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近年来废水处理过程中成本控制越来越受到关注,为了在不增加运行成本的情况下获得更高的出水水质,同步硝化反硝化工艺(simultaneous nitrification and denitrification,SND)的研究受到学者们的青睐,目前国内外对于SND工艺的研究已取得较好效果[1-3]。研究发现,SND的效率取决于3个因素:氧浓度、絮体大小和足够的有机碳基质的可用性[4-5]。Third等[1,6]基于SBR系统,通过控制溶解氧实现了SND,研究认为低溶解氧浓度(<2 mg·L−1)和大絮体是最佳SND的必要条件;Holman等[7]采用两组SBR系统,研究认为增加碳源浓度(100—1000 mg·L−1)有利于SND的实现;张可方等[8]研究发现,C/N为3.3—10时,C/N越高出水硝氮浓度越低,SND效果越好;同时刘军等[9]在序批式活性污泥反应器内,以模拟的城市污水为处理对象,研究认为DO=1.60—1.80 mg·L−1,COD/
${\rm{NH}}_4^{+} $ -N=6.5或BOD5/${\rm{NH}}_4^{+} $ -N=4时,TN的去除率分别达到最大;此外有学者采用侧沟式一体化OCO反应器,研究发现C/N约为8时SND速率最高,此时TN去除率达到最高(82%),当C/N小于8或大于8时SND率都呈现出下降趋势[10]。Iannaconea等[11]采用移动床膜生物反应器(C/N为2.7、4.2和5.6;HRT为2 d与1 d;溶解氧浓度,1.0 mg·L−1)研究认为,C/N为4.2时,总无机氮去除率达到68%,而C/N分别为2.7和5.6时,脱氮效率较低且不稳定;以及Zhou等[12]研究认为,降低C/N(20、10和5),TN的去除效率表现为降低的趋势,同时发现改变C/N将导致具有脱氮除磷功能的微生物种类有较大变化。由于SND的形成原因较为复杂,对于SND的机理性研究还应进一步深入,特别是微生物学的研究,现已发现的好氧反硝化菌约50多个属,130多个种[13],其中普遍存在的好氧反硝化菌为产碱杆菌属(Alcaligenes)[14-15]、Diaphorobacter[16]、不动杆菌属(Acinetobacter)[17-18]、气单胞菌属(Aeromonas)[19]、假单胞菌属(Pseudomonas)[20-21]、克雷伯氏菌(Klebsiella)[22]、根瘤菌属(Rhizobium)[23]、芽孢杆菌属(Bacillus)[24]、红球菌属(Rhodococcus)[25]和农杆菌属(Agrobacterium)[26]等,这就使得硝化和反硝化在同一反应器、同一条件下进行成为可能。
关于C/N对SND工艺微生物多样性影响的研究较少,同时基于SBR系统易实现SND现象,因此本文基于4种C/N(0、5、10和15)系统,考察了C/N对SND的影响,同时采用高通量测序技术探究了C/N对SBR活性污泥系统微生物群落分布的影响。
间歇式活性污泥法(SBR)系统碳氮比对同步硝化反硝化微生物群落分布及脱氮效能的影响
Effect of C/N ratio on the microbial community of simultaneous nitrification and denitrification (SND) and the biological nitrogen removal in sequencing batch reactor (SBR)
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摘要: 同步硝化反硝化(simultaneous nitrification and denitrification,SND)是一种节能型废水处理工艺,但C/N对SBR系统SND及活性污泥微生物种群的影响机理尚不清楚。本试验以人工模拟废水为研究对象,采用4组不同碳氮比(C/N)系统(R0、R5、R10和R15)对比分析了C/N对SBR系统SND及活性污泥微生物种群的影响,并通过高通量测序测定了SBR活性污泥系统微生物多样性。结果表明,C/N与SND效能的实现及提高显著正相关,随着C/N的升高,SBR系统SND率(19.2%→25.7%→35.0%→74.0%)和SND反应速率[(16.1→21.4→30.2→57.2) mg·(gSS·d)−1]显著升高,且R10和R15系统分别在第215和120周期后,SND对总氮去除贡献率达到63.7%和89%。高通量测序结果表明,门水平微生物具有较高的多样性,达到19门,主要包括变形菌门(55.10%),拟杆菌门(17.40%),蓝细菌门(7.90%),疣微菌门(5.00%)和硝化螺旋菌门(2.80%),其中变形门是优势菌种,并且属水平上也具有较高的多样性,数量达到112种以上,其中动胶菌属为优势菌属,且R0系统内硝化螺旋菌属的相对丰度是R5、R10和R15的106倍。此外,SBR活性污泥系统中包含反硝化菌的门和属主要由变形门、拟杆菌门和厚壁菌门中的22个菌属所组成。