| Nitrogen pollution is an important factor of causing water pollution. When the nitrogen concentration is too high,it will cause certain harm to water ecology and human health. Traditional denitrification theory hold the opinion that biological denitrification is composed of two independent reaction--nitrification and denitrification. Because of the different requirement of the different nitrifiers and denitrifiers for nourishment, the process of removal of nitrogen is very complex and the application is limited. Aiming at the above shortcomings, the research has isolated high efficiency heterotrophic nitrifying bacteria, denitrifying bacteria, aerobic denitrifying bacteria with same requirement for nourishment from the bio-contact oxidation reactor which was in stable operation, their performance and influencing factors were studied. Based on the actual application, this research invested the above isolated strains to self-designed bio-contact oxidation reactor which contacts both anaerobic and aerobic zones to research simultaneous nitrification and denitrification effect of the composite flora in treating domestic wastewater.Heterotrophic nitrobacteria JZ1-1, denitrifying bacterium aHD7and aerobic denitrifying bacterium DN7were isolated and mutagenized from the bio-contact oxidation reactor treating bamboo process wastewater. They were identified as Colloides sp., Pseudomonas mendocina, Deflnvibacter lusatiensis str. according to their morphological, physiological features biochemical/morphological characteristics and homologic analysis of16SrDNA sequence.The optimal carbon source of heterotrophic nitrobacteria JZ1-1was sodium citrate. Nitrification was favored when the C/N ratio was from10to14, temperature was30℃, rotating speed was more than150r·min-1, and the pH value was6-9. JZ1-1could degrade ammonia nitrogen effectively when the initial ammonia nitrogen concentration was among100mg·L-1to500mg·L-1. JZ1-1was stable after5generations of subculture.Denitrifying bacterium aHD7could grow on various nitrogen sources, When the initial nitrate concentration was less than276.95mg·L-1, nitrogen removal efficiency was nearly100%, The optimal carbon source was ethanol. Denitrification was favored when the C/N ratio was from6to8, and the pH value was6-9. aHD7had good anammox ability, and the average ammonium utilization rate reached4.56mg·L-1·d-1. The optimal carbon source of Aerobic denitrifying bacterium DN7were sodium citrate and glucose, and when the C/N ratio was9, nitrogen removal efficiency reached98.99%. DN7could degrade nitrate significantly effective with concentration below138.48mg·L-1.The nitrogen removal efficiency was more than96%with little nitrite accumulation. Strain DN7was not sensitive to DO (dissolved oxygen), and denitrification was favored under neutral or a bit alkaline condition. The strain could use either nitrate or nitrite as sole nitrogen source for aerobic denitrification. It preferred to utilize nitrate. Coexistence of nitrite had no significant effect on nitrate reduction, little amount of nitrate would inhibit the nitrite reduction. When ammonium nitrogen was served as sole nitrogen, both heterotrophic nitrification and aerobic denitrification occurred. Ammonium nitrogen removal efficiency reached85.66%in72h with no nitrate or nitrite accumulation. Aerobic denitrification of the strain could be favored in the presence of little amount of ammonium nitrogen, and vice versa.Self-designed nitegration contact oxidation reactor was used to research denitrification performance of composite flora. Due to the complex bacterium which had strong ability of adapting to the new environment, the nature start-up was finished after reactor launching for2days, and CODCr (chemical oxygen demand), NH4+-N (ammonia nitrogen), TN (total nitrogen)removal efficiency stabilized at80%,70%,45%or above after starting for6-7days. Compaed the treatment results of removal sewage by composite flora under different HRT, it indicated that a long time staying was benefit to fully reaction of microbial. |
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