Simultaneous nitrification and denitrification by controlling current density and dissolved oxygen supply in a novel electrically-induced membrane bioreactor

Abstract

In this work, a simultaneous nitrification and denitrification (SND) process in a novel electrically-induced membrane bioreactor (eMBR) was established to treat nitrogen (N) and carbon wastewater. The impact of applied current density (CD) on the important operational parameters of the eMBR was also explored. Furthermore, the performance of denitrification and N-removal at various applied CDs (0–23 A/m2) were investigated. Results showed that high biological oxidation of NH4+−N and total nitrogen (TN) removals were attained at an intermittent CD of 12.5 A/m2 with a low aeration (<2.5 mg/L DO) provided by the eMBR system. The maximum NH4+−N and TN removal efficiencies of the eMBR were 98.71% and 83.75%, respectively. The average denitrification rate was enhanced by the adequate application of DC fields to the eMBR with an increase of NO3−−N removal efficiency from 8.3% to 90.5% and SND rate from 40.3% to 96.28%. It is possible that autotrophic and heterotrophic denitrification together contributed to the high performance of the eMBR process and the complete removal of the nitrate, thereby achieving average TN effluent concentrations of <5 mg/L. The eMBR also reached constant and substantial chemical oxygen demand (COD) removal efficiencies of 99.45%. Taken together, such technology presented in this work could potentially decrease energy demands and could lead to the further development of an energy self-sustained N-removal process. The eMBR could be used in a new WWTP design or for retrofitting existing treatment plants.