Experimental study on the electro-dewatering transport of Hangzhou sludge

Abstract

Electro-dewatering is believed to be an alternative and effective technique to dewater sludge. The objective of this study is to explore the influence of process parameters (electrode materials, potential gradient, electrode arrangement, soil water content, and soil salinity) on the electro-dewatering transport, which determines the electro-dewatering efficiency. A series of experiments were performed using Hangzhou sludge. The results demonstrated a linear relationship between the electro-dewatering rate and the electric current during each test, which showed steady electro-dewatering transport. Moreover, the electro-dewatering transport was found to be independent of the electrode material, electric potential, and electrode arrangement, but was strongly correlated with soil properties. Electro-dewatering transport improved with a higher initial water content or lower initial soil salinity, but was steady when the real-time soil properties changed. An interpretation of the experimental results is presented from the perspective of the electro-dewatering mechanism. The solid–water–ion interaction system of the soil was believed to be fundamentally responsible for these results in terms of the water molecule concentration and cation concentration. For soils with a higher initial water content or lower initial salinity, the solid–water–ion interaction was enhanced and the electro-transport was higher. Moreover, for each particular electro-dewatering process, the equilibrium of the solid–water–ion interaction system was accessed and thus electro-dewatering transport was maintained despite of changes in the real-time soil properties. This study provides guidance for efficiency evaluations of the use of the electro-dewatering technique in drying soils.