Remediation applications

The leaching of heavy metals into groundwater from sites that have been used to dispose of these elements, or from areas that have been contaminated 

For a specific waste to be treated, the appropriate ratio of the treatment additive (phosphate) and pH control agent (magnesium oxide) that gives the best performance in terms of maximum contaminant level (MCL) and the secondary maximum contaminant levels (SMCL) for drinking water of the EPA s National Primary and Secondary Drinking Water Regulations is determined experimentally. One hundred grams of the waste is blended 

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Foams are being investigated as a technology for site remediation applications. Foams may be used to treat non-aqueous-phase liquids in the soil subsurface. Foams could be used to deliver gases, surfactants, chemicals, nutrients, and bacteria to the subsurface. 

Bio-Electrics, Incorporated, has developed the Electrofrac Detoxification System to treat hazardous contaminants in soil. The system, which was developed from gasification research, uses electrodes placed in soil to heat the site. There are potential applications of this technology for removal of volatile organic compounds (VOCs), pyrolysis of non-VOCs, treatment of organic residues, and in situ vitrification of soils and asbestos. There have been bench-scale tests of the technology for remediation applications. 

Moisture content of soil affects power requirements. The contaminants are not treated in a confined area, so some migration of the materials being treated is possible. This technology has not been field tested for remediation applications. 

TABLE 1 Cost Information for Full-Scale Remediation Applications... 

The vendor states that LTTD has been used during several full-scale remediation applications. Contaminated soils have been treated using the on-site and fixed-facility LTTD equipment (D22644I). On-site treatment costs were approximately 42 per ton. Treatment costs for the fixed-facihty applications ranged from approximately 35 per ton to 105 per ton. The cost data is summarized in Table 1. 

Forrester Environmental Services, Inc., has developed a group of technologies for the stabilization of wastes containing heavy metals, such as lead, cadmium, arsenic, mercury, copper, zinc, and antimony. These technologies have been used in both industrial pollution prevention and remediation applications. One version of the technology involves the use of water-soluble phosphates and various complexing agents to produce a less soluble lead waste. This process results in a leach-resistant lead product. 

The polywall barrier system was developed by Horizontal Technologies, Inc. (HTI), of Mat-lacha, Florida. The first polywall barrier system was completed in 1993. Since that time, the technology has been demonstrated at more than 10 other sites and used in full-scale remediation applications. The polywall barrier technology is currently commercially available through Horizontal Subsurface Systems, Inc. 

LLNL and Far West Group, Inc., signed a licensing agreement in lanuary 1997 to commercialize the CA-CDI process. CDI Technologies Partnership was created in November 1997 as an independent entity to develop and patent practical implementations of the basic technology. The technology is not yet commercially available for remediation applications. 

While no cost information is available on remediation applications of the technology, the vendor states that the installed costs for Living Machine system designed to treat wastewater starts around 100,000 (D203645, p. 4). 

The vendor claims that Houdini is qualified for a number of waste remediation applications. Uses for Houdini include mechanical waste retrieval, hot cell decommissioning, tank decontamination, material containerization, wall scabbling, tank inspection, pipeline cleaning and repair, and ship and barge cleaning. 

SBP Technologies, Inc., has closed for business. The solid-phase bioremediation technology has been used during fuU-scale remedial applications but is not longer commercially available. According to the vendor, the solid-phase bioremediation technology has several advantages ... 

Advantages over conventional pump-and-treat methods include reduced volumes of contaminated fluid to be treated, shorter times for remediation, applicability to contaminants above and below the water table, and potential for reuse of recovered contaminants. 

The average costs for a DUS remediation application is approximately 50/yd. According to the developer, energy costs are approximately 2/yd for steam and approximately 5/yd for electric applications. The system becomes more cost effective at larger sites (D11318Y, p. 3 D19516Y, p. 19 D201050, p. 1). 

A vendor of BioSolve technology states that the contaminant type and concentration, the amount of soil to be treated, and other site conditions will impact treatment costs (D171017, p. 1). Documents provided by the vendor indicate that the total cost of bioremediation using BioSolve can range from 25 to 90/yd of soil treated (D14680P, p. 93). Subsequent communication from the vendor stated that for remediation applications the cost of BioSolve was 1 to 5/yd of soil treated (personal communication, Jim Figueira, Western States BioSolve, October 1997). 

Abiotic environmental reductants are not as well characterized as the oxidants because there are fewer remediation applications of reductants, and natural reducing environments are characterized by especially complex biogeochemistry. The most familiar natural reduc-... 

