In Situ Reduction of Carbon Tetrachloride at Andrews AFB Using a Commercially Available Carbon Substrate

摘要

A commercially available carbon substrate was injected into groundwater at a fire training area at Andrews AFB. The design of the injection patterns and substrate dose were intended to accomplish the following primary objectives: (1) cleanup the groundwater to less than five micrograms per liter (μg/L) of carbon tetrachloride in the treated areas and (2) test the hypothesis that groundwater flow dispersion and advection would distribute the substrate substantially and clean areas that did not receive injections. Secondary objectives included: (1) monitor natural degradation of benzene under the geochemically reducing conditions induced by addition of a carbon substrate and (2) correlate the dissolution of iron, manganese, and arsenic with reducing conditions. Charts and data indicate that all four objectives were reached: 1. Carbon tetrachloride decreased from 274 ug/L to non-detection (<0.7 μg/L). 2. Due to advection and dispersion, the carbon substrate spread at least 90 feet longitudinal to groundwater flow and at leas 30 feet transverse to groundwater flow in 180 days. Distances are based on the locations of a limited amount of monitoring wells. 3. Indicators of biodegradation were measured and correlated with changes in pH, manganese, iron, sulfate, ORP, and phospholipid fatty acids. 4. Benzene degraded naturally before and after carbon substrate injections that were designed to treat chlorinated solvents. 5. Dissolution of iron, manganese, and arsenic were correlative with changes in geochemistry.