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Bioventing Page 4 of 5 <br /> of the soil. Generally, soils saturated with water prohibit air flow and oxygen <br /> delivery to bacteria, while dry soils lack the moisture necessary for bacterial growth. <br /> Bioventing promotes dehydration of moist soils through increased air flow through <br /> the soil, but excessive dehydration hinders bioventing performance and extends <br /> operation time. <br /> The optimum pH for bacterial growth is approximately 7; the acceptable range for <br /> soil pH in bioventing is between 6 and 8. Soils with pH values outside this range <br /> prior to bioventing will require pH adjustments prior to and during bioventing <br /> operations. <br /> Bacteria require inorganic nutrients such as ammonium and phosphate to support <br /> cell growth and sustain biodegradation processes. Nutrients may be available in <br /> sufficient quantities in the site soils but, more frequently, nutrients need to be added <br /> to soils to maintain bacterial populations. <br /> The presence of very high concentrations of petroleum organics or heavy metals in <br /> site soils can be toxic or inhibit the growth and reproduction of bacteria responsible <br /> for biodegradation. In addition, very low concentrations of organic material will also <br /> result in diminished levels of bacterial activity. <br /> Advantages and Disadvantages <br /> Advantages Disadvantages <br /> Uses readily available equipment; High constituent concentrations may initially <br /> easy to install. libe toxic to microorganisms. <br /> Creates minimal disturbance to site Not applicable for certain site conditions <br /> operations. Can be used to address (e.g., low soil permeabilities, high clay <br /> inaccessible areas(e.g., under content, insufficient delineation of <br /> buildings). subsurface conditions). <br /> Requires short treatment times: Cannot always achieve very low cleanup <br /> usually 6 months to 2 years under standards. <br /> optimal conditions. <br /> Cost competitive: $45-140/ton of Permits generally required for nutrient <br /> contaminated soil. injection wells (if used). (A few states also <br /> require permits for air injection.) <br /> Easily combinable with other Only treats unsaturated-zone soils; other <br /> technologies (e.g., air sparging, methods may also be needed to treat <br /> groundwater extraction). saturated-zone soils and groundwater. <br /> May not require costly offgas <br /> treatment. <br /> References <br /> Norris, R.D., Hinchee, R.E., Brown, R.A., McCarty, P.L., Semprini, L., Wilson, J.T., <br /> Kampbell, D.H., Reinhard, M., Bower, E.J., Borden, R.C., Vogel, T.M., Thomas, <br /> J.M., and C.H. Ward. 1994. Handbook of Bioremediation. Boca Raton, FL:CRC <br /> Press. <br /> U.S. Environmental Protection Agency (EPA). 1991a. Guide for Conducting <br /> Treatability Studies Under CERCLA: Aerobic Biodegradation Remedy Screening. <br /> Washington, DC: Office of Emergency and Remedial Response. EPA/540/2- <br /> 91/013A. <br /> http://www.epa.gov/swerustl/cat/biovent.htm 6/17/2004 <br />