specifically for
this document. Regulatory agencies in all 50 states were
contacted by mail in September 1990 and asked to
provide information concerning their current regulations
governing water reuse. After follow-up contact, all 50
states responded to the request for information. All of the
information presented in this section is considered current
as of March 1992.
Also as part of the survey, all states were asked to provide
an inventory of their existing reuse projects. The results
indicated there are approximately 1,900 reuse projects
currently operating throughout 34 states. This represents
a significant increase since the survey conducted in 1979
as part of the original 1980 Guidelines (EPA, 1980b),
when only 540 reuse projects were reported throughout
24 states.
Only California and Florida compile comprehensive
inventories of reuse projects by types of reuse application.
These inventories are available from the California Water
Resources Control Board in Sacramento and the Florida
Department of Environmental Regulation in Tallahassee,
respectively.
The U.S. Geological Survey compiles an estimate of
national reclaimed water use every 5 years in their
publication Estimated Use of Water in the United States.
The 1990 inventory estimated that approximately 900
mgd of the effluent discharged in the U.S. was used for
beneficial purposes.
Most states do not have regulations that cover all potential
uses of reclaimed water. Arizona, California, Florida,
Texas, Oregon, Colorado, Nevada, and Hawaii have
extensive regulations or guidelines that prescribe
requirements for a wide range of end uses of the
reclaimed water. Other states have regulations or
guidelines which focus upon land treatment of
wastewater effluent, emphasizing additional treatment or
effluent disposal rather than beneficial reuse, even
though the effluent may be used for irrigation of
agricultural sites, golf courses, or public access lands.
Based on the inventory, current regulations may be
divided into the following reuse categories:
123
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Q Unrestricted urban reuse - irrigation of areas in
which public access is not restricted, such as
parks, playgrounds, school yards, and
residences; toilet flushing, air conditioning, fire
protection, construction, ornamental fountains,
and aesthetic impoundments.
Q Restricted urban reuse - irrigation of areas in
which public access can be controlled, such as
golf courses, cemeteries, and highway medians.
Q Agricultural reuse on food crops - irrigation of
food crops which are intended for direct human
consumption, often further classified as to
whether the food crop is to be processed or
consumed raw.
Q Agricultural reuse on non-food crops - irrigation
of fodder, fiber, and seed crops, pasture land,
commercial nurseries, and sod farms.
Q Unrestricted recreational reuse - an
impoundment of water in which no limitations are
imposed on body-contact water recreation
activities.
Q Restricted recreational reuse - an impoundment
of reclaimed water in which recreation is limited
to fishing, boating, and other non-contact
recreational activities.
Q Environmental reuse - reclaimed water used to
create artificial wetlands, enhance natural
wetlands, and to sustain stream flows.
Q Industrial reuse - reclaimed water used in
industrial facilities primarily for cooling system
make-up water, boiler-feed water, process water,
and general washdown.
Table 26 provides an overview of the current water reuse
regulations and guidelines by state and by reuse
category. The table identifies those states that have
regulations, those with guidelines and those states which
currently do not have either. Regulations refer to actual
rules that have been enacted and are enforceable by
governmental agencies. Guidelines, on the other hand,
are not enforceable but can be used in the development
of a reuse program.
As of March 1992, 18 states had adopted regulations
regarding the reuse of reclaimed water, 18 states had
guidelines or design standards, and 14 states had no
regulations or guidelines. In states with no specific
regulations or guidelines on water reclamation and reuse,
programs may still be permitted on a case-by-case basis.
The majority of current state regulations and guidelines
pertain to the use of reclaimed water for urban and
agricultural irrigation. At the time of the survey, the only
states that had specific regulations or guidelines
regarding the use of reclaimed water for purposes other
than irrigation were Arizona, California, Florida, Hawaii,
Nevada, Oregon, Colorado, South Dakota, Texas, and
Utah.
Table 27 shows the number of states with regulations or
guidelines for each type of reuse. The category of
unrestricted urban reuse has been subdivided to indicate
the number of states that have regulations pertaining to
urban reuse not involving irrigation. Florida, Texas, and
Hawaii are the only states that have regulations pertaining
to the use of reclaimed water for toilet flushing. Florida,
Texas, and Hawaii all require a high degree of treatment
prior to use for toilet flushing. In addition, Texas requires
that the reclaimed water be dyed blue prior to distribution
for use as toilet flush water, while Florida requires that
reclaimed water may only be used for toilet flush water
where residents do not have access to the plumbing
system for repairs or modifications.
Florida and Hawaii are currently the only states with
regulations pertaining to the use of reclaimed water for
fire protection, while Nevada, Florida, Hawaii, and
Oregon have regulations for the use of reclaimed water
for construction purposes. The use of reclaimed waterfor
landscape or aesthetic impoundments is regulated in the
states of California, Florida, Hawaii, Oregon, Texas,
Colorado, and Nevada. Hawaii is currently the only state
with regulations or guidelines pertaining to the use of
reclaimed water for street cleaning.
At this time, Arizona, California, Colorado, Hawaii,
Nevada, Oregon, and Texas have regulations or
guidelines pertaining to recreational reuse, while Arizona,
Florida, and South Dakota have regulations or guidelines
pertaining to environmental reuse utilizing natural or
artificial wetlands. Reclaimed water used for industrial
purposes is currently regulated in Arizona, Hawaii,
Nevada, Oregon, Texas and Utah.
Summaries of each state's regulatory or guideline
requirements for each type of reuse are given in Appendix
A in Tables A-1 through A-8. The regulations pertaining
to each type of reuse are divided into the following
categories:
Q Reclaimed water quality and treatment
requirements
124
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Table 26. Summary of State Reuse Regulations and Guidelines
STATE
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Alabama ,
Alaska
Arizona
Arkansas
Caltfomia
Colorado
Delaware
'Florida
Georgia
Hawaii :
Idaho
Illinois
Indiana
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Jersey
Mew Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Bhdda Island
South Carolina
South Qakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
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(1) Draft or Proposed
(2) Specific regulations on reuse have not been adopted; however, reclamation may be approved on a case-by-case basis.
125
-------
Table 27. Number of States with Regulations
or Guidelines for Each Type of
Reuse Application
Type of Reuse
Number of States
Unrestricted Urban
Irrigation
Toilet Flushing
Fire Protection
Construction
Landscape Impoundment
Street Cleaning
Restricted Urban
Agricultural (Food Crops)
Agricultural (Non-Food Crops)
Unrestricted Recreational
Restricted Recreational
Environmental (Wetlands)
Industrial
22
22
3
2
4
7
1
27
19
35
5
7
3
6
Q Reclaimed water monitoring requirements
Q Treatment facility reliability
Q Storage requirements
Q Application rates
Q Groundwater monitoring
Setback distances (buffer zone)
4.1.1
Reclaimed Water Quality and Treatment
Requirements
Requirements for water quality and treatment receive the
most attention in state reuse regulations. States which
have water reuse regulations or guidelines have set
standards for reclaimed water quality and/or specified
minimum treatment requirements. Generally, where
unrestricted public exposure is likely in the reuse
application, wastewater must be treated to the highest
degree prior to its application. Where exposure is not
likely, however, a lower level of treatment is usually
accepted.
The most common parameters for which water quality
limits are imposed are biochemical oxygen demand
(BOD), total suspended solids (TSS), and total or fecal
coliform counts. Total and fecal coliform counts are
generally used as indicators to determine the degree of
disinfection. A limit on turbidity is usually specified to
monitor the performance of the treatment facility.
4.1.1.1 Unrestricted Urban Reuse
Unrestricted urban reuse involves the use of reclaimed
water where public exposure is likely in the reuse
application, thereby necessitating the highest degree of
treatment. Review of existing regulations, however,
reveals a wide variation in treatment and water quality
requirements for unrestricted urban reuse. For example,
Utah requires advanced treatment with BOD not to
exceed 10 mg/L and TSS not to exceed 5 mg/L. In
addition, total coliform is not to exceed 3/100 mL at any
time. South Dakota, on the other hand, requires only
secondary treatment with disinfection with the median
total coliform count not to exceed 200/100 mL.
In general, all states with regulations require a minimum
of secondary or biological treatment prior to unrestricted
urban reuse, with most requiring disinfection. However,
many states require additional levels of treatment. The
states of Idaho, California, and Colorado require
oxidation, coagulation, clarification, filtration, and
disinfection prior to unrestricted urban reuse. Other
states, such as Arizona and Texas, do not specify the
type of treatment processes required, but only set limits
on the reclaimed water quality.
Where specified, limits on BOD range from 5 mg/L to 30
mg/L. Texas requires that BOD not exceed 5 mg/L
(monthly average) except when reclaimed water is used
for landscape impoundments, in which case BOD is
limited to 10 mg/L. Georgia, on the other hand, requires
that BOD not exceed 30 mg/L prior to unrestricted urban
reuse. Limits on TSS vary from 5 mg/L to 30 mg/L. Both
Utah and Florida require that TSS hot exceed 5 mg/L,
with Florida requiring that the TSS limit be achieved prior
to disinfection and not be exceeded in any one sample.
Georgia requires that TSS not exceed 30 mg/L. Forthose
states that do not specify limitations on BOD or TSS, a
particular level of treatment is usually specified.
Average fecal and total coliform limits for those states
that limit conforms range from non-detectable to 200/100
mL. Higher single sample fecal and total coliform limits
are noted in several state regulations. Florida requires
that 75 percent of the fecal coliform samples taken over
a 30-day period be below detectable levels, with no single
sample in excess of 25/100 mL. Conversely, South
Dakota requires a'medial total coliform count not to
exceed 200/100 mL. Utah requires that no single sample
exceed a total coliform count of 3/100 mL for unrestricted
urban reuse, while Texas and Arizona require that no
single fecal coliform count exceed 75/100 mL.
Where specified, limits on turbidity range from 2 to 5 NTU.
For example, Oregon requires that the turbidity not
exceed 2 NTU (24-hour mean) and California requires
126
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the turbidity not exceed 2 NTU. Arizona requires that
turbidity not exceed 5 NTU. Florida requires continuous
on-line monitoring of turbidity; however, no limit is
specified.
At this time, Arizona and Hawaii are the only states that
have set limits on certain pathogenic organisms for
unrestricted urban reuse, in Arizona, the pathogens
include enteric viruses and Ascar/s lumbricoides
(roundworm) eggs. Arizona's allowable limit for the
enteric virus is 125 plaque forming units (pfu)/40 L and
none detectable for Ascaris lumbricoides. In Hawaii, the
pathogens are enteric viruses and the allowable limit is
less than 1 pfu/40 L. South Carolina requires that viruses
be monitored but does not specify the type of viruses to
be monitored or any limits.
4.1.1.2 Restricted Urban Reuse
Restricted urban reuse involves the use of reclaimed
water where public exposure to the reclaimed water is
controlled; therefore, treatment requirements may not be
as strict as in unrestricted urban reuse. Review of existing
regulations, again, reveals a wide variation in treatment
and water quality requirements for restricted urban reuse.
Only 12 of 22 states that regulate both categories adjust
requirements downward for this category. Five states do
not permit unrestricted urban reuse, but only allow
restricted urban reuse. For example, Utah requires
advanced treatment with BOD not to exceed 10 mg/L and
TSS not to exceed 5 mg/L. In addition, total coliform is not
to exceed 3/100 ml_ at any time. New Mexico, on the
other hand, requires that the reclaimed water be
adequately treated and disinfected with the fecal coliform
count not to exceed 1,000/100 mL.
In general, most states with regulations require a
minimum of secondary or biological treatment followed
by disinfection prior to restricted urban reuse. Again,
many states require additional levels of treatment, with
California, Idaho, and Colorado requiring disinfection and
biological oxidation prior to restricted urban reuse. South
Carolina requires secondary treatment with disinfection,
chemical addition, and filtration, except for golf course
irrigation where filtration and chemical addition are not
required. As in unrestricted urban reuse, Arizona does
not specify the type of treatment processes required, but
only sets limits on the reclaimed water quality.
Where specified, limits on BOD range from 5 mg/L to 30
mg/L. South Carolina requires that BOD not exceed 5
mg/L (monthly average), while Delaware, Hawaii,
Maryland, Georgia, and Texas require that BOD not
exceed 30 mg/L prior to restricted urban reuse. Limits on
TSS vary from 5 mg/L to 90 mg/L. Utah, Florida, South
Carolina, and North Carolina require that TSS not exceed
5 mg/L, while Maryland requires that TSS not exceed 90
mg/L. As in unrestricted urban reuse, forthose states that
do not specify limitations on BOD or TSS, a particular
level of treatment is usually specified.
Average fecal coliform limits for those states that limit
fecal conforms range from non-detectable to 1,000/100
mL, with some states allowing higher single sample fecal
coliform limits. As in unrestricted urban reuse, Florida
requires that 75 percent of the fecal coliform samples
taken over a 30-day period be below detectable levels,
with no single sample in excess of 25/100 mL. New
Mexico, on the other hand, requires the fecal coliform
count not to exceed 1,000/100 mL. North Carolina
requires that the maximumfecal coliform level not exceed
1/100 mL, while Arizona requires that no single fecal
coliform count exceed 1,000/100 mL.
Nevada is the only state that has set a limit on turbidity for
restricted urban reuse, requiring that no single sample
exceed a turbidity of 5 NTU.
4.1.1.3 Agricultural Reuse - Food Crops
The use of reclaimed water for irrigation of food crops is
prohibited in some states, while others allow irrigation of
food crops with reclaimed water only if the crop is to be
processed and not eaten raw. Most states require a high
level of treatment when reclaimed water is used for edible
crops, especially those which are consumed raw. As in
other reuse applications, however, existing regulations
on treatment and water quality requirements vary from
state to state and depend largely on the type of irrigation
employed and the type of food crop being irrigated. For
example, forfoods consumed raw, Colorado requires that
the reclaimed water be disinfected and biologically
oxidized when surface irrigation is used, with the mean
total coliform count not to exceed 2.2/100 mL. When
spray irrigation is utilized, Colorado requires that the
reclaimed water be disinfected, oxidized, coagulated,
clarified, and filtered, with the mean total coliform count
not to exceed 2.2/100 mL. Forprocessed foods, Colorado
requires only disinfection and oxidation regardless of the
type of irrigation, with the total coliform count not to
exceed 23/100 mL.
Treatment requirements range from primary treatment in
Arkansas for irrigation of processed food crops, to
biological oxidation, coagulation, clarification, filtration,
and disinfection in California, Colorado, and Idaho.
Where specified, limits on BOD range from 20 mg/L to 30
mg/L. Florida requires that the annual average CBOD not
exceed 20 mg/L after secondary treatment with filtration
and high level disinfection, while Texas requires that the
BOD not exceed 30 mg/L (monthly average) when the
127
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reclaimed water is treated using a pond system. In Texas,
spray irrigation is not permitted on foods to be consumed
raw. Limits on TSS vary from 5 mg/L to 25 mg/L. Florida
requires that TSS not exceed 5 mg/L in any one sample
prior to disinfection, while Utah requires that the TSS not
exceed 25 mg/L (monthly average). In Florida, direct
contact of reclaimed water on edible crops that are not
processed is prohibited, while Utah only considers the
irrigation of particularfood crops on a case-by-case basis
and does not allow the use of spray irrigation.
Average fecal and total coliform limits for those states
that lim'rt coliforms range from non-detectable to 2,0001
100 mL. Florida requires that 75 percent of the fecal
coliform samples taken over a 30-day period be below
detectable levels, with no single sample in excess of 25/
100 mL. Conversely, Utah requires a median total
coliform count of 2,000/100 mL. Again, some states allow
higher single sample coliform counts. California and
Oregon require that no single sample exceed a total
coliform count of 23/100 mL, while Arizona requires that
no single fecal coliform count exceed 2,500/100 mL for
irrigation of food crops that are to be processed.
Where specified, limits onturbidity range from 1 to 3 NTU.
For example, Arizona requires that the turbidity not
exceed 1 NTU for reclaimed water irrigated on food crops
to be consumed raw, while Texas requires that turbidity
not exceed 3 NTU.
At this time, Arizona and Hawaii are the only states that
have set limits on certain pathogenic organisms for
agricultural reuse of nonfood crops. In Arizona, the
pathogens include: enteric viruses, Entamoeba
histolytica, Giardia [amblia, and Ascaris lumbricoides.
The limits on these pathogenic organisms apply to
irrigation of unprocessed food crops. The allowable limit
for all of these organisms in Arizona, with the exception of
enteric viruses, is none detectable. The allowable limit for
enteric viruses is 1 pfu/40 L. In Hawaii, when reclaimed
water is used to irrigate root food crops or food crops with
the above-ground edible portion that touches the ground,
the pathogens that have set limits include: enteric viruses,
viable oocysts, Cryptosporidium, and cysts of Giardia and
Entamoeba. Hawaii's guidelines state that these
organisms, with the exception of enteric viruses, should
be non-detectable. The allowable limit for enteric viruses
is 1 pfu/40 L.
4.1.1.4 Agricultural Reuse - Nonfood Crops
The use of reclaimed water for agricultural irrigation of
nonfood crops presents the least opportunity of human
exposure to the water, resulting in less stringent treatment
and water quality requirements than otherforms of reuse.
Treatment requirements range from primary treatment in
Arkansas, California, and New Mexico, to secondary
treatment with disinfection in the majority of the states
with regulations. Arkansas, California and New Mexico
also require disinfection when irrigating pastures for
milking animals.
Where specified, limits on BOD range from 20 mg/L to 75
mg/L. Florida requires that the annual average CBOD not
exceed 20 mg/L after secondary treatment and basic
disinfection. Texas also requires that BOD not exceed 20
mg/L when using a treatment system other than a pond
system. Delaware and Georgia require that the BOD not
exceed 75 mg/L during peak flow conditions and 50 mg/
L during average flow conditions. Limits on TSS vary from
10 mg/L to 90 mg/L. Florida requires that the annual
average TSS not exceed 20 mg/L except when a
subsurface application is used, in which case the single
sample TSS limit is 10 mg/L. Maryland, on the other hand,
requires that TSS not exceed 90 mg/L.
Average fecal and total coliform limits for those states
that limit coliforms range from 2.2/100 mLto 2,000/100
mL. Nevada requires that the median fecal coliform count
not exceed 2.2/100 mL for spray irrigation sites with no
buffer zone. California, Hawaii, and Oregon all require
that the median total coliform count not exceed 23/100
mL. Conversely, Utah requires that the total coliform
count not exceed 2,000/100 mL. Some states allow
higher single sample coliform counts. Nevada requires
that no single sample exceed a fecal coliform count of 23/
100 mL for spray irrigation sites with no buffer zone, while
Arizona requires that no single fecal coliform count
exceed 4,000/100 mL.
At this time no states have any required limits on turbidity
for reclaimed water used for agricultural reuse on nonfood
crops.
As for pathogenic organisms, Arizona calls for no
detectable common large tapeworms when reclaimed
water is used for irrigation of pastures.
4.1.1.5 Unrestricted Recreational Reuse
As with unrestricted urban reuse, unrestricted
recreational reuse involves the use of reclaimed water
where public exposure is likely, thereby necessitating the
highest degree of treatment. Only five states (Arizona,
Colorado, California, Nevada, and Oregon) have
regulations pertaining to unrestricted recreational reuse.
Nevada requires secondary treatment with disinfection,
while California and Colorado require disinfection,
biological oxidation, coagulation, clarification, and
filtration. None of these five states have set limits on BOD
or TSS; however, California, Oregon, and Colorado all
require that the median total coliform count not exceed
128
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2.2/100 ml, with no single sample to exceed 23/100 ml_.
Nevada requires that the median fecal coliform count not
exceed 2.2/100 ml, with no single sample to exceed 23/
100 ml_, while Arizona requires that the median fecal
coliform count not exceed 200/100 ml, with no single
sample to exceed 800/100 ml.
Limits on turbidity range from 1 NTU in Arizona to 2 NTU
in California, Nevada, and Oregon. Colorado has no limit
on turbidity.
At this time, Arizona is the only state which has set limits
on certain pathogenic organisms for unrestricted
recreational reuse. The pathogens include: enteric virus,
Entamoeba histolytica, Giardia lambl/a, and Ascaris
lumbricoides. The allowable limit for all of these
organisms, with the exception of enteric virus, is none
detectable. The allowable limit for the enteric virus is 1
pfu/40 L.
4.1.1.6 Restricted Recreational Reuse
State regulations regarding treatment and water quality
requirements for restricted recreational reuse are
generally less stringent than for unrestricted recreational
reuse since the public exposure to the reclaimed water is
less likely. Only seven states (Arizona, Colorado,
California, Hawaii, Nevada, Oregon, and Texas) have
regulations pertaining to restricted recreational reuse.
With the exception of Arizona, all of the states with
regulations basically require secondary treatment with
disinfection. Arizona does not specify treatment process
requirements.
Texas is the only state with a limit on BOD, which is set at
10 mg/L. None of the seven states has set limits on TSS.
California, Oregon, and Colorado requirethatthe median
total coliform count not exceed 2.2/100 ml. Oregon also
requires that no single total coliform sample exceed 23/
100 mL. Nevada requires that the median fecal coliform
count not exceed 2.2/100 mL, with no single sample
exceeding 23/100 mL, while Texas requires that the fecal
coliform count not exceed 75/100 mL. Hawaii requires
that the mean total coliform count not exceed 23/100 mL,
with no two consecutive samples exceeding 240/100 mL.
Arizona, on the other hand, requires the median fecal
coliform count not to exceed 1,000/100 mL, with no single
sample exceeding 4,000/100 mL.
Limits on turbidity range from 3 NTU in Nevada and Texas
to 5 NTU in Arizona. Colorado, California, and Oregon
have no limits on turbidity.
At this time, Arizona is the only state which has set limits
on certain pathogenic organisms for restricted
recreational reuse. The pathogens include enteric viruses
and Ascaris lumbricoides. The allowable limit for enteric
viruses is 125/40 L and none detectable for Ascaris
lumbricoides.
4.1.1.7 Environmental - Wetlands
Review of existing reuse regulations show only three
states (Arizona, Florida and South Dakota) with
regulations pertaining to the use of reclaimed water for
creation of artificial wetlands and/or the enhancement of
natural wetlands.
South Dakota, whose regulations apply only to creation
of artificial wetlands, require pretreatment with
stabilization ponds prior to delivery to artificial wetlands.
Florida has comprehensive and complex rules governing
the discharge of reclaimed water to wetlands. Treatment
and disinfection levels are established for different types
of wetlands, different types of uses, and the degree of
public access. Most wetland systems in Florida are used
for additional treatment and only wetland restoration
projects are considered reuse. Arizona does not specify
the level of treatment required, but requires that the pH
remain between 6.5 - 8.6, the dissolved oxygen in the
receiving water not drop below 6 mg/L, and the mean
fecal coliform count not exceed 1,000/100 mL, with no
single sample exceeding 4,000/100 mL. Arizona also
requires that the temperature of the reclaimed water shall
not interfere with aquatic life and wildlife in the wetland
system.
4.1.1.8 Industrial Reuse
Based on review of the existing reuse regulations, five
states (Hawaii, Nevada, Oregon, Texas, and Utah) have
regulations pertaining to industrial reuse of reclaimed
water.
Nevada requires a minimum of secondary treatment and
disinfection, with the mean fecal coliform count not to
exceed 200/100 mL and no single sample exceeding 400/
100 mL. Oregon requires biological treatment and
disinfection, with the median total coliform count not to
exceed 23/100 mL and no two consecutive samples
exceeding 240/100 mL. Texas requires that the BOD not
exceed 30 mg/L with treatment using a pond system and
20 mg/L with treatment other than a pond system. Texas
also requires that the fecal coliform count not exceed
200/100 mL. Elsewhere, Utah requires advanced
treatment, with the BOD not exceeding 10 mg/L at any
time, TSS not exceeding 5 mg/L at anytime, and the total
coliform count not exceeding 3/100 mL at any time.
In addition to a total coliform count not to exceed 23/100
mL for a single sample, the state of Hawaii has set limits
for enteric viruses when reclaimed water is used for
industrial cooling water. The allowable limit for enteric
129
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viruses is 1 pfu/40 L. Hawaii also requires that reclaimed
water used for industrial cooling be treated with biocide or
other disinfection agent to prevent viability of Legionella
and Klebsiella.
4.1.2 Reclaimed Water Monitoring Requirements
Reclaimed water monitoring requirements vary greatly
from state to state and again depend on the type of reuse.
For unrestricted urban reuse, Arizona requires sampling
forf ecal coliform daily, while for agricultural reuse of non-
food crops sampling for fecal coliform is only required
once a month. Arizona also requires that turbidity be
monitored on a continuous basis when a limit on turbidity
is specified.
California, Florida, and Washington also require the
continuous on-line monitoring of turbidity. Oregon, on the
other hand, requires that turbidity be monitored hourly for
unrestricted urban and recreational reuse as well as
agricultural reuse on food crops and sampling for total
coliform be conducted either once a day or once a week,
depending on the type of reuse application.
Washington requires continuous on-line turbidity
monitoring for agricultural reuse on food crops, while
California requires that total coliform samples be taken
on a daily basis and turbidity be monitored on a
continuous basis for unrestricted urban and recreational
reuse, as well as agricultural reuse on food crops. For
unrestricted and restricted urban reuse, as well as
agricultural reuse on food crops, Florida requires the
continuous on-line monitoring of turbidity and chlorine
residual. Even though no limits on turbidity are specified
in Florida, continuous monitoring serves as an on-line
surrogate for SS. In addition, Florida requires that the
TSS limit must be achieved prior to disinfection and that
fecal coliform samples be taken daily for treatment
facilities with capacities greater than 0.5 mgd (22 L/s).
Florida also requires an annual analysis of primary and
secondary drinking water standards for reclaimed water
used in irrigation. Other states determine monitoring
requirements on a case-by-case basis depending on the
type of reuse.
4.1.3 Treatment Facility Reliability
Some states have adopted facility reliability regulations
or guidelines in place of, or in addition to, water quality
requirements. Generally, requirements consist of alarms
warning of power failure or failure of essential unit
processes, automatic stand-by power sources,
emergency storage, and the provision that each
treatment process be equipped with multiple units or a
back-up unit.
Articles 8, 9, and 10 of California's Title 22 regulations
provide design and operational considerations covering
alarms, power supply, emergency storage and disposal,
treatment processes, and chemical supply, storage and
feed facilities. For treatment processes, a variety of
reliability features are acceptable in California. For
example, for biological treatment, it is required that all
biological treatment processes be provided with one of
the following:
Q Alarm (failure and power loss) and multiple units
capable of producing biologically oxidized
wastewater with one unit not in operation.
Q Alarm (failure and power loss) and short-term
(24-hour) storage or disposal provisions and
stand-by replacement equipment.
Q Alarm (failure and power loss) and long-term (20
days) storage or disposal provisions.
Florida requires Class I reliability of its treatment facilities
when reclaimed water is used for irrigation of food crops
and restricted and unrestricted urban reuse. Class I
reliability requires multiple treatment units or back-up
units and a secondary power source. In addition, a
minimum of 1 day of reject storage is required to store
reclaimed water of unacceptable quality for additional
treatment. Florida also requires staffing at the water
reclamation facility 24 hours/day, 7 days/week or 6 hours/
day, 7 days/week as long as reclaimed water is delivered
to the reuse system only during periods when a qualified
operator is present; however, operator presence can be
reduced to 6 hours/day if additional reliability features are
provided.
Florida has also established minimum system sizes for
treatment facilities to aid in assuring the continuous
production of high-quality reclaimed water. Minimum
system size for unrestricted and restricted urban reuse is
0.1 mgd (4 L/s), with the exception of residential lawn
irrigation, which is 0.5 mgd (22 L/s). A minimum system
size of 0.5 mgd (22 L/s) is also required for edible crop
irrigation, with the exception of citrus irrigation under
restricted access conditions, which is 0.1 mgd (4 L/s).
In South Carolina, operator presence is required 24 hr/d,
7 days/week and a minimum system size of 1.0 mgd (44
L/s) is required. In addition, South Carolina requires a
back-up effluent disposal system for inclement weather
or unusual operating conditions.
Other states which have regulations or guidelines
regarding treatment facility reliability include Hawaii,
North Carolina, Oregon, and Washington. Washington's
130
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guidelines pertaining to treatment facility reliability are
similarto California's regulations. Both Oregon and North
Carolina require that multiple treatment units be provided
for all essential treatment processes and a secondary or
back-up power source be supplied.
4.1.4 Minimum Storage Requirements
Current regulations regarding storage requirements are
primarily based upon the need to limit or prevent surface
water discharge and are not related to storage required
to meet diurnal or seasonal variations in supply and
demand. Storage requirements vary from state to state
and are generally dependent upon geographic location
and site conditions. For example, Arizona requires a
minimum storage volume equal to 5 days of the average
design flow, while South Dakota requires a minimum
storage volume of 210 days of the average design flow.
The large difference is primarily due to the high number
of non-irrigation days due to freezing temperatures in the
northern states.
Most states that specify storage requirements do not
differentiate between operational and seasonal storage,
with the exception of Georgia and Delaware, which
require that both operational and wet weather storage be
considered. The majority of states that have storage
requirements in their regulations require that a water
balance be performed on the reuse system, taking into
account all inputs and outputs of water to the system
based on a specified rainfall recurrence interval. For
example, in additiontothe minimum storage requirement
of 60 days, Maryland also requires that a water balance
be performed based on a 1 -in-10 year rainfall recurrence
interval to determine if additional storage is required
beyond the minimum requirement of 60 days.
