United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
EPA-600/2-80-137
August 1980
Research and Development
Effects of Water
Conservation Induced
Wastewater Flow
Reduction
A Perspective
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EFFECTS OF WATER CONSERVATION INDUCED
WASTEWATER FLOW REDUCTION
A Perspective
by
Jimmy S. Koyasako
Department of Water Resources
The Resources Agency
State of California
Sacramento, California 95814
Grant No. R806262
Project Officer
John N^ English
Wastewater Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research Labora-
tory, U. S. Environmental Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily reflect the views and
policies of the U. S. Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorsement or recommendation
for use.
ii
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FOREWORD
The Environmental Protection Agency was created because of increasing public
and government co.ncern about the dangers of pollution to the health and
welfare of the American people. Noxious air, foul water, and spoiled land
are tragic testimony to the deterioration of our natural environment. The
complexity of that environment and the interplay between its components
require a concentrated and integrated attack on the problem.
Research and development is the necessary first step in problem solution and
it involves defining the problem, measuring its impact, and searching for
solutions. The Municipal Environmental Research Laboratory develops new and
improved technology and systems for the prevention, treatment, and management
of wastewater and solid and hazardous waste pollutant discharges from munici-
pal and community sources, for the preservation and treatment of public
drinking water supplies, and to minimize the adverse economic, social,
health, and aesthetic effects of pollution. This publication is one of the
products of that research, a most vital communications link between the
researcher and the user community.
This report measures the major effects of indoor water conservation and re-
sulting wastewater flow reduction in quantified terms and gives a perspective
of its relative positive and negative values. Through this study, data are
being obtained to determine in a rational way measures to protect and
conserve our national water resources.
Francis T. Mayo
Director
Municipal Environmental
Research Laboratory
111
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ABSTRACT
This study examines the effects of indoor water conservation induced waste-
water flow reduction in selected areas in California. The primary economic
benefits and costs of water conservation to a hypothetical community which
characterizes statewide conditions are quantified, and a perspective of their
relative values is presented.
Various municipal wastewater dischargers that experienced actual flow reduc-
tion during the 1976-77 drought in California provided data on the operation
of their collection and treatment systems prior to, during, and after the
drought. This report examines their experiences, along with other available
pertinent information, to determine the advantages and disadvantages of water
conservation. The results of the study quantitatively confirm the desirabil-
ity of promoting water conservation and show that the benefits exceed the
costs.
This report was submitted in partial fulfillment of Grant No. R806262010 by
the California Department of Water Resources under the sponsorship of the
U.S. Environmental Protection Agency. This report covers a period from
October 1, 1978 to April 30, 1980.
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CONTENTS
FOREWORD
ABSTRACT . iv
FIGURES. . . ' viii
TABLES ' x
ABBREVIATIONS AND SYMBOLS '• • xiii
ENGLISH TO METRIC CONVERSION FACTORS • • • xiv
ACKNOWLEDGMENTS " • • xv
SECTION 1. INTRODUCTION . 1
SECTION 2. CONCLUSIONS. . 4
Effects on Wastewater Facilities 4
Water Conservation Benefits and Costs • 5
Effects of Changes in Wastewater Effluent Quality ........ 6
Savings in Future Capital Expenditures for Secondary Treatment
Plants 6
SECTION 3. RECOMMENDATIONS. ..... . 7
SECTION 4. EFFECTS OF WASTEWATER FLOW REDUCTION ON WASTEWATER
FACILITIES 8
Summary 8
Study Approach. . - 8
Reduction in Wastewater Flow 10
Changes in Wastewater Quality • 10 ,
Summary 10
Treatment Plant Influent and Effluent Data ... 12
Operational Problems Encountered in, Collection and Treatment
Facilities 13
Changes in O&M Costs of Wastewater Collection Systems and
Treatment Plants 14
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CONTENTS (continued)
SECTION 5. WATER CONSERVATION, BENEFITS 46
Case I - New Wastewater Facilities Constructed as Additions to
Existing Facilities 48
Ways to Achieve Indoor Water Use Reduction 48
Relationship Among Flows . 50
Amount of Water Savings 50
Water Supply Benefits 52
Energy Benefits 52
Water Heating Benefits 53
Local Systems Benefits 53
Treatment Plant Cost Savings 53
Capital Cost Savings 53
O&M Cost Savings 55
Sewer System Cost Savings 55
Capital Cost Savings 55
O&M Cost Savings. . 57
Summary of Water Conservation Benefits, Case I 57
Case II - New Wastewater Facilities Constructed Independent of
Existing Facilities 57
Ways to Achieve Indoor Water Use Reduction 58
Relationship Among Flows 58
Amount of Water Savings 58
Water Supply Benefits 58
Energy Benefits '. . . 58
Treatment Plant Cost Savings 59
Sewer System Cost Savings. 60
Capital Cost Savings 60
O&M Cost Savings 60
Summary of Water Conservation Benefits, Case II 60
vi
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CONTENTS (continued)
SECTION 6. WATER CONSERVATION COSTS . . . . . 100
Basis of Analysis ....... 100
Case I - New Wastewater Facilities Constructed as Additions
to Existing Facilities 100
Cost of Water Conservation Measures. .... 100
Impact on Wastewater Reuse 101
Impact on Crop Irrigation 102
Impact on Landscape Irrigation 104
Impact on Industrial Uses . 104
Other Impacts 105
Case II - New Wastewater Facilities Constructed Independent of
Existing Facilities 106
Cost of Water Conservation Measures. ............ 106
Impact on Wastewater Reuse 106
SECTION 7. WATER CONSERVATION NET BENEFITS 120
Summary 120
Case I 120
Case II 121
SECTION 8. PENALTY COSTS 127
Background 127
Unit Penalty Costs. . 128
Annual Penalty Costs 128
Effect on Net Benefits. . . . 129
Alternative to Penalty Costs 129
SECTION 9. SAVINGS IN FUTURE EXPENDITURES FOR SECONDARY
. TREATMENT PLANTS . . 136
SECTION 10. IMPLEMENTATION OF WATER CONSERVATION MEASURES. ... . . . 138
REFERENCES ..;... ...... 141
APPENDICES 143
A. Assembly Bill No. 1395. An act to add Section 17921.3
to the Health and Safety Code, relating to water closets. . . 143
B. California Administrative Code. Title 20, Chapter 2.
Energy Conservation. Appliance efficiency standards 145
C. Factors used for computing energy savings . ... 152
vii
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FIGURES
Number
Page
1 Location of wastewater systems. . 17
2 Reduction in sewer operation and maintenance (O&M) costs. ... 42
3 Reduction in secondary treatment plant energy use . 43
4 Change in secondary treatment plant chemical uses , 44
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Change in operation and maintenance costs of secondary
treatment plants
Effect of wastewater flow reduction on new wastewater
system capacity
Residential water use in California .
Reduction in indoor water use, Case I
Percent reduction in treatment plant capital cost, Case I .
Annual water conservation benefits, Case I ...
Reduction in capital cost of secondary treatment plants,
Case II
Annual water conservation benefits, Case II
Annual unit cost of water conservation measures, Case I . .
Crop salt tolerance
Crop yield reduction due to increased salt concentration. .
Impact of water conservation on reclamation of wastewater
for crop irrigation • •
Survival rate of turf grass • •
45
61
62
. . 66
i
. . 74
86
. . 93
99
. . 110
, 112
. . 113
116
117
. . 123
viii
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FIGURES (continued)
Number
19
20
21
22
Annual water conservation net benefits, Case II
Annual net benefits of water conservation at optimum level of
indoor use reduction
Incremental increase in TDS arid hardness concentrations ....
Effect of penalty costs on net benefits .......
23 Comparative cost of alternative (by desalting) to penalty
costs
Page
124
125
131
133
135
IX
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TABLES
Number Page
1 Description of Secondary Treatment Plants 18
2 Wastewater Flow 21
3 Influent Biochemical Oxygen Demand (BOD) Concentration 23
4 Influent Suspended Solids (SS) Concentration ... 24
5 Influent BOD Load 25
6 Influent Suspended SS Load 26
7 Effluent BOD Concentration 27
8 Effluent SS Concentration 28
9 Percent Removal of BOD Load 29
10 Percent Removal of SS Load 30
11 Number of Times Treatment Plants Exceeded 30-Day Average
Effluent Limitations 31
12 Number of Treatment Plants Exceeding 30-Day Average
Effluent Limitations 32
13 Problems in Sewer Systems During Periods of Reduced
Wastewater Flow 33
14 Problems in Treatment Plants During Periods of Reduced
Wastewater Flow 34
15 Changes to Items Affected by Flow Reductions and Their
Effect on Total O&M Cost 36
16 Percent Expected Reductions in Community Indoor Water Use
Resulting From Water Conservation Measures 63
17 Amount of Water Savings, Case I. 67
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TABLES (continued)
Number Page
18 Water Supply Benefits, Case I -.- 70
19 Annual Energy Benefits, Case I 71
20 Percent Reduction in Secondary Treatment Plant (STP) Capital
Costs Due to Flow Reduction. 73
21 Capital Cost Savings for Secondary Treatment Plants, Case I. . . 75
22 Sample Calculation for Reducing New Sewer Pipe Sizes Due to
Reductions in Wastewater Flow , 76
23 Smaller Pipe Size Selection Due to Wastewater Flow
Reduction, Case I 77
24 Sample Calculation for Sewer Pipe Capital Cost Without
Reduction in Indoor Water Use, Case I ........ 78
25 Sample Calculation for Sewer Pipe Capital Cost With
Reduction in Indoor Water Use 79
26 Sewer Line Capital Cost Savings, Case I. . . . 80
27 Percent Savings in O&M Cost Due to Wastewater Flow Reductions. -. 80
28 O&M Cost Savings for New Sewer Systems, Case I . 81
29 O&M Cost Savings for Existing Sewer Systems, Case I. 82
30 Combined O&M Cost Savings for New and Existing Sewer
Systems , Case I 83
31 Summary of Annual Water Conservation Benefits at 10 Percent
Reduction in Indoor Water Use, Case 1 84
32 Summary of Annual Water Conservation Benefits at 20 Percent
Reduction in Indoor Water Use, Case I. 84
33 Summary of Annual Water Conservation Benefits at 30 Percent
Reduction in Indoor Water Use, Case I. 85
34 Summary of Annual Water Conservation Benefits at 35 Percent '
Reduction in Indoor Water Use, Case 1 85
35 Expected Reductions in Percent of Indoor Water Use, Case II. . . 87
xi
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TABLES (continued)
Number
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Amount of Water Savings Due to Water Conservation, Case II .
Water Supply Benefits, Case II
Annual Energy Benefits, Case II • • •
Capital Cost Savings for Secondary Treatment Plants,
Case II ' "..-..
Sewer Line Capital Cost Savings, Case II
Page
89
90
91
92
94
Annual O&M Cost Savings in Sewer Systems, Case II. ....... 95
96
Summary of Annual Water Conservation Benefits at 30 Percent
Reduction in Indoor Use, Case II .
Summary of Annual Water Conservation Benefits at 35 Percent
Reduction in Indoor Use, Case II
Summary of Annual Water Conservation Benefits at 40 Percent
Reduction in Indoor Use, Case II
97
98
Unit Cost of Water Conservation Measures, Case I 107
Annual Cost of Water Conservation Measures, Case I Ill
Summary of Crop Loss Determination ............... 114
Unit Cost of Water Conservation Measures, Case II. 118
Annual Cost of Water Conservation Measures, Case II. ...... 119
Net Benefits of Water Conservation, Case I 122
Net Benefits of Water Conservation, Case II 126
Annual Penalty Costs, Case I 132
Amount and Cost of Desalting 134
Estimated Savings in Capital Expenditure for Secondary
Treatment Plants Proposed for New Construction and
Enlargement in California.. 137
xii
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ABBREVIATIONS
ac-ft
AS
ADWF
bbl
BOD
BTU
cm
col
o
dam
EC
°F
ft
gpm or gal/min
k
kg'
kWh
1
Ib
1/min
m ,
m3/s
mgd
mg/1
mmho/cm
MUD
O&M
LIST OF ABBREVIATIONS AND SYMBOLS
acre-feet
activated sludge
average dry weather flow
barrel
biochemical oxygen demand
British thermal unit
centimeter
column
cubic dekametre
electrical conductivity
Farenheit degrees
feet
gallons per minute
constant
kilogram
kilowatt hour '
litre
pound
litres/minute
metre
cubic metres per second
million gallons per day
milligrams per litre
millimhos per centimetre
Municipal Utility District
operation and maintenance
xiii
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LIST OF ABBREVIATIONS AND SYMBOLS (continued)
ABBREVIATIONS
psi
Q
SD
SS
STP
T
TDS
pounds per square inch
flow
Sanitary or Sanitation District
suspended solids
sewage treatment plant
temperature
total dissolved solids
SYMBOLS
<
equal to or less than
greater than
similar to
ENGLISH TO METRIC CONVERSION FACTORS
Quantity
Length
Volume
Flow
English Unit
inches (in)
feet (ft)
gallons (gal)
million gallons
acre-feet (ac-ft)
cubic feet per
second (ft3/s)
million gallons per
day (mgd)
Multiply By
2.54
0.3048
3.7854
3785.4
1233.5
1.2335
28.317
0.043813
43.81250
To Get Metric Equivalent
centimetres (cm)
metres (m)
litres (1)
cubic metres (mr)
cubic metres (m )
cubic dekametres (dam )
litres per second (1/s)
cubic metres per
second (m /s)
litres per second (1/s)
xiv
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ACKNOWLEDGMENTS
The assistance and cooperation of Mr. John N. English, Project Officer, and
Mr. Mark•Zuckerman of the Environmental Protection Agency '(EPA), during the
preparation of this report are gratefully acknowledged. For providing data
on their wastewater systems, special thanks are extended to Carmel Sanitary
District, East Bay Municipal Utility District (Special District No. 1), City
of Grass Valley, City of Imperial Beach, Las Gallinas Valley Sanitary
District, Sanitary District No. 1 of Marin County, City of Millbrae, Novato
Sanitary District, Oro Loma Sanitary District, City of Palo Alto, County of
Sacramento, San Rafael Sanitary District, and West Contra Costa Sanitary
District. Assistance in making the study analyses was generously provided by
Mr. Terry Bursztynsky of the Association of Bay Area Governments, Takashi
Asano, -Ph.D., of the California State Water Resources Control Board, Wen H.
Huang, Ph.D., of EPA (Municipal Construction Division), and Mr. Ray Hoagland,
Mr. James Morris, and Mr. John Tenero of the California Department of Water
Resources. Mr. Andrew Launitz of the California State Water Resources
Control Board supplied projections for the reuse of wastewater.
xv
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SECTION 1
INTRODUCTION
During the last 10 years, urban water conservation has attracted much atten-
tion and has widely come to be considered as an essential part of effectively
managing our water resources. Urban water conservation saves water, and it
also saves another precious, commodity — energy. While saving water is be-
coming increasingly popular, across the country, perhaps the most intensive
water conservation effort took place in Northern California during the acute
drought of 1976-77. Although this study was not intended to investigate "the
effects of the drought, the drought did provide a good laboratory for measur-
ing some of the effects of water conservation.
During the drought, Californians in many areas were encouraged by governmen-
tal and water resources management agencies to conserve water both outside
and inside their homes. Some of the common practices included cutting back
'on or eliminating landscape irrigation, and installing low-flow faucet aera-
tors, low-flow showerheads or flow restrictors, and "water dams" or plastic
bottles in toilet tanks to reduce the amount of water used for flushing.
However, these and other measures were often undertaken without a full knowl-
edge of the positive and negative aspects of conserving water, particularly
with regard to reduced wastewater flows. Questions were raised then and
questions are raised now by many people who ask:
What are the effects of water conservation on wastewater collection and
treatment systems? J
What are the effects on wastewater reuse of any changes in the quality of the
treated wastewater?
What are the positive and negative aspects of water conservation and is water
conservation still worthwhile after they both have been considered?
Before we enter a new decade with an enthusiasm to promote water conserva-
tion, it is important that we find the answers to these questions, and assure
ourselves that water conservation is worthy of our continued support.
The purpose of this study was to find the answers to the questions posed by
assessing the effects of and estimating the long-term impact of water conser-
vation and the resulting reduction in wastewater flow. The results of the
study will help support policy and follow-up actions concerning water conser-
vation measures and future construction of wastewater collection and treat-
ment facilities.
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When water conservation measures were undertaken during the California
drought, it was anticipated that water and energy would be saved, but little
was known about the effects of wastewater flow reduction on the operation and
maintenance of the wastewater systems. Numerous local agencies in Northern
California experienced reductions in wastewater flows during the 1976-77
drought where nearly all of the major communities were under some form of
mandatory conservation.
Data were obtained from local municipal wastewater management agencies which
addressed the following two questions:
1. Did reduced wastewater flows resulting from water conservation cause
significant problems with regard to the operation and maintenance of
sewage collection and treatment systems?
2. Were changes required in operation and maintenance procedures as a re-
sult of reduced flow effects and did the changes alter operation and
maintenance (O&M) costs of the wastewater systems that could be applied
to estimate future O&M costs?
The first question was answered in the negative when study results generally
showed that during periods of reduced wastewater flows no serious systems
operational problems were encountered. An answer to the second question was
pursued by using the data collected, along with other available information,
to determine how varying degrees of indoor water conservation affect .waste-
water handling costs. The primary economic benefits and costs of water con-
servation to a hypothetical community which characterizes average statewide
conditions in California are quantified and gives the reader a perspective on
their relative values. Because the results depict average statewide
conditions, the reader should keep in mind that the effects of wastewater
flow reductions can vary measurably on a case by case basis depending on the
numerous variables involved.
Data were collected from local municipal wastewater agencies primarily to
measure any significant effects of flow reduction on their operation and were
not intended to be used for an in-depth evaluation to determine the reasons
for the effects. For this reason only a limited discussion on wastewater
quality and the extent of its changes and effects on the treatment plant per-
formance during periods of flow reduction has been included in this report.
Also, the reader should treat these data in the context of the purpose of the
study and should not use them to help establish design or operational stan-
dards for wastewater facilities.
The future benefits and costs of indoor water conservation measures are
assessed by using the next 20-year period, 1980-2000, as the basis for
analysis. This time span represents a period for which expanded or new
wastewater facilities would be sized for capacity. Two cases are examined as
follows:
Case I - Where new wastewater facilities are additions to or expansions
of existing facilities to take care of new population growth. Thus,
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Case I considers wastewater flows from both existing and new building
constructions.
Case II - Where new wastewater facilities serve new population growth
and operate independently of existing facilities. Thus, Case II con-
siders wastewater flows from new building construction only.
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SECTION 2
CONCLUSIONS
Effects on Wastewater Facilities
One-half of the 17 wastewater systems surveyed encountered operational
problems during periods of flow reductions. In general, however, the
problems were not severe enough to greatly affect the systems operations.
Common problems in the sewer systems were solids settling and odor. Com-
mon operational problems in the treatment plants were odor in the primary
and secondary clarifiers, and bulking in secondary clarifiers due to
excessive growth of filamentous bacteria.
Remedial measures were taken to resolve the problems, and there were
no documented cases where the wastewater facilities could not continue to
be properly maintained.
Changes in wastewater quality during periods of flow reduction did not
generally result in more frequent treatment plant violations of biochemi-
cal oxygen demand (BOD) or suspended solids .(SS) discharge requirements.
The BOD and SS concentrations of the wastewater entering the treatment
plant generally increased while the concentrations leaving the plant gen-
erally decreased during years of flow reduction. The efficiency of treat-
ment plant removal of BOD and SS generally increased slightly.
Energy and chemical uses were the primary items affected by wastewater
flow reduction.
The overall O&M costs for the wastewater collection system decreased
slightly, with a maximum of 3% cost reduction at 50% flow reduction. Most
of the reductions in cost resulted from decreased energy use for the lift
pumps.
The decrease in energy use for the treatment plants amounted to a
maximum of 20% at 50% reduction in flow due to lower pumping requirements
for the hydraulic load. Use of chemicals ranged from a decrease of 30% to
an increase of 50%. The overall O&M costs ranged from a decrease of about
5% to an increase of about 4%. For treatment plants that experienced,
higher costs, increased use of chemical was the major factor.
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Water Conservation Benefits and Costs
The conclusions are listed separately for .the two cases analyzed.
Case I - Where the new wastewater facilities are additions to or expansions
of the existing facilities to take care of new population growth.
Thus, wastewater flows from both existing and new building
constructions are considered.
0 Indoor water use reduction for the water conservation measures
examined ranged from 10% with minimal water conservation effort to a
potential of 35%.
o The major benefit is energy savings due to less use of hot water in
homes. Other benefits are cost savings in water supply and cost savings
in municipal wastewater systems.
0 More than 70% of the net benefits were attributable to water conserva-
tion measures in existing building construction.
° The optimum level of indoor water use reduction is nearly 30% and
would require a strong water conservation effort.
° At the optimum level of indoor water use reduction, the benefits of
water conservation are three times as great as its costs.
o Savings in capital cost of treatment plants ranged from 12% at 10%
indoor use reduction to 22% at 20% to 35% indoor use reduction.
° Savings in capital cost of wastewater collection pipes of 15% would be
made at all levels of indoor water use reductions.
° Savings in O&M costs of wastewater collection systems ranged from 1%
at 10% reduction to 15% at 35% reduction in indoor water use.
.° The annual cost of water conservation measures increased from $0.20
per household at 10% reduction in indoor use to $30 per household at 35%
reduction.
Case II - Where the new wastewater facilities serve new population growth
independently of existing facilities. Thus, wastewater flows from
new construction only are considered.
0 Indoor water use reductions for the water conservation measures
examined ranged from 30% with minimal water conservation effort to a
potential of 40%.
0 The major benefits are energy savings due to less household use of hot
water and cost savings in sewer systems. Other benefits are cost savings
in water supply and wastewater treatment plants.
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Savings in capital cost of treatment plants would increase linearly to
8% at 40% reduction in indoor use.
The average savings in capital cost of wastewater collection pipes is
7%. .
A small savings in the O&M costs of wastewater collection systems
would be achieved.
The annual cost of water conservation measures ranged from $0.10 per
household at 30% reduction in indoor use to $10 per household at 40% re-
duction. The costs are lower than those for Case I. The reason is that
water-saving toilet, shower, and faucet fixtures, which'are responsible
for most of the reductions, are mandatory in new construction and cost
less than retrofitting existing buildings.
