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Evaluation of Dewatering Characteristics of Wastewater Sludge from Various Treatment Processes Open Access

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A study was performed with different types of sewage sludge to determine the factors that impact polymer demand and cake total solids (TS), along with investigation of optimum polymer dose (OPD) for each sludge type. Results indicated that sludge from the thermal hydrolysis process (THP) required higher polymer dosage to dewater, compared to primary sludge, waste activated sludge (WAS) and the mixture of primary and WAS, due to high content of protein and polysaccharide release in the bulk liquid of the sludge. However, THP process increased the cake TS by 88% for the mixed sludge and 19% for the anaerobically digested sludge. This study showed that polymer demand was directly correlated with soluble protein and polysaccharide concentration of the sludge, but the relationship was not global, since thermally hydrolyzed sludge (THP) did not exhibit similar correlation. However, there was a good relation between OPD and sludge surface charge, and the relationship was true for all types of sludge including the THP one. On the other hand, the cake TS was related to the extracellular polymeric substances (EPS) and bound water. But the relationship between cake TS and bound water was not observed for cake TS greater than 15%. In contrast, sludge bound EPS showed a good relation with cake TS (R2=0.76), where all types of sludge followed the correlation curve.

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