Experimental study on dewatering of clay slurry under constant pressure and electric field conditions

To address dewatering challenges arising from increasing urban sludge production, this study employed kaolin clay to investigate the synergistic enhancement of electroosmosis integrated with traditional mechanical dewatering method through a combination of single-factor experiment and orthogonal experimental analysis. The single-factor tests revealed that both increased mechanical pressure and an earlier energization start time were positively correlated with improved dewatering performance (cumulative drainage volume and average drainage rate). Among these, mechanical pressure exerted the most significant effect on sample thickness, reducing it by 2.89 mm when mechanical pressure increased from 0.4 to 0.8 MPa. Optimal cumulative drainage was achieved at 3 mA/cm² current density. Orthogonal experiments were designed employing an L₉(3³) standard orthogonal array to identify the factors affecting dewatering efficiency. The primary-to-secondary order of influencing factors were determined as: mechanical pressure > pre-energization percentage (relative to filtration-consolidation phase threshold time under corresponding mechanical pressure) > current density. Signal-to-noise ratio analysis confirmed positive correlations between all factors and dewatering volume of clay slurry, with mechanical pressure exerting a statistically significant influence (p<0.05). The results demonstrate that the electroosmosis-mechanical integration can significantly enhance sludge drainage rates.