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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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slide1

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
Lethality of Toxins

1Lethal dose (µg/kg) x60 kg humanx 1000

2Toxicity of Botulinus relative to cyanide = 1000

public water system points of vulnerabilty
Public Water System: Points of Vulnerabilty

Reservoir

Water Treatment plant (WTP)

Distribution System

toxin added to water supply reservoir

y

Instantaneous Toxin Input

x

z

Governing equation:

Instantaneous

Point Source

Solution:

Toxin Added to Water Supply Reservoir

WTP

Water

Intake Location

Lake

Vx

toxin added to polymer feed tank
Toxin Added to Polymer Feed Tank

Sedimentation

Tanks

QF

Flocculation

Tanks

QP

Clear Well

Filters

Polymer

Feed

Disinfectant Additions

To distribution system

Toxin Addition

slide10

Water Treatment & Distribution

Flocculation

Sedimentation

Filtration

Disinfection &

Clearwell Storage

Distribution

slide11

Toxin Addition to Polymer Feed Tank

Flocculation

Sedimentation

toxin concentration after flocculation
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

toxin concentration after clearwell
Toxin Concentration After Clearwell

C(t)

Idealized as 3, completely

mixed devices in series

toxin concentrations

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

advanced modeling methods
Advanced Modeling Methods
  • Computational fluid dynamics (CFD)
  • Three dimensional flow
  • Temperature stratification
  • Complex physical boundaries
  • Reactions
  • Requires large time and money investment
slide17

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.

toxin added into distribution system
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
conclusions
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