Legionella
In Light of Recent Events
Drew Industrial
Ashland Canada Corp
Legionella Bacteria
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Source of Legionella
– Pervasive organism
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Conditions for growth
– 68 - 122 F (20 - 50 C)
– pH 6-8
– Stagnant waters
– A nutrient source
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Biofilms, organics
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Sediments, deposits
Factors Determining the Risk of
Contracting the Disease
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A source of Legionella
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Favorable growth conditions
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Aqueous aerosol
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Sufficient organisms to cause
infection
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Susceptible individual
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Systems Promoting Growth
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Cooling towers
Evaporative condensers
Hot and cold water systems
Taps and showerheads
Humidifiers and air washers
Spa and whirlpool baths
Decorative fountains
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We know that…
In order to minimize Legionella growth:
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Chemical treatment alone is not effective
Minimization is dependent upon design,
maintenance, contaminants, awareness and
consistent implementation
Effective Legionella management requires a
“best practices” approach: A system that is
properly treated, serviced and supervised
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Total System Approach:
Five Areas of Activity and Performance
 Comprehensive system
assessment
 Intensive microbiological treatment
program
 Sterilization and cleaning
 Monitoring and control
 Documentation
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 System Assessment
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System survey
– In-depth survey of system mechanical layout and
operating conditions
– Utilizes established protocol, ex BSRIABuilding Services Research Institute Assoc. (UK)
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Identify, evaluate and rank specific factors
associated with potential for microbiological
growth and Legionella
– Mechanical and chemical
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Determine risk minimization action plans
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“Ideal System”
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Water flow is continuous
No dead legs or stagnant
conditions
Basin and deck protected
from sun
No evidence of sludge,
debris, algae
Drift eliminators installed,
functioning
No evidence of aerosols, drift
System not near health care,
aged, residential facility
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Low number of people
potentially exposed
Halogen used
Biodispersant/biodispersing biocide used
Comprehensive water
treatment program
Automated biocide and
chemical dosing
Continuous automated
monitoring, control
Susceptibility to Legionnaires’
Disease
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Age – The very young and +40 year olds
Gender – Males are twice as likely to contract the
disease than females
Heavy Smoker
Heavy Drinker
Individuals with weakened immune systems –
Cancer, AIDS, HIV positive
Chronic Medical Problems – respiratory, diabetes,
asthma, renal dialysis
Certain Drug Therapies – corticosteroids or other
immunosuppressive therapies
Organ Transplants
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Legionella Risk Management in
Cooling Waters
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Outbreak Potential is typically the cumulative
effect of many high risk variables
– Population of those whom are susceptible
– Type of facility
– Susceptibility of the cooling system
– Microbiological control capability
– Monitoring and inspection frequency
– Documentation provides a management and
control feedback loop
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High Risk Facilities
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Hospitals
Retirement Homes
Long-term and chronic care facilities
Public facilities
– Offices
– Malls
– Hotels
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Process cooling systems that have the potential
for:
– Aerosol spray cooling – automotive
– Process contamination
- CPI/HPI
- Food/Beverages
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Cooling System Susceptibility
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High airborne dirt load potential
(utilization of side-stream filtration)
– Nearby construction
– Lack of ground coverings with aggregate
materials or vegetation
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High nutrient load potential
– Process side inleakage
– Tower near chemical, food or vehicle exhaust
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Cooling System Susceptibility
Cooling tower air discharge near proximity
to fresh air intakes or open windows of
building, and/or outdoor population
(i.e. ground level).
