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LIMITATION <br />A continuous-flow, bench-scale test system operated at Zenon's laboratory for 14 weeks <br />produced an effluent averaging 33 µg/L selenium. The maximum effluent concentration <br />was 54 µg/L. These statistics do not include one outher that was reported at 576 µg/L <br />(higher than the system feed concentration) ox data from the first month of operation while <br />the system was acclimating to the water. <br />The system did not achieve the agricultural standard of 20 µgf L selenium. However, the <br />residual selenium in the effluent is apparently not biodegradable, since testing showed that <br />doubling the residence time of biological treatment did not remove the residual. <br />COST ESTIMATE <br />Zenon estimates that a system sized fox a nominal 100 gpm flow rate has a total cost of <br />$600,000 (capital cost plus operation for approximately one year to treat 35 million gallons). <br />This amount includes pumps, reactor vessels, activated carbon, inoculum, acid and nutrient <br />delivery systems, instrumentation, controls, electrical equipment, a building, installation, <br />engineering support and supplies. CEMEX is presently purchasing and installing the acid <br />tank and neutralization system under TR-06, so this portion of the process could be <br />subtracted from the $600,000 Figure, but its inclusion will provide a contingency for the <br />project. <br />Labor fox operating the system is estimated at under $20,000 (two hours per day at $25 per <br />hour for one year). <br />Placing 2000 cubic yards of fill in the residual C-Pit pool at the end of the treatment period <br />will cost an additional $5000. Therefore, the total cost to eliminate a free water surface from <br />C-Pit is estimated at $625,000. <br />