EPA-600/2-77-183
September 1977
Environmental Protection Technology Series
REUSE OF MUNICIPAL WASTEWATER
FOR GROUNDWATER RECHARGE
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
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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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EPA-600/2-77-183
September 1977
REUSE OF MUNICIPAL
WASTEWATER FOR
GROUNDWATER RECHARGE
by
Curtis J. Schmidt
Ernest V. Clements, III
SCS Engi neers Inc.
Long Beach, California 90807
Contract No. 68-03-2140
Project Officer
Irwin J. Kugelman
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 Laboratory, 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.
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FOREWORD
The Environmental Protection Agency was created because of
increasing public and government concern about the dangers of
pollution to the health and welfare of the American people.
Noxious air, foul water, and spoiled land are tragic testimony to
the deterioration of our natural environment. The complexity of
that environment and the interplay between its components require
a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem
solution and it involves defining the problem, measuring its
impact, and searching for solutions. The Municipal Environmental
Research Laboratory develops new and improved technology and sys-
tems for the prevention, treatment, and management of wastewater
and solid and hazardous waste pollutant discharges from municipal
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
communi ty.
This report provides a comprehensive summary and evaluation of
current efforts throughout the U.S. to recharge groundwater sys-
tems with treated municipal wastewater. Through these recharge
programs, groundwater supplies are being replenished, saltwater
endangered-aquifers are being protected, and water is being
reclaimed for future reuse.
Francis T. Mayo, Director
Municipal Environmental
Research Laboratory
11
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ABSTRACT
A survey of groundwater recharge operations with municipal waste-
water effluent was conducted. It was found that this activity is
being practiced at 10 sites in the U.S. with a total capacity of
77 MGD. The most successful employ percolation with alternate
flooding and drying cycles. Well injection can be successful but
only if rigorous control of injected water quality is maintained.
Clogging of recharge wells is the major problem. Sufficient data
have not been developed to define the movement of pollutants such
as salts, trace organics or pathogens through groundwater as a
function of soil characteristics, groundwater hydraulics, and
groundwater characteristics. Thus, water quality requirements to
insure successful recharge over a long period can not be defined
quantitatively.
At the sites surveyed reasonable success has been achieved over
periods ranging from 1 to 20 years. It is recommended that
intensive monitoring of these and a few other new sites be con-
tinued and instituted to gather data on which rational design
criteria can be based.
This report was submitted in fulfillment of Contract No. 68-03-2140
by SCS Engineers under the sponsorship of the U.S. Environmental
Protection Agency. This report covers a period from October, 1974
to June, 1975, and work was completed as of July, 1975.
IV
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CONTENTS
Page
Foreword iii
Abstract iv
Figures vii
Tables ix
Acknowledgment xii
Sections
I Introduction 1
II Scope, Objectives and Approach 3
III Conclusions and Recommendations 5
IV Required Quality Criteria 9
V Description of Current Practices 15
VI Analysis of Recharge Economics 32
VII Appendices 36
A. Field Investigation Reports 36
1. Camp Pendleton, CA 37
(U.S. Marine Corps)
2. Hemet CA 44
(Eastern Municipal Water District)
3. Long Island, NY 50
(Nassau County Dept. of Public Works/
U.S. Geological Survey)
4. Oceanside, CA 59
(City of Oceanside)
5. Orange County, CA 65
(Orange County Water District)
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CONTENTS (continued).
Page
6. Palo Alto, CA 81
(Santa Clara Valley Water District)
7. Phoenix, AR 93
(U.S. Water Conservation Laboratory)
8. San Clemente, CA 104
(City of San Clemente)
9. St. Croix, Virgin Islands 109
(Government of the Virgin Islands)
10. Whittier, CA 112
(Los Angeles County Sanitation
Districts/L.A. Flood Control
Districts)
B. General Reference Bibliography 125
C. California State Health Department 128
Statement
D. Capital Cost Factors 134
E. Procedure for Cost Calculation 135
F. Conversions from English to 136
Metric Units
VI
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FIGURES
1 Growth of Recharge Practices 2
2 Basic Diagram of Salt Water Intrusion 23
A-l Schematic Diagram of Santa Margarita 40
River Basin Recharge Facilities, Camp
Pendleton, California
A-2 Tertiary Treatment Plant at Long Island, 51
New York
A-3 Injection Facilities at Bay Park, 54
Long Island, New York
A-4 Details of the Bay Park Injection Well 55
A-5 Present and Planned Recharge Facilities 62
at Oceanside, California
A-6 Hydraulic Seawater Barrier and Recharge 66
System, Orange County, California
A-7 Orange County Water District Advanced 68
Wastewater Reclamation Plant,
Fountain Valley, California
A-8 Typical Multi-Casing Injection Well 75
at Orange County
A-9 Planned Advanced Wastewater Treatment 82
Plant at Palo Alto, California
A-10 Proposed Wastewater Reclamation/Reuse 86
System at Palo Alto, California
A-ll Detail of Injection/Extraction Well 88
Features
A-12 Plan of Flushing Meadows Project
96
VTI
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FIGURES (continued).
No. Page
A-13 15 MGD Wastewater Recharge/Reclamation 101
System at Phoenix, Arizona
A-14 Cross-section of Two Parallel 103
Infiltration Strips with Wells Midway
Between Strips for Pumping Renovated Water
A-15 Schematic Diagram of Recharge 106
Facilities at San Clemente, California
A-16 Schematic Diagram of Sampling Pan Well 120
A-17 Location of Monitoring Wells, 122
Whittier Narrows Water Reclamation Project
VI 1 1
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TABLES
No. Page
1 Quality Requirements for Santa Ana 10
Groundwater Basin
2 Inventory of Recharge Operations 16
3 Treatment Systems and Effluent Quality 19
Characteristics
4 Comparison of IDS in Recharge Water 22
and Receiving Groundwater
5 Summary of Facilities and Management 24
Practices for Percolation Recharge
6 Characteristics of Injection Recharge 27
Systems
7 Estimated Total Costs of Recharge 33
Operations
A-l Typical Secondary Effluent 38
Characteristics at Camp Pendleton
A-2 Typical Groundwater Quality at a 42
200 foot Depth at Camp Pendleton
A-3 Average Municipal Effluent 46
Characteristics at Hemet, California
A-4 Effects of Percolation on Effluent 48
Characteristics
A-5 Typical Tertiary Effluent 53
Characteristics at Long Island, New York
A-6 Typical Characteristics of Treated 61
Wastewater for Recharge at Oceanside,
California
A-7 Estimated Capital and Operation and 63
Maintenance Costs for Recharge
System at Oceanside, California
ix
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TABLES (continued).
Page
No. —*—
A-8 Design Parameters for Orange County 69
Water District Water Reclamation Plant
A-9 Average Effluent Characteristics at 74
the Orange County Sanitation District
and the Orange County Water District
Wastewater Reclamation Plants
A-10 Santa Ana RWQCB Quality Requirements for 77
Water Recharged to the Santa Ana Ground-
water Basin
A-ll Capital Costs for Reclamation and 78
Recharge Facilities at Orange County,
California
A-12 Estimated Capital and Operation and 79
Maintenance Costs for the Wastewater
Reclamation/Recharge System at
Orange County, California
A-13 Anticipated Tertiary Effluent 85
Quality Characteristics at Palo
Alto, California
A-14 Estimated Capital Costs for Wastewater 90
Reclamation/Recharge System at Palo
Alto, California
A-15 Estimated Annual Operation and 91
Maintenance Costs at Palo Alto,
California
A-16 Typical Municipal Effluent 94
Characteristics at the 23rd Avenue
Plant, Phoenix, Arizona
A-17 Soil Profiles at Flushing Meadows 97
A-18 Estimated Capital and Operation and 100
Maintenance Costs of 15 MGD Recharge/
Extraction System at Phoenix, Arizona
A-19 Typical Effluent Characteristics 105
at San Clemente, California
A-20 Average Municipal Effluent 113
Characteristics at Whittier
Narrows and San Jose Creek
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TABLES (continued) .
No. Page
A-21 NPDES Effluent Limitations for 115
Whittier Narrows and San Jose
Creek Plants
A-22 Geologic Soil Profiles of San Gabriel 117
and Rio Hondo Basins
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ACKNOWLEDGMENTS
We wish to thank the following peopl
and assistance in providing informat
operations. Without their help, thi
been accomplished.
Richard Aldrich
Superintendent
Water and Sewer Department
Oceanside, California
Herman Bouwer
Director
U.S. Water Conservation
Laboratory
Phoenix, Arizona
Krisen Euros
Project Engineer
Black, Crow & Eidsness, Inc.
St. Croix, Virgin Islands
Paul Campo
Base Geologist
United States Marine Corps
Camp Pendleton, California
Gordon Elser
Public Information Officer
Orange County Water
District
Huntington Beach,
California
Jack Reinhard
Water Conservation
Department
L.A. County Flood
Control District
Los Angeles, California
John Vecchioli
Hydrologist
U.S. Geological Survey
Mineola, New York
e for their cooperation
ion on their recharge
s study could never have
Lloyd Fowler
Director of Engineering
Santa Clara Valley
Water District
San Jose, California
Claire Gillette
Eastern Municipal
Water District
Hemet, California
Joe Haworth
Pub!ic Information
Officer
L.A. County Sanitation
Districts
Whittier, California
Jim 01i v a
Engi neer
Nassau County Depart-
ment of Public Works
Mineola, New York
Phil Peter
City Engineer
San Clemente,
nia
Califor-
Bill Roman
Resources Engineer
Santa Clara Valley
Water District
San Jose, California
Curtis J. Schmidt and
and Project Engineer,
Long Beach Boulevard,
Ernest V. Clements, III are President
respectively, of SCS Engineers, 4014
Long Beach, California.
XI 1
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SECTION I
INTRODUCTION
Groundwater in the United States has historically been a
quantitatively minor water source whose chief use was in
individual homes or small communities. Today, however,
groundwater supplies a substantial percentage of the nation's
water requirements. The conservation, protection, and re-
plenishment of our groundwater resources has become increas-
ingly important as our reliance on this water grows.
As populations increase, demands for groundwater supplies in
many areas of the country have started to exceed the safe
perennial yield limits of the basins, causing significant
drops in water tables. This has forced authorities to seek
alternate supplies.
One such alternate supply is treated municipal wastewater
which can be recharged to replenish groundwater basins, to
establish saltwater intrusion barriers in threatened coastal
aquifers, or to provide further treatment for ultimate ex-
traction and reuse. Currently, an average of 45 mgd is used
in the United States specifically for these groundwater re-
charge purposes. This figure will have increased to nearly
69 mgd by late 1975, and to 77 mgd by 1977, when sites
presently under design and construction are operational.
It should be emphasized that the inadvertent, uncontrolled
recharge of treated effluent discharged to land, and the
continuous release of septic tank wastes is vastly greater
in magnitude than the volumes shown here from formal re-
charge programs.
Figure 1 depicts the rate of growth of recharge practices
from 1943 to 1976. While ten operations certainly cannot
be projected as indicative of a trend, the current studies
underway definitely show support of a continued increase in
effluent recharge practices.
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z
o
cr
LU
a
o
LU
o
a:
<
x
o
LU
a:
o
z
10
9 -
8
7
6
5
L
_L
_L
1943 1955
1960
1965
YEAR
1970
1975
1978
FIGURE I.
GROWTH OF RECHARGE PRACTICES
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SECTION II
SCOPE, OBJECTIVES, AND APPROACH
SCOPE
This study was limited
from municipal sewage
were those recharging
and/or to control salt
operations that extrac
charge for irrigation
application and percol
disposal purposes only
to groundwater recharge of wastewater
treatment plants. Programs covered
for groundwater basin replenishment
water intrusion, and included those
ted the treated effluent after re-
and other uses. Sites practicing land
ation of effluent for irrigation or
were not included in this study.
A total of 10 sites in the U.S. were found to be currently
operating effluent recharge systems, conducting pilot
studies prior to designing full scale operations, or con-
structing facilities specifically for recharge. Each of
these was investigated in a case study report. (See
Appendix A.)
It should be noted,
practicing recharge
water, storm water,
eluded here. ATso,
the nation (usually
posing of effluent
however, that there are many locations
with fresh water supplies (imported
and natural runoff) that are not in-
there exist many treatment plants across
small, rural facilities) that are dis-
on land or dry riverbeds^thereby ulti-
mately recharging aquifers. These operations, along with
thousands of individual septic tank facilities, are un-
controlled, unmonitored, non-deliberate recharge operations
and are not included in this study.
OBJECTIVES
The primary purpose of this study was to make a state-of-the-
art survey to bring together information about existing
groundwater recharge operations in a concise form. This
information can be used by planners and engineers in the
design of new recharge systems and by governmental decision
makers in determining whether such systems are appropriate
to their situations. The report is also a useful tool for
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responsible management and technical personnel in locating
existing recharge operations which can provide valuable back-
ground experience. Another purpose of the project is
to spotlight deficiencies that exist in the available infor-
mation concerning recharge with treated wastewater and to
suggest further research to overcome these deficiencies.
Specific project objectives were as follows:
Conduct a literature search to collect data on those
projects for which publications exist, and also to
obtain water quality criteria for recharge applica-
tions.
Supplement the literature search by various means
to locate and obtain descriptive information on un-
publicized recharge projects and update existing
information on publicized projects.
Conduct field investigations of important recharge
operations which are relatively little known.
For each recharge situation, obtain technical and
economic information pertinent to purpose, size,
design, performance, costs, and problems.
APPROACH
The following tasks were performed by the SCS project team
during the completion of this study:
A comprehensive literature search was conducted at
several large university libraries and in-house
for any information pertinent to municipal waste-
water recharge operations.
Field investigations of ten recharge sites were
made and case studies prepared (see Section VII, A).
Separate sections were prepared using information
from the case studies and other sources regarding
required quality criteria, types of treatment,
methods of recharge, monitoring and safeguards,
significant operational problems, and economic
factors.
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SECTION III
CONCLUSIONS AND RECOMMENDATIONS
CONCLUSIONS
As the demand for fresh water continues to grow,
and groundwater supplies become increasingly over-
extended, the problems of salt water intrusion
along coastal areas and diminishing groundwater
reserves are forcing authorities to look toward
domestic wastewater reuse, including groundwater
recharge, as a feasible conservation measure.
Ten locations in the U.S. are currently operating
or designing and constructing formal groundwater
recharge facilities for treated municipal waste-
water. Seven of these are percolation type pro-
grams, and three are well injection systems.
Percolation recharge operations have been shown to
be effective in forming subsurface barriers against
salt water intrusion. The use of effluent for this
purpose is likely to increase in coastal aquifers
threatened by seawater.
Preliminary studies^/have shown that percolation of
wastewater through soil provides significant treat-
ment. Three of the recharge programs plan to take
advantage of this phenomenon by extracting all re-
charged water for irrigation and recreational reuse.
' U.S. Water Conservation Lab, Phoenix, AR.
L.A. County Sanitation Districts, Whittier Narrows, CA.
Santee Co. Water District, Santee, CA.
City of Lake George, N.Y.
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Five of the locations studied (Whittier Narrows,
CA; Camp Pendleton, CA; Hemet, CA; Oceanside, CA; and
St. Croix, V.I.) replenish potable groundwater basins
with treated wastewater, or a mixture of effluent and
fresh water sources. None of these programs has
ever recorded any deleterious effects due to effluent
recharge activities. However, the difficulties of
tracing the subsurface flow of recharged water, its
mixing with existing groundwater, and the lack of
testing for potentially hazardous trace constituents
(residual organics, heavy metals, pesticides, etc.),
leaves the matter still open to question.
Recharge by percolation has several advantages over
recharge by well injection: standard quality second-
ary effluent can be used successfully, capital costs
and operation and maintenance requirements are
minimal, and the soil provides exceptional tertiary
treatment under proper operating conditions.
Recharge by percolation is most successful when:
the SS concentration in effluent is low ( < 20 mg/1);
infiltration rates are high ( > 2 ft/day); and
operation follows a cyclic flooding-draining-drying
schedule to reduce surface clogging.
No well injection recharge operations using treated
effluent are currently operating in the United States.
Preliminary tests at Palo Alto, CA, Orange County,
CA, Los Angeles, CA, and Long Island, NY, have shown
that injection recharge is feasible when high water
quality is rigorously maintained and when the
hydraulic and chemical characteristics of the
receiving aquifer are compatible for recharge. The
Palo Alto, Orange County, and Long Island programs
are all in various stages of design and construction.
The Los Angeles pilot study showed that the use of
tertiary effluent in a well injection system was
technically feasible but not economically competitive
with the recharge of alternate fresh water supplies.
Test injection studies have shown that successful
well injection recharge requires high quality ter-
tiary effluent (e.g., COD < 10 mg/1, SS < 1 mg/1,
P04 < 1 mg/1, Fe < 0.5 mg/1, JTU < 0.3 units)
with maximum allowable concentrations depending on
the aquifer characteristics. Treatment pYior to
injection recharge usually requires chemical coagu-
lation/settling, ammonia stripping or nitrification-
denitrification, filtration, and carbon adsorption.
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Initial performance of pilot well recharge facilities
has shown that full scale well injection programs
should be preceded by extensive pilot studies to
determine the hydraulic characteristics of the
receiving aquifer and the necessary effluent quality
for successful operation.
To avoid buildup of IDS in groundwater basins, re-
charge programs replenishing aquifers with waste-
water will ultimately have to provide some degree of
demineralization to maintain proper salt levels. The
need for demineralization depends on several factors:
TDS of groundwater, TDS of effluent, volume of re-
charge water, volume and assimilative capacity of
the groundwater basin, and extent of mixing with
fresh sources before recharge.
The future for groundwater recharge with treated
municipal wastewater is uncertain at the present
time. There exists a recognized lack of knowledge
concerning residual organic materials: their compo-
sition, the types of long term affects, synergistic
affects, methods of detection and identification,
and the levels at which long term health affects are
exerted. Until these questions are answered, most
public health agencies are likely to follow the
California Health Department's conservative stance
in opposing new recharge programs to replenish
potable aquifers.
RECOMMENDATIONS
Before recharge for basin replenishment can be
enthusiastically supported, further study into the
fate of virus, trace organics, and toxic elements
within the soil-aquifer environment is necessary.
This includes the development of improved methods of
tracing the movement of recharged waters, detecting
and identifying potentially hazardous trace con-
stituents, and collecting representative samples for
analysi s.
One important area needing further examination is in
the effect of operation techniques on pollutant re-
moval efficiencies for percolation systems. For
example, the U.S. Water Conservation Lab at Phoenix,
Arizona, has shown that carefully controlled flooding'
drying schedules can increase nitrogen removal from
a normal 30 percent to over 80 percent. Perhaps the
removals of virus, nutrients, trace organics, etc.,
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can also be optimized by control of the upper soil
environment by selective flooding-drying techniques.
The ultimate need for demineralization to maintain
salt levels in aquifers being recharged with higher
IDS waters, as is usually the case with wastewater
as the recharge source, has already been mentioned.
Further study of the cost-effectiveness of various
established and experimental demineralization systems
is needed.
The EPA and other concerned agencies should continue
to support research and fund pilot projects such as
those already receiving such aid at Phoenix,
Arizona, Long Island, New York, Orange County, Calif-
ornia, and Palo Alto, California. Groundwater re-
charge with treated wastewater for salt water intru-
sion barriers, for extraction and reuse, and for
basin replenishment, is a potential water conserva-
tion and reuse practice that could be used to ad-
vantage by many communities.
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SECTION IV
REQUIRED QUALITY CRITERIA
Augmenting the underground storage of water by artificial
recharge provides a supplemental source of water for irri-
gation, for industrial and domestic uses, and/or a barrier
to prevent salt water intrusion in coastal areas. A major
prerequisite to recharge, however, is the perpetuation of
an acceptable level of groundwater quality.
A groundwater basin system poses unique problems in (1) its
tendency to concentrate pollutants within the soil solution
and (2) its uncertain and slow purification once contaminated
However, the soil environment also acts to purify wastewater
passing through it by the processes of mechanical filtra-
tion, adsorption, and ion exchange. Each groundwater system
poses unique interactions between these phenomena.
REGULATIONS
There are currently no federal standards controlling the
quality of water for recharge. However, as a result of the
Safe Drinking Water Act, PL 93-523, passed by Congress in
late 1974, it is anticipated that federal standards will be
established in the near future.
Presently, regulations usually come from local or state
Water Quality Control Boards and State Health Departments.
For example, in California, the leading state in recharge
programs, Regional Water Quality Control Boards are enacting
basin plans that limit concentrations of contaminants in
water to be recharged to basins within their jurisdictional
area. Each basin carries its own requirements depending
upon its quality, assimilative capacity, etc. Table 1
summarizes Water Quality Control Board regulations for re-
charge operations in the basin to be recharged by the Orange
County Water District program (see case study report in
Appendix A).
State Health Departments are beginning to play a larger role
in regulating potable aquifer recharge operations. In
California, the State Health Department is discouraging
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Table 1. SANTA ANA REGIONAL WATER QUALITY CONTROL BOARD
QUALITY REQUIREMENTS FOR WATER
RECHARGED TO THE SANTA ANA GROUNDWATER BASIN
Constituent
Ammonium
Na
Total Hardness as Ca C03
S04
Cl
Total N
Electrical Conductivity
Hexavalent Cr
Cd
Se
Mn
Barium
Ag
Cu
Pb
Hg
As
Fe
Fl
B
MBAS
Max.
Concentration (mg/1)
1.0
no
220
125
120
10
900 (1)
0.05
0.01
0.01
0,05
1.0
0.05
1.0
0.05
0.005
0.5
0.3
0.8
0.5
0.5
(1) y mho/cm
10
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construction of new potable aquifer recharge systems and
expansion of existing facilities until the potential health
hazards of residual organics in treated wastewater can be
proved insignificant (see Appendix C for complete Health
Department statement).
PURIFICATION BY SOIL
Where groundwater systems are adaptable to recharge, waste-
water purification by vertical and horizontal filtration
through soil is highly effective. Results from testing at
the case study locations of Whittier Narrows, California, and
Phoenix, Arizona, show the following pollutant removals by
percolation of secondary effluent through soil:
Suspended solids are totally removed in the first
few feet of percolation.
Approximately 75 percent of the COD is removed in
the first four feet, but below four feet the COD
increases to 40 percent of the surface concentration.
Total nitrogen removals can reach 80 percent in the
first few feet of soil under proper system opera-
tion (see Phoenix case study, Appendix A).
Phosphorus removal is dependent on travel distance
through the soil with 50 percent removal after 30
feet, and 90 percent removal after several hundred
feet.
At Phoenix, fecal coliforms were reduced from 10
to generally less than 200 per 100 ml after 30 feet
of vertical percolation, and additional lateral
movement of 100 and 300 feet produced reductions to
10 and 0 per 100 ml, respectively.
Virus studies at Phoenix (and previous well-
documented studies at Santee, California) indicate
that viruses are effectively removed by soil filtra-
tion.
FACTORS AFFECTING RECHARGE WATER QUALITY AND REQUIREMENTS
Requirements for recharge water quality may vary from
location to location depending on several factors that
affect soil purification capability and/or the recharged
water's impact on the natural groundwater. Some of these
factors are: soil characteristics, depth to groundwater
table, native groundwater quality, assimilative capacity of
11
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the aquifer, distance and travel time to extraction point,
and method of recharge.
