ABSTRACT
This chapter focuses on the role of extracellular polymeric substances (EPS) in the cell surface hydrophobicity of pure cultures and mixed-culture aggregates such as biofilms, aerobic/anaerobic granules and activated sludge. It describes the role of cell surface hydrophobicity in the microbial aggregation, the relation between EPS and cell surface hydrophobicity, as well as the techniques applied in the characterization of hydrophobicity. Hydrophobic interactions can be viewed as the spontaneous tendency of nonpolar groups to aggregate or cluster to minimize their contact with the water molecules. Microbial aggregation, such as biofilm formation, activated sludge flocculation and granulation, is initiated by the microbial adhesion. An effective wastewater treatment by using activated sludge is largely dependent on the sludge flocculation and settling. Membrane biofouling is a result of biofilm formation on the solid substratum, in which membrane surface properties, i.e., hydrophobicity, play an important role.
