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Soil vapor extraction in cold climate regions
2002 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Soil Vapor Extraction, SVE, has proven to be a viable method for reducing volatile organic compounds, VOC, from soils that have been impacted by contamination. The operation of SVE systems has been fairly well documented, however the use of SVE systems in cold environments, such as Alaska, has not been adequately investigated to date. During the last decades the system has expanded to be used frequently in less temperate regions. Problems in the process have occurred associated with the colder climate. SVE involves pulling air through the soil to vaporize and carry off the contaminants. Blowers connected to wells induce the airflow and the extracted contaminated vapors are treated above ground. This thesis examines the use of SVE systems in cold environments with the main purpose of testing the hypothesis stated below. “Soil Vapor Extraction system operations in cold regions can be optimized with respect to mass removal cost.” Problems associated with SVE system operations in cold climate can be divided into two categories, maintenance and operational issues and decreasing removal rates. The first category involves problems with freezing of subsurface pipes, but also with temperature effects on the above ground equipment. The second category entails contaminant related matters. During winter low temperatures penetrates down through the ground causing subsurface cooling. The decreasing temperature affects the contaminant. The volatility is temperature dependent and decrease with decreasing temperature making it more difficult to remove the contamination. The discussed problems are all related to costs of running the system. Winter climate causes higher costs due to increased maintenance and equipment protections. Decreasing remediation rates because of the enhanced resistance of volatilization also affects the costs. This could result in an increase of operational costs when the remediation level decreases. Several SVE sites around interior Alaska have been studied to evaluate the impacts of temperature and climate. These investigations have confirmed most of the above mentioned problems. What was found difficult to prove was the decrease in removal rates in cold soils, as a number of parameters affected the operations making the data unreliable. Therefore were an analytical model used to show how the removal rates theoretically varies with seasonally fluctuating temperatures. Different methods for solving the problems or decrease the consequences is discussed in this report. Two solutions suggested are the use of a dynamic or a passive SVE operation during certain periods. A dynamic system is turned on and off during periods allowing VOC to accumulate in the pores by diffusion. As the process is reestablished a higher concentration can be removed. Passive SVE extracts contaminants due to atmospheric pressure changes. No mechanical pumping is needed thus minimizing costs for operation and maintenance of the system. The problems involving operation of SVE system in cold climate do need to be further investigated. Some questions have been answered in this report but there are still problems that have to be explored more thoroughly.

Place, publisher, year, edition, pages
Keyword [en]
Technology, soil vapor extraction, air sparging, remediation, volatile, organic compound, voc, cold climates, passive, barometric, pumping, vakuum extraktion, miljögeoteknik, kallt klimat
Keyword [sv]
URN: urn:nbn:se:ltu:diva-52937ISRN: LTU-EX--02/203--SELocal ID: a027ef28-1f51-4317-90ee-75eb68144b96OAI: diva2:1026310
Subject / course
Student thesis, at least 30 credits
Educational program
Civil Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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