In Situ Bioremediation (ISB) is the biological treatment of contaminants in the subsurface, typically in groundwater. ISB melds an understanding of microbiology, chemistry, hydrogeology, and engineering into a cohesive strategy for planned and controlled microbial degradation of specific classes of organic. In situ bioremediation creates subsurface environmental conditions, typically through manipulation of the degree of oxidation or reduction, which induces the degradation of chemicals via microbial catalyzed biochemical reactions. To accomplish this chain of events, the following aspects must be considered:
- type of microorganisms,
- type of contaminant, and
- geological conditions at the site.
ISB of chlorinated solvents in groundwater involves the input of an organic carbon source, nutrients, electron acceptors, and/or microbial cultures to stimulate degradation. ISB systems may be used to remediate high concentration areas within plumes or, in some cases, source areas, to help provide containment of a chlorinated solvent plume, or as part of a treatment train downgradient from a primary cleanup or containment system. The major biological processes by which chlorinated solvent compounds degrade include anaerobic reductive dechlorination, aerobic co-metabolism, and oxidation.
A key factor in the design of ISB systems is the mechanism of delivery of the various amendments to the targeted portion of the groundwater plume. Various types of delivery mechanisms have been used, including vertical well recirculation, horizontal well recirculation, filtration trench recirculation, direct liquid amendment injection, gas amendment injection, and pass-through or reactive cell designs.
ITRC ISB Team was operational from 1995-2003 and produced a number of useful documents and training courses. Documents included: