溶解氧对悬浮与附着生长系统短程硝化反应的影响机制

溶解氧(DO)是控制短程硝化的重要因素,其对不同的生物处理系统有不同的影响.本文研究了DO对悬浮污泥及生物膜系统短程硝化效果的影响,并利用高通量测序技术分析了微生物群落结构变化.结果表明,对于悬浮污泥系统,当DO从0. 25 mg·L~(-1)增加到0. 50 mg·L~(-1)时,氨氧化速率(AOR)从18. 08 mg·(L·h)-1升高至30. 27 mg·(L·h)-1;当曝气继续增加,DO达到3. 00 mg·L~(-1),仅运行14 d,进水氨氮(NH_4+-N)基本全部转化为硝酸盐氮(NO_3--N),且通过降低DO来恢复短程硝化效果需77 d,恢复过程缓慢.对于生物膜系统,DO由2. 50 mg·L~(-1)上升到3. 00 mg·L~(-1)的过程中,AOR稳定在11. 50～13. 50mg·(L·h)-1,当DO为3. 00 mg·L~(-1)时,80 d的运行结果显示,出水中氨氮与亚硝酸盐氮(NO_2--N)的比值可长期稳定在1∶1. 2～1∶1. 7,基本满足ANAMMOX工艺进水要求.微生物群落结构分析结果表明,悬浮污泥系统在DO从0. 25 mg·L~(-1)增加到3. 00 mg·L~(-1)的过程中,主要氨氧化菌(AOB)菌属Nitrosomonas丰度由10. 07%增长至18. 64%.当DO为3. 00 mg·L~(-1)时,生物膜系统中Nitrosomonas菌属丰度与悬浮污泥系统相近为20. 43%,且生物膜系统富集了0. 78%的ANAMMOX菌属Candidatus_Kuenenia.综上,生物膜系统内DO的变化受曝气量影响较小,短程硝化效果受DO影响较小,短程硝化速率更稳定,更适合作为ANAMMOX脱氮工艺的前处理单元.

Effect of Dissolved Oxygen on Partial Nitrification of Suspended and Attached Growth Systems

Dissolved oxygen (DO) is an important factor in controlling the partial nitrification process, and it has different effects on different biological treatment systems. The effect of different DO on performances of the partial nitrification process in suspended and attached growth systems, and the changes of microbial community structure by high-throughput sequencing technology were all investigated. The results showed that for a suspended sludge system, the ammonia oxidation rate (AOR) increased from 18.08 mg·(L·h)^-1 to 30.27 mg·(L·h)^-1 when the DO increased from 0.25 mg·L^-1 to 0.50 mg·L^-1. The ammonia nitrogen (NH₄⁺-N) in influent was completely changed into nitrate-nitrogen (NO₃^--N) after a 14-day operation; when the DO was kept at 3.00 mg·L^-1, it needed 77 days to restore the short-cut nitrification effect by reducing DO. In the attached growth system, the AOR was maintained within a narrow range of 11.50-13.50 mg·(L·h)^-1 when DO increased from 2.50 mg·L^-1 to 3.00 mg·L^-1. When DO was at 3.00 mg·L^-1, the ratio of NH₄⁺-N to nitrite nitrogen (NO₂^--N) in the effluent was maintained within 1:1.2 to 1:1.7 through investigating the results from an 80 day operation, and the ratio could meet the influent requirement of the anaerobic ammonium oxidation (ANAMMOX) process. Microbial community structure analysis indicated that the abundance of the Nitrosomonas genus belonging to ammonia-oxidizing bacteria (AOB) increased from 10.07% to 18.64% when the DO increased from 0.25 mg·L^-1 to 3.00 mg·L^-1 in a suspended sludge system; the abundance of the Nitrosomonas genus in the biofilm system was 20.43% and that of the Candidatus_Kuenenia genus was 0.78% when DO was 3.00 mg·L^-1. Conclusively, the biofilm system could be used as a pretreatment unit for the ANAMMOX process, because the partial nitrification process was less affected by DO and the partial nitrification rate was more stable.