title: Evidence for simultaneous abiotic-biotic oxidations in a microbial-Fenton's system.
abstract: The conditions that support the simultaneous activity of hydroxyl radicals (OH.) and heterotrophic aerobic bacterial metabolism were investigated using two probe compounds: (1) tetrachloroethene (PCE) for the detection of OH. generated by an iron-nitrilotriacetic acid (Fe-NTA) catalyzed Fenton-like reaction and (2) oxalate (OA) for the detection of heterotrophic metabolism of Xanthobacter flavus. In the absence of the bacterium in the quasi-steady-state Fenton's system, only PCE oxidation was observed; conversely, only OA assimilation was found in non-Fenton's systems containing X. flavus. In combined Fenton's-microbial systems, loss of both probes was observed. PCE oxidation increased and heterotrophic assimilation of OA declined as a function of an increase in the quasi-steady-state H2O2 concentration. Central composite rotatable experimental designs were used to determine the conditions that provide maximum simultaneous abiotic-biotic oxidations, which were achieved with a biomass level of 10(9) CFU/mL, 4.5 mM H2O2, and 2.5 mM Fe-NTA. These results demonstrate that heterotrophic bacterial metabolism can occur in the presence of hydroxyl radicals. Such simultaneous abiotic-biotic oxidations may exist when H2O2 is injected into the subsurface as a microbial oxygen source or as a source of chemical oxidants. In addition, hybrid abiotic-biotic systems could be used for the treatment of waters containing biorefractory organic contaminants present in recycle water, cooling water, or industrial waste streams.
authors.affiliation: Department of Civil & Environmental Engineering, Washington State University, Pullman, Washington 99164-2910, USA.
authors.forename: J
authors.initials: J
authors.lastname: Howsawkeng
authors.forename: R J
authors.initials: RJ
authors.lastname: Watts
authors.forename: D L
authors.initials: DL
authors.lastname: Washington
authors.forename: A L
authors.initials: AL
authors.lastname: Teel
authors.forename: T F
authors.initials: TF
authors.lastname: Hess
authors.forename: R L
authors.initials: RL
authors.lastname: Crawford
mesh_terms: D001673:Biodegradation, Environmental; D002273:Carcinogens / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D007501:Iron; D010070:Oxalates / Q000737:chemistry; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D013750:Tetrachloroethylene / Q000737:chemistry*; D014865:Waste Disposal, Fluid; D020584:Xanthobacter / Q000502:physiology*
chemical_list: D002273:Carcinogens; C045076:Fenton's reagent; D010070:Oxalates; D016877:Oxidants; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; D007501:Iron; D013750:Tetrachloroethylene