Soil composition, such as the relative amount of clay vs.
sand, determines such factors as cation exchange capacity,
affecting the removal of metal ions and viruses, and adsorptive
capacity affecting the removal of trace organisms and solids.
Porosity determines infiltration rates that affect residence
time in surface layers which may in turn determine aerobic or
anaerobic conditions. Impermeable clay layers may form
localized barriers preventing uniform diffusion of recharged
water. Thus, the total groundwater volume cannot be con-
sidered an effective diluting agent, and there may exist
considerable variation in water quality both areally and in
depth. (12, 16)
The depth to the groundwater table and distance to extrac-
tion point are important considerations in the removal of
phosphorus and bacteria and perhaps several other constituents
for which removals appear to be a function of travel distance.
Naturally, the quality of the groundwater should have a
bearing on the recharge quality requirements. For example,
a native groundwater of low TDS is more vulnerable to con-
tamination by high TDS recharge water than an aquifer already
high in salts. In some instances, however, quality require-
ments for successful hydraulic operation of injection
facilities may be more stringent and will thus take precedence
over requirements for protection of the native groundwater.
Quality requirements for recharge water should take into
account the assimilative capacity of the receiving aquifer.
If the recharged effluent volume is insignificant compared
to the natural volume of the groundwater basin then quality
regulations may not have to be as stringent as in the case
where recharge represents a major portion of the aquifer
volume. In this regard, the generally low velocity of ground-
water movement, which tends to inhibit mixing and diffusion
in a groundwater basin, must be taken into account. Water
movement through soils is laminar rather than the typically
turbulent flow found in surface waters; therefore, dilution
of the recharged water by the native groundwater may be
significantly reduced. (12, 16)
The different methods of recharge (percolation or injection)
require a different set of quality criteria. This results
because the treatment provided by the soil in the percola-
tion system may not be available to direct aquifer injection
programs. In addition, injection systems require a much
higher quality of water to meet hydraulic requirements than
12
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do spreading basin programs. Naturally, in all situations,
the greater the degree of treatment given to wastewater, the
more efficient will be the infiltration, diffusion, and in-
jection capabilities of the recharge water. (1) If re-
charge is to remain economical, the charging capacity of
individual wells and spreading basins must be maintained.
In all cases of direct injection (Long Island, New York,
Orange County, California, and Palo Alto, California), it is
anticipated that under full scale operation, the recharge
water will meet drinking water standards, and at Orange
County it is stipulated by the Water Quality Control Board
that the treated effluent be diluted 50:50 with a fresh
water source to achieve a IDS concentration of 550 mg/1 .
Naturally, all these operations require extensive tertiary
treatment to obtain desired pollutant removals.
REPORTED RECHARGE WATER QUALITY
The following concentrations reported by the case study
programs give a general indication of the quality provided
or anticipated for successful injection well recharge (note
that hydraulic characteristics of the aquifer can force
significant changes in these criteria): BOD < 5 mg/1,
SS < 0.5 mg/1, Fe < 0.6 mg/1, P04 < 1 mg/1,
turbidity < 0.4 mg/1 as S|02, and coliforms < 2.2/100 ml.
For successful operation, recharge by percolation does not
require as high a quality of water as injection systems.
Case study projects reported no problems of surface clogging,
significantly reduced infiltration rates, or degradation
of groundwater (within the constraints of their testing
programs) when good quality secondary effluent was used for
spreading (BOD and SS concentrations less than 20 mg/1).
CRITICAL QUALITY PARAMETERS
At present, the most significant detectable long term
hazard to groundwater quality caused by recharge
activities is the buildup of dissolved salts. The
U.S. Public Health Service (USPHS) has established, in a
22-city survey, that each use of water adds approximately
300 mg/1 of TDS to the supply. Over the long term, the
gradual increase of TDS in the groundwater may require the
use of in-plant demineralization or blending with fresh
water supplies to maintain low TDS in the aquifers.
The newest concern in regard to contamination of ground-
water basins through effluent recharge is residual organics.
13
-------
A group of scientists, particularly water quality specialists
in the field of water supply, wastewater disposal, and public
health, are concerned about residual organics and sources
of domestic wastewater. Questions about the fate of resid-
ual organics (present in treated effluent) within the soil-
aquifer system have not been answered (i.e., synergistic
effects between organics or other groundwater and soil con-
stituents, conversion of safe organics to hazardous com-
pounds in the soil, etc.).(10)
Other wastewater constituents which can potentially create
problems in groundwater systems include heavy metals and
detergents. As with dissolved salts, these contaminants
can accumulate in the aquifers, often rendering a ground-
water system unusable. As mentioned previously, soils of
higher clay content and ion exchange capacity will tend to
remove much higher percentages of metals than will the
sandy soils, which are prevalent at most percolation recharge
sites because of their high infiltration rates. Thus, the
extent of potential contamination depends to some extent
on the soil characteristics.
It should be emphasized that each potential recharge site
must be thoroughly studied to determine the acceptable
limits of water quality based on the parameters discussed
above. The peculiarities of a groundwater system may
require more stringent quality for certain wastewater
constituents.
14
-------
SECTION V
DESCRIPTION OF CURRENT PRACTICES
INVENTORY OF RECHARGE SITES
Table 2 provides a summary of the groundwater recharge sites
using municipal wastewater that are operational or under
construction in the United States.
As shown, six of the programs include groundwater basin re-
plenishment as one of the purposes of recharge; six involve
establishment of saltwater intrusion barriers; and three
also recharge to provide further land treatment before ex-
traction for reuse.
All but three of the sites are located in the arid south-
western area of the country where low precipitation patterns
force heavy reliance on groundwater supplies. Increasing
populations create critical overdraft situations that can be
alleviated in part by recharge of treated wastewater either
for direct basin replenishment for unrestricted reuse, or
for extraction and non-potable reuse.
Two of the recharge sites are located in temperate climates
at Long Island and Palo Alto. Both areas, however, are
heavily dependent on groundwater supplies and initiated
recharge programs to halt seawater intrusion into their
aquifers. The Long Island operation has since altered their
emphasis from coastal saltwater intrusion barriers to in-
land basin replenishment.
Economic conditions on St. Croix in the Virgin Islands lend
themselves to the recharge of wastewater, as potable water is
scarce and very expensive. At least two-thirds of the is-
lands' domestic supply is derived from distillation of sea-
water.
PRELIMINARY TESTING
All the recharge operations conducted some type of prelimi-
nary testing before commencing full scale operations.
Site testing at the percolation recharge sites generally
included: soil boring tests to ascertain soil profiles;
15
-------
Table 2. INVENTORY OF RECHARGE OPERATIONS
Location
Managing agency
Purpose of recharge
MGD
CT*
Camp Pendleton, CA U.S. Marine Corp.
Hemet, CA
Long Island, NY
Oceanside, CA
Orange County, CA
Palo Alto, CA
Phoenix, AZ
San Clemente, CA
St. Croix, V.I.
Whittier, CA
Eastern Municipal Water
District
Nassau County Department
of Public Works -
U.S. Geological Survey
Water and Sewer Dept.
Orange County Water
District
Santa Clara Valley
Water District
U.S. Water Conservation
Laboratory
City of San Clemente
Govt. of the V.I.
L.A. County Flood
Control District
Groundwater replenishment
Salt water barrier
Groundwater replenishment
Groundwater replenishment
Salt water barrier
Treatment for reuse
Groundwater replenishment
Salt water barrier
Salt water barrier
Treatment for reuse
Treatment for reuse
Salt water barrier
Groundwater replenishment
Salt water barrier
Groundwater replenishment
4
2
0.5
6(3)
15(D
2(2)
15(D
2
0.5
25
(1) Full scale facility on line in 1975.
(2) Full scale facility on line in 1976.
(3) Present system temporarily provides 1 MGD for
New 6 MGD program operational 1975.
groundwater replenishment,
-------
and percolation tests to aid in determining optimum re-
charge rates, system capacity, and clogging characteristics.
Soil profiles are important for locating impermeable clay
layers that can impede vertical migration and reduce in-
filtration rates or force the water in horizontal directions.
These profiles also show the size distribution of material
with depth so that the experimenter can determine where the
formation is likely to exhibit clogging, whether there is a
danger of the water table rising too close to the bottom of
the basins, whether there is likely to be significant cation
exchange phenomena due to the presence of clay, and other
important considerations.
Extensive percolation tests performed with representative
treated effluent are advantageous in that they provide
information as to initial infiltration rates, long term
hydraulic loading rates, the necessary area of the spreading
basins, and what types of problems with clogging will arise.
Soils comprised of gravels, coarse and medium sand, and
sandy loam offered the best results for percolation due to
their high percolation rates and reduced surface clogging.
Percolation tests and operational results at case study
locations showed infiltration rates ranging from 1 to 10
ft/day.
Preliminary testing at sites utilizing wells for injection
or extraction was more extensive than that for percolation
programs. The Santa Clara Valley Water District's prelimi-
nary test program at Palo Alto can serve as an example of
an in-depth study. Test holes were drilled initially with
samples taken every few feet to obtain accurate information
as to subsurface characteristics. After each hole was
drilled, geophysical logging was performed in the well to
verify the written descriptive log and to gather data on
water quality, permeability of formations, and variations
in material type (especially the presence of clay formations).
Observation wells were then drilled to monitor changes in
water level and to collect water quality samples during sub-
sequent testing. A test injection/extraction well was
drilled and recharge tests with fresh water initiated. The
main purposes of tnese recharge/extraction tests were to deter-
mine the maximum rates of recharge into the aquifers, the
changes of these rates with time, and the changes in water
quality with movement through the formation. The important
parameters were transmissivity (gpm/ft), which represent
the rate of yield (gpm) per foot of drawdown under extrac-
tion conditions, and the rate of injection (gpm) per foot of
head during injection. Higher aquifer transmissivity denotes
17
-------
a more porous or permeable formation. Typical values at
Palo Alto ranged from 3,000 gpd/ft to 12,000 gpd/ft.
Once all the aquifer and recharge characteristics were
determined, a computer simulation of the system was devised
to calculate optimum locations for the series of injection
and extraction wells.
This basically concluded the test program at Palo Alto. One
possible disadvantage was the fact that recharge tests were
all run with fresh water. Whenever possible, the optimal
choice would be to use the same or nearly identical water
source to that to be used under full scale operation. This
was done at Long Island, New York, where the test program
included a pilot tertiary treatment plant that provided
treated effluent to the test well complex.
TREATMENT PRIOR TO RECHARGE
The degree of treatment provided before recharge depends on
the purpose of the program and the method of recharge.
Three of the coastal sites (Long Island, Palo Alto, and
Orange County) are faced with saltwater intrusion problems
and are either designing, constructing, or operating terti-
ary treatment plants with well injection effluent systems to
create salinity intrusion barriers. Due to the nature of
the subsurface materials, a high quality water is needed to
prevent clogging of the pore spaces in the aquifer and to
assure that no degradation of ambient groundwater quality
occurs. These injection systems require extensive terti-
ary treatment prior to recharge to reduce solids, phosphorous
nitrogen, iron, other precipitate-forming compounds, en-
trained gases, bacteria, viruses, and other contaminants.
See Appendix A case studies for a more detailed discussion.
The other seven programs employ percolation to recharge
aquifers for groundwater replenishment, saltwater barriers,
and/or treatment before reuse. Five of these operations
rely on percolation through depths of soil to yield the
tertiary treatment that injection systems must provide in-
plant. These sites operate directly with secondary effluent,
although three of the five provide final polishing ponds to
reduce solids and prevent surface clogging during spreading.
Two percolation operations, San Clemente, California, and
St. Croix, Virgin Islands, provide dual media filtration as
a tertiary treatment step prior to spreading.
Table 3 provides a summary of treatment systems and typical
effluent quality characteristics.
18
-------
Table 3. TREATMENT SYSTEMS AND EFFLUENT QUALITY CHARACTERISTICS
Location
Camp Pendleton, CA
Hemet, CA
Long Island, NY
Oceanside, CA
OT-anrre> Countv. CA
Effluent Quality ( 2
Treatment 1
Secondary (T.F.)
Secondary (A.S)
Tertiary
- chem. clar.
- filtration
- carbon adsorp.
- chlorination
Secondary (A.S.)
Tertiary
30D SS
10 10
20 18
5 0.5
6 18
<1 <1
Total
N
11
40
35
23
10
Total
P
2.0
Col i form
100/ml
—
Fe
0.0
1.8 x 106 —
0.4
31
<1
•C 1
25
< 1
0.4
0.07
0.6
TDS
790
674
394
1,280
1,100
(1)
Palo Alto, CA
(1)
- chem. clar.
- ammonia strip.
- recarb.
- filtration
- carbon adsorp.
- chlorination
Tertiary
- chem. clar.
- ammonia strip.
- recarb.
- filtration
- carbon adsorp.
- chlorination
10
<1
<2.2 0.2
600
(1) Anticipated characteristics
A.S. - activated sludge
T.F. - trickling filter
-------
Table 3 (continued). TREATMENT SYSTEMS AND EFFLUENT QUALITY CHARACTERISTICS
Location
Phoenix, AZ
San Clemente, CA
St. Croix, V.I.
Whittier, CA
Treatment BOD
Secondary (A.S.) 15
Tertiary 4
- filtration
Tertiary 12
- chem. coag.
- filtration
Secondary (A.S.) 8
Effluent
Total I Total
SS N ! P
50 36 15
3 — 20
— — --
12 27 8
Quality (2)
Coll/
100/ml F«
106 -
< 2.2
W>M •- •
2 TDS
1,100
1,100
1,000
190 0.10 640
ro
o
(2) Expressed in mg/1 except for the coliform values which represent per 100 ml.
-------
As would be expected, the three extensive tertiary operations
provide a very high quality effluent with BOD's below 5 mg/1,
SS less than 1 mg/1, coliform less than 2 per 100 ml, and
other low contaminant concentrations. Note that the Orange
County effluent will be mixed 50-50 with desalinated water
before injection which will roughly halve all contaminant
concentrations.
With the exception of high suspended solids in the Phoenix
wastewater, the secondary effluents used for percolation
recharge were of good to excellent quality for that degree
of treatment with all BOD and SS concentrations under 20
mg/1. Nutrient values were typical of secondary effluent.
IDS concentrations were quite high at all locations
except Long Is!and,indieating that possibly the aquifers
were intruded or otherwise high in salts; that
the recharge water was to be extracted; that the effluent
was mixed with low IDS sources before recharge; or that
some form of demineralization would ultimately be necessary
to prevent IDS buildup in the groundwater basin. Table 4
compares the IDS concentration of the recharge water with
the existing IDS level of the receiving groundwater aquifer.
The individual case study reports provide detailed summaries
of effluent characteristics.
Methods of Recharge
There are two basic methods of groundwater recharge utilized
by the surveyed sites. The simplest and most widely
used consists of conveying the treated effluent to shallow
spreading basins and allowing the water to percolate through
the soil to the groundwater. The other method consists of
conveying the effluent to a well field and injecting the
water directly into the aquifer for basin replenishment or
to form a pressure mound which can be effective in retard-
ing salt water instrusion. Figure 2 shows a basic diagram
of the salt water intrusion problem. Intrusion is usually
accelerated by drawdown of the water table and lowering of
the potentiometric head in the fresh water aquifer due to
extraction for potable supplies. The recharge pressure
mound also shown in Figure 2 serves as a pressure barrier
against the intruding seawater.
Table 5 provides a summary of facilities and management
practices for the seven high rate percolation recharge
sites. The programs using percolation had varying numbers
of basins from one to 20 acres each. Basin berms were
roughly three to six feet high, and flooding depths ranged
21
-------
Table 4. COMPARISON OF TDS IN RECHARGE
WATER AND RECEIVING GROUNDWATER
Location
TDS mq/1
Recharge Water Aquifer
Camp Pendleton, CA 790 680
Hemet, CA 700 500-900
Long Island, NY 390 50
Oceanside, CA 1,280* '*'
Orange County, CA 550^' 520
Palo Alto, CA 850^' 4,500-6,500(3)
Phoenix, AR 1,100(4) 800
San Clemente, CA 1,100 480-850
St. Croix, V.I. 1,000*5> 1,200
Whittier, CA 640 250-850
(1) High concentration due to: use of high TDS Colorado River
water for supply, salt water infiltration into sewer
lines, and high evaporation rates from holding lagoons.
(2) After blending 1:1 with desalinated water.
(3) Salt water intruded aquifer.
(4) All recharged water to be extracted with virtually no
mixing with natural groundwater.
(5) High concentration due in part to limited use of
saltwater for toilet flushing.
22
-------
EXTRACTION WELL
FOR POTABLE SUPPLY
INJECTION WELL OR
PERCOLATION BASINS
r\>
SEAWATER LEVEL
PRESSURE
MOUND
WATER BEARING AQUIFER
FIGURE 2
BASIC DIAGRAM OF
SALTWATER INTRUSION
INTO FRESH WATER AQUIFER
-------
Table 5. SUMMARY OF FACILITIES AND MANAGEMENT
PRACTICES FOR PERCOLATION RECHARGE
Location
Camp Pendleton, CA
Loading
Rate
mg/acre/yr
N/A
Ave . Per-
colation
Rate
ft/day
8
Flood Sch.
. As water
becomes
available
Soil Type
coarse sand
Spreading
Area
Maintenance
Operations
. berm redeve.
opment
. remove surf<
Hemet, CA
ro
Oceanside, CA
Phoenix, AZ
San Clemente, CA
29
47
137
140
2.5
4.5
2.5
5-10
. Fill 1 day medium &
(2.5'depth) coarse
. Drain 2 days sand
. Dry 1 day
coarse sand
. Fill to 31
depth
. Drain & dry
. Refill
. Fill 10 days . loamy
. Dry 14 days sand
surface
. coarse
sand and
gravel
Continuous
coarse sand
and gravel
solids every
other year
. periodic ro-
totilling of
basins
. basins scari-
fied periodi-
cally
. closely main-
tain flooding
schedule
. periodic scari-
fying
none
-------
Table 5 (continued). SUMMARY OF FACILITIES AND
MANAGEMENT PRACTICES FOR PERCOLATION RECHARGE
Location
Loading
Rate
mg/acre/yr
Ave. Per-
colation
Rate
ft/day
Flood Sch.
Soil type
Spreading
Area
Maintenance
Operations
,, ,. -><• -, ^ • Fill 18 days»silt, sand
St. Croix, V.I. 36 1-2 ^ Dry 3Q days and clay
Whittier, CA 46 5-10 . Fill 6 days sandy loam . basins scari
(41 depth)
Drain 6 days
Dry 6 days
fied period-
ically
ro
ui
-------
from one to four feet. Successful high rate percolation
requires porous soil. All the sites surveyed had good
percolation rates ranging from roughly one foot per day at
Phoenix to over ten feet per day at Camp Pendleton. These
infiltration rates are much higher than evaporation rates,
and thus the salt content is not concentrated during flood-
ing. Soil composition was generally of sand, loam, and
gravel composition with clay stratas at varying depths.
Most sites maintain bare earth bottoms in their basins.but
at Whittier Narrows natural vegetation was not removed
as its presence increased performance.
Management techniques varied with location. All sites
except San Clemente, which has very high percolation rates,
operated on some type of flooding-drying cycle to reduce
clogging and retain high percolation rates. Hemet,
California, operated a short (four day) cycle to reduce
algae growth that had been stimulated by long flooding
periods and significant nutrient content in the wastes.
The Flushing Meadows project at Phoenix adopted a longer
flooding-drying technique to achieve maximum removals of
nitrogen. By controlling the aerobic and anaerobic con-
ditions in the soil, optimum nitrification-denitrification
can be realized with nitrogen removals as high as 80
percent. Some sacrifice in maximum volume percolated has
to be made due to the controlled flooding techniques
necessary to achieve significant nitrogen removals.
Operation and maintenance requirements are very minimal for
percolation recharge systems. The entire operation is
simple and only requires basic allocation of water to the
basins and periodic tilling of pond bottoms to break up
solids.
Recharge systems incorporating injection are naturally more
sophisticated and complicated than spreading-percolation
facilities. Table 6 summarizes basic characteristics of the
injection well systems. None of the three systems had
operated at full scale operation at the time of the study.
Anticipated startup dates are: early 1975 - Orange County,
1976 - Palo Alto, and 1977 or later for Long Island. All
three sites have run pilot studies to determine the
characteristics of the aquifers, spacing of barrier wells,
injection techniques, etc.
Both the Long Island and Palo Alto systems achieve recharge
by injection pumps at each well. Orange County, however,
maintains one force main at 50 psi with three large effluent
pumps supplying the head to all 23 wells.
26
-------
Table 6. CHARACTERISTICS OF INJECTION RECHARGE SYSTEMS
Location
No.
Injection
Wells
Ave.
Injection
Depth (ft)
Well Dia.
(in.)
J
Max.
Pumping Rate
per Well
(gpm)
ro
Long Island, NY
(1)
Orange County, CA
(2)
Palo Alto, CA
(3)
23
9
450
90, 150,
250, 340
45
18
400
900
150
Max.
Injection
Pressure
(psi)
100
50
20
(1) Pilot operation only
(2) 1975 start-up
(3) 1976 start-up
-------
Three of the 10 case study programs plan to extract the re-
charged water for reuse and to minimize mixing of the
treated effluent with native groundwater supplies. These
programs, Oceanside and Palo Alto, CA, and Phoenix, AR,
are designing extraction systems such that all gradients
in the local groundwater zone will be directed toward the
extraction wells to virtually eliminate migration of re-
charged waters out into the aquifers. By recovering the
recharged waters, these programs will avoid having to meet
the quality requirements or health considerations that
would be asked of a straight basin replenishment program.
At Phoenix, the three extraction wells will be located in
the middle of the spreading basins and will each pump up to
4,000 gpm to a local irrigation district. At both Palo
Alto and Oceanside, extraction will occur downstream from
the recharge point (1/2 mile at Oceanside, 1,000 ft at Palo
Alto) to provide further soil treatment before reuse.
The pilot well at Long Island provided both injection and
extraction capabilities. Extraction was for purposes of
regeneration or backwashing to remove solids and precipi-
tate from the clogged aquifer. Due to the heavy clogging
phenomenon, initially extracted water was highly contam-
inated with solids, precipitates of iron and phosphate,
and bacteria. Authorities do not anticipate the use of
extraction wells under full scale operation.
The Orange County program will utilize both injection and
extraction wells to form a hydraulic pressure barrier
against intrusion. As shown in Figure A-6 of the case study
report, injected water will not be recovered as at Palo
Alto and Phoenix, but will serve both to replenish the
four fresh water aquifers and to form the seawater barrier.
The existing line of 7 extraction wells located two miles
seaward from the injection points will continue to pump
out intruding salt water and return it to the ocean.
Of the 10 recharge operations, seven used only treated
effluent in their systems. The other three (Camp Pendleton
Orange County, and Whittier Narrows) used a mixture of
effluent and other fresh water sources to make up their re-
charge supply. Camp Pendleton and Whittier Narrows used
effluent continually and mixed in natural runoff when
available. Orange County will mix its effluent 50:50 with
desalted water to meet their TDS restriction.
