Optimal Groundwater Remediation by Pump and Treat Using FEM- and EGA-Based Simulation-Optimization Model

Groundwater contamination is one of the most serious environmental problems in many parts of the world. For remediation of dissolved phase contaminants in groundwater, a pump-and-treat method is found to be a successful remediation technique. Developing an efficient and robust design to solve groundwater pollution remediation problems using a pump-and-treat method is very important because of the large construction and operating costs involved. In this study, an attempt is made to develop a coupled simulation-optimization model based on the finite-element method (FEM) and an evolutionary approach of an elitist genetic algorithm (EGA) for the optimal design of groundwater remediation by pump and treat. The model couples an EGA, a global search technique, with FEM for coupled flow, and a solute transport model to optimize the pump and treat groundwater pollution problems. The simulation-optimization model is used to optimize the remediation of a large-field unconfined aquifer polluted with total dissolved solids (TDSs) to obtain optimal pumping rates. In the remediation design, it is assumed that the location and number of pumping wells are fixed and the pumping rates in the selected wells are optimized. Using the FEM-EGA model, the optimal pumping pattern for the fixed number of abstraction wells located at highly contaminated area is obtained to minimize the total lift costs of groundwater along with treatment cost. The study shows that an optimal pumping policy for large aquifer remediation using the pump-and-treat method can be established using the developed FEM-EGA model.