Nitrogen removal from low-C/N-ratio wastewater using a three-dimensional bioelectrical reactor

Abstract

A three-dimensional bioelectrical reactor (3D-BER) with a treatment capacity of 1 m3/d was constructed for the high-level denitrification of wastewater treatment plant effluent. The results indicated that with activated carbon and light ceramsite (volume ratio was 1:1) as the particle electrodes and applied current of 5 A, the removal efficiency of NO3−-N in the 3D-BER was 78.99 ± 4.10 %, the selectivity of nitrogen was 83.48 ± 4.20 %, and the energy consumption was 1.20 ± 0.13 kWh/m3. Nitrate and sulfate concentrations decreased rapidly based on the samples withdrawn at a reactor height of 47.5 cm, and they both decreased to their lowest values at a reactor height of 75 cm, indicating that nitrate reduction took place preferentially in the 3D-BER. Proteobacteria and Campilobacterota were selectively enriched in the 3D-BER compared with the inoculated sludge, and the microbial community composition of 3D-BER at 75 cm was significantly different from that at other heights. Sulfurimonas (20.96 %), Sulfuricurvum (5.32 %), Thauera (4.40 %) and Denitratisoma (3.87 %) were the dominant bacteria at 75 cm in the 3D-BER, and the relative abundance of bacteria with denitrifying functions was the highest at 75 cm. Fieldwork demonstrated the feasibility and sustainability of using a 3D-BER for nitrogen removal.