COMPOSITION OF EXTRACELLULAR POLYMERIC SUBSTANCES IN THE ACTIVATED-SLUDGE FLOC MATRIX

The precise role of extracellular polymeric substances (EPS) in relati on to the formation and physicochemical properties of microbial flee i n wastewater treatment systems is not well known. Studies were underta ken to provide more comprehensive descriptions of EPS and properties o f microbial floc. Acidic polysaccharides and DNA were relatively labil e components of the EPS when biomass was stored sit 4 degrees C or at -20 degrees C, and significant losses of these components were observe d within 24 hours. The composition and properties of activated sludge were found to vary between different full-scale treatment systems refl ecting the importance of wastewater composition and operation conditio ns on microbial communities and the response to environmental conditio ns. The COD:N:P ratio was found to influence hydrophobicity, surface c harge and the EPS composition of microbial flocs in well-controlled be nch-scale sequencing batch reactors. Phosphorus depleted and P-limited conditions resulted in a decrease in surface charge but increases in acidic polysaccharides which corresponded to a strong carboxyl stretch at 1740 cm(-1) when the biomass was analysed by FTIR-spectroscopy. El ectron dense particles, identified by energy-dispersive spectroscopy a s containing iron, phosphorus and sulfur, were observed in the fibrils of the flee matrix by transmission electron microscopy. (C) 1998 IAWQ . Published by Elsevier Science Ltd.