Cooling Tower Maintenance Legionella Awareness

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Cooling Tower Maintenance Legionella Awareness

• 4th Installment

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CTM/Ashland Presentations

• Legionella Awareness 2003
• Filtration of Cooling Waters 2005
• Legionella Risk Management 2006
• Legionella Proactive Protocol 2008
• Legionella Refresher -- 2011
• Literature References

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Legionella Proactive Protocol2008

• Introduction/Refresher
• Systems that may Harbor Legionella and What to Do
• Risk Category
• Legionella Testing Requirements
• Frequency of Cleaning/Disinfection
• Action Levels and Associated Response and
  Cleaning Steps
• Cooling Tower Design Best Practice
• Maintenance Considerations

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Legionella Refresher2011

• Legionella Sources
• Legionella Control
• Planning and Record Keeping

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Legionella Sources
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Legionella Bacteria
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Factors Determining the Risk of Contracting the
Disease

• A source of Legionella
• Favorable growth conditions
• Aqueous aerosols less than or equal to 5 microns
• Sufficient organisms to causeinfection
• Susceptible individual

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Systems Promoting Growth

• 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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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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Cyclic Operation and Biofilms

• AOC supports bofilm growth
• Flow and AOC supply stopped results in biofilm
  starvation and detachment
• - 90 in 24 hours
• - 80 in 12 hours
• - 60 in 10 hours
• - 40 in 8 hours
• Continuous flow without AOC achieves 90 biofilm
  detachment in 3 days

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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)
Aerobic Bacteria Fungi Anaerobic Bacteria Higher Life Forms
Flowing Bulk Water Basin Chip Scale lt10 1600 lt10 10 lt10 1,000,000 No Yes
Basin Sludge 3,500,000 20 1,000,000 Yes
Dead Head (off) Plate/Frame XER 400 lt10 10,000 Yes
Slip Stream By-pass (10) Plate/Frame lt10 lt10 lt10 No
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Legionella Control
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Microbiological Control Capability

• 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

• 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 Active Concentration mg/l Contact Time
Glutaraldehyde 25 - 54 1 Hour
Isothiazolin 2.25 - 2.6 6 Hours
2 Bromo-2-Nitro Propane-1,3, diol (BNPD) 25 400 24 Hours 60 Minutes
Dithiocarbamates 40.0 - 60.0 6 Hours
Di-bromo-nitrilo-propionamide (DBNPA) 4 - 8 2 Hours
Note System potential contaminants and operational pH must be checked for compatibility with the non-oxidizing biocide Note System potential contaminants and operational pH must be checked for compatibility with the non-oxidizing biocide 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

• Continuous feed for chlorine, bromine, BCDMH or
  stabilized bromine
• Dosage
• 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

• 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
• 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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Oxidant Feedrate
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Legionella Testing Requirements
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Action Levels

• Immediate response to positive test results
• On-line treatment requires a minimum of 14 days
  to produce results
• Unrealistic a system could be totally Legionella
  free

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Direct Testing of Legionella

• 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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Suggested Legionella Remedial Action Criteria
Legionalla (CFU/ml) Cooling/Tower Evaporative Condenser Potable Water Humidifier/Fogger
Detectablelt1 1 2 3
1-9 2 3 4
10-99 3 4 5
100-999 4 5 5
gt1000 5 5 5
Actions Review Maintenance Follow-up Analysis and Implement Action 1 Implement Action 2, Conduct review of Direct and Indirect Bio aerosol Contact of Occupants and Health Risk Status of Occupants May Lead to Increased Biocide Applications or Online Clean Implement Action 3, Cleaning/Biocide Improvement is Indicated Immediate Biocide Improvement and Cleaning is Indicated Levels have a Potential for Outbreak Actions Review Maintenance Follow-up Analysis and Implement Action 1 Implement Action 2, Conduct review of Direct and Indirect Bio aerosol Contact of Occupants and Health Risk Status of Occupants May Lead to Increased Biocide Applications or Online Clean Implement Action 3, Cleaning/Biocide Improvement is Indicated Immediate Biocide Improvement and Cleaning is Indicated Levels have a Potential for Outbreak Actions Review Maintenance Follow-up Analysis and Implement Action 1 Implement Action 2, Conduct review of Direct and Indirect Bio aerosol Contact of Occupants and Health Risk Status of Occupants May Lead to Increased Biocide Applications or Online Clean Implement Action 3, Cleaning/Biocide Improvement is Indicated Immediate Biocide Improvement and Cleaning is Indicated Levels have a Potential for Outbreak Actions Review Maintenance Follow-up Analysis and Implement Action 1 Implement Action 2, Conduct review of Direct and Indirect Bio aerosol Contact of Occupants and Health Risk Status of Occupants May Lead to Increased Biocide Applications or Online Clean Implement Action 3, Cleaning/Biocide Improvement is Indicated Immediate Biocide Improvement and Cleaning is Indicated Levels have a Potential for Outbreak
1998, PathCon Laboratories, Pathogen Control Associates Inc. 1998, PathCon Laboratories, Pathogen Control Associates Inc. 1998, PathCon Laboratories, Pathogen Control Associates Inc. 1998, PathCon Laboratories, Pathogen Control Associates Inc.
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Frequency of Cleaning/Disinfection
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Frequency of Cleaning/Disinfection

