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KMID : 0545120080180111826
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Journal of Microbiology and Biotechnology
2008 Volume.18 No. 11 p.1826 ~ p.1835
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Bacterial Community and Biological Nitrate Removal: Comparisons of Autotrophic and Heterotrophic Reactors for Denitrification with Raw Sewage
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Lee Han-Woong
Park Yong-Keun
Choi Eui-So
Lee Jin-Woo
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Abstract
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An autotrophic denitrification reactor (ADR-1) and a heterotrophic denitrification reactor (HDR-2) were operated to remove nitrate and nitrite in an anoxic environment in raw sewage. The NO3-N removal rate of ADR-1 was shown to range from 52.8% to 78.7%, which was higher than the NO3-N removal rate of HDR-2. Specific denitrification rates (SDNR) of ADR-1 and HDR-2 were 3.0 to 4.0 and 1.1 to 1.2mgNO3- N/gVSS/h, respectively. From results of restriction fragment length polymorphism (RFLP) of the 16S rRNA gene, Aquaspirillum metamorphum, Alcaligenes defragrans, and Azoarcus sp. were β-Proteobacteria that are affiliated with denitrifying bacteria in the ADR-1. Specifically, Thiobacillus denitrificans was detected as an autotrophic denitrification bacteria. In HDR-2, the β-Proteobacteria such as Denitrifying- Fe-oxidizing bacteria, Alcaligenes defragrans, Acidovorax sp., Azoarcus denitrificans, and Aquaspirillum metamorphum were the main bacteria related to denitrifying bacteria. The β-and α-Proteobacteria were the important bacterial groups in ADR-1, whereas the β-Proteobacteria were the main bacterial group in HDR-2 based on results of fluorescent in situ hybridization (FISH). The number of Thiobacillus denitrificans increased in ADR-1 during the operation period but not in HRD-2. Overall, the data presented here demonstrate that many heterotrophic denitrifying bacteria coexisted with autotrophic denitrifying bacteria such as Thiobacillus denitrificans for nitrate removal in ADR-1. On the other hand, only heterotrophic denitrifying bacteria were identified as dominant bacterial groups in HDR-2. Our research may provide a foundation for the complete nitrate removal in raw sewage of low-COD concentration under anoxic condition without any external organic carbon or the requirement of post-treatment.
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KEYWORD
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Bacterial communities, autotrophic denitrification, heterotrophic denitrification
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