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i05 May 1997 <br /> AGE-NC Project No 95-0173 <br /> Page 24 of 29 <br />' 8 2 5 Cost <br /> Ground water extraction is usually a very costly method of ground water treatment Costs for <br /> installation of a "pump and treat" system typically ranges from $25,000 to $40,000, including the <br /> installation of one or more large-diameter extraction wells Once extracted. the contaminated water <br /> must be treated and/or will require disposal Treatment is highly dependant upon the concentrations <br />' of dissolved hydrocarbons in the ground water, the cost per gallon could be as great as $2 00 Based <br /> upon the extraction/treatment of approximately 1,000,000 gallons of contaminated ground water <br /> Costs for the entire treatment project would likely exceed $2,000,000 <br /> 1 <br /> 8 3 IN--SITU BIOREMEDIATION/BIOENHANCEMENT <br />' 83 1 Basic Principles <br />' Bioremediation involves the introduction of hydrocarbon-degrading microbes or supplemental <br /> nutrients to enhance naturally-occurring bacteria,through wells into the ground water The microbes <br /> degrade hydrocarbons and spread laterally (and vertically) by migration and reproduction <br /> Hydrocarbon-degrading microbes are able to metabolize hydrocarbons and assimilate the resulting <br /> organic chemicals into biomass for reproduction and growth Typically, the light-end hydrocarbons <br /> are degraded first, followed by heavier compounds <br /> 8 3 2 Nutrient Requirements And Toxicity <br /> 1 The microbes require certain essential nutrients that are usually available in ground water If <br /> supplemental nutrients are required, such as nitrogen and phosphorus as ammonium phosphate in <br /> liquid phase,the quantity is usually very low However, a Waste Discharge Permit is required by the <br /> CVRWQCB for the injection of nutrients into ground water <br /> Typically, the microbes utilized in bioremediation are aerobic and usually require additional oxygen <br /> to ctirnrnlement dicgolvPd oxygen concentrations in ground water Generally several air marging or <br /> in-well aeration sources are sufficient to provide the necessary oxygen However, in some cases the <br /> addition of hydrogen peroxide is necessary <br />' 8 3 3 Monitoring Activities <br /> • After inoculation, the inoculation wells and ground water monitoring wells should be monitored for <br /> 1 Advanced GcoEnvfronmental,Inc <br />