Correlating TMP increases with microbial characteristics in the bio-cake on the membrane surface in a membrane bioreactor

Byung Kook Hwang, Woo Nyoung Lee, Kyung Min Yeon, Pyung Kyu Park, Chung Hak Lee, In Soung Chang, Anja Drews, Matthias Kraume

Research output: Contribution to journalArticlepeer-review

164 Citations (Scopus)


Subcritical flux operation is widely practiced in membrane bioreactors (MBRs) to avoid severe membrane fouling and, thus, to maintain sustainable permeability. Filtration at a constant subcritical flux, however, usually leads to a two-stage increase in the transmembrane pressure (TMP): initially slowly, then abruptly. We have investigated the mechanism of this two-stage TMP increase through analyses of the structure and microbial characteristics of the bio-cake formed on the membrane. The MBR was operated under various subcritical and supercritical flux conditions. Under subcritical conditions, we observed the typical two-stage TMP increase. When a constant flux augmented and reached the supercritical conditions, however, the dual TMP change gradually transformed into a steeper, one-stage TMP increase. The second stage TMP increase under the subcritical flux was closely related to the sudden increase in the concentration of extra-cellular polymeric substances (EPSs) at the bottom layer of the bio-cake; we attribute the one-stage TMP increase under the supercritical conditions to the accumulation of microbial flocs and the reduced porosity of the bio-cake under compression. We explain the variation of the EPS concentration in the bio-cake in terms of the spatial and temporal changes of the live-to-dead ratio along the depth of the bio-cake.

Original languageEnglish
Pages (from-to)3963-3968
Number of pages6
JournalEnvironmental Science and Technology
Issue number11
Publication statusPublished - 2008 Jun 1

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry


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