The optimum level of indoor water use reduction is 37% and would
require a strong water conservation effort.
The benefits far exceed the costs.
Effects of Changes in Wastewater Effluent Quality
The impact of increased salt concentration (as a result of flow reduc-
tion) on wastewater reuse for crop irrigation, landscape irrigation, and
industrial uses has no noticeable effect on the "net benefits" (gross
benefits minus costs) of water conservation. Thus, water conservation is
not counterproductive to wastewater reuse.
"Penalty costs" reduce the net benefits only slightly. Penalty costs
are costs borne by consumers as a result of increased salt concentration
and are associated with use of home water softeners, soap and detergent,
bottled water, and water heaters.
Desalting and blending of the effluent would mitigate any increased
salt concentration. However, the cost of desalting would be considerably
greater than the penalty costs.
Savings in Future Capital Expenditures for
Secondary Treatment Plants
At the optimum level of indoor water use reductions in new and exist-
ing building constructions, the expected savings in capital expenditures
of secondary treatment plants proposed for new construction and enlarge-
ment in California is on the order of $210 million.
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SECTION 3
RECOMMENDATIONS
It is recommended that:
* In view of its overwhelming beneficial effects, indoor water conserva-
tion measures be vigorously supported and undertaken by all interests con-
cerned with the development and use of water. An intensive water conser-
vation effort will be required to attain the greatest benefits over
costs.
0 Particular attention be given to water conservation measures in exist-
ing buildings because they are responsible for generating most of the
benefits.
0 The financial/social gains or losses of water conservation be investi-
gated from different points of view in the community. When community
interests find their own incentives as well as appreciate the benefits to
the total community, they will be more willing to take actions leading to
the development and implementation of a workable plan.
0 In view of the paucity of data on wastewater effluent mineral quality,
adequate information should be obtained for specific constituents affect-
ing proposed wastewater reuse projects. The data should include, as a
minimum, analyses of total dissolved solids (TDS), hardness, and boron
concentrations and sodium adsorption ratios.
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SECTION 4
EFFECTS OF WASTEWATER FLOW REDUCTIONS
ON WASTEWATER FACILITIES
Summary
This section examines wastewater systems that actually experienced the
effects of water conservation induced wastewater flow reductions. It shows
that the effects did not result in any serious systems operational problems
that could not be readily resolved. Although the wastewater constituents
generally increased in concentrations in flows entering the treatment plants,
the plants were able to operate satisfactorily. In fact the plant efficiency
increased slightly.
The energy and chemical uses were the primary items affected by wastewater
flow reduction. However, changes in these uses did not significantly change
the overall O&M costs of the wastewater facilities. Since a definite trend
of changes in O&M costs for the sewer systems developed in relation to waste-
water flow reductions, these changes are used later in this report in the
benefit/cost analysis.
However, changes in treatment plant O&M costs will not be applied in the
benefits/costs analysis because (1) a definite relationship of changes in O&M
cost with flow reductions did not develop, and (2) the changes were not sig-
nificant enough to be crucial to the results of the analysis. Also included
in this section are limited' data on the quality of the wastewater entering
and leaving the treatment plants to show plant performance during periods of
flow reduction.
Study Approach
A community can reduce its residential indoor water use in many ways. Some
of the common ways are use of low-flow toilet, shower, and faucet fixtures.
It was understood that water and energy would be saved by these measures, but
little was known about the effects of reduced wastewater flow resulting from
water conservation measures on the operation and maintenance of wastewater
collection and treatment facilities. For this reason, various local agencies
were contacted to obtain actual data concerning:
• reduction in wastewater flow
• changes in wastewater quality
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° specific operational problems encountered in collection and treatment
facilities.
The agencies selected were those with systems that:
° experienced flow reduction
^
0 had separate sanitary sewer systems rather than combined sewer
systems .
o had not made major modifications or expansions to its treatment plant
during the period for which data was sought
o had both the collection and treatment facilities operated as a single
unit as opposed to systems with multiple treatment plants where
operational flexibility allowed changes in flow routes
° provided secondary treatment
o produced at least .043 m^/s (1 mgd of wastewater).
The selection criteria were established to determine the relationship between
indoor water use and was.tewater flow, and to narrow the large field of waste-
water facilities to survey in California. The 1976-77 drought in California
created a condition requiring water conservation measures which resulted in
various local wastewater management agencies experiencing reduction in waste-
water flows. In general, many of these agencies were located in the
San Francisco Bay area where the water shortage problem was critical. The
agencies from which data on wastewater collection systems and/or treatment
plants were obtained are:
o Sanitary District No. 1 of Marin County
o San Rafael Sanitary District
o Las Gallinas Valley Sanitary District
o Novato Sanitary District
0 West Contra Costa Sanitary District
° East Bay Municipal Utility District - Special District No. 1
° Oro Loma Sanitary District
o Carmel Sanitary District
° City of Palo Alto
° City of Millbrae •
° County of Sacramento
9
-------
• City of Grass Valley
0 City of Imperial Beach.
The locations of these agencies are shown on Figure 1 and their secondary
treatment plants are described in Table 1.
Numerous agencies operating secondary treatment plants were contacted in
Southern California where a large portion of the State's wastewater is
produced. In general, it was found that wastewater flow reductions did not
occur there. While the flow per capita generally lessened during the
drought, the increased service connections caused the total wastewater pro-
duction to either stay at the same level or increase.
Reduction in Wastewater Flow
The measurement of wastewater flow reduction was necessary because it was
directly affected by the reduction in residential indoor water use. Some
agencies experienced 2 years of wastewater flow reduction, in 1976 arid 1977.
For them, 1975, the year prior to the occurrence of flow reduction, was
selected as the base year. Other agencies experienced only one year of flow
reduction, in 1977. For them, 1976 was selected as the base year. The flow
reductions for the various agencies are listed on Table 2. The values repre-
sent the average daily flows for the calendar year. The number of wastewater
systems that experienced flow reduction, the range of flow reduction, and the
average flow reduction are shown below:
First year
Second year
Number of
Wastewater
Systems with
Flow Reduction
18
10
Range of Flow
Reduction Change
(in percent)
5-33
16-63
Average Flow
Reduction Change
(in percent)
17
39
Las Gallinas Valley Sanitary District experienced the greatest flow reduction
at 63% in 1977. It was found that flow reduction in the City of Imperial
Beach was primarily attributable to the curtailment of infiltration from the
high ground water table near the ocean rather than from water, conservation.
However, data from this city has been included because it will be applicable
in assessing the energy costs of its sewer lift pumps as discussed later in
this report.
Changes in Wastewater Quality
Summary
The operational parameters of BOD and SS were measured in both the influent
and the effluent. The effects during flow reduction on these parameters were
evaluated in terms of changes in their concentration, loading rate, and
10
-------
removal efficiencies. It must be emphasized that the values measured are
those resulting from the total effects of flow reduction rather than just a
physical reduction in the quantity of wastewater.
Other effects observed or actions taken during periods of flow reduction that
contributed to change of wastewater quality include:
0 Increased detention time of the waste in the sewer lines due to lower
flow velocity
° Solids settling in the sewer systems due to lower flow velocity
0 Addition of chemical oxidants in the sewer systems for odor control
0 Additional recirculation of waste such as digester and sludge
thickener supernatants to the headworks.
Influent quality data were obtained for 14 treatment plants and effluent
quality for 13 plants. The changes in the quality for these plants are
discussed in this section and are summarized below:
0 The influent BOD and SS concentrations generally increased on the
order of 15%-40%'.
» The influent BOD and SS mass loading generally decreased on the order
of 5%-25%.
0 The effluent BOD concentration decreased in eight plants on the order
of 10%-15%. It increased in three plants between 1% to" 78% and did not
change in two plants.
0 The effluent SS concentration decreased in 10 plants on the order of
20%-30% and increased in three plants between 3%-60%.
0 The percent removal of BOD and SS generally increased slightly between
l%-6%.
The increase in the influent concentrations for the two parameters (BOD and
SS) was expected because of the decreased dilution of the influent caused by
a reduction in flow, but one would have expected the mass loading of influent
constituents to remain constant. However, the loading rate generally
decreased. There is no definite answer for this occurrence, but based on
interviews of local agencies and work by others (I)!/ and (2), a combination
of the following factors appears to be the likely cause:
0 Increased residence time of organic wastes in the sewer systems (which
probably increased biological decomposition prior to entering the
treatment plant).
I/ A numbered list of references is presented at the end of this report.
11
-------
<> Deposition of solids in the sewer system due to lower flow velocity.
• Hydrogen peroxide used as a chemical oxidant in some sewer systems to
control odor problems may have increased biological decomposition of
organic wastes.
0 Less use of garbage grinders to save water.
The quality of the effluent from the treatment plants was compared with the
30-day average effluent limitations (30 mg/1 concentration and 85% removal)
for BOD and SS imposed on waste dischargers. The number of times the- treat-
ment plants exceeded the limitations during years of. flow reduction and the
number of plants exceeding the effluent limitations were examined and are
summarized below:
8 The number of treatment plants exceeding the effluent limitations
generally decreased during years of flow reduction.
o There were generally a greater number of treatment plants with less
occurrence of exceeding the limitations than those with more during years
of water conservation induced flow reduction.
Treatment Plant Influent and Effluent Data
The discussion for this portion of the section deals with some specifics on
the available influent and effluent quality data for the treatment plants.
The BOD influent concentration, as expected, generally increased with reduc-
tions in flow due to less dilution. As shown on Table 3, 12 plants had an
increase ranging from 4% to 43% in the first year of flow reduction. One
plant showed a decrease of 8% and one plant showed no change. In the second
year of flow reduction, seven plants showed an increase between 4% and 82%.
In general, the SS influent concentrations also increased as shown in
Table 4. In the first year of flow reduction, nine plants had an increase^
ranging from 4% to 42% and five plants showed a decrease between 2% and 18%.
In the second year of flow reduction, five plants showed an increase between
13% and 87% while two plants showed a decrease, one 10% and the other'12%.
Contrary to expectations, influent BOD mass loading generally decreased with
reduction in flow (see Table 5). The likely reasons for this decrease were
stated earlier in this section. Eleven plants showed a decrease between 2%
and 21% while two plants showed an increase, one with 6% and the other with
10%, during the first year of flow reduction. One plant showed no change.
During the second year, six plants had a decrease between 2% and 55%, while
one plant had an increase of 20%.
The SS influent mass loading also showed a general decrease as shown in
Table 6. In the first year of reduction, 12 plants showed a decrease between
2% and 28% and two plants had an increase, one with 11% and the other with
22%. In the second year, six plants had a decrease between 4% and 59%'while
one plant had an increase of 33%.
12
-------
Table 7 shows that the BOD effluent concentration generally decreased. In
the first year, eight plants showed a decrease between 8% and 42%, three
plants had an increase between 1% and 39%, and two plants had no change. In
the second year, four plants showed a decrease between 2% and 37% while two
plants showed an increase, one 46% and the other 78%.
The SS effluent concentration also generally had a decrease as shown on
Table 8. In the first year, 10 plants showed a decrease between 9% and 39%,
and three plants showed an increase between 3% and 60%. In the second year,
four plants showed a decrease between 20% and 31% while two plants showed an
increase, one 13% and the other 23%. Tables 9 and 10 show that the Percent
Removal of BOD and SS generally increased slightly between 1% to 6%.
The frequency of the 30-day average effluent limitations of 30 mg/1 and 85%
removal for BOD and SS exceeded by the plants during years of flow reduction
are shown on Table 11. It is expressed in another way as the number of
plants exceeding the effluent limitations in Table 12. These tables show
that during years of flow reduction (1) the number of treatment plants
exceeding the limitations generally decreased, and (2) there were generally a
greater number of plants with less occurrence of exceeding the limitations
than those with more. Seven plants had exceeded at least one of the effluent
limitations in the base year'(year prior to flow reduction). During years of
flow reduction, four of these plants had a decrease in the number of occur-
rences of exceeding the limitations and three plants had an increase.
Operational Problems Encountered in
Collection and Treatment Facilities
During periods of wastewater flow reduction, problems with various systems
were encountered, but none so severe as to greatly upset system operations.
The only exception was at the Las Gallinas Valley S.D. treatment plant in
1976, when growth of sulfur bacteria on the rock media caused ponding in the
trickling filter. This ponding and the subsequent application of chlorine to
kill the sulphur bacteria upset the secondary treatment processes for several
months .
Seven sewer systems and nine treatment plants experienced problems. Ten
sewer systems and seven plants did not. The common problems in the sewer
system and treatment plants caused by reduced wastewater flow, and actions
taken by plant operators to rectify them, are tabulated below.
SEWER SYSTEMS
Problem
Odor
Solids settling in lines
Action
Used chlorine or other
oxidizing chemicals
Cleaned lines more often
13
-------
TREATMENT PLANTS
Problem
Large grit load after first heavy
rain clogged sludge draw-off line
at primary clarifiers.
Odor in primary and secondary
clarifiers
Odor in wet well or sludge
thickener
Bulking in clarifiers due to
excessive filamentous bacteria
growth in aeration tanks.
Action
Dewatered clarifier and
pressure-hosed off silt, or
stepped up sludge draw-off
rate.
Added chlorine. Recirculated
primary effluent to headworks,
Added chlorine
Added chlorine. Reduced mean
cell residence time in aera-
tion tanks.
The specific problems encountered by each agency and the actions it took to
resolve the problems are shown in Tables 13 and 14. With the exception of
the large grit load after the first heavy rain, the other problems encoun-
tered generally occurred during the summer months. It is not suggested that
wastewater flow reduction was necessarily the sole cause of all the problems.
However, the problems were those not usually encountered during normal years
of rainfall and therefore it is reasoned that wastewater flow reduction was a
major factor. When the remedial measures were taken, the problems were re-
solved and there were no documented cases where continued proper operation of
the wastewater facilities could not be made. Thus, the question "Did reduced
wastewater flows resulting from water conservation cause significant problems
with regard to the operation and maintenance of sewage collection and treat-
ment systems?" was answered in the negative.
A number of agencies reported that plant roots clogged their sewer lines.
The drought increased the tendency of the roots to seek moisture in the sewer
lines and cause clogging. This problem is attributed to the dry soil condi-
tions caused by the drought rather than the reductions in wastewater flow due
to water conservation and therefore is not included among the problems.
Changes in O&M Costs of Wastewater Collection Systems
and Treatment Plants
All local agencies contacted indicated that energy and chemicals were the
primary O&M cost items affected by wastewater flow reductions. The major
change in energy use for the wastewater collection system was due to de-
creased operating time by lift station pumps. Chemical uses not governed or
affected by flow, such as polymer used in sludge handling, were not included.
The energy and chemical uses were identified from available data for the var-
ious agencies contacted. The amounts of these uses during years of flow
reductions were identified and expressed in terms of the effect on the over-
all O&M costs for the individual sewer systems and treatment plants (see
14
-------
Table 15). The values used to determine the proportionate cost (percent of
total O&M costs) of energy and chemical uses pertained to the year as near as
possible to the base year of flow. The overall O&M costs include all the
variable costs of operating and maintaining the facilities, such as person-
nel, chemicals, utilities, materials, equipment, and administrative
expenses.
The changes in the overall O&M costs for the sewer systems from Table 15 were
plotted against the changes in wastewater flow reductions from Table 2 (see
Figure 2). A linear regression curve for the plotted points showed that the
O&M costs decreased slightly with reductions in flow. The decrease amounted
to a maximum of 3%-at about 50% flow reduction. As is evident in Table 15,
most of the reductions in cost resulted from decreased pumping energy for the
lift pumps.
"\
A linear regression curve was also fitted to the changes in the energy use
plotted against changes in flow for the treatment plants. The decrease in
energy use amounted to a maximum of 20% at 50% reduction in flow due to less
pumping requirements for the hydraulic load (see Figure 3).
A plot of changes in chemical use for the treatment plants showed a scattered
pattern and ranged from a decrease of 30% to an increase of 120% (see
Figure 4). It is reasoned that the overall chemical uses can increase or
decrease depending on the operational practice during the flow reduction
period. The kinds .of chemicals used during flow reduction periods along with
the likelihood of plus or minus changes are shown below:
Chemical Used
Chlorine
Chlorine
Chlorine
Polymer, lime, alum,
or ferric chloride
Sulfur dioxide
Purpose
Disinfection
Control of
filamentous
bacteria
Odor Control
Coagulation
Dechlorination
Change in Quantity Used
The net effect of the changes in energy and chemical uses in terms of changes
in the overall O&M costs of treatment plants is also shown on Table 15.
These changes are plotted in Figure 5 and show a scattered pattern ranging
from a decrease of about 5% to an increase of about 4%.
While substantial changes occurred in the chemical or energy uses for some
systems, the overall O&M costs changed only slightly. The reason for this is
that the costs, of energy and chemicals were relatively small percentages of
the overall O&M costs. For treatment plants that experienced increased
15
-------
costs, greater chemical use was the influencing factor. To illustrate these
points let us examine Novato Sanitary District's Novato Plant in the second
year of flow reduction as an example (see Table 15):
Change in energy use
Change in chemical use
Energy cost as % of total O&M costs
Chemical cost as % of total O&M costs
Change in O&M cost caused by change in
energy use - (-17.4%) (12.3%)
Change in O&M costs caused by change in
chemical use - (+119.6) (2.9%)
Net change in O&M costs
-17.4%
= +119.6%
12.3%
2.9%
-2.1%
+3.5%
+1.4%
16
-------
1 CITY OF GRASS VALLEY
2 COUNTY OF SACRAMENTO
CORDOVA PLANT
S. D. NO. 6 PLANT
NORTHWEST PLANT
MEADOWVIEW PLANT
ARDEN PLANT
3 WEST CONTRA COSTA S. D.
4 EAST BAY M. U. D.
6 S. D. NO. 1 OF MARIN CO.
6 SAN RAFAEL S. D.
7 LAS GALLINAS VALLEY S.D.
8 NOVATO S. D.
NOVATO PLANT
IGNACIO PLANT
9 CITY OF MILLBRAE
10 CITY OF PALO ALTO
11 ORO LOMA S. D.
12 CARMEL S. D.
13 CITY OF IMPERIAL BEACH
Figure 1. Location of wastewater systems.
17
-------
TABLE 1. DESCRIPTION OF SECONDARY TREATMENT PLANTS
Agency
Typ.
I/
Design
Flow
m^/s
(mgd)
Description
S. D. No. 1 of
Marin County
San Rafael S. D.
Las Gallinas
Valley S. D.
Novato S. D.
Novato Plant
Ignacio Plant TF
Carmel S. D.
TF 0.206 Facilities include primary clarifiers,
(4.7) two-stage high rate trickling filter,
secondary clarifier, microscreens, and
a chlorine contact chamber. Effluent
is discharged to San Francisco Bay.
Sludge is removed to a sludge thickener,
digester, and land disposal.
AS 0.219 Major units include a primary clarifier,
(5.0) activated sludge tanks, secondary clar-
ifiers, effluent outfall line to San
Pablo Bay. Outfall line is used as
chlorine contact chamber. Sludge is
removed to a sludge thickener, digest-
ers, and land disposal.
TF 0.131 Treatment plant includes primary clari-
(3.0) fiers, trickling filters, final clari-
fiers, and chlorine contact pond.
Effluent is discharged to Miller Creek,
thence to San Pablo Bay. Sludge is
removed to a sludge thickener, digest-
ers, and land disposal.
AS 0.131 Major units include a primary clarifier,
(3.0) trickling filter, activated sludge
tanks, secondary clarifier, and effluent
polishing pond. Chlorinated effluent is
discharged to San Pablo Bay. Sludge is
removed to a sludge thickener, digester,
and sludge drying beds.
0.088 Major units include primary sedimenta-
(2.0) tion tanks, trickling filter, secondary
sedimentation tank, and a chlorine con-
tact pond. Effluent is discharged to
San Pablo Bay. Sludge is removed to a
thickener, digester, and sludge drying
beds.
AS 0.105 Major units include a primary sedimenta-
(2.4) tion tank, activated sludge tank, and
secondary tank. Chlorinated effluent
is discharged to the Pacific Ocean.
Sludge is removed to thickener, digest-
er, and sludge drying beds.
\J AS s Activated sludge;
TF « Trickling filter.
(continued)
18
-------
TABLE 1 (continued)
Agency
Design
Flow
m3/s
Description
City of
Millbrae
City of Grass
Valley
West Contra
Costa S. D.
Oro Loma S. D.
City of Palo
Alto
County of
Sacramento
Cordova Plant
I/ AS = Activated sludge; TF
AS 0.131 Treatment plant includes primary sedi-
(3.0) mentation tank, activated sludge tanks,
final clarifiers, and a chlorine con-
tact tank. Effluent is discharged to
San Francisco Bay. Sludge is removed to
thickener, digesters, and centrifuges.
TF 0.057 Treatment plant includes a primary
(1.3) , clarifier, trickling filters, chlorine
contact tank, and effluent polishing
ponds. Effluent is discharged to Wolfe
Creek. Sludge is removed to digesters
and sludge lagoons/drying beds.
AS 0.548 Treatment plant includes primary sedi-
(12.5) mentation tanks, trickling filter,
activated sludge tanks, secondary clar-
ifier, and chlorine contact chamber.
Effluent is discharged to San Pablo
Bay. Sludge is removed to a thickener,
digester, and drying beds.
AS 0.876 Treatment plant includes a primary set-
(12.0) tling tank, activated sludge tanks,
final settling tank, and a chlorination
tank. Effluent is discharged to San
Francisco Bay. Sludge is removed to a
thickener, digester, settling tank,
filter, and an incinerator.
AS 1.533. Major units include primary sedimenta-
(35.0) tion tanks, activated sludge tanks,
final clarifiers, and chlorine contact
tank. Effluent is discharged to San
Francisco Bay. Sludge is removed to
sludge thickeners, centrifuges, and
solids incinerators.
AS 0.118 Erocesses include primary sedimentation
(2.7) and oxidation by activated sludge. Raw
primary and waste activated sludge is
pumped into the county's central plant
system. Chlorinated secondary effluent
passes through a series of earthen ponds
and is discharged to the American River.
Trickling filter.
(continued)
19
-------
TABLE 1 (continued)
Agency Type-
County of TF
Sacramento
S. D. No. 6
Plant
Northeast AS
Plant
Meadowview TF
Plant
Arden Plant AS
Design
Flow
m3/s
(mgd)
0.088
(2.0)
0.920
(21.0)
0.110
(2.5)
0.438
(10.0)
Description
Features of the plant include primary
clarifiers, primary and secondary trick-
ling filters, secondary clarifiers,
sludge digesters, and chlorination
facilities,. Sludge is exported to the
county's Northeast plant. Effluent is
discharged to the Sacramento River via
a drainage canal.
