United States
Environmental Protection
Agency
May
1985
&EPA Water Reuse
Via
Dual
Distribution
Systems
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Public Acceptance
Colorado Springs' non-potable irrigation system has a
history of trouble-free operation with regard to
community health. An extensive epidemiology study to
assess the impacts of the system on community health
has indicated that there are no apparent differences in
gastrointestinal illness rates between users of parks
irrigated with potable versus non-potable water. Public
acceptance of reuse technology in general, and the
existing irrigation system in particular, is high. Strong
local participation in the Areawide Water Quality
Management Plan (the 208 Plan) has resulted in
repeated endorsement of wastewater reuse.
St. Petersburg, Florida
The city of St. Petersburg operates the largest effluent
spray irrigation system in the United States. In
response to PL 92-500 and a state legislative act that
required either advanced treatment or zero discharge
to Tampa Bay, the City Council adopted the concept of
zero discharge through wastewater reuse in 1977.
Three of the City's four wastewater plants currently
supply water to the effluent distribution system. When
the fourth plant is tied to the system (scheduled for
1986), the recycled water potential will increase to 68.4
mgd. Although current demand requirements are less
than 20 mgd, the City's program for extending the dual
water system will continue to increase effluent usage.
In addition, other nearby communities may eventually
use the City's effluent.
System Design
Each of the four wastewater plants is a standard
Complete Mix Activated Sludge plant without primary
clarifiers. Complete Mix requires a shorter aeration
detention time for treatment, and therefore, a smaller
aeration basin. The shorter aeration period normally
prevents nitrification. The nitrogen and phosphorus in
the effluent reduce lawn fertilizer requirements - a good
selling point. A treated wastewater main ties all four
plants together in a complete loop, eliminating any
problems in supply or pressure drops due to shut-down
at any one plant.
Probably the most important process in meeting
effluent quality restrictions is filtration. Pre-filter alum
addition for enhanced solids capture is used at two of
the plants. Sufficient chlorination after the filters is also
important in disinfection and virus inactivation.
With the major percentage of reuse irrigation at night, a
shift in effluent discharge from the normal daily flow is
required. Four ground storage tanks (capacity 23
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Water Reuse Via Dual Distril
Introduction !
Many communities are experiencing water supply
shortages. In particular, communities with rapidly
growing populations, in arid climates, or with partial
water supply contamination, may have a demand far
water that exceeds their supply. One remedy to this
problem is development of a dual distribution water
reuse system. Dual distribution water systems transport
reclaimed water from treatment plants to irrigation or
industrial sites. In many areas, development of a
wastewater reuse system would provide reclaimed
wafer at a lower cost than potable water. Substitution
of reclaimed water for potable water can reduce
demands on ground water supplies and can reduce or
eliminate the amount of wastewater treatment plant
effluent discharged to environmentally stressed surface
waters (See Figure 1). i
Potable
Water
Source -7
-***
Reclaimed Water
Distribution System —,
Water
Distribution
System^
Treatment 1 >£"j
(If Needed)
/
Wastewater
pCollectlon
System
1
Treatment
~*s"
i
Figure 1. Dual Distribution System Schematic
A look at four operating dual distribution systems
shows a cross-section of benefits available from
operating a wastewater reuse system. The experiences
of the wastewater reuse facilities in Irvine, CA; Tucson,
AZ; Colorado Springs, CO; and St Petersburg, FL
clearly demonstrate the benefits of utilizing this kind of
wise management of a scarce and vital resource...our
water.
Irvine, California \
Nature intended this land to be brown; if you want it to
be green, bring your own water. }
So go the opening lines of a historical article about
Southern California, where Orange County's Irvine
Ranch Water District (IRWD) is located. Encompassing
70,000 acres, nearly one-sixth of the county, IRWD
imports water from the Feather River in north-central
California via the California Aqueduct and from the
Colorado -River via the Colorado River Aqueduct.
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Public Acceptance
It would not have been possible for a project such as
Tucson's to be constructed and institutionalized in such
a short time without political leadership and widespread
public acceptance. Public officials in Tucson are
committed to managing the region's limited water
supply. The reuse of reclaimed effluent is an important
element in achieving the basinwide water balance
mandated by state law.