Abstract: Simultaneous nitrification and denitrification (SND) is an energy-saving process of wastewater treatment, but the mechanism of C/N ratio effect on the SND and the microbial population of activated sludge in sequencing batch reactor (SBR) system are not clear. In this study, the long-term effect of C/N ratio on SND and bacterial community compositions of activated sludge in SBR system treating synthetic wastewater was investigated under four C/N ratio conditions (0, 5, 10, 15), besides Illumina high-throughput sequencing technology was applied to investigate microbial communities of SBR system. The results showed that the C/N ratio was significantly positively related to the realization and improvement of SND performance. With the increase of C/N ratio (0→5→10→15), SND rate(19.2%→25.7%→35.0%→74.0%) and SND reaction rate[(16.1→21.4→30.2→57.2) mg·(gSS·d)−1] observably increased, meanwhile, after cycles of 215 and 120, 63.7% and 89% of total nitrogen removal in R10 and R15 systems were attributed to SND. And the results of high-throughput sequencing technology showed that the level of phylum was diversities and richness and 19 phylums, which mainly included Proteobacteria (55.10%), Bacteroidetes (17.40%), Cyanobacteria (7.90%), Verrucomicrobia (5.00%) and Nitrospirae (2.80%), among which, the Proteobacteria was dominant phylum. Meanwhile, the level of genus was diversities and richness and 112 genera, among which Zoogloea was the dominant genus, besides the relative abundance of Nitrospira in R0 system was 106 times of R5, R10 and R15. In addition, the genus containing denitrifying bacteria in SBR system were mainly composed of 22 genera that belonged to the phylums of the Proteobacteria, Bacteroidetes and Firmicutes.
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表 1 4个SBR反应器运行条件
Table 1. Operating conditions of four SBR reactors
反应器
React-ors周期时间/min
HRT进水/min
Influent
times曝气/min
Aeration
times沉淀排水/min
Sedimentation
and drainageCOD/
(mg·L−1) -N/${\rm{NH}}_4^{+} $
(mg·L−1)MLSS/
(mg·L−1)T/℃ DO/
(mg·L−1)pH R0 300 5 270 25 0 20 2540 25±2.0 1.0—2.5 7.5±0.2 R5 340 5 300 35 300 60 3345 25±2.0 1.0—2.5 7.5±0.2 R10 330 5 270 55 300 30 3154 25±2.0 1.0—2.5 7.5±0.2 R15 270 5 210 55 300 20 2989 25±2.0 1.0—2.5 7.5±0.2 表 2 4个SBR系统内反硝化细菌的相对丰度
Table 2. The relative abundance of denitrifying bacterium communities of samples at genus level
反应器
Reactors包含反硝化细菌的属/%
The genus of denitrifying
bacterium好氧反硝化菌/%
Aerobic denitrifying
bacterium好氧反硝化菌/%
Aerobic denitrifying bacteriumBacillus Diaphorobacter Klebsiella Pseudomonas Acinetobacter R0 25.4 0.9 0.85 0.02 0.01 0.008 0.004 R5 59.5 0.3 0.07 0.23 0.003 0.003 0.007 R10 47.0 0.9 0.83 0.004 0.004 0.006 0 R15 44.1 0.6 0.54 0.004 0.006 0.004 0.004 -
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