Texas, on the other hand, requires that a water balance
be performed based on average rainfall conditions, while
Illinois requires that a water balance be performed based
on a 1 -in-20 year rainfall recurrence interval to determine
if storage beyond the minimum requirement of 150 days
is needed.
4.7.5 Application Rates
When regulations specify application or hydraulic loading
rates, the regulations generally pertain to land application
systems that are used primarily for additional wastewater
treatment for disposal rather than reuse. When systems
are developed chiefly for the purpose of land treatment
and/or disposal, the objective is often to dispose of as
much effluent on as little land as possible; thus,
application rates are often far greater than irrigation
demands and limits are set for the maximum hydraulic
loading. On the other hand, when the reclaimed water is
managed as a valuable resource, the objective is to apply
the water according to irrigation needs rather than
maximum hydraulic loading, and application limits are
rarely specified.
Many states do not have any specific requirements
regarding reclaimed water application rates, as these are
generally based on site conditions; however, some states
require that the hydraulic loading rate not exceed 2.0 to
2.5 in (51-64 mm)/week. Nebraska's guidelines suggest
that hydraulic loading rates not exceed 4.0 in (102 mm)/
week.
In addition to hydraulic loading rates, some states also
have limits on nitrogen loading. For example, Georgia
and Delaware both require that the effluent percolating
from the reuse system have a nitrate-nitrogen
concentration of 10 mg/L or less, while Missouri and
Nebraska both require that the nitrogen loading not
exceed the nitrogen uptake of the crop.
4.1.6 Groundwater Monitoring
Groundwater monitoring programs associated with
irrigation of reclaimed water are required by Arkansas,
Delaware, Florida, Georgia, Illinois, Maryland, Missouri,
South Carolina, Washington, Wisconsin, West Virginia,
New Jersey, Hawaii, Tennessee, and Montana. In
general, these groundwater monitoring programs require
that one well be placed hydraulically upgradient of the
reuse site to assess background and incoming
groundwater conditions within the aquifer in question and
two wells be placed hydraulically downgradient of the
reuse sites. Groundwater monitoring programs
associated with reclaimed water irrigation generally focus
on water quality in the surficial aquifer. Groundwater
monitoring programs associated with reclaimed water
irrigation generally focus on water quality in the surficial
aquifer. Florida generally requires a minimum of three
monitoring wells at each reuse site. Some states also
require that a well be placed within each reuse site. South
Carolina's guidelines suggest that a minimum of 9 wells
be placed in golf courses (18-holes) that irrigate with
reclaimed water. Sampling parameters and frequency of
sampling are generally considered on a case-by-case
basis.
4.1.7 Setback Distances for Irrigation
Many states have established setback distances or buffer
zones between reuse irrigation sites and various facilities
such as potable water supply wells, property lines,
residential areas, and roadways. Setback distances vary
depending on the quality of reclaimed water and the
method of application. For example, Illinois requires a
50-ft (15 m) setbackf rom the edge of the wetted perimeter
of the reuse site to a residential lot for a non-spray
application system, but requires a 150-ft (45-m) setback
131
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for a spray irrigation system. For restricted and
unrestricted urban reuse and irrigation of food crops,
Florida requires a 75-ft (23-m) setback to potable water
supply wells;but for agricultural reuse on non-food crops,
Florida requires a 500-ft (150-m) setbackto potable water
supply wells and a 100-ft (30-m) setbackto property lines.
Florida will allow reduced setback distances for
agricultural reuse on non-food crops if additional facility
reliability and treatment are provided. Colorado
recommends a 500-ft (150-m) setback distance to
domestic supply wells and a 100-ft (30-m) setbackto any
irrigation well regardless of the quality of the reclaimed
water.
Oregon and Nevada do not require setback distances
when reclaimed water is used for unrestricted urban
reuse or irrigation of food crops due to the high degree of
treatment required; however, setback distances are
required for irrigation of non-food crops and restricted
urban reuse. In Nevada, the quality requirements for
reclaimed water are based not only on the type of reuse,
but also on the setback distance. For example, for
restricted urban reuse and a 100-ft (30-m) buffer zone,
Nevada requires that the reclaimed water have a mean
fecal coliform count of no more than 23/100 ml_ and a
turbidity of no more than 5 NTU. However, with no buffer
zone, the reclaimed water must have a mean fecal
coliform count of no more than 2.2/100 mL and a turbidity
of no more than 3 NTU.
4.2 Suggested
Reuse
Guidelines for Water
Table 28 presents suggested wastewater treatment
processes, reclaimed water quality, monitoring, and
setback distances for various types of water reuse.
Suggested guidelines are presented for the following
categories:
Q Urban Reuse
Q Restricted Access Area Irrigation
Q Agricultural Reuse - Food Crops
- Food crops not commercially processed
- Commercially processed food crops and
surface irrigation of orchards and vineyards
Q Agricultural Reuse - Non Food Crops
- Pasture for milking animals and fodder, fiber,
and seed crops
Q Recreational Impoundments
Q Landscape Impoundments
Q Construction Uses
Q Industrial Reuse
Q Environmental Reuse
Q Groundwater Recharge
- Spreading or injection into nonpotable aquifer
Q Indirect Potable Reuse
- Spreading into potable aquifer
- Injection into potable aquifer
- Augmentation of surface supplies
These guidelines apply to domestic wastewater from
municipal or other wastewater treatment facilities having
a limited input of industrial waste. The suggested
guidelines are predicated principally on water reclamation
and reuse information from the U.S. and are intended to
apply to reclamation and reuse facilities in the U.S. Local
conditions may limit the applicability of these guidelines
in some countries (see Chapter 8). It is explicitly stated
that the direct application of these suggested guidelines
will not be used by AID as strict criteria for funding.
The suggested treatment processes, reclaimed water
quality, monitoring frequency, and setback distances are
based on:
Q Water reuse experience in the U.S. and
elsewhere;
Q Research and pilot plant or demonstration study
data;
Q Technical material from the literature;
Q Various states' reuse regulations, policies, or
guidelines (see Appendix A);
Q Attainability; and
Q Sound engineering practice.
These guidelines are not intended to be used as definitive
water reclamation and reuse criteria. They are intended
to provide reasonable guidance for water reuse
opportunities, particularly in states that have not
developed their own criteria or guidelines.
Adverse health consequences associated with the reuse
of raw or improperly treated wastewater are well
documented (Lund, 1980; Feachem etal., 1983, Shuval
et al., 1986). As a consequence, water reuse standards
and guidelines are principally directed at public health
132
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ble28. Suggested Guidelines for Water Reuse (Page 6 of 6)
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Some stabilization pond systems may be able to meet this coliform limit without disinfection.
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drinking water standards.
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138
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protection and generally are based on the control of
pathogenic organisms. These guidelines address health
protection via suggested wastewater treatment unit
processes, reclaimed water quality limits, and other
controls (setback distances, etc.):
Both treatment processes and water quality limits are
recommended for the following reasons:
Q Water quality criteria that include the use of
surrogate parameters may not adequately
characterize reclaimed water quality;
Q A combination of treatment and quality
requirements known to produce reclaimed water
of acceptable quality obviate the need to monitor
the finished water for certain constituents, e.g.,
some health-significant chemical constituents or
pathogenic microorganisms;
Q Expensive, time-consuming, and, in some
cases, questionable monitoring for pathogenic
organisms, such as viruses, is eliminated without
compromising health protection; and
Q Treatment reliability is enhanced.
It would be impractical to monitor reclaimed water for all
of the chemical constituents and pathogenic organisms
of concern, and surrogate parameters are universally
accepted. In the U.S., total and fecal conforms are the
most commonly used indicator organisms in reclaimed
water. The total conform analysis includes enumeration
of organisms of both fecal and nonfecal origin, while the
fecal coliform analysis is specific for coliform organisms
of fecal origin. Therefore, fecal conforms are better
indicators of fecal contamination than total conforms, and
these guidelines use fecal coliform as the indicator
organism. Either the multiple-tube fermentation
technique or the membrane filter technique maybe used
to quantify the coliform levels in the reclaimed water.
These guidelines do not include suggested parasite or
virus limits. Parasites have not been shown to be a
problem at water reuse operations in the U.S. at the
treatment and quality limits recommended in these
guidelines. Viruses are of concern in reclaimed water,
but virus limits are not recommended in these guidelines
for the following reasons:
Q A significant body of information exists indicating
that viruses are reduced or inactivated to low or
immeasurable levels via appropriate wastewater
treatment, including filtration and disinfection
(Sanitation Districts of Los Angeles County,
1977; Engineering-Science, 1987; Crook, 1989);
Q The identification and enumeration of viruses in
wastewater are hampered by relatively low virus
recovery rates, the complexity and high cost of
laboratory procedures, and the limited number
of facilities having the personnel and equipment
necessary to perform the analyses;
Q The laboratory culturing procedure to determine
the presence or absence of viruses in a water
sample takes about 14 days, and another 14
days are required to identify the viruses;
Q There is no consensus among virus experts
regarding the health significance of low levels of
viruses in reclaimed water; and
Q There have been no documented cases of viral
disease resulting from the reuse of wastewater
at any of the water reuse operations in the U.S.
The removal of suspended matter is related to the virus
issue. It is known that many pathogens are particulate-
associated and that paniculate matter can shield both
bacteria and viruses from disinfectants. Also, organic
matter consumes chlorine, thus making less of the
disinfectant available for disinfection. There is general
agreement that paniculate matter should be reduced to
low levels, e.g., 2 NTU or 5 mg/L SS, prior to disinfection
to ensure reliable destruction of pathogenic
microorganisms during the disinfection process.
Suspended solids measurements are typically performed
daily on a composite sample and only reflect an average
value. Continuously monitored turbidity is superiorto daily
SS measurements as an aid to treatment operation.
The need to remove organic matter is related to the type
of reuse. Some of the adverse effects associated with
organic substances are that they are aesthetically
displeasing (may be malodorous and impart color),
provide food for microorganisms, adversely affect
disinfection processes, and consume oxygen. The
recommended BOD limit is intended to indicate that the
organic matter has been stabilized, is nonputrescible, and
has been lowered to levels commensurate with
anticipated types of reuse. SS limits are suggested as a
measure of organic and inorganic paniculate matter in
reclaimed water that has received secondary treatment.
The recommended BOD and SS limits are readily
achievable at well operated water reclamation plants.
The suggested setback distances are somewhat
subjective. They are intended to protect drinking water
139
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supplies from contamination and, where appropriate, to
protect humans from exposure to the reclaimed water.
While studies indicate the health risk associated with
aerosolsf rom spray irrigation sites using reclaimed water
is low (EPA, 1980), the general practice is to limit, through
design or operational controls, exposure to aerosols and
windblown spray produced from reclaimed water that is
not highly disinfected.
Unplanned or incidental indirect potable reuse occurs in
many states in the U.S., while planned or intentional
indirect potable reuse via groundwater recharge or
augmentation of surface supplies is a less-widely
accepted practice. Whereas the water quality
requirements for nonpotable water uses are tractable and
not likely to change significantly in the future, the number
of water quality constituents to be monitored in drinking
water (and, hence, reclaimed water intended for potable
reuse) will increase and quality requirements will become
more restrictive. Consequently, it would not be prudent to
suggest a complete list of reclaimed water quality limits
for all constituents of concern. Some general and specific
information is provided in the guidelines to indicate the
extensive treatment, water quality, and other
requirements that are likely to be imposed where indirect
potable reuse is contemplated.
4.3 References
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
(703) 487-4650
Crook, J. 1989. Viruses in Reclaimed Water. In:
Proceedings of the 63rd Annual Technical Conference,
pp. 231-237, sponsored by Florida Section American
Water Works Association, Florida Pollution Control
Association, and Florida Water & Pollution Control
Operators Association, November 12-15, St. Petersburg
Beach, Florida.
Engineering-Science. 1987. Monterey Wastewater
Reclamation Study for Agriculture: Final Report.
Prepared forMonterey Regional Water Pollution Control
Agency by Engineering-Science, Berkeley, California.
Feachem, R.G., Bradley, D.J.,, Garelick, H., and Mara,
D.D. 1983. Sanitation and Disease: Health Aspects of
Excreta and Wastewater Management. Published for
the World Bank by John Wiley & Sons, New York.
Lund, E. 1980. Health Problems Associated with the
Re-Use of Sewage: I. Bacteria, II. Viruses, III. Protozoa
and Helminths. Working papers prepared for WHO
Seminar on Health Aspects of Treated Sewage Re-Use,
1-5 June 1980. Algiers.
Sanitation Districts of Los Angeles County. 1977.
Pomona Virus Study: Final Report. California State Water
Resources Control Board. Sacramento, California.
Shuval, H.I., Adin, Al, Fattal, B., Rawitz, E., and Yekutiel,
P. 1986. Wastewater Irrigation in Developing Countries
- Health Effects and Technical Solutions. World Bank
Technical Paper Number 51, The World Bank,
Washington, D.C.
U.S. Environmental Protection Agency. 1980.
Wastewater Aerosols and Disease. Proceedings of
Symposium, H. Pahren and W. Jakubowski (eds.), EPA-
600/9-80-028, NTIS No. PB81-169864. U.S.
Environmental Protection Agency, Health Effects
Research Laboratory, Cincinnati, Ohio.
140
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CHAPTER 5
Legal and Institutional Issues
This chapter provides a general discussion to identify
major legal and institutional issues associated with
assessing the feasibility of water reuse. Specific parts of
this chapter might not apply in every state, but should still
support an overall understanding of primary legal and
institutional issues. Existing state regulations and
guidelines governing reuse are reviewed in Chapter 4.
Discussed in this section are:
Q Legal issues at federal, state, and local levels;
Q Organizations typically involved in water reuse;
Q General steps to follow throughout
implementation of a reuse project; and
Q Case studies illustrated legal issues related to
reuse.
in the simplest terms, the legal and institutional issues
relate to what may and may not be done and, in the case
of the former, how it may be done. These issues arise in
the context of federal, state and local statutes,
regulations, case law and agency policies, and the
institutions that promulgate and enforce them. The
available body of statutory and case law directly
addressing the area of water reuse is generally not well
developed or well settled at the present time. As a result,
the assessment of potential legal and institutional issues
for a given water reuse project should give due regard to
the risks inherent in this area.
5.1 Identifying Legal Issues
A critical aspect of any legal and institutional analysis of
the feasibility of a water reuse project, and perhaps the
most difficult, is the identification of potential issues
affecting implementation of the project. Major sources of
law that could raise issues or provide guidance in this
area include:
Q Federal Statutes - The federal statutes directly
concerned with water reuse are currently limited.
However, federal statutes governing interstate
and international water rights may warrant
careful review.
Q Federal Case Law - Although existing court
opinions at the federal level are not abundant on
the subject of water reuse, available case law in
the areas of federal water rights and applicable
constitutional provisions may need to be
considered.
Q State Statutes - State legislation generally can
have a major impact on many aspects of.water
reuse. Such legislation and administrative
agency regulations can be particularly important
in the areas of water rights, enabling authority for
local governmental units (cities, towns, villages,
counties, districts, regional agencies, and
interjurisdictional arrangements), water service
area franchise rights, public health, and
environmental quality.
Q State Case Law - Although many states may
currently have no reported court opinions directly
addressing the topic of water reuse, it may be
necessary to look to other states for nonbinding
guidance in this area, and there maybe important
cases within the subject state that indirectly
impact implementation of the project.
Q Local Ordinances - To the extent that a water
reuse program or project does not exist in a
given local jurisdiction, it is unlikely that water
reuse ordinances would be currently in effect.
However, implementation of a new water reuse
project normally would require the adoption of a
new ordinance and possibly the amendment of
existing ordinances.
141
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5.2 Federal Legal Issues
There are limited federal laws or regulations concerned
directly with wastewater reclamation and water reuse.
Currently, when the United States government sets aside
or reserves land, it has the right to adequate water from
sources on or adjacent to the property to meet the
required needs of the land. Referred to as federal
reserved water rights, the quantity of water reserved by
the government need not be established or used at the
time of the land acquisition. These rights to water are not
tost due to non-use or abandonment and can be used for
purposes otherthan that which it was originally intended,
as long as consumption does not increase. These rights
may be set aside by executive order, statute, treaty, or
agreement (Weinberg, 1990).
Water may also be appropriated by the federal
government in orderto carry out purposes established by
Congress on non-reserved lands. The government may
be using lands in accordance with the direction of
Congress but not hold these lands as reservations. Like
the federal reserved rights, this right to water for
unreserved lands may not cause harm to other users of
the water and the appropriation may not take priority over
already existing appropriations. There is some question
as to whether there is sufficient legal basis for claiming
water under the non-reserved rights. Congress does,
however, appear to have the power to authorize the use
of unappropriated water for federal purposes on federal
land, whether such land is reserved or unreserved
(Weinberg and Allan, 1990).
Although there have been many court decisions relating
to the water rights of Indian reservations and other federal
lands, there still a great deal of uncertainty as to how
those decisions should be interpreted. If there is any
potential of conflict with the federal reserved water rights,
eitherfroman Indian reservation or other federal reserve,
a very careful legal interpretation of such water rights
should be obtained.
5.3 State Legal Issues
A review of existing and any proposed legislation relating
to water rights, health, environmental quality and utility
regulation for the state should be done during the initial
development and planning phase of the reuse system.
New legislation at the state level can affect reuse
opportunities; thus, as new legislation is enacted and as
proposed legislation is filed, it should be carefully studied.
A determination should be made regarding what is
regulated, facilitated or prohibited by the state law, by
whom, and by what process. The state statutes deserve
careful review and can provide a good source of
information in determining legal steps to take in orderto
help secure a successful reuse program. Relevant case
law should also be carefully reviewed, and can be helpful
where state statutes are silent or ambiguous. Such
judicial decisions can also provide assistance in
identifying potential issues that may not yet have been
resolved. Normally such court opinions will provide some
insight into the judicial reasoning underlying a given
decision and often will identify a need for new state
legislation or for changes in the administrative practices
of state agencies.
5.3.1 State Water Rights
It generally can be assumed that water rights are an
especially important issue. The water rights system in a
given state can actually promote reuse measures, or it
can pose an obstacle to reuse.
It generally can be assumed that water rights will be an
issue in water-poor areas and/or if reclaimed water will be
utilized in a consumptive fashion. These, ironically, are
both conditions under which water reuse might be most
attractive.
A water right is a right to use water. It is not a right of
ownership. The state generally retains ownership of so-
called natural or public water within its boundaries, and
state statutes, regulations and case law govern the
allocation and administration of the rights of private
parties and governmental entities to use such water. A
"water right" allows water to be diverted at one or more
particular points and a portion of the water to be used for
one or more particular purposes. A basic doctrine in
water-rights law is that harm cannot be rendered upon
others who have a claim to the water.
There are two main systems of water rights - the
appropriative doctrine and the riparian doctrine.
5.3.1.1 Appropriative Rights System
The appropriative rights system is found in most western
states and in areas that are water-poor (California has
both appropriative and riparian rights). It is a system by
which the right to use water is appropriated—that is, it is
assigned or delegated to the consumer. The basic notion
is: first in time, first in right. In other words, the right derives
from beneficial use on a first-come, first-served basis and
not from the property's proximity to the water source. The
first party to use the water has the most senior claim to
that water. The senior users have a continued right to the
water, and a late user generally cannot diminish the
quantity or quality of the water to the senior user. This
assures the senior users of adequate water under almost
any rainfall conditions, and the later users having some
142
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moderate assurance to the water. The last to obtain water
rights may be limited to water only during times when it is
available (wet season). The right is for a specific quantity
of water, but the appropriator may not divert more water
than can be used. If the appropriated water is not used, it
will be lost. The system does, however, allow for the
storage of water on either a temporary or seasonal basis
(Viessman and Hammer, 1985).
Generally, appropriative water rights are acquired
pursuant to statutory law; thus, typically, there are
comprehensive watercodes which govern the acquisition
and control of the water rights. The acquisition of the water
right is usually accompanied by an application to state
officials responsible for water rights and granted with a
permit or license. The appropriative rights doctrine allows
for obtaining water by putting it to beneficial use in
accordance with procedures set forth in state statutes
and judicial decisions. This right has been supported by
statutes and high court decisions as well as constitutional
provisions (Viessman and Hammer, 1985).
The appropriative water rights system is generally used
for groundwater throughout the United States. Water
percolating through the ground is controlled by three
different appropriative methods: absolute ownership,
reasonable use rule, or specific use rule. Absolute
ownership occurs when the water located directly
beneath a property is considered to belong to the property
owner to use in any amount regardless of the effect on
the water table of the adjacent land, as long as it is not for
a malicious use. The reasonable use rule limits the
withdrawal to the quantity necessary for reasonable and
beneficial use in connection with the land located above
the water. Water cannot be wasted or exported. The
specific use rule occurs when the use of the water has
been restricted to one use.
During times of excess water supply, storage alternatives
may be considered as part of the reuse project so water
may be used at a later date. A determination of the
ownership or rights to use of reclaimed water which has
been stored in an aquifer,_for example, will need to be
made before consideration is given to this alternative.
Ownership claims may be made by those who have
previously been withdrawing the groundwater, since the
reclaimed water has been commingled with the existing
groundwater (Water Pollution Control Federation, 1989).
5.3.1.2 Riparian Rights System
The riparian water rights system is found primarily in the
east and in water-abundant areas. The right is based on
the proximity to water. The owner of land containing a
natural stream or abutting a stream is entitled to receive
the full natural flow of the stream without change in quality
or quantity" (Viessman and Hammer, 1985).
A riparian user is not entitled to make any use of the water
that substantially depletes the stream flow or that
significantly degrades the quality of the stream. Such
riparian use can only be for a legal and beneficial purpose.
The right of one riparian owner is generally correlative
with the rights of the other riparian owners, with each land
owner being assured some water when available.
Water used under a riparian right can be used only on the
riparian land and is acquired by the purchase of the land.
The water withdrawn for the riparian property cannot be
extended to another property. However, unlike the
appropriative doctrine, under riparian right, the right to
the unused water can be held indefinitely and without
forfeiture. This limits the ability of the water authority to
quantify the amount of waterthat has a hold against it and
can lead to water being allocated in excess of that
available. This doctrine does not allow for storage of
water.
In the United States versus the Rio Grande Dam and
Irrigation Company, the United State Supreme Court has
determined that each state has the right to change the
rules of common law referring to the rights of the riparian
owner to the continuous natural flow of the stream and to
permit appropriation of waters for such purposes as it
deems wise (Viessman and Hammer, 1985).
5.3.1.3 Water Rights as Related to Reuse
In the western U.S., many users of reclaimed water have
found that reclaimed water can offer a more reliable
source of water, ratherthan obtaining appropriated water
rights from the state's water board. This is particularly
true when the water appropriation would be designated a
low-priority right and would be withdrawn in times of water
shortages. Because of the difficulty associated with
obtaining an uninterrupted supply of water in the West,
water reuse becomes an attractive alternative for
procuring water. Water rights issues can constrain
reclamation/reuse projects by imposing restrictions and
requirements regarding the use and return of that water.
The impact of the water rights issue on a water reuse
program can be serious and may require professional
legal counsel experienced in this area. The following
generalizations are offered:
Q Injury to Others - If the water reuse program
could substantially reduce natural flows in a local
watercourse, there may be obstacles associated
with water rights.
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Q Water Sources - Water-rights law for streams
and rivers is relatively clear and well-defined, but
is less so for other surface water sources and
even less so for groundwater. An even more
careful review of the water rights laws will be
necessary if contemplating a program that will
affect groundwater.
Q Reducing Withdrawals - A water reuse program
that reduces withdrawals from the water supply
will probably pose no third-party conflict with
water-rights issues, but the impact of such
reductions on water rights of the project
proponent should be evaluated.
Q Reducing Discharge - Some uses of reclaimed
water can reduce or eliminate the discharge of
water to the watercourse from which water is
withdrawn. Examples of such uses include
evaporative cooling, infiltration/percolation
through irrigation, or diversion to a different
stream or watershed. Multiple uses of water is
generally acceptable underthe law, but reducing
watercourse flows through reuse can pose
problems. Therefore, although a discharger of
wastewater treatment plant effluent is not
generally bound to continue the discharge,
reduction or elimination of its effluent due to
reuse could face legal challenge and could result
in serious economic and environmental losses
downstream.
Q Changes in Point-of-Discharge or Place-of-Use
- In appropriative states, the statutes might
contain laws designed to protect the area of the
origin of the water, to limit the places of use, or to
require the same point of discharge. In riparian
states, the place of use can be an issue; potential
users located outside the watershed from which
the waterwas originally drawn (or, forthat matter,
outside the jurisdiction abutting the watercourse)
might have no claim to the water.
Q Hierarchy of Use - Generally with water reuse,
the concept of "reasonable-use" and "beneficial
use" should not present an obstacle, particularly
if such recycling is economically justified.
Nevertheless, a hierarchy of use still exists in
both riparian and appropriative law, and in times
of water shortage, it is possible that a more
important use could make claim to reclaimed
water that, for example, is being used for
industrial process water.
5.3.2 State Liability Laws
Generally, when a person fails to take reasonable
precautions with a product to protect users and others
from foreseeable injuries, the person may be considered
negligent and liable for the damage caused by use of the
product. A party tends to be considered negligent if they
violate certain statutes or regulations. Most states have
well-defined liability laws relating to defects in design and
manufacture of products. Legal precedents exist for
considering distributed potable water a product that is
subject to these laws (Zeitzew, 1979). The municipal
officials planning to implement a program of water reuse
must take direction in assuring safety and reliability in the
reclaimed water system.
Understanding the potential for product and other
theories of liability can minimize exposure by providing
clear direction on accepted uses for reclaimed water and
stating the hazards of its use and misuse. Exposure to
liability may be decreased by including information within
contract documents regarding the possibility of dangerto
crops, potential for property damage, and correct usage
procedures for the reclaimed water.
Liability suits can also arise from not delivering the
reclaimed water in the quantity or quality promised. This
may be considered breach of contract or of warranty,
either expressed or implied. This potential for liability will
need to be considered when determining the treatment
levels, reliability, distribution system, public information
procedures, and insurance coverage for a reuse project
(Richardson, 1985).
5.3.3 State Franchise Law
A franchise is generally an exclusive right or license
granted to a private individual or corporation to market
goods or services in a particular area. Franchises are
often granted when economies-of-scale and capital
investment levels disfavor competition, such as in the
instance of electric or water.utilities. A problem that could
apply to water reuse would be where reuse conflicts with
a service that is exclusively the right of some other entity.
Some other water-supplying entity might have the
exclusive right to sell water in its service area. A municipal
wastewater treatment agency attempting to institute
reuse in an area receiving water service from a private
water supply corporation could find itself in direct conflict
with the corporation's right to be the exclusive provider of
water.
The scope of such franchise rights, like that of water
rights, varies from state to state. In each case, the
potential infringement upon franchise rights should be
carefully considered.
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5.3.4 State Case Law
Case law should be assessed carefully where potential
conflicts might exist or where previous conflicts have
been resolved in the courts.
5.4 Local Legal Issues
Steps to minimize liability in implementing a reuse
program include developing an informed awareness of
issues that can accompany use of reclaimed water;
selecting highly qualified design and operations
personnel; monitoring reclaimed water quality, including
monitoring of known hazardous substances not yet
regulated by state statute; and developing and
maintaining contingency plans and emergency backup
procedures to assure system reliability (Zeitzew, 1979).
5.4.1 Reuse Ordinance
It may be necessary to develop a clear and concise
municipal ordinance to address issues and requirements
of the reuse system. In addition to delegating which
municipal entity is responsible for the reuse program, at
a minimum a reuse ordinance should contain each of the
items summarized below. However, in each case, the
adequacy of state enabling authority must be considered
as well.
Q Requirements for Connection - Define when
property owners will be required to connect to
the reuse system. Examples include the
requirement for turf grass facilities (parks, golf
courses, cemeteries, schools, etc.) to connect
when the system becomes available,
requirements for new developments to connect
prior to being inhabited, and requirements for all
properties to connect as the reuse system
becomes available.
Q Cross-Connection Control Measures - Clearly
state the protective measures to be taken to
avoid cross connection of the reclaimed water
lines with potable water lines in the reuse
ordinance. This may include the requirement for
backflow preventers and use of color-coded
pipes for the reclaimed and potable water.
Q Inspection Policy - System inspection
procedures and requirements should state which
department(s) is responsible for inspection,
under what conditions inspection may be
required, and the consequences if users refuse
to allow inspection (i.e., disconnection of
service). Inspection is recommended to
determine if there are any illegal hook-ups,
violations of ordinances, or cross connections.
Q Irrigation System Limitations - The reuse
ordinance might specify the type of irrigation
system to be used in order to receive reclaimed
water. This could include the requirement that
the system be a permanent below ground
system, or that a single hose connection to a
hose bibb be allowed for hand watering. It might
also include limitations to the size and type of
pipe to be used in the irrigation systems. The
requirements for a timer for the irrigation system
may also be included.
Q Penalties for Violation of the Ordinance - In the
event the ordinance is violated, penalties should
be specified at a level adequate to deter violation.
These may include disconnection of service and
a fee for reconnection. Fines and jail time are
provided for in some ordinances (Mesa, Arizona
and Brevard County, Florida) for major
infractions.
