title: Highly efficient secondary dewatering of dewatered sewage sludge using low boiling point solvents.
abstract: Secondary dewatering of dewatered sludge is imperative to make conventional drying and incineration of sludge more economically feasible. In this study, a secondary dewatering of dewatered sludge with selected solvents (i.e. acetone and ethanol) followed by vacuum filtration and nature drying was investigated to achieve in-depth dewatering. After the entire secondary dewatering process, the sludge was shown to be odourless and the organic matter content was greatly retained. Increased mean particle size of sludge after solvent contact improved solid-liquid separation. With an acetone/sludge ratio of 3:1 (mL:g) in solvent contact and subsequent nature drying at ambient temperature after 24 h, the moisture content of sludge can be reduced to a level less than 20%. It is found that the polysaccharides were mainly precipitated by acetone, whereas the release ratios of protein and DNA were increased significantly as the added acetone volumes were elevated. During nature drying, accumulated evaporation rates of the sludge after solvent contact were 5-6 times higher than original dewatered sludge. Furthermore, sludge after acetone contact had better nature drying performance than ethanol. The two-stage dewatering involves solvent contact dewatering and solvent enhanced evaporation dewatering. Through selecting an appropriate solvent/sludge ratio as well as economical solvents and minimizing the solvent loss in a closed-pilot system, this dewatering process can be competitive in industrial applications. Therefore, this solvent-aided secondary dewatering is an energy-saving technology for effective in-depth dewatering of dewatered sludge and subsequent sludge utilization.
authors.affiliation: Residues and Resource Reclamation Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, I Cleantech Loop, Singapore 637141, Singapore.
authors.forename: Chao
authors.initials: C
authors.lastname: He
authors.affiliation: Residues and Resource Reclamation Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, I Cleantech Loop, Singapore 637141, Singapore.
authors.forename: Chia-Lung
authors.initials: CL
authors.lastname: Chena
authors.affiliation: Environmental Science Research and Design Institute of Zhejiang Province, Hangzhou, Zhejiang 310007, People's Republic of China.
authors.forename: Zhirong
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Residues and Resource Reclamation Centre, Nanyang Environment and Water Research Institute, Nanyang Technological University, I Cleantech Loop, Singapore 637141, Singapore.
authors.forename: Jing-Yuan
authors.initials: JY
authors.lastname: Wang
mesh_terms: D000096:Acetone / Q000737:chemistry*; D003890:Desiccation / Q000379:methods*; D000431:Ethanol / Q000737:chemistry*; D005374:Filtration / Q000379:methods; D012722:Sewage / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*; D044366:Transition Temperature; D014867:Water / Q000737:chemistry*; D017155:Wettability
chemical_list: D012722:Sewage; D012997:Solvents; D014867:Water; D000096:Acetone; D000431:Ethanol