Contaminated sites site conditions

Sediment toxicity testing strategies are used to evaluate the potential toxicity of the sediment. The characteristics of the sediment, such as the water column or elutriate, pore water and bulk sediment, are evaluated using different testing regimes to tease out the impacts of various aspects of the complex sediment toxicity. Each of these aspects in concert with unknown contaminants or site conditions provides a weight of evidence for the overall impact of sediment toxicity on aquatic organisms. 

Depending on the contaminants, the site conditions, the level of cleanup required, and the types of plants, phytoremediation technology can be used for containment (phytoimmobilization and phytostabilization) or removal (phytoextraction and phy-tovolatiUzation) purposes (Padmavathiamma and Li, 2007). 

The CAP can serve as the technical framework for a Corrective Action program. The CAP provides a "menu" of activities or information requirements that may be necessary for each phase of the process. Site-specific conditions and the nature and extent of the contamination will determine which tasks will be necessary. The necessary tasks will be enforceable through permit conditions or by an administrative order or judicial action. The (TAP can serve as a flexible engineering guide for the regulatory community in implementing their own Corrective Action Program. 

Insulation is subjected to abuse onsite, in storage and often in transit. To ensure minimum wastage through breakage, contamination or deformation, select products which are resilient or robust enough to tolerate site conditions and malpractice. 

The refractory nature of some pollutants, notably, persistent polyhalogenated compounds, has raised problems of bioremediation of contaminated sites (e.g., sediments and dumping sites). There has been interest in the identification, or the production by genetic manipulation, of strains of microorganisms that can metabolically degrade recalcitrant molecules. For example, there are bacterial strains that can reductively dechlorinate PCBs under anaerobic conditions. 

Mixed cultures of organisms that were isolated from sediments contaminated with PCBs and polybrominated biphenyls (PBBs) were shown to debrominate PBBs under anaerobic conditions (Morris et al. 1992), and the dominant congener—2,2, 4,4, 5,5 (245-245)-hexabromobiphenyl—could be successively debrominated to 2,2 -dibromobiphenyl. However, in sediments from the most heavily contaminated site containing contaminants in addition to PBBs, very little debromination occurred and the recalcitrance was attributed to the toxicity of the other contaminants (Morris et al. 1993). 

This was previously used as a herbicide, and attention has been directed to its degradation in storage areas or where it has been spilled. A strain of Clostridium bifermentans KMR-1 (that is protected by a U.S. patent) was unable to use dinoseb as carbon or energy source. In the presence of a starch extract, however, a low level of transformation was observed, and the products could subsequently be mineralized by aerobic bacteria (Hammill and Crawford 1996). These observations have been extended to the remediation of soil slurries from a contaminated site by adding phosphate and starch waste that achieved anaerobic conditions, and inoculation with a culture from a pilot-scale... 

Field experiences have demonstrated that the successful application of in situ chemical oxidation requires the consideration of several factors through an integrated evaluation and design practice. Matching the oxidant and in situ delivery system to the contaminants of concern and the site conditions is the key to successful implementation of such techniques [1778]. 

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... 

Tetrachoroethylene (perchloroethylene, PCE) is the only chlorinated ethene that resists aerobic biodegradation. This compound can be dechlorinated to less- or nonchlorinated ethenes only under anaerobic conditions. This process, known as reductive dehalogenation, was initially thought to be a co-metabolic activity. Recently, however, it was shown that some bacteria species can use PCE as terminal electron acceptor in their basic metabolism i.e., they couple their growth with the reductive dechlorination of PCE.35 Reductive dehalogenation is a promising method for the remediation of PCE-contaminated sites, provided that the process is well controlled to prevent the buildup of even more toxic intermediates, such as the vinyl chloride, a proven carcinogen. 

There are a number of critical parameters to be considered for the application of in situ soil flushing, including the hydrogeological conditions of the contaminated site, the type and properties of contaminants, the properties of the additives, and the treatability of the flushing solution.76 80... 

Bioremediation also has its limitations. Some chemicals are not amenable to biodegradation, for instance, heavy metals, radionuclides, and some chlorinated compounds. In some cases, the microbial metabolism of the contaminants may produce toxic metabolites. Bioremediation is a scientifically intensive procedure that must be tailored to site-specific conditions, and usually requires treatability studies to be conducted on a small scale before the actual cleanup of a site.13 The treatability procedure is important, as it establishes the extent of degradation and evaluates the potential use of a selected microorganism for bioremediation. A precise estimate on vessel size or area involved, speed of reaction, and economics can therefore be determined at the laboratory stage. 

The manner in which phytoremediation can be applied to treat MTBE and other fuel oxygenates is highly variable, based on the site conditions, specific contaminants to be treated, cleanup goals, and other factors. Information relevant to the application of phytoremediation at sites contaminated with MTBE and other oxygenates is available in the literature.105-109... 

In both cases, the samples from contaminated sites were rinsed with a solvent to obtain an extract of contaminated transformer oil. The effects of biological degradation were investigated by using a commercial mixture of microorganisms and pure strain under aerobic and anaerobic condition. In the thermal method, a laboratory plasma system was used to decompose the contaminated transformer oil by a direct injection of the oil extract into the plasma system or by melting the extract samples with power plant fly ash in the plasma reactor. For the contaminated transformer oil both methods showed a destruction efficiency of 99.99% and the products of destruction were environmentally friendly. 

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