Monitoring and Safeguards
Extensive monitoring and safeguard measures were not prac-
ticed by most of the percolation type recharge operations
28
-------
because they could rely on the soil to provide significant
treatment and thus ensure a high quality water entering the
groundwater basins, and also because of the significant
difficulties in tracing the movement of the recharge water
in the subsurface system and in obtaining representative
samples. Monitoring usually consisted of the standard
effluent tests (BOD, SS, coliform, etc.) conducted daily
and other typical tests run periodically. Volume of efflu-
ent diverted to flooding basins was often monitored with
flow recorders to assure proper flooding depths and periods.
The case study reports showed that supply wells, extracting
from basins replenished to some extent by treated waste-
water, were monitored periodically for signs of contamina-
tion due to the use of treated wastewater for recharge.
Except for minor increases in IDS concentrations, no de-
gradation of native groundwater quality was reported. It
is important to note that none of the sites monitored
potentially hazardous trace pollutants such as pesticides,
trace organics, and viruses.
In addition to monitoring potable supply wells, two of the
percolation programs (Hemet and Phoenix) operated networks
of observation wells to monitor groundwater levels and
quality. At Phoenix, the effluent quality was analyzed
before recharge and after extraction to determine pollutant
removal efficiencies of their various soil systems and
operation techniques. In a similar fashion, sampling pans
were constructed under small test basins at Whittier Narrows
to measure the effect on water quality of percolation
through varying depths of soil.
Due to the high quality requirements and low tolerance of
injection systems, treatment plant and well operations were
more closely monitored than in the percolation programs.
This generally consisted of more extensive and frequent
effluent monitoring and closer operational control to ensure
that treatment plant upsets were minimized and that poor
quality effluent was not sent to the well.
To safeguard injection well operation, storage capacity for
the final effluent was provided so that treatment plant
shutdowns would not affect injection. This storage also
provided the capability to mix the effluent with other water
sources if desired. All the injection-type recharge pro-
grams inlcude a by-pass safeguard so that poor quality
effluent due to plant upset or breakdown can be discharged
without entering the injection well system and causing
problems there.
29
-------
At Long Island, the recharged effluent was extracted and
analyzed to determine the dispersion patterns of pollutants
in the aquifer and the causes of the severe clogging
occurrences. The problem was traced to preci pi tates of phos-
phate and iron, and residual particulate matter clogging
fine pore spaces. The Long Island case study fully delineates
dispersion patterns and these operational problems.
Problems Encountered
One of the advantages of percolation recharge systems is
the virtual absence of equipment and instrumentation. The
simplicity of the facilities greatly reduces the number and
degree of operational problems.
The most prevalent setback is clogging of the surface soil
layer, thus reducing infiltration rates. The clogging is
due to the accumulation of solids from the effluent and
algae growth stimulated by nutrients in the wastewater.
This problem can be eliminated for the most part by an
alternate flooding-drying schedule with intermittent
scarification or rototilling of the pond bottom. This
cyclic schedule also serves to interrupt the life cycles
of mosquitoes and other aquaphilic insects.
Both Whittier Narrows and Hemet noted difficulties in
monitoring the movement of the effluent once it had perco-
lated. Mixing with native groundwater and horizontal
deflection due to impermeable clay layers were cited as the
causes of the problems.
Problems are more inherent in injection recharge systems
due to the sophistication of both the tertiary treatment
plant and the injection well facilities. The problems
associated with extensive tertiary treatment have been well-
documented elsewhere. Of the five tertiary systems included
in this study, only two were operational -- Long Island and
San Clemente. The only difficulties reported were at Long
Island and included: frequent breakdown of the activated
carbon regeneration furnace; anaerobic bacteria in the
carbon towers converting iron to soluble forms that
precipitated during injection and clogged the well; and
surges of suspended solids in the effluent immediately
following mixed media filter backwash. The latter two
problems were successfully eliminated.
The injection well system can also present operational
problems depending upon the quality characteristics of the
effluent and the hydraulic characteristics of the aquifer.
30
-------
Pilot well programs at Orange County and Palo Alto were
carried out with a minimum of setbacks. The experience
with the pilot deep well injection with tertiary effluent
at Bay Park, Long Island, was not as fortunate. Due to the
very small pore spaces in the deep aquifer, clogging in the
immediate injection area was a continual problem. Clogging
occurred whenever the effluent turbidity was greater than
0.3 JTU, when P04 concentration rose above 1.0 mg/1, when
Fe increased over 0.5 mg/1, or when surges of higher solids
concentrations were injected. This test proved that recharge
water quality must be rigidly controlled and that injection
of treated effluent into aquifers with small pore spaces
was difficult even with very high quality water.
The difficulty in controlling the recharge-extraction
process to ensure that little recharged water enters the vir-
gin groundwater (if that is not desired) can be overcome
by proper system operation and design as planned at Phoenix,
Palo Alto, and Oceanside. Explained in greater detail in
the Phoenix case study report (Appendix A), the method
basically involves establishing a slight gradient in the
groundwater basin toward the extraction point.
The problem of native groundwater contamination by recharged
effluent has not been reported to date at the 10 sites
surveyed. Water extracted from basins being replenished
with effluent or a mixture of sources has not shown any
measurable degradation and program coordinators are con-
fident that their recharge operations are not contaminating
the aquifers, except where high recharge water TDS is a
potential long term problem. Health authorities, on the
other hand, argue that the potential still exists for
contamination by effluent recharge until research proves not
only that the soil effectively removes trace orgamcs over
the long term, but that satisfactory monitoring and analysis
techniques have been developed to prove it.
31
-------
SECTION VI
ANALYSIS OF RECHARGE ECONOMICS
The costs for recharge were analyzed for each of the case
study sites. Included in this analysis were the costs
associated with recharge only, not treatment, unless re-
charge required specific treatment units beyond normal
secondary facilities (i.e., tertiary treatment for well
injection). In cases where recharged water was extracted
for reuse (Oceanside, Palo Alto, and Phoenix), the costs
of extraction were also included.
Table 7 summarizes estimated costs for the recharge
operations. Two of the tertiary treatment/injection re-
charge programs (Palo Alto, California, and Orange County,
California) received substantial state and federal grant
monies that covered a large percentage of the total project
capital cost. Total project costs, including grants, are
shown in parentheses along with the costs paid only by the
host water districts. As would be expected, there is
generally a significant difference in cost between the
percolation type and the injection type operation because
of the expensive tertiary treatment and well systems
necessary for the latter.
The total costs for percolation recharge ranged from $8/mg
at Phoenix to $147/mg at Oceanside with an average of $43/mg
for all seven sites. Costs appear to be basically a function
of distance and elevation difference between treatment plant
and spreading basins. Piping and pumping, along with land
acquisition, are the major costs.
The lowest cost system (Phoenix at $8/mg) was situated
adjacent to the treatment plant, and effluent was gravity
fed through gate valves directly to the spreading basins;
thus there are no piping or pumping costs except for the
extraction process that represents the major portion of the
total cost. Oceanside, on the other hand, was anticipating
a cost of over $1,600,000 for over eight miles of large
diameter piping and a pump station. Land costs were also
high for acquisition of extensive holding pond spreading
32
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CO
co
Table 7. ESTIMATED TOTAL COSTS OF RECHARGE OPERATIONS(1) (1972$)
$/MILLION GALLON
Location
Camp Pendleton, CA
Hemet, CA
Long Island, NY
Oceanside, CA
Orange County, CA(2)
Palo Alto, CA
Phoenix, AZ
San Clemente, CA
St. Croix, V.I.
Whittier, CA
MGD
Recharged
4
2
inter-
mittent
6
15
3
15
2
0.5
25
Type of
Treatment
Sec.
Sec.
Tert.
Sec.
Tert.
Tert.
Sec.
Tert.
Tert.
Sec.
Capital
Type of Cost (4)
Recharge (3)
P 7
P 9
I
P,E 111
I 94(253
I,E 30(176
P,E 3
P 37
P — —.
P 8
0 & M Total
Cost Cost
8 15
21 30
320
36 147
) 574 670(827)
) 137 167(313)
5 8
5 42
— —
7 15
(1) Excluding revenues from sale of water
(2) Cost includes both the wastewater treatment portion of the project and the R & D
(3) P - percolation desalination activities
I - well injection
E - immediate extraction for reuse
(4) Costs in parenthesis represent total project costs including all state and federal
grant monies for those projects receiving such funding; the other cost figure for
these programs is that portion of the cost paid by host agency
-------
basins and extraction areas totalling 150 acres. Note that
Phoenix, with 2-1/2 times the flow of Oceanside, used less
than 1/3 the land for recharge. The capital costs at San
Clemente were significantly increased by nearly five miles
of pipeline and two high power pump stations along with two
dual media filters to provide tertiary polishing.
Total costs for the three tertiary treatment/injection re-
charge systems ranged from $313/mg anticipated at Palo
Alto ($167/mg of which will be paid by the SCVWD) to over
$800/mg reported by the operation at Orange County. Costs
reported by the latter are inflated substantially over what
they will be under full scale operation due to the unusually
high operation and maintenance costs associated with R & D
work on the desalting module. Costs at Orange County can
be broken down as follows: $240/mg for the advanced waste-
water treatment plant, $2,722/mg for the desalination plant,
and $10/mg for the distribution and well system.
It is important to note that both the Santa Clara Valley
Water District (Palo Alto) and the ORange County Water
District will have to pay only a portion of the total cost.
The Santa Clara Valley Water District is responsible for
12-1/2 percent of the total capital cost and the Orange
County Water District needs to contribute only 20 percent
of the advanced wastewater treatment plant capital cost,
42 percent of the desalination facility costs, and 60 per-
cent of recharge facilities capital cost. The remaining
funding is provided by state and federal grants.
In contrast to the percolation programs, the major cost on
a yearly basis for the injection systems is operation and
maintenance of the extensive tertiary treatment plants.
For the two full scale injection systems, 0 and M costs
represent roughly 40-70 percent of the total annual cost
with capital recovery costs for treatment and injection facil
ities (amortized at 5.5 percent for 25 years) constituting
the remainder.
Analysis of the economics of recharge shows that percolation
is a very inexpensive method of replenishing groundwater
basins. It can provide treatment prior to reuse and/or
protection against salt water intrusion. Costs are excep-
tionally low if recharge areas can be located in close
proximity to the treatment plant.
If injection is necessary to repel saltwater instrusion due
to lack of available land or proper soil features for perco-
lation, the costs of the program will be significant.
34
-------
These costs, however, can be deferred to some extent by
extraction and sale of the recharged water for reuse and
by the elimination or delay of the development of new
sources due to the protection and/or replenishment of pre-
sent groundwater supplies.
Only two of the sites (Palo Alto and Phoenix) were planning
to obtain direct revenue from the sale of water extracted
after recharge. A significant portion of the recharge
program cost can be recovered as Palo Alto plans to sell
roughly 2 mgd at $130/mg and Phoenix will sell approximately
15 mgd at $5/mg.
35
-------
SECTION VII
APPENDICES
APPENDIX A
FIELD INVESTIGATION REPORTS
Sections Page
United State Marine Corps (Camp Pendleton, 37
Cali fornia)
Eastern Municipal Water District (Hemet, 44
Cal i form" a)
Nassau County Department of Public Works/The U.S. 50
Geological Survey (Long Island, New York)
The City of Oceanside, California 59
Orange County Water District (Fountain Valley, 65
Cali fornia)
Santa Clara Valley Water District (Palo Alto 81
and San Jose, California)
U.S. Water Conservation Laboratory (Phoenix, 93
Ari zona)
The City of San Clemente, California 104
St. Croix, Virgin Islands (Government of the 109
Virgin Islands)
Los Angeles County Sanitation and Flood Control 112
Districts (Whittier Narrows/San Jose Creek,
Cal i form" a)
36
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UNITED STATE MARINE CORPS (CAMP PENDLETON, CALIFORNIA)
Introduction
The USMC base at Camp Pendleton has been operating an
extensive water resource management program since 1943. The
main purpose of this program is to allocate, protect, and
replenish the groundwater resource to ensure that quality
is not degraded nor volumes depleted over the long-term.
The base has always relied solely on groundwater for its
water supply and hopes to avoid any reliance on external
sources in the future by proper management of their ground-
water basins. The basins are continually recharged with re-
claimed sewage, stored surface runoff, and local precipita-
tion (13 in/yr) when available. The volume of reclaimed
effluent recharged is equivalent to roughly 2/3 of the total
volume extracted for potable use.
Domestic Treatment
The base, with a total population of 35,000, presently oper-
ates nine small sewage treatment plants that treat a total
of 4 MGD.
By October, 1975, all the plants will have been updated to
provide primary and biological secondary (trickling filter)
treatment. All effluent is heavily chlorinated and a portion
receives some degree of tertiary treatment in oxidation
ponds, all of which will be mechanically aerated by 1976.
Table A-l summarizes typical effluent characteristics from
one of the secondary plants.
Recharge Program
Potable water for Camp Pendleton is supplied by extracting
deep groundwater from basins of four of the five stream
systems on the base. These basins are recharged continuously
with reclaimed effluent, surface runoff, and local precipi-
tation. Water allocations are constrained within the safe
perennial yields of the basins. This ensures that water may
be extracted over a long term without depleting the storage
to the point where seawater intrusion occurs, chemical
deterioration of the groundwater results, or extraction be-
comes economically infeasible.
Since the four productive basin areas are basically similar
in physical characteristics and recharge operations, the
remainder of this section will provide a more detailed descrip-
tion of only one of the basins.
37
-------
Table A-l. TYPICAL SECONDARY EFFLUENT
CHARACTERISTICS AT CAMP PENDLETON
Constituent
Concentration
mg/1
Constituent
Concentration
mg/1
BOD
SS
TDS
Total hard-
ness as
CaC03
Ca
Mg
Na
K
10
10
790
184
48
16
144
38
S04
Cl
Total N
B
Total Fe
Mn
ABS
Total P
145
184
11
0.4
0.0
0.14
0.44
2.0
38
-------
The Santa Margarita River, with a watershed area of approxi
mately 750 square miles and groundwater basins with 26,000
acre-ft capacity, is the largest and most important of the
streams discharging into the ocean within the confines of
Camp Pendleton. The lower portion of the river system con-
sists of an alluvial valley, and coastal basin of 4,580
acres that have been subdivided in three interconnected basins
for recharge purposes.
Recharge of the basin is accomplished by utilizing various
water conservation techniques: on-channel water spreading
structures, off-channel water spreading structures, recycling
of sewage effluents, phreatophyte control, and construction
of erosion control structures.
Figure A-l shows a schematic diagram of the Santa Margarita
recharge facilities. During the rainy season, surface flow
in the Santa Margarita River is diverted by a rock weir to
either Lake O'Neill or off-channel spreading basins, All
the basins are composed of coarse sand with very high infil-
tration rates of up to 5 in/hr. The 1,320 acre-ft capacity
lake is constantly fed by 1.4 MGD from the town of Fallbrook's
sewage treatment plant, and may also receive effluent from
Pendleton's Plant No. 1, if so desired. The lake serves as
a storage reservoir during the rainy season with impounded
water being released to on-channel spreading basins during
the dry summer and early fall months.
Nine on-channel water spreading structures are situated below
the rock weir diversion to Lake O'Neill. They are comprised
of river sand and are constructed similar to levees with spill-
ways. During heavy runoff periods, surface flow spills over
the rock weir diversion and continues down the Santa Margarita
River filling and spilling each on-channel structure succes-
sively. These structures are not designed to withstand major
flows.
Effluents from five sewage treatment plants are utilized to
recharge the basins and to maintain a salt water intrusion
barrier. Figure A-l shows the treatment plants and their
discharge points.
In order to further conserve the groundwater source, phreato-
phytes are physically removed from Lake O'Neill and the
spreading basins to reduce the loss of water to these plants.
Authorities estimate that for every acre of phreatophytes
cleared, two acre-feet per year of groundwater is saved.
Program monitoring consists of weekly water level observa-
tions at key wells throughout the basins, as well as periodic
39
-------
DIVERSION
DAM
DYKES
•^ SANTA MARGARITA
RIVER
(UNDERGROUND
MOST OF YEAR)
FALLBROOK
CREEK
C1.4 MGD OF
SECONDARY
EFFLUENT)
OXIDATION
POND
TREATMENT
PLANT
ON-CHANNEL
SPREADING
GROUNDS
TREATMENT
PLANT
OXIDATION
POND
I
GOLF
COURSE
IRRIGATION
SPREADING GROUNDS
FOR SALT WATER
INTRUSION BARRIER
COASTLINE
FIGURE A-l
SCHEMATIC DIAGRAM OF SANTA MARGARITA
RIVER BASIN RECHARGE FACILITIES,
CAMP PENDLETON, CA.
40
-------
sampling of groundwater (quarterly) and incoming surface
water quality (monthly) in all the basins. Data from these
observations and tests is used to allocate water for re-
charge and to schedule extraction so as to maintain the
highest possible quality and safe perennial yields within
the aquifers.
Table A-2 summarizes typical groundwater quality. The high
TDS concentration is due basically to added salts from up-
stream users and to the Colorado River Water source utilized
by these towns that eventually finds its way into Camp
Pendleton basins. To the present, there have been no
instances of virus, bacteria or other contamination of the
potable water supply due to the recharge with treated waste-
water and natural supplies.
Twelve wells are used in the Santa Margarita basin to extract
the potable water supply for the base. These wells are
located in the Upper Valley and Chappo Valley Basins of the
system with the lower Ysidora Basin used only for salt water
intrusion prevention. The sixteen inch diameter wells range
from 150-300 ft deep and are capable of pumping up to 1,400
GPM. The upper 50 feet of each well is covered with a
sanitary seal and the deepest 60 feet provided with perfora-
tions. Water extracted is heavily chlorinated at the well
sites before being pumped to reservoirs. It is chlorinated
again prior to entering the distribution system.
It is important to note that although the recharged water
enters the potable aquifer, it basically forms a layer at
the top of the groundwater basin and has little chance to
mix with water in the deeper potable zone (150-300ft). Dur-
the rainy season, natural precipitation and runoff tend to
carry the upper zone of the aquifer (containing most of the
treated effluent) into the ocean. The actual amount of re-
charged water reaching the potable zone and being pumped
out for domestic reuse is estimated to be quite low.
Economics
Costs for the recharge system at Camp Pendleton are minimal.
Annual operation and maintenance costs are $12,000 which
covers the costs of maintaining the berms, diversion chan-
nels, etc., and of removing a thin silt layer from the per-
colation basins every other year. Annual capital recovery
costs are estimated at $10,000 per year for construction of
basins, piping, flow meters, and pumps, Thus, the total
cost for the recharge operation breaks down to $15/MG
(1972 $).
41
-------
Table A-2. TYPICAL GROUNDWATER QUALITY AT A
200 FOOT DEPTH AT CAMP PENDLETON
Constituent
TDS
NO 3
P04~3
S04
Cl
K
Concentration
mg/1
680
0.01
0.11
138
158
Constituent
SiO2
F~
B
Total Fe
Mg
2.9 Total Hardness
Concentration
mg/1
38
0.64
0.11
0.05
13
240
42
-------
The base is realizing a substantial savings due to its
water recharge management program. The base currently uses
over 8,000 acre-ft per year as potable water. At present
costs of $75/acre-ft for imported Colorado River water, it
would cost $600,000 per year if all its fresh water had
to be imported.
Future for Recharge Program
The .successful recharge/water resource management program at
Camp Pendleton will continue to save both water and money
into the foreseeable future.
Anticipated improvements include updating of all treatment
plants to secondary treatment; mechanical aeration of all
oxidation ponds; and nutrient removal either by tertiary
in-plant treatment or by proper flooding/drying techniques
as practiced at Flushing Meadows, Arizona.
43
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EASTERN MUNICIPAL WATER DISTRICT (HEMET, CALIFORNIA)
Introduction
The Hemet-San Jacinto groundwater basin is an important
source of irrigation and potable water for the local area.
The basin is essentially a closed system with a long-term
yield of 11,000 acre-ft per year. However, an overdraft
condition exists as over 23,000 acre-ft are being withdrawn
each year.
Authorities estimate that by 1980, 10,500 acre ft/yr of
wastewater will be available to the region for irrigation
and limited recharge''), which would amount to a doubling
of the long-term basin yield. Conservation and replenish-
ment of the groundwater resource reduces the need for
imported Colorado River water of high mineral content for
irrigation and domestic use, and therefore retards degrada-
tion of the high quality groundwater by this source.
In July, 1965, the Eastern Municipal Water District completed
the construction of and began operating a new 2.5 MGD
activated sludge treatment plant in conjunction with a new
trunk sewer system. Soon after, the EPA provided funds for
a project to demonstrate the feasibility and safety of re-
charging groundwater basins with the treated secondary
effluent. Since that time, treated wastewater from the
Hemet-San Jacinto treatment plant has been spread in perco-
lation basins both as a method of disposal and for replen-
ishment of the groundwater basin. In 1971, the Hemet-
San Jacinto plant was expanded to 5 MGD capacity, but
currently (1975) flow is only about 3 MGD with equal volumes
going to local irrigation and groundwater recharge.
Municipal Treatment
The treatment plant at Hemet-San Jacinto is a conventional
activated sludge plant. A chlorine contact chamber follows
the final clarifiers to provide a 20 minute contact time
The recently adopted basin plan for the Santa Ana River
Basin (RWQCB, Santa Ana Region) essentially precludes
continuation of the present effluent recharge program at
Hemet. In the future, effluent not used for irrigation
will be substantially diluted with imported fresh water
prior to recharge.
44
-------
prior to two 1.5 MG flow equalization ponds. In addition,
three emergency storage ponds are available and a sealed
brine evaporation pond maintained to receive tank truck
deliveries of brine water generated by a local water soften-
ing industry.
The final effluent is then transported by four pumps (two
50 H.P. electric and two 250 H.P. gas motors) one mile out
to the spreading basins via two pressure mains (20 in and
14 in). Water sold for irrigation is taken directly from
these force mains.
Table A-3 summarizes typical effluent quality characteristics
for the treatment plant.
Recharge Program
The recharge area is located approximately four miles east
of the plant site and is comprised of 10 ponds covering an area
of approximately 16 acres. The ponds are arranged in two
parallel groups with the effluent main running along the
median strip. The reclaimed water can be diverted to any
combination of pads via individual tees, valves, and meters
with a nominal size of 8 in. The effluent drops into each
pond from an upturned elbow onto a concrete splash pad.
The basins are interconnected with overflow gates to allow
transfer of water from one basin to another.
The basins are filled on a rotational basis with maximum
infiltration rates achieved by following the schedule: fill -
1 day (to average 2.5 ft depth), drain - 2 days, dry - 1 day.
When longer cycles of two or three weeks were tried, clogg-
ing of soil pores and reductions in infiltration rates
resulted. Much of this clogging was caused by algae growths
stimulated by the high nutrient concentrations in the re-
claimed water. (See Table A-3.) Apparently, the shorter
flooding-drying cycle effectively interrupted the algae
life cycle and eased this problem.
The soil profile in the spreading area shows medium and
coarse sand down to approximately 50 ft with horizontal clay
layers interspersed at greater depths. Infiltration rates
are fairly high at roughly two to three ft per day when short
flooding-drying cycles are used. Experimentation showed
that infiltration rates were not enhanced by vegetative or
gravel cover in the basins. To control vegetation and also
to prevent surface clogging, the basins are periodically
rototil1ed.
