Bioelectricity production and shortcut nitrogen removal by microalgal-bacterial consortia using membrane photosynthetic microbial fuel cell

Abstract

Membrane photosynthetic microbial fuel cell (MPMFC) utilizes O2, NO3− and NO2− as cathodic electron acceptors, enabling simultaneous treatment of nitrogen, CO2 and organic carbon in the cathode compartment. In this work, development of a novel cathodic process with in situ nitritation via microalgal photosynthesis during the light period is reported for achieving shortcut nitrogen removal (SNR) from ammonium-rich wastewater. Moreover, a tubular low-cost ceramic membrane was used to separate and recycle the microalgal-bacterial biomass to the cathode compartment during the continuous operation. The influence of NH4+ concentration and ratio of chemical oxygen demand to total nitrogen on the MPMFC performance was examined. Denitritation under dark and anoxic conditions occurred due to denitrifying bacteria (DNB) subsequent to nitritation under light and aerobic conditions by ammonia-oxidizing bacteria (AOB) in the consortia. Final concentrations of NH4+ and NO2− in the effluent of 0.10 mg NH4+-L−1 and 0.02 mg NO2−-L−1, respectively, were obtained using MPMFC which resulted in a nitrogen removal efficiency of 99 ± 0.5%. The maximum electricity production achieved using the MPMFC was 56 ± 0.1 mA. This study demonstrated that combining microalgal photosynthesis, nitritation and denitritation in the cathode compartment of MPMFC is advantageous for avoiding the cost due to external aeration and organic carbon source necessary for ammonium removal as well as utilization of NO2− or NO3− as an electron acceptor.