Technical Protocol for Using Soluble Carbohydrates to Enhance Reductive Dechlorination of Chlorinated Aliphatic Hydrocarbons.

摘要

Chlorinated aliphatic hydrocarbons (CAHs) are proving to be one of the most widespread, recalcitrant constituents of concern (COC) encountered in the age of environmental awareness. This class of compounds includes widely used solvents such as carbon tetrachloride (CT), methylene chloride, trichloroethane (TCA), trichloroethene (TCE) and tetrachloroethene (PCE). In addition to their roles in many industrial processes, CAHs have historically been used for cleaning and degreasing such diverse products as aircraft engines, automobile parts, electronic components and clothing in both the military and civilian sectors. Contamination of groundwater by mobile metals (e.g., chromium, lead, arsenic, nickel, mercury and cadmium) is also widespread at the same military facilities due to the use of these metals in ordnance, armament, armor, and as components of corrosion prevention coatings on vehicles. Both the number and complexity of sites impacted by CAHs and the threat to human and ecological health represented by this class of anthropogenic chemicals have resulted in mounting costs for the implementation of conventional remediation methods. This is related, in part, to the generally low solubility of the typical source solvents, and their tendency to sink in an aquifer after release or to adsorb to the aquifer materials. The more traditional remediation methods that rely on the extraction of groundwater will quickly reach an asymptotic state of mass removal and will be diffusion limited. In addition, risk based levels for TCE have been recently decreased in some jurisdictions making remediation more costly. As late as 1998, conventional remediation options for sites contaminated with CAHs were considered to be pump and treat with treatment consisting of air stripping, granular activated carbon adsorption, and ultraviolet oxidation (Nyer 1998).