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炼焦企业为工业废水排放大户。每年焦化企业排放废水量达到4.3×108 m3,焦化废水COD排放量约为3.29×104 m3,总氮排放量约为8.2×104 m3,极大威胁了企业周边的水环境[1]。焦化废水为典型的高含氮难降解工业废水,主流的生化处理工艺为AO(缺氧-好氧)、AAO(厌氧-缺氧-好氧)和多级AO等[2]。通常,主流工艺利用微生物氨化、硝化和反硝化作用进行生物脱氮。焦化废水生化工艺结束后,在后续的焦化废水深度处理工艺中,压力驱动的纳滤膜技术已成功应用于生产实践,实现了焦化废水回用的目的[3]。唐山化工焦化废水系统年处理量6×105 m3,采用纳滤(nanofiltration,NF)工艺后,废水回收率大于75%[4]。在纳滤工艺处理焦化废水的过程中,纳滤膜分离出来的氯离子、硫酸根离子、硝酸根离子和含氮杂环有机物等均留在纳滤浓水中。有研究[5]表明,焦化纳滤浓水为高含盐、高含氮和高COD的“三高”废水,其中,总氮(total nitrogen,TN)主要由硝态氮(
${\rm{NO}}_3^{-} $ -N)和有机氮构成。针对高盐废水中的TN和${\rm{NO}}_3^{-} $ -N,生物反硝化脱氮为最可行的方法。有研究[6-7]表明,经过驯化后的耐盐微生物菌群可高效去除浓水中的${\rm{NO}}_3^{-} $ -N。OSAKA等[8]研究表明,在3 g·L−1 NaCl的含盐废水中,以甲醇为碳源的反硝化过程中,${\rm{NO}}_3^{-} $ -N去除率可达到95%以上。YOSHIE等[9]发现,当浓水含盐量为2%时,微生物反硝化速率远低于浓水含盐量为10%时的硝化速率。该研究中的微生物菌群分析结果表明,在低含盐量(为2%时)情况下,嗜盐和非嗜盐微生物竞争碳源,使反硝化效率降低;而当含盐量(10%左右)较高时,嗜盐的反硝化菌属占主导地位,反而提高了反硝化效率。本研究以焦化纳滤工艺中产生的高电导率浓水为研究对象,通过投加外加碳源(甲醇),考察序批式反应器(sequencing batch reactor,SBR)对焦化浓水中总氮和硝态氮的去除效果;同时,采用高通量测序技术和qPCR定量技术深入分析纳滤浓水生物脱氮过程中微生物菌群结构和反硝化功能基因变化,以期为优化生物反应器的运行提供参考。
焦化纳滤浓水的生物脱氮及其微生物菌群结构分析
Biological denitrifying processes and microbial communities analysis in a sequencing batch reactor treating NF concentrate from coking wastewater
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摘要: 针对焦化纳滤浓水中高总氮的问题,采用序批式反应器(SBR)对纳滤浓水进行了生物脱氮实验,并对其反硝化脱氮效果和反应器中微生物菌群特征开展了研究。结果表明,在SBR系统稳定运行期间,总氮和硝态氮的平均去除率分别为58.2%和93.8%,出水中硝态氮平均浓度为2.0 mg·L−1。微生物菌群结构分析表明:变形菌门和拟杆菌门为纳滤浓水反硝化过程中的核心菌门,相对丰度之和为90.0%~96.0%;反硝化功能基因定量检测表明,在纳滤浓水反硝化过程中,亚硝酸盐还原酶nirS的拷贝数高于亚硝酸盐还原酶nirK约1~2个数量级,这说明nirS在亚硝酸转化为一氧化氮过程中起到了重要作用。SBR工艺处理焦化纳滤浓水具有良好的效果,为解决高盐水生物脱氮提供了新的途径。Abstract: Aiming at the problem of the high total nitrogen (TN) in NF concentrate from coking wastewater, a biological denitrifying process with a sequencing batch reactor (SBR) was employed to treat this concentrate. The denitrification effect and microbial communities characteristics were determined. The results showed that during stable operation of SBR, the average removal efficiencies of TN and nitrate were 58.2% and 93.8%, respectively, and the average effluent nitrate was 2.0 mg·L−1. The most abundant bacterial phyla in the SBR were Proteobacteria and Bacteroidetes, the sum of their relative abundances accounted for 90.0%~96.0%. It shows that Proteobacteria and Bacteroidetes are the important contributors for both nitrate removal and COD degradation in NF concentrate from coking wastewater. Quantitative real-time PCR was used to assess the absolute abundance of microbial genera, the quantity of nitrite reductase for nirS was higher than that of nirK by 1~2 orders of magnitude, indicating that the denitrifying bacterial genera containing nirS may be more responsible for the reduction of nitrite to nitrate. This study provides new insights to the understanding of microbial community dynamics and structures during the denitrifying processes of NF concentrate.
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Key words:
- coking wastewater /
- NF concentrate /
- denitrification /
- microbial community
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表 1 样品的生物多样性
Table 1. Microbial diversity of different samples
取样时间/d 测序序列/条 OTU/个 香农指数 菌种丰富度指数 测序深度指数 辛普森指数 1 49 825 6 359 8.6 18 561.8 0.89 0.97 31 56 729 7 328 8.8 24 112.2 0.88 0.98 51 56 076 7 072 8.5 23 946.2 0.88 0.98 71 51 461 5 944 8.5 18 782.3 0.87 0.96 91 54 792 5 737 7.7 16 664.3 0.91 0.96 -
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