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

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