Unit processes include primary sedimen-
tation, oxidation by activated sludge,
anaerobic digestion, and chlorination.
Effluent is discharged to the American
River.
Processes include primary sedimentation,
trickling filtration, final settling,
and effluent chlorination. Sludge is
pumped into the Sacramento City main
system. Effluent is discharged to the
Sacramento River .
Major units of the plant include acti-
vated sludge basins and secondary clari-
fiers. Secondary sludge is exported to
the Sacramento City main plant via force
main. Chlorinated effluent is discharged
to the American River.
I/ AS » Activated sludge; TF = Trickling filter.
20
-------
TABLE 2. WASTEWATER FLOW
Base Year 1975
Agency
(Systems with 2
years of flow
reduction)
Plant De-
sign Flow
m3/s (mgd)
3
Wastewater Flow m /s (mgd)
Base
Year
1975
1st Year
Reduction
1976
Percent
Change
2nd Year
Reduction
1977
Percent
Change
S.D. #1 of
Marin County
San Rafael S.D.
Las Gallinas
Valley S.D.
Novato S.D.
Novato Plant
Novato S.D.
Ignacio Plant
East Bay M.U.D.
S.D. #1
Camel S.D.
City of
Millbrae
County of
Sacramento
Arden Plant
City of
Grass Valley
0.206
(4.7)
0.219
(5.0)
0.131
(3.0)
0.131
(3.0)
0.088
(2.0)
Sewer
System
Only
0.105
(2.4)
0.131
(3.0)
0.438
(10.0)
0.057
(1.3)
0.276
(6.3)
0.180
(4.10)
0.109
(2.48)
0.127
(2.90)
0.052
(1.18)
3.360
(76.6)
0.092
(2.09)
0.096
(2.25)
0.267
(6.1)
0.067
(1.53)
0.184
(4.2)
0.155
(3.53)
0.086
(1.97)
0.111
(2.54.X
0.046
(1.04)
3.019
(68.9)
0.087
(1.98)
0.084
(1.91)
0.250
(5.7)
0.043
(0.99)
-33
-14
-21
-12
-12
-10
-5
-15
-7
-35
0.131
(3.0)
0.092
(2.11)
0.040
(0.91)
0.084
(1.91)
0.034
(0.78)
2.751
(62.8)
0.047
(1.08)
0.071
(1.61)
0.215
(4.9)
0.036
(0.83)
-52
-49
-63
-34
-34
-18
-48
-28
-16
-46
(continued)
21
-------
TABLE 2 (continued)
Base Year 1976
Agency
(Systems with 2
years of flow
reduction)
Plant De-
sign Flow
m Is (mgd)
Base
Year
1976
Wastewatei
1st Year
Reduction
1977
3
: Flow m
Percent
Change
Is (mgd)
2nd Year
Reduction
1977
Percent
Change
West Contra
Costa S.D.
Oro Loma S.D.
City of
Palo Alto
County of
Sacramento
Cordova Plant
S.D. #6 Plant
Northeast
Plant
Meadowview
Plant
City of
Imperial Beach
0.548
(12.5)
0.876
(20.0)
1.533
(35.0)
0.118
(2.7)
0.088
(2.0)
0.920
(21.0)
0.110
(2.5)
Sewer
System
Only
0.311
(7.1)
0.556
(12.7)
1.244
(28.4)
0.097
(2.21)
0.087
(2.0)
0.835
(19.06)
0.059
(1.35)
0.092
(2.11)
0.228
(5.2)
0.394
(9.0)
0.986
(22.5)
0.077
(1.75)
0.079
(1.8)
0.691
(15.78)
0.050
(1.15)
0.084
(1.91)
-27
-29
-21
-21
-10
-17
-15
-10
• No
Second
Year
Flow
Reduction
-
Average
-17
-39
22
-------
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*
§
-------
TABLE 13. PROBLEMS IN SEWER SYSTEMS DURING
PERIODS OF REDUCED WASTEWATER FLOW
Agency
Problem
Action Taken
S.D. #1 of Marin County
San Rafael S.D.
Las Gallinas Valley
S.D.
East Bay MUD S.D. #1
City of Millbrae
Carmel S.D.
City of Grass Valley
Novato S.D.
Ignacio System
Novato System
West Contra Costa S.D.
Oro Loma S.D.
City of Palo Alto
County of Sacramento
Cordova System
S.D. #6 System
Northeast System
Arden System
Meadowview System
Slight Odor
Odor
Odor
Odor
Solids settling
Solids settling
Solids settling
None
None
None
None
None
None
None
None
None
None
Applied hydrogen
peroxide at lift
stations
Applied hydrogen
peroxide at lift
stations
Applied chlorine
dioxide
Applied more sodium
hypochlorite than
usual
Hauled water with
tank truck and flushed
lines
Cleaned lines more
often
Cleaned lines more
often
33
-------
TABLE 14. PROBLEMS IN TREATMENT PLANTS DURING
PERIODS OF REDUCED WASTEWATER FLOW
Agency
Problem
Action
S.D. $1 of Marin County
San Rafael S.D.
Las Gallinas Valley S.D.
City of Millbrae
Slight odor
problem at sludge
thickener.
Odor
Large load of
grit after first
heavy rainfall.
Sludge draw-off
at primary clari-
fiers clogged due
to excessive grit.
Sulfur bacteria
grew on rock media
and clogged and
ponded trickling
filter. Sulfur
also caused odor.
Ponding of bio-
filter caused
efficiency of
final clarifier
to go down.
Septic influent
caused sludge
thickener to
receive septic
sludge.
Odor in wet well.
Bulking in clari-
fiers due to
excessive growth
of, filamentous
bacteria.
(continued)
34
Added chlorine to
return sludge line.
Added hydrogen
peroxide and more
chlorine at primary
clarifier.
Removed grit.
Stepped up pumping
time.
Added chlorine to
kill sulfur
bacteria.
Added alum to in-
crease clarifier
efficiency.
Added more chlorine
at sludge thickener.
Prechlorination.
Used more coagulants.
Used more post-
chlorination. Recycled
water from clarifiers
to headworks. Changed
mean cell residence time
in aeration tanks.
-------
TABLE 14 (continued)
Agency
Problem
Action
Camel S.D.
Novato S.D.
Ignacio Plant
Novato Plant
West Contra Costa S.D.
City of Palo Alto
More filamentous
bacteria growth
than usual in
aeration tanks.
None
Odor in primary
and secondary
clarifiers.
Large grit load
after first heavy
rain clogged
sludge lines and
clarifier mech-
anisms . Could
not maintain good
control with instru-
mentation at low
flows.
Slight bulking of
secondary clari-
fier caused by
filamentous bac-
teria.
Chlorinated return
activated sludge and
reduced.mean cell
residence time.
Prechlorination.
Recirculated primary
effluent to headworks.
Dewatered clarifier
and pressure-hosed
off the silt.
Instruments for
chlorination, dechlori-
nation, and pH controls
set at minimum values
which caused over-
application.
Chlorinated return
activated sludge.
Oro Loma S.D.
City of Grass Valley
Sacramento County
Cordova Plant
S.D. #6 Plant
Northeast Plant
Arden Plant
Meadowview Plant
None
None
None
None
None
None
None
35
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SECTION 5
WATER CONSERVATION BENEFITS
In order to answer the question "Is conservation of indoor water use worth-
while?", the positive and negative effects of indoor water conservation,
i.e., its primary benefits and primary costs, must be analyzed in
perspective. This can be done by choosing conditions for analysis to
represent what could be expected in the future on a statewide basis if indoor
water conservation measures were taken. One of the major items in this
analysis is to estimate the primary benefits of water conservation.
Benefits resulting from savings in water, energy, and wastewater facilities
costs will be examined in this section. The approach used to make the bene-
fits analysis are as follows:
o Select conditions for analysis. This involves choosing a period of
analysis and two cases for which new sewer systems and secondary treatment
plants are commonly constructed to serve new population growth.
• Identify how indoor water use can be reduced. Various scenarios of
water conservation measures are. examined to determine the amounts of
indoor water use reduction at different levels of water conservation
efforts ranging from minimal to potential.
° Establish the relationship among indoor water use reduction, design,
flow, average flow, and average dry weather flow (ADWF). This is
necessary so that the indoor water use (assumed as being similar to the
ADWP) can be expressed in terms of design flow and average flow. Design
and average flows are used to estimate cost savings (benefits) in the
wastewater facilities due to wastewater flow reductions.
o Select levels of indoor water use reduction and sizes of wastewater .
collection and treatment systems. Benefits are analyzed for small,
medium, and large systems at different levels of indoor water use
reduction.
» Determine amount of water savings. This is done by applying the
selected levels of indoor water use reductions to the wastewater systems.
e Determine amount of water supply benefits. The amount of water saved
is treated as the amount of water that does not need to be supplied in the
future. The cost of supplying that water which otherwise would most
likely be incurred in the absence of water savings is used as a measure of
water supply benefits.
46
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0 Determine energy benefits. Two types of energy savings are
considered. One is the savings due to less use of hot water and the other
is the savings that results because less water needs to be treated and
conveyed in the local water supply distribution systems.
° Determine cost savings (benefits) in wastewater collection and
treatment systems. The extent to which future construction of these
systems can be sized smaller and construction costs saved as well as
savings in the operation and maintenance cost due to reductions in
wastewater flow are examined.
0 Determine total benefits. This is the total of all the benefits
described above. The benefits are measured in terms of annual equivalent
benefits. For brevity, they will be referred to as "annual benefits"
hereafter. An interest rate of 7% and a service life of 25 years for
secondary treatment plants and 50 years for sewer systems are used (3).
A 20-year period of analysis, from 1980 to 2000, was selected to assess the
benefits and costs of. indoor water conservation. It also represents the
period for which new wastewater facilities are being constructed to serve new
growth and sized for capacity. , During a 20-year period, the expected average
statewide population growth is about 26% (4). For this period, two cases
will be examined.
Under Case I conditions, existing sewer systems are enlarged to cover a
larger service area and existing treatment plants are expanded to receive a
larger flow due to new population growth. Thus, water conservation induced ,
reductions in wastewater flows from both existing and new building construc-
tions affect the sizing of new wastewater facilities and are therefore
considered. The proportion of flow in a wastewater system at the end of the
20-year period is:
Flow from existing construction _
1.26
= 80%
Flow from new construction _
J)-26 = 20%
1.26
The conceptual reduction in the new system capacity, when wastewater flows
are decreased due to indoor water use reductions in existing and new
buildings constructions is depicted in Figure 6.
Under Case II conditions, new sewer systems and treatments are constructed to
serve the new population growth independent of the existing facilities.
Thus, water conservation induced reductions in wastewater flows from new
building construction only affect the sizing of new wastewater facilities and
are therefore considered. The conceptual reduction in the new system capa-
city is also depicted in Figure 6.
47
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Case I — New Wastewater Facilities
Constructed as Additions to Existing Facilities
Case I will be examined first. Some discussions in Case I would be applica-
ble to Case II but will not be always repeated.
Ways to Achieve Indoor Water Use Reduction
More than half of the residential water use in California occurs indoors (5).
Figure 7 shows that 74% is used in the bathroom, 22% is used for washing
dishes and laundry, and 4% is used for cooking. The greatest potential for
water and energy savings occurs in the bathroom where three-fourths of the
water used indoors occurs. Conventional tank toilets use about 18.9 litres
(5 gallons) of water (6) to rinse the bowl, evacuate the waste, and provide a
water trap to prevent the sewer gas from entering the bowl. Most convention-
al toilets use more water than is needed to perform these functions. The
amount of water that is flushed away can be reduced by placing plastic
bottles or "water dams" in the toilet tank or by other modifications. On
January 1, 1978, a State law (see Appendix A) went into effect that requires
low-flush toilets using no more than 13.2 litres (3.5 gallons) per flush in
new buildings.
The conventional showerheads deliver up to 45.4 1/min (12 gal/min) (6), which
is more water than needed. While the amount of flow desired is variable,
depending on personal taste and habits, a survey of more than 5,500 house-
holds in the Metropolitan San Diego area in 1977 showed low-flow showers had
general consumer acceptance (7). The flow through the showerhead can be
controlled by a low-flow showerhead or installing a flow restrictor. In late
1977, the California Energy Commission adopted efficiency standards (see
Appendix B) for new showerheads and faucets sold in California after
January 1, 1979. The standards set a maximum flow of 10.4 - 11.4 1/min
(2.75 - 3.00 gal/min) for showerheads depending upon pressure and 10.4 1/min
(2.75 gal/min) for faucets.
The scenarios of water conservation measures to reduce the amount of indoor
water use were developed and are shown in Table 16 for three levels of water
conservation efforts — potential, moderate, and minimal. Low-flow toilets,
showers, and faucets are considered to be the most important reduction be-
cause they are now mandatory in California. These fixtures also provide for
most of the water savings. More savings could be achieved by the use of low
; water-using dish and clothes washers, pressure-reducing valves, and hot water
insulation. These measures need'to be undertaken-voluntarily by the consum-
ers since they are not mandatory and would require public education and
promotional campaigns.
The procedures used in developing Table 16 are as follows:
e Identified water conservation measures to be taken.
• Identified the type of building construction in which indoor water use'
reductions would be made.
48
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0 Identified the potential savings for each water conservation measure per
household. '
° Selected the percent of households installing the various water conser-
vation measures for the three scenarios. A 100% installation rate was
used for mandatory measures in new building constructions. The installa-
tion rates for the nonmandatory items for new and existing buildings were
selected on the basis of judgment, considering various factors including
the period of analysis, the expected trend of appliance manufacturers
employing water and energy saving features, and the expected replacement
rate of appliances and plumbing fixtures in homes. •
0 The expected indoor water use reductions take into account•a mix of
.existing and new building construction in the community.
0 For each scenario, the,expected reductions in hot water and total water
use were estimated. The scenarios do not include indoor use reduction by
such means as correcting leaky faucets or shutting off the faucets when
brushing teeth or shaving. Also, advanced technology such as graywater
reuse systems, air-assisted showers, and vacuum sewer lines were not
included. However, the major conventional water conservation measures,
under the current state-of-the-art, are considered as being in the
scenarios for the purposes of this study.
Table 16 shows that:
The reduction in indoor water use will be as follows:
Scenario
1
2
3
Degree 6f
Water Conservation
Effort
Potential
Moderate
Minimal
Percent Reduction
in Indoor Water Use
35
25
10
Beyond 20% total reduction in community indoor water use, most of the
reductions are caused by retrofitting and replacement of fixtures and
appliances in existing construction (see Figure 8).
The approximate hot water savings will be as follows:
Percent Reduction
in Indoor Water Use
10 - 20
30
35
Hot Water Savings as—
Percentage of Total Water Savings
80
70
60
_!/ The amount of hot water savings from Table 16 was expressed as a per-
centage of total savings and plotted against the percent reduction in
indoor water use. A curve drawn for the plotted points provided these
VSlllGS •
49
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Relationship Among Flows
In order to assess the benefits and costs, the relationship among design
flow, average flow, and average dry weather flow (ADWF) for wastewater facil-
ities must be established. This is necessary because indoor water use
(assumed as being similar to the ADWF) can be expressed in terms of average
flow and design flow. Average and design flows are used to estimate cost
savings (benefits) in wastewater facilities due to water conservation induced
reductions in wastewater flow. The following relationship is used:
0 Average flow
0 Design flow
0 ADWF
0 Indoor use s ADWF
at 100%
at 125%
at 75%
Plant capacities that are representative of small, medium, and large .treat-
ment plants are selected as follows:
Small
0 Medium
Large
Metric Unit
<_ 0.22 m3/s: use 0.04
and 0.11 m3/s
0.22 - 0.88 m3/s: use
0.55 m3/s
> 0.88 m3/s: use 1.10
and 2.19 m3/s
English Unit
_<_ 5 mgd: use 0.8 -and
2.5 mgd
5.1 - 20 mgd: use
12,5 mgd
> 20 mgd: use 25 and
50 mgd
These systems will be analyzed at indoor water use reductions of 10%, 20%,
30%, and 35%.
Amount of Water Savings
By applying the indoor water use reduction in existing and new building con-
struction and the flow relationships established, the amount of water savings
for various sizes of wastewater systems over a 20-year period can also be
determined by using the equation below (see also Table 17):
50
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Total water saved =
(% reduction in indoor use )
(of new building )
(construction )
+ (% reduction in indoor use )
(of existing building )
(construction )
(Average ADWF new building )
(construction over a 20-year)
(period )
(ADWF existing building
(construction
Where : ADWF = Average dry weather flow •
Average ADWF of new building construction over 20-year period
ADWF new building construction
~ 2
ADWF existing building construction =
ADWF new building construction over 20-year period
26% population growth factor
Hot water saved =
(Hot water savings as)
(percentage of total )
(water savings )
(Total water saved)
The subtle differences in the percent reductions in indoor water use applied
in the above equations and the percent reductions in community indoor water
use developed in Table 16 and shown in Figure 8 bear explanation. Let us use
an example of 20% overall reduction of indoor water use,in the community with
a. housing mix of existing and new building construction. Thirteen percent of
this reduction would be caused by existing buildings and 7% by new buildings,
which is a measure of relative reductions .in domestic wastewater flow
contribution. However, these percentages cannot be directly applied to the
above equation for determining the "total water saved". They must first be
translated into percent indoor water use reduction for each of the new and
existing building constructions separately before wastewater flows become
mixed., This can be done by removing the effect of 20%/80% housing mix that
was used to determine the 7% and 13% reductions in this example. Therefore,
% reduction of
indoor use in
new buildings
% reduction of •
indoor use in
existing buildings
% reduction in overall community
indoor water use caused by new
buildings
% of new housing in community
of reduction in overall community
indoor water use caused by exist-
ing buildings
% of existing housing
in community
= 7% = 35%
20%
= 13% = 16%.
80%
51
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using the above procedures, the percent reduction of indoor use in the new
building construction and in the existing building construction at various
levels of overall community indoor water use reductions is as follows:
Percent Reduction in Overall
Community Indoor Water Use
(Values from Figure 8)
Percent Reduction in
Indoor Water Use
Caused by Caused by
Existing New
In Existing Building
Col 2 -r 80% Housing
In New Building
Col 3 t 20% Housing
Total
10
20
30
35
Buildings
3.8
13.0
22.5
27.2
Buildings
6.2
7.0
7.5
7.8
Mix
4.8
16.3
28.1
34.0
Mix
31.0
35.0
37.5
39.0
Water Supply Benefits
The amount of water saved is treated as the amount of water that does not
need to be supplied in the future. The price users are willing to pay for
water which otherwise would be needed in the absence of water conservation is
measured as the value of water savings. The "willingness to pay" is a diffi-
cult value to determine because it is really not known until people are put
to the test to pay a particular price. For instance, gasoline prices have
risen dramatically in recent years. As the energy crunch continues, people
might say that they would be willing to pay $2 or even $4 for a gallon of
gas. But no one is certain how much people will actually pay until they are
put to the test of doing so. One measure is the price users are willing to
pay for water that is equal to the least costly alternative of developing the
next increment of California's State Water Project, which is on the order of
$142/dam^ ($175/ac—ftXi/on a statewide basis. The water supply benefits
are shown in Table 18 and are determined by multiplying the amount of total
water saved from Table 17 times the price of water.
Energy Benefits
Two types of energy benefits were determined. The primary benefits were due
to reduction in hot water use, thus requiring less heating energy, and local
system energy benefits relating to reduction of treatment and delivery of
water supply. The procedures and calculations for determining energy bene-
fits are described below:
I/ Unpublished data by California Department of Water Resources, Division of
Planning, Statewide Planning Branch, 1980.
52
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Water Heating Benefits. The benefits were computed by determining the
energy required to heat the amount of water saved and then converting this
energy into equivalent barrels of oil valued at $28 per barrel (bbl). The
general equation for the energy benefits =
x (amount of hot water saved) x ($28/bbl)
Where: kL = 26.1 bbl/dam3 (32.2 bbl/ac-ft)
(a detailed explanation for derivation of
contained in Appendix C).
s
The values of annual water heating energy savings are shown in Table 19.
Local Systems Benefits. The reduction in energy required by local systems
to treat and convey water supplied to the homes due to water conservation was
determined and converted into equivalent barrels of oil.
The general equation for this energy benefit =
(k2) (amount of total water saved) ($28/bbl)
Where: k2 = 0.32 bbl/dam3 (0.39 bbl/ac-ft)
(a detailed explanation of the derivation for
k2 is contained in Appendix C).
The values of annual energy savings in local systems are al-so shown in
Table 19.
Treatment Plant Cost Savings
Capital Cost Savings. The treatment plant process, units that could be
reduced in size with flow reductions are those based on hydraulic loading and
include headworks , primary and secondary clarifiers, effluent chlorination
facilities, and effluent outfall (10). It is stressed that the reduction in
sewage treatment plant (STP) design flow as a result of water conservation
was applied to the above process units but not to the biological process
units of secondary treatment. Of the agencies surveyed, two that experienced
excessive growth of filamentous bacteria decreased the mean cell residence
time in the aeration tanks to rectify the problem. This seems to suggest
that some reduction in the size of the tanks may be possible. However, no
attempt was made to reduce the size of the aeration tanks because ,1) there is
no certainty that future water conservation during normal water years would
decrease the mass loading of organic constituents as was experienced during
the drought years, and 2) a more conservative analysis of water conservation
benefits results by not reducing the aeration tanks. The percent reduction
in the STP design flow at various levels of reductions in indoor water use
can be determined from the following equation:
Percent Reduction
in STP Design =
Flow
7% Reduction \ /ADWF \ /% ReductionX /ADWF \
/ Indoor Use JxlNew H- / Indoor Use \ x /Exist. \
I New Building/ Uldg. Exist. Bldg.l 'iBldg.
\Constr. / \Constr.I \Constr. / \Constr./.
.125
STP Design Flow
New Bldg. Constr.
53
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where: STP Design Flow = ADWF
New Bldg. Constr. New Bldg. Constr. x 125
75
ADWF Exist.
Bldg. Constr.
Percent Reduction
in STP Design
Flow
ADWF New Bldg. Constr.
