| In this research, 27 mixed aerobic denitrifiers were isolated from the sediments of a reservoir of Shandong Province, the enhanced raw water without sediments system, the enhanced raw water with sediments system and the raw water of reservoir. Among them, the 10# mixed denitrifiers owned perfect nitrogen removal performance. Then, two efficient aerobic denitrifying bacteria strains named SF9 and ZHF3 were isolated from the 10# flora. Strains SF9 and ZHF3 were identified as Delftia sp. and Acinetobacte sp. by 16 S rDNA sequencing analysis, respectively.Studies on denitrification characteristics of 10# mixed flora concluded that the strains demonstrated efficient denitrification at the high C/N ratio among C/N ratio of 2-8. In order to investigate the influence of temperature and pressure on nitrogen removal, the temperature gradient and pressure experiment through hanging hard bottles(with pressure influence)and soft bottles(without pressure influence)at different water layers were carried on in the reservoir. Results showed that the temperature increased from 11℃ at the bottom of the reservoir to the top 28℃, the higher temperature the better performance of nitrogen removal. Nitrate completely removed in 48 h in surface 28℃ conditions, while that in 144 h in the bottom 11℃ conditions. Compared with the same depth of hard bottle and soft bottle systems, the results showed that pressure had a negative effect on nitrogen removal. Even so, under low temperature and high water pressure conditions, the nitrate removal rate of soft bottle system reached 65% in the bottom of the reservoir. Moreover, the excellent adaptability to temperature and pressure presented by mixed flora was beneficial for nitrogen removal from the reservoir environment.Researches on denitrification characteristics of strain SF9 and strain ZHF3 showed that strains could carry out simultaneous denitrification and total organic carbon(TOC) removal using nitrate as the sole nitrogen source under aerobic conditions. The nitrate removal rates were 81% and 77%, respectively, and TOC were completely removed. Using nitrite as the sole nitrogen source, the nitrite removal rates reached 64% and 79%, respectively. Ammonia removal rates were 40% and 45% in ammonia medium, and TOC were completely removed which reflected the heterotrophic nitrification characteristic of aerobic denitrifiers. When cultured in simultaneous nitrification and denitrification medium, strain SF9 and strain ZHF3 would give priority to utilize of ammonia nitrogen.Added 10# mixed denitrification bacteria to the raw water to investigate the removal effect. The reactor was 20 L glass bottle and the amount of bacteria was 20 mL/ 20 L. The dissolved oxygen was controlled between 3~5 mg/L and temperature was room temperature. The blank system was without any strains. The results showed that the total nitrogen removal rate of bacteria system reached 46%. However, the total nitrogen of blank system was unchanged. The aerobic denitrification numbers of the bacteria system increased from 1.82×105 to 4.10×105 cfu/mL, that of the blank system decreased from 7.32×105 to 2.9×103 cfu/mL. It is, therefore, suggested that the mixed denitrification bacteria can be used as microbial inoculum for nitrogen removal, and had a practical application in micro-polluted water treatment process. |
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