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® Cooling Tower Maintenance Legionella Awareness 4 th Installment.

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Presentation on theme: "® Cooling Tower Maintenance Legionella Awareness 4 th Installment."— Presentation transcript:

1 ® Cooling Tower Maintenance Legionella Awareness 4 th Installment

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

3 ® Legionella Proactive Protocol 2008  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

4 ® Legionella Refresher 2011 Legionella Sources Legionella Control Planning and Record Keeping

5 ® Legionella Sources

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

7 ® 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 cause infection Susceptible individual

8 ® Cooling towers Evaporative condensers Hot and cold water systems Taps and showerheads Humidifiers and air washers Spa and whirlpool baths Decorative fountains Systems Promoting Growth

9 ® Field Study on Biofilm Growth PhaseTime Colonization15 Minutes Growth Detection2 Days Biofilm Formation (Exopolymer/ Minimum Biofouling) 5 Days Maximum Biofilm Growth (8 – 10 Cells Thick) 14 Days Fully Mature Biofilm Matrix31 – 40 Days

10 ® 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

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) Aerobic Bacteria Fungi Anaerobic Bacteria Higher Life Forms Flowing Bulk Water Basin Chip Scale < <10 10 <10 1,000,000 No Yes Basin Sludge3,500,000201,000,000Yes Dead Head (off) Plate/Frame XER 400<1010,000Yes Slip Stream By-pass (10%) Plate/Frame <10 No

12 ® Legionella Control

13 ® Microbiological Control Capability Efficacious biocides selection Biodispersant supplement for biofilm Effective application for required concentration and contact time –System dynamics (ART, T ½ ) 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

14 ® 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)

15 ® Legionella Control with Non-Oxidizing Biocides Chemical Compound Active Concentration mg/ ℓ Contact Time Glutaraldehyde Hour Isothiazolin Hours 2 Bromo-2-Nitro Propane-1,3, diol (BNPD) Hours 60 Minutes Dithiocarbamates Hours Di-bromo-nitrilo-propionamide (DBNPA) Hours Note: System potential contaminants and operational pH must be checked for compatibility with the non-oxidizing biocide

16 ® Continuous feed for chlorine, bromine, BCDMH or stabilized bromine –Dosage: Recommended 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 Continuous Oxidant Feed Protocol

17 ®  Intermittent Oxidant Feed Protocol Intermittent Oxidant Feed –Chlorine, bromine, BCDMH or stabilized bromine –Minimum dosage: Hold 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

18 ® Oxidant Feedrate

19 ® Legionella Testing Requirements

20 ® 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

21 ® 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

22 Suggested Legionella Remedial Action Criteria Legionalla (CFU/ml) Cooling/Tower Evaporative Condenser Potable WaterHumidifier/Fogger Detectable;< > Actions – 1. Review Maintenance 2. Follow-up Analysis and Implement Action 1 3. 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 4. Implement Action 3, Cleaning/Biocide Improvement is Indicated 5. Immediate Biocide Improvement and Cleaning is Indicated Levels have a Potential for Outbreak © 1998, PathCon Laboratories, Pathogen Control Associates Inc.

23 Implications of the Need for Biocide Improvements Action Days After Action 2 Completed –Non oxidizers 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

24 ® Implications of the Need for Biocide Improvements Action Level 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 Online Clean Within 30 Days –Retest Within 3-5 Days

25 ® 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

26 ® Implications of the Need for Biocide Improvement Special Notes 1.Action Levels Are a Forward Progression 2.Upon Attaining Steady State Correction Move Backwards on the Action Levels Assuring No Return to Control State Loss 3.It is not Unusual to have to Repeat Online or Offline Cleans as Previous Suppressed Biofilms, Sludge and Muds have now been Conditioned/ Loosened for Release to the Bulk Water

27 ® OSHA/Wisconsin Protocol Confirmed Cooling Tower Source of Outbreak 1.Turn off tower fans 2.Shock dose chlorine donor to 50 ppm FAC 3.Add Biodispersant 4.Hold 10 ppm FAC for 24 hours 5.Drain cooling system and repeat steps Inspect for biofilms. If present, drain and mechanically clean.

