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~ ~ <.:j'i N C) develop the process material balances, equipment estimates and final costs for .:) al I the configurations chosen for final evaluation. SCREENING OF PROCESS OPTIONS Eight process options were developed from the available saline water use tech- nologies and were screened using the following criteria: . Economic advantage . Demonstrated performance in power plants . Appl icabil Ity to the two water sources studied . Emerging technologies with strong economic and/or technical poten- tial Option numbers with the "LV" suffix refer to the Lower VirgIn RIver Unit and option numbers with the "SE" suffix refer to the secondary effluent water source. Ix Softenlng/Sldestream Softenlng/VCE/EvAporatlon Ponds This option uses ion exchange softeners to reduce calcium in the makeup water supply to the cool ing towers. The softened water is concentrated In the cir- culating water system which raises the concentration of the dissolved solids including sodium, chloride, sulfate, and any residual hardness passed through the Ion exchange softeners. The concentration of sodium In the blowdown from the circulating water system can be used to regenerate the ion exchange sof- teners. Silica, which is not removed from the makeup water by the ion ex- change softeners, could limit the cycles of concentration and consequently the available sodium concentration. Sldestream treatment Is applied to the cir- culating water to remove silica with a portion of the residual hardness (particularly magnesium) passed by the Ion exchange softeners. This maintains sIlica below the desired 150 mg/I limit whi Ie allowing the cooling tower to operate at the concentration required to regenerate the Ion exchange softeners and minimize blowdown. The sldestream system also provides reduction of the phosphate level In the circulating water. Recyclable wastewaters are further concentrated In vapor compression evaporators. Non-recyclable wastewaters and sludges are dis- charged to evaporation ponds. The high quality product water from the vapor compression evaporators Is polished and used as condensate makeup with the excess blended with raw water to supply the scrubber and ash systems. This configuration Is an extension of established technologies and has favorable economic potential. For these reasons, It Is Included for further evaluation and Is Identified as Option I-LV. Lime/Soda SldestreAm Softening lFGD & Ash MakelJpl/VCE/Evaporatlon Ponds In this process option, raw water Is used sldestream lime/soda softening appl led to concentrations In the circulating water. sufficient additional capacity to supply requirements with softened cooling tower for cooling tower makeup with reduce calcium, silica and phosphate The softening system Is sized with the scrubber and ash systems water blowdown. Vapor compression 4-10 11