纳米银和二氧化铈对MBBR脱氮性能及微生物群落的影响研究

发布时间：2017-12-27 05:18

本文关键词：纳米银和二氧化铈对MBBR脱氮性能及微生物群落的影响研究　出处：《安徽大学》2017年硕士论文　论文类型：学位论文

【摘要】：银纳米颗粒(AgNPs)和二氧化铈纳米颗粒(CeO_2NPs)因其优良特性,被广泛用于各领域。AgNPs和CeO_2NPs在生产、运输、使用及废弃过程中不可避免地会通过各种环境介质释放至水体例如污水处理系统,对其效能产生潜在的不利影响。本文以移动床生物膜反应器(MBBR)为研究对象,通过构建高效脱氮体系,探究AgNPs和CeO_2 NPs(10 mg/L)单独及共存时对MBBR脱氮性能的短期影响和长期影响及微生物群落的长期影响。主要结论如下:(1)AgNPs和CeO_2 NPs短期内(12 h)通过抑制氨单加氧酶(AMO)和硝酸还原酶(NR)活性影响总氮(TN)去除。AgNPs、CeO_2 NPs、AgNPs和Ce02 NPs混合物使MBBR TN去除率从79.00%(对照组)分别降至73.13%、76.82%和76.18%。AgNPs和CeO_2NPs长期(100 d)作用于MBBR后,AMO活性恢复、NR活性被抑制和生物量减少导致TN去除率下降。AgNPs、CeO_2NPs、AgNPs和CeO_2 NPs混合物使TN去除率分别为降至75.49%、72.10%和69.98%,与对照组(80.07%)有显著差异。(2)MBBR暴露于AgNPs和CeO_2 NPs后,大量纳米颗粒(NPs)附着在微生物表面,短期内细胞膜完整性受到严重损伤,长期适应后细胞膜受损减少。(3)AgNPs和CeO_2NPs改变MBBR胞外聚合物(EPS)产量和性质。短期内AgNPs和CeO_2NPs显著增加松散型胞外聚合物(LB-EPS)含量;长期暴露后,AgNPs 增加 MBBR EPS 含量,CeO_2 NPs、AgNPs 和 CeO_2 NPs 混合物显著降低TB-EPS含量。EPS主要通过蛋白(PRO)和多糖(PS)抵御AgNPs和CeO_2NPs 毒性。(4)NPs长期作用于MBBR后,微生物多样性高低程度顺序为:添加CeO_2 NPs添加AgNPs对照组添加AgNPs和CeO_2 NPs混合物。两种NPs单独存在增加了微生物多样性以抵抗外界冲击,共存时对MBBR系统冲击性大,微生物难以做出调整。群落差异性分析表明AgNPs和CeO_2NPs使MBBR微生物群落结构产生较大差异。对样本进行不同水平上群落结构分析,AgNPs和CeO_2NPs改变群落优势菌群占比,增加硝化细菌(Nitrosomonas和Nitrospira)丰度,显著降低反硝化细菌(Dechloromonas和Thauera)丰度,抑制反硝化活性,影响MBBR脱氮。AgNPs增加Zoogloea(具抗重金属作用)丰度,而O_2NPs、AgNPs和CeO_2NPs混合物降低其丰度。(5)总体上,CeO_2NPs对MBBR的影响作用大于AgNPs,两种NPs共存时对MBBR的毒性大于其单独存在时。
[Abstract]:Silver nanoparticles (AgNPs) and two cerium oxide nanoparticles (CeO_2NPs) are widely used in various fields because of their excellent properties. In the process of production, transportation, utilization and abandonment, AgNPs and CeO_2NPs will inevitably be released to water bodies through various environmental mediums, such as sewage treatment systems, which will have potential adverse effects on their efficiency. In this paper, a moving bed biofilm reactor (MBBR) was used as the research object. By building an efficient nitrogen removal system, we explored the short-term and long-term effects of AgNPs and CeO_2 NPs (10 mg/L) on the MBBR denitrification performance and the long-term effects of microbial community. The main conclusions are as follows: (1) AgNPs and CeO_2 NPs (12 h) affect the removal of total nitrogen (TN) by inhibiting the activity of ammonia monooxygenase (AMO) and nitrate reductase (NR) in the short term. The mixture of AgNPs, CeO_2 NPs, AgNPs and Ce02 NPs reduced the removal rate of MBBR TN from 79% (control group) to 73.13%, 76.82% and 76.18%, respectively. After AgNPs and CeO_2NPs (100 d) acted on MBBR, the recovery of AMO activity, the inhibition of NR activity and the decrease of biomass resulted in the decrease of TN removal rate. The mixture of AgNPs, CeO_2NPs, AgNPs and CeO_2 NPs decreased the removal rate of TN to 75.49%, 72.10% and 69.98% respectively, which were significantly different from those of the control group (80.07%). (2) when MBBR was exposed to AgNPs and CeO_2 NPs, a large number of nanoparticles (NPs) adhered to the surface of microorganisms. In the short term, the integrity of cell membrane was seriously damaged, and the damage of cell membrane decreased after long-term adaptation. (3) AgNPs and CeO_2NPs change the yield and properties of MBBR extracellular polymer (EPS). In the short term, AgNPs and CeO_2NPs significantly increased the content of loose extracellular polymeric substances (LB-EPS). After long-term exposure, AgNPs increased the content of MBBR EPS, and CeO_2 NPs, AgNPs and CeO_2 NPs mixture significantly decreased the content of AgNPs. EPS protects against AgNPs and CeO_2NPs toxicity mainly through protein (PRO) and polysaccharide (PS). (4) after the long-term effect of NPs on MBBR, the order of microbial diversity was as follows: adding CeO_2 NPs to AgNPs control group adding AgNPs and CeO_2 NPs mixture. The two types of NPs alone increase the microbial diversity to resist external shocks, and have a great impact on the MBBR system when they coexist, and the microbes are difficult to adjust. The group fall heterosexual analysis showed that AgNPs and CeO_2NPs made large differences in the microbial community structure of MBBR. The community structure of samples was analyzed at different levels. AgNPs and CeO_2NPs changed the proportion of dominant bacteria in the community, increased the abundance of nitrifying bacteria (Nitrosomonas and Nitrospira), significantly reduced the abundance of denitrifying bacteria (Dechloromonas and Thauera), inhibited the denitrification activity, and affected the MBBR denitrification. AgNPs increases the abundance of Zoogloea (with heavy metal resistance), while the mixture of O_2NPs, AgNPs and CeO_2NPs reduces its abundance. (5) on the whole, the effect of CeO_2NPs on MBBR is greater than that of AgNPs, and the toxicity of the two kinds of NPs is greater than that of the MBBR when it exists alone.
【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703;X172

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