Full-Scale Application of Activated Carbon to Reduce Pollutant Bioavailability in a 5-Acre Lake

Abstract

The first full-scale remediation project in North America to use the direct placement of activated carbon (AC) into sediments was completed in 2013 in a 2-ha lake on the St. Jones River in Dover, Delaware. The sediment cleanup remedy at this site aims to enhance the sorption capacity of native sediments in the lake to reduce the exposure of bioaccumulative pollutants that currently contribute to fish consumption advisories in the lake. In November 2013, approximately 36 t of AC was applied to the lake over a 2-week period. Posttreatment sampling indicated an average AC concentration of 4.3% by dry weight in surface sediments. The primary monitoring was performed immediately prior to AC application and 1 and 3 years following application. Sediment porewater and surface water measurement using passive samplers showed reductions of 60%–80% of total freely dissolved polychlorinated biphenyls (PCBs), and both were reduced to below the Delaware Human Health Water Quality Criteria. Fish tissue analysis of resident fish samples collected before and 3–5 years after treatment showed reductions of approximately 70% on a lipid-normalized basis and agree with modeled predictions. In contrast, two migratory species caught in the lake showed limited changes in PCB concentrations, likely reflecting greater regional exposure while these fish migrated beyond the lake. Overall, the project demonstrates AC amendment as a viable and effective sediment remediation technology.