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碳纳米管是单层或多层的石墨烯层围绕中心轴按一定的螺旋角卷曲而成的无缝纳米级管状结构,根据管壁层数分为单壁碳纳米管(single-walled carbon nanotubes,SWCNTs)和多壁碳纳米管(multi-walled carbon nanotubes,MWCNTs),具有优异的电学、光学、力学性能,以及良好的生物兼容性、表面功能和高反应性,不仅广泛应用于电化学、生物医学、催化等领域,还被应用于纳米复合材料合成和环境污染修复中[1,2]。在生产、使用和处理过程中,碳纳米管将不可避免地进入大气、水体、土壤等环境中,其对环境的生态风险已引起广泛关注。
碳纳米管可能会随污水进入污水处理设施,活性污泥法是常用的生物处理工艺。由于碳纳米管的疏水性能和团聚性能,碳纳米管会沉积在活性污泥中,可能会对活性污泥性能产生影响,进而影响污水处理性能。目前,已有不少关于碳纳米管对活性污泥系统性能影响的研究[3-8]。不同官能团MWCNTs对序批式活性污泥反应器(sequencing batch reactor, SBR)运行性能及微生物种群结构的研究[6-8]表明,10 mg·L−1的羧基化、羟基化和氨基化MWCNTs在SBR长期暴露对系统运行性能无显著影响,但30 mg·L−1的羧基化和氨基化MWCNTs对和氨氮去除率均有显著影响,而且3种MWCNTs对系统硝化反硝化速率以及相关酶活性、微生物种群丰度均有影响。
实际废水中,碳纳米管往往与其他污染物共存,但关于碳纳米管与共存污染物对活性污泥系统的影响研究还较少[9-10]。QU等[9]研究表明废水中与苯酚共存的SWCNTs显著提高了活性污泥中Zoogloea(动胶菌属)丰度,降低了苯酚对活性污泥的毒性。ZHOU等[10]研究了MWCNTs和氨比西林对SBR系统微生物种群的影响,研究表明MWCNTs可以降低氨比西林对微生物的毒性,并改变了系统微生物种群结构。碳纳米管不仅会影响共存有毒物质对活性污泥的影响,其自身性质也会受到某些共存污染物影响。表面活性剂是污水中常见的有机污染物,其在生活污水和工业废水中的质量浓度分别可高达10 mg·L−1和300 mg·L−1[11]。而表面活性剂与碳纳米管共存时,将会影响碳纳米管的表面性质及悬浮性能,从而影响碳纳米管对活性污泥系统的影响。目前还未见关于碳纳米管与表面活性剂共存时对活性污泥工艺性能及微生物种群影响的报道。
与SWCNTs相比,MWCNTs具有更高的比表面积和表面活性,本研究选择MWCNTs为碳纳米管代表,以常见的阴离子表面活性剂十二烷基苯磺酸钠(sodium dodecylbenzenesulfonate,SDBS)作为表面活性剂代表,通过SBR活性污泥实验,探究了表面活性剂和MWCNTs复合污染对活性污泥系统的污水处理效果及微生物种群结构的影响。
多壁碳纳米管和十二烷基苯磺酸钠对SBR运行性能及微生物种群结构的影响
Effects of multi-walled carbon nanotubes and sodium dodecylbenzenesulfonate on the performance and microbial community of SBR
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摘要: 随着多壁碳纳米管(multi-walled carbon nanotubes, MWCNTs)的广泛应用,其进入污水处理系统后可能对活性污泥系统产生影响。表面活性剂是污水中的常见污染物,MWCNTs对表面活性剂的吸附可能会改变MWCNTs对活性污泥系统的影响。为探明MWCNTs和表面活性剂对活性污泥系统的影响及机制,以十二烷基苯磺酸钠(sodium dodecylbenzene sulfonate, SDBS)为表面活性剂代表,研究MWCNTs和SDBS单独和共同存在条件下对序批式活性污泥反应器(sequencing batch reactor, SBR)运行性能及微生物种群结构的影响。结果表明:SBR连续运行22 d期间,SDBS和MWCNTs对系统COD去除率有不同程度的增强,MWCNTs对总氮去除率影响不大,而SDBS对总氮去除有轻微抑制。高通量测序结果表明:MWCNTs和SDBS均降低了微生物物种数量,并对微生物种群结构造成显著影响,门水平上,Chloroflexi(绿弯菌门)和Nitrospirae(硝化螺旋菌门)相对丰度下降,而Bacteroidetes(拟杆菌门)相对丰度增加,属水平上,Dechloromonas(脱氯单胞菌属)相对丰度从31%下降至20%左右,MWCNTs单独存在使得Zoogloea(动胶菌属)相对丰度从18%增加到30%,而SDBS存在使得Thauera(陶厄氏菌属)相对丰度从10%增加到20%以上。两者共存条件下,SDBS对微生物种群结构影响占主导地位。Abstract: With the widespread application of multi-walled carbon nanotubes (MWCNTs), they may have an impact on the activated sludge system after entering the sewage treatment system. Surfactants are common contaminants in wastewater, and the change in the impact of MWCNTs on activated sludge systems may occur after surfactants adsorption on MWCNTs. To explore the effects and mechanisms of multi-walled carbon nanotubes (MWCNTs) and surfactants on activated sludge systems, sodium dodecylbenzene sulfonate (SDBS) was used as a representative surfactant to investigate the effects of MWCNTs or SDBS on the operational performance and microbial community structure of a sequencing batch reactor (SBR). The results showed that during the 22-day continuous operation period of SBR, SDBS and MWCNTs enhanced its COD removal rate to varying degrees. MWCNTs had slight effect on the total nitrogen removal rate, while SDBS slightly