Enhancement of sludge dewaterability by three-dimensional electrolysis with sludge-based particle electrodes

Abstract

Electrochemical sludge conditioning was widely used to enhance sludge dewaterability. However, the limited area of plane electrodes results in poor dewatering efficiency and high energy consumption. The long period electrolysis with high cell voltage leads to the dissolution of extracellular polymeric substance (EPS), which accelerates the deterioration of sludge dewaterability. Herein, a clean and cost-saving method was proposed to enhance sludge dewaterability in this study. The capillary suction time (CST) of sludge conditioned with a three-dimensional electrochemical reactor (3D-ER) with sludge-based particle electrodes (SPE) decreased from 65.5 s to 29.6 s within 10 min while the water content decreased from 98.56% to 65.30% by mechanical filtration. The polarization of SPE in the electric field induced significant sludge flocs decomposition and EPS dissolution with a low energy consumption of 0.0020 kWh·L−1. The addition of commercial activated carbon (CAC) and SPE increased the calorific value of dewatered sludge as solid fuels. The SPE with the hydrophilic groups and silicon oxide provided more polar channels for water release than CAC, leading to an enhanced sludge dewaterability. These findings provided a new insight for improving sludge dewaterability and resource utilization in a closed loop in wastewater treatment plants.