Remediation of municipal wastewater sludge by electrokinetic geobox

A pilot-scale study was conducted on in situ decontamination of municipal wastewater sludge containing relatively high concentrations of target metal contaminants such as cadmium (6.85 mg/kg), chromium (117.5 mg/kg), copper (335.7 mg/kg) and lead (64.1 mg/kg). A new type of geosystem (a cellular geobox) composed of geocomposites (electrokinetic geosynthetic, GEK) was developed for waste remediation. A low-level direct current results in physicochemical changes in the applied media, leading to species transport by coupled mechanisms, such as electromigration, electro-osmosis, electrophoresis and electrolysis of water. The removal efficiencies for heavy metals were significantly dependent on their speciation in the sludge matrices and on various geosynthetic properties. The modified geotextile and geocomposite with functions of filtration, drainage, conduction, and ion exchange capacity accelerated the contaminant removal rate. The electrokinetic removal efficiencies of abiotic heavy metals exceeded 85% for the mobile and weakly bound fractions, such as the exchangeable and carbonate fractions, and were higher than 69% for the strongly bound fractions, such as the organic/sulphide and residual fractions. The final product can be used as landfill material.