In Situ Vertical Circulation Column: Containment System for Small‐Scale DNAPL Field Experiments

Abstract

The in situ vertical circulation column (ISVCC) is a cylindrical containment system consisting of an instrumented steel cylinder used for experimental ground water studies in sandy aquifers. Vertical flow is imposed inside the ISVCC. Although vertical wells are an option, the ISVCC installed in the Borden Aquifer is instrumented with horizontal wells and monitoring ports to avoid creating vertical preferential flow paths. The cylinder was driven downward into the aquifer using a small backhoe equipped with a vibrating plate. The ISVCC penetrates the 2.3‐m‐thic sand aquifer and is keyed 20 cm into the underlying clay aquitard. The cylinder was installed inside a 2 m X 2 m steel sheet pile enclosure so that the enclosed segment of aquifer could be conveniently dewatered and then excavated to allow installation of the horizontal wells. The dispersivity of the column was comparable to literature values for long sand‐packed laboratory columns. Pure phase DNAPL (tetrachloroethene and 1,1,1‐trichloroethane) was slowly pumped into two ports in the center of the column. Following this DNAPL injection, an aqueous solution of vitamin B12 and reduced titanium was circulated through the column to promote degradation of the solvents. Processes observed in the ISVCC included DNAPL distribution, dissolution, and degradation, and geochemical evolution of the aquifer. The ISVCC provides a convenient means for testing in situ technologies in the experimental stage or for selection of proven technologies to find the most effective at a specific site. It is inexpensive, easy to install, and maximizes control over flow distribution in a heterogeneous aquifer. Its application will be restricted where low hydraulic conductivity beds are present in the aquifer.

Variability in the carbon isotope fractionation of trichloroethene on its reductive dechlorination by vitamin B12

“…Remediation technologies based on reductive dechlorination by vitamin B 12 have been developed and have potential for treating chlorinated organic contaminants in groundwater. [1][2][3][4] It is important to investigate the reaction pathways involved in remedial technologies. Effective remediation also requires detailed knowledge of the extent to which the contaminants at a site are degraded.…”

A Different Mechanism for the Reductive Dechlorination of Chlorinated Ethenes: Kinetic and Spectroscopic Evidence

“…Vitamin B12 (cyanocobalamin) has been used, as a substitute for anaerobic bacteria, in biomimetic systems to conduct studies on the mechanism of reductive dechlorination ( − ). It has also been used as a groundwater remediation method ( − ). Reductive dechlorination occurs naturally at some, but not all, contaminated sites requiring remedial action.…”

Experimental investigation of the removal of hydrophobic organic compounds from two Iowa soils using food grade surfactants and recovery of used surfactants

“…Nash commented that the extremely high concentrations of oil and grease which were present may have caused the observed clogging of the field test holes and thus restricted flow of the surfactant solution through the contaminated regions. Field testing showed ineffective removal of contaminants where low hydraulic conductivity beds are present in the aquifer (Sorel et a!., 1998). Ang and Abdul (1991) reported that about 80% of polychlorinated biphenyls (PCBs) can be washed from sandy soils in laboratory and field experiments.…”