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t� <br /> wa <br /> Reinjection of treated water through an infiltration gallery in the source <br /> area <br /> The remedial alternatives are distinguished only by the method of groundwater <br /> treatment. Three treatment alternatives are compared in the following section: air <br /> stripping with granular activated carbon (GAC) offgas control, air stripping with <br /> catalytic oxidation offgas control, and ultraviolet (UV) tight-peroxide treatment. <br /> As discussed above, bioremediation will also be stimulated by the introduction of <br /> oxygen through the sparging well. A nutrient addition system ( -trogen and <br /> phosphorus)can be added to the groundwater recirculation system if monitoring results <br /> indicate that biodegradation of BTEX is not occurring. <br /> All three alternatives are capable of meeting the remedial goals for this site. <br /> Therefore, this evaluation focuses on comparing the capital, operating, and <br /> - maintenance costs for each treatment system (Appendix H). Other aspects evaluated <br /> include system flexibility and tolerance of changing influent characteristics. An initial <br /> influent stream of 15 gallons per minute containing about 12 mgn benzene is assumed <br /> for all alternatives. <br /> Alternative 1,4ir Stripping with O gas GAC <br /> .. A vapor-phase activated carbon unit would collect hydrocarbons purged from the water <br /> ' in a dual-tower air-stripping system. Two strippers in series are necessary to achieve <br /> the required effluent level of less than 1 µg11 benzene. The carbon would periodically <br /> - be replaced and regenerated. <br /> are ease of construction and startup. All components are <br /> Advantages of this system <br /> readily available, and performance is well-documented. The system can be expanded if <br /> o larger flow rates are desired or'reduced if lower concentrations of BTEX are <br /> encountered. <br /> Disadvantages include maintenance of the air strippers to remove scale and fouling, <br /> and the cost of carbon regeneration. Capital cost is estimated to be $228,000 for the <br /> installation of the system; operation and maintenance adds about$66,000 per year. <br /> t Alternative 2--,4ir Stripping with Oftas Catalytic Oxidation <br /> This alternative would avoid the expense and effort associated with carbon replacement <br /> by destroying the hydrocarbons in a catalytic oxidizer. The oxidizer is essentially an <br /> incinerator that uses a catalyst to reduce the temperature required to destroy the <br /> organic compounds. <br /> 4-7 <br /> SF031604\RP1007.51 <br />