A review of the state of development of aerobic granular sludge technology over the last 20 years: Full-scale applications and resource recovery

Abstract

The aerobic granular sludge (AGS) biotechnology has gained increasing interest during the past two decades as a potential replacement of the conventional activated sludge (CAS) process, due to its ability to improve the overall wastewater treatment efficiency and the strong potential to attain sustainable development with this biotechnology. This paper provides an overview of the AGS biotechnology, focusing on its global application, sludge digestion, and resource recovery from waste AGS. The main value-added products obtainable from AGS include phosphorus, alginate-like exopolymers (ALE), biodegradable plastics, and biogas. AGS is becoming increasingly common worldwide, where the number of full-scale installations has doubled during the past two years to reach 88 by mid-2021. Yet, its application has gained interest mainly in Europe, specifically in the Netherlands, which is home to the first AGS plants by Nereda®. In the Americas, its application is limited to the United States and Brazil. AGS has not been utilized in Canada despite its numerous benefits. The feasibility of AGS biotechnology requires a better understanding of the cultivation of compact and stable granules which is essential to an efficient wastewater treatment plant (WWTP) operation. Research should focus on finding innovative reactor configurations to promote fast granulation in continuous flow regime and scaling-up the recovery technologies of value-added resources from AGS surplus sludge in order to realize the AGS application in full-scale mainstream WWTPs.