In-situ Substrate Addition to Create Reactive Zones for Treatment of Chlorinated Aliphatic Hydrocarbons: Cost and Performance Report

摘要

Chlorinated solvent contamination of groundwater is a widespread problem at many military and civilian facilities. This class of compounds includes widely used chlorinated aliphatic hydrocarbons (CAH) such as carbon tetrachloride, methylene chloride, trichloroethane, trichloroethene (TCE) and tetrachloroethene. In addition to their roles in many industrial processes, CAHs have been used extensively for cleaning and degreasing. The U.S. Armed Forces are faced with widespread, costly remediation problems related to these compounds. The conventional remedies for CAH contamination in groundwater are groundwater extraction and ex situ treatment, also known as pump and treat, or in situ air sparging. An alternative approach is anaerobic in situ reactive zone (IRZ) technology for the remediation of CAHs and metals. Anaerobic IRZ technology involves the addition of a food grade, soluble carbohydrate substrate, which serves as a supplemental energy source for microbiological processes in the subsurface. The substrate is typically molasses, but other substrates can be used, including high fructose corn syrup, whey, etc. Through subsurface carbohydrate injection, aerobic or mildly anoxic aquifers can be altered to highly anaerobic reactive zones. This creates suitable conditions for the biodegradation of CAHs and/or the precipitation of selected metals in insoluble forms. This technology is more specifically referred to as enhanced reductive dechlorination (ERD) for CAHs or enhanced anaerobic reductive precipitation (EARP) for metals. The primary benefits of ERD technology include its ease of regulatory acceptance, its in situ nature and its relatively low cost. Benefits of ERD technology include its record of successful application at various constituent concentrations, in varied geologies, and under multiple regulatory programs.