Department of Civil and Environmental Engineering, University of Michigan, 1353 Beal Ave., Ann Arbor, MI 48109, USA.
Ann Arbor Water Treatment Plant, City of Ann Arbor, 919 Sunset Rd., Ann Arbor, MI 48103, USA.
Water Res. 2024 Jun 15;257:121702. doi: 10.1016/j.watres.2024.121702. Epub 2024 Apr 30.
While online monitoring of physicochemical parameters has widely been incorporated into drinking water treatment systems, online microbial monitoring has lagged behind, resulting in the use of surrogate parameters (disinfectant residual, applied dose, concentration × time, CT) to assess disinfection system performance. Online flow cytometry (online FCM) allows for automated quantification of total and intact microbial cells. This study sought to investigate the feasibility of online FCM for full-scale drinking water ozone disinfection system performance monitoring. A water treatment plant with high lime solids turbidity in the ozone contactor influent was selected to evaluate the online FCM in challenging conditions. Total and intact cell counts were monitored for 40 days and compared to surrogate parameters (ozone residual, ozone dose, and CT) and grab sample assay results for cellular adenosine triphosphate (cATP), heterotrophic plate counts (HPC), impedance flow cytometry, and 16S rRNA gene sequencing. Online FCM provided insight into the dynamics of the full-scale ozone system, including offering early warning of increased contactor effluent cell concentrations, which was not observed using surrogate measures. Positive correlations were observed between online FCM intact cell counts and cATP levels (Kendall's tau=0.40), HPC (Kendall's tau=0.20), and impedance flow cytometry results (Kendall's tau=0.30). Though a strong correlation between log intact cell removal and CT was not observed, 16S rRNA gene sequencing results showed that passage through the ozone contactor significantly changed the microbial community (p < 0.05). Potential causes of the low overall cell inactivation in the contactor and the significant changes in the microbial community after ozonation include regrowth in the later chambers of the contactor and varied ozone resistance of drinking water microorganisms. This study demonstrates the suitability of direct, online microbial analysis for monitoring full-scale disinfection systems.
虽然在线监测理化参数已广泛应用于饮用水处理系统，但在线微生物监测却落后了，因此使用替代参数（消毒剂余量、投加剂量、浓度×时间、CT）来评估消毒系统的性能。在线流式细胞术（online FCM）可实现总微生物和完整微生物细胞的自动定量。本研究旨在探讨在线 FCM 用于实际规模饮用水臭氧消毒系统性能监测的可行性。选择高石灰固体浊度进水的水厂臭氧接触池来评估在线 FCM 在挑战性条件下的可行性。总细胞和完整细胞计数监测持续 40 天，并与替代参数（剩余臭氧、臭氧剂量和 CT）和细胞内三磷酸腺苷（cATP）、异养平板计数（HPC）、阻抗流式细胞术和 16S rRNA 基因测序的水样检测结果进行比较。在线 FCM 深入了解了实际规模臭氧系统的动态，包括提供了接触池出水细胞浓度增加的早期预警，而这是替代测量方法无法观察到的。在线 FCM 完整细胞计数与 cATP 水平（肯德尔 tau=0.40）、HPC（肯德尔 tau=0.20）和阻抗流式细胞术结果（肯德尔 tau=0.30）呈正相关。虽然未观察到完整细胞去除对数与 CT 之间存在很强的相关性，但 16S rRNA 基因测序结果表明，臭氧接触池的通过显著改变了微生物群落（p<0.05）。接触池中总细胞灭活率低和臭氧氧化后微生物群落发生显著变化的潜在原因包括接触池后段的再生长和饮用水微生物对臭氧的不同抗性。本研究证明了直接在线微生物分析监测实际规模消毒系统的适用性。
