The use of activated carbon (AC) for contaminated sediment site management is making the jump from research and demonstration/validation to full-scale remedial applications. Because AC can be applied to manage contaminated sediments in place, this technology replaces or augments other intensive management practices such as dredging or capping. With extensive support from SERDP and ESTCP, this technology has moved into the mainstream “tool box” for contaminated sediment remediation.
Activated carbon has long been used to remove organic contaminants from water. AC filters are used to clean industrial and municipal wastewater and are commonly sold for use in home filtration units to polish drinking water. AC works by stripping and tightly binding organic contaminants such as polychlorinated biphenyls (PCBs) and pesticides from the water. Applying this same principle, research funded by SERDP demonstrated that adding precise doses of AC into sediments has the same effect; organic contaminants are bound up and are then not available for uptake into organisms. Additions of as little as 2 percent AC resulted in 10- to 100-fold reductions in PCB uptake into marine organisms.
Based on the success of the initial bench-scale work sponsored by SERDP, the work was extended into field demonstration and validation in ESTCP. While the laboratory-scale demonstrations were relatively easy, developing engineering solutions for applying the AC into sediments in the field required work on multiple levels. AC floats, so one of the early ESTCP developments was to formulate the carbon into a pelletized form that would sink and could be applied using conventional equipment, achieving an even distribution on the sea floor with the pellet then dissolving to release the AC into the contaminated sediments. Completed or ongoing demonstrations at DoD sites have included the Army's Aberdeen Proving Ground (ESTCP Projects ER-200835 and ER-200825), Hunters Point Naval Shipyard (SERDP Project ER-1207), Naval Air Station Dallas (SERDP Project ER-1493), and the Puget Sound Naval Shipyard (ESTCP Project ER-201131).
AC is a sediment remedial alternative that is now being applied in many types of aquatic environments—rivers, lakes, wetlands, and deeper water in active channels and piers. Sites that have used AC as part of a remedy or are considering doing so include the Grasse River in New York, the Lower Duwamish Waterway in Washington, the Willamette River in Oregon, and two sites in Norway.
SERDP and ESTCP are also funding work to develop amendments for sequestering metals. Ongoing efforts include minerals such as apatite, zeolites, bauxite, and alumina for metals or metalloids; ion exchange resins for metals or other inorganic contaminants; and lime for pH control or nitroaromatics degradation. Other related work includes mixtures of permeable concrete and chemically active amendments to produce caps that prevent the migration of sediment contaminants while being stable on sloping shorelines and environments subject to dynamic forces (SERDP Project ER-2134).
For more information on SERDP and ESTCP’s work to develop amendments for contaminated sediments, visit http://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Sediments.