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I ':7 3. <br /> i <br /> Air Sparging and Groundwater Recirculating Wells 33 <br /> _ <br /> TABLE 2. Results from ozone pilot test, Hawthorne, California. <br /> Concentration (PPB) Decay Half Life <br /> Compound Start End* Coefficient (k) (Days) <br /> Tetrachloroethene 750 430 -.012 58 <br /> Trichloroethene 8200 4500 -.020 35 <br /> Cis-1,1 dichloroethene 5600 2800 -.023 30 <br /> Cis-1,2 dichloroethene 5600 1700 -.032 22 j <br /> Vinyl chloride 6 ND --- <20 <br /> 1,1,1-trichloroethane 6700 3500 -.023 30 <br /> 1,1-dichloroethane 340 100 -.035 20 <br /> Chloroform 9 ND --- <20 <br /> Carbon tetrachloride 2 ND --- <20 PR <br /> TrichIorotrifluoroethane 4800 820 -.044 16 u - <br /> yr <br /> *Start and end times vary with sampling. See Figure 2 for plotted results . <br /> Independent testing of the reaction has verified that the Criegee ' <br /> �a <br /> mechanism dominates in gaseous and aqueous reactions. The formation of major <br /> products can be explained on the sole basis of the Criegee mechanism with 1 <br /> ethylene, PCE, TCE, DCE and cinyl chloride. No detrimental products of partial <br /> cleavage have been detected in field pilot tests or remedial efforts: <br /> The effectiveness of reaction is not limited to ethenes, but extends to °< <br /> ' alkane derivatives as well. Chloroform, methylene chloride and carbon <br /> tetrachloride are selectively and rapidly removed due to high Henry's constants, <br /> even though cleavage is not as rapid as in the case of ethenes. Reactions in field <br /> situations show rapid destruction of chloro-fluoro-hydrocarbons, such as Freon. } <br /> Kinetic rates of reaction observed in field trials are given for a variety of <br /> compounds. <br /> Field use over the past three years has demonstrated economical operation, <br /> effectiveness and cleanliness which may qualify the process for use of removing <br /> chlorinated ethenes in drinking water aquifers or water streams. The rates of <br /> reaction are shown in various groundwater conditions, ranging from acidic sands <br /> to basic carbonate limestones. The use of microbubble injection by microporous <br /> materials (C-SpargingTM) has repeatedly shown the capacity to lower chlorinated <br /> solvent spill aqueous plume regions below drinking water MCLs. Normally, a pH <br /> change of only .5 units towards acidity is observed. An increase in dissolved <br /> oxygen occurs when ozone is supplied in quantities greater than the <br /> decomposition reaction. Third party economic analysis has shown operating costs <br /> far below standard air sparging. <br /> REFERENCES <br /> Dowideit, P. and C. von Sonntag. 1998. "Reaction of ozone with ethene and its <br /> methyl- and chlorine-substituted derivatives in aqueous solution. Envi. Sci <br /> ( & Tech. 32(8):1112-1119. <br /> Dreiling, D. N. L. G. Henning, R. D. Jurgens, and D. L Ballard. 1998. "Multi- <br /> Site Comparison of Chlorinated Solvent Remediation Using Innovative <br />