Ex situ soil treatment

All ex situ soil treatment methods involve a two-step approach soil excavation and aboveground treatment of the excavated soil. The differences in the various ex situ excavation/treatment methods for soil remediation lie only in the methods of soil treatment aboveground, such as soil washing plus extraction, and slurry biodegradation. 

STRATEX, or the stratified temperature extractor technology, is an integrated ex situ soil treatment technology that uses solidification/stabilization, thermal desorption, and steam stripping. 

SPSH has several advantages. It is applicable to sites where contaminants are present as non-aqueous-phase liquids (NAPLs). The technology reduces volatile organic carbon (VOC) removal time to a few weeks for a typical site, whereas soil vapor extraction (SVE) alone requires years for remediation. This reduction in removal time can signrhcantly decrease costs over SVE (from 2 to 10 times). Excavation and ex situ soil treatment is typically much more expensive to implement than SPSH, especially at deep sites. 

Ex Situ Biological Treatment on Excavated Soil by Slurry Biodegradation... 

SafeSoil is an ex situ, biostimulation treatment technology that is specifically designed to remediate soil contaminated with organic compounds. The SafeSoil process biologically oxidizes... 

In 1993, ex situ soil vapor extraction using nondrilled horizontal wells was used at a contaminated site in Douglasville, Georgia. The U.S. Environmental Protection Agency (EPA) reported that the total cost of the remediation project was 2.2 million. Treatment costs were estimated to be 413/yd of soil treated (D20793M, pp. 20, 21). Treatment costs are summarized in Table 1. 

Western Environmental Science and Technology (WEST) had developed an ex situ soil washing technology designed for the treatment of lead-contaminated soil. This technology was particularly developed for use at shooting ranges. 

They may be favored over in situ treatment where they will reduce cleanup times, their operation and capabiHties are considered more reHable or better understood, or they can achieve lower cleanup levels. Both in situ and ex situ treatment for soil and ground water rely on a combination of unit processes, which often include biological degradation of organics. 

Ex situ bioremediation may use various biological wastewater treatment processes, soil piles, or land appHcation. With in situ bioremediation, the basic process is the same microbes, soil, and water working together as a bioreactor. Where the in situ techniques differ are in how contaminants and microbes are brought in contact and how oxygen, nutrients, and other chemical supplements ate distributed in the soil—water—air matrix. Typical in situ bioremediation techniques include natural or intrinsic attenuation, air sparging, and bioventing. 

In cases where in situ biological treatment cannot be applied, the contaminated soil is excavated and transferred to specially prepared areas where bioremediation can be carried out under well-controlled conditions. Some common ex situ biological methods are the landfarming technique and the biopile or biopit treatment options.32... 

Mindevalli, O. and Pedram, E.O., Soil bioventing and vapor extraction (in-situ and ex-situ) and ground-water treatment and reinjection at a diesel and gasoline contaminated site, Proc. HAZMACON 94, Bursztynsky, T., Ed., 1994, pp. 386-398. 

Land farming. This is a solid-phase treatment system for contaminated soils it may be carried out in situ or ex situ. 

The main advantage of in situ thermal methods is that they allow soil to be treated without being excavated and transported, resulting in significant cost savings however, in situ treatment generally requires longer time periods than ex situ treatment, and there is less certainty about the uniformity of treatment because of the variability in soil and aquifer characteristics and because the efficacy of the process is more difficult to verify. 

The thermal desorption process could be an excellent first step in soil treatment if used in conjunction with another ex situ treatment. Thermal desorption can remove TCE, most diesel fuel, and perhaps organically bound lead. Chemical Waste Management, Inc., has claimed that thermal desorption can reduce volatile organics to less than 1 mg/L and inorganics to less than 10 mg/L (sometimes even to less than 1 mg/L), and has shown a removal of 96 to 99+% of PCBs from soils containing 120 to 6000 mg/L of initial PCBs.17-91... 

The bottom water recovery system uses existing wells or new wells to create the water recovery system for removal of the water used to wash the contaminated soil. Reverse leaching or soil washing can be conducted by controlling the water levels within the tank. This design minimizes the volume of clean ex situ water entering the system for treatment. Extremely dense clays may be difficult to treat with this technology. 

U.S. EPA s MTBE Treatment Profiles Website3 provides site-specific data about the use of in situ and ex situ technologies that have been used to treat MTBE in groundwater, soil, and drinking water. The website contains information about more than 400 projects, including information about the technology used, project scale, performance, and cost. The treatment performance and cost data presented in this chapter provide readers with... 

Treatment Technology Groundwater Soil In Situ or Ex Situ Description... 

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