Bacterial communities in the activated sludge (AS) determine the wastewater treatment performance in the municipal wastewater treatment plants (WWTPs). Aiming at identifying the affecting factors and the variation patterns of the bacterial assemblages in AS, a 2-year time-series AS samples were collected from two separated WWTPs and metagenomic sequencing was conducted. Obvious seasonal shift and succession of the bacterial community were observed in both WWTPs on the genus and species levels, especially for the persistent taxa, implying that temperature was a decisive factor for maintaining bacterial assemblage patterns in long-term period. Taxa abundance distribution (TAD) concerning occurrence frequency and average abundance were found fitting for exponential formulations, and the approximately equal total abundance of persistent taxa suggested that stable and high abundance (~ 90%) of core functional bacterial groups would help to maintain wastewater treatment performance. Drastic changes of environmental factors were found causing temporally significant bacterial structure variation, while the innate correlations between bacterial species could recover the community gradually and maintain relative stability of the AS system. Delayed correlations between environmental factors and abundant (persistent or intermittent) bacterial species were observed widely, while synchronous biotic interactions were identified more frequently. Besides, bacterial species with similar functions were prone to cluster together and shared the same seasonal variation pattern, implicating that the cooperation of functional correlated taxa played the most dominant role in shaping the bacterial assemblages. Furthermore, rare bacterial groups were to be explored for removing emerging pollutants with lower concentrations. The results of this study would assist dealing with operational defect and optimize the treatment system in WWTPs.

中文翻译：

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表征社区动态并探索两种活性污泥系统中的细菌聚集。

活性污泥（AS）中的细菌群落决定了市政废水处理厂（WWTP）的废水处理性能。为了确定AS中细菌集合体的影响因素和变异模式，从两个分离的污水处理厂中收集了一个为期2年的AS系列样品，并进行了宏基因组测序。在污水处理厂的属和物种水平上都观察到明显的季节变化和细菌群落的连续变化，特别是对于持续性的分类单元，这表明温度是长期维持细菌聚集模式的决定性因素。发现有关发生频率和平均丰度的分类群丰度分布（TAD）适合于指数公式，持久性分类单元的总丰度大致相等，这表明核心功能细菌群的稳定和高丰度（〜90％）将有助于维持废水处理性能。发现环境因素的剧烈变化会导致暂时的细菌结构变化，而细菌物种之间的先天相关性可以逐渐恢复群落并维持AS系统的相对稳定性。广泛观察到环境因素与丰富（持久性或间歇性）细菌物种之间的延迟相关性，而同步生物相互作用被更频繁地识别。此外，功能相似的细菌容易聚集在一起，并具有相同的季节性变化模式，暗示功能相关的分类单元的合作在塑造细菌组合中起最主要的作用。此外，将探索稀有细菌群以去除浓度较低的新兴污染物。这项研究的结果将有助于处理操作缺陷并优化污水处理厂的处理系统。