inhibited the total nitrogen removal. The high-throughput sequencing results showed that both MWCNTs and SDBS reduced the number of microbial species, and had a significant impact on the microbial population structure. At the phylum level, the relative abundance of Chloroflexi and Nitrospirae decreased, while the relative abundance of Bacteroidetes increased. At the genus level, the relative abundance of Dechromonas decreased from 31% to around 20%, while MWCNTs alone increased the relative abundance of Zoogloea from 18% to 30%, and SDBS alone increased the relative abundance of Thauera from 10% to over 20%. Under the coexistence of the MWCNTs and SDBS, SDBS dominated the impact on microbial community structure.
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Key words:
- multi-walled carbon nanotubes /
- SDBS /
- activated sludge /
- microbial community
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表 1 MWCNTs和SDBS对污泥性能指标的影响
Table 1. Effects of MWCNTs and SDBS on sludge properties
反应器 MLSS/
(mg·L−1)SV30/
%SVI/(mL·g−1)
(以MLSS计)SOURa/
(mg·(g·h)−1)SOURb/
(mg·(g·h)−1)CK 2 840 25 88.0 21.7 16.7 SD 1 085 10 92.2 40.0 15.9 MC 3 465 25 72.2 118 11.5 MC-SD 1 124 10 89.0 190 19.2 注:SOURa为有基质时的耗氧速率,SOURb为内源呼吸耗氧速率。 表 2 MWCNTs和SDBS对微生物alpha多样性指数的影响
Table 2. Effects of MWCNTs and SDBS on microbial alpha diversity indexes
样品 OTU Chao1
指数覆盖度 Pielou
均匀度指数Shannon
指数Simpson
指数CK 3 446 3 473 0.996 0.665 7.811 0.966 MC 2 334 2 369 0.997 0.658 7.366 0.976 SD 2 520 2 584 0.995 0.662 7.482 0.979 MC-SD 2 309 2 361 0.996 0.656 7.329 0.975 表 3 不同处理组中优势菌门及菌属的相对丰度
Table 3. Relative abundance of dominant bacterial phyla and genera in different treatment groups
分类单元 物种 相对丰度/% CK SD MC MC-SD Proteobacteria 87.2 87.9 86.8 88.9 Bacteroidetes 8.4 11.1 11.2 10.0 门 Chloroflexi 1.2 0.2 0.4 0.1 Nitrospirae 1.0 0.1 0.3 0.1 Dechloromonas 31.3 21.1 21.0 18.8 Zoogloea 18.1 22.5 30.4 23.8 Thauera 10.1 22.3 9.8 24.4 Bdellovibrio 8.6 1.7 8.1 1.2 Flavobacterium 0.7 7.4 3.6 7.0 属 Brevundimonas 0.1 0.9 0.2 0.6 Terrimonas 2.5 0.4 2.6 0.3 Ferruginibacter 0.8 0.6 1.7 0.3 Sphaerotilus 0.7 0.5 1.5 0.5 Nitrospira 1.0 0.1 0.3 0.1 -
[1] PENG Z, LIU X, ZHANG W, et al. Advances in the application, toxicity and degradation of carbon nanomaterials in environment: A review[J]. Environment International, 2020, 134: 105298. doi: 10.1016/j.envint.2019.105298 [2] SAJID M, ASIF M, BAIG N, et al. Carbon nanotubes-based adsorbents: Properties, functionalization, interaction mechanisms, and applications in water purification[J]. Journal of Water Process Engineering, 2022, 47: 102815. doi: 10.1016/j.jwpe.2022.102815 [3] HAI R, WANG Y, WANG X, et al. Impacts of multiwalled carbon nanotubes on nutrient removal from wastewater and bacterial community structure in activated sludge[J]. Plos One, 2014, 9(9): e107345. doi: 10.1371/journal.pone.0107345 [4] MA Q, QU Y, SHEN W et al. Activated sludge microbial community responses to single-walled carbon nanotubes: community structure does matter[J]. Water Science and Technology, 2015, 71(8): 1235-1240. doi: 