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0 0 <br />Ms. Lori Duncan <br />April 12, 2002 <br />Page 7 <br />Air Sparging <br />Project 880-039.1A <br />Air sparging is implemented by injecting pressurized air into a contaminated aquifer so <br />that air streams traverse horizontally and vertically through the soil column, creating an <br />underground stripper that removes contaminants by volatilization. The stream air <br />typically carries the contaminants to a vapor extraction system that removes the <br />volatilized contamination. This technology operates at high flow rates to maintain <br />increased contact with the groundwater and soil, and to strip more contaminants from the <br />impacted media. <br />In addition to removal of contaminants by volatilization, an increased level of dissolved <br />oxygen (DO) would enhance aerobic biodegradation of the contaminants. Reducing the <br />air sparging flow rate to emphasize biodegradation through supply of oxygen in contrast <br />to contaminant stripping is sometimes called biosparging. <br />There are several enhancements to air sparging. One enhancement is called cometabolic <br />air sparging. Propane, which is injected along with air, acts as another nutrient for <br />microorganisms. <br />Ozone can also be injected to increase the amount of available oxygen to the subsurface. <br />Vapor -phase ammonia can also be injected with air sparging for soils low in nitrogen. <br />Physical enhancements are also possible. Ozone injection technology has proven to be <br />effective in delivering high oxygen concentrations via a micro -porous sparge point. Air <br />or ozone can be injected into the subsurface from two points in each treatment well. The <br />injections are delivered in pulses that create a recirculating treatment zone. This is a <br />two-phase process. First, fine bubbles are injected into the groundwater to extract <br />dissolved VOCs out of contaminated groundwater. Second, ozone contained within the <br />bubbles reacts rapidly with the volatile compounds to decompose them into end products <br />consisting of carbon dioxide, dilute hydrochloric acid and water. <br />IT CORPORATION <br />SAC:\\\SACRFP 1 \COMMON\sacDP\2002\PRJ\PJ8\880\8800391 A.2ac.doc <br />(01040000) <br />