We provide innovative solutions to complex and challenging problems. Backed by a network of senior associates, we routinely assemble teams to tackle diverse project needs. What distinguishes Terran Corporation from the myriad of environmental consulting firms available today? Terran`s proven ability to design and implement innovative solutions to solve specific environmental problems and fulfill regulatory requirements. A large inventory of state-of-the-art environmental equipment and instruments, providing rapid, cost effective and timely delivery of services to the client. A well-educated, broadly experienced and highly motivated staff. Terran Corporation is recognized for high quality scientific investigations, successful and timely delivery of services and is respected by the regulatory community for its knowledge, thoroughness and integrity.
DC Electro Thermal Soil Remediation - the integration of DC electrical resistive heating, electroosmosis and in-situ zero-valent iron reductive technologies for the remediation of clays and glacial tills contaminated with chlorinated solvents.
DC Electro-thermal Remediation is the integration of direct current (DC)electrical heating and in-situ treatment developed specifically designed to treat chlorinated solvent contamination in low permeability soils totally below grade. Terran Corporation is the leader in large scale electrokinetic process installations.
The DC electricity provides two primary functions. The first is heating the soil to about 90°C helping to disperse residual dense non-aqueous phase liquid (DNAPL) pools or ganglia and creating vapor phase transport. Maintaining a lower temperature can assist in biodegradation, if desired. The second function is to induce electroosmotic flow. Electroosmosis is the directional movement of pore water in soil, from anode to cathode, providing a flushing action even, in the tightest clays. This electroosmotic flow is the proven advantage of using DC electricity over AC (including 6-phase resistive heating) or steam and allows the addition of in-situ reactive treatment zones (or curtains). These zones are emplaced perpendicular to the electroosmotic flow to intercept and degrade contaminants. In-situ destruction means no extraction or above ground treatment is necessary, which keeps operations and maintanence to a minimum. The treatment zones for chlorinated solvents typically are spaced 5 feet apart and consist of zero-valent iron suspended in kaolin clay. The treatment zones for biodegradation based systems can be a source of electron donors or acceptors such as organic carbon, sulfate, ferrous or lactate.
Electro-thermal remediation has been used to treat clays and glacial tills contaminated with solvent such as trichloroethylene (TCE) perchloroethylene (PCE), vinyl chloride, cis-1,2-dichloroethylene (cis-DCE), 1,1-dichloroethylene (DCE), 1,1,1-trichloroethane (TCA), 1,1-dichloroethane (1,1-DCA) and others. When applied to the source zones, 99% or more removals can be achieved. Even DNAPL areas can be treated to levels well below 1 mg/kg for about one third, or less, the cost of excavation and disposal. This technology can be applied above (vadose zone) or below the water table (saturated zone).
Terran has developed and refined the process of in-situ treatment materials emplacement, driving down installation costs. Using modified sheet-pile driving equipment and common mixing and pumping equipment, a large amount of materials can be emplaced in a short period of time in a very cost-effective manner. The sheet-pile driving equipment has been modified to direct push a large hollow mandrel up to 50 feet into the ground. A disposable shoe is placed on the leading edge to open the hole and keep materials from filling the mandrel on the down-stroke. Materials can be pumped into the mandrel on the down-stroke or added to the mandrel once it is driven to depth. For example, a 20 inch by 2 inch opening mandrel can be driven 25 feet, filled with a zero-valent iron (ZVI) slurry on the down-stroke, and removed in about a 2 minute cycle time. Up to 500 feet per day of 2-inch thick wall can be emplaced per day (see the installation videos below).
How Does It Work?
Electroosmosis has been known since the 1930s as an efficient means of dewatering clays and silts for soil stability. It can also be used to move pore water and contaminants through all types of soils. This attribute, plus the resistive soil heating that occurs makes it a useful tool for reclaiming solvent contaminated soils.
When a DC electric field is applied to soil, cations begin to move toward the cathode and anions move toward the anode. Since soil typically has a negative surface charge there are more cations than anions in the pore water (conservation of charge). These extra cations, lined up along the pore walls and moving toward the cathode, drag the pore water along causing a net pore water flow to the cathode that is uniform and predictable. In low permeable soils (clays and silts), this process is much more efficient and thorough than conventional hydraulic based processes. The directional movement through the soil allows for the effective use of in-situ capture and/or reduction zones. The application of DC energy also results in the heating of the soil, which is a bonus when dealing with VOC contamination. The soil heating can be harnessed to assist in the efficient mobilization of DNAPL pools and residuals much like a thermal technology. The combination of heat and pore water movement (flushing) gives electrokinetics (EK) a powerful one-two punch dealing with VOC contamination in low permeable soils.