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showed that microorganisms could be adapted to elevated levels of <br /> hydrogen peroxide, that hydrogen peroxide could supply the <br /> necessary oxygen , and that it was most effective if the organisms <br /> r had first been exposed to needed nitrogen and phosphorous (11, <br /> f The importance of nutrients to microbial adaptation for chemical <br /> f <br /> transformations was recently reinforced by Lewis et al . (13). <br /> These authors found that lag periods were longer for <br /> microbial. populations in nitrogen or phosphorous-limited <br /> environments, and lag times decreased witty he addition of <br /> nitrogen or phosphorous (13) . In' 1987,; Bark et al . <br /> demonstrated the .limitations to natur iodegradation in studies <br /> which. showed that BTX remained i -fifer in layers low in <br /> dissolved oxygen (14). A11' 0 e data confirm the importance <br /> o$ understanding the.. �utri an oxygen requirements of the <br /> indigenous microbial for <br /> <, Thus,:.aver. 15.`years XN <br /> o d and iaboratory .work have <br /> demonstrated that enhanced''biaremediation .through the addition of j <br /> �1 a nitrogen and phosphorous :source coupled with oxygen' is an <br /> effective and efficient procedure for removing petroleum <br /> hydrocarbons from the subsurface environment. This process ; <br /> results in microbial mineralization of the contaminants to CO2 <br /> and water and removes petroleum hydrocarbons from both T.iie <br /> groundwater and subsurface soils. <br /> t <br /> MICROBIOL0GICAL NUTRIENT OPTIMIZATION <br /> :Alter site characteri`xatior�, the first step in. an ISB program is <br /> to determine what' nutrients .are limiting the degradation of the <br /> i asoline to CO2, biomass, and water. Preliminary work has <br /> determined <br /> .that both.'. nitrogen and phosphorousare limiting. the <br /> ^24- <br /> s�wc <br /> i <br /> e — <br /> rr+ <br />