0.26 Population Growth Factor
125
-j^ x ADWF New Bldg. Constr.I
x ADWF New Bldg. Constr.j
% Reduction Indoor
Use Existing Bldg. Constr.
k0.26 Population Growth
Factor
x
% Reduction
Indoor Use
New Bldg.
\Constr. I
% Reduction
Indoor Use
New Bldg. Constr.
% Reduction Indoor
Use Exist. Bldg.
Constr.
0.26 Population Growth Factor
By using the percent reductions in indoor water use in the new and existing
building constructions previously determined, the above equation gives the
following reductions in the STP design flow:
Percent Reduction
in Overall Community
Indoor Use
10
20
30
35
Percent Reduction
in Indoor Use
New Bldg. Exist. Bldg.
Constr. Constr.
31.0
35.0
37.5
39.0
4.8
16.3
28.1
34.0
Percent Reduction—
in STP Design Flow
(From Above Equation)
49.5
97.7
100
100
The capital cost of a secondary treatment can be expressed as a function of
design flow, (jO-89 (9). The percent reduction in the cost then can be
determined by applying the function qO.89 to t^e percent reduction in
the design flow. For example,
Let design Q = 10. Then (10)°-89 = 7.76
At a. reduction in overall community indoor water use of 20%, design
Qreduction = (10) (97.7%) =9.77.
Then, design Q0-89 = (9.77)0-89 = 7.60
' 6 deduction
% reduction in capital cost
7-60 = 97.9%
7.76
if Values only apply to plant process units affected by hydraulic load.
Reduction cannot exceed 100%
54
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However, the entire plant cannot be reduced in size because all the process
units are not sized on wastewater flow rate. As discussed earlier, the
process units which are affected by hydraulic load are headworks, primary and
secondary clarifiers, effluent chlorination facilities, and effluent
outfall.
These units constitute about 22%— of the total secondary treatment plant
costs. The reduction in capital cost in this illustration amounts to (97.9%)
(22%) = 21.5%. Using this procedure, the percent reduction in the capital
cost increases linearly to a maximum of 22% at 21% to 35% reduction in indoor
use (see Table 20 and Figure 9).
The capital cost of a secondary treatment plant can be estimated by using the
simplified procedure suggested in EPA Report MCD-37 (9). The equation for
the cost is expressed as:
Cost ($1,000) = kQ°-89
where: k = constant
Q = plant capacity
Metric Unit
40 806
n
English Unit
2,523
in mgd
The annual capital cost savings for secondary treatment plants are shown in
Table 21 by multiplying the values obtained by using the above equation times
the percent reduction in treatment plant capital cost from Table 20.
O&M Cost Savings. As discussed earlier, cost data from nine secondary
treatment plants w.ere evaluated. The percent change in the O&M costs varied
in a "scatter shot" pattern from -5% to about +4% (see Figure 5). Because of
this variance and because the average difference amounted to only -0.3%, no
attempt was made to adjust the O&M costs.
Sewer System Cost Savings
Capital Cost Savings. Because the sewer design flow is directly propor-
tional to the ADWF (similar to indoor water use), the percent reduction in
the sewer design flow is the.same as the percent reduction in indoor water
use. The percent reduction in indoor water use determined in the analysis of
the treatment plant capital cost savings also applies to the sewer system.
However, the sewer systems that serve the new and existing buildings must be
examined separately because they are essentially in parallel operation. For
example, the effects of a 30% overall community reduction in indoor water use
are as follows:
_!_/ Based on information from EPA Report MCD-37, "Construction Costs for
Municipal Waste Water Treatment Plants: 1973-1977" January 1978 (9) and
represents an average of 25% for activated sludge plants and 20% for
trickling filter plants.
55
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New sewer system:
° Percent reduction in indoor use = 37.5%
• Reduction affects capital and O&M costs.
Existing sewer system:
« Percent reduction in indoor use = 28.1%
0 Reduction affects O&M costs only.
The determination of the sewer design flow depends on many factors such as
climate, population growth, domestic, commercial, institutional, and indus-
trial discharges, topography, and the judgment pf the design engineers. In
assessing any water conservation induced reduction in pipe sizes, it is pru-
dent then to work within a range of sewer design flows rather one specific
^design flow for a given pipe size. Therefore, the range of design flows for
various pipe sizes shown in EPA Report MCD-38 (11) was used. The percent re-
ductions in the sewer design flow as a result of wastewater. flow reductions
were used to determine the new sewer design flows and the new pipe size
selections. A sample calculation is shown in Table 22. Using this proce-
dure, the complete new pipe size selections are shown in Table 23. It was
found that:
° For sewer systems requiring a maximum pipe size of 137.2 cm
(54 inches), pipes can be selected one size smaller at 10%, 20%, 30%, and
35% reductions in overall community indoor water use.
• For sewer systems requiring a maximum pipe size of 152.4 cm
(60 inches) to 213.4 cm (84 inches), pipes can be selected one size
smaller at 10% reduction and two sizes smaller at 20%, 30%, and 35%
reductions.
In order to estimate the capital cost savings for the sewer lines, it was
necessary to determine the capital cost with and without flow reduction and
assume the following conditions for California.
0 Average occupants per home = 2.75 (12)
I/
Typical residential frontage = 18.3 m (60 ft)—
Length of sewer'collector pipe = 18.3 m =6.7 m/capita
2.75 occupants/home "(21.8 ft/capita)
Length of sewer interceptor =0.3 m/4.9 m of collector pipe
(1 ft/16 ft) from EPA Report MCD-38 (11)
= 0.3m x 6 • 7 m = 0.4 m per capita
4.9 m
I/ Typical residential frontage is on the order ,of 18.3 m (60 ft) based on
information from the Sacramento County Assessor's Office.
56
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0 Total sewer pipe length required = 6.7 + 0.4 =7.1 m/capita
(23 ft/capita)
/: ~
0 Average indoor residential use = 3.3 x 10 m /s per capita
(75 gal/capita/day). From.references
. (13) and (14).
A sample calculation for the sewer pipe capital cost without flow reduction
and with flow reduction is shown in Tables 24 and 25, respectively. Savings
in capital cost of sewer pipes are:
Equivalent Annual Cost w/o Indoor Use Reduction = $1,470,000
Equivalent Annual Cost w/Indoor Use Reduction at 10%, 20%, 30%,
and 35% = $1,265,000
Cost Savings = $1,470,000 - 1,265,000 = $205,000/yr.
Using this procedure, the capital cost of the sewer lines and the cost
savings for the various size systems are shown in Table 26.
O&M Cost Savings. The annual O&M cost for sewer systems can be estimated
by using the procedure suggested in EPA report MCD-39 (15). For a sewer sys-
tem that is integrated with the operation of the treatment plant, the O&M
cost is shown at $6.35 per capita. The cost adjusted to 1979 dollars = $7.05
per capita. The population served is estimated by choosing a unit indoor use
of 3/29 x 10~6 m3/s per capita (75 gal/capita/day).
The savings in sewer O&M costs must be examined separately for existing arid
new sewer systems. The percent reductions in O&M costs based on actual
survey data previously discussed are obtained from Figure 2 at various levels
of wastewater flow reductions and are shown in Table 27. The percent
reductions are applied to the annual O&M cost, and the annual dollar savings
for new and existing sewer savings are shown in Tables 28 and 29,
respectively, and combined in Table 30.
Summary' of Water Conservation Benefits, Case I
v • ..
Case I water conservation benefits consisting of energy and water supply
benefits and treatment plant and sewer system cost savings are summarized in
Tables 31 through 34 at 10%, 20%, 30%, and 35% reductions in indoor water
use. An example of the benefits for a corresponding treatment plant size .of
0.55 m^/s (12.5 mgd) is depicted in Figure 10. It is evident that the
major benefits come from energy savings.
Case II - New Wastewater Facilities
Constructed Independent of Existing Facilities
Case II will be examined in this section in a manner similar to Case I. Some
discussions in Case I will be applicable to Case II but will not be repeated
in all instances. Case II is a condition whereby new wastewater facilities
serve new population growth and operate independent of existing facilities.
Thus, Case II considers wastewater flows from new building construction only.
57
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Ways to Achieve Indoor Water Use Reduction
From the scenarios of water conservation measures examined for Case I, the
expected percent reductions in indoor water use pertaining to new building
construction only are shown in Table 35 and summarized as follows:
Scenario
Degree of
Water Conservation
Effort
Percent Reduction
in Indoor Water Use
Hot Water Savings—
as Percentage of
Total Water Savings
1
2
3
Potential
Moderate
Minimal
40
35
30
55
60
55
Relationship Among Flows
The flow relationships established for Case I will be applicable to Case II.
The small, medium, and large wastewater facilities will be analyzed at indoor
water use reductions of 30%, 35%, and 40%. The relationship between indoor
water use reductions and treatment plant design flows are as follows:
0 30% reduction in indoor use = 30% x '->'•> x design flow
, 125%
- 18% of plant design flow
• 35% reduction in indoor use = 21% of plant design flow
8 40% reduction in indoor use = 24% of. plant design flow.
Amount of Water Savings
Based on the indoor water use reductions and flow relationships previously
discussed, the amount of total water savings at 30%, 35%, and 40% indoor use
reductions were estimated (see Table 36).
Water Supply Benefits
The water supply benefits are determined in the same manner as in Case I and
are shown in Table 37.
Energy Benefits
The water heating and local systems energy benefits are determined in the
same way as in Case I. The only .difference is the amount of water savings.
The annual benefits are shown in Table 38.
I/ From Table 35.
58
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Treatment Plant Cost Savings
The capital cost of secondary treatment plants can be estimated by using the
simplified procedure suggested in EPA Report MCD-37 (9). The equation for
the cost is expressed as:
Cost ($1000) = kQ°-89
where:
k = constant =
Q = plant capacity =
Metric Unit
40 806
n
English Unit
2,523
in mgd
By applying this equation at various levels of indoor use reduction, the
treatment plant capital costs are decreased linearly to 36.5% at 40% reduc-
tion in indoor use.
The treatment plant process units that could be reduced in size with flow
reductions are those based on hydraulic loading and include (10):
° Headworks •
0 Primary and secondary clarifiers
0 Effluent chlorination facilities
° Effluent outfall.
These units constitute about 22%— of the total'treatment plant costs.
Therefore, the capital cost savings increases linearly to (36.5%) x (22%) =
8% at 40% reduction in indoor use (see Figure 11). Using the cost reduction
shown in Figure 11, the savings in capital costs at various levels of flow
reduction are' shown on Table 39.
As discussed earlier, cost data from nine secondary treatment plants were
evaluated. The percent change in the O&M costs varied in a "scatter shot"
pattern from -5% to about +4% (see Figure 5). Because of this variance and
because the average difference amounted to only -0.3%, no attempt was made to
adjust the O&M costs.
_!_/ Based on information from EPA Report MCD-37, "Construction Costs for
Municipal Waste Water Treatment Plants: 1973-1.977" January 1978 (9) and
represents an average.of 25% for activated sludge plants and 20% for
trickling filter plants.
59
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Sewer System Cost Savings
Capital Cost Savings. The sizing of collector and interceptor sewers was
assessed in a way similar to Case I. It was found that the reductions in
pipe size selections were essentially the same as that for the new sewer
system in Case I. The capital cost of the sewer lines and the cost savings
for the various size systems were determined in the same manner as in Case I
and are shown in Table 40. The average savings for -the capital cost of the
sewer lines at all levels of indoor water use reductions is about 7%.
O&M Cost Savings. The annual O&M cost for sewer systems can be estimated
by using the procedure suggested in EPA Report MCD-39 (15). For a sewer
system that is integrated with the operation of the treatment plant, the O&M
cost is shown at $6.35 per capita. The cost adjusted to 1979 dollars = $7.05
per capita. The population served is estimated by choosing a unit indoor
use of 3/ 29xlO~6 nrVs per capita (75 gal/capita/day). The percent
reductions in O&M cost based on actual survey data previously discussed (see
Figure 2) are: ,
Percent Reduction In
Indoor Water Use
30
35
40
Percent Reduction In
Sewer O&M Cost
1.5
1.8
2.2
The annual cost savings in sewer O&M costs are shown in Table 41.
Summary of Water Conservation Benefits, Case II
Case II water conservation benefits consisting of energy and water supply
benefits and treatment plant and sewer system cost savings are summarized in
Tables 42 thru 44 at 30%, 35%, and 40% reductions in indoor use. An example
of the benefits for a 0.55 m3/s (12.5 mgd) treatment plant size are graphi-
cally depicted in Figure 12. It is evident that the major benefits come from
energy and sewer system cost savings. • • - •
60
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Flow from existing and new
buildings without water conservation
Water conservation induced
flow reduction from new
buildings only, Case H.-
o
_l
u.
£E
UJ
EXISTING SYSTEM CAPACITY
Water conservation induced
flow reduction from both
existing and new buildings
Case I
New facilities
sized for capacity
to serve new
population growth
without water
conservation-i
"— New facilities
sized for capacity
in Case n.
L- New facilities
sized for capacity
in Case I.
1980
2000
NEXT 20- YEAR PERIOD OF ANALYIS
Figure 6. Effect of wastewater flow reduction on new
wastewater system capacity.
61
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• •;?:::::• BATH 32%-.
::?:•••••..::::?: ':
COOKING 4%
SOURCE: Bulletin 198,"Water Conservation in California, May 1976,
California Department of Water Resources ( 5 )
Figure 7. Residential water use in California.
62
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FOOTNOTES FOR TABLE 16
I/ For the various scenarios, the expected reductions are determined by
~~ multiplying the reduction potential times percent of households
installing the measures times 80 percent for existing building construc-
tion and 20 percent for new building construction.
21 Percent of households installing water conservation measures.
3/ Measures generating hot water energy savings.
4/ Use volume of conventional toilets = 19.76 litres (5.22 gallons).
California Department of Water Resources (DWR) Bulletin 191, Appendix G
( 6 ). Low-flush toilets = 13.2 litres (3.5 gal) per flush (mandatory).
Savings -6.51 litres (1.72 gal) = 33 percent per flush.
19.76 litres (5.22 gal)
Toilet use ^ 42 percent of indoor use. Therefore, 33 percent times
42 percent equals 14 percent of indoor use saved by low-flush toilets.
5/ Average savings of common retrofit devices (toilet dams, bottles, and
~~ plastic bags) = 4.5 litres (1.2 gal) per flush. DWR Bulletin 191,
Appendix G ( 6 ) •
Savings = 4.5 litres (1.2 gal) =23 percent per flush.
19.76 litres (5.22 gal)
Toilet use = 42 percent of indoor use. Therefore, 23 percent times
42 percent equals 9.5 percent of indoor use saved by retrofitting
existing toilets.
6f Average flow of conventional showerheads at 310 kilopascals (45 psi)
~ equals 31.61 litres per minute (8.35 gpm). DWR Bulletin 191, Appen-
dix G ( 6 ). Flow of low-flow showerheads = 11.36 litres per minute
(3 gpm) (mandatory).
Savings = 20.25 litres/min (5.35 gal/min)
31.61 litres/min (8.35 gal/min)
= 64 percent per shower
Daily use per household based on data in DWR Bulletin 206 Appendix
( 8 ): Shower = 2.6 times
Bathtub = 1.8 times
Volume of shower use = 31.61 litres/min (8.35 gpm) x 6 min x 2.6
- 492 litres (130 gal)
Volume of tub use = 189 litres (50 gal) x 1.8 = 341 litres (90 gal)
Total equals 833 litres (220 gal)
Bathing use = 32% of indoor use. Therefore, shower savings
savings x 492 litres (130 gal) x 32% = 12% of indoor use
833 litres (220 gal)
(continued)
64%
64
-------
FOOTNOTES FOR TABLE 16 (continued)
TJ DWR Bulletin 198 ( 5 ).
%l Generates hot water savings because less water needs to be run through
the faucet before hot water begins to flow.
J3/ Assumes that all new machines manufactured in the next 20 years will,
employ a water saving feature. While not all households will own
washers, the assumption is that they will be using water saving
machines at the laundromat.
10/ Assumes that all dishwashers manufactured in the next!20 years will
employ a water saving feature. 24 percent of households own dish-
washers. DWR Bulletin 198 ( 5 ).
65
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— x
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TOTAL REDUCTION IN COMMUNITY INDOOR
WATER USE (PERCENT)
Figure 8. Reduction in indoor
water use, Case I.
66
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(continued)
67
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TABLE 18. WATER SUPPLY BENEFITS. CASE I
Treatment Plant
Design Flow
m3/s
(ragd)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
Annual
Levels
10%
30
100
500
1,000
1,995
Water Supply
of Indoor Use
(in $1,000)
20%
75
235
1,175
2,360
4,715
Benefits at Various
Reduction
30% 35%
120 140
275 440
1,860 2,205
2,730 4,420
7,460 8,835
70
-------
TABLE 19. ANNUAL ENERGY BENEFITS, CASE I (in $1,000)
Treatment
Plant Size
m3/s (mgd)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10'
(25)
2.19
(50)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
Water
Heating
At 10
132
411
2,056
4,116
8,232
At 20
312
972
4,852
9,718
19,437
Local
Systems
Percent Reduction in
+2
6
31
62
125
Percent Reduction
5
15
73
147
294
Total-/
Indoor Use
135
415
2,085
4,180
8,355 "
315
985
4,925
9,865
19,730
At 30 Percent Reduction
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
I/ Rounded to
431
1,345
6,714
the nearest $5,
7
23
116
000
(continued)
71
440
1,370
6,830
-------
TABLE 19 (continued)
Treatment
Plant Size
tn3/s (mgd)
1.10
(25)
2.19
(50)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
Water
Heating
13>448
26,897
At 35 Percent
437
1,366
6,900
13,658
27,317
Local '
Systems
233
465
Reduction
9
28
138
276
551
Total-/
13,680
27,360
445
1,395
7,040
13,935
27,870
_!/ Rounded to the nearest $5,000
72
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REDUCTION IN OVERALL COMMUNITY
INDOOR WATER USE
(PERCENT)
Figure 9. Percent reduction in treatment plant
capital cost, Case I.
74
-------
TABLE 21.
Treatment Equiv.
Plant Annual
Size Capital
in m /s Costi'
(mgd) (in $1,000)
0.04 280
(0.8)
0.11 660
(2.5)
0.55 2,460
(12.5)
1.10 5,110
(25)
2.19 9,470
(50)
Annual Capital
Cost Savings
For Treatment Plants (in $1,000)
Flow
Reduction = 10% 20%
Cost!/
Reduction = 11.8% 21.
35 60
80 140
290 530
605 1,100
1,115 2,035
30%
5% 22.0%
60
- 145
540
1,125 1,
2,085 2,
35%
22.0%
60
145
540
125
085
I/ Cost derived from the equation, cost = kQ , adjusted from national
average to California prices, adjusted to reflect 1979 dollars (EPA
cost index) with a 7% interest rate and 25 years of service life.
2/ From Table 20.
75
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TABLE 23. SMALLER SEWER PIPE SIZE SELECTION
DUE TO WASTEWATER FLOW REDUCTION, CASE I
Original Pipe
Diameter in
centimetres
(inches)
20.3
(8)
25.4
(10)
30.5
(12)
38.1
(15)
45.7
(18)
53.3
(21)
61.0
(24)
68.6
(27)
76.2
(30)
91.4
(36)
106.7
(42)
121.9
(48)
137.2
(54)
152.4
(60)
167.6
(66)
182.9
(72)
213.4
(84)
t,,»,.'i.j Pipe
New Pipe Diameter in centimetres (inches)
Percent Reduction in Overall ,«
Community Indoor Water Use
Percent Reduction in Sewer ^i
Design Flow
15*2
«• (6)
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76,2
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(54)
158,4
(60)
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76
108 « 7
, (4-2}
3.21*0?
^(48)
^m*f
f-> t„"
^ KffU
j*:v t«6> .
30
37,5
15*2.
|6>
2S,3
(S>
^S*4
OO!}
36*5
(£2)
3S.1
> > ^
4$?^^ /
l&fy^>
,152vC
> ,< {^
"i6T,
20.3
X'jWN
1 O I
25,4
(IS)
30*5
45.7
(18)
55*3
<2t)
61.0
O*)
6^*6
(2?)
76x2
(30)
91*4
<36)
106.7
{422
121«9
(48)
121*9
^4>C4E) •-
V \ ' *
13?. a- '
; ^50? t>
-" |5i*.4 *'
* C wO,? -^ x
•i >?•>¥ j«r >
i'fr/ wO-
^^'
Pipe selection 2 sizes smalle
77
-------
TABLE 24, SAMPLE CALCULATION FOR SEWER PIPE CAPITAL COST
WITHOUT REDUCTION IN INDOOR WATER USE, CASE I
1
Pipe Size
cm
(inches)
15.2
(6)
20.3
(8)
25.4
(10)
30.5
(12)
38.1
(15)
45.7
(18)
53.3
(21)
61.0
(24)
2
Percent—
of Total
Length
67.7
16.1
5.1
3.7
3.1
1.9
1.5
0.9
100.0
3
Length
of Pipe
m (feet)
94 920
(311,420)
22 570
(74,060)
7 150
(23,460)
5 190
(17,020)
4 350
(14,260)
2 660
(8,740)
2 100
(6,900)
1 260
(4,140)
140 200
(460,000)
4
21
Average-
Unit Cost
$/m
($/ft)
79
(24)
141
(43)
154
(47)
194
(59)
240
(73)
308
(94)
387
(118)
407
(124)
5
3/
Pipe— Cost Adjus
$1,000 Pipe
Col. 3 x $1,
Col. 4
7,470
3,180
1,100
1,000
1,040 ,
820
810
510
6 7
ted— Equivalent^
Cost Annual Cost
000 $1,000
15,930 20,340 1,470
NOTE: This sample calculation pertains to a corresponding treatment
plant size of 0.11 nrVs (2.5 mgd). For this size system, the following
applies: 2/
Pipe diameter required = 61 cm (24 inches)— g/
• Average Dry Weather Flow (ADWF) = 0.066 m3/s (1.5 mgd)—
• New population served by 0.11 m3/s (2.5 mgd) treatment plant =
20,000 people!/ "
• Total length of sewer pipe required = 140 200 metres (460,000 feet)
If From pipe size distribution for Sacramento County sewer system.
2[/ From EPA Report MCD - 38 (11).
3j National average cost in January 1978 dollars.
_4/ Adjusted to California construction cost index of 1.14 and updated
to 1979 EPA construction cost index of 1.12.
5J Seven percent interest and 50-year life.