45
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Table A-3. AVERAGE MUNICIPAL EFFLUENT
CHARACTERISTICS AT HEMET, CALIFORNIA
Constituent
BOD
SS
TDS
Na
Cl
pH
Hardness Cas CaCO 1
Ca
Mg
K
NH,
4
N03
CO3
HCO3
S°4
Fl
B
Concentration
Cmg/D
15-25
15-20
700
145
114
7.6
208
75
12
19
15
24
0
259
131
0.8
0.7
46
-------
Monitoring facilities consist of ten (160-260 ft) wells, a
network of peizometer holes at various depths from 10 to
94 ft, and a shallow test pan unit for sampling under one
of the basins at two, four, six, eight, ten ft depths.
Table A-4 shows the effects of percolation on the effluent
character!' sti cs .
As shown in the table, nitrate concentration increased
rapidly in the first two feet due to oxidation of ammonia,
Total COD decreased 68 percent through eight ft of soil wnile
total hardness increased from 205 to 340 mg/1 through the
same depth. The coliform concentration dropped sharply to
a level of 120 per 100 ml while fecal coliform concentration
dropped from 58,000 to only 10 MPN per 100 ml.
Efforts to trace the percolating groundwater down to the
present water table at 200 ft have failed due to horizontal
displacements caused by layers of silt and clay. It is
generally agreed, however, that the only degradation of the
groundwater basin caused by recharge with secondary effluent
has been a gradual increase of groundwater TDS over the long
term.
Economi cs
Annual costs for the recharge operation only (including
effluent pumps, four miles of main pipeline, equipment,
meters, ponds, labor, overhead) are as follows:
$/year (1972)
Equipment amortization, overhead 6,500
Maintenance of basins 15,000
Repairs 600
Total $ 22,100
Therefore, total costs for recharge are $22,100 per year
(1972), for an average flow for two MGD (assuming one mgd to
irrigation), or approximately $30 perMG. This represents
approximately 15 percent of the total cost of wastewater
treatment and disposal. As shown, the main operational cost
appears as maintenance of the basin berms and percolation
surfaces (rototi11ing ).
Future for Recharge Program
Groundwater recharge will probably play an important part
in the water resource management program of the Hemet-
47
-------
Table A-4. EFFECTS OF PERCOLATION ON
EFFLUENT CHARACTERISTICS
Constituent
N03
COD
Depth (ft)
0 2
~N(mg/l) 13 29
(mg/1) 50 20
4
28
17
6
25
17
8
30
16
Total hardness
(as mg/1
205 280 330 350 340
Coliform, MPN per 100 ml 250,000 1,000 1,000 180 120
48
-------
San Jacinto Basin area. To a great extent, however, use
of secondary effluent is being shifted from direct recharge
to agricultural irrigation. Increases in groundwater IDS and
state health department fears that organo-phosphate pesticides
and viruses (potentially present in the effluent) may degrade
groundwater supplies have reduced the appeal of effluent as
a recharge source.
In the event that primary use of wastewater shifts again to
direct recharge, low IDS state project water can be
blended with wastewater to achieve an acceptable IDS level
in the recharge water.
49
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NASSAU COUNTY DEPARTMENT OF PUBLIC WORKS/THE U.S. GEOLOGICAL
SURVEY (LONG ISLAND, NEW YORK)
Introduction
The U.S. Geological Survey, in cooperation with the Nassau
County Department of Public Works, conducted a series of
artificial recharge experiments at Bay Park, New York, from
1968 to 1973. The purpose of these experiments was to obtain
some of the scientific and economic data needed to evaluate
the feasibility of injecting reclaimed wastewater (tertiary
treated sewage) into a proposed network of barrier-recharge
wells in an area of potential seawater intrusion.
Groundwater is the only local source of water on Long Island.
The demand for this water has been increasing steadily with
the population, while a massive expansion of sewage collec-
tion systems has reduced recharge from cesspools and
septic tanks by collecting and discharging effluents to the
ocean.
The main concern presently is that the productive Magothy
aquifer will become depleted over the years, forcing the
purchase of imported water. The lowering of the water table
and the potentiometric head in the Magothy will also increase
the risk of salt water intrusion.
Municipal Treatment
The Nassau County Public Works Department constructed an
0.6 mgd pilot tertiary treatment plant in 1968 to upgrade
activated sludge secondary effluent to drinking water quality
for the recharge tests. Figure A-2 on the following page
shows a flow diagram of the advanced treatment system.
The tertiary facility consisted of: chemical coagulation/
clarification, filtration, carbon adsorption, and chlorina-
tion. The upflow clarifier was 40 feet in diameter, had a
rise rate of 720 gpd/sq ft, and used a 225 mg/1 alum dosage
as its principal coagulant. Two ten ft diameter dual media
filters followed, comprised of three feet of anthracite over
one foot of sand, and were operated at a hydraulic loading
of 3.3 gpm/sq ft. The effluent was then pumped to four
activated carbon towers operated in series. Each tower was
8 ft in diameter, and was packed with 7,000 Ibs of activated
carbon. Total empty bed contact time was 30 minutes. The
activated carbon was regenerated in a multi-hearth, gas-
fired furnace. Conventional chlorination completed the
treatment chain.
50
-------
ACTIVATED
SLUDGE
EFFLUENT
ALUM
PUMP
UP-FLOW
CLARIFIER
DUAL
MEDIA
FILTERS
ACTIVATED
CARBON
TOWERS
CHLORINATION
0.5 MILE
TO INJECTION
WELL SITE
FIGURE A-2
TERTIARY TREATMENT PLANT AT
LONG ISLAND, N.Y.
51
-------
The effluent was then pumped 1/2 mi in a six in.line to a
small holding tank at the injection well site. This tank
provided two hrs. of storage to provide for continuous
injection during brief treatment plant shutdowns.
Table A-5 summarizes typical effluent quality of the tertiary
effluent for recharge.
Recharge Operation
Facilities - At the injection well site, additional treat-
ment including degasification, pH adjustment, and dechlorin-
ation, were available if desired. Later tests were to show
that none of these provided any significant improvement in
operations. Figure A-3 depicts the injection facilities.
Reclaimed wastewater and/or fresh water to be injected was
stored in a 50,000 gal tank (providing roughly two hours of
retention). If pH control chemicals were to be used, they
were introduced at the tank outlet where the water discharged
into a splashbox for mixing. Optional cascade degasification
followed in a few tests after which the water was pumped
down the well.
The injection well complex consists of two wells within a
single drill hole, 36 in, in diameter. The major element
is an 18 in. diameter fiberglass casing that extends to
a depth of 418 ft. below land surface. A stainless steel
screen 16 in. in diameter and 62 ft in length was attached
to the bottom of the 18 in. casing in the Magothy aquifer.
Various smaller pipes for monitoring were also housed in the
casing. See Figure A-4 for a detail of the well.
The injection pump assembly consists of a 40 HP electric
motor connected to a centrifugal pump through a variable
speed hydraulic transmission. This system allows the in-
jection rate to be controlled in the range from zero to
more than 400 gpm against a maximum head of 100 psi.
The well facility also includes a redevelopment or backwash
pump. The major element of this system is a 50 HP vertical
deep-well turbine pump, which is suspended in the injection
well at a depth of 150 ft. The backwash flow can be con-
trolled within the range of 200-1,000 gpm.
In addition to sampling of water during well "redevelopment,"
fourteen wells, ranging in depth from ten to 726 ft, were
used to monitor water quality at various depths and distances
from the point of injection.
52
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Table A-5. TYPICAL TERTIARY EFFLUENT
CHARACTERISTICS AT LONG ISLAND, NEW YORK (1)
Parameter
COD
BOD
SS
TDS
ci-
Si02
Total Al
Total Fe
Total Mn
Ca
Mg
Na
K
HCO-.
S04
Chlorine residual
F
Org. N
NO-
NH, - N
NO4
To^al P as P04
Hardness as CaCO-j
pH
Concentration
Cmg/1)
9
5
0-1
394
99
13
0.1
0.4
0.07
20
6.4
86
13
59
160
2.1
0.3
0.6
0.01
23
0.1
0.08
79
6.1
Color (platinum cobalt scale) 2
Turbidity as Si02
DO
Coliforms/100 ml
Fecal Coliforms/100
0.4
4.5
< 1
ml < 1
Fecal Streptococci/100 m. C 1
' ' Vechioli, John, Oliva, J. A., Ragone, S. E., and
Ku, H. F. H., 1975, Wastewater Reclamation and
Recharge, Bay Park, N.Y., ASCE, Env. Eng. Div.,
V. 101, No. EE2.
53
-------
TERTIARY
TREATED
EFFLUENT
FRESH WATER
NA2S03
TO WASTE
-GATE VALVE
123 ~ BUTTERFLY VALVE
STORAGE TANK
50,000 GAL.
DEGASIFIER
FLOW METER
FLOW CONTROLLER/RECORDER
WELL PUMP
INJECTION
FIGURE A-3
INJECTION FACILITIES AT BAY PARK,
LONG ISLAND, N.Y.
54
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Depth b«tow
land surface.
in f««t
3-in.-diamet«r
fibers) ass
tremie pipe
4-in.-diameter
annular-space
observatton-
wall casing
5-in.-X 62-f t
long stainless-
steal annular-
space observa-
tion-welt screen
10-ft-long stain-
less-steal sand
traps
433-
508-
18-in.-diameter fiberglass
injection casing
36-in.-diameter drill hole
,4-in_-diameter fiberglass
injection pipe
l-in.-diameter fiberglass
pressure-measuring pipe
3-in.-diameter fiberglass
tremie pipe
Cement grout
2-«.-«lick layer of
fine sand
16-in.-X62-tt-long
stainless-steel
injection screen
Filter pack
Cement grout
FIGURE A -4
DETAILS OF THE BAY PARK INJECTION WELL
TAKEN FROM COHEN, P. AND C.N. DURFON. ^DESIGN
& CONSTRUCTION OF A UNIQUE INJECTION WELL ON
LONG ISLAND, N.Y." U.S. GEOLOGICAL SURVEY.
PROF. PAPER sso-D, PAGES D 253-0257.
55
-------
Results - The series of continuous pumping tests (a 33-day
continuous test and a 6-month interrupted test) during the
1968-1973 period showed that successful injection of high
quality tertiary effluent into the deep Magothy aquifer
was achieved only during peak performance of the advanced
wastewater treatment facility. During less efficient treat-
ment periods, the main problem encountered was clogging of the
fine pore spaces in the aquifer, forcing frequent well re-
generation (backwashing) to restore initial hydraulic
specific capacity (recharge rate/head.
The clogging was basically a physical, straining problem.
Although loading rates of 0.6 gpm/ft^ of well screen area
were achieved in the medium sand aquifer (similar to the
lower range of a slow sand filter), residual particulate
matter, and phosphate and iron precipitates frequently
clogged the pore spaces and forced regeneration.
The head buildup distribution in the aquifer at distances of
20 to 200 ft from the point of injection was virtually equal
to the drawdown distribution observed during the original
pumping test. This would indicate that clogging of the
aquifer was restricted to the immediate vicinity of the well.
This was corroborated during regeneration after injection
when the first slugs of water recovered were consistently
high in turbidity and iron.
Clogging accelerated with several minor quality changes; i.e.
when effluent turbidity increased over 0.5 mg/1 or
P04"3 concentrations climbed above 1.0 mg/1, or Fe rose
above 0.5 mg/1. The iron problem had been almost elimin-
ated by the end of the project by frequent backwashing of
the carbon towers. This maintained aerobic conditions
throughout the towers. Thus iron compounds precipitated
there instead of in the well as had occurred when anaerobic
bacteria in the carbon had reduced iron to a soluble state
before injection. Another improvement was the elimination
of the peak solids loads occurring in the first slug of
effluent after filter backwashing. This slug was discharged
instead of being sent to the well. Authorities agreed that
future reclamation/injection projects should be designed
with large effluent storage capacity to provide greater
flexibility in by-passing surge loads from the treatment
plant and in assuring continuous injection during periods of
treatment plant shutdown.
Other sources have stated that well clogging problems can be
caused by the release of entrained air or dissolved gases
from the injected water. The dissolved gases can themselves
clog soil pores, or excessive amounts of free oxygen, by
56
-------
establishing aerobic conditions, can cause the oxidation of
iron, aluminum, and phosphorous to insoluble precipitate
forms which clog the aquifer. However, five tests at Long
Island showed that clogging caused by gas entrainment was
minimal compared to the clogging effects of other parameters
(turbidity, iron, phosphate). Thus, degasification was rarely
used.
Significant changes did not occur in the chemical characteris-
tics of the injected water as it moved through the aquifer
for distances up to 20 ft. The slight changes which did
take place included a decrease in calcium, bicarbonate, pH,
and phosphate. Iron, on the other hand, increased.
Economi cs
Operation and maintenance costs for the 1968-1973 advanced
water reelamation/groundwater recharge program were as
follows:
$/MG (1972 $)
Treatment plant
Labor 120
Chemicals 20
Utilities 10
Other 120
Injection facility
(power, chemicals, labor) 50
TOTAL (1972 $) 320
Capital costs for the injection well were approximately
$125,000 and $860,000 for the tertiary treatment plant
(1972 $).
Future for Recharge Programs
Although this test showed that injection into the deep
Magothy aquifer to establish a salt water intrusion barrier
and to replenish the groundwater supply was difficult,
authorities of the USGS and Nassau County Department of
Public Works feel that recharge does have potential at Long
Island.
A new system is currently in the design phase that would
provide 5 mgd of tertiary treated effluent for recharge of
the upper glacial and Magothy aquifers. They hope to
57
-------
replenish the shallow aquifer at a location in the middle
of the island where a vertical gradient exists, allowing
recharged water to percolate to the deeper Magothy aquifer.
The 5 mgd plant will consist of: grit removal; biological
treatment for carbonaceous removal; lime clarification for
phosphate and solids removal; biological nitrification/
denitrification to reduce nitrogen concentrations; dual
media filtration for further suspended solids removal; acti-
vated carbon adsorption to remove dissolved organics; and
finally chlorination for bacteriological control.
A group of 100 foot wells along with several percolation
basins will be used to recharge the shallow groundwater basin
This aquifer is composed of coarse sand with large pore
spaces, and therefore clogging problems are not expected to
be as severe as in the deep well tests. Spreading basins
will be used where feasible (some old basins from the 1930's
are still being used for storm water runoff collection and
percolation), with the effluent and available storm water
being mixed and recharged.
The effluent to be recharged will undergo advanced waste-
water treatment as listed above to bring it up to drinking
water standards prior to injection or percolation. No
mixing with fresh water sources will be necessary for many
years because the TDS of the effluent will be approximately
400 mg/1. Eventually, some type of demineralization will be
necessary to maintain a proper salt balance in the aquifers.
Ultimately, authorities hope to recharge approximately 100
mgd of combined treated wastewater and natural runoff
throughout Nassau County by percolation and injection. This
large scale recharge would represent roughly 10 percent of
the total recharge to the Long Island groundwater basin. In
this way Nassau County hopes to conserve their high quality
groundwater supply and to avoid purchase of costly imported
water from New York City .
58
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THE CITY OF OCEANSIDE, CALIFORNIA
Introduction
The city of Oceanside, California, has been extracting
groundwater for its potable supply since the 1930's. By
1958, however, increasing demands had drastically lowered
the water level in the aquifer, and salt water intrusion
had become significant.
Therefore, in 1958 the city initiated a groundwater recharge
program using primary effluent. The wastewater was pumped
three miles inland and percolated to replenish the basin and
to retard salt water instrusion.
As the population continued to increase and two more treat-
ment plants were constructed, the total recharge program over-
loaded the localized groundwater basin capacity, and the
water table rose to fifteen ft above sea level. By 1970,
the basin in the area of recharge had become saturated, and
effluent was flowing as a stream into the ocean.
An outfall was constructed to temporarily discharge the
effluent to the ocean while a new secondary treatment plant
and percolation basins were constructed. The new basins,
approximately six miles inland, are located further upstream
than the old spreading areas at a site where the aquifer can
accept a greater volume. Ultimately, all the effluent will
be extracted downstream from the percolation areas and used
for irrigation and filling of recreational lakes. Any excess
effluent will be discharged through the ocean outfall.
Municipal Treatment
When the San Luis Rey treatment plant is completed in early
1975, the single primary plant will be closed, leaving one
other secondary plant and the new facility to treat the
city's wastewater.
Both plants are conventional activated sludge plants although
the new San Luis Rey plant has optional chemical precipitation
for nutrient removal. Before the effluents are pumped to
the spreading grounds, however, they enter a series of five,
five to ten acre oxidation ponds (no aeration) and/or a 180
acre-ft effluent-filled pond called Whelan Lake. The pond is
clay-lined and has a floating 50 HP brush aerator to maintain
aerobic conditions. Two additional lakes may provide further
storage at the spreading site. Thus the total effluent flow
from the two plants of 6.5 mgd is stored from ten to 20 days
in ponds before being recharged.
59
-------
Table A-6 summarizes typical effluent characteristics of the
discharge from Whelan Lake. The high TDS concentration is
due to three factors: the use of high TDS Colorado River
water as part of the potable supply; the infiltration of salt
water into the sewer lines near the coast; and evaporation
in the oxidation ponds and Whelan Lake.
Recharge Program
Figure A-5 provides a schematic diagram of the present and
planned facilities. The new recharge program to begin in
1975 will consist of pumping 6.5 mgd of treated wastewater
from Whelan Lake in a two mile 33 in. diameter pipeline to
two series-operated oxidation ponds. The effluent will then
flow to the percolation area which will cover a total of 50
acres dyked into several basins. The basins are of coarse
sand composition with high infiltration rates of four
to five ft/day. They will be flooded to a three ft. depth
in a flooding-drying cycle such that several basins are being
flooded while the others are drying. The basins will be
periodically scarified to reduce bottom clogging by solids.
The current plan is to construct extraction wells 1/2 miles
downstream from the recharge basins. With the finished
system, all treated wastewater percolated will be extracted
by the wells and used for irrigation and for filling rec-
reational lakes. With this percolation/extraction system,
all groundwater gradients in the recharge area will be
directed toward the extraction wells thus ensuring that no
renovated water volumes of any significance will migrate
directly into the native groundwater. After extraction, a
portion of the water will be demineralized to a TDS of
850 mg/1 before irrigation reuse. In this way, tjie salt
content of the groundwater basin will not be significantly
increased due to percolation of the irrigation water.
Monitoring of the groundwater to check for possible degrada-
tion will be carried out downstream from the percolation
basin. Existing wells of roughly 100 ft depth will be used
to collect the samples for this purpose.
Economics
Table A-7 on page 64 summarizes basic estimated capital and
operation and maintenance costs for the complete recharge
portion of the Oceanside system. Annual capital recovery
costs are $263,000 (1972 $) per year at a 5.5 percent
interest for a 25 year life. Adding the annual operation
and maintenance cost of $85,000 yields a total annual cost
of $348,000 (1972 $) or, $147 per mg, at 6.5 MGD.
60
-------
Table A-6. TYPICAL CHARACTERISTICS OF TREATED
WASTEWATER FOR RECHARGE AT OCEANSIDE, CALIFORNIA
Constituent
BOD
SS
TDS
Na+
el"
Coliform
so4=
Total Org. N
N03=
NH3
P04-3
Concentration
Cmg/1}
6
18
1280
285
303
3-43/100 ml
453
1.3
2.2
20
31
Constituent
F-
B
Fe
Total Cr
Zn
As
Pb
Cu
Se
Cu
Cd
Ag
Concentration
Cmg/1)
0.86
0.72
0.07
< 0.05
< 0.05
< 0.01
0.05
< 0.01
< 0.01
< 0.01
< 0.05
< 0.05
61
-------
UNDER CONSTRUCTION
PLANNED
OJ
in
tf)
UJ
Ul
OJ
OXIDATION
POND
OXIDATION
POND
OXIDATION
POND
BASINS
(50 ACRES)
EXTRACTION
^ wtuLs
»
r-»
PARTIAL
DEMINERALIZATION
RECREATIONAL
LAKES AND
GROUNDS
IRRIGATION
OVERFLOW
TO SAN LUIS
REY RIVER
CHANNEL
68
LAKE
40 ACRE
SPRAY
IRRIGATION
33 IN0
OXIDATION
PONDS
EXCESS
EFFLUENT
SAN LUIS REY
SECONDARY PLANT
LA SALINA
SECONDARY
PLANT
OCEAN
FIGURE A-5
PRESENT AND PLANNED RECHARGE FACILITIES
AT OCEANSIDE, CA.
62
-------
Table A-7. ESTIMATED CAPITAL AND OPERATION AND
MAINTENANCE COSTS FOR RECHARGE
SYSTEM AT OCEANSIDE, CALIFORNIA
Capital Cost
$1000 (1972)
Effluent force mains
33 in /?, 1/2 mile
33 in 0, 2 miles plus
pump station
Improvements to Whelan Lake
& existing spreading grounds
Construction and installation of
standby aeration and chlorination
facilities and flow meter
Construction of new spreading basins
and flow meter
Construction of extraction wells and
facilities to transport percolated
wastewater to recreational lakes
Demineralization plant (for a portion of
the flow)
Land acquisition (45 acres)
Engineering contingencies
Total Capital
Cost for Recharge/
Reclamation System Only
300
560
180
230
120
240
1500
200
200
$3,530
Operation & Maintenance Cost (Annual)
$1000 (1972)
Estimated Labor
Estimated Power Costs
Total 0 & M Cost
for Recharge/Reclamation
System
15
70
$ 85
63
-------
Authorities feel that the extensive benefits that would be
realized with this system offset the cost of the reclamation
facilities. Not only will high quality renovated water be
available for irrigation of park land and filling of recre-
ational lakes, but groundwater supplies will be conserved,
ana valuable ocean and coastline assets will be protected by
elimination of most effluent discharges to the ocean.
Future for Recharge Programs
Future plans for groundwater recharge/reclamation systems in
Oceanside are contingent upon the success of the program
presently being constructed.
By the year 2000, expected sewage flow from the city will be
15 mgd. It is anticipated that all this wastewater will be
fed to the recharge/renovation system for reuse in recrea-
tional lakes and for irrigation.
64
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ORANGE COUNTY WATER DISTRICT (FOUNTAIN VALLEY, CALIFORNIA)
Introduction
Since the 1950's, continued overdrafting of the Orange County
groundwater basin has lowered the groundwater table to below
sea level, resulting in significant salt water intrusion. The
intrusion occurs at the mouth of an ancient underground
channel cut millions of years ago by the Santa Ana River. The
years of continuous flows of the river, which formed the
alluvial fan now known as Orange County, have buried this
ancient river under several feet of clay.
In order to prevent further seawater intrusion, which was
evident as far as six miles inland, and to replenish existing
groundwater sources, the Orange County Water District is
constructing a 30 mgd wastewater reclamation and desalting
plant. Effluent from this plant will be injected in to 23
multi-point wells to form a salt water intrusion barrier and
to recharge the groundwater basin. Seven extraction wells,
located two miles seaward from the injection line, will extract
intruding salt water before it reaches the barrier and return
it to the ocean. The combination of salt water extraction
and fresh water injection will serve to create an underground
hydraulic pressure mound preventing intrusion.
