Effects of pH on Antibiotic Denitrification and Biodegradation of Sulfamethoxazole Removal from Simulated Municipal Wastewater by a Novel 3D-BER System

Abstract

A three-dimensional bioelectrochemical reactor (3D-BER) system combining heterotrophic and autotrophic denitrification processes was developed, which possesses the effects of pH on nitrate or nitrite removal and simultaneously elimination of antibiotic sulfamethoxazole (SMX) from simulated municipal wastewater. The experimental results demonstrated that the variation of microbial communities was examined with electric current from 0 to 90 mA at pH 6.50±0.12 to 7.9±0.04. When the current increased from 0 to 90 mA, the nitrate removal efficiency increased from 59.05% to 99.21%, and SMX removal efficiency of 43.9%–93.9% was achieved. The optimum pH of this reactor was 7.0±0.20 to 7.50±0.31, and a lower or higher pH condition may effect autotrophic and heterotrophic denitrification processes. Simultaneously, the denitrification mechanism in this system was analyzed through pH variation in the effluent. The CO2 produced from the anode acted as a good pH buffer, automatically controlling pH in the reaction zone. A low current intensity does not effect the degradation by-products but increases the SMX removal efficacy. Bacterial community analysis revealed substantial changes in microbial communities at the phylum, class, and genus levels after SMX acclimatization. Thauera, a well-known aromatic-degrading bacteria, was the most dominant genus present in acclimatized conditions at 60 mA. In summary, this study shows that high currents changed the microbial structure, and the acclimatized sludge can play a vital role in the biodegradation of SMX, and removal of NO3−─ N from simulated municipal wastewater by a novel 3D-BER.