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I r ' 14 November 1995 i AGE-NC Project No 95-0121 ' Page 17 of 20 t ' 7 3 IN-SITUBIOREMEDIATION/BIOENHANCEMENT 7 3 1 BASIC PRINCIPLES Bioremediation involves the introduction of hydrocarbon-degrading microbes'and/or nutrients to I ; enhance naturally-occurring bacteria, through wells into the ground water The microbes degrade' ' hydrocarbons and spread laterally(and vertically) by migration and reproduction ; r Hydrocarbon-degrading microbes are able to metabolize hydrocarbons and assimilate the resulting lorganic chemicals into biomass for reproduction and growth Typically, the light-end hydrocarbons are degraded more rapidly, and heavier hydrocarbon compound are degraded more slowly t 7 3 2 NUTRIENT REQUIREMENTS AND TOXICITY ' The microbes require certain essential nutrients that are sometimes available in ground water If supplemental nutrients are required, which consist of nitrogen and phosphorus as ammonium phosphate in liquid phase, the quantity is usually very low However, a Waste Discharge Permit is required by the Regional Water Quality Control Board for the infection of nutrients into ground ' water Typically, microbes utilized in bioremediation are aerobic and usually require additional oxygen to supplement dissolved oxygen concentrations in ground water Generally, several air sparging or-in- well rin-well aeration sources are sufficient to provide the necessary oxygen However, in some cases the addition of hydrogen peroxide is necessary 7 3 3 FEASIBILITY STUDIES , , IResults of the bioremediation pilot test indicate that lighter,petroleum hydrocarbons, such as gasoline compounds are biodegraded more readily than,longer-chain (heavier) hydrocarbons, succi as diesel K fuel compounds Based upon favorable results, an in-situ treatmenfwith the addition of sufficient oxygen supplement appears to be feasible The additional oxygen could be supplied through an air sparging system or by adding an oxygen-laden solution such as hydrogen peroxide - 7 3 4 DURATION s' y , I Cleanup durations for in-situ bioremediation will vary,, depending upon specific site characteristics iHowever, 12'to 24 months is generally considered an achievable remediation tune Comparing 3 , , I I ; 1