The performance of a submerged membrane bioreactor (SMBR) has been investigated for abattoir wastewater (AW) treatment. The chemical oxygen demand (COD) of permeate has not exceeded 25 mg L(-1) providing an average COD removal of 98%. Microbiological analysis showed that the SMBR has allowed a complete removal of fecal coliforms, Listeria and Salmonella. A significant reduction in the excess biomass production was also observed. In fact, the yield of biomass production (Yobs) ranged between 0 and 0.106 g suspended solids/g COD removed. The study of the dynamic of bacterial communities using the single strand conformation polymorphism (SSCP) method showed a significant change in the population structure and revealed a correlation between the sludge production yield and the bacterial communities. (C) 2011 Elsevier Ltd. All rights reserved.