Optimal Remediation Design of Unconfined Contaminated Aquifers Based on the Finite Element Method and a Modified Firefly Algorithm

Remediation of contaminated sites requires an optimal decision making system to develop remediation techniques in a cost-effective and efficient manner. A coupled simulation–optimization solution approach, based on the finite element method (FEM) and a modified firefly algorithm (MFA), is developed in this study for optimal contaminated groundwater remediation design. A new modified firefly optimization algorithm is proposed by modifying the traditional firefly algorithm in three ways: (i) adding memory, (ii) preventing premature convergence to local optima and thus accelerating the optimization process, and (iii) proposing a new updating formula. Modifications performed in the present study improved the applicability and efficiency of the traditional metaheuristic firefly optimization algorithm, and led the MFA to outperform both its predecessor and conventional optimization methods (e.g., genetic algorithm). A hypothetical, unconfined contaminated field is considered and remediated by considering pump and treat and flushing methods. Pumping rates are considered as design variables while the number of pumps and pump locations, as well as the pumping period, are initially assumed. The coupled simulation-optimization model (FEM-MFA) proposed in this study constitutes an effective way to determine an optimal remediation design for a contaminated aquifer. The results of the present investigation will contribute to improve groundwater management in contaminated aquifers.