ARCHIVED REPORTS_XR0005088 - Laserfiche WebLink

Home Browse Search

' 11 February 2003 AGE-NC Project No. 98-0520 Page 17 of 21 7.3'. IN-SITU BIOREMEDIATION/BIOENHANCEMENT In-situ bioremediation involves the introduction of hydrocarbon-degrading microbes and/or ' supplemental nutrients to enhance naturally-occurring or injected bacteria, through wells into the ground water.The microbes degrade hydrocarbons and spread laterally(and vertically)by migration and reproduction. There is considerable variation in the types of bacteria used by different remediation consultants for bioremediation.' The bacteria are cultured and selected for their ability to degrade petroleum hydrocarbons.They are microaerophilic and facultatively anaerobic,and therefore abundant oxygen ' is not necessary for the process to occur. Exotic forms of oxygen (such as hydrogen peroxide) are usually not required, but free oxygen does increase the metabolic rates in the bacteria..Therefore a compressed or pressurized source of delivering atmospheric air to the subsurface at a rate of at least 4"to 6 scfm per injection well can be used to enhance air flow and oxygen concentrations during the process. For in-situ bioremediation of theound water, h drocatbon-degrading bacteria are propagated in �• Y a liquid medium or solid, which is then injected directly into ground water and inoculation wells ' screened into ground water. Once in the contaminant plume, the bacteria metabolize and therefore degrade hydrocarbons and spfead laterally by migrating and reproducing, creating an advancing remediation front. . 1 7.3.1. Nutrient Requirements and Toxicity The bacteria are not tolerant to a wide range of ground water conditions. For instance, pH should range from 6 to 8.5. In addition, the possible presence of high concentrations of pesticides or fumicides at the site may have a"biotoxic effect on some bacteria. The microbes require certain essential nutrients that are commonly available in ground water. If supplemental nutrients are required, such as nitrogen and phosphorus as ammonium phosphate in liquid phase, the quantity is usually very low. However, a Waste Discharge Permit is required by ' the RWQCB for the injection of nutrients into ground water. Typically,the 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 aeration sources are sufficient to provide the necessary oxygen. In some cases, addition of hydrogen peroxide is beneficial. Advanced GeoEnvironmental,Inc..,