Q Fees and Rates for Receiving Reclaimed Water
- Any fees charged for reclaimed water
connection and the rates associated with service
should be addressed in an ordinance. Reclaimed
water rate ordinances are generally separate
from those regulations that control reclaimed
water use. Chapter 6 provides a discussion of
the development of the financial aspects of water
reuse fees and rates.
Q System Reliability - In addition to the elements
presented above, it is often helpful to establish
the system reliability as part of a reclaimed water
use ordinance. Is the supplier going to provide a
level of service comparable to that of the potable
system or will the service be "interruptible"?
When reclaimed water is used for an essential
service such as fire protection, a high degree of
system reliability must be provided. However, if
reclaimed water use is limited to irrigation,
periodic shortages or service interruption may
be tolerable. Finally, the supplier of reclaimed
water may wish to retain the right in the ordinance
to impose water use scheduling as a means of
managing shortages or controlling peak system
demands.
Q Public Information - The ordinance may also
contain requirements for public education about
the reuse project. This educational program may
include providing information on the hazards of
reclaimed water, the requirements for service,
the accepted uses, and the penalties for
violation. In Cocoa Beach, Florida, the applicant
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r
for reclaimed water must be provided an
informative brochure to explain public safety and
reuse in accordance with their ordinance. A
detailed discussion of public information
programs is provided in Chapter 7.
Q Allowable Operating Structures - A determination
of the best municipal organizations or
departments to operate a reclamation and reuse
program should be made in the development
phases of the reuse project. For example, even
if the municipal wastewater treatment service is
permitted by law to distribute reclaimed water, it
might make more sense to organize a reuse
system under the water supply agency or under
a regional authority (assuming that such an
authority can be established under the law). A
regional authority could operate more effectively
across municipal boundaries and could obtain
distinct economies-of-scale in operation and
financing (Okun, 1977). To form an authority, it
might be possible to establish a new public entity
under existing legislation, or it might be
necessary to enact new legislation.
Q Financing Power - Any financing constraints that
apply to the reuse system should be identified.
For example: Can it assume bonded
indebtedness? What kinds of debt? To what
limits? How must the debt be retired? How must
the costs of operating the water reclamation
facility be recovered? What restrictions are there
on cost-recovery methods? What kinds of
accounting practices are imposed upon the
entity?
Q Contracting Power - Finally, a determination
should be made of any constraints on how and
with whom services can be contracted. For
example, can contracts be formed with other
municipalities? Could contracts be formed under
another operating structure? Is city council
approval needed or can the controlling entity
operate independently of the municipal
governments?
5.4.2 User Agreements
Not all reclaimed water systems require development of
a reclaimed water ordinance. This is particularly true
where only a limited number of users are to receive
reclaimed water. For example, it is not uncommon for a
supplier of reclaimed water to a small number of large
users, such as agriculture or industrial customers, to forgo
development of a reuse ordinance and rely instead on
user agreements. In water intensive activities, a single
user may well encumber all of the water available from a
given reclaimed water source. Where such conditions
exist, it is often more appropriate to deal with the customer
through the negotiation of a reclaimed water user
agreement. However, all of the items discussed in Section
5.4.1 (Reuse Ordinance) should be addressed in
developing user agreements.
5.4.3 Institutional Structures
Many different types of institutional structures can be
utilized for implementation of a water reuse project. For
example, the Irvine Ranch Water District in California is
an independent, self-financing entity. Under its original
enabling legislation, it was strictly a water supply entity,
but in 1965, state law was amended to assign it sanitation
responsibilities within its service area. Thus, the district is
in a good position to deal directly, as one entity, with
conventional potable water and nonpotable water
services.
Where separate institutional entities existfor water supply
and wastewater service, the water supply entity has to
deal first with the wastewater service before procuring
reclaimed water users. In Contra Costa County,
California, this was the case. A reuse project was
established as a joint venture between the county's Water
and Sanitation Districts. The water district purchases
reclaimed water from the Sanitation District, and then
treats and redistributes it to its water customers (Weddle
era/., 1973).
In the Los Angeles area, the institutional arrangement is
more complex. The Pomona Water Reclamation Plant is
operated by the Sanitation Districts of Los Angeles
County, which sells reclaimed waterto several purveyors,
including the municipal Pomona Water Department, who
then redistribute it to a number of users.
In general, the simpler the structure the better. The Irvine
Ranch Water District approach is preferred, even though
it required new legislation to establish its combined
responsibility. In Contra Costa, hurdles posed by having
two water and wastewater agencies were overcome
contractually. Even in this case, new legislation was
required. Each district's board of directors adopted
resolutions indicating their intent to work jointly (Weddle
era/., 1973).
5.5 Institutional
Assessment
Inventory and
Institutions that should be contacted can include federal
and state regulatory agencies, administrative and
operating organizations, and general units of local
yovernrnent. It is necessary to develop a thorough
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understanding of which organizations and institutions are
concerned with which aspects of the proposed reuse
system. This understanding should include an inventory
of required permits and agency review requirements prior
to construction and operation of the reuse system,
economic arrangements, subsidies, ground and surface
water management policies, and administrative
guidelines and issues.
If the costs of a project are to be subsidized, the total cost
of the project will not be paid by the users. In areas where
subsidies for water are common, there tends to be a lack
of willingness to change the water system and to accept
new sources (i.e., reuse). Because some users receive
water at a discounted rate, any change which may
increase the cost of the water or affect the subsidy is
resisted. The economic encouragement for going to
reuse in areas where water is subsidized may be
decreased. Further discussion of funding benefits and
subsidies is presented in Chapter 6.
The various departments and agencies within
government can come into conflict over the proposed
reuse system unless steps are taken early in the planning
stages to find out who will be involved and to what level.
Close internal coordination between departments and
branches of local government will be required to ensure
a successful reuse program. Obtaining the support of
other departments will help to minimize delays caused by
interdepartmental conflicts.
In addition to internal coordination, several outside
institutions may be concerned with the proposed project.
These include the health department, the water
management district or water control board, and
regulatory agencies. An example of multi-institutional
coordination is the development of island-wide reuse
guidelines for Hilton Head Island, South Carolina, by the
Hilton Head Island Utility Committee. This committee
consisted of members of the four local wastewater
management entities. The guidelines are used to assist
in the development and planning of the island to
accommodate maximum usage of reclaimed water
(Hirsekorn and Ellison, 1987).
Often, different departments within one agency can come
into conflict overthe direction of the agency. For example,
in 1982, the Kesterson National Wildlife Refuge reported
high selenium concentrations and deformed birds. This
required the coordination of two departments within the
United States Department of the Interior, the Bureau of
Reclamation, and the Fish and Wildlife Service. These
agencies had different direction. The Bureau of
Reclamation was assigned the role of promoting
settlement in the West by providing irrigation water. The
Fish and Wildlife Service was to protect and maintain
migratory bird populations. Initially, these two goals
appeared to be in conflict. Through careful coordination
between the departments, a solution was reached.
One of the best ways to gain the support of the other
agencies is to make sure that they are involved from the
beginning of the project and are kept informed as the
project progresses. Any potential conflicts between these
agencies should be identified as soon as possible.
Clarification on which direction the overall agency should
follow will need to be determined. By doing this in the
planning stages of the reuse project, delays in
implementation may be avoided.
There is, on occasion, an overlap of jurisdiction of some
agencies. For example, it is possible for one agency to
control the water in the upper reaches of a stream and a
separate agency to control the water in the lower reaches.
Unless these agencies can work together, there may be
little hope of a successful project which impacts both.
5.6 Guidelines for Implementation
The following institutional guidelines can assist with the
planning and implementation of a reuse system:
Q Maintain Contact with the Agencies - Throughout
development of the reuse project, contact should
be maintained with the federal, state and local
agencies involved. The intent is to promote such
agencies' understanding of the project and to
keep them informed of impending permit reviews
or the enactment of new legislation. Continued
contact and an open flow of information can
keep the process from becoming an obstacle.
Q Develop a Realistic Schedule - A comprehensive
implementation schedule, should be developed
at the outset and periodically revised, including
lengthy review procedures, the time needed to
enact any required legislation, and the timing of
any public hearing that must be held. It is
especially important to identify any permit review
procedures and whether they can occur
concurrently or must occur consecutively, and in
what order.
Q Assess Cash Flow Needs - An accurate
assessment of cash flow needs is required to
anticipate funding requirements, formulate
contract provisions, and devise cost-recovery
techniques.
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Q Consider Institutional Structure - Consider in
detail the alternative institutional structure for
operation of the water reuse system and evaluate
the advantages and disadvantages of each.
Identify as early as possible any legislative
changes that might be required to create the
necessary institutions and the level of
government at which the legislation must be
enacted.
Q Prepare Contracts - Formal contracts are usually
required to establish usage of the reuse system
and to govern its operation. Provisions relating
to the quality and quantity of the reclaimed water
are essential, and may include a range in which
each can fluctuate, and the remedies, should the
quantity or quality go outside that range.
Responsibility for any storage facilities and/or
supplemental sources of water should be
defined. There must be an explicit statement as
to how the reuserwill pay for the recycled water,
and to what extent, and for what reasons he is
responsible and liable for costs. Both parties
must be protected explicitly in case either party
defaults, either by bankruptcy or by the inability
to comply with the commitments of the
agreement. The monitoring responsibility must
be specified, especially if the reclaimed water is
being utilized for irrigation purposes and a
monitoring program is required.
Specific compliance with environmental
regulations must be assigned to each party. For
example, if the crops grown are not to be utilized
for human consumption, it is appropriate to
assign the responsibility for compliance with
such regulations to the user.
Finally, the ownership and maintenance of the
facilities must be stated, particularly for the
transmission and distribution facilities of the
reclaimed water. The point at which the water
conveyance facilities become the property and
responsibility of the user must be explicitly stated.
In the case where the user is a private enterprise,
that statement should be reasonably
straightforward. However, in the case where the
user is another municipal entity, it is especially
important that each party knows its responsibility
in the operations and maintenance of the
facilities.
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5.7 Case Studies
A summary of two state court cases, one decided in 1979
by the Supreme Court of Wyoming and the other decided
in 1989 by the Supreme Court of Arizona, are provided to
illustrate the legal issues that can arise regarding water
reuse systems and how courts in these states resolved
those issues. While the Wyoming case does not deal
directly with a proposed reuse scheme, it does address,
both in terms of majority and dissenting opinions, various
issues that can arise when major reuse programs are
considered.
It should be noted, however, that the rules, policies and
guidelines enunciated by these courts apply only to the
parties and factual circumstances of each case, and the
outcome of similar disputes may be different depending on
the state and the current statutes and case law in effect.
5.7.1 1979 Wyoming Case: Thayer vs. City of
Rawllns, Wyoming (594 p.2d 951)
Faced with more stringent federal and state standards for
the treatment of its municipal wastewater, the City of
Rawlins, Wyoming proposed to construct a new treatment
facility and to change the location of its existing effluent
discharge point in Sugar Creek. Downstream of the
existing discharge point, several parties since 1914 had
been diverting the waters of Sugar Creek (comprised
entirely of the city's effluent) for irrigation, stock water,
and other purposes. Such diversions were made
pursuant to certificates of appropriation issued by the
State of Wyoming, and the holders of such certificates
sought compensation from the city for the loss of water
caused by the proposed change of location in the city's
effluent discharge to a point further downstream and
beyond the points of diversion authorized by the
certificates.
The court by majority opinion held that since the waters of
Sugar Creek were not "natural waters" and since a priority
relates only to the natural supply of the stream at the time
of appropriation, the downstream users had no priority of
use and no right to compensation for the loss of such
waters. The determination that such waters were not
"natu ral waters" was based on the fact that the city, via its
water supply system, imported these waters from basins
outside the natural drainage basin of Sugar Creek. The
majority opinion cited a 1925 Wyoming case (Wyoming
Hereford Ranch v. Hammond Packing Company, 33
Wyo. 14, 236 P. 764) in support of a policy to the effect
that a municipality should be able to utilize a means of
sewage disposal that would completely consume water
and to change the location of its effluent disposal point
without any consideration of the demands of water users
who might benefit from its disposal by other means. The
court also held that the State Engineer and Board of
Control had no jurisdiction over this dispute.
A strong dissenting opinion indicated that this dispute
should be decided by the State Engineer and Board of
Control on the basis of the concept of beneficial use,
and should be subject to court review only after such
expertise is applied. The dissent would not utilize a
distinction between "natural waters" and "imported
waters" as a basis for a decision, but would have the
State Engineer and Board of Control apply the concept
of beneficial use to determine whether the city would be
required to compensate or otherwise respect the
appropriation rights of downstream users of its
wastewater effluent.
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5.7.2 1989 Arizona Case Study: Arizona Public
Service vs. Long (773p.2d 988)
Several cities in the Phoenix metropolitan area, including
the City of Phoenix, contracted in 1973 to sell reclaimed
waterto a group of electric utilities, including the Arizona
Public Service Company, for use as cooling water for
the Palo Verde nuclear power project. Pursuant to the
contract, the utilities spent some $290 million to construct
a 50-mile pipeline and a facility to furthertreat the effluent,
and were utilizing approximately 60 mgd of effluent.
Several parties brought suit seeking a court determination
that the contract was invalid on various grounds. The
Arizona Department of Water Resources filed an amicus
brief siding with the parties seeking to have the contract
ruled invalid.
The parties opposing the contract included a major real
estate developer in the Phoenix area and owners of
ranches located downstream of the effluent discharge
point. The real estate developer argued that the contract
was in violation of statutory restrictions on the
transportation of groundwater contained in the Arizona
Groundwater Code, and the ranch owners argued that
the cities had no right to sell unconsumed effluent
because surface waters belong to the public and unused
surface waters must be returned to the river bed. The
cities and utilities, on the other hand, argued that
reclaimed water is water that has essentially lost its
character as either ground or surface water and becomes
the property of the entity which has expended funds to
create it.
In deciding this case in 1989, the Supreme Court of
Arizona, forthe most part, rejected the basic arguments
of all the parties. The Court's majority opinion validated
the contract, holding that the cities can put the reclaimed
water to any reasonable use they see fit. The Court
determined that effluent is subject to appropriation by
downstream users, but that the cities were not obligated
to continue to discharge effluent to satisfy the needs of
such appropriators. It was pointed out that if scientific
and technical advances enabled the utilization of water
to eliminate such waste, then the appropriators had no
reason to complain.
In reaching this decision, reclaimed water was
determined not to be subject to regulation under Arizona's
Surface Water Code or Groundwater Code, and the
available body of case law dealing with rights to and the
use of effluent was found lacking. The Court indicated
that a case-by-case approach to the questions of water
use in a desert state was unsatisfactory and urged the
state legislature to enact statutes in the area.
A dissenting opinion concluded that the sale of the
groundwater portion of the reclaimed water is not
regulated by the Arizona Groundwater Code and that
the concept of beneficial use under the Arizona Surface
Water Code should be applied to the surface water
component. In this regard, although the sale of reclaimed
water may be embodied within the concept of full
beneficial use, the cities may be precluded from entering
into the contract for the sale of reclaimed water on the
grounds that the discharge constituted an abandonment
of their right to increase consumptive use under
applicable provisions of the Surface Water Code.
5.8 References
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
(703) 487-4650
Hirsekorn, R.A., and R.A. Ellison, Jr. 1987. Sea Pines
Public Service District Implements a Comprehensive
Reclaimed Water System. In: Wafer Reuse Symposium
IV Proceedings, August 2-7,1987, Denver, Colorado.
Okun, D.A. 1977. Principles for Water Quality
Management. Journal of Environmental Engineering
(ASCE), 103(EE6):1039-1055.
Richardson, C.S. 1985. Legal Aspects of Irrigation with
Reclaimed Wastewater in California. In: Irrigation with
Reclaimed Municipal Wastewater-A Guidance Manual,
Lewis Publishers, Inc.
Viessman, W. Jr., and M.J. Hammer. 1985. Water Supply
and Pollution Control, 4th Edition.
Water Pollution Control Federation. 1989. Water Reuse
Manual of Practice, Second Edition. Alexandria, Virginia.
Weddle, C.I., D.G. Miles, and D.B. Flett. 1973. The Central
Contra Costa County Water Reclamation Project in
Complete Water Reuse: Industry's Opportunity. In:
Proceedings of the National Conference on Complete
Water Reuse, American Institute of Chemical Engineers,
pp. 644-654.
Wienberg, E. and R.F. Allan. 1990. Federal Reserved
Water Rights. In: Water Rights of the Fifty States and
Territories, American Waterworks Association, Denver,
Colorado.
Zeitzew, H. 1979. Legal Liability of Reclaimed Water
System Operators Under California's Products Liability
Laws. Brown and Caldwell. Pasadena, California. April
1979.
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CHAPTER 6
Funding Alternatives for Water Reuse Systems
In general, implementation of reuse facilities requires a
substantial capital expense. Residential irrigation system
reuse capital costs can range from $1,200 and $2,000
per single family home. Unless agricultural and industrial
reuse sites, public parks, or golf courses are very close to
the source of reclaimed water, new transmission facilities
may be required. Also, capital improvements at the
wastewater treatment facility are normally required.
In addition to capital costs associated with reclaimed
water facilities, there are also additional operation,
maintenance, and replacement (OM&R) and
administration costs. Such costs include the repair and
maintenance or replacement of the facilities, power for
pumping, monitoring the water quality, as well as
customer billing and administration. These costs are
typically calculated into a reclaimed water rate, expressed
either as a gallonage charge or fixed monthly fee.
Consequently, multiple financial alternatives should be
investigated in order to fund a reclaimed water system.
6.1 Decision Making Tools
As a means of clarifying the issues to be discussed,
some general terms are defined below:
Q Cost-effectiveness - the analysis of alternatives
using an effectiveness scale as a measurement
concept. U.S. EPA formulated "Cost-
Effectiveness Analysis Guidelines" as part of its
Federal Water Pollution Control Act (40 CFR
Part 35, Subpart E, Appendix A). This technique
requires the establishment of a single base
criterion for evaluation such as annual water
production of a specific quality expressed as an
increase in supply or decrease in demand.
Alternatives are ranked according to their ability
to produce the same result. The alternatives can
include such factors as their impact on quality of
life, environmental effects, etc. which are not
factored into a cost/benefit analysis.
Q Cost/Benefit - is the relationship between the
cost of resources and the benefits expected to
be realized using a discounted cash-flow
technique. Non-monetary issues are notfactored
into these calculations.
Q Financial Feasibility - is the ability to finance both
the capital costs and operating/maintenance
costs through locally raised funds. Examples of
revenue sources include userfees, bonds, taxes,
grants, and general utility operating revenues.
In the context of the above definitions, the first analysis to
be performed would be a cost-effectiveness analysis. In
other words, given the alternative of providing additional
water from fresh water sources versus reclaimed water,
what are the relevant costs and benefits?
Such benefits which can be factored into the equation
are:
Q Environmental
Q Economic
- the reduction of nutrient-rich
effluent discharges to surface
waters.
- the conservation of fresh
water supplies and reduction
of salt-water intrusion
- delay in or avoidance of
expansion of water supply
and treatment facilities
- increased levels of water and
wastewater treatment
delayed or eliminated (e.g.,
reverse osmosis treatment of
water supply avoided or
advanced wastewater
treatment needs for
wastewater reduced).
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Examples of shared benefit are as follows: if a benefit is
received by water customers (deferred rate increase)
from a delay in expanding water supply, a portion of
reclaimed water costs could be shared by existing and
future water customers. A similar analysis can also be
made forwastewater customers that benefit from a delay
or elimination of AWT construction associated with
reduced surface water discharges.
The cost/benefit analyses are conducted once feasible
alternatives are selected. The emphasis of these
analyses is on defining the economic impact of the project
on various classes of users, i.e., industrial, commercial,
residential, agricultural.
The importance of this step is that it relates the
marketability of reuse in comparison to alternative
sources, based on the end use. To elaborate, given the
cost of supplying reclaimed water versus fresh water for
urban use, what is the relationship of water demand to
price, given both abundant and scarce resources? The
present worth value of the benefits are compared to
determine whether the project is economically justified
and/or feasible.
Primarily, financial feasibility is addressed, or simply, can
sufficient financial resources be developed to construct
and operate the required reclamation facilities? Specific
financial resources available will be explained in the
following subsections.
6.2 Externally Generated Funding
Alternatives
While not impossible, it is difficult to create a totally self-
supporting reuse program financed wholly by reclaimed
water user fees. To satisfy the capital requirements for
implementation of a reuse program, the majority of the
construction and related capital costs are generally
financed through long-term water and wastewater
revenue bonds. Supplemental funds may be provided by
grants, developer contributions, etc. The various
externally generated capital funding sources are
described in further detail, with the following alternatives
discussed:
Q Municipal Tax-Exempt Bonds - The total capital
cost of construction activities forthe reuse project
could be financed from the sale of long-term (20-
30 yr) bonds.
Q Grants and State Revolving Fund Programs -
Capital needs could be funded partially through
state or local grants programs or through state
revolving fund loans, particularly those programs
designed specifically to support reuse.
Q Capital Contribution - At times, there are special
agreements reached with developers or
industrial users, requiring the contribution of
either assets or money to offset the costs of a
particular project.
6.2.1 Municipal Tax-Exempt Bonds
A major source of capital financing for a municipality is to
assume debt—that is, to borrow money by selling
municipal bonds. With many water reclamation projects,
local community support will be required to finance the
project. Although revenue bond financing is a means of
matching the revenue stream from the use of reclaimed
facilities with the costs of the debt used for construction,
voter approval is not usually required. However, voter
approval may be required for general obligation bonds.
Among the types of bonds commonly used for financing
public works projects are:
Q General Obligation Bonds - Repaid through
collected general property taxes or service
charge revenues; and generally requires a
referendum vote.
Q Special Assessment Bonds - Repaid from the
receipts of special benefit assessments to
properties (and in most cases, backed by
property liens if not paid by property owners).
Q Revenue Bonds - Repaid through user fees and
service charges derived from operating reuse
facilities (useful in regional or sub-regional
projects because revenues can be collected
from outside the geographical limits of the
borrower).
Q Short-Term Notes - Usually repaid through
general obligation or revenue bonds.
A municipal finance director and/or bond advisor can
describe the requirements to justify the technical and
economic feasibility of the reuse project. The municipality
must substantiate projections of the required capital
outlay, of the anticipated OM&R costs, of the revenue-
generating activities (i.e., the user charge system, etc.)
and of the "coverage" anticipated—that is, the extent to
which anticipated revenues will more than cover the
anticipated capital and operations, maintenance, and
replacement costs.
6.2.2 Grant ana State Revolving Fund Programs
Where available, grant programs are an attractive source
to provide resources to fund reuse systems, provided
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that the proposed system meets grant eligibility
requirements. Some funding agencies have an
increasingly active role infacilitatingwater reuse projects.
In addition, many funding agencies are receiving a clear
legislative and executive mandate to encourage water
reuse.
To be financially successful overtime, a reuse program,
however, must be able to "pay for itself." It is true that
state-supported subsidies underwrite substantial portions
of the capital improvements necessary in a reuse
project—and grant funds can also help a program to
establish itself in early years of operation. But grant funds
should not be relied upon unless their availability is
assured. Most federal and state programs require that
funds be appropriated each year by Congress orthe state
legislature, and, in many instances, the amounts
appropriated are far less than those needed to assist all
eligible projects. Forthe same reason, once the project is
underway, the program should strive to achieve self-
sufficiency as quickly as possible—meeting OM&R costs
and debt service on the local share of capital costs by
generating an adequate stream of revenues through local
budget set-asides, tax levies, special assessments and
user charges.
6.2.2.1 State Revolving Fund
The State Revolving Fund (SRF) is a financial assistance
program established and managed by the states under
general EPA guidance and regulations and funded jointly
by the federal government (80 percent) and state
matching money (20 percent). It is designed to provide
financial assistance to local agencies to construct water
pollution control facilities and to implement non-point
source, groundwater, and estuary management
activities.
Under SRF, states make low-interest loans to local
agencies. Interest rates are set by the states and must be
below current market rates and may be as low as 0
percent. The amount of such loans may be up to 100
percent of the cost of eligible facilities. Loan repayments
must begin within 1 year after completion of the facility
and must be completely amortized in 20 years.
Repayments are deposited back into the SRF to be
loaned to other agencies. Cash balance in the SRF may
be invested to earn interest which must accrue to the
SRF.
States may establish eligibility criteria within the broad
limits of the Clean Water Act. Basic eligibility includes
secondary and AWTtreatment plants, pump stations and
force mains needed to achieve and maintain NPDES
permit limits. States may also allow for eligibility,
collection sewers, combined sewer overflow correction,
storm water facilities and purchase of land for such
facilities (only in some cases), combined sewer overflow
correction, stormwaterfacilities, and purchase of land that
is a functional part of the treatment process.
States select projects for funding based on a priority
system, which is developed annually and must be
subjected to public review. Such priority systems are
typically structured to achieve the policy goals of the state
and may range from "readiness to proceed" to very
specific water quality or geographic area objectives.
Each state was allowed to write its own regulations, with
different objectives being met. Many states provide
assistance based on assessing the community's
economic health, with poorer areas being more heavily
subsidized with lower interest loans (e.g., Virginia). Other
states target specific treatment objectives, such as
Florida, with pollution abatement a priority. The
availability of state revolving fund loans for reuse projects
varies from state to state, with the priority list management
specific to each state.
Further information on the SRF program is available from
each state's water pollution control agency.
6.2.2.2 Federal Policy
The language of the Clean Water Act of 1977, and its
subsequent amendments, supports water reuse projects
through the following provisions:
Q Section 201 of PL 92-500 was amended to
ensure that municipalities are eligible for "201"
funding only if they have "fully studied and
evaluated" techniques for "reclaiming and reuse
of water."
Q Section 214 was added, which stipulates that
the EPA administrator "shall develop and
operate a continuing program of public
information and education on recycling and
reuse of wastewater..."
Q Section 313, which describes pollution control
activities at federal facilities, was amended to
ensure that WWTFs will utilize "recycle and reuse
techniques: if estimated life-cycle costs for such
techniques are within 15 percent of the most
cost-effective alternative."
6.2.2.3 Other Federal Sources
There are at least four other sources of potentialjederal
support. First there is the Farmers Home Administration
(FmHA) of the U.S. Department of Agriculture (USDA).
Under the FmHA programs, grants and loans are
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available to public agencies and non-profit corporations
which serve areas with populations under 10,000. The
amount of the grant or loan is restricted by that amount
necessary to lower the user costs to a reasonable rate,
based on the median family income of the community. In
addition, the sum of the FmHA grant and other state and
federal grants cannot exceed 50 percent of the project
costs. Thus, projects funded by Clean Water loans will
not be eligible under FmHA program.
The U.S. Small Business Administration (SBA) provides
low interest loans to small businesses for wastewater
control equipment required by regulatory agencies. The
funds can be used for pretreatment of industrial waste to
reduce toxic and saline constituents in reclaimed water.
For a project to be eligible for a loan from the SBA, the
EPA must be able to certify that the project is required to
comply with either federal or state water pollution control
requirements and that other funds are not available.
Finally, the Office of Water Research and Technology
(OWRT) of the Department of the Interior will provide
research and development funds for water reclamation
projects, particularlyfordemonstration projects, that meet
OWRT-identified priority needs.
Information of specific source possibilities can be found
in the Catalog of Federal and Domestic Assistance,
prepared by the Federal Office of Management and
Budget and available in federal depository libraries. It is
the most comprehensive compilation of the types and
sources of funding available.
6.2.2.4 State Grant Support
State support is generally available for wastewater
treatment facilities, water reclamation facilities,
conveyance facilities, and, under certain conditions, for
onsite distribution systems. Obviously, a prime source of
funding is the state support that usually accompanies
SRF loans.
A comprehensive water reuse study in California
recognized funding as the primary constraint in
implementing new water reuse projects (State of
California, 1991). The study recommended that large
water agencies that provide regional service should
financially support the development of local water
reclamation projects. Water developed through local
reclamation projects displaces a demand for potable
water which can be used elsewhere in the service area,
thereby providing a regional benefit. For instance, the
Metropolitan Water District of Southern California through
its Local Project Program provides financial assistance
to its member public agencies for development of water
reuse projects which reduce demand on Metropolitan's
imported water supplies.
6.2.3 Capital Contributions
In certain circumstances where reclaimed water is to be
used for a specific purpose, such as cooling water, it may
be possible to obtain the capital financing for new
transmission facilities directly from one or more major
users that benefit from the available reclaimed water
supply.
Another example of capital contribution for a major
transmission line construction may be to have a major
transmission line for reuse constructed by a developer
and contributed (transfer ownership) to the utility for
operation and maintenance. A residential housing
developer, golf course, or industrial user may provide the
pipeline, financing for the pipeline, or provide for a pro-
rata share of construction costs for a specific pipeline.
6.3 Internally Generated Funding
Alternatives
While the preceeding funding alternatives describe the
means of generating construction capital, there is also a
need to provide financing for OM&R costs as well as
repay funds borrowed. Examples of various internally
generated funding sources are highlighted with details
provided in following sections.
In most cases, a combination of several funding sources
will be used to cover capital and OM&R costs. The
following alternatives may exist for funding water reuse
programs.
