Electrochemical study of enhanced nitrate removal in wastewater treatment using biofilm electrode.

Bioelectrochemical enhanced nitrate removal in wastewater with high total nitrogen and low organic carbon was electrochemically investigated focusing on the relationship between biochemical and electrochemical nitrogen cycles. Under optimized external voltage of -0.6 V, apparent nitrate removal rate of bioelectrochemical denitrification was 76% higher than normal biofilm denitrification. And with the introduction of biofilm on the electrode, new reduction peak of NO, much larger current density, and 0.4 V positively shift of on-set potential of nitrate reduction reaction were observed, suggesting a synergy of electrochemical reaction and biological reaction through enhanced electrochemical reduction of intermediate products from biological process. Oxygen reduction reaction could not be avoided during nitrogen electrochemical reduction reaction since their similar reduction potential. But it led to decrease of oxygen concentration and therefore contribute to biological denitrification. Bacteria community tests also supported a dominant bacteria which could denitrify and use external electron.