United States
Environmental Protection
Agency
Office Of Water
(WH-595)
EPA 430/09-91-022
September 1991
•PA Municipal Wastewater Reuse
Selected Readings On
Water Reuse
5ra^*^3hsSS5WSi56»i»ft!*SE
Printed on Recycled Paper
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EPA 430/09-91-022
September 1991
MUNICIPAL WASTEWATER REUSE:
SELECTED READINGS ON WATER REUSE
Reprinted Articles From The
Water Pollution Control Federation's
T.'
Water Environment & Technology Journal
Reprinted with Permission by
U.S. Environmental Protection Agency .
Office of Water
Office of Wastewater Enforcement & Compliance
Washington, D.C. 20460
Selected Readings on Water Reuse •
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i — Selected Readings on Water Reuse
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TABLE OF CONTENTS
i document contains reprints of the following articles from the Water Pollution Control Federation's Water Environment
technology Journal:
[CF's Committment to Water Reuse - Completing the Cycle 2
| by Ron Young (Chairman, WPCF Water Reuse Committee) (October, 1990)
(idelines for Developing a Project , 3
by Ramond Fl. Longoria, David C. Lewis & Dwayne Hargesheimer (October, 1990)
/s to Better Water Quality „ 9
by Kenneth J. Miller ({November, 1990)
[NSERV'90 brings together experts on water reuse 10
by Alan B. Nichols (November, 1990)
|ter Reuse in Riyadh, Saudi Arabia 11
by James M. Chansler (November, 1990)
allzlng the Benefits of Water Reuse in Developing Countries 13
by Daniel A. Okun (November, 1990)
|>. Water Reuse: Current Status and Future Trends 18
by Kenneth J. Miller (November, 1990)
^site Wastewater Reclamation and Recycling 25
byJohnlrwin (November, 1990)
[stewater Reuse Gains Public Acceptance 27
by J. Gordon Milliken (December, 1990)
acles to Implementing Reuse Projects 28
by Scott B. Ahlstrom (December, 1990)
|ne Ranch's Approach to Water Reclamation „ 30
by John Parsons (December, 1990)
f rida's Reuse Program Paves the Way 34
by David W. York & James Crook (December, 1990)
jnomic Tool for Reuse Planning „ 39
by J. Gordon Milliken (December, 1990)
fter Reuse: Potable or Nonpotable? There is a Difference! 43
by Daniel A. Okun (January, 1991)
3ort Sets New Water Reuse Guidelines .44
by Christopher Powicki (January, 1991)
^riflcation and Filtration to Meet Low Turbidity Reclaimed Water Standards 46
by Joel A. Faller & Robert A. Ryder (January, 1991)
|table Water Reuse 53
by Carl L. Hamann & Brock McEwen (January, 1991)
(table Water via Land Treatment and AWT 59
by Sherwood Reed & Robert Bastian (August, 1991)
jndwater Recharge with Reclaimed Water in California 67
by James Crook, Takashi Asano & Margret Nellor (August, 1990)
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iv — Selected Readings on Water Reuse
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PRELUDE
WPCF's Committment to Water
Reuse—Completing the Cycle
This month marks the twenty-fifth anniversary of the
establishment of WPCF's Water Reuse Committee. During the
last 25 years WPCF, through this committee, has committed
programs that promote and aid in the development of water
reuse technology. In this anniversary year, coincidentally, WPCF
received an EPA grant to publish information on water reuse as
section in four issues of Water Environment & Technology,
beginning with this October issue.
EPA representatives, speaking at the WPCF Annual Conference
held in San Francisco, 1989, affirmed WPCF's position on water
reuse, "Effluent reuse is a resource management option whose time
has come. EPA encour-
ages the reuse of treated
wastewater effluents
because of the great
potential for resource
recovery and for pollution
minimization." In the
presentation, EPA repre-
sentatives affirmed, also,
that reuse projects can be
difficult to implement.
Thus, in these WE&T
sections, experts in the
field describe successful
projects and provide
guidance to those who
may be considering or are
involved in managing
water reuse and recla-
mation projects.
Many of the contrib-
utors to this EPA-funded
project are WPCF Water
Reuse Committee mem-
bers. Along with the
committee's long range
plan, their contributions
demonstrate that the
Water Reuse Committee
is more active than ever. For example, as part of its
long range plan, the committee is focusing on the need for
national water reuse standards or guidelines. As chairman and
member of this committee, I share my colleague's enthusiasm
for a project of such scope.
With this project, WPCF hopes to focus attention of its members
on what can be accomplished, today, in recovering wastewater and
what is needed to meet the growing public expectation for
renewable resources in the future.
On the Cover and In this Issue:
Officials and engineers are becoming
increasingly concerned over the clean water
supply. Thus, wastewater reclamation plants
have been designed and more are being
planned in areas where the water supply is
diminishing or where demand is greater than
supply. TJje Upper Occoquan Reclamation
Plant, Centreville, Va., is one such plant that
discharges treated wastewater, that meets
stringent discharge permit limits, into a
drinking water source; it's design and
operation was the model for the Abilene, Tex.,
Reclamation Project Plan, whose story is told in
this WE&T inset. The Abilene, Tex.,
Reclamation Plant, when completed, will
discharge its effluent to the Lake Fort Phantom-
Hill reservoir.
One acceptable reuse ofwastewater is
irrigation. (Thepicutre of the spicket spraying
water was taken by Carl Morrison). A recent
poll of 1102 residents of California showed that
a vast majority—89% of the polled residents—
felt that reclaimed water would be safe for
outdoor uses. Public attitudes and issues on
wastewater reuse will be covered in a future
inset.
II
Ron Young
Chairman, WPCF Water Reuse Committee
2-Selected Readings on Water Reuse
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WATER RECLAMATION/REUSE
GUIDELINES FOR
DEVELOPING A PROJECT
Raymond R. Longorm, David C. Lewis,
and Dwayne Har^esheimer
Today's technology provides
a variety of water reclama-
tion/reuse techniques to
help meet the growing
demand for high-quality,
treated water. An organized
management strategy is
necessary to completely
evaluate available options and select
the proper approach. A four-phase
planning effort was used in the
development of a water reclamation/
reuse project initiated in 1988 to
indirectly augment potable water
supplies for Abilene, Tex., by
increasing the flows into the surface
water supply reservoir. The four
work phases focused on project defi-
nition and formation, creation of
baseline data, treatment process eval-
uation and selection, and implemen-
tation.
Under this management approach,
each phase is nearly independent,
with distinct orientation meetings
and schedules. The information gen-
erated from the major tasks in each
phase is assembled in separate techni-
cal memoranda (TM) that deal with
specific issues, focusing the
approach.
Each phase ends hi an intensive 1-
to 2-day project team meeting fol-
lowed by a coordination meeting
with the owner (in this case, officials
from the city of Abilene) and a pub-
lic advisory committee. Thus, each
TM can be drafted, reviewed by the
project team, reviewed with the
owner, modified, and then prepared
in final form before the next phase
begins.
Together, the TMs form a com-
prehensive report. During the final
phase, they are condensed, providing
the basis for the summary report.
This report, a concise, 40- to 60-
page account of the key project
issues, is intended for a broad and
often non-technical audience. All of
the elements of the project are
assembled into two volumes: the
summary report and an appendix con-
taining TMs (Table 1).
PHASE 1: PROJECT DEFINITION AND
FORMATION
Phase 1 involves formation of the
project team, including a public advi-
sory committee (PAC), and requires
the project team to develop, in
detail, the specific goals and objec-
tives of the project.
Establishing a team. In addition
Table 1—Titles of Technical
Memoranda for the Abilene Project
Research Project Objective, Goals
and Approach
Public Advisory Committee Activities
and Meetings
Baseline Data Development
Water-Quality Assessment
Lake Fort Phantom Hill - Water
Quality Studies
Water-Quality Criteria and Goals
Process Selections, Conceptual
Designs and
Preliminary Cost Options
Process Selection, Sizing and
Location
Bench-Scale Study - High Lime and
Alum Coagulation
Bench-Scale Study -
N itrif ication/Den itrif ication
Recommended Plan
Evaluation of Financing Options
Non-potable Water System
to the owner, engineers, and a PAC,
the project team might include envi-
ronmental scientists, virologists, epi-
demiologists, the owner's financial
consultant, a water rights attorney, a
public relations consultant, agron-
omists, economists, and other spe-
cialists.
Despite all the technological and
economic elements that comprise a
water-reclamation research project, it
is foremost a public involvement
project requiring unwavering public
support to be successful. Therefore,
the PAC, as an advisory group of
local citizens with scientific and non-
scientific backgrounds, is vital to
project success. PAC candidates
should have good communication
skills and a history of sound judg-
ment, open-mindedness, and public
activity. It is likely—and possibly
preferable—that the PAC members
will not be familiar with wastewater
treatment technologies. They should
be introduced to current technology
through visits to successful full-scale
reuse/reclamation projects.
The PAC's charter is to provide
guidance to the project team and to
express the community's interests in
the project. It should also choose the
appropriate level of public participa-
tion. For example, the Abilene PAC
recommended that the project team
provide it with regular project
updates, hold informal meetings with
it frequently, and hold only one for-
mal public meeting. This was
designed to allow the PAC to dis-
seminate accurate information to the
public and channel citizens' concerns
back to the project team.
Raising issues and forming
goals. The PAC should identify,
Selected Readings on Water Reuse - 3
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PROPOSED
IMPLEMENTATION SEQUENCE
WATER SUPPLY v?s WATER DEMAND
TRIBUTARY
FACILITY
IMPLEMENTATION
WATER, §UPRt-Y
-INCREASE FROM
RECLAMATION
STACY RESERVOIR
15,000 AC-FT
LJi wo
HAMBY < g
FACILITY E S
PROJECTED
WATER SUPPLY
'- WATER REDUCTION.
BY USE OF:NON POTABLE WATER
NOTES, : :/ .: .
1. SUPPLY AND DEMAND FIGURE ARE FOR WEST i
CENfRAL TEXAS (ABILENE REPRESENTS 75-80X OF TOTAL)
2. PROJECTED WATER DEMAND IS FOR "DRY- YEAR USE
APPROXIMATELY 10JC ABOVE; NORMAL USE,
with the project team, the project
goals, objectives, and key issues and
approve of the technical experts
selected to address those issues.
Once the basic project structure is in
place, the project team assembles for
a 2-day meeting.
The meeting begins with a clear
restatement of the goals, which are
usually established well before the
first project team meeting (see Box).
Part of the first day is set aside for
"brainstorming," while the remain-
der of the meeting is focused to
refine the issues and statement of
objectives, to establish relative levels
of importance, and prepare the draft
TMs.
The project team should plan to
address key issues identified by the
PAC promptly, to the satisfaction of
die PAC. Timely issue resolution will
improve the chances of public accep-
tance. The Abilene PAC narrowed
the key issues to two questions: "Is
water reclamation needed? Is water
reclamation safe?"
CREATION OF BASELINE DATA
In Phase 2, the project team com-
piles fact sheets of relevant baseline
information on a specific subject.
The fact sheets, no more than 3
pages long, arc incorporated in a sin-
gle document—the baseline data
TM. For the Abilene project, fact
Goals and Objectives
Plan, test, and verify the feasibility of reclaiming water
from wastewater
Provide a meaningful increase in water supply
Prevent adverse effects on water quality in Lake Fort
Phantom Hill that would limit its potential uses
Comply with state and federal water-quality regulations on
wastewater effluent discharges
Provide a source of drinking water of equal or higher quality
than that currently produced
Maintain or enhance the aesthetic conditions of waters in Lake
Fort Phantom Hill
Reduce or prevent increases in public-health risks associated with
the potable water supply and the wastewater treatment and dis-
posal method
Recommend implementation of water reclamation only if it is
shown to be economically favorable
Select treatment technology consistent with the city's
operations and maintenance capabilities
Investigate non-potable water reuse options to reduce demands
on the potable water supply
Secure public involvement and participation in the
development and execution of trie project
sheets summarized data on existing
and projected population, reservoir
models, historical water quality,
potable water production and use,
wastewater flows and quality,
wastewater treatment plant capacity,
water treatment plant capacity, water
rights, climatological data, and water
conservation measures. These data
are used to evaluate the need for
water reclamation and the adequacy
of potential treatment processes and
to provide a context within which
alternatives are considered.
Sources of historical water-quality
data and water quality model calibra-
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WATER -RECLAMATION/REUSE
Table 2—Phase 2 Monitoring Progam:
Water Quality Parameters
Algal identification
Alkalinity
Aluminum
Ammonia
Arsenic
Barium
Biochemical oxygen demand
Boron
Bromide
Cadmium
Calcium
Chloride
Chlorophyll a
Chromium
Cobalt
Color
Copper
Cyanide
Dissolved oxygen
Fecal coliform
Fecal streptococcus '."
Fluoride
Iodide
Iron
Lead
Magnesium
Manganese
Mercury
Methylene blue active substances (MBAS)
Nitrate-N
Nitrite-N
Nitrogen, total Kjeldahl
Pesticide scan
Phosphorus
Potassium
Selenium
Silica
Silver
Sodium
Standard plate count
Strontium
Sulfate
Temperature
Threshold odor
Total dissolved solids (TDS)
Total hardness
Total organic carbon
Total organic halogens
Total suspended solids (TSS) . ... .
Total trihalomethanes (THM
Total THM forming potentia
Turbidity
.Virus
Volatile organic carbon
Zinc
tion information include the owner,
state regulatory agencies, the U.S.
Geological Survey, and other users of
water bodies, such as power plants or
park and wildlife departments.
Because available data may be
incomplete or of questionable validi-
ty, supplemental data should be
acquired. An intensive water-quality
monitoring program, specifically
designed for the project, should be
established early on in the project or,
if possible, before the project is start-
ed. Monitoring for a full year,
including hot, cold, dry, and wet sea-
sons, should be conducted. Several
parameters should be monitored
(Table 2) and samples should be
taken from at least two points in the
reservoir and at least one spot in
each major tributary feeding the
reservoir. A sample should also be
drawn from the existing wastewater
treatment plant effluent.
Because unexpected areas of con-
cern may arise, the monitoring bud-
get should contain contingency
funds. Special testing was required
on the Abilene project after the pro-
ject team determined that Giardia,
lamblia. and Cryptosporidium sp.
could be present.
PROCESS EVALUATION AND SELECTION
In Phase 3, fundamental technical
information is developed. Water-
Lake Fort Phantom Hill will received reclaimed effluent from the Abilene, Tx., wastewater treatment plant when the project is completed.
Selected Readings on Water Reuse — 5
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quality standards arc identified, com-
puter modeling is conducted to
determine the impact of the stan-
dards on the receiving water, and
treatment alternatives are developed
and evaluated.
The establishment of appropriate
water-quality standards for treated
effluents and receiving streams is
crucial. Numerous federal and state
regulations must be considered, and
other regional and local water-quali-
ty regulations may be applicable.
Water-quality modeling for the
receiving water begins with these
standards. The project team uses the
computer model to evaluate the
discharge effects on the reservoir at
various flows and degrees of treat-
ment. For modeling, the recom-
mended minimum flow is a flow that
would increase the lake's volume by
approximately 5 to 10%. This water
supply increase should produce a
measurable positive or negative
impact on the lake water quality. The
maximum flow should be based on a
projection of the practical limit of
wastcwatcr that would be available for
reclamation during the study period.
For treatment levels, one set of
model parameters should be set
equal to the normal effluent dis-
charge permit requirements of the
receiving stream. One or two other
sets that meet more and less strin-
gent water-quality requirements also
should be selected.
In the Abilene project (Table 3),
one effluent set represented the rea-
sonable best practical treatment level
obtainable by current treatment pro-
cesses (Row A in the table) and
another set represented the treat-
ment to maintain the state's water-
quality standards (Row C). Row B
represented the highest treatment
level obtainable without chemical
coagulation. The project team used
the U.S. Army Corps of Engineers
River and Reservoir Water Quality
Model with flow values that ranged
from 3 to 17 mgd under conditions
of a 2-ycar critical drought period.
The water-quality standards review
and the water-quality modeling
results reveal the appropriate effluent
quality criteria and allow selection of
appropriate treatment processes.
Specific effluent criteria will be
required for the different reclaimed
water uses proposed in the water
reclamation plan. This could include
reclaimed water used for irrigation,
discharged to a tributary stream of
CITY OF ABILENE
ffexAS WATER DEVELOPMENT BOARD
PROPOSED
TEH RECLAMATION PROCESS
SCHEMATIC
BIOLOGICAL
PHYSICAL *
CHEMICAL
LAKE FORT PHANTOM HILL
CHLORINE
CONTACT. CHAMBER
the reservoir, and discharged directly
to the reservoir (Tables 4 and 5).
Demonstrating effectiveness. In
selecting alternative treatment pro-
cess configurations, the project team
should give preference to ones cur-
rently in tise elsewhere. The PAC can
be more confident in support of the
project if members have visited a suc-
cessful project that uses the same
process scheme.
Regardless of other treatment pro-
cess successes, bench-scale tests
should be conducted for key process
parameters to demonstrate to the
public that a process successful in
other areas of the country is equally
successful under local conditions.
For example, the water-quality
model for the Abilene project indi-
cated sensitivity to phosphorous and
nitrates. High lime coagulation
bench-scale tests demonstrated that
phosphorous could be removed ade-
quately within a range of dosages,
while nitrification/denitrification
rate tests determined the appropriate
design criteria.
The project team reviews the pro-
cess alternatives (Tables 6, 7, and 8),
prepares a detailed analysis of the
advantages and disadvantages of
each, selects a process, and then pre-
pares a detailed description of the
selected process.
During this phase, the project
team should meet twice, once to
address the water-quality standards
and once to evaluate the process
alternatives.
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WATER RECLAMATION/REUSE
Table 3—Sample of Water-Quality Modeling Values
Degree of Treatment
Effluent
Set
A
B
c:
BOD5
.3.0 ,
5.0
1.0.0..
TSS
1,0
5.0
15.0
ortho-
Phosphate
0,2 ;
2.0
10.0
Ammonia
2.0
3.0
3,0
Nitrate
10.0
25.0
25.0
Table 4—Recommended Reclamation Levels for Irrigationa
Contaminant
Levels for
controlled access
Levels for limited
control access areas
Biochemical oxygen
demand (BOD), mg/L 20
Total suspended
solids (TSS), mg/L
Chlorine residual
Fecal coliform, per
100 mL
Total coliform, per
lOOmL
Turbidity, NTU
20
1.0
100
not specified
not specified
20
20
not specified
not specified
2.2
2 ;
a Levels at the time when the Abilene project was being planned.
Table 5—Recommended Reclamation Level for Supply Augmentation
Contaminant or Quality Quantity Flow, mgd
BOD, mg/L
Turbidity, NTU
Ammonia nitrogen, mg/L
Nitrate/nitrite nitrogen, mg/L
Total phosphorus
Dissolved oxygen
v 5 . ; .; :
2
; 2
20
10
2.0
0.2
>5.0
<3
>3
<3
>3
IMPLEMENTATION
By the onset of the fourth phase,
the major TMs are completed, and
the project team should be ready to
draft the summary report. In this
final phase, the recommended treat-
ment plan and other infrastructure
requirements are combined in a
comprehensive water reclamation
plan. Non-potable water system or
water conservation plans should also
be incorporated into the reclamation
plan during this phase.
The implementation phase should
delineate the needed system
improvements, establish an imple-
mentation schedule, develop a water
supply vs. demand curve, enumerate
costs, and identify any non-structural
requirements. In addition to the
treatment units, implementation
plans should include the required
wastewater collection system
improvements and the pumping and
non-potable water distribution sys-
tem requirements.
The implementation schedule and
the supply vs. demand curve should
complement one another. The exist-
ing supply vs. demand conditions are
used to determine when improve-
ments will be needed and to develop
an implementation schedule. The
changes in the supply vs. demand
curve caused by system improve-
ments are then observable in a modi-
fied supply vs. demand curve (see
Figure).
At this stage, estimated costs
should be considered in planning
budget estimates, which will be used
to establish project financing needs,
and should provide adequately for
contingencies. In addition to overall
capital costs and annualized costs,
the project dollars should be
expressed in terms of cost per vol-
ume (dollars/1000 gal) and cost for
developing a water supply in terms of
volume per year (dollars/ac-fbyr).
These figures would be compared to
conventional surface water supply
project costs.
Non-structural (management and
operations) needs, which are
addressed in this phase, include
water rights, water-quality monitor-
ing, financing, and public informa-
tion. Because water rights to
reclaimed wastewater have become
complex, a water rights attorney
should be retained to prepare a posi-
tion paper on the owner's legal
authority for reuse of wastewater to
supplement surface water sources.
Selected Readings on Water Reuse - 7
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WATER RECLAMATION/REUSE
Monitoring for ongoing evalua-
tion. The water-quality monitoring
program should be continued
through Phase 4 to provide data
needed to evaluate the impact of the
reuse improvements. The program,
however, could be scaled back. Loca-
tions, both within the reservoir and
on its tributaries, should continue to
be sampled. While sampling and test-
ing of the more sensitive parameters
should be stepped up, many parame-
ters repeatedly shown to be below
detection limits or well within crite-
ria can be tested less frequently or
eliminated from the monitoring pro-
gram.
Testing should involve a local uni-
versity or some other independent
agency to increase the likelihood of
public acceptance. A technical com-
mittee could be appointed to review
the water-quality data.
Financing and public
acceptance. Financing options for a
reclamation project are similar to
those for conventional wastewater
treatment systems. Reclamation pro-
jects also may qualify for funding
from programs geared toward water
supply development. Additionally,
most non-potable water supply sys-
tem improvements will benefit spe-
cific entities that should be asked to
assist in financing the non-potable
system improvements.
In general, the public perception
of water reuse is positive as long as a
project is presented using the proper
approach. Because the connection
between wastewater and water is not
one that the public desires to make,
asking the public to accept wastewa-
ter as a water source is a "difficult
sell."
It normally requires a public infor-
mation and relations campaign to
convince the public to accept this
concept. The development of a public
information and acceptance program
should begin with the study and con-
tinue throughout the implementation
phase. There are several approaches
and the owner's public information
staff should develop and direct the
public acceptance program. •
Raymond R. Lonjjoria is an engi-
neer with Freese and Nichols, Inc., in
Fort Worth, Tex.; David C. Lewis is
an engineer with CH2M Hill in
Austin, Tex.; and Dwnyne
Hargesbeimer is the director of the
water utility department of the city of
Abilene, Tex.
Table 6—Four Treatment Process Alternatives; System Train
High-Lime
Activated isludge
Nitrification
Denitrification
Clarification
High-lime
Recarbonafion
Filtration
Chlorinatipn
Post aeration .,__
Alum
Activated sludge
Nitrification
Denitrification
Coagulation
Chemical phosphorus removal
Clarification
Filtration
Break-point chlorination
Post aeration
Table 7—Treatment Alternative Design (and Average) Operating Conditions
Treatment Type
Alum and biophcsphorus removal
Activated sludge
Nitrification
Biological phosphorus removal
Coagulation
Filtration
Clarification
Filtration
Break-point chlorination
Post aeration
Nitrification
Activated sludge
Nitrification
Biological phosphorus removal
Clarification
Filtration :
Chlorination
Post aeration and force main
Effluent quality,
mg/L
BOD
TSS
TKN
Nitrate
Phosphorus
Dissolved, oxygen
Coliform, per
100 ml
Turbidity, NTU
° Not detected.
" Not applicable.
High-Lime
5.0 (2.0)
5.0(1.0)
2.0 (1 .0)
10.0 (5-7)
0.2(0.1)
5.0 (6.0)
2.2 (2.0)
2.0(1.0)
Alum
5.0 (2.0
5.0(2.0
2.0(0.1
1 0.0 (5-7
0.2 (0.15
6.0 (6.0
Alum and Nitrification
biological
phosphorus
removal
5.0 2.0
5.0(1.0
2.0(0.1
15-20(15-20
0.2(0.15
5.0 (6.0
2.2 (ND)a 2.2 (ND
5.0
5.0
2.0
3.0)
5.0)
1.5)
15-20(15-20)
2.0 (2.0)
5.0
6.0)
200.0(100)
2.0(1.0) 2.0(1.0) NAb (4-10)
Table 8—Preliminary Cost Data for Abilene, Tex., Reuse Project
Treatment Type
Cost, million
dollars
Capital
Operations and
High-Lime
13.41
0.70
Alum
11.26
0.56
Alum and
biological
phosphorus
removal
10.12
0.46
Nitrification"
11.58
0.35
maintenance
Equivalent
annual"
2.09
1.73
1.51
1.55
a Includes construction of pump station and force main to pump beyond
reservoir during droughts.
b Based on 20 years at 8% interest.
8-Selected Readings on Water Reuse
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PRELUDE
Keys to Better Water Quality
Larger populations and a higher standard of living require more
water—from all available resources—to satisfy domestic and
industrial needs. Unfortunately, growth and population increas-
es have generally been associated with water-quality deteriora-
tion. The quality of many of Earth's surface supplies will continue
to show deterioration until, at some point, planned reuse and its
associated treatment process will offer a higher-quality product
than conventional treatment. Thus, the key to dealing with water-
resource problems will lie in our ability to extend and augment
existing supplies through various reclamation processes. Success in
water-reuse technology
will probably depend
on our ability to com-
municate and apply the
technological advances
that are achieved.
The government's
role should be to coor-
dinate research and
demonstration projects
and promulgate con-
trolling rules and regu-
lations. Over ten gov-
ernment agencies have
some interest in water
reuse and recycling.
For the sake of effi-
ciency and sound man-
agement, one agency
should coordinate and
manage all reuse re-
search and demonstration projects.
Public participation is necessary during each step of reuse
programs: the public should not be expected to automatically
understand and support reuse projects and, although increasingly
recognized as a significant natural resource, reuse or disposal of
wastewater will continue to receive greater scrutiny. The public's
role can be one of a supporting partner or major antagonist. The
difference seems to be involvement by the public—local and
national—in all parts of the reuse effort.
Water reuse began out of necessity brought about by expanding
industries, ever-increasing populations, and the need for larger vol-
umes of water to support growing agricultural needs. As mankind
approaches the 21st century with a world population projected to
nearly double by the year 2000, it is realistic to project that, with-
out significant change, existing water resources will be taxed
beyond our current abilities to satisfy demand. The role of water
reuse must therefore, be expanded.
About this section
This is the second installment in a series
devoted to the subject of water reuse. •
Installments were scheduled for publica-
tion in four issues of Water Environment
& Technology. The -publication of these
insets was made possible by a grant from
the Environmental Protection Agency.
Last month WE&T published an arti-
cle on planning a reclamation project.
This month WE&T focuses on the world-
wide status of wastewater reclamation.
The trends-in reuse in developing coun-
tries, in the arid Middle East, and in the
U.S. are described. Papers on reclamation
and reuse of wastewater that were fea-
tured, in several sessions of the recent Con-
serv 90 are also summarized in an article.
, , Irrigated with wastewater
reclaimed by the Riyadh Wastewater Ireat-
i ment Plant, soil and plant samples are
c - collected in Dirob, Saudi Arabia,.
; for analysis.
Kenneth J. Miller
Vice President and Director
Water Supply and Treatment
CH2MHill
Denver, Colo.
-------
WATER RECLAMATION/REUSE
Conserv 90 brings together experts
on water reuse
Conserv 90 was conceived in the
wake of the 1988 drought that
devastated the country and raised
concerns about water supply and use.
Conserv 90 is a joint effort of the
American Society of Civil Engineers,
American Water Resources Associa-
tion, American Water Works Associa-
tion, and the National Water Well
Association. The theme of Conserv 90,
which was held in Phoenix, Ariz., in
August, was "Offering Water Supply
Solutions for die 1990s." This summa-
rizes the session Effluent Reuse.
EFFLUENT REUSE
Water reclamation and reuse is
taking on added significance in a cli-
mate in which increased community
development is putting a lot of pres-
sure on water resources and sewer
services.
To minimize subsurface discharge
of wastewatcr in an arid rural area of
poor drainage not served by public
sewer services, a new 800-student
high school in a rural Texas school
district included an on-site advanced
treatment system that included the
use of reclaimed water for flushing
toilets. This system reduced wastew-
atcr discharge by 85%.
In Houston, Tex., a sewer mora-
torium imposed on a high-growth
area meant that all new construction
projects could discharge no more
than 1600 gpd/ac of property. High
property values could not be sup-
ported by the level of development
which the discharge limit imposed.
As a solution, a construction project
of the Alliance Bank and Trust Com-
pany included an on-site wastewater
treatment and recycling system with
water conservation plumbing fix-
tures. When fully completed, the
200,000-sq-ft building will discharge
only 1000 gpd.
Similarly, on-site treatment and
use of reclaimed water greatly
reduced the wastewater discharges of
the Squibb Corp. building in Mont-
gomery Township, N.J., near Prince-
ton, that does not have public sewer
sendees. The system has enabled the
township to control growth and
avoid unwanted sewer infrastructure
expenses while maintaining environ-
mental goals.
In conservation-conscious Santa
Monica, Calif., a 1.3-mil sq-ft com-
plex consisting of four buildings for
office and retail space is, when com-
pleted, expected to produce only
40,000 gpd as opposed to an
expected 70,000 gpd. The reason:
low flush toilets and other water
conserving fixtures, on-site treat-
ment and reclamation for landscape
irrigation.
A successful on-site wastewater
treatment system like those described
above typically consists of on-line
flow equalization and emergency
storage tanks, biological nitrification
and denitrification, membrane filtra-
tion, activated carbon, and disinfec-
tion. Membrane filtration is used to
clarify biological process solids down
to a particle size of about .005 u,.
Granular activated carbon is used for
color removal and is a backup for
organic carbon removal. Typical
removal rates are: biochemical oxy-
gen demand (BOD) and total sus-
pended solids (TSS) < 5 mg/L, tur-
bidity < 0.5 NTU, total coliform <
2.2/100 mL.
Factors inhibiting the wider prac-
tice of on-site reclamation and recy-
cling include lack of state regula-
tions, lack of standards for reclaimed
water quality, and ambiguous
plumbing codes.
In another paper, a project in
Beaufort County near Hilton Head
Island, S.C., which is experiencing
rapid population growth, is
described. To accommodate this
growth, the Beaufort-Jaspar Water
and Sewer Authority is planning
two wastewater treatment plants
which would be designed to pro-
duce effluent that could be applied
to area golf courses. Also, the
authority has been investigating the
development of a wet-weather dis-
charge system that would combine
the flows of both plants and dis-
tribute the treated effluent to a
forested floodplain wetland. The
wetland would provide additional
treatment while protecting the adja-
cent tidal freshwater river.
In the rural areas of Brevard
County, Fla., reclamation is a neces-
sity in light of the growth of the
county along the coast. Just com-
pleted is the South Central Regional
Wastewater System which will serve a
25-sq mile area of the mainland and
, will provide total reuse of effluent. It
consists of four pumping stations,
several miles of force main, a 3-mgd
plant, and effluent reuse for irriga-
tion of sod, farms. The county has
also decided to provide filtration and
high-level disinfection because the
effluent will eventually be extended
to irrigation.of public contact areas.
Venice, Fla., which has a critical
water supply problem and a high
growth rate, is constructing a new
plant, the East Side WWTP, which
will provide advanced secondary
treatment to produce reclaimed
water suitable for urban irrigation.
The reclaimed effluent must meet
state standards for public access irri-
gation: 20 mg/L BOD, 5 mg/L
TSS and no detectable fecal col-
iforms. Nutrients are not regulated
because their presence in irrigation
water is beneficial as a fertilizer. The
reclaimed water will greatly reduce
pressure on local aquifers which have
been the source of golf course irri-
gated water:
One of the most water conserva-
tion-conscious states is Arizona,
where Tucson and Phoenix have
developed elaborate reclamation sys-
tems for golf course and other forms
of irrigation. Reclamation takes great
pressure off of the groundwater sup-
plies in a state that is heavily agricul-
tural.
Meanwhile, in Southern Califor-
nia, where the water supplies are
under great stress, the Irvine Ranch
Water District has expanded its 15-
year-old reclamation system to
include nonpublic-contact use of
reclaimed water for office and other
highrise buildings. Feasibility studies
began in 1987 for a dual-distribution
system that delivers potable water
and reclaimed wastewater to these
sites. Pipes and fixtures are color-
coded to allow easy distinction.
Almost all of the hurdles, from test-
ing to design approval, have been
surmounted and officials announce
that the system will be in actual
operation in a building soon.
Also in Southern California, a
blend of groundwater and highly
treated wastewater is being injected
underground to stem saltwater intru-
sion that has resulted from ground-
water overdrafting.
-Man's. Nichols, senior staff writer
y»r Water Environment & Technology.