Q Operating budget and cash reserves of the utility
Q Local property taxes and existing water and
wastewater user charges
Q Special assessments or special tax districts
Q Connection fees
Q Reuse user charges
6.3.1 Operating Budget and Cash Reserves
Activities associated with the planning and possibly
preliminary design of reuse facilities could be funded out
of an existing wastewater utility or department operating
budget. (In some instances, a water supply agency
seeking to expand its water resources would find it
appropriate to apply a portion of its operating funds in a
similar way). In addition, available cash balances in
certain reserve accounts may possibly be utilized.
It may be appropriate, for example, to utilize funds from
the operating budget for planning activities or business
costs associated with assessing the reuse opportunity.
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Furthermore, if cash reserves are accruing for
unspecified future capital projects, those funds could be
used or a portion of the operating revenues can be set
aside in a cash reserve for future needs. The obvious
advantage of using this alternative source of funding is
that the utility board or governing body of the wastewater
treatment department or utility can act on its own initiative
to allocate the necessary resources.
These sources are especially practical when relatively
limited expenditures are anticipated to implement or
initiate the reuse program, or when the reuse project will
provide a general benefit to the entire community (as
represented by the present customers of the utility). In
addition, utilizing such resources is practical when the
reclaimed water will be distributed at little or no cost to the
users, and therefore will generate no future stream of
revenues to repay the cost of the project. While it is ideal
to fully recover all direct costs of each utility service from
customers, it may not be practical during early phases of
a reuse system implementation.
6.3.2 Property Taxes and Existing User Charges
If the resources available in the operating budget or the
cash reserves are not sufficient to cover the necessary
system OM&R activities and capital financing debt, then
another source of funds to consider is revenues
generated by increasing existing levies or charges. If
some utility costs are currently funded with property taxes,
levies could be increased and the new revenues
designated for expenses associated with the reuse
project. Similarly, the user charge currently paid for water
and sewer services could be increased. As with the use
of the operating budget or cash reserves, the use of
property taxes or user charges may be desirable if the
expenditures for the project are not anticipated to be
sizable or if a general benefit accrues to the entire
community.
Ad valorem property taxes, unlike user charges, raise
funds on the basis of assessed value of all taxable
property, including residential, commercial and industrial.
Property value can be an appropriate means of allocating
the costs of the improvements of service if there is a
"general good"to the community. It is also a useful means
of allocating the cost of debt service for a project in which
there is general good to the community and in which the
specific OM&R costs are allocated to the direct
beneficiaries. The ad valorem allocation of the costs
might be appropriate for such reuse applications as:
Q Irrigation of municipal landscaping,
Q Fire protection,
Q Water for flushing sewers,
Q Groundwater recharge for saltwater intrusion
barriers, and
Q Parks and recreational facility irrigation.
All such projects have benefits, either to the residents of
the municipality in general, or to those who can be
isolated in an identifiable special district.
Similar use can be made with resources generated by
increasing any existing user charges. However, to do so
equitably, benefits of the proposed project should
primarily accrue to those presently utilizing the services
of the water or wastewater utility. This would be the case,
for example, when water reuse precludes the need to
develop costly advanced treatment facilities or a new
water supply source.
Contributions from the water and wastewater systems
may be warranted whenever there is a reduction in the
average day orpeak day water demand orwhen the reuse
system serves as a means of effluent disposal for the
wastewater system. The City of St. Petersburg, Florida,
for example, provides as much as 50 percent of the urban
reuse system operations costs from water and
wastewater system funds. The significant reduction in
potable water demand achieved through water reuse has
allowed the city to postpone expansion of its water
treatment plant.
6.3.3 Special Assessments or Special Tax Districts
When a reuse program is designed to be a self-supporting
enterprise system, independent of both the existing water
and wastewater utility systems, it may be appropriate to
develop a special tax or assessment district to recover
capital costs directly from the benefited properties. The
advantage of this cost recovery mechanism is that it can
be tailored to collect the costs appropriate to the benefits
received. An example of an area using special
assessments to fund dual water piping for fire protection
and irrigation water is the City of Cape Coral, Florida, with
an approximate cost of $1,600 per single family residence
with financing over 8 years at 8 percent annual interest.
Special assessments may be based on lot front footage,
lot square footage, or estimated gallon use relative to
specific customer types. This revenue alternative is
especially relevant if the existing debt for water and
wastewater precludes the ability to support a reuse
program, or if the area to be served is an independent
service area with no jurisdictional control over the water
or wastewater systems.
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6.3A Connection Fees
Connection fees or impact fees are a means of collecting
the costs of constructing an element of infrastructure,
such as water, wastewater, or reuse facilities, from those
new customers benefiting from the service. Connection
fees collected may be used to generate construction
capital orto repay borrowed funds. Frequentlythesefees
are used to generate an equitable basis for cost recovery
between customers connecting to the system in the early
years of a program and those connecting in the later
years. The carrying costs (interest and expense) are
generally not fully recovered through the connection fee,
although annual increases above a base cost do provide
equity between groups connecting in the early years and
those in later years.
Connection fees for water reuse systems are
implemented at the discretion of the governing body.
However, the requirement of a connection fee to be paid
upon application for service prior to construction can
provide a strong indication of public willingness to
participate in the reuse program. Incentive programs can
be implemented in conjunction with connection fees by
waiving the fee for those users who make an early
commitment to connect to the reclaimed water system
(e.g., for the first 90 days after construction completion)
and collecting the fee from later connections.
6.3.5 Reclaimed Water User Charges
A user charge may be imposed on customers receiving
the reclaimed water. User charges would be utilized to
generate a stream of revenues with which to defray the
OM&R costs of the reuse facility and the debt service of
any bonds issued.
With many current reuse applications, reclaimed water
user charges tend to incorporate fixed fees that do not
correlate to the actual cost of delivering the water.
Historically, effluent had been thought of as something to
be disposed of, not as a valuable product to be sold.
Consequently, the fees associated with reclaimed water
have not generally reflected actual reclaimed water usage
or the full cost of the service. More recently, however,
water reuse programs are shifting toward charges based
on metered flow.
In a reclaimed water user charge system, the intent is to
allocate the cost of providing reuse services to the
recipient. With a user charge system, it is implicit both
that there is a select and identifiable group of beneficiaries
to which the costs of treatment and distribution can be
allocated, and that the public in general is not the
beneficiary.
Determining an equitable rate policy requires
consideration of the different service needs of individual
residential users as compared to other users with large
irrigable areas, such as golf courses and green space
areas. These "large" users may receive reclaimed water
into ons'rte storage facilities and subsequently repump
the water into the irrigation system. This enables the
municipality to deliver the reclaimed water, independent
of daily peak demands, using low-pressure pumps, rather
than providing direct service from the distribution system
during peak demand at the higher pressures required to
drive a golf course irrigation system. Because of this
flexibility in delivery and low-pressure requirements, a
lower user rate can be justified for large users than for
residential customers, who require high-pressure delivery
on demand. Another consideration for large users is
keeping reclaimed water rates competitive with any
alternative sources of water, such as groundwater.
The residential customer categories are generally two
types: single-family and multi-family. Some multi-family
customers may be treated as large users if they provide
onsite storage and accept reclaimed water at low
pressures. However, if the reclaimed water is delivered
to the multi-family customer at high pressures directly
into the irrigation system, a residential reuse rate may
apply.
The degree of participation from other sources, such as
the general fund and other utility funds must be
considered in determining the balance of the funding that
must come from reuse rates. Again, residential user fees
must be set to make water reuse an attractive option to
potable water or groundwater. Although reclaimed water
must be priced below potable water to encourage its use,
reuse rates may also be set to discourage indiscriminate
use by instituting volume (per gallon) charges rather than
a flat fee.
There are two prime means of allocating costs that are to
be incorporated into a user charge: the proportionate
share cost basis and the incremental cost basis. These
two methods will be discussed in more detail in the
following section.
6.4 Incremental Versus Proportionate
Share Costs
6.4.1 Incremental Cost Basis
The incremental cost basis allocates only the marginal
costs of providing service. This system can be used if the
communityfeels that the marginal user of reclaimed water
is performing a social good by conserving potable water,
and so should be allocated only the additional increment
of cost of the service. However, if the total cost savings
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realized by reuse are being enjoyed only by the marginal
user, then in effect the rest of the community is subsidizing
the service.
6.4.2 Proportionate Share Cost Basis
Underthe commonly used proportionate share basis, the
total costs of the facilities are shared by the parties in
proportion to usage of the facilities. In apportioning the
costs, consideration must be given to the quantity and
quality of the water, the reserve capacity that must be
maintained, and the use of any joint facilities, particularly
means of conveyance. In determining the eventual cost
of reuse to the customer base, the appropriation of costs
between wastewater users, potable water users, and
reclaimed water users must be examined. The
appropriation of costs between users also must consider
the willingness of the local community to subsidize a
reuse program.
A proportional allocation of costs can be reflected in the
following equations:
Total $ wastewater service =
Total $ potable water service =
$ wastewater treatment to
permitted disposal standards +
$ effluent disposal +
$ transmission + $ collection.
$ water treatment+$ water supply
+ $ transmission + $ distribution.
Total $ reclaimed water service = [$ reclaimed water treatment - $
s treatment to meet permitted
disposal standards]
+ $ additional transmission +
$ additional distribution
The above equations illustrate an example of distributing
the full costs of each service to the appropriate system
and users. The first equation distributes only the cost of
treating wastewater to currently required disposal
standards, with any additional costs for higher levels of
treatment, such as filtration, coagulation, or disinfection,
appropriated to the cost of reclaimed water service. In the
event that the cost of wastewatertreatment is lowered by
the reuse alternative because current effluent disposal
standards are more stringent than those required for the
reuse system, the credit accrues to the total cost of
reclaimed water service. This could occur, for example, if
treatment for nutrient removal had been required for a
surface water discharge but would not be necessary for
agricultural reuse.
It has been noted that because reclaimed water is a
different product from potable water, with restrictions on
its use, it may be considered a separate, lower valued
class of water and priced below potable water (Ferry,
1984). Thus, it maybe important that the user charges for
reuse be below or at least competitive with those for
potable water service. However, often the current costs
of constructing reuse facilities cannot compete with the
historical costs of an existing potable water system. One
means of creating a more equitable basis for comparison
is to associate new costs of potable water supplies to the
current costs of potable water, as well as any more costly
treatment methods or changes in water treatment
requirements that may be required to meet current
regulations. In fact, when creating reuse userfees, it may
be imperative to deduct incremental potable water costs
from those charged for reuse because reuse is allowing
the deferral or elimination of developing new potable
water supplies or treatment facilities.
To promote certain objectives, local communities may
desire to alter the manner of cost distribution. For
example, to encourage reuse for pollution abatement by
eliminating a surface water discharge, the capital costs of
all wastewater treatment, transmission, and distribution
can be allocated to the wastewater service costs. To
promote water conservation, elements of the incremental
costs of potable water may be subtracted from the reuse
costs to encourage use of reclaimed water.
For water reuse systems, the proportionate share basis
of allocation may be most appropriate. The allocation
should not be especially difficult, because the facilities
required to support the reuse system should be readily
identifiable. A rule of thumb might be to allocate to
wastewater charges the costs of all treatment required
for compliance with NPDES permits; all additional costs,
the costs of reclamation and conveyance of reclaimed
water, would be allocated to the water reuse usercharge.
General administrative costs could also be allocated
proportionately: all wastewater administration would be
charged to the sewer use charge, and all additional
administration to the water reuse user charge. In some
cases, a lesser degree of wastewater treatment will be
required as a result of water reuse. The effect may be to
reduce the wastewater user charge. In this case,
depending on local circumstances, the savings could be
allocated to either or both the wastewater discharger and
the reclaimed water user.
With more than one reclaimed water user on the system,
different qualities of reclaimed water may have to be
produced. If so, the user charge becomes somewhat
more complicated to calculate, but it is really no different
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than calculating the charges fortreating different qualities
of wastewater for discharge. If, for example, reclaimed
water is distributed for two different irrigation needs, one
requiring higher quality water than the other, then the
userfee calculation can be based on the cost of treatment
to reach the quality required.
The estimation of the operating cost of a reclaimed water
distribution system involves determination of those
components of treatment, distribution, and OM&R that
are directly attributable to the reclaimed water system.
Direct operation costs involve advanced treatment
facilities, distribution, additional water quality monitoring,
inspection and monitoring staff. The costs saved from
effluent disposal may be considered as a credit. Indirect
costs include a percentage of administration,
management and overhead. Anothercost is replacement
reserve, i.e. the reserve fund to pay for system
replacement in the future. In fiscal year 1986/87 the Irvine
Ranch Water District calculated this cost at 1.5 percent of
the original facility cost (Young et a/., 1987). The study
also found that the total cost of producing and distributing
reclaimed water (including acquisition of additional
source water) was $303/acft ($0.93/1,000 gal). The cost
of potable water distribution was $449/acft ($1.38/1,000
gal). The savings of $146/acft ($0.45/1,000 gal) overthe
life cycle of the project was considered nearly enough to
pay the debt service to payforthe dual distribution system
(Young et a/., 1987).
6.5 Phasing and Participation Incentives
The financing program can be structured to construct the
water reuse facilities in phases, with a percentage
financial commitment required prior to implementation of
a phase. This commitment assures the municipal
decision makers that the project is indeed desired and
ensures the financial stability to begin implementation.
Incentives can be used to promote early connections or
participation, such as a reduction or waiver of the
assessment or connection fee for those connections to
the system within a set time frame.
Adequate participation to support implementation can be
determined by conducting an initial survey in a service
area, followed up with a formal voted service agreement
by each neighborhood. If the required percent of the
residents in a given neighborhood agree to participate,
facilities will be constructed in that area. Once this type of
measure is taken, there is an underlying basis for either
assessing pipeline costs or charging through a monthly
fixed fee, because the ability to serve exists. The rate
policy may also include a provision for assessments or
charges for undeveloped properties within a
neighborhood served by a reclaimed water system.
6.6 Sample Rates and Fees
6.6.1 Connection Fees
Connection fees may be collected to pay for capital
construction costs of all or a portion of a reclaimed water
distribution system. These fees can be used to pay off
bonds or loans of capital costs associated with the project.
Depending on the specific circumstances, a reclaimed
water rate structure may not be designed to be financially
self-sufficient. In such cases, system costs are
supplemented through alternative sources and the end
user costs are less than the true cost of providing the
service. Connection charges to a dual distribution system
are often based on the size of the reclaimed water system
being served. For example, in Cocoa Beach, Florida,
customers are charged a connection fee based on the
size of the reclaimed water service line. The connection
fees are $100, $180, and $360 for a 3/4-in (19-mm), 1-in
(25-mm), and 1-1/2-in (38-mm) service line, respectively.
As an alternative to connection fees, a flat monthly rate
can be charged to each user for a specified length of time
until the capital costs associated with the system are paid
off. This alternative is often preferred because of the high
initial costs associated with connection fees.
6.6.2 User Fees
To offset the costs associated with OM&R for a dual
distribution, a monthly user fee may be collected. The
procedure for establishing rates for reclaimed water can
be similar to the procedure for establishing potable water
and sewer rates. If reclaimed water is metered, then user
rates can be based upon the amount of reclaimed water
used. If meters are not utilized, then a flat rate can be
charged. The use of meters will tend to temper excessive
use of reclaimed water since customers are generally
charged on the amount of reclaimed water used. For
example, studies conducted on the Denver area potable
water system revealed that water use in metered homes
averaged about 453 gal (1,715 L)/d, while water use in
flat-rate homes average above 566 gal (2,140 L)/d.
Therefore, metering can reduce total potable water use
by approximately 20 percent on an annual basis. It is
recommended that all connections to the reuse system
be metered. Table 29 presents user fees for a number of
existing urban reuse systems.
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Table 29. User Fees for Existing Urban Reuse Systems
6.7 Case Studies
Location
User Fee
Altamonte Springs, FL
Aurora, CO
Cape Coral, FL
Cocoa Beach, FL
Colorado Springs, CO
St. Petersburg, FL
Venice, FL
Detached single-family residential
units:
• Inside City - $5/month user fee for
one acre lot, + $1.50/month user fee
for each additional one-half acre, +
$3/month availability charge
• Outside City - $6.25/month for one
acre lot, + $1.875/month for each
additional one-half acre, + $3.75/
month availability charge
Multi-family, office, commercial, public,
industrial and warehouse facilities:
• $0.50/1,000 gal (inside city)
• $0.625/1,000 gal (outside city)
$0.78/1,000 gal
Single-family residential & duplexex:
• $5.00/month
Multi-family
• $0.004/sq ft of total property area
Commercial, professional, industrial,
agricultural, and worship users with
1" meter or less
• $0.0004/sq ft of total property area
Commercial, professional, industrial,
agricultural, and worship users with
greater than 1" meter
• $Metered and billed at $0.25/1,000
gal
$6/month for one acre tract, + $1.20/
month/each additional one-half acre
$0.60/1,000 gal
Flat Rate Customers:
$10.36/month for one acre lot, +
$1.20/month/each additional
one-half acre.
Metered Customers:
$0.30/1,000 gal
$1.25/month (5/8" meter) to
$5.60/month (2" meter) +
$0.50/1,000 gal used
6.7.1 Financial Incentives for Water Reuse: Los
Angeles County, California
The Sanitation Districts of Los Angeles County has an
established reuse program, which supplies waterfor such
purposes as public area landscape irrigation, irrigation of
food crops, livestock watering, groundwater recharge,
recreational lakes, oil-bearing zone injections, and
industrial processing.
Public support for reclaimed water has increased due to
recent drought conditions, with expansion of the system
expected to increase from the 1989 usage figure of over
66 mgd (2,890 L/s) to over 100 mgd (4,380 L/s) by the
Year 2000. In addition to the shortage of water, there
have been financial incentives which have made
reclaimed water an attractive alternative to potable water.
Various agencies have contributed to the ability of
reclaimed water costs to compete with those of potable
water. The following incentives have assisted in creating
a cost-effective reuse program:
Q Sanitation districts provide the reclaimed water
supply at approximately 20 percent of the O&M
costs forthe water reclamation facilities. In 1989,
reclaimed water was supplied at $15/ac-ft.
Q The State Water Resources Control Board
provides low interest loans for reuse projects.
Q The Metropolitan Water District of Southern
California provided a rebate of $154/ac-ft in 1990
for local conservation projects, including
reclaimed water.
Q "Greenbelt" areas have been developed near
the water reclamation plants, making distribution
facilities more economical.
Q Nutrient levels from reclaimed water have
decreased the dependence on standard fertilizer
treatments, with a cost saving&to one golf course
of $10,000 per year.
In summary, the district has successfully implemented a
reclaimed water program that is cost-effective (lowerthan
potable water costs). The end user cost ranges from a
high of 85 percent to a low of 44 percent of the potable
cost.
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6, 7.2 The Economics of Urban Reuse: Irvine Ranch
Water District, California
In the early 1970's, the Irvine Ranch Water District
completed studies showing water reclamation and reuse
as a cost-effective alternative to ocean discharge of
wastewater effluent. This finding was based on results
indicating that comparable AWT levels of treatment were
required for both alternatives, and ocean disposal was
estimated to be more costly due to the governmental
permitting process, and based upon the potential for
revenues from reclaimed water sales. However, the cost
comparison was affected when secondary treatment was
allowed for ocean discharges. As a result, advanced
treatment required for landscape irrigation made
reclamation the more costly treatment alternative. Also,
increased energy costs for reclaimed water pumping
madethe purchase of potable waterfrom the Metropolitan
Water District of Southern California (MWDSC) less
costly than reclaiming wastewater. Given these changes,
the economics of water reclamation were revisited in
1987.
Based on 1986-87 cost data, the tables below present
the costs ($303/ac-ft) associated with water reclamation
in the IRWD and the projected costs of potable water
($449/ac-ft) by the Year 2000.
Costs of Water Reclamation, Irvine Ranch Water District
(1986-87)
Cost Category $/ac-ft
Cost of Additional Treatment
Wages & benefits 33
Energy 13
Chemicals 1 1
Maintenance 1 3
Other 4
Subtotal $74
Distribution O&M Costs
Energy 58
Wages & benefits 29
Maintenance 1 3
Vehicle Usage 5
Monitoring 1 2
Other 15
Subtotal $132
Indirect Costs 50
Replacement reserve 47
TOTAL $303/ac-ft
($0.93/1 ,000 gal)
The IRWD receives potable water from a wholesaling
agency at a rate of $230/ac-ft. Additional potable
transmission facilities are expected to be required by the
Year 2000 at a cost of $81/ac-ft. Expansion of the
reclamation program is expected to reduce and possibly
eliminate this potable transmission expansion. The cost
of distributing this additional potable water is expected to
be $60/ac-ft with indirect costs (accounting,
administration and overhead) of $31/ac-ft. As with the
reclaimed water distribution system, replacement
reserves were estimated to be $47/ac-ft.
The comparison of the costs of reclamation vs. obtaining
additional water from the MWDSC are $303 and $4497
ac-ft, respectively. Based on the estimated costs
presented above, reclaimed water will be $146/ac-ft less
expensive than the purchase of additional potable water.
This savings is likely to be conservative given expected
increases in potable water costs.
This case study illustrates that although current
wastewater discharge standards do not support cost
savings with a reuse alternative, program costs for
additional potable water supplies can be eliminated or
delayed with implementation of a water reuse system to
cost-effectively meet existing and future irrigation water
needs.
Source : Young et al. 1 987.
Projected Cost of Potable Water, Irvine Ranch Water District
(2000)
Cost Category $/ac-ft
Treated water 230
Additional source water 81
Direct distribution costs 60
Indirect distribution costs 31
Replacement 47
TOTAL $449/ac-ft
($1.38/1 ,000 gal)
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6.7.3 Determining the Financial Feasibility of
Reuse In Florida
In Florida, water reuse is mandatory in areas designated
as critical water supply problem areas, unless such reuse
is not economically, environmentally, or technically
feasible. To ensure consistency in the economic
evaluations, the Florida Department of Environmental
Regulation (FDER) released "Guidelines for Preparation
of Reuse Feasibility Studies for Applicants Having
Responsibility for Wastewater Management" in
November 1991. The guidelines include a methodology
for an economic evaluation of implementing reuse.
Generally, the reuse feasibility study considers the
evaluation of at least two alternatives:
Q No action
Q Implementation of a public access/urban reuse
system
The feasibility guidelines specify the means by which the
present value of each alternative will be developed. The
period of analysis is given as 20 years. The discount rate
to be used in the analysis is the current discount rate as
developed annually by the U.S. Bureau of Reclamation.
Capital construction costs are to include the cost of
wastewater collection and treatment, and reclaimed
water transmission to the point of delivery for the end
user, plus reasonable levels of other related costs such
as engineering, legal service, and administration.
Assumed levels of wastewater treatment must be
commensurate with the proposed end use. For example,
it is highly improbable that a secondary effluent could be
discharged to a surface water in Florida. Therefore, it
would be inappropriate to assume this level of treatment
in comparison to an advanced secondary level of
treatment required in most reuse systems.
Applicants under the same ownership/control as a public
water system are able to consider the costs avoided in
expanding potable water systems where reuse is
anticipated to reduce that demand. The cost of potable
water supplies must include the cost of water withdrawal,
treatment, and transmission to the point where the
potable water leaves the water-treatment plant. In addition
to outlining procedures for establishing some sunk costs,
revenues, salvage values, replacement and the basis of
the cost, the feasibility guidelines also allow for an
economic evaluation of water saved by implementing the
reuse alternatives. This water savings is over and above
that obtained by deferring expansion to the potable water
system and addresses the immediate reduction in potable
water supplies that may be realized through the
implementation of a reuse program. The volume of
potable water saved is calculated by establishing
anticipated potable water demands under the "no action
alternative" and the prescribed reuse alternative.
Subtracting the annual water use projected under no
action and reuse alternatives yields the projected annual
water savings. This water savings will be valued at the
average residential rate for potable water charged by the
predominant water supply utility within the proposed
reuse service area. The value of this water may then be
taken as a revenue (benefit) for the reuse alternative.
This method of evaluating water savings is proposed
solely for the preparation of reuse feasibility studies but
recognizes the inherent value of reclaimed water systems
and, in essence, sets its worth equal to that of the potable
supplies it will offset.
The following table presents an example of the economic
evaluation.
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Economic Evaluation for Water Reuse
Given:
Initial Capital Investment
Expansion
Average Annual O&M Costs
Planning Parameters
Water Savings
20 Year Useful Life $3 million/year 0 .
20 Year Useful Life $2 million/year 10
Years 1-10 = $500,000/yr
Years 11 -20 =. $750,000/yr
20-year horizon
Discount rate of 10 percent
1991 Dollars
Years 1-10 Reuse will save 0.5 mgd potable water
Years 11-20 Reuse will save 1.0 mgd potable water
Average residential water cost = $1.00/1,000 gal
Datormlno: Present value of this project In 1991 dollars with and without the credit from the potable water savings
Capital Cost
$3,000,000
2,000,000
Without Water Credit
Salvage Value
Annual Costs
Construction cost
Initial (a)
Salvage (b)
Expansion (c)
Salvage (d)
O&M Costs
Years 1-10 (a)
Years 11-20(1)
Toial Present Value
The above costs minus:
Water Savings
Years 1-10 (g)
Years 11-20 (h)
Total Present Value Adjusted for Water Savings
(1,000,000)
With Water Credit
(182,500)
(365,000)
500,000
750,000
Present Value
$3,000,000
0
771,000
(149,000)
3,072,000
1.776.000
$8,470>000
(1,121,000)
( 865.000^
$6,484,000
(a) The Initial construction is already at present value.
(b) The Initial construction useful life is 20 years; therefore, there is no salvage value.
(c) The expansion construction cost is converted to present value, using the present worth factor for a single payment, which in this example is the present value
lor Year 10, with a 10 percent discount rate, or a factor of 0.3855.
(d) The expansion construction cost salvage value equals the ratio of the remaining useful life/useful life times construction cost ($1,000,000). The present
value of the salvage value equals the present worth factor for a single payment, which in this example, is the present value for Year 20, with a 10 percent
discount rate, or a factor of 0.1486.
(e) The present value of the O&M costs for Years 1-10 equals the present worth factor for payment in Years 1-n, given a discount rate of 10 percent. In this
instance, the years are 10 and the present worth factor is 6.144 (6.144 times $500,000 = $3,072,000).
(0 The present value of the O&M costs for Years 11 -20 equals the present worth factor for payments in Years 11 -20 (or for 10 years) brought back to year 1
value using the present worth factor for a single payment, given a disount rate of 10 percent. In this instance, the years are 10 and the present worth factor
is 6.144. The present worth factor for a single payment is 0.3855 ($750,000 times 6.144 times 0.3855 =. $1,776,000 rounded to the nearest $1,000).
(0) The water savings In Years 1-10 were computed at the rate of 0.5 mgd for 365 days, or 182,500,000 gal/yr., with a value of $1.00/1,000 gal = $182,500/yr.
Ths present value equals the present worth factor for payments in Years 1-n, given a discount rate of 1 o percent. In this instance, the years are 1 o and the
present worth factor is 6.144 (6.144 times $182,500 = $1,121,000 rounded to the nearest $1,000).
(h) Ths water savings in Years 11-20 were computed at the rate of 1.0 mgd for 365 days, or 365,000 gal/yr, with a value of $1.00/1,000 gal =» $365,ooo/year.
The present value comparison is the same as footnote (f) or $365,000 times 6.144 times 0.3855 = $865,000 (rounded to nearest $1,000).
162
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6. 7.4 An Innovative Funding Program for an Urban
Reclaimed Water System: Boca Raton,
Florida
In 1989, the City of Boca Raton, Florida, established a
water conservation rate structure for potable water. The
purpose of this rate structure, which is shown in the table
below, was to promote potable water conservation and to
set aside funds, $2,500,000 annually, for a reclaimed
water system. As the reclaimed water system becomes
operational and potable water consumption is reduced, it
will be necessary to increase these rates to some degree
to maintain the annual $2,500,000 set aside. However,
as the reclaimed water system expands, it will move
toward being self-supporting, reducing these increases
in potable water rates. In addition, the reclaimed water
system will eliminate the need for an $8,500,000
expansion of the city's water treatment plant that would
have been necessary without the reclaimed water system
off-setting the current potable water system irrigation
demand.
As of October 1990, the water conservation rate fund had
a beginning balance of $4,858,000 and average annual
contributions of $3,500,000 were budgeted. It is
estimated by the Year 2000, the total accumulated fund
amount will be $29,858,000. This accumulated total does
not include accrued interest on the fund balance because
this balance will be constantly changing depending upon
the construction schedule. This funding program for the
reclaimed water system may be assisted by a bond issue
if it becomes desirable to complete the entire 15.0 mgd
(657 L/s) program in a shorter period of time.
This program will provide reclaimed water service to 75
to 80 percent of the proposed service district over the 1 0-
year period and will serve four large users: Florida Atlantic
University, and three golf courses, and slightly more than
10,000 single-family homes together with other public and
private landscaped areas within Phases 1 through 3 of
the transmission main system. The estimated average
daily reclaimed water use under this program in the Year
2000 will be 11.68 mgd (512 Us), and the reduction in
potable water consumption will be about 8.34 mgd (365
Us). This program will serve approximately 79 percent of
the single-family homes in the proposed service district
and will use about 78 percent of the 15.0 mg/d (657 L/s)
of reclaimed water projected to be available by the Year
2000. Construction of transmission and distribution mains
to serve Phase 4 of the service district will take place after
the Year 2000.