• Immediately prior to new system being
  commissioned
• If the system has been out of use for one month
  or longer
• If the system has been modified, entered or
  disturbed in such a way to lead to contamination
• If the cleanliness of the system is in any doubt
• If microbiological monitoring indicates there is
  a problem
• At least twice a year

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Frequency of Cleaning/Disinfection

• Preconditioning/Disinfection
• End of Operating Season
• 2 per Year Minimum for 24/7 Systems (4)
• Disinfection Only
• At Peak Seasonal Demand
• Occurrence of Outbreaks in the Area
• Upon System Restarts of 4 weeks Idleness ( 3
  Days?)
• Idle System of 1 Month or More to be Drained

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Sterilization Only

• 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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Planning and Record Keeping
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Total System ApproachFive Areas of Activity and
Performance

• ? Comprehensive system assessment
• ? Intensive microbiological treatment
  program
• ? Sterilization and cleaning
• ? Monitoring and control
• Documentation
• All Information is Available in Previous
  Presentations 03, 06, 08

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? System Assessment

• System survey
• In-depth survey of system mechanical layout and
  operating conditions
• Utilizes established protocol, ex BSRIA-Building
  Services Research Institute Assoc. (UK)
• Identify, evaluate and rank specific factors
  associated with potential for microbiological
  growth and Legionella
• Mechanical and chemical
• Determine risk minimization action plans

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Documentation

• 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

• 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 make-up 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

• 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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Influence Risk Associated With Legionella
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Survey of Process Risk
HIGH LOW
Humididifer/Fogger Aerosol Producing Process Misters, Atomizers Air Washers Decorative Fountains and Waterfalls Whirl Pools Hot Tubs Shower Heads Potable Water Hot/cold Shower Heads Cooling Towers/ Evaporative Condensers Risk increases with Location (i.e. Grounds Levels, Near Air Intakes/Windows), Local Ground Cover, Air Contamination/ Proximity to Exhaust See C.T.I. Design and Maintenance Consideration
Sludge/Settled Solids gt?? - ¼? Non-Visible
Temperature 35ºC (95ºF) To 46ºC (115ºF) lt20ºC (68ºF) gt50ºC (124ºF)
Biological Activity gt104 CFU/ml gt105 CFU/cm2 Presence of Higher life forms (OMEBA, PROTOZOA, ALGAE, MOLD, FUNGUS). 103 CFU/ml 104 CFU/cm2 No Higher Life Forms
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Monitoring and Inspection

• Inspection for visible slime or sludge's
• Decks
• Mist eliminators
• Fill
• Sumps
• Corrosion or biofilm coupons

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Biofilms

• Biofilms Dont Just Harbour Legionella, They
• Restrict Air Flow
• Restrict Water Flow
• Reduce Heat Transfer
• Reduce Heat Rejection
• Induce Localized Corrosion
• Biological Control
• Higher Life Forms None
• Bacteria CFU/ml lt104, gt 105 Do something
• Bacteria CFU/cm2 lt105, gt106 Do something

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Preventive Action

• Use your Biocides in a Prudent Manner
• And Remember
• Sterility Does Not Exist Except in Higher Life
  Forms

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