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Cooling System Susceptibility
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No operation or intermittent operation of
equipment while wet:
– Drain if stagnant > 1 month
– Idle - rotate weekly or install 5 – 10% slip
stream flow
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Dead legs or seasonal cross-over lines
– Remove them or
– Loop them with 5 – 10% slip stream flow
– Close shut-off valves at flowing supply and
drain the remainder of the branch system and
equipment
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Effects of Cooling System Dynamics –
cfu/ml Same Day Comparative Samples
(Example System Treated with Continuous Oxidant and
Slug Feed of Glutaraldehyde Once Per Week)
Flowing Bulk Water
Basin Chip Scale
Basin Sludge
Dead Head (off)
Plate/Frame XER
Slip Stream
By-pass (10%)
Plate/Frame
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Aerobic
Bacteria
Fungi
Anaerobic
Bacteria
Higher
Life Forms
<10
1600
<10
10
<10
1,000,000
No
Yes
3,500,000
20
1,000,000
Yes
400
<10
10,000
Yes
<10
<10
<10
No
Microbiological Control Capability
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Efficacious biocides selection
Biodispersant supplement for biofilm
Effective application for required concentration and contact
time
– System dynamics (ART, T½) and volume
– Dedicated automated feed of microbiocides
– Feedback control Loop (ORP, self verifying feed pumps)
Pre-conditioning/sterilization
– Preseason start-up
– Idle restarts
– Sterilization/hyper chlorination at the summer peak
– End of season shutdown
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Microbiological Control Additives of Choice
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Oxidation
– Bleach (CSW 20)
– Sodium Bromide/Bleach (Drewbrom)
– BCDMH (Biosperse 261T)
– Chlorine Dioxide
Non Oxidants
– Glutaraldehyde 1º (Biosperse 254/255)
– Isothiazolin 2º (Biosperse 250)
Biodispersants
– Nonionic Surfactants (Drewsperse 739)
– Protein cross linking/cationic surfactant blend
(Performax 405)
– Anionic surfactants (Drewsperse 7211)
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Legionella Control with Non-Oxidizing Biocides
Chemical Compound
Glutaraldehyde
Isothiazolin
2 Bromo-2-Nitro Propane-1,3, diol
(BNPD)
Dithiocarbamates
Di-bromo-nitrilo-propionamide (DBNPA)
Active Concentration mg/ℓ
Contact Time
25 - 54
1 Hour
2.25 - 2.6
6 Hours
25
400
24 Hours
60 Minutes
40.0 - 60.0
6 Hours
4-8
2 Hours
Note: System potential contaminants and operational pH must be checked for
compatibility with the non-oxidizing biocide
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Continuous Oxidant Feed Protocol
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Continuous feed for chlorine, bromine,
BCDMH or stabilized bromine
– Dosage:
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Recommended 0.2 - 0.4 FAH and/or equivalent mV ORP
with a minimum requirement of a measurable residual FAH
For higher risk systems increase FAH residual as needed
to control CFU level and biofilm
Feed a supplemental organic biocide*
– Recommend biocide be glutaraldehyde or an
alternate biocide fed with biodispersant
– Feed once per week or as needed to control biofilm
*Alternative choices of non-oxidizing biocide should be based on Relative
Population Density (RPD) lab results
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 Intermittent Oxidant Feed Protocol
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Intermittent Oxidant Feed
– Chlorine, bromine, BCDMH or stabilized bromine
– Minimum dosage: Hold 0.5 - 1.0 FAH and/or
equivalent mV ORP for a minimum of 2 hours each
day
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Feed alternating supplemental organic
biocides*
– Recommend one biocide be glutaraldehyde or an
alternate biocide fed with biodispersant
– Feed an additional compatible organic biocide*
– Alternate feed once per week
*Alternative choices of non-oxidizing biocide should be based on RPD results
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Chlorine Dioxide
A Selective Oxidant
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Oxidation potential not affected by pH
Selective oxidant
No dissociation; does not react with water
Does not react with amines, nitrogen
compounds
Highly effective against biofilm
Continuous Chlorine Dioxide Feed
Protocol
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Continuous chlorine dioxide feed
– Minimum dosage: 0.1 ppm residual ClO2 or
equivalent mV ORP
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Feed a supplemental organic biocide as
needed based on biofilm control
– Recommend biocide is glutaraldehyde or an
alternate biocide fed with biodispersant*
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Feed once per week or as needed to
control biofilm
*Alternative choices of non-oxidizing biocide should be based on RPD results
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Intermittent Chlorine Dioxide Feed Protocol
 Intermittent chlorine dioxide feed
– Minimum dosage: 0.5 ppm residual ClO2 and/or
equivalent mV ORP for a minimum of 2 hours per day
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Feed alternating supplemental organic
biocides*
– Recommend one biocide be glutaraldehyde or an
alternate biocide fed with biodispersant
– Feed an additional compatible organic biocide*
– Alternate feed once per week
Chlorine dioxide is also an effective supplemental biocide
for process cooling systems where contaminants that
increase bacterial growth are present.
