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Membrane Water Treatment
  Volume 6, Number 6, November 2015 , pages 501-512

Relation between sludge properties and filterability in MBR: Under infinite SRT
Haifeng Zhang, Bing Wang, Haihuan Yu, Lanhe Zhang and Lianfa Song

    A laboratory-scale submerged membrane bioreactor (MBR) was continuously operated for 100 d at an infinite sludge retention time (SRT) with the aim of identifying possible relation between the filterability of mixed liquor and sludge properties, such as extracellular polymeric substances (EPS), soluble microbial products (SMP), viscosity of mixed liquor, zeta potential of flocs and particle size distributions (PSD). Research results confirmed that MBR can operate with a complete sludge retention ensuring good treatment performances for COD and NH3-N. However, the long term operation (about 40 d) of MBR with no sludge discharge had a negative influence on sludge filterability, and an increase in membrane fouling rates with the time was observed. There as a strong correlation between the sludge filterability and the fouling rate. Among the different sludge properties parameters, the concentration SMP and EPS had a more closely correlation with the sludge filterability. The concentrations of SMP, especially SMP with MW above 10 kDa, had a strong direct correlation to the filterability of mixed sludge. The protein fractions in EPS were biodegradable and available for microorganism metabolism after about 60 days, and the carbohydrates in EPS had a significantly negative effect on sludge filterability in MBR at an infinite SRT.
Key Words
    membrane bioreactor (MBR); sludge retention time (SRT); activated sludge; soluble microbial products (SMP); extracellular polymeric substances (EPS)
(1) Haifeng Zhang, Bing Wang, Haihuan Yu, Lanhe Zhang:
School of Chemistry Engineering, Northeast Dianli University, Jilin 132012, Jilin, P.R. China;
(2) Lianfa Song:
Department of Civil, Environmental, and Construction Engineering, Texas Tech University, Boston, Lubbock, TX 79409-1023, USA.

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