The total 30 mgd supplied by the advanced wastewater treat-
ment plant and the seawater desalting plant will supply a
volume equivalent to roughly ten percent of the total Orange
County water demand.
Municipal Treatment
Ultimately the wastewater treatment facility and the desalt-
ing plant will each supply fifteen mgd which will be blended
to provide 30 mgd of 550 mg/1 TDS water for recharge. At
startup, the desalter will be operated to produce three mgd with
plans to expand following a trial period. Initially, the
wastewater reclamation plant will provide roughly eleven
mgd. An additional nine mgd, temporarily supplied by deep
wells, will be mixed with the reclaimed and desalted waters
to lower TDS within required limits. The deep well water is
also needed temporarily to satisfy the state requirement that
reclaimed water injected directly to the groundwater must be
blended 50:50 with a fresh water supply regardless of the
treated effluent quality. The use of deep well water will be
terminated when full scale operation is achieved. The
remainder of this section will deal only with the advanced
wastewater treatment plant.
65
-------
rRESH WATER EXTRACTION WMLLS FOH
ORANGC COUNTY CONSUMPTION
HIC,H OUALJTY WATER TOR HIGH PfJESSUPE
INJECTION INTO 3ALT.ENOANGEHLD At}Ui~~
SEA V/ATER EXTRACTION FrtOM TALDCRT
AQUIFER — RETURNED TO OCEAN
GROUND SURPACE_
...•^..•.•.t^MrtVvrtrt^
'•>•••••' ' •' "< -^^y .... , •• . ,
UNOcnanourm WATKR BASIN
FIGURE A-6
CROSS-SECTION OF HYDRAULIC
SEAWATER BARRIER AND RECHARGE
SYSTEM, ORANGE COUNTY, CA.
-------
The Orange County Water District advanced wastewater reclama-
tion plant is one of the most sophisticated in the world.
Ultimately it will provide tertiary treatment to fifteen mgd
of secondary effluent from the adjacent Orange County Sani-
tation District's trickling filter plant.
Figure A-7 shows a flow diagram of the basic treatment units.
Detailed design criteria are provided in Table A-8.
The secondary effluent first enters the two chemical floccu-
lation/clarification basins. Each unit consists of a small
rapid mix tank, flocculation chamber, and settling basin.
The main purpose of these units is to remove suspended solids
and phosphates, and also to raise the pH to facilitate
subsequent ammonia stripping. In addition, calcium,
magnesium, many trace elements, bacteria, and virus may
also be removed by the chemical clarification.
Conventional ammonia stripping in plastic media, forced
draft towers follows;after which the water is recarbonated.
A first stage recarbonation chamber lowers the pH from
11.0 to 9.3 by diffusing carbon dioxide gas, supplied by
compressed stack gases from the lime recalcining furnace,
into the wastewater. The recarbonated water is then held
for 40 minutes in an intermediate settling basin to allow
complete formation and some sedimentation of calcium carbonate.
The sludge from the basin is continually removed and returned
to the initial clarification tank to aid in flocculation and
settling. The third section of the basin is the secondary
recarbonation chamber where the pH is lowered from 9.3 to
7.5 to drive all excess calcium carbonate back into solution
to prevent deposition and scale formulation on following
filter beds and piping.
The process stream is then given multi-media (anthracite
coal, silica sand, and garnet sand) filtration to remove
suspended solids and colloidal material. The filters are
periodically backwashed with final blended product water.
Following filtration, the water is pumped up through carbon
towers that provide a 30 minute contact time for the adsorp-
tion of organics onto the carbon particles. The carbon
towers are effective in removing color and odor as well. A
carbon regeneration furnace will be used to regenerate spent
carbon from the towers.
Effluent from the carbon adsorption process flows to the
chlorine contact basin for breakpoint chlorination to oxidize
any residual ammonia, and to destroy an remaining bacteria
and virus. Chlorine will be added, through a diffuser in the
pipeline, just upstream of the entrance to the contract basin
67
-------
11
15
MGD
MGD
INITIAL
ULTIMATE
LIME
LIME
SLUDGE
THICKENER
WASTE
fSOLIDS
TO
LANDFILL
LIME
RECALCINING
FURNACE
STACK GASES
CQ2
COMPRESSORS
LIME
STORAGE
DESALTED
WATER
CLARIFIER
3 MGD
15 MGD
DEEP WELL
WATER
9 MGD INITIAL
o MGD ULTIMATE
SECONDARY
EFFLUENT FROM OCSD
CHEMICAL
FLOCCULATION/
CLARIFICATION
BASINS
AMMONIA
STRIPPING
TOWERS(2)
RECARBONATION
BASINS (2)
MULTI-MEDIA
FILTERS (4)
CARBON ADSORPTION
TOWERS (17)
CHLORINATION
BASIN
BLENDING AND
STORAGE TANK
INJECTION
WELLS
MGD INITIAL
MGD ULTIMATE
INJECTION
WELL PUMPS
FIGURE A-7
ORANGE COUNTY WATER DISTRICT
ADVANCED WASTEWATER RECLAMATION PLANT,
FOUNTAIN VALLEY. CALIFORNIA
68
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Table A-8. DESIGN PARAMETERS FOR ORANGE COUNTY
WATER DISTRICT WATER RECLAMATION PLANT (MGD)
Clarification Basins
Rapid Mixing;
Number of basins: 2
Each basin equipped with a mechanical mixer
Detention time: 1 minute (each basin)
Flocculation:
Number of 3-compartment basins: 2
Each compartment equipped with mechanical flocculator
Detention time: 30 minutes
Settling:
Number of basins: 2 „
Overflow rate: 1560 gpd/ft
Detention time: 85 minutes
Each basin equipped with settling tubes
Ammonia Stripping Towers
Number of towers: 2 2
Hydraulic loading: 1 gpm/ft
Air flow: 400 ft3/gallon
Depth of packing: 25 ft. (7.6 m)
Number of 18 ft. diameter fans: 12
(develop 350,000 cfm air flow) each
Heat transfer capacity: Cool seawater desalting
plant waters to 80° - 85°F and heat ammonia stripp-
ing air to 8?o _ 97°F.
Recarbonation Basins
Number of 3 compartment basins: 2
1st and 2nd stage recarbonation detention times:
15 min. each
Settling basin detention times: 40 min.
1st stage recarbonation basin equipped with
mechanical flocculators
69
-------
Table A-8 (continued). DESIGN PARAMETERS FOR ORANGE
COUNTY WATER DISTRICT WATER RECLAMATION PLANT (MGD)
Sludge Handling
Sludge Pump Station;
Number of pumps: 3
Pump capacity: 700 gpm at a total head of
35 feet (10.7m)
Sludge Thickener;
Flow: 1000 gpm
Surface overflow rate: 1000 gpd/ft2
Surface dry solids loading: 200 Ibs/day/ft2 (90.7
Kg/day/m2)
Thickened sludge solids: 8%-20%
Lime Recalcining
Lime Recalcining Furnace;
Capacity dry CaO: 30 tons/day
Lime Storage Tanks;
No. of tanks: 2
Capacity: 35 tons bulk quicklime
(CaO) ea.
Centrifuges;
No. of centrifuges: 2
Capacity: 2000 Ibs/hr each
Lime Feeders and Slakers:
No. of feeders and slakers: 2
Capacity: 4000 Ibs/hr each
CO2 Compressors:
No. of compressors: 3
Capacity: 1600 cfm each
70
-------
Table A-8 (continued). DESIGN PARAMETERS FOR ORANGE
COUNTY WATER DISTRICT WATER RECLAMATION PLANT (MGD)
Multi-Media Filtration
Design Criteria
Plant Capacity;
15 mgd
16,800 a.f./year
20,714,400 mVyr.
10,400 gpm
23 cfs
Filtration;
No. of filters: 4
Hydraulic loading: 5 gpm-/ft
Backwash rate: 15 gpm/ft^
o
Surface Wash flow: 0.6 gpm/ft
Backwash water receiving tank
capacity: 160,000 gal
Carbon Adsorption
Carbon Adsorption;
No. of upflow pressure units: 17
Contact Time: 30 man
Carbon volume, ea. unit:
2700 ft3
Tank diameter: 12 ft
Carbon depth: 24 ft
Hydraulic loading: 5.8 gpm/ft
Carbon Regeneration Furnace:
Capacity, dry carbon:
12,000 Ibs/day
71
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Table A-8 (continued). DESIGN PARAMETERS FOR ORANGE
COUNTY WATER DISTRICT WATER RECLAMATION PLANT (MGD)
Chlorination Basin/Blend Tank/Backwash Water Tank
Chlorination Basin;
1 basin - inline feeding and mixing
Contact time: 30 minutes
Blending Reservoir;
1 basin - prestressed concrete
Capacity: 1 million gallons
100 feet (30.4m) diameter x 20 feet deep
Backwash Water Receiving Tank;
1 underground concrete basin
Capacity: 160,000 gallons
Pumping capacity: 800 gpm (50.46 L/sec)
Injection Pump & Chlorine Supply Station
Chlorine Feeders;
Number of feeders: 3
Feeder capacity: 1000 Ib/day each
On-site chlorine manufacturing: 2000 Ib/day
Injection Pumps;
Number of pumps: 3
Type: vertical turbine
Engine type: natural gas
Pump capacity: 5000 to 7200 gpm
Backwash Pump;
Number of pumps: 1
Type: vertical turbine
Engine type: electric
Pump capacity: 15 gpm
72
-------
Effluent from the chlorination basin flows by gravity to the
blending and storage reservoir where it will bejblended
with desalted water and/or deep well water to achieve a
final IDS of 550 mg/1 ; as required by the local Water Quality
Control Board.
Table A-9 summarizes secondary effluent characteristics from
the OCSD trickling filter plant, expected final reclaimed
water characteristics, and expected final blended recharge
water characteristics.
Solids handling is extensive, including sludge thickening,
centrifugation, and recalcination in a lime reclaiming
furnace. It is estimated that 50 tons of solids per day will
be removed from the process water, of which 24 tons will be
recovered as lime.
Recharge Program
The purpose of the advanced wastewater and desalting plants
is to ultimately produce 30 mgd of high quality water for the
salt water intrusion/groundwater replenishment injection
system.
From the one MG reservoir, where chlorinated effluent,
desalted seawater and/or deep well water are blended, the
water will be pumped to the injection wells. Pumping is
accomplished with three,vertical turbine cam-type injection
pumps (one always on standby) with 408 HP variable speed
drives. Each of these units is capable of pumping 5,000 to
7,200 gpm.
The water is pumped through a main distribution line at 50
psi to a series of 23 injection wells placed approximately
every 600 ft along Ellis Avenue.
Figure A-8 shows a typical well cross-section with four
six in. wells located within a 30 in. casing. Each six in.
well penetrates to one of four separate aquifers from 80 to
350 ft below ground level.
A network of 170 water supply wells will aid in monitoring
changes in the groundwater quality due to the injection
program. Actually, the expected TDS concentration of the
final recharge water, 550 mg/1, is only slightly higher than
the average TDS of the groundwater (509 mg/1); while the
hardness of the recharge water will be significantly lower
than groundwater hardness, 100 mg/1 vs.276 mg/1.
In addition, the new recharge water is substantially better
in quality than the Colorado and Santa Ana River water
73
-------
Table A-9. AVERAGE EFFLUENT CHARACTERISTICS AT
THE ORANGE COUNTY SANITATION DISTRICT
AND THE ORANGE COUNTY WATER DISTRICT
WASTEWATER RECLAMATION PLANTS
Constituents
TDS
BOD
COD
Total
Hardness
SS
ci-
Na+
so4=
Fe
NH_
Characteristics
Expected
OCSD
Secondary
Effluent
1300
50
150
350
50
240
220
250
—
25
OCWD
Tertiary
Effluent
1100
1
10
200
1
240
220
250
0.6
2.0
(mg/1)
Blended
Product
Water
550
0
5
100
0
125
110
125
0.3
1.0
74
-------
TYPICAL MUI.TIPLE WELL
HAS t -6* CASINGS
WITHIN A 30* CASING
GftOl'VD
FEET
FIGURE A-8
TYPICAL MULTI-CASING INJECTION WELL
AT ORANGE COUNTY
75
-------
(IDS 700-800 mg/1) that has been used for percolation re-
charge since 1949. Therefore, it is anticipated that the
new injection/recharge program will have no adverse effects
on groundwater quality.
However, the recharge operation will be under close sur-
veillance from both the Santa Ana Regional Water Quality
Control Board and the State Health Department. Table A-10
summarizes the water quality requirements for the recharge
water as stipulated by WQCB. The presence of the electrical
conductivity or TDS limit has forced the water district to
blend effluent and low TDS fresh water or desalinated water
50:50 in order to reduce TDS below the requirements.
In addition, the State Health Department has imposed a
number of restrictive provisions and requirements to the
program including, ". . . an alternate source of domestic
water supply shall be provided any user whose groundwater
is found to be impaired by the injection program."
Economics
Table A-ll shows the capital cost breakdown for the entire
reclamation, desalination, recharge project. As can be
seen, Orange County is responsible for approximately 37 per-
cent of the total project cost. Table A-12 provides a
further cost breakdown of capital and operation and main-
tenance costs at design 15 mgd flow. Amortized at 5.5
percent over a 25-year life, the annual capital recovery
cost to the Water District alone is $620,000. Adding the
anticipated annual operation and maintenance costs of
$3,774,000 yields an annual cost to the District of
$4,394,000 or an average of $668/MG. This breaks down to
roughly $240/MG for the advanced wastewater treatment plant
(15 MGD), $2,722/MG for the desalting facility (3 MGD), and
$10/MG for the injection facilities (30 MGD). The total cost
for the entire project including all grant monies is $827/MG
(1972 $). It is important to note, however, that the very
high anticipated 0 & M costs for the initial desalting oper-
ation, $2,730,000 per year for the 3 MGD facility, result
because the present desalting module is basically an R & D
vessel and, as such, will be used extensively in costly
testing programs to optimize operation before expanding the
facility. Authorities estimate that 0 & M costs under
76
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Table A-10. SANTA ANA REGIONAL WATER QUALITY CONTROL
BOARD QUALITY REQUIREMENTS FOR WATER RECHARGED
TO THE SANTA ANA GROUNDWATER BASIN
Constituent
Ammoni urn
Na
Total Hardness
$04
Cl
Total N
Electrical Conductivity
Hexavalent Cr
Cd
Se
Mn
B e r i u m
Ag
Cu
Pb
Hg
As
Fe
Fl
B
MBAS
Max.
Concentration (mg/1)
1.0
110
220
125
120
10
900(1 )
0.05
0.01
0.01
0.05
1.0
0.05
1.0
0.05
0.005
0.5
0.3
0.8
0.5
0.5
(1) y mho/cm
77
-------
•vj
00
Table A-ll. CAPITAL COSTS FOR RECLAMATION AND
RECHARGE FACILITIES AT ORANGE COUNTY, CALIFORNIA (4)
. Investigations
Improvements
. Wastewater Reel
. Injection Barri
Faci lities
and
atnation
er
. Seawater Desalting Module
TOTALS
Total
2,070
10,920
1 ,365
7,917
22,272
Cost ($1 .000 1972 $)
Federal ^ ' State^ '
118
6,006 2,730
364 182
4,550
11,038 2,912
Local(3)
1 ,952
2,184
819
3,367
8,322
Federal participation was through:
. Office of Saline Water, Department of the Interior
. Environmental Protection Agency
State grant funds were made available through:
State Water Resources Control Board
.
(3) Local financing was by:
. Orange County Water District
(4) All cost expressed as January 1972 $ (see Appendix D for capital
cost factors)
-------
Table A-12. ESTIMATED CAPITAL AND OPERATION AND
MAINTENANCE COSTS FOR THE WASTEWATER
RECLAMATION/RECHARGE SYSTEM AT
ORANGE COUNTY, CALIFORNIA
tCOST REFERENCE JANUARY 1972)
CAPITAL COST
Wastewater Reclamation Plant
Land
Influent Pipelines & Pump Station
Clarification
Ammonia Stripping
Recarbonation
Filtration
Granular Carbon Adsorption
Chlorination
Sludge Treatment
Blending & Storage Reservoir
Maintenance & Laboratory Bldgs.
Engineering
Miscellaneous
Total
Injection Barrier Facilities
Seawater Desalting Module
ANNUAL OPERATION & MAINTENANCE COST
Thousands
of $
182
310
688
2,579
347
784
2,755
329
1,536
214
218
910
68_
10,920
1,365
7,917
Thousands
of $
. Wastewater Reclamation Plant
Influent Pipelines & Pump Station
Clarification
Ammonia Stripping
Recarbonation
Filtration
Granular Carbon Treatment
Chlorination
Sludge Treatment
Total
. Injection Barrier Facilities
. Seawater Desalting Module
30
120
254
55
75
185
50
229
998
46
2,730
79
-------
15 MGD desalting operations will be close to this initial
$2,730,000 figure. When these costs are compared to the
costs of imported water, filtered Colorado River water at
$205/MG and filtered state water at 240/MG, it can be seen
that the District is accepting a significant negative cost
differential to produce a high quality recharge supply and
preserve groundwater quality.
Future for Recharge Programs
Barring unforeseen problems, the 15 mgd OCWD tertiary treat-
ment plant will produce reclaimed water for recharge for
many years. However, due to the relatively high IDS con-
centrations of the source waters for the area and the fact
that the community adds an incremental 200-300 mg/1 IDS with
each pass, the District is looking to a combination of sea-
water desalting and wastewater reclamation as the only way
to effectively maintain proper IDS levels and protect the
groundwater supplies over the long term.
80
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SANTA CLARA VALLEY WATER DISTRICT (PALO ALTO AND SAN OOSE, CA)
Introduction
A significant portion (roughly 50 percent) of the water supply
in Santa Clara County is derived from the underground resource,
However, the groundwater supply has been in the past and may
again in the future, be adversely affected by overdraft!ng.
Lowered water tables have accelerated salt water intrusion in
the Palo Alto-Los Altos-Mountain View area, which is the area
most remote from future imported fresh water supplies.
Saline water intrusion has become extensive in the shallow
aquifers of the region, and much of this water is now non-
potable. The most important deeper ( 150 feet) aquifers,
however, are endangered due to possible vertical migration
of the salt water from these shallow, intruded basins.
Heavy pumping of good quality water from the lower aquifers
has reduced their pressure and increased the possibility of
salt water migrating vertically through the overlying pro-
tective clay layers.
In light of the fact that the present water supply will not
be able to meet demands by 1978, it is especially important
to protect the groundwater resource against contamination
by intrusion. To do this, the water district has developed
and designed an advanced wastewater treatment/groundwater
recharge system.
The first phase of the program, due to go into construction
in 1975, will consist of tertiary treatment of up to 4 mgd,
of which 2 mgd will be injected and extracted from a line of
parallel injection/extraction wells to form a hydraulic
salt water intrusion barrier. Streamlines from each pair of
injection/extraction wells, termed doublets, will effectively
"block out" a segment of the groundwater basin and prevent
inland migration of saline waters. Because of a developing
recreational and landscaping need, additional treatment
capacity of 2 mgd will be provided for production of re-
claimed waters intended only for irrigation usage. Upon
"flushing out" of the intruded saline waters, plans call for
the eventual extraction of all the recharged water for
irrigational or even industrial reuse.
Municipal Treatment
Figure A-9 shows a flow diagram of the proposed tertiary
treatment plant due to go into construction following
approval of plans and specifications. Tertiary treatment for
the effluent to be used directly for irrigation will consist
81
-------
CHLORINATED
SECONDARY EFFLUENT
LIME
INCINERATOR
LIME SLUDGE
LINE RECALCIN.
AND CARBON REGEN.
FURNACE
Z
0
ID
tr
^-
z
ui
Q.
SLUDGE
TO WASTE
U POLYMER
I
$
MIX TANK
FLOCCULATOR/CLARIFIER
AMMONIA STRIPPING
2-STAGE
RECARBONATION
TANKS
POLYMER
MIXED MEDIA
FILTERS
CARBON
ADSORPTION
TOWERS
CHLORINE CONTACT
TANK AND STORAGE
TO WELL INJECTION SYSTEM
FIGURE A-9
PLANNED ADVANCED WASTEWATER
TREATMENT PLANT AT PALO ALTO
82
-------
of filtration and chlorination only and will take place in
a separate facility not shown in the figure.
The chlorinated secondary effluent is treated with both lime
and polymer before entering a reactor clarifer that provides
30 minutes of flocculation and 120 minutes of settling for
removal of suspended solids, heavy metals, and phosphorus.
The highly alkaline water, now at pH 11, next enters the
ammonia stripping surface aeration tanks where the release
of ammonia gas to the atmosphere is enhanced by surface
agitation. High pH provides the chemical conditions that
maximize conversion of ammonium ions in solution to ammonia
as dissolved gas.
The effluent then enters a three-chamber recarbonation tank.
In the first chamber, the wastewater is neutralized by
diffusing carbon dioxide gas, supplied by compressed stack
gases from an existing sludge incineration facility, into
the water. Provisions have also been made for future inter-
mediate settling basin followed by second stage recarbona-
tion. To widen the spectrum of trace organic removals,
ozonation will be utilized following the recarbonation
process. Flexibility is also provided to utilize ozonation
following activated carbon.
The process stream is then given mixed media filtration to
remove suspended solids and colloidal material, and to pro-
tect and prolong the life of the activated carbon. However,
because of the stringent requirements to insure maximum
recharge capabilities, the process is designed with the
flexibility to provide filtration after activated carbon
treatment or two stage filtration before and after carbon
adsorption. The two filters will be operated at a four
gpm/ft2 hydraulic loading rate.
The water is then pumped through four carbon towers that
provide a 34 minute contact time for the adsorption of
organics reducing the COD. These columns will be piped to
permit operation of the individual beds in series, or in
parallel. In addition, chlorination after the first two
carbon columns is possible when the towers are operated as
four in a series. This sequence will permit the second two
carbon columns to perform the added function of residual
chlorine removal.
Effluent from the carbon adsorption process flows to the
chlorine flash-mix basin and into the contact basin. The
80 minute detention time in the chlorine contact basin
storage tank will provide sufficient chlorine and retention
83
-------
time to practice break-point chlorination for disinfection
and stripping of residual ammonia. Chlorination to a free
residual (HOC!) of one mg/1 held for 80 minutes should
assure complete inactivation of all virus.l1'
The effluent will then be pumped to the injection well
system.
Solids handling at the treatment plant will include carbon
regeneration in a multi-hearth furnace. Lime sludge will
initially be incinerated with recalcining being evaluated
as a future addition.
Important features of the plant include the ability to choose
a variety of unit process combinations and to by-pass any
individual element due to piping system design.
Anticipated quality of the effluent from the tertiary treat-
ment plant is summarized in Table A-13. This water for
recharge is expected to meet current drinking water standards
Recharge Program
The proposed reclamation facility capacity is four mgd,
two mgd for groundwater recharge and two mgd for direct
irrigation use.
The complete recharge/reuse system is diagrammed in Figure
A-10. As shown, the ultimate goal (1979) is to inject the
two mgd of tertiary effluent into shallow aquifers and then
to extract the recharged water for irrigation reuse without
allowing it to commingle with native groundwater used for
potable supply.