*Alternative choices of non-oxidizing biocide should be based on RPD results
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Dual Non-Oxidizer Feed Protocol
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Slug feed of non-oxidizer
– Alternately twice per week, evenly spaced
– Timer/Pump (self verifying optional) automated
feed is preferred over manual
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Oxidant feed once per week
– Minimum dosage to hold 1 – 2 ppm FAH for 2
hours. Based upon system demand this may
require the feed of 5 to 10 ppm active oxidant
– Dosing a day prior to a nonoxidizer addition is
the preferred method.
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Preconditioning and Sterilization
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Frequency
– Minimum once per year for season equipment
operation
• End of season preferred
– Minimum twice per year for year round system
operation
• During turn around on process systems and 6
months later
• Beginning and end of cooling season
– Confirmed Out Break
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Preconditioning and Sterilization
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Procedure
• Ensure all air intakes and windows within at
least 100 feet of the tower are closed
• Open all cross over lines
• Ensure complete recirculation of the total
system and all equipment
• Turn fans off and activate stand-by pump
• Blowdown flush all strainers, risers, water
boxes and dead legs.
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Preconditioning and Sterilization
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Procedure Cont’d
• Add biodispersant (200 ppm) and non-oxidizer
recirculate for 24 hours (120 – 360 ppm)
• Blowdown/flush etc.
• Add oxidant to produce 5 ppm FAH (due to
system demand, dosage may be 15 to 25 ppm –
1.5 to 2.5 lbs. 10% bleach/1,000 gal) test verify 5
ppm at end of 6 hours
• Drain system blowdown/flush etc.
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Preconditioning and Sterilization
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Procedure Cont’d
• Water Wash/Hose out Tower
•
Upper deck
Drift eliminators
Fill
Sumps and companion indoor sumps and storage tanks
through to pump strainer
If high pressure water jetting is employed then
ensure suitable respiratory protective equipment
is worn.
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Preconditioning and Sterilization
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Procedure – Cont’d
• Leave drained for seasonal outage
• If wet storage is employed, refill with inline
blend of protecsol and 300 – 400 ppm of 1.5 %
Isothiazolin non-oxidizer.
• Immediate placement into service
- Refill
- Start pumps
- Slug feed corrosion and deposit control
compounds and non-oxidizer
(i.e. prime the system volume)
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Sterilization Only
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Frequency
– During restart of idle/stagnant towers,
condensers, heat exchangers
– Seasonal restart of HVAC system, which was
preconditioned and sterilized the end of the
previous season
– Peak of summer cooling demand
(i.e. beginning of August).
– Known outbreaks in the area
– Biological dip slide counts exceed 105 – 106
CFU/ml. Visible slime (i.e. biofilm) present.
