Comparative evaluation of activated sludge and aerobic granular sludge for biological treatment of real domestic wastewater with oxytetracycline dosing

Aerobic granular sludge technology is an emerging choice for effective and sustainable wastewater treatment. The aim of this study was to determine the effect of antibiotics such as oxytetracycline on biological nutrient removal pathways in aerobic granular sludge and activated sludge sequencing batch reactors treating real domestic wastewater. The aerobic granular sludge and activated sludge reactors were operated in parallel for evaluating treatment of domestic wastewater and its response to 50-300 mu g/L oxytetracycline dosing. The aerobic granular sludge and activated sludge sequencing batch reactors were dominated by compact granules (sludge volume index (SVI): 60 mL/g) and flocs (SVI: >100 mL/g), respectively, during treatment of real wastewater. Aerobic granular sludge has significantly outperformed activated sludge in achieving high phosphate removal of similar to 99% against just 57%. This was corroborated with higher abundance of polyphosphate accumulating organisms and enhanced bio-P removal in the aerobic granular sludge system. In contrast, phosphate removal was achieved through normal bio-P removal in the activated sludge reactor. Oxytetracycline removals were distinct at 90% and 23%, respectively, in the aerobic granular sludge and activated sludge systems. High total nitrogen and phosphate removals of 97% and 96%, respectively, were maintained in the aerobic granular sludge system even during OTC dosing. In contrast, the total nitrogen and phosphate removals have dropped to 78% and 16%, respectively, in the activated sludge system due to oxytetracycline stress. Efficient biological nutrient removal and process stability along with environmental sustainability are critical for choosing aerobic granular sludge technology in wastewater treatment plants.