28 ® Frequency of Cleaning/Disinfection

29 ® 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

30 ® 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

31 ® 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 10 5 – 10 6 CFU/ml. Visible slime (i.e. biofilm) present.

32 ® Implications of the Need for Biocide Improvement Off-line Cleaning –Pre Conditioning with 1. Blowdown to ½ COC 2. Biodispersant and Non Oxidizer for 24 Hours -Hyper Chlorination 1. pH 7.5 – Biodispersant 3. ≥ 10 ppm FAC for 24 hours 4. 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

33 ® Planning and Record Keeping

34 ® Total System Approach: Five Areas of Activity and Performance  Comprehensive system assessment  Intensive microbiological treatment program  Sterilization and cleaning  Monitoring and control Ä Documentation Ä All Information is Available in Previous Presentations 03, 06, 08

35 ® 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  System Assessment

36 ® 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.

37 ® 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

38 ® 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.

39 ® 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 Low number of people potentially exposed Halogen used Biodispersant/bio- dispersing biocide used Comprehensive water treatment program Automated biocide and chemical dosing Continuous automated monitoring, control “Ideal System”

40 ® High Risk Facilities Hospitals Retirement Homes Long-term and chronic care facilities Public facilities –Offices –Malls –Hotels Process cooling systems that have the potential for: –Aerosol spray cooling – automotive –Process contamination ­ CPI/HPI ­ Food/Beverages

41 ® Cooling System Susceptibility High airborne dirt load potential (utilization of side-stream filtration) –Nearby construction –Lack of ground coverings with aggregate materials or vegetation High nutrient load potential –Process side inleakage –Tower near chemical, food or vehicle exhaust

42 ® 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).

43 ® Cooling System Susceptibility No operation or intermittent operation of equipment while wet: –Drain if stagnant > 1 month –Idle - rotate weekly or install 5 – 10% slip stream flow 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

44 ® Influence Risk Associated With Legionella

45 Survey of Process Risk HIGHLOW 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 >⅛″ - ¼″ Non-Visible Temperature 35ºC (95ºF) To 46ºC (115ºF) <20ºC (68ºF) >50ºC (124ºF) Biological Activity >10 4 CFU/ml >10 5 CFU/cm 2 Presence of Higher life forms (OMEBA, PROTOZOA, ALGAE, MOLD, FUNGUS). ≤10 3 CFU/ml ≤10 4 CFU/cm 2 No Higher Life Forms

46 ® Factors Contributing to Legionella Health Risks in Cooling Systems Biofilm Temperature and pH Organic Contamination Aerosols Algae and Protozoa Scale and Corrosion Stagnant Water Condition of Drift Eliminators High Levels Of Heterotrophs (i.e. CFU/ml) Exposure to Sunlight Intermittent Operation Tower Repair Presence of Legionella Water Quality Bio-Control Program Proximity To Populations

