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unilogo Universität Stuttgart
Institute of Hydraulic Engineering

Research: VEGAS - Research Facility for Subsurface Remediation

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Pore to Core Scale-up studies of Transport of Organic Pollutants with Natural Attenuation
Project manager:Prof. Dr.-Ing. Andreas Dahmke
Research assistants:Prof. Dr. Markus Ebert
Duration:1.11.1997 - 31.10.2000
Funding:European Commission

This project is part of the research area:
Natural Attenuation


Natural attenuation is a process of fundamental importance for soil remediation in many cases of prime importance. This is especially so in the case of sites where the plume of organic liquid pollutants extends to large dcpths under and around the site, because in such cases intrusive technologies (such as excavation/leaching, flooding processes, etc.) are not viable from the economic, and perhaps even the technical, standpoint. Natural Attenuation is the collective term used to denote a complex network of physical (spreading of the plume through 3-phase flow in the soil, volatilization, vapor and biogas emission through the soil to the air, solution, adsorption, etc.), chemical (oxidation, chemisorption, etc.), and biochemical (intrinsic biodegradation by soil microorganisms) processes that curb the growth, and eventually cause the decline of the plume of pollutants. At present we have very little qualitative knowledge of the actual mechanisms and interdependence of these processes, and virtually no quantitative, true-to-mechanism, models. Consequently, toxicological and ecotoxicological risk assessment is usually done without proper accounting for natural attenuation, an omission that can lead to seriously erroneous estimates. Furthermore, luck of adcquate understanding of the key mechanisms is a severe hindrance in devising melhods to stimulate natural attenuation and to make it more effective in dealing with hard-to-biodegrade chemicals, such as chlorinated aromatics, etc. The overall objective of the proposed project is threefold: (a) to develop quantitative understanding of all the aforementioned mechanisms and their interactions, by performing a series of carefully-controlled and well-characterized laboratory experiments at two different scales, namely pore-scale and core-scale (comparable degrees of precision of control and thoroughness of characterization would not be possible in the field, at reasonable cost); (b) to develop a self-consistent and reliable theoretical model of natural attenuation that incorporates the above mechanisms in appropriate form, through rigorous scaling up from pore-scale to core-scale to macro-scale; (c) to develop a practical methodology for lhe determination (calculation or measurement) of all the relevant macroscopic mass-transfer and rate coefficients. Successful completion of the project will produce a powerful tool for better practice and further improvements in soil remediation through natural attenuation, and for reliable risk assessment. An abandoned tar factory in a EU country will be used as generic site for the project, in order to ensure the practical relevance and applicability of the results. The partners of the consortium have been carefully chosen so that their respective areas of expertise and their technical capabilities are complementary, mutually-supportive, and match the objectives and tasks of the project in an excellent way.

Further information is available at http://cordis.europa.eu/data/PROJ_ENV/ACTIONeqDndSESSIONeq26796200595ndDOCeq13ndTBLeqEN_PROJ.htm