Simultaneous biodegradation of carbon tetrachloride and trichloroethylene in a coupled anaerobic/aerobic biobarrier

• Published in: Journal of hazardous materials 2016-08, Vol.313, p.60-67
• Main Authors: Kwon, Kiwook, Shim, Hojae, Bae, Wookeun, Oh, Juhyun, Bae, Jisu
• Format: Article
• Language: English
• Subjects: Biodegradation; Biodegradation, Environmental; Biofilms; Carbon tetrachloride; Carbon Tetrachloride - metabolism; Carriers; Coupled removal; Hydrogen Peroxide; Microorganisms; Oxygen; PEG biobarrier; Polyethylene glycol; Soil Microbiology; Temperature; Toluene; Toluene - metabolism; Trichloroethylene; Trichloroethylene - metabolism
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2016.03.057

[Display omitted] •Coupled biodegradation of carbon tetrachloride (CT) and trichloroethylene (TCE) in biobarrier with polyethylene glycol carriers.•TCE aerobically cometabolized and CT anaerobically dechlorinated.•Removal efficiencies of over 98%, leaving residuals below or near the regulatory standards.•Coupled aerobic/anaerobic environments established by H2O2 injected at 50% of electron donor.•Longer retention time (from 3.6 to 7.2 days) achieved satisfactory removal at lower temperature (18°C). Simultaneous biodegradation of carbon tetrachloride (CT) and trichloroethylene (TCE) in a biobarrier with polyethylene glycol (PEG) carriers was studied. Toluene/methanol and hydrogen peroxide (H2O2) were used as electron donors and an electron acceptor source, respectively, in order to develop a biologically active zone. The average removal efficiencies for TCE and toluene were over 99.3%, leaving the respective residual concentrations of ∼12 and ∼57μg/L, which are below or close to the groundwater quality standards. The removal efficiency for CT was ∼98.1%, with its residual concentration (65.8μg/L) slightly over the standards. TCE was aerobically cometabolized with toluene as substrate while CT was anaerobically dechlorinated in the presence of electron donors, with the respective stoichiometric amount of chloride released. The oxygen supply at equivalent to 50% chemical oxygen demand of the injected electron donors supported successful toluene oxidation and also allowed local anaerobic environments for CT reduction. The originally augmented (immobilized in PEG carriers) aerobic microbes were gradually outcompeted in obtaining substrate and oxygen. Instead, newly developed biofilms originated from indigenous microbes in soil adapted to the coupled anaerobic/aerobic environment in the carrier for the simultaneous and almost complete removal of CT, TCE, and toluene. The declined removal rates when temperature fell from 28 to 18°C were recovered by doubling the retention time (7.2 days).