Long-term aerobic granular sludge stability through anaerobic slow feeding, fixed feast-famine period ratio, and fixed SRT

Publication date: Available online 10 January 2020Source: Journal of Environmental Chemical EngineeringAuthor(s): Oliver Terna Iorhemen, Mohamed Sherif Zaghloul, Rania Ahmed Hamza, Joo Hwa TayAbstractThe deterioration of the structural integrity of aerobic granular sludge (AGS) in long-term operation is a major limitation of the AGS biotechnology. The present study explored AGS long-term stability at semi-pilot-scale using the combined strategy of long anaerobic slow feeding, 1:3 fixed ratio of feast-famine period within each cycle, and selective discharge of mature granules. Biomass characteristics, extracellular polymeric substances (EPS), dissolved oxygen and removal profiles were monitored. Results indicate that the 1:3 ratio of feast-famine period controlled the EPS content at a suitable level to allow for granular sludge stability. The system exhibited high proteins (PN) content of EPS, resulting in high PN/polysaccharides (PS) ratios: 0.01 - 19 and 2.05 - 13.15 for loosely-bound EPS (LB-EPS) and tightly-bound EPS (TB-EPS), respectively. Selective withdrawal of mature granules from the bottom of the reactor resulted in a good mix of new and old granules in the system. The strategy allowed for system stability as the reactor was operated for over 240 d without any granule disintegration. High removals of COD (98.3 ± 0.8%), NH3-N (98±5%), and TN (89±6%) were achieved. Phosphate-P removal was in the range 50 - 100%. EPS producers (Thauera, Flavobacterium and Meganema) a...
Source: Journal of Environmental Chemical Engineering - Category: Chemistry Source Type: research