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
Lenz, M. ; Hullebusch, E.D. van; Farges, F. ; Nikitenko, S. ; Corvini, P.F.X. ; Lens, P.N.L. - \ 2011
Environmental Science and Technology 45 (2011)3. - ISSN 0013-936X - p. 1067 - 1073.
anaerobic granular sludge - reducing bacterial biofilms - agricultural drainage - waste-water - selenate - removal - bioremediation - reduction - oxyanions - sediments
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
Bioconversion of Selenate in Methanogenic Anaerobic Granular Sludge
Astratinei, V. ; Hullebusch, E.D. van; Lens, P.N.L. - \ 2006
Journal of Environmental Quality 35 (2006). - ISSN 0047-2425 - p. 1873 - 1883.
soluble selenium removal - bacillus sp sf-1 - elemental selenium - sequential extraction - reducing bacterium - toxic metals - reduction - speciation - oxyanions - reactor
The capacity of anaerobic granular sludge to remove selenate from contaminated wastewater was investigated. The potential of different types of granular sludge to remove selenate from the liquid phase was compared to that of suspended sludge and contaminated soil and sediment samples. The selenate removal rates ranged from 400 to 1500 µg g VSS¿1 h¿1, depending on the source of biomass, electron donor, and the initial selenate concentration. The granular structure protects the microorganisms when exposed to high selenate concentrations (0.1 to 1 mM). Anaerobic granular sludge "Eerbeek," originating from a UASB reactor treating paper mill wastewater, removed about 90, 50, and 36% of 0.1, 0.5, and 1 mM of Se, respectively, from the liquid phase when incubated with 20 mM lactate at 30°C and pH 7.5. Selenite, elemental Se (Seo), and metal selenide precipitates were the conversion products. Enrichments from the anaerobic granular sludge "Eerbeek" were able to convert 90% of the 10-mM selenate to Seo at a rate of 1505 µg Se(VI) g cells¿1 h¿1, a specific growth rate of 0.0125 g cells h¿1, and a yield of 0.083 g cells mg Se¿1. Both microbial metabolic processes (e.g dissimilatory reduction) as well as microbially mediated physicochemical mechanisms (adsorption and precipitation) contribute to the removal of selenate from the Se-containing medium