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Managing Cryptosporidium Risk

Managing Cryptosporidium Risk. Risk Assessment. All stages of the process need to be examined Catchment Source Treatment Distribution Consumer’s premises. Starting Point?. Methodology recommended by NDSC and EPA contained in the EPA Handbook 2004

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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

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