Engineered in situ anaerobic reactive zones

Abstract

An in situ method and system for reductive dechlorination, the precipitation of chromium, the precipitation of heavy metals, and microbial denitrification. The invention comprises the formation of in situ anaerobic reactive zones to precipitate and filter out dissolved heavy metals as metallic sulfides, to degrade nitrate to nitrogen gas, to reduce chlorinated hydrocarbons to ethene, and to precipitate and filter out chromium. The invention is comprised of an injection well or wells that extend into a contaminated groundwater. A conduit located within the injection well conveys a reagent to the contaminated groundwater. The reagent may be a carbohydrate rich solution. Microbes digest the carbohydrates to produce sulfate reducing and methanogenic conditions within the reactive zone that include a dissolved oxygen level less than about 0.5 mg/l, a redox potential less than about −250 mv, and a dissolved organic carbon to contaminant ratio of greater than about 50:1. These biogeochemical conditions lead to the reduction of PCE to TCE to DCE to VC and eventually to ethene. These biogeochemical conditions also lead to the precipitation of heavy metals, the precipitation of chromium, and microbial denitrification.

Dependencies are inferred from the claim text.