title: Relationship between enhanced dewaterability and structural properties of hydrothermal sludge after hydrothermal treatment of excess sludge.
abstract: Hydrothermal treatment is an effective method to enhance the deep dewaterability of excess sludge with low energy consumption. In this study, an insight into the relationship between enhanced dewaterability and structural properties of the produced hydrothermal sludge was presented, aiming at better understanding the effect of hydrothermal process on excess sludge dewatering performance. The results indicated that hydrothermal effect induced the transformation of surface water to interstitial and free water by lowering the binding strength between adjacent water and solid particles and that free water became the main form for moisture existence in hydrothermal sludge as temperature was higher than 180 °C. Increase in temperature of hydrothermal treatment generated a significant size reduction of sludge flocs but treated sludge with a higher rigidity, which not only strengthened the network of hydrothermal sludge but also destroyed the binding of EPS with water. Hydrothermal process caused crevice and pore structures of excess sludge to disappear gradually, which was a main driving force of water removal as temperature was below 150 °C. With the temperature of hydrothermal treatment exceeding 180 °C, the morphology of hydrothermal sludge became rough which linked closely to the solid precipitation of condensation polymerization, and further became smooth at higher temperature (210 °C) due to the coal-like structures with higher aromaticities, indicating that hydrothermal reaction pathways began to play a main role in enhanced dewaterability. Hydrothermal treatment led to more alkyl and aromatic carbon, but lower O-alkyl, carboxyl and carbonyl carbon.
authors.affiliation: College of Environment & Resources, Inner Mongolia University, Hohhot 010021, Inner Mongolia, China. Electronic address: lipwangood@imu.edu.cn.
authors.forename: Liping
authors.initials: L
authors.lastname: Wang
authors.affiliation: School of Environmental Science & Technology, Dalian University of Technology, Industrial Ecology and Environmental Engineering Key Laboratory of Ministry of Education, Dalian 116024, Liaoning, China.
authors.forename: Aimin
authors.initials: A
authors.lastname: Li
authors.affiliation: Environmental Monitoring Center, Jining Environmental Protection Bureau, Ulanqab 012000, Inner Mongolia, China.
authors.forename: Yuzhi
authors.initials: Y
authors.lastname: Chang
mesh_terms: D006358:Hot Temperature; D012722:Sewage / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D012722:Sewage; D014867:Water
keywords: Apparent structure; Excess sludge; Hydrothermal treatment; Moisture distribution; NMR