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Cooling Tower Maintenance Legionella Awareness
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  1. Cooling Tower Maintenance Legionella Awareness 3rd Installment

  2. CTM/Ashland Presentations • Legionella Awareness – 2003 • Filtration of Cooling Waters – 2005 • Legionella Risk Management – 2006 • Legionella Proactive Protocol – 2008 • Literature References

  3. Legionella Proactive Protocol • Introduction/Refresher • ASHRAE - Systems that may Harbour 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

  4. Legionella Proactive Protocol • Implement Risk Management Criteria • Maintenance and Record Keeping • Begin now as Legislation will be forth coming • Allows for a Basis of Estimation • Man • Methods • Materials • Estimates can be Reported to Management. While Focus has been Reduction of Costs they will need Estimates as the Cost of Ownership is Going Up.

  5. Refresher Information

  6. Source of Legionella • Pervasive organism • Conditions for growth • 68 - 122 F (20 - 50 C) • pH 6-8 • Stagnant waters • A nutrient source • Biofilms, organics • Sediments, deposits Legionella Bacteria

  7. Factors Determining the Risk of Contracting the Disease • A source of Legionella • Favorable growth conditions • Aqueous aerosol • Sufficient organisms to causeinfection • Susceptible individual

  8. Total System Approach:Five Areas of Activity and Performance Comprehensivesystem assessment  Intensive microbiological treatment program  Sterilization and cleaning  Monitoring and control  Documentation

  9. Preventive Actions • Inspect and Test • Domestic Waters • Fountains • Spas • Air Handling Units • Humidifying/Dehumidifying Equipment/Coils • Cooling Towers

  10. Field Study on Biofilm Growth

  11. 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)

  12. 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

  13. Oxidant Feedrate

  14. Inspection for visible slime or sludge's Decks Mist eliminators Fill Sumps Corrosion or biofilm coupons Monitoring and Inspection

  15. Monitoring and Inspection • 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

  16. Systems That May Harbour Legionella

  17. 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

  18. Potable Water Supply (AWWA) • New Piping and Additions • High Velocity Flush (HVF) initially at 8-15 ft./sec. if possible • Continuous Flush at 2.5 ft/sec. • ≥ 10 ppm FAC for 24 Hours • ≥ 50 ppm FAC for 3 Hours • Slug and Hold at ≥ 100 ppm FAC for 3 Hours is an alternative

  19. Potable Water Systems • Emergency Water Systems • Stagnant/Idle • Ideal Temperatures – Reach Room Temp • Eye Wash/Showers (Low to no Atomization) • Fire Systems • Periodically Flush

  20. Potable Water Systems • Cold Water – Store at ≤ 20ºC (68ºF) • Hot Water - Store at 50 - 60ºC (124-148ºF) - Operate Return Water ≥ 50ºC (124ºF) • Eradication • Thermal - 66ºC to 70ºC (150ºF) for 8 hours and Flush outlets for 30 minutes • Chemical - ≥ 2 ppm (10 ppm) FAC for 2-24 hours at pH 7-8; Flush for 5 minutes • Copper/Silver Ionization, • 0.2 – 0.8 ppm Copper • 0.02 – 0.08 ppm Silver

  21. Legionnella and Water Temperature

  22. SPAS • Hydrotherapy Pools, Whirl Pools, Hot Tubs • pH 7.2 - 7.8; 7.4 - 7.6 Ideal • FAC 3 - 10 ppm; 4 - 5 ppm Ideal • FABr 4 - 10 ppm; 4 - 6 ppm Ideal • Ultra Violet Plus Peroxide • Ozone • Maintenance Once per day for 1 to 4 hours at 10 ppm FAC or 10X FAC in use

  23. Other Water Systems • Treat and Maintain Similar to Cooling Tower Protocols • Fountains and Waterfalls • Filtration • Drain Regularly • Misters/Atomizers, Humidifiers, Air Washers • Coils, Spray Bars, Sumps, Mist Eliminators • Pre/Post Air Filtration • Bleed/Drain • Clean/Disinfect • Sludge Removal • UV – Air Space

  24. RISK CATEGORY

  25. Influence Risk Associated With Legionella

  26. Dutch Frequency of Legionella Testing Minimum

  27. Dutch Risk Category • Highest Risk – Cooling Towers < 200 meters from Hospital, Nursing Home or Health Care Facility where Occupants maybe immunologically compromised • Cooling Tower < 200 meters of Retirement Home, Hotel or Building Accommodating a Large Number of People • Cooling Tower in Residential and Industrial Neighbourhoods • Lowest Risk – Cooling Tower in Industrial Area > 600 metres Away from a Residential Area.

