The operation characters of biocathode microbial electrochemical system with microbial separator for domestic wastewater treatment: Power generation, long-term stability, and organic removal

Biocathode microbial electrochemical system (MES) is considered as a sustainable and eco-friendly technology for wastewater treatment. With domestic wastewater, the anode/cathode matching ratios of biocathode MES are optimized to match the anodic respiration and cathodic oxygen reduction rates. One anode module matched with two identical cathode modules obtains the highest power density. The long-term stability of MES is examined for one year with optimized architecture. Stable power generation and organic removal performance are achieved. A low effluent chemical oxygen demand (COD) is obtained at 36 ± 14 mg L⁻¹ with a COD removal of 89 ± 4%. To meet the discharge standard in China (COD<50 mg L⁻¹), the required hydraulic retention time (HRT) shows a linear relationship with influent COD concentration, and the COD removal rates fluctuant from 0.80 ± 0.05 to 1.13 ± 0.04 kg m⁻³ day⁻¹. In the view of stable electrode function and current generation, the influent COD range of 200–800 mg L⁻¹ is the stable range for biocathode MES. The bio-diversities of electrode and microbial separators are changed with influent COD. High influent COD reduces the relative abundance of exoelectrogens on the anode and introduces heterotrophic bacteria on the cathode.