Remediation options

TCDD). The majority of these samples have been collected and analyzed at an average cost of 700 per sample. This includes per diem, labor, equipment, expendable supplies, transportation, and 400 per analysis by contract laboratories. An evaluation of this data has suggested that field sampling and sample handling methods have a significant impact upon the precision and accuracy of the resulting data which, in turn, impact the cost and feasibility of various remedial options. 

Bioremediation systems in operation today rely on microorganisms indigenous to contaminated sites. The two main approaches, based on the actions of native microbial communities, are biostimulation and intrinsic bioremediation. In biostimulation, the activity of native microbes is encouraged, creating (in situ or ex situ) the optimum environmental conditions and supplying nutrients and other chemicals essential for their metabolism. The vast majority of bioremediation projects are based on this biostimulation approach. Intrinsic bioremediation is a remedial option that can be applied when there is strong evidence that biodegradation will occur naturally over time without any external stimulation i.e., a capable microbial community exists at the site, the required nutrients are available, and the environmental conditions are favorable. An additional prerequisite is that the naturally... 

Bioremediation is generally recognized as being less costly than other remedial options (e.g., pump-and-treat or chemical oxidation). 

NWRI, Evaluation of MTBE Remediation Options, National Water Research Institute. Available at www.nwri-sa.org, April 2004. 

Confirmation of certain conditions usually needs to be demonstrated for natural attenuation to be deemed acceptable as a remedial option. This demonstration may involve showing the contaminant plume to be stable and contained, shrinking, or to be intrinsically remediated at the same rate as its spreading (Figure 10.11). When the plume is essentially being remediated at the same rate that it is spreading, dynamic equilibrium conditions exist. 

Certain basic chemical reactions can sometimes be used to remediate organic chemical contaminants in the unsaturated zone. Introduction of reacting chemicals to alter the Eh (oxidation state/electron availability), the pH (hydrogen ion availability), or a contaminant to an immobile state occasionally presents a viable remedial option. This procedure can be rather expensive in dealing with organic chemicals, and typically is only used in specific situations. 

With only data from three monitor wells, the radius of influence was intuitively determined to be 25 ft. A water column vacuum of 0.06 in. was only slightly detectable. Results of calculations based on this value was considered satisfactory to determine if SVE was a viable remediation option. 

Evaluation the total project costs of each remediation option. 

At many sites, the investigation phase is performed in two tasks (Phase 1 and Phase 2). Phase 1 focuses on the large picture, a definition of overall site conditions. Data developed are used to assess potential risks and identify potential remedial options. Phase 2 work fills in data gaps and defines the level of detail necessary to establish site-specific remediation goals and to evaluate probable remediation procedures or to indicate the need for pilot cleanup studies. 

Information about construction materials used in the system may be contained within the plant records and can be useful in evaluating the fate and transport of a particular chemical contaminant through a system. For example, a particular contaminant may adsorb to the pipe material used in a utility s distribution system, and this type of information would be critical in evaluating remediation options following a chemical contamination incident. 

The average net cost for this technology is 30 to 45 per ton of soil treated. As shown in the following table, the net cost per unit volume is reduced by subtracting the recovered value of the reusable product. The following table provides a comparison between asphalt-stabilized base/engineered backfill and other remediation options and disposal (D16903T, p. 4). 

TABLE 1 Estimated Cost of Comparable Remediation Options... 

A site-specific, cost-benefit analysis is required to determine if an active remediation system or MNA would be the most effective remediation option (D11322U, p. 8). In 1999, the U.S. Army prepared an analysis of the cost of MNA, in situ bioremediation, and pump-and-treat systems for the treatment of explosives-contaminated groundwater at the Louisiana Army Ammunition Plant in Min den, Louisiana (D22026Y). This comparison is summarized in Table 1. 

At a U.S. Air Force site in south central California, the cost for implementation of MNA was estimated to be 4 million. The least costly alternative remedial option (in situ air sparging/soil... 

Areas where there are currently few remediation options but where bioremediation may provide an option include oiled marshes, mangroves, and coral reefs. Bioremediation also offers options for dealing with oiled material, such as seaweed, that gets stranded oil shorelines composting has been shown lo be effective. 

Smith. SJ. (2005) Naturally Occurring Arsenic in Ground Water, Norman, Oklahoma, 2004, and Remediation Options for Produced Water, U.S. Geological Survey Fact Sheet 2005-3111. 

Smith, L.A., Means, J.L., Chen, A. et al. (1995) Remedial Options for Metals-Contaminated Sites, CRC Lewis Publishers, Boca Raton, FL. 

One particularly vexing problem for waste management professionals is that of mixed wastes (radioactive plus RCRA and/or TSCA waste) disposal. Caught between conflicting regulatory jurisdictions and remediation options, which frequently prove to be mutually exclusive, mixed waste streams and matrices contaminated with two or more types of contaminant represent a... 

Remediation options for the treatment of electroplating and leather tanning effluent containing chromium -A review. Miner. Proc. Extractive Metall. Rev., 2, 99-130. 

Natural attenuation encompasses processes that lead to reduction of the mass, toxicity, mobility, or volume of contaminants without human intervention. The US EPA has recently published guidelines for the use of MNA for a variety of contaminated sites (US EPA, 1997). For inorganic constiments, the most potentially important processes include dispersion and immobilization (reversible and irreversible sorption, co-precipi-tation, and precipitation) (Brady et al, 1998). Studies of remediation options at UMTRA sites (Jove-Colon et al, 2001) and the Hanford Site (Kelley et al, 2002) have addressed the viability of adopting an MNA approach for uranium and strontium, respectively. As discussed below, different approaches are required to establish the viabihty of MNA for these radioelements. 

Kelley M., Mafifit L., McClellan Y., Siegel M. D., and Williams C. V. (2002) Hanford 100-N area remediation options evaluation summary report. Sandia National Laboratories. 

Natural attenuation by itself, however, often is not sufficient to achieve a desired extent or rate of contaminant removal from an aquifer. In these instances, one remedial option may be to enhance the natural rate of biodegradation of pollutant chemicals in the aquifer. This strategy, called in situ bioremediation, is considered to be one of the most attractive remedial techniques from a cost perspective, because many of the high costs associated with pumping and treating groundwater or excavating contaminated aquifer material are avoided. Furthermore, the potential exposure of cleanup workers to pollutant chemicals is reduced if many of the contaminants are mineralized while still in the aquifer. 

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