The initial effect of injection into the shallow, non-
potable, salt water intruded aquifers will be to establish
a pressure barrier against further intrusion and to flush
the high salinity water out the extraction system, thus
gradually replacing and improving the quality of the water
in those aquifers. After an initial period of operation, it
0) Taken from Eliassen, Rolf, Environmental Safeguards
for Control of Viruses in the Proposed Wastewater
Reclamation Plant of the Santa Clara Valley Control &
Water District, Palo Alto, CA, 1974.
84
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Table A-13. ANTICIPATED TERTIARY EFFLUENT
QUALITY CHARACTERISTICS AT PALO ALTO, CALIFORNIA
Constituent
Maximum Concentration (mg/1)
BOD
COD
Suspended Solids
Turbidity (JTU)
MB AS
Coliform (MPN)
Ammonia
TDS
Chlorides
Arsenic
Barium
Cadmium
Chromium (+6)
Copper
Lead
Manganese
Selenium
Silver
Zinc
Mercury
Phosphate
1
10
0.3
0.1
2.2/100 ml
5-15
850
350
0.05
0.1
0.02
0.05
0.3
0.2
0.05
0.05
0.01
0.03
1.0
0.005
1
85
-------
PALO ALT(? WATER
QUALITY CONTROL
FACILITY (EXISTING)
oo
CTi
ADVANCED
WATER
TREATMENT
PLANT(FIG.A-9)
2 MGD
IRRIGATION
FILTRATION
1 MGD
VALVE
EFFLUENT
DISPOSAL
TO BAY
I
' I I I I !
rNINE INJECTION WELLSi
GROUNDWATER BASIN
NINE EXTRACTION WELLSJ
I M 1 1
To IRRIGATION USES
VALVES
I
\
SALINE
WASTES
TO BAY
FIGURE A-10
PROPOSED WASTEWATER RECLAMATION/REUSE SYSTEM
AT PALO ALTO, CALIFORNIA
-------
is anticipated that the intruded groundwaters will have been
replaced with the recharge water, and that when extracted,
this reclaimed water will be suitable for use in unrestricted
irrigation. None of the treated effluent will be used to
replenish potable aquifers.
The nine injection and nine extraction wells will be similar
in construction to the test well used for experimentation
between August & November, 1974, except that only two PVC
casings will be used. One will terminate in tbe 20 foot
aquifer, the other will extend into the 45 foot aquifer.
Figure A-ll provides a detail of the original well features.
The drill hole was 24 inches in diameter and housed three
six-inch diameter casings, one to each of the three aquifers
(20 ft, 45 ft, and 185 ft deep). The two shallow aquifers,
both invaded by seawater, were separated from the deep high
quality aquifer by an extensive clay aquiclude, while the
aquitard material separating the 20 and 45 foot aquifer
was of the "leaky" type which provided a vertical path for
hydraulic connection between the aquifers.
Three test hole-observation wells, located at various dis-
tances and directions from the injection/extraction well,
were used to monitor the pumping and injection tests. The
injection tests were conducted with potable Palo Alto water
supply to yield information concerning the aquifer character-
istics and confirm the relationships between aquifers in
response to pumping and injection. Authorities feel that the
treated effluent will be of high enough quality to perform
in a similar fashion under recharge conditions. It should be
noted, however, that this may not always be the case. In
similar injection tests at Mineola, New York (see Long Island,
New York case study in Appendix A), utilizing a similar
quality tertiary effluent to that anticipated at Palo Alto,
it was shown that very minor concentrations of certain
components in the final effluent stream (iron, phosphate,
turbidity) caused clogging problems in the injection well.
Naturally, the characteristics of the aquifer will determine
acceptable quality limits for successful operation.
The test program demonstrated the following:
Injection into the 45 ft aquifer is a feasible
method of creating the hydraulic changes necessary
to control seawater intrusion.
Injection into the 45 ft aquifer resulted in a
reduction in chlorides in the 20 ft aquifer.
87
-------
ELEV 2 86ms I
ELEV. 2.34 msl
ELEV 262 msl
/—GROUND SURFACE
6" PVC COUPLING (TYP)
6" SCH. 80 PVC
CASING (TYP)
GRAVEL-PACK, "LAPIS
NO <»" (TYP)
— 6" WIRE -WOUND, PIPE
SIZE, STAINLESS STEEL
WELL SCREEN (TYP)
FILL GRAVEL (TYP)
CEMENT SEAL (TYP)
34" DIA DRILLED HOLE
STEEL CENTRALIZER (TYP)
PVC PLUG-END BELL (TYP)
BOTTOM OF DRILLED HOLE
FIGURE A-ll
DETAIL OF INJECTION/EXTRACTION WELL
FEATURES
88
-------
The spacing between the injection well and the
extraction well in a particular doublet should be
approximately 1,000 ft, the pumping rate should be
approximately 150 gpm for each well, and the injec-
tion pressure should be no more than 20 psi.
The critical spacing between doublets as anticipated
is approximately 1,800 ft. The spacing to be used
for design purposes, however, is conservatively
established at 1 ,000 ft.
Economi cs_
Table A-14 summarizes capital costs (in 1972 $) for the ter-
tiary treatment plant and injection/extraction system.
Table A-15 summarizes estimated operation and maintenance
costs for the treatment plant and barrier system. The
costs are based on year-round operation, and are referrenced
to Jan. 1972.
Due to federal and state grants, the Santa Clara Valley Water
District is only required to provide 12-1/2 percent of the
total project capital costof $2,444,000 or $306,000. Add-
ing $143,000 for transmission pipelines to ultimate irriga-
tion users, the total annual capital recovery cost would be
$193,000 of which the Water District's share would be
$33,500 (5.5 percent interest and 25 year life). Assuming
year-round operation, the total annual cost, including 0 and
M, would be $183,000 (1972 $) to the Water District and
$343,000 for the project as a whole.
Since full-year operation would produce an average of 3 mgd
for irrigation, the cost to the Water District breaks down
to $167 per MG.
A major portion of this cost (approximately $130 per MG)
will be recovered by the District through sale of the
reclaimed water for irrigation.
Future for Recharge Program
The Santa Clara Valley Water District hopes to realize the
following benefits from its proposed system:
. To restore the shallow groundwater aquifers
presently degraded by intruding salt water, and
to protect deeper high quality aquifers from
future contamination;
89
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Table A-14. ESTIMATED CAPITAL COSTS FOR WASTEWATER
RECLAMATION/RECHARGE SYSTEM AT
PALO ALTO, CALIFORNIA
Element
$1,000 (Jan. 1972)
Clarifier-Flocculator 240
Filters 300
Carbon Adsorption System 510
Main Structure and Appurtenances 73Q.
Subtotal - Treatment Facility 1,780
Well System (9 pairs) 290
Power Supply and Controls 80
Subtotal - Barrier 370
Total Construction Cost 2,150
Technical Services 210
Legal, Fiscal, and Administrative 4
Contingencies 80
TOTAL 2,444
90
-------
Table A-15. ESTIMATED ANNUAL OPERATION AND
MAINTENANCE COSTS AT
PALO ALTO, CALIFORNIA
Ite*" $1,000 (Jan. 1972)
Administrative and Fixed Charges 7
Salaries 36
Power and Utilities 28
Lime 29
Act. Carbon 7
Chlorine 23
Repair and Maintenance 6
Miscellaneous 9
$ 145
Barrier System 5
Total $ 150
91
-------
To reclaim wastewater and reuse it so as to
conserve precious fresh water supplies;
To gain extensive knowledge into the art of wastewater
treatment, recharge, and recovery for reuse.
If extensive monitoring of the planned "Phase I" system
herein described shows positive results, authorities antici-
pate further expansion of the barrier system and perhaps
eventual direct replenishment of the deep, high water quality.
aquifer with tertiary wastewater.
92
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U.S. WATER CONSERVATION LABORATORY (PHOENIX, ARIZONA)
Introducti QJI
In 1967, an experimental high-rate land treatment system
called the Flushing Meadows project (partially funded by EPA)
was installed by the U.S. Water Conservation Laboratory
and Salt River Project in the Salt River bed west of
Phoenix, Arizona. The purpose of the project was to study
the feasibility of renovating secondary effluent for unre-
stricted irrigation, recreation, and certain industrial uses.
an
Extensive use of groundwater supplies by agriculture and
increasing population have created an overdraft situation
such that'the groundwater levels in some parts of the valley
have been dropping at ten ft per year. To aid in^conserving
the groundwater resource, authorities are initiating re-
claimed wastewater reuse programs to reduce the demand for
groundwater. By the year 2000, the wastewater flow from
Phoenix and adjacent cities is expected to reach 250 mgd
which, if reused, could irrigate nearly 70,000 acres (more
than the projected remaining agricultural land in the area),
while leaving a portion for recreational lakes, industry,
and other uses.
To permit large-scale reuse of wastewater in the Salt River
Valley, the effluent should meet the requirements for
"unrestricted" irrigation and recreation. One possibility
for obtaining the necessary quality improvement of conven-
tional secondary effluent is by land treatment with high-rate
infiltration basins in the bed of the Salt River. The
purpose of the Flushing Meadows project was to evaluate the
feasibility of such a system.
Municipal Treatment
The 91st Avenue sewage treatment plant in Phoenix is a
step aeration, spiral flow, activated sludge plant
treating 80 mgd.
Table A-16 summarizes typical effluent characteristics from
the plant.
Recharge Program
The Flushing Meadows project is located about 1.5 miles
downstream from the 91st Avenue wastewater treatment plant.
The project, which was put into operation in September, 1967,
consists essentially of six horizontal basins, 20 x 700 ft
93
-------
Table A-16. TYPICAL MUNICIPAL EFFLUENT
CHARACTERISTICS AT THE 91ST AVENUE
PLANT, PHOENIX, ARIZONA
Constituent
BOD
COD
SS
TDS
TDC
NH4-N
NO3~N
N02~N
Org . N .
E. Coli/100 ml
Concentration
(mg/1)
15
45
20-100
1,100
20
30
1
2
3
106
Constituent
Na+
Ca++
Mg++
K+
HCO3
ci-
S04
P04
C03
Concentration
(mg/1)
200
82
36
8
381
213
107
30
0
94
-------
each, spaced 20 ft apart. Figure A-12 shows a plan view of
the recharge site. Secondary effluent is pumped from the
effluent channel into these basins with the rate of flow
into each basin recorded with a critical depth flume.
Shallow gravel dams were placed across the basins approxi-
mately 50 ft from the inlets to form small sedimentation
basins to reduce occasional high SS concentrations in the
effluent. Water depths in the basins are controlled by
outlet/overflow structures and overflow was measured with
critical-depth flumes so that other parameters could be
evaluated without interference from varying water depths.
Table A-17 provides a soil profile from two wells in the
basin area. The profiles indicate an irregular succession
of coarse sand and gravel layers, with an impermeable clay
boundary at.247 ft.
This soil profile is favorable for rapid infiltration
because of its basic coarse sand nature allowing high per-
colation rates, and because the finer material is on the
surface, thus confining clogging phenomena to the upper
layer where it can most easily be controlled.
Of the several flooding techniques and the different surface
covers used (earth, vegetation, and gravel), it was deter-
mined that maximum hydraulic loading rates were obtained
with bare soil basins and flooding periods of about 20 days
alternated with drying periods of ten days in the summer and
20 days in the winter. The maximum infiltration rate
achieved with a 1 foot water depth in the basins was roughly
400 ft/yr. Higher rates may be obtained by increasing the
water depth by several feet. For optimum nutrient removal,
however, the infiltration rate should be lowered to around
300 ft/yr as explained below.
By proper management of the system, nutrient removal by the
soil can be maximized. At Flushing Meadows, this was best
achieved by using flooding periods of about ten days and
drying periods of two weeks. With this schedule, oxygen was
soon depleted in the soil during flooding causing nitrogen,
in the ammonium form, to be absorbed by the clay and organic
particles. Flooding was terminated before the cation ex-
change complex in the soil was saturated with ammonium. Upon
drying, oxygen entered the soil and ammonium was nitrified
under aerobic conditions to nitrate. Concurrently, some of
the nitrate formed was denitrified in micro-anaerobic
pockets in the otherwise aerobic upper soil zone to nitrogen
gas that escaped to the atmosphere. When flooding was
resumed, if the basins were immediately flooded to a depth
above one ft, the nitrates were quickly leached out of the
95
-------
VO
CONSTANT-MEAD
STRUCTURE
100 METERS
i i i I i i i i I
100
200
300 FEET
0-7
FIGURE A-12
PLAN OF FLUSHING MEADOWS PROJECT
•-DRAINAGE LINE
•-LINED
PONDS
—Q-UNLINED POND
-O»-EAST WELL
-------
Table A-17. SOIL PROFILES AT FLUSHING MEADOWS
East Well
Depth Material
(ft)
West Center Well
Depth Material
(ft)
0-3 Fine loamy sand 0-3
3-27 Sand, gravel, and 3-33
boulders 33-44
27-30 Clean sand, gravel, 44-50
and boulders 50-57
30-49 Clean,fine sand with
occasional cobbles 57-63
49-81 Clean, fine sand with 63-72
occasional thin
gravel strata 72-86
81-123 Clean,fine sand
123-126 Fine sand with trace 86-98
of clay
126-136 Clean, fine sand 98-100
136-146 Clean sand and
gravel
146-197 Clean, fine sand
197-200 Fine sand and
gravel
200-247 Fine sand
247 Start of clay layer
Fine loamy sand
Sand and gravel
Boulders and gravel
Sand and gravel
Sand and traces of
clay
Coarse, clean gravel
Sand, gravel, traces
of clay
Coarse gravel and
boulders
Sand, gravel, and
traces of clay
Fine sand
Note: Ft x 0.3048 = m.
97
-------
top few feet of soil to the groundwater. However, if initial
flooding was shallow (a few inches deep), the lower head
allowed a lower infiltration rate, larger nitrate retention
time in the microbiologically active soil zone, and further
denitrification. At these lower initial hydraulic loading
rates, nitrogen removals were as high as 80 percent, whereas
if high rates are consistently maintained, nitrogen removal
was only 30 percent with a peak nitrate surge to the ground-
water after the start of a new flooding cycle.
Essentially no nitrogen was removed if short, frequent flood-
ing periods (two days flooding, five to ten days drying)
were used. Apparently, the flooding cycle was not long
enough to allow oxygen depletion in the soil; thus aerobic
conditions dominated, and all ammonium was nitrified to
nitrate, which was then leached to the qroundwater.
The flooding schedule and desired infiltration rates for
maximizing denitrification in a high rate system depend on
several factors: soil cation exchange capacity, ammonium
exchange percentage, the form and concentration of the
nitrogen in the wastewater* the oxygen diffusion rate into
the soil, the temperature, and other factors. Therefore,
authorities cautioned that each recharge situation is some-
what unique and a proper flooding schedule must be developed
accordingly.
Phosphorous removal at Flushing Meadows was found to be
basically dependent upon the distance traveled through the
soil. The chief removal mechanism wasprecipitation as cal-
cium phosphate or magnesium ammonium phosphate. Underground
travel distances of 30 ft produced a 50 percent reduction,
and distances of several hundred feet were found to be
sufficient for a 90 percent phosphorous removal.
At the Flushing Meadows project, fecal coliforms were reduced
from about TO6 to generally less than 200 per 100 ml after
30 ft of downward percolation. Additional lateral movement
reduced the coliform density to generally less than ten per
100 ml after 100 ft and to zero after 300 ft.
Virus studies were performed bi-monthly in 1974 to determine
the fate of virus in the soil system.
No virus has been detected in the renovated water sampled
at depths of 20 ft and 30 ft below the basins. The mechanism
of removal appears to be one of adsorption and is governed
by the same factors as ion exchange.
98
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Economics
The economic costs summarized in Table A-18 are those pro-
jected for the 15 mgd full-scale recharge/extraction system
detailed in the following section. The main capital costs are
for the extraction well system. The largest portion of the
operating costs go toward operation of the well pumps. The
system would be comprised of four ten-acre rectangular
basins with three extraction pumps located on the center
berms.
The total capital cost of $212,000 (January 1972 $) repre-
sents an annual capital recovery cost of $16,000 at 5.5
percent interest and 25-year life, or $2.9/MG at 15 mgd.
Adding the operation and maintenance costs of $28,000/yr,
the total annual cost becomes $44,000 or approximately $8/MG.
This figure is a small fraction of the cost to treat second-
ary effluent in-plant to provide a similar quality water.
Future for Recharge Program
The City of Phoenix, with funds supplied through an EPA
grant, has completed construction of a 15 mgd wastewater
recharge/extraction facility in Phoenix, Arizona. The first
well was to be in operation by 1975. The project is a
first step towards extensive wastewater renovation and reuse
for unrestricted irrigation, and ultimately for a large green
belt recreational zone and nuclear power plant cooling water.
Irrigation, and recreation reuse water must meet the
following standards: BOD5 < 5 mg/1, SS < 5 mg/1, and fecal
coliform < 200/100 ml. Authorities estimate that the ren-
ovated water should be well within required limits for this
use. Industrial reuse will most likely require further treat-
ment at the plant site as required by the specific use.
Figure A-13 on page 102 shows a schematic diagram
of the 15 mgd recharge/reclamation system. Secondary efflu-
ent from the 23rd Avenue plant will flow through an open
concrete channel to an 80-acre, pre-sedimentation pond for
settleable solids removal and further polishing. The
effluent will then be discharged through gate valves into
the loamy sand and gravel spreading basins. The basins will
be managed to achieve maximum nitrogen removal as detailed
previously with two of the basins being flooded while the
other two are in the drying cycle. Expected infiltration
rates are about 400 ft per year.
The basins will be equipped with discharge gate valves to
rapidly drain the basins after the inflow is stopped, thus
99
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Table A-18. ESTIMATED CAPITAL AND OPERATION
& MAINTENANCE COSTS OF 15 MGD RECHARGE -
EXTRACTION SYSTEM AT PHOENIX, ARIZONA
Capital Costs
$ 1,000 (1972)
Land acquisition (D 0
Construction of basins & effluent
distribution system 35
Extraction wells & discharge system
(assuming 3 wells @ $44,000 each) 177
Total $ 212
Operation « Maintenance Costs $ 1,000 (1972)
4-
Maintenance of basins, etc. 7
Extraction well operation 21
(based on power costs of $0.018/acre/
ft/ft of lift and 100 ft of total lift)
Total $ 28
City of Phoenix already owns land to be used in
project (estimated value of the land is roughly
$l,780/acre or $71,000 total (1972 $) .
100
-------
23RD AVENUE PLANT
SECONDARY EFFLUENT
80 ACRE
PRE-SEDI MENTATION
POND
31 DEPTH
EXTRACTION
WELL
5 MGD
TO ROOSEVELT
IRR. DIST.-
RECHARGE
BASINS
,, OVERFLOW
TO RIVER BED
FIGURE A-13
15 MGD WASTEWATER RECHARGE/EXTRACTION
SYSTEM AT PHOENIX, AR.
101
-------
accelerating the drying cycle. This overflow is discharged
to a dry riverbed.
Three extraction wells, located along the center berm, will
be used to recapture all the recharged effluent for unlimited
irrigation at the Roosevelt Irrigation District. Each well
will be approximately 200 ft deep with the last 100 ft per-
forated. The wells will extract an average of 3,500 gpm each
of a total of approximately 15 mgd. The water will initially
be pumped through a 24 in., asbestos-cement pipeline to the
irrigation district.
One of the important concepts of this system is that no
significant amount of recharged effluent will mix with the
native groundwater causing possible degradation of that
fresh water source. All recharged water will be extracted
and the underground flow controlled so that a very slight
gradient will exist toward the recharge basins, making
it impossible for renovated water to move out into the
aquifer. Figure A-14 shows a profile through the recharge/
extraction zone. Note that the water table drops toward the
well, thus causing a gradient in the aquifer toward the
extraction point.
It should be noted that ultimately the extracted water will
reach the groundwater when reused for irrigation. However,
the low hydraulic loading rates of irrigation operations,
fine particle composition and higher clay content of the
soil, mineral uptake by the plants, and other soil treat-
ment mechanisms, will provide extensive additional treatment
to the water before it reaches the groundwater table. The
only danger of groundwater degradation after this second
passage through the soil is the unavoidable TDS buildup in
the percolate due to the large evaporation and trarisevapora-
tion losses during irrigation.
An extension of this 15 mgd recharge/reuse project is
currently being planned in Phoenix (Rio Salado Project) that
would involve extensive recharge and extraction to renovate
wastewater for use in a large green belt recreation zone.
The green belt will follow the Salt River bed through Phoenix
and will involve a series of lakes, parks, riding trails, and
picnic areas.
102
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RECHARGE BASIN
EXTRACTION
WELL
J2L
RECHARGE BASIN
Mill
IMPERMEABLE LAYER
FIGURE A-14
CROSS-SECTION OF TWO PARALLEL
INFILTRATION STRIPS WITH WELLS
MIDWAY BETWEEN STRIPS FOR
PUMPING RENOVATED WATER
103
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THE CITY OF SAN CLEMENTE, CALIFORNIA
Introduction
Throughout the 1950's and 1960's, salt water intrusion into
the main aquifer at San Clemente (supplying 1/3 of the city
supply) had been growing increasingly significant, and
authorities feared the loss of the entire basin to intrusion.
Therefore, in March, 1968, an agreement was entered with the
United States Marine Corps to percolate reclaimed water into
the San Mateo River Basin on Camp Pendleton. These recharged
waters were to att as a salt water barrier to protect the
underground resources of both the city and the base, and to
serve as irrigation water for the base after extraction.
the trend
well water
Since the recharge program has been in operation,
of increasing salinity in the San Clemente supply
has been reversed
Domestic Treatment
The city of San Clemente operates one tertiary treatment plant
that treats an average of 2.3 mgd (plant capacity is four
mgd to provide for future growth).
The plant includes conventional activated sludge treatment
followed by 30 minutes of chlorination and dual media
filtration. The two gravity filters are each 22 ft in
diameter, fifteen ft deep, and capable of treating 700 gpm.
The filters are comprised of one ft of 0.9 mm anthrafilt over
one ft of 0.5 mm sand. At a five ft head loss, the units
are automatically backwashed. The final effluent enters a
sump pump for distribution to recharge, irrigation, or ocean
disposal.
Table A-19 summarizes typical final effluent characteristics.
Recharge Operation
Figure A-15 shows a schematic diagram of the recharge
facilities.
From the final sump tank, the effluent is pumped 3.5 miles
by two 1,750 gpm pumps in a 12 in line. If the pipeline is
unable to handle the entire volume
charged through the ocean outfall.
port the water uphill to a holding
43 acre-ft of capacity. From this
of 0.3 mgd is pumped for golf course irrigation
gravity fed through a pipeline to the spreading
San Mateo River Basin.
the overflow is dis-
Two booster pumps trans-
pond with approximately
holding pond, an average
and 2 mgd is
area in the
104
-------
Table A-19. TYPICAL EFFLUENT CHARACTERISTICS
AT SAN CLEMENTE, CALIFORNIA
Constituent
BOD5
SS
Total Hardness
TDS
P04 as P04
NO3 - N
Na
Fl
Concentration
(mg/1)
4
3
350
1100
45
14
225
0.6
Constituent
Zn
Cr
Pb
Cu
Ni
Cd
B
Coliform/
100 ml
Concentration
(mg/1)
0.05
0.05
0.05
0.05
0.05
0.05
1.0
2.2
105
-------
DUAL
MEDIA
FILTERS
TWO
1750 GPM
PUMPS
SECONDARY
TREATMENT
PLANT
12
LINE
3.5 MILES
TWO 250 HP,
1750 GPM
PUMPS
SALT WATER
INTRUSION
FIGURE A-15
SCHEMATIC DIAGRAM OF RECHARGE
FACILITIES AT SAN CLEMENTE, CALIFORNIA
-------
The flooding basin is simply a five-acre dyked area in the dry
riverbed consisting of coarse sand and gravel. The infiltra-
tion rate is very high, roughly five to ten ft per day, and
the effluent is continuously discharged to the riverbed where
it percolates immediately.
