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.-4 " l(j ',' ;.~ ~ C\J \;,. 0 Co tlon and represents the configuration used In the Bechtel study for the pul iverized coal-fired plant with rail-del ivered coal. Comh I ned Makeup and S I destream lime/Soda Soften I ng -;, In this process option, both makeup and sldestream lime/soda softening are ap- pi led to the circulating water system. Recycleable wastewaters are con- centrated In vapor compression evaporators. Non-recyclable wastewaters and sludges are discharged to evaporation ponds. High quality water from the was- tewater evaporators Is used as condensate makeup. Softened water Is used to supply the scrubber and ash systems. ,. ;, The combined makeup/sidestream softening process provides partial makeup sof- tening by using high pH effluent from the sldestream softener. Chemical costs may be reduced, but capital costs are greater than makeup or sldestream sof- tening alone. -r This option shows economic and technical promise for the sewage effluent op- tion, but the scope of the study precluded In-depth analysis. The additional system complexity, higher capital cost and lack of demonstrated commercial operations were the main reasons for eliminating this configuration from fur- ther consideration. " .. Summary of Process Options for Economic Evaluation The five process options selected from the screening process for economic analysis are: Option I-I V Option II-LV Option 111-1 V Option IV-SE ~ Option V-SE Ix Softenlng/Sldestream Softenlng/VCE/Ponds Sldestream Softenlng/VCE/Evaporatlon Ponds Makeup Lime/Soda Softenlng/VCE/Evaporatlon Ponds Makeup Lime/Soda Softenlng/VCE/Evaporatlon Ponds Makeup Lime/Soda Softening/Recycle Softenlng/VCE/Evaporatlon Ponds The study addressed process options applicable to the Lower Virgin River Unit. The two cases which used secondary effluent were done as a base case and a special applications case. WATER TREATMENT PROCESS DESIGN i Appraisal level process designs were developed for the five selected options based on the Harry Allen power plant configuration. Process and material balances and process flow diagrams were developed for each option. ., ~ The raw water supply system Is assumed to be the same for each option. raw water supply system Includes polymer Injection into either the Las secondary effluent or the Lower Virgin River water upstream of the raw The Vegas water 4-13 ,