Potable Water Rate Structures (Bi-monthly)
City of Boca Raton
Consumption Rate Charge
(Gallons) (Per 1 ,000 Gallons)
Basic Rate Structure (Prior to 10/1/89):
0 - 50,000 $ .30
50,000+ .50
Water Conservation Rate Structure (After 10/1/89)
0-25,000 $ .35
25,000 - 50,000 .85
50,000+ 1.10
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6.8 References
California State Water Resources Control Board. 1991.
Water Recycling 2000: California's Plan for the Future.
Office of Water Recycling, Sacramento, California.
Florida Department of Environmental Regulation. 1991.
Guidelines for Presentation of Reuse Feasibility Studies
for Applicants Having Responsibility for Wastewater
Management. Tallahassee, Florida.
Ferry, W. 1984. Determining Financial Feasibility for a
Reclaimed Water Enterprise. In: Water Reuse
Symposium III, San Diego, California, AWWA Research
Foundation, Denver, Colorado.
Fowler, L.C. 1979. Water Reuse for Irrigation — Gilroy,
California. In: Proceedings of the Water Reuse
Symposium, Volume 2, AWWA Research Foundation,
Denver, Colorado.
Murphy, R. and Hancock, J. 1991. Urban Reuse in the
City of Boca Raton, Florida—The Master Plan, Presented
at 1991 Water Pollution Control Federation Annual
Conference, Toronto, Ontario, Canada.
Young, R., Lewinger, K., and Zenk, R. 1989. Wastewater
Reclamation—Is It Cost Effective? Irvine Ranch Water
District—A Case Study. In: Water Reuse Symposium
IV, August 2-7,1987, Denver, Colorado.
164
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CHAPTER 7
Public Information Programs
A workable water reuse program grows out of successive
stages of study in the technical, legal/institutional, and
financial aspects of reuse as they apply to a community.
Just as crucial to successful program implementation is
the support and encouragement, fromthe outset, of active
public involvement in the reuse planning and
implementation process.
This chapter provides an overview of the key elements of
public participation, as well as several case studies
illustrating public involvement approaches.
7.1 Why Public Participation?
Public involvement begins with the earliest exploratory
contacts with potential users, and can continue through
to formation of an advisory committee and holding of
public workshops on candidate reuse schemes. It
involves the two-way flow of information, helping to
ensure that adoption of a selected water reuse program
will fulfill real user needs and generally recognized
community goals regarding public safety, program cost,
etc.
7.1.1 Source of Information
The term "two-way flow" cannot be too highly
emphasized. In addition to building community support
for a reuse program, public participation can also provide
valuable community-specific information to the reuse
planners. As stated in EPA's Public Involvement Activities
Guide: "Local residents often have a more intimate
understanding of particular community problems.. .Their
information is pertinent and up-to-date... (reflecting) the
community's values, concerns, and goals" (Rastatter,
1979). Citizens have legitimate concerns, quite often
reflecting their knowledge of detailed technical
information. In reuse planning, especially, where one
sector of "the public" comprises potential users of
reclaimed water, this point is critical. Potential users
generally know what flow and quality of reclaimed water
are acceptable for their applications.
7.1.2 Informed Constituency
By soliciting expression of public concerns and
incorporating suggestions made by members of the
public, a public participation program can build, overtime,
an informed constituency that is "at home" with the
concept of reuse, knowledgeable about the issues
involved in reclamation/reuse, and supportive of program
implementation. Citizens who have taken part in the
planning process will be effective proponents of the
selected plans. Having educated themselves on the
issues involved in adopting reclamation and reuse, they
will understand how various interests have been
accommodated in the final plan. Their understanding of
the decision-making process will, in turn, be
communicated to the larger interest groups—
neighborhood residents, clubs, and municipal agencies—
of which they are a part. Indeed the potential reuse
customer enthusiastic about the prospect of receiving
service may become one of the most effective means of
generating support for a program. In the urban reuse
programs in St. Petersburg and Venice, Florida,
construction of distribution lines is contingent on the
voluntary participation of a percentage of customers
within a given area. Experience indicates that a small
numberof motivated individuals can often be responsible
for developing the required commitment. Likewise, golf
course superintendents and agricultural customers will
discuss the merits of a program among themselves,
thereby increasing overall awareness of the program.
Since many reuse programs may ultimately require a
public referendum of some fashion to approve a bond
issue for funding reuse system capital improvements,
diligently soliciting community viewpoints and addressing
any concerns early in the planning process can be
invaluable in garnering support. Public involvement early
in the planning process, even as alternatives are
beginning to be identified, allows ample time for the
dissemination and acceptance of new ideas among the
constituents. Public involvement can even expedite a
165
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reuse program by uncovering any opposition early
enough to adequately address citizen concerns.
7.2 Defining the "Public"
Many contemporary analyses of public involvement
define "the public" as comprising various subsets of
"publics" with differing interests, motivations, and
approaches to policy issues. For example, in discussing
public participation forwastewaterfacilities planning, one
planning consultant identifies the following publics:
general public, potential users, environmental groups,
regulators, political leaders, and business/academic/
community leaders (Heilman, 1979).
EPA regulations (EPA, 1979a) identify the public as the
general public, the organized public (public and private
interest groups), the representative public (elected and
appointed officials), and the economically concerned
public (in this case, those whose interests might be
directly affected by a reuse program). Examples of groups
falling under the organized, representative and
economically concerned publics can include the news
media and the chief elected officials of the involved
communities, neighborhood organizations, any citizens
advisory committee, the Sierra Club, the League of
Women Voters, business groups such as the Chamber of
Commerce, the Rotary Club, industries and unions,
sportsmen's clubs, historical societies, public works
departments, recreation commissions, health
departments, and state legislatures (Stern and Reynolds,
1979).
If a program for reuse truly has minimal impact on the
general public, limited public involvement may be
appropriate. For example, use of reclaimed water for
industrial cooling and processing—with no significant
capital improvements required of the municipality—may
require support only from technical and health experts in
other municipal and state agencies and from
representatives of the prospective user and its
employees. Reuse for irrigation of pasture land in isolated
areas might be another example warranting only limited
public participation.
But consideration of a broad range of candidate reuse
systems, as is being advocated in these Guidelines,
involves choices among systems with widely varying
economic and environmental impacts for many segments
of the public. Successful plan implementation will be
assured in these cases only when officials, interest
groups, and citizens share "a significant voice in (project)
development" (Hollnsteiner, 1976).
"The public," in reuse planning, encompasses area
residents, potential users of reclaimed water, freshwater
purveyors, citizens with special areas of expertise
pertinent to reuse, and the interest groups whose support
is vital as representing diverse viewpoints shared by
many in the community. From the outset of reuse
planning, informal consultation with members of each of
these groups, and formal presentations before them,
should both support the development of a sound base of
local water-reuse information and, simultaneously, build
a coalition that can effectively advocate reuse in the
community. Keeping in mind that different groups have
different interests at stake, the presentation should be
tailored to the special needs and interests of the
audience.
7.3 Overview of Public Perceptions
Surveys overthe last two decades indicate a surprisingly
large measure of public support for water reuse
programs. In both 1984 and 1987, Bruvold presented
summaries and evaluations of available surveys
regarding a variety of reuse options (Bruvold, 1984 and
1987). The results of seven surveys carried out from 1972
to 1985 are summarized in Table 30. The primary goal of
most of the surveys was to gauge the public reaction to
reuse projects involving some form of potable reuse, but
questions on a wide variety of reuse alternatives were
also included. All surveys indicate that the public's
reluctance to support reuse increases as the degree of
human contact with the reclaimed water increases. As a
result of this trend, the use of reclaimed water as a source
of potable water received the greatest opposition.
However, as Bruvold points out, the surveys indicate that
there is even a sizable minority who are not opposed to
potable reuse (Bruvold, 1984). Results of a survey done
in Denver regarding the use of reclaimed water as a
source of potable water suggest that approximately one
third of the respondents have significant opposition to the
program, one third express some opposition, and one
third indicate little or no objections (Lohman, 1987). The
results of the surveys also indicate that socioeconomic
and environmental factors play a role in the perception of
water reclamation. Acceptance tends to increase with
income and education.
The public also tends to support reuse for environmental
benefits such as conservation or water quality protection
of water resources. Also reviewed were surveys
conducted in communities where reclamation projects
were being considered. For those persons where water
reuse was an imminent possibility (i.e., construction to
provide reclaimed water service was being considered),
the issues of concern became in the following order: (1)
the ability of the project to conserve water, (2)
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Table 30. Percentage of Respondents Opposed to Various Uses of Reclaimed Water in General Opinion Surveys
Use
Drinking Water
Food Preparation
in Restaurants
Cooking in the Home
Preparation of
Canned Vegetables
Bathing in the Home
Swimming
Pumping Down
Special Wells
Home Laundry
Commercial
Laundry
Irrigation of
Dairy Pasture
Irrigation of
Vegetable Crops
Spreading on
Sandy Areas
Vineyard Irrigation
Orchard Irrigation
Hay or Alfalfa
Irrigation
Pleasure Boating
Commercial Air
Conditioning
Electronic Plant
Process Water
Home Toilet
Flushing
Golf Course
Hazard Lakes
Residential
Lawn Irrigation
Irrigation of
Recreation Parks
Golf Course
Irrigation
Irrigation of
Freeway Greenbelts
Road Construction
Bruvold
(1972)
(N=972)
56
56
55
54
37
24
23
23
22
14
14
13
13
10
8
7
7
5
4
3
3
3
2
1
1
Stone & Kasperson Olson Milliken Lohman
Kahle etal. etal. Bruvold & Lohman & Milliken'
(1974) (1974) (1979) (1981) (1983) (1985)
(N=1,000) (N=400) (N=244) (N=140) (N=399) (N=403)
46 44 54 58 63 67
_ _ 57 — — —
38 42 52 — 55 55
38 42 52 — 55 55
22 — * 37 — 40 38
20 15 25 — - — —
40
— 15 19 — 24 30
16 — 18 — — - —
-. — — .- ^ Q __ __
— 16 15 21 79
— - — 27 — — —
— — 15 — — —
— — 10 — — —
9 — 8 — — —
14 13 5 — — • —
g
5 3 12 — — —
5 — 7 — 34
8 — 5 8 — —
6 — 6 5 1 3
^- — 5 4 — —
52 3 4 — —
— — 5 — — —
_ _ 4 _ _ _
— Not included in survey.
Source: .Bruvold, 1987.
167
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environmental enhancements achieved by the project,
(3) protection of public health, (4) the cost of treatment
required, and (5) the cost of distribution.
From the results of the existing surveys, Bruvold
concludes that the findings expressed in Table 30 are
very stable and may be used in the development of
reclamation policies. The basis for such policies should
consider (1) the degree of contact envisioned, (2) public
health protection, (3) the conservation and environmental
benefits, and (4) treatment and distribution costs. As the
initial objections are addressed and overcome, the issue
of customer cost typically becomes the deciding factor in
the success or failure of a program.
There is no question that the public's enthusiasm for
reuse (as perceived in the cited studies) might more
reflect the hypothetical conditions set up by the survey
questions and interviews used than signify a genuine
willingness to endorse local funding of real programs that
could involve distribution of reclaimed water for
nonpotable use in their neighborhood. Survey results do
indicate, however, that, at least on the intellectual plane,
"the public" is receptive to use of reclaimed water in well
thought out programs. The results also support
conclusions that this initial acceptance hinges in large
measure on:
Q The public's awareness of local water supply
problems and perception of reclaimed water as
having a place in the overall water supply
allocation scheme.
Q Public understanding of the quality of reclaimed
water and how it would be used.
Q Confidence in local management of the public
utilities and in local application of modern
technology. Stone (1976) found that residents in
communities with good quality water were more
accepting of the use of reclaimed water than
were residents in communities with water quality
problems.
Q Assurance that the reuse applications being
considered involve minimal risk of accidental
personal exposure.
Bruvold and Ongerth (1974) concluded that "the public is
not yet ready for intimate uses of reclaimed water... (nor
does the public favor) a low level of treatment of
wastewater and its discharge into the environment
without further reuse." This assertion is reaffirmed in
Bruvold's 1987 work. The reluctance to ingest reclaimed
water is understandable.
The apparent opposition by the public to the disposal of
water that may be reclaimed is encouraging. Often reuse
enjoys its greatest public acceptance where both water
resource issues and pollution abatement issues combine.
Such is the case in southwest Florida. Many
municipalities draw groundwaterof poor quality requiring
expensive treatment to produce their drinking water. At
the same time, low flow conditions in local streams and
rivers and poor flushing of the bay and estuaries make
surface water discharge environmentally unacceptable.
7.4 Involving the Public in Reuse Planning
Even where water reclamation is common, there is a need
to establish a flow of information to and from the potential
reuse customer. From an implementation standpoint, the
designer requires information on the system(s) to receive
the reclaimed water and to ensure compatibility. The
customer, on the other hand, will wish to have a clear
understanding of the program and provide input regarding
their needs.
Of 200 reclamation projects surveyed in Florida, only 20
reported some type of problems in implementing reuse
(Florida Department of Environmental Regulation, 1990).
Twenty-five percent of the problems, the single largest
factor reported, were associated with public acceptance
(Wright, 1991). For example, the City of Cape Coral had
developed plans to implement an urban irrigation
program over a 110-sq mi (280 km2) service area using
treated canal water and reclaimed water from municipal
wastewater. A formal public information program was
considered unnecessary, as it was perceived that the
publicity generated in the planning period was sufficient
to create a basis of understanding in the residential
customers. However, when residents received an
assessment, this assumption was proven incorrect. The
ensuing groundswell of opposition resulted in election of
a counsel opposed to the project and years of delay to
project implementation (Wright, 1991). However, the
project was implemented after the incorporation of a
public information/education program.
In order to avoid difficulty associated with public
acceptance, it is of paramount importance that the
expected benefits of the proposed project be established.
If the project is intended to extend water resources, the
preliminary studies should address how much water will
be made available and compare the cost of reclamation
to that of developing additional potable water sources. If
the cost of reclamation is not competitive with potable
water in cost, there must be overriding non-economic
issues that equalize the value of the two alternative
sources. Where reclamation occurs for environmental
reasons, such as the reduction or elimination of a surface
168
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Figure 33. Public Participation Program for Water Reuse System Planning
General
Survey
¥T
Plan
Stuc
^
of
iy
Public
Notification/
Involvement
^-
>
Public
Meetings
specinc
Users
Survey
14
Alternatives
dentification
& Evaluation
'•
>
)
f
^ Plan
•^ selection
\t
Y
t
Customer- Public
Specific Notification/
Workshops Involvement
^ Proje
•^ impieme
^
set
ntation
Customer-Specific
Information
Program
water discharge, the selected reuse alternative must
again be competitive with other disposal options.
When firmly established, those benefits then become the
planks of a public information program and it is possible
to state "why" the program is necessary and desirable.
Without such validation, reclamation projects will be
unable to withstand public inspection and the likelihood
of project failure is greatly increased.
7.4.1 General Requirements for Public
Participation
Figure 33 provides a flow chart of a public participation
program for water reuse system planning. In addition to
the public meetings and workshops commonly included
in public information efforts, the program includes surveys
as a public education/information tool. In the early stages,
a general distribution survey may be helpful in identifying
level of interest, potential customers, and any initial
concerns that the population might have. Where specific
concerns are identified, later public information efforts
can be tailored to address them. This could include
participation of other public agencies that can provide
information on water reuse and regulatory requirements,
informal discussions with some potential users to
determine interest orf ill data gaps, and initial background
reports to appropriate local decision making bodies. As
the program progresses to alternative identification and
evaluation, another survey might be considered. This
survey could serve to confirm earlier results, monitor the
effectiveness of the ongoing education program, ortarget
specific users.
It might be helpful to identify at the outset the level of
interest different individuals and groups will have in the
reuse planning process. For example, Boston's
Metropolitan District Commission (MDC) determined in a
public participation program that some "publics" would
want only to be kept informed on a regular basis, some
would want periodic opportunities to ask questions and
offer comments, and some would want to play a very
active review and advisory role (Stern and Reynolds,
1979). The MDC's public participation program
incorporated tasks and activities that ensured the desired
degree of involvement for each group. Table 31 lists tools
of public participation that might be useful in informing
and involving the public to different degrees.
Table 31. The Tools of Public Participation
Purpose
Tools
Education/I nf ormation
Review/Reaction
Interaction Dialogue •
Newspaper articles, radio and TV
programs, speeches and presentations,
field trips, exhibits, information
depositories, school programs, films,
brochures and newsletters, reports,
letters, conferences.
Briefings, public meetings, public
hearings, surveys and questionnaires,
question and answer columns, advertised
"hotlines" for telephone inquiries.
Workshops, special task forces,
interviews, advisory boards, informal
contacts, study group discussions,
seminars.
Source: Rastatter, 1979.
169
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7.4.1.1 Public Advisory Groups
If the scope or potential scope of the reuse program
warrants it (e.g., reclaimed water may be distributed to
several users or types of users), formation of a public
advisory group will assist in defining system features and
resolving problem areas. In its regulations for full-scale
public participation programs, EPA requires that group
membership contain "substantially equivalent"
representation of the private (noninterested), organized,
representative and affected segments of the public. It is
recommended that group membership for reuse planning
provide representation for potential users and their
employees, interest groups, neighborhood residents, the
other public agencies, and citizens with specialized
expertise in areas (such as public health) that pertain
directly to reclamation/reuse.
There is no reason to consider the group fixed at its
original membership; other interested citizens can be
added as the reuse program takes shape and as new
issues or opportunities develop. What is important,
however, is to institutionalize the group and its activities
so that its efforts are directed effectively to the task at
hand: planning and implementation of a reuse program in
which the legitimate interests of various sectors of the
public have been fully considered and addressed. I n order
to achieve this, the proposed formation of the advisory
group should be publicized to solicit recommendations
for, and expression of interest in, membership.
The group's responsibilities should be well-defined,
whether it is intended that the group should simply
conduct a study of some particular aspect of the reuse
plan, or that it should serve throughout program planning
and implementation as a broad-based representative
body that can develop and advocate the program. Its
meetings should be open to the public at times and places
announced in advance. The group's members should
designate at an early meeting a single individual who can
serve as a contact point for the press and other news
media. The group should fully recognize its shared
responsibility for developing a sound reuse program that
can serve both user requirements and community
objectives. In subsequent public meetings, the group will
assert its combined role as source of information
representing numerous interests, and advocate of the
reuse program as it gains definition.
7.4.1.2 Public Participation Coordinator
EPA regulations for full-scale public-participation
programs require appointment of a public participation
coordinator—an individual skilled in developing,
publicizing, and conducting informal briefings and work
sessions as well as formal presentations for various
community groups. Whether or not a program requires
designation of a public participation specialist, the
significant value of providing public contact and liaison
through a single individual should be considered. Such a
person, whether an agency staff member, advisory group
memberor specialist engaged from the larger community,
should be thoroughly informed of reuse planning
progress, be objective in presenting information, and
have the "clout" necessary to communicate and get fast
response on issues or problems raised during
To accomplish this goal, many communities involved in
urban and agricultural reuse have created a dedicated
reuse coordinator position. The specifics of the areas of
responsibility of such a position will vary according to
specific conditions and preferences of a given
municipality. In many Florida programs, the reuse
coordinator Is part of the wastewater treatment
department. This position may be independent of both
water and wastewater or associated with the water
system.
7.4.2 Specific Customer Needs
As alternatives for water reuse are being considered, the
customer associated with each alternative should be
clearly identified. The needs of the customers must then
be ascertained and addressed, as described in previous
sections. In the past, failure to take this step has resulted
in costly and disruptive delays to reclamation projects.
7.4.2.1 Urban Systems
In urban reuse programs, the customer base may consist
of literally thousands of individuals. These people may be
reached through the local newspaper, radio and public
workshops. Identification of homeowner associations and
civic organizations may allow for presentations to large
numbers of potential customers at a single time.
The use of direct mail surveys may also be an effective
means of informing the potential customer base of a
proposed program, as well as receiving feedback from
that base. In the City of Venice, Florida, a survey
consisted of a one page letter of introduction and a one
page survey. The letter of introduction explained what
reclaimed water was, cited examples of local areas where
it had been successfully used, explained why it was
desirable in Venice, and requested completion and return
of the survey. Approximately 30 percent of the surveys
were returned. Reclamation was viewed as a favorable
option by 71 percent of those responding city wide (COM,
1990). Through this process, the city ultimately developed
a voluntary urban reuse program involving over 2,000
single and multi-family units.
As part of the Denver potable reuse demonstration
program, the effectiveness of different public information
170
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programs were studied. A control group was established
that received no specific attention. A second group was
provided literature on the program. A third group was
provided literature and given a tour of the treatment
facilities. The results of this study, indicate the group
receiving the plant tour as having the greatest change in
attitude (Olson etal., 1979).
7.4.2.2 Agricultural Systems
In agricultural water reuse programs, the issues of
concern may differ from those of the urban customer. In
agricultural programs, the user is concerned with the
suitability of the reclaimed water for the intended crop.
Water quality issues that are of minor importance in
residential irrigation may be of significant importance for
agricultural production. For example, nitrogen in
reclaimed water is generally considered a benefit in turf
and landscape irrigation. However, as noted in the
Sonoma Case Study in Chapter 3, the nitrogen in
reclaimed water could result in excessive foliage growth
at the expense of fruit production. While turf grass and
many ornamental plants may not be harmed by elevated
chlorides, similar chloride levels may delay crop
maturation and effect the product marketability, as
occurred in the strawberry irrigation study in the Irvine
Ranch Water District discussed in Section 3.4.
In assessing the agricultural customer, it is necessary to
modify the public participation approach used for the
urban customer. Agencies traditionally associated with
agricultural activities can provide an invaluable source of
technical information and means of transmitting
information to the potential user.
Local agricultural extension agents may prove to be the
most important constituency to educate as to the benefits
of reclamation. The agents will likely know most, if not all,
of the major agricultural sites in the area. In addition, they
will be familiar with the critical water quality and quantity
issues facing the local agricultural market. Finally, the
local farmers see the extension office as a reliable source
of information and are likely to seek their opinion on issues
of concern, as might be the case with new reclamation
projects. The local extension agent will be able to discuss
the issues with local farmers and hopefully endorse the
project if familiar with the concept of reuse. The local soils
conservation service may also prove an important target
of a preliminary information program. Lack of
endorsement from these agencies can hinder the
implementation of agricultural reclamation.
7.4.3 Agency Communication
As noted in Chapters 4 and 5, the implementation of
wastewater reclamation projects may be subject to review
and approval of numerous state and local regulatory
agencies. In locations where such projects are common,
the procedures for agency review may be well
established. Where reclamation is just being started,
formal review procedures may not exist. In either case,
establishing communication with these agencies early in
the project is as important as addressing the needs of the
potential customers. Early meetings may serve as an
introduction or may involve detailed discussions of the
permitability of a given project. As with the agricultural
experts, the proposed project must be understood and
endorsed by the permitting agencies. It may also be
appropriate to contact other agencies that may still
become involved with a public education program. Such
is the case with local health departments, which may not
participate directly in the permitting process but may be
contacted by citizens with questions on the project. It
would indeed be unfortunate for a potential customer to
contact the local health department only to find that
agency was unaware of the project in question; even
worse would be the damage caused by a negative
reaction from such an agency.
Where multiple departments in the same agency are
involved, communication directly with all concerned
departments will ensure coordination. It is worthwhile to
establish a master list of the appropriate agencies and
departments that will be copied on status reports and
periodically asked to attend review meetings.
This communication will be beneficial in developing any
reclamation project. It will be critical to establish
communication with and between agencies when specific
regulatory guidance on a proposed project does not exist.
Such a condition is most likely to occur in states lacking
detailed regulations or in states with very restrictive
regulations that discourage reuse projects.
171
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7.5 Case Studies
7.5.1 Using Public Surveys to Evaluate Reuse:
Venice, Florida
In 1987, the City of Venice initiated the development of a
water reuse program to irrigate golf courses and parks.
By 1989, because of potable water use restrictions and
state regulations that encourage reuse, the city began to
consider the implementation of a water reuse program
that would also serve single- and multi-family homes. To
gauge public interest in residential reuse, public
workshops and a reuse survey were conducted.
The public workshops included invited speakers such as
the director of the neighboring St. Petersburg urban reuse
system and public health experts. Some presentations to
homeowners associations were also arranged. In
addition, the City of Venice developed a reuse survey for
distribution to all water customers. This survey consisted
of a cover letter introducing the reuse project and a survey
to develop an understanding of irrigation practices and
citizen knowledge of reuse. The text of the letter and
survey are provided on the following page.
Approximately 30 percent of the surveys were returned;
of these, 71 percent indicated that they would use
reclaimed water. The results of the survey were organized
by subdivision and any objections noted. As the project
proceeded, the public education program was modified
to address the issues stated in the survey. Public health
concerns were successfully addressed early in the project
and the primary question became one of cost.
The survey consisted of eight questions that could be
easily completed. This is credited for the high return rate.
While the results of the survey did not yield detailed
information, they did identify general objections to the
use of reclaimed water the city might face. The cover
letter was an important component of the public education
process. Even after three years of workshops, program
implementation, and newspaper articles, many
customers'only awareness of the prospect of water reuse
was the survey sent by the mayor.
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Cover Letter
RE: City of Venice
Reclaimed Water for Irrigation
Dear Venice Resident:
I am writing to you to consider the possibility of using
reclaimed water for residential irrigation. The City of
Venice, like many cities in Southwest Florida, faces the
constant problem of supplying high quality drinking water
to its citizens. With an average rainfall of 55 in (140 cm)/
yr and surrounded by canals, creeks, and ponds, it may
surprise you to know that Venice is required to use an
expensive reverse osmosis treatment process to provide
the quality and quantity of drinking water needed.
Unfortunately, as much as 1.3 mgd (57 Us) of this highly
treated water is used for residential and commercial
landscape irrigation. To reduce the amount of drinking
water used for irrigation, the city is considering the use of
reclaimed water to meet residential irrigation needs.
What is reclaimed water?
Reclaimed water is wastewater that has received a high
level of treatment and disinfection. The reclaimed water
is odorless and virtually indistinguishable from drinking
water. The city has plans to provide reclaimed water to
four golf courses and residential developments in Venice.
The City of St. Petersburg has practiced reuse for 10
years and supplies over 20 million gal/d of reclaimed
water to over 3,000 homes. The use of reclaimed water is
accepted and encouraged by the Water Management
District and the Florida Department of Environmental
Regulation as a proven method of conserving water
resources.
We are asking for your help in considering the potential
for reuse in the City of Venice. Enclosed please find a
reuse survey form. Please complete this survey and
return it to the city by folding and stapling the survey form
so that the city's address and postage is showing.
Returning'the survey will not obligate you in any way. If
sufficient interest in reuse is found in your area, the city
will contact you regarding implementation of a reuse
system. Thank you for your cooperation in this matter.
Harry E. Case
Mayor
Reuse Survey
1. Name:
2. Address:
3. Name of Subdivision:
4. Type of Irrigation:
[ ] Residential Lawns
[ ] Landscape Irrigation (Condominium)
[ ] Plant Nurseries
[]. Other:
5. What is your current source of irrigation:
[] City Water [] Well [] Other:
6. Would you use reclaimed water for irrigation?
[] Yes [] No
If your answer to question 6 was no, what is your
objection to the use of reclaimed water?
7. Would you be interested in receiving more information
on reuse?
[] Yes [] No
8. Other Comments:
If you have any questions, please feel free to call the City
of Venice.
RETURN INSTRUCTIONS: Please fold and staple or
tape this self-addressed, postage paid form at your
earliest convenience.
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7.5.2 Having the Public Evaluate Reuse
Alternatives: San Diego
Planning of a wastewater reclamation and reuse project
In the San Diego Clean Water Program (CWP) included
public involvement for the evaluation of system
alternatives. As shown in the planning model depicted
below, the public was involved early in the planning
process in assessing the system options and again in
ratifying the selected alternative.
The initial technical evaluation identified 21 alternatives,
which were reduced through further analyses to seven
before presentation to the public. A survey of the general
population in the greater metropolitan area of San Diego
was conducted in 1989. A total of 600 respondents,
selected as representative of area demographics, were
interviewed. The interviews were conducted in the
respondents'homes by trained interviewers. Each 1-hour
interview followed a prescribed format that noted
appropriate demographics, carefully defined wastewater
treatment and water reuse, assessed general attitudes
towards various forms of reuse, and presented the seven
alternatives and their associated costs, and obtained an
assessment and ranking of each alternative.
Concurrent with the interview process, technical planners
performed a comprehensive analysis for the seven
alternatives. The technical and public rankings agreed
on four alternatives, with both groups ranking the same
alternative as their first choice.
Based on these results, the CWP proceeded with
development of plans and specifications for the selected
alternative. Two more surveys were conducted, each
using 600 new respondents and focusing only on the
selected alternative. These surveys confirmed the
favorable evaluations of the first survey, and indicated a
strong inclination to support public ratification of the
program.
The San Diego survey illustrates several interesting
points:
Q Technical findings and public opinion may be in
concert with one another when reuse alternatives
are being considered.
Q Preliminary surveys reliably predicted project
acceptance for the reuse program.
