The aperiodic changes in the quantity and community of planktonic and particle-associated bacteria have hampered the understanding and management of microbiological water quality in drinking water distribution systems. In this study, online sampling was combined with the microbial fingerprint-based SourceTracker2 to capture and trace the spatiotemporal variations in planktonic and particle-associated bacteria in an unchlorinated distribution system. The results showed that spatially, the particle load significantly increased, while in contrast, the quantity of particle-associated bacteria decreased sharply from the treatment plant to the distribution network. Similar to the trend of particle-associated bacterial diversity, the number of observed OTUs first slightly decreased from the treatment plant to the transportation network and then sharply increased from the transportation network to the distribution network. The SourceTracker2 results revealed that the contribution of particle-associated bacteria from the treatment plant decreased along the distribution distance. The spatial results indicate the dominant role of sedimentation of particles from the treatment plant, while the observed increases in particles and the associated bacteria mainly originated from the distribution network, which were confirmed directly by the increased contributions of loose deposits and biofilm. Temporally, the daily peaks of particle-associated bacterial quantity, observed OTU number, and contributions of loose deposits and biofilms were captured during water demand peaks (e.g., 18–21 h). The temporal results reveal clear linkages between the distribution system harboring bacteria (e.g., within loose deposits and biofilms) and the planktonic and particle-associated bacteria flowing through the distribution system, which are dynamically connected and interact. This study highlights that the spatiotemporal variations in planktonic and particle-associated bacteria are valuable and unneglectable for the widely on-going sampling campaigns required by water quality regulations and/or drinking water microbiological studies.

浮游和颗粒相关细菌数量和群落的非周期性变化阻碍了对饮用水分配系统中微生物水质的理解和管理。在这项研究中，在线采样与基于微生物指纹的 SourceTracker2 相结合，以捕获和追踪未氯化分配系统中浮游生物和颗粒相关细菌的时空变化。结果表明，在空间上，颗粒负荷显着增加，而相比之下，从处理厂到分配网络，颗粒相关细菌的数量急剧下降。与颗粒相关细菌多样性的趋势相似，从处理厂到运输网络，观察到的 OTU 数量首先略有减少，然后从运输网络到配送网络急剧增加。SourceTracker2 结果显示，来自处理厂的颗粒相关细菌的贡献随着分布距离而降低。空间结果表明来自处理厂的颗粒沉降占主导地位，而观察到的颗粒和相关细菌的增加主要来自分配网络，这直接通过松散沉积物和生物膜的贡献增加得到证实。在时间上，在需水高峰期（例如，18-21 小时）。时间结果揭示了含有细菌的分配系统（例如，在松散的沉积物和生物膜内）与流过分配系统的浮游和颗粒相关细菌之间的明确联系，它们是动态连接和相互作用的。本研究强调，浮游生物和颗粒相关细菌的时空变化对于水质法规和/或饮用水微生物研究所需的广泛持续的采样活动是有价值且不可忽视的。