| Recently , some new de-nitrogen theories and processes absorbed people's eyes.It is often found that in these processes , nitrification is in the important role of deciding the whole rate of reaction.So , the study on the enhancing ammonia oxidation rate is necessary .In the mean time , it was found that ammonia bacteria have the potential of diverse metabolic types,including using NO2 as electron accepter in anaerobic ammonium oxidation.This paper aimed to study the ammonia oxidation rate of enriched sludge under the atmosphere of NO2/O2/CO2 at different levels,which could provide expriment data for the furture combination of activated sludge and de-nitrogen technology.Accroding to the expeiment of selecting the specially microorganisms from normal acitvated sludge,it was show that ammonia oxidizer could be selected and enriched in SBR after 120d cultivated.And the controlling of pH, DO and temperature is very important in the operation process.The experiment involved with mixed gas supported that ammonia oxidizer could use NO2 as electron accepter when there is no molecule oxygen. And ammonia oxidation rate is comparatively high in the atmosphere with low NO2 level. After adding the O2, the increase of ammonia oxidation rate was observed. The max ammonia oxidation rate 0.033mmolNH4+-N/gMLSS.h was obtained in the atmosphere of 40ppmNO2 /21%O2 . And certain synergistic reaction between NO2 and O2 was found when the concentration of NO2 was in the range of 20-40ppm. Further enhancement of NO2 concentration to 250ppm cause the decrease of the ammonia oxidation rate .NO was found as gaseous products in the reaction .And the caculation result showed that there are unknown N loss in the reaction ,which may be caused by the production of N2 or N2O from denitrification.
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