| As aerobic denitrifying bacteria can denitrify in the aerobic condition, bionitrification and biodenitrification can be achieved in the same reactor, which would save the infrastructure costs and facilitate the system operation. Heterotrophic bacterium Vibrio sp. Y1-5was isolated in the Kiaochow bay sediments which exhibited high ability of absorbing ammonium and assimilating nitrate reduction to ammonium under fully aerobic conditions. At optimized conditions of inoculation10%, salinity3%, C/N=15, pH=7, temperature25℃and the dissolved oxygen (DO=7.62mg/L), bacterium Vibrio sp. Y1-5could remove TN above90%in mediums of83mg/L nitrate. And the removal efficiency of CODcr was synchronous with the TN, in the medium of CODcr=3000mg/L, CODcr removal efficiency was up to95%in48h. C/N had a mainly effect on NO3-N removal efficiency of bacterium Vibrio sp. Y1-5. When C/N was from2to20. NO3-N removal efficiency increased from16%to90%. while C/N was in2～12, aerobic denitrifying bacteria had a better effect as C/N increase. Bacterium Vibrio sp. Y1-5was better acclimated to high C/N environment than aerobic denitrifying bacteria. Comparing the high oxygen(7.62mg/L) with the low oxygen(4.26mg/L) in the nitrate medium, transformations of different nitrogen forms (NH4+、NO2-、NO3-and organic nitrogen) and the removal efficiency of CODcr were analyzed. In the high oxygen condition, the NO3-concentration declined fast, and the concentrations of NH4+and NO2-were both in a low level(under10mg/L), the gaseous NOx was produced low. In the low oxygen conditions, the NO2-and NH4+concentration were accumulated consecutively, production of gaseous NOx was less than6mg/L, but it could still finished the process of nitrate reduction. Most aerobic denitrifying bacteria could tolerate DO less than3mg/L, but in a higher DO, denitrifying activity of aerobic denitrifying bacteria was affected, the final product was mainly greenhouse gas of N2O. However, the effect of oxygen on the production of gaseous NOx was not obvious. Bacterium Vibrio sp. Y1-5could tolerate higher DO and produce less N2O.Traditional biological treatment for ammonium salt wastewater was through the nitration reaction. However, the autotrophic nitrifying bacteria were sensitive to the high concentrations of organic matter and ammonia. They could not compete with the heterotrophicy bacteria in the O2and the nutriment. It was found that in the NH4+mediums, the production of NO3-was low, and the NH4+removed by Vibrio sp. Yl-5was not in the nitration but in the direct absorbtion. For the bionitrification occupied much oxygen consumption in the secondary sewage treatment, this removal mechanism could save energy by reducing the O2consumption. Bacterium Vibrio sp. Yl-5could tolerate a wide range of NH4+concentration, and could grow well in the concentration of1590.9mg/L. The Fourier infrared spectra of the thallus showed bacterium utilized the nitrogen as the protein or the storage organic nitrogen material. Above all, bacterium Vibrio sp. Y1-5could simultaneously remove nitrate and ammonia by assimilation nitrogen from nitrogen-rich wastewater. This could effectively prevent the nitrogen loss and make the sludge fertile for agriculture reuse.For the high interception of membrane bioreactor (MBR), inoculated denitrifying bacteria could avoid fast lossing. Transformation of nitrogen forms and the performance in nitrogen. CODcr and TP removal were studied by inoculate bacterium Vibrio sp. Y1-5to the MBR. Results demonstrated that TN and TP removal were improved to some extent. However, further study was still needed to optimize the operation conditions, such as salinity, ratio of carbon to nitrogen, etc., to obtain higher denitrification of bacterium Vibrio sp. Y1-5growth in the reactor. |
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