Comparison and Evaluation of in-situ Bio-Denitrification Systems for Nitrate Reduction in Groundwater

Nitrate contamination of groundwater is a growing problem in the U.S. and throughout the world. This paper examines the potential application of in-situ bio-denitrification to reduce nitrates in groundwater to an acceptable level as well as pertinent parameters that control the process. Results from laboratory experiments designed to simulate in-situ bio-denitrification using an aquifer model are compared to results of experiments reported in the literature. The results indicate that while denitrification can be effective in reducing nitrates in contaminated groundwater, serious aquifer plugging problems can be expected. Furthermore, the avoidance of the plugging problem requires that careful management schemes be implemented during in-situ treatment The results of field-scale experiments in Europe and other areas generally confirm the efficacy of bio-denitrification. However, aquifer plugging was not reported by some of these studies or appeared to be downgraded by others. In some cases, this problem was reported as having serious ramifications on the success or failure of bio-denitrification. In addition to aquifer plugging, other problems can be expected. These include residual organics and the presence of large bacterial counts in the treated water with subsequent potential effects on the water turbidity, disinfection requirements, and public health acceptability.