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A theoretical approach to assess microbial risks due to failures in drinking water systems
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
Water Environment Transport, Chalmers University of Technology, Göteborg, Sweden.
Linköping University, The Tema Institute. Linköping University, Faculty of Arts and Sciences.
School of Civil and Environmental Engineering, University of New South Wales. Sydney, Australia.
2003 (English)In: International Journal of Environmental Health Research, ISSN 0960-3123, Vol. 13, no 2, 181-197 p.Article in journal (Refereed) Published
Abstract [en]

A failure in treatment or in the distribution network of a surface water-works could have serious consequences due to the variable raw water quality in combination with an extended distribution. The aim of this study was to examine the theoretical impact of incidents in the drinking water system on the annual risk of infection in a population served by a large water treatment plant in Sweden. Reported incidents in the system were examined and a microbial risk assessment that included three pathogens, Cryptosporidium parvum, rotavirus and Campylobacter jejuni, was performed. The main risk incidents in water treatment were associated with sub-optimal particle removal or disinfection malfunction. Incidents in the distribution network included cross-connections and microbial pollution of reservoirs and local networks. The majority of the annual infections were likely to be due to pathogens passing treatment during normal operation and not due to failures, thus adding to the endemic rate. Among the model organisms, rotavirus caused the largest number of infections. Decentralised water treatment with membranes was also considered in which failures upstream fine-pored membranes would have little impact as long as the membranes were kept intact.

Place, publisher, year, edition, pages
2003. Vol. 13, no 2, 181-197 p.
Keyword [en]
Microbial Risk Assessment, Drinking Water Treatment, Distribution, Risk Incidents, Pathogens
National Category
Oceanography, Hydrology, Water Resources
URN: urn:nbn:se:liu:diva-13458DOI: 10.1080/0960312031000098080OAI: diva2:20789
Available from: 2004-12-19 Created: 2004-12-19
In thesis
1. Microbial risk assessment and its implications for risk management in urban water systems
Open this publication in new window or tab >>Microbial risk assessment and its implications for risk management in urban water systems
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Infectious disease can be transmitted via various environmental pathways, many of which are incorporated into our water and wastewater systems. Quantitative microbial risk assessment (QMRA) can be a valuable tool in identifying hazard exposure pathways and estimating their associated health impacts. QMRA can be applied to establish standards and guidelines and has been adopted by the World Health Organisation for the management of risks from water-related infectious diseases. This thesis aims at presenting a holistic approach for the assessment of microbial health risks in urban water and wastewater systems. The procedure of QMRA is presented, together with the data collected for the case studies, and the results are discussed in a risk management framework.

Decentralised drinking water treatment with membranes was shown to be competitive with centralised conventional treatment regarding environmental impacts and health. To attain sufficient die-off of pathogens in order to reduce risks to acceptable levels, facilities that permit the long-term storage of locally collected faeces are required. Issues of operation and mangement are likely to determine the health risks in decentralised systems. While failures in distribution are more likely to result in detectable waterborne disease outbreaks, the number of people at risk of becoming infected with pathogens passing normal treatment, calculated on a yearly basis, can be larger. Site-specific pathogen monitoring of source waters was identified as an important factor for the accurate estimation of risk. Noroviruses, an emerging waterborne pathogen, were shown to have fluctuating concentrations in surface water, with significant peaks during the wintertime. Time series analysis has potential as an early warning system if complemented by regular monitoring to discriminate peaks from random fluctuations. Groups already sensitive to infection, i.e. the elderly, the sick and children, were shown to consume higher volumes of cold tap water than the rest of the population, which may call for special atention in the risk management of drinking water systems. Microbial health risks associated with the handling and reuse of wastewater and sludge were shown to be successfully addressed within the management system Hazard Analysis and Critical Control Points (HACCP). Most exposure points identified could be controlled through easy measures.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2004. 84 p.
Linköping Studies in Arts and Science, ISSN 0282-9800 ; 304
Quantitative microbial risk assessment, pathogens, urban, decentralised, failures, noroviruses, water consumption, HACCP, drinking water, wastewater, sludge, faeces, risk management
National Category
Oceanography, Hydrology, Water Resources
urn:nbn:se:liu:diva-4880 (URN)91-85295-98-1 (ISBN)
Public defence
2004-12-10, Elysion, Hus T, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Copyright Agreement: Figure 6-1, page 49 and figure 6-2, page 50 in the summary/introduction are reprinted from Water Science and Technology: Water Supply 2(2) 11-18, with permission from the copyright holders, IWA. Note: the median values are missing in the article but the figures have been corrected in the summary/introduction.Available from: 2004-12-19 Created: 2004-12-19 Last updated: 2012-01-25Bibliographically approved

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Westrell, ThereseStenström, Thor-Axel
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Department of Water and Environmental StudiesFaculty of Arts and SciencesThe Tema Institute
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