Location and Schedule Optimization of Soil Vapor Extraction System Design

Abstract

Soil vapor extraction is a cost-effective technique for removing volatile organic compounds (VOCs) immobilized in the unsaturated zone. The design of a soil vapor extraction system (SVES) requires that the number and location of extraction wells and the extraction schedule for each extraction well be determined. In this study, schedule optimization for selected active wells is embedded in location optimization to provide an equal basis for system comparison. A combinatorial two-change local search is employed in both optimizations, but with different user-defined properties to address their distinct problem characteristics. The results indicate that the proposed two-change local search is robust and produces reliable designs. Impacts of soil heterogeneity and initial guess of design are evaluated. A detailed analysis of optimization results indicates that extraction well locations dominate the efficiency of contaminant removal. To reduce additional computation, a screening test based on results at the early stage of schedule optimization is suggested to reject obviously inferior designs.