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• Reinjection of treated water through an infiltration 'galleryin the source <br /> area <br /> The remedial alternative's are distinguished only by the method of groundwater <br /> treatment. Three treatment alternatives are compared in the following section: air <br /> r stripping with granular activated carbon (GAC) offgas control, air stripping with <br /> catalytic oxidation offgas control, and ultraviolet (UV) light-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 (nitrogen and <br /> phosphorus) can be added to the groundwater recirculation system if monitoring results <br /> i' <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 mg/l benzene is assumed <br /> for all alternatives. <br /> Alternative Y-4ir Stripping with Offgas 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 µg/l benzene. The carbon would periodically <br /> be replaced and regenerated. <br /> 1 <br /> Advantages of this system are ease of construction and startup. All components are <br /> readily available, and performance is well-documented. The system can be expanded if <br /> 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 /> f installation of the system; operation and maintenance adds about $66,000 per year. <br /> Alternative 2-- 4ir Stripping with Offgas 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 /> SF0316041RP1007.51 4-7 <br />