Q When the public is substantially involved in the
planning process, the public support necessary
to obtain funding for the projects proposed is
more likely.
The experience and results of the San Diego survey
illustrate how public involvement may be accomplished
in a way that appears to appropriately balance the need
for both technical expertise and public input in the
planning and development of major wastewatertreatment
and reclamation facilities.
Source: Bruvold, 1987.
Public Involvement in Project Planning, San Diego Clean Water Program
Option
Development
& Selection
Construction Plan
Development
& Approval
Construction &
Operational
Testing
1. Technical Component Planning
a. Analysis & Short List of Options
b. Technical Assessment of Options
c. Public Assessment of Options
2. Political Component Planning
3. Public Sector Ratification
174
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7.5.3 Accepting Produce Grown with Reclaimed
Water: Monterey, California
Surveys on reuse are frequently targeted at the end user.
As part of the Monterey Wastewater Reclamation Study
for Agriculture, individuals involved with produce
distribution were interviewed regarding the use of
reclaimedwaterfor vegetable irrigation. One hundred and
forty-four interviews were conducted with the following
persons:
Q Twenty four brokers and receivers at terminal
markets throughout the U.S. and Canada where
the bulk of study area produce is shipped.
Q Ten buyers for major cooperative wholesalers in
principal cities.
Q Nineteen buyers and merchandisers with large
chains, both at corporate and regional levels.
Q Ten buyers with medium chains.
Q Two buyers with small chains.
Q Fifteen store managers.
The primary focus was the need or desire for labeling
produce grown with reclaimed water. To balance the
survey findings and obtain accurate responses, the
interviewers were questioned about other possible
situations analogous to the sale of crops grown with
reclaimed water. This included questions on crops that
had been genetically altered to grow in salty water and
the use of hydroponics for crop production, as well as
reclaimed water irrigation. The study assumed that each
production alternative presented no health risk to the
public and would yield acceptable produce. The results
are given in the tables below.
The responses indicated the product would be accepted
and that labels would not be considered necessary.
According to federal, state, and local agency staff who
were contacted, the source of the water used for irrigation
is not subject to labeling requirements. Produce trade
members indicated labeling would only be desirable if it
added value to the product. Buyers stated that good
appearance of the product is foremost.
The study was intended to gauge the marketability of
produce irrigated with reclaimed water in the Monterey
area but noted locations where this practice has been
underway for a number of years. Many vegetables and
fruits, such as tomatoes and strawberries, are grown in
Mexico with reclaimed water and sold in the United
States. The multi-year record of this practice suggests
acceptance on the part of the distribution and consumers.
In Orange County, California, the Irvine Company has
been furrow-irrigating broccoli, celery, and sweet corn for
almost 20 years.
Source: Engineering-Science, 1987.
Trade Reactions to Carrying Produce Grown
in Reclaimed Water
Knowledgeable Not Aware
About of
Reclaimed Water Reclaimed Water
Total
Would Carry
Would Not Carry
Don't Know
TOTAL
Base = 68
28
9
7
44 (65%)
12
6
6
24 (35%)
40 (59%)
15 (22%)
13(20%)
Trade Expectations About Labeling Produce Irrigted with
Reclaimed Water
Knowledgeable Not Aware
About of
Reclaimed Water Reclaimed Water
Total
Would Not Expect
it to be Labeled 30
16
46 (68%)
Would Expect it
to be Labeled
Don't Know
TOTAL
Base = 68
9
5
44 (65%)
6 15 (22%)
2 7(10%)
24 (35%)
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7.5.4 Water Independence In Cape Coral - An
Implementation Update
The City of Cape Coral is a rapidly developing southwest
Florida community. As is the case throughout many parts
of the country, the availability of an economically
acceptable supply of potable water to meet a continually
growing demand, was, and is, a major concern to the city.
The situation facing Cape Coral was the need to support
a population of nearly 400,000, almost eight times its
1985 population. Cape Coral is unique in that growth was
predestined by the enterprising developer-the entire area
is platted, every lot is sold, every street is paved, and
street and stop signs are in place. Potable water is
supplied solely from the saline groundwater aquifer
through treatment by reverse osmosis (RO).
With water supply issues to consider, plus the need to
find an acceptable method for ultimately disposing of 42
mgd of wastewater effluent, the city developed the "Water
Independence in Cape Coral" (WICC) concept of a dual
water system. Potable water would be provided through
one piping system for potable needs only and secondary
water would be provided through a second piping system
for irrigation. The sources of secondary water would be
reclaimed water and freshwater canals throughout the
City.
Implementation of WICC did not come easy. The WICC
master plan was prepared, presented and adopted by
the city with relatively little interest from the public.
However, when attempts were made to move forward
with Phase 1 (issuance of special property assessment
notices), certain elements of the public became very vocal
and were successful in delaying the project. Though the
WICC Program is now well underway, the following
chronology provides a sense of how difficult
implementation was. From the time the city committed to
proceed, it took 6-1/2 years to start up Phase 1. This
experience should prove to be a valuable lesson to other
communities considering a reuse water system.
In summary, had the city implemented a formal public
awareness and education program regarding the benefits
of reuse in 1985, the city could have addressed citizen
concerns prior to finalizing the special assessment
program. A more timely consideration of concerns and
program benefits could have prevented the delays in
program implementation.
Chronology of WICC Implementation
November 1985
January 1988
April 1988
October 1988
November 9, 1988
November 1988 to
October 1989
November 1989
December 1989
February 1990
March 1992
September 1992
October 1994
City WICC report prepared
WICC concept is born!
WICC master plan adopted
Assessment hearing with 1,200 vocal
citizens
WICC Program stopped
Phase 1 advertised for bids
City council election
Pro-WICC/Anti-WICC campaign
Low voter turnout/Anti-WICC prevailed
Deadlocked city council
State Water Management threatens
potable allocation cut back
Supportive rate study
Supportive water resource study
Supportive citizen's review committee
Requested increase to potable water
allocation denied
WICC Referendum
60% voter turnout
WICC wins 2 to 1
Second assessment hearing
Construction started for Phase 1
Phase 1 starts up
Phase 2 start up scheduled
Phase 3 start up scheduled
Source: Curran and Kiss, 1992.
176
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7.6 REFERENCES
Baumann, D.D. and R.E. Kasperson. 1974. Public
Acceptance of Renovated Waste Water: Myth and
Reality. Water Resources Research, 10(4): 667-674.
Bruvold, W.H. 1987. Public Evaluation of Salient Water
Reuse Options. In: Proceedings of Water Reuse
Symposium IV, Denver, Colorado, August 2-7, 1987,
Published by the AWWA Research Foundation, Denver,
Colorado.
Bruvold, W.H. 1984. Obtaining Public Support for
Innovative Reuse Projects. In: Proceedings of Water
Reuse Symposium III, San Diego, California, August
26-31, 1984, Published by the AWWA Research
Foundation, Denver, Colorado.
Bruvold, W.H. 1981. Community Evaluation of Adopted
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Bruvold, W.H., 1972. Public Attitudes Toward Reuse of
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Resources Center, Los Angeles, California.
Bruvold, W.H., and H.J. Ongerth. 1974. Public Use and
Evaluation of Reclaimed Water. Journal AWWA
(Management), May 1974. pp. 294-297.
Bruvold, W.H., and P.C. Ward. 1972. Using Reclaimed
Wastewater—Public Opinion. Journal of the Water
Pollution Control Federation, 44(9): 1690-1696.
Camp Dresser & McKee. 1990. 201 Facilities Plan
Update, Residential Reuse Master Plan, Appendix G,
Prepared for the City of Venice, Florida.
Curran, T.M. and S.K. Kiss. 1992. Water Independence
in Cape Coral: An Implementation Update. In:
Proceedings of Urban and Agricultural Water Reuse,
Water Environment Federation, Alexandria, Virginia.
Engineering-Science. 1987. Monterey Wastewater
Reclamation Study for Agriculture, Final Report.
Prepared for the Monterey Regional Water Pollution
Control Agency, Monterey, California.
Florida Department of Environmental Regulation. 1990.
1990 Reuse Inventory. Tallahassee, Florida.
Heilman, C.B. 1979. Join Forces with John Q. Public.
Waters Wastes Engineering, July 1979.
Hollnsteiner, M.R. 1976. People Power: Community
Participation in the Planning and Implementation of
Human Settlements. Philippine Studies, 24:5-36.
Johnson, B.B. 1979. Waste Water Reuse and Water
Quality Planning in New England: Attitudes and Adoption.
Water Resources Research, 15(6): 1329-1334.
Kasperson, R.E. et at. 1974. Community Adoption of
Water Reuse Systems in the United States. Office of
Water Resources Research, U.S. Department of the
Interior, Washington, D.C.
Lohman, L.C. 1987. Potable Wastewater Reuse Can
Win Public Support, In: Proceedings of Water Reuse
Symposium IV, Denver, Colorado, August 2-7, 1987,
Published by the AWWA Research Foundation, Denver,
Colorado.
Lohman, L.C. and J.G. Milliken. 1985. Informational/
Educational Approaches to Public Attitudes on Potable
Reuse Wastewater. Denver Research Institute,
University of Denver, Denver, Colorado.
Milliken, J.G. and L.C. Lohman. 1983. Analysis of
Baseline Survey: Public Attitudes About Denver Water
and Wastewater Reuse. Denver Research Institute,
University of Denver, Denver, Colorado.
Olson, B.H. et a/., 1979. Educational and Social Factors
Affecting Public Acceptance of Reclaimed Water.
Proceedings Wter Reuse Symposiu
m I. AWWARF, Denver, Colorado.
Rastatter, C.L. 1979. Municipal Wastewater
Management: Public Involvement Activities Guide.
Prepared by The Conservation Foundation for the U.S.
Environmental Protection Agency, Washington, D.C.,
January 1979.
Stern, C. and M. Reynolds. 1979. Public Participation
Regulations: A New Dimension in EPA Programs. Public
Works, October 1979.
Stone, R. 1976. Water Reclamation: Technology and
Public Acceptance. Journal of Environmental
Engineering, American Society of Civil
Engineers,102(EE3): 581-594.
U.S. Environmental Protection Agency. 1979a. Public
Participation in Programs under the Resource
Conservation and Recovery Act, the Safe Drinking Water
Act, and the Clean Water Act; Final Regulations. Federal
Register, Vol. 44, No. 34, Part V, February 16,1979, pp.
10286-10297.
177
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U.S. Environmental Protection Agency. 1979b. State
and Local Assistance, Grants for Construction of
Treatment Works. Federal Register, Vol. 44, No. 34,
Part VI, Februar^.16,1979, pp. 10300-10304.
Wright, R.R., 1991. Conditions Which Will Contribute to
the Success or Failure of a Wastewater Reuse Project.
In: Proceedings of the Water Pollution Control Federation
Annual Conference, October 7-10, 1991, Toronto,
Canada.
178
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CHAPTER 8
Water Reuse Outside the U.S.
Water reclamation and reuse are widely practiced outside
the United States both in industrialized and developing
countries. Reclamation and reuse practiced with proper
attention to public health began understandably in cities
and regions of industrialized countries, where wastewater
collection and treatment have become common practice.
Water reuse, for agricultural irrigation and nonpotable
urban uses, also holds tremendous promise for
developing countries, as well as countries in Eastern
Europe and the Newly Independent States of the former
Soviet Union.
This chapter provides an overview of water reuse in
countries outside the United States, with particular
emphasis on implementing reuse in developing countries,
where the planning, technical, and institutional issues
may differ markedly from industrialized countries.
Examples are provided of reuse projects in industrialized
and developing countries.
8.1 Water Reuse in Other Countries
Many cities in Asia, Africa and Latin America are
unsewered; where sewers are available, they often
discharge untreated wastewater to the nearest drainage
channel or water course. Collecting the wastewaters for
treatment is a formidable and expensive task. But reuse
cannot begin until sewers, interceptors, trunk sewers and
treatment plants are built.
In the countries of Eastern Europe and the Newly
Independent States, the urban areas are generally
sewered, but the wastewater treatment plants are often
not providing sufficient treatment for reuse. As these
countries rehabilitate their urban infrastructure, there will
be significant opportunities to upgrade wastewater
treatment plants to reclaim wastewater for urban reuse.
Although one of the two driving forces for reclamation,
more economical pollution abatement, has only recently
been put on the agenda of many of these countries, the
need for additional water resources in urban areas may
make water reclamation for nonpotable reuse less costly
and more feasible than developing new sources of fresh
water.
Urban growth impacts in developing countries are
extremely pressing. Whereas only one of a total of three
"giant" cities (with more than 10 million population) was in
a developing country in 1950, it is projected that 18 of a
total of 22 such cities will be in developing countries by
the year 2000. By 2020, more than half the total
population of Asia, Africa, and Latin America will be living
in cities (Figure 34). All these cities will be needing
additional water supplies, and one likely source will be
reclaimed water.
Another driving force for properly planned water
reclamation does exist in developing countries: public
health protection. Because alternative low-cost sources
of water are generally not available for irrigation of high
value market crops near these cities, the common
practice is to use raw wastewater directly or to withdraw
from nearby streams that may be polluted with raw
wastewater. The consequent contamination of foodstuffs
to be eaten raw maintains a high level of enteric disease
in the area and has serious impacts on visitors to the
cities. Thus, the protection of the public health, as well as
the provision of additional water supply, is an incentive to
the initiation of agricultural reuse projects near the cities
of developing countries. Accordingly, national and local
public health agencies in developing countries may need
to involve themselves more in reclamation projects than
is the case in the U.S.
Almost all water reuse in developing countries is for
agricultural purposes. Most often, however, the
wastewater is applied untreated. Farmers who need
water for market crops will use even heavily polluted
water if it is available. The ubiquity of agricultural reuse
was evidenced at a 1991 conference on Wastewater
Reclamation and Reuse sponsored by the International
179
-------
Association on Water Pollution Research and Control
(IAWPRC, 1991) in Spain. Of some 35 papers, most were
devoted to agricultural reuse and only a few to urban
reuse.
FIguro 34. Changes In Urban and Rural Populations
In Latin America, Africa, and Asia
Latin America
10 2020
800
700
Africa
10 2020
Asia
2500-
2000-
1500-
1000-
500-
0
1 \
J
19*0 1
rs
s
\
s
s
\
\
\
\
s,
580
-<;
S
S
S
s
s
s
\
s
\
^
990
\
\
S
\
s
\
s
s
\
\
^
00
s
\
V
s
s
s
\
s
\
\
\
\
i»
010
rf-sl
s
\
\
\
\
s
\
s
\
s
V-
02<
Source: United Nations, 1989.
The literature on agricultural reuse in developing
countries is abundant, and guidelines and standards have
been promulgated (International Reference Center for
Waste Disposal, 1985; Shuval et al., 1986: Mara and
Cairncross, 1989; World Health Organization, 1989).
These guidelines and standards advocate an appropriate
level of treatment for the intended practices; however,
they are not always followed. Any improvement over the
use of untreated wastewater discharges, whether directly
or via a river, represents a significant health improvement.
Although agricultural reuse is far more widely practiced in
the developing world, there is also strong promise for
reuse to meet nonpotable water demands in the rapidly
growing urban areas of Asia, Africa, Latin America,
Eastern Europe, and the Newly Independent States.
Nonpotable urban reuse offers opportunities for sound
water resources management, and has begun to be
adopted in the industrial world; the U.S. and Japan are
good examples. Similar opportunities exist in the urban
areas of the developing world (Okun, 1990). Several
advantages are realized by urban reuse that do not
accrue to agricultural reuse:
Q Much urban reuse, such as toilet flushing, vehicle
washing, stack gas cleaning, and industrial
processing are nonconsumptive, and the water
can be reclaimed again for subsequent
consumptive use in agriculture or evaporative
cooling.
Q The urban marketsfor reuse are generally closer
to the points of origin of the reclaimed water than
agricultural markets.
Q The value of water in urban use is generally far
greater than its value in agricultural irrigation. It
can be metered and appropriate charges levied
so that cost recovery is far more feasible in urban
reuse than when the reclamation is solely for
agricultural use. It must be remembered,
however, that costs of providing potable quality
water for domestic urban use are higher than
providing water for irrigation use.
Agricultural irrigation will continue to dominate reuse
practice in developing countries for many years into the
future. However, reclamation projects are not likely to be
built to serve agriculture; the primary objective of such
wastewater treatment plants as are built will be to achieve
pollution control in urban areas, particularly those that
serve tourism. Nevertheless, reuse for agricultural
purposes is important and the subject is covered
extensively in Section 3.4.
8.1.1 Planning Water Reclamation Projects
Planning water reclamation and reuse projects in cities in
developing countries is different from planning in the
180
-------
United States. Cities in the U.S. are generally already
fully sewered and almost all have wastewater treatment
facilities, so that the funds required are limited to providing
some additional treatment, storage, and distribution of
the reclaimed water. For sewered areas in cities in the
developing world, interceptors and treatment facilities,
as well as the distribution system for the reclaimed water,
would need to be built virtually in their entirety. The
magnitude of up-front capital costs requires that the
planning provide for implementation in stages, but with
each stage contributing a benefit while fitting in with the
ultimate plan.
One advantage that does accrue to reclamation in cities
in developing countries is that planning can consider
reuse from the outset. For example, reclamation facilities
might be located near markets for the reclaimed water
rather than at points of disposal, which is the common
approach where reuse is not contemplated. Also, in cities
where additions to the sewerage system are required,
the simultaneous construction of pipe lines for reclaimed
water will reduce the total cost. Retrofitting reclamation
facilities in industrialized cities with fully developed
sewerage and treatment facilities is far more costly than
where the reclamation facilities can be installed with other
new infrastructure.
Other major differences between planning for cities in
developing and industrialized countries result from
differences in their costs for labor and equipment. (Okun,
1982) The principles on which water reclamation facility
design and operation are based are the same wherever
they are installed. The difference between
implementation of projects in industrialized and
developing countries results from the fact that the former
are capital-intensive while the latter are labor-intensive,
although there is a threshold level in water reuse and
wastewater technology that requires a certain level of
capital input. In developing countries, factor costs of
relatively inexpensive labor and higher capital costs
dictate that a facility that can be built and operated with
local labor will be more cost effective than a facility
utilizing more modern capital-intensive technology.
Many instances arise, however, where mechanization
and automation are appropriate in the developing world.
This would be when the task to be performed cannot be
readily performed by labor, no matter how low cost that
labor may be. For example, the pumping of water in large
quantities is a mechanical process not easily replaced by
labor.
As an illustrative example, considerthe difference in labor
costs of operating a wastewater treatment facility in an
industrialized country and a developing country. While
this example is not based on actual salaries, it does serve
to illustrate an important difference between capital-
intensive and labor-intensive economies. Assume that
the annual cost of labor for operating a wastewaterfacility
in the United States or another industrialized country is
about $600,000 for an around-the-clock attendant. (This
is based on an assumed total cost of $20,000/yr for each
of the four persons required to provide an attendant
continuously, including all fringe benefits, 15-year
equipment life, and 10 percent interest.) Under these
assumptions, an automated device that replaces this
labor and has a total investment cost less than $600,000
would result in savings. On the other hand, the lower
labor costs in a developing country would probably not
warrant an investment of more than about $20,000 to
supplant an around-the-clock attendant. (This is based
on an assumed total cost of $1,000/yr/person,10-year
equipment life, and 20 percent interest.) The 30-fold
disparity is exacerbated by the higher costs of equipment
to developing countries because of transport and
customs duty. Equipment for mechanization and
automation that can replace labor must generally be
manufactured in the industrialized world, so that spare
parts and maintenance skills must be imported from the
industrialized world and are available only at high cost
and with long delay.
The difference in availability of qualified engineers,
scientists and technicians calls for a different approach to
planning. Not only are sufficient numbers of qualified staff
available to utilities in the larger cities in the U.S., if they
have problems they need only contact their consulting
engineers, the manufacturers of their equipment, a
nearby university, or their state agency. In a developing
country, these supporting resources are less available.
Accordingly, investments in reliability and simplicity, even
at higher initial cost, may be warranted in developing
countries.
The different situations can be illustrated by an example
in the planning and design of transmission mains. A
selection between a gravity transmission main or an
intercepting sewer and lines which require pumping
would be determined in the U.S. by the lowest annual
cost, considering both capital cost and operation and
maintenance. In the U.S., pumping with force mains
would often be lower cost than gravity lines. Such an
analysis of the same project in a developing country might
show that gravity lines, despite the greater construction
involved, might be lower cost because such labor-
intensive construction is less costly in a developing
country and the costs of pumps and power are greater.
However, even if the gravity system were to cost out
somewhat more in a developing country, it might be the
wiser choice because the maintenance costs and the
181
-------
likelihood of failure are so much less. Powerf orthe pumps
Is often unreliable, preventive maintenance of the pumps
may be inadequate, and replacement parts forthe pumps
are difficult to obtain. If pumping cannot be avoided,
constant-speed pumps are preferable to the more
complex variable-speed pumps used in the U.S., even if
the latter might save operating personnel. Design for
projects in developing countries requires considerably
greater planning than for similar projects in the
industrialized world due to manpower and financial
constraints.
Another difference affecting planning is in the institutional
resources for reclamation and reuse, particularly with
regard to sewerage, because relatively small investments
have been committed to wastewater collection and
treatment in developing countries. Virtually all cities in the
Industrialized world are provided with water-carried
wastewater facilities. As shown in Table 32, as of 1990
only about 70 percent of the urban population in
developing countries is provided with some type of
sanitation facilities and those facilities that exist are often
fragmentary, with few cities in Asia, Africa and Latin
America having operable wastewater treatment plants.
As noted in the examples in Section 8.2, reuse projects in
the cities of developing countries are often not
satisfactory; most constitute serious health hazards.
8.1.2 Technical Issues
This section provides an overview of some of the
technical issues for water reuse in developing countries
that may differ from those presented in Chapter 2 forthe
U.S. Many of the issues flow from the different technical
solutions that are appropriate in a labor-intensive
economy as compared with the capital-intensive
economy of the U.S. Other differences occur from
differences in financial resources, equipment and
material resources, and human resources, and most
particularly the differences in existing wastewater
collection, treatment, and disposal facilities and the
difference in the health status of the populations involved.
The principles are essentially the same; the practices can
be expected to be different.
8.1.2.1 Sources of Reclaimed Water
Whereas the principal sources of reclaimed water in the
U.S. are the effluents from municipal wastewater
treatment plants, in the developing countries the sources
are frequently the raw wastewaters collected from
existing sewerage systems. Other sources of reclaimed
water, particularly appropriate in developing countries,
are the polluted streams that flow through or near cities,
essentially being used as natural interceptors, which
provide water for irrigation of market crops. Treatment of
the water would have substantial health benefits. As the
cities grow and displace the agricultural areas, the
treatment can be upgraded to serve other urban uses.
Probably fewerthan half of the 1.3 billion urban population
in the developing countries have conventional sewerage,
and a very small percent of these have any functioning
treatment. In many cities, the sewerage systems are
limited in extent, involving many separate points of
discharge to local drainage channels and streams in or
near the city. The first requirement, which would involve
a substantial portion of the investment, is for the
construction of trunk and intercepting sewers to carry
water to sites for treatment.
Table 32. Extent of Water and Sanitation Services in Urban Areas of Developing Countries
Service
Provision
Source: Okun, 1991.
Number of Number of
people in Percentage people in
1980 of urban 1990
Change in Percentage
Percentage of number from change from
urban 1980 to 1990 1980 to
population (mil) 1990
Water supply Served
Sanitation
Total Urban
Unserved
Served
Unserved
Population
720
213
641
292
933
77
23
69
,31
1,088
244
955
377
82
18
72
28
1,332
+368
+ 31
+314
+ 85
+399
+51
+15
+49
+29
182
-------
While the planning and design of sewerage systems is
beyond the scope of these Guidelines, it is an important
consideration for water reclamation and reuse in
developing countries where the installation of sewers will
often be a major part of reclamation projects. Although
the cost of sewers provided for the purpose of sanitation
in urban areas cannot be charged entirely to water
reclamation, some attention needs to be given to what
will undoubtedly be a significant element of many
reclamation projects in cities in developing countries.
Sewerage is costly, particularly where cities have been
permitted to grow over decades, with many high-rise
residential, public, and commercial buildings provided
with water supply but without sewers, and where sewers
have to be retrofitted. "Low cost" sanitation alternatives
involving onsite disposal are generally not feasible in
urban areas, particularly where high-rise buildings are to
be served. Several approaches to reducing the cost of
sewers in developing countries are appropriate. These
involve modifying the design and construction standards
that govern conventional U.S. practice. For example:
Q Reducing the minimum slopes specified in U.S.
standards. This could sharply reduce
construction and pumping costs at the price of
more frequent maintenance. With the low cost of
labor in developing countries, the greater
maintenance costs would be offset by the
savings in construction.
Q Increasing the distance between manholes.
Again, the more costly maintenance would be
acceptable.
Q Using indigenous materials which may be labor-
intensive as compared with sewerage practice in
the U.S., which is designed to minimize costs of
construction.
Q Using computer-aided design to obtain least-
cost sewerage system layouts.
Such modifications require strong institutions that can
provide the personnel required for preventive
maintenance and other labor-intensive programs of
construction and operation.
One situation that does not permit a low cost approach to
water reclamation is in the provision of sewers in coastal
areas where they may be impacted by saltwater
infiltration. If the sewers cannot be kept above the water
table, sewers with tight joints properly laid to avoid
subsidence are essential to prevent chloride
contamination.
The best prospects for reclamation and reuse are in the
newly developing areas of the larger, richer, rapidly
growing cities of the developing world where water
supplies are short, where some sewerage already exists,
and where pressures to control pollution are being
exerted. One example is Sao Paulo, Brazil (Section
8.2.2), the third largest metropolis in the world, where the
high quality effluent produced by the first module of an
activated sludge treatment plant inspired thoughts of
reuse for industry and for new developments being
constructed as the city expands (Okun and Crook, 1989).
8.1.2.2 Water Quality
Few developing countries have established water quality
criteria or standards for water reuse. Guidance in
establishing regulations is provided by the World Health
Organization (WHO). In 1971, WHO sponsored a
meeting of experts on reuse, culminating in a report
recommending health criteria and treatment processes
for various reuse applications (WHO, 1973). The
applications ranged from irrigation of crops not intended
for human consumption, for which the criteria were
freedom from gross solids and significant removal of
parasite eggs, all the way to potable reuse for which
secondary treatment followed by filtration, nitrification,
denitrification, chemical clarification, carbon absorption,
ion exchange or membranes, and disinfection were
recommended.
For nonpotable urban reuse and contact recreation,
secondary treatment followed by sand filtration and
disinfection were recommended. However, the health
criteria differed in that for the urban reuse only a general
requirement for effective bacterial removal and some
removal of viruses was specified, while for contact
recreation a bacterial standard of no more than 100
coliform/100 mL in 80 percent of samples and the
absence of skin-irritating chemicals were specified.
In 1985, a meeting of scientists and epidemiologists was
held in Engelberg, Switzerland, to discuss the health risks
associated with the use of reclaimed waterf or agricultural
irrigation. (This meeting did not consider other nonpotable
uses.) The meeting was sponsored by WHO, the World
Bank, United Nations Development Programme, United
Nations Environment Programme, and the International
Reference Centre for Wastes Disposal. Health-related
and other research made available since publication of
the 1973 WHO guidelines were reviewed, and a revised
approach to the nature of health risks associated with
agriculture and aquaculture was developed. A model was
developed of the relative health risks from the use of
untreated excreta and wastewater in agriculture or
aquaculture. It also concluded that the health risks of
irrigation with well treated wastewater were minimal and
183
-------
that the California bacterial standards were unjustifiably
restrictive (International Reference Center for Waste
Disposal, 1985).
The Engelberg Report developed tentative microbial
quality guidelines for reclaimed water used for irrigation.
It was recommended that the number of intestinal
nematodes should not exceed one viable egg/L for all
irrigation and that for the irrigation of edible crops, sports
fields, and public parks, the number of fecal coliform
organisms should not exceed 1,000/100 mL. The
participants recognized, in addition, that social and
behavioral patterns are of fundamental importance in the
design and implementation of reuse projects.
A WHO Scientific Group on Health Aspects of Use of
Treated Wastewaterfor Agriculture and Aquaculture met
in Geneva in 1987, and their report has been published
by WHO as "Health Guidelines forthe Use of Wastewater
in Agriculture and Aquaculture" (WHO, 1989). These
WHO guidelines reaffirm the recommendations of the
Engelberg Report. The recommended microbiological
quality guidelines for reclaimed water used mainly for
agricultural irrigation are summarized in Table 33.
The guidelines are based on the conclusion that the main
health risks associated with reuse in developing countries
are associated with helminthic diseases and, therefore, a
high degree of helminth removal is necessary forthe safe
use of wastewater in agriculture and aquaculture. The
intestinal nematodes covered serve as indicator
organisms for all of the large settleable pathogens. The
guidelines indicate that other pathogens of interest
apparently become non-viable in long-retention pond
systems, implying that all helminth eggs and protozoan
cysts will be removed to the same extent. The helminth
egg guidelines are intended to provide a design standard,
not a standard requiring routine testing of the effluent.
