Remediation of aquifer contaminated with dense non-aqueous phase liquids (DNAPLs) using emulsion

Abstract

Recently, contamination of aquifer by chlorinated solvents has gained increased interest. The most effective in-situ remediation technology, surfactant-enhanced aquifer remediation (SEAR), caused the secondary contamination of pristine aquifer by free dense phase and sorption of surfactants. For successful remediation, more studies on SEAR or other alternatives are necessary. This dissertation focused on the removal characteristics of chlorinated solvents such as trichloroethylene (TCE), perchloroethylene (PCE) and 1,2-dichlorobenzene (DCB) by emulsion as an alternative method to SEAR. Mechanical homogenization was conducted for emulsification and the effects of parameters on the properties of emulsion were observed. More than 99 % of emulsion particles were distributed between 1 and 10 μm in diameter. In the solubilization of chlorinated solvents, 2 % (v/v) silicone emulsion could solubilize 90.7 % of 10,000 ppm TCE, 97.3 % of 4,000 ppm PCE and 99.7 % of 7,800 ppm DCB. With use of non-ionic surfactants below their critical micelle concentration (CMC), the surfactant of large hydrophile-lipophile balance (HLB) number dispersed oil sufficiently. However, the enhanced emulsion properties by addition of surfactants did not lead to the increase in the solubilization efficiency because of increased hydrophilicity of emulsion surface. Flushing with 2 % (v/v) silicone emulsion was employed to study the feasibility for contaminant removal. The aqueous solubility and organic carbon partition coefficient of contaminant were the important factors influencing emulsion performance. The use of surfactant, Brij 35, accelerated the initial solubilization of TCE, however enhancements in other removal performance were not observed. In flushing with real soils, the inhibition on TCE solubilization depended on the organic, silt and clay content. As organic, silt and clay content increased, the initial lag phase in dissolution of TCE increased. In three dimensional flushing, th...