WSP05341

• File Number: 8278.100
• Description: Title I - Yuma Desalting Plant
• Basin: Colorado Mainstem
• Date: 12/23/1992
• Author: USDOI/BOR
• Title: Yuma Desalting Plant - Alternatives for the Interim Period
• Water Supply Pro - Doc Type: Publication

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

WMIDD irrigation drainage (feed water) will be diverted from the MODE to
grit sedimentation basins where solids and biomass will be removed. The
water will then be pumped to three SCRs. A single-unit partial lime-
softening pretreatment process will remove calcium, bicarbonates, iron,
and manganese and reduce suspended solids. Under normal operation, the
pretreatment process will use about 100 tons of lime and produce about
360 tons of calcium carbonate sludge by-product per day. The by-product
will be piped to sludge disposal ponds.

From the SCRs, the water will flow by gravity to dual-media filters
(anthracite over sand), which will provide the final clarification.
From the filters, the water will flow to a clear well. Then the water
will be pumped to the reverse osmosis desalting equipment, the heart of
the Desalting Plant.

This reverse osmosis equipment consists of "pressure vessels" that are
8 inches and 12 inches in diameter and 20 feet long. Each pressure
vessel will contain spiral-wound, semipermeable membranes. These
membranes, through a process known as reverse osmosis, will remove
dissolved materials (mostly mineral salts) from the pretreated water.

Operation

Under the planned operation, the Desalting Plant is sized to accommodate
about 108,000 af of irrigation drainage annually with a salinity of
about 2,900 to 3,200 ppm. About 98,000 af of saline irrigation drainage
will be fed into the Desalting Plant, producing about 68,500 af of
desalted water (product. water) with a salinity of about 250 to 300 ppm
and about 29,500 af of reject stream with a salinity of about 9,400 ppm.

The planned operation will blend the 68,500 af of desalted water with
about 10,000 af of untreated irrigation drainage. This blended water
will be returned to the Colorado River, mixed with other Colorado River
water, and then delivered to Mexico at the Northerly International
Boundary, upstream from Morelos Dam.

The 29,500 af of reject stream from the Desalting Plant will be
discharged into the Bypass Drain where it will be combined with excess
untreated WMIDD irrigation drainage (if any) and conveyed to the Slough.

Power Source

The Desalting Plant, PRPU, and their associated facilities require a
total of 27 megawatts of capacity: the Desalting Plant requires
22 megawatts of ca~acity in a full-load daily operation, as currently
constructed, and the PRPU requires a maximum of 5 megawatts of capacity.
The Bureau of Reclamation (Reclamation) has entered into two interagency
agreements with Western Area Power Administration (Western). The term
of these agreements extends to September 30, 2021, unless terminated by
Reclamation upon a 2-year notice.

Under the first agreement, Pacific Northwest-Southwest 1ntertie and the
Parker-Davis Transmission Systems ~rovide firm transmission capacity.

6