Multi-objective optimization for optimal groundwater remediation design and management systems

Abstract

Groundwater remediation and management systems generally encompass multiple often conflicting objectives. This paper proposes a multi-objective groundwater remediation and management methodology based on pump-and-treat technology to determine optimal strategies for cleaning up the affected portion of a contaminated aquifer and at the same time removal of sufficient quantity of clean water from the unaffected portion of the same aquifer for supply to end users for drinking purposes. Two objective functions are incorporated into the proposed optimization model: (i) minimization of the total remediation cost, and (ii) maximization of clean water extraction rate. Pumping rates and well locations are the decision variables of the optimization model with imposed constraints on hydraulic heads and contaminant concentrations at several specified locations. This work employs a new and very efficient technique for interfacing C with FORTRAN programs to couple NSGA-II coded in C with FORTRAN programs MODFLOW and MT3DMS and use in this methodology to obtain a tradeoff between remediation cost and clean water extraction rate. The Pareto front thus obtained consists of several optimal solutions to the problem and is used to analyze the variation of remediation cost with the extraction rate of uncontaminated water. Sensitivity analyses on some important input parameters have been carried out to account for the effects of variability of these parameters on the model result. Main contributions of this paper are: (i) use of a novel technique of linking C programs with FORTRAN programs, and (ii) revelation and exploitation of insightful features of multi-objective optimization algorithms applicable to pump-and-treat groundwater remediation problems. Results are satisfactory and show great promise for wide applicability in the field of groundwater remediation.