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Abstract: High-pressure size-exclusion liquid chromatography and infrared microscopy were coupled to investigate the molecular weight and nature of extracellular polymeric substances (EPS) from various activated sludges. Six main families of compounds (proteins, polysaccharides, organic acids, lipids, mineral phases) were found either as a single molecule or as associations. The molecular weight of proteins varied from small (10kDa) to large (600kDa) sizes, while all polysaccharides were smaller than 1kDa. Association of different molecules implied the presence of species large in size. The EPS chromatographic fingerprints of sludge from various origins remained stable in normal operating conditions, but were drastically modified during settling crises. In poor settling conditions, the EPS with smaller molecular sizes always prevailed and large polymers were underrepresented. The EPS identified in activated sludge were collected in a chemical database which provides the basis for comparison of municipal and industrial wastewater treatment plants (WWTP). [Copyright &y& Elsevier]

Extracellular polymeric substances were extracted from activated sludge using a resin exchange method and analyzed. The separation and identification of EPS were carried out by size exclusion chromatography and Fourier transform infrared micro-spectroscopy. Chromatograms of extracted EPS exhibited seven peaks. Proteins varying in molecular weights from 670 to 45 kDa were present in all the peaks. Polysaccharides corresponding to molecular weights of ∼1 and ∼0.5 kDa were present in only three peaks. Strong association of polysaccharides and proteins was observed. Infrared results revealed the presence of one type of polysaccharide and two types of proteins (A and B). Proteins differed mainly in the length of their associated alkyl chains and in the ratio of ester/acidic functionalities. [Copyright &y& Elsevier]