A Simulation-Optimization Model for "Air Sparging" and "Pump and Treat" Groundwater Remediation Technologies

Abstract

Using a new concept of sub-period, a simulation-optimization model for initial evaluation of air sparging (AS) and pump-and-treat (PAT) groundwater remediation technologies is presented in order to facilitate the study of aquifers contaminated with soluble volatile organic compounds. The new simulation and optimization process assumes a specific type of contaminant and a homogeneous soil texture. The simulation module connects two existing models (MODFLOW and MT3DMS) to Henry's Equation. Simulation is performed by dividing the simulation period into sub-periods and using Henry’s equation for each sub-period. An optimization module minimizes the cost of the remediation using an objective function subjected to quality and quantity constraints, and derived using a classic form of genetic algorithm. In addition to demonstrating how to solve a typical problem using the optimization module, we demonstrate field application of the simulation module for an aquifer near the Tehran Refinery, which is contaminated by methyl tertiary-butyl ether. One constraint for this problem is that installation of remediation equipment is prohibited in urban areas. Due to this constraint, AS wells must be positioned upward the urban area. Therefore, these wells act as a barrier that restricts contaminant flow downward into the city. The results of the simulation show the advantages of employing simultaneous remediation technologies.

Keywords: pump-and-treat, air sparging, simulation, optimization, remediation