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| Process | ||
The granular iron technology destroys dissolved volatile organic compounds (VOCs) in groundwater, including common chlorinated solvents such as tetrachloroethene (PCE), trichloroethene (TCE), dichloroethenes (DCEs), vinyl chloride (VC) and trichloroethane (TCA). This patented process uses granular iron placed below-ground such that it intercepts the contaminated groundwater path of a plume. As the plume passes through the granular iron PRB, under natural flow conditions, the VOCs are degraded to nontoxic end products such as ethene, ethane, methane and chloride ions.
The degradation process is a abiotic reductive dehalogenation process occurring on the surface of the granular iron, with the iron acting as an electron source. During the dehalogenation process, the halides on the compound (chloride, fluoride and bromide) are replaced by hydrogen resulting in the transformation of halogenated VOCs to ethene, ethane, methane and halide ions (Cl-, Fl- and Br-).
Dehalogenation proceeds by three processes commonly referred to as
b
-elimination, hydogenolysis and hydrogenation. For chlorinated ethenes such as PCE and TCE,
b
-elimination involves the removal of two chlorides on adjacent carbons resulting in the formation of a lesser chlorinated acetylene intermediate and is considered to be the dominant dechlorination process for most chlorinated ethenes.
Degradation rates using the process are several orders of magnitude greater than under natural conditions. As a consequence of multiple degradation processes, only a small fraction (less than 10%) of the original PCE and TCE will be degraded to cis-1,2-dichloroethene (cDCE) and VC within the treatment zone, then these compounds in contact with the iron, rapidly degrade to ethene and ethane as well. Thus, for all but a few chlorinated ethenes, ethanes and methanes the process does not result in the formation of unwanted, potentially persistent toxic compounds.
The granular iron technology is applicable in most geochemical conditions and does not require frequent reapplications, resulting in a predictable, reliable, long-term treatment solution!
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| Advantages: | ||
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remediation of broad range of groundwater contaminants
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