Investigation of Activated Carbon and Protein Polysaccharide Amendments in Capping Applications for Sediment Remediation

Contaminated sediment is a major environmental problem in numerous sites across the US and requires costly treatment to effectively remediate the sediment and prevent contaminants from entering the water column. Capping of contaminated sediment has emerged as the preferred treatment design as it is more cost effective and effectively isolates the contaminants in-situ. Powdered Activated Carbon (PAC) is commonly introduced in capping designs due to its high sorption capacity of organic contaminants. However, its low bulk density and fine particle size result in significant carbon resuspension during cap placement. This report provides experimental and modeling results focused on the effects of PPB treatments on PAC placement in a sand matrix. Laboratory test results indicate that sand/PAC mixtures treated with PPBs exhibit an increase in cohesion, and a \u3e 93% reduction in water turbidity. PPB treatment also resulted in a homogeneous mixture of sand. At the end of a 40-yr run, CapSim modeling results indicate that contaminant porewater concentrations at the top of a sand/PAC cap were approximately 20% lower when a homogeneous sand/PAC layer was present (PPB-treated case) than when stratified sand and PAC layers are present (untreated case). This indicates that having a homogeneous layer of sand and PAC as a result of the PPB treatment provides more effective contaminant adsorption, thereby reducing recontamination risks of the water column even after decades of cap installation. The results of the study indicate that PPB-treated sand/PAC is a promising method for the design of effective and less erosion-prone sediment capping systems