Comparison between a fixed bed hybrid membrane bioreactor and a conventional membrane bioreactor for municipal wastewater treatment: a pilot-scale study.

A hybrid membrane bioreactor (HMBR) was developed, by adding biofilm support media into a conventional membrane bioreactor (CMBR), and operated in parallel with a CMBR. Results showed that effluent quality was significantly better with the HMBR. The removal efficiencies of COD, BOD5, NH4(+)-N and TN with the HMBR were 84%, 98%, 97% and 75%, respectively, as compared to 80%, 96%, 93% and 38% with the CMBR. There were no differences in phosphorus removal. The membrane fouling rate in the HMBR was on average only 57% of that in the CMBR. The lower concentration of colloidal biopolymer clusters in the HMBR sludge, probably due to their retention by the biofilm, could be partially responsible for this difference. Filterability and settleability of the sludge were also better in the HMBR. Consequently, it is concluded that the addition of fixed support media for biofilm growth can improve the performance of CMBRs.