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Hydraulic Fracturing to Improve Nutrient and Oxygen Delivery for in Situ Bioreclamation
Citation:
DAVIS-HOOVER, W. J., L. C. Murdoch, S. J. Vesper, H. R. Pahren, O. L. Sprockel, C. L. Chang, A. Hussain, AND W. A. Ritschel. Hydraulic Fracturing to Improve Nutrient and Oxygen Delivery for in Situ Bioreclamation. In Proceedings, In Situ and On-Site Bioreclamation, San Diego, CA, March 19 - 21, 1991.Butterworth Heinemann Publishers, Burlington, MA, 67-82, (1991).
Impact/Purpose:
To investigate many possibilities to develop solid materials that could facilitate in situ bioremediation with the intention of delivering them by injection into hydraulic fractures.
Description:
The in situ delivery of nutrients and oxygen in soil is a serious problem in implementing in situ biodegradation. Current technology requires ideal site conditions to provide the remediating organisms with the nutrients and oxygen required for their metabolism, but the shortage of oxygen in many subsurface sites is the factor that most frequently limits biological activity (Brown et al. 1984; Hinchee et al. 1984; Wilson et al. 1986). Several strategies have been utilized to solve this problem of subsurface delivery. In some cases oxygen, as a gas or dissolved in water or hydrogen peroxide, has been injected into the subsurface. Delivery of oxygen or peroxide by injection into common groundwater wells requires the subsurface to be fairly permeable, with 10-4 cm/sec as the lower limit of hydraulic conductivity. Moreover, preferred flow-paths, such as fractures or macropores, will channel fluids and leave large blocks unexposed to injected oxygen. These procedures have other problems. They generally require continuous pumping, which means continuous expense and extended time at a site. In the case of hydrogen peroxide, the microbial toxicity limits the exposure concentration. Also, populations of bacteria in the vicinity of the injection site limit the usefulness of the peroxide by destroying it through the catalase reaction. Vertical wells are typically used to access subsurface soils. At the Center Hill Laboratory, hydraulic fracturing techniques have been developed to create flat-lying lenses of solid, granular material at shallow depths in unlithified glacial drift. When filled with sand, hydraulic fractures act as permable channels that increase the rate and area of delivery of fluids to the subsurface (or recovery therefrom), a quality that will benefit a variety of remedial technologies including bioremediation. When filled with granules of slow-dissolving nutrients or oxygen-releasing chemicals, hydraulic fractures could produce a reservoir of these compounds that enhance bioremediation. Investigating these possibilities is the purpose of the research described here.
