Several studies have focused on the influences of sludge
properties on membrane fouling and the foulant compositions
of the cake layer in OMBRs. Zhang et al. (2012a) investigated
the impacts of different sludge types on the FO
membrane fouling in OMBRs and found that the solute and
bound polysaccharides had negative relationships with the
flux decline rate while the bound and solute proteins had
positive impacts. With regard to the characterization of the
membrane foulants, Lay et al. (2011) reported that the extracellular
polymeric substances (EPS) with small numbers of
scattered bacterial cells were found in a thin gel-like secondary
layer on the FO membrane surface, but no mature biofilm
was formed. Subsequently, Qiu and Ting (2014) further
demonstrated that small sludge floc/particles and EPS (in
particular, proteins) were enriched in the FO membrane
fouling layer according to the analyses of the membrane
foulants. Meanwhile, the FO membrane-associated biofilms
were characterized by confocal laser scanning microscopy
(CLSM) and rRNA gene-tagged pyro-sequencing (Zhang et al.,
2014b). Based on these results on the characterization of the
membrane foulants, it could be concluded that the biofouling
integrated the EPS and bacterial cells is a main contributor to
OMBR fouling.