Bioterrorism Scenarios in

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21 Φεβ 2014 (πριν από 3 χρόνια και 6 μήνες)

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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

Toxin

µg for a person drinking 1 L of Water
1


Botulinus
2


1.8

Tetanus


60

Tetradotoxin


540,000

1
Lethal dose (
µg/kg)
x

60 kg human

x 1000

2
Toxicity of Botulinus relative to cyanide = 1000

Distribution System

Water Treatment plant (WTP)

Reservoir

Public Water System:
Points of Vulnerabilty

Typical Water
Supply Reservoir

Case Study: Water
Supply Reservoir

Flow rate through reservoir,
Q

18.9 MGD

Velocity, v
x


Usable Volume

0.0078 ft/s

449 MG

Average depth

5.5 ft

Length

4,000 ft

Average width

670 ft

Dispersion coef.
D
x
, D
y
, D
z

1400, 250, 250
m
2
/day

Toxin Mass,
M, added

10 kg (22 lbs)

Toxin Added to

Water Supply Reservoir

Solution:

]
4
4
4
)
(
exp[
)
(
)
4
(
)
,
,
,
(
2
2
2
2
/
1
2
/
3
t
D
z
t
D
y
t
D
t
v
x
D
D
D
t
M
t
z
y
x
C
z
y
x
x
z
y
x






y

x

z

V
x

Water

Intake Location


Lake

Instantaneous
Toxin Input

WTP



















2
2
2
2
2
2
z
C
D
y
C
D
x
C
D
x
C
V
t
C
z
y
x
x
Governing equation:

Instantaneous

Point Source

Toxin Concentration Moving
Through Reservoir


Location of Water
Intake

Toxin Concentration
Entering Water Intake

3000 ft Away from Toxin Entry Pt


Lethal Human
Response to
Botulinus Toxic
A

Toxin Added to

Polymer Feed Tank

Polymer

Feed

Q
F

Q
P

Flocculation

Tanks

Sedimentation

Tanks

Clear Well

To distribution system

Filters

Toxin
Addition

Disinfectant
Additions

Water Treatment &
Distribution

Flocculation

Sedimentation

Filtration

Disinfection &

Clearwell Storage

Distribution

Toxin Addition to Polymer Feed Tank

Flocculation

Sedimentation

Case Study WTP

Flowrate of water,
Q
WTP

10 MGD

Polymer feed tank volume

750 gal

Flow rate of polymer,
Q
PF

2.5
L
/min

Flocculation tank volume

0.2 MG

Sedimentation tank volume

1.25 MG

Clear well storage volume

1 MG

Toxin mass added to feed tank

100 g (0.22 lbs)

Toxin Concentration

After Flocculation



Governing equation:



Solution:


tank

floc
PF
WTP
PF
WTP
V
dt
dC
C
)
Q
Q
(
C
Q















]
t
V
Q
Q
exp[
C
C
tank

loc
f
PF
WTP
1
0
]
t
V
Q
Q
exp[
C
C
tank

floc
PF
WTP
day

t




1
As toxin enters from PT


for 1 day

After tank is refilled

on 2
nd

day w/o toxin


PF
PF
WTP
PF
C
Q
Q
Q
C


0
Where

Toxin Concentration
After Clearwell

C

(t)

Idealized as 3, completely

mixed devices in series

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


Lethal Human
Response to
Botulinus Toxin
A

Advanced Modeling
Methods


Computational fluid
dynamics (CFD)


Three dimensional flow


Temperature
stratification


Complex physical
boundaries


Reactions


Requires large time and
money investment

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.

http://www.watertechonline.com/news.

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

Detection of Toxins & Response?

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