Electro-dewatering of sewage sludge: Influence of combined action of constant current and constant voltage on performance and energy consumption

• Published in: The Science of the total environment Vol. 667; pp. 751 - 760
• Main Authors: Qian, Xu, Zhou, Xingqiu, Wu, Jiandong, Liu, Changyuan, Wei, Yijun, Liu, Jiangyan
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.06.2019
• Subjects: Combined action; Electro-dewatering; Energy consumption; Kinetics; Sludge treatment; Energy consumption; Combined action; Kinetics; Sludge treatment; Electro-dewatering
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2019.02.329

In this study, mechanically-dewatered sludge was used to investigate the effect of electro-dewatering (EDW) under two electrical modes, which are constant current mode followed by constant voltage mode (CV-EDW), and constant voltage mode followed by constant current mode (VC-EDW). The effect of current and voltage changes on dewatering efficiency and energy consumption of sludge electroosmosis under CV-EDW and VC-EDWs was evaluated The results show that compared with constant current mode (C-EDW), CV-EDW can improve the final dry solids content and reduce the heating rate, and the final dry solids content and unit energy consumption increase with the decrease of current and the increase of voltage. Under CV-EDW, when the dry solids content is 32%, the energy consumption can be reduced by changing to the constant voltage stage, and the energy consumption is 0.093–0.113 kWh/kgwater. Compared with constant voltage mode (V-EDW), VC-EDW significantly improves sludge dewatering rate. Under VC-EDW, the final dry solids content of sludge increases with the decrease of current and voltage. When the voltage is decreased by 10 V, the unit energy consumption is reduced by 27.15 ± 1.77% on average, and the energy consumption is 0.132–0.163 kWh/kgwater. Compared with CV-EDW, the dehydration rate of VC-EDW is increased by 72.9% on average. However, the unit energy consumption required for dehydration increases by 43.09% when the dry solids content is less than 45%. [Display omitted] •Constant current and voltage modes are combined for sludge electro-dewatering.•The combination shows advantage over constant current or voltage mode.•Constant current-to-voltage mode yields higher dry solids content and saves energy.•Best point for constant current-to-voltage mode is a dry solids content of 32%.•Constant voltage-to-current mode yields higher dehydration rate.