10-Selected Readings on Water Reuse
-------
Above: In Dariyah, Saudi Arabia, palm trees and fodder crops grow where land was irrigated with reclaimed wastewater. Below Right: Plants in this Dirab, Saudi
Arabia, greenhouse are watered with wastewater reclaimed by the Riyadh Wastewater Treatment Plant.
Water Reuse in
Riyadh, Saudi Arabia
Riyadh, the capital of Saudi Arabia,
is nestled in the central part of
the arid Najd highlands. Its loca-
tion, combined with a population
that has nearly tripled to almost 2
million people over the last 10 years,
guarantees water shortages and
necessitates water reclamation. In the
city, there are approximately 30 pro-
jects involving water reuse. Industrial
and agricultural programs rely on
effluent from the Riyadh Wastewater
Treatment Plant (RWWTP).
The first stage of the RWWTP
began operations in 1976 with a
capacity of 40,000 m3/day (10.6
mgd) to serve a population of
160,000 persons. Because of the
city's rapid growth, the plant was
almost immediately overloaded, and
plans were quickly made to expand
the facility. By 1980 the plant's
capacity was expanded to 80,000
m3/d (21.2 mgd), and, in 1983, the
second stage of development was
completed giving the
site an average daily
capacity of 200,000
m3/d (52.8 mgd). The
collection system uses
1980 km (1228 miles)
of lines and no lift sta-
tions. Greater collec-
tion-line depths are
tolerated in order to
avoid lift-station oper-
ation and maintenance
costs.
The plant, which
provides preliminary,
primary, secondary,
and chlorination treat-
ment, is a high-rate
trickling filter-system
with random-fill plastic
media, followed by
two aerated lagoons,
and finally chlorina-
tion.
Sludge treatment is
achieved by anaerobic
digestion, followed by sand drying
beds. The dried sludge is hauled
away by farmers who use the material
as a soil conditioner or additive.
Plans have been completed to pro-
vide tertiary treatment of the
wastewater; this will be gravity sand
filtration of the final effluent.
Selected Readings on Water Reuse — 11
-------
WATER RECIMMION/REUSE
Riyadh WWTP Influent and Effluent Composition
Constituent
Concentration, mg/L
Influent
Effluent
Total dissolved solids
Suspended solids
SeHleable solids (ml/L)
BOD5, 20°
Chemical oxygen demand (COD)
Ammonia-nitrogen
Nitrate-nitrogen
Phosphates
Chlorides
Alkalinity
Grease
Temperature, °C
Free available chlorine
Total chlorine residual
PH
Dissolved oxygen
Total coliform
1300
250
3
250
450
25
-
10:
180
240
TOO
29
0,0
0.0
7.3
0
< lOYmL
1200
40
ND
45
100
25
< 1
7
160
200
10
27
0.8
4.0
7.4
5
50 tol 00/1 00 ml
••••II , i .1 i. i .. •-.——.---•-•. -..i |.. , i^r, mn, nihmh mi • 1 .ii,.ii— ~..»— ^ ,— .-..—_ „ , „ ...........
A center pivot irrigation system sprays reclaimed wastewater on crops in Dirab, Saudi Arabia.
REUSE PRACTICES
The Pctromin Oil Refinery uses
some 20,000 m3/d (5.3 mgd) of
RWWTP's effluent. About 75% is
treated to produce high-quality boil-
er feed water, while the balance is
treated and used for crude oil desalt-
ing and cooling water and is also
available for fire fighting should that
prove necessary.
About 3600 m3/d (0.9mgd) of
effluent is used for landscape irriga-
tion at the RWWTP. The grassed
areas arc aerial-spray irrigated while
the shrubs and flowers are flood irri-
gated. Areas adjacent to the housing
and main offices at the plant are
watered with potable water to pre-
vent any unwarranted use of the
effluent.
The largest portion of the plant's
effluent is pumped to Dirab and
Dariyah for agricultural irrigation.
The pumping station at Riyadh has a
capacity of 120,000 m3/d (31.7
mgd) with an on-line storage of
300,000 m3/d (79.3 mgd). The
transmission line to Dariyah, which
has a capacity of 200,000 m3/d
(52.8 mgd), is 50 km (31 miles)
long and 800 mm (41.5 in.) in
diameter. The transmission line to
the Dirab irrigation site is 55 km (34
miles) long and 1000 mm (39.4 in.)
in diameter.
i
MEETING STANDARDS AND DEMANDS
In 1985, 92,000 m3/d (24 mgd)
of RWWTP effluent was pumped to
Dirab and spread generally over
2000 ha (5,000 acre) The farms at
Dirab average around 65 ha (106
ac.) in size and the main crops are
wheat, fodder, and vegetables. In
1985, 70,400 m3/d (19 mgd) of
RWWTP effluent was pumped to
Dariyah. The farms at Dariyah aver-
age about 15 ha (37 acre) and the
main crops are date palms, fruit
trees, vegetables, and fodder.
The irrigation water has made it
possible to more than double the
land under cultivation at Dirab; as in
the past, the wells at Dirab used for
irrigation would be dry during the
summer months. Also, the nutrients
in the effluent (see Table), especially
nitrogen and phosphorus, reduce the
need for fertilizers, thus, reducing
costs, and substantial savings are
being realized. Farmers are also
using treated sludge from the plant
as a soil.conditioner.
The tentative Saudi Arabian
Water Quality Standards for unre-
stricted agricultural irrigation are 10
mg/L for 5-day biochemical oxygen
demand (BOD5) and 10 mg/L for
suspended solids. The effluent does
not meet the tentative standards,
but, as soon as the tertiary plant is
completed, there should be little
difficulty in producing an effluent
that meets these requirements.
However, overloading, also, pre-
sents problems.
Wastewater flows to the RWWTP
have been increasing dramatically,
and at present the flows are over
330,000 m3/d (87 mgd). Plans have
been completed and construction is
presently underway on a new,
200,000 m3/d (52.8 mgd) plant
located just to the north of the exist-
ing plant.
The new plant will also provide
preliminary, primary, secondary, and
tertiary treatment. The secondary
treatment process, however, will be
an activated sludge system incorpo-
rating a nitrification-denitrification
process, and tertiary treatment will
consist of sand filtration and chlori-
nation.
-James M. Cha-nsler, Wastewater
Management Division, Broward
County Office of Environmental Ser-
vices, Pompa.no Beach, Flo,.; Donald
R. Rowe, Lctrox Research Corpora-
tion, Bowling Green, Ky.; Khaled Al-
Dhowalia, Civil Engineering Depart-
ment, King Saud University, Riyadh,
Saudi Arabia; and Alan Whitehead,
Riyadh Water and Sewerage Authori-
ty, Riyadh, Saudi Arabia.
12-Selected Readings on Water Reuse
-------
Sao Ptiufo, Brazil, fie world's second largest city,
plans to build a reclaimed water system for urban,
industrial, and agricultural use
15!-'
SH
REALIZING THf BENEFITS OF
IN DEVELOPING COUNTRIES
t: .;-' .... ' .";• -.." L. ; ...;1^%,-'.^i .-^^^v^:'. I-.-.;...'1 -." ' l-j'1*'* .(.•,'>;
The proportion of the
world's population living in
urban areas is rapidly
increasing, especially in
developing countries in
Asia, Africa, and Latin
America. In 1950, only
New York and London had
populations exceeding 10 million; by
1975, the number of "megacities"
had grown to seven, including three
in developing countries. By the year
2000, forecasts indicate that there
will be some 25 of these huge popu-
lation centers, with 20 in developing
countries.
Inevitably, the water-supply
demands of growing urban regions
will outstrip available water
resources, especially in developing
countries. As a result, large industri-
al, commercial, and residential devel-
opments often develop their own
supplies— frequently by tapping
local groundwater—without ade-
quate planning or government
supervision. This causes problems
such as land subsidence and saltwater
intrusion.
Also, because of water shortages,
water service in most urban areas of
developing countries is intermittent,
Daniel A. Okun
allowing the distribution system to
be contaminated by infiltration of
contaminated groundwater, posing a
serious threat to public health. Water
reclamation, by reducing the
demand on the potable supply, may
help maintain water pressure.
The location of burgeoning urban
centers creates other problems.
About half of all megacities and most
secondary cities are inland, in areas
where there is insufficient water for
the disposal and dilution of their
increasing wastewater flows.
In industrialized countries, the
practice of water reclamation for
nonpotable purposes has been
increasingly relied on to provide a
new source of water to meet urban
needs. For cities in developing areas,
water reclamation has the potential
to reduce the magnitude of
inevitable problems by providing
additional water while at the same
time reducing the amount of
wastewater that must be discharged.
As in recent water and wastewater
planning efforts for municipalities in
Florida, California, and the south-
west U.S., engineers formulating
plans for cities in developing coun-
tries should assess the potential for
Daniel A. Ota
integrating water-supply and sewer-
age-system planning to maximize the
benefits that water reclamation can
provide.
PLANNING CONSIDERATIONS
The costs of developing new water
resources for urban areas are high—
much higher in constant dollars than
the costs of developing existing
sources because the latter were the
lowest-cost options when they were
selected. Thus, water reclamation, by
substituting nonpotable for potable
water where feasible, may be a more
attractive alternative. Also, for inland
cities where wastewater treatment
costs are high because of the need to
protect downstream water quality,
water reclamation for reuse may well
be economically attractive.
Direct potable reuse should not be
considered because it is not yet
proven or acceptable, nor is it likely
to be hi the current planning hori-
zon. Moreover, because of the fre-
quent occurrence of water-borne
infectious diseases in the developing
world, the risks of transmitting
cholera, typhoid, and dysentery
through reclaimed water are far
greater than in the industrialized
Selected Readings on Water Reuse -13
-------
WATER RECLAMATION/REUSE
Parameter
world, where these diseases have vir-
tually been eliminated.
Groundwater recharge, a form of
indirect potable reuse, is also con-
strained by public-health uncertain-
ties. Agricultural reuse, which is
widely practiced throughout the
world, should not be a prime consid-
eration for urban planners because
the water is far more valuable in
urban use. In the early stages of a
water-reclamation project, providing
reclaimed water to nearby agricultur-
al lands may be attractive. However,
as the metropolitan area
expands, displacing agricul-
ture, the reclaimed water
would be shifted to urban
uses. Also, irrigation is a
consumptive use, whereas
many other nonpotable
uses, such as industrial pro-
cessing and toilet flushing,
permit another cycle of
reuse.
For a water-reclamation
program to be instituted,
urban areas must be sew-
ered. In developing coun-
tries, while 50% to 80% of
urban areas are provided
with water service, only 10%
to 50% arc provided with
sewerage. Programs to
increase urban sewerage ser-
vice now have a high priori-
ty, but systems intended for
water reclamation should be
planned differently than
conventional systems
designed to discharge
wastcwater to a receiving
body of water.
doses of either coagulant, polymer, or
both; dirett conventional sand filtra-
tion; and chlorine disinfection can
easily and continuously provide a sat-
isfactory product. The design, opera-
tional, and quality parameters that
have been adopted in California are
shown in' Table 1. These criteria,
which may be modified for cities in
developing countries, are best deter-
mined by pilot studies.
Reclamation plants differ from
typical wastewater treatment plants,
which are built to treat and discharge
Table 1—California Criteria for Urban Nonpotable
Reuse
remainder of the wastewater may
travel to another plant for disposal.
Finally, and perhaps most impor-
tantly, the effluent is a marketable
product arid should be treated as
such: quantity and quality are
important if customers are to be sat-
isfied.
Therefore, reclamation plants are
designed for reliability, with duplicate
units, standby power sources, and
continuous on-line monitoring of
effluent turbidity and chlorine
residual, as well as monitoring for
chlorine residual on the
— distribution system.
Criteria
Coagulant (alum/polymer)
Rapid mix
Fijter media
Effective media size
Anthracite
Sand
Filter bed depth
Filter loading rate
Chlorine residual
Chlorine contact time
Required unless effluent
-furbidityxS NTU
High energy
Anthracite and sand
1 .0 to 1 .2 mm
0.55 to 0.6 mm
12 m/h (5gpm/sqft)
Minimum of 5 mg/L
...after. 2. hours._ ...............
2 hours
Chlorine chamber 40:L(length:width_or depth)
WATER QUALITY FOR REUSE
In urban settings, be-
cause significant numbers of
people could potentially be
exposed to nonpotable
reclaimed water used for
landscape irrigation, indus-
trial purposes, toilet flushing, and
many other uses, there must be no
hazard. The most important water-
quality objective is that the water
must be adequately disinfected, and
a chlorine residual should always be
present. Also, the water must be
clear, colorless, and odorless; other-
wise, it would be aesthetically unac-
ceptable.
Research by the Los Angeles
County Sanitation Districts' has
demonstrated that a high-quality sec-
ondary effluent, treated with small
Coliform bacteria, MPN
7-day median
maximum
Filter effluent turbidity,
24-hour average
2.2/100 ml
23/100 ml
2.NTU
effluent to receiving waters, in sever-
al ways. The location of the plant is
primarily influenced by potential
markets for the reclaimed water,
rather than the service area's topog-
raphy or the location of the receiving
water. The sludge that is produced is
not necessarily treated at the recla-
mation plant because it may be
returned to the sewer for treatment
and disposal at another plant. The
amount of wastewater treated at the
reclamation plant depends on the
demand for reclaimed water; the
NONPOTABLE REUSE
PROGRAMS
Water-reuse programs
in the industrialized world
are instructive in gauging
the chances for success in
the developing world.
The widest experience
with water reclamation
and nonpotable reuse is in
the U.S., not only in the
arid Southwest but also in
humid Florida; in Singa-
pore, where, despite
extraordinarily high pre-
cipitation, water resources
are limited; in Israel,
where innovative reuse
practices have a long his-
tory; in the oil-rich coun-
tries of the Middle East,
where 1 L of fresh water
may cost more than 1 L
of petrol, and costly
desalination practices are
common along with high-
tech systems of reclama-
tion; and in the resort
islands of the West Indies
where the value of fresh
water for tourism also jus-
tifies the high cost of
reclamation.
A typical approach
involves the reclamation of wastewa-
ter for a single large user, such as a
program initiated in Baltimore, Md.,
in 1942. About 4.5 m3/s (100 mgd)
of effluent from the city's Back River
activated-sludge plant was chlorinat-
ed and conveyed 7.2 km (4.5 miles)
through a 2.44-m (96-in.) pipeline
to the Sparrows Point plant operated
by Bethlehem Steel Co. This is gen-
erally the way reuse begins in many
urban centers.
Power plants with evaporative
cooling towers are large users of
14-Selected Readings on Water Reuse
-------
reclaimed water. A 58-km (36-mile)
transmission main was installed in
1982 to carry secondary effluent
from Phoenix, Ariz., to a 3.9-m3/s
(90-mgd) reclamation plant at the
Palo Verde nuclear power station. At
the plant, biological nitrification (on
trickling filters), lime-soda softening,
coagulation, dual-media filtration,
and chlorination are provided to
meet the special water-quality
requirements of cooling towers. A
large Phoenix developer who needed
the water for a housing and commer-
cial development sued the city for
making this agreement, illustrating
the value of reclaimed water.
A growing practice involves the
use of dual-distribution systems—
one for potable water and the other
for nonpotable purposes. The first
system was installed in 1926 in
Grand Canyon Village, Ariz., where
scarce drinking water is pumped
from a spring near the bottom of the
canyon about 1 km below.
Reclaimed wastewater is used in the
village for most nonpotable purpos-
es, including extensive landscape irri-
gation and toilet flushing.
The Irvine Ranch Water District in
southern California initiated waste-
water reclamation using a dual sys-
tem, mainly for urban irrigation as an
alternative to ocean disposal of efflu-
ent. However, even when the
requirement for secondary treatment
for ocean discharge was waived, it
was determined that reclaimed water
service was about 33% less expensive
than drawing additional potable
water from the local water supplier.
Consequently, all new development
in the district is provided with a dual
system, and this is being extended to
high-rise office buildings for toilet
flushing. Currently, about 25% of all
the water used in Irvine is non-
potable water produced by its recla-
mation plant. The district hopes to
provide about 0.6 m3/s (13 mgd) of
reclaimed water to its customers by
the year 2000.2
An important feature of reclama-
tion programs, as illustrated by those
of the Los Angeles County Sanita-
tion Districts, is that the reclamation
plants are located far up on the sew-
erage network, near the markets for
reclaimed water. The plants do not
treat the sludge produced; it goes
back into the sewerage system to be
treated at a plant near the point of
wastewater disposal. This is also the
practice in Irvine and other reclama-
tion plants in Orange County, Calif.
The largest dual system in opera-
tion began to be retrofitted in St.
Petersburg, Fla., in 1977. One major
reason for installing the dual system
was because the cost of treatment for
reclamation was considerably less
than the cost to provide the
advanced wastewater treatment that
is required for discharge to Tampa
Bay and the Gulf of Mexico. Another
major benefit evolved from the city's
reliance on a groundwater source for
potable water that is limited and
located a considerable distance away.
The city provides an annual aver-
age total water supply of about 2.7
m3/s (60 mgd). About 0.9 m3/s (20
mgd) of this is reclaimed water, which
goes to some 6000 customers, includ-
ing about 5650 residential users and
250 commercial, industrial, and other
users. This represents only a small
fraction of the potential market,
which is being serviced as rapidly as
facilities can be provided. The city has
experienced about 10% growth since
1976, without any increase in potable
water demand, because of its success-
ful water-reclamation program.
The Japanese have confronted
problems similar to those facing the
developing world. In Japan, a rela-
tively small portion of urban areas—
about 40%—is sewered while the
entire country has serious water-sup-
ply shortages because of its very high
population density.3
Water reclamation was first prac-
ticed in Japan through recycling.
Reclamation plants were built "on-
site," primarily for toilet flushing in
large buildings. Emphasis is now
shifting to reclamation at municipal
publicly owned treatment works
(POTWs). The country currently
uses about 3.2 m3/s (72 mgd) of
reclaimed water from POTWs (Table
2). Up to now, the reclamation
plants installed at POTWs have been
small-—generally about 0.05 m3/s
(1.0 mgd)—and less than 1% of all
wastewater is reclaimed, but plans
are underway to extensively increase
such reuse.
About 1.3 m3/s (30 mgd) is used
in buildings (Table 3). In Tokyo, the
use of reclaimed water for toilet
flushing is mandated in buildings
larger than 10,000 m2 (100,000 sq
ft). The many diverse uses of
reclaimed water in urban dual sys-
tems in Japan are shown in Table 4.
Because of the heavily urban setting,
landscape irrigation is far less impor-
tant than in the U.S.
In Singapore, secondary wastewa-
ter is discharged to the ocean
through outfalls. At one location,
effluent is intercepted, filtered, and
chlorinated at a 0.5-m3/s (10-mgd)
plant to provide water to an industri-
al park. This program has been
extended to provide water for flush
toilets for some 25,000 residents in
12-story apartment buildings.
Throughout the world, dual distri-
bution systems are proliferating,
speeded up by policies adopted by
states in the U.S. and governments
elsewhere. An important feature of
all these reclamation systems is that
customers pay for the reclaimed
water, but generally at a price signifi-
cantly less than for fresh water.
REUSE PLANNING
Cities in the industrialized world
have a major advantage in initiating
reclamation programs: they already
have the necessary sewerage systems
and secondary treatment plants.
However, this is not always positive,
as treatment plants are typically situ-
ated to minimize treatment and dis-
posal costs. Consequently, plants are
generally at a low elevation, located a
great distance from reuse markets.
Also, the costs to retrofit streets and
buildings in developed urban areas
to add a new service may be pro-
hibitive.
In developing countries, on the
other hand, the investment in urban
infrastructure is so far short of the
need that the costs of conventional
and dual systems may not be so dif-
ferent; with a dual system, the sav-
ings incurred in avoiding the need to
exploit an additional water supply
may, in fact, offset the cost differen-
tial. If the initial cost for needed
facilities is too great to be borne,
which is generally the case in devel-
oping countries, at least the planning
might be done to facilitate reclama-
tion and reuse in the future. Further,
an important feature of reclamation
is that it can be staged, with
reclaimed water being introduced
into the system in small, affordable
increments.
In any event, it is clear that the tra-
ditional practice of considering sewer-
age separately from water supply is
inappropriate. With the difficulties
inherent in financing systems in devel-
oping countries, planners can lower
costs by considering water reclama-
tion in initial planning stages and by
Selected Readings on Water Reuse -15
-------
WATER RECLAMATION/REUSE
Table 2—Uses of Reclaimed Water in Japan
Category Percent of total
Nonportable in dual systems 40
Industrial 29
Agricultural 15
Stream flow augmentation 12
Snow removal 4
Total 100
Amount, m3/s (mgd)
' 1.3 (29)
0.9 (21)
0.5 (11)
0.4 (8)
0.1 (3)
3.2 (72)
Table 3—Buildings Using Reclaimed Wafer in Japan
Type
Percent
Schools
Office buildings
Public halls
Factories
Hotels
Others (residences, shopping centers, etc.)
Total
1.8.
17
9
8
:4
44
100
Table 4—Uses of Reclaimed Water in Dual Systems in Japan
Use
Percent
Toilet flushing
Cooling water
Landscape irrigation
Car washing
Washing and cleansing
Flow augmentation
Other
Total
37
9
15
7
16
6
10
100
situating plants in appropriate areas.
In developing countries, where the
impetus for reuse comes from water
resource needs, the plants should be
located upstream on the sewerage sys-
tem, nearer the potential markets.
This has a further advantage in that
reclaimed water that is not sold can
help sustain the flow in urban streams
that would otherwise run dry.'
Another characteristic of cities hi
developing countries is that storm
drainage is inadequate, and stormwa-
tcr management programs might be
somewhat different if reclamation is
being considered. Depending on
local circumstances, stormwater may
be stored and then fed into die recla-
mation system.
EXPERIENCES IN DEVELOPING COUNTRIES
Water reuse in urban areas in
developing countries has generally
been unplanned and indirect. In
Bogota, Colombia, for example, the
city installed a good sewerage sys-
tem, but the sewers discharge
untreated wastewater to the Rio
Bogota. Water is taken from the
heavily polluted river to irrigate mar-
ket crops, with inevitable negative
health consequences, particularly to
unwary visitors.
The city of Sao Paulo in Brazil is
illustrative of large, rapidly growing
urban areas that confront water
shortages while planning extensions
to their sewerage systems and
wastewater treatment plants. A 3.5-
m3/s (80-mgd) module of a sec-
ondary treatment plant went into
operation in 1988 in the western
part of the city in the vicinity of
rapidly growing urban and industrial
areas. The quality of the effluent was
so high that pilot-plant studies were
initiated to determine whether coag-
ulation, sedimentation, and sand fil-
tration would produce an effluent
that would meet quality require-
ments for urban reuse.
The research results were so
encouraging that Sao Paulo is now
surveying industry requirements for
nonpotable water. Paper and chemi-
cal plants are the largest water users.
Other uses, such as seasonal land-
scape and local market crop irriga-
tion and toilet flushing in the large
office and residential buildings that
characterize SSo Paulo, are also
being evaluated. Further pilot-plant
studies are being undertaken to
develop design criteria for reclama-
tion, with the aim of eliminating the
sedimentation step, which sharply
reduces coagulant dosages.
The Beijing-Tianjin region of
China, with a total area of 28,000
km2 (11,000 sq miles) and a popula-
tion of about 18 million, 60% of
which is urban, provides another
example of the potential for reuse. In
1984, water allocations totaled about
200 m3/s (4500 mgd)—about 65%
for agriculture and 35% for industrial
and domestic use.* Studies showed
that the most economical source of
additional water for the region
would be through reclamation of
wastewater for agricultural, industri-
al, and domestic uses with the recog-
nition that, Over lime, the reclaimed
water for agriculture would be
switched to urban and industrial use.
The major problem is that much
of the region's population is not yet
served by sewerage, and that only
about 10% and 20% of the municipal
wastewater in Beijing and Tianjin,
respectively, receives treatment. Pro-
jects for urban sewerage, wastewater
treatment, and water reclamation
and reuse are underway. It is expect-
ed that a total of about 25 m3/s
(600 mgd) will be available for non-
potable reuse in 2000.
The practice of nonpotable reuse
will also be valuable in the arid Mid-
dle East:and North Africa. Other
than in oil-rich countries, the focus
has been on reclamation of urban
wastewater for agriculture. Reclama-
tion in the region has followed the
pattern elsewhere, where farmers
take water from polluted drains and
rivers that would be dry most of the
year except for the wastewater. This
focus is understandable, as the tradi-
tional priority use for fresh water in
arid areas has been agriculture. How-
ever, it is now being recognized that
in many countries in this region,
urban and industrial demands for
water may constitute 30 to 45% of
the total demand, representing a
substantial need, but also providing a
potential source of reclaimed water.
Plans for Jordan exemplify the new
approach to water reclamation.
About 70% of the population is
urban, and this percentage is grow-
ing. The portion of total water
demand for urban and industrial use
is expected to increase from about
16-Selected Readings on Water Reuse
-------
Figure 1: Typical Flow Diagram for Los Angeles County Sanitation Districts Reclamation Plant.
Chlorine and
coagulant Chlorine
Final settling r—|_Mixer r~l Pumo
tank I
-------
WATER RECLAIS/PON/REUSE
U.S. WATER REUSE:
CURRENT STATUS
AND FUTURE TRENDS
Kenneth J. Miller
The hydrologic cycle repre-
sents the ultimate water-
reuse process: the finite
amount of water on the
planet undergoes continu-
ous use and regeneration
while travelling through the
various stages of the hydro-
logic continuum. Today, the world's
rising population and its concurrent
increase in industrialization have out-
paced the slow-moving natural cycle.
Many areas already lace severe water
shortages, and things are
only going to get worse.
To meet the growing
demand for water, the
pace of regeneration and
subsequent reuse must be
accelerated.
Planned, unplanned,
direct, and indirect water
reuse have been practiced
for over 2000 years.
Unfortunately, water-
reuse technology has been
negatively affected by the
public's reticence to
accept historical and exist-
ing reclamation practices.
The best example that
supports this claim is the
water-supply industry in
the U.S. There are very
few surface-water bodies
in the U.S. that do not
receive wastcwatcr dis-
charges from the upstream munici-
palities and industries. In fact, by the
early 1950s, nearly all surface-water
and some groundwater supplies
showed evidence of man's industrial
and municipal wastes. The public
does not want to hear this, however,
and when a water reuse project is
proposed, the initial public reaction
is generally .negative.
Notwithstanding the sentiment of
the consuming public, indirect and
direct reuse has been contributing to
Agricultural irrigation in Santa Rosa, Calif., reclaims 16 mil. gal
ofwastewateraday.
our recreational and agricultural
water, aquifer recharge, and potable
water supply for more years than we
care to acknowledge.
BENEFITS OF WASTiWATER RECLAMATION
Benefits attributable to wastewater
reclamation generally fall into two
categories: supplementing available
resources and pollution abatement.
Water reclamation and reuse supple-
ment or enlarge what may otherwise
be a fixed quantity of water available
for use in a given area.
The quality of water
required for various
uses often dictates the
most desirable form of
reclamation and reuse.
For example, water for
most agricultural uses
and many industrial
uses need not be of as
high a quality as that
used for human con-
sumption. In such cases,
water reclamation
through crop irrigation
and use of treated efflu-
ents for industrial pur-
poses may relieve the
burden of supplying
these needs with high-
quality potable water.
Artificial recharge of
groundwater, either by
injection or spreading
18 -Selected Readings on Water Reuse
-------
of reclaimed water is often possible
in areas that depend largely on
groundwater sources. This also
results in augmenting the available
source by essentially "banking"
reclaimed water in the subsurface
against the time when withdrawal of
groundwater exceeds natural
recharge.
Finally, hi areas where sufficient
potable water is not available, highly
purified reclaimed water can be recy-
cled into the potable water system.
This should not be implemented
without considerable research cover-
ing all possible effects. It is not, how-
ever, an action without precedent;
direct or semi-direct domestic recy-
cling is now being practiced in some
areas of the world and will undoubt-
edly become more widespread.
The other major pollution abate-
ment benefit of water reuse and recla-
mation involves the removal of more
pollutants than conventional sec-
ondary waste treatment processes can
accomplish. Generally, the quality
standards for water reuse are such
that some additional waste treatment
is necessary to reduce oxygen
demand; nutrient content; avoid
undesirable algal growths; remove
suspended solids, color, taste, odor,
and refractory materials; and remove
or inactivate potential disease-causing
organisms.
In the U.S. today, water reuse
practices can be broken down into
the following categories: indirect
potable reuse, agricultural reuse,
urban landscape irrigation, industrial
reuse, groundwater recharge, and
potable reuse demonstration.
INDIRECT POTABLE REUSE
Indirect potable reuse is practiced
by nearly all communities dependent
on surface water. The difference
from city to city can, in several
instances, be quantified by the dilu-
tion factor. The classic case in the
U.S. is the Upper Occoquan Sewage
Authority (UOSA) that provides
potable water to the suburbs of
Washington, D.C.
The 9.8-bil.-gal Occoquan Reser-
voir—the principal water supply in
Northern Virginia—serves more than
660,000 people. In the 1960s,
before the formation of UOSA in
1971, discharges of conventionally
treated wastewater deteriorated the
reservoir's water quality. To reverse
this trend, the Virginia State Water
Control Board adopted a compre-
Toble 1—Agricultural Reuse Statistics
Agricultural Reuse Statistics
Leesburg, Fla.
maximum reuse volume:
irrigation area:
reservoir capacity:, .~T....~
pumping station capacity:
irrigariqn pipeline: '"'..
irrigation guns/gun spray rate:
Maui, Hawaii
maximum', reuse, volume:
irrigation area:
distribution system type: ...'."'."..
distribution distance:
Sonora, Calif.
reservoir capacity: ."."."...
distribution system:
number of release points:
irrigation area:
flow rate, per release point:
3 mgd (3400 ac-ft/yr)
330 ac of total 915-ac site
10 mil. gal
6400 gpm
44,000ft :
83/620 gpm
4 mgd (4500ac-fr/yrj -
400 ac
3 side-wheel roll systems
960ft
;T800ac-ft "
9 miles
19:: :.-.".'..:.:::.:
1300ac
100 to 1300 gpm
hensive policy that required con-
struction of a highly sophisticated,
regional, advanced wastewater recla-
mation plant to replace the 11
largest existing secondary treatment
plants, and to reclaim the wastewater
as a water resource.
Criteria accompanying the policy
specified treatment standards for
UOSA that are among the most
stringent in the U.S. Additional cri-
teria established treatment processes
deemed necessary to achieve the pre-
scribed level of treatment. A 15-mgd
treatment plant designed to meet
these criteria began operation in
June 1978 (see Box). The facility
has performed so well that the
plant's capacity has been expanded
to treat 27 mgd and planning con-
tinues for further expansion to 54
mgd. Operating costs for conven-
tional and advanced wastewater
treatment are $0.83/1000 gal to
$1.37/1000 gal.
AGRICULTURAL REUSE
To provide for its inevitable
growth and to minimize impact on
its natural environment, in 1970,
Leesburg, Fla., began exploring ways
to improve its wastewater treatment
plant and to discontinue the practice
of discharging effluent to Lake Grif-
fin. Efforts culminated in an
improved 3-mgd (3400 ac-ft/yr)
secondary treatment plant and new
wastewater reuse irrigation system,
which began operation in January
1981. Effluent was diverted away
from Lake Griffin by pumping 8
miles west of the plant. At this site,
approximately 330 ac are irrigated
with reclaimed wastewater.
This wastewater reuse irrigation
system is currently the largest solid-
set (fixed-gun) system in the state
(Table 1). Because of the seasonally
high water table, approximately 100'
ac of the irrigated areas are planted
with Coastal Bermuda grass, which is
harvested using city-owned agricul-
tural field machines and tractors.
Reclaiming wastewater for irriga-
tion not only makes Maui Hawaii's
first large-scale wastewater reclama-
tion facility and new collection sys-
tem a zero-discharge plant, but also
converts the reclaimed wastewater
into a valuable resource for the arid
Kihei region. The Kihei secondary
treatment plant serves Maui's south-
west coast and has an average design
capacity of 4 mgd (Table 1).
Designed to eventually serve a
4400-ac area, the collection system
includes eight pump stations that
deliver collected wastewater to the
main-9-mgd pump station that deliv-
ers wastewater to the Kihei plant.
Most of the reclaimed water is
used for irrigating ranch land and
newly landscaped roadways. About
250,000 gpd are treated further by
mixed-media filtration and chlorina-
tion to produce higher quality water
for park irrigation.
