title: Immobilization of Cr(VI) and its reduction to Cr(III) phosphate by granular biofilms comprising a mixture of microbes.
abstract: We assessed the potential of mixed microbial consortia, in the form of granular biofilms, to reduce chromate and remove it from synthetic minimal medium. In batch experiments, acetate-fed granular biofilms incubated aerobically reduced 0.2 mM Cr(VI) from a minimal medium at 0.15 mM day(-1) g(-1), with reduction of 0.17 mM day(-1) g(-1) under anaerobic conditions. There was negligible removal of Cr(VI) (i) without granular biofilms, (ii) with lyophilized granular biofilms, and (iii) with granules in the absence of an electron donor. Analyses by X-ray absorption near edge spectroscopy (XANES) of the granular biofilms revealed the conversion of soluble Cr(VI) to Cr(III). Extended X-ray absorption fine-structure (EXAFS) analysis of the Cr-laden granular biofilms demonstrated similarity to Cr(III) phosphate, indicating that Cr(III) was immobilized with phosphate on the biomass subsequent to microbial reduction. The sustained reduction of Cr(VI) by granular biofilms was confirmed in fed-batch experiments. Our study demonstrates the promise of granular-biofilm-based systems in treating Cr(VI)-containing effluents and wastewater.
authors.affiliation: Environmental Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Y V
authors.initials: YV
authors.lastname: Nancharaiah
authors.forename: C
authors.initials: C
authors.lastname: Dodge
authors.forename: V P
authors.initials: VP
authors.lastname: Venugopalan
authors.forename: S V
authors.initials: SV
authors.lastname: Narasimhan
authors.forename: A J
authors.initials: AJ
authors.lastname: Francis
mesh_terms: D000085:Acetates / Q000378:metabolism; D000332:Aerobiosis; D000693:Anaerobiosis; D018441:Biofilms; D002857:Chromium / Q000378:metabolism*; D017608:Chromium Compounds / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D010084:Oxidation-Reduction; D010710:Phosphates / Q000378:metabolism*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D000085:Acetates; D017608:Chromium Compounds; D003470:Culture Media; D010710:Phosphates; D002857:Chromium; C074702:chromium hexavalent ion; C509369:chromic phosphate