Systems Analysis of Pump-and-Treat Groundwater Remediation

Abstract

The design and operation of complex remediation projects can often benefit from an analysis from a systems perspective, that is one in which the various components of the system are viewed holistically, and a specific objective and associated constraints are articulated. This paper reports on such an analysis of a multiyear pump-and-treat scheme for removing light nonaqueous phase liquid from groundwater with subsequent treatment of the water for removal or destruction of the sum of benzene, toulene, ethylbenzene, and xylene concentrations, polynuclear aromatic hydrocarbon, carbon oxygen demand, particulate iron, and suspended solids prior to discharge. The treatment train consists of eight unit processes linked in series. The objective is to minimize total net present value of operating costs over the projected life of the treatment facility given constraints on permitted discharge limits, and the performance characteristics and requirements of the contaminant removal processes. Results indicate that the system is especially sensitive to flow rate, fixed costs of operation, and the projected quantity of oil to be recovered prior to disengagement, with the greatest cost penalty existing for underutilization of the treatment facility. Matching pumping rate with treatment capacity is seen to be the most important design factor in minimizing overall costs, however various options available to management to improve upon non-optimal conditions are discussed.