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传统污水处理工艺如A/O、CASS、氧化沟等采用单一污泥悬浮生长体系因其具有工艺简单、氮磷去除效果较好得到广泛应用,但采用单污泥体系的污水处理工艺在培养硝化菌、反硝化菌进行脱氮除磷过程中存在有机负荷、泥龄以及碳源需求上的竞争与矛盾,很难获得良好的污染物去除效果[1-2]。因此,在20世纪80年代JONES等[3-4]提出了构建双污泥体系工艺即A2N(厌氧/缺氧-硝化)工艺的思路,通过将硝化菌和反硝化菌分别独立培养,从而提高生物脱氮工艺对污水中碳源的利用效率,解决了硝化菌和反硝化菌泥龄矛盾等问题。
与单污泥体系的传统生物脱氮工艺相比,双污泥体系生物脱氮工艺具有污泥产量低、不同功能菌分开培养、有效利用碳源等优点[5],但是也存在固有缺陷。目前双污泥体系生物脱氮工艺包含间歇式和连续式两种模式,间歇式A2N工艺采用2座SBR(sequencing batch reactor)分别培养硝化菌和反硝化菌,工序较长,且有效污水处理时长受到污泥沉降性等因素影响,如果采用膜生物反应器,膜污染问题也会增加运行成本。而连续式A2N工艺由于处理设施较多,工艺流程与一般单污泥体系生物脱氮工艺更长,实际应用中建设成本和运行成本有所增加,同时间歇式和连续式A2N工艺均存在出水氨氮浓度较高的问题[6]。
本研究利用自主设计的实验室规模泥水分离反应器替代SBR,在反应器内截留污泥,富集培养功能微生物,将双污泥体系与A/O工艺相结合,构建缺氧和好氧污泥完全独立的双污泥生物脱氮工艺,根据运行模式特点称为A/O双污泥工艺。通过连续稳定运行实验,验证A/O双污泥工艺的脱氮性能,根据批次实验研究了工艺运行过程的氮素转化规律,并通过16S rRNA测序手段揭示了工艺运行过程中微生物群落结构对脱氮性能的影响方式。最后基于以上实验结果评估A/O双污泥工艺进一步开发研究的潜力,总结工艺需要优化的问题点,为工艺实际应用研究提供数据支撑。
A/O双污泥工艺脱氮性能
Nitrogen removal performance of A/O process with two-sludge system
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摘要: 针对传统A/O(anaerobic/oxic)工艺中反硝化细菌对有机物的利用效率低、A2N(anaerobic/anoxic-nitrification)工艺工序繁琐和出水氨氮浓度较高的问题,提出了一种泥水分离反应器,将双污泥体系与A/O工艺结合构建A/O双污泥工艺。对工艺运行过程的脱氮性能、微生物群落变化及氮素转化规律进行了研究,根据研究结果评估泥水分离反应器和A/O双污泥工艺在实际应用中的开发潜力,并总结工艺和反应器需要优化的问题,提出解决问题的思路。结果表明:在进水氮负荷为0.11 kg·(m3·d)−1条件下,工艺的氮去除负荷可以达到0.089 kg·(m3·d)−1,NH4+-N去除率超过95%、COD去除率超过90%,TN去除率达到80%以上,该工艺能够实现长期稳定运行。反硝化过程反应速率是提升A/O双污泥工艺脱氮效率的限速步骤,强化有机物在缺氧池中的接触停留是有机物利用率提高的关键。因此,需要对现有碳源的投加方式、污水的进水方式或工艺的反应器数量进行优化,进一步提高工艺对碳源的利用效率。微生物群落结构表明陶厄氏菌(Thauera)、硝化螺杆菌(Nitrospira)、Caldilineaceae等硝化反硝化功能菌属与主导异养硝化-好氧反硝化过程的副球菌(Paracoccus)共同协作是维持高NH4+-N去除率和TN去除率的原因之一。综上所述,A/O双污泥工艺具有良好的脱氮性能,具备实际应用价值,同时该研究结果可为工艺及反应器存在的缺陷进行后续优化研究提供参考。Abstract: To address the low utilization efficiency of organic matter by denitrifying bacteria in traditional A/O processes, the complexity of A2N(anaerobic/anoxic-nitrification) process steps, and the high concentration of effluent ammonia nitrogen, a sludge-water separation reactor was proposed. The two-sludge system and A/O process were combined to build the A/O two-sludge process to tackle these challenges. The denitrification performance, variations in microbial communities, and nitrogen transformation patterns during the process operation were studied, the development potential of the sludge-water separation reactor and the A/O two-sludge process based on the research results were evaluated. Additionally, the issues that require optimization in both the process and reactors were summarized and the strategies to address these challenges were raised. The result showed that at an influent nitrogen loading of 0.11 kg·(m3·d)−1, the nitrogen removal load of the process could reach 0.089 kg·(m3·d)−1. The NH4+-N removal efficiency exceeded 95%, COD removal rate surpassed 90%, and TN removal rate exceeded 80%, which could ensure the long-term stable operation of systems. Analysis of the nitrogen transformation patterns indicates that the reaction rate of the denitrification process was the limiting factor in improving the denitrification efficiency of A/O two-sludge process. Increasing the contact time of organic matter in the anoxic tank was crucial for improving the organic matter utilization rates. Therefore, it is necessary to optimize the current carbon source addition method, influent mode, or the number of reactors in the process for further increasing the process efficiency in utilizing carbon sources. The microbial community structure suggests that the cooperative action of denitrifying bacteria, such as Thauera, Nitrospira, Caldilineaceae, along with the predominant heterotrophic nitrification-aerobic denitrification bacterium Paracoccus, was the key factor in maintaining high removal efficiencies of NH4+-N and TN. In conclusion, the A/O two-sludge process had an excellent denitrification performance and a practical application value. The results of this study can provide a reference for subsequent optimization research to address existing deficiencies in both the process and reactors.
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表 1 不同阶段工艺运行条件
Table 1. Conditions of process operation at different stages
阶段 时间/d 运行周期/h DO/(mg·L−1) 内循环速度/(mL·min−1) C/N 氨氮负荷/(kg·(m3·d)−1) Ⅰ 1~7 12 2~4 31 4 0.073 Ⅱ 8~44 12 2~4 78 4 0.073 Ⅲ 45~80 8 2~4 78 5 0.11 表 2 泥水分离反应器脱氮性能对比
Table 2. Comparing the nitrogen removal performance of sludge-water separating reactors
工艺 进水水质 NH4+-N进水/
(mg·L−1)TN进水/
(mg·L−1)C/N 氮容积负荷/
(kg·(m3·d)−1)氮去除负荷/
(kg·(m3·d)−1)来源 A/O双污泥 合成废水 400 400 5 0.11 0.089 本研究 A/O 合成废水 60 83 9 0.083 0.071 [8] A2NSBR 生活污水 35.31 37.28 6~7 0.074 0.061 [9] MBBR 合成废水 50 100 10 0.2 0.16 [10] MBR 生活污水 85~115 — 6~10 0.11~0.15 0.0847~0.12 (仅氨氮) [11] A2/O 合成废水 31 31 >10 0.124 0.074 [12] A/O 合成废水 45 45 6~7 0.12 0.1056 [13] UMSR 猪场废水 393 394 0.93 0.179 0.164 [14] A2/O 猪场废水 (575±116) (688±143) (2.83±0.67) (0.057±0.012) (0.037±0.003) [15] -
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