Colorado Springs, Colorado
Colorado Springs has reclaimed wastewater for
landscape irrigation since 1955. Secondary effluent
from both an activated sludge treatment plant and a
trickling filter plant is polished by seven gravity
sand/anthracite dual media filters and stored in
uncovered reservoirs prior to final chlorination and
distribution. The system has a production capacity of
10 mgd. Non-potable irrigation water is delivered to
users via a 13-mile distribution system. Average daily
summer irrigation use is 5 mgd. Non-potable water is
used to irrigate approximately 600 acres of landscaping
in Colorado Springs including the wastewater treatment
facility, municipal parks, golf courses, cemetaries, and
private commercial establishments. Also, construction
firms purchase non-potable water for construction
purposes and dust control.
System Operation
The sand filtration operation is manned by wastewater
treatment facility personnel, while the
distribution-system and storage lakes are maintained by
a single caretaker. Non-potable system customers own
and operate the distribution system on their own sites
in accordance with a Use Policy issued and enforced
by the City Wastewater Division in accordance with
guidelines from the Colorado Department of Health.
The Wastewater Division conducts an extensive
sampling program of the irrigation system to assure a
high quality product.
Costs
The reclaimed wastewater portion of the irrigation
system was put on line in 1955 and expanded in 1971.
The system is financed entirely by user charges. The
non-potable water rate is set at $.54 per hundred cubic
feet as opposed to a potable water rate of $1.22 per
hundred cubic feet. Since Colorado water law operates
on the appropriations doctrine, the nori-potable
irrigation system is an important element in the plan for
the beneficial use of Colorado Springs water resources.
This indirect economic benefit of securing the city's
water rights vastly outweighs the operating expenses of
the irrigation system.
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tion Systems
IRWD's Plan for Water Reclamation
Once imported, the water used and disposed of as
sewage by the District's 35,000 customers is reclaimed.
Reclaimed water, about 9 mgd in 1984, irrigates
cropland, a regional park, school grounds, street
medians and edgeways, golf courses, residential lawns,
and greenbelt pathways. Wastewater is reclaimed and
recycled by the District at the Michelson plant rather
than disposed of into streams or the nearby Pacific
Ocean. IRWD's Water Resources Master Plan of 1972
triggered the construction of suitable treatment facilities
and the requirement that any new development include
dual distribution facilities for potable and reclaimed
water. :
I
The Treatment Process
Sewage treatment at the Michelson plant is fairly
typical, consisting of conventional primary and activated
sludge treatment, with a capacity of 15 mgd. The
reclaimed water facilities consist of the addition of
coagulation chemicals, direct filtration (seven sand/fines
carbon gravity filters), and two-hour chlorination.
All effluent leaving the plant must meet strict water
quality criteria established by the California Department
of Health Services. Stringent reliability features are
included throughout the plant and storage ponds are
available to contain, and return to treatment, any plant
effluent not meeting the criteria. !
Dual Distribution System i
The dual distribution system includes an extensive
array of storage reservoirs, pump stations, and a
transmission/distribution piping system. Water in the
dual distribution system is available upon demand by '
customers. It is delivered through regular service
connections and meter facilities. In most cases use of
reclaimed water for landscape irrigation must occur !
between the hours of 9 p.m. and 6 a.m. Automatic !
controllers are used throughout.
Reclaimed water is sold at 85% of the price of
domestic water. The reduction in price is in recognition
of the limitations upon use and as an incentive for
choosing reclaimed water. The costs of reclamation
and operation of a dual distribution system are high.
Under 1984 conditions, the IRWD reclaimed-water
system required a small payment in lieu of alternative
disposal costs from the users of the sewerage system.
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City of Tucson, Arizona
In Tucson, a Metropolitan Wastewater Reuse
Assessment was completed in March of 1983 to
assess the demand for reclaimed water for turf
irrigation in the metropolitan area (See Figure 2). The
results of this study were used to provide a basic plan
for a reclaimed water system providing pretreatment by
pressure filtration of 8.2 mgd (expandable to 25 mgd).
The project was completely constructed with local
funds and was designed and placed in operation in
only eight months.
50
to 40
| 30
S
I 20
u.
I 10
43,000
18,800
1980
1990
2000 2010
Year
2020
2030
Figure 2. Projected Annual Reclaimed Water Demand
for Turf Irrigation
A demonstration recharge project is being constructed
to store up to 1.5 mgd of reclaimed water underground
during low demand winter months which will be
pumped to the system during peak summer demand.
