Aerobic Denitrification as an Innovative Method for In situ Biological Remediation of Contaminated Subsurface Sites

摘要

The objective of this project was to conduct laboratory testing of an aerobic denitrification concept for the enhancement of in situ bioremediation of subsurface sites. Microbial enrichments using phenol, dodecane, toluene, naphthalene, and methylene chloride demonstrated that many soil organisms classically associated with degradation of these organics are also capable of respiring with nitrate. Chemostat experiments with an isolate from the enrichments were performed to follow phenol degradation at varying oxygen concentrations. Nitrate respiration and aerobic phenol degradation could occur simultaneously at oxygen concentrations as high as 10 percent in the sparging gas. Thus the concept of aerobic denitrification was proven. An enhancement of biodegradation of phenol occurred when the isolate was provided nitrate, in lieu of oxygen, as a final electron acceptor for respiration. This enhancement was attributed to the decreased oxygen demand for phenol oxidation. Tentative evidence using a mixed culture demonstrated that nitrate could increase mineralization of certain organics in limiting oxygen. The study provided proof of concept that the addition of nitrate could enhance in situ biodegradation of organic contaminants in subsurface sites by decreasing the oxygen demand. Keywords: Soil contamination, Ground water pollution. (aw)