47 TABLE 2 – COOLING SYSTEM SUSCEPTIBILITY TO LEGIONELLA RISKS ISSUECONDITIONCORRECTIVE MEASURE COOLING TOWER (C.T.) LOCATION GROUND LEVEL AND/OR DIRECT EXPOSURE TO POPULATION C.T. AIR DISCHARGE NEAR BUILDING FRESH AIR INTAKE C.T. AIR DISCHARGE NEAR WINDOWS IN BUILDINGTHAT OPEN NONE A DESIGN CONSTRAINS NONE, A DESIGN CONSTRAINT, USE THERMOGRAPHY TO DETECT DISTANCE OF AIR TRAVEL WRT INTAKE LOCATION NONE, A DESIGN CONSTRAINT, OR FIX WINDOWS CLOSED, USE THERMOGRAPHY TO DETECT DISTANCE OF AIR TRAVEL WRT WINDOW LOCATION. MAKE-UP UNCLARIFIED, UNFILTERED, NO DISINFECTION PRETREATMENT EFFECTIVELY OR GO TO POTABLE WATER SOURCE HIGH AIRBORNE DIRT LOAD NEAR BY CONSTRUCTION AND OR EXCAVATION LACK OF GROUND COVER TEMPORARY, STEP-UP BIO TREATMENT APPLICATIONS, USE SIDE STREAM FILTRATION COVER EXPOSED EARTH WITH AGGREGATE MATERIALS OR VEGETATION, USE SIDE STREAM FILTRATION (SEE ATTACHMENT I) WATER FLOWINTERMITTENT LEADING TO STAGNATION, BIOFILMS, BIO- SEDIMENTS, ANAEROBIC CONDITIONS DRAIN IF STAGNATION > 1 MONTH ROTATE EQUIPMENT WEEKLY WITH MILD STERILIZATION (5 PPM FAH, 6 HOURS) UPON RESTARTS INSTALL 5-10% SLIP STREAM FLOW PROVIDED COOLING WATER IS LOW IN SUSPENDED SOLIDS (I.E., ≤ 5NTU) OR SIDE STREAM FILTERING IS PRESENT (I.E. ≤ 25 NTU THEORETICAL).

48 ® TABLE 2 – COOLING SYSTEM SUSCEPTIBILITY TO LEGIONELLA RISKS ISSUECONDITIONCORRECTIVE MEASURE DEAD LEGS, SUPPLY/RETURN HEADER DEAD HEADS, SEASONAL CROSSOVER LINES BIOFILMS, BIO-SEDIMENTS, ANAEROBIC CONDITIONS REMOVE DEAD LEGS OR BLOWDOWN (HIGH VELOCITY FLUSH) EVERY 5 TO 7 DAYS LOOP SUPPLY/RETURN HEADERS WITH 5- 10% SLIP STREAM FLOW PROVIDED COOLING WATER LOW IN SUSPENDED SOLIDS OR BLOWDOWN EVERY 5 -7 DAYS. SEASONAL CROSSOVER LINES AND EQUIPMENT. PROVIDE 5-10% SLIP STREAM FLOW PROVIDED COOLING WATER IS LOW IN SUSPENDED SOLIDS OR INSTALL ISOLATION VALVE AT THE FLOWING LINE TAKE OFF WITH A BLOCK AND BLEED VALUE ARRANGEMENT AND DRAIN THE SEASONAL LINE AND EQUIPMENT HIGH NUTRIENT LOAD POTENTIAL PROCESS INLEAKAGE EXHAUSTING AIR/GASES FROM CHEMICAL OR FOOD PROCESSING (VOC’S) AND VEHICLES NEAR COOLING TOWER INTAKES EMPLOY DETECTION AND CONTINGENCY MITIGATION METHODS AS DONE FOR TRADITIONAL CHEMICAL TREATMENT PROGRAMS REDIRECT EXHAUSTING AIR/GASES DIRECT SUNLIGHT ABSORPTION BY COOLING TOWER BASIN UPPER DISTRIBUTION DECK NONE, A DESIGN CONSTRAINT ENCLOSE WETTED EXPOSED AREAS WITH HINGED COVERS THAT ALLOW FOR ACCESS AND INSPECTION

