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 applicatio n of in-situ bio-denitrification to reduce nitrates in groundwater to an acceptable level as well as pertinent parameters that control the p rocess. Results from laboratory experiments designed to simulate in-si tu bio-denitrification using an aquifer model are compared to results of experiments reported in the literature. The results indicate that w hile denitrification can be effective in reducing nitrates in contamin ated groundwater serious aquifer plugging problems can be expected. Fu rthermore, the avoidance of the plugging problem requires that careful management schemes be implemented during in-situ treatment. The resul ts of field-scale experiments in Europe and other areas generally conf irm 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 ra mifications on the success or failure of bio-denitrification. In addit ion to aquifer plugging, other problems can be expected. These include residual organics and the presence of large bacterial counts in the t reated water with subsequent potential effects on the water turbidity, disinfection requirements, and public health acceptability.