Salt Heterotrophic Nitrification - Screening Methods For Aerobic Denitrifying Bacteria And Denitrification Mechanisms And Their Biological Strengthen The System Of Partial Nitrification

A new method for enrichment and domestication of heterotrophic nitrification-aerobic denitrification bacteria was studied. The enrichment and domestication was accomplished by adopting high C/N ratio, gradually reducing DO, inoculating domestic bacteria to new culture medium in log phase and increasing the proportion of sea water for culture medium, and 38 strains were screened in this process. Furthermore, a train qy37 of heterotrophic nitrifying bacteria were isolated from enrichment and domestication system. In the light of its morphological and physiological characters as well as its sequence analysis of the 16S rDNA, strain qy37 was identified as Pseudomonas sp.The mechanism of heterotrophic nitrification and aerobic denitrification was compared. The characterization in nitrogen removal of a heterotrophic nitrification-aerobic denitrification bacteria qy37 was studied. A strain coded as qy37 which had simultaneous heterotrophic nitrifying and aerobic denitrifying ability was screened. In the light of its morphological and physiological characters as well as their sequence analysis of the 16S rDNA, strain qy37 was identified as Pseudomonas sp. In heterotrophic nitrifying system utilized ammonium chloride as nitrogen source, the concentration of NH4+-N reduced from 138.52 mg/L to 7.88 mg/L and COD reduced from 2408.39 to 1177.49mg/L by strain qy37 in 32 hours, the maximum accumulation of NH2OH and NO2--N were 9.42 mg/L and 0.02 mg/L respectively, it was speculated that NH20H was transformed to N2O and N2 directly by strain qy37. In aerobic denitrifying system utilized sodium nitrite as nitrogen source, the concentration of NO2--N reduced from 109.25 mg/L to 2.59 mg/L by strain qy37 in 24 hours, and the maximum accumulation of NH2OH was 3.28mg/L. Compared with heterotrophic nitrifying system, aerobic denitrifying system had a higher bacterial growth whereas the lower removal rate of TN and COD, as well as the accumulation of NH2OH. NO3--N was also detected In aerobic denitrifying system. It is considered that the upgrowth of bacterium and utilization of energy in aerobic denitrifying system were more efficient than that in heterotrophic nitrifying system.The heterotrophic nitrification- aerobic denitrification system was studied. In heterotrophic nitrification- aerobic denitrification system, the removal rate of NH4+-N improved 37.31% in 16 hours than that in heterotrophic nitrifying system, the accumulation of NH2OH was less but N2O was higher than that in both heterotrophic nitrifying system and aerobic denitrifying system. These results should be useful for practical application of heterotrophic nitrification- aerobic denitrification bacteria in sewage disposal.The feasibility of heterotrophic nitrification- aerobic denitrification bacteria applied in shortcut nitrification system was studied. Four heterotrophic nitrification-aerobic denitrification strains mixed with halotolerant activated sludge was added into SBR in order to test their bioaugmentation ability for shortcut nitrification system, which was treating for sewage containing sea water, and the difference between bioaugmentation system and original system was compared. The results showed that the maximum accumulation of NO2--N in bioaugmentation system was 34.92% lower than that in original system, and the time of maximum accumulation of NO2--N was 2 hours earlier than that in original system. The TN and COD was continuously decreasing in the later phase of nitrification in bioaugmentation system, and finally the removal rate of TN and COD were 15.24% and 5.39% higher than that in original system respectively, as well as the removal rate of NH4+-N and the nitrosation rate were 6.85% and 14.47% higher than that in original system. And the pH was 0.46 higher than that in original system, whereas the ORP was 25.84 mV lower. It was considered that the function of heterotrophic nitrification-aerobic denitrification bacteria should strengthen the performance of bioaugmentation system. When the seawater content raised to 70%, the stability of bioaugmentation system was better than that in original system, and the current that transforming shortcut nitrification to complete nitrification was restrained by heterotrophic nitrification- aerobic denitrification bacteria effectively. The number of heterotrophic nitrification-aerobic denitrification bacteria was changed when bioaugmentation system and original system ran in different phase and the bacteria had a great loss with the discharge of activated sludge. These results may provide a theoretical reference about the feasibility that the heterotrophic nitrification-aerobic denitrification bacteria applied in shortcut nitrification system.