Highly efficient carbon assimilation and nitrogen/phosphorus removal supported by photosynthetic O2 in algal-bacterial aerobic granular sludge system

Reductions in CO2 emission and energy consumption are crucial for sustainable wastewater treatment plant (WWTP) management. In this study, the newly developed algal-bacterial aerobic granular sludge (AGS) was adopted to fix carbon (C) with highly efficient nitrogen (N) and phosphorus (P) removal under no mechanical aeration. In this algal-bacterial AGS system, the photosynthetic O2 production by phototrophic organisms maintained dissolved oxygen (DO) level at 3-4 mg/L in bulk liquor via automatically switching on/off LED lights, which further reduced 10-30% of light energy consumption. Results showed that 52 % of input dissolved total carbon (DTC) was assimilated in the biomass; At the same time, the produced O2 could simultaneously support aerobic nitrification and P uptake in the system where the coexisting phototrophs served as a C fixer and O2 supplier.