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Specific Resistance to Filtration of Biomass from Membrane Bioreactor Reactor and Activated Sludge: Effects of Exocellular Polymeric Substances and Dispersed Microorganisms
Author(s) -
Ng How Y.,
Hermanowicz Slawomir W.
Publication year - 2005
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143005x41753
Subject(s) - volatile suspended solids , mixed liquor suspended solids , chemical oxygen demand , chemistry , activated sludge , filtration (mathematics) , microorganism , suspended solids , biomass (ecology) , bioreactor , membrane bioreactor , wastewater , pulp and paper industry , chromatography , environmental engineering , bacteria , environmental science , biology , organic chemistry , ecology , statistics , mathematics , engineering , genetics
This study investigates the effect of dispersed microorganisms and exocellular polymeric substances on biomass dewaterability. Specific resistance to filtration (SRF) was measured for biomass from a membrane bioreactor and a completely mixed activated sludge system. Both laboratory‐scale reactors were fed with synthetic wastewater and operated at a high food‐to‐microorganism ratio (F/M) (1 to 11 kilograms chemical oxygen demand per kilogram mixed liquor volatile suspended solids per day [kgCOD/(kg MLVSS·d)]) and short solids retention times (0.25 to 5 d). The SRF values were affected by strong interactions of three parameters: (1) the mixed liquor suspended solids concentration, (2) the amount of dispersed microorganisms, and (3) the exocellular polymeric substances (EPS) concentration. At F/M smaller than 2 kg COD/(kg MLSS·d) and mixed liquor suspended solids (MLSS) concentration higher than 2000 mg/L, increasing amount of dispersed microorganisms in the biomass yielded higher SRF values. However, at high F/M (>5 kg COD/kg MLSS·d) and low MLSS concentrations (<600 mg/L), lower EPS concentrations resulted in slightly smaller SRF values, even though the amount of dispersed microorganisms in the biomass was much higher. Thus, at low MLSS concentrations, EPS concentrations rather than the amount of dispersed microorganisms tend to control SRF.