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Bioterrorism Scenarios in Public Water Supplies: Modeling Concepts to Predict Impacts

Bioterrorism Scenarios in Public Water Supplies: Modeling Concepts to Predict Impacts. Francis A. DiGiano Chongxun (Doris) Pan, Vanessa Speight Dept. of Environmental Sciences & Engineering University of North Carolina at Chapel Hill. Lethality of Toxins.

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Bioterrorism Scenarios in Public Water Supplies: Modeling Concepts to Predict Impacts

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  1. Bioterrorism Scenarios in Public Water Supplies: Modeling Concepts to Predict Impacts Francis A. DiGiano Chongxun (Doris) Pan, Vanessa Speight Dept. of Environmental Sciences & Engineering University of North Carolina at Chapel Hill

  2. Lethality of Toxins 1Lethal dose (µg/kg) x60 kg humanx 1000 2Toxicity of Botulinus relative to cyanide = 1000

  3. Public Water System: Points of Vulnerabilty Reservoir Water Treatment plant (WTP) Distribution System

  4. Typical Water Supply Reservoir

  5. Case Study: Water Supply Reservoir

  6. y Instantaneous Toxin Input x z Governing equation: Instantaneous Point Source Solution: Toxin Added to Water Supply Reservoir WTP Water Intake Location Lake Vx

  7. Toxin Concentration Moving Through Reservoir Location of Water Intake

  8. Lethal Human Response to Botulinus Toxic A Toxin Concentration Entering Water Intake3000 ft Away from Toxin Entry Pt

  9. Toxin Added to Polymer Feed Tank Sedimentation Tanks QF Flocculation Tanks QP Clear Well Filters Polymer Feed Disinfectant Additions To distribution system Toxin Addition

  10. Water Treatment & Distribution Flocculation Sedimentation Filtration Disinfection & Clearwell Storage Distribution

  11. Toxin Addition to Polymer Feed Tank Flocculation Sedimentation

  12. Case Study WTP

  13. Toxin ConcentrationAfter Flocculation • Governing equation: • Solution: As toxin enters from PT for 1 day Where After tank is refilled on 2nd day w/o toxin

  14. Toxin Concentration After Clearwell C(t) Idealized as 3, completely mixed devices in series

  15. Lethal Human Response to Botulinus Toxin A Toxin Concentrations 100 g (0.22 lbs) added to polymer feed tank over 1 day Flocculation tank: CMFR Sedimentation tank: PFR Clear well: 3 CMFRs in series

  16. Advanced Modeling Methods • Computational fluid dynamics (CFD) • Three dimensional flow • Temperature stratification • Complex physical boundaries • Reactions • Requires large time and money investment

  17. http://www.watertechonline.com/news. Industry Outlook - 2/20/2002 12:12:29 PM Four arrested in plot to poison water ROME — Italian police were investigating today whether the US Embassy in Rome was the object of a plot to poison the city's water,a scheme uncovered with the arrest of four Moroccans in possession of large quantities of the deadly poison cyanide. Media reports said today that the suspects had maps of Rome highlighting the city's water supply and the US Embassy building. Police said they suspect the men, arrested early Tuesday in an outlying suburb as part of a covert operation, could have been plotting to poison the city's water or attack the embassy. They are probing possible links to Osama bin Laden, the Arizona Republic reported. Those arrested were found with about 10 pounds of cyanide and charts of Rome's water network and about 100 counterfeit resident permits, police said.

  18. Toxin Added Into Distribution System • Botulism toxin • WHO Scenario: A city of 50,000, each person drinking 0.5 L of water per day would require adding 240 g (0.5 lbs) over 6-hour period (several assumptions) • Our Case Study: 24 g of toxin fed into DS of city of 125,000 over 6 hours (5 am to 11 am) • Introduce into large diameter pipe near treatment plant and flowrate is about 10 million gallons per day

  19. Detection of Toxins & Response?

  20. Conclusions • Most vulnerable location would be toxin injection into distribution system • Simulation exercises for worst case are useful • Amount of toxin needed to cause serious problem could be small but depends on the nature of the toxin (toxicity and its solubility in water) • Security and monitoring are essential

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