title: Combined speciation analysis by X-ray absorption near-edge structure spectroscopy, ion chromatography, and solid-phase microextraction gas chromatography-mass spectrometry to evaluate biotreatment of concentrated selenium wastewaters.
abstract: In this study we evaluate the potential of anaerobic granular sludge as an inoculum for the bioremediation of selenium-contaminated waters using species-specific analytical methods. Solid species formed by microbial reduction were investigated using X-ray absorption near-edge structure (XANES) spectroscopy at the selenium K-edge. Furthermore, dissolved selenium species were specifically determined by ion chromatography (IC) and solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC-MS). Least-squares linear combination of the XANES spectra for samples incubated with the highest selenate/selenite concentrations (10(-3) M) show the predominance of elemental selenium and a Se(-I) selenide, such as ferroselite, the thermodynamically most stable iron selenide. In contrast, elemental selenium and Se(-II) selenides are the main species detected at the lower selenate/selenite concentrations. In each repeated fed batch incubation, most aqueous selenite anions were converted into solid selenium species, regardless of the type of electron donor used (acetate or H(2)/CO(2)) and the selenium concentration applied. On the other hand, at higher concentrations of selenate (10(-4) and 10(-3) M), significant amounts of the oxyanion remained unconverted after consecutive incubations. SPME-GC-MS demonstrated selenium alkylation with both electron donors investigated, as dimethyl selenide (DMSe) and dimethyl diselenide (DMDSe). Selenite was even more alkylated in the presence of H(2)/CO(2) (maximum 2156 μg of Se/L of DMSe + DMDSe) as compared to acetate (maximum 50 μg of Se/L). In contrast, selenate was less alkylated using both electron donors (maximum 166 and 3 μg of Se/L, respectively). The high alkylation potential for selenite limits its bioremediation in selenium laden waters involving H(2)/CO(2) as the electron donor despite the fact that nontoxic elemental selenium and thermodynamically stable metal selenide species are formed.
authors.affiliation: Sub-Department of Environmental Technology, Wageningen University, 6700 EV Wageningen, The Netherlands. Markus.Lenz@fhnw.ch
authors.forename: Markus
authors.initials: M
authors.lastname: Lenz
authors.forename: Eric D
authors.initials: ED
authors.lastname: van Hullebusch
authors.forename: François
authors.initials: F
authors.lastname: Farges
authors.forename: Sergei
authors.initials: S
authors.lastname: Nikitenko
authors.forename: Philippe F X
authors.initials: PF
authors.lastname: Corvini
authors.forename: Piet N L
authors.initials: PN
authors.lastname: Lens
mesh_terms: D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D019149:Bioreactors; D002852:Chromatography, Ion Exchange; D008401:Gas Chromatography-Mass Spectrometry; D012643:Selenium / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D012722:Sewage / Q000737:chemistry; D052617:Solid Phase Microextraction; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D056928:X-Ray Absorption Spectroscopy
chemical_list: D012722:Sewage; D014874:Water Pollutants, Chemical; D012643:Selenium