Managing Cryptosporidium Risk - PowerPoint PPT Presentation

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Managing Cryptosporidium Risk
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Managing Cryptosporidium Risk

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  1. Managing Cryptosporidium Risk

  2. Risk Assessment • All stages of the process need to be examined • Catchment • Source • Treatment • Distribution • Consumer’s premises

  3. Starting Point? • Methodology recommended by NDSC and EPA contained in the EPA Handbook 2004 • Catchment, source and treatment processes examined in detail • A risk score is produced adjusted for the population served

  4. Catchment risk score • Animals within the catchment • Agricultural practices within the catchment • Discharges to the catchment/water source • Water source type • Catchment inspections • Raw water intake management for direct abstractions

  5. Treatment and Supply Risk Score • Water treatment processes • Treatment works monitoring of coagulation and filtration • Treatment works operational practices

  6. Final Weighted Risk Assessment Score (Catchment Risk Score + Treatment & Supply Risk Score) x Population weighting factor Population weighting factor 0.4 x log10 (population served by the supply)

  7. Water Supply Risk Classification (from EPA Handbook)

  8. Monitoring - Can Risk be reduced? - Continuous monitoring min 40 l/hr - Less than 1 oocyst/10 litres Very High / High Risk

  9. Reducing Risk Catchment • Apply Nitrates Regs. • Identify potential pollution locations • Fence off water sources • Catchment inspections • Automatic shutdown for poor source quality • Implement action plan to prevent pollution • Monitor effectiveness of action plans

  10. Reducing Risk Treatment Plant & Supply • Provide appropriate treatment barrier • Maintain plant within design throughput • Avoid by-passing filters • Optimise pH for coagulation/sedimentation • Avoid disturbing sludge blanket • Maintain filter media above minimum level • After backwash, run to waste until turbidity is satisfactory

  11. Reducing Risk • Do not return filter backwash water without membrane filtration • Monitor turbidity in filtered water and maintain at lowest possible level • Identify capital works requirements

  12. Reducing Risk Distribution Network • Inspect and clean out service reservoirs regularly • Prohibit grazing of reservoir sites by livestock • Significant leaks should be repaired promptly • Reduce overall leakage level

  13. Outbreaks • 5 in Ireland (Mullingar, Ennis, Roscommon, Carlow & Galway) • 61 in England & Wales 1993 to 2005 involving 7118 cases • 12 No. > 200 cases (greater than Galway) • Milwaukee (1993, 100 deaths), Sydney (1998, 3m people),

  14. In Conclusion….. • Risk assessment helps to focus resources and identify where testing is needed • Provide barrier to crypto breakthrough and monitor effectiveness • Documented quality management system • Best to be prepared