Hydrogen Release Compound
Hydrogen Release Compound (HRC) is a controlled release, electron donor material, sold by Regenesis. When hydrated, it is specifically designed to produce a controlled release of lactic acid. The acid is critical for the production of hydrogen to fuel anaerobic biodegradation processes in soil and groundwater. The lactic acid undergoes fermentation by subsurface microbes that in turn generates hydrogen. Hydrogen is key to the anaerobic contaminant degradation process known as reductive dechlorination. Reductive dechlorination is the mechanism by which chlorinated compounds are biodegraded into less harmful constituents such as ethene and ethane. Some of these chlorinated contaminants include Perchloroethylene (PCE), Trichloroethylene (TCE), Dichloroethylene (DCE) and Vinyl Chloride (VC).
Some of the field applications include:
1. Direct injection for source area and permeable reactive barrier applications.
2. Recirculation wells.
3. Straight HRC application in excavations and ex situ soil mixing.
4. Hydraulic fracturing of tight soil media.
5. Fractured bedrock injection using straddle packers.
6. Direct application into wells via gravity feed.
Due to stoichiometric limitations, HRC is generally ineffective in source areas where the concentration of the contaminant is too high. However, there are variants on the HRC (Extended and 3DMe) that can be effective on high concentrations of contaminants (including residual DNAPL).
Some of the benefits of HRC are:
1. Controlled release of lactic acid to promote reducing conditions and produce hydrogen in 8 to 10 nM range which is optimal for anaerobic reductive dechlorination.
2. Long-term source of lactic acid/hydrogen to the subsurface (up to 24 months or longer).
3. Single product application (for majority of sites).
4. Clean, low-cost, non-disruptive application.
5. Eliminates costs associated with operation and maintenance of mechanical systems
6. Faster and often lower cost than drawn out monitored natural attenuation (MNA).
HRC, similarly to other bioremediation products, is generally more expensive than in situ chemical oxidation, when compared on the basis of unit cost . This may not reflect the total project costs.
Remediation using HRC takes longer than other processes such as in situ chemical oxidation when dealing with mid-to-high range contaminant concentrations.
Parameters required to evaluate HRC applicability:
1. Contaminant concentrations/phase
2. Groundwater depth/flow rates
3. pH, alkalinity
4. Contaminant type and mass
5. Geology of contaminated subsurface (sand, bedrock)
6. Viscosity/Pumping (heating of material)
7. Natural attenuation parameters (nitrate, iron, manganese, sulfate)
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