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废水生物脱氮是水环境治理中一个重要的方向[1]。近年来,工艺流程短、能耗低、污泥产量少的新型生物自养脱氮工艺——厌氧氨氧化(anaerobic ammonium oxidation, Anammox)已成为这个方向的研究热点。
厌氧氨氧化菌(anaerobic ammonium oxidation bacteria,AnAOB)由于世代周期长、对环境条件要求较高,导致厌氧氨氧化工艺启动时间较长。选择和控制适合AnAOB 生长的条件,使反应器快速启动和稳定运行是目前Anammox应用于实际污水处理中亟待解决的难题[2]。Anammox生物膜工艺在一定程度上可以避免微生物的流失,并持留足够的生物量[3],是常用的Anammox工艺类型。Anammox生物膜反应器高效运行的前提是AnAOB能附着于填料表面,形成有活性的生物膜,因此,填料性能对Anammox生物膜反应器的快速启动与稳定运行有重要的影响。
现阶段对于生物膜填料的研究主要针对不同工艺类型的填料,如流化床中的聚乙烯填料[4],固定床中的海绵[5]、木质碳[5]、火山岩[5-6]、陶粒[6]等,膜生物反应器中的无纺布[7]以及混合填料[8]等;对于生物填料的改性多采用具有强氧化性的无机或有机试剂,通过化学氧化改变材料表面分子结构,或在惰性填料表面引入羧基、羰基、磺酸基等极性基团,改善材料亲水性;改性过程中须使用大量化学药剂,如硫酸、硝酸等强氧化性酸,高锰酸钾、重铬酸钾等易制毒强氧化剂及氯磺酸、甲基磺酸等有机溶剂,易对环境造成严重污染[9]。曾涛涛[6]分别以火山岩和陶粒为填料,研究2种填料对Anammox生物滤柱的脱氮效果的影响,发现火山岩填料的总氮去除率相比于陶粒提高20%,其表面富集的AnAOB相对丰度提高25%,菌群多样性更高;刘杰等[10]曾采用添加生物酶促进剂配方的新型高分子改性填料BMTM研究了其对上流式填料床生物膜反应器Anammox工艺启动的影响,发现添加改性填料BMTM后,反应器启动时间可以缩短57 d。而低温等离子体技术是对材料进行干式处理的表面处理技术[11],与传统的湿法处理不同,它无须添加化学药剂,对环境无二次污染,且处理高效,效果较好。目前低温等离子体技术主要应用于高分子材料、生物功能材料和无机填料性能的优化,以及废气、废水中各类污染物的净化处理和杀菌等方面[12]。陈冰等[13]采用低温等离子体处理苯二甲酸乙二醇酯(PET)高分子材料薄膜表面后,发现材料表面C=O和C=C双键数量增加,酯基减少,亲水性明显改善;田冶等[14]利用低温等离子体技术成功在壳聚糖膜表面接枝了N-乙烯基吡咯酮,使其接触角变小、粗糙度增加,进而导致材料表面细胞亲和性提高;侯建等[15]在处理H2S和CS2等废气问题时,发现使用低温等离子体技术对H2S和CS2的去除率可分别达到90%和70%。
由于低温等离子体改性技术无须添加化学药剂,对环境无二次污染,且对高分子材料表面性能有较好的改性效果,故本研究采用低温等离子体技术对聚氨酯填料进行了改性,对比了改性前后填料表面特性、Anammox工艺生物膜量、长期运行脱氮效果,并结合MiSeq高通量测序技术和实时荧光定量PCR(qPCR)技术对改性前后Anammox生物膜系统的微生物群落结构特征和功能基因相对丰度的变化进行了分析,为低温等离子体技术应用于Anammox生物膜工艺提供参考。
低温等离子体技术改性填料前后Anammox工艺运行及微生物群落变化
Variation of operating and microbial community of Anammox process with convertional and modified filler by low temperature plasma technology
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摘要: 采用低温等离子体技术对普通聚氨酯泡沫塑料填料进行表面改性处理,研究了改性前后填料的表面特征、厌氧氨氧化生物膜量、脱氮性能、微生物群落结构及其功能微生物基因丰度的变化。结果表明:低温等离子体改性以后填料表面与蒸馏水的静态接触角减少33.27°,单点比表面积和吸附平均孔径分别由8.98 m2·g−1和3.01 nm提高至9.66 m2·g−1和4.98 nm,材料表面粗糙度增加,亲水性能明显改善;未改性单位质量填料生物膜干质量为0.18 g,改性后单位质量填料生物膜干质量为0.37 g,相同时间内单位质量填料上的生物膜量相比于填料改性前提高了53%;填料改性前后系统总氮去除率均在80%以上。高通量测序结果显示,2系统菌群结构相似,主要功能菌属是Candidatus Kuenenia,改性填料相比于未改性填料其微生物种类丰富程度更高。实时荧光定量PCR(qPCR)结果显示,改性后hzo基因相对丰度由59.50%增至73.50%,提高了14%,nxrB基因相对丰度由21.10%减至17.70%,降低了3%。由此可见,填料经改性后表面生物膜量增加,生物膜上功能微生物种类丰富性也有所增加,但在较低氮基质负荷条件下脱氮效率基本不变。
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关键词:
- 厌氧氨氧化 /
- 低温等离子体改性 /
- 高通量测序 /
- 实时荧光定量PCR技术
Abstract: The conventional polyurethane foam plastic carrier was modified by low temperature plasma technology. The variations of surface physicochemical properties, anaerobic ammonium oxidation (Anammox) biofilm quantity, nitrogen removal performance, microbial community structure and functional microbial gene abundance of conventional and modified filler were investigated. The results showed that the static contact angle between the surface of modified filler and distilled water decreased by 33.27° compared with conventional filler, single point specific surface area and adsorption average pore diameter of modified filler increased from 8.98 m2·g−1 and 3.01 nm to 9.66 m2·g−1 and 4.98 nm, respectively. As a result, the surface roughness of modified filler increased, and its hydrophily improved obviously. The biomass on the conventional filler was 0.18 g, while the biomass on the modified filler was 0.37 g, over the same period, the biomass on per mass filler increased by 53%, therefore the biofilm formation rate improved obviously. For both the conventional and modified filler, the total nitrogen removal rates maintained over 80%. Furthermore, Illumina MiSeq sequencing indicated that Candidatus Kuenenia was the dominant bacterial genus in the biofilm on the conventional and modified filler. Compared with the conventional filler, the biofilm on the modified filler had a higher microbial species diversity. Quantitative real-time PCR (qPCR) showed that the hzo gene abundance increased by 14% from 59.50% to 73.50%, while the nxrB gene decreased by 3% from 21.10% to 17.70%. It could be concluded that the biofilm quantity on the modified filler increased, and the richness of functional microbial improved, however, the nitrogen removal efficiency presented slight change under low nitrogen influent loading condition. -
表 1 填料改性前后微生物菌群多样性指数统计
Table 1. Diversity statistics of microflora on fillers before and after modification
填料类别 OTUs/个 Shannon Simpson Chao1 ACE 相似度/% 未改性填料生物膜 739 5.36 0.93 803.08 816.57 97 改性填料生物膜 838 5.67 0.94 847.85 866.03 97 -
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