@article {27300,
	title = {Impact of AnMBR operating conditions on anaerobic digestion of waste activated sludge},
	journal = {Water Environment Research },
	year = {2020},
	abstract = {
	
		The impact of solids retention time (SRT) and hydraulic retention time (HRT) on anaerobic digestion of thickened waste activated sludge (TWAS) in a pilot-scale anaerobic membrane bioreactor (AnMBR) was compared with that achieved in conventional anaerobic digestions (CD). The AnMBR was able to successfully digest municipal TWAS at HRTs ranging from 7 to 15\&nbsp;days and SRTs ranging from 15 to 30\&nbsp;days. Increasing SRT in the AnMBR resulted in a significant improvement in COD and VS removal efficiency when compared against CD operating at the same HRT. The VS and COD destructions (35\%{\textendash}50\%) observed in the AnMBR were similar to those observed in CD operating at the same SRT but longer HRTs. Operation at elevated ratios of SRT/HRT resulted in the production of a thickened biosolid (2\%{\textendash}3\% TS). Specific methane production values for AnMBR operating at HRT-SRT ratios of 15{\textendash}30, 7{\textendash}30, and 7{\textendash}15 were 0.19, 0.19, and 0.14\&nbsp;m3\&nbsp;CH4/kg of COD fed, respectively, showing a 25\% increase in methane production with SRT. A model based upon describing hydrolysis of biodegradable solids using first-order kinetics was able to describe VS destruction as a function of SRT.
	

	
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		Practitioner points
	

	
		
			The AnMBR process was able to successfully digest waste activated sludge at a shorter seven-day HRTs
		
		
			Operation at elevated ratios of SRT/HRT resulted in enhanced biogas and thickened biosolid (2\%{\textendash}3\% TS) production requiring reduced downstream processing
		
		
			The AnMBR process produces a particle-free permeate that might be suitable for side stream nutrient recovery
		
		
			A model developed by considering hydrolysis as a limiting process can be used to determine design SRTs.
		
	

	
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},
	author = {Wayne Parker and Martha Dagnew}
}
