High nitrate removal by autohydrogenotrophic bacteria in a biofilm-electrode reactor

摘要

A biofilm-electrode reactor has been developed to effectively treat high nitrate-polluted wastewater. The novelty of this system is that the biological degradation of -N (electron acceptor) was enhanced by the generation of H-2 (electron donor) and direct immobilization of autohydrogenotrophic bacteria on the surface of the cathode. Nitrate degradation rate increased as current increased from 10 to 120mA. When current was increased above 120mA, the degradation rate was decreased. Meanwhile, nitrite accumulation decreased as current (below 120mA) increased. If current was increased further to higher than 120mA, nitrite was observed to accumulate again. Denitrification rate increased with initial nitrate loading below 350mg -NL-1. However, the denitrification was found to be inhibited at high nitrate loading (350-500mg -NL-1). Meanwhile, nitrite accumulation increased as nitrate loading increased and the highest accumulated nitrite level reached 16.07mg -NL-1 at nitrate loading of 500mg -NL-1. The reactor obtained optimum denitrification when C/N, temperature, and pH were 1.0, 25-30 degrees C, and 6.0-7.0, respectively.