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| Assessment of biomass characteristics and membrane permeability in a membrane bioreactor under thickening operation |
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Abstract A pilot-scale aerobic membrane bioreactor (MBR) process was operated to treat municipal wastewater regarding on the influences of biomass characteristics on membrane permeability as well as the membrane permeability recovery. Sucrose solution was added to maintain system operation of a constant food to microorganisms (F/M) ratio at 0.13 and a series of physicochemical and biochemical parameters of activated sludge were also measured throughout the whole trial, with correlations between biomass properties and membrane permeability as well as the membrane permeability recovery were further assessed by using Statistical Product and Service Solutions (SPSS) analyses. Results showed the mixed liquor suspended solids (MLSS) concentration exerted the greatest influence on membrane permeability (rp=-0.958, P=0.000); soluble microbial products (SMP) concentration, soluble chemical oxygen demand (sCOD) concentration and particle size diameter (PSD) had similar weaker effects on membrane permeability (|rp|=0.82~0.85). Whereas the sludge settleability, and filamentous index (FI) had no evident influences on membrane permeability. The accumulated clogged solids (ACS) in membrane channels and absolute membrane permeability recovery increased with the increasing MLSS concentrations, implying that the MLSS concentration had direct effects on membrane clogging propensity and further proved that membrane clogging being another important factor affecting the membrane permeability except for membrane fouling. The off-line declogging combined with enhanced chemically backflushing (CEB) could ensure the sustainable membrane permeability recovery under the condition of low-flux [5~6L/(m2·h)] operation at high MLSS concentrations.
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Received: 28 December 2014
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