This can be explained by the fact that the total bio-sludge mass of the MSBR system was higher than that of the SBR system due to the increased amount of biofilm mass on the media of the MSBR system (Wanneret al., 1998; Watanabe et al., 1994), and as a result
the MSBR showed a higher removal efficiency than the SBR system (Gebara, 1999).