The recharged water migrates downstream toward the ocean
where it intercepts intruding salt water and forces it back
toward the shoreline.
Although the exact course of the recharged water migration is
not known, city authorities speculate that a small portion
of this water is mixing with the native aquifer supply and
is subsequently being extracted for domestic use.
Economics
The major cost of the recharge system is the long pipeline
and pumps to transport the water from the plant to the
recharge area. The estimated capital cost for pipeline and
pumps was $200,000 in 1957 ($350,000 in January, 1972 $).
Costs for tertiary treatment, two dual media filters, is
the equivalent of $61,000 in 1972 dollars. Total capital
cost for recharge facilities of $411,000 amortized at 5.5
percent for 25 years results in an annual capital recovery
cost of $31 ,000.
Operation and maintenance requirements are very minimal,
estimated at two man-hours per day on the average for check-
ing pipelines and fixing periodic breaks, etc. Assuming a
labor cost of $5 per hour, the annual 0 and M cost just for
recharge operations is roughly $3,600.
Thus, the total cost of the recharge facilities is approxi-
mately $35,000 or, at a flow of 2.3 mgd, $42/MG.
Sale of 0.3 mgd of this water for golf course and state
highway landscape irrigation brings an annual revenue of
roughly $20,000 to the city. At present, no revenue is
generated through the recharge operation.
Future for Recharge
By the end of 1976, authorities in San Clemente hope to
implement construction to increase treatment plant capacity
to eight mgd. In addition to current tertiary filtration,
a portion of this water will be demineralized by ion
exchange techniques and remixed with the rest of the effluent
to lower overall TDS to 700 mg/1.
107
-------
The final effluent will then be piped directly inland several
miles (via a $1.1 million pipeline) and recharged in the
Christianitis Canyon River Basin. At this point, the re-
charged water will percolate to great depths in the sand and
gravel profile and slowly migrate downstream to the San Mateo
River Basin aquifer and ultimately to the present recharge
site.
The long distances and time involved in underground travel,
as well as the in-plant demineralization, will ensure very
high quality water for recharge and ultimate extraction and
reuse.
108
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ST. CROIX, VIRGIN ISLANDS (GOVERNMENT OF THE VIRGIN ISLANDS)
Introduction
In 1971, the government of the U.S. Virgin Islands (Division
of Environmental Health) and the federal Environmental Pro-
tection Agency co-sponsored a project on the island of
St. Croix to demonstrate the feasibility of using highly treat-
ed wastewater for artificial recharge of potable groundwater
basins.
St. Croix is the largest of more than 50 islands and cays
which comprise the Territory of the U.S. Virgin Islands. It
is 84 square miles in area and in the past 10 years has shift-
ed from a rural agricultural economy to an island which is
oriented toward tourism and industry. With this shift there
has been a rapid increase in population and a rise in the
standard of living on the island. Along with these changes
has come a massive increase in water consumption so that the
traditional sources of supply, rainwater collected in cisterns
and well water, have proven inadequate for the populace. The
continued consumer demand has been met, in a large part, by
the use of desalinization plants for the conversion of sea-
water into fresh water.
The source of public water is now divided fairly evenly
between groundwater, water derived from the Water and Power
Authority (WAPA) desalinization plant in Christiansted, and
water purchased from the desal inization plant operated by the
Martin-Marietta Alumina Company (the latter soon to be
phased out).
The purpose of the groundwater recharge project is to pro-
duce a high quality effluent and percolate it into the
potable aquifers on the island. In this way, the yields of
the wells in the area will be improved, and the recharged
water will assist in preventing further seawater intrusion
which is currently threatening one of the government's major
well fields on the island. Hopefully, this wastewater
reuse program will result in a lower demand for desalinated
water and a subsequent drop in water costs now at $4/1,000
gal Ions.
Municipal Treatment
Wastewater from many parts of St. Croix flows initially into
the primary treatment plant located at the western end of the
Water Pollution Control complex at Estate Bethlehem Middle
Works. Primary effluent (roughly 0.75 MGD) is discharged to
the ocean through a 48 inch outfall sewer. As part of the
109
-------
recharge project, a weir on the outfall diverts 0.1 to 0.5
MGD into a lift station where it is pumped to the advanced
wastewater treatment plant.
The plant employs secondary and tertiary treatment processes.
Secondary treatment consists of completely mixed extended
aeration activated sludge treatment using surface aerators,
followed by conventional secondary clarification. Tertiary
facilities include a solids contact or chemical flocculation
unit and multi-media filtration. The solids contact unit
uses an alum chemical feed to induce coagulation/flocculation
and aid in solids removal by the filters. The two mixed
media filters are operated in parallel and use anthracite
coal, silica sand, and garnet sand as media. The final
effluent is chlorinated before transmission to the spreading
basins.
Typical quality characteristics of the water for recharge are
as follows: BOD - 12 mg/1, turbidity - 1 to 3 JTU, TDS -
1,000 mg/1, chlorides - 400 mg/1, and coliform MPN - 0.
Heavy metals are not significant. The high TDS results from
the use of saltwater for toilet flushing on parts of the
island. It is anticipated that once this practice has been
stopped, that the TDS concentration of the recharge water
will drop.
Recharge Program
Initial recharging operations commenced upon completion of
treatment and percolation basin facilities in February, 1974.
Testing continued until November, 1974, when the spreading
ponds and portions of the is!and's wastewater collection
systems were severely damaged by a flood. Currently, the
facilities have been repaired and are in operation.
Final effluent from the plant is pumped 9,000 ft through a
6 inch ductile iron pipe to 100,000 gallon storage tank
and the recharge area. The major recharge facilities con-
sist of six spreading basins each with a surface area of
7,500 sq. ft.
The recharge area consists basically of geologically recent
alluvial deposits up to 70 ft thick laid down on top of a
lower Miocene formation. Spaced within the alluvial clays
are thin horizontal aquifers of clay, sand, and gravel
material. These aquifers are usually no more than 5 ft
thick and are not interconnected except in the vicinity of
supply wells. The upper 18 inches of soil is a dark clay
with the subsequent lower material being lighter in color
and containing a higher percentage of silt and sand. The
110
-------
upper clay layer was removed to expose the more porous lower
horizons and enhance percolation. Bermuda grass is being
grown in the basins to stabilize the soil and to aid in
maintaining infiltration rates. It is hoped that the grass
will utilize a portion of the nutrients contained in the re-
charge water, and that these nutrients will thus be removed
when the grass is harvested.
The silt, sand, and clay soil in the recharge area had an
infiltration rate of about 1-2 ft per day during the first
nine months of operation. The optimal flooding schedule is
just being established. Initial runs have established that
a flooding period of 15 to 20 days followed by 30-40 days of
drying can be successful.
Monitoring is achieved by using wells drilled in the area
of recharge activity. Samples are taken from tnese
wells and analyzed in the project area for chlorides, con-
ductivity, calcium, total hardness, nutrients, BOD, coliforms,
and other constituents. These initial results will provide
background concentrations to aid in tracing the subsurface
movement of the recharge water once full scale operations
resume. Presently, the recharged water enters a semi-confined
aquifer where it is highly diluted by existing groundwater.
A significant change in groundwater quality has not been
monitored to date.
Economi cs
Economic conditions on this island lend themselves to the
reuse of wastewater, as potable water is scarce and at least
two-thirds of the island's domestic supply is derived from
distillation of seawater. The remainder comes from ground-
water and rainwater catchments. Potable water is sold to
the public for $4/K gal. by the Territorial Government which
loses money even at that price.
Costs for the tertiary treatment and recharge facilities
were not available, but authorities estimate the total cost
to produce the recharge water at roughly $1,000 per MG.
Future for Recharge
The future of groundwater recharge at St. Croix depends on
the results obtained during this year's operation. To
date, substantial data nave not been collected regarding
systems performance, long term infiltration rates, possible
groundwater degradation, and the success of the program in
halting saltwater intrusion.
Ill
-------
LOS ANGELES COUNTY SANITATION AND FLOOD CONTROL DISTRICTS
(WHITTIER NARROWS/SAN JOSE CREEK, CALIFORNIA)
Introduction
The Los Angeles County Sanitation District, in conjunction
with the Central and West Basin Water Replenishment District,
and the Los Angeles County Flood Control District, has been
practicing groundwater recharge with effluent from its
Whittier Narrows Wastewater Reclamation Plant since 1962.
Additional effluent from the District's San Jose Creek plant
has been used since 1972 for the groundwater replenishment
program. Treated wastewater from the two plants is mixed
with storm water runoff (when available), and imported state
water prior to percolation on 690 wetted acres of basins in
the Montebellow Forbay spreading area of the San Gabriel
and Rio Hondo River Basins.
This recharge operation is the largest in the U.S. in terms
of the volume of treated sewage percolated to the ground-
water, an average of 25 mgd. All of the water that reaches
the groundwater table (including the recharged effluent) is
or eventually will be pumped out by water supplies in the
central and west basins. This water comprises part of the
municipal water supply for many communities in the area
including, Los Angeles, Long Beach, Lakewood, and Downey.
It is virtually impossible for authorities to monitor the
underground movement of the recharged water and to determine
the amounts withdrawn by supply wells throughout the basin.
However, community groundwater supplies drawn from immediately
below the basins (i.e., Montebello, CA), may contain up to
15% reclaimed effluent (the percentage of treated wastewater
in the mixed recharge water); while supplies taken further
south in the basin area most likely contain only traces of
effluent; if any at all.
Municipal Treatment
The Whittier Narrows and San Jose Creek olants are nearly
identical in design. Both are step feed acti-
vated sludge treatment plants followed by chlorination
Both are operated,at times, under excess aeration
conditions to effect nearly complete nitrification.
Table A-20 on the following page summarizes typical effluent
quality for these plants.
In order to prevent pollution of surface or groundwater,
the Regional Water Quality Control Board has promulgated
112
-------
Table A-20. AVERAGE MUNICIPAL EFFLUENT CHARACTERISTICS
AT WHITTIER NARROWS AND SAN JOSL CREEK
Constituent Whi
BOD
SS
TDS
MBAS
pH
Cl
Na
B
Fl
Cu
Fe
Mn
Cd
Cr
Pb
Se
Ag
Zn
As
Cn
Hg
j
Ni
NH3"N
NOa-N
N02-N
Org-N
Total N
Total P04 as P04
S04
Total coliform MPN/100 ml
Fecal coliform MPN/100 ml
SAR
Oil and grease
Phenolic compounds
Total pesticides
Concentration (mg/1 )
ttier Narrows San Jose Creek
4 4.4
7 8
597 687
0.1 0.13
7.0 7.1
93 154
130 150
0.56 0.71
1.02 0.44
0.05 0.01
0.12 0.09
0.02 0.02
0.006 0.012
0.03 0.02
0.026 0.024
0.007 0.006
0.004 0.002
0.064 0.062
0.013 0.012
0.02 0.024
0.0002 0.0003
0.13 0.02
1.5 4.3
14.4 1.2.3
0.09 0.17
2.1 1 .8
1—ff* T f\ C
7.8 18.6
20 27
113 107
42 2.4
10 2.0
55%
1.2 1.2
0.006 0.004
0.16 0.16
113
-------
requirements for the Whittier Narrows and San Jose Creek
discharges.
Under the NPDES program, the local Water Quality Control
Board has established effluent limitations on the discharge
to surface water from the two plants, some of which are
summarized in Table A-21.
In addition, maximum limits on heavy metals, arsenic, cyanide,
nitrogen, phenolic compounds, chlorinated hydrocarbons, and
other constituents will become effective August 1, 1978.
Effluent used for groundwater recharge or landscape irriga-
tion will have to meet the same requirements (legislation
pending)as listed in Table A-21 with the following two
exceptions: (1) wastes discharged shall not contain concen-
trations of heavy metals, arsenic, or cyanide in concentra-
tions exceeding the limits contained in the State of Calif-
ornia Department of Health Drinking Water Standards; and
(2) the wastewater discharged must be adequately disinfected
to a coliform MPN/100 ml of less than 23.
In addition, the State Department of Public Health has
advised the WQCB that they believe, in order to protect the
public health, the following conditions should be observed
in reusing treated wastewater:
"1. The public should be prevented from having
contact with the sewage and sewage effluent.
2. The chemical and bacterial content of the sewage
percolated into the groundwater should be regulated
so that waters taken therefrom for domestic use
are not contaminated.
3. Use of the sewage effluent for irrigation should
comply with the provisions of the regulations of
the State Department of Public Health.
4. The breeding of nuisance and/or disease vectors
in the sewage effluent should be prevented.
5. A monitoring program of the effluent quality and
the quality of the receiving waters should be
maintained."
Recharge Program
Effluent from the Whittier Narrows and San Jose Creek plants
flows from three to five miles to the Whittier Narrows Dam
114
-------
Table A-21. NPDES EFFLUENT LIMITATIONS FOR
WHITTIER NARROWS AND SAN JOSE CREEK PLANTS
7-Day
Parameter Average Daily Max.
BOD (mg/1) 3.0
SS (mg/1) 40
Fecal (MPN/100 ml) 400
Oil and grease (mg/1) 10 15
Settleable solids 0.1 0.2
TDS -- 750
B -- 1.5
Cl -- 175
Coliform (MPN/100 ml) 2.2
pH 6.5 - 9.0
115
-------
where it can be diverted by the Flood Control District as
needed through a network of canals to the spreading grounds.
When storm water is available as natural runoff, a blend of
water (approximately 10 to 15 percent effluent, 35 to 40
percent natural runoff, and 50 percent imported state water)
is diverted to the spreading basins. During dry periods
with little runoff, the mix of state water to effluent is two
to one.
The two nearly adjacent spreading basins, San Gabriel and
Rio Hondo, total 750 acres (Rio Hondo - 455 wetted acres;
San Gabriel - 101 wetted acres of basin area, 133 acres of
unlined river bottom, plus structures, facilities, unused
area - 60 acres). All the effluent from the Whittier
Narrows plant (an average of 15 mgd) is diverted to the Rio
Hondo spreading area, while roughly one half of the 30 mgd
San Jose Creek plant flow is channeled to the San Gabriel
River area. The quantity of effluent diverted for recharge
depends on precipitation patterns, and effluent TDS in the
case of the San Jose Creek Plant.
The individual basins range from four to 20 acres in surface
area and are interconnected with canal networks to allow for
greater flexibility in the flooding schedule (i.e., several
basins can be filled simultaneously or selected basins can
be filled while others drain, etc.).
The Flood Control District rotates batteries of percolation
basins for spreading purposes. Basins are filled for six
days to an average depth of four ft (the San Gabriel River
bed when used for spreading is flooded to an average two ft
depth). The basins are then allowed to drain for six days
and then to dry for six days to complete an 18-day cycle.
Hence, at any given time, essentially one-third of the
available acreage is being wetted. The combined capacity of
both systems on a rotational basis is 200 mgd. During storm
periods, when all basins are employed simultaneously, the
combined capacity is over 600 mgd.
Soil profiles for the two recharge basins are shown in Table
A-22. Soil materials are basically sandy loam above the
groundwater table and bedrock below. Following the recharge
flooding cycle described above, infiltration rates have
averaged two ft per day with a range of 0.6 to five ft per
day.
Percolation activities have created abounding" effect of
the groundwater table such that depth to the groundwater
table may be as little as ten ft directly under the recharge
116
-------
Table A-22. GEOLOGIC SOIL PROFILES
OF SAN GABRIEL AND RIO HONDO BASINS
0-
2-
4-
6-
8-
10-
San Gabriel Test Basin(l)
Depth
below
surface
(feet)
Unit
thick-
ness
(ft-in.)
From
(ft-in.)
To
(ft-in.)
At
(ft-in.)
Description
1' 10"
21 2"
0
I1 10"
10"
I1 6"
2' 2"
6"
4"
6"
7'
8'
8"
4'
6"
7' 8"
8'
9'
I1 10"
6"
8"
i" 8'
8' 6"
(1) Soil profile taken on 27 December 1962.
Information supplied by the L.A. County Flood
Control District.
Dark brown very fine to medium
silty sand and soil.
Light brown to tan fine to medium
sand with lenses of gray fine
sand. Moist, oxidized, orange
fine sand streaks are common
in tan portion.
Wood fragments up to 3 in. long
in dark brown to black medium
to fine sand. Sans is highly
micaceous.
Tan fine to medium soft, mica-
ceous sand, with gray fine
sand lenses. Tan portions
commonly show orange streaks
of oxidized fine sand.
Dark brown to black micaceous
fine sandy silt stringer.
Gray medium to coarse sand.
Gray medium to coarse sand and
"pea gravel" with occasional
gravels to 3/8 in.
-------
Table A-22 (continued). GEOLOGIC SOIL PROFILES
OF SAN GABRIEL AND RIO HONDO BASINS
Rio Hondo Test Basin (2)
oo
Depth
below Unit
surface thickness F
(feet) (feet) (f
0-
11
2-
4-
6-
8-
10-
rom To At
eet) (feet) (feet)
0 11
3
3.5
4
7
8.5
12- 3.5 11 14.5
12
12.5
13.5
16- 2 14.5 16.5
Description
Tan fine to medium sand.
Gray fine sand.
Gray to tan medium sand.
Occasional pebble.
Trace of orange streaks/
Micaceous material.
Tan medium to coarse sand with
1/2 inch pebbles.
Light orange color with pebbles.
A few gravels to 2 inches.
Occasional clay ball.
Tan-gray medium sand. Water
level at 16 feet.
(2) Soil profile taken on 11 December 1962. Information supplied by the L.A. County
Flood Control District)
-------
basins when the basins are in full operation, whereas, the
average water table depth in the area is 50-60 ft.
Chemical treatment (coagulation with a cationic polymer -
Jaguar MRL22AA) is practiced at each forebay to eliminate
silt problems. The first basin in both spreading areas serves
as a desilting facility. In addition, basins in both spread-
ing areas are scraped and scarified when necessary. It has
been determined that vegetative growth enhances infiltration
rates; hence, natural weed and grass growth has not been
discouraged.
The rotational flooding program also aids in reducing insect
and algae problems by interrupting life and growth cycles.
When necessary, chemical treatment is also employed for
insect control through a contract with the Southeast Mosquito
Abatement District.
During the first few years of pilot operation with Whittier
Narrows effluent (1963-1965), experiments were conducted in
a test basin upstream of the spreading grounds with sample
pans to collect recharged water at various depths to determine
quality changes in the reclaimed water due to percolation.
Figure A-16 shows a schematic diagram of the test basin and
sampling apparatus. Although recent attempts to identify and
sample percolating effluent directly beneath the full scale
basins has been futile (due to dilution with other water
sources and natural blending promoted by the mounding effect),
past test results are felt to accurately characterize the
current situation. Pertinent results from these tests are
indicated below:
Suspended solids were toally removed in the first
few feet of percolation.
75 percent COD removal was exhibited in the first
four ft; however, below four ft, the COD increased
again to 40 percent of the surface concentration.
One explanation for this phenomenon is that the COD
naturally present in the soil (roughly 11 ,000 kg
COD for a two-meter depth and 324 sq. m. basin sur-
face area) appears to be higher than the total
amount added by the recharge operations. It is
possible, therefore, that organic carbon could be
synthesized under anaerobic conditions in the soil
system and that a portion of this organic carbon
(probably in the form of bacterial bodies) could be
leached downward to appear in the percolates at
lower sampling pans.
119
-------
PONDED WATER
g
7
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LL
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UJ
z
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TO CENTRAL WELL
• . '- ' SAMPLE'.
' • ' •• BOTTLE '
GROUND SURFACE
\\\\\\/// / / //A \ \\ \\\\\\/4 /
' ••• ' .'*.'-•' 2ft"
.SATURATED ZONE
DIA ,J4 GUAGE SHEET
METAL SAMPLING PAN, 9" DEEP,
PACKED WITH SAND AND GRAVEL
CENTRAL WELL 4ft DIA
CORRUGATED METAL PIPE
-WATER TABLE ' -
LAYOUT OF A TEST BASIN
•LEVEE ON FOUR SIDES OF
BASIN
•WALKWAY
CENTRAL
WELL
^-SAMPLING PAN
FIGURE A-16
SCHEMATIC OF A SAMPLING PAN WELL
120
-------
The sum of organic and ammonia nitrogen was reduced
by 95 percent in the first two ft.
Fecal coliforms were effectively removed. On the
other hand, heavy growths of soil coliforms were
generated, but it was postulated that those bacteria
were removed by deep percolation and/or lateral
travel in the zone of saturation.
IDS increased slightly due to the leaching of
minerals by weak nitrous acid formed during the
intermediary steps of ammonia-to-nitrate conversion
in the soil.
Testing for viruses was inconclusive.
Groundwater levels and quality have been continually monitored
throughout the program by a series of wells located in the
basin area. Figure A-17 shows the location of the 31 wells
utilized for routine sampling. These wells are classified as
shallow wells penetrating only the Gaspur Zone of aquifers
near the surface ( 250 ft). This zone was of most interest
because effluent introduced into the groundwater basin from
spreading grounds first came in contact with groundwater in
the Gaspur Zone. Each of the shallow wells was sampled on
a routine basis with a 3-month to 6-month interval between
samplings.
A special selective-depth pumping unit was fabricated by the
Los Angeles County Flood Control District for sampling in
the shallow wells. This special unit is portable and per-
mits the collection of a water sample from a particular level
in a well. Inflatable balloons or packers are positioned
above and below the pump intake. When inflated, the
packers close off the well above and below the pump intake
so *:hat water can be pumped from a particular level in a well.
This lype of operation permits the taking of water samples
at multiple depths within a well. Limitations are caused
by the spacing of the perforations in a cased well and the
location of zones of impervious material. The purpose of
sampling the shallow well network at multiple depths was
twofold: first, to discover any changes in water quality
attributable to the spreading of the reclaimed water; and
second, to delineate, if possible, any near surface patterns
in the groundwater movement. Because of the complex nature
of the groundwater basin and the lack of any clearcut tracers
in the effluent, the second purpose was not attainable.
According to the results of the testing program, there have
been virtually no adverse effects on groundwater quality due
to the recharge of effluent mixed with natural runoff and
121
-------
MERCED
WATER RECLAMATION PLANT
2936 WHITT1ER HARROWS
TEST BASIN
SPRCAOINC SROUNDS/ /i2939GG
01S97BB
1587 Y // \«9
1562
FIGURE A-17
LOCATION OF MONITORING WELLS
WHITTIER NARROWS WATER RECLAMATION PROJECT
122
-------
imported state water. The only change has been a slight
increase in groundwater IDS concentrations because the raw
sewage has a IDS of over 600 mg/1.
