Remediation of contaminated intertidal sediment by increasing permeability using active capping material

Abstract

A novel approach for the remediation of clayey sediment in intertidal zones was proposed, which entails increasing the soil permeability using an active capping agent. The agent, granulated coal ash (GCA), was developed using the granulation processes for coal fly ash. The GCA increased the permeability coefficient of the sediment by seven times, changing its the properties from a typical clayey silt to that of silt, according to the soil classification standards based on permeability coefficient. Increased permeability was attributed to Ca2+ ions, and adsorbed Na+ was immediately discharged, leading to a decrease in the sodium adsorption ratio. The activated flow of pore water stimulated nutrient loadings; PO4–P and NH4–N loads decreased by 55% and 44%, respectively. The GCA increased the dissolved oxygen by 1.8 mg/L and increased the redox potential in pore water from −370 to −306 mV vs. Ag/AgCl. According to the results presented in this study, active capping with GCA to increase soil permeability is a novel and promising technology for reducing the nutrient loads and increasing the oxidation of contaminated clayey sediment in intertidal zones.