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<br />'u'" <br /> <br />'; :~. <br /> <br /> <br /> <br />>'" <br />','- " <br /> <br />~ <br />/~~i <br /> <br />;>;':';' <br /> <br />'f,';\ <br />,~"-'> <br />. .;~.'~ <br />, ~':~~~{~ <br />.k','_ <br /> <br />~~~\ <br /> <br />;'-' " <br />~.~::;~ <br />.!:h, <br />t''\Simi <br /> <br />t... <br />C\1 <br />"7' <br />C\1 <br />c::' <br />C) <br /> <br />EXECUTIVE SUMMARY <br /> <br />This report presents the results of Task 4 of Bureau of Reclamation Contract <br />4-AB-81-03600 which evaluated the use of Lower Virgin River Unit saline water <br />as a primary raw water source for the proposed Harry Allen Generating Station <br />In Nevada. The Task 1 study addressed sal ine water use and associated cooling <br />water and wastewater management technologies at the Hunter Generating Station <br />in Utah. The Task 2 study evaluated the use of the Big Sandy River Unit <br />saline water supply as a partial raw water source for the Jim Bridger Gener- <br />ating Station In Wyoming. The Task 3 study, which Is In progress, evaluates <br />the use of the Palo Verde Irrigation Outfal I water supply as a primary water <br />source for a generic power plant located In the desert area of California. <br />The Task 3 study also Includes an evaluation of an ongoing ion exchange sof- <br />tening field test program at the Etiwanda Generating Station in California. <br /> <br />The Task 4 study focused primarily on the In-plant cost differences for water <br />supply using either the Lower Virgin River Unit water or Clark County secon- <br />dary treated sewage effluent as the sources for the Harry Allen Generating <br />Station. The Harry Allen power plant configuration, recently developed by Be- <br />chtel Power Corporation for Nevada Power Company, was used as the basis for <br />the comparative water system studies. In the Bechtel plant design, secondary <br />treated sewage effluent from the Clark County Advanced Wastewater Treatment <br />Plant Is assumed as the primary water supply for the plant. The present Harry <br />Allen power plant design includes four 250 megawatt pulverized coal-fired <br />units with wet I imestone scrubbers for sulfur dioxide control. <br /> <br />The Lower Virgin River Unit Is a sal ine water source under study by the Bureau <br />of Reclamation as part of the Colorado River Water Quality Improvement <br />Program. The unit study area Is located along the Virgin River between Lit- <br />tlefield Springs, Arizona and Lake Mead, Nevada. The unit plan for water <br />supply Includes groundwater from wel I fields developed by Reclamation In the <br />flood plain, plus surface water from the Lower Virgin River which contributes <br />to recharge of the wel I field. The Lower Virgin River Unit water has an <br />average sal inity of approximately 2,500 mg/I and is relatively high in hard- <br />ness, sodium, chloride and sulfate. <br /> <br />Water treatment process options were developed for the Lower Virgin River Unit <br />water qual ity and compared with the base case plant design which uses secon- <br />dary treated sewage effluent. The base case design uses makeup lime/soda sof- <br />tening for primary water treatment and softened cool ing tower blowdown for <br />makeup to the ash and scrubber systems. Technical and economic evaluations of <br />water treatment process options for use of Lower Virgin River Unit water <br />produced three viable options: (I) ion exchange makeup softening with <br />sidestream cooling tower treatment for sll ica control, (I I) sidestream <br />lime/soda softening of the cool ing tower circulating water and (I I I) makeup <br />lime/softening of the raw water supply. These were compared with process op- <br />tions for secondary sewage effluent Including: (IV) lime/soda softening of <br />raw water supply with brine concentrator distillate used for ash and scrubber <br />system makeup, and (V) lime/soda softening of raw water supply with softened <br />cool ing tower blowdown used for ash and scrubber system makeup (base case.) <br /> <br />iii <br />