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Sterilization Only
Procedure
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• Deconcentrate via bleed-off and blowdown of dead legs,
risers, water boxes, and strainers to achieve 2 cycles of
concentration. Close bleed
• Fans off
• Add oxidant to produce 5 ppm FAH (Due to system
demand, dosage may be 15 to 25 ppm – 1.5 to 2.5
lbs/10% bleach/1,000 gal). Test hourly to verify 5 ppm
held for 6 hours
• Blowdown dead legs, risers water boxes and strainers
• Resume treatment program cycles of concentration
• Add Non-oxidizing Biocide
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Monitoring and Inspection
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Inspection for visible slime or sludge's
– Decks
– Mist eliminators
– Fill
– Sumps
– Corrosion or biofilm coupons
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Monitoring and Inspection
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Testing
• Bulk water dip slides
- Prior to non-oxidizing biocide addition
- Minimum once per week
- Target ≤ 104 CFU/ml
• Coupon surfaces - if available
- Prior to non-oxidizer and/or biodispersant
addition
- Every 30 to 60 days, but be consistent
- Target ≤105 CFU/cm2
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Direct Testing of Legionella
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Frequency Consideration
• Prior to peak summer sterilization (i.e.
beginning/mid August) for seasonally operated
HVAC or after a sterilization.
• After cleaning of a confirmed cooling tower
sourced outbreak
• If a confirmed outbreak has occurred in the
area (≤3 km minimum)
• Three times per year of 24/7 Industrial process
cooling systems of higher risk noted earlier
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Legionella Testing –
Pathcon/Biosans
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Ship via air direct
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7 days to culture
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If positive, species and type is determined,
requiring additional time
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E-mail results within 2 days after the 10th
day after receipt by lab
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OSHA/Wisconsin Protocol
Confirmed Cooling Tower Source of Outbreak
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1.
2.
3.
4.
5.
6.
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Turn off tower fans
Shock dose chlorine donor to 50 ppm FAC
Add Biodispersant
Hold 10 ppm FAC for 24 hours
Drain cooling system and repeat steps 2 - 4
Inspect for biofilms. If present, drain and
mechanically clean.
OHSA/Wisconsin Protocol
Refill system and operate for 1 hour at 10 ppm FAC
Flush system
Recharge system with water treatment additives for
deposit, corrosion and biological control and return
to service
7.
8.
9.
Note test monthly:
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Legionella ≤10 CFU/ml
HPC ≤105 CFU/ml
Field Study on Biofilm Growth
Phase
Time
Colonization
15 Minutes
Growth Detection
2 Days
Biofilm Formation
(Exopolymer/ Minimum Biofouling)
5 Days
Maximum Biofilm Growth
(8 – 10 Cells Thick)
14 Days
Fully Mature Biofilm Matrix
31 – 40 Days
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Documentation
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Why Document?
• When a pneumonia outbreak occurs in a facility
it allows for:
- Speed in identifying the source for eradication
purposes, removing a potential and continual
threat. After all it may not be cooling system
derived.
- Clinical micro biologists and physicians to select
appropriate antibiotics, dosages and monitor the
progress without the presence of further
stressors.
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Documentation
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To name a few:
• Simplified line drawing of the cooling system and all
equipment, dead legs cross over lines, chemical feed
points/lines/control, system volume, recirculation makeup and blowdown rates
• Key water test results/date
- Chlorides or conductivity for cycles of concentration
assessment
- Make-up, blowdown water meter readings
- FAH and/or ORP for Halogen concentration
- Biological Tests – CFU/ml; CFU/cm2
- Start, end and expiry dates of dip slide lots for bio testing
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Documentation
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To name a few:
• Chemical pump and timer settings
• Biocide usage
• Start-up/shutdown and other application logs
of preconditioning/sterilization and sterilization
only
• Inspection/observations for slimes, muds,
algae in cooling tower and on coupons and
what was done to improve
• Contingency plans procedures, and
results/check offs when performed.
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Use of Proper Monitoring &
Control Equipment is Critical!
