Lenz Markus, Hullebusch Eric D Van, Hommes Gregor, Corvini Philippe F X, Lens Piet N L
Sub-Department of Environmental Technology, Wageningen University, Wageningen, The Netherlands.
Water Res. 2008 Apr;42(8-9):2184-94. doi: 10.1016/j.watres.2007.11.031. Epub 2007 Dec 3.
This paper evaluates the use of upflow anaerobic sludge bed (UASB) bioreactors (30 degrees C, pH=7.0) to remove selenium oxyanions from contaminated waters (790 microg Se L(-1)) under methanogenic and sulfate-reducing conditions using lactate as electron donor. One UASB reactor received sulfate at different sulfate to selenate ratios, while another UASB was operated under methanogenic conditions for 132 days without sulfate in the influent. The selenate effluent concentrations in the sulfate-reducing and methanogenic reactor were 24 and 8 microg Se L(-1), corresponding to removal efficiencies of 97% and 99%, respectively. X-ray diffraction (XRD) analysis and sequential extractions showed that selenium was mainly retained as elemental selenium in the biomass. However, the total dissolved selenium effluent concentrations amounted to 73 and 80 microg Se L(-1), respectively, suggesting that selenate was partly converted to another selenium compound, most likely colloidally dispersed Se(0) nanoparticles. Possible intermediates of selenium reduction (selenite, dimethylselenide, dimethyldiselenide, H(2)Se) could not be detected. Sulfate reducers removed selenate at molar excess of sulfate to selenate (up to a factor of 2600) and elevated dissolved sulfide concentrations (up to 168 mg L(-1)), but selenium removal efficiencies were limited by the applied sulfate-loading rate. In the methanogenic bioreactor, selenate and dissolved selenium removal were independent of the sulfate load, but inhibited by sulfide (101 mg L(-1)). The selenium removal efficiency of the methanogenic UASB abruptly improved after 58 days of operation, suggesting that a specialized selenium-converting population developed in the reactor. This paper demonstrates that both sulfate-reducing and methanogenic UASB reactors can be applied to remove selenate from contaminated natural waters and anthropogenic waste streams, e.g. agricultural drainage waters, acid mine drainage and flue gas desulfurization bleeds.
本文评估了上流式厌氧污泥床（UASB）生物反应器（30℃，pH = 7.0）在产甲烷和硫酸盐还原条件下，以乳酸作为电子供体，从受污染水体（790μg Se L⁻¹）中去除硒酸盐阴离子的效果。一个UASB反应器以不同的硫酸盐与硒酸盐比例接收硫酸盐，而另一个UASB在进水无硫酸盐的情况下进行了132天的产甲烷条件运行。硫酸盐还原反应器和产甲烷反应器中的硒酸盐流出物浓度分别为24和8μg Se L⁻¹，对应的去除效率分别为97%和99%。X射线衍射（XRD）分析和连续萃取表明，硒主要以元素硒的形式保留在生物质中。然而，总溶解硒流出物浓度分别为73和80μg Se L⁻¹，这表明硒酸盐部分转化为另一种硒化合物，很可能是胶体分散的Se(0)纳米颗粒。未检测到硒还原的可能中间体（亚硒酸盐、二甲基硒、二甲基二硒、H₂Se）。硫酸盐还原菌在硫酸盐与硒酸盐摩尔过量（高达2600倍）且溶解硫化物浓度升高（高达168mg L⁻¹）的情况下去除硒酸盐，但硒去除效率受所施加的硫酸盐负荷限制。在产甲烷生物反应器中，硒酸盐和溶解硒的去除与硫酸盐负荷无关，但受硫化物（101mg L⁻¹）抑制。产甲烷UASB运行58天后，硒去除效率突然提高，这表明反应器中形成了专门的硒转化菌群。本文表明，硫酸盐还原和产甲烷UASB反应器均可用于从受污染的天然水体和人为废水中去除硒酸盐，例如农业排水、酸性矿山排水和烟气脱硫废水。
