Victor Viñas Chalmers University of Technology

Transkript

1 Victor Viñas Chalmers University of Technology

2 Agenda Kort introduktion Bedömning av hälsomässiga risker Åtgärder att minska risken för mikrobiologisk smitta vid händelser på nätet Goda internationella exempel på arbete för att inte få smitta på nätet. Slutsatser

3 Introduktion Mikrobiell risker Mikrobiell risker i vattenledningsnät Inträngning Korskoppling och återströmning Hygieniska brister vid reparation och förnyelse Reservoar brister Biofilm

4 Bedömning av hälsomässiga risker Bästa tillgängliga ramverk: QMRA Hazard identification Dose response Fortsätter på nästa bild Which events can contaminate the network? How many pathogens needed to infect an individual? Dose response curves available from previous studies

5 Bedömning av hälsomässiga risker Bästa tillgängliga ramverk: QMRA Exposure assessment Risk characterization Risk management Determining dose that consumers are exposed to via modelling: Mike Urban, EPANET, GIS, Excel, consumption pattern studies, etc. Monte Carlo simulations combining hazards, dose response and exposure assessments. Infektionrisk (1/ p.; DALYs/QALYs) Unacceptable risk control measures CBA, MCDA, etc.

6 Vilka parametrar kontrolleras i Sverige? Källa Typ Parameter Ja? US National Research Council National Research Council. (2006). Drinking water distribution systems : assessing and reducing risks. Washington, DC: National Academies Press. Biological Hydraulik Kemi Heterotrophic Plate Count E. coli Koliforma Enterokocker Clostridium perfringens Tryck Flöde Turbiditet ph TOC Kloröverskott

7 Bedömning av hälsomässiga risker Nuvarande övervakning och kontroller är indikationer på förorening. Att genomföra en mer grundlig utvärdering av hälsorisker kräver modellering. Indata: Kombination av tryckövervakning + transient modellering Avstånd av avloppsrör från dricksvattenrör Markegenskaper Diameter Ålder Material Grundvatten tabell Tidigare ledningsbrott Läckage, etc.

8 Vilka åtgärder är kostnadseffektiva för att minska risken för mikrobiologisk smitta vid händelser på nätet? This concept hinges on viewing a water distribution network as a linkage of processes working together to maintain flow, pressure, and water quality (NRC 2006)

9 (GRATIS) Standad operating procedures (SOPs) Cross-connection control programs Leak detection and control Replacement and rehabilitation of nearby sewer lines Proper hydrant and valve operations Routine monitoring program Staff education (t. ex. Svenskt Vatten kurser)

10 CASE #1 Use of GIS-based software to predict microbial contamination of the distribution network in India Källa: WHO. (2014). Water safety in distribution systems. Retrieved from Geneva:

11 CASE #1 IRA-WDS GIS-based software Uses system-specific input data about pipe condition, such as: Installation year Diameter Material Length Depth Traffic load Max. pressure Location of sewage pipes, etc. Relative ranking of pipes based on risk of contamination intrusion into the network Recommendation of control measures is based on this ranking

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13 Measures Rehabilitation of the high risk pipes (rank 1 & 2) Regular monitoring and maintenance of medium risk pipes (rank 3) Subsequent water quality testing indicated 0 CFU/100ml at all rehabilitated points.

14 CASE #2 Evaluation of microbial risk after a main break Källa: Yang, J., Schneider, O. D., Jjemba, P. K., & Lechevallier, M. W. (2015). Microbial Risk Modeling for Main Breaks. Journal American Water Works Association, 107(2), E97-E108. doi: /jawwa

15 CASE #2 HYPOTHETICAL QMRA Model development in 7 steps: 1. Determine pathogen concentrations near mains. 2. Determine the concentration of pathogens in the main. 3. Evaluate the reduction in pathogen levels by flushing and disinfection. 4. Incorporate the volume of water consumed by the first customer. 5. Determine the dose response levels for pathogen infection. 6. Characterize the risks using Monte Carlo simulations. 7. Evaluate the risk management options to mitigate risk if needed. Yang et al. (2015) Literature review Experiments Literature review Literature review Simulation Simulation

16 CASE #2 RESULTS Yang et al. (2015)

17 Slutsatser System-specific information about the distribution network is needed to assess microbial risks and associated health risks in the distribution network. Standard operating procedures provide a good starting point for any municipality concerned with handling their health risks. More detailed documentation of the network is needed as input data for modelling.

18 Slutsatser More work is needed for health risks to be considered during renewal planning Hälssomässiga risker Medellivslängd Driftstörningar

19 Acknowledgements I would like to thank the Göteborg Region Association of Local Authorities (GR) for financing this project and sharing their experience throughout the development of this work.