Microbiological
Residuals,
Corrosion, Scale
& Biofouling
On-line
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Action Levels
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Immediate response to positive test results
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On-line treatment requires a minimum of
14 days to produce results
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Unrealistic a system could be totally
Legionella free
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Preventive Actions
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Legionella is as Common as “Dirt”
Keep Systems Mechanically and
Microbially Clean
Minimize or Rotate Idle Equipment
Employ Filtration and Keep Filter Media
Clean
Mist Eliminators Clean and Functioning
Properly
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Preventive Actions
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Inspect and Test
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–
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–
–
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Domestic Waters
Fountains
Spas
Air Handling Units
Humidifying/Dehumidifying Equipment/Coils
Biofilms
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Biofilms Don’t Just Harbour Legionella, They:
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–
–
–
–
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Restrict Air Flow
Restrict Water Flow
Reduce Heat Transfer
Reduce Heat Rejection
Induce Localized Corrosion
Biological Control
– Higher Life Forms – None
– Bacteria CFU/ml <104, > 105 Do something
– Bacteria CFU/cm2 <105, >106 Do something
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Preventive Action
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Use your Biocides in a Prudent Manner
And Remember
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Sterility Does Not Exist Except in Higher
Life Forms
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Additional Information Upon
Request

Legionella: Minimizing Risks, August 2000, Water
Engineering and Management
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Environmental Aspects of Legionnaires’ Disease, February
1988, Journal AWWA
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Legionella Treatment Strategies: First Response and
Minimization Action Plan, 2002 International Water
Conference Paper 02-12
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Who Should Be Responsible for Legionella, ASHRAE
Journal May 1999, Volume 41, No. 5, 62-68, ref. ISSN-00012491
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Why Evaporative Coolers Have Not Caused Legionnaires’
Disease, ASHRAE Journal, January 1995, page 29-33
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Additional Information Upon
Request
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Legionellosis, Guideline: Best Practices
for Control of Legionella, February 2000,
Cooling Technology Institute
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Minimizing Risk of Legionellosis
Associated with Building Water Systems,
February 2000, ASHRAE Standard 12-2000
(ISSN 1041-2336)
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What Can You Anticipate
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Expert group review of design and
maintenance of cooling towers in longterm care homes, hospitals and other
facilities housing people with complex
health needs.
What Can You Anticipate
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Review of other existing HVAC/Legionella standards and
development/adoption of a standard for use;
• ASHRAE Guideline 12-2000“Minimizing the risk of Legionellosis associated with building
water systems”
• Cooling technology institute February 2000 Guidelines –
“Legionellosis guideline: “Best Practices for control of
Legionella”
• Health and Safety Commission, U.K., approved code of practice
and guidance – L8, “Legionnaires” disease, the control of
Legionella bacteria in water systems”
• The chartered institution of Building Services Engineers, U.K.
TM 13- 2000, “Minimizing the risk of Legionnaires’ disease”
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Walker Report
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http://www.health.gov.on.ca/english/public/pub
/ministry_reports/walker_legion/rep_intro...
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Report of the expert panel on the
Legionnaires” disease outbreak in the city of
Toronto – September/October 2005, December
2005.
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Industrial Hygienists
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Employ Certified Industrial Hygienists
Employ HVAC Engineers
– Can fully evaluate potable cold and hot
Domestic Water systems
– Can calculate cooling tower plume
relationships and re-entrainment of plume into
air intakes or windows
– Can assess air handling systems
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Industrial Hygienists
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A firm such as:
– Stantec Consulting
– Resource Environmental Associates
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Complete air quality, risk assessments on
all aspects of exposure to Legionella and
other environmental conditions such as
molds and asbestos
Firms may also have a division that does
complete sterilizations of systems – hot
and cold domestic, air handling, etc.
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Ashland
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Ashland is capable of a cursory review of cooling
systems to assist a customer in targeting certain
areas, as related to:
– System Cleanliness
– Microbiocide addition – whether oxidizing or nonoxidizing biocide.
– Capable of applying chemicals to meet the protocols –
continuous chlorination, shock feeding
– Mechanical/operational conditions that can lead to high
risk
– Assist in providing documentation tools
– Can provide routine microbiological testing and has a
sample protocol and a lab arrangement to test for
Legionella
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Thank You
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Registered trademark and ™ trademark of Ashland Inc.
Ashland Inc.
© 2001
®