A standby injection well is used
Selected Readings on Water Reuse — 19
-------
WATER RECLAlftlON/REUSE
Table 2—Urban landscape Irrigation Statistics
Sh Petersburg, Fla.
delivery volume:
distribution network:
residential user fees:
industrial user fees:
Tucson, Ariz.
annual delivery volume
demonstration delivery volume:
spreading basin area:
extraction well:
monitoring wells:
suction lysimeters:
access wells:
Colorado Springs, Colo.
annual delivery volume
flow design:
daily flow design:
user fees:
Aurora, CoSo.
golf course irrigation area:
golf course reservoir:
plant effluent reservoir:
annual average volume reused:
distribution pipeline:
user fees:
68.4 mgd .. . .
92 miles
!i6/mo
$6/mo for the first ac-ff and
il .20 for each 0.5 ac-ff increment or
iO.25/1000 gal ($81/ac-ft)
35,000 ac-fr/yr
1000 ac-ft
3 ac
1 on-site
10
6
20
1000-1250 ac-fr/yr
7 mgd
$0.60/1000 gal ($196/ac-ft)
120ac
6 mil. gal
0.5 milgal
100 mil. gal
4 miles
$0.78/1000 gal
during the infrequent, but heavy,
rainy periods. The well takes the
reclaimed water through solid rock
layers into a cinder layer more than
100 ft below sea level.
The unique Tuolumne County
Water District in Sonora, Calif.,
reuse plan called for an irrigation
system rather than a wastewater dis-
posal system. Reclaimed water is
delivered to individual ranchers
based on a predetermined irrigation
schedule, adjusted each year for
cropping patterns, rainfall, and other
factors. Over 30 ranchers, with a
combined 1300 ac, will use the
reclaimed water for irrigation.
Acceptable uses of the reclaimed sec-
ondary effluent, according to the Cal-
ifornia State Department of Health,
include irrigation of pasture, fodder,
fiber, or seed crops, plus stock-water-
ing and aesthetic uses where public
contact is prohibited.
Each rancher signs a contract with
the district to take a specified quanti-
ty of water—depending on irrigated
acreage—during the April through
October irrigation season. The water
is free, but the rancher agrees to take
the water for 20, 30, or 40 years.
The contract is also binding on suc-
cessive property owners. If a rancher
does not take the water, the district
may enter'the land and apply the
water as contracted. To provide sys-
tem flexibility, each rancher agrees to
take all water made available up to
125% of the contracted amount. At
the same time, the district is obligat-
ed to make every effort to temporari-
ly reduce the water delivered in any
given year if there are cropping pat-
tern changes.
A unique feature of the irrigation
system is the automated operation of
the irrigation turnouts (Table 1).
Solenoid-actuated, hydraulically
operated globe valves on each pipe
turnout are remotely operated by
command from a control panel at
the Sonora Treatment Plant. Com-
mands are transmitted by radio sig-
nals initiated on a keyboard at the
treatment plant. Flow rates and
totalized flows at each turnout can
be displayed on a cathode ray tube
(CRT) screen or line printed on
command at the treatment plant
control panel. The remote station
transmits actual flow data to the
CRT for visual confirmation.
URBAN LANDSCAPE IRRIGATION
The use of reclaimed wastewater
for urban irrigation of landscaped
areas is one of the fastest growing
reuse types in the U.S. Many munici-
palities find this die easiest and least
costly method of reuse. The benefits
can also be great because exterior
residential and commercial watering
on a yearly basis can average more
than 40% of a residential customer's
total water consumption in arid and
semiarid areas.
In St. Petersburg, Fla., which is
located in a water-short region,
potable water must be piped in from
limited well fields located 30 to 50
miles from St. Petersburg.
In the mid-1970s, the city decided
to embark on a water-reuse program
to help solve its wastewater and
water supply problems by construct-
ing a limited dual distribution system
(Table 2) that would provide non-
potable water for irrigation of public
and private properties, including golf
courses, parks, school grounds, com-
mercial and residential sites, and
street medians.
Secondary wastewater treatment,
including grit removal, aeration, and
clarification, results in a greater than
90% reduction of biochemical oxygen
demand (BOD) and total suspended
solids (TSS). The wastewater is then
filtered, chlorinated, and placed in a
12-hour retention area. When neces-
sary, treated wastewater is rechlori-
nated. An auxiliary deep-well injec-
tion system ensures zero-discharge or
reduces use during rainy periods.
The dual water system has had a
profound effect upon the city's water
system, reducing potable water
demands by 10% to 15% of the water
use in 1982 and 1983. The potable
water savings in 1983 was nearly
14,700 ac-ft, saving the city thou-
sands of dollars. Reclaimed water is
sold to other city departments and to
private and public entities at $6/mo.
In 1982, Tucson, Ariz., initiated a
metropolitan wastewater reuse pro-
gram mandating that reclaimed
wastewater be used to irrigate all
municipal and private golf courses,
school grounds, cemeteries, and
parks, as well as for other identified
uses. By 1984, the Tucson Water
Department was operating the first
elements of a wastewater reuse treat-
ment plant, reservoir, and transmission
system. To date, $23 million has been
spent on the system, and a 10-year
capital development program calls for
20 -Selected Readings on Water Reuse
-------
an additional $40 million to complete
the system. The completed system will
provide approximately 35,000 ac-ft/yr
of reclaimed wastewater.
Because irrigation water demands
vary as much as 400% from winter to
summer, subsurface storage of
reclaimed wastewater in an aquifer
storage-and-recovery system was
installed. A demonstration recharge
project showed that effluent could
be safely recharged and later recov-
ered. The recharge system has been
expanded for large-scale controlled
recharge and recovery.
Colorado Springs, Colo., is locat-
ed at the eastern base of the Rocky
Mountains in a water-short area. To
reduce dependence on water from
the western slopes of the mountains,
in the early 1960s the city imple-
mented a limited dual-distribution
system in which reclaimed wastewa-
ter and surface water from a nearby
stream was used to meet major irri-
gation demands. This is one of the
oldest operating systems in the U.S.
in which reclaimed wastewater is
used for urban landscape irrigation.
Reclaimed water, which comes
from the city's secondary wastewater
treatment facility, is recycled through
two major distribution systems that
parallel the city on the east and west
sides (Table 2). Current users include
parks, golf courses, cemeteries, and
commercial properties. Each site must
provide its own pumping to meet
individual pressure requirements.
Since 1970, Aurora, Colo., has
used reclaimed domestic wastewater
to irrigate the Aurora Hills Golf
Course (Table 2). Aurora uses an
average of 100 mil. gal/yr of
reclaimed wastewater pumped from
the Sand Creek Wastewater Reclama-
tion Facility to an onsite nonpotable
water reservoir. In 1982, four city
parks were added to the reclaimed
water system, and their irrigation
requires an additional 50 mil. gal/yr.
The plant uses conventional
screening and grit removal followed
by aeration and final clarification. A
chlorine solution is added to the final
clarifier effluent immediately
upstream from the contact basin.
From an onsite 0.5-mil.-gal reser-
voir, the effluent is either reused or
discharged into a nearby stream. The
reuse system pumps the water from
the reservoir through multi-media
pressure filters and a 14-in.-diameter
pipeline.
In 1982, when irrigation of city
Table 3—Inverness Reclaimed Wastewater Characteristics
Characteristics
Concentration
5-day BOD
Total suspended solids
Total dissolved solids
Ammonia nitrogen
Sodium
Sulfur oxide
PH :
Fecal coliform
20 mg/L
20 mg/L
460 mg/L
14 mg/L
20 mg/L
30 mg/L
6.9 to7.3;
20 organisms/100 mL
Table 4—Water Factory 21 Performance and Requirements
Constituent
Secondary
effluent
Blended
injection
water
Requirements
for blended
injection
water
COD,:mg/L : : 130
Methylene blue active
substances, mg/L 2.7
Ammonia nitrogen, mg/L 45
Cadmium, mg/L 29
Chromium, mg/L .154
Mercury, mg/L 9
E-coli, MPN/1 00 ml 41 x ID6"
Turbidity, NTU 36
10
0.08
0.9 ,
0.6
88
2.4
>2
0.4
so •'.•;_ :
0.05
1.0
10
50
5
>2 •... : :v:
1.0
parks began, the reuse facility's
capacity was doubled, and the plant's
effluent standards were tightened.
When reclaimed water was used
exclusively for golf course irrigation,
the standards required a discharge
limit of 30 mg/L each of BOD and
TSS and 200 fecal coliform organ-
isms/100 mL. However, because
football and soccer are played at the
parks—sports that promote frequent
human contact with irrigated grass—
the mean total coliform standard was
made more stringent at 23 col-
iform/100 mL.
Process modifications were made
to meet the proposed standards,
including the addition of a flow-
paced jet disinfection system to
replace the old chlorine solution sys-
tem. The reuse water for the park is
taken directly from the line that
feeds the onsite reservoir, rather than
from the reservoir itself, thus maxi-
mizing the available chlorine residu-
al. In the filter complex, a polymer-
feed system was added to improve
solids recovery hi the pressure filters.
An additional chlorine-feed system
allows for post-chlorination of all
reclaimed water. The 4-mile pipeline
allows for an additional 80-minute
contact time at peak pumping rates.
Three operational problems are
currently being addressed. To allevi-
ate problems with algal growths,
which contribute to unsightly condi-
tions and some sprinkler nozzle-
clogging, algacides are used on a
continuous basis. To prevent reser-
voir debris from causing nozzle-clog-
ging, a self-cleaning drum strainer
was installed on the pump discharge.
Salt buildup in low-lying areas where
ponding of surface runoff occurs is
being mitigated by eliminating
ponding or by seeding those low-
lying areas with more salt-resistant
strains of grasses.
The economics of the Sand Creek
reuse program have been quite favor-
able for the city. In the past, an aver-
age of 100 mil. gal/yr were used for
irrigation. The 1980, costs of the
reuse system, including debt service
of the original filtration complex and
transmission line, but excluding irri-
gation pumping costs, averaged
$0.43/1000 gal.
Since 1975, the Inverness Water
and Sanitation District, Colo., has
reclaimed wastewater from the com-
mercial office park it services to irri-
gate the park's 18-hole, 140-ac golf
course. The park, located south of
Denver, will ultimately have over
Selected Readings on Water Reuse -21
-------
WATER RECLAlMlON/REUSE
Table 5—Denver Demonstration Plant Quality Goals
Characteristic, unit of measure
Average,
potable
water
Turbidity .., :..._.n_i1.711711777._.:;:.:::;.:17:: 0.67:11:.
Carbon alcohol extract, mg/L 0.09
Alkalinity,.mg/LasCaCO3 :i.777 77117777777.160.077771
Harmful organics None present
Suspended solids, mg/L 1,'....!„.71771111.77710.0:: 771
Total coliform, no./l 00 mL 0.1
Total dissolved solids, mg/L '....".. 7.1 11 7777.: 1 157.0.1171
Fecal coliform, no./l 00 mL 0.0
Nitrate nitrogen, mg/L.717 7-1711 71777 711.I7D".3171
Fecal strep, no./l 00 mL 0.0
Ammonia nitrogen, mg/L. 7777.111771771717777.' 70.07717
Virus None present
Total phosphate, mg/L as Pill 777177777711777770107.. 177
Gross metals None harmful
Hardness, mg/L as CaCO3 1 .777 77.7 17188.0 777 7
Taste Unobjectionable
BOD, mg/L 77 77 77777 1:117717177
-------
1000 ac-ft/yr of potable water.
Water was an important raw mate-
rial for the initial 200-MW stage of
the R.D. Nixon Power Plant, a coal-
fired, steam/electric plant near Col-
orado Springs, Colo. Although
brackish, the well-water supply was
selected to provide water to the facil-
ity. As the power plant expands,
however, reclaimed water will be
relied on because the well-water sup-
ply is limited. With conventional
blow-down practices for cooling-
water systems relying on well water,
effluents from the power plant would
exceed state water-quality limits for
dissolved salts and metals in the small
receiving stream. Thus, it was neces-
sary to develop an effluent recovery
and recycle system that would allow
these supplies to be reused. The
selected process recovers and recycles
power plant cooling-water effluent,
attaining zero discharge. Well water
is softened by ion exchange; effluent
is treated and recovered by floccula-
tion, clarification, filtration, reverse
osmosis, and vapor-recompression
evaporation. Brine concentrates are
disposed in evaporation ponds.
Within the recovery system, flows
range up to 1 mgd with salinities
ranging from one-fifth to over five
times that of seawater.
The system produces water and
treats effluents for less than alterna-
tive systems using municipal waste-
water or purchased water.
GROUNDWATER RECHARGE
In 1975, the Orange County
Water District (OCWD) began oper-
ating a water reclamation facility—
Water Factory 21—capable of
reclaiming 15 mgd of secondary
effluent and injecting it into the
coastal aquifer to prevent seawater
intrusion and to recharge the exist-
ing potable groundwater basin.
Processes similar to those used at
South Lake Tahoe, Calif., along with
breakpoint chlorination and reverse
osmosis, were selected. This combi-
nation was chosen to help ensure a
product water able to meet drinking-
water standards. Blending of
reclaimed wastewater with at least
50% desalinated seawater or deep
well water was provided as further
insurance.
Specific unit processes include lime
clarification with sludge recalcining,
ammonia stripping, recarbonation,
breakpoint chlorination, mixed-
media filtration, activated-carbon
adsorption with carbon regeneration,
post-chlorination, and reverse-osmo-
sis demineralization.
The 5-mgd, high-pressure, reverse
osmosis system was designed to
operate in parallel with the 15-mgd
activated carbon facility. Today, the
activated carbon system operates in
standby mode largely because of
high-quality secondary effluent and
because of reduced groundwater
recharge needs.
Performance and treatment
requirements for Water Factory 21
are shown in Table 4. Total capital
and operating costs, based on 1983
dollars, were estimated to be
$1510/mil. gal (491/ac-ft). The
lime/reverse-osmosis process tested
at Water Factory 21 offers significant
potential for meeting treatment
needs. The process would eliminate
ammonia stripping, sand filtration,
and activated-carbon adsorption and
regeneration. Costs for the new low-
pressure system are estimated to be
$1346/mil. gal ($438/ac-ft), as
compared to $1510/mil. gal
($492/ac-ft) for the Water Factory
21 treatment trains.
POTABLE REUSE DEMONSTRATION
Chanute, a relatively small com-
munity in southeast Kansas, relies
entirely on the Neosho River for its
water supply. Chanute maintained
and operated a conventional rapid-
sand-filtration plant to treat Neosho
River water before it entered the
city's potable water distribution sys-
tem. During the years 1953 through
1957, a record drought struck the
Neosho drainage basin. Flow
decreased and, in early 1956, it prac-
tically ceased. Although all possible
water conservation measures were
instituted and flow-augmentation
procedures were attempted, the
water supply continued to dwindle.
On October 14, 1956, without any
fanfare, city officials opened a valve
that permitted mixing of effluent
that had received conventional sec-
ondary treatment with water stored
in the Neosho River channel behind
the water treatment plant impound-
ment dam.
The recycling process was used for
a total of 5 months during the fall
and winter of 1956 and 1957. Dur-
ing this period, treatment removed,
on the average, 86% of the BOD and
76% of the chemical oxygen demand
(COD) contents of the wastewater.
It substantially reduced both total
nitrogen and ammonia-nitrogen
concentrations; detergent concentra-
tions decreased an average of 25%. It
was estimated that one complete
cycle through the waste treatment
and back through the water treat-
ment required about 20 days. Thus,
during the total period of time dur-
ing which water recycling was prac-
ticed, the same water passed through
the treatment plant approximately
seven times.
The Denver Water Department is
operating a 1-mgd demonstration
plant that produces potable water
from secondary treatment plant
effluent. The need for the project
grew out of the recognition that
additional conventional sources, if
available, might cost $5000/ac-ft to
develop b^ the year 2000; and indus-
trial reuse of wastewater would not
substantially reduce water demands.
The construction of the demonstra-
tion plant is part of a $35-million, 7-
year project by the department to
demonstrate that high-quality water,
equal to or better than Denver's cur-
rent drinking water, can be produced
safely and reliably from treated
wastewater treatment plant effluent.
EPA is also participating in this
demonstration project by contribut-
ing approximately $7 million of the
total cost.
The demonstration plant cost
approximately $16.2 million to
build. Its capacity is 1 mgd for the
initial processes through the first
stage of carbon adsorption, and 0.1-
mgd for the remaining processes.
Water treated by this facility has
undergone 5 years of extensive test-
ing for more than 200 potential con-
taminants, and an exhaustive pro-
gram of health-effects testing is
underway.
None of the reuse water produced
from this demonstration plant will be
added to drinking-water supplies. It
will be allocated strictly for industrial
use at the Metropolitan-Denver
Sewage Disposal District No. 1
(MDSDD) Treatment Plant and for
the extensive testing program. If the
absolute dependability of this reuse
facility is established, reuse may be
instituted on a full-scale basis.
The treatment process was devel-
oped from information obtained
from 10 years of operation of a 5-
gpm pilot plant by the Denver Water
Department and University of Col-
orado and from information gained
by CH2M Hill from the design, con-
Selected Readings on Water Reuse -23
-------
WATER-KECLAMATIdN/REUSE
struction, and review of the Lake
Tahoc Advanced Wastewater Treat-
ment Plant, Occoquan Advanced
Wastewater Treatment Plant, and
several other projects.
The MDSDD Treatment Plant is
adjacent to the Denver Water
Department's reuse demonstration
plant. Unchlorinated secondary
effluent is pumped from the treat-
ment plant to the reuse plant. Sec-
ondary effluent enters the reuse plant
at the rapid-mix basins, where lime is
added and mixed with the water.
Lime facilitates the removal of sus-
pended particles, phosphorous, and
some heavy metals, and aids in the
destruction of viruses and most
microbiological organisms. Water
then flows to flocculation basins. If
necessary, aluminum sulfate and
polymer are added to enhance floc-
culation and settling characteristics.
Following flocculation, the water
enters the chemical clarifiers, which
remove scttlcablc solids and reduce
solids loading into the filters. The
%vater then passes into the recarbona-
tion basin, where carbon dioxide is
added to reduce the pH to between 7
and 8, and through ballast ponds to
equalize the flow to downstream pro-
cesses. Pressure filters remove most of
the remaining suspended particles,
improving the subsequent treatment
steps. The treated water then flows
into the selective ion-exchange pro-
cess, which removes nitrogen in the
form of ammonium (NH4) from the
process flow by passing the water
through a naturally occurring zeolite
media (dinoptilolite). Sodium chlo-
ride is added to regenerate the zeo-
lite media. The ammonia recovery
and removal system them removes
the ammonium ions from the regen-
erate solution. Ammonium sulfate, a
commercial-grade fertilizer produced
as a byproduct of the system, is
stored onsitc and sold to reduce
treatment expenses. The water then
passes through first-stage carbon
adsorption process. This process
removes remaining dissolved organic
compounds. The product water then
passes through the ozonation pro-
cess. Ozone oxidizes organic sub-
stances that remain after first-stage
carbon adsorption and also acts as a
primary disinfectant. The water then
passes on to second-stage granular
activated carbon treatment where the
remaining organics that have been
rendered more absorbable by ozone
oxidation arc removed. In addition,
biological activity on the carbon fil-
ter is used to remove organics by
biodegradation.
The demonstration plant can
regenerate and store spent granular
activated carbon. A fluidized bed
regeneration furnace that can operate
at a maximum temperature of 2000°
F regenerates the carbon that has
adsorbed 'the. organics. The water
then flows to the reverse-osmosis
system where dissolved salts are
removed back to the range of Den-
ver's present supply. Reverse osmosis
also serves as the final physical barrier
to the passage of a variety of poten-
tial contaminants.
Following reverse osmosis, the
water passes through an air-stripping
tower that removes carbon dioxide
and volatile organic compounds. The
final product water is treated with
either chlorine dioxide or chlorine to
destroy any disease-causing organ-
isms and provide a residual disinfec-
tant for transmission and storage.
Recognizing that true standards
for potable wastewater reuse fail to
exist, the Denver Water Board elect-
ed to meet the same water quality as
the potable water currently being
consumed by the Denver citizens.
Table 5 contains a partial list of the
water-quality goals for this demon-
stration facility.
WATER REUSE PRACTICES IN THE FUTURE
In 1983, Tampa began a study to
determine reuse alternatives for an
extremely high-quality effluent from
the Hooker's Point Advanced
Wastewater Treatment Plant. To
evaluate the effects of additional
treatment on the effluent, a pilot
plant has been constructed with
capabilities that, include pre-aeration,
high-lime treatment, multi-media fil-
tration, reverse osmosis, ultrafiltra-
tion, granular activated carbon, and
disinfection.
A research program has been
designed to determine the health
risks associated with reuse of the
pilot-plant:product water as a com-
ponent blended into a raw potable
water supply.
The ultimate goal of the Tampa
Water Resources Recovery Project is
to treat ah advanced wastewater
treated effluent to potable quality.
The final product will be placed into
the Tampa bypass canal to recharge
an adjacent aquifer and then flow
into the Hillsboro River upstream of
a raw water intake. To date, water-
quality parameters of the treated
water exceed those of the river water.
Surface supplies, while improving,
may never be swimmable and fishable,
if indeed they ever were, and ground-
waters are showing evidence of man's
encroachment and of his industrial
renaissance. The quality of many sur-
face supplies, like that of the Hills-
boro River, will continue to deterio-
rate until planned reuse and its associ-
ated treatment process will offer a
higher-quality product than conven-
tional treatment. The need for ever-
improving advanced wastewater treat-
ment processes and recycling technol-
ogy will continue to grow worldwide
as the population increases and the
standard of living of the third-world
developing nations begins to improve.
The key to our success in dealing with
the water-resource problems will lie in
our ability to extend and augment
existing supplies through various
reclamation processes.
The task of applying current state-
of-the-art in water reuse will tax the
ingenuity of all sectors of our soci-
ety, not just the water-supply com-
munity. Research and demonstration
projects will be required. Moreover,
water reuse will not be limited by
the ability to successfully treat
wastewater, but by the costs associ-
ated with the construction and oper-
ation of the treatment. Water quality
standards will be required to process
or recycle water to qualities that will
be desired; conceivably, five or six
water quality standards for agricul-
tural use, alone, could be developed.
In addition to effluent discharge
standards, standards which relate
directly to industrial needs are likely
to be promulgated.
Water reuse in both the U.S. and
worldwide will inevitably increase as
existing water supplies are incapable
of meeting future demand brought
about by increasing world popula-
tions and industrialization. The
municipal, industrial, and agricultur-
al demands will, thus, have to be met
and, this prospect, thereby, clearly
reveals the need for expanded water
reuse research in the 21st century.
Kenneth J. Miller is vice president
and director of water engineering with
CH2M HILL Consulting Engineers
in Denver, Colo. This updated report
wets reprinted for 1987 Annual Con-
ference Proceedings, American Water
Works Association, Denver Colo.
24-Selected Readings on Water Reuse
-------
lEY
NOTES
m-Site Wastewater
leclamation and Recycling
iJohnlrwin
ith the onset of the
1990s, many com-
munities and town-
kips have been strug-
jling with the problem of
Dviding for increasing
tsidential and commer-
fcal growth at a time
rhen water resources are
|iore scarce and envi-
jnmental capacity to
Idequately manage
astes is severely limited.
lis is evidenced by the
movement in many
bwns and states to adopt
lew standards for water
Dnservation in plumbing fixtures. It is also
Ividenced by the significant number of
|ommunities that have imposed sewer
noratoriums or sewer-capacity restrictions.
finding additional water supplies and ex-
landing wastewater treatment plant ca-
pacity is expensive, sometimes impractical,
nd, at best, involves long-range planning
aen an immediate solution to the prob-
is needed.
On-site water reclamation and reuse
Jystems have been successfully used to solve
tiese problems. A rural school district in
Central Texas experienced significant
rowth, making it necessary to build a new
feOO-student high school. Numerous po-
lential sites were evaluated. None of the
Icceptable and available locations were
lerved with public sewers, and poor soil
conditions in the area made conventional
Jeptic and drainfield wastewater manage-
ment very difficult. Some means had to be
found to reduce the wastewater volume so
hie site could be served with only a small
iibsurface discharge. On-site, advanced
vastewater treatment and use of reclaimed
ter for flushing toilets within the school
educed the wastewater discharge by about
35%. This solution to a difficult wastewa-
jter management problem also had a major
pact on water conservation for the en-
|tire school district.
In southwest Houston, Tex., the Alli-
nce Bank and Trust Company owned
|several acres of prime commercial property.
lis site was served by the municipal sewer
(district, but years of growth and the inabi-
ity to increase the capacity of the existing
municipal wastewater facility resulted in a
sewer moratorium. Under the moratorium,
a new project could discharge no more than
1600 gpdofwastewater/ac, meaning new
office construction could not exceed
16,000 sq ft/ac of
property. This pro-
perty's very high value
could not support the
small amount of devel-
opment, which the
sewers would permit.
But using an on-site
wastewater treatment
and recycling system
and water-conserving
fixtures permitted
construction of a
200,000-sq-ft facility
on the site. The waste-
water system is in the
building's basement
and provides reclaimed
water for toilet flushing
throughout the 12-
story structure. The sewer discharge is less
than 1000 gpd when the building is fully
occupied.
Montgomery Township, N.J., a rural
area adjacent to Princeton, is undergoing
tremendous development pressure as a
result of hi-tech growth near Princeton
University. The township is without sew-
ers and residents have no desire to build a
wastewater facility that would encourage
commercial and industrial development.
But development in the township seems
inevitable, and office and research facilities
are therefore not discouraged. Local resi-
dents are concerned about the impact of
this development on the local water supply
resources and on groundwater quality.
In 1985, the Squibb Corporation began
developing a 366,000-sq-ft office and R&D
complex in Montgomery Township. Initial
construction involved a 60,000-sq-ft office
which would use a conventional septic and
subsurface drainfield wastewater system.
During initial construction, the New Jersey
Department of Transportation established
a new highway alignment that crossed
through a major portion of the Squibb
property. The only way to proceed with
the project was to substantially reduce the
wastewater volume and the corresponding
size of the subsurface disposal system. On-
site wastewater treatment and recycling of
reclaimed water for toilet flushing was
evaluated and found to satisfy project re-
quirements. In addition, the on-site recla-
mation system was found to be less costly
than alternatives.
The success of this project, which has
been on-line for 3 years, has convinced the
Montgomery Township officials of the
environmental benefits of recycling, water
conservation, and a much lower pollution
impact, and now other projects within the
township are on-line or are in the design
phase. With on-site treatment and recy-
cling, Montgomery Township has been
able to control growth, avoid a major sewer
infrastructure expense, and achieve envi-
ronmental goals.
The city of Santa Monica, Calif., is also
evaluating the impact of growth under
severe resource restrictions. The city has a
controlled but healdiy development climate
which has added many new facilities over
the past few years. This continuing devel-
opment however, is viewed with mixed
emotions. In California, water supplies are
limited. For years citizens have been in-
censed by periodic sewage overflows into
Santa Monica Bay. Last year, Los Angeles
County, from which Santa Monica con-
tracts for wastewater disposal, issued a sewer
moratorium which could severely restrict
new development. These conflicts between
growth and environmental resources have
led Santa Monica to become an outspoken
advocate of water conservation and envi-
ronmental protection. The city has been a
forerunner in adopting strict water con-
servation regulations. In addition, on sev-
eral major development projects, it has re-
quired use of on-site wastewater treatment
and water reclamation.
The first example of this aggressive ap-
proach to resource conservation is a project
called Water Garden, a 1,300,000-sq-ft
complex consisting of four buildings con-
taining office and retail uses. The typical
wastewater volume from a facility of this
size is approximately 70,000 gpd. Using
ultra-low flush toilets and other water
conserving fixtures required under city or-
dinance, the projected flow can be reduced
to 40,000 gpd. Using a creative mix of
landscaping (which includes a small orna-
mental pond system), on-site wastewater
treatment, and reclamation for landscape
watering and pond evaporative loss make-
up will virtually eliminate any sewer dis-
charge during the project's first phase which
includes two buildings comprising 650,000
sq ft. The need for potable water for land-
scape purposes is also eliminated. Phase two
of the project is intended to incorporate a
second on-site wastewater treatment system,
which will recycle the reclaimed water fortoilet
flushing in the phase-two buildings. Total
water use can be reduced by about 75% and
wastewater discharge can be reduced by almost
95% in this project, which is currently under
construction.
Selected Readings on Water Reuse - 25
-------
WASTEWATER TREATMENT
A critical component in establishing a
successful on-site wastewater reclamation
facility is providing a reliable treatment
process that can produce reclaimed water
on a consistent basis. The figure shows a
system that has been used very effectively.
The process includes on-line flow equal-
ization and emergency storage tanks, bio-
logical nitrification and denitrification,
membrane filtration, activated
carbon, and disinfection. The
emergency storage tank provides
several days' flow accumulation
in the event of any mechanical
malfunction. Membrane filtra-
tion is used to provide fail-safe
clarification of biological process
solids down to a particle size of
approximately .005 (j. Granular
activated carbon is used for color
removal and provides a backup
for organic carbon removal.
Disinfection with ultraviolet light
or ozone provides an essentially
pathogen-free effluent. Post-
chlorination can also be added
to provide a distribution system
residual. Typical water quality
achieved is BOD and TSS < 5
mg/L, turbidity < 0.5 NTU,
and total colifbrm^.2.2/100mL.
Just as critical and perhaps
more important is the operation
and management of the recla-
mation facility. There is no
greater assurance of success than
providing single responsibility for
process equipment and system
operation and management.
Several years of providing systems
under a wastewatcr management
service contract have demon-
strated that process performance
is more reliable when routine
preventive maintenance and in-
spection is provided rather than
periodic emergency response.
Long-term operating costs are
most effectively controlled when
the equipment manager is made
responsible for parts and equipment re-
placement under a fixed management fee
arrangement
REGULATORY OBSTACLES
The use of on-sitc water reclamation and
recycling, although a successful and grow-
ing practice, is relatively new and is not yet
widely used. In many states, lack of expe-
rience with water reclamation and lack of
specific standards and regulations have se-
verely restricted its use. Four areas are of-
ten obstacles to reclamation.
Regulatory codes. Some codes impose
guidelines for wastewater treatment but
don't recognize water conservation and
water-reclamation activities. Many states
use a "cookbook" code approach involving a
lengthy variance procedure for applications
which aren't part of the listed recipes.
Lack of a standard for reclaimed wa-
ter quality. In many states projects can be
rejected or significantly delayed in the ab-
sence pf an approved standard.
Ambiguous plumbing codes. Most
standards include language stating that each
plumbing fixture (including toilets and
Potable Water
luctant to consider using noa-potah
water in a building because of a lack |
experience with procedures used
control dual plumbing systems.
More than 10 years of experience in t
U.S. with on-site wastewater treatment i
recycling in commercial facilities has derj
onstrated that it is a safe, environmenta
superior, and economically viable practid
There have been no public health pro!
N6n-Potable
'Flush Water
Color
Removal
Disinfection,
Solids Recycle
Trash Storage
Removal •_.
Biological Treatment
, Annual
-J Sludge
O Removal
Membrane
Filtration
urinals) shall be provided with potable wa-
ter except where not deemed necessary by
the administrative authority . The caveat
"except where not deemed necessary by
the administrative authority" was specifi-
cally added to the codes to encourage the
use of safe applications for non-potable
water, such as recycling. Many local ad-
ministrators are not aware of the purpose
of the enabling language and are unwilling
to consider such proposals.
Lack of confidence in standard
practices for controlling cross con-
nections. Although all the experience
with using reclaimed water for toilet
flushing has been successful, many
building and safety departments are re-
Discharge
to sewer or
disposal field
lems and use of recycled water has no|
caused any adverse reaction from buildin J
owners or occupants. The systems are reli|
able, efficient in producing a high-qualit
water for toilet flushing or landscape irril
gation, and have a positive impact on thJ
environment by conserving water and rel
turning a highly treated effluent back tq
the environment.
John Irwin is vice president of Thetfor\
Systems, Inc., in Ann Arbor, Mich. The abov\
presentation was given at the Conserv
Conference in August 1990.
26-Selected Readings on Water Reuse
-------
PRELUDE
Wastewater Reuse
Gains Public Acceptance
Twelve years ago, Orange County, Calif., Water District's
Water Factory 21 was completed. The widespread and
growing attention given to wastewater reuse over the past
dozen years is gratifying, if somewhat astonishing, to those
of us who have been concerned with reuse during this period. It
is clear that water resource planners now consider reuse as an
acceptable alternative method of meeting increasing water
demands, not only for agriculture, but also for municipal and
industrial uses.
The technological and engineering concepts underlying
wastewater reuse projects
are becoming increasingly
well understood. This is
true even with our knowl-
edge of health effects of
potable reuse, which has
been the most difficult
area in which to achieve
general acceptance. Indirect potable reuse, as from groundwa-
ter injection, appears to be fully accepted. Direct potable reuse
is just a few years away from implementation in Denver, Colo.,
and its public acceptance is expected to be fairly uneventful.
