Wolfe R L, Lieu N I, Izaguirre G, Means E G
Metropolitan Water District of Southern California, La Verne 91750.
Appl Environ Microbiol. 1990 Feb;56(2):451-62. doi: 10.1128/aem.56.2.451-462.1990.
Nitrification in chloraminated drinking water can have a number of adverse effects on water quality, including a loss of total chlorine and ammonia-N and an increase in the concentration of heterotrophic plate count bacteria and nitrite. To understand how nitrification develops, a study was conducted to examine the factors that influence the occurrence of ammonia-oxidizing bacteria (AOB) in a chloraminated distribution system. Samples were collected over an 18-month period from a raw-water source, a conventional treatment plant effluent, and two covered, finished-water reservoirs that previously experienced nitrification episodes. Sediment and biofilm samples were collected from the interior wall surfaces of two finished-water pipelines and one of the covered reservoirs. The AOB were enumerated by a most-probable-number technique, and isolates were isolated and identified. The resistance of naturally occurring AOB to chloramines and free chlorine was also examined. The results of the monitoring program indicated that the levels of AOB, identified as members of the genus Nitrosomonas, were seasonally dependent in both source and finished waters, with the highest levels observed in the warm summer months. The concentrations of AOB in the two reservoirs, both of which have floating covers made of synthetic rubber (Hypalon; E.I. du Pont de Nemours & Co., Inc., Wilmington, Del.), had most probable numbers that ranged from less than 0.2 to greater than 300/ml and correlated significantly with temperature and levels of heterotrophic plate count bacteria. No AOB were detected in the chloraminated reservoirs when the water temperature was below 16 to 18 degrees C. The study indicated that nitrifiers occur throughout the chloraminated distribution system. Higher concentrations of AOB were found in the reservoir and pipe sediment materials than in the pipe biofilm samples. The AOB were approximately 13 times more resistant to monochloramine than to free chlorine. After 33 min of exposure to 1.0 mg of monochloramine per liter (pH 8.2, 23 degrees C), 99% of an AOB culture was inactivated. The amounts of this disinfectant that are currently used (1.5 mg/liter at a 3:1 ratio of chlorine to ammonia-N) may be inadequate to control the growth of these organisms in the distribution system.
氯胺消毒饮用水中的硝化作用会对水质产生多种不利影响，包括总氯和氨氮的损失，以及异养平板计数细菌和亚硝酸盐浓度的增加。为了解硝化作用的发展过程，开展了一项研究，以考察影响氯胺消毒配水系统中氨氧化细菌（AOB）出现的因素。在18个月的时间里，从一个原水水源、一个常规处理厂的出水以及两个曾经历过硝化事件的加盖成品水蓄水池采集了样本。从两条成品水管道的内壁表面以及其中一个加盖蓄水池采集了沉积物和生物膜样本。采用最大可能数技术对AOB进行计数，并分离和鉴定分离株。还考察了天然存在的AOB对氯胺和游离氯的抗性。监测计划的结果表明，被鉴定为亚硝化单胞菌属成员的AOB水平在源水和成品水中均具有季节性依赖性，在温暖的夏季月份观察到的水平最高。两个蓄水池中的AOB浓度，这两个蓄水池都有由合成橡胶（Hypalon；E.I. du Pont de Nemours & Co., Inc., Wilmington, Del.）制成的浮动盖，其最大可能数范围从小于0.2到大于300/ml，并且与温度和异养平板计数细菌水平显著相关。当水温低于16至18摄氏度时，在氯胺消毒的蓄水池中未检测到AOB。该研究表明硝化菌存在于整个氯胺消毒配水系统中。在蓄水池和管道沉积物材料中发现的AOB浓度高于管道生物膜样本中的浓度。AOB对一氯胺的抗性比对游离氯的抗性大约高13倍。在暴露于每升1.0毫克一氯胺33分钟后（pH 8.2，23摄氏度），99%的AOB培养物被灭活。目前使用的这种消毒剂的量（以氯与氨氮3:1的比例为1.5毫克/升）可能不足以控制配水系统中这些微生物的生长。