The Recharge Project will be studied to evaluate the
treatme, it provided by the vadose (unsaturated soils)
zone to assess the potential application of this
treatment for future recharge projects.
Costs
A 10-year capital program is in place to provide 24,000
acre-feet per year of reclaimed water to identified users
at a cost of $39 million. Operating and maintenance
costs are projected to be $70 per acre-foot which
includes $24 per acre-foot for pumping. Users of the
reclaimed water pay 80% of the applicable potable
water rate, presently $348 per acre-foot.
Effects on Potable Water System
As turf irrigation users shift from the potable system to
reclaimed water, overall utility revenues will decline
somewhat. This loss of revenue is generally offset by
the reduced need for well capacity. More importantly,
the reclaimed water system allows high quality, potable
ground water to be reserved for future use by Tucson's
growing population.
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million gallons) provide the reservoir for nighttime
pumping. The closed storage tanks eliminate algae
problems, as well as mosquitoes, bird contamination,
etc. !
Effluent Disposal System
Effluent disposal is accomplished through spray
irrigation or deep-well injection. The spray irrigation
system consists of a complete secondary water main of
100 miles, carrying effluent to the four quadrants of the
City. Branches of the water main supply both large
water users - golf courses, parks, school grounds - and
also the critical water quality (CWQ) areas. CWQ areas
(generally residential users) are areas where wells
produce salt water, which is unacceptable for irrigation
and would therefore require potable water for irrigation.
Excess effluent not used for irrigation is injected via
deep wells into a brine zone a thousand feet below the
ground. An impermeable layer of rock and clay
over-laying the brine zone prevents vertical migration of
the effluent, eliminating the possibility of contaminating
ground water.
Reclaimed Water Use
Since the program was initiated in 1977, the City has
experienced a substantial decline in the increasing rate
of potable water consumption and attributes this decline
to the introduction of the Reclaimed Water System
(See Figures). Reclaimed water, on a limited scale, is \
V
D)
50
45
40
35
30
25
Potable
Water
i
1968
1972
1976
Year
1980
1984
Figure 3. St. Petersburg Water Usage
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available throughout the current system for fire
protection. The City is also engaged in a pilot program
utilizing the reclaimed water as make-up water for
cooling towers, illustrating the flexibility of the system.
Charges for reclaimed water are based on the area to
be served, not on water volume. Currently, charges for
the first acre or less are $6.00 per month for
unrestricted use. Large users pay an additional $1.20
per half acre irrigated. These sites are not metered.
The exception to this is the industrial user, where the
water is used for boiler make-up or cooling water, etc.
The charge for metered industrial users is, 25 cents per
thousand gallons.
For More Information:
Colorado Springs
Dennis T. Cafaro
Mgr. Wastewater Division
P.O. Box 1103
Colorado Springs, CO 80947
(303) 636-5823
Tucson Water
Kirke Guild
City of Tucson
P.O. Box 27210
Tucson, AZ 85726
(602) 791-4331
Irvine Ranch Water District
Joyce Wegner-Gwidt
P.O. Box D-1
Irvine, CA 92716
(714)833-1223
St. Petersburg, FL
J. David Shulmister
Mgr.Wastewater Operations
Public Utilities
1635 Third Avenue North
St. Petersburg, FL 33713
(813) 893-7171
EPA-OMPCtWH-595)
401 M Street, SW
Washington, DC 20460
(202)382-7368/7369
EPA Region 1
John F. Kennedy Federal Building
Boston, MA 02203
EPA Region 2
26 Federal Plaza
New York, NY 10278
EPA Region 3
841 Chestnut Street
Philadelphia, PA 19107
EPA Region 4
345 Courtland Street, NE
Atlanta, GA 30365
EPA Region 5
230 South Deaibom Street
Chicago, IL 60604
EPA-WERL (489)
26 West St. Clair Street
Cincinnati, OH 45268
(513)684-7611
EPA Region 6
1201 Elm Street
Dallas, TX 75270
EPA Region 7
726 Minnesota Avenue
Kansas City, KS 66101
EPA Region 8
999 18th Street
Denver, CO 80202
EPA Region 9
215 Fremont Street
San Francisco, CA 94105
EPA Region 10
1200 6th Avenue
Seattle, WA 98101
Prepared by Environmental Resources Management, Inc.
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