Technology Description

Biogeochemical transformation is defined as "processes where contaminants are degraded by abiotic reactions with naturally occurring and biogenically formed minerals in the subsurface." These biogenically formed minerals are created as a result of biogeochemical reactions that occur typically under anaerobic iron- and sulfate-reducing conditions. Biogenically formed minerals are particularly important because they are continuously replenished in the subsurface under these redox conditions and have high surface area and reactivity. In situ biogeochemical treatment systems are defined as systems that capitalize on or enhance such natural processes via engineered reaction zones in the subsurface. Examples of this application include permeable reactive barriers (e.g., biowalls), in situ bioreactors, and injection of organic carbon (e.g., soluble electron donors or vegetable oil emulsions) into a contaminated aquifer with the specific purpose of creating biogenically formed minerals. In situ biogeochemical transformation involves biological formation of reactive minerals that can destroy chlorinated solvents such as trichloroethene (TCE) without accumulation of toxic intermediates such as vinyl chloride. Iron sulfides are one class of minerals that have been identified as being reactive with chlorinated solvents.