Planners, engineers, and the public have accepted waste-
water reuse; the spotlight next turns to the economists. These
economists playfully ask, "Well, it works in practice, but I
wonder if it will work in theory?"
On the Cover and In this Issue:
In this section, Water Environment &
Technology publishes the third installment of
a series on wastewater reuse and reclamation
made possible by the Environmental Protection
Agency. Economics and case studies in Irvine,
Calif., and in Florida are the selected topics.
"**" '^f
—Introduction to the paper,
"Economics of Potable and Non-
potable Wastewater Reuse," presented
at the 1987 American Water Works
Association Annual Conference
byj. Gordon Milliken of the Milliken
Research Group in Littleton, Colo.
Selected Readings on Water Reuse -27
-------
NEWS
Obstacles to Implementing
Reuse Projects
In 1988 the American Water Works
Association (AWWA) Research
Foundation commissioned a study
to determine what obstacles exist in
water reuse implementation and to
identify activities that could help
remove these obstacles. Information
about reuse projects, regulations,
practices, and experience was collect-
ed through a questionnaire and fol-
low-up telephone survey. The study
included 188 participants, most of
whom were selected because of their
expressed interest in or experience
with water reuse. The broad nature
and experience of the individuals
who provided input to the study
served to significantly strengthen the
recommendations and emphasized
the need for action.
Based on the experience of the
study participants, there are three
obstacles of primary concern when
implementing a reuse project: cost
effectiveness, information dissemina-
tion and education, and water-quali-
ty and health issues.
The degree to which these issues
become obstacles depends on the
type of reuse anticipated and the
environmental appeal of the project.
For example, if the reuse application
conserves a valuable water resource
or benefits the environment, it is
more likely to be acceptable to the
community.
In a few states, special issues like
water ownership are major deterrents
to reuse. For example, in New Mexi-
co, credits against groundwater
pumping are given to those cities
that return their treated effluent to
the river system. Reuse would entail
returning less effluent to the river
system, thus constraining die utility
to pump less groundwater. There-
fore, while conservation is encour-
aged, reuse is not.
QUANTIFYING THE OBSTACLES
The cost effectiveness of reclaim-
Ing water varies significantly with
current practices and raw water sup-
ply. Unusual circumstances would
need to exist in order to proceed
with a reuse project that is not cost
efFeetive. Most reuse projects have
resulted from a need to identify new
water sources. A number of reuse
applications have also grown out of a
need to find an alternative to more
stringent discharge standards.
Survey results demonstrate that
urban irrigation of public use areas
such as golf courses and parks, indus-
trial reuse, and agricultural reuse
projects are easiest to accomplish.
When project implementation is
economically appropriate, few seri-
ous obstacles exist. This is demon-
strated in California and Florida
where irrigation projects number in
the hundreds. The general public's
attitude about health and water qual-
ity is an occasional implementation
obstacle, but it is seldom the major
issue. However, if education, water
quality, and health issues are not
properly dealt with, even these easily
implemented reuse projects will be
halted.
The principal obstacle limiting
either direct or indirect potable reuse
is public attitude. Cost effectiveness
is also a significant obstacle to
potable reuse projects. However, the
results of the survey showed that,
unless careful attention is paid to in-
formation dissemination and water-
quality and health issues, a cost effec-
tive potable reuse project—either
direct or indirect—will be difficult to
implement.
Ten specific activities were recom-
mended in the study. However,
action is most urgently needed in
information dissemination to all par-
ties involved in potential reuse pro-
jects, including engineers, regulators
and other technical staff, community
officials, and the general public; and
water-quality and health-effects guid-
ance for the implementation of dif-
ferent types of reuse projects.
INFORMATION DISSEMINATION
Many of 'the barriers to reuse stem
from a lack of information. Fortu-
nately, much of the information
needed already exists. One of the
most pressing needs is to compile the
body of knowledge into a format
that those who are responsible for
implementing reuse can use. Equally
pressing is the need to assemble
information into a format that can be
presented and understood by the
public that is trying to make an
informed decision about a proposed
reuse project in its community.
An information dissemination pro-
gram covering the following subjects
can be key to the success of a reuse
program: the need for, availability
and cost of, additional water supplies
and the environmental impact of
reuse versus developing additional
raw water supplies; and the effective-
ness of the water-reuse technology
applicable to the type of reuse antici-
pated and the safeguards incorporat-
ed in the water reclamation and
reuse processes. Utilities practicing
indirect potable reuse found public
awareness of a water shortage to be
the best way to overcome a negative
public attitude.
WATER QUALITY AND HEALTH EFFECTS
There is a universal call for consis-
tency and informed decision making
in the area of guidelines and regula-
tions for reuse. A clearer definition
of requirements for both potable and
non-potable reuse projects is urgent-
ly needed.
A significant effort associated with
current reuse projects involves the
definition of treatment and water-
quality standards. Even where state
regulations qxist, significant effort is
often expended to define necessary
treatment requirements or to
demonstrate the efficacy of alterna-
tive treatment methods.
Assurances that the proposed
method of water reuse is safe may
not be adequate to allay public fears.
Regulatory agencies and the general
public want to know that the reuse
system will consistently perform at
levels that provide that safety.
Reuse projects that are the first of
their kind for a state or that involve
potable reuse generally require a
demonstration project. A well-
thought-out and staged reuse plan
that includes a demonstration pro-
gram will serve to generate confi-
dence and foster success.
CONCLUDING OBSERVATIONS
Attitudes will not change by them-
selves. A more concerted effort to
make water reuse a universally
understood and accepted water sup-
ply practice is needed.
—Scott B. Ahlstrom is division
manager for water and waste-water at
CH2M HILL in Denver, Colo.
28 - Selected Readings on Water Reuse
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Selected Readings on Water Reuse - 29
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The ever-increasing demands
for water have thrust water
reclamation practices to the
forefront of water and
wastcwater system planning
efforts throughout the
world. Because of skyrock-
eting populations and limit-
ed water resources, water and
wastewatcr districts in Southern Cali-
fornia received early lessons on the
importance of a careful, organized,
and comprehensive approach to the
successful design and implementa-
tion of water reuse systems. Main-
taining control, from planning stages
all the way to operational monitor-
ing, is key to a system that operates
effectively, economically, and, most
importantly, safely.
The Irvine Ranch Water District
(IRWD) serves an area of about
72,000 ac and an existing population
of 100,000 people. The service pop-
ulation is expected to grow to over
300,000 after the year 2000. The
district, located in Orange County
about midway between Los Angeles
and San Diego, provides potable
water service, treats and disposes of
wastcwater, and also distributes irri-
gation water for landscape and agri-
cultural uses.
The area is a semi-arid region
receiving only about 12 to 14 in. of
rain annually. The rainfall occurs
during the winter months, not dur-
ing the traditional growing season
when demand is highest. Even with
an extensive reservoir system built to
capture natural runoff, the water
docs not provide a year-round source
for irrigation for either landscape or
agricultural crops. Additional water
supply then must be either diverted
from the Colorado River to the east
and piped 240 miles to the district or
imported from Northern California
through a 450-mile system of canals,
reservoirs, and large pumping sta-
tions. Natural groundwater provides
an additional source.
To reduce the area's reliance on
these limited supplies, IRWD began
the installation of a dual distribution
system in the 1960s.
Dual distribution system. The
heart of the district's dual distribu-
tion system is the irrigation system
which contains the network of
pipelines that distributes reclaimed
water to its users. When the system
was designed, IRWD prepared an
Irrigation Master Plan outlining
future pipe sizes and locations so
To reduce reliance on limited water
supplies, Hie livine Ranch Water District in:
Irvine, Calif., developed a dual-distribution
* i* H !«. imJt tufa
^
that adeqiiate pressure and flow
could be maintained for all the
future uses. This was done to prevent
growth and retrofitting problems.
The irrigation system provides
water for three different uses. The
first system is for the landscape users
including parks, schools, street medi-
an strips, and homeowner associa-
tions that water open-space areas
within the district. There are about
850 individual meters for these
areas. Water is reclaimed mainly for
agricultural purposes such as or-
chard crops—oranges and avoca-
dos—but it.is also used in row crops
such as asparagus, corn, pole toma-
toes, peppers, and cabbage. There
are 12 individual meters for differ-
ent fields within the district.
The landscape irrigation and agri-
cultural systems serve a network of
about 107 miles of pipe varying from
2 to 54 in. in diameter. About 2050
ac are irrigated for landscape uses,
while the agricultural land comprises
about 1000 :ac. The sizes of these
two areas will vary as agricultural
land is taken out of service and dis-
placed by residential development in
the growing city area.
The third system, which provides
reclaimed water to high-rise build-
ings, is now in the development
stages. It will be used for toilets, uri-
nals, and trap drains, as up to 80% of
the water used in a high-rise may be
for toilet flushing.
30 -Selected Readings on Water Reuse
-------
WATER RECLAMATION/REUSE
* £ >•*• t. "* ^ •»•>*• jT•.-^^^!?^??^^9^4?
*.'-xl^SrfiEfe^y " tl""" "-*"""'"' "" - —" *"*-• * " ' ,...,»- j. .-., ... . -». . -.~_»..---.» ,....„..»
ENCOURAGING USE
Landscape irrigation is the main
end use of reclaimed water from the
dual system. Between 8000 and
9000 ac-ft/yr are used for landscape
irrigation, while the agricultural sys-
tem uses 3000 to 4000 ac-ft/yr. It is
projected that ultimately the 15-mgd
Michelson Water Reclamation Plant
will be able to supply almost double
the current amount for landscape
users as the agricultural demand
declines because of development in
the district.
The district requires new develop-
ments to be designed with dual dis-
tribution systems so that all appro-
priate areas can be irrigated with
reclaimed water rather than potable
water. In fact, IRWD has a set of
rules and regulations similar to city
ordinances that require developers to
use reclaimed water as a water con-
servation measure in extending the
supply of potable water throughout
the district.
IRWD has established the authori-
ty and a procedure for expanding the
dual system into the developing areas
by working closely with developers,
designers, and contractors as the sys-
tems are constructed. It has a set of
standard specifications that outline
the basic materials required for this
type of system. These materials
include the pipe, meters, strainers,
and various fixtures that are required
for irrigation.
The process of expanding the dual
system is atypical of many govern-
mental reviews, as it includes early
contact with the developing compa-
ny when it applies for a will-serve
notice. The will-serve certifies that
the district has reclaimed water avail-
able so the developer can proceed
through the city planning process
during which the tract map is
reviewed and approved. For the
development to receive approval, the
developer's engineer must put
together plans showing the distribu-
tion system to be built by the devel-
oper. This system is reviewed by the
IRWD reclaimed water section staff
that works with the engineer to
finalize plans and specifications. Once
Selected Readings on Water Reuse - 31
-------
the review is complete and the devel-
oper's plans arc approved, the devel-
oper engages a contractor to con-
struct facilities for the development.
CONFORMING TO THE SYSTEM
During construction, IRWD staff
provides on-sitc inspection as all the
facilities arc built to ensure that they
meet the standard specifications of
the district.
Once the developer has completed
a tentative tract map outlining the
scope of his development and
requested a will-serve, a service
agreement is entered into with the
district for water, sewer, and land-
scape irrigation service. As part of the
agreement, the district collects funds
to cover the plan check and inspec-
tion fees incurred during the process
of designing and installing the system.
Most of the equipment and pipe
used in the on-site facilities—those
on the property owners' side of the
meter—arc typical for the irrigation
industry. Special specifications
required by the district are used to
distinguish between the use of
reclaimed water and potable water
for irrigation. The health and safety
reasons for this provide added pro-
tection to the customer.
One of the most important princi-
ples of irrigating with reclaimed
water is that all facilities must be
clearly marked so that there is no
possibility of future cross connec-
tions to the potable system with
reclaimed water or vice versa. This is
carefully checked during the design
phase when IRWD staff work with
the design engineer to ensure compli-
ance with the standard specifications.
Specifications include the prohibi-
tion of hose-bib connections to the
reclaimed water system. This pre-
vents incidental use and possible
drinking of the water by users.
Quick-coupling valves used in the
reclaimed water system are operated
by a key with an Acme thread. This
thread is not used in the potable
water system. The covers on
reclaimed water quick-couplers are
required to be green and made of
rubber or vinyl. The potable system,
on the other hand, is distinguished
by having cither brass or yellow cov-
ers. All pressure piping used for the
reclaimed water system must be
labeled as reclaimed water by using
labeled purple pipe, marking the pipe
with a colored tape, or by actually
stenciling on the pipe "reclaimed
water." If potable water pipe is also on
the same site, it must also be labeled so
that the difference is obvious.
When IRWD evaluates the devel-
opment's plans, the acreage irrigated
must be provided. This is used to
predetermine watering rates using
evapotranspiration data and to check
meter readings for overwatering once
the system is on-line. It's also impor-
tant not to overlook basic items such
as the point of connection where the
landscape architect connects irriga-
tion hose to the IRWD system.
Often the architect will choose a
location without checking the best
available district facility, let alone
whether or not there is an IRWD
pipe on that particular street.
Pipe classes are required'to ensure
that they match district specifica-
tions, and water pressures and sprin-
kler patterns are set to cover areas
properly without overwatering. If a
project has several reclaimed water
meters, they are checked to ensure
that there are no cross connections.
Reclaimed water meters cannot be
cross-connected because of difficulty
in isolating problems if several
meters must be shut off. The word-
ing in plan notes is checked to
ensure that the district, is not
exposed to undue liability.
IRWD staff ensure that a master
pressure regulator or pressure-regu-
lating valves are used and require the
strainer screen to be 30 mesh or
greater to protect the sprinkler sys-
tem and the pressure regulator.
Another item is the inclusion of the
plan notes regarding the installation
of an on-site reclaimed water system.
This is a must, as it points out to the
landscape contractor what is required
by the district inspection team and
surveyor.
Last and not least, the IRWD
looks for incorrect items such as a
backflow device on the reclaimed
water system. Backflow devices are
not used in reclaimed water systems;
if they are installed in a reclaimed
water system they could cause confu-
sion because of the similarity to the
domestic water system.
During this plan check procedure,
as each plan set is received it is given
a permanent file number. File books
containing all communication or
comments made on a project from
start of construction to operation are
kept as a record for the future. The
architect provides a set of mylar
drawings of approved plans, which
are kept on file, thus completing the
file on each project.
Some of this information is input
to a computer, allowing IRWD staff,
by typing in the meter number or
account number, to bring forward
information on any irrigation project
built in Irvine 011 the Reclaimed
Water System.
FIELD REVIEW
Once the plans are approved,
IRWD monitors the actual construc-
tion of the project to ensure proper
installation and hook up. During the
field review, which is accomplished
by the same staff that did the plan
review, various important points are
stressed to again ensure compliance
with the rules and regulations of the
water district. The inspectors will
look at meter and strainer devices to
ensure that they are properly labeled
and installed. The strainers are a safe-
ty precaution to ensure maintenance-
free use of the system. Either Y-
strainers or basket strainers provide a
backup for maintaining an easy dis-
tribution of the water through the
irrigation system. When improper
water construction has taken place,
the work must be corrected.
There are several common
improper construction techniques.
Domestic and reclaimed water lines
may be too close together. There
must be a vertical separation of at
least 6 in. and a horizontal separa-
tion of 10 ft from either domestic
water or sewer lines, and the
reclaimed water line must be sleeved
to 5 ft on either side of a per-
pendicular crossing of a domestic
water line.
Improper labeling sometimes
occurs. A contractor once put in 1.5
miles of reclaimed water line and
taped the pipe with domestic tape
instead of reclaimed water tape. The
quick-connect coupling whick is
checked; if the wrong type is used,
reclaimed water could be used incor-
rectly. Pipe depths are checked, as
building codes are not always fol-
lowed.
Other important points include
the application of the label tape so
that future construction will be able
to determine the type of water that is
used in the pipeline. On some appli-
cations, the pressure in the distribu-
tion system may need to be reduced
in order to best fit the design pres-
sure used in the irrigation design.
Pressure-reducing valves have been
successfully used for extensive peri-
ods without any excessive mainte-
nance or problems that might have
32-Selected Readings on Water Reuse
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Irvine's Irrigation Guidelines
Irrigate between the hours of 9:00 p.m. and 6:00 a.m. only.
Watering outside this time frame must be done manually with quali-
fied supervisory personnel on-site. No system shall at any time be left
unattended during use outside the normal schedule.
Irrigate in a manner that will minimize runoff pooling and ponding.
The application rate shall not exceed the infiltration rate of the soil.
Timers must be adjusted so as to be compatible with the lowest soil
infiltration rate present. This procedure may be facilitated by the effi-
cient scheduling of the automatic control clocks by employing the
repeat function to break up the total irrigation time into cycles that will
promote maximum soil absorption.
Adjust spray heads to eliminate overspray onto areas not under the
control of the customer such as pool decks, private patios, streets, and
sidewalks.
Monitor and maintain the system to minimize equipment and materi-
al failure. Broken sprinkler leads, leaks, and unreliable valves should
be repaired as soon as they become apparent.
Educate all maintenance personnel, on a continuous basis, of the
presence of reclaimed water and the fact that it is not approved for
drinking purposes. Given the high turnover rate of employees in the
landscape industry, it is important that this information be disseminat-
ed frequently. It is the landscape contractor who is responsible for
educating each and every one of these employees.
Obtain prior approvals for all proposed changes and modifications
to any on-site facilities. Such changes must be submitted to, and
approved by, the IRWD engineering office and designed in accor-
dance with district standards.
been caused by the quality of the
water. The pressure regulator is used
to minimize fogging and misting of
sprinklers.
The final step in the field inspec-
tion is cross-connection control. A
cross-connection control test is per-
formed on all reclaimed water sys-
tems to be absolutely sure that there
are no connections between the
domestic and reclaimed water lines.
The system is then tested to check the
spray patterns of the sprinkler devices.
Normally, typical irrigation products
are used. These are important parts of
the irrigation system.
Spray patterns are tested; one of
the requirements is that overspraying
not be allowed to prevent the
reclaimed water from running into
the storm drain system. Besides wast-
ing water, this is important in Irvine
because the water drains into a sensi-
tive area that includes an ecological
preserve and wetlands.
During the overspray test, the sys-
tem is operated at full pressure with
reclaimed water and, where improper
spray patterns occur, the contractor
is required to replumb the system or
use different spray devices to control
the overspray. There are also over-
spray aesthetic concerns, such as
watering the concrete and asphalt
and interfering with the appearance
of a newly washed and waxed car,
creating potential ill-will within the
community.
MONITORING AND GUIDELINES
The IRWD uses guidelines that
were developed in a joint effort
between the local health depart-
ments. The guidelines (see Box) are
posted in the system's control center
in both Spanish and English. Com-
pliance with these guidelines is fre-
quently monitored.
The monitoring is designed to
police the system to ensure that the
facilities are maintained and operated
properly so that new problems are
not created. Monitoring includes
working with the contract operators
and irrigation users to make sure that
timers are set so that water is used
between the restricted hours of 9:00
p.m. and 6:00 a.m., when contact
with the public is minimized. The
automatic timer systems include
Rainbird, Griswold, and Toro, and
are the modern electronic timers
used because, as the price of water
continues to increase, it is easy to
justify the use of sophisticated timers
to control the application of water so
that proper irrigation takes place.
The monitoring work also includes
detection of main breaks and other
malfunctions in the system. This is
done by selecting random evenings
and actually patrolling the district
during the evening hours between
9:00 p.m. and 6:00 a.m. to look for
broken sprinkler heads, main breaks,
and overwatering situations—espe-
cially when they cause gutter rivers,
which are used to locate the prob-
lem. Monitoring also includes check-
ing the water quality throughout the
distribution system. Several stations
or sampling points are located
throughout the system and random
samples are taken during the normal
use times to ensure that the bacterial
quality of the water is similar to the
water's quality when it leaves the
treatment plant.
Another important aspect of the
monitoring program is the visual
assessment of new construction
areas. This is important because
there is always someone trying to
save time or money by building with
no inspections or plan checks. This
avoids many headaches by catching
the contractor early before the trans-
gressions endanger the public and
become expensive to fix.
The previously mentioned 1.5
miles of pipe that were laid with the
wrong pipe identification had to be
dug up and re-labeled—an unneces-
sary expense that could easily have
been avoided. Another example
involved a sprinkler system that was
installed without IRWD's knowl-
edge. It was discovered around a
new office building on a weekend
inspection. The developer applied
for a meter, but did not receive
one because th.e plans were not
approved by the district. To top it
off, the installed system did not fol-
low the reclaimed water rules and
regulations, requiring costly field
modifications.
IRWD is trying to avoid similar
complications by getting involved hi
the initial planning stages for a devel-
opment and then following through
for the direction of the project. The
district's goal is to maximize water
reuse and limit the unnecessary use
of potable water in the safest and
most effective manner. Control from
planning and permitting through
operational monitoring is essential
for this goal to be met. •
John Parsons is irrigation services
supervisor/engineering technician III
for the Irvine Ranch Water District
in Irvine, Calif.
Selected Readings on Water Reuse -33
-------
Because conditions i t flbridtf Messtfate water
reuse, spray jrrig'at orrsysjeMysing rMaitMd.
water, s'uch (is tliifS leln Ta1lalillee*:aferbeffl|i!:
/ -'" :-.•-• I encouraged by t(ie slated;
FLORIDA'S REUSE
PROGRAM PAVES
THE WAY
iDarid W. York, James Crook
-------
WATER RECLAMATION/REUSE
Florida is different than the
major reuse states in the
semi-arid southwest U.S. In
Florida, it rains an average of
54 in./yr and the state seem-
ingly has abundant water
resources—particularly
groundwater, which ac-
counts for about 90% of all water
used for domestic purposes. Howev-
er, there are, increasing demands on
the state's water resources.
Florida continues to face rapid
population growth. Its population,
which nearly doubled from 1960 to
1980, continues to increase by more
than 6000 persons each week.
Between 1980 and 1990 the popula-
tion rose 33%, and from 1990 to
2000 the population is expected to
grow an additional 19%.
Almost 79% of Florida's 13 million
people lives near the coast, and
about 82% of the anticipated popula-
tion growth will occur in coastal
counties. These coastal growth areas
are served primarily by shallow
aquifers that are most vulnerable to
overdraft and saltwater intrusion.
These conditions necessitate water
reclamation and reuse. The state has
developed programs that encourage
the reuse of reclaimed
water and comprehensive
regulations that govern
reuse projects. The rules
provide detailed require-
ments for development of
reuse projects that involve
irrigation in public access
areas such as parks, play-
grounds, and golf courses,
as well as irrigation of resi-
dential property and edible
crops and must address the
use of reclaimed water for
fire protection, toilet flush-
ing, and aesthetic purposes
such as decorative ponds
and fountains. The reuse
rules provide requirements
for preapplication treat-
ment, reliability, operation
control, buffer zones, stor-
encourage development of reuse pro-
jects by reducing storage require-
ments.
DEVELOPMENT OF REUSE
During the last 20 years, the pri-
mary driving force behind implemen-
tation of reuse projects in Florida has
been effluent disposal. While the
state has many streams, they typically
have low flows, are shallow, have low
gradients, flow slowly, are warm all
year, and flow into lakes or estuaries.
Most, surface waters in Florida simply
will not assimilate large quantities of
effluent. As a result, many communi-
ties have turned to land application
to dispose of unwanted effluent.
Regulations developed in the early
1980s for reuse and land application
are in the manual, Land Application
of Domestic Wa.steva.ter Effluent in
Florida1, that contains detailed
design and operation requirements
for slow-rate land application sys-
tems, rapid-rate land application sys-
tems, absorption fields, overland
flow systems, and other land applica-
tion systems. Irrigation of public
access areas or edible crops was
allowed, but requirements for such
activities were incomplete.
Table 1 - Disinfection Levels Defined by Florida Rules
Disinfection
level
Fecal coliform limit Application
High-level No detectable
Intermediate
"'" UTTOCTmLTor""
discharge to waters
: tributary to Class II
surface waters
(shellfish propaga-
age, cross-connection con- ; _ tion or harvesting)^
trol, and other design and
Basic 200/100 ml For most land appli-
cation systems, for
most discharges to
surface waters.
operational features. These
rules also provide a mecha-
nism for limited discharge
of excess reclaimed water
during wet-weather, high-
stream-fiow conditions
when demand for re-
claimed water is lowered.
Such limited wet-weather
discharge provisions should
Low-level
"2460/1 op'
maximum
The land application manual was
designed to be used hi conjunction
with Chapter 17-6, Florida Adminis-
trative Code (FAC), titled "Waste-
water Facilities." As shown in Table
1, four levels of disinfection were
denned in the rule.
The high-level disinfection
requirements were developed in the
early 1980s based largely on the tes-
timony of epidemiologists and virol-
ogists before the Florida Environ-
mental Regulation Commission. The
criteria were designed to provide
treated water that was essentially
pathogen free. Where chlorine was
used for disinfection, maintenance of
a 1.0-mg/L total chlorine residual
after a 15-minute contact time at
maximum daily flow or after a 30-
minute contact time at average daily
flow was to be accepted as evidence
that the fecal coliform criteria would
be met.
Secondary treatment was estab-
lished hi Chapter 17-6, FAC, as the
minimum pretreatment level for
most land application and reuse sys-
tems. Florida's definition of sec-
ondary treatment requires that the
wastewater treatment facility be
designed to produce an effluent con-
taining not more than 20
mg/L of biochemical
oxygen demand (BOD)
and total suspended
.solids (TSS) or 90%
removal of BOD and
TSS, whichever is more
stringent. The annual
average BOD and TSS
concentrations may not
exceed 20 mg/L and the
monthly average may not
exceed 30 mg/L. A
lower level of secondary
treatment—40 to 60
mg/L for BOD and
TSS—was allowed for
overland flow systems
and for some under-
drained irrigation sys-
tems.
In September 1989,
Chapter 17-6, FAC, was
rewritten into a new
series of rules. Regula-
tions governing domestic
wastewater treatment
and disinfection are now
found hi Chapter 17-600,
For overland flow '_ P.AC, titled "Domestic
systems and some Wastewater Facilities."
underdrained irriga- During the 1970s and
tioni systems. 1980s, the number of
projects involving reuse
Public access maxi-
mum fecal coliform
TSS 5 mg/L. Irriga-
tion and irrigation
of edible crops, for
discharge to Class I
surface waters
(potable water sup-
plies).
Selected Readings on Water Reuse - 35
-------
or land application increased sub-
stantially. By 1985, more than 100
individual projects involved some
form of reuse, including several
excellent reuse projects such as the
St. Petersburg dual water distribu-
tion system, the Tallahassee spray
irrigation system, and the CONSERV
II citrus irrigation project serving
Orlando and Orange Counties.
The 1990 Reuse Inventory1 identi-
fied about 200 reuse projects in
Florida. These projects use about
320 mgd of reclaimed water for a
wide range of beneficial uses.
With the growing popularity and
acceptance of water reuse projects,
the state has begun to promote
water reclamation. Statewide com-
prehensive planning has been imple-
mented to ensure that adequate
infrastructure is provided. Increased
attention is being placed on protec-
tion of water resources and provision
of adequate water supply. Reuse of
reclaimed water is receiving greater
attention as a means to reduce
demands on potable water resources
and recharge groundwater.
THE STATE'S REUSE PROGRAM
Beginning in 1987, the Florida
Department of Environmental Regu-
lation embarked on an ambitious
program of rule making designed to
facilitate and encourage reuse of
reclaimed water. Three rules were
effected: Chapter 17-6, FAC,
"Wastewater Facilities", Chapter 17-
40, FAC, "Water Policy", and Chap-
ter 17-610, FAC, "Reuse of
Reclaimed Water and Land Applica-
tion."
In addition, 1989 state legislation
and other related rule making also
affected reuse in Florida.
Updated reuse rules were devel-
oped with significant assistance from
a technical advisory committee con-
sisting of representatives of the Flori-
da Pollution Control Association,
Florida Engineering Society, Ameri-
can Water Works Association Florida
Section, American Water Resources
Association, a representative of a pri-
vate utility, and the former head of
California's reuse program. Commit-
tee members offered a wealth of
experience and expertise covering a
wide range of reuse activities.
Consistent definitions for reuse
and reclaimed water were included in
all three rules. Reclaimed water is
water that has received at least sec-
ondary treatment and is reused after
flowing out of a wastewater treat-
Wastewater restoration, occurring in this Orlando, Fla., wetland, is identified as a reuse
application for surface-water enhancement.
ment facility. Reuse is the deliberate
application of reclaimed water in
compliance with applicable rules for
a beneficial purpose.
The rules identify landscape irriga-
tion, agricultural irrigation, aesthetic
uses, groundwater recharge, industri-
al uses, and i fire protection as legiti-
mate beneficial purposes. Environ-
mental enhancement of surface
waters resulting from discharge of
reclaimed water that has received at
least advanced wastewater treatment
or from discharge of reclaimed water
for wetlands restoration also are
identified as reuse applications.
Chapter 17-40, FAC The "Water
Policy" rule [outlines the state's poli-
cy for the use and regulation of
water. It provides general guidance
to the state's five water-management
districts that are responsible for
water-quantity management, includ-
ing the consumptive-use permitting
program.
An October 1988 amendment to
Chapter 17-40, FAC, created a pro-
gram for mandatory reuse of
reclaimed water. The water-manage-
ment districts were required to assess
the water resources within their juris-
dictions—including an estimate of
water needs and sources for the next
20 years—and to publish a compre-
hensive district water-management
plan. As part of this planning activi-
ty, the water-management districts
were required to identify critical
water-supply problem areas. Reuse
will be required within critical water-
supply problem areas that exist
today, and in areas that are projected
to develop over a 20-year planning
horizon. The program will be in full
operation by November 1991.
The rule also allows the water-
management districts to require
reuse outside of critical water-supply
problem areas if reclaimed water is
readily available to the applicant for a
consumptive-use permit. This mea-
sure was designed to facilitate imple-
mentation of reuse at the local level.
The primary responsibility for imple-
mentation of this program rests with
the water-management districts
through the consumptive-use per-
mitting process.
Chapter 17-6, FAC Amendments
to the rule focused on two areas.
First, the high-level disinfection
requirements were modified to
reflect existing technology and expe-
rience. Revised high-level disinfec-
tion criteria include requirements
that 75% of all fecal coliform obser-
vations be less than the detection
limit and that no sample exceed
25/100 mL for fecal coliform. Daily
sampling for fecal coliform was
36-Selected Readings on Water Reuse
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Table 2 - Requirements for Reuse
Parameter
Requirements
Minimum treatment level
Secondary with filtration and chemical feed,
maximum TSS of 5 mg/L
'Disinfection
Minimum system size
Reliability
k,-
Staffing
High-level.
Continuousjnonitoring
Operating protocol
Storage requirements
Reject storage
limits on reuse
Cross-connection control
-,.
{Setback distances
378.5 m3/d (0.1 mgd) for any public
access irrigation system, 1893 m3/d (0.5
mgd) for residential lawn irrigation or edible
crop irrigation.
Class 1—requires multiple units or backup
units and a second power source.
24 hr/day, 7 days/wk; may be reduced to
6 hr/day, 7 days/wk, if additional reliabili-
ty measures are included.
_ Required for turbidity ancLdisinfectant residual.
Required—a formal statement of how the
treatment facility will be operated to ensure
compliance with treatment and disinfection
requirements.
System storage (minimum 3 days, may be
unlined) or back-up system required; golf
course lakes may be used for system stor-
.age, :
Minimum 1 day, lined, to hold unacceptable
quality product water for return for addition-
al treatment.
Only product water meeting the criteria of
the operating protocol shall be released to
the reuse system; reclaimed water shall not
be used to fill swimming pools, hot tubs, or
•..wading., pools
Prohibit cross-connections to potable water
systems; reclaimed water shall not enter a
dwelling unit; minimum standards for sepa-
ration of reclaimed water lines from water
lines and sewers; color coding or marking
required; back-flow prevention devices
required on potable water sources entering
property served by reclaimed water systems;
dual check valves are acceptable.
22.9 m (75 ft) to potable water-supply wells;
.otherwise, none .
Other O&M requirements
Approved operating protocol; approved
cross-connection control program; documen-
tation of controls on individual users (agree-
ments or ordinance); assess need for indus-
trial pretreatment program.
included as a requirement for reuse
systems. The TSS limitation remains
at a maximum of 5 mg/L before
application of the disinfectant. Tur-
bidity is not incorporated in the
rule as a permitting parameter.
However, for public access irrigation
and for irrigation of edible crops,
continuous on-line turbidity moni-
toring is required as part of the oper-
ational control provision in Chapter
17-610, FAC Disinfection require-
ments are now found in Chapter
17-600, FAC.
