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<br />Title I Program <br />Colorado River Basin Salinity Control Act <br /> <br />proposed YDP desalting equipment, and <br />(3) to test pretreatment systems, <br /> <br />After mid-1978, testing focused on obtaining <br />final design data for the pretreatment <br />process and proof-testing the selected <br />desalting equipment. All testing work was <br />completed in 1982, <br /> <br />Sizing and Pilrfonnance <br /> <br />Public Law 93-320 authorized construction <br />of a desalting plant with a 129-million- <br />gallon-per-day (MGD) capacity. However, a <br />19771 sizing study recommended con- <br />struction of a 96-MGD plant with the <br />"operational characteristics for a reverse <br />osmosis desalting process..,capable of <br />recovering 70 percent of the plant feed <br />water," The report stated that while the <br />actual desalting plant might not be built <br />with the same processes, it would have to <br />perform in substantially the same way. <br /> <br />Using the criteria established in the 1977 <br />study, contracts specifying a total treatment <br />capacity of about 96 MGD were awarded to <br />two manufacturers of reverse osmosis <br />desalting equipment, <br /> <br />However, by 1979, the WMIDD irrigation <br />drainage reduction program. was proving so <br />successful that irrigation drainage was <br />projected to be reduced eventually to <br />108,000 acre-feet per year, As a result, the <br />required capacity of the desalting plant was <br />reduced to 72.4 MGD, and a new plan was <br />developed based on the premise of staged <br />plant construction, That is, the 96-MGD <br />design was completed, but specific <br />increments of capacity (solids contact <br />reactors [SCR's], filters, and associated <br /> <br />equipment) in construction were deleted, <br />This approach was less costly than <br />redesigning the plant. <br /> <br />./ <br /> <br />Description of the YDP and <br />Desalting Process <br /> <br />The YDP is divided into two distinct <br />systems: (1) the partial lime-softening <br />pretreatment system and (2) the reverse <br />osmosis desalting system, <br /> <br />WMIDD irrigation drainage (feed water) <br />will be diverted from the MODE to grit <br />sedimentation basins where settleable <br />solids and biomass will be removed. The <br />water will then be pumped to three SeR's. <br />A single-unit, partial lime-softening <br />pretreatment process will remove calcium, <br />bicarbonates, iron, and manganese and <br />reduce suspended solids, Under normal <br />operation, the pretreatment process will use <br />about 100 tons of lime and produce about <br />360 tons of calcium carbonate sludge <br />byproduct per day. The byproduct will be <br />piped to sludge disposal ponds. <br /> <br />From the SCR's, the water will flow by <br />gravity to dual media filters (anthracite <br />over sand), which will provide the fmal <br />clarification, From the filters, the water <br />will flow to a clear well. Then the water will <br />be pumped to the reverse osmosis desalting <br />equipment, the heart of the desalting plant, <br />(See photograph 2,) <br /> <br />Hydranautics Water Systems provided <br />reverse osmosis desalting equipment <br />capable of producing 22.4 MGD of desalted <br />water. This equipment consists of "pressure <br />vessels" that are 8 inches in diameter and <br />20 feet long. Fluid Systems Corporation <br /> <br />1 Colo1Vdo Ri..... BlJBin StJlinity Control Projet:t, Title I Viviaion, V..c&lting Complu Unit, Sizing Study, <br />YU/7I(J VeatJlting PlBnt, ArizolltJ, I..unm Report, June 1977, Lower Colorado Region, Bureau of Reclamation. <br /> <br />8 <br />