6/ From flow relationship of des^fflow = iff'* 0.11*3/8 - 0.066m3/s(2.5mgd)
. ADWF 0.066m3/s
—• unit indoor water use 3.3 x 10-6m3/s per capita
= 20,000 people.
78
-------
TABLE 25. SAMPLE CALCULATION FOR SEWER PIPE CAPITAL COST WITH
REDUCTION IN INDOOR WATER USE, CASE I
1
Old Pipe!/
Size cm
(inches)
15.2
(6)
20.3
(8)
25.4
(10)
30.5
(12)
38.1
(15)
45.7
(18)
53.3
(21)
61.0
(24)
2
New Pipe
Size cm
(inches)
15.2
(6)
15.2
(6)
20.3
(8)
25.4
(10)
30.5
(12)
38.1
(15)
45.7
(18)
53.3
(21)
3
2J Length^
m
(feet)
94 920
(311,420)
22 570
(74,060)
7 150
(23,460)
5 190
(17,020)
4 350
(14,260)
2 660
(8,740)
2 100
(6,900)
1 260
(4,140)
140 200
(460,000)
4
Unit Pipe^
Cost
$/m
($/ft)
79
(24)
79
(24)
141
(43)
154
(47)
194
(59)
240
(73)
308
(94)
387
(118)
5 6
4/ 5/
Pipe^' Adjusted^-'
Cost Pipe Cost
$1,000 $1,000
Col. 3 x
Col. 4
7,470
1,777
1,010
800
840
635
650
490
13,667 17,450
7
Equivalent-
Annual Cost
$1,000
1,265
NOTE: This sample calculation pertains to a corresponding treatment plant
size of 0.11 m3/s (2.5 mgd).
JL/ From Table 24.
_2/ From Table 23.
_3/ From EPA Report MCD-38 (11).
47 National Average Cost in January 1978 Dollars.
_5/ Adjusted to California Construction Cost Index of 1.14 and updated
to 1979 EPA Construction Cost Index of 1.12.
-------
TABLE 26. SEWER LINE CAPITAL COST SAVINGS, CASE I
Corresponding
Treatment
Plant Size
m3/s
(mgd)
Equivalent^'
Annual Capital
Cost in 1979
Dollars (in $1,000)
Percent
Reduction in
Overall Com-
munity Indoor
Water Use
I/ 7% interest and 50-year life (13)
Equivalent-
Annual Capital
Cost Savings
(in (in
$1,000) percent)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
430
1,470
8,860
18,630
35,660
10 - 35
10 - 35
10-35
10
20-35
10
20 - 35
60
205
1,420
2,875
2,945
5,195
5,480
14
14
16
15
16
15
15
TABLE 27. PERCENT SAVINGS IN O&M COST
DUE TO WASTEWATER FLOW REDUCTIONS
Percent Overall
Reduction in
Community Indoor
Water Use
New Sewer System Existing Sewer System
Percent Percent Percent Percent
Flow O&M Cost Flow O&M Cost
Reduction Reduction Reduction Reduction
, 10
20
30
35
31.0
35,0
37.5
39.0
1.5
1.8
2.0
2.1
4.8
16.3
28.1
34.0
0
0.5
1.3
1.7
'80
-------
TABLE 28. O&M COST SAVINGS FOR NEW SEWER SYSTEMS, CASE I
1
Corres-
ponding
Treat-
ment
Plant
Size
r\
m3/s
(mgd)
. 0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
I/ Col.
2/ Col.
3/ Col.
2
Average
ADWF
for New
Sewer
System
Over 20
Year
Period
m3/s
(mgd)
0.01
(0.24)
0.03
(0.75)
0.16
(3.75)
0.33
(7.5)
0.66
(15)
2 -f 3.29 x
3 x $7.05
4 x Col. 6.
3 4 5 ,
If 21
Popula-~~ Annual" Percent
tion O&M Overall
Served Cost Reduc-
(in tion in
$1,000) Commun-
ity In-
door
Water
Use
3,200 23 10
20
30
35
10,000 71 10
20
30
35
50,000 353 10
20
30
35
100,000 705 10
20
30
35
200,000 1,410 10
20
30
35
6
1
Annual
O&M Cost
(in
Percent)
1.5
1.8
2.0
2.1
1.5
1.8
2.0
2.1
1.5
1.8
2.0
2.1
1.5
1.8
2.0
2.1
1.5
1.8
2.0
2.1
Savings
(in 3/
$1,000)-
0
0
0
0
1
1
1
1
5
6
7
7
11
13
14
15
21
25
28
30
—6 T
10 raj/s/capita (75 gal/capita/day)
81
-------
TABLE 29. O&M COST SAVINGS FOR EXISTING SEWER SYSTEH CASE I
Corres-
ponding
Treat-
ment
Plant
Size
m3/s
(mgd)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
i / 21
Average Popula — Annual—
ADWF tion O&M
for new Served Cost
Sewer (in
System $1,000)
Over 20
Year
Period
m3/s
(mgd)
0.08 24,700 174
(1.85)
0.25 76,900 542
(5.77)
1.26 384,000 2,707
(28.8)
2.53 769,300 5,424
(57.7)
5.06 1,538,700 10,848
(115.4)
Percent
Overall
Reduc-
tion in
Commun-
ity In-
door
Water
Use
10
20
30
35
10
20
30
35
10
20
30
35
10
20
30
35
10
20
30
35
Annual
O&M Cost
(in
percent)
0
0.5
1.3
1.7
0
0.5
1.3
1.7
0
0.5
1.3
1.7
0
0.5
1.3
1.7
0
0.5
1.3
1.7
Savings
(in
•*/
$1,000)-'
0
1
2
3
0
3
7
9
0
14
35
46
0
27
71
92
0
54
141
.184
—6 3
JL/ Col. 2 * 3.29 x 10 m /s capita (75 gal/capita/day)
2J Col. 3 x $7.05
3/ Col. 4 x Col. 6
82
-------
TABLE 30. COMBINED 0 & M COST SAVINGS FOR NEW
AND EXISTING SEWER SYSTEMS, CASE I
Corresponding
Treatment
Plant Size
m3/s
(mgd)
Percent Overall
Reduction in
Community Indoor
Water Use
Annual 0 & M Cost Savings
(in $1,000)
New Sewer
System
0.04 10 0
(0.8)
Existing Sewer Tni.all/
System iotal
0 0
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
20
30
35
10
20
30
35
10
20
30
35
10
20
30
,35
10
20
30
35
0
0
0
1
1
1
1
5
6
7
1
11
13
14
15
2.1
25
28
30
1
2
3
0
3
7
9
0
14
35
46
0
27
71
92
0
54
141
184
0
0
0
0
5
10
10
5
20
40
55
10
40
85
105
20
80
170
215
\J Rounded to nearest,$5,000.
83
-------
TABLE 31. SUMMARY OF ANNUAL WATER CONSERVATION BENEFITS
AT 10 PERCENT REDUCTION IN INDOOR WATER USE, CASE I (In $1.000)
Sewage
Treatment
Plant
Design
Flow
m^/s (mgd)
Energy Benefits
Hot Water! Local
Heating I Systems
Total
Water
Supply
Benefits
STP
Capital
Cost
Savings
Collec-
tion
System
Cost
Savings
Capital! O&M
Gross
Benefits
0.04 132
(0.8
0.11 411
(2.5)
0.55 2,056
(12.5)
1.10 4,116
(25)
2.19 8,232
(50)
2 135 30 35 60 0 260
6 415 100 80 205 0 800
31 2,085 500 290 1,420 5 4,300
62 4,180 1,000 605 2,875 10 8,670
125 8,355 1,995 1,115 5,195 20 16,680
TABLE 32. SUMMARY OF ANNUAL WATER CONSERVATION BENEFITS
AT 20 PERCENT REDUCTION IN INDOOR WATER USE. CASE I (in $1.000)
Sewage
Treatment
Plant
Design
Flow
nr/s (mgd.
Energy Benefits
Hot Water
Heating
0.04 312
(0.8)
Local
Systems
5
Total
Water
Supply
Benefits
STP
Capital
Cost
Savings
Collec-
tion
System
Cost
Savings
Capital! O&M
Gross
Benefits
315 75 60 60 0 510
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
312
972
4,852
9,718
19,437
5 315 75
15 985 235
73 4,925 1,175
147 9,865 2,360
294 19,730 4,715
60 60 0 510
140 205 5 1,570
530 1,420 20 8,070
1,100 2,945 40 16,31(5
2,035 5,480 80 32,040
84
-------
TABLE 33. SUMMARY OF ANNUAL WATER CONSERVATION BENEFITS
AT 30 PERCENT REDUCTION IN INDOOR WATER USE. CASE I (in $1.000)
Sewage
Treatment
Plant
Design
Flow
vr/8 (mgd'
Energy Benefits
Hot Water
Heating
0.04 431
(0.8)
Local
Systems
7
Tota3
Water
Supply
Benefits
STP
Capital
Cost
Savings
Collec-
tion
System
Cost
Savings
Capital] O&M
Gross
Benefits
440 120 60 60 0 680
0.11
(2.5)
0.55
(12.5)
1,345
6,714
1.10 13,448
(25)
2.19 26,897
(50)
23 1,370
275
145 205 10 2,005
116 6,830 - 1,860 540 1,420 40 10,690
233 13,680 2,730 1,125 2,945 85 20,565
465 27,360 7,460 2,085 5,480 170 42,555
TABLE 34. SUMMARY OF ANNUAL WATER CONSERVATION BENEFITS
AT 35 PERCENT REDUCTION IN INDOOR WATER USE, CASE I (In $1,000)
Sewage
Treatment
Plant
Design
Flow
nr/s (mgd)
Energy
Hot Water
Heating
0.04 437
(0.8)
Benefits
Local
Systems
9
Total
Water
Supply
Benefits
STP
Capital
Cost
Savings
Collec-
tion
System
Cost
Savings
Capital! O&M
Gross
Bene-
fits
445 •„ 140 60 60 0 705
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
1,366 28 1,395 440
6,900 138 7,040 2,205
145 205 10 2,195
540 1,420 55 11,260
13,658 276 13,935 4,420 1,125 2,945 105 22,530
27,317 551 27,870 8,835 2,085 5,480 215 44,485
85
-------
12,000-]
o
o
o
CD
<
r>
10,000-
8,000-
6,000-
4,000-
2,000-
TREATMENT PLANT
0 10 20 30
REDUCTION IN INDOOR WATER USE
(PERCENT)
EXAMPLE: 0.55 m3/s (12.5mgd) Treatment Plant Size,
Figure 10. Annual water conservation benefits, Case I.
86
-------
TAB'LE 35. EXPECTED REDUCTIONS IN PERCENT
OF INDOOR WATER USE, CASE II
Water
Scenario 1
Potential
Conser- Poten- Expected
vation tial Percent!./ Reduc-
Measures Savings Installing tions
Toilet
21
Shower—
21
Faucet-
Pressure
Reducing
Valve
Hot Water
Pipe
Insula-
tion
Clothes
Washer—'
Dish 2/
Washer-
Hot Water
Savings
Hot and
Cold
Water
Savings
14-' 100 14
12-/ 100 , 12
5/
2- 100 2
4-/ 100 4
2-/ 100 2
&-* 100 5
0.5^ 100 0.5
TOTAL 21.5
TOTAL 39.5
(Rounded) (40)
Scenario 2 Scenario 3
Moderate Water Minimal Water
Conservation Effort Conservation Effort
Expected Expected
Percent Reduc- Percent Reduc-
Installing tions Installing tions
100 14 100 14
100 12 ' 100 12
,
100 2 100 2
10 0.4 0 0
50 1 0 0
100 5 50 2.5
100 0.5 50 0.2
20.5 16.7
34.9 30.7
(35) (30)
J7 Percent of households installing water conservation measures.
2j Measures generating hot water energy.
(continued)
87
-------
FOOTNOTES FOR TABLE 35,(continued)
3/ Use volume of conventional toilets = 19.76 litres (5.22 gallons).
California State Department of Water Resources (DWR) Bulletin 191,
Appendix G (6).
Low-flush to.ilets = 13.2 litres (3.5 gallons) per flush mandatory.
_ . 6.51 litres (1.72 gal) 00gl litres/min (8<35 gai/min)
s 64% per shower.
Daily use per household based on data in DWR Bulletin 206, Appendix (8):
Shower =2.6 times
Bathtub = 1.8 times.
Volume of shower use « 31.61 litres/min (8.35 gpm) x 6 min x 2.6
= 492 litres (130 gal)
Volume of tub use = 189 litres (50 gal) x 1.8 - 341 litres (90 gal)
TOTAL 833 litres (220 gal)
Bathing use = 32% of indoor use. Therefore, shower savings =
,.„ . 492 litres (130 gal) ,9
-------
TABLE 36. AMOUNT OF WATER SAVINGS DUE
TO WATER CONSERVATION, CASE II
Treatment
Plant
Design
Flow
m3/s
(mgd)
0.04
(0.8)
0.11
(12.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
ADWF-
New Bldg
Construc-
tion
m3/s
(mgd)
0.02
(0.48)
0.07
(1.5)
0.33
(7.5)
0.66
(15)
1.31
(30)
Avg ADWF-
New Bldg Con-
struction
Over 20-year
period
m3/s
(mgd)
0.01
(0.24)
0.03
(0.75)
-1
0.16
(3.75)
0.33
(7.5)
/
0.66
(15)
Percent
Reduction
in Indoor
Water Use
30
35
40
30
35
40
30
35
40
30
35
40
30
35
40
Total.,
Water^'
Saved
dam3
(ac-ft)
199
(161)
232
(188)
265
(215)
622
(504)
725
(588)
829
(672)
3 108
(2,520)
3 626
(2,940)
4 145
(3,360)
6 .217
(5,040)
7 253
(5,880)
8 289
(6,720)
12 434
(10,080)
14 506
(11,760)
16 578
(13,440)
Hot WateiA'
Saved
dam3
(ac-ft)
110
(89)
199
(161)
146
(118)
342
(277)
435
(353)
456
(370)
1 710
(1,386)
2 176
(1,764)
2 280
(1,848)
3 419
(2,772)
4 352
(3,528)
4 559
(3,696)
6 839
(5,544)
8 704
(7,056)
9 118
(7,392)
1 / T*i**"i rt 4-»wj-»« 4- <*> 1 *•»*-*+• ft r* e* *t rvv* ^1 ^\T.T -o*
2J Col. 2 v 2
_3/ Col. 3 x Col. 4
4/ Col. 5 x percent hot water savings
89
-------
TABLE 37. WATER SUPPLY BENEFITS, CASE II
Treatment Plant
Design Flow
m3/s
(mgd)
Annual Water Supply Benefits at Various
Levels of Indoor Water Use Reductions
(in $1.000)
30%
35%
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
15
45
220
440
880
15
50
255
515
1,030
20
60
295
590
1,175
90
-------
TABLE 38. ANNUAL ENERGY BENEFITS, CASE II
(in $1.000)
Treatment
Plant Size
m3/s
(mgd)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
Percent
Reduction
in Indoor
Use
30
30
30
30
30
35
35
35
35
35
40
40
40
40
40
Water
Heating
40
125
625
1,250
2,499
51
160
795
1,590
3,181
53
167
833
1,666
3,332
Local
Systems
1
3
14
28
55
1
3
16
32
64
1
4
18
37
73
Total-/
40
130
640
1,280
2,555
50
165
810
1,620
3,245
55
170
850
1,703
3,405
J7 Rounded to nearest $5,000.
-------
TABLE 39. CAPITAL COST SAVINGS FOR SECONDARY
TREATMENT PLANTS, CASE II
Annual Capital Cost Savings
for Treatment Plants
Treatment
Plant
Size
in m3/s
(mgd)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
Equiv.
Annual Flow
Capital Reduction =
Cost!/ Cost
(in $1,000) Reduction =
280
660
2,460
5,110
9,470
'
30%
6%
15
40
150
305
570
(in $1,000)
35% 40%
7% 8%
20 20
45 50
170 195
360 410
665 760
0 8Q
_!/ Cost derived from equation, cost = kQ , adjusted from national
average to California prices, adjusted to reflect 1979 dollars
(EPA cost index), and applying 7% interest and 25 years of service
life(3).
92
-------
8 -i
z
UJ
u
a:
o
o
o.
o
z
z
g
i-
u
Q
UJ
(K.
6-
4-
2-
10 20 30
REDUCTION IN INDOOR WATER USE
(PERCENT)
40
Figure II. Reduction in capital cost of secondary
treatment plants, Case n.
93
-------
TABLE 40. SEWER LINE CAPITAL COST SAVINGS, CASE II
Corresponding
Treatment
Plant Size
m3/s
(mgd)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
Capital Cost,
1979 dollars
(in $1,000)
5,890
20,340
122,220
257,050
492,170
Percent Flow
Reduction
30-40
30-40
30-40
30
35 - 40
30
35 - 40
Equivalent Annual
Cost Savings I/
(in $1,000)
20
75
775
1,690
1,760
2,750
3,035
I/ 7% interest and 50-year life (3).
94
-------
TABLE 41. ANNUAL 0 & M COST SAVINGS IN SEWER
SYSTEMS. CASE II
1
Correspond-
ing Treat-
ment Plant
Size
m3/s
(mgd)
2
Percent
Reduction
In Indoor
Water Use
3
Average I/
ADWFs
Indoor
Water Use
Over 20-
Year Period
m3/s
(mgd)
4
Popula-
tion!/
Served
5
Annual—
0 & M
Cost
(in $1,000)
6
0 & M
Cost
Savings
Percent $1,000^
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
30
35
40
30
35
40
30
35
40
30
35
40
30
35
40
0.011 3,200 23
(0.24)
0.033 10,000 71
(0.75)
0.16 50,000 353
(3.75)
0.33 100,000 705
(7.5)
0.66 200,000 1,410
(15)
0.5
1.0
1.5
0.5
1.0
1.5
0.5
1.0
1.5
0.5
1.0
1.5
0.5
1.0
1.5
0
0
0
0
0
0
5
5
5
5
10
10
15
15
20
J7 Col.
i 75 . 9
125 '
2J Col. 3 4- 3.29 x 10~6m3/s/capita (75 gal./capita/day)
J3/ Col. 4 x $7.05/capita
47 Rounded to nearest $5,000
95
-------
TABLE 42. SUMMARY OF ANNUAL WATER CONSERVATION BENEFITS
AT 30 PERCENT REDUCTION IN INDOOR USE, CASE II
(in $1,000)
Treatment
Plant
Design
Flow •
m3/s(ragd)
Energy Benefits
Water Local , /
Heating Systems Total-
Water
Supply
Benefits
Treatment
Plant
Capital
Cost
Savings
Sewer System
Cost Savings
Capital O&M
Gross
Benefits
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
40
125
625
1,250
2,499
1
3
14
28
55
40
130
640
1,280
2,555
15
45
220
440
880 ,
15
40
150
305
570
20
75
775
1,690
2,750
0
0
5
10
20
90
290
1,790
3,725
6,775
I/ Values rounded to nearest $5,000.
96
-------
TABLE 43. SUMMARY OF ANNUAL WATER CONSERVATION BENEFITS
AT 35 PERCENT REDUCTION IN INDOOR USE, CASE II
(in $1,000)
Treatment
Plant
Design
Flow
m3/s (mgd)
Energy Benefits
Water Local . ,
Heating Systems Total—
Water
Supply
Benefits
Treatment
Plant
Capital
Cost
Savings
Sewer System
Cost Savings
Capital O&M
Gross
Benefits
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
51
160
795
1,590
3,181
'
1
3
16
32
64
50
165
810
1,620
3,245
15
50
255
515
1,030
20
45
•
170
360
665
20
75
775
1,760
3,035
0
0
5
15
25
105
335
2,015
4,270
8,000
I/ Values rounded to nearest $5,000.
97
-------
TABLE 44. SUMMARY OF ANNUAL WATER CONSERVATION BENEFITS
AT 40 PERCENT REDUCTION IN INDOOR USE, CASE II
(in $1,000)
Design
Flow
m3/s
(mgd)
Energy Benefits
Water Local Total— ^
Heating Systems
Water
Supply
Benefits
Treatment
Plant
Capital
Cost
Savings
Sewer System
Cost Savings
Capital O&M
Gross
Benefits
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
53
167
833
1,666
3,332
1
4
18
37
73
55
170
.850
1,703
3,405
20
60
295
590
1,175
20
50
195
410
760
20
75
775
1,760
3,035
0
0
10
15
tf
30
115
355
2,125
4,478
8,405
I/ Values rounded to nearest $5,000.
98
-------
2,500^
o
o
o
•vr
vt
UJ
z
UJ
ffi
2,000-
1,500
1,000
500-
REDUCTION IN INDOOR WATER USE
(PERCENT)
EXAMPLE: 0,55 m3/s (I2.5mgd) Treatment Plont Size.
Figure 12. Annual water conservation benefits, Case n.
99
-------
SECTION 6
X
WATER CONSERVATION COSTS
Basis of Analysis
The negative effects, or costs, of water conservation measures and their
impact on wastewater reuse will be examined in this section. The cost analy-
sis was based on the following approach:
o Select conditions for analysis. This involves a 20-year period of
analysis and two cases -- Case I and Case II — for which new sewer col-
lection and treatment facilities are commonly constructed to serve new
population growth as was done in Section 5, "Water Conservation
Benefits". ,
o Estimate the cost of various scenarios of water conservation measures
at different levels of water conservation efforts ranging from minimal to
potential. The cost of water conservation measures is estimated in terms
of annual unit cost per household. The number of households served by the
various sizes of wastewater systems are multiplied by the annual unit cost
to determine the total cost of the measures.
o Assess the impact on wastewater reuse. Three major uses of waste-
water, namely, crop irrigation, landscape irrigation, and industrial use,
are examined to determine how much they are affected by changes in waste-
water quality as a result of flow reduction.
Case I — New Wastewater Facilities
Constructed as Additions to Existing Facilities
Cost of Water Conservation Measures
In Section 5, "Water Conservation Benefits", various scenarios of water con-
servation measures to achieve different levels of indoor water use reductions
were examined. The scenarios showed us that the following levels of indoor
use reduction could be achieved:
Scenario
1
2
3
Percent Reduction
in Indoor Use
35
25
ID
Water Conservation
Effort
Potential
Moderate
Minimal
100
-------
For scenarios 1 and 2, the measures to reduce indoor water use include low-
water-using tank toilet, shower, and faucet fixtures; pressure-reducing
valves; insulated hot water pipes; clothes and dishwashers with water-saving
features; and educational and advertising campaigns. Scenario 3 includes the
same measures except pressure-reducing valves and insulated hot water pipe;"s.