Provisions for limited wet-weather
discharge were added to the
"Wastewater Facilities" rule. This
section is designed to facilitate dis-
charge of reclaimed water during
wet-weather, high-flow periods when
demand for reclaimed water normal-
ly is reduced. When the applicant
demonstrates sufficient dilution dur-
ing periods of high stream flow, the
state will permit a discharge with
minimal water quality review.
Required dilution ratios are based on
the quality of the reclaimed water
and the anticipated frequency of dis-
charge:
SDF= P(0.085 CBODS+ 0.272
TKN- 0.484)
Where
SDF = minimum required stream
dilution factor, dimensionless;
P = percent of the days of the year
that limited wet-weather discharge
will occur during an average rainfall
year;
CBODS = the treatment facility's
design monthly maximum limitation
for carbonaceous BOD5 in mg/L;
and
TKN = the treatment facility's
design monthly maximum limitation
for total Kjeldahl nitrogen expressed
in mg/L of nitrogen.
The dilution ratio is increased if
travel time to sensitive downstream
environments such as lakes, estuaries,
and water supplies is less than 24
hours. Limited wet-weather dis-
charge provisions were subsequently
relocated to Chapter 17-610, FAC:
Chapter 17-610, .FAC The "Reuse
of Reclaimed Water and Land Appli-
cation" rule was adopted in 1989. It
supersedes and expands upon the old
land application manual.1 The focus
of this rule making was to provide
detailed requirements for the design
and operation of reuse projects in
public access areas, including irriga-
tion of residential lawns, parks, golf
courses, landscape areas, as well as
for the irrigation of edible food
Selected Readings on Water Reuse - 37
-------
crops. These requirements are con-
tained in Part III of the rule.
Table 2 presents a summary of the
key provisions of this part for public-
access irrigation systems, irrigation of
residential lawns, and irrigation of
edible crops. Reclaimed water that
has received high-level disinfection,
secondary treatment, and filtration,
and that meets the fiill requirements
of Part III may also be used for toilet
flushing in commercial and industrial
facilities that do not contain dwelling
units, for fire protection, for con-
struction dust control, for aesthetic
purposes, and for other uses.
Any reuse system regulated by Part
III must provide a minimum of sec-
ondary treatment, filtration, and
high-level disinfection. Class I relia-
bility and full-time operator atten-
dance are required; some reduction
in operator attendance is allowed if
additional reliability measures are
provided. Each facility must develop
an operating protocol; a clear state-
ment of how the facility will be oper-
ated to ensure that only acceptable
reclaimed water is discharged into
the reuse system. While turbidity and
disinfectant residual must be contin-
uously monitored for operational
control, these are not permit limita-
tions. The facility must be operated
such that the high-level disinfection
criteria (TSS and fecal coliform lim-
its) will be met. Unacceptable prod-
uct water must be diverted to a
lined, reject storage system for addi-
tional treatment before being
released to the reuse system.
As shown in the Table, minimum
system sizes were established for
treatment facilities that make
reclaimed water available for irriga-
tion in public access areas or for irri-
gation of edible food crops. These
minimum size limits reflect reduced
confidence in a small facility's ability
to continuously produce high-quality
reclaimed water. Both the technical
advisory committee and the Florida
Department of Health and Rehabili-
tative Services recommended mini-
mum size limits.
Rules that existed before 1989
allowed die irrigation of edible food
crops if high-level disinfection was
provided and the permit applicant
demonstrated that processing of the
food crop would inactivate or
remove pathogens. Few edible crop
irrigation systems were proposed.
The original provisions of the rule
allowed irrigation of edible food
crops without restriction beyond
Part III requirements. This position
represented a consensus from the
technical advisory committee, which
noted that the potential for disease
transmission from an edible food
crop irrigation system is not signifi-
cantly different from that of a resi-
dential lawri irrigation system, as
long as the full requirements of Part
III are met. However, in response to
concerns raised by the Florida
Department of Health and Rehabili-
tative Services, the issue was revisited
in July 1989. It was amended to pro-
hibit direct contact of reclaimed
water on edible food crops that
will not be peeled, skinned, cooked,
or thermally processed before hu-
man consumption. Indirect applica-
tion methods such as ridge and
furrow, drip irrigation, or subsur-
face distribution systems are still
allowed for these crops. No restric-
tions were placed on the irrigation
of citrus, tobacco, or other crops
that are peeled, skinned, cooked,
or thermally processed before con-
sumption.
Other Legislation and Rule
making. The Department of Envi-
ronmental Regulation pursued state
legislation in 1989 to allow the
department to require that waste-
water treatment facilities located
within designated critical water-sup-
ply problem areas make reclaimed
water available for reuse. Unfortu-
nately, the resulting legislation3
stopped short of vesting such author-
ity. The law does require that, begin-
ning in 1992, applicants for wastew-
ater-management permits located
within critical water-supply problem
areas complete reuse feasibility stud-
ies. The law clearly establishes that
reuse of reclaimed water and conser-
vation of water are formal state
objectives.
In 1989, die Department of Envi-
ronmental Regulation also revised
Rule 17-302, FAC, "Surface Water
Quality Standards," and Rule 17-4,
FAC, "Permits," to include an
antidegradation policy. This policy
requires that any new or expanded
surface-water discharges be clearly in
the public interest. The applicants
for surface-water discharges must
demonstrate that reuse of domestic
reclaimed water is not economically
or technologically reasonable.
Rule clean-up. Chapter 17-610,
FAC, was revised in 1990. Setback
distance (buffer zone) requirements
were updated throughout the rules.
Streamlined permitting requirements
and associated forms were added.
The use of reclaimed water for toilet
flushing and fire protection was
extended to motels, hotels, apart-
ments, and other units where the
resident does not have ready access
to the plumbing system for repairs or
modifications.
THE FUTURE
Reuse of reclaimed water will
increase significantly during the next
decade. Recent droughts in southern
Florida emphasized the need for
conservation of valuable potable
water supplies and for reuse of
reclaimed water. As the water-man-
agement districts identify critical
water-supply problem areas and
implement mandatory reuse provi-
sions, additional pressures will be
placed on communities to move
toward reuse. Requirements for
applicants for wastewater-manage-
ment permits to conduct reuse feasi-
bility studies also will focus the com-
munity's attention on the need for
reuse. Continued population
growth, most of which will occur in
coastal areas, will increase the pres-
sure on cities, counties, and utilities
to protect valuable and fragile water
resources by conserving water and
reusing reclaimed water for non-
potable purposes.
The Florida Department of Envi-
ronmental Regulations strongly sup-
ports reuse of reclaimed water. The
goal is to increase the amount of
reuse in Florida by 40% above 1987
levels by 1992. Recently adopted
technical reuse rules, the mandatory
reuse program, 1989 state legisla-
tion, and the antidegradation policy
will contribute to the promotion of
reuse. •
David W. York is reuse coordinator
for the Florida Department of Envi-
ronmental Regulation in Tallahassee,
Flo,.; James Crook is principal engi-
neer with Cainp Dresser & McKee,
Inc., in Clearwater, Fla.
REFERENCES
1. Land Application of Domestic
Waste-water Effluent in Florida..
Florida Department of Environ-
mental Regulation, Tallahassee, Fl.
(1983).
2. 1990 Reuse Inventory. Florida
Department of Environmental Regu-
lation, Tallahassee, Fla. (1990).
3. Section 403.064, Florida,
Statutes. State of Florida, Tallahas-
see, Fl. (1989).
38 - Selected Readings on Water Reuse
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WATER RECLAMATION/REUSE
ECONOMIC TOOL FOR
REUSE PLANNING
/. Gordon Milliken
Economics provides several
useful tools to guide plan-
ners contemplating a poten-
tial wastewater reuse project,
but the tools and their appli-
cations to water-resource
development are not univer-
sally well understood by
engineers and managers. If cost-
effectiveness, cost/benefit, and
financial feasibility analyses and a
market research pricing study are
conducted, many of the key ques-
tions faced in water-resource plan-
ning can be answered.
MAKING DECISIONS
Planners in all areas have a com-
mon goal: meeting future water
demands in the best possible man-
ner. Local conditions complicate this
common goal, throwing a variety of
alternatives that must be considered
into the ring. The simplest example
involves the choice of either con-
structing a water reclamation plant
or developing a new water supply
and expanding the existing conven-
tional wastewater treatment plant.
It's never that easy in the real world,
but the first question that must be
answered is, among the alternatives,
which is the best?
Cost/benefit calculations have
been used for decades to compare
the returns offered by different pro-
posed investments. The costs of the
resources required are related to the
market value of the flow of benefits
expected, using discounted cash-flow
techniques.
When comparing alternatives that
cause complex social and environ-
mental effects, such as changes in the
quality of life or permanent changes
in rivers and forests, this technique is
hard to use. The investments and
expenditures really do not fit the
cost/benefit framework because the
outcomes often cannot be measured
in dollars. In such cases, cost-effec-
tiveness comparisons are more use-
ful. This technique uses an effective-
ness scale as a measurement concept.
The alternative methods for
achieving water-resource (supply or
quality) goals differ in many ways: in
amount and timing of the capital
investment required; hi amount of
operating and maintenance cost; in
useful life of capital investment in
facilities; in effectiveness, both as to
magnitude of effect and certainty of
effect; and in impact on the rest of
the economy, the environment, pub-
lic health, and other factors.
Cost-effectiveness. To establish a
clear basis to compare the alterna-
tives, this methodology requires a
single, uniform measure of effective-
ness such as the volume of water of a
specified quality produced annually,
either in added supply or in reduced
demand, at a selected confidence
level. All other measures of differ-
ences among alternatives are treated
as costs or ranked according to their
degree of effect. By this means, all of
the alternatives can be equated on
the basis of their ability to produce a
unit quantity of water of a specified
quality. Their relative types and
degrees of cost, such as direct cost,
quality of life effect, environmental
effect, and others, can then be com-
pared. The various costs and effects
can be arrayed together to help plan-
ners choose among the competing
alternatives.
Cost benefit and feasibility anal-
yses. Once an alternative is selected,
a true cost/benefit analysis should be
conducted. The analysis should ask
and answer two basic questions: Is
this reuse project economically desir-
able—does society receive a net ben-
efit if resources are used to build it?
Are the total benefits greater than
the total costs?
The analysis, if properly conduct-
ed, will identify the various beneficia-
ries of the project, estimate the
amount of their benefits, and deter-
mine when these benefits will be
received.
U.S. federal law specifies that fed-
eral agencies involved in water plan-
ning use the economic and environ-
Selected Readings on Water Reuse - 3"9
-------
mental principles and guidelines
developed by the U.S. Water Re-
sources Council.1 The framework
provides the means to identify all
costs and parties on whom the direct
or indirect costs fall and to identify
beneficiaries and the amount of ben-
efit they will receive. To the extent
possible, the framework provides the
means to allocate costs appropriately
to beneficiaries.
A financial feasibility analysis
determines whether the plans for the
proposed reuse plant are financially
sound—if the costs of capital invest-
ment plus the costs of operation and
maintenance can be covered by user
charges and rev-
enues from sales
of reuse water.
Studies of fi-
nancial feasibility
require that reuse
project costs be
estimated with
substantial accura-
cy, although some
estimating uncer-
tainty is inevita-
ble. Capital costs
may be paid from
an existing capital
construction fund
(typical of an
industrial firm) or
by bonded debt
(typical of a gov-
ernmental utility).
Bonded debt requires a forecast of
the bond interest rate, which varies
with the credit rating of the issuing
organization, and the degree of risk
of the bonds, whether backed by
future revenues or by taxes. Op-
eration and maintenance (O&M)
costs will vary because of inflation of
energy and labor costs and possible
technological improvements in
future operating efficiency.
In the financial feasibility analysis,
the future stream of costs, including
bond payments, is projected and
compared with a future stream of
revenues that will come from user
fees and charges, contracts to sell
reuse water, and perhaps from gov-
ernment grants. Although it violates
sound economic principles, some
revenue may be planned from tax
subsidies if the user fees are con-
sidered so high as to be politically
unacceptable.
In any case, the future revenues
must equal the future costs for the
plan to be financially sound. In
industrial projects, it is customary to
plan a reserve fund for ultimate
replacement of the facility after its
useful life ends or it becomes obso-
lete. This forward planning is less
common in government because
officials customarily do not consider
that accruing reserves from taxes or
excess user fees is good public policy.
Market pricing research. The
financial feasibility analysis relies
largely on market research pricing
studies. Setting the price of reuse
water may or may not be a com-
plex problem, depending on several
factors.
For example, if the reuse water is
Significant Economic Factors Impacting
Future Wastewater Reuse
The rapidly rising costs of alternative sources of water in a great
many metropolitan areas, not only the traditionally water-poor,
semi-arid cities;
The stabilization of wastewater reuse production costs and their
increasing competitiveness with other water supply sources;
The very serious limitations on water supply and the reduction in
volume of traditional water supplies faced by certain cities; and
The growing impact of water-qualify regulations that place bur-
densome costs on wastewater discharges and thus narrow the
cost differential between discharge and reuse.
used by the governmental entity that
produces it, such as by a municipality
that operates both a water supply
and a wastewater treatment utility,
the question of pricing may never be
raised. The price will be set as is cus-
tomary on a cost-of-service basis—
uniformly—for the blend of reuse
water and the water from traditional
sources.
A more complex problem arises
when the reuse water is offered as a
nonpotable supply to customers—
usually industrial firms that have the
option of buying it, buying potable
water, or obtaining water from an-
other source, such as a self-supplied
groundwater or an in-plant reuse sys-
tem. In such a case, a thorough mar-
ket-research study is necessary to
determine whether potential cus-
tomers are willing to pay for reuse
water and how this compares to the
actual cost of producing suitable
reclaimed water. The most compre-
hensive study to date was conducted
in 1981 and involved 250 on-site
interviews of industrial water users in
Orange and Los Angeles Counties.
ECONOMICS OF WASTEWATER RECYCLING
Simple economic models of a con-
ventional water system and a waste-
water recycling project exist.2 The
conventional water supply/wastewa-
ter treatment system costs compo-
nent includes operating and mainte-
nance costs and amortization of capi-
tal expenditures (Equation 1). The
costs of an equivalent water reuse
system are somewhat different
(Equation 2).
An equivalent water supply system
using recycled water would incur vir-
tually identical
costs for raw water
treatment, distri-
bution, and waste-
water treatment.
Some costs differ
where recycling
provides a portion
of the water sup-
ply: the cost of
water collection
(raw supplies ver-
sus effluent); and
the additional cost
necessary to bring
wastewater from
the quality neces-
sary for its dis-
charge or disposal
under applicable
regulations to a
useful and marketable quality as recy-
cled water.
Some additional distribution costs
also may be incurred as the recycled
water must be transferred from the
wastewater treatment location to a
point where it can be reused or inte-
grated into a supply system.
Primarily, however, the cost of
renovated water is a direct function
of the relative levels of wastewater
treatment required for effluent dis-
posal and the particular reuse con-
templated. The higher the quality of
treated wastewater, the lower the
additional cost necessary to produce
recycled water. The true cost of recy-
cled water is only its net cost above
the cost associated with all elements
of a conventional water system. This
additional cost is the appropriate one
to use when comparing the cost of
recycled water with, that of new sup-
plies from conventional sources.
The economic feasibility of a
municipal or industrial wastewater
reuse system, therefore, is a function
40 -Selected Readings on Water Reuse
-------
WATER RECLAMATION/REUSE
of added costs less cost savings and
revenues (see Box).
Transport costs may be substantial
if they involve a dual distribution sys-
tem. They will at least include the
costs of transport from the reuse
plant to the place of use or of inte-
gration into the supply system. For
example, if the system is potable
reuse, costs for transport into supply
reservoirs or onto the spreading
ground for groundwater recharge
must be considered.
The interaction of these factors in
individual cases will determine the
cost of recycling as compared to the
cost of once-through water use, and
thus the advisabili-
ty of reuse.
building a large reservoir and diver-
sions of water from the Colorado
River drainage basin through the
Continental Divide will have a
capital cost of about $8.11/m3
($10,000/ac-ft) of safe annual yield.
The marginal long-term capital cost
of new supplies is estimated at
$ll,000/household in addition to a
share of the amortized cost of the
existing water system.
Although the quantity of water
available for reuse is strictly limited
by state law to water imported
from other basins, the relative cost
of reuse is low. Nonpotable reuse,
providing an annual safe yield of
Equation 1
Total $ Water
Equation 2
Total $ Water Service ••
ECONOMIC FACTORS
Some economic
factors that affect
the decision to
build a reuse facili-
ty are reasonably
constant and pre-
dictable regardless
of geographic loca-
tion. Some vary
widely depending
on location, site
conditions, and the
use to be made of the reuse water.
Local supply and demand. If the
local water supply is ample or inex-
haustible, or if municipal demand is
steady, reflecting no population
growth, there is little incentive to
create new water supplies through
reuse. Reuse may still be chosen,
however, for reasons related to
wastewater quality regulations.
It is far more important to consid-
er reuse when a municipality has
exhausted all other supply alterna-
tives and still faces growing demand,
or when part of the existing supply is
threatened with elimination. El Paso,
Texas, and the Los Angeles/San
Diego Region are examples. Both
metropolitan areas have strong pro-
grams for water conservation and
reuse because their historical supply
sources are threatened with decline
and no economical alternatives are
available.
Costs of water from alternative
sources. As cities grow and exhaust
their traditional water supply
sources, they must seek alternative
supplies, usually by diversion from
ever more distant streams or by buy-
ing agricultural water for municipal
use. One scenario that includes
System Cost Equations
Service = $ Collection + $ Treatment +
$ Distribution +
$ Wastewater treatment
$ Conventional wastewater treatment +
$ Effluent collection +
$ Additional treatment for reuse +
$ Additional transportation to supply system +
$ Distribution
ater effluent flowing into Water Fac-
tory 21 from the Santa Ana River
and local wastewater treatment
plants is at 700 mg/L TDS. Thus
the water must be demineralized by
reverse osmosis (RO) as well as treat-
ed for normal wastewater contami-
nants before recharge into the
groundwater. The current RO cost
at Water Factory 21 is $0.34/m3
($415/ac-ft), but the cost is expect-
ed to be reduced to $0.30/m3
($375/ac-ft) after investment hi new
pumps.
Currently, some 246 X 106 m3
(200,000 ac-ft) of water are being
discharged to the ocean from
Orange County.
As population and
demand grow,
there will be a
growing incentive
to increase reuse.
Regulato'ry
constraints on
wastewater dis-
charge. Another
economic incen-
tive to re-use
wastewater is the
likelihood of
12.1 X 106 m3 (9830 ac-ft), would cost
about $0.45/m3 • a ($560/ac-ft/yr).
Potable reuse water from Denver's
pioneering 3.79 X 106 L/d (1 mgd)
Potable Water Reuse Project is cur-
rently produced at an operational
cost, including facility O & M, of
$0.52/1000 L ($1.97/1000 gal) or
$640/ac-ft. Based on 1989 experi-
ence, Denver expects a full-scale
reuse plant to convert sewage efflu-
ent to potable water at a cost of
$0.45 to $0.59/1000 L ($1.72 to
$2.25/1000 gal), or from $560 to
$733/ac ft, including amortized cap-
ital cost. This is substantially less
than the cost of raw water obtained
from structural diversion from the
Colorado River Basin.
Quality standards for direct
addition to potable supplies. Water-
quality regulations can significantly
affect the cost of reuse water pro-
duced for potable purposes. For
example, in Southern California,
Regional Water Quality Control
Board regulations require that water
injected in the groundwater aquifers
which serve as seawater intrusion
barriers have a maximum salinity
level of 540 mg/L total dissolved
solids (TDS). However, the wastew-
increasing con-
straints on the
quality of treated wastewater dis-
charge that may degrade groundwa-
ter supplies. For example, the Santa
Ana Regional Water Quality Control
Board requires that water or waste-
water used for groundwater replen-
ishment, or discharged into the
Santa Ana River or another open
channel, cannot exceed the salinity of
present groundwater or 600 mg/L
TDS, whichever is less. If it does,
more fresh water must be provided
for dilution, the discharge must be
treated to remove salt, or the dis-
charge must be sent directly to an
ocean outfall via a brine line. Thus
far, capital costs for the brine line
from the upper reaches of Riverside
County are $50 million. Another
$30 million in capital investment is
being planned to extend the line into
San Bernardino County. Current
yearly O 8c M costs for the brine line
are $6.1 million, and these costs will
rise to $10.8 million before the
year 2010.
In some areas, such high disposal
costs may be spent instead on facili-
ties that desalt and reuse the waste-
water. Within the Santa Ana water-
shed, desalting plants are being
planned or projected for future con-
Selected Readings on Water Reuse - 41
-------
struction in three areas, with a
potential capital cost of $58 million
and annual O & M of up to $21 mil-
lion. Two of these plants will be
necessary for water supply purposes
and one is necessary to successfully
implement planned water reuse
programs.
Under Arizona's new groundwater
protection law, similar constraints on
salinity levels of treated wastewater
used for groundwater recharge may
come into play in Tucson, once it
receives deliveries of Central Arizona
Project (CAP) water which is sub-
stantially more
saline than Tuc-
son's present sup-
ply. As CAP water
is intended for
direct use, to con-
serve groundwater
supplies, the ground-
water protection
law may result in
a requirement for
demoralization
of effluent.
Quality stan-
dards for non-
potable uses.
Nonpotablc reuse
water used for
landscape irriga-
tion, or even some
crop irrigation, is
normally accept-
able for use after
decrease as plant size increases.
Significant economies of scale can
be realized by large reuse plants but
these economics can be achieved
only as long as the plants operate at
near capacity. Given the seasonal
variation in urban water use and the
variability of return flow, however, a
plant designed to recycle the maxi-
mum amount of effluent will neces-
sarily run at less than capacity for
part of the year.
A more modest-sized plant,
though it continually operates at
capacity, not only will have the high-
Economic Feasibility
Added costs of a reuse system
• Added capital facility costs.
• Added operating costs to collect wastewater effluent.
• Added operating costs to treat wastewater to quality standards.
• Added transport costs.
Savings of a reuse system
• Avoidance of part of the costs of treating wastewater to the
extent necessary to meet pollution control requirements before
discharge.
• Curtailment of water supply acquisition costs through extension
of the use available from existing supplies, that is, reduction or
postponement of water supply development costs.
Revenues for a reuse system
• Sale of water.
• Use by the municipality itself, following a first use.
secondary treatment. Restrictions
apply to contact uses, such as swim-
ming, and to irrigation of food chain
crops. Nonpotable water also is
acceptable for industrial cooling,
although it may require cold lime
softening to protect from scale, and
the addition of biocides and biodis-
pcrsants to water in cooling towers.
For other industrial processes, a vari-
ety of treatment is used, and quality
Standards for reuse water prior to
treatment are not usually severe. The
primary criterion from industry's
viewpoint is that the water supply be
of consistent quality so that pretreat-
mcnt can be maintained routinely.
Economics of scale. Some costs
associated with reuse treatment are
expected to remain nearly constant
per unit volume of water treated,
such as membranes, energy, chemi-
cals, and other materials. Other
costs related to facility construction,
laboratory analysis, and labor for
supervision and operation will
er unit costs of a smaller plant but
will also be unable to process all of
the effluent. The overflow that can-
not be recycled back into the system
still must be treated to meet dis-
charge standards, but it then is dis-
charged and lost. In areas where
water is scarce and expensive, this
may be a cosdy loss.
The choice of plant capacity is
therefore a complex one. It is worth
noting, however, that the larger the
metropolitan area and the greater the
amount of effluent, the simpler the
decision about plant size becomes,
since even a large, efficient plant may
have a capacity significantly lower
than the total amount of effluent
available for reuse.
Market behavior. Market behav-
ior exhibits anomalies despite price
differentials between conventional
and recycled water. For example,
Long Beach, Calif., obtains a high-
quality nonpotable reuse water from
the Los Angeles County Sanitation
District that is tertiary-treated and
chlorinated. The water is used with-
out further treatment for landscape
irrigation on parks:, golf courses, and
schools. The reuse water is available
for sale to industrial users for
$0.029/1000 L ($0.083/100 01 ft) com-
pared with potable water selling for
$0.25/1000 L ($0.71/100 cu ft).
Long Beach petroleum producers
who are on an interruptible supply of
potable water had considered using
recycled water for reinjection and
secondary recovery from oil wells,
but have since opted to use the more
expensive potable
water instead. Evi-
dently the reuse
water must be
treated with a
chemical agent to
avoid a slime con-
dition that blocks
the aquifer. Even
• though the cost of
chemical treat-
ment adds little
to the cost of
reuse water, the
use of potable
water avoids the
inconvenience of
treatment.
CONCLUSION
The most signi-
ficant economic
factors impacting
future potable and non-potable
water reuse (see Box) show trends
that favor the future expansion
of both potable and nonpotable
reuse. •
J. Gordon Milliken is senior research
economist with Milliken Research
Group, Inc., in Littleton, Colo. This
paper was reprinted with permission
from K1987 Annual Conference Pro-
ceedings, " American Water Works
Association.
REFERENCES
l.U.S. Water Resources Council,
Economic and Environmental Princi-
ples and Guidelines for Water and
Related Land Resources Implementa-
tion Studies,. Government Printing
Office, Washington, D.C. (1983).
2.Milliken, J. Gordon, and
Trumbly, Anthony S., "Municipal
Recycling of Wastewater," Journal
AWWA, 71,10, 548 (1979).
42-Selected Readings on Water Reuse
-------
PRELUDE
This last segment in a, series on reuse
was made possible by a grant from
EPA. WE&T hopes that the four seg-
ments in the series, which began in
October, have provided readers with a
better sense of the reuse potential of
wastewater.
Water reuse: potable or
nonpotable? There is a difference!
ater reclamation and reuse offers an increasingly attractive option
for meeting the growing water shortages facing urban, industrial,
and agricultural consumers throughout the world. However, the
failure to identify clearly whether a project,a principle or practice,
or a table of water-quality parameters refers to potable or nonpotable reuse
may easily confuse the reader. Both potable and nonpotable reuse have the
potential for adding to the water resource and reducing water pollution,
but in every other aspect the two practices are very different.
• Water-quality monitoring and
treatment for potable reuse needs
to address all parameters embod-
ied in primary drinking-water reg-
ulations with due attention to the
many contaminants soon to be in-
cluded in the regulations. For
nonpotable reuse, the concerns
are only with microbiological con-
taminants and some parameters in secondary drinking-water regulations.
• A potable water reuse project requires extensive preliminary study
including less conventional treatment processes and more intensive
monitoring, often of organic compounds difficult to analyze. A nonpotable
reuse project uses fewer and only conventional treatment processes and
simple monitoring of only a handful of contaminants.
• There are hundreds of pipe-to-pipe nonpotable reuse systems in the
U.S., Japan, and elsewhere, some of which incorporate full dual-
distribution systems. On the other hand, there are no pipe-to-pipe potable
reuse systems in service anywhere in the world. The discharge of reclaimed
wastewater to a reservoir that formerly had only fresh water to supplement
a potable supply may be more acceptable than pipe-to-pipe reuse, but it
introduces new health concerns that those cities that now draw on run-of-
river supplies already face.
• An obstacle that faces potable water reuse projects is public acceptance,
and public education programs are vital. On the other hand, nonpotable
reuse for urban, industrial, and agricultural purposes is widely accepted and
engenders public enthusiasm as being environmentally appropriate.
EPA regulations state that "...priority should be given to selection of the
purest source. Polluted sources should not be used unless other sources are
economically unavailable..." Should we really be trying to persuade the
public that we should draw our drinking water from sewers? To claim that
it is better than some presently used waters does not inspire confidence.
The distrust of public supplies is already widespread, with increased use
of costly bottled water and point-of-use treatment devices.
Accordingly, while nonpotable reuse continues to be seen as having the
potential to be immediately feasible, it should not have to carry this
baggage of uncertainties and public resistance that constrain potable reuse.
More precise labelling in the literature would be helpful.
Daniel A. Okun
Kenan Professor of Environmental Engineering, Emeritus
University of North Carolina at Chapel Hill
;f
Selected Read!
-------
NEWS
Report Sets New Water
Reuse Guidelines
Christopher Powicki
For nearly 20 years, the U.S. World
Health organization (WHO) has
been considering the implications
of reclaiming wastewater treatment
plane effluent and has been evaluat-
ing die safeguards needed to protect
human health. Most recently, in 1987,
WHO sponsored a meeting of inter-
national experts in the wastewater
treatment and public-health fields
that resulted in the 1989 publication
of a report, "Health Guidelines for
the Use of Wastewater in Agriculture
and Aquaculture."
The report discusses historical and
current reuse practices from a public-
health perspective, recommends
guidelines and alternative mea-
sures for the control of infectious
diseases, and identifies areas of
uncertainty that require future re-
search. It affirms that wastewater
is a viable and valuable resource
needed to meet "perhaps the
greatest challenge of the next cen-
tury: appropriate management of
the limited water resources avail-
able."
NEW GUIDELINES
Conventional primary and sec-
ondary treatment practices empha-
size the reduction or removal of bio-
chemical oxygen demand and sus-
pended solids—the traditional para-
meters of water quality. Treatment
for reuse requires the removal of
pathogenic organisms for which con-
ventional treatment practices are not
very effective. Engineers designing
reuse plants are further challenged by
the variation in the maximum per-
missible concentrations of specified
pathogenic organisms for the differ-
ent end uses of reclaimed water. This
variation is based on the potential
levels of human exposure to the re-
claimed water for each reuse scheme.
To achieve the highest level of
health protection, engineers must
have clearly defined quality standards
for each end use, and they must con-
sider economic and operational fac-
tors. According to the report, "waste-
watcr of the required quality should
be produced at all times...without the
need for continuous monitoring.
Emphasis must therefore be placed
on careful selection and design of
treatment plants rather than on a
high degree of care in operation."
The report states that this is most
important in developing countries,
where money and adequate infras-
tructure are lacking and there is lim-
ited experience in operating treat-
ment plants. In these areas, "the sim-
plest and cheapest technology will
have the greatest chance of success."
Unfortunately, in many poor coun-
tries, organized water reuse programs
have made little headway, primarily
Reuse is the greatest
challenge of the
next century.
because many wealthy countries
committed to reuse have relied on
advanced and expensive technology,
according to the report. Wealthy
countries often rely on tertiary treat-
ment, including rapid sand filtration
and chlorination, to meet strict micro-
biological standards for effluents ap-
plied to agricultural lands.
The report states that recent epi-
demiological research indicates that
the risks from irrigation with re-
claimed water have been overesti-
mated and that these standards are
"unjustifiably restrictive, particularly
with respect of bacterial pathogens."
The report recommends new guide-
lines containing less stringent stan-
dards for fecal coliform.
The guidelines contain stricter stan-
dards for the concentration of hel-
minth eggs (Ascaris sp., Trichuris
sp., and hookworms), which are the
main public-health risks associated
with wastewater irrigation in areas
where helminthic diseases are en-
demic, such as developing countries.
According to the report, stabilization
ponds with a retention time of 8 to
10 days are particularly effective in
achieving helminth concentrations
less than or equal to 1 egg/L.
The guidelines do not cover all
helminths and protozoa that poten-
tially threaten humans exposed to re-
claimed water. For example, GiarAia
sp. are not cited. According to the
report, the helminths that are cov-
ered should serve as indicator organ-
isms for all large, settleable patho-
gens. Other pathogens of interest ap-
parently become non-viable in long-
retention-time pond systems. "It is
thus implied by the guidelines that
all helminth eggs and protozoan
cysts will be removed to the same ex-
tent," states the report.
The previous high standards and
the need for costly, sophisticated
treatment technologies to meet them
have caused poor countries to fail to
incorporate wastewater reuse into
new sewerage schemes, resulting in
the uncontrolled use of raw sewage
or treated effluent by farmers for irri-
gation purposes. The new guide-
lines, which are in line with the
quality of river water used for the
unrestricted irrigation of all crops
in many countries without
known ill effects, were designed
to eliminate these problems. The
idea was to "increase public-
health protection for a greater
number of people, while at the
same time set targets that were both
technologically and economically
feasible."
The report states that the guide-
lines must be carefully interpreted and
that they may need to be modified in
light of local epidemiological, socio-
ctdtural, and environmental factors.
OTHER ISSUES
The report describes the treatment
technologies that can be used to
meet the revised guidelines in the
most economical manner. It also
outlines application methods and
other measures that can reduce the
risks associated with ingesting crops
irrigated with > wastewater. It suggests
an institutional framework for the
implementation of health safeguards
including the development of appro-
priate regulations.
Research needs are outlined in sev-
eral areas: water-quality assessment
methods, treatment technologies, ir-
rigation technologies, epidemiology,
sociology, and economics.
