Optimal groundwater remediation design of a pump and treat system considering clean-up time

This study presents the optimal groundwater remediation design using a pump and treat method by optimizing the clean-up time, which is a critical factor to determine an optimal remediation design in practical applications. In this study, a simulation-optimization approach was used to determine an optimal remediation design. For a simulation-optimization approach, MOD-FLOW and MT3D models were used for simulating groundwater flow and mass transport, and the genetic algorithm (GA) was applied for optimizing the number and locations of pumping wells for applications of the pump and treat methods. The optimal remediation design was determined by using two objective functions: minimizing the total pumping rate and total pumping volume with optimizing clean-up time, respectively. Results revealed that major pumping wells were mainly located on the centerline at down-gradient of regional flow regardless of the objective functions. However, the number and locations of optimal pumping wells varied with time and unnecessarily excessive pumping occurred when clean-up time was treated as a fixed constraint. Therefore, it is concluded that clean-up time must be optimized by considering it as a decision variable in order to design the optimal pump and treat system. The sensitivity analysis showed that there is an appropriate range of hydraulic conductivity for the practical and effective pump and., treat remediation design. However, this sensitivity analysis is very limited and model-specific. Thus, the sensitivity of a remediation design to other hydraulic parameters, boundary and initial conditions, and contaminant concentrations should be further investigated.