The unit annual cost of these measures and the description of conditions
assumed to estimate this cost are contained in Table 45. The annual unit
cost of. the water conservation measures is also depicted in Figure 13..
The annual cost of water conservation measures was determined by multiplying
the number of households served by the wastwater system by the unit cost (see
Table 46).
Impact on Wastewater Reuse
The reuse of wastewater for beneficial use is an increasingly important water
conservation measure being taken in California. Reclaimed wastewater is
presently being used,in a variety of ways. A reduction in wastewater flow
would change the quality of the water that is reused, which in turn could
affect the uses to which such water can be put. Crop and landscape irriga-
tion uses constitute' about 74% of the wastewater currently reused (16) and
projected to be reclaimed by 1984,—'and thus are the primary uses considered
for analysis. The remaining projected uses—'are industrial (19%), ground
water recharge (5%), and other uses (2%). The use of reclaimed water
specifically for ground water recharge involves numerous variables and is a
complex subject that is outside the scope of this study. In California,
ground water recharge with reclaimed wastewater is allowed only on a \
case-by-case basis.
In general, salt concentration is the most significant factor likely to
affect both irrigation and industrial uses. It is recognized that high
values of boron concentration and sodium absorption ratios in the sewage
effluent would also cause problems for crop irrigation. However, these prob-
lems were not included in the analysis because they are not widespread in
California. Also, the curtailment of supply'due to wastewater flow reduction
is not normally a problem because the amount reclaimed is usually only a
fraction of the wastewater produced. In 1977, the amount reused in
California was about 6%^/of the wastewater production.
I/ From unpublished data by California State Water Resources Control Board,
Office of Water Recycling, 1979.
27 From California Department of Health Services Report, 1978 (16) and
California Department of Water Resources unpublished data, Division of
Planning, Water Reclamation and Supply Branch, 1979.
101
-------
Currently, wastewater is largely used to irrigate the following crops and
landscapes (16):
Hay (alfalfa)
Pasture
Qorn
Grape (vineyard)
Citrus Orchard
Deciduous orchard
Cotton
Barley
Landscape (largely turfgrass)
Golf course
Parks
Schoolgrounds
Playgrounds
To vfaat extent does increased salt concentration affect these uses? The
approach used in answering this question in quantified terms is to examine
the effect of incremental increase in salt concentration on crop yield and
the survival rate of the landscape. Crop loss due to lower yield will be
determined in the case of crop irrigation. For landscape irrigation, the
cost of replacing the turf that does not survive will be the primary
consideration. The value of the crop loss and the cost of turf replacement
can be considered as a fair reduction in the price for reclaimed water that
the user would pay to compensate for these losses.
Impact on Crop Irrigation. The degree of salt tolerance differs with the
kinds of crops grown. For instance, citrus and deciduous orchards are much
more sensitive to salt concentration than cotton or barley. One way of mea-
suring the crop tolerance to salt is to determine the crop yield at different
levels of salt concentration in the irrigated water. As salt concentrations
are increased, the crop tends to reduce its yield (17) as shown in Figure 14.
The salt concentration is expressed in terms of electrical conductivity of
the irrigation water. It is also expressed in approximate TDS values by
multiplying the EC values by 640.
Cotton and barley as shown in Figure 14 have a high tolerance to salt and are
not considered to be affected by the range of incremental increase in TDS
expected from reductions in flow. In assessing the effect on other crops,
the following assumptions were made because adequate TDS data from the treat-
ment plants surveyed or other plants were not available.
0 Domestic use causes a salt pick-up of 300 mg/1— in the water .used.
0 The quality of the effluent applied to the crops is such that any
incremental increase in TDS will begin to,cause a reduction in crop
yield.
IJ State Water Pollution Control Board, Publication No. 9 (18).
102
-------
The incremental TDS increase attributable to reductions in indoor use are
estimated as follows:
Percent Reduction
in Indoor Use
10
20
30
35
TDS Pick-up Due to
Domestic Use with Wat.er
Conservation (in mg/1)
300 = 333
0.9
375
429
462
Incremental TDS
Increase (in mg/1)
333-300 = 33
75
129
162
Based on values from Figure 14, the amounts of crop yield reduction can be
approximated at different levels of incremental TDS increase and are shown in
Figure' 15. Because of the lack of TDS data, Figure 15 reflects the assump-
tion that the effluent applied to each crop has a TDS level such that any
incremental TDS increase affects crop yield.
The value of the crop loss was determined by analyzing the crop yield reduc-
tion along with the following considerations:
10 Identification of crops by specific regions in counties.
0 Determination of applied water by specific regions in counties.
0 Determination of acreage of crops using reclaimed water.
0 Determination of , value of crops grown.
A summary for the determination of the value of unit crop loss ($/dam3) is
shown in Table 47 and depicted in Figure 16. Because one can only speculate
about the specific crops -that would use reclaimed water in the future, it was
assumed that the current pattern of crop irrigation would continue.
The amount of crop loss varied considerably depending on the type of crop
using the reclaimed water. For example, at 30% flow reduction, the annual
crop loss ranged from $1.40/dam3 ($1 .73/ac-ft) for hay to $26.09/dam3
($32,18/ac-ft) for citrus orchard (see Table 47 and Figure 16). However, to
depict a condition characterizing average statewide conditions, it was neces^-
sary to adjust this range of crop loss values in proportion to the acreage
for each crop using reclaimed water (weighted average). The weighted average
of the crop loss was found to be not very significant, with values ranging
from ,$0.44/dam3 ($0.54/ac-ft ) to $2.23/dam3 ($2. 75/ac-ft) at 10% and 35%
reduction in indoor use, respectively (see Table 47). The amount of water
.Projected for crop irrigation constitutes about 9%i/of wastewater production
_!_/ From unpublished data from California State Water Resources Control Board,
Office of Water Recycling, and California Department of Water Resources,
Division of Planning, Water Reclamation and Supply Branch, 1979.
103
-------
at the mid-point of the next 20-year period. When this projection is taken
into account, the crop loss is minimal and represents the average impact on a
statewide basis. This can be illustrated with the following example for
Case I:
For a treatment plant size of 0.55 m3/s (12.5 mgd), the average dry
weather flow (ADWF), for new and existing building constructions, at the
mid-point of the next 20-year period of analysis is 1.42 m3/s
(32.6 mgd) (see Table 17). The average wastewater flow
=* 1.42 m3/s x iP_°_ = 1.89 m3/s (43.2 mgd).
The amount of water reused
= (1.89 m3/s) (9% reuse) = 0.17 m3/s (3.9 mgd)
= 5 665 dam3/yr (4,350 ac-ft/yr).
Amount of crop loss, at 30% flow reduction, for example
= (5 365 dam3/yr) ($1.73/dam3) = $9,300/yr.
This compares with a gross benefit of $10,905,000/yr (see Table 33) or
less than 1/10 of 1%.
Reductions in wastewater flow would increase the concentrations of nutrients
and could be beneficial to the crops. This would tend to offset the crop
loss due to higher TDS concentrations but no attempt was made to quantify
this effect.
The reader should keep in mind that the impact on specific reuse projects
could vary measurably on a case-by-case basis. For example, in a case where
the water reused has an incremental mineral increase that is excessively high
and is applied to an orchard, the impact on crop loss would be much greater
than the average values shown.
Impact on Landscape Irrigation. For turfgrass, the primary landscape for
golf courses, parks, schoolgrounds, and playgrounds, the survival rate rather
than the yield response as forage was considered to be important (21). The
kinds of grass commonly used for turf were found to have good survival rates
using irrigation water with a high salt concentration. The average survival
rate for four kinds of common turf grass was shown to be about 98% at a TDS
concentration as high as 5 000 mg/1 (see Figure 17). It is concluded that
the magnitude of incremental increase in salt concentration resulting from
reduction in indoor water use has little impact on turfgrass irrigation. ;
Impact-on Industrial Uses. One way of measuring the impact of water con-
servation on industrial uses is to estimate the cost of mitigating the incre-
mental increase in salt concentration induced by water conservation. One
method of mitigation is to desalt a portion of the reclaimed wastewater and
104
-------
then blend the desalted water with the effluent to attain the salt concentra-
tion prior to reduction in wastewater flow. This is discussed in greater
detail in Section 8, "Penalty Costs".
Water conservation induced wastewaster flow reduction is not expected to
cause an impact of any significance on industrial uses when compared to the
overall benefits it would generate on a statewide basis. This can be illus-
trated by using the example discussed under crop irrigation as follows:
Treatment plant size = 0.55 m3/s (12.5 mgd)
Average wastewater flow = 1.89 m3/s (43.2 mgd).
The amount of water projected for industrial uses constitutes about 4%—
of wastewater production at the mid-point of the next 20-year period. The
amount of water that would be reused for industrial uses
i
= (1.89 m3/s) (4% reclamation) = 0.076 m3/s (1.73 mgd)
= 2 385 dam3/yr (1,935 ac-ft/yr)
Cost of desalting at 30% wastewater flow reduction, for example,
=•. (2 385 dam3/yr) ($31.20/dam3)-/ = $74,400/yr.
This compares with a gross benefit of $10,905,000/yr (see Table 33) or
less than 1%.
Other Impacts
During the recent drought years when it was necessary to undertake many water
conservation measures, there were no known cases of adverse impacts on the
aquatic environment that were attributable to changes in water conditions
brought about by reductions in indoor water use. However, the determination
of the specific effects of water conservation induced wastewater flow reduc-
tions on the aquatic environment would entail a biological study and is, con-
sidered outside the scope of this study. The San Diego Water Reclamation
Agency is currently studying a related subject, the feasibility of using
reclaimed water for the purpose of creating a live stream.
!_/ From unpublished data from California State Water Resources Control Board,
Office of Water Recycling, and California Department of Water Resources,
Division of Planning, Water Reclamation and. Supply Branch, 1979.
2/ Derivation of this cost is discussed later in Section 8, "Penalty Costs".
105
-------
Case II - New Wastewater Facilities
Constructed Independent of Existing Facilities
Cost of Water Conservation Measures
The annual unit cost of water conservation measures for the various scenarios
and description of conditions assumed to estimate this cost are contained in
Table 48. The annual cost of water conservation measures were determined by
multiplying the number of households served by the wastewater system by the
unit cost (see Table 49).
Impact on Wastewater Reuse
The discussions for Case I also apply to Case II and will not be repeated
here. The main point is that water conservation has only minimal impact on
wastewater reuse.
106
-------
TABLE 45. UNIT COST OF WATER CONSERVATION MEASURES, CASE
Water
Conservation
Measures
Existing
Construction
New •
Construction
Annual Unit
Cost (in
$/household)
Toilet
Shower
Faucet
Pressure-
Reducing
Valve
Hot Water
Pipe
Insulation
Dishwasher/
Clothes
Washer
Education/
Advertising
Scenario 1 - Potential
Cost of material (mixture
of toilet dams, plastic
bottles, plastic bags)
included. Installation
cost by plumber included.
Cost of material
(showerheads and restric-
tors) included. Installa-
tion cost by plumber
included.
Cost of material (faucet
aerators) included.
Installation cost by
plumber included.
Cost of material in-
cluded. Installation
cost by plumber included.
Cost of material in-
cluded. Installation
cost by plumber included.
No additional cost for
water-saving feature of
replacement appliances.
Cost included.
Toilet -=-
No additional
cost.
Showerhead -
No additional
cost.
Faucet - No
additional
cost.
Cost of material
included.
Cost of material
included.
No additional
cost.
Cost included.
TOTAL
13.
0.153/
30.30
J7 Material costs are based on bid prices for the Department of Water
Resources water conservation pilot projects in 1977 and updated to
1979 prices. All installation costs by plumbers were based on the
current (1979) wage scale for plumbers. Annual unit cost reflects
capital costs amortized at 7% interest and a 5-year life.
2J Capital costs amortized at 7% interest and a 20-year life.
_3/ Education cost based on current student education program for water
conservation by DWR. Advertising cost based on DWR water conservation
pilot program in San Diego in 1977 updated to 1979 dollars.
(continued)
107
-------
TABLE 45 (continued)
Water
Conservation
Measures
Existing
Construction
New
Construction
Annual Unit
Cost (in
$/household.)
Toilet
Shower
Faucet
Pressure-
Reducing
Valve
Hot Water
Pipe
Insulation
Dishwasher/
Clothes
Washer
Education/
Advertising
Scenario 2 - Moderate Water Conservation Effort
Cost of material (mixture
of toilet dams, plastic
bottles and plastic bags)
included. No installation
cost included.
Cost of material (shower-
heads and restrictors)
included. No installation
cost included.
Cost of material (faucet
aerators) included. No
installation cost included.
Cost of material included.
Installation cost by
plumber included.
Cost of material included.
Installation cost by
plumber included.
No additional cost for
water-saving feature of
replacement appliances.
Cost included.
Toilet -
No additional
cost.
Showerhead -
No additional
cost.
Faucet - No
additional
cost.
s
Cost of material
included.
Cost of material
included.
No additional
cost.
Cost included.
TOTAL
9.01-
0.652/
13.55
I/ Material costs are based on bid prices for the Department of Water
- Resources water conservation pilot projects in 1977 and updated to
1979 prices. All installation costs by plumbers were based on the
current (1979) wage scale for plumbers. Annual unit cost reflects
capital costs amortized at 7% interest and a 5-year life.
2J Capital costs amortized at 7% interest and a 20-year life.
I/ Education cost based on current student education program for water
conservation by DWR. Advertising cost based on DWR water conservation
pilot program in San Diego in 1977 updated to 1979 dollars.
(continued)
108
-------
TABLE 45 (continued)
Water
Conservation
Measures
Existing
Construction
New
Construction
Annual Unit
Cost (in
S/hous'ehold1)
Toilet
Shower
Faucet
Dishwasher/
Clothes
Washer
Education
Scenario 3 - Minimal Water Conservation Effort
No retrofitting
Cost of material (shower-
heads and restrictors)
included. No installation
cost included.
Cost of material (faucet
aerator) included. No
installation cost included.
No additional cost for
water-saving feature of
replacement appliances.
Cost included.
Toilet - No
additional cost.
Showerhead -
No additional
cost.
Faucet - No
additional cost.
No additional
cost.
Cost included.
TOTAL
0.20
_!/ Material costs are based on bid prices for the Department of Water
Resources water conservation pilot projects in 1977 and updated to
1979 prices. All installation costs by plumbers were based on the
current (1979) wage scale for plumbers. Annual unit cost reflects
capital costs amortized at 7% interest and a 5-year life.
J2/ Capital costs amortized at 7% interest and a 20-year life.
31 Education cost based on current student education program for water
conservation by DWR. Advertising cost based on DWR water conservation
pilot program in San Diego in 1977 updated to 1979 dollars.
109
-------
Percent
Reduction
In Indoor
Water Use
Annual Unit Cost
of Water
Conservation
Measures
$/Household
10
REDUCTION
T r
20 30
IN INDOOR WATER USE
(PERCENT)
Condition
• 20-year growth factor = 1.26
- Reflects mix of new and existing construction
(a) mid-point of 20-year period.
Figure 13. Annual unit cost of
water conservation measures, Case I.
no
-------
I/ 21
Indoor- Indoor— House-
Water Use Water Use Total holds3/
Treatment New Bldg Existing Indoor Served
Plant Construe- Bldg Con- Water New Plus
Size
m3/s
(mEd)
0.035
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
tion
Q *
mj/s
(med)
0.011
(0.24)
0.03
(0.75)
0.16
(3.75)
0.33
(7.5)
0.66
(15)
struction Use Existing
m3/s
(mgd)
0.081
(1.85)
0.25
(5.77)
1.26
(28.85)
2.53
(57.7)
5.06
(115.4)
m3/s Bldg Con-
(mgd) struction
0.092 10,130
(2.09)
0.29 31,610
(6.52)
1.43 158,060
(32.60)
2.86 316,120
(65.2)
5.71 632,240
(130.4)
Annual
Unit Cost
Percent of Water
Reduc- Conserva-
tion tion
Indoor
Water
Use
10
20
30
35
10
20
30
35
10
20
30
35
10
20
30
35
10
20
30
35
Measures
(in $ per
household)
0.20
8.50
22.80
30.30
0.20
8.50
22.80
30.30
0.20
8.50
22.80
30.30
0.20
8.50
22.80
30.30
0.20
8.50
22.80
30.30
no£i J.
Annual Cost
of Water
Conservation
Measures
(in $1,000)
,0
85
230
305
5
270
720
960
30
1,345
3,605
4,790
65
2,685
7,210
9,580
125
5,375
14,415
19,155
J7 Indoor water use = ADWF.
Average ADWF of new construction s (design flow) -flip- * 2 and
represents ADWF at the mid-point of 20-year growth period.
21 Population growth factor at mid-point of 20-year period = 1.13.
Then ADWF of existing construction =
ADWF (of new construction at mid-point of 20-year period)
0.13
_3/ Use indoor water use at 3.29 x 10-6m3/s/capita (75 gal/capita/day)
and 2.75 persons per household. Total indoor use s total ADWF.
Number of households =
Total indoor use in m3/s Total indoor use in mgd .
(3.29 x 10-t»m3/s/capita)(2.75) °r (75 gal/capita/day)(2.75)
111
-------
50
0
1000
TOTAL DISSOLVED SOLIDS (TDS) IN mg/l
2000 30.00 40.00 50.00
80_£0
4 6 8 10 12
ELECTRICAL CONDUCTIVITY (E.C.) OF IRRIGATION WATER
14
Guidelines For Interpretation of Quality of Water For Irrigation", May 1974,
Univ. of Calif., Agricultural Extension (17), Soil leaching requirements
are reflected in the values.
^/Approximate conversion, I E.C. mmho/cm = 640 mg/l .
Figure 14! Crop salt tolerance.-!-/
112
-------
NOTE:
This chart portrays a condition whereby the effluent applied to each
crop has a IDS level such that any incremental increase in IDS will
begin to cause a crop yield decrement.
o
a:
o
LU
cc.
a.
o
cc
O
FLOW REDUCTION
(indoor use)
20%
50 100 150 200
' INCREMENTAL EFFLUENT TDS INCREASE (mg/l)
Figure 15. Crop yield reduction due to increased salt concentration.
113 .
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-------
FOOTNOTES FOR TABLE 47
J7 From Department of Health Services Survey Report, "Wastewater
Reclamation Facilities". 1978 (16).
2J Crop types were first identified within specific regions in
each county. The appropriate value of unit applied water for
the crops was obtained from California Department of Water
Resources Bulletin 113-3, "Vegetative Water Use in California,
1974" (19) and then used to estimate the number of hectares
(acres) grown for each crop by the ratio:
amount water reclaimed dam3 ,ac-ft. , _ , .
(acre).
unit applied water
dam^/hectare acre
3/ Amount of water reclaimed 4 crop land irrigated.
4/ From California Department of Food and Agriculture Report, "California
Principal Crop and Livestock Commodities 1978" (20).
5J Value crops ($/hectare) * unit applied water.
115
-------
Deciduous
Orchard
Vineyard
Weighted Avg.
(All Crops)
Corn 8 Hoy
Pasture
40
REDUCTION IN INDOOR USE
(PERCENT)
Figure 16. Impact of water conservation
on reclamation of wastewater for
crop irrigation.
116
-------
APPROXIMATE TOTAL DISSOLVED SOLIDS (TDS) OF IRRIGATION WATER (mg/I)
0 2000 4000 6000 8000 10000 12000 14000
AVERAGE OF
ALL GRASSES
KENTUCKY
BLUEGRASS
0
48 12 16 20
ELECTRICAL CONDUCTIVITY (EC) OF IRRIGATION WATER (mmho/cm)
Survival Rate based on values from "Saliriity Tolerance of Five Turfgrass Varieties
by 0. R. Lunt , V. B. Younger, and J. J. Oertli, Agronomy Journal (21).
Figure 17. Survival rate of turfgrass.
117
-------
TABLE 48. UNIT COST OF WATER CONSERVATION MEASURES. CASE II
Water Conservation
Measures
New Building Construction
Only ,
Annual Cost
$/Household
Toilet
Shower
Faucet
Pressure-Reducing
Valve
Hot Water Pipe
Insulation
Dishwasher/Clothes
Washer
Education/Advertising
Scenario 1 - Potential
No additional cost
No additional cost
No additional cost
Cost of material included
Cost of material included
No additional cost
Cost Included
0
0
0
A
6.
Toilet
Shower
Faucet
TOTAL 10.35
Scenario 2 - Moderate Water Conservation Effort
0
0
0
Pressure-Reducing
Valve
Hot Water Pipe
Insulation
Dishwasher/Clothes
Washer
Education/Advertising
No additional cost
No additional cost
No additional cost
Cost of material included
Cost of material included
No additional cost
Cost included
0.60^
2.05^
0.15^
Toilet, Shower,
Faucet, Dishwasher/
Clothes Washer
Education
TOTAL 2.80
.Scenario 3 - Minimal Water Conservation Effort
0
No additional cost
Cost included
'TOTAL
0.10^
0.10
_!/ All installation costs by plumbers were based on current (1979)
plumber's wage scale. Annual unit cost reflects capital costs amortized
at 7% interest, 5-year life.
2/ Education cost based on current student education program for water conser-
vation by DWR. Advertising cost based on DWR water conservation pilot
program in San Diego in 1977 updated to 1979 dollars.
118
-------
TABLE 49. ANNUAL COST OF WATER CONSERVATION MEASURES, CASE II
Treatment
Plant
Size
m3/s
(mgd)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
Average—
ADWF During
20-year
Period
m3/s
(mgd)
0.01
(0.24)
0.03
(0.75)
0.16
(3.75)
0.33
(7.5)
0.66
(15)
Annual Cost of Water Conservation
Measures.!/ (in $1,000)
Number—
of
Households
Served
1,165
3,635
18,180
36,365
72,730
4/
Scenario 1—
40% Indoor
Water Use
Reduction
10
40
190
375
750
Scenario 2—
35% Indoor
Water Use
Reduction
5
10
50
100
205'
Scenario 3—
30% Indoor
Water Use
Reduction
0
0
0
5
5
757
_!/ (Treatment plant size) x (12° flow relationship) * 2.
—>ft *5 - *
2J Average ADWF * 3.29 x 10~ nT/s/capita(75 gal/day/capita) x
(2.75 occupants per household).
3f (Number of households served) x (unit water conservation cost).
