Kistemann T, Classen T, Koch C, Dangendorf F, Fischeder R, Gebel J, Vacata V, Exner M
Institute for Hygiene and Public Health, WHO'CC for Health Promoting Water Management and Risk Communication, University of Bonn, D-53105 Bonn, Germany.
Appl Environ Microbiol. 2002 May;68(5):2188-97. doi: 10.1128/AEM.68.5.2188-2197.2002.
Hygienic and microbiological examinations of watercourses are usually not carried out during heavy rainfall and runoff events. After rainfall or snowmelt, there are often massive increases in turbidity in flooding creeks in mountain ranges, which are frequently interpreted as an indication of microbial contamination. The aim of this study was to quantify the microbial loads of watercourses during such runoff events and to compare these loads with loads occurring during regular conditions. In a 14-month monitoring period we investigated the microbial loads of three tributaries of different drinking water reservoirs. A total of 99 water samples were taken under different runoff conditions and analyzed to determine physical, chemical, bacterial, and parasitic parameters. Thirty-two water samples were considered event samples during nine measuring series. The criteria for events, based on duration and intensity of precipitation, water depth gauge measurements, and dynamics, had been fixed before the investigation for each creek individually. Of the physical and chemical parameters examined, only the turbidity, pH, and nitrate values differed clearly from the values obtained for regular samples. Most of the bacteriological parameters investigated (colony, Escherichia coli, coliform, fecal streptococcal, and Clostridium perfringens counts) increased considerably during extreme runoff events. If relevant sources of parasitic contamination occurred in catchment areas, the concentrations of Giardia and Cryptosporidium rose significantly during events. The results show that substantial shares of the total microbial loads in watercourses and in drinking water reservoirs result from rainfall and extreme runoff events. Consequently, regular samples are considered inadequate for representing the microbial contamination of watercourse systems. The procedures for raw water surveillance in the context of multiple-barrier protection and risk assessment ought to include sampling during extreme runoff situations.
通常不会在暴雨和径流事件期间对水道进行卫生和微生物检查。降雨或融雪后，山区洪水溪流中的浊度通常会大幅增加，这常常被解释为微生物污染的迹象。本研究的目的是量化此类径流事件期间水道中的微生物负荷，并将这些负荷与正常情况下的负荷进行比较。在为期14个月的监测期内，我们调查了不同饮用水水库的三条支流的微生物负荷。在不同径流条件下共采集了99份水样，并对其进行分析以确定物理、化学、细菌和寄生虫参数。在九个测量系列中，有32份水样被视为事件样本。事件的标准基于降水的持续时间和强度、水深测量以及动态变化，在调查前针对每条溪流分别确定。在所检测的物理和化学参数中，只有浊度、pH值和硝酸盐值与正常样本的值有明显差异。在极端径流事件期间，所调查的大多数细菌学参数（菌落、大肠杆菌、大肠菌群、粪链球菌和产气荚膜梭菌计数）大幅增加。如果集水区存在相关的寄生虫污染源，事件期间贾第虫和隐孢子虫的浓度会显著上升。结果表明，水道和饮用水水库中总微生物负荷的很大一部分来自降雨和极端径流事件。因此，常规样本被认为不足以代表水道系统的微生物污染情况。在多重屏障保护和风险评估背景下的原水监测程序应包括在极端径流情况下进行采样。
