Field test of high molecular weight alcohol flushing for subsurface nonaqueous phase liquid remediation

Abstract

Abstract. A pilot scale field test of non-aqueous phase liquid (NAPL) removal using high molecular weight alcohols was conducted at Operable Unit 1, Hill Air Force Base, Utah. Petroleum hydrocarbons and spent solvents were disposed of in chemical disposal pits at this site, and these materials are now present in the subsurface in the form of a light nonaqueous phase liquid (LNAPL). This LNAPL is a complex mixture of aromatic and aliphatic hydrocarbons, chlorinated solvents, and other compounds. The field experiment was performed in a 5 rn by 3 rn confined test cell, formed by driving interlocking sheet pile walls through the contaminated zone into an underlying clay. The test involved the injection and extraction of about four pore volumes (1 pore volume = 7000 L) of a mixture of 80% tert-butanol and 15% n-hexanol. The contaminants were removed by a combination of NAPL mobilization and enhanced dissolution, and the results of postflood soil coring indicate better than 90% removal of the more soluble contaminants (trichloroethane, toluene, ethylbenzene, xylenes, trimethylbenzene, naphthalene) and 70-80% removal of less soluble compounds (decane and undecane). The results of preflood and postflood NAPL partitioning tracer tests show nearly 80% removal of the total NAPL content from the test cell. The field data suggest that a somewhat higher level of removal could be achieved with a longer alcohol injection. IntroductionIt is now known that relatively small nonaqueous phase liquid (NAPL) source zones are capable of producing large contaminated groundwater plumes. While methods such as pumping and treating the contaminated water or funneling the water through reactive walls have been effective for plume control, they do not effectively address the source of the plume. Given that these source zones may continue to release contaminants for many decades or centuries, a large effort is now focused on the development of source zone removal methods. Often these techniques must be applied in situ, owing to the depth of contamination or to the presence of buildings and utilities which prevent excavation. The Rao et al. [1997] field test was performed in an isolated test cell, and it consisted of injecting about nine pore volumes of a 70% ethanol, 12% n-pentanol solution. They reported a bulk NAPL removal of -81%, with a higher removal efficiency for several individual compounds.

Effect of Enhanced-Solubilization Agents on Dissolution and Mass Flux from Uniformly Distributed Immiscible Liquid Trichloroethene (TCE) in Homogeneous Porous Media

“…Chemical agents have been utilized in laboratory, intermediate, and field-scale experiments including cosolvents Rao et al 1985;USEPA 1985;Boyd and Farely 1992;Brandes and Farley 1993;Peters and Luthy 1993;Augustijn et al 1994;Imhoff et al 1995;Roy et al 1995;Wang and Brusseau 1995a;Wood 1995;Rao et al 1997;Sillan et al 1998;Falta et al 1999;Jawitz et al 2000;Chawla et al 2001;Brooks et al 2004), surfactants (Abdul et al 1990;Abdul and Gibson 1991;Edwards et al 1991;Fountain et al 1991;Pennel et al 1993;Rouse et al 1993;Brown et al 1994;Shiau et al 1994;Adeel and Luthy 1995;Hasegawa et al 1997;Childs et al 2006), and complexing sugar agents Brusseau 1993, 1995a b;Brusseau et al 1994Brusseau et al , 1997Bizzigotti et al 1997;Wang et al 1998;Brusseau 1998, 1999;Boving et al 1999;Boving and Brusseau 2000;McCray et al 2000;Blanford et al 2001;Tick et al 2003;Carroll and Brusseau 2009).…”

Remediation with cyclodextrin: Recovery of the remedial agent by membrane filtration

“…Besides conventional methods, there are many innovative treatment approaches available now to remediate sites contaminated with chlorinated solvents. Some techniques rely on zero-valent metals (Gilham & O'Hannesin, 1994), others on microorganisms (Chapelle, 2001), and others are based on destruction (e.g., in situ oxidation by permanganate or peroxide; Huling & Pivetz, 2006), or chemically enhanced flushing with surfactants, cosolvents, or cyclodextrin solution (Boving et al, 1999;Falta et al, 1999;Jawitz et al, 1998;Sabatini et al, 1996). Of these innovative remediation technologies, this study focuses on in situ cyclodextrin-enhanced chemical flushing of a DNAPL source zone in conjunction with ex situ treatment of the postaquifer flushing solution by ultrafiltration (UF).…”

Federal Integrated Biotreatment Research Consortium (FIBRC): Flask to Field Initiative

“…They also reported an approximate 81% reduction in NAPL saturation based on pre-and post-flushing partitioning interwell tracer tests (PITTs). Falta et al (1999) presented results from a second cosolvent flushing study at Hill AFB wherein the remedial mechanisms were NAPL mobilization and enhanced dissolution. Their test cell was approximately 5 m long by 3 m wide, and the clay confining unit was 9 m below grade.…”

“…Two cosolvent flushing demonstrations were conducted at Hill Air Force Base (AFB), Utah in isolated test cells installed in a sand and gravel aquifer contaminated with a multi-component NAPL Sillan et al, 1998a;Falta et al, 1999). Rao et al (1997) demonstrated NAPL remediation by enhanced dissolution.…”