Ionic response of algal-bacterial granular sludge system during biological phosphorus removal from wastewater

Biological phosphorus removal (BPR) from wastewater can be generally realized through alternative non-aeration and aeration operation to create anaerobic and aerobic conditions respectively for P release and uptake/accumulation by polyphosphate accumulating organisms (PAOs), with P removal finally achieved by controlled discharge of P-rich sludge. In this study, the response of algal-bacterial aerobic granular sludge (AB-AGS) during BPR to main ions including Ac- (acetate), Cl-, SO42-, NH4+, K+, Mg2+, Ca2+ and Na+ in wastewater was investigated with conventional bacterial AGS (B-AGS) as control and acetate as the sole carbon source. Results show that BPR process mainly involved the changes of Ac-, K+, Mg2+, and Ca2+ rather than Cl-, SO42-, NH4+ and Na+. The mole ratio of Delta P/Delta Ac kept almost unchanged during the non-aeration (P release) phase in both B-AGS and AB-AGS systems (Delta PB-AGS/Delta AcB-AGS > Delta PAB-AGS/Delta AcAB-AGS), and it was negatively influenced by the light in AB-AGS systems, in which 62% of acetate was not utilized for P release at the high illuminance of 81 k lux. During the entire non-aeration/aeration period, both Delta K/Delta P and Delta Mg/Delta P remained constant, while Delta KAB-AGS/Delta PAB-AGS > Delta KB-AGS/Delta PB-AGS and Delta MgAB-AGS/Delta PAB-AGS approximate to Delta MgB-AGS/Delta PB-AGS. The presence of algae seemed not beneficial for PAOs to remove P, while more K+ and P uptake by algae in AB-AGS suggest its great potential for manufacturing biofertilizer. (C) 2020 Elsevier Ltd. All rights reserved.