Biological Alkylation and Colloid Formation of Selenium in Methanogenic UASB Reactors
| Autor: | M.P.J. Smit, Patrick Binder, Adriaan C. van Aelst, Markus Lenz, Piet N.L. Lens |
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| Rok vydání: | 2008 |
| Předmět: |
waste-water
Environmental Engineering Alkylation chemistry.chemical_element Electron donor Management Monitoring Policy and Law Waste Disposal Fluid Selenate bed reactors law.invention Selenium chemistry.chemical_compound Colloid Bioreactors law agricultural drainage sediment selenate-reducing bacterium dimethyl selenone Bioreactor Soil Pollutants Anaerobiosis Colloids anaerobic granular sludge Waste Management and Disposal Effluent Filtration enterobacter-cloacae sld1a-1 Water Science and Technology Chromatography Chemistry Temperature toxicity food and beverages Laboratorium voor Celbiologie Pollution Laboratory of Cell Biology elemental selenium Environmental Technology Milieutechnologie Methane bacillus sp sf-1 Water Pollutants Chemical Mesophile Nuclear chemistry |
| Zdroj: | Journal of Environmental Quality 37 (2008) 5 Journal of Environmental Quality, 37(5), 1691-1700 |
| ISSN: | 0047-2425 |
| DOI: | 10.2134/jeq2007.0630 |
| Popis: | Bioalkylation and colloid formation of selenium during selenate removal in upflow anaerobic sludge bed (UASB) bioreactors was investigated, The mesophilic (30 degrees C) UASB reactor (pH = 7.0) was operated for 175 d with lactate as electron donor at an organic loading rate of 2 g COD L-1 d(-1) and a selenium loading rate of 3.16 mg Se L-1 d(-1). Combining sequential filtration with ion chromatographic analysis for selenium oxyanions and solid phase micro extraction gas chromatography mass spectrometry (SPME-GC-MS) for alkylated selenium compounds allowed to entirely close the selenium mass balance in the liquid phase for most of the UASB operational runtime. Although selenate was removed to more than 98.6% from the liquid phase, a less efficient removal of dissolved selenium was observed due to the presence of dissolved alkylated selenium species (dimethylselenide and dimethyldiselenide) and colloidal selenium particles in the effluent. The alkylated and the colloidal fractions contributed LIP to 15 and 31%, respectively, to the dissolved selenium concentration. The size fractions Of the colloidal dispersion were: 4 to 0.45 mu m: up to 21%, 0.45 to 0.2 mu m: up to 11%, and particles smaller than 0.2 mu m: up to 8%. Particles of 4 to 0.45 pin were formed in the external settler, but did not settle. SEM-EDX analysis showed that microorganisms form these Selenium containing colloidal particles extracellularly on their Surface. Lowering the temperature by 10 degrees C for 6 h resulted in drastically reduced selenare removal efficiencies (after a delay of 1.5 d), accompanied by the temporary formation of all unknown, soluble, organic selenium species. This study shows that a careful process control is a prerequisite for selenium treatment in UASB bioreactors, as disturbances in the operational conditions induce elevated selenium effluent concentrations by alkylation and colloid formation. |
| Databáze: | OpenAIRE |
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