title: Hydrothermal and alkaline hydrothermal pretreatments plus anaerobic digestion of sewage sludge for dewatering and biogas production: Bench-scale research and pilot-scale verification.
abstract: To test the feasibility and practicability of the process combing hydrothermal pretreatment for dewatering with biogas production for full utilization of sewage sludge, hydrothermal/alkaline hydrothermal pretreatments and in turn anaerobic digestion of the filtrates obtained after dewatering the pretreated sludge were performed at bench- and pilot-scales. The hydrothermal temperature fell within the range of 140 °C-220 °C and the pretreatment time varied from 30 min to 120 min. For the alkaline hydrothermal pretreatment the pH value of the sludge was adjusted to 9.0-11.0 by adding Ca(OH)2. The results showed that the dewaterability of the sewage sludge was improved with increasing pretreatment temperature but the impact of the pretreatment time was not significant. The addition of Ca(OH)2gave better performance on the subsequent mechanical dewatering of the pretreated sludge compared to pure hydrothermal pretreatment, and the higher the pH value was, the better the dewaterability of the pretreated sludge was. The conditions of 180 °C/30 min and 160 °C/60 min/pH = 10.0 (for hydrothermal and alkaline hydrothermal pretreatments, respectively) resulted in relatively good results in the theoretical energy balance, which were verified in the pilot-scale tests. Based on the data from the pilot tests, the alkaline hydrothermal process realized self-sufficiency in energy at the cost of a proper amount of CaO.
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Science, Xiamen 36102, China.
authors.forename: Chunxing
authors.initials: C
authors.lastname: Li
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Science, Xiamen 36102, China.
authors.forename: Xingdong
authors.initials: X
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Multi-Phase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China. Electronic address: gyzhang@ipe.ac.cn.
authors.forename: Guangyi
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Science, Xiamen 36102, China.
authors.forename: Guangwei
authors.initials: G
authors.lastname: Yu
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Science, Xiamen 36102, China.
authors.forename: Jingjiang
authors.initials: J
authors.lastname: Lin
authors.affiliation: Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Science, Xiamen 36102, China. Electronic address: yinwang@iue.ac.cn.
authors.forename: Yin
authors.initials: Y
authors.lastname: Wang
mesh_terms: D056804:Biofuels; D012722:Sewage; D013696:Temperature
chemical_list: D056804:Biofuels; D012722:Sewage
keywords: Biogas; Dewatering; Energy balance; Hydrothermal pretreatment; Sewage sludge