title: Sludge cycling between aerobic, anoxic and anaerobic regimes to reduce sludge production during wastewater treatment: performance, mechanisms, and implications.
abstract: Alternate cycling of sludge in aerobic, anoxic, and anaerobic regimes is a promising strategy that can reduce the sludge yield of conventional activated sludge (CAS) by up to 50% with potentially lower capital and operating cost than physical- and/or chemical-based sludge minimisation techniques. The mechanisms responsible for reducing sludge yield include alterations to cellular metabolism and feeding behaviour (metabolic uncoupling, feasting/fasting, and endogenous decay), biological floc destruction, and predation on bacteria by higher organisms. Though discrepancies across various studies are recognisable, it is apparent that sludge retention time, oxygen-reduction potential of the anaerobic tank, temperature, sludge return ratio and loading mode are relevant to sludge minimisation by sludge cycling approaches. The impact of sludge minimisation on CAS operation (e.g., organics and nutrient removal efficiency and sludge settleability) is highlighted, and key areas requiring further research are also identified.
authors: Strategic Water Infrastructure Laboratory, School of Civil, Mining and Environmental Engineering, University of Wollongong, Wollongong, NSW 2522, Australia.
authors: Galilee U
authors: GU
authors: Semblante
authors: Strategic Water Infrastructure Laboratory, School of Civil, Mining and Environmental Engineering, University of Wollongong, Wollongong, NSW 2522, Australia. Electronic address: faisal@uow.edu.au.
authors: Faisal I
authors: FI
authors: Hai
authors: Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, Broadway, NSW 2007, Australia.
authors: Huu H
authors: HH
authors: Ngo
authors: Centre for Technology in Water and Wastewater, School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, Broadway, NSW 2007, Australia.
authors: Wenshan
authors: W
authors: Guo
authors: Department of Bioenvironmental Engineering and R&D Centre for Membrane Technology, Chung Yuan Christian University, Chungli 320, Taiwan.
authors: Sheng-Jie
authors: SJ
authors: You
authors: Strategic Water Infrastructure Laboratory, School of Chemistry, University of Wollongong, Wollongong, NSW 2522, Australia.
authors: William E
authors: WE
authors: Price
authors: Strategic Water Infrastructure Laboratory, School of Civil, Mining and Environmental Engineering, University of Wollongong, Wollongong, NSW 2522, Australia.
authors: Long D
authors: LD
authors: Nghiem
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D010084:Oxidation-Reduction; D012722:Sewage / Q000032:analysis / Q000382:microbiology*; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D012722:Sewage; D062065:Wastewater
keywords: Bacterial predation; Endogenous decay; Metabolic uncoupling; Oxic-settling-anaerobic; Sludge minimisation