Demonstration of optimization techniques for groundwater plume remediation

We examined the potential use of standard optimization algorithms for the solution of aquifer remediation problems. Costs for the removal of dissolved or free-phase contaminants depend on aquifer properties, the chosen remediation technology, and operational parameters (such as number of wells drilled and pumping rates). A cost function must be formulated that may include actual costs and hypothetical penalty costs for incomplete cleanup; the total cost function is therefore a measure of the overall effectiveness and efficiency of the proposed remediation scenario. In this study, the cost function is minimized by automatically adjusting certain operational parameters. The impact of these operational parameters on remediation is evaluated using a state-of-the-art three-phase, three-component flow and transport simulator, which is linked to nonlinear optimization routines. The report demonstrates that methods developed for automatic model calibration are capable of minimizing arbitrary cost functions. Two illustrative examples are presented. While hypothetical, these examples demonstrate that remediation costs can be substantially lowered by combining simulation and optimization techniques. The second example on co-injection of air and steam also make evident the need for coupling optimization routines with an accurate state-of-the-art process simulator. Simplified models are likely to miss significant system behaviors such as increased downward mobilizationmore » due to recondensation of contaminants during steam flooding, which can be partly suppressed by the co-injection of air.« less