Annual cost rounded to nearest $5,000.
4/ Scenario 1 - potential.
5j Scenario 2 - moderate water conservation effort.
6/ Scenario 3 - minimal water conservation effort.
119
-------
SECTION. 7
WATER CONSERVATION NET BENEFITS
Summary
The benefits and costs of water conservation were examined in previous sec-
tions in order to view them in perspective to answer the question, "Is-water
conservation worthwhile?" The net worth of water conservation can be mea-
sured by determining its "net benefits", which is the difference between all
its benefits and costs. Stated in another way, it is the excess of benefits
over cost. A positive value indicates that a project or an effort is econom-
ically justified and a negative value that it is not. The point where the
maximum excess benefits occur is the point of optimum development. An exam-
ination of the net benefits for Case I (new and existing building construc-
tions) and Case II (new building construction only) showed that:
e There are considerable excess benefits over costs. For Case I, the
optimum level of indoor water use reduction is nearly 30% and the benefits
are about three times as great as the costs. For Case II, the optimum
level is about 37% and the benefits far exceed costs.
• The optimum levels of water conservation would require an intensive
water conservation effort.
• Water conservation in existing buildings for Case I is responsible for
generating about 70% of the total net benefits.
Case I
The net benefits were examined for small, medium, and large wastewater sys-
tems and all showed the following:
e There are considerable excess benefits over costs.
0 The optimum point of water conservation occurs at an overall community
indoor water use reduction of almost 30% and would require a strong water
conservation effort.
0 The "impact on wastewater reclamation" has no noticeable effect on the
net benefits.
The net benefits are shown in Table 50, and an example of a net benefit curve
is shown in Figure 18.
120
-------
Case II
As in Case I, the net benefits were examined for small, medium, and large.
wastewater systems and showed the following:
0 There are considerable excess benefits over costs.
0 The optimum point of water conservation effort occurs at an indoor
water use reduction of about 37%
° The "impact on wastewater reclamation" has no noticeable effect on the
net benefits.
0 The net benefits are considerably less than those for Case I. An
example of a net benefit curve is shown in Figure 19. It has been plotted
at the same scale as for Case I for easy comparison. Another comparison
in Figure 20 shows the dramatic beneficial effect of water conservation in
existing buildings.
The net benefits for all of the wastewater system sizes examined are shown in
Table 51. <
«
121
-------
TABLE 50. NET BENEFITS OF WATER CONSERVATION, CASE I
Treatment
Plant Size
m3/s
(mgd)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
Percent
Reduction
in Indoor
. Water Use
10
20
30
35
10
20
30
35
10
20
30
35
10
20
30
35
10
20
30
35
Annual
Gross
Benefits
(in $1,000)
260
510
680
705
800
1,570
2,005
2,195
4,300
8,070
10,690
11,260
8,670
16,310
20,565
22,530
16,680
32,040
42,555
44, 485
Annual
Costs
(in $1,000)
0
85
230
305
5
270
720
960
30
1,345
3,605
4,790
65
2,685
7,210
9,580
125
5,375
14,415
19,155
Annual
Net
Benefits
(in $1,000)
260
425
450
400
795
1,300
1,285
1,235
4,270
6,725
7,085
6,470
8,605
13,625
13,355
12,950
16,555
26,665
28,140
25,330
122
-------
12,000-1
o
o
o
•co-
cn
O
UJ
uj
CB
10,000-
8,000-
6,000
4,000-
2,000-
GROSS
BENEFITS
OPTIMUM
REDUCTION
10 20 30
REDUCTION IN INDOOR WATER USE
(PERCENT)
NOTE: Optimum level of indoor water use reduction is nearly 30%
and requires an intense water conservation effort.
This illustration pertains to 0.55 m3/s (12,5mgd) treatment
plant size.
Figure 18. Annual water conservation net benefits, Case I
123
-------
o
o
o
-V)-
-------
$8,000
$6,000
$4,000-
$2,000
NEW
AND
EXISTING
BUILDINGS
Increased net benefits
due to water conservation
measures in existing buildings
NEW
BUILDINGS
CASE I CASE IL
EXAMPLE: 0.55 m3/s {12.5mgd) Treatment Plant Size.
Figure 20. Annual net benefits of water conservation
at optimum level of indoor use reduction.
125
-------
TABLE 51. NET BENEFITS OF WATER CONSERVATION, CASE II
Treatment
Plant Size
m3/s
(mgd)
0.04
(0.8)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
Percent
Reduction
in Indoor
Water Use
30
35
40
30
35
40
30
35
40
30
35
40
30
35
40
Annual
Gross
Benefits
(in $1,000)
90
105
115
290
335
355
1,790
2,015
2,125
3,725
4,270
4,478
6,775
8,000
8,405
Annual
Costs
(in $1,000)
0
5
10
0
10
40
0
50
- 190
5
100
375
5
205
750
Annual
Net
Benefits
(in $1,000)
90
100
105
290
325
315 :
1,790
1,965
1,935
3,720
4,170
4,103
6,770
7,795
7,655
126
-------
SECTION 8
PENALTY COSTS
Background
In this section, the "penalty cost's" of water conservation will be examined.
Pena.lty costs are costs borne by domestic water users as a result of in-
creased TDS and hardness concentrations and are associated with:
° Home water softeners
0 Soap and detergent
0 Bottled water
0 Shorter service life of water heaters.
These costs are often borne in areas where the water supply usually has a
high salt concentration. When an incremental increase in effluent hardness
and TDS concentrations occurs as a result of wastewater flow reduction, some
consumer, somewhere, at some time could bear penalty costs. No attempt will
be made to measure the actual penalty cost to a particular consumer be.cause
it depends on many variables such as the place of discharge of the sewage
effluent, the amount of effluent that mixes with a usable water supply, the
extent to which the effluent alters the quality of that water supply, and the
quality of the water supply that is being used by the consumer.
For example, if the effluent is discharged to the ocean, it is being returned
to a "nonusable" water supply and therefore no penalty costs would be
incurred. The worst possible case would be a direct domestic use of the
effluent, although this is highly unlikely in the forseeable future. Never-
theless, this condition sets an upper limit of penalty costs to get some per-
spective in relation to the net benefits of water conservation and therefore
will be examined in this section.
In the Section 6 discussion on impact on wastewater reuse for Case I, it was
found that there were an incremental increase in the TDS concentration in the
wastewater when reductions occurred in indoor water use. In a similar way,
there is an incremental increase in the hardness concentration. Because
adequate data was not available from treatment plants surveyed or other
plants on this factor, the incremental increase in TDS and hardness
concentrations were estimated as follows and are shown on Figure 21:
127
-------
Percent
Reduction
in Indoor
Water Use
10
TDS Pick-up Due
to Domestic Use
with Water
Conservation
(in mg/1)
300 _ ,,, •
0.9 333
Incremental
TDS Increase
(in mg/1)
333-300 = 33
Hardness Pick-up
Due to Domestic
Use with Water
Conservation
(in mg/1)
60 - 67
0.9 67
Incremental
Hardness
Increase
(in mg/1)
67-60 = 7
20
30
35
375
429
462
75
129
162
75
86
92
15
26
32
The incremental increases are based on mineral pick-up in water due to domes-
tic use of 300 mg/1 TDS and 60 mg/1 hardness (18).
Unit Penalty Costs
Information from a study!/ indicates the following unit penalty costs:
e Cost of soap and detergent
• Cost of home water softeners
0 Cost of bottled water
0 Capital cost related to shorter
service life of water heaters
$56.10/dam3 ($69.20/ac-ft)
per 100 mg/1 hardness increase
$4.08/dam3 ($5.03/ac-ft)
per 100 mg/1 TDS increase
The study considered TDS and hardness as the major water quality factors that
apply to areas of water supply with high TDS and hardness concentrations such
as in Southern California. The above values do not account for all ,of the
consumer costs associated with TDS and hardness such as costs associated with
washing machines, pipes, and plumbing fixtures which would tend to increase
the consumer costs. On the other hand, the scaling problems in plumbing fix-
tures caused by hard water would be lessened with greater use of home water
softeners and would tend to offset those costs not taken into account. In
summary, the penalty costs shown are considered ..to include the major compo-
nents and are adequate to give an indication of the magnitude of values.
Annual Penalty Costs
The unit penalty costs were applied to the amount of water saved to find the
annual penalty costs (see Table 52).
I/ "Consumer Costs of Water Quality in Domestic Water Use Lompoc Area",
~~ California Department of Water Resources. June 1978 (22).
128
-------
Effect on Net Benefits
To illustrate the effect of penalty costs on the net benefits, take the Case
I net benefits curve for a 0.55 m3/s (12.5 mgd) treatment plant size and
apply the upper limit of the penalty costs. We find that this does not
significantly change the net benefits curve (see Figure 22). The net bene-
fits curve for the other treatment plant sizes is' similarly affected.
Alternative to Penalty Costs
An alternative to penalty costs through mitigation of the incremental in-
crease^ in the effluent salt concentration will be examined here. The cost of
desalting a portion of the effluent and then blending the desalted water with
the effluent to attain the salt concentration prior to reduction in waste-
water flow will be approximated and compared with the penalty costs.
In order to quantify the cost of desalting, it is necessary to know the TDS
concentration of the effluent. In an area where penalty costs are commonly
incurred as in Southern California, an effluent TDS of 1050 mg/1 (23) is
chosen as typical for that area. As discussed earlier in this section, a
mineral pick up of 300 mg/1 due to domestic use will also be used. The,
amount^of effluent required to be desalted and the unit cost of desalting is
shown in Table 53. The details of determining the amount requiring desalting
are shown below:
LET:
TDS,
TDS
1-x
V=l
1-x
V=l
TDS2
TDS2
TDSX
volume of effluent to be desalted
= total volume of effluent
= volume of effluent before blending
(This neglects a small portion of
the effluent that would be lost
as a concentrated process brine).
= TDS of effluent before flow
reduction (1 050 mg/1)
= TDS of effluent after flow
reduction
TDS1 = TDS change due to flow
reduction
= TDS of desalted water
(100 mg/1)!/
If From experiences of Orange County Water District desalting plant and pilot
desalting plant in Marin County at about 90% salt removal.
129
-------
Effluent quality before reduction = Effluent quality after blending
TDS! (1) - TDS2 (1-x) + TDSX (x)
TDS2 Cx) - TDSX (x) = TDS2 -
x% - TDS2 - TDS1
[TDS Change due to flow reduction
TDS2 - TDSX [TDS of effluent after flow reduction - 100]
x 100
The unit cost of desalting without the cost of brine removal is about the
same as the upper limit of the penalty costs, whereas those with brine remov-
al costs are considerably greater (see Figure 23). Brines are a concentrated
by-product of the desalting process which must be removed to a suitable
place. For desalting plants located near a saline body of water, the brine
removal costs are either minimal or non-existent. It seems that with the
current state-of-the-art of desalting secondary treated wastewater, desalting
is not a justifiable measure as an alternative to incurring penalty costs.
130
-------
o>
E
UJ
Ul
cc
o
to
o
CO
tO
o
or
UJ
a:
o
A HARDNESS-17
10 20 30 40
REDUCTION IN INDOOR WATER USE
(PERCENT)
-I/Based on mineral pickup in water due
to domestic use of 300 mg/l IDS
and 60 mg/l hardness. SOURCE: State
Water Pollution Control Board
Publication No. 9, 1954 (18).
Figure 21. Incremental increase in
TDS and hardness concentrations.
131
-------
TABLE 52. ANNUAL PENALTY COSTS, CASE I
Treatment
Plant
Size
Percent
m3/s Indoor Use
(main Reduction 10
0.04 224
(0.8) (182)
Water Savings
dam-*
(ac-ft)
20 30
533 842
(432) (683)
Annual Penalty Costs
(in $1,000)
35 10 20 30 35
998 0 10 20 30
(809)
0.11
(2.5)
0.55
(12.5)
1.10
(25)
2.19
(50)
703
(570)
1 662 2 629 3 115 5
(1,347) (2,131) (2,525)
25 65
3 515 8 299 13 123 15 548 25 120 325
(2,850) (6,728) (10,639) (12,605)
7 038 16 620 26 285 31 143 45 240 650
(5,706) (13,474) (21,309) (25,248)
95
475
955
14077 33239 52571 62287 90 4751,3051,910
(11,412) (26,947) (42,619) (50,496)
132
-------
12,0001
o
o
o
cn
o
o
UJ
z
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m
10,000-
8,000-
-------
TABLE 53. AMOUNT AND COST OF DESALTING
Percent
Reduction
in Indoor
Water Use
Effluent
TDS Before
Flow
Reduction
mg/1
TDS Change
Due to
Flow
Reduction
me/1
Effluent
TDS After
Flow
Reduction
mg/1
Col. 2 +
Col. 3
Amount of
Effluent
to be
Desalted
Blended
(in %)
Col. 3
Col. 4-100
Cost of
Desalting
$/dam3
($/ac-ft)
Col. 5 x
$673/dam3
(830/ac-ft)!'
Col. 5 x
$2 11 /dam3
(260/ac-ft)!'
10
20
30
35
1050
1050
1050
1050
33
75
129
162
1083
1125
1179
1212
3.4
7.3
12.0
14.1
22.90
(28.20)
49.10
(60.60)
80.70
(99.60)
94.90
(117.00)
7.10
(8.80)
15.40
(19.00)
25.30
(31.20)
29.80
(36.70)
J7 Based on City of Ramona reverse osmosis plant.
Capacity =0.01 m3/s (0.25 mgd).
Desalting cost = $673/dam3 ($830/ac-ft).
Brine removal constitutes about 63% of desalting cost
2/ Based on Orange County Water District reverse osmosis plant,
~~ Capacity =0.22 m3/s (5 mgd).
No brine removal.
Desalting cost - $164/dam3 ($202/ac-ft) at July 1975 prices,
Cost adjusted to 1979 prices = $211/dam3 ($260/ac-ft).
134
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100-
CO
o
o
Desolting Cost
With Brine
Removal
Desalting Cost
Without Brine
Remove I
0 10 20 30
REDUCTION IN INDOOR WATER USE
(PERCENT)
NOTE: The cost of desalting shown reflects
the costs in terms of the total
volume of blended wastewater.
Figure 23. Comparative cost of
alternative (by desalting) to
"Penalty Costs"
135
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SECTION 9
SAVINGS IN FUTURE EXPENDITURES FOR
SECONDARY TREATMENT PLANTS
The estimated capital expenditures (24) for secondary treatment plants in
California to the year 2000 is $764,920,000 for enlargement of existing
plants and $566,390,000 for construction of new plants that would be operated
independent of existing facilities. Previously two cases were analyzed for
the same conditions as follows:
Case I - New wastewater facilities are additions to or expansions of
existing facilities to take care of new population growth.
Case II - New wastewater facilities serve new population growth and
operate independent of existing facilities.
Therefore, the analyses for these cases are applicable and were used to
approximate the order of magnitude of capital savings in future expenditures
when water conservation is undertaken. The estimated savings are shown in
Table 54 and are additive.
At the optimum level of water conservation effort, the approximate savings
from Table 54 are:
Case
Approximate— Optimum
Level of Water
Conservation Effort
(in %)
Approximate Future
Capital Savings
(in $1,000).
I 30
II 37
Total
Rounded
168,000
44,000
212,000
210,000
There would also be expected savings in capital expenditures for two other
categories — upgrading to secondary treatment level and upgrading and
enlargement of existing plants. However, there was not sufficient available
information to examine this aspect.
I/ From net benefits curves.
136
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TABLE 54. ESTIMATED SAVINGS IN CAPITAL EXPENDITURE
FOR SECONDARY TREATMENT PLANTS PROPOSED FOR NEW
CONSTRUCTION AND ENLARGEMENT IN CALIFORNIA
Case I - Enlargement of Existing Plants
Estimated
Expenditures
to Year 2000
(in $1,000)
764,920
566,390
Percent
Reduction
Water Use
10
20
30
35
Case II - New Plant
30
35
40
Capital Cost
(in percent)
11.8
21.5
22.0
22-.0
Construction
6
7
8
Savings
(in $1,000)
90,260
164,460
168,280
168,280
33,980
39,650
50,980
137
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SECTION 10
IMPLEMENTATION OF WATER CONSERVATION MEASURES
In summary, the results of the study concerning indoor water conservation
showed the following major points:
8 The benefits of water conservation substantially exceed its costs.
Benefits are generated by savings in energy and water uses and expendi-
tures on wastewater systems.
• Water conservation measures in existing buildings are highly important
since substantial greater benefits are generated by measures in existing
buildings than in new buildings.
0 The operational problems encountered in wastewater systems during
periods of flow reductions were generally not so severe that they greatly
upset systems operations. Remedial measures were taken to resolve the
problems so that proper operation could be continued.
o Changes in wastewater quality during periods of flow reduction did not
generally cause treatment plants to more frequently exceed their BOD and
SS effluent limitations.
• Water conservation is not counterproductive to wastewater reclamation.
0 An intensive water conservation effort is necessary to attain the
optimum level of water use reductions where the greatest benefits over
costs occur.
In recent years, water conservation has gained much attention and is publicly
acclaimed by many as an essential element of effectively managing our water
resources. As a result, many have undertaken water conservation measures,
but often without the benefit of a full knowledge of its positive and nega-
tive effects. This study quantitatively confirms the desirability of water
conservation, and supports the need to vigorously implement water conserva-
tion measures. The importance of water conservation in reducing the expendi-
tures in wastewater systems is also recognized in the Federal Water Pollution
Control Act (PL 92-500) as amended. It requires an analysis of cost effec-
tive water conservation measures for each facility planning area as a condi-
tion for federal grant funding of wastewater facilities.
138
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However, the positive results of this study, the public acclaim, the federal
regulations for cost effective analysis, or existing policies which all pro-
mote water conservation do not necessarily cause a community to undertake
concerted water consevation efforts in a non-crisis water supply situation.
This is indicated by the sudden increase in the amount of wastewater flow
in California during the year immediately following the drought. This
increase—'averaged 34% although the flow quantity did not reach the
pre-drought flows. However, the tendency for the community to revert to old
habits does point out a need for an understanding — an understanding of the
"incentives" of water conservation from different points of view in the
community. Urban water use involves various elements of interests concerning
water supply development and treatment, delivery, consumer use, and waste-
water treatment and disposal. Although water conservation may result in a
net economic gain to a community when viewed as a whole system as was done in
this report, the financial impact differs with each element in the system.
The solution approach is to investigate the financial/social gains or losses
of water conservation from at least three points of view — the water sup-
plier, the consumer, and the waste discharger and include the following
considerations:
Water Supplier
° Reduced water delivery requirements
0 Cost savings due to reduced distribution of water
0 Cost savings in treatment of water delivered
0 Cost savings in future capital expenditures for water supply
facilities
• Deferred capital expenditure for future water supply facilities
0 Reduction in purchased water
° Loss of revenues requiring adjustment of price and/or reduction in
operation cost
Consumer
0 Energy cost savings
0 Water cost savings
_!/ In the year immediately following the drought, wastewater flows increased
34% as compared to the previous year, but were still 15% less than the
predrought flows.
139
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Waste Discharger
0 Cost savings in operation and maintenance of sewer systems
0 Cost savings in future capital expenditures for wastewater facilities
0 Deferred capital expenditures for future wastewater facilities
e Satisfaction of grant requirements for financing wastewater facilities
Items Common to All Elements
8 Positive public image and ethics for promoting water conservation
9 Cost of water conservation measures
Various communities in California and elsewhere experienced the effects of
water conservation during the drought. Their experiences in the form of
available data could be used in analyzing the financial/social gains and
losses.
When community interests understand the benefits to themselves as well as to
the total community a willingness to take action is generated and leads to
the development and implementation of a workable plan.
140
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REFERENCES
1. DeZellar, Jeffrey T. and Maier, Walter J. "Effects of Water
Conservation on Sanitary Sewers and Wastewater Treatment Plants". Water
Pollution Control Federation Journal. Vol. 52, No. 1. January 198(h
2. Sakaji, Richard H. "Water Conservation and Wastewater Treatment
Plants". ASCE Environmental Engineering Conference. July 1979.
3- Federal Register, Vol. 43, No. 188. "Environmental Protection Agency,
Rules and Regulations: Municipal Wastewater Treatment Works,
Construction Grants Program". September 27, 1978.
4. U.S. Environmental Protection Agency, Region IX. Letter Approving
Population Projections Used by Planning Agencies for the 208 Water
Quality Planning Program. January 1980.
5., California Department of Water Resources. Bulletin 198.
Conservation in California. May 1976.
10.
11,
12.
Water
6. California Department of Water Resources. Bulletin 191. A Pilot Water
Conservation Program. Appendix G. Device Testing. March 1978.
7. California Department of Water Resources. • Bulletin 191. A Pilot Water
Conservation Program. San Diego Metropolitan Area. Appendix A.
March 1978. '. :! :
8. California Department of Water Resources. Bulletin 206. The Impact
of Severe Drought in Marin County, California. Appendix. Supporting
Studies. November,1979.
Dames and Moore. Construction Costs for Municipal Wastewater Treatment
Plants: 1973-1977~EPA Technical Report (MCD-37).January 1978.
Bursztynsky, Taras A. and John A. Davis. Effects of Water Conservation
on Municipal Wastewater Treatment Facilities. Association of Bay Area
Governments. Water Pollution Control Federation Conference.
October 4, 1978.
Dames and Moore. Construction Costs' for Municipal Wastewater Conveyance
Systems: 1973-1977. EPA Technical Report (MCD-38).May 1978.
California Department of Finance. Provisional Household Projections of
California Counties to Year 2000. Report 77, P-2. December 30, 1977.
141
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13. Gilbert, J. B. and Associates. Report on Water Conservation Reuse and
Supply, San Francisco Bay Region.
14. Metcalf and Eddy, Inc. Wastewater Engineering: Treatment/Disposal/
Reuse. McGraw-Hill Book Co. 1979.
15. Dames and Moore. Analysis of Operations and Maintenance Costs' for
Municipal Wastewater Treatment Systems. EPA Technical Report (MCD-39).
February 1978.
16. Ling, Catherine S. Wastewater Reclamation Facilities Survey.
California Department of Health Services. Survey Report. 1978.
17. University of California, Agricultural Extension. Guidelines for
Interpretation of Quality of Water for Irrigation. Davis, CA.
September 13, 1974.
18. California Water Pollution Control Board. (Predecessor of California
Water Resources Control Board). Studies of Wastewater Reclamation and
Utilization. Publication No. 9. 1954.
