Properties and occurrence of lipids in extracellular polymeric substances (EPS) of activated sludge flocs

grantor: University of TorontoThe objective of this study was to improve our understanding of the composition of extracellular polymeric substances (EPS), particularly lipids, and their influence on floc structure and surface chemistry of microbial flocs. Total carbohydrates and lipids were the dominant components in capsular EPS extracted from the microbial floc grown in reactors at different sludge retention time (SRT), followed by humics, protein, acidic polysaccharides and DNA. The relative hydrophobicity of microbial floc was affected by SRT. Sludge surfaces at higher SRTs (16 and 20 days) were more hydrophobic than those at lower SRTs (4 and 9 days). Lipids comprised about 31% of the total EPS content extracted from microbial floc with different SRTs. The strong correlation between the concentration of lipids; in slime and capsular EPS, improved emulsification properties of EPS, and sludge retention time all indicate the importance of lipids in influencing the surface activity of floc.M.A.Sc