| The damage caused by the excessive emissions of nitrogen oxides (NOx) hasattracted widespread attention. The main source of NOx, more than90%, is from thecombustion of fossil fuels due to the coal-based energy structure of our country.Further more, more than95%of the NOx in flue gas is NO, which is insoluble inwater and adding more difficulties to remove it from the flue gas. The most commonused method in NOxremoval from flue gas is catalytic reduction due to the highremoval efficiency, however, there are some drawbacks, such as high cost, easydeactivation of the catalysts and producing secondary pollutants. Other methods arestill under investigation to demostrate the feasibility and economy for industralization.Therefore, it is urgent to find a safe and efficient NOxremoval method withoutproducing secondary pollution. A promising method of chemical absorptioncombined with biological reduction (BioDeNOx) is proposed recently for NOxremoval, however, the dominate bacteria strains and their reduction properties are stillneed to be further studied.In this paper, two dominant strains in the BioDeNOxprocess are isolated. Bothof the two strains are identified as Klebsiella Trevisan, and one is a FeII(EDTA)-NOreducing bacteria named DL-1, the other is a FeIII(EDTA) reducing bacteria namedFD-3. The growth characteristics, the effects of the environmental conditions and thecoexisting ions in the absorption solution on the restore of FeII(EDTA)-NO andFeIII(EDTA)by DL-1and FD-3are investigated respectively. The kenictics model ofthe relationship between the microbial cell growth and substrate concentration wereestablished. Furthermore, the effects of nitrogen-containing compounds on cellgrowth and reduction properties of FD-3were sdudied. The main results were asfollows:Bacteria strain DL-1can reduce FeII(EDTA)NO efficiently. Glucose is more suitablethan ethanol, acetate and other substances as a plus carbon source for DL-1in the reductionof FeII(EDTA)NO. DL-1can adapt to temperature and pH value in a wide range of35-55°Cand4.4-9.0with a optimal temperature of45°C and pH of7.8or9.0, respectively. S2-has a significant inhibition on the bacterial FeII(EDTA)NO reduction and cell growth of DL-1,while SO32-in the system does not affect the FeII(EDTA)NO reduction and even beneficial toFeII(EDTA)NO reduction due to the chemical reaction with FeII(EDTA)NO to generate N2and SO42-. The low concention of NO2-can promote FeII(EDTA)NO reduction, but has aninhibition effect at high concentrations, however, the inhibition eliminated gradually withprolonged reaction time, The reason may be that the DL-1itself is a denitrifying bacteria, soit can take advantage of the NO3-and NO2-. The established kenictics model can explain thebacterial growth and substrate reduction well.Bacteria strain FD-3can restore FeIII(EDTA) effectively. The FD-3can adapt totemperature and pH in wide range of35-55°C and5.0-9.0, respectively; S2-has asignificant inhibition on bacterial FeIII(EDTA) reduction, but it will stimulate cellgrowth. FeIII(EDTA) reduction and cell growth decreases with the increase of SO32-concentration in the cultivation liquid. SO42-has no inhibition on the bacterialFeIII(EDTA) reduction and cell growth of FD-3. NO3-stimulates the FeIII(EDTA)reduction and cell growth slightly, probably due to the utilization of nitrate asnitrogen source in the domestication process, which makes the bacteria with a goodability to use nitrate. Low concention of NO2-can promote FeIII(EDTA) reduction, buthas an inhibition effect at high concentrations, however, the inhibition eliminatedgradually with prolonged reaction time, and NO2-also has a certain inhibition effecton cell growth. In addition, FD-3has a certain reduction capacity of FeII(EDTA)NO,NO3-and NO2-. Kenitics model based on the Logistic equation can exlpain therelationship between cell growth and substrate reduction well. |
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