Efficient nitrogen removal by simultaneous photoelectrocatalytic oxidation and electrochemically active biofilm denitrification.

A novel nitrogen removal strategy, the combined photoelectrocatalytic oxidation and autotrophic biofilm denitrification, was developed to achieve simultaneous NH 4 + -N oxidation and NO 3 − -N reduction in a single reactor. AgI/TiO 2 -NTs and autotrophic denitrifying biofilm were used as anode and cathode, respectively. NH 4 + -N oxidation efficiency was enhanced by 3 times after the introduction of visible light. Moreover, NO 3 − -N and NO 2 − -N generated in the process of NH 4 + -N oxidation could be further removed by biocathode. Applied voltage and pH have significant effects on nitrogen removal. The NO 3 − -N and NH 4 + -N removal efficiencies gradually increased from 27.2% to 74.3% and 60.0% to 83.1%, respectively, when the voltage increased from 1.0 V to 3.0 V. Neutral or slightly alkaline condition was favorable on account of the autotrophic denitrifying biofilm. The optimum TN (TN NH 4 + -N + NO 3 − -N + NO 2 − -N) removal efficiency was up to 89.6% at pH 8 with 3.0 V voltage. [ABSTRACT FROM AUTHOR]