Zhang Weidong, DiGiano Francis A
Department of Environmental Sciences and Engineering, School of Public Health, The University of North Carolina at Chapel Hill, 27599-7400, USA.
Water Res. 2002 Mar;36(6):1469-82. doi: 10.1016/s0043-1354(01)00361-x.
Bacterial regrowth was investigated over a 15-month period in distribution systems (DSs) of Durham and Raleigh in North Carolina. These two water utilities were chosen because they are adjacent to one another, have similar service area characteristics, and treat surface waters of similar characteristics with conventional processes (coagulation-sedimentation and dual-media filtration). The finished waters have similar chemical quality and regrowth potential as measured by assimilable organic carbon (AOC). The major difference in treatment is the choice of final disinfectants (chlorine in Durham and chloramine in Raleigh). Ten sampling sites (monthly sampling) were chosen in each system to give wide geographic coverage and correspondingly, a wide range of water residence times. Significant losses were observed in both chlorine and chloramine residual in the DSs that produced bacterial regrowth as measured by heterotrophic plate count (HPC). The frequency distributions for log HPC (133 observations from Durham and 135 observations from Raleigh) were statistically the same in the chlorinated and chloraminated DSs. A correlation analysis indicated that disinfectant residual is the most important factor determining HPC level. However, the resulting R2 value for a non-linear regression model that also included AOC, temperature, and pH as independent variables was less than 0.7. Bacterial regrowth as measured by HPC, is dependent upon a complex interaction of chemical, physical, and operational parameters that may not be captured by such a simple statistical relationship.
在北卡罗来纳州达勒姆和罗利的配水系统（DSs）中，对细菌再生长情况进行了为期15个月的调查。选择这两家供水公司是因为它们彼此相邻，具有相似的服务区特征，并且采用常规工艺（混凝沉淀和双层介质过滤）处理具有相似特征的地表水。通过可同化有机碳（AOC）测量，成品水具有相似的化学质量和再生长潜力。处理过程中的主要差异在于最终消毒剂的选择（达勒姆使用氯，罗利使用氯胺）。在每个系统中选择了10个采样点（每月采样），以实现广泛的地理覆盖范围，相应地，也涵盖了广泛的水停留时间。通过异养平板计数（HPC）测量发现，在出现细菌再生长的配水系统中，氯和氯胺残留量均有显著损失。氯化和氯胺化配水系统中，对数HPC的频率分布（来自达勒姆的133次观测和来自罗利的135次观测）在统计学上是相同的。相关性分析表明，消毒剂残留是决定HPC水平的最重要因素。然而，一个还包括AOC、温度和pH作为自变量的非线性回归模型的R2值小于0.7。通过HPC测量的细菌再生长取决于化学、物理和运行参数的复杂相互作用，而这种简单的统计关系可能无法捕捉到这些相互作用。
