Investigation of extracellular polymer substances (EPS) and physicochemical properties of activated sludge from different municipal and industrial wastewater treatment plants.

This paper examines the chemical constituents of extracellular polymeric substances (EPS) and physicochemical properties of eight different sludge flocs from seven full-scale wastewater treatment plants. The physicochemical properties included floc properties (floc size, turbidity and effluent suspended solids (ESS) content of the supernatant), sludge volume index, capillary suction time and specific resistance to filtration. The relationships between the chemical constituents of EPS and the flocculation, settleability and dewaterability of sludge flocs were also assessed. The results showed that higher amounts of EPS were found in the municipal sludge flocs than in the industrial sludges. The content of tightly bound EPS (TB-EPS) was much greater than that of loosely bound EPS (LB-EPS). The amounts of total EPS, LB-EPS, TB-EPS and protein in LB-EPS were strongly related to ESS. The ratios of total protein to EPS and total carbohydrate to EPS showed positive correlation to the flocs size. It was surprising that there was no correlation between settleability or dewaterability and the chemical constituents of EPS.