Aström J, Petterson S, Bergstedt O, Pettersson T J R, Stenström T A
Department of Civil and Environmental Engineering, Water Environment Technology, Chalmers University of Technology, SE-412 96, Göteborg, Sweden.
J Water Health. 2007;5 Suppl 1:81-97. doi: 10.2166/wh.2007.139.
Short-term peaks in pathogen concentrations may increase the risks for waterborne diseases considerably. In this study the occurrence of indicator organisms and pathogens in the river Göta älv at the raw water intake to Göteborg was evaluated and related to risk for drinking water consumption. About half of the 24 pathogen samples, taken during event and non-event conditions, were positive for at least one of the following: Cryptosporidium, Giardia, norovirus, enterovirus, Campylobacter and E. coli O157. Positive pathogen detects were often associated with heavy rainfalls and viruses with a sewage emergency discharge. The annualised probability of infection from this type of event was calculated from pathogen concentrations in a QMRA model. Given that the water intake is not closed, the risk given present water treatment seems to be acceptable for Giardia; however, it is at a borderline for Cryptosporidium and insufficient for noro- and enteroviruses. Present results emphasise the need for an appropriate intake regulation with respect to high pathogen loads, as the risk increases with time of exposure to pathogen contaminants. Rather than a threshold level on E. coli, reports on upstream microbial discharges are valuable for quick pathogen indications.
病原体浓度的短期峰值可能会大幅增加水传播疾病的风险。在本研究中，对哥德堡原水取水口处哥特河中的指示生物和病原体的出现情况进行了评估，并将其与饮用水消费风险相关联。在事件和非事件条件下采集的24份病原体样本中，约有一半对以下至少一种病原体呈阳性：隐孢子虫、贾第虫、诺如病毒、肠道病毒、弯曲杆菌和大肠杆菌O157。病原体检测呈阳性通常与暴雨以及病毒随污水紧急排放有关。通过QMRA模型中的病原体浓度计算出此类事件的年化感染概率。鉴于取水口未关闭，就目前的水处理而言，贾第虫的风险似乎是可接受的；然而，隐孢子虫的风险处于临界值，而诺如病毒和肠道病毒的风险则不足。目前的结果强调，鉴于接触病原体污染物的风险会随着时间增加，因此需要针对高病原体负荷制定适当的取水规定。与大肠杆菌的阈值水平相比，上游微生物排放报告对于快速指示病原体很有价值。
