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Soil Washing of PCBs-Contaminated Sites

Conventional soil and groundwater treatment methods are in many cases not very effective for PCBs, which are characterized by their low vapor pressures, high affinity to organic matter and low solubility in water. A research project has been started in Chile to develop a cost-effective and flexible remediation methodology for soils and groundwaters contaminated with PCBs, utilizing soil flushing and a subsequent PCBs-degradation process in reactive walls. Goal of this work was the identification and selection of cleaning solutions for flushing the PCBs present in contaminated soils. Synthetic soils were prepared and conditioned in terms of their organic matter content, with the addition of corn starch. Soil spiking was performed by adding 45 μL of a standard certificate of PCBs (PCB Mix 3) to 2.5 g of the prepared soils. Finally, pH was conditioned into three levels with HCl and NaOH. Selection and optimization of variables influencing the extraction of PCBs was performed using a multivariate method. Based on the obtained results, best conditions for extraction of PCBs were determined and it was concluded that it is possible to obtain a mixed, water-soluble solution which could be treated in a passive remediation system such as reactive walls in a subsequent remediation step.

The Chilean contaminated sites situation up to this date has not yet been explored, neither concerning the amount and location of the potential contaminated sites, nor concerning the associated risks upon human health and environment. Since 2003, the Chilean National Environmental Commission (CONAMA) has worked on the identification of priority Regions in which to perform the first evaluations of the dimensions of the soil pollution situation (Bezama 2008).
Landfill Technology/Site Remediation The Region of the Bio Bio, due to its social and economic importance at a national level, has been selected as one of these priority regions. The regional economy is based on strong exporting forest, fishing- and chemical industries. In terms of population and productivity, as well as from its culture and educational activities, this is the second most important region of Chile, after the Metropolitan Region of Santiago. The large number of industries present in the Region opens a broad range of potential sources of contamination for soil, surface- and groundwaters. These industrial activities generate different types of solid and liquid wastes and off-gases, many of which are not treated suitably.
One of the most important pollutants in this sense is the group of the polychlorinated biphenyls, also known as PCBs. Being the Region of the Bio Bio the second area in Chile where these substances where utilized the most, this work focuses on PCBs, by recognizing them as a major regional concern of pollution in the atmosphere, soils and aquifers. Conventional groundwater treatment methods, e.g. based on sorption onto granular activated carbon, are in many cases not very effective, in particular for PCBs, which are characterized by their low vapor pressures, high affinity to organic matter and low solubility in water.

Copyright:	© Lehrstuhl für Abfallverwertungstechnik und Abfallwirtschaft der Montanuniversität Leoben
Quelle:	Depotech 2010 (November 2010)
Seiten:	4
Preis:	€ 2,00
Autor:	Dr. Alberto Bezama Dr. Alberto Araneda Ricardo Barra Roberto Quiroz Químico Analista Alejandra Flores
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