Pump and Treat and Wait (Available only in the Geo/Environmental Special Issue)

by Richard A. Sullivan, P.E., (M.ASCE), Consultant; Orange County, CA,

Serial Information: Civil Engineering—ASCE, 1996, Vol. 66, Issue 11, Pg. 8A-12A

Document Type: Feature article


Pump and treat, a common ground-water cleanup technique, is slow to clean up deep contaminated aquifers. Adaptive intermittent pumping can increase the cleanup rate—and decrease costs—by accelerating decontamination of the microenvironment. With so many domestic and industrial requirements for water, communities today must keep water costs at a minimum. In southern California the cost of ground water is about one half the cost of surface water imported from northern California or the Colorado River but, unfortunately, leaks and spills of organic chemicals have caused deep, widespread ground-water contamination at many locations. The common remedial approach today is to extract contaminated ground water from deep wells more than 20 m below ground surface, and treat it at a surface treatment plant. This technique is known as pump and treat. The surface treatment plant of a pump-and-treat system is sized to handle a selected ground-water flow and to reduce contaminant levels to target levels. Disappointment with pump-and-treat performance results more often from the slow rate of contaminant removal from the ground water rather than from inefficient surface treatment. On the basis of microenvironmental behavior, ground-water cleanup can be hastened by substituting conventional constant pumping with an inexpensive technique of controlled intermittent pumping. Also, any approach that can reduce pumping time on a project will also reduce pump-and-treat operational costs. Other in-situ technologies, such as bioremediation and air sparging, are available for remediation of NAPLs contaminated ground water. However, pump and treat remains the preferred technology for remediating deep, widespread, contaminated ground water, and controlled intermittent pumping is a simple and inexpensive technique that may be applied to existing or new pump-and-treat systems to accelerate decontamination of the microenvironment and increase the rate of ground-water cleanup.

Subject Headings: Pumps

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