Activated sludge mass reduction and biodegradability of the endogenous residues by digestion under different aerobic to anaerobic conditions: Comparison and modeling

• Published in: Bioresource technology Vol. 203; pp. 32 - 41
• Main Authors: Martínez-García, C.G., Fall, C., Olguín, M.T.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.03.2016
• Subjects: Aerobiosis; Anaerobiosis; Biodegradation, Environmental; Bioreactors; Digestion; Endogenous residues; Intermittent aeration; Modeling; Models, Biological; Recycling; Sewage; Sludge minimization; Waste Management - methods; Intermittent aeration; Sludge minimization; Digestion; Endogenous residues; Modeling
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2015.12.015

•Modeling and comparing digestion rates in seven different aeration conditions.•A model-sludge with only 2 fractions (the heterotrophs and its residues) was used.•The endogenous residues biodegradation constant was estimated (0.001–0.004d−1).•Sludge reduction was faster in the 12 h–12 h (ON/OFF) intermittently aerated digester.•Nitrif-denitrification activity and acid pH could be clues of the best performances. 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 (0.02–0.05d−1) and the endogenous residue biodegradation constant (bP, 0.001–0.004d−1) were determined across the different mediums. The digesters with intermittent aeration cycles of 12h–12h and 5min–3h (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.