title: Activated sludge mass reduction and biodegradability of the endogenous residues by digestion under different aerobic to anaerobic conditions: Comparison and modeling.
abstract: This study was performed to identify suitable conditions for the in-situ reduction of excess sludge production by intercalated digesters in recycle-activated sludge (RAS) flow. The objective was to compare and model biological sludge mass reduction and the biodegradation of endogenous residues (XP) by digestion under hypoxic, aerobic, anaerobic, and five intermittent-aeration conditions. A mathematical model based on the heterotrophic endogenous decay constant (bH) and including the biodegradation of XP was used to fit the long-term data from the digesters to identify and estimate the parameters. Both the bH constant (0.02-0.05 d(-1)) and the endogenous residue biodegradation constant (bP, 0.001-0.004 d(-1)) were determined across the different mediums. The digesters with intermittent aeration cycles of 12 h-12 h and 5 min-3 h (ON/OFF) were the fastest, compared to the aerobic reactor. The study provides a basis for rating RAS-digester volumes to avoid the accumulation of XP in aeration tanks.
authors.affiliation: Centro Interamericano de Recursos del Agua (CIRA), Universidad Autónoma del Estado de México (UAEM), Apdo postal 367, Toluca C.P. 50091, Mexico.
authors.forename: C G
authors.initials: CG
authors.lastname: Martínez-García
authors.affiliation: Centro Interamericano de Recursos del Agua (CIRA), Universidad Autónoma del Estado de México (UAEM), Apdo postal 367, Toluca C.P. 50091, Mexico. Electronic address: c-fa-ll@hotmail.com.
authors.forename: C
authors.initials: C
authors.lastname: Fall
authors.affiliation: Instituto Nacional de Investigaciones Nucleares (ININ), México, Departamento de Química, La Marquesa Ocoyoacac, Mexico.
authors.forename: M T
authors.initials: MT
authors.lastname: Olguín
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D019149:Bioreactors; D008954:Models, Biological; D059027:Recycling; D012722:Sewage; D018505:Waste Management / Q000379:methods*
chemical_list: D012722:Sewage
keywords: Digestion; Endogenous residues; Intermittent aeration; Modeling; Sludge minimization