New insights into the effect of thermal treatment on sludge dewaterability.

The changes of the sludge dewaterability in different thermal treatments and the factors influencing these changes were examined in this study. The experimental results showed that the sludge dewaterability deteriorated by the thermal pretreatment with temperature range from 20 to 170 °C, but the deterioration decreased above a certain temperature threshold (120-150 °C). The factors which affected the dewaterability of thermal-treated sludge in two temperature ranges (20-105 °C and 105-170 °C) were different. The dewaterability of thermal-treated sludge was influenced by the protein, humic acid, and polysaccharide contents of different extracellular polymeric substance fractions and the molecular distribution and fluorescence intensity of tightly bound extracellular polymeric substance in the range from 20 to 105 °C. From 105 to 170 °C, while, the thermal-treated sludge dewaterability was influenced mainly by the α-helix of protein in soluble extracellular polymeric substance. These experimental results provide a new insight into the effect of thermal treatment on sludge dewaterability, which will help guide subsequent research.