氨氮对反硝化型甲烷厌氧氧化细菌的影响机理研究

反硝化型甲烷厌氧氧化(Denitrifying Anaerobic Methane Oxidation,DAMO)是以甲烷为电子供体和唯一碳源,以硝酸盐或亚硝酸盐为电子受体的一种氧化还原反应,可用于废水脱氮,而氨氮是含氮废水中存在的主要形式.目前的研究认为主导DAMO过程的微生物主要有DAMO细菌和DAMO古菌.本文以DAMO细菌为优势菌种的系统为研究对象,通过短期和长期试验,从宏观和微观上研究了氨氮对该系统短期和长期的影响,并比较了不同pH体系下影响效果差异,揭示了相关影响机理.短期试验研究表明,氨氮对该系统的安全浓度为250 mg·L~(-1).当氨氮浓度为500 mg·L~(-1)时,对该系统的脱氮效率造成明显的抑制作用,并且随着浓度、时间的增加,氨氮对其的抑制效果增强;不同pH条件下抑制效果的差异对比发现,在碱性条件下,真正起抑制作用的是氨氮的质子化形式FA(Free Ammonia),在中性及酸性条件下,真正起抑制作用的抑制因子是离子化的NH_4~+.通过扫描电镜对系统中絮状污泥分析发现,在氨氮的短期抑制后,系统内的微生物出现了明显皱缩,丝状菌的数量增加;采用高通量测序技术分析了长期氨氮抑制后的系统,结果显示,系统内菌群结构发生较大改变,物种的多样性和丰度都大大降低.通过菌属分析认为,系统脱氮效率的降低是由于Methylomonas(甲基单胞菌属)数量的减少引起的.

Effect mechanism of ammonia on denitrifying anaerobic methane oxidation bacteria

Denitrifying anaerobic methane oxidation (DAMO) is an anaerobic process, which uses methane as the electron donor and nitrate or nitrite as the electron accepter, which can be used for biological nitrogen removal in wastewater. The current studies suggest that the dominant microorganisms in the DAMO process are mainly DAMO bacteria and DAMO archaea. This study was carried out based on the DAMO system in which DAMO bacteria was the dominant. The effects of NH₄⁺-N on the DAMO system were investigated from macro to micro through short- and long-term experiments. The effects of different pH were compared and the relevant mechanisms were revealed. Short-term experimental results show that the safe concentration of ammonia to the DAMO system is 250 mg·L^-1. When the concentration of ammonia was up to 500 mg·L^-1, the efficiency of denitrification of the system was significantly inhibited. And with increase of concentration and time, the inhibitory effect of ammonia was enhanced. Different inhibitory effects of ammonia nitrogen on the system were found under different pH conditions. The results show that the protonated form of ammonia nitrogen (Free Ammonia, FA) actually played an inhibitory role under alkaline conditions, and ionized NH₄⁺ played an inhibitory role under neutral and acidic conditions. The analysis of the flocculent sludge in the system by scanning electron microscopy indicated that after the short-term inhibition of ammonia, the microorganisms in the system were significantly shrunk and the number of filamentous bacteria increased. Analysis by using high-throughput sequencing, the results show that the microbial community structure of bacteria in the system changed greatly, and microbial diversity and abundance were greatly reduced. According to the genetic analysis, the decrease of nitrogen removal efficiency of the system is caused by the decrease of the population of Methylomonas.