Research on evaluation and optimization of soil and groundwater remediation technology

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When soil and groundwater remediation is carried out in the contaminated site, the rate of removal of contaminants falls with progress of time. Therefore, using single remediation technology, the effect of removal does not go up although cost increases. In order to clean up the contaminated soil and groundwater efficiently, it is necessary to select and combine the suitable technologies. For that purpose, it is important to understand the migration of contaminants in subsurface. The purpose of this research is to clarify the procedure to clean up the contaminated soil and groundwater efficiently and economically based on the characteristics of migration of contaminants in subsurface. It focuses on volatile organic compounds and nitrate nitrogen as contaminants this time.In 1999 and 2000, we classified and arranged the existing soil and groundwater remediation technologies and evaluated the in situ air sparging through the field trial. In situ air sparging attracts attention as technology which cleans up soil and groundwater contaminated with the volatile organic compounds. In addition, we investigated the groundwater contamination with nitrate nitrogen near tea plantation area. In 2001, the optimal employment method of in situ air sparging was examined based on the field trial and laboratory experiment. On the other hand, it was cleared that the reduction in fertilizer application had great influenced on the decrease of the concentration of nitrate nitrogen in groundwater and the reactive barrier is effective to decompose and remove the nitrate nitrogen in groundwater. As a result, the reactive barrier coupled with the reduction of fertilizer application is the most effective remediation technology for groundwater contamination with nitrate nitrogen at present.