University of Maryland - Baltimore County (Ghosh)
Superfund Research Program
Pilot-scale Research of Novel Amendment Delivery for in situ Sediment Remediation
Sediment-bound persistent organic contaminants such as PCBs and DDT pose a public health risk through contamination of the food chain and through direct exposure. This field research evaluated the effectiveness of a novel approach to alter the binding capacity of sediments to reduce ecosystem and human exposure to such contaminants. While recent work has demonstrated the feasibility of reducing contaminant bioavailability in situ through the amendment of strong sorbents like activated carbon, a major challenge in full-scale implementation of this approach is the difficulty in delivering low density amendment materials into sediments. A novel approach for delivery of amendments was recently developed through a USEPA funded project that formulated the amendments into engineered pellets named SediMite that could be easily deployed through a water column into sediments. The pellets are designed to withstand dispersal through the water column with minimal release of active ingredients followed by slow disintegration and mixing into the bioactive zone of sediments through natural sediment mixing processes such as bioturbation. This pilot-scale demonstration study evaluated the effectiveness of this engineering approach to achieve the desired delivery of amendments, effectiveness of mixing by bioturbation, and effectiveness of the amendments delivered in this form in reducing contaminant bioavailability.
The pilot-scale demonstration study was conducted at a USEPA Superfund site (Bailey Creek, Ft. Eustis, VA) in an estuarine wetland environment impacted with PCBs. A site-specific treatability study was first performed to demonstrate the effectiveness of activated carbon amendments to reduce PCB bioavailability to benthic invertebrates. This was followed by scale up of production of the pelletized carbon at an industrial facility to produce the required quantity of the product for a pilot-scale study. Pilot-scale control and treatment sites were 15meters by 15meters, half within the channel segment and half in the bordering marsh. Activated carbon in the form of SediMite was applied using a boat-mounted dispersion device similar to a commercial fertilizer/herbicide spreader. The treatment was deployed in the summer of 2009. Samples were collected and examined before treatment, two months, and 15 months after treatment. Black carbon measurement in sediment cores demonstrated that the applied activated carbon remained in sediment after application and was found in the top 5 cm of sediment. Bioaccumulation studies using the benthic organism Leptocheirus plumulosus as well as aqueous concentration measurement using a passive sampler showed reductions in PCB bioavailability at the treatment sites after deployment. Benthic community sampling after application demonstrated no significant impact of the application on native biota.
The development of this technology for contaminated sediment management offers the potential to protect human health and ecosystems while significantly reducing costs and negative impacts on ecosystems. The SediMite technology has been commercialized through a startup company and is currently being implemented at several contaminated sites impacted with PCBs, PAHs, and mercury.