10.2166/wst.2015.095 [5] QU Y, ZHANG X, SHEN W, et al. Illumina MiSeq sequencing reveals long-term impacts of single-walled carbon nanotubes on microbial communities of wastewater treatment systems [J]. Bioresource Technology 2016, 211: 209-215. [6] GAO M, GAO F, MA B, et al. Insights into long-term effects of amino-functionalized multi-walled carbon nanotubes (MWCNTs-NH2) on the performance, enzymatic activity and microbial community of sequencing batch reactor[J]. Environmental Pollution, 2019, 254: 113118. doi: 10.1016/j.envpol.2019.113118 [7] GAO F, MA B, SHE Z, et al. Performance evaluation, enzymatic activity and microbial community of sequencing batch reactor under hydroxyl-functionalized multi-walled carbon nanotubes (MWCNTs-OH) stress[J]. Environmental Technology & Innovation, 2021, 21: 101213. [8] MA B, GAO F, YU N, et al. Long-term impacts of carboxyl functionalized multi-walled carbon nanotubes on the performance, microbial enzymatic activity and microbial community of sequencing batch reactor[J]. Bioresource Technology, 2019, 286: 121382. doi: 10.1016/j.biortech.2019.121382 [9] QU Y, MA Q, DENG J, et al. Responses of microbial communities to single-walled carbon nanotubes in phenol wastewater treatment systems[J]. Environmental Science & Technology, 2015, 49(7): 4627-4635. [10] ZHOU W, WANG Y, WANG M, et al. The co-effect of ampicillin and multi-walled carbon nanotubes on activated sludge in sequencing batch reactors: microbial status, microbial community structure and ARGs propagation[J]. Environmental Science-Nano, 2021, 8(1): 204-216. doi: 10.1039/D0EN00668H [11] SIYAL A A, SHAMSUDDIN M R, LOW A, et al. A review on recent developments in the adsorption of surfactants from wastewater[J]. Journal of Environmental Management, 2020, 254: 109797. doi: 10.1016/j.jenvman.2019.109797 [12] 国家环境保护总局. 水和废水监测分析方法 [M]. 北京: 中国环境科学出版社, 2002. [13] DERESZEWSKA A, CYTAWA S, TOMCZAK-WANDZEL R, et al. The effect of anionic surfactant concentration on activated sludge condition and phosphate release in biological treatment plant[J]. Polish Journal of Environmental Studies, 2015, 24(1): 83-91. [14] ZHANG T, SHAO M, YE L. 454 Pyrosequencing reveals bacterial diversity of activated sludge from 14 sewage treatment plants [J]. ISME Journal 2012, 6(6): 1137-1147. [15] HUANG T L, ZHOU S L, ZHANG H H, et al. Nitrogen removal characteristics of a newly isolated indigenous aerobic denitrifier from Oligotrophic drinking water reservoir, Zoogloea sp. N299[J]. International Journal of Molecular Sciences, 2015, 16(5): 10038-10060. doi: 10.3390/ijms160510038 [16] 毛跃建. 废水处理系统中重要功能类群Thauera属种群结构与功能的研究[D]. 上海: 上海交通大学, 2009. [17] 吴蔓莉. 两株优势菌对多环芳烃的降解机理研究[D]. 西安: 西安建筑科技大学, 2010. [18] 雷萍, 聂麦茜, 张志杰等. 一株多环芳烃降解菌在焦化废水降解中的应用研究[J]. 西安: 西安交通大学学报, 2001(10): 1055-1058. [19] LI H, WU S, YANG C. Performance and biomass characteristics of SBRs treating high-salinity wastewater at presence of anionic surfactants[J]. International Journal of Environmental Research and Public Health, 2020, 17(8): 2689. doi: 10.3390/ijerph17082689