esm 223 09 Pump and treat summary doc

esm 223 09 Pump and treat summary doc - Suthersan S.S"PUMP...

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Suthersan , S . S . PUMP AND TREAT SYSTEMS Remediation engineering : design concepts Ed. Suthan S. Suthersan Boca Raton: CRC Press LLC, 1999 c ± 1999 by CRC Press LLC
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© 1999 by CRC Press LLC PUMP AND TREAT SYSTEMS 11.1 INTRODUCTION Until the very recent past, almost all groundwater cleanup systems installed involved variations of the technology called “pump and treat.” Between 1982 and 1992, 73% of the cleanup agreements at Superfund sites where groundwater is contaminated specified the use of pump and treat technology. 1,2 At most of these sites, the cleanup goal is to restore the aquifer so that the water extracted from it will be suitable for drinking without further treatment. Yet, within the past few years, the experience in the industry indicates that drinking water standards may be essentially impossible to achieve in a reasonable time frame at certain sites. Pump and treat systems operate by pumping groundwater to the surface, removing the contaminants, and then either recharging the treated water back into the ground or discharging it to a surface water body or municipal sewage plant. Once groundwater has been pumped to the surface, contaminants can be removed to very low levels with established technologies used to treat drinking water and wastewater. However, pumping the contaminated water from the aquifer does not guarantee that all of the contaminants have been removed from beneath the site. Contaminant removal is limited by the behavior of contaminants in the subsurface (a function of contaminant characteristics), site geology and hydrogeology, and extraction system design. The experience accumulated in the industry indicates that the performance of pump and treat systems can be depicted as in Figure 11.1 . The theoretical removal curve shows the number of pore volumes of groundwater that must be pumped to remove the contamination, assuming all of it dissolves readily. The removal with tailing curve shows the number of aquifer volumes of groundwater that must be pumped to remove the contamination when significant undissolved sources of contamination are present. Examples of such sources are adsorbed phase contamination in the saturated zone and capillary fringe, nonaqueous phase liquids (NAPLs) floating on the water table or present below the water table. Pump and treat systems can be designed to meet two very different objectives: (1) containment, to prevent the contamination from spreading, and (2) restoration, to remove the contaminant mass. In pump and treat systems designed for containment, the extraction rate is generally established as the minimum rate sufficient to prevent enlargement of the contam- inated zone. In systems designed for restoration, the pumping rate is generally established to be much larger than that required for containment so that clean water will flush through the contaminated zone at an expedited rate. Because of their reduced pumping requirements, pump and treat systems designed for containment are much less costly to operate than systems designed for restoration. In all other fundamental ways, the two types of systems are identical.
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This note was uploaded on 08/06/2008 for the course ESM 235 taught by Professor Dunne during the Winter '08 term at UCSB.

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esm 223 09 Pump and treat summary doc - Suthersan S.S"PUMP...

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