19. California Department of Water Resources. Bulletin 113-3. Vegetative
Water Use in California, 1974. April 1975.
20. California Department of Food and Agriculture. California Principal
Crop and Livestock Commodities 1978. June 1979.
21. Lunt, 0. R., Youngner, V. B., and Oertli, J. J. "Salinity Tolerance of
Five Turfgrass Varieties". Agronomy Journal. Vol. 53:247-249. 1961.
22. Hassan, Ahmad A., Ph.D. and Zawadski, Michael, Ph.D.. Consumer Costs of
Water Quality in Domestic Water Use Lompoc Area. California Department
of Water Resources, Southern District. June 1978.
23. California Department of Water Resources. Bulletin 130-71. Hydrologic
Data: 1971. Volume V: Southern California. December 1972.
24. U.S. Environmental Protection Agency, Unpublished Data in support of EPA
"1978 Needs Survey". From EPA Washington D.C. Staff. February 1980.
142
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APPENDIX A
ASSEMBLY BILL NO. 1395. AN ACT TO ADD SECTION 17921.3
TO THE HEALTH AND SAFETY CODE, RELATING TO WATER CLOSETS
»
CHAPTER 91
An act to add Section 17921.3 to the Health and Safety Code,
relating to water closets.
[Approved by Governor April 2, 1976. Filed with
Secretary of State April 2, 1976.]
LEGISLATIVE COUNSEL'S DIGEST
AB 1395, Keene. Water closets.
There is no statutory existing law regarding the use of water closets
in construction of buildings used for human habitation.
This bill would prohibit the construction of new hotels, motels,
apartment houses, and dwellings after January 1, 1978, which are
equipped with tank-type water closets which use more than an aver-
age of y/2 gallons of water per flush and are not approved by the State
Department of Housing and Community Development according to
specified standards. Such requirement would only be applicable to
new additions to, or renovations of, existing structures if compliance
would not require substantial modification of the existing plumbing
system. The bill would require the department to permit the installa-
tion of tank-type water closets equipped with devices reducing aver-
age water consumption to no more than .3% gallons per flush. The
department would be required to periodically publish a list of accept-
able water closets and devices in its regulations.
This bill would permit a manufacturer to sell water closets which
do not meet such requirements in a quantity sufficient to meet the
need for water closet installation or replacement in structures other
than new hotels, motels^ apartment houses, and dwellings, or when
authorized by the local enforcement agency.
This bill would permit the local enforcement agency to allow the
use of standard flush toilets under specified circumstances. The re-
quirements of the bill would be inapplicable in areas subject to pre-
scribed waste discharge requirements.
The bill would also permit the Commission of Housing and Com-
munity Development to suspend the requirements imposed by this
bill by adoption of a regulation based upon a determination that
there is ah inadequate supply of such water closets to meet the need
in new construction or that such water closets are not available at a
reasonable price.
Violations of the provisions of this bill would be misdemeanors
under existing statutory law.
The bill would provide that there would be no reimbursement of,
or appropriation to, local governmental agencies for state-mandated
local program costs imposed by the bill because of a specified reason.
143
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Ch.91
— 2 —
The people of the State of California do enact as follows:
SECTION 1. Section 17921.3 is added to the Health and Safety
Code, to read:
17921.3. After January 1, 1978, no new hotel, motel, apartment
house, or dwelling shall be constructed which employs a tank-type
water closet that uses more than an average of 3% gallons, of water
per flush and which is not approved by the department as meeting
adequate standards of safety and sanitation. Such requirement shall
only be applicable to new additions to, or renovations of, existing
hotels, motels, apartment houses, and dwellings if, compliance with
the requirements of this section will not require substantial
modification of the existing plumbing system. In satisfaction of the
requirements of this section, the department shall permit the
installation of tank-type water closets equipped with devices which
are found by the department to meet applicable performance
standards, that reduce average water consumption to no more than
3Va gallons per flush, in water closets having a tank capacity in excess
of 3l/z gallons. The department shall periodically publish a list of
acceptable water closets and devices to reduce water consumption.
A manufacturer may sell water closets in this state which do not
meet the foregoing requirements in a quantity sufficient to serve the
need for water closet installation or replacement in structures other
than new hotels, motels, apartment houses, or dwellings, or when
authorized by the local enforcement agency.
Any local enforcement agency may allow the use of .standard flush
toilets, when, in the opinion of the local agency, the configuration of
the building drainage system requires a greater quantity of water to
adequately flush the system.
This section shall not apply in any local jurisdiction, area, or region
of the slate subject to waste discharge requirements imposed
pursuant to Article 4 (commencing with Section 13260) of Chapter
4 of Division 7 of the Water Code when the local enforcement agency
determines that the waste water discharges would exceed such waste
discharge requirements if this section was made applicable.
The requirements prescribed by this section may be suspended for
a specified period of time by a regulation adopted by the commission
when the commission finds that there is an inadequate supply,
including a choice of styles or colors for the consumer, of water
closets specified in this section to meet the needs of new
construction, or such water closets are not available at reasonable
prices as compared to water closets not complying with the
requirements of this section.
SEC. 2. Notwithstanding Section 2231 of the Revenue and
Taxation Code, there shall be no reimbursement pursuant to that
section nor shall there be any appropriation made by this act because
the duties, obligations or responsibilities imposed on local
government by this act are minor in nature and will not cause any
financial burden to local government.
144
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APPENDIX B^-'
CALIFORNIA ADMINISTRATIVE CODE
TITLE 20, CHAPTER 2
SUBCHAPTER 4: ENERGY CONSERVATION
ARTICLE 4: APPLIANCE EFFICIENCY STANDARDS
1601. Scope. Unless otherwise indicated, the provisions of this article
shall apply to the following types of new appliances sold in California:
(f) Plumbing fittings, including showerheads, lavatory faucets and sink,
faucets. '
1602. Definitions. For the purpose of this article the following defini-
tions shall apply:
(a) General
(1) "Accepted laboratory" means any testing laboratory approved by
the Commission for testing of a particular type of appliance.
(2) "Date of sale" means the day when the appliance is physically
delivered to the buyer.
(3) "Failure modes and effects analysis" means an analysis of a
particular design which describes the most probable ways systems
and components can fail, the consequences of such failures, and
design steps taken to minimize or reduce the possibility of their
occurrence.
t (4) "Intermittent type ignition device" means any ignition system
on a gas appliance which is not a continuously burning gas pilot
light.
I/ This appendix contains excerpts from the California Administrative Code
and pertains only to plumbing fixtures. Omissions applying to other
appliances are denoted by *****.
145
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(5) "Manufacturer" means any person engaged in the production or
assembly of an appliance. Manufacturer also includes,any person
whose brand or trademark appears on such appliance, if the brand or
trademark of the person actually producing or assembling the
appliance does not appear on the appliance.
(6) "Marking plate" means a plate, located so as to be easily read
when the appliance is in a normally installed position.
(f) Plumbing Fittings
(1) "Lavoratory faucet" means a plumbing fitting designed for
discharge into a lavoratory. '
(2) "Plumbing fittings" means a device designed to control and/or
guide the flow of water into or convey water from a fixture.
(3) "Showerhead" means a device through which water is discharged
for a shower bath.
(4) "Sink faucet" means a plumbing fitting designed for discharge
into a sink. "Sink faucet" does, not include utility faucets
designed for use with service sinks.
1603. Test Methods.
*
*
(f) Plumbing Fittings. The manufacturer shall cause the testing of
samples of each model of showerhead, lavatory faucet and sink faucet to
be sold in California.
A sample of sufficient size of each model shall be tested to insure that
the flow rate certified under the provisions of Section 1605 shall be no
less than the mean of the sample or the upper 97-1/2 percent confidence
limit of the true mean divided by 1.05.
The maximum flow rate shall be measured using the test procedure
approved by the American National Standards Institute on October 2,
1975, and known as ANSI A112.18.1-1975 with Section 5.14 modified to
read as follows:
"5.14 Discharge
The inlet(s) of the fitting, with standard accessories, shall be
connected to smooth pipe or tubing of the same nominal diameter as
the fitting outlet, which is at least 20 inside diameters long.
Upstream pressure tap(s) shall be located 1/2 to 2-1/2 inside
diameters upstream from the fitting inlet. Pressure tap size and
146
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configuration shall conform with ASME Performance Test Code
Supplement, Instruments and Apparatus, PTC 19.2-1964 Part
2—Pressure Measurement, paragraph 2.05. Pressure Transducers on
gauges shall be calibrated as per PTC 19.2-1964, Chapter 4.
The fitting shall be .thoroughly flushed before measuring the flow
rate.
Water at a temperature of 140°F plus or minus 5°F shall be dis-
charged from the fitting for 10 minutes. The test for water dis-
charge rate shall then be performed with water whose temperature is
100°F plus or minus 5°F. The fitting shall then be examined to
ensure that the parts have not been damaged by the hot water. The
test pressure at the inlet shall cover a range between 20 and
80 psig •«hen flowing. All fittings shall be tested at maximum flow
setting. The rates of flow used for certification under the provi-
sions of Section 1605 shall be the maximum rate of flow at any
supply pressure between 20 and 45 psig and the maximum rate of flow
at any supply pressure between 45 and 80 psig.
If a fluid meter is used to measure flow rate, the installation
shall be in accordance with ASME Supplement 19.5 on Instruments and
Apparatus, Application, Part II of Fluid Meters, 1972."
1604. Efficiency Standards.
(f) Plumbing Fittings
The maximum flow rate of all new showerheads, lavatory faucets, and
sink faucets manufactured on or after the date specified in Table F
shall be certified not to exceed the values shown.
TABLE F
Effective
Date
December 22,
1978
Appliance
Plumbing Fittings
Showerheads
Lavatory faucets
Sink faucets
Test Pressure
20-45 psig
45-80 psig
20-80 psig
20-80 psig
Maximum Flow
Rate
2.75 'gpm
3.00 gpm
2.75 gpm
2.75 gpm
147
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1605. Certification.
(a) No new gas appliance of the type described in Table G may be sold or
offered for sale in California on or after the effective date shown, unless
it has been certified by the Commission to comply with the requirements of
Subsections 1603(d)(4), 1603(d)(5), 1603(d)(6), 1603(e)(3), 1603(e)(4),
1603(g) and 1603(h) of this Article.
TABLE G .
Effective Date
Appliance
July 8, 1978
February 10, 1979
December 22, 1979
24 months after certification
of the first swimming pool
heater
Fan type central furnaces
Household cooking appliances
Clothes dryers
Fan type wall furnaces
Swimming pool heaters
(b) No new appliance described in Subsections 1601(a) through (f) of these
regulations (except swimming pool heaters) may be sold or offered for sale in
California on or after the effective dates listed in Section 1604 of these
regulations unless the manufacturer has provided sufficient information about
the model number or other indentification by which the date of manufacture
can be readily ascertained.
(c) No new appliance described in Subsections 1601(a) through (f) of these
regulations, (except swimming pool heaters), which was manufactured on or
after the effective dates listed in Section 1604 of these regulations, shall
be sold or offered for sale in California, which is not certified by its man-
ufacturer to be in compliance with the provisions of this* Article. One year
after such effective date, no new appliance described in Section 1601 of
these regulations, regardless of the date of manufacture, may be sold or
offered for sale in California, which is not,certified by its manufacturer to
be in compliance with the provisions of this Article. Certification is not
required, however, for models of appliances whose production ceased before
November 3, 1977, if it can be readily ascertained from the label or name-
plate that its efficiency meets the applicable value specified in
Section 1604 of this Article. The requirements referred to in Subsec-
tion 1665(a) are excluded from the requirements of this subsection.
148
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(e) The manufacturer shall submit a certification statement to the executive
director for each model, containing the following information, except as pro-
vided in Subsection (f):
(1) Name and address of manufacturer.
(2) Type of appliance.
(3) Brand name.
(4) Model number, as it appears on the appliance name plate.
(5) Name and address of laboratory where test for efficiency was
performed.
(6) Date of test for efficiency.
(7) Results of the test for efficiency as follows:
******
(F) Plumbing Fittings
1. Maximum flow rate (showerheads at 20-45 psig).
2. Maximum flow rate (showerheads at 45-80 psig).
3. Maximum flow rate (lavatory faucets and sink faucets
at 20-80 psig).
(8) Sufficient information about the model number or other identifica-
tion by which the date of manufacture can be readily ascertained.
(9) A declaration that the appliance model complies with Article 4,
Subchapter 4, of Title 20, of the California Administrative Code. the
executive director may at his discretion, prescribe a standard form for
the certification statement. ,
1606. Identification of Complying Appliances. (a) Sufficient information
shall be shown on the outside of the shipping carton for any appliance
described in Subsections 1601 (a,) through 1601 (f) (and unit carton in the case
of plumbing fittings) to permit the determination of whether the appliance
complies with the requirements of this article. The manufacturer may display
the following information on the outside of the carton to show compliance:
(1) The Commission's, compliance seal;
(2) The appropriate measure of energy consumption or efficiency;
(3) The model number as it has been certified and information to deter-
mine date of manufacture; or
(4) Other information sufficient to show compliance.
149
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The executive director or his designee may require additional information if
necessary to permit determination of compliance.
(b) The name or brand of the manufacturer shall appear on each appliance.
*****
1607. Enforcement. • (a) Notwithstanding the provisions of Section 1605 of
these regulations, the executive director shall have authority to challenge
the efficiency test results provided by the manufacturer and cause the appli-
ance model to be retested at any voltage for which it is Labeled.
(b) The executive director shall cause periodic inspections to be made of
manufacturers, distributors or retailers of the new appliances described in
Section 1601 of these regulations, including appliances that have been or are
to be installed by contractors or builders at building sites, in order to
determine their compliance with this Article.
(c) The test would involve one unit selected by the executive director.
(1) If the performance of the appliance falls within the tolerances
listed below, no further "action is necessary, and the Commission will
pay the cost of testing.
Appliance
Plumbing fittings
Characteristic
Water flow rate
* * *
*
Tolerance Limits
(percent of certified value)
Not more than 110 percent
*
(2) If the performance of the appliance does not fall within the toler-
ances listed above, the manufacturer must pay the cost of testing and
take whatever steps are'necessary either to recertify the appliance at a
lower efficiency rating or to provide information to the satisfaction of
the executive director that:
(A) in the initial certification of the model, the method of
selecting the test sample complied with the requirements of
Section 1603 and
(B) in the initial certification of the model, the value certified
was in conformance with the requirements of Section 1603.
Even if this information is provided, the manufacturer shall be required
to test a second unit, selected by the executive director, in a labora-
tory acceptable to the executive director, at the manufacturer's
expense.
(3) If the performance of that second unit described in subsection (c)
(2) falls within the tolerances listed in Subsection (c)(l), no further
action will be taken. If the'performance of that second unit does not
fall within those tolerances, the certification for that model shall be
150
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suspended by Commission order. The manufacturer may retest and
recertify the model based on a new sample selected from his current
production.
(4) If any of the tests of units required by the executive director
pursuant to this subsection are not undertaken by a manufacturer, the
certification for that model shall be suspended by Commission order.
1608. Release of Manufacturer Information. (a) Any manufacturer who sub-
mits information to an accepted laboratory for the purpose of complying with
the intermittent ignition device requirements of this article may designate
that such information be kept confidential as within an exception of the
California Public Records Act (Sections 6250-6261 of the California
Government Code) by so marking such information in a plain and legible
manner. Thereafter, the Commission shall not disclose or otherwise make
available to the public such information unless the procedures in this sec-
tion have been followed.
(b) If the Commission or any person desires public disclosure of information
designated confidential as presented above, the Commission shall promptly
notify, in writing, the affected manufacturer and allow the manufacturer
opportunity to demonstrate to the Commission that the requested information
falls within an exception of the California Public Records Act (Sections
6250-6261 of the California Government Code), and therefore should not be
disclosed. The Commission shall give written notice of its decision to the
manufacturer and any other persons requesting notification. Information
shall not be publicly disclosed until fifteen days after the Commission deci-
sion has been rendered and notice thereof has been received by the
manufacturer.
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APPENDIX C
FACTORS USED FOR
I/
COMPUTING ENERGY SAVINGS-'
The values and assumptions used in computing the energy savings for the study
are contained in this appendix.
Water Heating Energy Savings
Average blended water temperature rise
(Used in Department of Water Resources
Bulletin 198, May, 1976, calculations;
conservative compared to Sacramento tests
and 52° rise assumed in model by L.K. Baker
et al in Household Water Conservation
Effects on Water, Energy, and Wastewater
Management, Water Use Conference, May 4-8,
1975 (Chicago)
Electric water heater efficiency (American
Gas Association, Science Application,
Inc., tests)
Gas water heater efficiency (same source)
Water heater by type (average) (Southern Cal
Edison, Southern Cal Gas, San Diego Gas &
Electric, Pacific Gas and Electric)
1 BTU (gas) equivalent to 1 BTU refined
oil.
1 BTU (electric) equivalent to 2.89 BTU
(refined oil) (Above two values from
Energy Requirements of Alternatives in
Water Supply, Use, and Conservation: A
Preliminary Report, by E.B. Roberts and
R.M. Hagan, Appendix A-3, December 1975.)
42 °F
90% .
65%
90% gas
10% electric
\J From an unpublished memorandum by J. Koyasako and D. Engdahl, California
Department of Water Resources, 'June 1976.
152
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Average energy content of oil
(Federal Power Commission, January 1976)
1 bbl oil
1 BTU
1 gallon water
1.44 x 105 BTU/gal
42 gal
1°F Delta T/lb water
8.34 Ib.
Gas saved would replace oil in power plant electrical generation.
Electricity saved would have been generated by oil burning.
Oil is taken as power plant-ready refined.
Energy Saved in Gas Water Heaters
= (.90 fraction heaters gas) (3.26 x 105 gal/ac-ft)
(8.34 Ibs/gal) (42° Delta T) (1/0.65 heater efficiency) (BTU/lb°F Delta T)
= (.90) (3.26) (8.34) (I/.65) (42) (105) BTU/ac-ft
= 1.58 x 108 BTU/ac-ft
Gas Saving Conversion to Oil
= (BTU oil) (1.58 x 108 BTU gas/ac-ft)
(BTU gas) (1.44 x 105 BTU oil/gal) (42 gal/bbl)
= 26.12 bbl/ac-ft
Energy Saved in Electric Water Heaters . •
= (0.10 fraction heaters electric) (3.26 x 105 gal/ac-ft)
(8.34 Ibs/gal) (42°F Delta T) (I/.90 heater effic)
(BTU/lb°F Delta T)
= (0.10) (3.26) (8.34) (1/.90) (105) (42) BTU
= 1.27 x 107 BTU/ac-ft
Electric Saving Conversion to Oil
= (2.89 BTU oil) (1.27 x 107 BTU elec/yr/ac-ft)
(BTU elect) (1.44 x 105 BTU oil/gal) (42 gal/bbl)
=6.07 bbl/ac-ft
Total Heating Energy Savings (Constant ki)
kj = 26.1 + 6.1 = 32.2 bbl/ac-ft
153
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Local Systems Savings
Pre-treatment Energy Savings
Calculations of savings in energy in pre-treatment of water were based on the
East Bay Municipal Utility District model described in Energy Reqgirements of
Alternatives in Water Supply, Use, and Conservation; A Preliminary Report by
E.B. Roberts and R. M. Hagan, December 1975, at page 40.
Total energy for pre-treatment, including chemical production and
transportation and plant operation energy is 37.2 kWh/ac-ft.
Distribution Energy Savings
From the same source, pp. 40-41, the East Bay MUD distribution system energy
is given as an average of 203 kWh/ac-ft, and was taken as representative of
systems statewide.
Conversion to Oil Savings
1 BTU electric = 2.89 BTU oil
1 kWh = 3.41 x 103 BTU
1 gallon refined oil contains 1.44 x 105 BTU
1 barrel oil - 42 gallons
1 kWh electric '» (3.41 x 103 BTU electric) (2.89 BTU pil/BTU electric)
- 9.85 x 103 BTU oil
BTU/bbl = (1.44 x 105 BTU/gal) (42 gal/bbl)
- 6.05 x 106 BTU/bbl
bbl/kWh electric - 9.85 x 103 BTU oil/kWh electric
6.05 x 106 BTU/bbl
- 1.63 x 10"3 bbl/kWh
Local Systems Cost Summation (Constant k?)
The sum of pre-treatment plus local distribution energy costs is:
Pre-treatment
Distribution
TOTAL
37.2 kWh/ac-ft
203.0 kWh/ac-ft
240.2 = 240 KWH/ac-ft
If all savings are in electricity, oil saving
k2 - (2.40 x 102 kWh/ac-ft) (1.63 x 10~3 bbl/kWh)
» 0.39 bbl/ac-ft
154
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-80-137
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
EFFECTS OF WATER CONSERVATION INDUCED WASTEWATER
FLOW REDUCTION
A Perspective
5. REPORT DATE
August 1980 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Jimmy S. Koyasako
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
California Department of Water Resources
1416 Ninth Street
Sacramento, California 95814
10. PROGRAM ELEMENT NO.
35B1C, SOS #4, Task 17
11. CONTRACT/GRANT NO.
R806262
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory—Ctn.,OH
Office of Research and Development
U. S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final 10/78 to 5/80
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: John N. English
Telephone: 513/684-7613
16. ABSTRACT
This study examines the effects of indoor water conservation induced wastewater
flow reduction ,in selected areas in California. The effects are quantified in
economic terms by viewing the net economic gain to a hypothetical community
which characterizes average statewide conditions. In addition, the major benefits
and costs of indoor water conservation and a perspective of their relative values
are presented.
Various municipal wastewater dischargers that experienced actual flow reduction
during the 1976-77 drought in California provided data on the operation of their.-
collection and treatment systems prior to, during, and after the drought. This
report examines their experiences, along with other available pertinent information,
to determine the advantages and disadvantages of water conservation. The results
of the study quantitatively confirm the desirability of promoting water conservation
and show that the benefits exceed the costs.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFlERS/OPEN ENDED TERMS
c. COS AT I Field/Group
Water conservation
Water reclamation
Water resources
Water supply
Wastewater treatment
Wastewater reuse
Domestic reuse
Flow reductiori-
13B
8. DISTRIBUTION STATEMENT
Release to public
.19. SECURITY CLASS (ThisReport)'
Unclassified
21. NO. OF PAGES
171
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
155
U.S. GOVERNMENT PRINTING OFFICE: 1980--657-165/0134
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