LeChevallier M W, Welch N J, Smith D B
American Water Works Service Company, Inc., Voorhees, New Jersey 08043, USA.
Appl Environ Microbiol. 1996 Jul;62(7):2201-11. doi: 10.1128/aem.62.7.2201-2211.1996.
An 18-month survey of 31 water systems in North America was conducted to determine the factors that contribute to the occurrence of coliform bacteria in drinking water. The survey included analysis of assimilable organic carbon (AOC), coliforms, disinfectant residuals, and operational parameters. Coliform bacteria were detected in 27.8% of the 2-week sampling periods and were associated with the following factors: filtration, temperature, disinfectant type and disinfectant level, AOC level, corrosion control, and operational characteristics. Four systems in the study that used unfiltered surface water accounted for 26.6% of the total number of bacterial samples collected but 64.3% (1,013 of 1,576) of the positive coliform samples. The occurrence of coliform bacteria was significantly higher when water temperatures were > 15 degrees C. For filtered systems that used free chlorine, 0.97% of 33,196 samples contained coliform bacteria, while 0.51% of 35,159 samples from chloraminated systems contained coliform bacteria. The average density of coliform bacteria was 35 times higher in free-chlorinated systems than in chloraminated water (0.60 CFU/100 ml for free-chlorinated water compared with 0.017 CFU/100 ml for chloraminated water). Systems that maintained dead-end free chlorine levels of < 0.2 mg/liter or monochloramine levels of < 0.5 mg/liter had substantially more coliform occurrences than systems that maintained higher disinfectant residuals. Free-chlorinated systems with AOC levels greater than 100 micrograms/liter had 82% more coliform-positive samples and 19 times higher coliform levels than free-chlorinated systems with average AOC levels less than 99 micrograms/liter. Systems that maintained a phosphate-based corrosion inhibitor and limited the amount of unlined cast iron pipe had fewer coliform bacteria. Several operational characteristics of the treatment process or the distribution system were also associated with increased rates of coliform occurrence. The study concludes that the occurrence of coliform bacteria within a distribution system is dependent upon a complex interaction of chemical, physical, operational, and engineering parameters. No one factor could account for all of the coliform occurrences, and one must consider all of the parameters described above in devising a solution to the regrowth problem.
对北美的31个供水系统进行了为期18个月的调查，以确定导致饮用水中大肠菌群出现的因素。该调查包括对可同化有机碳（AOC）、大肠菌群、消毒剂残留和运行参数的分析。在2周的采样期内，27.8%检测到大肠菌群，且与以下因素有关：过滤、温度、消毒剂类型和消毒剂水平、AOC水平、腐蚀控制和运行特性。研究中的4个使用未过滤地表水的系统，占所采集细菌样本总数的26.6%，但占大肠菌群阳性样本的64.3%（1576个样本中的1013个）。水温>15摄氏度时，大肠菌群的出现率显著更高。对于使用游离氯的过滤系统，33196个样本中有0.97%含有大肠菌群，而来自使用氯胺系统的35159个样本中有0.51%含有大肠菌群。游离氯消毒系统中大肠菌群的平均密度比氯胺消毒水高35倍（游离氯消毒水为0.60 CFU/100 ml，氯胺消毒水为0.017 CFU/100 ml）。维持终端游离氯水平<0.2 mg/升或一氯胺水平<0.5 mg/升的系统，其大肠菌群出现情况比维持较高消毒剂残留的系统多得多。AOC水平大于100微克/升的游离氯消毒系统，其大肠菌群阳性样本比平均AOC水平小于99微克/升的游离氯消毒系统多82%，大肠菌群水平高19倍。维持基于磷酸盐的缓蚀剂并限制无内衬铸铁管数量的系统，大肠菌群较少。处理过程或配水系统的几个运行特性也与大肠菌群出现率增加有关。该研究得出结论，配水系统中大肠菌群的出现取决于化学、物理、运行和工程参数的复杂相互作用。没有一个因素能解释所有大肠菌群的出现情况，在设计解决再生长问题的方案时，必须考虑上述所有参数。
