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7 . 1.2 . In-situ Biodegradation <br /> Biodegradation is a general term referring to the biological <br /> transformation of any organic chemical to another form. In-situ <br /> biodegradation processes enhance natural biological activity in <br /> the soil in order to increase decomposition of petroleum hydro- <br /> carbons by biodegradation. Most petroleum hydrocarbons can be <br /> degraded by microbial processes. The actual biodegradation of a <br /> compound under field conditions is affected by many factors which <br /> include dissolved oxygen levels, soil moisture content, soil <br /> permeability, oxidation reduction potential, temperature, pH, <br /> compound availability and concentration, and the natural <br /> microbial community. Because all these factors act together to <br /> determine the biodegradability of a compound in a particular <br /> setting, it is difficult to make generalizations about the <br /> importance of any one factor. <br /> The basic cost for the installation and maintenance of biodegra- <br /> dation units are moderate. Again, as was the case for the ISV <br /> system, site characterization is an important step in determining <br /> the efficiency of the system. The estimated costs for in-situ <br /> bioremediation of soils at the site are as follows: <br /> Site Characterization $25, 000 <br /> Bio Remediation System 50, 000 <br /> Monitoring 15, 000 <br /> Misc. (Manpower, elect, etc. . ) 20,000 <br /> $110, 000 <br /> Contingency (20%) 22 , 000 <br /> Total Estimate $132, 000 <br /> 7. 2 . Non 1n-situ Remedial Alternatives <br /> For the remedial alternatives presented within this section, the <br /> alternatives are broken down into on-site and off-site catego- <br /> ries. In addition, due to the compound presence in the groundwa- <br /> ter, groundwater treatment (section 6. 2 . 3) must also be included. <br /> 7 . 2 . 1. Land Treatment <br /> Land treatment and composting removes petroleum hydrocarbons from <br /> soils using a combination of the following processes: <br /> volatilization, leaching, incorporation of the hydrocarbons into <br /> the soil matrix by sorption, and degradation. Although <br /> volatilization removes a large portion of the lighter hydrocar- <br /> bons, the effects of the first three of these mechanisms on the <br /> land treatment of heavy hydrocarbons are minor when compared to <br /> degradation. <br /> In land treatment, degradation of petroleum hydrocarbons in <br /> soils is responsible for the decomposition of the heavier <br /> - <br /> 14 - <br />