The Scientific Group concluded that no bacterial guideline
is necessary in cases where the only exposed
populations are farm workers, due to a lack of evidence
indicating a health risk to workers from bacteria. The
recommended bacterial guideline of a geometric mean
fecal coliform level of 1,000/100 mL was based on the
most recent epidemiological evidence and is considered
to be technically feasible in developing countries. The
Scientific Group indicated that the potential health risks
associated with the use of reclaimed water for lawn and
park irrigation may present greater potential health risks
than those associated with the irrigation of vegetables
eaten raw and, hence, recommended a fecal coliform
limit of 200/100 mL for such urban irrigation.
A number of infections caused by excreted pathogens
are of concern in connection with aquaculture using
wastewater. A review of the literature (Strauss, 1985)
concluded that:
Q Invasion of fish muscle by bacteria is very likely
when fish are grown in ponds containing
concentrations of fecal conforms and salmonella
greater than 104 and 105/100 mL, respectively.
The potential for muscle invasion increases with
the duration of exposure of the fish to the
contaminated water.
Q Some evidence suggests there is little
accumulation of enteric organisms and
pathogens on, or penetration into, edible fish
tissue when the fecal coliform concentration in
the pond water is below 1,000 /100 mL (Buras et
a/., 1985).
Q Even at lower contamination levels, high
pathogen concentrations may be present in the
digestive tract and the intraperitoneal fluid of the
fish.
The guidelines recognize that there are limited health
effects data for reclaimed water used for aquaculture and
do not recommend definitive bacteriological quality
standards for this use. However, a tentative bacterial
guideline of a geometric mean number of fecal coliforms
of 1,000/100 mL is recommended in the guidelines, which
is intended to insure that invasion of fish muscle is
prevented. The same fecal coliform standard is
recommended for pond water in which aquatic vegetables
(macrophytes) are grown. Since pathogens may be
accumulated in the digestive tract and intraperitoneal fluid
of fish and pose a risk through cross-contamination of
fish flesh or other edible parts, and subsequently to
consumers if standards of hygiene in fish preparation are
inadequate, a further recommended public health
measure is to ensure that high standards of hygiene are
maintained during fish handling and gutting. A total
absence of viable trematode eggs, which is readily
achieved by stabilization pond treatment, is
recommended as the appropriate helminth quality
guideline for aquacultural use of reclaimed water. A
comprehensive review of the use of human wastes, as
excreta or in wastewater, in aquaculture describes
current practices and health hazards, concluding that the
economic benefits can defray some of the costs of
sanitation while assisting in fish production (Edwards,
1992).
The 1989 WHO guidelines identify waste stabilization
ponds as the method of choice in meeting these
184
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Table 33. Recommended Microbiological Guidelines for Wastewater Use in Agriculture (a)
Reuse Exposed
Category Conditions Group
A Irrigation of Workers,
crops likely consumers,
to be eaten public
uncooked,
sports fields,
public parks (d)
B Irrigation of Workers
cereal crops,
industrial crops,
fodder crops,
pasture and
trees (e)
C Localized None
irrigation of
crops in
Category B if
exposure of
workers and the
public does not
occur
Intestinal
nematodes (b),
(arithmetic
mean no. of
eggs per
litre) (c)
£1
s1
Not
applicable
Faecal
coliforms
(geometric
mean no. per
100 ml) (c)
i1,000(d)
No standards
recommended
Not
applicable
Wastewater
treatment expected
to achieve the
required
microbiological
quality
A series of
stabilization ponds
designed to achieve
the microbiological
quality indicated, or
equivalent treatment
Retention in
stabilization ponds
for 8-10 days or
equivalent helminth
and faecal coliform
removal
Pretreatment as
required by the
irrigation
technology, but not
less than primary
sedimentation
(a) In specific cases, local epidemiological, sociocultural, and environmental factors should be taken into account and the guidelines
modified accordingly.
(b) Ascar/s and Trichuris species and hookworms.
(c) During the irrigation period.
(d) A more stringent guideline (^200 fecal coliforms/100 mL) is appropriate for public lawns such as hotel lawns, with which the public may
come into direct contact.
(e) In the case of fruit trees, irrigation should cease 2 weeks before fruit is picked, and no fruit should be picked off the ground Sprinkler
irrigation should not be used. or
Source: WHO, 1989.
guidelines in warm climates where land is available at
reasonable cost. Based on helminth removal, the
guidelines call for pond retention time of 8 to 10 days, with
at least twice that time required in hot climates to reduce
bacterial levels to the guideline level of 1,000 FC/100 mL.
Comprehensive manuals and publications are available
addressing the planning, design, operation, and
maintenance of stabilization ponds (EPA, 1983; World
Bank, 1983; WHO, 1983). It was recognized that tertiary
treatment of conventional biological secondary-treatment
effluent may also be used to meet the recommended
microbial guidelines. The expected removal efficiencies
of major microbial pathogens in various wastewater
treatment processes are shown in Table 34, although the
most widely used tertiary treatment for nonpotable reuse
in the U.S., filtration, is not mentioned.
The WHO guidelines, which apply mainly to agricultural
and aquacultural applications and for unrestricted
irrigation, are considerably less stringent than U.S.
standards. Many of the standards for reuse in the U.S.,
which are designed mainly for application in urban
settings, are more rigorous. As practiced in the U.S. and
Japan, reuse includes residential and landscape
irrigation, roadway and parkland landscaping, air
conditioning, toilet flushing, construction, vehicle
washing, fire protection, industrial processing and
cooling, and myriad other nonpotable uses. It involves
the exposure of large populations and hence should have
appropriate standards to protect public health.
In instances where urban dual systems are used, and
these are growing, the reclaimed water system serves
many functions. If one of these should be agricultural
irrigation near the city and the reclaimed water system is
designed to serve the urban uses, the water used for
irrigation would necessarily meet the water quality
requirements for urban uses.
185
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Table 34. Expected Removal of Excreted Microorganisms
In Various Wastewater Systems
Treatment Process (a)
Removal (log 10 units) (i)
Bacteria Helminths Viruses Cysts
Primary sedimentation
Plain 0-1
Chemically assisted(b) 1-2
Activated sludge(c) 0-2
Bk>filtration(d) 0-2
Aerated lagoon (d) 1-2
Oxidation ditch (c) 1-2
Dislnfection(e) 2-6(h)
Waste stabilization ponds (f) 1-6(h)
Effluent storage reservoirs(g)1-6(h)
0-2
1-3(h)
0-2
0-2
1-3(h)
0-2
0-1
1-3(h)
1-3{h)
0-1
0-1
0-1
0-1
1-2
1-2
0-4
1-4
1-4
0-1
0-1
0-1
0-1
0-1
0-1
0-3
1-4
1-4
(a) Conventional filtration is not included among the processes in
the original table.
(b) Further research is needed to confirm performance.
(c) Including secondary sedimentation.
(d) Including settling pond.
(e) Chlorination or ozonation.
(f) Performance depends on number of ponds in series and other
environmental factors.
(g) Performance depends on retention time, which varies with
demand.
(h) With good design and proper operation, the recommended
guidelines are achievable.
(i) A log 10 removal represents a 90 percent reduction; 2 log 10
units represents 99 percent removal, etc.
Source: Adapted from Mara and Cairncross, 1989.
In instances where space for wastewater treatment is
limited, and this too is increasing in developing countries,
especially in and near the larger cities that are likely to
have the sewerage necessary for water reclamation, the
use of ponds is generally not feasible economically or
aesthetically. With conventional wastewater treatment,
chlorine disinfection is required for irrigation of market
crops. The use of filtration following conventional
secondary (biological) treatment sharply reduces the cost
of Chlorination and increases its effectiveness. This
treatment results in a higher quality water than required
by WHO guidelines.
In many developing countries in warm climates, major
sources of income are tourism and export of fruits and
vegetables that are out of season in other countries. In
such instances, the perception of appropriate standards
may well change, as the objective is the same as with any
product in the importing country ratherthan the country of
origin. For tourists from Europe and for consumers in
Europe, the target for water quality must be Europe.
Shelef (1991) has proposed standards for Israelthat meet
these objectives (Table 35). Cyprus is a developing
country that is facing just such issues and their approach
is described in Section 8.2.4.
Integral to quality guidelines and standards is the
necessity for reliability of operations, including the
establishment of a protocol for monitoring quality.
Because reclaimed water is a product, and not just an
effluent, the provision of promised quantity and quality
must be assured. For agricultural applications, brief
intervals of nondelivery may be tolerable; for urban
applications, a continuous supply is mandatory. With
regard to quality, deviations may be permissible for
wastewater discharges to a river where only the long-
term effect is important; for reclaimed water, particularly
in urban reuse, deviations above the standard are no
more acceptable than they are for drinking water.
Accordingly, monitoring is important. Although not always
feasible in developing countries, on-line, real-time
monitoring is preferable to sampling and laboratory
analysis where the results arrive too late to take corrective
action. A simple and useful measure of reclaimed water
quality is turbidity. Experience can relate turbidity to other
parameters of interest but, more importantly, a sudden
increase in turbidity beyond the operating standard
provides a warning that corrective action is required. For
example, practice in the U.S. often requires that, should
the turbidity exceed 2 NTU for more than 10 minutes, the
reclaimed water be diverted to storage to be retreated.
More information on monitoring is available in Section
2.4.
It is fair to say that the WHO guidelines continue to be
controversial. Forthe many instances where raw sewage
or rivers heavily polluted with raw sewage are used for
irrigation, any treatment would be an improvement. If
ponds are feasible and WHO guidelines can be attained,
that would be a major public health advance. If ponds are
not feasible, the standards maybe approached in stages,
but certainly should not be perceived as a constraint to
any improvements that are affordable. The approach
might well be to begin with a first stage of primary
treatment, a very major first step in cities that now provide
no treatment because it necessarily includes interceptors
and trunk sewers, and proceed to secondary treatment
and finally filtration as resources and public health
conditions dictate.
Those responsible for public health decisions need to
consider the health status of their communities. The
higher the level of infectious disease in a community, the
more prudent health authorities need to be. The
unfortunate circumstance is that such communities are
the least likely to be able to afford the investments
required and the reuse of wastewater may be ill-advised
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Table 35. Quality Criteria of Treated Wastewater Effluent to be Reused for Agricultural Irrigation in Israel
Group of Crops
Principal Crops
A
Cotton, sugar
beet, cereals,
dry fodder
seeds, forest
irrigation
B
Green fodder,
olives, peanuts,
citrus, bananas,
almonds, nuts,
etc. . .
C
Deciduous fruits (a),
conserved
vegetables, cooked
and peeled
vegetables, green-
belts, football
fields, and golf
courses
D
Unrestricted
crops, including
vegetables
eaten uncooked
(raw),~parks,
and lawns
Effluent Quality
BODs, total, mg/L
BOD5, dissolved, mg/L
Suspended solids, mg/L
Dissolved oxygen, mg/L
Conforms counts/100 mL
Residual avail, chlorine,
mg/L
Mandatory Treatment
Sand filtration or equiv.
Chlorination, minimum
contact time, minutes
Distances
From residential areas,
m
From paved road, m
(requirements should be met in at least 80 percent of samples taken)
60(b)
—
50(b)
0.5
45(b)
40(b)
0.5
35
20
30
0.5
250
0.15
60
15
10
15
0.5
12(80%)
2.2 (50%)
0.5
required
120
300
30
250
25
, must st°P 2 weeks before fru't Picking; no fruit should be picked from the ground
(b) Different standards will be set for stabilization ponds with retention time of at least 15 days.
Source: Shelef, 1991.
because of the increased risk to public health from the
greater exposure that would result.
8.1.2.3 Treatment Requirements
In developing countries, the choice between modes of
treatment, either conventional treatment comprising
primary sedimentation, biological secondary treatment
(activated sludge, trickling filtration, rotating biological
contactors or something similar), sand filtration, and
disinfection, or the use of stabilization ponds depends
upon the local circumstances. Where smaller
communities have or can expect to have sewerage,
ponds may be most appropriate if land is available nearby
at reasonable cost. The effluent produced will be suitable
for agricultural irrigation, and the WHO guidelines may
be acceptable, even for market crops, with recognition
that the fruit and vegetable products may need to be
disinfected before use. Filtration and chemical
disinfection of pond effluents are not likely to be feasible
operationally and because of high cost.
However, in the larger cities with existing sewerage, the
most likely situations where reclamation and reuse are
promising, conventional treatment is likely to be the
treatment of choice because of limited availability of
appropriate land, its high cost, the considerable distance
of transmission to reach the treatment site, and public
acceptability particularly as the city expands to the vicinity
of the sites. As a guide to selection, Table 36 indicates
the land requirements for conventional and pond
treatment for towns and cities of various sizes.
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Table 36. Typical Land Area Required for Pond Treatment Svstems and
Secondary Treatment Plants
Secondary WWTF
Population
Served
5.000
10,000
50.000
100.000
250,000
1,000.000
Wastewater Flows (a)
(mgd) (Us)
0.06
0.13
0.65
1.3
3.25
526.0
2.6
5.7
28.5
57.0
142.4
50,000
Pond Area Required (b)
(ac) (ha)
2
4
20
40
100
400
0.8
1.6
8
16
40
160
Land Requirements(c)
(ac) (ha)
0.1
0.3
1-4
3.0
7.0
30.0
0.04
0.12
0.56
1.2
2.8
12.0
(a) Assumes wastewater flows of approximately 13 gcd (50 L/capita/d) (Shuval et al.. 1986).
0>) Area required to meet effluent standard of 1,000 FC/100 mL,
Temperature = 25°C; includes anaerobic pond (World Bank, 1983).
(<0 Excluding ancillary facilities.
The design of facilities for developing countries is similar
to practice in the U.S., presented in Chapter 2, except for
recognition of the need to minimize equipment and
instrumentation requirements. With regard to the
wastewater elements of treatment, including the handling
of sludge, WHO has published Community Wastewater
Collection and Disposal (Okun and Ponghis, 1975) and
with regard to tertiary treatment, filtration, the Water and
Sanitation for Health (WASH) project has published
Surface Water Treatment for Communities in Developing
Countries (Schulz and Okun, 1984), which covers
filtration practices that are applicable to reclamation.
Examples of simple technology that serve with much the
same effectiveness as conventional U .S. practice are the
use of steep hopper bottoms for primary sedimentation
(in the fashion of Imhoff tank sedimentation
compartments) rather than sludge collection
mechanisms, hydraulic in place of mechanical mixing,
pipe and manifold filter bottoms rather than proprietary
underdrains, hypochlorite rather than chlorine
disinfection, etc.
Requirements for reliability are little different, but they
can be met in developing countries by using more
personnel and larger detention periods in treatment units,
neither of which entails the relatively high costs that they
do in the U.S. The institutional problems associated with
assuring quantity and quality reliability in cities in
developing countries are discussed in Section 8.1.3.
While agricultural reuse projects not involving market
crops are appropriate throughout Asia, Africa and Latin
America, unrestricted urban reuse projects need to be
undertaken selectively because of the potential health
consequences resulting from wide public exposure to the
reclaimed water.
8.1.3 Institutional and Legal Issues
Despite the frequent assertion that urban sanitation is as
important as water supply, the fact is that in developing
countries the sewerage service is far behind water service
both in the fraction of the population that is served and the
quality of the service. The water distribution system
requires a source of water, transmission lines, and
treatment. The sewerage system, on the other hand,
often serves only the commercial buildings and the more
wealthy households and, even then, only carries the
wastewater away from the buildings; trunk sewers or
interceptors and wastewatertreatment plants are seldom
available.
8.1.3.1 Managing Reclaimed Water
While reasonably strong institutions for managing water
supply systems exist in developing countries, agencies
for managing wastewater collection, treatment, and
disposal are poorly organized and lacking in funds.
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Furthermore, the water supply agencies, which have a
potential for recovering some of their costs through user
fees for water service, hesitate to join with those
responsible for sewerage who depend almost entirely
upon the very limited financial resources of local
government.
Leadership in the initiation of studies of water reclamation
and reuse in the U.S. may be undertaken by the water
supply agency if increased water resources are the
driving force or the sewerage agency if pollution
abatement is the primary objective, or by both together,
particularly if they exist in a single agency. In developing
countries, where the purpose of reclamation is to provide
additional water, the leadership most often will fall upon
the water supply agency or a large water user, such as
the Ministry of Agriculture.
The, need for water reclamation may, in fact, be a factor
in institution-building in the water sector. When large
investments are to be made in urban sewerage, it is often
recommended that the water agency undertake
sewerage and wastewater treatment responsibilities
ratherthan creating orstrengthening a sewerage agency.
This approach has the advantages of bringing an
operating organization with experienced officials to the
enterprise, of profiting from economies and efficiencies
of scale, and of providing an accepted mechanism for
cost recovery. The advantages of such joint enterprise
are enhanced where water reclamation and reuse are
being considered.
Sao Paulo, Brazil, offers a good example (Section 8.2.2)
of how a joint water and sewerage agency, SABESP,
with responsibilities for seeking additional sources of
water and for reducing pollution of nearby waters, was
able to initiate a program of water reclamation and reuse
with no interagency or bureaucratic conflicts (Okun and
Crook, 1989). Just the opposite situation exists in Beijing,
China, where the urgent need for water reuse had been
established and widely recognized but where the
existence of entirely separate municipal water and
sewerage agencies has blocked action towards even
planning for implementation (Section 8.2.10).
Sound planning and implementation of reuse projects is
possible where separate water and sewerage agencies
exist if both of these agencies are relatively strong. An
example is in the Los Angeles Metropolitan area where
six separate agencies, the water and sanitation agencies
of the City of Los Angeles, Los Angeles County, and
Orange County, joined in making a plan for water
reclamation for an area serving some 15 million people.
Joint efforts may be more difficult where one agency is
strong and the other weak.
Recognizing that initiating significant institutional
changes while undertaking a major capital program is
difficult, an examination of the existing relevant
institutions and a plan for their modification to permit them
to undertake the capital program should be the first order
of business (Okun, 1991; UN Development Programme
1991).
8.1.3.2 Legal Issues
Water reuse in developing countries generally creates
two types of legal issues: (1) the protection and creation
of water rights and the power of government to allocate
water among competing users; and (2) the protection of
public health and environmental quality. Other legal
issues may also be relevant in specific circumstances.
a. Water Rights and Water Allocation
Untreated wastewater is often used near large cities in
developing countries for irrigating crops, particularly
vegetable crops that are sold in the city. The water may
be drawn from the raw wastewaterflow orfrom rivers and
streams that receive wastewater discharges. Diverting
existing wastewater flows to a treatment facility will, at a
minimum, change the point at which the flow is
discharged to surface waters, and may change the
amount of water available to current users. A water reuse
project may completely deprive existing users of their
current supply if reclaimed water is sold to new users
(e.g., industrial facilities) or allocated to new uses (e.g.,
municipal use).
Traditional practice and customary law in most
developing countries, and formal law in many, recognize
that a water user acquires vested rights to use a certain
quantity of waterunderdefined circumstances. Changing
the amount of waterthat is available to a current user with
vested rights may entitle the user to some type of remedy,
including monetary compensation or a supplemental
water supply. Municipalities may need express authority
to condemn private water rights. Persons planning a
water reuse project should be careful to analyze its
potential impact on current patterns of water use and to
determine what remedies, if any, are available to or
should be created for current users if the project interferes
with their water uses.
b. Public Health and Environmental Protection
The use of reclaimed water for agricultural irrigation and
various municipal uses may result in human exposure to
pathogens or chemicals, creating potential public health
problems. Water reclamation and reuse and the disposal
of sludge from wastewater treatment may also have
adverse effects on environmental quality if not managed
properly.
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Planning for water reuse projects should include the
development and implementation of regulations that will
prevent or mitigate public health and environmental
problems. Such regulations include:
Q A permit system for authorizing wastewater
discharges; technical controls on wastewater
treatment;
Q Water quality standards for reclaimed water that
are appropriate to various uses;
Q Controls that will reduce human exposure, such
as restrictions on the uses of reclaimed water;
Q Controls on access to the wastewater collection
system, and controls to prevent cross-
connections between the distribution networks
for drinking water and reclaimed water;
Q Regulations concerning sludge disposal and
facility siting; and
Q Mechanisms for enforcing all of the above
regulations, including monitoring requirements,
authority to conduct inspections, and authority to
assess penalties for violations.
c. Other Legal Issues
A number of other legal issues discussed in Chapter 5 of
this document may also arise in developing countries.
The FAO/WHO Working Group on Legal Aspects of
Water Supply and Wastewater Management (WHO,
1990) has recommended that any regime for wastewater
management include the following provisions, which have
been abbreviated for inclusion herein:
Q Define "wastewater" or "reclaimed water."
["Wastewater" is used water piped from a
community, including discharges from
residences, commercial buildings, industrial
facilities and the like, which is disposed of into
the environment; "reclaimed water" is treated
wastewater collected for reuse.]
Q Specify who has rights of ownership in reclaimed
water.
Q Establish a system for licensing the use of
reclaimed water.
Q Determine how persons with vested rights will be
protected from harm due to wastewater
diversions that reduce stream flows.
Q Establish restrictions on uses, reclaimed water
quality, and facility siting to protect public health
and the environment.
Q Identify mechanisms for enforcing such
restrictions.
Q Specify procedures for pricing reclaimed water
and allocating system costs.
Q Specify institutional arrangements for system
administration.
Q Specify the legal and institutional relationships
between the water reclamation project and
existing programs in water supply, sewerage,
and environmental protection.
8.1.4 Economic and Financial Issues
A principal difference between the U.S. and the
developing countries in addressing economic and
financial issues concerning reuse arises from the
acceptance in the U.S. that the user is responsible for
meeting the costs of water and sanitation services.
(Exceptions are in the heavy subsidies for agricultural
irrigation in the West and, until recently, for wastewater
treatment facilities for cities throughout the country.) In
the developing countries, however, water has often been
provided free or at a nominal charge. Only in recent years
have any attempts been made at cost recovery, and that
only for O&M. Costs for sewerage are still commonly
funded from the local or national exchequers, or property
taxes.
The economic justification for water reclamation and
reuse depends principally on offsetting the costs of
developing necessary additional water sources. Where
these costs are subsidized by governments or from low-
interest loans or grants from external support agencies
(ESAs), and are not passed through to users, costs of
water are under-reported and appear low. Unless the real
cost of providing water and sewerage services becomes
more transparent, consumers are unlikely to be interested
in changing existing services if they are adequate. Also,
because ESAs approach water supply and sewerage
projects separately, and the ministries of government as
well as local utilities also deal with them separately,
assessments of economic benefits are difficult to perform.
Whereas economic justification in the U.S. involves only
the local government and its agencies, in developing
countries the national agencies and ESAs need to be
involved from the start.
For water reclamation and reuse, water supply and
sewerage costs need to be considered together, which
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obliges all the agencies involved to approach water
reclamation projects in an integrated fashion, an
approach being assiduously pursued by the UN family of
agencies led by the UN Development Programme (1991)
in its Capacity Building initiative.
The economic rationale for water reuse is little different
from that set out in Chapter 6. Cost savings, based on the
additional water sources, additional water transmissions
mains, and additional treatment that would not be
required or that would be postponed, would represent
benefits and, therefore, decrease the present value of
the necessary investments. Further, in developing
countries the costs for collection and treatment of
wastewater can be construed as benefits in terms of
providing sewerage services that would be necessary
even in the absence of reclamation and reuse.
The financial strategies, specifically in terms of alternative
capital financing scenarios in the U.S. context, as
described in Chapter 6, are probably not feasible in many
developing countries. This is mainly due to the immaturity
of the capital markets in many of these countries.
Benefits other than cost need to be considered more
extensively than in the U.S. For example, a water
reclamation project in a developing country, through
substitution for potable water used needlessly, may
permit potable water service and accompanying benefits
to be extended to people who otherwise would have to
fetch water themselves for their households, purchase
water at a high price from water vendors, or use water
from contaminated sources. Given the considerable
variety of situations in urban areas of developing
countries, specific approaches cannot be generalized,
but need to be developed on a case-by-case basis.
A reclamation program can be the vehicle for introducing
a rational pricing structure, based on a rational market
mechanism for water. The price for fresh or reclaimed
water to residential, commercial, industrial, and
agricultural customers should reflect their full cost of
production plus opportunity costs. The lack of the ability
to appreciate the opportunity cost of water will undervalue
it as a resource and lead to misallocations among users.
The premium or scarcity value of fresh water implicit in
the use of reclaimed water should assure that the full
resource costs of reclaimed water are less than that of
fresh water. Market mechanisms need to reflect this
differential.
8.1.5 Implementation of Reuse In Developing
Countries
Where water is scarce in urban areas in developing
countries, reuse of untreated wastewaters directly or
indirectly, via drainage canals or streams, is widely
practiced without initiatives from or regulation by public
authorities. The health effects of such practices,
particularly when used for irrigation of market crops near
cities, are well known.
Constraints to implementation of engineered and
regulated reclamation and reuse programs in developing
countries result from inadequate sewerage systems,
most particularly the absence of sewerage, interceptors
and trunk sewers, and the absence of functioning
treatment facilities. The decades of urban construction
without a concomitant investment in wastewater
collection and treatment has left a heavy burden on
present populations not faced by people in the
industrialized countries. Accordingly, implementation of
reuse in most cities in the developing world must begin
with the provision of these basic sanitation needs, which
is beyond the scope of these guidelines.
Where adequate treatment has been provided for a
portion of a city, as is the case in Sao Paulo and Cairo, the
availability of a high quality effluent stimulates interest in
reuse, and the approach to implementation would follow
paths similar to those discussed in earlier sections.
8.2 Examples of Reuse Programs Outside
the U.S.
This section illustrates practice by means of brief
descriptions of projects in several industrialized countries
otherthan the U.S., including specialized situations such
as the oil-rich countries of the Middle East, where
practices are essentially those of the industrialized
countries. Also included are brief descriptions of practices
and standards for reuse in several developing countries
where an interest in reuse has been demonstrated. This
inventory is intended to be illustrative rather than
exhaustive.
One conclusion that can be drawn from these examples
is that reuse of urban wastewaters, generally untreated,
occurs where sewerage and wastewater treatment
facilities are not in place, often with highly undesirable
health and environmental effects. On the other hand,
where treatment facilities are constructed, and operated
to discharge a reasonably good effluent, reuse is likely to
be exploited beneficially.
For cities where stabilization ponds are the selected
method of treatment, restricted reuse may well be
economically attractive, particularly for crops that are not
to be eaten raw. Where conventional treatment is
provided, potential exists for providing tertiary treatment,
including filtration and chlorination, which permits
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unrestricted agricultural irrigation and, more importantly,
a wide range of nonpotable urban uses may become
economically attractive by permitting substitution of the
reclaimed water for limited supplies of high quality fresh
water.
The appropriateness of water reclamation and reuse
internationally depends on local circumstances and
varies considerably from country to country, and even, as
in the U.S., among cities in any one country.
8.2.1 Argentina
Effluent from the primary treatment facility of Campo
Espejo in Mendoza Province drains into an agricultural
canal and is used for unrestricted irrigation of 5,000 ac
(2,000 ha) of land. At the city of Ortega, stabilization pond
effluent of poor quality is mixed with river water and used
for unrestricted irrigation of vegetable crops. It was found
that the use of these effluents poses a relatively high
health risk. There are no crop restrictions in Argentina,
and both workers and consumers were stated to be at
risk (Strauss and Blumenthal, 1990).
8.2.2 Brazil
Sao Paulo, with a metropolitan population of about 17
million people, is the third largest city in the world. Its
rapid growth promises to raise it to the second largest,
after Mexico City, by the end of the 20th century. With the
prospect of a limited supply of water, SABESP, the water
supply and sewerage agency for the State of Sao Paulo,
initiated a study of the feasibility of reclaiming its
secondary (activated sludge) effluent for industrial
purposes.
Average water demand in Sao Paulo is about 1,000 mgd
(43,800 Us). Some 30,000 industries and large
commercial establishments account for about 25 percent
of the demand. Because only about 50 percent of the
population was served by sewers in 1990, increasing
sewerage service now enjoys a high priority.
One unit, 80 mgd (3,500 Us) of the Barueri activated
sludge treatment plant, which is to have an ultimate
capacity of 640 mgd (28,000 Us), was placed in operation
in 1988 in the rapidly growing area west of the city. Its
effluent was of such high quality that tertiary treatment
pilot plants, consisting of coagulation, filtration and
disinfection, were built to assess the potential for
reclamation forindustrial use. An initial pilot plant of about
600 gpd (2 m3/d) was so successful that a second pilot
plant of 20,000 gpd (80 m3/d) was started up in 1989. The
reclaimed waterturbidity of this pilot plant effluent ranged
from 0.3 to 0.6 NTU, with a COD of 9.8 mg/L.
Although SABESP had assumed that the greatest
potential for reuse is in industry, a nonpotable distribution
system would be required because the demand of no
single plant or grouped set of plants is large enough to
provide a market for a major transmission main. A study
sponsored by the Pan American Health Organization
(Okun and Crook, 1989) on behalf of SABESP revealed
many other potential uses in the newly developing areas
of Sao Paulo:
Q Urban irrigation: Sao Paulo experiences dry
periods from July through September and
watering of parks and gardens requires
significant amounts of water.
Q Toilet flushing: The largest residential and
commercial uses for water are for toilet flushing.
While not currently economical for single-family
houses, or for retrofitting existing high-rise
buildings, it can be economical for new high-rise
residential and commercial buildings which
constitute the major form of new construction in
Sao Paulo.
