No abstract

Methods for controlling leakage from water distribution systems vary with respect to cost and personnel requirements. The benefits of leakage reduction should be compared to the cost of alternative management options to determine which is the most cost effective. This study presents a new method for evaluating leakage from water distribution systems via combined cost benefit analysis (CBA) and uncertainty analysis. The case study considers four alternatives for leakage control. The results show that the inclusion of uncertainty analysis represents an improvement over traditional CBA where there is a high degree of uncertainty in the input data. Moreover, a clearer understanding of the available alternatives is obtained in situations where multiple alternatives show similar performances and there is no clear best choice. It was determined that in the case study distribution system, it is significantly more cost-effective to reduce leakage volumes by reactively repair broken pipes than to proactively replace them, despite large leakage losses. Abbreviations CARLCurrent annual real losses; leakage on transmission and/or distribution mains, at utility storage tanks and on service connections up to point of costumer metering CBA Cost benefit analysis DFM District flow meters for flow measurement on the distribution network DMA District-metered areas, a sectioned zone of a WDS where the flow can be univocally measured ILI Infrastructure leakage index, representing the ratio of CARL and UARL (Lambert et al. 1999) NPVNet present value is defined as the sum of the present values of cash flows over a period of time SCADA Supervisory control and data acquisition, a communication system WDS Water distribution system UARL Unavoidable annual real losses is the lowest technically achievable real losses and depend on service connection density, system pressure and the average length of the service connection pipes between the water mains and the consumer's water meters.

During recent years, knowledge gaps on drinking water-related gastrointestinal illness have been identified, especially for non-epidemic cases. Pathogen contamination of drinking water during distribution has been suggested to contribute to these cases, but the risk factors are not yet fully understood. During 2014-2015, we conducted an epidemiological study in five municipalities in Sweden, to assess whether incidents in the drinking water distribution system influence the risk of gastrointestinal illness. Telephone interviews were conducted in the affected areas and in reference areas 7-14 days after a reported incident. Symptoms of gastrointestinal illness occurring during the period were documented for each household member. The results showed a significantly elevated risk of vomiting and acute gastrointestinal illness (AGI) in the affected areas, compared to the reference areas (OR = 2.0, 95% CI: 1.2-3.3; OR = 1.9, 95% CI: 1.2-3.0). Certain conditions, or risk factors, during the incidents, such as sewage and drinking water pipelines at the same level in the trench, were associated with an elevated risk of AGI and vomiting. Safety measures taken during repair work, like flushing, were also associated with an elevated risk of AGI and vomiting. These results show that incidents in the drinking water distribution network contribute to endemic gastrointestinal illness, especially AGI and vomiting, and that external pathogen contamination of the drinking water is a likely cause of these cases of gastrointestinal illness. The results also indicate that safety measures used today may not be sufficient for eliminating the risk of gastrointestinal illness.