In-Situ Alcohol Flushing of a DNAPL Source Zone at a Dry Cleaner Site

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• 作者：James W. Jawitz ; Randall K. Sillan ; Michael D. Annable ; P. Suresh C. Rao ; and Kevin Warner
• 刊名：Environmental Science & Technology
• 出版年：2000
• 出版时间：September 1, 2000
• 年：2000
• 卷：34
• 期：17
• 页码：3722 - 3729
• 全文大小：126K
• 年卷期：v.34,no.17(September 1, 2000)
• ISSN：1520-5851

文摘

A pilot-scale field test of in-situ alcohol flushing forenhanced solubilization and extraction of a dense nonaqueousphase liquid (DNAPL) source zone was conducted at aformer dry cleaner site located in Jacksonville, Florida. Thisstudy was conducted to evaluate the feasibility of in-situflushing for remediation of DNAPL sites in Florida. Groundwaterat this site was contaminated with tetrachloroethylene(PCE) that had migrated below the water table, located at3 m below ground surface (bgs), and collected at highsaturations in thin, discontinuous layers in the 7.9 m to 9.4m bgs depth interval. An oblong source zone (7.3 m ×2.7 m) was delineated using direct-push technologies andfurther characterized using soil coring and partitioningtracer techniques. Tracer tests and in-situ alcohol flushingwere conducted using three injection wells that approximately bisected the source zone and six recoverywells located on the outer perimeter of the source zone. Over-extraction through the recovery wells ensured hydrauliccontainment within the test zone. A partitioning tracer testconducted before the alcohol flood provided an estimateof about 68 L of PCE within the zone swept by the wells. Thetest zone was flushed with 34 kL (equivalent to 2 porevolumes) of a 95% ethanol/5% water mixture over a periodof 3 days. Packers were used in the injection wells tofocus the flushing solution delivery to regions of the sweptzone that showed larger initial NAPL saturations. Alcoholflushing removed approximately 43 L of PCE from thetest zone (62% removal effectiveness). These results werein agreement with soil core data that indicated approximately65% removal and a postflushing partitioning tracer test thatindicated approximately 26 L of PCE remaining (63%removal). Postflushing groundwater concentrations of PCEwere an average of 92% lower than preflushing valuesat 21 of 35 multilevel sampling locations within the test zone,but the combined effects of residual ethanol andincomplete flushing resulted in elevated postflushing PCEconcentrations at the other 14 locations. Alcohol flushingsuccessfully removed a substantial volume of DNAPL;however, evidence indicated that continued alcohol flushingwould have resulted in a greater NAPL removal effectiveness.