A dicyclic-type electrode-based biofilm reactor for simultaneous nitrate and Cr(VI) reduction

A dicyclic-type electrode-based biofilm-electrode reactor (BER) was investigated for simultaneous removal of nitrate and Cr(VI). In the absence of Cr(VI), almost complete denitrification of 50 mg/L NO₃^--N was achieved at a very low C/N ratio of 0.8 with the optimal current of 50 mA. Cr(VI) was removed by biological reduction and co-precipitation when Cr(VI) was taken as the only electron acceptor, and the removal efficiencies of Cr(VI) were 99.8%. In the coexistent system of nitrate and Cr(VI), nitrate removal was the result of the cooperation of hydrogenotrophic denitrification and heterotrophic denitrification. The methanol and H₂ were also used as electron donors for biological reduction Cr(VI). The denitrification process was slightly inhibited by 1.00 mg/L Cr(VI) and 94.15% removal efficiency was achieved at current = 50 mA and HRT = 8 h. The present results show that the biofilm-electrode reactor is an effective way to simultaneous remove co-contaminants.