o_19f3m1n7k170b14e9u0oqipgu4a.pdf

• Prevention of improper operation of the system
• Prevention of cross-connections with potable water
lines
• Prevention of improper use of nonpotable water
To avoid cross connections, all above-ground appurtenances
and equipment associated with reclaimed water
systems must be clearly marked. National color standards
have not been established, but most manufacturers,
counties, and cities have adopted the color purple
for reclaimed water lines. The State of Florida has accepted
Pantone 522C as the color of choice for reclaimed
water material designation. Florida also requires signs
to be posted with specific language in both English and
Spanish identifying the resource as nonpotable. Additional
designations include using the international symbol
for “Do Not Drink” on all materials, both surface and
subsurface, to minimize potential cross connections. A
more detailed discussion of distribution safeguards and
cross connection control measures is presented in Section
3.6.1, Conveyance and Distribution Facilities.
2.1.3 Design Considerations
Urban water reuse systems have 2 major components:
1. Water reclamation facilities
2. Reclaimed water distribution system, including storage
and pumping facilities
2.1.3.1 Water Reclamation Facilities
Water reclamation facilities must provide the required
treatment to meet appropriate water quality standards
for the intended use. In addition to secondary treatment,
filtration, and disinfection are generally required for reuse
in an urban setting. Because urban reuse usually involves
irrigation of properties with unrestricted public access or
other types of reuse where human exposure to the reclaimed
water is likely, reclaimed water must be of a higher
quality than may be necessary for other reuse applications.
In cases where a single large customer needs a
higher quality reclaimed water, the customer may have
to provide additional treatment onsite, as is commonly
done with potable water. Treatment requirements are presented
in Section 3.4.2.
2.1.3.2 Distribution System
Reclaimed water operational storage and high-service
pumping facilities are usually located onsite at the water
reclamation facility. However, in some cases, particularly
for large cities, operational storage facilities may be
located at appropriate locations in the system and/or near
the reuse sites. When located near the pumping facilities,
ground or elevated tanks may be used; when located
within the system, operational storage is generally
elevated.
Sufficient storage to accommodate diurnal flow variation
is essential to the operation of a reclaimed water system.
The volume of storage required can be determined
from the daily reclaimed water demand and supply curves.
Reclaimed water is normally produced 24 hours per day
in accordance with the diurnal flow at the water reclamation
plant and may flow to ground storage to be pumped
into the system or into a clear well for high-lift pumping to
elevated storage facilities. In order to maintain suitable
water quality, covered storage is preferred to preclude
biological growth and maintain chlorine residual. Refer to
Section 3.5.2 for a discussion of operational storage.
Since variations in the demand for reclaimed water occur
seasonally, large volumes of seasonal storage may be
needed if all available reclaimed water is to be used, although
this may not be economically practical. The selected
location of a seasonal storage facility will also have
an effect on the design of the distribution system. In areas
where surface storage may be limited due to space
limitations, aquifer storage and recovery (ASR) could prove
to be a viable enhancement to the system. Hillsborough
County, Florida has recovered ASR water, placed it into
the reuse distribution system, and is working to achieve
a target storage volume of 90 million gallons (340,700
m 3 ) (McNeal, 2002). A detailed discussion of seasonal
storage requirements is provided in Section 3.5.
The design of an urban distribution system is similar in
many respects to a municipal potable water distribution
system. Materials of equal quality for construction are
recommended. System integrity should be assured;
however, the reliability of the system need not be as
stringent as a potable water system unless reclaimed
water is being used as the only source of fire protection.
No special measures are required to pump, deliver,
and use the water. No modifications are required
because reclaimed water is being used, with the exception
that equipment and materials must be clearly identified.
For service lines in urban settings, different materials
may be desirable for more certain identification.
The design of distribution facilities is based on topographical
conditions as well as reclaimed water demand
requirements. If topography has wide variations, multilevel
systems may have to be used. Distribution mains
must be sized to provide the peak hourly demands at a
pressure adequate for the user being served. Pressure
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