Electrolytic denitrification: Long term performance and effect of current intensity

The long-term performance of the biofilm-electrode reactor is demonstrated for denitrification. The total nitrate and nitrite concentration, oxidation-reduction potential (ORP), total organic carbon (TOC), color, and viable cell count in the effluent, were monitored to evaluate the performance of the reactor. Initially, the applied electric current intensity was varied from 0 to 100 mA. A nitrate removal efficiency exceeding 98% was achieved at a current of 20 mA when phosphate was used as a buffer. Current intensities between 20 to 25 mA resulted in the lowest effluent concentrations of nitrate, whereas, lower current intensities affected proportionately less nitrate reduction. For higher current intensities, hydrogen inhibition and charge induced repulsion caused decreased reduction efficiencies. ORP was governed by both the concentrations of hydrogen and effluent nitrate. A total nitrate removal efficiency of 85% was achieved at a current level of 25 mA in the absence of any nutrient. No appreciable change occurred in viable cell count in the effluent with time.