Response of extracellular polymeric substances to thermal treatment in sludge dewatering process

• Published in: Environmental pollution (1987) 2017-12, Vol.231 (Pt 2), p.1388-1392
• Main Authors: Wang, Long-Fei, Qian, Chen, Jiang, Jian-Kai, Ye, Xiao-Dong, Yu, Han-Qing
• Format: Article
• Language: English
• Subjects: Aerobic sludge; Anaerobic sludge; Desiccation; Dewatering; Extracellular polymeric substances (EPS); Polymers - chemistry; Polysaccharides, Bacterial - chemistry; Sewage - chemistry; Temperature; Thermal treatment; Waste Disposal, Fluid - methods; Waste Water - chemistry; Water - chemistry
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2017.08.119

Sludge dewatering is an important process in municipal wastewater treatment and critically influences the subsequent transportation and disposal. Thermal treatment coupled with other chemical processes has been widely used to improve sludge dewaterability. However, information about the response of sludge extracellular polymeric substances (EPS) to thermal treatment and its role in sludge dewatering is still limited. In this work, the effects of thermal treatment on anaerobic and aerobic sludges were investigated with an emphasis on the colloid properties of released EPS in sludge dewatering process. The results indicate that sludge dewaterability became deteriorated with the increased temperature in the range of 30–170 °C, which was ascribed to the disintegration of sludge flocs and change of EPS characteristics. Disintegrated sludge induced the release of the negatively charged EPS, resulting in the weakened bridging interaction and lower compactness. After thermal treatment, the EPS with a higher average molecular weight and stretched coil configuration retained more water. In addition, difference in dewaterability between anaerobic and aerobic sludges was found to be attributed to their different contents and structures of EPS components. These results provide an insight into thermal-dependent sludge dewatering process and are useful to facilitate water-sludge separation. [Display omitted] •Sludge filterability deteriorates with increasing temperature from 30 to 170 °C.•Released EPS and sludge disintegration result in deteriorated filterability.•EPS colloids retained more water in stretched state after thermal treatment.•Differences between different sludge stem from intrinsic distinction of components. Stretched coil configuration of released EPS retained more water and deteriorate the dewaterabiligy of sludge.