Enhancement of wastewater nutrient removal at low carbon/nitrogen ratio using a submerged membrane electro-bioreactor

The objective of this research was to explore the feasibility of removing ammonium and nitrate in a single electro-bioreactor at low carbon concentration. For that purpose a submerged membrane electro-bioreactor was operated at three influent carbon/nitrogen ratios (3:1, 2:1 and 1:1). For each carbon/nitrogen ratio, a submerged membrane electro-bioreactor and a membrane bioreactor were operated at the same conditions for 60 days. Results showed that the submerged membrane electro-bioreactor successfully removed ammonium and nitrate at all carbon/nitrogen ratios over membrane bioreactor. At carbon/nitrogen ratio of 1:1, the submerged membrane electro-bioreactor exhibited 9%, 55% and 25% higher removal efficiency over membrane bioreactor for ammonium, nitrate and total nitrogen, respectively. At carbon/nitrogen ratio of 3:1, the submerged membrane electro-bioreactor exhibited 0.0%, 89% and 14% higher removal efficiency over membrane bioreactor for ammonium, nitrate and total nitrogen, respectively. Submerged membrane electro-bioreactor system showed its capacity to remove ammonium, nitrate and total nitrogen regardless of carbon/nitrogen ratio. Submerged membrane electro-bioreactor capacity to remove nitrogen components is feasible because the system can be electrically controlled to operate at alternative aerobic/anaerobic conditions. The efficiency of the submerged membrane electro-bioreactor to remove nitrogen components was found to enhance over time, even though carbon is at low concentration, as higher concentrations of anammox bacteria are built up in the system. Beside nitrogen removal, submerged membrane electro-bioreactor showed on average more than 90% removal of orthophosphate.