Current decay mitigation through optimized electric field control modes in sludge electro-dewatering

Abstract

Electro-dewatering technology has attracted attention in sludge treatment due to its rapid dewatering kinetics, chemical-free operation, and low energy consumption. However, the traditional constant voltage mode is constrained by rapid current decay, impacting efficiency and increasing energy usage. This study proposed two electric field control modes, segmented voltage mode and constant current to constant voltage mode, to address this decay. The experiment evaluated current stability, thermal effects, and dewatering performance. Results indicate that the segmented voltage mode mitigated current decay by implementing stepwise ascending voltage, lowering current standard deviation from 2.17 to 0.59, achieving 48.60 % sludge moisture content at 0.188 kWh·kg⁻¹. The constant current to constant voltage mode further enhanced current stability, achieving 0.45 current standard deviation and 47.85 % moisture content at 0.178 kWh·kg⁻¹. Furthermore, quadratic regression models were developed to correlate process parameters with dewatering performance. Optimization of weighting coefficients for the dewatering effect ($W_a$) and energy consumption constraint ($W_b$) achieved the optimal balance between process performance and energy expenditure. This study aims to enhance electrical field control modes by accurately adjusting current to address the challenges posed by current decay on dewatering efficiency, offering a practical solution for optimizing electro-dewatering technology.