Department of Civil and Environmental Engineering, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA.
Water Sci Technol. 2011;64(1):7-13. doi: 10.2166/wst.2011.536.
The mechanisms and factors that affect microbial resistance to chlorine disinfection have not been fully elucidated. In this study, we investigated the impact of the cell growth stage on chlorine disinfection efficiency. Specifically, we evaluated the impact of the growth stage on chlorination resistance by comparing the inactivation efficiencies of two indicator bacterial strains (Escherichia coli K12 and Escherichia coli O157:H7) obtained from various growth phases, using Chick-Watson kinetic parameters. For both E. coli strains (K12 and O157:H7), the inactivation rate constants are the lowest at stationary phase (0.19 and 0.32) compared to those at initial lag (0.54 and 0.76) and exponential growth phase (0.63 and 0.69), respectively. These results suggested that the abundance of resistant subpopulations increases at stressed stationary conditions and E. coli cells obtained from the stationary growth phase exhibited more resistance and lower inactivation efficiency compared to those from the lag and exponential phases. This implies that microbes in wastewater treatment process with varying solids retention times (SRTs, which indicate growth rates) may show different extents of chlorine resistance. Comparison of the coefficient of dilution (n) values in both E. coli strains for the various growth phases suggest that cells seem to be more sensitive to disinfectant concentration at the stationary-lag phase than that at the exponential stage. Comparing the two E. coli strains, higher inactivation rates were observed for the pathogenic O157:H7 than for K12 at different stages of growth. The strain-to-strain variability in survivability to chlorine exposure has to be considered when selecting indicator microorganisms for water quality monitoring.
微生物对氯消毒的抗性的机制和影响因素尚未完全阐明。在本研究中，我们研究了细胞生长阶段对氯消毒效率的影响。具体来说，我们通过使用 Chick-Watson 动力学参数比较了来自不同生长阶段的两种指示菌（大肠杆菌 K12 和大肠杆菌 O157:H7）的氯化抗性的影响，评估了生长阶段对氯化的影响。对于两种大肠杆菌菌株（K12 和 O157:H7），与初始迟滞期（0.54 和 0.76）和指数生长期（0.63 和 0.69）相比，静止期的灭活率常数最低（0.19 和 0.32）。这些结果表明，在应激静止条件下，抗性亚群的丰度增加，并且与迟滞期和指数生长期相比，从静止生长阶段获得的大肠杆菌细胞表现出更高的抗性和更低的灭活效率。这意味着具有不同固体停留时间（SRT，指示生长速率）的废水处理过程中的微生物可能表现出不同程度的氯抗性。对两种大肠杆菌菌株在不同生长阶段的稀释系数（n）值进行比较表明，与指数期相比，细胞在静止-迟滞期似乎对消毒剂浓度更敏感。比较两种大肠杆菌菌株，在不同生长阶段，致病性 O157:H7 的灭活率均高于 K12。在选择用于水质监测的指示微生物时，必须考虑到氯暴露时存活能力的菌株间变异性。