49 ® TABLE 2 – COOLING SYSTEM SUSCEPTIBILITY TO LEGIONELLA RISKS ISSUECONDITIONCORRECTIVE MEASURE HIGH DRIFT AND AEROSOLS IN COOLING TOWER AIR EXHAUST  DRIFT ELIMINATORS MISSING OR  IMPROPERLY INSTALLED  OLD, LOW EFFICIENCY DRIFT ELIMINATORS PRESENT CHECK DRIFT ELIMINATORS FOR PRESENCE AND CORRECT INSTALLATION. REFIT REPLACE BROKEN ELIMINATORS UPGRADE TO HIGHER EFFICIENCY DRIFT ELIMINATORS COOLING TOWER INSPECTION OF FILL, ELIMINATORS, BASIN, DISTRIBUTION DECK VISIBLE BIOFILMS, ALGAE, SLUDGE, DEBRIS ANAEROBIC/SEPTIC SMELLING MUDS, H2S RELEASE UPON HC ADDITION APPLY AGGRESSIVE CLEAN STERILIZATION PRECONDITIONING/FLUSH OF RECIRCULATION SYSTEM PAST/PRESENT BIOLOGICAL CONTROL BIOFILMS PRESENT ON DRYING COUPONS (I.E. SHEEN TO TANNISH/BROWN COLOR DEVELOPMENT) >10 5 CFU/ML H.B.C. > 10 6 CFU/CM2 H.B.C. APPLY ONLINE MODERATE PRECONDITIONING STERILIZATION HALOGEN IN USE WITHOUT BIODISPERSANT NOT EFFECTIVE IN MINIMIZING BIOFILMS SEE TABLE 4 FOUR OXIDANT LEVEL CONTROL AND TABLE 5 FOR ACCEPTABLE BIODISPERSANT DOSAGES NON-OXIDIZERS IN USE NOT BASED ON GLUTARALDEHYDE, ISOTHIAZOLINE, BROMONITROPROPANEDIOL, OR DIBROMONITRILOPROPIONAMIDE CHEMISTRY LITTLE TO NO EFFICACY TOWARD LEGIONELLA CONTROL SEE TABLE 6 FOR CORRECT NON- OXIDIZER, DOSAGE AND CONTACT TIME REQUIRED FOR LEGIONELLA CONTROL

50 Site Survey Pretreatment/Precleaning Need Assessment

51 DEPOSIT ANALYSIS Precleaning Determination < 10% LOI <40% MOISTURE <10 4 CFU/CM 2 <10 5 CFU/GM  NO SRB’S, IRB’S, MOLD  COUPONS TUBERCLATED WITH HARD SINTERED CORROSION PRODUCT AND SHINY SILVER TUBERCLE BASE  HIGH % IRON >10% LOI >40% MOISTURE >10 5 CFU/CM 2 >10 6 CFU/GM  POSITIVE SRB’S, IRB’S, MOLD COUPONS/SURFACES HIGHLY TUBERCULATED AND SHINY SILVER BASE >10% LOI >40% MOISTURE >10 5 CFU/CM 2 >10 6 CFU/GM  POSITIVE SRB’S, IRB’S MOLD  COUPONS AND SURFACES NOT SEVERELY TUBERCULATED, BASE NOT SHINY SILVER LOW % IRON OFF LINE CLEANING OF AFFECTED EXCHANGERS FOR TUBERCLE REMOVAL AND REPASSIVATION, IMPROVEMENT IN CORROSION CONTROL PROGRAM REQUIRED. ON LINE BIOFILM CLEAN-UP AND STIFLING OF TUBERCLES – PLUG APPARENT POROSITY, MIXED BIO/CORROSION FOULING ON LINE BIOFILM CLEAN- UP, BIOFOULING ONLY

52 ® Monitoring and Inspection Inspection for visible slime or sludge's –Decks –Mist eliminators –Fill –Sumps –Corrosion or biofilm coupons

53 ® Monitoring and Inspection Testing Bulk water dip slides ­ Prior to non-oxidizing biocide addition ­ Minimum once per week ­ Target ≤ 10 4 CFU/ml Coupon surfaces - if available ­ Prior to non-oxidizer and/or biodispersant addition ­ Every 30 to 60 days, but be consistent ­ Target ≤10 5 CFU/cm 2

54 ® Preventive Actions Inspect and Test –Domestic Waters –Fountains –Spas –Air Handling Units –Humidifying/Dehumidifying Equipment/Coils –Cooling Towers

55 ® 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

56 ® Biofilms Biofilms Don’t 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 10 5 Do something –Bacteria CFU/cm Do something

57 ® Preventive Action Use your Biocides in a Prudent Manner And Remember Sterility Does Not Exist Except in Higher Life Forms


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