Validation of a full-scale membrane bioreactor and the impact of membrane cleaning on the removal of microbial indicators

The removal of microbial indicators through a full-scale membrane bioreactor (MBR) was characterised. The overall log reduction of Escherichia coli and total coliforms were in the range of 5.0-5.9 log10 units, while the reduction of clostridia was marginally less at 4.9 log10 units. Removal of bacteriophage was in excess of 4.6 log10 units. The impact of membrane cleaning on the elimination of microbial indicators was also assessed since this had been identified by pilot-scale studies as a potential hazardous event. Membrane cleaning temporarily reduced the log removal values of E. coli and total coliforms each by 1 log10 unit, but did not affect the removal of bacteriophage or clostridia. Very little research has previously examined the consequences of hazardous events on the performance of full-scale MBRs, and thus the findings presented here will facilitate improvements for the risk assessment and management of MBRs used in water recycling schemes.