Anaerobic biotransformation of explosives in aquifer slurries amended with ethanol and propylene glycol [An article from: Chemosphere]

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Description:
Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and 2,4,6-trinitrotoluene (TNT) are explosives that are frequently found as environmental contaminants on military installations. Hydrogen has been shown to support the anaerobic transformation of these explosives. We investigated ethanol and propylene glycol as electron donors for providing syntrophically produced H"2 for stimulating the anaerobic biodegradation of explosives in contaminated soil. The study was conducted using anoxic microcosms constructed with slurries of the contaminated soil and groundwater. The addition of 5mM ethanol and propylene glycol enhanced the biodegradation of RDX and HMX relative to the control bottles. Ethanol was depleted within about 20days, resulting in the transient formation of hydrogen, acetate, and methane. The hydrogen headspace concentration increased from 8ppm to 1838ppm before decreasing to background concentrations. Propylene glycol was completely degraded after 15days, forming hydrogen, propionate, and acetate as end-products. The hydrogen headspace concentrations increased from 56ppm to 628ppm before decreasing to background concentrations. No methane formation was observed during the incubation period of 48days. Our findings indicate the addition of ethanol and propylene to the aquifer slurries increased the hydrogen concentrations and enhanced the biotransformation of RDX and HMX in the explosive-contaminated soil.