-^The report is available from the
WHO Publications Centre, 49 Sheri-
dan Ave., Albany, NT 12210.
44-Selected Readings on Water Reuse
-------
Selected Readings on Water Reuse -45
-------
The use of treated wastewater
for field and crop irrigation
has a long history in the state
of California but, hi the last
25 years, wastewater reclama-
tion has become even more
prevalent in the state. This change
was largely driven by the need for
restrictions on wastewater effluent
discharges to watercourses and by
increased urbanization and ground-
water depletion. Primary uses for
reclaimed wastewater include irriga-
tion of parks, green belts, and golf
courses; impoundment of seasonal
waste discharges; and percolation to
recharge groundwater basins.
California water and wastewater
High-rate solids-contact clarification is
being used sud
management districts have been chal-
lenged to incorporate reclaimed water
into existing treatment and convey-
ance systems while meeting tighten-
ing state water-quality standards.
Wastewater treatment plants (WWTPs)
using trickling filters in their secon-
dary treatment train have a unique
problem: trickling filter effluent meets
secondary treatment standards, but
has higher turbidity levels than efflu-
ent from die activated-sludge process.
Therefore, for trickling-filter effluent,
die standard reclamation approach—
rapid sand filtration followed by chlo-
rination—does not meet California's
turbidity standard.
At a reclamation plant operated by
the Marin Municipal Water District
(MMWD), an in-depth evaluation of
clarification and filtration options was
undertaken to identify the most eco-
nomical and effective process to treat
trickling-filter effluent to meet tur-
bidity standards for reclaimed water.
TIGHTER STANDARDS
In 1978, the MMWD constructed
a water reclamation plant at Las Galli-
nas Valley Sanitary District's WWTP
north of San Rafael, Calif. The 1-mgd
reclamation plant used direct sand fil-
tration and chlorination processes to
treat effluent from die final clarifier of
the adjacent two-stage trickling filter,
secondary treatment plant. Reclaimed
CLARIFICATION AND
TO MEET LOW TURB
RECLAIMED WATER
Joel A. Fatter, Robert A. Ryder
46 - Selected Readings on Water Reuse
DARDS
-------
WATER'RECUIIMATION/REl/SE
wastewater has been used to irrigate
nearby Mclnnis Park and freeway
landscaping, and for utility services at
the WWTP.
Before the reclamation facility was
completed, the clarity requirements
for reclaimed wastewater used for irri-
gation of unrestricted public-access
landscaped facilities and recreational
impoundments were modified. The
California State Department of Health
(DOHS) proposed reclamation criteria
based on operation of several operat-
ing WWTPs. The DOHS required
that reclaimed water for use on these
areas have an average turbidity of less
than 2 nephelometric turbidity units
(NTUs), with a maximum not-to-ex-
ceed value of 5 NTU; and an average
coliform count of less than 2.2/100
mL, with a maximum not-to-exceed
value of 23/100 mL. Turbidity mea-
surement was established as a surro-
gate for effective removal of patho-
genic organisms, including viruses,
following extensive testing of re-
claimed water processes in California.
The reclamation plant was able to
meet the bacterial requirement, but
there was considerable difficulty meet-
ing the clarity standard. This was de-
spite the maintenance of good opera-
tions and the installation of several
improvements, including chemical
feed and prefiltration of the waste-
water effluent.
Direct filtration processes, with the
aid of chemical coagulants, have suc-
cessfully operated when the secon-
dary effluent turbidity is 10 NTU or
less, as is typical for many activated-
sludge secondary effluents. However,
trickling-filter effluent typically has
higher turbidity levels, and direct fil-
tration as a single treatment process
will not produce reclaimed water that
meets the turbidity standard.
After extensive testing by MMWD
staff, it was decided in 1987 that the
criteria for unrestricted landscape irri-
gation could be met by the plant if
the water was coagulated, settled,
and filtered through improved media.
Process improvements evaluated by
on-site pilot-plant testing were rec-
ommended to determine the type of
treatment necessary to achieve state
reclamation standards. The pilot-
plant tests would also identify the
cost of modifications and attendant
operational costs.
The MMWD authorized a study in
winter 1987 to evaluate and test pro-
cesses for improving wastewater treat-
ment. The study would also suggest
the apparent best process for provid-
ing a present capacity of 2 mgd, ex-
pandable to 4 mgd, that would use
the current and projected dry-weath-
er wastewater flows of Las Gallinas.
WASTEWATER TREATMENT
The processes and operations of
Las Gallinas have major impacts on
the operation and performance of the
reclamation plant. The WWTP uses a
two-stage, high-rate rock trickling-fil-
ter process that has a dry-weather
capacity of 2.9 mgd and wet-weather
peaks of up to 8 mgd. The WWTP
was upgraded in 1984 to provide ad-
vanced secondary treatment through
a nitrification fixed-film reactor tower
and effluent polishing through deep-
bed filters. Disposal to storage ponds
for dry-season irrigation of pastures
and hay fields, and to a marsh pond
for effluent enhancement before wet-
season discharge to Miller Creek was
improved.
The MMWD reclamation plant
was an in-line filtration facility that
has alum and polymer coagulant
addition and storage, a static rapid
mixer, deep course-media silica-sand
filtration, chlorination, and storage in
a combination chlorine-contact and
distribution reservoir.
The quality of influent delivered to
the reclamation plant depends on
whether the influent is pumped di-
rectly from the WWTP's final clarifier
Figure
Turbid
60
50
0 40
1
if>
330
T3
0)
-o
5
S-20
10
10
0
(
j 1 — Suspended Solids/
ify Relationship
•
j
/
/
/
. /
'//
.•
/
/
) 10 20 30 40 50
Turbidity — NTU
or from its filters. Average influent
turbidity is 10 to 20 NTU. At times,
turbidity is lower, but often it is
much higher.
The existing reclamation plant re-
moved most of the influent turbidi-
ty. Typically, the treated-water tur-
bidity was 4 to 8 NTU, despite rela-
tively high coagulant doses. It was
apparent that the influent was highly
variable and difficult to effectively
coagulate, clarify, and filter with the
available process facilities.
TRICKLING-FILTER QUALITY
Trickling filter effluent is usually
Selected Readings on Water Reuse -47
-------
Figure 2—High-Rate Solids-Contact Clarification
Winter Discharge
to MiUcr Creek
UaGoHinoiVoScy
Sanitary District
Woitawofcr Treatment
Focilite^^ ^^
Pond
/ Final
ye*4 Clarifier
(t v:....
FromTtfclJing*
Fi|OT
Marin Municipal
Water District
Reclamation Facilitie
•Daniadog" .
|2 MOD Capacity! Polymer (N)
Wastowator
Sludge Track
loDiiposol
Poitura (E)
related in terms of biochemical oxy-
gen demand (BOD) and suspended
solids (SS). EPA requires secondary
treatment to reduce wastewater con-
centrations of both to 30 mg/L. Las
Gallinas' permit has seasonal and
temporal SS limits (Table 1).
To achieve the treatment levels,
discharge from the secondary clari-
ficrs is the final effluent from June to
August, when discharge to San Fran-
cisco Bay is prohibited and the efflu-
ent is stored in holding ponds for irri-
gation. The nitrification fixed-film
reactor and effluent filter are in use
for the remainder of the year when
the final effluent is discharged to San
Francisco Bay via nearby Miller
Creek. Reclaimed water is used for
irrigation between April and Novem-
ber; thus, water-quality standards and
effluent quality differ periodically.
For tridding-filter effluent, the SS
concentration usually exceeds the tur-
bidity value. A plot of the relationship
of turbidity and SS for Las Gallinas
effluent shows that the summer ratio
was about 1.75:1, during the winter
it was only 0.75:1, with an overall
average of 1.25:1 and considerable
scattering of dam (Figure 1).
FILTRATION OF TRICKL1NG-
FIITER EFFLUENT
The literature reports that the
average removal of SS by rapid sand
Direct and Tertiary Filtration
Trickling-filter effluent achieved a poorer degree of biological floccula-
tion than activated sludge. The strength of the biological floe is also great-
er than chemical coagulation, as it is more difficult to achieve low turbidi-
ty by direct filtration of trickling filter effluent.
A review of tertiary filtration of wastewater found that the greatest fac-
tor affecting SS removal efficiency is the size of the particles in the influent
wastewater, and that about 30% of trickling filter effluents contain very
small particles that are not easily filtered. It was also found that trickling
filter effluent contains large quantities of submicron colloidal material, ana
because of the stoichiomefric effect for chemical destabilization, large
coagulant doses can be required. Other tests conducted in Seattle found
that over 95% of the number of particles in trickling filter effluent were in
the 0.5 to 2 micron range and that they contributed the greatest portion of
the turbidity. Also, only 30% of the particles in this size range were
removed by filtration.
There are specific recommendations for treatment processes to produce
a highly treated effluent; however, for reclaiming trickling filter effluent,
full flocculation sedimentation before filtration is highly recommended,
and for activated-sludge effluent, only direct filtration is recommended.
filters is two-thirds to three-fourths
of the settled water concentration. In
the nearby Ignacio WWTP that uses
a shallow-bed rapid sand filter, SS is
reduced by about 50%.
In fact, data on available technolo-
gy was for direct filtration used
mostly in activated-sludge treatment
processes, while clarification and fil-
tration were required for most trick-
ling- filter effluents to achieve the
standard of an average of less than 2
NTU (see Box). There are many ref-
erences to support what has practi-
cally been found in the years of oper-
ation of Las Gallinas WWTP—that
direct filtration alone is not sufficient
to produce reclaimed water with an
average turbidity of less than 2 NTU.
The DOHS recognized that, for
wastewater reclamation plants with
direct filtration, secondary effluent
should have a turbidity of less than 10
NTU. This was not usually achieved
48-Selected Readings on Water Reuse
-------
i WATER RECLAMATION/REUSE
Table 1—las Callings Effluent Limits for Suspended Solids, mg/L
Measurement Period
Period
Monthly average Weekly maximum Daily maximum
November to
March -
April to May
September
to October
June to August
30
15
15
not required
45
18
18
not required
60
20
20
not required
Upf low adsorption clarification is a new development that combines flocculation and solids capture in
a granular-media bed before filtration.
at Las Gallinas for the WWTP's sec-
ondary clarifier or polishing filter pro-
cesses.
There are effective means of up-
grading trickling-filter effluent, usual-
ly by the installation of a coupled or
short-detention aeration of activated
sludge to achieve effective biological
oxidation. In view of the district's
existing plant layout and need for
biological nitrification reaction, it was
not a viable consideration.
CLARIFICATION PROCESSES
Several clarification processes were
considered for Las Gallinas WWTP.
Conventional coagulation and
settling. Conventional coagulation
and settling have been used success-
fully to clarify wastewater before fil-
tration to provide flexibility for coag-
ulant chemical doses, flocculation
energy, and sludge recirculation.
Coagulation times range from 15 to
30 minutes, settling overflow rates
range from 0.5 and 0.75 gpm/sq ft,
and detention times are 1 to 2 hours.
To provide effective conventional
clarification of wastewater, it is nor-
mal that alum doses range from 75 to
250 mg/L and polymer doses range
from 2 to 10 mg/L.
The tests conducted in this investi-
gation found that conventional clari-
fication used the normal amount of
coagulant, flocculation energy, and
time. The tests also showed that set-
tling overflow rates that produced a
settled-water turbidity of less than 3
NTU could then be filtered to pro-
duce a finished-water turbidity of 1.2
to 1.8 NTU. This requires a dose of
70 to 100 mg/L of alum, 2 to 5
mg/L of polymer, 10 to 15 minutes
of flocculation, and an overflow rate
of 0.75 gpm/sq ft.
High-rate inclined-plate tube
settlers. Inclined-plate and tube set-
tlers have been used in several clarifi-
cation applications following floccu-
lation.
In all instances, there is an accumu-
lation of sludge near the top of the
inclined tubes that is most effectively
removed by periodically shutting off
the plant and dropping the water
level below the tubes. The floe slides
off and plates or tubes are cleaned.
This tube cleaning is necessary every
5 to 7 days and takes several hours.
Water-jet cleaning of the surface of
the tubes can also be used, but is
more time consuming and less satis-
factory than the draining practice.
Solids-contact clarification.
Solids-contact clarification has been
used in several wastewater clarifica-
tion processes. It usually combines
high-rate flocculation with a turbine
mixer and upflow clarification. Usual
overflow rates are 1 to 1.5 gpm/sq ft.
A recently developed high-rate
solids clarifier has been successfully
used in Germany to clarify wastewa-
ter effluents with an overflow rate of
5 gpm/sq ft without tubes, and 10
gpm/sq ft with tubes. One advan-
tage of this clarifier is that the blow-
down sludge concentration can
approach 10%, as compared to the
usual 1% or less of conventional or
upflow clarifiers. This new process
was selected for the pilot-plant test at
Las Gallinas.
Adsorption clarification. The ad-
sorption clarification process is a new
Selected Readings on Water Reuse - 49
-------
development that combines the
functions of flocculation and solids
capture in a granular-media bed
before filtration. The process is akin
to two stages of filtration in that the
initial adsorption clarificr uses a high
flow rate of 5 to 10 gpm/sq ft and
large media of 3 to 5 mm. Coagulant
chemicals are introduced before the
adsorption clarifier and are flocculat-
ed within the granular bed by the
high-flow energy and turbulence
passing through die bed. This causes
an enlargement of floe size and
retention within the granular bed.
There are two basic types of ad-
sorption clarificrs: the downflow
mode and the upflow mode. The
downflow mode, developed in the
early 1970s, is used extensively in
Europe and South America. Down-
flow adsorption clarifiers have had
limited use in wastewater clarifica-
tion. Both types of clarifiers use an
air-wash-aided backwash, silica-sand,
and 4 to 6 ft of anthracite media.
The clarified-water turbidity is moni-
tored to aid in the adjustment of
coagulant dose, and a polyelectrolyte
filter aid is used to enhance the filter-
ability of the clarified water.
Pilot-plant trials of upflow adsorp-
tion clarification were conducted by
the Desert Water Agency at the Palm
Springs WVVTP on trickling-filter
effluent in 1984 and 1985. The clari-
ficr used a 4-ft bed on polyethylene
beads retained by a stainless-steel
screen. The clarifier was back-washed
by an air-water backwash cycle when
the head loss was 4 ft through the bed.
The pilot-plant tests were success-
ful in producing a reclaimed water
with turbidity of less than 2 MTU at
influent turbidity concentrations as
high as 19 NTU when operating at a
flow rate of 10 gpm/sq ft, using a
minimal alum and an anionic poly-
electrolyte dose controlled by a
microprocessor that monitors fil-
tcrcd-water turbidity. Water produc-
tion was 94.4% in summer when
influent turbidity was less than 10
NTU, and 92.4% in winter when
turbidity was between 10 and 19
NTU. Thus, a relatively high propor-
tion of water is used in backwash—
5.5% to 7.5%.
Based on these tests, the Desert
Water Agency constructed a 5-mgd
treatment facility using upflow
adsorption clarification, and Las Gal-
linas pilot tested the same option.
Dissolved-air flotation.
Dissolvcd-air flotation (DAF)
has been used for clarification of
Table 2-Copital Cost of Clarifier
Treatment capacity
Alternatives
Process
1 mgd
2 mud
Rank
1
2
3
4.
5
d
7
'... :.8,:.'. .:.
9
CRFS
CCSF
SCUC
: FIPS .;:
DAF
DEF:
HRSFS
".".:: UAC
DAY
$581 000
556000
360 000
230 ooQ :
324 000
618 000
337 000
262 000
265 000
$1 025 000
810000
540 000
: 3:45:000
396 000
975000
41 1 000
446000
450 000
9
7
6
: : 4
2
8
3
4
5
Capital costs for construction of process units exclusive of any piping, electrical,
sludge handling, site, or ancillary facilities at February 1988 costs.
2Based on 2 mgd capacity.
wastewater effluents at several Euro-
pean installations with typical over-
flow rates of 1 to 2 gpm/sq ft.
Bench-scale tests were conducted at
Las Gallinas and it was found that
direct flotation was not too success-
ful, but recycle pressure flotation
could provide a clarified water with a
turbidity of less than 4 NTU at an
overflow rate of 0.25 gpm/sq ft.
This is not nearly as good as the 1-
gpm/sq ft!for a settling process.
DAF did not seem to be a promising
clarification process for wastewater
reclamation 'at Las Gallinas.
Diatomaceous-earth filtration.
Diatomaceoius-earth filtration (DEF)
can, with adequate precoat, produce
a highly clarified effluent with only a
trace of suspended solids—but at a
high cost. Frequently there is a prob-
lem in handling variations in suspend-
ed-solids loading, and automation of
body feed and backwash are required
for the process to be reliable.
Bench-scale tests of DEF on the
direct filtered effluent of Las Gallinas
achieved a reduction in turbidity
from 2.2 to 1.7 NTU. Because of
this relatively low turbidity reduction
(30%), it was concluded that DEF
would not provide sufficient polish-
ing clarification when filtered-water
turbidities were above 5 NTU. This
process was, however, tested for a
limited period at Las Gallinas and
found to require excessive doses of
diatomaceous earth to produce the
desired low-turbidity effluent.
Ozonation microflocculation
clarification. Ozonation, which has
been used at several WWTPs for dis-
infection, may provide microfloccula-
tion of organic color compounds, de-
crease coagulant dose, and improve
effectiveness. Usually, ozone doses
for disinfection are high—from 10 to
25 mg/L. Doses of about 10 mg/L
in wastewater effluent can provide
microflocculation benefits with 5 to
10 minutes of contact time and re-
duce coagulant dose requirements by
50% before clarification and filtration.
Chlorination is still required after fil-
tration to produce a coliform concen-
tration of less than 2.2/100 mL.
Clarification costs. Preliminary
capital and operations and mainte-
nance (O & M) costs were devel-
oped for each clarification alternative
to relate probable cost-effectiveness
(Tables 2 and 3). In addition, non-
cost factors including reliability, flex-
ibility, implementation, and aesthet-
ics were compared for each alterna-
tive (Table 4). This information
determined the rationale for why cer-
tain processes were selected for pilot-
plant testing. The information also
provided a reference of the more
detailed clarification process analyses
that were used to formulate an
apparent-best-process for upgrading
Las Gallinas.
BENCH- AND PILOT-SCALE TESTING
Bench-scale studies were conduct-
ed to evaluate conventional coagula-
tion, flocculation, and clarification
processes. DAF and DEF processes
were also screened, The bench-scale
tests indicated that conventional
flocculation and clarification were
the best processes; however, high
concentrations of alum—70 to 100
mg/L—were required to produce
good settling.
The objective of the pilot-plant
testing was to identify and demon-
strate the effectiveness of various
treatment processes in removing tur-
bidity and suspended solids in the
50-Selected Readings on Water Reuse
-------
WATER RECLAMATION/REUSE
Table 3—Operation and Maintenance Costs of Clarifier
Alternatives Process
." 1
2
3
4
5
6
7
8
9
CRFS
CCFS
SCUC
F1PS
DAF
DBF
HRSFS
UAC
DAC
Energy
hp $/yr
15
14
17
6
27
150
14.5
3
6
5,250
4,900
5,950
2,100
9,450
52,500
5,100
1,050
2,100
Chemical
Ib/day $/yr
1,280
1,280
1,200
1,280
1,680
5,000
1 ,030
600
600
24,600
24,600
23,400
24,600
30,400
121,800
20,000
20,000
20,000
Operation Maintenance
hr/day $/yr $/yr
0.5
0.5
0.5
1
1
2
1
1
1
2,100
2,100
2,100
4,200
4,200
8,400
4,200
4,200
4,200
10,200
8,200
8,400
6,900
7,300
9,800
8,250
13,400
13,600
Total
$/yr
42,150
39,800
39,850
37,800
51,350
192500
37,550
38,650
39,900
Table 4—Comparison of Clarifier Alternatives for Cost and Non-Cost Factors
Alternative
Proportionate
evaluarion%
1
2
3
4
5
6
7
8
9
Process
Type
CRFS
CCFS
SCUC
FIPS
DAF
DEF
HRSFS
UAC
DAC
Capital
cost1
25
0
8
18
25
23
2
23
21
21
O&M
costs Reliability2
25
25
25
25
25
23
0
25
25
25
15
15
13
12
5
10
2
12
8
8
Flexibility
10
10
9
8
5
2
3
8
7
7
Implement- Permit-
ability ability
5
1
1
1
3
3
5
4
5
5
5
5
5
3
3
3
2
2
2
2
Expand-
ability
5
1
1
1
2
3
4
4
5
5
Aesthetics
10
10
10
8
6
8
8
6
4
4
Total
valuation
100
52
59
76
74
75
24
84
77
77
Rank
_
7
8
4
6
5
9
1
2
3
'Capital and annual O&M valuations are on the basis of full 25% for the lowest cost alternative and 0% for the most costly, with every
other alternative as a cost proportion of this scale.
2Non-cost factors amount to 50% of worth and are based on estimate of process performance reliability; relative ease to implement at
the site; and appearance, noise, and odor aesthetics.
wastewater effluent to meet the
reclamation requirements. The pilot
processes were evaluated, on chemical
coagulant requirements, loading
rates, impact of source water-quality
variables, waste volumes and concen-
trations, and O&M considerations.
Three pilot processes were tested:
high-rate solids-contact and upflow
clarification processes for treatment
upstream of the existing direct filtra-
tion reclamation plant, and a DEF
process for polishing treatment down-
stream of the existing sand filters.
All three of the pilot plants tested
were successful in removing turbidity
in the wastewater to less than 2
NTU. The upflow adsorption clarifi-
er used the least amount of chemical
coagulant but produced the most
backwash water. This resulted in a
low 90% net production of filtered
water. The high-rate solids-contact
clarifier required about twice the
dose of chemical coagulant but pro-
duced little blowdown waste, result-
ing in a 99.7% net production of
clarified water. The high-rate clarifier
met the 2-NTU turbidity require-
ment without filtration; however, fil-
tration was required to meet DOH's
virus removal requirements. Because
of filter backwash requirements, the
net production of the combined high-
rate solids contact clarification and
filtration process exceeds 97%.
The DEF polishing was successful
in producing a final effluent with tur-
bidity less than 2 NTU, with the
existing filters producing an effluent
with a turbidity of 3.4 to 4.5 NTU.
However, higher turbidities from the
filters required greater body feed of
diatomaceous earth and further
reduced the short 9- to 10-hour fil-
tration cycle. For this system to be
effective, the existing filters would
need to produce a constant effluent
turbidity of less than 4.5 NTU.
CLARIFIER COMPARISONS
Results of the pilot-plant tests were
evaluated to develop alternative plant
process and operating configurations
to meet requirements for virus-free
water. Particular emphasis was given
to pilot-plant testing of alternative
clarification processes, effluent flow
and water quality produced by Las
Gallinas, operating experience and
planning objectives of the current
MMWD reclamation plant, and cur-
rent and future requirements for
reclaimed wastewater in California.
Alternative plant improvement
facilities were compared on the basis
on capital costs, O&M costs, annual
cost effectiveness, and non-monetary
factors including reliability, flexibility,
ease in construction, ease in imple-
mentation, institutional and intera-
gency requirements, aesthetics, and
environmental factors. Proportionate
ranking of these factors favored the
high-rate solids-contact clarification
process as the best project to design
and construct (Figure 2).
The suggested improvement facili-
ties included more than the clarifica-
tion process. Other features of the pro-
ject include a new inlet pump station
and pipeline from Las Gallinas' stor-
age and marsh ponds, improved and
expanded filtration facilities, and wash-
water and sludge-handling facilities. •
Joel A. Fuller and Robert A. Ryder
are environmental engineers for
Kennedy/ Jenks/ Chilton in San
Francisco, Calif.
Selected Readings on Water Reuse - 51
-------
Water reuse is becoming
an increasingly common
component of water re-
source planning as op-
portunities for conven-
tional water-supply de-
velopment dwindle and costs for
wastcwatcr disposal climb. Both non-
potable and potable reuses of re-
claimed wastewater offer means to
extend and maximize the utility of
limited water resources.
Factors that contribute to the
consideration of potable reuse as an
alternative water supply include fu-
ture water demand exceeding sup-
ply, limited locally available conven-
tional surface-water and groundwa-
tcr supplies; polluted local conven-
tional supplies; lack of politically vi-
able, demand-reduction measures;
lack of economically viable nonpot-
ablc reuse opportunities; high cost
of wastewatcr disposal; water rights
favoring reuse rather than disposal;
and high cost and environmental im-
pacts of developing remote conven-
tional water supplies.
Successful implementation of a
potable reuse project hinges on satis-
factory response to common concerns
often raised regarding both planned
indirect and direct potable reuse.
WATER-QUALITY STANDARDS
AND PUBLIC HEALTH
For indirect, potable reuse, the re-
covered water must be of equal or
better quality than the receiving
water source. For instance, if the re-
ceiving water source is a potable
water aquifer requiring only disinfec-
tion before distribution, then the re-
covered water recharged to the
aquifer needs to be of drinking-water
quality. Similarly, if the receiving
water source is a river requiring full
conventional water treatment before
distribution, then the recovered water
augmenting the river flow need only
be of a quality equal to the natural
quality of the river water. In either
case, the recovered water should be
of a quality to prevent deleterious ef-
fects in the receiving water source
Public Education
Program
A public education program
should consider the following
subjects:
• The need for additional
water supplies.
• The availability of additional
water supplies.
• The cost of additional water
supplies.
• The environmental impact of
developing additional water
supplies.
• me status of potable water
recovery technology.
• The safeguards incorporated
in potable water recovery and
reuse processes such as multi-
ple barriers, extensive moni-
toring, and possible blending
of the recovered water with
another water source.
such as dissolved oxygen depletion,
eutrophication, increased total dis-
solved solids, or accumulation of
trace organics or inorganics.
For direct, potable reuse, the re-
covered water must be of equal or
better quality than the finished water
produced from the highest quality
source water .locally available.
At this stage in the development
of potable reuse projects, a demon-
stration-scale plant: is required to sat-
isfy regulatory agencies that the re-
covered water quality is suitable for
reuse. The recovered water should
be produced for at least 1 year to
document the reliability of the quali-
ty during seasonal variations. The re-
covered water should be subjected to
extensive physical, chemical, micro-
biological, and toxicological testing
for direct comparison to either the
receiving water source (indirect
potable reuse) or the highest quality
finished water available (direct
potable reuse). In addition, the re-
covered water quality should be
compared with existing and pro-
posed drinking-water standards and
public health advisories.
The U.S. Environmental Protect-
ion Agency (EPA) does not explicitly
regulate the practice of potable reuse.
However, the Clean Water Act and
the Safe Drinking Water Act (SDWA)
establish laws that: govern the opera-
tion of facilities that treat wastewater
and drinking water. Outside of these
constraints, EPA delegates permitting
of specific wastewater reuse opera-
tions to the states. Currently, individ-
ual states prohibit potable reuse, do
Reuse Terms
Unplanned, indirect, potable reuse occurs when a
water supply is withdrawn for potable purposes from a
natural surface or underground water source that is fed in
part by the discharge of a wastewater effluent. The
wastewater effluent is discharged to the water source as a
means of disposal and subsequent reuse of the effluent is
a byproduct of the disposal plan. This type of potable
reuse commonly occurs whenever an upstream water user
discharges wastewater effluent into a water course that
serves as a water supply for a downstream user.
Planned, indirect potable reuse is similar to unplanned,
indirect potable reuse; however, the wastewater effluent is
discharged to the water source with the intent of reusing
the water instead of as a means of disposal. This type of
potable reuse is becoming more common as water re-
sources become less plentiful and the luxury of wastewater
disposal declines.
Direct potable reuse is the piped connection of water
recovered from wastewater to a potable water-supply dis-
tribution system or a water treatment plant. Currently,
there are no examples of direct potable reuse in practice
in the U.S.; however, demonstration of direct potable
reuse is occurring in Denver, Colo., and San Diego, Calif.
Conventional-plant water recovery involves linking the ex-
isting wastewater treatment plant with a new water resource
recovery treatment facility designed to reclaim wastewater
to a qualify suitable for either indirect or direct potable
reuse. The conventional-plant approach to water recovery
has been the method or choice to date for most existing
planned, indirect, potable reuse facilities,.
Single-plant water recovery is the reclamation of previ-
ously untreated municipal wastewater to a quality suitable
for either indirect or direct potable reuse in a single treat-
ment facility. The single-plant approach may have advan-
tages over the conventional-plant approach under some cir-
cumstances for the following reasons.
e A single plant can be located near both a source of
untreated wastewater and a desired point of introduction
to either a water source or a finished water distribution
system. In contrast, a conventional plant is linked to an ex-
isting treatment plant that is often far removed from the
52-Selected Readings on Water Reuse
-------
/I
//
y'
~4
POTABLE
WATER
desired point of recovered water distribution. Therefore, a
single plant has increased siting flexibility that could re-
duce the cost of pumping associated with distribution of
the recovered potable water.
• The siting flexibility of the single plant relative to the
conventional plant could allow location near a wastewa-
ter interceptor conveying predominantly domestic
wastewater as opposed to a conventional plant possibly
downstream of industrial and commercial dischargers.
Domestic wastewater is generally lower in contaminants,
which eases the burden on the potable water recovery
treatment process.
• Water recovery in a single plant may be more oper-
ationally convenient than water recovery in individual
plant modules. A single plant would have a single treat-
ment objective—to recover water for indirect or direct
potable reuse from untreated wastewater—while the
treatment plant link of the conventional plant may have
two treatment objectives—to meet National Pollutant
Discharge Elimination System requirements for disposal
and to meet performance standards for contribution to a
potable reuse treatment.
Multiple contaminant barriers refers to the provision of
more than one unit process capable of treating the physi-
cal, chemical, and microbiological contaminants of con-
cern. Multiple contaminant barriers provide treatment reli-
ability because failure of one unit process to effectively re-
move a contaminant of concern does not preclude effective
overall treatment, because additional contaminant barriers
are available. For instance, provision of biological treat-
ment, GAC adsorption, and reverse osmosis in a potable
water recovery treatment train establishes multiple barri-
ers to the passage of total organic carbon into the recov-
ered water. Similarly, unit process combinations can be
configured to deal with other contaminant categories such
as heavy metals, nutrients, and pathogens. Fortunately,
many unit processes act as barriers to move more than
one contaminant category, so the number of unit processes
required for potable water recovery does not become ex-
cessive.
Process redundancy refers to the provision of duplicate
unit processes to provide treatment reliability in the event
that equipment failure or maintenance requirements ren-
der a particular unit process inoperable.
Selected Readings on Water Re.use - 53
-------
not have regulations regarding
potable reuse, or evaluate potable
reuse projects on a case-by-case basis.
Therefore, it is essential to identify
and involve concerned state agencies
early in a potable reuse assessment.
Similarly, it is important to involve
local agencies. Agencies should be
identified that have specific responsi-
bility to public health, water-quality
standards, development of reclama-
tion policies or requirements, water
ownership issues, permit require-
ments, and potential funding sources.
Close involvement with such agen-.
cics is paramount to the develop-
ment of a potable reuse implementa-
tion program that encourages a vari-
ance from regulation prohibition,
serves as a catalyst for the develop-
ment of potable reuse regulations,
and persuades responsible agencies
of the benefits and safety of the
potable reuse project.
Public acceptance is generally the
most crucial element in determining
the success or failure of a potable
reuse project, particularly because
regulatory agencies often have politi-
cal roots that react to public senti-
ment. A potable reuse project can be
technically viable, the recovered
water proven safe by the best scientif-
ic procedures available, and regulato-
ry agencies poised for acceptance; yet,
a project can still fail because of a lack
of public acceptance. A public educa-
tion program is vital to the success of
a potable reuse program (see Box).
Several technical issues and con-
cerns arc often raised during the de-
velopment of a potable reuse pro-
ject, all of which can be addressed
by the operation of a demonstration
plant, thoughtful engineering de-
sign, and sound operations manage-
ment (see Box).
POTABLE REUSE TREATMENT PROCESSES
AND PERFORMANCE
Unit processes and their relative ca-
pabilities to remove specific contami-
nants are shown in the Figure.
Contaminant removal is considered to
be a relative measure of unit-process
ability to act as a barrier to that con-
taminant. Unit processes identified as
contaminant barriers are expected to
remove at least 50% of the contami-
nant. Potable water recovery systems
contain more contaminant barriers
than a conventional water treatment
plant, because wastewater is typically
of poorer quality than a conventional
surface-water or groundwater supply.
Unit processes often included in a
potable reuse facility are biological
treatment with or without nitrogen
removal, high-lime treatment with
two-stage recarbonation, granular-
media filtration, granular activated
carbon (GAC), demineralization
(membrane treatment), air stripping,
rapid infiltration and recovery, and
disinfection (see Box).
