This seminar will feature SRP grantees Dr. Upal Ghosh (Associate Professor and Graduate Program Director at the Department of Civil and Environmental Engineering, University of Maryland Baltimore County) and Dr. Joel Burken (Professor of Civil, Architectural & Environmental Engineering and Interim Director of the Environmental Research Center). Dr. Ghosh will present an overview of ongoing research on activated carbon amendments to reduce contaminant bioavailability in sediments. This in-situ technique binds toxic chemicals in sediments and reduces their exposure to the aquatic food web. Dr. Burken will present his research using a traditionally high pressure waterjet in a new and innovative manner to inject remediation amendments like powdered activated carbon at varying depths in contaminated sediments. This method also decreases contaminant bioavailability, minimizes resuspension and the impact on benthic communities.
Dr. Joel Burken, Professor of Civil, Architectural & Environmental Engineering and Interim Director of the Environmental Research Center
Research presented here involves using a traditionally high pressure waterjet in a new and innovative manner to inject remediation amendments at varying depths in contaminated sediments. Previously published works identify Powdered Activated Carbon (PAC) as effective remedial amendment to decrease contaminant bioavailability. This investigation focuses on delivering remedial amendments such as PAC to depths by varying pressure, stand-off distance, nozzle geometry, and amendment delivery methods. Laboratory testing has thus far focused on means of injecting maximum solid amendment concentrations to targeted concentrations and concurrently minimizing resuspension and impacton benthic communities.
Both single injection and continuous injection tests have been conducted to determine timing and the effective delivery methods. Waterjetting of amendments was tested on sediments and also treating "capped" contaminated sediments. A means to rapidly dewater these tests was also needed identified as a limiting factor to timely completion. The authors developed a unique and innovative use of electro-osmosis to dry samples from saturation to a degree of "dryness" acceptable for analytical analysis of amendment distribution in surrogate sediments, in as little as 4 hours.
Results to date include the ability to jet amendments to depths of 70 cm in dense, cohesive sediments, but minimal distribution was observed horizontally. Other methods can apply amendments uniformly into the surface sediments using slurries of PAC of up to 35% by weight, thereby adding minimal water to the contaminated sediment. The impacts to benthic communities have also been assessed, showing viable populations can survive and benthic impacts at the sediment surface are minimized, as measured as % disturbed. The surface disturbance was also beneficial in jetting through capped amendments. Testing on aged, PAH-contaminated sediments also reveal a drop of over 95% in the bioavailable porewater concentration as measured using SPME methods, continuing to depths of over 30 cm. Further testing is ongoing to optimize the distribution at a desired depth and to develop pilot scale units.
Sorbent amendment to reduce contaminant bioavailability in sediments
Dr. Upal Ghosh, Associate Professor and Graduate Program Director at the Department of Civil and Environmental Engineering, University of Maryland Baltimore County
Bioavailability of persistent organic contaminants such as PCBs is impacted by the nature of organic matter in sediments. In this research we show that fresh black carbon in the form of activated carbon can be added to sediment to bind toxic chemicals and reduce their bioavailability to sediment-dwelling organisms and flux into the water column. This talk will present results from recent laboratory studies and ongoing pilot demonstrations at USEPA Superfund sites of carbon amendment into contaminated sediments.