In piped drinking water distribution systems, microbial water quality depends on the quantities and types of microorganisms present as well as the physicochemical conditions that influence them. Accurately assessing microbial water quality in these systems is important to maintain water quality throughout distribution. Microbial water quality can be assessed directly, using measures of microbial abundance, and indirectly, by measuring pH, temperature, and disinfectant residual. In the United States, total coliform bacteria measurement is the only regulated parameter for microbial abundance, but because levels are required to be maintained below the quantification limit, this parameter provides little insight into the total microbial abundance. In this study, alternate measures of microbial abundance were assessed in six drinking water distribution systems with a wide range of free chlorine (<0.02 to 2.14 mg L⁻¹ as Cl₂) and total chlorine residuals (<0.02 to 2.9 mg L⁻¹ as Cl₂). Five measures of microbial abundance were compared for quantifiability and variability throughout distribution: total and intact cell counts, total and intracellular ATP concentrations, and heterotrophic plate counts. We found that: intracellular ATP and intact cell counts had significant and strong correlations with disinfectant concentration; these correlations were stronger in chlorinated systems compared to chloraminated systems; 97.6% of samples had a quantifiable intact cell counts, with only four samples below the intact cell count quantifiaction limit at the highest residual concentration in chlorinated drinking water distribution systems (1.5–2.0 mg L⁻¹ as Cl₂); and variance between technical replicates was lowest for total ATP followed by total and intact cell counts, as compared to heterotrophic plate counts and intracellular ATP. We also demonstrated that a generalized linear mixed model could be used to estimate the combined effect of common water quality parameters on intact cell counts in a chloraminated distribution system: total chlorine had the greatest inverse effect on intact cells with a greater positive effect of temperature at lower levels of total chlorine. We discuss the purpose and interpretation of typical microbial water quality parameters, such as heterotrophic plate count and disinfectant residual, and consider the future role of ATP and flow cytometry-based methods.

中文翻译：

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消毒剂残留，pH和温度对消毒饮用水分配系统中微生物丰度的影响

在管道式饮用水分配系统中，微生物的水质取决于存在的微生物的数量和类型以及影响它们的物理化学条件。准确评估这些系统中的微生物水质对于维持整个分配过程中的水质至关重要。可以使用微生物丰度的方法直接评估微生物水质，也可以通过测量pH值，温度和消毒剂残留量间接评估微生物水质。在美国，大肠菌群总数的测量是微生物丰度的唯一调节参数，但是由于需要将水平保持在定量限以下，因此该参数对总微生物丰度了解甚少。在这个研究中，^-1（作为Cl ₂）和总氯残留物（<0.02到2.9 mg L ^-1作为Cl ₂）。比较了五种微生物丰度测量方法在整个分布过程中的可量化性和可变性：总和完整细胞计数，总和细胞内ATP浓度以及异养平板数。我们发现：细胞内ATP和完整细胞计数与消毒剂浓度有显着且强烈的相关性。与氯化系统相比，这些相关性在氯化系统中更强；97.6％的样品具有可量化的完整细胞计数，只有四个样品在含氯饮用水分配系统中残留浓度最高的情况下（1.5–2.0 mg L ^-1）低于完整细胞计数的定量限值作为Cl ₂）；与异养平板数和细胞内ATP相比，总ATP的技术复制之间的差异最低，其次是总细胞数和完整细胞数。我们还证明，可以使用广义线性混合模型来估计常见水质参数对氯化分配系统中完整细胞数的综合影响：总氯对完整细胞的反作用最大，而在温度下，正温度的影响更大。总氯含量较低。我们讨论了典型微生物水质参数（例如异养菌板数和消毒剂残留）的目的和解释，并考虑了ATP和基于流式细胞术的方法的未来作用。