The Study Of Characterization In Nitrite Denitrification Process And Mechanism By Comamonas Aquatica LNL₃

With the developing of economy and population, the discharge of nitrogen compounds increases sharply, which has great influence on the nitrogen balance.Nitrogen had become one of the predominant pollutants in water, which draws the attention of the society. Biological nitrogen removal has been used widely presently, which can be realized by different bacteria. However, this study would introduce a novel bacterium called Comamonas aquatica LNL3, which can oxidize ammonia to nitrite and also can achieve nitrite removal at the existence of organic carbon, that is to say Comamonas aquatica LNL3can removal ammonia to nitrogen gas without any other microorganism. Therefore it is interesting to research this bacterium and we hope the results obtained from this study can help its use in the industry.Therefore the aim of this paper was to study the characterization of Comamonas aquatica LNL3in the nitrite denitrification process and optimize the operating parameters using the response surface methodology and the mechanism of denitrification. The main conclusions are as follows:1、Fluidized bed reactor is used to enrich and immobilize bacteria in aerobic condition and domesticate the microorganism in anaerobic conditions. Nitrite removal efficiency could reach90%at the existence of organic carbon; the nitrite removal rate reached the peak when influent nitrite was200mg/L.2、Poly(HEA)-Poly(HEMA) can be used for immobilizing the bacteria because of its biocompatibility which is suitable for growth and immobilization.SEM and FT-IR indicates the bacteria has been successful growing inside the carrier,biomass was about1.072×104(nmol P/g dry carrier), which means1.072×1012E. Coli per gram dry carrier.3、Response surface methodology (RSM) is a well-known experimentation technique for assessing the effects of parameters on treatment results. Box-Behnken was used to evalue the influence of temperature, pH, C/N and DO on the nitrite removal rate. When temperature31.5℃pH=8.41, C/N=5, DO=3.37mg/L, nitrite removal rate reached the maxium. The influence order of environmental factor on nitrite removal rate was DO> temperature>C/N>pH.4、The condition for shortcut nitrification has no obivious to that of nitrite denitrification by Comamonas aquatica LNL3, which indicates Comamonas aquatica LNL3can achieve ammonia removal alone.5、Comamonas aquatica LNL3can remove ammonia as well as nitrite in aerobic condition, however the nitrite removal rate was larger then that of ammonia removal.6、Comamonas aquatica LNL3can transfer different inorganic nitrogen compounds; the model has been built and proved. Comparing to the traditional shortcut nitrification and denitrification process, the denitrification process of Comamonas aquatica LNL3has more advantages.