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与传统的硝化-反硝化污水生物脱氮工艺相比,以厌氧氨氧化原理为核心的自养脱氮技术具有曝气能耗和处理成本较低、温室气体排放更少等优势[1]。为缩小占地面积、使操作更便捷,更加经济的一段式自养脱氮工艺成为研究热点[2-4]。一段式自养脱氮工艺是将亚硝化过程和厌氧氨氧化过程耦合在一个反应器中,利用氨氧化菌(ammonia oxidizing bacteria,AOB)和厌氧氨氧化菌(anammox bacteria,AnAOB)的协同作用实现废水中氮素的去除。因此,为保持该工艺稳定高效的自养脱氮性能,需维持系统内AOB和AnAOB的良好协作关系,同时排除亚硝酸盐氧化菌(nitrite oxidizing bacteria,NOB)的干扰[5-6]。
在实际应用中,工艺操作条件的变化会直接影响功能菌的活性,从而影响工艺的脱氮性能。其中,溶解氧(dissolved oxygen,DO)是一段式自养脱氮工艺中的关键控制因素[7-9]。DO能促进亚硝化并为厌氧氨氧化反应提供底物,但同时会抑制AnAOB活性,且DO过大还会造成NOB大量生长,从而导致系统性能恶化。功能菌对溶解氧的需求矛盾会影响工艺的自养脱氮性能,使得系统难以维持长期稳定。因此,如何平衡AOB和AnAOB的溶解氧环境需求,从而促进功能菌的富集强化成为亟待解决的问题[10-11]。
为保证一段式自养脱氮工艺的高效处理性能,需维持系统各反应段不同的溶解氧微环境——既可通过间歇曝气的方式实现好氧段与厌氧段的交替[12-13],也可维持厌氧段持续的低氧环境[7, 14]。近年来,研究者们一直在尝试通过不同类型的生物脱氮反应器搭建一段式自养脱氮工艺,以期获得稳定高效的处理性能。序批式活性污泥反应器是最普遍的一段式自养脱氮反应器,具有厌氧/好氧交替运行的特点。该反应器通过间歇曝气在时间序列上产生溶解氧梯度以实现亚硝化和厌氧氨氧化反应的发生[10, 15]。移动床生物膜反应器则是通过投加载体形成了生物膜,在一定程度上缓解溶解氧对内层AnAOB的抑制作用,因此被广泛应用[7, 16]。然而,以上工艺在本质上都未能实现溶解氧在各反应段的差异,故无法充分发挥具有不同溶解氧需求的功能菌群的脱氮效果。
以溶解氧分区调控为策略,设计研发了一种新型一段式自养脱氮反应器,通过改变进水负荷和调控曝气量来考察反应器的溶解氧分区效果,探究长期运行过程中工艺的自养脱氮性能和微生物变化特征,以期为强化自养脱氮工艺的性能提供新思路,并为一段式自养脱氮工艺的工程化应用提供参考。
溶解氧分区控制的一段式自养脱氮工艺的性能及其中微生物的特征
Performance and microbial characteristic of one stage autotrophic denitrification process controlled by dissolved oxygen zone
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摘要: 针对一段式自养脱氮工艺普遍存在脱氮性能较差或不稳定的问题,提出了溶解氧分区控制的策略,研发了一种内外分层、溶解氧分区的新型自养脱氮反应器。通过改变反应器的进水氮负荷和调控曝气量,考察其溶解氧分区效果和脱氮性能变化,并探究长期运行过程中微生物群落结构特征。结果表明:在为期250 d的连续实验中,新型反应器能实现良好的溶解氧分区效果,可有效强化氨氧化速率和厌氧氨氧化速率,总氮去除率到达84.3%,氮去除速率为0.84 kg·(m3·d) −1,自养脱氮性能得到了提升;反应器中微生物群落结构趋向单一,浮霉菌门始终维持较高丰度(7.6%~10.5%),厌氧氨氧化菌的优势菌属则发生了由Candidatus Kuenenia向Candidatus Brocadia的演替,而亚硝酸盐氧化菌生长受到抑制。本研究结果可为自养脱氮工艺的应用提供参考。Abstract: In order to solve the problem of poor or unstable denitrification performance in one-stage autotrophic denitrification process, the strategy of zonal control of dissolved oxygen was proposed and a novel autotrophic nitrogen removal bioreactor with internal and external layers and dissolved oxygen partitions was developed. By changing the influent nitrogen load and regulating aeration, the effect of the dissolved oxygen partition and the change of nitrogen removal performance were investigated, the microbial characteristics during long-term operation were also explored. The results showed that the novel reator could achieve good partition effect of dissolved oxygen and enhanced the rates of ammonia oxidation and anammox during the continuous operation of 250 days. The total nitrogen removal efficiency reached 84.3%, and the nitrogen removal rate was 0.84 kg·(m3·d) -1. The autotrophic nitrogen removal performance was improved. The microbial community tended to be simple and the abundance of Planctomycetes was at a high level (7.6%~10.5%). The dominant bacteria of anaerobic ammonium oxidation bacteria gradually transformed from Candidatus Kuenenia to Candidatus Brocadia, while the growth of nitrite oxidizing bacteria was inhibited. The results of this study could provided technical support for the application of autotrophic denitrification process.
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表 1 反应器运行条件
Table 1. Operational conditions of reactor
阶段 时间/d HRT/h 曝气量/
(L·min−1)进水氮
质量浓度/
(mg·L−1)进水氮负荷/
(kg·(m3·d)−1)Ⅰ 1~60 12 0.20 250 0.50 Ⅱ 61~160 8 0.40/0.60 250 0.75 Ⅲ 161~250 6 0.90 250 1.00 表 2 不同阶段样本的Alpha多样性指数
Table 2. Alpha diversity values of the samples at different stages
阶段 Shannon Simpson ACE Chao Coverage/% I 3.31 0.104 473.53 472.02 99.88 II 3.26 0.115 462.65 451.51 99.86 III 2.33 0.280 436.08 438.03 99.88 -
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