在分析之前，人们经常对运输途中的饮用水样本中大肠菌群计数的可靠性表示担忧。本研究的目的是通过使用当前的方法研究样本保持效应，并提供更可靠的数据，供未来修订饮用水法规时参考。从市政分配系统收集的样本被分割，储存在环境温度（22摄氏度）和冰箱温度（5摄氏度）下，并随时间分析总大肠菌群和异养细菌密度。24小时后，两种温度下的大肠菌群均显著下降。22摄氏度时的下降率比5摄氏度时大2.5个数量级。 24小时内的平均损失在5℃时为34%，在22℃时为87%。对于在环境温度下保持30小时的样品，经常观察到异养细菌与膜滤板上大肠菌群的生长和干扰。建立了一个基于实际大肠菌群回收率的模型，用于预测在检查前不同时间保存的样本中的初始大肠菌群计数。对于所检查的水域，在22摄氏度下保持30小时，初始大肠菌群计数高达100/100毫升的样本可能被报告为令人满意，从而导致不准确和误导性信息。包括15个参考文献、表格和图表。

Concern is often expressed about the reliability of coliform counts from drinking water samples held in transit before analysis. The purpose of this study was to investigate sample-holding effects by using current methodology and to supply more reliable data for consideration in future revisions in drinking water regulations. Samples collected from a municipal distribution system were split, stored at ambient (22 C) and refrigerator (5 C) temperatures, and analyzed over time for total coliform and heterotrophic bacterial densities. Coliform populations declined significantly at both temperatures after 24 hours. The rate of decline was 2.5 orders of magnitude greater at 22 C than at 5 C. Average losses in 24 hours were 34 percent at 5 C and 87 percent at 22 C. Growth and interference of heterotrophic bacteria with coliform colonies on membrane filter plates were frequently observed for samples held at ambient temperatures for 30 hours. A model based on actual coliform recovery was developed to predict initial coliform counts in samples held at various times before examination. For the waters examined, samples held at 22 C for 30 hours with initial coliform counts as high as 100/100 mL could have been reported as satisfactory, thus resulting in inaccurate and misleading information. Includes 15 references, tables, figures.