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| Resource Library > Technology Transfer > Programs and Initiatives > Enhanced In Situ Anaerobic Bioremediation > Alternative Remedial Strategies |
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Enhanced in situ anaerobic bioremediation can be applied to achieve source reduction or plume-wide treatment, and it may be possible to complete the remedy in
as little as 1 or 2 years. It is currently thought that not all CAH source zones can be economically or feasibly cleaned up. In these cases, mass flux reduction
strategies or barrier configurations may be employed, but they would need to be operated over several to tens of years to meet remedial objectives. For very
large or difficult sites, it may be advantageous to combine enhanced anaerobic bioremediation with other remedial strategies or measures. In situ enhanced
bioremediation of DNAPL sources is being researched, and may someday be a feasible remedial alternative. For now, mass flux reduction strategies or barrier
configurations can be employed, but they may need to be operated over several to tens of years to meet remedial objectives.
Strategies or measures that can be utilized in combination with an enhanced bioremediation application to either expedite treatment or to achieve site closure
at lower life-cycle cost include the following:
- Monitored Natural Attenuation: MNA can often be employed as a polishing technique after enhanced bioremediation or to address large areas of low-level
contamination that cannot be cost-effectively remediated with enhanced in situ anaerobic bioremediation. For very large, dilute plumes at DoD sites, this may be
the only feasible and cost-effective approach.
- Supplementary Engineered Remedial Measures: Supplemental measures, particularly source reduction measures [e.g., soil vapor extraction (SVE),
excavation, chemical oxidation, thermal technologies], can be utilized to quickly reduce contaminant source mass. Use of enhanced bioremediation as a polishing
step following source reduction may facilitate more rapid attainment of remedial endpoints.
- Bioaugmentation with Enriched Cultures: Bioaugmentation with enriched commercial cultures may be considered if indigenous bacterial communities are
unsuitable for enhanced anaerobic bioremediation, or if it is determined that the added cost of bioaugmentation is justified by a need for rapid treatment due
to impending base closure and property transfer.
- Maximizing Mass Removal with Ongoing Treatment Techniques: Many sites have inefficient long-term pumping systems in place for hydraulic containment
and/or mass removal. These systems are typically diffusion-limited, and often exhibit asymptotic mass removal rates. An enhanced bioremediation approach may be
used in conjunction with an ongoing pumping system, in order to expedite mass removal in source areas while pumping maintains containment of the contaminant
plume.
- Aggressive Source Removal. Aggressive in situ source removal technologies such as chemical oxidation or electrical resistive heating may be used
to as a first step for source removal, with enhanced anaerobic bioremediation used as a polishing step to remediate residual contaminant mass. However, some
source removal methods may adversely alter the subsurface environment for application of enhanced bioremediation. However, this option has been suggested and
is being considered as a potential remedy.
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