Effect of feeding strategy and organic loading rate on the formation and stability of aerobic granular sludge

Abstract

Aerobic granular sludge (AGS) has emerged as a novel biotechnology for the effective treatment of both municipal and industrial wastewater. Two of the practical parameters that affect aerobic granule (AG) formation and stability are the feeding strategy and organic loading rate (OLR). In this paper, the impact of feeding strategy and OLR on AG formation and stability are reviewed. The feeding strategy that appears suitable for stable AG formation using all substrates is slow anaerobic feeding. Despite the long duration for AG cultivation at low OLR, compact and stable AG are formed. High OLRs result in fast AG formation but the developed granules are unstable due to the large size resulting from excessive microbial growth. The recommended strategy for stable AG formation with enhanced treatment performance is stressed (high) OLR for fast granule formation followed by reduced OLR to ensure stability. This can be combined with slow anaerobic feeding to select for slow-growing microorganisms and nutrients removers such as phosphate-accumulating organisms (PAOs). Further research is recommended to explore AG formation at high OLR using the slow anaerobic feeding strategy for long-term stability.