The only minor problem reported by the Flood Control District
due to the use of secondary effluent for recharge has been a
reduction of infiltration rates when long term ponding has
caused some basins to go anaerobic stimulating bacterial
slime growth that sealed the soil surface. Problems with
silt buildup decreasing infiltration rates are attributable
to silt in the natural runoff waters, not the effluent.
Economics
Total costs to the Flood Control Districts for the recharge
program only (based on the percolation of storm, reclaimed,
and imported waters) were approximately $15 per MG. This
cost is broken down as follows:
$/m*l gal (1972)
Development and engineering 5.86
. Right-of-way 1.90
Cleaning and repair 3.10
Operation and maintenance 4.48
Total $ 15.34
Purchase costs for the reclaimed water to be recharged are
paid by the Central and West Basin Water Replenishment
District to the Sanitation Districts and are estimated as
shown below:
,,x
Whittier Narrows effluent^) 90 190,000
San Jose Creek effluent 15 27,000
(1) High price for Whittier Narrows effluent is due to
contractual agreement with Water District to help sub-
sidize and stimulate the initial effluent recharge pro-
gram This price will drop down to approximately
$21/MG when capital costs for the Whittier Narrows plant
are fully paid.
123
-------
Thus, the Flood Control District gains needed water supplies
and the L. A. County Sanitation District realizes a revenue
of $220,QOO/year from the sale of treated wastewater.
Future for Recharge Programs
The future for groundwater replenishment programs using
reclaimed water is uncertain in Los Angeles County at this
time.
It can be assumed that the successful, established Whittier
Narrows recharge operation will continue. However, doubts
among officials of the California State Board of Health
concerning the possible transmission of residual organics in
secondary effluent to the groundwater have temporarily
discouraged attempts to increase the volume of treated waste-
water recharge by the L. A. Sanitation District.
One project that is currently in full scale planning follow-
ing pilot studies is recharge of an operating oil field with
reclaimed water to prevent subsidence and increase oil
recovery. During pilot studies, the Los Angeles County
Sanitation Districts verified that suspended and colloidal
matter remaining in the secondary effluent from their Long
Beach, California, plant would clog the shale rock pores.
They concluded that relatively expensive tertiary treatment
of the six mgd with polyelectrolytes, inert media filtration
and disinfection (probably with ozone) to remove most of
these impurities would be necessary to preserve infiltration
rates and soil porosity.
Inert media filters will be added to the Long Beach plant
in 1976 and the costs for additional tertiary treatment to
make the water suitable for well injection are still under
review. It is anticipated that 3 mgd of the filtered
secondary effluent will be used by the City of Long Beach
for park and golf course irrigation.
124
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APPENDIX B
GENERAL REFERENCE BIBLIOGRAPHY
1. Baffa, John J. and Nicholas J. Bortilucci. Wastewater
Reclamation by Ground Water Recharge on Long Island.
Journal WPCF. March 1967.
2. 1965 Biennial on Ground Water Recharge, Development and
Management. California Department of Water Resources.
3. Boen, Doyle F., James H. Bunts, Jr., and Robert Currie.
A Study of Reutilization of Wastewater Recycled through
Groundwater, Vol. I. Office of Research and Monitoring,
U.S. Environmental Protection Agency, July 1971.
4. Boen, Doyle F., James H. Bunts, Jr., and Robert Currie.
A Study of Reutilization of Wastewater Recycled through
Groundwater, Vol. II. Office of Research and Monitoring,
U.S. Environmental Protection Agency, July 1971.
5. Bouwer, Herman. Infiltration - Percolation Systems.
U.S. Water Conservation Laboratory, Agricultural Research
Service, U.S. Department of Agriculture, Phoenix, Ari-
zona.
6. Bouwer, Herman, J.C. Lance, and M.S. Riggs. High-Rate
Land Treatment II: Water Quality and Economic Aspects
of the Flushing Meadows Project. Journal WPCF. 46:5,
May 1974.
7. Bouwer, Herman, R.C. Rice, and D. Escarcegh. High-Rate
Land Treatment I: Infiltration and Hydraulic Aspects of
the Flushing Meadows Project. Journal WPCF. 46:5, May
1974.
8. Deaner, David G. California Water Reclamation Sites.
Bureau of Sanitary Engineering, California State Depart-
ment of Public Health, June 1971.
9. Deaner, David G. Directing Wastewater Reclamation Opera-
tions in California. Bureau of Sanitary Engineering,
California State Department of Public Health, August
1969.
10. Dryden, Franklin D. and Henry J. Ongerth. Health As-
pects of Water Reuse. Presented at the 47th Annual
Conference of the Water Pollution Control Federation.
Denver, Colorado, October 7, 1974.
125
-------
11. Engineer's Report on Groundwater Conditions Water Supply
and Basin Utilization in the Orange County Water Dis-
trict. Fountain Valley, California. February 13, 1974.
12. Groundwater Basin Management. ASCE, Irrigation and
Drainage Division, Committee on Groundwater, 1961.
13. Koch, Ellis, Anthony A. Giaima, and Dennis J. Sulane.
Design and Operation of the Artificial Recharge Plant
at Bay Park, New York. Geological Survey Professional
Paper 751-B. U.S. Government Printing Office. Washing-
ton, 1973.
14. Linsley, Ray K. and Joseph B. Franzini. Water Resources
Engineering. 1964.
15. McKee, J.E. Water Quality Criteria. 1971.
16. McKinzie, Gary D. and Russell O. Utgard (eds). Man
and His Physical Environment. 1972.
17. McMichael, Francis Clay and Jack Edward McKee. Waste-
water Reclamation at Whittier Narrows. Environmental
Health Engineering, California Institute of Technology.
Pasadena, California. September 1965.
18. Pound, Charles E. and Ronald W. Crites. Wastewater
Treatment and Reuse Land Application: Volume I - Sum-
mary. Office of Research and Development, U.S. Environ-
mental Protection Agency. Washington, D.C. August
1973.
19. Pound, Charles E. and Ronald W. Crites, Wastewater Treat-
ment and Reuse by Land Application: Volume II. Office
of Research and Development, U.S. Environmental Protec-
tion Agency, Washington, D.C. August 1973.
20. A Program for Water Reclamation and Groundwater Recharge,
Environmental Impact Statement, Santa Clara Flood Con-
trol and Water District, April 1973.
21. A Program for Water Reclamation and Groundwater Re-
charge: Predesign Report. Environmental Impact State-
ment, Santa Clara Flood Control and Water District,
October, 1974.
22. Rose, John L. Injection of Treated Wastewaters into
Aquifers. Water and Wastes Engineering. October 1968.
23. Stewart, James M. Proceedings: Workshop on Land Dis-
posal of Wastewaters. Water Resources Research Insti-
tute. North Carolina. February 1973.
126
-------
24. Subsurface Water Pollution: A Selective Annotated
Bibliography, Part I - Subsurface Waste Injection.
Office of Water Programs, Division of Applied Technology,
U.S. E.P.A. Washington, B.C. March 1972.
25. Subsurface Water Pollution: A Selective Annotated
Bibliography, Part II - Saline Water Intrusion. Office
of Water Programs, Division of Applied Technologv,
U.S.E.P.A. Washington, D.C. March 1972.
26. Subsurface Water Pollution: A Selective Annotated
Bibliography, Part III - Percolation from Surface Sources
Office of Water Programs, Division of Applied Technology,
U.S.E.P.A. Washington, D.C. March 1972.
27. Vecchioli, John. Experimental Injection of Tertiary-
Treated Sewage in Deep Well at Bay Park, Long Island,
New York: A Summary of Early Results. New England
Water Works Association. 86:2, June 1972.
28. Vecchioli, John and Henry F. H. Kee. Preliminary Results
of Injecting Highly Treated Sewage-Plant Effluent into
Deep Sand Aquifer at Bay Park, New York. Geological
Survey Professional Paper. 751-A, U.S. Government
Printing Office. Washington, D.C. 1972.
29. Water Conservation by Reclamation and Recharge. ASCE,
Proc. 94 (SA 4 #6065), p. 625-39. August 1968.
30. Wesner, G.M. and D.C. Baier. Injection of Reclaimed
Wastewater into Confined Aquifers. American Water Works
Association Journal. March 1970.
127
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APPENDIX C
WATER SANITATION SECTION
CALIFORNIA STATE DEPARTMENT OF HEALTH
POSITION ON BASIN PLAN PROPOSALS
FOR
RECLAIMED WATER USES INVOLVING INGESTION
September, 1973
128
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WATER SANITATION SECTION
CALIFORNIA STATE DEPARTMENT OF HEALTH
POSITION ON BASIN PLAN PROPOSALS
FOR
RECLAIMED WATER USES INVOLVING INGESTION
Introduction
The purpose of the position statement is to provide guide-
lines for Department of Health review and recommendations on
basin plan reclamation components that involve augmentation
of a domestic water supply. The Department of Health
responsibility is to represent the best health interests of
the State in this matter by assuring protection of the
domestic water resource.
Three uses of reclaimed water are considered in the state-
ment:
1. groundwater recharge by surface spreading,
2. direct injection into an aquifer suitable for use
as a domestic water source, and
3. direct discharge of reclaimed water for supply
augmentation into a domestic water system or
storage facility.
Health risks from the use of renovated wastewater may arise
from pathogenic organisms and toxic chemicals. The nature
of the phenomenon associated with pathogens and heavy-metal
toxicants are well enough understood to permit setting
limits and creating treatment control systems. This is not
the case, however, with regard to some organic constituents
of wastewater. In particular, the ingestion of water
reclaimed from sewage may produce long-term health effects
associated with the stable organic materials which remain
after treatment.
This is an area of unknowns -- unknowns involving the com-
position of the organic materials, the types of long-term
effects, synergistic effects, metabolite formations, treat-
ment effects, methods of detection and identification, and
ultimately, the levels at which long-term health effects
are exerted.
The urgent need for knowledge in this area has generated
increased calls for answers by health authorities, the
water industry, resource managers, and the scientific
129
-------
community. It now appears that the need for research is
recognized and there should be action in the near future. As
a suggestion of the time frame needed for research activity,
it has been estimated that the interval needed before
information can be generated through animal feeding experiments
(one possible method of study) could range from six to ten
years or longer depending on the results that are obtained.
The health effects of concern are not immediate or acute.
They are related to ingestion over an extended period,
measured in years or decades, and may be serious but quite
subtle.
In summary, stable organics pose a health question when
reclaimed water is used to augment a domestic water supply.
This question will not be answered for years, and years of
exposure may be involved for the occurrence of adverse
effects. It is in this setting that the position statement
has been developed.
Uses Involving Ingestion
Three uses of reclaimed water have been identified which
involve augmentation of a domestic water supply. These are
ranked in ascending order of health significance for the
reasons given.
1. Groundwater replenishment by surface spreading.
Health protection will depend on treatment, changes
or removals which occur during percolation, dilution,
and time.
There are presently four planned recharge systems in
operation in California which replenish aquifers
used for domestic supply. The largest and one which
has operated for more than a decade is the Whittier
Narrows recharge operation which involves the re-
charge of 12,000-18,000 acre-feet of reclaimed water
and 160,000 acre-feet of natural surface water annually
into a large groundwater basin. The degree of
monitoring to determine effects on the organic
quality of groundwater from the several planned
operations to this time has not been significant.
2. Injection into a groundwater aquifer.
Health protection would depend upon treatment and
time. There is little assurance that beneficial
changes or removals will occur with horizontal move-
ment through a saturated aquifer. Movement will
130
-------
most likely occur as a physical displacement
of the natural groundwater with little mixing or
diluti on.
Most injection proposals thus far have been for the
purpose of saline water repulsion. With mound and
trough systems, there is opportunity for partial
control of the movement of reclaimed water. The one
proposal which has advanced to the construction
stage (Orange County Water District) has a number of
restrictive provisions and requirements applied to
it including ". . . an alternate source of domestic
water supply shall be provided any user whose ground-
water is found to be impaired by the injection
program." Two other proposals for saline water re-
pulsion are in the development stage in California.
3. Direct discharge into the domestic water system.
Health protection would depend on treatment and
dilution. Except for extreme situations where the
lack of water has been of greater health significance
than that associated with use of water reclaimed
from wastewater, no responsible authority has
embarked on deliberate, direct augmentation by intro-
ducing water reclaimed from sewage into the water
system. There are proposals for the future.
The Basin Plans
In the Water Quality Control Plans, it is expected that re-
claimed water use involving ingestion may be categorized in
the following manner:
1. The plan involves an immediate or near-term decision
regarding the reclamation element. Funds are to be
committed to near-term physical facilities based on
the decision and, once the selection has been made,
the options are pretty well closed off. This is
essentially an immediate "go or no go" decision.
2. The plan involves an immediate or near-term decision
reagrding the reclamation element, however, there
are reasonable options for other reclamation uses
or for waste disposal employing the physical facil-
ities. There will be some loss if the intended
project is not completed in the proposed manner,
however, regardless of eventual health findings the
plan does not constitute an unalterable commitment
to domestic supply augmentation.
131
-------
3. The reclamation element is in a latter stage of
the plan, 10 or more years in the future, and does
not significantly affect earlier stages. A clear
decision on health acceptability will be available
prior to construction.
There are, of course, many other shadings, but the three
categories should suffice for general direction within which
reasonable judgment can be applied.
Position on Plans for Direct Discharge into a Mater System
A plan which involves direct discharge into a domestic water
supply system or storage unit for the near future (within
the next decade) is not acceptable because of the uncertain
health implications. The Department will recommend against
the element of a basin plan which contains such a proposal.
Where a plan requiring a near-term decision involves options
or alternatives for the use or disposal of the wastewater,
the Department will reject the domestic water reuse alterna-
tive and consider the remaining options as the proposals
for evaluation.
Direct discharge into a water system may be presented in a
plan as a future option which may be appraised as additional
information becomes available and future needs and attitudes
are clearer.
Position on Plans for Injection for Groundwater Replenishment
The Department will recommend against injection for ground-
water replenishment as a plan element which is to be
implemented in the near future (within next decade). Injec-
tion may be considered as a future option, contingent upon
the availability of new supportive information and future
needs.
Injection of reclaimed water for saline water repulsion and
reclamation of saline aquifers is an acceptable use when
accompanied by proper controls. Community domestic water
supply may not be drawn from the immediate injection area and
preferably, injection should be into the brackish water zone.
Position on Groundwater Recharge by Surface Spreading
Surface spreading appears to have the greatest potential for
use of reclaimed water in the basin plans. It is expected
that most groundwater recharge will be through this method
since surface spreading involves the least cost and has the
greatest history of practice.
132
-------
Although this potential exists, it must be restated that
there are no reclamation criteria for domestic use of re-
claimed water, information relative to health effects from
ingestion is uncertain and the interval involved before
conclusive information is available may be considerable. It
should also be emphasized that if new information indicates
adverse effects are created with substantial recharge, clo-
sure of those basins involved would be required with regard
to domestic use.
The application of limits on specific percentages of reclaimed
water allowable in groundwater would be inappropriate because
knowledge of health effects is lacking.
For near-term proposals, plans which involve the recharge
of a substantial volume of reclaimed water into a small basin
will be recommended against.
If information indicates uncertain or adverse effects are
associated with recharge operations of this magnitude, the
results would require a costly effort to reclaim the basin
or might result in abandonment of the basin for domestic
use. The serious implications of this situation, therefore,
require the Department of Health to recommend against such a
proposal.
Where recharge operations would constitute a small fraction
of water in the underground, near-term proposals may be
acceptable. Location relative to community wells will be
considered as well as the domestic use of the basin waters.
By limiting such proposals to operations involving only small
percentages of reclaimed water in the groundwater, the
corrective action, if required, may be without undue cost or
loss of the basin as a domestic source. Near-term plans
with available options to surface spreading are desired.
Surface spreading presented as a future option in a plan
would be acceptable.
133
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APPENDIX D
CAPITAL COST FACTORS
The following factors were used to convert all capital costs
to equivalent 1972 dollars.
Year
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973 (Jan.)
1974 (Nov.)
Conversion
Factor
1.75
1
1
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
1,
69
66
64
63
1.61
,53
,56
,54
,48
44
,39
,30
,20
,08
,00
0.91
0.79
To obtain cost in 1972 multiply actual cost by conversion
factor given above for the year of actual construction.
1957-1972 cost factors were derived from FWPCA, Department
of Interior, Dec., 1967, and Treatment Optimization Research
Program, Advanced Waste Treatment Research Laboratory,
Cincinnati, OH. 1973, 1974 cost factors were derived from
ENR Construction Cost Index.
134
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APPENDIX E
PROCEEDING FOR COST CALCULATION
The following steps were used to determine final $/MG costs
for recharge:
Convert recharge facilities capital costs to
equivalent 1972 dollars using Appendix D.
Calculate annual capital recovery factor by
multiplying equivalent 1972 cost by 0.07455
(capital recovery factor assuming 5.5 percent
interest and 25 year life).
Add equivalent 1972 annual recharge operation and
maintenance cost to annual capital recovery cost.
Divide resultant total annual cost by 365 days x
MGD to get final $MG for recharge.
135
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APPENDIX F
CONVERSIONS FROM CUSTOMARY UNITS TO METRIC
Customary Units
Description
Acre
British
thermal unit
British
thermal units
per cubic
foot
British
thermal units
per pound
British
thermal units
per square
foot per hour
Cubic foot
Cubic foot
Pounds per
thousand
cubic feet
per day
Cubic feet
per minute
Cubic feet
per minute
per thousand
cubic feet
Cubic feet
per second
Cubic feet
per second
per acre
Cubic inch
Cubic yard
Fathom
Foot
Feet per hour
Feet per
minute
Foot-pound
Gallon
Symbol
Multiply
ac
Btu
Btu/cu
ft
Btu/lb
Btu/sq
ft/hr
cu ft
cu ft
lb/1000
cu ft/
day
cfm
cfm/1000
cu ft
cf s
cfs/ac
cu in.
cu yd
f
ft
ft/hr
fpm
ft-lb
gal
Multiplier
By
0.4047
1.055
37.30
2.328
3.158
0.02832
28,32
0.01602
0.4719
0.01667
0.02832
0.06998
0.01639
0.7646
1.839
0.3048*
0.08467
0.00508
1.356
3.785
Metric Units
Symbol
To Get
ha
kJ
J/l
kJAg
o
J/m sec
m5
1
O
Reciprocal
2.471
0.9470
0.02681
0.4295
0.3167
35.31
0.03531
kg/mj day 62.43
I/sec
3
1/m sec
m-^/sec
•5
2.119
60.00
35.31
m-Vsec ha 14.29
1
m3
m
m
mm/sec
m/sec
J
I
61.01
1.308
0.5467
3.281
11.81
196.8
0.7375
0.2642
136
-------
APPENDIX F(Continued)
Customary Units
Description
Symbol
Multiply
Multiplier
By
Metric Units
Symbol
To Get
Reciprocal
Gallons per
acre
Gallons per
day per
linear foot
Gallons per
day per
square foot
Gallons per
minute
Grain
Grains per
gallon
Horsepower
Hoursepower-
hour
Inch
Knot
Knot
Mile
Miles per
hour
Million gal-
lons
Million gal-
lons per day
Million gal-
lons per day
Ounce
Pound (force)
Pound (mass)
Pounds per
acre
Pounds per
cubic foot
Pounds per
foot
Pounds per
horsepower-
hour
Pounds per
square foot
gal/ac
gpd/lin
ft
gpd/sq
ft
gpm
gr
gr/gal
hp
hp-hr
in.
knot
knot
mi
mph
mil gal
(MG)
mgd (MGD)
mgd (MGD)
oz
Ibf
Ib
Ib/ac
Ib/cu ft
Ib/ft
lb/hp-hr
Ib/sq ft
0.00935
0.01242
0.04074
0.06308
0.06480
17.12
0.7457
2.684
25.4*
1.852
0.5144
1.609
1.609
3785.0
43.81
0.04381
28.35
4.448
0.4536
1.121
16.02
1.488
0.1690
4.882
m3/ha 106.9
"D
mj/m day
o *p
mj/mz day
I/sec
g
mg/1
kW
MJ
mm
km/h
m/sec
km
km/h
,u
I/sec
•5
iir/sec
g
N
kg
kg/ha
->
kg/nr
kg/m (KG/m)
mg/J
2
kgf/m
80.53
24.54
15.85
15.43
0.05841
1.341
0.3725
0.03937
0.5400
1.944
0.6215
0.6215
0.000264
0.02282
22.82
0.03527
0.2248
2.205
0.8921
0.06242
0.6720
5.918
0.2048
137
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APPENDIX F (Continued)
Customary Units
Description
Symbol
Multiply
Multiplier
By
Metric Units
Symbol
To Get
Reciprocal
Pounds per
square inch
Pounds per
square inch
Square foot
Square inch
Square mile
Square yard
Ton , short
Yard
psi
psi
sq ft
sq in.
sq mi
sq yd
ton
yd
703.1
6.895
0.09290
645.2
2.590
0.8361
0.9072
0.9144*
2
kgf/in
•)
Wnr
m2
imn^
o
knr
m2
t
m
0.001422
0.1450
10.76
0.001550
0.3861
1.196
1.102
1.094
*Indicates exact conversion factor.
Note: The U.S. gallon is assumed. If the conversion from
the Imperial gallon is required, multiply factor by
1.201.
Standard gravity, g = 9.80665* m/s2
= 32.174 ft/s2.
138
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
REPORT NO.
EPA-600/2-77-183
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Reuse of Municipal Wastewater for Groundwater
Recharge
5. REPORT DATE
September 1977 (Issuing Date
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
Schmidt, Curtis J.
Clements. Ernest V. Ill
PERFORMING ORGANIZATION NAME AND ADDRESS
SCS Engineers
4014 Long Beach Blvd.
Long Beach, CA 90807
10. PROGRAM ELEMENT NO.
1BC611 C611B SOS 4 Task 15
11. CONTRACT/GRANT NO.
68-03-2140
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory—Cin.
Office of Research & Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
OH13- TYPE OF REPORT AND PERIOD COVERED
Final 10/74 - 6/77
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: Irwin J. Kugelman (513) 684-7633
16. ABSTRACT
A survey of groundwater recharge operations with municipal wastewater
effluent was conducted. It was found that this activity is being practiced
at 10 sites in the U.S. with a total capacity of 77 MGD. The most successful
employ percolation with alternate flooding and drying cycles. Well injec-
tion can be successful but only if rigorous control of injected water
quality is maintained. Clogging of recharge wells is the major problem.
Sufficient data have not been developed to define the movement of pollutants
such as salts, trace organics or pathogens through groundwater as a
function of soil characteristics, groundwater hydraulics, and groundwater
characteristics. Thus, water quality requirements to insure successful
recharge over a long period can not be defined quantitatively.
At the sites surveyed reasonable success has been achieved over periods
ranging from 1 to 20 years. It is recommended that intensive monitoring
of these and a few other new sites be continued and instituted to gather
data on which rational design criteria can be based.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Water Reclamation
Water Conservation
Water Resources
Water Supply
Groundwater
Wastewater Renovation
Wastewater Reuse
Water Recycle
Recharge Wells
Reuse Technology
13 B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
151
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
139
•&U.S. GOVERNMENT PRINTING OFFICE: 1977-757-056/6552 Region No. 5-11
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