Integrating solar photovoltaic capacitor into algal-bacterial photo-bioelectrochemical system towards all-weather synchronous enhanced antibiotic and nitrogen removal from wastewater

Algal-bacterial photo-bioelectrochemical system (ABPBS) operated with daily light/dark cycle provides a novel approach for sustainable treatment of wastewater through the uses of solar energy and bioenergy . However, it can not be effectively driven when the photosynthetic oxygen supply by algae at the cathode stops at night. In this study, a solar photovoltaic capacitor discharging was integrated into the ABPBS to achieve all-weather synchronous enhanced antibiotic and nitrogen removal from wastewater. The results showed that 3.3 F, 10 F and 100 F capacitor discharge increased the degradation rate of florfenicol (FLO) by 44%, 89%, and 582% at the anode, the removal rate of ammonia nitrogen by 20.4%, 39.8%, and 55.6%, the accumulated nitrate was decreased by 70.0%, 86.5%, and 93.3%, and the accumulated nitrite was decreased by 48.6%, 45.7%, and 87.1% at the biocathode, respectively. There was a significant positive correlation between the capacity of the capacitor and its ability to promote FLO degradation and nitrogen removal. The capacitor discharge promoted the photosynthetic oxygen release and biocatalytic oxygen reduction , and stimulated the growth of functional bacteria capable of degrading complex organics through extracellular electron transfer in the anode and diverse nitrogen removal bacteria in the cathode, but there were structural differences of functional bacteria groups induced by the different capacities of capacitor discharges.