Algal-bacterial aerobic granule based continuous-flow reactor with effluent recirculation instead of air bubbling: Stability and energy consumption analysis

Algal-bacterial aerobic granular sludge (AGS) based continuous-flow reactors (CFRs) were examined with effluent recirculation instead of air bubbling usually used for AGS cultivation and application. Under effluent recirculation, algal-bacterial AGS exhibited better overall performance and stability over bacterial AGS, achieving averagely dissolved organic carbon (DOC), total nitrogen (TN) and total phosphorus (TP) removals of 40, 60, and 15 in comparison to 32, 35, and 10 by the bacterial AGS, respectively. More importantly, after being switched from effluent recirculation to intermittent aeration, the algal-bacterial AGS could quickly adapt to the change in operation conditions, clearly indicated by the recovered removals of DOC from averagely 40 to 100, TN from 60 to 98, and TP from 15 to 64 along with the improved sludge settleability and stability after 24 day operation. Energy consumption analysis also suggested that algal-bacterial AGS-based CFR systems may have more potentials for energy saving and stable performance under proper operation strategies. © 2019 Elsevier Ltd