温度和DO对MBBR系统硝化和反硝化的影响

在缺氧/好氧/好氧串联运行的移动床生物膜反应器（MBBR）系统中考察了温度和好氧反应器中溶解氧（DO）水平对生物膜硝化和反硝化过程氮素去除的影响，并通过高通量测序技术探究温度和DO的变化造成的MBBR系统中脱氮功能菌群结构的差异，从而在微观水平解释硝化和反硝化受温度和DO影响的生物学机理.结果表明，系统温度的升高可以同时强化生物膜硝化和反硝化过程，且好氧反应器中DO水平的提高对硝化过程有利，从而提高系统的脱氮效果.本研究中，在系统连续运行阶段，当系统温度和好氧O₁反应器的DO浓度为本研究范围内的最高水平时（即温度=20~22℃、DO=5~8mg O₂/L），比硝化负荷可达1.60g NH₄⁺-N/（m²·d）以上，而相同温度范围内比反硝化负荷可高达2.84g NO₃^--N/（m²·d），从而使MBBR系统在该工况条件下获得了最佳的NH₄⁺-N和TN去除率（分别达到了98.7%和85.7%）.温度和DO影响硝化和反硝化的根本原因是温度和DO变化引起了脱氮功能菌群数量和群落结构的改变：当好氧反应器的DO水平下降时，硝化功能细菌的OTUs比例显著降低，尤其是异养硝化细菌的生长受到了严重的抑制；而温度的变化对反硝化细菌的影响主要体现在群落结构的变化.

Effects of temperature and dissolved oxygen on nitrification and denitrification in MBBR system

The effects of system temperature and DO level in aerobic reactor on nitrification and denitrification in three lab-scale moving bed biofilm reactors(MBBRs)in series operated under anoxic/aerobic/aerobic conditions respectively, were investigated. The microscopic mechanism based on the changes in the structure of nitrogen removal functional bacteria in biofilm affected by temperature and DO were discussed using high-throughput sequencing technology. The results indicated that the increase in system temperature could enhance not only nitrification but also denitrification process in biofilm, and the increase in the DO level in aerobic reactor was beneficial to nitrification process. During the continuous operation of the processes, when the system temperature and the DO level in the aerobic reactor were at the highest level (i.e., temperature=20~22℃, DO=5~8mg O₂/L), more than 1.60g NH₄⁺-N/(m²·d) of the specific nitrification loading rate could be achieved, and the specific denitrification loading rate was as high as 2.84g NO₃^--N/(m²·d). The optimal removal efficiencies of NH₄⁺-N and TN could reach 98.7% and 85.7% respectively. The essential reasons for the changes in the population and community structure of nitrogen removal functional bacteria resulted from the variation in temperature and DO level. When the DO level in the aerobic reactor decreased, the OTUs proportion of nitrifiers, especially heterotrophic nitrifiers, decreased significantly. The effect from the temperature on the denitrifiers could be mainly attributed to the structural change in the community.