Q Cleansing: The cleansing of streets, sidewalks,
vehicles, etc. are suitable markets for reclaimed
water.
Q Urban beautification: Fountains, ponds, and
lakes are ideal uses for reclaimed water,
reducing fresh water losses from evaporation.
Q Construction: Most major construction in Sao
Paulo is reinforced concrete, which requires
significant amounts of water for cement mixes.
Q Air pollution control: Scrubbers to wash
contaminants from industrial air emissions.
Q Agricultural irrigation: Market crops grown in the
vicinity of Sao Paulo can be irrigated with high
quality reclaimed water, which might be provided
by a single transmission main. Such uses are
likely to be transient as urbanization replaces
agriculture, but in the interim it is a useful market.
The only majoruse currently not appropriate in Sao Paulo
is for cooling towers associated with power production
because electricity is generated by hydropower.
The need for a market survey in Sao Paulo is evident, as
is the need for a larger, more flexible pilot plant to
determine the next steps in implementation of the
reclamation program.
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8.2.3 Chile
All of Santiago's wastewater is used indirectly for crop
irrigation. Seventy to 80 percent of Santiago's raw
wastewater is collected into an open drainage canal,
which is then distributed for irrigation. Fecal conforms
average 106 -108/100 ml. The irrigated area immediately
outside the city provides almost all the salad vegetables
and low-growing fruits to the population of Santiago.
Circumstantial evidence suggests a connection between
the use of raw wastewater for irrigation and the higher
incidence of typhoid in Santiago than in the rest of Chile
(Strauss and Blumenthal, 1990).
8.2.4 Cyprus
An island with a population of 700,000 in the
Mediterranean and a vigorous tourism industry, Cyprus
is facing two major obstacles to its continued
development: a growing scarcity of water resources in
the semi-arid regions of the country and degradation of
water at its beaches. The government perceives that a
program of water reclamation and reuse would address
both problems. It has begun implementation of new
sewerage and wastewater treatment and reuse in two
major tourist areas, Limassol on the south coast and
Larnaca and Ayia Napa-Paralimini on the southeast
coast.
An objective of both projects is to prevent discharge of
wastewater to the sea, even after filtration and
disinfection, to curtail eutrophication of shore waters that
has already begun. Accordingly, storage is to be provided
to hold reclaimed waters for reuse during dry periods.
While interest is initially in reuse for agricultural irrigation,
studies are being inaugurated in Limassol into other uses
and the economic aspects of reuse. Water quality for
reuse is an issue in Cyprus, with the government opting
for standards similar to U.S. practices. Others have
believed these to be unnecessarily rigorous and costly
for Cyprus and that, in keeping with WHO guidelines,
stabilization ponds are all that are necessary. Also,
stabilization ponds are seen as performing better in
removing helminths than conventional secondary
treatment, although helminths have not been identified
as a problem in Cyprus.
While stabilization ponds are used in Cyprus, because of
the high cost of land in coastal areas and the need for
protection of environmental and aesthetic amenities for
tourism, conventional secondary treatment is appropriate
for specific sites.
The resolution of the quality controversy is that standards
and the treatment required are seen to be site-specific,
even in so small a country as Cyprus. Conventional
biological treatment and tertiary filtration and disinfection
are more feasible and acceptable in some situations in
Cyprus, such as tourist areas along the coast, than the
use of ponds. In other areas, and depending upon the
crops to be grown, ponds may be the proper alternative.
The Limassol area is expected to have a population of
about 150,000 in 2010. The current project area will serve
about 50,000. Later phases will serve another 50,000.
The initial phase of the project, for which the World Bank
is providing assistance, is to include laterals, main
sewers, a conventional secondary (activated sludge)
treatment plant of 5 mgd (219 L/s) capacity and a 36-in
(90-cm) sea outfall that is to discharge 2,000 ft (600 m)
from shore into waters about 40 ft (12 m) deep. The outfall
is sized to take only the initial phase effluent. Storage for
higher flows is to be provided in impoundments to permit
full use of the reclaimed water and limit sea discharges.
The initial phase of the project includes inter alia effluent
and sludge reuse and studies to identify the range of
appropriate options for other cities in Cyprus. The first
phase of the study will identify the most promising uses,
taking into account for each use the quality and quantity
of the reclaimed water to be produced, potential markets,
health hazards, costs and benefits, etc. The required
treatment and infrastructure needs will be identified and
pilot demonstration projects will be designed. The second
phase will include a review of the pricing policy for
reclaimed water.
The Southeast Coast Sewerage and Drainage Project in
Larnaca, which is to serve Larnaca and the communities
of Ayia Napa and Paralimni some 25 mi (40 km) to the
east, includes sewerage systems, treatment plants (with
a common plant serving Ayia Napa and Paralimni), and
distribution systems for the reclaimed water. Some
service areas in Larnaca are low-lying, and because of
the potential danger from saltwater infiltration care is to
be taken to protect the quality of the reclaimed water.
Financial arrangements for cost recovery are to be
integrated (as a surcharge on water consumption) forthe
sewerage and the reclaimed water services.
The benefits to be addressed by the project include
improved sanitation, simplicity, and reliability over what is
provided by onsite systems, environmental protection,
promotion of the tourist industry, and development of a
perennial reliable source of waterfor irrigation in a water-
scarce environment.
8.2.5 India
Irrigation with untreated wastewater is widely practiced in
India. Some 180,000 ac (73,000 ha) of land were irrigated
with wastewater in 1985 on at least 200 sewage farms.
193
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The law prohibits irrigation of salad vegetables with
wastewater, yet the practice is widespread and
government agencies reportedly do not actively enforce
regulations governing reuse. Furthermore, in many states
there is no microbiological standard and hence no
parameter with which to control the level of treatment.
Enteric diseases, anemia and gastrointestinal illnesses
are high among sewage farmworkers, and quite possibly
consumers of salad and vegetable crops are at risk. A
Ganges River program is to include treatment facilities
for six cities in Uttar Pradesh. These projects are to
incorporate reuse for agriculture and forestry.
8.2.6 Israel
Some 230 reclaimed water projects in Israel in 1987
produced about 70 mgd (3,000 Us) of reclaimed water
from a population of over 4 million people (Argaman,
1989). Nearly 70 percent of the wastewater was reused;
approximately 92 percent of the wastewater was
collected by municipal sewers and of this 72 percent was
reused for irrigation (42 percent) orgroundwater recharge
(30 percent). Reuse constitutes approximately 10 percent
of the water supply in Israel, but by 2010 it is projected
that reuse will account for about 20 percent, with about
one-third of the total water resource allocated to
agricultural irrigation.
Reuse up to 1982 amounted to about 25 percent of the
wastewater generated. Since that time the development
of several large projects, namely the Kishon project at
Haifa and the Dan Region Phase II project at Tel Aviv, led
to a large increase in water reuse. The majority of reuse
projects in Israel make use of surface impoundments to
store the water during the winter and have it available for
the summer irrigation season. There are more than 120
seasonal reservoirs in operation throughout Israel with
capacities ranging from 130,000 to 3,000 million gal
capacity (50,000 to 12 million m3).
The Kishon reclamation project receives an average of
about 15 mgd (657 L/s) of reclaimed water from the Haifa
sewage treatment facility. The water is pumped 50 mi (30
km) to the farms in the Yzre'el Valley, where it is used for
irrigation. The facility includes reservoirs for seasonal
storage because irrigation normally occurs over a 4-
month period. The reclaimed water is chlorinated at
different points and its quality generally meets Israeli
standards for unrestricted irrigation. (Table 35) The
irrigated area is approximately 40,000 ac (15,000 ha),
with the main crop being cotton.
The Dan Region Wastewater Reclamation Project, with
an average flow of about 50 mgd (2,200 Us) was
developed in two phases. Each phase involves
reclamation for groundwater recharge for agricultural
irrigation. Phase I, which receives wastewater from
southern Tel Aviv (receiving pond treatment and chemical
precipitation), has been in operation since 1970. Water is
applied by means of intermittent flooding to spreading
basins and percolates to the local coastal aquifer. Phase
II uses conventional activated sludge treatment with
nitrogen removal. The reclaimed water is recharged by
spreading into a sandy aquifer with a minimum of 300
days detention time. It is withdrawn by recovery wells and
conveyed by a 70-in (178-cm) diameter pipe for distances
up to 50 mi (80 km) to irrigation sites. Following
disinfection and storage, the reclaimed water meets the
Israel standards for unrestricted irrigation, including those
for vegetables to be eaten raw.
The use of reclaimed water must be approved by local,
regional, and national authorities. Effluent used for
irrigation must meet water quality standards set by the
Ministry of Health. The trend is toward unrestricted use
with wider crop rotation .which will necessitate more
storage and higher levels of treatment in the future. This
trend toward higher levels of treatment, approaching
drinking water quality, is being promoted by
environmental concerns and by farmers who export
produce to highly competitive foreign markets.
8.2.7 Japan
Because of the great density of population in Japan and
its limited water resources, programs of reclamation and
reuse were begun early. The principal target to reduce
water demand was through provision of reclaimed water
for toilet flushing in multi-family, commercial, and school
buildings. In one respect, Japan is in a situation faced by
cities in the developing world; only about 40 percent of its
total population are sewered. Buildings being retrofitted
for flush toilets and new buildings offer excellent
opportunities for reuse. Their program began by recycling
in a building or group of buildings, with a reclamation
plant treating all the wastewaters to furnish water for
toilets and other incidental nonpotable purposes. It was
soon perceived that using municipal treatment works and
a reclaimed water system as part of a dual system would
be more effective and economical than individual
reclamation facilities.
As of 1986, Japan used about 71 mgd (3,100 L/s)
distributed as shown in Table 37. At that time about 40
percent of the reclaimed water was being distributed in
dual systems. Of this, as shown in Table 38, more than
one-third was being used for toilet flushing, and about 15
percent each for urban irrigation and cleansing. A wide
variety of buildings were fitted for reclaimed water, as
shown in Table 39, with schools and office buildings being
most numerous. In Tokyo, the use of reclaimed water is
mandated in all new buildings larger in floor area than
194
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300,000 sq. ft. (30,000 rn2). Multi-family dwellings of about
200 household units (10 floors with 20 units each), which
would meet this criterion for such buildings, are not large
by current urban housing standards in many developing
countries.
Table 37; Uses of Reclaimed Water in Japan
Use
1,000 m3/d mgd
Nonpotable in dual systems
Industrial
Agricultural
Stream flow augmentation
Snow removal
40
29
15
12
A
100
110
77
40
32
11
270
29
20
11
8
_S
71
Source: Murakami, 1989.
Table 38. Uses of Reclaimed Water in Dual Systems in
Japan
Use
Percent
Toilet flushing
Cooling water
Landscape irrigation
Car washing
Washing and cleansing
Flow augmentation
Other
37
9
15
7
16
6
•|Q
100
Source: Murakami, 1989.
Table 39. Types of Buildings Using Reclaimed Water in
Japan
Buildings
Percent
Schools
18
Office Buildings 17
Public Halls g
Factories 8
Hotels 4
Others(residences, shopping centers, etc.) 44
100
Source: Murakami, 1989
Japan offers a very good model for urban cities in
developing countries because their historical usage has
been for meeting urban water needs rather than only
agricultural irrigation requirements. Their reclaimed water
quality requirements, shown in Table 40, are different
from those in the U.S., more stringent for coliform counts
for unrestricted use, while less restrictive for other
applications.
5.2.8 Kuwait
With a population estimated at about 2 million, most of
Kuwait can be considered urban. The country is arid, with
average annual rainfall less than 5 in (12.5 cm). With no
surface sources, water is drawn from groundwater at the
rate of about 0.6 mgd (26 Us), mainly for producing
bottled water. Most water needs are met by desalination.
About 85 percent of the population is on a central
sewerage system.
Kuwait provides tertiary treatment (activated sludge
treatment, filtration ,and chlorination) for reclamation for
agricultural irrigation. Their standards are shown in Table
41. Three reclamation plants have atotal capacity of more
than 80 mgd (3,500 Us), with plans to use all of it for
agricultural irrigation and some landscape irrigation.
8.2.9 Mexico
Approximately 90 percent of Mexico City's wastewater is
reused in agriculture in the Mezquital Valley (Tula) and
10 percent is reused for green belt irrigation.
Approximately 80 percent, 900 mgd (40,000 Us), of an
average of about 1,200 mgd (52,600 Us) of irrigation
water is provided by sewage and storm runoff from
Mexico City. The concentrations of fecal coliform in the
irrigation water varies between 106 -108/100 ml_. Farmers
interviewed by a visiting team of researchers complained
of enteric and other diseases (Strauss and Blumenthal,
1990). The irrigation district practices crop restriction;
however irrigation of maize, beans, chili, green tomatoes,
and alfalfa is not restricted. The distribution of the
irrigation water is managed by six irrigation districts, and
plans have been developed for the creation of 11 more
districts in other parts of Mexico. The long term National
Water Development Program envisages that irrigation
with reclaimed water will be extended to 125,000 ac
(50,000 ha), industrial reuse is projected to increase from
about 100 mgd (4,380 Us) to 300 mgd (13,150 Us).
8.2.10 People's Republic of China
Beijing and Tianjin, the principal ports in northern China,
are two of the country's largest and most important cities.
The Beijing-Tianjin region, an" extensively industrialized
area with 18 million people, sits at the bottom of the Hei
River basin, where little flow remains in the river after
water is drawn for the household, industrial, and
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Table 40. Reclaimed Water Criteria in Japan
Parameter
Toilet Rush Landscape Ornamental Environmental
Water Irrigation Lakes & Streams (aesthetic setting)
Environmental
(limited public contact)
E. Coli (count/100 mL)
-------
problems do not flounderfrom lack of technology or even
from a lack of funds but from the lack of a capacity to
effect change. One bright spot in China is a modern
wastewater treatment plant that serves about 25 percent
of Tianjin with a well operated activated sludge plant
followed by polishing ponds that produce an effluent that
is beginning to be reclaimed for urban use.
8.2.11 Peru
Reuse is widely practiced in communities along the
coastal desert strip. In Lima, about 12,000 ac (5,000 ha)
are irrigated with raw wastewater. A project is being
prepared to irrigate about 10,000 ac (4,000 ha) south of
Lima, with effluent that will receive primary pond
treatment followed by infiltration or finishing ponds, lea,
located 180 mi (300 km) south of Lima, uses effluent
treated in facultative lagoons for restricted irrigation of
1,000 ac (400 ha). At Tacna, Peru's southernmost town,
effluent treated in lagoons is used to irrigate 500 ac (200
ha) of land. Typical of the situation in many developing
countries are several cities cited by Yanez (1992) where
raw sewage is used for irrigation of market vegetables
that are eaten without processing. Furthermore, the
effluent produced by stabilization ponds throughout Peru
is of generally low quality because of design deficiencies,
operational problems, or overloading. Numerous enteric
bacterial and viral infections are reported, although the
many possible transmission routes preclude attributing a
direct link to irrigation practices (Strauss and Blumenthal,
1990).
8.2.12 Republic of South Africa
The Republic of South Africa has adopted standards
similar in character to those in the U.S. Elements of their
research establishment had long been advocates of
potable reuse, although the practice has never been
adopted by the utilities in the country. They do require
tertiary treatment with no fecal coliform permitted for
unrestricted nonpotable uses such as for irrigation of
sports fields, pasture for milking animals, toilet flushing
and dust control, with reclaimed water meeting the
contaminant levels called for in their drinking water
standards for food crops eaten raw, residential lawns,
children's play parks, and human washing. Their
requirements are listed in Table 42.
8.2.13 Saudi Arabia
Saudi Arabia is committed to a policy of complete reuse.
In 1978, the amount of reclaimed water used was
estimated at 25 mgd (1,100 Us), and the projection for
the year 2000 is about 500 mgd (22,000 Us). By 2000 the
Kingdom expects to meet almost 10 percent of its water
demand through reuse. Regulations require secondary
treatment with tertiary treatment for unrestricted irrigation,
with standards shown in Table 43 (Kalthem and Jamaan,
1985).
Table 42. Reclaimed Water Guidelines in South Africa
Reuse Application
Level of
Treatment
Maxiumum
Fecal Coliform
(count/1 00 ml)
Irrigation of dry fodder,
seed crops, trees,
non-recreational parks,
nurseries (restricted
access)
Food crops not eaten
raw, cut flowers,
orchards and vineyards,
pasture, parks, sports
fields, school grounds
(restricted access)
Pasture for milking
animals, sports fields,
school grounds
(unrestricted access)
Food crops eaten raw,
lawns, nurseries,
school grounds,
play parks
(unrestricted access)
Industrial reuse
Toilet flushing
and dust control
Human washing
Primary and <1,000
secondary; humus
tank effluent
Primary, secondary, <1,000
and tertiary;
oxidation pond system
Standard - primary, 0.0
secondary, and
tertiary
Advanced
(general drinking
water standards)
Primary, secondary, <1,000
and tertirary;
oxidation pond system
Standard - primary, '0.0
secondary, and
tertiary
Advanced —
(general drinking
water standards)
Of special interest are the projects at Riyadh, Jeddah,
and Mecca and Jubail Industrial City. At Riyadh the
trickling filter facility treats over 30 mgd (1,300 Us). Of
this, about 15 percent is used by the General Petroleum
and Minerals Organization (Petromin) for industrial reuse,
and the reyt is available for agricultural irrigation on about
7,800 ac (3,100 ha). A10-mgd (440-L/s) activated sludge
facility at Jeddah is designed to exceed WHO standards
and is the first in the region which was designed to meet
tne equivalent of drinking water standards. Advanced
treatment includes reverse osmosis, desalination,
filtration, and disinfection. Other plants are planned for
197
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Jeddah and Mecca. In both cities the reclaimed water will
be used for municipal, industrial, and agricultural reuse.
The City of Jubail is planned to have a 30-mgd (1,300-L/
s) treatment capacity by 1992, with plans for nonpotable
industrial, urban landscaping, and other reuses.
In all, 22 wastewatertreatment plants are in operation, 10
of which are waste stabilization ponds. Most are currently
discharging to wadis or to the sea, although plans are
underway to increase reuse (Yanez, 1989).
Table 43. Reclaimed Water Standards for
Unrestricted Irrigation in Saudi Arabia
Parameter (a)
BOD
TSS
PH
Coliform (count/100 ml)
Turbidity (NTU)
Aluminum
Arsenic
Beryllium
Boron
Cadmium
Chtoride
Chromium
Cobalt
Copper
Cyanide
Fluoride
Iron
Load
Lithium
Manganese
Mercury
Molybdenum
Nickel
Nitrate
Selenium
Znc
Oil & Grease
Phenol
Maxiumum
Contaminant
Level
10.0
10.0
6-8.4
2.2
1.0
5.0
0.1
0.1
0.5
0.01
280
0.1
0.05
0.4
0.05
2.0
5.0
0.1
0.07
0.2
0.001
0.01
0.02
10.0
0.02
4.0
Absent
0.002
(a) In mg/L unless otherwise specified.
8.2.14 Singapore
Singapore is a city-state with a dense and growing
population of almost 3,000,000 people on an island with
heavy rainfall, averaging 100 in (250 cm)/yr, but limited
water resources because of its small size, only about 210
sq mi (540 sq km). Several secondary (activated sludge)
plants discharge their effluents to the sea. At one location,
nearthe Jurong Industrial Estate, a portion (10 mgd, [440
L/s]) of the effluent is withdrawn from the outfall for serving
industrial needs on the estate. Treatment involves
conventional sand filtration and chlorination, and the
reclaimed water is pumped to a covered tank on a hilltop
on the estate. When a major housing development for the
estate was built, for a population of about 25,000 in 15-
story buildings, all the toilets were served with reclaimed
water.
Originally, operation of the reclamation facility was the
responsibility of the estate but, after some difficulties,
O&M was taken over by the Singapore Public Utilities
Board, which is responsible for wastewatercollection and
treatment in Singapore.
8.2.15 Sultanate of Oman
In Oman, water has been reused in the Capital Area
around Muscat since 1987. Currently effluent from two
treatment plants—at Darsait and at Shatti al Qurm—is
used mainly to irrigate extensive amenity plantings by
drip irrigation. Spray irrigation is not used in recreation
areas, but between 1 a.m. and 6 a.m., some spray
irrigation is conducted in controlled areas. Pressure in
the distribution system, which extends to more than 2.5
mi (40 km) is some 30 to 45 psi (210to 310 kPa). Effluent
requirements are set in the Regulations for Wastewater
Reuse and Discharge.
The Darsait plant is currently operating at capacity and
treating about 3.2 mgd (140 L/s) of wastewater. This plant
serves the local business district and also receives
septage and wastewater pumped from holding tanks. The
treatment processes include screening, grit removal in
aerated grit chambers, primary settling, activated sludge
treatment by contact stabilization, dual-media filtration,
and chlorination. If the chlorine concentration exceeds
0.2 mg/L after chlorine contact, air is added to strip out
the excess chlorine. Effluent is pumped to a storage tank
that provides pressure to the water reuse transmission
system.
The Shatti al Qurm plant is a package extended-aeration
plant followed by filtration in pressure units and
disinfection. This plant has a capacity of about 0.36 mgd
(16 L/s); plant flow is about 0.2 mgd (9 L/s). The
wastewater to this plant comes from embassies and
residences in the area. Treated effluent is stored and
pumped into the water reclamation transmission system.
Athird plant, at Al Ansab, treats only wastes from septage
and wastewater haulers. The plant capacity is about 3.5
mgd (150 L/s), and current flows are about 1.3 mgd (57 U
s). Treatment processes include screening, degritting,
denitrification in an anoxic zone, nitrification, secondary
settling, filtration, and disinfection, and storage. The plant
has facilities to load trucks that can apply treated effluent.
198
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Plans are to connect the plant to the reclamation
distribution system.
During the summer, all the reclaimed water in the area is
used, and demands are not met. But during the winter
about 40 percent of the effluent from the Darsait plant is
discharged through an outfall to the Gulf of Oman. In the
future, the reuse network will be expanded so that all the
effluent is reused.
8.2.16 Tunisia
Although all the countries of North Africa have an interest
in water reclamation, Tunisia has done the most, making
reuse a priority in their national water resources strategy
(Bahri, 1991; Asano and Mujeriego, 1992).
Some 1,500 ac (600 ha) of citrus and olive tree orchards
near Tunis had been irrigated with groundwater from
shallow aquifers since the 1960s but, because of
overdraft and seawaterintrusion, secondary effluentfrom
a portion of Tunis wastewaters was used for irrigation
seasonally, in spring and summer. The effluent is pumped
into a 1.5-milIion gal (5.7-million L) pond and then to a 1 -
million gal (3.8-million L) reservoir, and then flows by
gravity about 5 mi (8 km) to the farmers.
Currently, the effluent from four treatment plants, with a
total flow of about 65 mgd (2,850 L/s) is used to irrigate
about 12,000 ac (4,500 ha) of orchards, forage crops,
cotton, cereals, golf courses and lawns. About 70 percent
of the irrigated area around Tunis will use about 60
percent of the available wastewater effluent.
Considerable research has been undertaken, particularly
to assess the fertilizer value of reclaimed water and the
sewage produced in treatment. Reclaimed water
irrigation produced higher yields than groundwater
irrigation. Studies of the contamination of crops and
groundwater when reclaimed water is used revealed little
significant impact on soils, crops, or groundwater (Bahri,
1991).
The National Sewerage and Sanitation Agency is
responsible for the construction and operation of all
sewerage and treatment infrastructure in the larger cities
in Tunisia. When effluent is to be used for agricultural
irrigation, the Ministry of Agriculture is responsible for
execution of the projects, which include the construction
and operation of all facilities for pumping, storing and
distributing the reclaimed water. Various departments of
the Ministry are responsible for the several functions,
while regional departments supervise the Water Code
and collection of charges, about $0.10/1,000 gal ($0.02-
0.03/m3).
The Water Code, enacted in 1975, prohibits the use of
untreated wastewater in agriculture to be eaten raw. More
recent legislation covers the regulation of contaminants
in the environment, including reclaimed water, and
specifies the responsibilities of the Ministries of
Agriculture and Public Health, and the National
Environmental Protection Agency. Table 44 illustrates the
maximum concentrations for several contaminants in
reclaimed water to be used in agriculture.
Table 44. Maximum Concentrations for Reclaimed Water
Reused in Agriculture in Tunisia
Parameters (a)
Maximum
Concentration
PH
Electrical Conductivity (US/cm)
Chemical Oxygen Demand
Biochemical Oxygen Demand
Suspended Matters
Chloride
Fluoride
Halogenated Hydrocarbons
Arsenic
Boron
Cadmium
Cobalt
Chromium
Copper
Fluoride
Iron
Manganese
Mercury
Nickel
Lead
Selenium
Zinc
Intestinal nematodes
(Arithmetic man no. of eggs/L)
6.5 - 8.5
7000 (b)
90
30b)
30b)
2000
3
0.001
0.1
3
0.01
0.1
0.1
0.5
3
5
0.5
0.001
0.2
1
0.05
5
(a) All units in mg/L unless otherwise specified.
(b) 24-hour composite sample.
Source: Bahri, 1991.
8.2.17 United Arab Emirates
Extensive nonpotable reuse has been practiced in Abu
Dhabi since 1976. The system, designed for 50 mgd (219
L/s), includes a dual distribution network which uses
reclaimed water for urban irrigation of public gardens,
trees, shrubs and grassed areas along roadways. The
treatment facility provides tertiary treatment with rapid
sand filtration and disinfection by chlorination and
ozonation. The reclaimed water distribution system is
operated at lower pressure than the potable system to
reduce wind spraying; elements of the system are marked
and labeled to avoid cross-connections.
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AJ-Ain, with a projected population of 250,000 by the year
2000, produces reclaimed water that may be used only
for restricted irrigation. The reclaimed water is pumped
about 7 mi (12 km) outside the city where it is used for
irrigation in designated areas. Treatment includes dual-
media filtration and chlorination for disinfection.
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in the Middle East. Report to the World Bank,
Washington, D.C.
201
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Appendix A
State Reuse Regulations and Guidelines
203
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Appendix B
Abbreviations and Acronyms
245
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Table B-1. Abbreviations for Units of Measure
acre
British thermal unit
cubic meter
cubic meters per day
cubic meters per second
Curie
cycles per second
degrees Celsius
degrees Fahrenheit
feet (foot)
gallon
hectare
horsepower
hour
inch
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micrometer
mile
mile per hour
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m3
m3/d
m3/s
Ci
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°F
ha
hp
hr
in
kg
km
kPa
kW
kWh
Lori
m
M
ug/L
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mi
mph
milligram
millilter
millimeter
million gallons per day
milliquivalent per liter
minute
megawatt
most probable number
pascal
plaque forming unit
pound
pounds per square inch
roentgen
second
square meter
year
mg
ml or ml
mm
mgd
meq/L
min
mW
MPN
Pa
pfu
Ib
psi
R
246
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Table B-2.
Acronyms/Abbreviations
AID U.S. Agency for International Development
ANSI American National Standards Institute
AWT advanced wastewater treatment
AWWA American Water Works Association
BNR biological nutrient removal
BOD biochemical oxygen demand
CBOD carbonaceous biochemical oxygen demand
CPU colony forming units
COD chemical oxygen demand
COE U.S. Army Corps of Engineers
CWA Clean Water Act
DO dissolved oxygen
EC electrical conductivity
EIS environmental impact statement
EPA U.S. Environmental Protection Agency
ESA external support agency
ET evapotranspiration
FC . fecal coliform
FmHA Farmers Home Administration
GAC granular activated carbon
GC/MS gas chromatography/mass spectroscopy
HPLC high pressure liquid chromatography
IAWPRC International Association on Water Pollution
Research and Control
ICP inductively coupled plasmography
I/I infiltration/inflow
IOC inorganic chemicals
IRCWD International Reference Centre for Waste Disposal
IRWD Irvine Ranch Water District
MCL maximum contaminant level
MCLG maximum contaminant level goal
MDL method detection limit
MPN most probable number
NEPA National Environmental Policy Act
NPDES National Pollutant Discharge Elimination System
NPDWR National Primary Drinking Water Regulations
NRC National Research Council
NTU nephelometric turbidity units
O&M operations and maintenance
OM&R operations, maintenance and replacement
OWRT Office of Water Research and Technology
PAC powder activated carbon
PCB polychlorinated biphenyls
POTW publicly owned treatment works
PVC polyvinyl chloride
QA/QC quality assurance/quality control
RAS return activated sludge
RBC rotating biological contactor
RO reverse osmosis
SAR sodium adsorption ratio
SAT soil aquifer treatment
SBA Small Business Administration
SDWA Safe Drinking Water Act
SOC synthetic organic chemical
SRF State Revolving Fund
SS suspended solids
TCE trichloroethylene
TDS total dissolved solids
THM trihalomethane
TKN total Kjeldahl nitrogen
TN total nitrogen
TOC total organic carbon
TOH total organic hydrocarbons
TOX total organic halides
TP total phosphorus
TPH total petroleum hydrocarbon
TSS total suspended solids
UN United Nations
USDA U.S. Department of Agriculture
UV ultraviolet
VOC volatile organic chemicals
WAS waste activated sludge
WASH Water and Sanitation for Health
WHO World Health Organization
WPCF Water Pollution Control Federation
WRF water reclamation facility
WWTF wastewater treatment facility
247
•U.S. Government Printing Office: 1996 - 750-001/41012
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