Treatment of polluted soils

The monitoring of a biological treatment carried out in laboratory has been done for two PAH-contaminated soils, soil 1 mainly polluted by heavy PAHs, and soil 2 mainly contaminated by light PAHs. UV spectra according to treatment time are given in Fig. 12, 

No significant difference exists between HPLC measurement and UV estimation. The yield of decontamination is roughly of 75% for soil 1, after 110 days of treatment. For soil 2, it aims for only 20% after 130 days of treatment. These results are in agreement with those of the literature. Heavy PAHs are less sensitive to microbiological degradation during biological treatment, which takes place into the soil under natural conditions [4]. 

In conclusion, PAH and soil evolution indexes are simple and rapid tools for the characterisation of PAH-contaminated soils in terms of level and repartition of pollution and for the prediction of their potential biotreatability. From an environmental point of view, they permit pointing out sensitive zones and defining priorities in terms of decontamination. 

For field analysis, a kit, using a field UV spectrophotometer, has been developed and gives the two index values directly [5], 

Hydrocarbon concentration has been measured by IR spectrophotometry, after a carbon tetrachloride extraction step [6]. The UV estimation (256 nm absorptiometry) has been tested compared to IR data for the 15 studied polluted soils (Fig. 15). The absorbance ratio A228 nm 256 nm can reflect, during a biological treatment, the composting degree of soils contaminated by petroleum hydrocarbons, as for PAH pollution. Quantitative data are collected in Table 9. 

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The point of zero charge of oxides. 14. Electrochemical treatment of polluted soils. 

Characterize the physical and chemical principles of electrokinetic treatment of polluted soils. Give examples. 

Many conventional soil vashing processes are based on the principle that pollutants adsorb onto very small particles fine fractions of the soil such as silt, clay and humic matter ivhich tend to be attached to coarser sand and gravel particles. These larger particles make up the majority of the soil content. A primary aim in soil washing is therefore to dislodge and separate these fine components from the bulk soil. If the pollutant materials can be detached from the bulk, possibly together with some other surface contamination, a concentrated volume of polluted soil can be produced. This can then be treated or disposed of and a large volume of residual soil which requires relatively little treatment and can be returned to the site as back fill. 

Ex situ remediation techniques require the excavation of polluted soil for subsequent treatment or disposal. Ex situ treatments can be broadly classified into extraction versus stabilization treatments that will render the polluted soil less harmful and suitable for deposition in a landfill or backfill. Soil washing is an example of an ex situ extraction technique in which the treated soil can either be returned to its original site (backfill) or be land filled, depending on the success of the cleanup stage. Asphalt incorporation, thermal treatment, and encapsulation are ex situ stabilization techniques in which the metal(loid)-contaminated soil is either incorporated (e.g., asphalt) or contained (encapsulation) by secondary materials that are subsequently land filled. Thermal treatments involve the incineration of the metal(loid)-polluted soil and the conversion of the pollutants into their metallic (zero-valent) states. In the following section we present an overview of the various technologies based on their mechanism of action. 

Kahn, L, Para, D., Karelson, M. and Maran, U. (2005) QSPR treatment of the soil sorption coefficients of organic pollutants./. Chem. Inf. Model., 45,94—105. 

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). 

Christensen TH, Bjerg PL, Kjeldsen P. (2001). Natural attenuation as an approach to remediation of groundwater pollution at landfills. In Treatment of Contaminated Soil... 

Bioreactors are vessels of various configurations and arrangements (Admassu and Korus 1996) that contain degradative microbes and possibly other catalytic agents that function cooperatively with microbial systems. They are a common means of ex situ treatment of contaminated soil that has been excavated from a polluted site or groundwater that has been pumped from a polluted aquifer. 

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... 

Treatment of dairy waste streams from CIP and other operations is not a significant portion of plant energy use, but waste from the dairy industry can contribute to the pollution of water and soil (Kosseva, 2009). 

Martin, I. and Bardos, P., A Review of Full Scale Treatment Technologies for the remediation of Contaminated Soil, Report for the Royal Commission on Environmental Pollution, EPP Publications, UK, 1996. 

Paulsson, K. and K. Lundbergh. 1991. Treatment of mercury contaminated fish by selenium addition. Water Air Soil Pollut. 56 833-841. 

A broader and more detailed evaluation can be done by performing a Life Cycle Analysis (LCA). The central idea of a LCA is that the environmental effects during the entire life cycle of a process are quantified. These environmental effects are caused by the use of fossil fuels for heating and production of electricity, the use of non-renewable raw materials for the production of materials and chemicals, and the emissions of pollutants to air, water and soil. These environmental effects can be subdivided further in various levels of detail. The five major effects mentioned are derived from the more general effects considered in the framework of the LCA. Based on the environmental sustainability of each of the complete treatment scenarios considered as technically feasible, a ranking according environmental... 

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