Performance of a biological aerated filter coupled with three-dimensional biofilm electrode reactor for coking wastewater treatment

Ammonium nitrogen (NH4+-N) is the main component of nitrogenous pollutants in coking wastewater and is associated with high biological toxicity. In this work, a coupled system consisting of a biological aerated filter (BAF) and a three-dimensional biofilm electrode reactor (3D-BER) was developed to treat coking wastewater. The results demonstrate that the removal efficiencies of total nitrogen (TN) and chemical oxygen demand (COD) in the BAF/3D-BER coupled system are 96.64 % and 54.38 % at 10 mA, significantly higher than those of BAF/ 3D-BER at 0 mA (2.20 % and 49.45 %) and 3D-BER at 10 mA (75.19 % and 21.51 %). The BAF is responsible for converting NH4+-N to nitrite nitrogen (NO2--N) and reducing wastewater toxicity through microbial nitrification. The 3D-BER contributes predominantly to the removal of residual NO2--N through bio-electrochemical denitrification. Microbial community analysis reveals that Thauera, Hydrogenophaga, Gemmoactor, and Nitrospira are enriched in the BAF/3D-BER at 10 mA. The proposed BAF/3D-BER system offers a novel solution for coking wastewater treatment.