Influence of solids retention time on membrane fouling: characterization of extracellular polymeric substances and soluble microbial products

Abstract

The objective of this study was to investigate the influence of solids retention time (SRT) on membrane fouling and the characteristics of biomacromolecules. Four identical laboratory-scale membrane bioreactors (MBRs) were operated with SRTs for 10, 20, 40 and 80 days. The results indicated that membrane fouling occurred faster and more readily under short SRTs. Fouling resistance was the primary source of filtration resistance. The modified fouling index (MFI) results suggested that the more ready fouling at short SRTs could be attributed to higher concentrations of soluble microbial products (SMP). Fourier transform infrared (FTIR) spectra indicated that the SRT had a weak influence on the functional groups of the total extracellular polymeric substances (TEPS) and SMP. However, the MBR under a short SRT had more low-molecular-weight (MW) compounds (<1 kDa) and fewer high-MW compounds (>100 kDa). Aromatic protein and tryptophan protein-like substances were the dominant groups in the TEPS and SMP, respectively.

Keywords:

• membrane bioreactor
• extracellular polymeric substances
• soluble microbial products
• membrane fouling
• solids retention time

Conflict of interest disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental material

The supplemental material for this paper is available online at http://dx.doi.org/10.1080/08927014.2015.1020303.

Additional information

Funding

This study was supported by the Foundation of the State Environmental Protection Key Laboratory of Microorganism Application and Risk Control [SMARC. 2013D005]; the National Natural Science Foundation of China [No. 51108437]; and the Special Fund for Basic Scientific Research Business of Central Public Research Institutes [2013YSKY11].