Electrokinetic stabilization of sewage sludge using calcium chloride and zeolite: geotechnical behavior

This study investigates the effectiveness of electrokinetic stabilization combined with calcium chloride (CaCl₂) and zeolite in improving the long-term mechanical performance of sewage sludge. A horizontal electrokinetic model was employed, and a constant electric potential gradient of 1 V/cm was applied throughout the treatment period. The experimental program was conducted in two stages. In the first stage, sewage sludge specimens were treated using distilled water and different CaCl₂ concentrations (0.1, 0.3, and 0.5 M) to determine the optimum electrolyte concentration. In the second stage, the optimum electrolyte concentration was combined with zeolite additions of 5%, 10%, and 15% by dry weight of sludge. The results demonstrated that 0.1 M CaCl₂ provided the most effective electrokinetic response, increasing electroosmotic discharge from 85 mL to 123 mL and enhancing electroosmotic permeability from 3.28 × 10⁻6 to 4.75 × 10⁻6 m2/V·s. The incorporation of zeolite further improved sludge behavior, with the 10% zeolite mixture (REK10Z) exhibiting the optimum overall performance. Compared with untreated sludge, the liquid limit decreased from 138% to approximately 60%, while the water content was reduced by about 37%. The unconfined compressive strength increased from 12.47 kPa to 217 kP a.