Effect of substrate COD/N ratio on performance and microbial community
structure of a membrane aerated biofilm reactor |
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Authors: | Huijun Liu Fenglin Yang Shuyi Shi and Xincheng Liu |
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Institution: | 1. China Agriculture University, Yantai 264670, China 2. School of Environmental and Biological Science and Technology, Dalian University of Technology, Dalian 116024, China |
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Abstract: | Two parallel carbon-membrane aerated biofilm reactors were operated at well-defined conditions to investigate the e ect of substrate
COD/N ratios on the performance and microbial community structure of the bioreactor. Results showed that at substrate COD/N of 5,
organic and nitrogen could be eliminated simultaneously, and COD removal degree, nitrification and denitrification e ciency reached
85%, 93% and 92%, respectively. With increasing substrate COD/N ratios, the specific oxygen utilization rates of nitrifying bacteria in
biofilm were found to decrease, indicating that nitrifying population became less dominant. At substrate COD/N ratio of 6, excessive
heterotrophs inhibited the activity of nitrifying bacteria greatly and thus led to poor nitrification process. With the help of fluorescence
in situ hybridization (FISH), Nitrosomonas and Nitrosospira were identified as dominant ammonia-oxidizing bacteria in the biofilm at
substrate COD/N of 0, whereas only Nitrosospira were detected in the biofilm at COD/N ratio of 5. Nitrospira were present as dominant
nitrite-oxidizing bacteria in our study. Confocal laser scanning microscopy images revealed that at substrate COD/N ratio of 0 nitrifying
bacteria existed throughout the biofilm and that at COD/N ratio of 5 they were mainly distributed in the inner layer of biofilm. |
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Keywords: | substrate COD/N ratio simultaneous organic and nitrogen removal biofilm activity fluorescence in situ hybridization |
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