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ABSTRACT: This study studied the cultivation of granules from an expanded granular sludge bed reactor that simultaneously transforms sulfates, nitrates, and oxygen to elementary sulfur, nitrogen gas, and carbon dioxides, respectively. The living cells accumulate at the granule outer layers, as revealed by the multicolor staining and confocal laser scanning microscope technique. The microbial community comprises sulfate-reducing bacteria (SRB, Desulfomicrobium sp.), heterotrophic (Pseudomonas aeruginosa and Sulfurospirillum sp.), and autotrophic denitrifiers (Sulfurovum sp. and Paracoccus denitrificans) whose population dynamics at different sulfate and nitrate loading rates are monitored with the single-strand conformation polymorphism and denaturing gradient gel electrophoresis technique. The Desulfomicrobium sp. presents one of the dominating strains following reactor startup. At high sulfate and nitrate loading rates, the heterotrophic denitrifiers overcompete autotrophic denitrifiers to reduce SRB activities. Conversely, suddenly reducing nitrate loading rates completely removes the heterotrophic denitrifier Sulfurospirillum sp. from the granules and activates the autotrophic denitrifiers. The physical fixation of different groups of functional strains in granules fine-tunes the strains' activities, and hence the reactor performance.
Applied Microbiology and Biotechnology 08/2008; 79(6):1071-7. · 3.42 Impact Factor
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ABSTRACT: Aiming at inorganic sulfate-laden wastewater biotreatment, sulfate reduction (SR) coupling with denitrifying sulfide removal (DSR) is an effecitve method for sulfate removal in this kind of wastewater. In order to implement this method, two process patterns could be adopted, process pattern I (SR+DSR) and process pattern II (SRrarrDSR). For process pattern I, the courses of SR and DSR are integrated in one bioreactor. While, for process pattern II, the courses of SR and DSR are in separate bioreactors. In this study, comparison tests were performed to investigate which pattern is of more superiority in terms of desulfurization effieciency. Based on the experimental results and the analysis of desulfurization, nitrate consumption, elemental sulfur conversion rate and sulfur mass between the two patterns, it is found that process pattern II (SR rarrDSR) is much optimal than that of pattern I (SR+DSR).
Bioinformatics and Biomedical Engineering, 2008. ICBBE 2008. The 2nd International Conference on; 06/2008
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ABSTRACT: High-rate biological conversion of sulfide and nitrate in synthetic wastewater to, respectively, elemental sulfur (S(0)) and nitrogen-containing gas (such as N(2)) was achieved in an expanded granular sludge bed (EGSB) reactor. A novel strategy was adopted to first cultivate mature granules using anaerobic sludge as seed sludge in sulfate-laden medium. The cultivated granules were then incubated in sulfide-laden medium to acclimate autotrophic denitrifiers. The incubated granules converted sulfide, nitrate, and acetate simultaneously in the same EGSB reactor to S(0), N-containing gases and CO(2) at loading rates of 3.0 kg S m(-3) d(-1), 1.45 kg N m(-3) d(-1), and 2.77 kg Ac m(-1) d(-1), respectively, and was not inhibited by sulfide concentrations up to 800 mg l(-1). Effects of the C/N ratio on granule performance were identified. The granules cultivated in the sulfide-laden medium have Pseudomonas spp. and Azoarcus sp. presenting the heterotrophs and autotrophs that co-work in the high-rate EGSB-SDD (simultaneous desulfurization and denitrification) reactor.
Applied Microbiology and Biotechnology 05/2008; 78(6):1057-63. · 3.42 Impact Factor