POTABLE REUSE CONCEPTUAL LAYOUT
AND TREATMENT SELECTION
Selection of a potable reuse treat-
ment and its planned integration
into a water-supply system is site-
specific. The geographic layout of a
city's water resource system should
be evaluated to determine factors
that may inhibit or favor develop-
Potable Reuse Technical Issues and Concerns
The following are common issues of concern:
• The ability to recover potable water from wastewater, safe for either in-
direct or direct human consumption.
• The process redundancy or operational procedures necessary to assure
product safety in the event of mechanical and operational malfunction.
• The flexibility to modify water recovery treatment processes in response
to changes in raw water qualify and new regulatory requirements.
• The method of reuse or disposal of potable water waste residuals.
• The distribution of recovered potable water so that the benefits are
shared equitably.
• The chemistry and benefits of blending recovered potable water with
other finished waters.
• The cost and reduced environmental impact of potable water recovery
in comparison to other alternative water supplies.
Potable Reuse History
Unplanned, indirect, potable reuse has been in practice
since humans first began disposing wastewater into wa-
tersheds that are hydrologically connected to raw water
supplies. As population has increased, so has the quantity
of wastewater and the technology to manage the in-
creased volumes of wastewater. Potable reuse is one of
the developing strategies to manage wastewater and re-
cover and reuse water resources.
The following is a summary of some of the historical
milestones marking the development of planned potable
reuse as a viable component of a water resource man-
agement plan.
In 1931, Los Angeles, Calif., demonstrated that prima-
ry sedimentation, secondary biological treatment, and
sand filtration treatment of wastewater created a recov-
ered water suitable for spreading on soil, thereby con-
tributing significantly to the groundwater supply without
impairing its quality.
In 1956 and 1957, severe drought conditions forced
the city of Chanute, Kans., to practice direct potable
reuse. Secondary treated water was impounded and re-
cycled back through the city's water treatment plant
where it received super chlorinafion to inactivate the
greater pathogen concentrations associated with the re-
cycled effluent. No adverse health effects were noted;
however, after several cycles, the water became pale yel-
low in color and was aesthetically unappealing.
In 1960, the Advanced Waste Treatment Research Pro-
gram of the United States Public Health Service was direct
ed to develop new treatment technology for renovating
wastewater to allow more direct and deliberate water reuse.
In 1962, at Whittier Narrows, near Los Angeles, Calif.,
disinfected secondary effluent from a 10-mgd water re-
clamation plant was spread on the ground for infiltration
to an underground potable water supply. This operation
continues and the amount of reclaimed water recharged
annually averages 16% of the total inflow to the ground-
water basin. Depending on the physical characteristics,
54-Selected Readings on Water Reuse
-------
WATER RECLAMATION/REUSE
ment of indirect versus direct pot-
able reuse and single-plant versus
conventional-plant water recovery.
The treatment selected should pro-
vide multiple contaminant barriers
and process redundancy to assure
product reliability. The conceptual
layout and specific treatment select-
ed should satisfactorily address
health, regulatory, social, and techni-
cal issues and concerns.
Conceptual layout. The selection
of indirect versus direct potable re-
use and single-plant versus conven-
tional-plant water recovery starts
with a review of the geographic lay-
out of the overall water and waste-
water system. Important factors to
review and evaluate include location
and character of existing and future
water supplies and transmission sys-
tems, location and character of exist-
ing and future water treatment facili-
ties and distribution systems, cus-
tomer service area existing and fu-
ture demographics and zoning, and
location and character of existing
and future wastewater collection and
treatment facilities.
Treatment selection. Based on the
conceptual layout of the potable reuse
facility, a water recovery treatment
Unit Process Coi
Gross
Containment
Category
Disolved Solids
Biological Oxygen
Demand
Total Organic
Volatile Organic
Chemicals
Heavy Metals
Nutrients
Radionuclides
Microbial Factors
itainment Barriers
"c
O
£
o
-o
s
^^
VMS
w
t/ljfJl
*****
fFrTn
§ Biological Treatment
with Nitrogen Removal
^'(/l
y)jF*
**#
^«
'r'r*&
1*43
%&!
,/Zf
r&"iP
.1
"8-5
'roS
il
ca a:
r^'iP
tf>'?n
§High Lime with
Recarbonation
V6f
Membrane
Demineralizah'on
Eifl^{/i
I fj\rf
H Solar Distillation
'&r7
%&$
<=8
.1
1
It
-D 1
'§-§
a£a£
&??A
'4&$
l/l'^A
r^'in
Chemical
Oxidation/Disinfection
L/7y>Vj
system must be selected to reclaim
the wastewater influent to a suitable
quality for reuse. Usually, alternative
systems are conceptually developed,
evaluated, and screened to arrive at a
selected alternative for further devel-
opment. Generally, a qualitative and
quantitative analysis of evaluation cri-
teria is used to arrive at a selected
treatment system (see Box).
Based on existing planned, indi-
rect, potable reuse projects in opera-
tion and on existing or planned,
demonstration-scale direct potable
reuse projects, there are several likely
treatment scenarios for the defined
potable reuse systems. These treat-
ments vary on a case-by-case basis.
Planned, indirect potable reuse
with single plant water recovery and
recycle to a groundwater of firface-
water supply. Likely treatment in-
cludes primary treatment, secondary
treatment, biological nitrogen re-
moval, high-pH lime treatment with
recarbonation, filtration, activated
carbon adsorption, slip-stream re-
verse osmosis with decarbonation,
ozonation, and storage.
Planned, indirect potable reuse with
conventional plant water recovery and,
recycle to a groundwater or surface-
water supply. Likely treatment is the
same as the previous single-plant
water recovery except the primary
treatment, secondary treatment, and
possibly the biological nitrogen re-
moval would be offset to an existing
treatment plant with such capabilities.
Direct potable reuse with single-
plant water recovery and recycle to a
finished water distribution system.
Likely treatment includes primary
location, and pumping history of a given well, the popu-
lation drawing potable water from the groundwater basin
is estimated to be exposed to a reclaimed wastewater
percentage ranging from 0% to 23%. After extensive data
acquisition, evaluation, and statistical analysis, no mea-
surable adverse health effects have been correlated to the
use of the groundwater replenished with recovered water.
In 1965, the South Lake Tahoe Water Reclamation
Plant was the first large-scale facility to use advance
wastewater treatment processes to remove nutrients and
organ ics from wastewater.
In 1968, the Windhoek, South Africa, experimental di-
rect potable reuse plant was commissioned; and in 1970,
the experimental 1.2-mgd Strander Water Reclamation
plant in Pretoria, South Africa, was commissioned. Since
1968, finished water from the Windhoek plant has occa-
sionally been used to directly augment potable water sup-
plies. No identifiable diseases have been associated with
this water recovery and reuse practice.
In 1972, the Federal Water Pollution Control Act stated
that discharge of pollutants into all navigable waters will be
eliminated, thereby encouraging water recovery and reuse.
In 1976, the Orange County, Calif., Water District's
Water Factory 21 began operation. The 15-mgd facility re-
claims unchlorinated secondary effluent to drinking-water
quality and recharges it into a heavily used groundwater
supply to prevent salt water intrusion. The water recovery
treatment includes lime clarification, air stripping, recarbon-
ation, filtration, carbon adsorption, slip-stream reverse os-
mosis, and disinfection. Estimates project that no more than
5% of the recovered water actually comprises the domestic
supply. The Orange County Water District has found no evi-
dence that indicates that this indirect potable reuse practice
poses a significant risk to users of the groundwater.
In 1 978, the 1 5-mgd Upper Occoquan Sewage
Authority (UOSA) Water Reclamation plant in Fairfax
County, Va., began reclaiming wastewater for subsequent
discharge to the Occoquan Reservoir. The Occoquan
Reservoir serves more than 1 million people and is the prin-
ciple water-supply reservoir in Northern Virginia. During
(continued on page 78)
Selected Readings on Water Reuse -55
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treatment, secondary treatment, bio-
logical nitrogen removal, high-pH
lime treatment with recarbonation,
filtration, GAG adsorption, full-
stream reverse osmosis, ozonation,
residual disinfection, and storage.
Direct potable reuse with conven-
tional plant water recovery and recy-
cle to a. finished, water distribution sys-
tem. Likely treatment is the same as
die previous single-plant water recov-
ery except the primary treatment, sec-
ondary treatment, and possibly the
biological nitrogen removal would be
offset to an existing treatment plant
with such capabilities.
Based on these scenarios, the in-
direct and direct potable reuse water
recovery plants are very similar, except
that the direct potable reuse treat-
ment includes residual disinfection
and fall-stream rather than slip-stream
reverse osmosis. The difference seems
marginal, but the cost for full-stream
versus slip-stream reverse osmosis is
substantial because of the difficulty in
handling increased volumes of brine
concentrate from die higher-capacity
reverse osmosis process.
One mcdiod to reduce the direct
potable reuse reverse osmosis re-
quirement is to evaluate die includ-
ing of a rapid infiltration and recov-
ery process in the treatment train.
This option, however, is highly site
specific, as land requirements and soil
and aquifer characteristics are crucial
to its feasibility.
The treatment scenarios focused
on die liquid side of the treatment;
however, waste residuals such as pri-
mary and biological sludges, lime
sludges, filter backwash wastewater,
and spent activated carbon must also
be handled.
Beyond liquid and waste treat-
ment, there are often considerable
costs associated widi pumping and
conveyance of the recovered water
to the point of distribution. These
requirements and costs are site spe-
cific and mlist be evaluated on a case-
by-case basis.
POTABLE REUSE COSTS
The factors that have the greatest
influence on the capital and operat-
ing costs associated with a potable
reuse project include the capacity of
the proposed potable reuse project;
die level and type of treatment select-
ed to recover the potable water; die
volume and type of wastes requiring
disposal; proximity of the potable
reuse project to a wastewater source
and recovered water point of distri-
bution; and the provision of ade-
quate storage capacity in die potable
recycle stream to monitor potable
quality bqfore reuse. This storage
may be natural (aquifers, lakes) or
manmade (tanks, impoundments).
The economic feasibility of potable
reuse should be based on a cost com-
parison of Developing odier raw water
supplies. Those cost components that
are the same, regardless of the source
of die raw water supply, should be
deleted to; simplify the analysis. The
cost benefits of potable reuse need to
be accounted for; potable reuse
deletes some wastewater disposal
costs that would otherwise increase if
water supplies were increased and
reuse was hot practiced.
The economics of potable reuse
should be evaluated against other
water supplies at the margin or in-
crement of additional water supply.
The financial feasibility of potable
reuse, however, should be evaluated
from a system-wide perspective. The
financial feasibility of implementing
a potable reuse project comes down
to cash flow that depends on system-
wide revenues and debt service.
POTABLE REUSE IMPLEMENTATION
The steps necessary to implement a
potable reuse project address the is-
sues and concerns regarding water-
quality standards and public healdi;
legal, regulatory, and political influ-
ences; public acceptance; and techni-
cal process engineering. First and
foremost, early inclusion of all state,
county, and local regulatory agencies
in the development of a potable reuse
project is paramount to project suc-
cess and helps to clarify agency per-
spectives and identify potential flaws.
Second, a demonstration facility is
required at this stage of potable
reuse development in the U.S.
Although demonstration projects are
underway in Denver, Colo., San
Diego, Calif., and Tampa, Ha., site-
specific demonstration is necessary
to address unique regulatory, public,
and technical concerns.
Third, a regulatory approval pro-
gram is required to promulgate
potable reuse standards of perfor-
mance and operation and to define
procedures to gain acceptance.
Fourth, a public involvement pro-
gram is required to educate and gain
public acceptance of potable reuse.
Therefore, a potable reuse imple-
exfended droughts, the plant discharge has accounted for
as much as 80% of the flow into the reservoir. The recla-
mation treatment includes primary treatment, secondary
treatment, biological nitrification and denitrification, lime
clarification and recarbonation, filtration, activated-carbon
adsorption, and disinfection. The plant is currently being
expanded to a 38-mgd average capacity to handle in-
creased wastewater volumes. No negative health effects
attributable to the plant or effluent discharges have been
reported since the plant has been in operation.
Also, in 1978, the 4.83-mgd Tahoe-Truckee Sanitation
Agency Water Reclamation Plant in Reno, Nev., began
operation. This plant also uses advanced wastewater recla-
mation processes to recover water suitable for release to
the Truckee River that is used as a water supply by Reno.
From 1981 to 1983, the 1-mgd Potomac Estuary
Experimental Water Treatment Plant was operated with a
plant influent blend of Potomac estuary water and nitrified
secondary effluent to simulate the influent water quality ex-
pected during drought conditions when as much as 50% of
the estuary flow would be comprised of treated wastewa-
ter. Treatment included aeration, coagulation, clarification,
predisinfection, filtration, carbon adsorption, and post dis-
infection. An independent National Academy of Science
and National Academy of Engineering panel reviewed the
extensive testing performed by the Army Corps of Engi-
neers. The panel concluded that the advanced treatment
could recover water from a highly contaminated source
that is similar in quality to three major water supplies for
the Washington, D.C., metropolitan area.
In 1983, the 1 -mgd Potable Reuse Demonstration Plant
in Denver, Colo., began operation. This plant was de-
signed to evaluate the feasibility of direct potable reuse of
secondary-treated municipal wastewater. After several
years of testing and evaluating alternative treatments, a
conventional-plant potable water recovery system has
been selected for comprehensive health-effects testing. The
results of this health-effects testing will be integrated with
chemical, physical, and microbiological examinations to
provide a basis to determine the suitability of recovered
56-Selected Readings on Water Reuse
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WATER RECLAMATION/REUSE
Unit Processes
Biological treatment removes
gross levels of organic matter from
water, thus preparing the water for
further processing. Although biologi-
cal treatment removes substantial
amounts of suspended matter, its
principal function is to reduce the
dissolved organic matter to relatively
low levels. Well-operated biological
treatment plants produce effluent
with soluble 5-day biochemical oxy-
gen demand values of 1 to 2 mg/L.
Additional benefits of biological
treatment include reduction of path-
ogen content; removal of heavy met-
als and radionuclides depending on
the food to microorganism ratio in
the system, the sludge age, and the
concentration of metals and ra-
dionuciides in the raw water; strip-
ping 80% to 90% of volatile organic
chemicals; and stripping radon if it
is present in the wastewater.
Biological nitrogen removal by ni-
trification and denitrification pro-
duces water from secondary effluent
with a total nitrogen content of 5
mg/L. It also results removes sus-
pended solids, volatile organic
chemicals, heavy metals, and
pathogens.
High-lime treatment with two-
stage recarbonation provides a
number of barriers: coagulation
and precipitation of suspended mat-
ter, where an average filtered water
turbidity less than 0.5 NTU is rou-
tinely achievable; coagulation and
precipitation of pathogen concen-
trations and a high pH at a level at
which pathogens are destroyed;
and precipitation of heavy metals,
radionuclides, and phosphorus.
High-lime treatment is the usual
method of reducing the concentra-
tions of nearly all heavy metals to
less than SDWA limits.
Granular-media filtration re-
moves the majority of suspended
matter remaining after biological
treatment or coagulation and pre-
cipitation. Following biological treat-
ment, filtration produces turbidity
levels of 1 to 2 NTU. Following co-
agulation, filtration reduces the tur-
bidity to less than 0.5 NTU. The re-
moval of suspended matter auto-
matically results in a reduction of
the microbial contamination of the
water (approximately 1 to 2 logs).
The benefit of GAC is the re-
moval of organic chemicals—
whether biodegradable, synthetic,
or volatile—by adsorption. Because
the degree of adsorption depends
on the nature of the compound, for
example its molecular weight and
polarity, and a number of other
Factors, exact removals cannot be
predicted. However, the fact that
GAC is used in all treatment sys-
tems concerned with producing
high-qualify water in compliance
with SDWA requirements for or-
ganic compounds is an indication
of its effectiveness.
Demineralization, specifical ly
membrane treatment, is the one
method that bars all contaminants,
including pathogenic organisms,
organic chemicals, heavy metals
and radionuclides, nutrients, and
dissolved solids. Reverse osmosis
and ultrafiltration are the most
widely used membrane processes.
Although ultrafiltration is less costly
to operate, reverse osmosis remains
the favored process because of its
greater removal efficiency.
Air stripping following mem-
brane treatment removes excess
carbon dioxide from the water. It
also provides a barrier to volatile
organic compounds.
Rapid infiltration and recover/
bars the passing through of sus-
pended matter and microbial or-
ganisms. Infiltration is also an effec-
tive barrier to heavy metals and ra-
dionuclides, depending on the ion
exchange capacity of the soil.
Suspended solids can be removed
by infiltration, phosphorus by ad-
sorption, and nitrogen by nitrifica-
tion and denitrification in the soil.
Nitrogen removal is dependent on
the organic carbon content of the
wastewater and is reduced as the
biodegradable organic content of
the water is reduced.
Chemical oxidation with ozone
and hydroxyl radical promoters
breaks down and conditions organ-
ics to a state more amenable to re-
moval in subsequent unit processes.
Breakpoint chlorination provides a
means to remove nitrogen.
Disinfection is normally the final
barrier to microbial organisms. It is
most effective at the end of the
treatment process where very little
suspended matter remains in the
water, and oxidant demand has
been greatly reduced.
water as a drinking-water supply.
The final report, including the health-effects study results,
will be completed in 1992. Based on analytical testing
data to date, the water produced by this system will be the
highest purity ever proposed for a municipal potable water
supply. The treatment includes high-pH lime clarification,
recarbonation, filtration, ultraviolet disinfection, activated-
carbon adsorption, reverse osmosis, air stripping, ozond-
tion, and chlorination as a residual disinfectant.
In 1983, the San Diego, Calif., 1-mgd single-plant
potable water recovery demonstration facility was commis-
sioned as part of a total resource recovery program estab-
lished in San Diego. The treatment system includes primary
treatment, a water hyacinth aquaculture system, coagula-
tion, clarification, filtration, ultraviolet disinfection, reverse
osmosis, aeration, carbon adsorption, and disinfection. The
program still in progress includes an extensive health-effects
study designed to determine the potential health effects re-
sulting from reuse of the recovered water and to compare
the recovered water to current supplies used by San Diego.
Results of the health-effects study are pending. A change
in California state law would be required to allow reuse of
the recovered water for potable purposes.
In 1 985, the 10-mgd Fred Hervey Water Reclamation
Plant began operation in El Paso, Tex. Recovered water is
recharged to a drinking-water aquifer where, over a 2-
year period, the water travels to one of El Peso's potable
water wells to become part of the potable water supply.
The treatment of raw wastewater to recharge qualify
water includes primary treatment, activated-sludge and
powdered activated-carbon treatment, lime treatment, re-
carbonation, filtration, ozonation, and GAC adsorption.
In 1986, the Tampa, Fla., Water Resource Recovery
Pilot Plant began operation. The pilot project was de-
signed to evaluate the feasibility of reclaiming denitrified
secondary effluent to a quality suitable for blending with
existing surface-water and groundwater sources for indi-
rect potable reuse. Several alternative treatments were
evaluated and one was selected for health-effects testing
after 2 years of evaluation. The treatment selected includ-
(continued on page 80)
Selected Readings on Water Reuse - 57
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WATER RECLAMATION/REUSE
mentation plan should include three
primary parallel programs with com-
plementary objectives.
Technical Demonstration Pro-
gram. A technical demonstration
program should include elements
and activities such as defining goals
and objectives; the design and con-
struction of the demonstration facili-
ty; the development of a demonstra-
tion-plant operation and mainte-
nance manual, performance criteria,
and reporting requirements; require-
ments for start-up, operation, shut-
down, and process control; the de-
sign and implementation of water-
quality monitoring and health-effects
testing; and the formation of a tech-
nical awareness committee.
Public Involvement Program.
The technical demonstration program
should be developed with public in-
volvement in mind. Emphasis should
be placed on attractive architecture
and beneficial uses of demonstration-
plant product water. A public involve-
ment program may include a commu-
nity awareness committee to help dis-
seminate information and media re-
leases, and organize tours, educational
programs, and research opportunities.
Regulatory Approval Program.
The regulatory approval program is
best developed by the appropriate reg-
ulatory agencies. Documentation, re-
ports, meetings, or other supporting
information should be identified early
so these programs can be designed to
satisfy regulatory requirements.
Successful completion of the dem-
onstration phase of the potable reuse
implementation plan would then al-
low progress toward design and con-
struction of a full-scale facility.
CONCLUSION
Prudent use of our water resources
Evaluation Criteria
• Water-quality results refer to the ability of an alternative water recovery
treatment to meet physical, chemical, microbiological, and toxicological
standards of performance and to meet or exceed the quality of the exist-
ing receiving water source (indirect reuse) or finished water (direct reuse).
• System reliability refers to the ability of the system to consistently pro-
duce the required water quality through the use of multiple contaminant
barriers, process equipment redundancy, and provision of adequate stor-
age to allow monitoring and assessment of water quality before reuse.
• System operability refers to the ease of operation of the system that
can be based on the labor expertise and man-hours required to operate
and maintain the system.
• System flexibility refers to the ability of the treatment system to respond
to variations in source wastewater quality and quantify and to future
variables that may affect performance requirements such as stricter re-
covered water standards and change over from indirect to direct reuse.
• Waste residuals refer to the quantity, character, and handling require-
ments to properly dispose of waste residuals. Disposal of brine concen-
trate from a reverse osmosis process is always a major consideration
with potable reuse projects.
• Physical requirements refer to the land and housing requirements to
support the water recovery system.
• System costs refer to the capital and operation and maintenance costs
associated with the liquid processing and waste-residuals handling.
Most important to this analysis is organizing these costs, on a basis that
provides fair comparison to other new water-supply alternatives. For in-
stance, importing a remote groundwater source would entail costs for
pumping and transmission, but also may include additional costs for
necessary water and wastewater treatment, distribution, and collection
systems to handle the increased water flow. However, development of a
water recovery plant for potable reuse may preclude construction of
water and wastewater treatment facilities.
• Regulatory and public acceptance refers to the site-specific concerns
or biases that may inhibit development of a particular potable reuse
system alternative.
assures that water in all its states of other undeveloped water sources, i
both natural beauty and manmade
utility is .available for future genera-
tions to enjoy. Potable reuse is one
of many methods available to extend
the utility of our existing water
sources and reduce the pressure on
Carl L. Hamann is director of in-
novative technology and Brock
McEwen is assistant director of water
reuse at CH2MHUI in Denver, Colo.
ed aeration, high-pH lime clarification, two-stage recar-
bonation, filtration, GAC adsorption, and ozonation. Final
results of the study should be available in 1990. If imple-
mented, the recovered water would comprise as much as
30% of the Hillsboro River raw water supply during low
flow conditions.
In 1988, the city of Phoenix, Ariz., conducted a potable
reuse feasibility study to evaluate the cost-effectiveness, in-
stitutional constraints, and social constraints associated with
direct potable reuse. The feasibility study results suggested
that potable reuse is cost competitive with other alternative
water-supply development projects for this desert-based
city. The city is currently evaluating the pursuit of a 0.1 -
mgd demonstration plant to document technical feasibility
and to gain public and regulatory acceptance.
In summary, planned, indirect potable reuse is currently
practiced at the following locations in the U.S.:
• Whittier Narrows, Calif.,
• Orange County, Calif. Water District's Water Factory
21.,
« UOSA Water Reclamation Plant in Fairfax County, Va.,
• Tahoe-Truckee Sanitation Agency Water Reclamation
Plant in Nevada County, Calif., and
• Fred Hervey Water Reclamation Plant in El Paso, Tex.
Direct potable reuse is still in the demonstration phase of
development in the U.S. Results from the Denver and San
Diego demonstration projects will contribute to the ad-
vancement of direct potable reuse as a technically feasible
water-supply alternative. The major impediments to full-
scale implementation of direct potable reuse will likely con-
tinue to be regulatory and social acceptance.
Nevertheless, the existing evidence to date does not indi-
cate that existing potable water recovery projects present
an unusual or unacceptable risk to public health.
58 -Sslected Readings on Water Reuse
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WATER REUSE
Potable Water Via Land
Treatment and AWT
Sherwood Reed, Robert Bastion
f hat would have
been the result
if the land treat-
ment planners,
designers, and
community had
opted for advanced wastewater treat-
ment (AWT)?" Finding the answer to
this question was, in part, the purpose
of a study conducted for the U.S. En-
vironmental Protection Agency (EPA).
The study determined if land treatment
systems constructed in the 1970s were
Wastewater
Treatment History,
Clayton County
In the early 1970s, the county
had several secondary treatment
plants discharging to surface wa-
ters. Two of these, the Casey
plant and the Jackson plant, dis-
charged to the Flint River. The
mean annual flow in this river is
only 0.34 m3/s (12 ftVs) and
wastewater effluent discharges
averaged 0.14 m3/s (5 fP/s) in
1974. During summer months,
the wastewater effluent exceeded
natural streamflow. The state of
Georgia imposed new discharge
standards and a limited flow al-
location for these existing systems.
Because the projected wastewa-
ter flows were significantly higher
that the discharge allocation, it
was necessary to limit growth in
the county, provide very high lev-
els of treatment to satisfy the dis-
charge limits, or develop a new
treatment method discharging to
another watershed.
meeting their original expectations
with respect to performance and costs.
The study included comparisons of
land treatment systems and AWT sys-
tems operating in the same regions and
having similar performance require-
ments. One of these comparisons in-
volved water reuse: effluent from each
system entered the potable water sup-
ply for its respective community.
As part of the study, two wastewa-
ter treatment systems were evaluated:
a land treatment system in Clayton
County, Ga. (see Box on Clayton
County History), and an AWT system
in Centerville, Va.- (see Box on UOSA
History). The Clayton County system
is a municipally operated, forest-cov-
ered, slow-rate land treatment system;
the Upper Occoquan Sewage Author-
ity (UOSA) system, in Centerville, Va.,
uses AWT in a mechanical-plant.
Although it was not the purpose of
the study to critique the planning, de-
sign, and selection decisions made at
the communities where the AWT pro-
cesses actually exist, the study allowed
a side-by-side comparison of a land
treatment system and a realistic AWT
alternative. In all cases, selecting AWT
was appropriate.
SYSTEM DESCRIPTIONS
Clayton County, which is immedi-
ately south of Atlanta, Ga., is a subur-
ban area with some light industrial and
commercial establishments. The county
government provides water supply,
wastewater treatment and disposal, and
power distribution. The population
served by the land treatment system was
about 85,000 in 1988.
The area has a relatively mild climate,
with a mean annual temperature of
17°C. Typically one or two light snow-
falls occur during the winter, and daily
average minimum temperatures never
fall below 0°C. Because of the mild cli-
mate, year-round Operation is possible
using suitable vegetation.
Major system components in the se-
lected process (see Box on Choosing
Land Treatment) included upgrades of
the two existing treatment plants, the
0.1-m3/s (2.3-mgd) Casey plant and
the 0.5-m3/s (11.8-mgd) Jackson plant,
and a land application facility (Table 1).
The land treatment system re-
charges, via soil percolation, to Pates
Creek, which is the major source for
the Clayton County municipal water
supply. The surface soils at the land
treatment site are sandy clay loams with
moderate permeabilities, the deeper
soils and those underlying the surface
drainage network are sandy clays and
clays. The groundwater table varies
from 2 to 24 m (10 to 80 ft) below
the ground's surface depending on el-
Wastewater
Treatment History,
UOSA
In 1971, the state of Virginia
determined that the 11 existing
wastewater treatment plants dis-
charging into the Occoquan wa-
tershed were accelerating eu-
trophication in the Occbquan
Reservoir and increasing the po-
tential risks to the potable water
supply. As a result, the 11 sys-
tems were taken off-line, and the
flow was combined and given
state-of-the-art treatment in a re-
gional AWT plant. UOSA was
established as an independent
regional authority to construct
and operate the new facility.
Selected Readings on Water Reuse -59
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Choosing Land Treatment in Clayton County
The major alternatives considered were providing high levels of AWT at
the two existing activated sludge plants, or using land treatment at another
location for wastewater management. Five potential land treatment sites
were evaluated, all within 12l?'«"'• ""
'
Whole-tree harvest at the Clayton County land
heolment system. The growing trees remove nutrients,
nwtob, ond olfier wosfewoter constituents. The whole
tree is then harvested and removed as wood chips on o
Zltyew rotational cycle.
60 -Selected Readings on Water Reuse
-------
Table I—Clayton County System Components
Primary & activated sludge secondary treatment
Jackson plant and Casey plant
Transmission lines from the two treatment plants to a 20-mgd pumping
station carrying undisinfected effluent.
Transmission line to the land application facility
Land application facility"
Effluent storage pond: 12 days detention, 66 ac
Distribution pumps: 3 each, 1500 hp; 2 each, 28,000 gpm.
Distribution pipes: 270 mi of buried pipe, 1.5 to 40 in.
Risers and sprinkler nozzles: 17,500
Land treatment area, 2650 ac
Buffer zones: 440 ac
Buildings and roads: 81 ac
Flood plains and inaccessible areas: 363 ac
Total site area: 3600 ac
"metric conversions are mgd X 0.04383 = m3/s; ac X 0.404 = ha;
hp X 0.745 = kW; mi X 1.609 = km; and in. X 25.4 = mm.
mental to the receiving water.
The major components in the
UOSA system are listed in Table 2. All
of the components listed have at least
one backup redundant unit.
DESIGN AND OPERATING CONDITIONS
Determining the land area needed
for the treatment system was a critical
step in the design and was based on
the limiting design parameter (LDP)
approach (see Box on LDP).
At Clayton County, the hydraulic ca-
pacity of the surface soils limits the de-
sign wastewater application rate to 6.4
cm/wk (2.5 in./wk). Thus, the design
wastewater application would be 3.3 m/
yr (10.8 ft/yr), and the average design
daily hydraulic loading would be about
8 L/m2»d (0.2 gal/ft2»d). At this load-
ing rate, the design projections indicated
that nitrate-nitrogen in percolate enter-
ing Pates Creek or the groundwater
would be well below the 10-mg/L limit
required for drinking water. Moreover,
this rate is equivalent to the lower rates
typically used for household leach-field
systems and illustrates that the hydrau-
lic loading on most slow-rate land treat-
ment systems is quite conservative.
Land treatment operation. The
wastewater is sprinkled, in rotation, on
the forested units in the land treatment
site. Some of the applied wastewater
percolates vertically and reaches the
native groundwater table, but most of
the applied wastewater infiltrates to a
relatively shallow depth, percolates lat-
erally through the soil, and emerges as
surface or subflow in the site's drain-
age network, which eventually flows
into Pates Creek. Operating the land
treatment system has significantly in-
creased flow in Pates Creek. During
very dry summers a major portion of
the flow in this creek is probably per-
colate from the land treatment site.
The site was divided into 42 blocks,
each averaging about 24 ha (60 ac).
The dominant tree species on the site
is loblolly pine, and there are also sig-
nificant stands of mixed pine and hard-
wood trees. Open land was also planted
with loblolly pine. Distribution piping
was buried and wide access lanes were
cleared at each sprinkler distribution
row. Five blocks are irrigated every day.
Seven blocks on the site are reserved
for contingency use when other areas
need maintenance or timber is being
harvested. Currently, all of the sprinklers
in a given section are replaced on a regu-
lar schedule, and the removed units are
taken to the shop for repair and reha-
bilitation and then used as replacement
units elsewhere. This is more efficient
than trying to find and repair individual
malfunctioning sprinklers.
The original management plan called
for clear-cut harvesting for pulpwood
of several blocks per year by a contrac-
tor on a 20-year rotation. The cleared
areas would then be replanted with
pine. This procedure was used for the
first year of operations and then aban-
doned because of excessive erosion and
Table 2—UOSA AWT System, Major System Components"
Wastewater Management
Emergency storage pond, 45 X 10* gal
Screening, grit removal, and conventional primary treatment
Conventional activated sludge secondary treatment
Chemical clarification (lime + polymer)
Two-stage recarbonation, with settling
Flow equalization
Multi-media filtration
Granular activated carbon (GAC) adsorption
Nitrogen treatment
normal weather: nitrification only, total Kjeldahl nitrogen(TKN), 1 mg/L
drought conditions: ammonia removal with ion exchange
to 4 mg/L, breakpoint chlorination to 1 mg/L
Final filtration: ion-exchange columns
Chlorine disinfection and dechlorinatiori
Final effluent reservoir, 180 X 106 gal
Final discharge to tributary of water supply reservoir
Solids Management
Biological solids: anaerobic digestion, filter press, composting
Chemical solids: thickeners, filter press, landfill
Spent GAC: on-site regeneration by carbon furnace
Ion Exchange Regeneration
Purge columns with sodium chloride, volatilize ammonia with sodium hydrox-
ide, and strip the ammonia with sulfuric acid in adsorption tower. Final product
is ammonium sulfate, which could be sold as a fertilizer
ametric conversion for gallons is 106 gal X 3785 = m3.