Several of the key issues are reflected in the debate over the appropriate use of pe to describe redox conditions in natural waters (129-131). The parameter is defined in terms of the activity of solvated electrons in solution (i.e., pe = - log e ), but the species e aq does not exist under environmental conditions to any significant degree. The related concept of pe (132), referring to the activity of electrons in the electrode material, may have a more realistic physical basis with respect to electrode potentials, but it does not provide an improved basis for describing redox transformations in solution. The fundamental problem is that the mechanisms of oxidation and reduction under environmental conditions do not involve electron transfer from solution (or from electrode materials, except in a few remediation applications). Instead, these mechanisms involve reactions with specific oxidant or reductant molecules, and it is these species that define the half-reactions on which estimates of environmental redox reactions should be based. 

Chang, L. C, Shoemaker, C. A., and Liu, P. L. F. (1992). "Optimal time-varying pumping rates for groundwater remediation Application of a constrained optimal control algorithm." Water Resour. Res., 28(12), 3157-3171. 

Ko, S.-O., and Schlautman, M.A. (1998). Partihoning ofhydrophobic organic compounds to sorbed surfactants. 2. Model development/predictions for surfactant-enhanced remediation applications. Environ. Sci. Technol., 32,2776-2781. 

The reactivity of initial products will have a dramatic effect on their buildup during oxidation. Those that react rapidly (e.g., benzoquinones) will be seen only in minor amounts, whereas less reactive initial or subsequent products will tend to accumulate. One weakness of in situ remediation applications, using Fenton or other biochemical or chemical degradation methods, is a failure to monitor potentially harmful degradation products. 

The scope of this review is centered around permeable reactive barriers (PRBs) of ZVMs. Among the ZVMs used in remediation applications, iron metal (ZVI or Fe°) is by far the most important. PRBs of ZVI (sometimes designated FePRBs) are the technology known colloquially as iron walls. However, as illustrated in Fig. 1, not all PRBs are made from ZVMs and not all remediation applications of ZVMs are PRBs. 

Figure 1 Venn diagram showing the relationship between various types of PRBs and various remediation applications of ZVMs. The intersection of these two categories represents PRBs with ZVI as the reactive medium (i.e., FePRBs or iron walls ). 

The rapid increase in interest and knowledge associated with remediation applications of ZVMs and PRBs has led to a number of reviews on these subjects. To date, these include Refs. 2, 3, 18, and 42-53. In general, these reviews do not attempt to provide comprehensive coverage of the primary literature in this field, as it has already become too vast. Fortunately, most of the primary literature is included in several databases that are available on the World Wide Web. These databases can be found at http //cgr.ese. ogi.edu/ironrefs and http //www.rtdf.org. 

Although the majority of interest in remediation applications of corrodable metals revolves around Fe°, other possibilities have been investigated, including magnesium, tin, and zinc. The bulk of this work has used Zn° as a model system for comparison with Fe° (e.g., Refs. 95, 96, 125, and 126), but a few studies have surveyed a range of metals as possible alternatives to Fe° in environmental applications other than PRBs (e.g., Refs. 127 and 128). 

Shoemaker SH, Greiner JF, Gillham RW. Permeable reactive barriers. In Bodocsi A, Ryan ME, Rumer RR, eds. Barrier Containment Technologies for Environmental Remediation Applications (Final Report of the International Containment Technology Workshop, Baltimore, MD, 29-31 August 1995). New York Wiley, 1995 301-353. 

Daylight Photocatalysis by Carbon-Modified Titanium Dioxide. Titanium tetrachloride precursor hydrolyzed with nitrogen bases to yield (surprisingly) C-doped (instead of N-doped) Ti02. Study oriented toward environmental remediation applicability. 309... 

UV oxidation of organic water pollutants in the presence of hydrogen peroxide, ozone or both with powerful medium-pressure mercury lamps is performed on industrial scales (Gottschalk et al., 2000). The synergistic combination of ozone and UV is especially suited for water sanitation, i.e. treatment of swimming pool and spa water (Rice, 1997). Many full-scale remediation applications of photo-initiated AOPs using hydrogen peroxide or ozone are already in operation (Chem-viron Carbon, 1997, Freeman and Harris, 1995). 

Polyurethane coatings can be used for remedial applications in sewers and effluent-treatment plants, but they are suitable for milder conditions only. Two-pack polyurethane coatings are employed in this case. However, difficulties may be encountered during application if the system is sensitive to surface moisture. Polyurethane coatings in such applications need several coats to attain the necessary film thickness. 

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