The GRACE Bioremediation Technologies organic amendment-enhanced bioremediation technology (DARAMEND™) is designed to degrade many organic contaminants in industrial soils and sediments, including pentachlorophenol (PCP), polynuclear aromatic hydrocarbons (PAH), and petroleum hydrocarbons. The technology has been applied both in situ and ex situ. In either case, soil may be treated in lifts up to 2 feet deep using available mixing equipment. The technology may also be applied ex situ, as a biopile.
The technology treats batches of soil using DARAMEND™ soil amendments. These amendments are introduced using conventional agricultural equipment (see photograph below), followed by regular tilling and irrigation. DARAMEND™ soil amendments are solid-phase products prepared from natural organic materials to have soil-specific particle size distribution, nutrient content, and nutrient release kinetics. Soil amendments sharply increase the ability of the soil matrix to supply water and nutrients to the microorganisms that degrade the hazardous compounds. The amendments can also transiently bind contaminants, reducing the acute toxicity of the soil aqueous phase. This reduction allows microorganisms to survive in soils containing very high concentrations of toxic compounds.
DARAMEND™ Bioremediation Technology
DARAMEND™ treatment involves three fundamental steps. First, the treatment area is prepared. For the ex situ application, a lined treatment cell is constructed. In situ application requires the treatment area to be cleared and ripped to reduce soil compaction. Second, the soil is pretreated; this includes removing debris larger than 4 inches, such as metal or rocks, that may damage the tilling equipment. Sediments under-going treatment must be dewatered. And third, the DARAMEND™ soil amendment is incorporated, usually at 1 percent to 5 percent by weight, followed by regular tilling and irrigating.
Soil is tilled with a rotary tiller to reduce variation in soil properties and contaminant concentrations. Tilling also incorporates the required soil amendments and helps deliver oxygen to contaminant-degrading microorganisms.
An irrigation system is used to maintain soil moisture in the desired range. If the treatment area is not covered, leachate or surface runoff caused by heavy precipitation is collected and reapplied to the soil as needed.
Equipment needed to implement this technology includes a rotary tiller, irrigation equipment, and excavation and screening equipment. Depending on site-specific factors such as contaminant type and initial concentration, and project schedule and climate, a waterproof cover may be constructed over the treatment area.
The DARAMEND™ technology can treat soil, sediment, and other solid wastes such as lagoon sludge. These matrices may be contaminated by a wide range of organic compounds including, but not limited to, PAHs, PCP, petroleum hydrocarbons, and phthalates. Matrices of lead, manganese, and zinc have been effectively treated with the DARAMEND™ technology.
This technology was accepted into the SITE Demonstration Program in spring 1993. The ex situ application of the technology was demonstrated from fall 1993 to summer 1994 at the Domtar Wood Preserving facility in Trenton, Ontario, Canada. The demonstration was one component of a 5,000-ton remediation project underway at the site.
Currently, the DARAMEND™ technology and cycled modification is being applied on a large scale, and is awaiting regulatory approval for application at four sites in the U.S. In addition, the technology is being applied at a number of Canadian sites, including a 2,500-ton biopile in Eastern Canada, and two projects targeting pesticides and herbicides in Ontario.
In the ex situ demonstration area, the DARAMEND™ technology achieved the following overall reductions: PAHs, 94 percent (1,710 milligram/kilogram [mg/kg] to 98 mg/kg); chlorophenols, 96 percent (352 mg/kg to 13.6 mg/kg); and TPH, 87 percent. These reductions were achieved in 254 days of treatment, including winter days when no activity occurred because of low soil temperatures. The control area showed a reduction of 41 percent in PAH concentrations; no reduction was seen in the concentration of either chlorinated phenols or TPH during the treatment time. Results from the toxicity analysis (earthworm mortality and seed germination) showed that the toxicity was eliminated or greatly reduced in the treated soil.
EPA PROJECT MANAGER:
Teri Richardson
U.S. EPA
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7949
Fax: 513-569-7105
TECHNOLOGY DEVELOPER CONTACTS:
Alan Seech or Paul Bucens
GRACE Bioremediation Technologies
3451 Erindale Station Road
Mississauga, Ontario, Canada L5A 3T5
905-272-7480
Fax: 905-272-7472