Selected Readings on Water Reuse - 61
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Limiting Design
Parameter
The LDP is the parameter or
wastewater constituent that re-
quires the largest land area for
acceptable performance. The
LDP might be based on the abil-
ity of the soil to pass the design
volume of water or on some
wastewater constituent such as
nitrogen, phosphorus, organics,
or metals. Experience with typi-
cal municipal effluents has shown
that the LDP for this type of
project is usually the hydraulic
capacity of the soil or the ability
to remove nitrogen and thereby
maintain drinking-water levels
for nitrate in the groundwater at
the project boundary.
Table 3—UOSA Discharge Limits
Chemical oxygen demand (COD), 10 mg/L
Total suspended solids (TSS), 1.0 mg/L
Phosphorus, 0.1 mg/L
Surfactants, 0.1 mg/L
Turbidity, 0.5 JTU 1
total Kjeldahl nitrogen (TKN), 1.0 mg/L in normal weather
Total nitrogen, 1.0 mg/L during drought
related problems caused by the con-
tractor's equipment.
In-house staff has since harvested the
trees to produce wood chips in the
field. The wood chips are then trucked
to the county's secondary treatment
plants and cither used as fuel for sludge
drying and pellctizing or as a bulking
agent for in-vcssel composting.
AWT system. The design capacity
of the UOSAsystem was 0.66 m3/s (15
mgd) in 1987, and the actual flow that
year averaged 0.53 m3/s (12.2 mgd).
Future expansions to 1.18 m3/s (27
mgd) and then to 2.37 m3/s (54 mgd)
were planned. Stringent discharge-lim-
its were established for the UOSA de-
sign (Table 3). Nitrogen limits for nor-
mal weather and drought were
established. In normal weather condi-
tions, base flow from other surface
streams that feed the Occaquan Res-
ervoir would dilute the effluent nitrate
to acceptable levels, and the concen-
tration of the unoxidized nitrogen
forms represented by total Kjeldahl
nitrogcn(TKN) was a suitable limit. In
extreme droughts, water in surface
streams is not adequate and the limit
changes to 1 mg/L total nitrogen.
Under extreme drought conditions,
the AWT effluent is the major flow
component of the reservoir.
The variable nitrogen limits require
two different modes of operation for the
activated sludge system component.
Under normal weather conditions when
the TKN limits prevail, the activated
sludge component is operated in an ex-
tended aeration mode. This typically
results in a final effluent having a TKN
of 0.5 mg/L or less and a nitrate con-
Table 4— Clayton County System Annual Loadings
Parameter
BOD5
TSS
Total nitrogen
Total phosphorus
lb/ac»yrx 1.121
Design
assumption, lb/ac»yr
896
896
404
224
= kg/ha «yr
1987
actual load, lb/ac«yr
226
178
139
76
Table 5—Clayton County System Groundwater Quality
Year
1979
1980
1981
1982
1983
1984
1985
1986
1987
Nitrogen
0.69
0.54
0.63
0.34
0.44
0.43
0.15
0.65
0.18
Parameter, mg/L
Phosphorus
0.03
0.03
0.04
0.03
0.02
0.09
0.01
0.01
0.04
Chloride
1.0
1.6
2.3
3.6
10.8
12.6
15.4
21.0
21.5
Table
Year
1978
1984
1985
1986
1987
6— Pates Creek Water Quality
Nitrogen
0.65
0.96
V.I 5
2.02
1.04
Parameter, mg/L
Phosphorus
0.05
0.05
0.26
0.32
0.17
Chloride
1.0
7.5
13.3
18.3
18.9
centration of 19 mg/L or more, so that
the total nitrogen concentration in the
effluent approaches 20 mg/L. Under
drought conditions, when the total ni-
trogen limit of 1 mg/L controls, the
activated sludge process is operated with
a short detention time to provide only
carbon oxidation so that most of the
ammonia remains unoxidized. Ion ex-
change and break-point chlorination will
be used to remove remaining nitrogen.
The activated sludge component,
when operated in the nitrification mode,
requires more aeration energy, but pro-
duces less sludge. The effluent is more
stable and easier to treat in the remain-
ing AWT units. The ion exchange col-
umns are also part of the process in the
nitrification mode (see Box on Nitro-
gen Removal), but in this case serve as
final filters to remove the carbon fines
and other particulates in the granulated
activated carbon (GAG) effluent. The
680 X 109-m3 (180 X 106-gal) storage
pond provides 12 days effluent storage
at the 0.66-m3/s (15-mgd) design flow.
The land area requirements for the
Occoquan system were 24 ha (60 ac)
for the treatment plant, 22 ha (55 ac)
for the final effluent reservoir, and 20
62-Selected Readings on Water Reuse
-------
Table 7—UOSA System Water Quality Concentration Data
Parameter
BOD5
COD
TSS
Influent,
mg/L
200
400
170
Permit Limit,
mg/L
10.0
1.0
Effluent,
mg/L
<1.0
8.0
0.1
Nitrogen
normal weather 34.2 (total N) 1.0(TKN)°
drought periods 34.2 (total N) 1.0 (total N)
Phosphorus 9.0 0.1
Surfactants 5.3 0.1
Turbidity — 0.5 JTU
0.5 (TKN)a
19.3(NO3)°
0.05
0.04
0.1 JTU
°As nitrogen
Table 8—Clayton County System Capital Costs, $ x 106
Upgrade Casey Plant
Upgrade Jackson Plant
Sub total
Pump station and transmission line
6.95
1.42
8.37
1.70
Land treatment facility
Storage ponds
Pump and distribution system
Structures, roads, and the like
Land costs (3000 ac)°
Future salvage value of the land
0.46
5.30
0.60
10.30
Sub total
Total
Total, with salvage
16.66
26.73
-(10.30)
16.43
°ac X 0.404 = ha
Table 9 — Clayton County System
Item
Secondary
treatment
Land
treatment
1976 Estimate,
1987$
1,251,000
837,000
Annual 0 & M Costs
1987 Actual,
1987$
2,084,000
1,015,000
1987,
$/1000gal°
0.40
0.20
°$/3.785x 1000 = $/L
ha (50 ac) for the sludge landfill. This
total of 67 ha (165 ac) is much less
than the 1477 ha (3650 ac) required
for the Clayton County system.
SYSTEM PERFORMANCE
It was clear from the data that the
existing activated sludge plants in
Clayton County were producing bet-
ter than secondary effluent with respect
to 5-day biochemical oxygen demand
(BOD5) and TSS and it was likely that
the short detention time in the stor-
age pond contributed to further treat-
ment. The total flow in 1987 was only
0.62 m3/s (14.1 mgd), which was 0.14
ms/s (3.4 mgd) lower than that as-
sumed for design. Thus, the actual an-
nual loadings on the 1072-ha (2650-ac)
treatment area were lower than the as-
sumed annual loadings (Table 4).
The data suggest that the design as-
sumptions were conservative and that
the land treatment site was not stressed
and was underused during the first 10
years of operation. This then suggests
that Clayton County might gain eco-
nomically by reducing the performance
efficiency at the activated sludge plants,
thereby allowing removal of higher
concentration of soluble BOD and the
related nutrients on the land treatment
site. System performance is evaluated
using monitoring wells on the appli-
cation sites and in Pates Creek as it
flows away from the site. Nitrogen was
Nitrogen Removal
The UOSA system has never
been required to operate in the
nitrogen removal mode since the
plant was constructed, so the
more liberal TKN limits have pre-
vailed. However, during a 4-
month trial period in 1982, the
ion-exchange system was oper-
ated for ammonia removal. This
long-term test concluded that it
was not practical to reach the 1 -
mg/L ammonia standard with
just ion exchange. The current
plans are to use the ion-ex-
change columns to reach 3 to 4
mg/L ammonia and then break-
point chlorination will be used to
achieve the required 1 mg/L.
the greatest concern, because nitrogen
was the LDP for the Clayton County
secondary treatment design. Nitrate
contamination of drinking-water
sources had to be avoided. Total ni-
trogen concentration in the groundwa-
ter and in Pates Creek at the project
boundary were monitored because
wastewater was applied beginning in
1979 (Tables 5 and 6). Phosphorus
was monitored because of its eutrophi-
cation potential. Chlorides were moni-
tored because they served as a tracer,
confirming that wastewater percolate
reached the sampling point.
The data indicate that chlorides in-
creased significantly from start-up un-
til 1986 and then leveled off. The fi-
nal concentration of chlorides is about
one-half of that present in the applied
wastewater, indicating that there is sig-
nificant mixing and dilution with the
surface water and groundwater.
The nitrogen and phosphorus data
indicate excellent removal efficiency and,
although the pattern for nitrogen is
somewhat erratic, the concentration has
always remained below the 10-mg/L
target value. At the present nitrogen
loading rates, this performance can be.
expected to continue indefinitely. Even
if the chloride values in the ground-
water and surface water were to
double, a phenomenon that would in-
dicate the presence of wastewater per-
colate without any dilution, the nitro-
gen concentration should only increase
proportionally and still not exceed 5
mg/L. If the nitrogen loadings ever
reach the design values, the percolate
nitrogen reaching the groundwater and
Pates Creek may approach, but still not
exceed, the 10-mg/L target value.
AWT system. In comparison,
Selected Readings on Water Reuse - 63
-------
Use of wood chips at the Clayton County land
treatment system as the fuel source for a sludge
peSetizing operation. Chips are also used as a bulking
ogent for composting.
the county had constructed aerated la-
goons for preliminary treatment, the
total costs might have been about $32
million (all 1976 dollars).
The salvage value of the land should
be much higher at the end of the 20-
year design period; the cost for land
adjacent to the treatment site was ap-
proaching $27,750/ha ($10,000/ac)
in 1988. The costs for just the land
treatment facility would be about
$13,600/ha ($5500/ac), not includ-
ing the salvage value.
The actual annual operations and
maintenance (O & M) costs for sec-
ondary treatment are about 67% higher
than the original estimate because la-
UOSA's performance is demonstrated
by its effluent characteristics. Table 7
compares typical influent and effluent
values to the permit requirements for
the UOSA system.
MANPOWER AND COSTS
The 1987 Clayton County staffing
requirements, including the secondary
treatment and sludge pelletizing opera-
tions and the land treatment compo-
nent, totalled 61. The staff at the land
treatment facility increased from 13
people when land treatment operations
began in 1978 to 24 people in 1987.
Staff was needed to harvest trees and
to maintain and repair the sprinklers
and appurtenant equipment.
At the present flow rate of 0.62 m3/s
(14.1 mgd) of capacity the manpower
requirements would be 9.8 people/
m3»s (4.3 pcople/mgd) of capacity.
The actual capital costs of the total
project were within 2% of the estimate
(Table 8). About 30% of the total was
used to upgrade the existing activated
sludge plants. If Clayton County had
been required to build entirely new ac-
tivated sludge systems, the cost for these
components might have been about
$10.2 million and the total would have
been about $37 million, rather than the
$26.73 million shown in the table. If
bor costs for the skill levels required
to operate the system were higher than
planned (Table 9). The land treatment
costs are about 20% higher that the
original estimate. In-house tree har-
vesting accounts for most of the in-
crease. With respect to the distribution
of these O & M costs for the second-
ary treatment system and the land
treatment component, the labor costs
for secondary treatment are two times
that for the land treatment component,
and costs reflect the skill levels in-
volved—the number of people for each
component is about the same (Table
10). The power costs for land treat-
ment are slightly higher than for sec-
Table 10—Clayton County System Distribution of Direct 1987 0 & M Costs
Costs, $/1000 gal
Item
Secondary treatment
Land treatment
Labor
Chemicals
Power
Other
0.14
0.03
0.09
0.14
0.07
0.00
0.10
0.03
"$/3.785x 1000 gal = $/L
Table 11—Clayton County System Total Annual Costs (1987, $)°
Total direct costs _ 3,088,000
Depreciation/debt service 2,004,000
Indirect and administrative \ 1,595,000
Sale of sludge pellets -(199,000)
" Total I 6,488,000
Secondary treatment, $/l 000 gal
Land treatment facility, $/1 000 gal
Total
0.85
0.41
1.26
"Total gallons treated = 5,146,500,000
Table 12— UOSA System Capital Cos
Treatment system
Land acquisition
Engineering and administration
"Unit cost = $4.31 million/mgd($89.2
Table 13— UOSA 1 987 Total 0 & M
Activity
Secondary treatment
Phosphorus removal
Filtration
Carbon adsorption
Final filters
Totals
Unit O & M with ion exchange
its, 1982 $x!06"
Total
3 X 10Vm3»s)
1
Costs
Total Costs,
1987$
2,229,333
1,319,023
363,508
472,598
270,851 ,
4,655,313
1
52.04
1.69
10.87
64.60
Unit Costs,
$/1000gal°
0.50
0.29
0.08
0.11
0.06
1.04
$1.72
"metric conversion for unit cost is $/3.785 X 1000 = $/L
64-Selected Readings on Water Reuse
-------
Table 14—UOSA 1987 Total Annual Costs, 1987 $
Operation maintenance and management, $
Depreciation/debt service, $
Total
4,655,313
2,077,280
6,732,593
1.50
2.18
2.46
"Nitrification mode, $/gal
Ion-exchange mode, $/gal
Ion-exchange plus breakpoint chlorination, $/gal
"Total gallons treated = 4,474,706,000 (16,936.76 m3)
Table 15—Distribution of 0 & M Costs, UOSA and Clayton County
Costs ($/1000 gal)
Item
Labor
Chemicals
Power
Other
UOSA, Va
Clayton Co., Ga
Total
0.52
0.11
0.25
0.16
$1.04°
0.21
0.03
0.19
0.17
0.60
"with ion exchange, costs are $1.72/1000 gal and with ion exchange and
break-point chlorination costs are $2.00/1000 gal.
ondary treatment because of the need
for transmission pumping to the site
and then distribution pumping on the
site. Using the wood chips as fuel how-
ever significantly reduces the cost of the
pelletizing operation as compared to
using natural gas or oil as a fuel source.
The total annual cost for secondary
treatment was $225/L ($0.85 /1000
gal), and S108/L ($0.41/1000 gal)
for the land treatment component, for
a total of $333/L ($1.26/1000 gal)
(Table 11).
If a completely new activated sludge
plant-had been built, the total annual
cost might approach $373/L ($1.41/
1000 gal) because of the higher capi-
tal costs and related debt service. If a
new aerated lagoon had been con-
structed, the total annual costs would
have been close to $356/L ($1.35/
1000 gal).
The state of Georgia requires treat-
ing wastewater to secondary treatment
levels before applying the wastewater.
Experience elsewhere with slow-rate
land treatment indicates excellent results
with influent treated to primary stan-
dards. A partial relaxation of the second-
ary requirement might allow a signifi-
cant expansion of future plant capacity
without additional capital expense.
AWT system. UOSA 1987 staff re-
quirements, including all on-site person-
nel, totalled 81. At this flow rate, UOSA
uses 15 people/m3«s (6.6 people/
mgd).
Capital costs for construction—at
the plant site only—were about $64
million (Table 12). The total cost of
the entire AWT system in 1982 dol-
lars was $82 million. These costs in-
clude the provision of 100% redun-
dancy in all components to protect the
water supply system, but do not in-
clude the costs of the new break-point
chlorination facilities. The unit cost at
design capacity is $98 million/m3»s
($4.31 million/mgd).
O & M costs for the UOSA system
were compared in terms of the total
annual expenditure and the unit costs
per 3.8 m3 (1000 gal) treated (Table
13). During this period, the system was
in the nitrification mode and did not
use ion exchange and break-point chlo-
rination for ammonia removal, so these
costs are not included. The unit costs
with ion exchange for ammonia re-
moval would be $454/L ($1.72/1000
gal) treated. The break-point chlorina-
tion facilities costs are not included in
the analysis.
The total 1987 costs for the UOSA
system are given in Table 14. The unit
cost per 3.8 m3 (1000 gal) is based on
actual expenditures. The values for the
unit costs with ion exchange and with
ion exchange plus break-point chlori-
nation are estimates.
COST COMPARISON
Because construction costs are
higher in Northern Virginia as com-
pared to Clayton County, a direct com-
parison is not possible. Adjusting the
unit costs for location produces an es-
timate of $88 million/m3»s ($3.84
million/mgd) if the system had been
constructed in Georgia in 1982. Up-
dating the previously cited Clayton
County capital costs to 1982 dollars
produces an estimate of $52 million/
m3»s ($2.27 million/mgd) for com-
parison with the AWT value.
The Clayton County system paid
$8500/ha- ($3433/ac) for 1212 ha
(3000 ac) of land; in Virginia, the unit
cost was $25,350/ha ($10,242/ac) for
67 ha (165 ac). At that rate, the land
costs in Northern Virginia would have
been over $30 million for 1212 ha
(3000 ac). This amount of land would
not have been available in a single block
or a few large parcels in Northern Vir-
ginia, so construction costs for the
other land treatment components
would have been much higher than at
Clayton County. In addition, the soil
characteristics in the vicinity of the
UOSA plant are not well suited for a
slow-rate land treatment system. It
seems clear that land treatment would
not have been an economical alterna-
tive for UOSA. However, the purpose
of the analysis was to determine what
the costs would be had the Clayton
County authorities selected a similar
AWT system instead of land treatment.
The UOSA O & M costs for oper-
ating in the nitrification mode for the
gallons actually treated in 1987 are dis-
tributed to the major cost factors and
are compared to the values from
Clayton County (Table 15).
The addition of break-point chlori-
nation might increase UOSA's total
O&M costs to about $528/L ($2.00/
1000 gal). The comparable cost for the
Clayton County system, which achieves
<1 mg/L total nitrogen, is $159/L
($0.60/1000 gal).
The labor costs for UOSA are sig-
nificantly higher partly because of the
location and because die skill levels re-
quired are much higher for the AWT
process. The unit costs for the labor at
the land treatment facility are signifi-
cantly less than at the secondary treat-
ment systems because less skilled labor
is required.
The difference in chemical costs re-
flects the fact that Clayton County uses
few chemicals. The difference in power
costs are significant but are closer than
many would expect. Land treatment
systems such as Clayton County, where
extensive transmission and distribution
pumping are required, are not neces-
sarily low-energy systems.
PROCESS COMPARISONS
Both systems are satisfying their
project goals and producing a final
product that is acceptable for reuse in
their water supply systems. This capa-
bility, it seems, will not diminish over
the long term.
Selected Readings on Water Reuse - 65
-------
UOSA's unit cost values can be com-
pared to the S333/L ($1.26/1000 gal)
for Clayton County's land treatment
system as constructed, with upgrading
of the existing secondary treatment
units. However, such a comparison is
biased in favor of land treatment be-
cause Occoquan had to build a com-
pletely new system including the sec-
ondary treatment components. It is
estimated that if a new secondary treat-
ment plant had been built at Clayton
County, the total annual unit cost
might be $373/L ($1.41/1000 gal).
At this level, the cost advantage for land
treatment is smaller, but still significant.
The cost comparison is also biased in
favor of the AWT process because the
S396/L ($1.50/1000 gal) represents
the nitrification mode when the system
is discharging close to 20 mg/L nitrate.
The land treatment system discharges
about 1 mg/L (average 1980 to 1987
0.7 mg/L) total nitrogen to ground-
A typlta! sprinkler used for wastewafer application
at m Goyfon County, Go., fend treatment system.
water and surface water. Therefore, on
a water-quality basis, it is necessary to
compare the land treatment process to
the AWT ammonia removal process ef-
fluent to have equivalent water qual-
ity. On this basis, the total annual costs
for land treatment with a new second-
ary treatment plant would be $373/L
($1.41/1000 gal) compared to $528/L
($2.00/1000 gal) for the AWT pro-
cess. At the present flow, Clayton
County:would produce a cost savings
of over $3 million/yr.
CONCLUSIONS
It can be concluded from the com-
parisons that the goals and projections
for the Clayton County system were
valid and that the land treatment con-
cept was the proper choice. The land
treatment system was, and remains, the
most cost effective alternative for the
situation in Clayton County, when com-
pared to the costs for an AWT process
capable of producing the same-quality
final effluent. The Clayton County sys-
tem continues, after 10 years, to pro-
duce a high-quality effluent that can be
directly introduced into the drinking-
water sources for the community. That
capability is expected to continue indefi-
nitely. Similarly, selection of the AWT
process at Occoquan was the proper
choice for the circumstances prevailing
at that location.
The availability of a sufficient area of
suitable land at a reasonable cost is
probably the major factor for imple-
menting a cost-effective land treatment
system. The cost of all other compo-
nents and the O & M requirements
should be less for land treatment than
for alternative processes.
The comparison indicated that the
land treatment system could reliably
produce an equivalent effluent at a sig-
nificantly lower cost than the AWT
process. This suggests that in locations
where a sufficient area of suitable land
is available at a reasonable cost, land
treatment will be the more cost effec-
tive alternative. •
Sherwood Reed is an environmental
engineering consultant in Norwich, Vt.;
Robert Bastian is a scientist at the U.S.
Environmental Protection Agency in
Washington, D. C.
66-Selected Readings on Water Reuse
-------
WATER REUSE
Groundwater Recharge
with Reclaimed Water
in California
James Crook, Takeshi Asano, Margaret Nellor
Ste
n California, increasing de-
mands for water have given rise
to surface water development
and large-scale projects for wa-
ter importation. Economic and
environmental concerns associ-
ated with these projects have expanded
interest in reclaiming municipal waste-
water to supplement existing water
supplies. Groundwater recharge repre-
sents a large potential use of reclaimed
water in the state. For example, several
projects have been identified in the Los
Angeles area that could use up to 150 x
106 m3/a (120,000 ac-ft/yr) of re-
claimed water for groundwater re-
charge. Recharging groundwater with
reclaimed wastewater has several pur-
poses: to prevent saltwater intrusion
into freshwater aquifers, to store the
reclaimed water for future use, to con-
trol or prevent ground subsidence, and
to augment nonpotable or potable
groundwater aquifers.1 Recharge can
be accomplished by surface spreading
or direct injection.
With surface spreading, reclaimed
water percolates from spreading basins
through an unsaturated zone to the
groundwater. Direct injection entails
pumping reclaimed water directly into
the groundwater, usually into a con-
fined aquifer. In coastal areas, direct
injection effectively creates barriers that
prevent saltwater intrusion. In other
areas, direct injection may be preferred
where groundwater is deep or where
the topography or existing land use
makes surface spreading impractical or
too expensive. While only two large-
scale, planned operations for ground-
water recharge are using reclaimed water
in California, incidental or unplanned
recharge is widespread.
The constraints of groundwater re-
charge with reclaimed water include
water quality, the potential for health
hazards, economic feasibility, physical
limitations, legal restrictions, and the
availability of reclaimed water. Of these
constraints, the health concerns are by
far the most important, as they pervade
all potential recharge projects. Health
authorities emphasize that indirect po-
table reuse of reclaimed wastewater
through groundwater recharge en-
compasses a much broader range of
potential risks to the public's health
than nonpotable uses of reclaimed
water. Because the reclaimed water
eventually becomes drinking water and
is consumed, health effects associated
with prolonged exposure to low levels
of contaminants and acute health ef-
fects from pathogens or toxic substances
must be considered. Particular atten-
tion must be given to organic and in-
organic substances that may elicit
adverse health responses in humans
after many years of exposure.
HISTORICAL DEVELOPMENT
In the early 1970s several water-
quality control plans (Basin Plans) were
developed under the direction of the
State Water Resources Control Board
(SWRCB). The Basin Plans identified
as many as 36 potential projects for
groundwater recharge in the state.
Regulatory agencies involved in
wastewater reclamation and reuse play
a key role in the management of
California's water resources and any
projects involving the recharge of
groundwater with reclaimed water (see
Box). In 1973, the'Department of
Health Services (DOHS) prepared a
position statement in response to pro-
posals in the Basin Plans for augmenta-
tion of domestic water sources with
reclaimed water. Three uses of reclaimed
water were considered in the state-
ment: groundwater recharge by surface
spreading, direct injection into an aqui-
fer suitable for use as a domestic water
source, and direct discharge of reclaimed
water into a domestic water supply.
Position statement. The DOHS
position statement recommended
against direct discharge into a domestic
water-supply system and direct injec-
tion into aquifers used as a source of a
domestic water supply stating that some
organic constituents of wastewater are
not well enough understood to permit
setting limits and creating treatment-
control systems. In particular, the in-
gestion of water reclaimed from
wastewater may produce long-term
health effects associated with die stable
organic materials that remain after
treatment. It also stated that injection
to prevent saline water intrusion could
be considered in the future. With re-
gard to surface spreading, the position
statement contained the following:
surface spreading appears to have great
potential; information relative to health
effects is uncertain; if new information
indicates adverse effects are created with
recharge, closure of basins may be nec-
essary; specification of allowable per-
centages of reclaimed water in
groundwater is inappropriate at this
time because of a lack of information
on health effects; proposals for the re-
charge of small basins with large quan-
tities of reclaimed water will not be
Groundwater recharge, occurring at the Rio Hondo
Spreading Grounds in Los Angeles, represents a large
potential use of reclaimed water in California.
Selected Readings on Water Reuse - 67
-------
II
" . .
1 "'•!' iii.,:i'J:j..'5 ':i'ia.:::11.. "'i:;.;.,
in1'! HI, li|ii|ii''iiiii iii'1,1 'iiiiin finfii, «ii!"
ilillllllllllplllllfflpifli ,,
i*£S33E*'
i •••*•,. *ffy*m-
68 -Selected Readings on Water Reuse
-------
Milestones in Historical Development
of Groundwater Recharge
716 ^'rs> 'ar9e"sca'e planned operation for groundwater recharge was imple-
mented when secondary effluent from the Whittier Narrows Water Reclamation Plant in
Los Angeles County was spread in the Montebello Forebay area of the Central
Groundwater Basin.
1973 The California Department of Health Services (DOHS) developed a position
statement on the uses of reclaimed water involving ingestion, essentially placing a
moratorium on new projects for groundwater recharge.
1975 The State of California convened a Consulting Panel on the Health Aspects of
Wastewater Reclamation for Groundwater Recharge to provide recommendations for
research thatwould assist DOHS in the establishmentof statewide criteria forgroundwater
recharge.
1976 DOHS developed draft regulations for groundwater recharge that were subse-
quently used as guidelines.
1976 Groundwater recharge by direct injection was initiated by the Orange County
Water District to prevent saltwater intrusion.
1978 The Sanitation Districts of Los Angeles County (LACSD) initiated a 5-year Health
Effects Study to investigate the health significance of using reclaimed water for ground-
water replenishment.
1986 The state of California appointed a Scientific Advisory Panel on Groundwater
Recharge with Reclaimed Wastewater to provide information needed for the establish-
ment of statewide criteria forgroundwater recharge. .
1987 Sfate.regulatory agencies approved a 50% increase in the amount of reclaimed
water that could be spreadin the Montebello Forebay area.
Research Tasks
i Water-quality characterizations of qroundwater, reclaimed water, and
other recharge sources in terms of trteir microbiological and inorganic
chemical content.
i Toxicoloqical and chemical studies of qroundwater, reclaimed water, and
other recharge sources to isolate and identify health-significant organic
constituents.
Percolation studies to evaluate the efficacy of soil in attenuating inorganic
and organic chemicals in reclaimed water.
Hydrogeological-studies to determine the movement of reclaimed water
through qroundwater and the relative contribution of reclaimed water to
municipal water supplies.
Epidemiological studies of populations ingesting groundwater containing
reclaimed water to determine if their health characteristics differ signifi-
cantly from a demographically similar control population.
recommended; proposals
for recharge of large basins
with small amounts of
reclaimed water may be
possible depending on
community well locations
and other conditions; and
surface spreading as a fu-
ture option may be a
possibility.
Consulting panel. In
1975, a Consulting Panel
on the Health Aspects of
Wastewater Reclamation
for Groundwater Re-
charge was established by
three state agencies—
DOHS, SWRCB, and the
Department of Water
Resources (DWR). Its
purpose was to recom-
mend a program of re-
search that would provide
information to assist
DOHS in establishing
reclamation criteria for
groundwater recharge
and to assist DWR and
SWRCB in planning and
implementing programs
to encourage use of re-
claimed water consistent
with those criteria. A state-
of-the-art report on the health aspects
of wastewater reclamation for ground-
water recharge was prepared as a back-
ground document.
The Consulting Panel confined its
discussions to groundwater recharge
by surface spreading and reached sev-
eral conclusions. The panel concurred
with DOHS that there were uncertain-
ties regarding potential health effects
associated with groundwater recharge
using reclaimed wastewater. The panel
suggested that comprehensive studies
directed at the health aspects associated
with groundwater recharge be initiated
at existing projects, and that new dem-
onstration projects would be needed to
gain field information under selected
and controlled conditions. The panel
stated that to provide a database for
estimating health risk, contaminant
characterization, toxicology, and epi-
demiological studies of exposed popu-
lations were needed.
Health Effects Study. In the after-
math of the 1976-77 California
drought, there was considerable pres-
sure to use supplies of reclaimed water
in southern California, particularly for
groundwater recharge. However, an
unofficial moratorium suspended new
projects and the expansion of existing
operations until some health-related
issues associated with groundwater re-
charge were answered and the Consult-
Selected Readings on Water Reuse - 69
-------
ing Panel's recommendations were
implemented. In 1978, the Sanitation
Districts of Los Angeles County
(LACSD) initiated a 5-year, $1.4 mil-
lion study of the Montebello Forebay
Groundwater Recharge Project that had
been replenishing groundwater with
reclaimed water since 1962. By 1978,
the amount of reclaimed water spread
averaged 33 x 106 m'/a (26,500 ac-ft/
yr) or 16% of the total inflow to the
groundwater basin with no more than
40 x 10* m3 (32,700 ac-ft) of reclaimed
water spread in any year. The percent-
age of reclaimed water contained in the
potable water supply ranged from 0 to
23% on an annual basis, and 0 to 11%
on a long-term (1962-1977) basis.
Historical impacts on groundwater
quality and human health and the rela-
tive impacts of the different replenish-
ment sources—reclaimed water,
stormwater runoff, and imported sur-
face water—on groundwater quality
were assessed after conducting a wide
range of research tasks (see Box).
The study's results indicated that the
risks associated with the three sources
of recharged water were not signifi-
cantly different and that the historical
proportion of reclaimed water used for
replenishment had no measurable im-
pact on either groundwater quality or
human health.2 The Health Effects
Study did not demonstrate any measur-
able adverse effects on the area's
groundwater or the health of the popu-
lation ingesting the water. The cancer-
related epidemiological study findings
were weakened by the minimal ob-
served latency period (about 15 years)
between first exposure and disease for
human cancers. Because of the rela-
tively short time that groundwater con-
taining reclaimed water had been
consumed, it is unlikely that examina-
tion of cancer incidence and mortality
rates would have detected an effect of
exposure to reclaimed water resulting
from this groundwater recharge opera-
tion.
Groundwater recharge regula-
tions. In 1976, DOHS developed draft
regulations for groundwater recharge
of reclaimed water by surface spread-
ing. The proposed criteria were princi-
pally directed at the control of stable
organics. The level of treatment speci-
fied in the draft regulations was con-
ventional secondary treatment followed
by carbon adsorption and percolation
through at least 3 m (10 ft) of unsatur-
ated soil. Reclaimed water-quality re-
quirements were specified for inorganic
chemicals, pesticides, radioactivity,
chemical oxygen demand (COD), and
total organic carbon (TOC). Require-
ments for groundwater quality were
specified for inorganic chemicals and
pesticides. An effluent monitoring pro-
gram was proposed for 20 specific or-
ganic compounds. The draft regulations
Water Factory 21 is an advanced wastewater
treatment facility whose effluent is used to prevent
saltwater intrusion into potable water-supply aquifers.
70 -Selected Readings on Water Reuse
-------
Table 1—Analyses of Reclaimed Water—Montebello Forebay, 1988-1989
Constituent Units San Jose Whittier Pomona Discharge
Creek Narrows limits
Arsenic
Aluminum
Barium
Cadmium
Chromium
Lead
Manganese
Mercury
Selenium
Silver
Lindane
Endrin
Toxaphene
Methoxychlor
2,4-D
2,4,5-TP :
Suspended
solids '.. .'
BOD
Turbidity
Total
coliform
Total
_ dissolved solids
Nitrate and
nitrite
Chloride
Sulfate . ' ;. "
Fluoride
mg/L
mg/L
mg/L
-mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
M-9/L
M-g/L
Mfl/L
"WjA
p-gA
(jig/L
mg/L :
mg/L
TU
No./lOOmL
mg/L
mg/L ;
mg/L
mg/L
mg/L
0.005
<0.06
0.06
ND
<0.02
ND
<0.02
<0.0003
<0.001
-------
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