  28. Survey of Process Risk

  29. Factors Contributing to Legionella Health Risks in Cooling Systems

  30. TABLE 2 – COOLING SYSTEM SUSCEPTIBILITY TO LEGIONELLA RISKS

  31. TABLE 2 – COOLING SYSTEM SUSCEPTIBILITY TO LEGIONELLA RISKS

  32. TABLE 2 – COOLING SYSTEM SUSCEPTIBILITY TO LEGIONELLA RISKS

  33. Site Survey Pretreatment/Precleaning Need Assessment

  34. Precleaning Determination DEPOSIT ANALYSIS COUPONS/SURFACES HIGHLY TUBERCULATED AND SHINY SILVER BASE LOW % IRON ON LINE BIOFILM CLEAN-UP AND STIFLING OF TUBERCLES – PLUG APPARENT POROSITY, MIXED BIO/CORROSION FOULING ON LINE BIOFILM CLEAN-UP, BIOFOULING ONLY

  35. Breakdown of Bacteria Often Found in Cooling Water

  36. Legionella Testing Requirements

  37. Survey Summary Requirements For Legionella Testing

  38. 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

  39. Frequency of Cleaning/Disinfection

  40. 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 any doubt • If microbiological monitoring indicates there is a problem • At least twice a year

  41. Frequency of Cleaning/Disinfection • Preconditioning/Disinfection • End of Operating Season • 2 per Year Minimum for 24/7 Systems • 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

  42. 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.

  43. Actions Levels/AssociatedCleaning Disinfection

  44. OSHA Technical Manual (Section III: Chapter 7)

  45. Suggested Legionella Remedial Action Criteria

  46. Implications of the Need for Biocide Improvements • Action 3 - 14 Days After Action 2 Completed • Nonoxidizers Review Dosing Schedule and Amount Used vs. Contact Time (Feed/Bleed Issues) • Oxidizer – Semi-Continuous; Frequency and Duration for 1 to 2 ppm FAC Applied. Minimum 0.5 – 1.0 ppm 4hours/24hours • Oxidizer – Continuous; 0.2 to 0.5 ppm FAC go to 0.5 – 1.0 ppm FAC • Retest within 3-5 Days

  47. Implications of the Need for Biocide Improvements • Action Level 4 - 14 Days After Action Level 3 Completed • Non-oxidizer Program May Require Oxidant Use At 1/Week in Summer and ½ Weeks Winter at 1-2 ppm FAC for 1 Hour CT (i.e. 2 Hour Run Time) • Semi-Continuous Oxidizer may require either or both non-oxidizer or Biodispersant Once per Week • Continuous Oxidizer at 1-2 ppm FAC may Require Either or Both Non-Oxidizer or Biodispersant once per Week • Non-Oxidizer or Biodispersant Addition Maybe Required Every System Retention Time (Vol/BD Loss) • May Require On-line Clean Within 30 Days • Retest Within 3-5 Days

  48. Implications of the Need for Biocide Improvement • Action Level 5 – 14 Days After Action Level 4 Completed • On-line Clean within 7 Days of This State • Biodispersant Plus ≥ 5 ppm FAC for OR • Biodispersant Plus ≥ 25 ppm FAC for 2 Hours OR • Biosdispersant Plus ≥ 50 ppm for 1 Hour • Test 3-7 Days Latter – Poor Results Repeat or Go to Off-line Approach

  49. Implications of the Need for Biocide Improvement • Off-line Cleaning • Pre Conditioning with • Blowdown to ½ COC • Biodispersant and Non Oxidizer for 24 Hours • Hyper Chlorination • pH 7.5 – 8.0 • Biodispersant • ≥ 10 ppm FAC for 24 hours • Drain and Flush • Post Conditioning of ≥ 10 ppm FAC for 1 Hour • Test 3-7 Days Latter – Poor Results Repeat or Go to Wisconsin Protocol

  50. Implications of the Need for Biocide Improvement • Special Notes • Action Levels Are a Forward Progression • Upon Attaining Steady State Correction Move Backwards on the Action Levels Assuring No Return to Control State Loss • It is not Unusual to have to Repeat Online or Off-line Cleans as Previous Suppressed Bioflims, Sludge and Muds have now been Conditioned/ Loosened for Release to the Bulk Water