Contaminants decontamination applications

The triplate line is suitable for those soil decontamination applications where the contaminants have penetrated more than three feet below the surface and for contaminants that require treatment temperatures in excess of 130° to 150°C,... 

The view at Cadmium changed with time starting from a valuable resource and ending up as a toxic element with a limited number of applications not substituted by alternative products. The decontamination of the technosphere works to a certain extent. Due to the character of Cd as trace contamination of phosphate fertilizers and of Zn ores and fossil fuels, there is no final solution for the environmental contamination. Due to the restrictions issued in many countries, there is reason to fear that Cd could end up in unknown material streams. From an analysis of the refining of Zn ores in 2002, it has been concluded that about one quarter of Cd generated as by-product ( 7,000-8,000 Mg) could not be found either in the products analyzed or in the emissions from the process [27]. 

Chemical remediation refers to the application of various minerals or chemicals to adsorb, bind, precipitate or co-precipitate trace elements and heavy metals in soils and waters thereby reducing their bioavailability, toxicity, and mobility. In situ immobilization refers to the treatment of contaminants in place without having to excavate the soils or waste, often resulting in substantial cost savings. However, in situ immobilization or extraction by these physicochemical techniques can be expensive and are often only appropriate for small areas where rapid and complete decontamination is required. 

Cleaning is a form of maintenance which is particularly relevant where a piece of equipment is used repeatedly, but is also applicable to decontamination of equipment after use in dirty environments. The purpose of cleaning is to ensure that when the piece of equipment is used for an application or measurement, the risk of contamination from previous samples, chemicals, standards or the laboratory environment will be minimized. In the majority of cases, the process of cleaning introduces new chemicals to whatever is being cleaned. After cleaning, the equipment must be well rinsed to remove all traces of the cleaning chemicals, and then dried. 

Other manufacturing procedures requiring validation include cleaning, decontamination and sanitation (CDS) procedures developed for specific items of equipment/processing areas. Of particular importance is the ability of such procedures to remove bioburden. This may be assessed by monitoring levels of microbial contamination before and after application of CDS protocols to the equipment item in question. 

This area of recombinant DNA technology also has application in the degradation of solid waste materials In waste water recovery, in leaching minerals from ore-containing rock, in improved oil recovery, and in the decontamination of chemical waste dumps through the engineering of microorganisms that can destroy specific toxic contaminants. 

Decontaminating a site where chemical agents have been applied is its own unique challenge. At a 1998 NATO conference in Bucharest, military decontamination was discussed and examined. Most of the military applications of decontamination were primarily for the equipment and materials, and it did not, at that time, consider any civilian reoccupation of the contaminated battle sites. I had the opportunity to learn some other interesting things about decontamination activities. 

An application well-suited for IMS is the decommissioning and cleanup of sites where extensive manufacturing of explosives has taken place in the last century and where widespread contamination of soils and waters has occurred [74]. Decontamination of model metal scrap artificially contaminated with TNT and of decommissioned mortar rounds stiU containing explosives residue was followed by sampling surfaces with analysis by a portable mobility spectrometer. Mixed anaerobic microbial populations of bioslurries were employed in decontamination of scrap and the mortar rounds, and the IMS analyzer was seen as a sensitive field... 

Aqueous biphasic systems offer the potential for highly selective and low-cost separations. Aqueous biphasic extraction for soil decontamination is based on the selective partitioning of either dissolved solutes or ultrafine particulates between two immiscible aqueous phases. Both soluble and particulate uranium contaminants can be separated from soil using this technique. Aqueous biphasic extraction may also have application for separation of plutonium and thorium from soil or waste. 

Although HGMS has been used commercially on a large scale for more than 2 decades for some applications, it has been tested only at the bench-scale level for remediation of radioactive-contaminated soils and process streams. This technology is not currently commercially available for radioactive solid or liquid decontamination. 

The studies with sediment cultures indicate natural degradation potential for aquatic sediments exposed to anthropogenic CP pollution. However, in situ remediation rates for CP-contaminated sediments may be difficult to enhance. Possibilities involve nutrient and electron donor/acceptor amendments. Ex situ remediation could involve sediment dredging and application of methods developed for soil decontamination, such as slurry reactors and composting. 

Decontamination of soils using supercritical fluids is an attractive process compared to extraction with liquid solvents because no toxic residue is left in the remediated soil and, in contrast to thermal desorption, the soils are not burned. In particular, typical industrial wastes such as PAHs, PCBs, and fuels can be removed easily [7 to 21]. The main applications are in preparation for analytical purposes, where supercritical fluid extraction acts as a concentration step which is much faster and cheaper than solvent-extraction. The main parameters for successful extraction are the water content of the soil, the type of soil, and the contaminating substances, the available particle-size distribution, and the content of plant material, which can act as adsorbent material and therefore prolong the extraction time. For industrial regeneration, further the amount of soil to be treated has to taken into account, because there exists, so far, no possibility of continuous input and output of solid material for high pressure extraction plants, so that the process has to be run discontinuously. 

Another type of classification is outlier selection or contamination identification. As an example, in Fig. 4.23(b), the butter is the desired material and bacteria the contamination. An arbitrary threshold for this image would be 0.02, in which all pixels >0.02 are considered suspect, and hopefully, because this is a food product, decontamination procedures are pursued. In these two examples of classification, only arbitrary thresholds have been defined and, as such, confidence in these classifications is lacking. This confidence can be achieved through statistical methods. Although this chapter is not the appropriate place for an involved discussion of application of statistics toward data analysis, we will give one example often used in chemometric classification. 

One equipment blank collected after the sampling equipment has been cleaned the first time may often provide a satisfactory resolution of this issue. Once a decontamination procedure has been established and verified by an equipment blank analysis, the application of the same procedure should render the same level of cleanliness of the sampling equipment. If site conditions suddenly change with respect to the type of the sampled medium or the contaminant nature and suspected concentrations, another equipment blank sample may be collected to verify that the change in conditions did not reduce the effectiveness of the established decontamination procedure. 

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