Mobility of Soluble and Non-Soluble Hydrocarbons in Contaminated Aquifer

Abstract

After the contamination of an aquifer by petroleum products, the residual oil trapped is a constant source of pollution by the entrainment of the most soluble hydrocarbons. By studying the exchanges of residual hydrocarbons between oil-water-air and soil, we pointed out that the liquid/gas exchange is the major factor of retention of soluble alkanes masking the adsorbing materials effects. For the soluble aromatic hydrocarbons, the main phenomenon observed is the liquid/solid exchange. The role of residual air is no more preponderant. The residual contamination of the vadose zone thus plays a preponderant role in the long-term pollution of a groundwater table. It is thus imperative to implement methods to prevent such harmful effects. The use of surfactants, by lowering the oil/water interfacial tension seems to be a new and effective method. Their adsorption into a natural matrix was studied with different porous substrates (sand, sand/silt). Their retention on sand is poor, but it increases with silt content. This is mainly due to a cationic exchange (Ca2+/Na+). In order to avoid this phenomenon a salt preflush by a 10 g/l Na Cl solution is effective. That allows a gas-oil recovery enhancement by reducing loss of surfactant in soil. Moreover, a surfactant partition between oil and water is underscored. A better understanding of these parameters would lead to the optimizing of the enhanced drainage technique for recovering residual oil trapped in an aquifer.

Enhanced Transport of Low-Polarity Organic Compounds through Soil by Cyclodextrin

“…The observation of no sorption, retardation, or pore exclusion of HPCD during transport is in contrast to results reported for other organic materials. For example, the transport of dissolved organic matter (8,11,12) and surfactants (7,(13)(14)(15) through soil has been shown to be significantly retarded by sorption interactions. In addition, data have been reported showing pore exclusion of large organic materials during transport in soil (7, 16).…”

Saturated Column Feasibility Study Using Cationic Surfactants for In Situ Removal of Lead from Soil

“…In recent years, the potential use of biodegradable surfactants in environmental remediation has gained significant attention. Saturated soil column flushing tests by Ang and Abdul (1991) and Ducreux et al (1990) showed the feasibility of using surfactants to mobilize residual hydrocarbons. Pilot tests by Sale and Pitts (1989), Abdul et al (1992), and Abdul and Ang (1994) indicate the effectiveness and efficiency of using surfactants to flush organic contaminants from both saturated and unsaturated sediments under typical field conditions.…”

Properties of Food Grade (Edible) Surfactants Affecting Subsurface Remediation of Chlorinated Solvents

“…Recently, extensive research has demonstrated surfactant flushing to be a viable alternative for improving the efficiency of pump-and-treat remediation (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). Despite successful laboratory studies, several field demonstrations of surfactant flushing have illustrated potential problems: lower contaminant removal than anticipated (8), poor economics due to high surfactant costs [illustrating the need for proper separation and reuse of the surfactant(s)] (4), and changes in the hydrogeological nature of the aquifer [e.g., plugging the media (8)].…”

“…d SXS, sodium xylene sulfonate, a non-food-grade hydrotrope (molecular weight = 208). Unless otherwise noted, values determined in this research 3. Values taken from Wiliams et al(38).…”