Water soil, decontamination

Soil samples Water samples Decontamination solutions Existing ROPs were tested... 

Another very important green chemistry solvent is supercritical water (SCW) [14], Water under supercritical conditions is an extremely powerful oxidizing and cleansing agent that has been proven remarkably promising as a soil decontaminant by efficiently degrading persistent organic toxic wastes that are difficult to eliminate from polluted soils, and in the treatment of several types of industrial wastes such as textile and cellulose wastewater [2],... 

It is necessary to understand the behavior of soil-water and its mineral components (e.g., nutrients, con taminants) for the purpose of developing conceptual and/or mechanistic process models. Such models can be used to predict nutrient fate in soil-water or contamination-decontamination of soil-water and to develop soil-water remediation-decontamination technologies. To gain an understanding of the soil-water mineral components, their physical and chemical properties need to be known. 

Electroremediation using electrical current is the final purification method discussed in this chapter. Here, an array of anodes are placed in the soil opposite an array of cathodes. When electric potential is apphed the following processes occur electrolysis of water in the soil, dissolution of polluting ions, migration of ions under the influence of the apphed potential field, and reduction or pH based precipitation at the cathode [68,69]. This technique, also known as electroreclamation or electrochemical soil decontamination, does not require a membrane however, improved electroremediation has been reported when ion-exchange membranes were incorporated into the system [70]. The function of the membrane is to retain OH ions produced at the cathode. Migration of these OH ions is prevented to avoid precipitation of the heavy metal ions in the sod. 

Ozone has been applied successfully and extensively for water and wastewater treatment. Ozone also has been used as a safe and effective antimicrobial agent in many food applications. Other applications of ozone include soil decontamination, polymer surface modification, and bleaching paper pulps. It is recognized that for water treatment, the combined use of ozone with either biological treatment, or heterogenous catalysts, or UV and/or H2O2 makes the whole process more efficient. 

Surfactants and microemulsion systems can be used for ex situ treatment of contaminated soil or in situ soil decontamination. In situ remediation is usually preferred if excavation of the contaminated soil is not possible or expensive, e.g. beneath buildings or for contaminations at great depth. Often bioremediation or natural attenuation is used for decontamination. In most cases, these techniques only permit the effective degradation of contaminants in the plume formed by dissolved pollutants which may be very large. However, for the remediation of a contaminated site, it is also necessary to remove the source where the pollutants maybe adsorbed in large quantities or may be present as solid or liquid phases. The latter are called NAPL (non-aqueous phase liquids) and a differentiation is made between LNAPL (light non-aqueous phase liquids) with a lower density than water and DNAPL (dense non-aqueous phase liquids) with a higher density than water (see Fig. 10.1). 

The suitability of supercritical water for decontamination of soil material can be proved by several semibatch extraction experiments [6]. At 380 °C and 250 bar, the extraction results of hydrocarbons from soil material are excellent, even if it has been weathered for over 20 years. This kind of soil material, often the highly contaminated effluent of a soil washing process, can not be further decontaminated by biological treatment because the hydrocarbon contamination has been exposed to microorganisms throughout the weathering... 

Soil decontamination has developed from the small-scale superheated water extraction of PAHs, pesticides and polychlorinated biphenyls (PCBs). This has been carried out on a pilot scale and at 250 C almost complete soil clean-up is achieved in... 

In addition, attempts have also been made in the recent past, to employ fly ash for some specific applications (1) treatment of polluted water, (2) decontamination of less fertile soils for agriculture, (3) removal of heavy metal ions from aqueous... 

Hydroxy-sodalite, Sodalite, Na-X and Philipsite are also established for uptake of Ni, Cd, Cu, Cs, Pb, Hg and Sr cations from contaminated water, soil and gas as adsorbent. In short, zeolites can act as detoxing agent to decontaminate the environment and hence facilitate its conservation. 

TAetection of the highly potent impurity, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), necessitated an environmental assessment of the impact of this contaminate. Information was rapidly needed on movement, persistence, and plant uptake to determine whether low concentrations reaching plants, soils, and water posed any threat to man and his environment. Because of the extreme toxicity of TCDD, utmost precautions were taken to reduce or minimize the risk of exposure to laboratory personnel. Synthesis of uniformly labeled C-TCDD by Muelder and Shadoff (I) greatly facilitated TCDD detection in soil and plant experiments. For unlabeled experiments it seemed wise to use only small quantities of diluted solutions in situations where decontamination was feasible and to rely on the sensitivity afforded by electron capture gas chromatography... 

The facility would use a dry scrubber system for emission control, which would eliminate the need for wastewater treatment. Any water from emission control and from decontamination procedures would be treated in the on-site groundwater treatment system. The residual soil and collected ash is assumed to be nonhazardous and can be disposed of in a solid waste disposal facility in compliance with subtitle D of RCRA. In the event that they cannot be delisted due to the presence of metals, the residuals will be managed as part of the closure of Area 2 shown in Figure 16.21 (lead-contaminated soil). 

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. 

Berthet, B., C. Amiard-Triquet, and R. Martoja. 1990. Effets chimiques et histologiques de la decontamination de l huitre Crassostrea gigas Thurberg prealablement exposee a 1 argent. Water Air Soil Pollut. 50 355-369. 

Wester, R. C. et al., In vivo and in vitro percutaneous absorption and skin decontamination of arsenic from water and soil, Fund. Appl. Toxicol., 20, 336, 1993. 

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... 

Decontamination techniqnes and processes, involving chemical, mechanical, and thermal methods, have been developed for the removal of hazardons materials from systems, strnctnres, and components (SSCs), to soil and water. The primary objectives of decontamination are to rednce exposnre, rednce the potential release of hazardons materials to clean areas, and enable decontaminated eqnipment and materials to be salvaged and rensed. For J AC ADS closnre, a key objective will be to meet the end-state criteria for the land and the SSCs that are left in place. 

The technology is commercially available for the decontamination of soil and porous concrete but is still being developed for the decontamination of water. 

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