Cooling Tower Maintenance Legionella Awareness

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
• ASRAE System 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
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 ApproachFive Areas of Activity and
Performance

• ? Comprehensive system 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
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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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
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
Monitoring and Inspection

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

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

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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

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RISK CATEGORY
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Influence Risk Associated With Legionella
26
Dutch Frequency of Legionella Testing Minimum
Risk Category Frequency
Highest Monthly
2. Quarterly
3. Quarterly to Yearly
4. Lowest Yearly
Tests to be performed when seasonal/environmental amplification is highest, equipment change over or start ups Tests to be performed when seasonal/environmental amplification is highest, equipment change over or start ups
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Dutch Risk Category

1. Highest Risk Cooling Towers lt 200 meters from
   Hospital, Nursing Home or Health Care Facility
   where Occupants maybe immunologically compromised
2. Cooling Tower lt 200 meters of Retirement Home,
   Hotel or Building Accommodating a Large Number of
   People
3. Cooling Tower in Residential and Industrial
   Neighbourhoods
4. Lowest Risk Cooling Tower in Industrial Area gt
   600 metres Away from a Residential Area.

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Survey of Process Risk
HIGH LOW
Humidifier/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 Risking increases with Location (i.e. Grounds Levels, Near Air Intakes/Windows), Local Ground Cover, Air Contamination/Approximately 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 Forms (OMEBA, PROTOZOA, ALGAE, MOLD, FUNGUS). 103 CFU/ml 104 CFU/cm2 No Higher Life Forms
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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 Heterotrophy (i.e. CFU/ml) Exposure to Sunlight Intermittent Operation Tower Repair
Presence of Legionella Water Quality Bio-Control Program Proximity To Populations
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TABLE 2 COOLING SYSTEM SUSCEPTIBILITY TO
LEGIONELLA RISKS
ISSUE CONDITION CORRECTIVE 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 FLOW INTERMITTENT LEADING TO STAGNATION, BIOFILMS, BIO-SEDIMENTS, ANAEROBIC CONDITIONS DRAIN IF STAGNATION gt 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).
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TABLE 2 COOLING SYSTEM SUSCEPTIBILITY TO
LEGIONELLA RISKS
ISSUE CONDITION CORRECTIVE 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 (VOCS) 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
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TABLE 2 COOLING SYSTEM SUSCEPTIBILITY TO
LEGIONELLA RISKS
ISSUE CONDITION CORRECTIVE 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) gt105 CFU/ML H.B.C. gt 106 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
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Site Survey Pretreatment/Precleaning Need
Assessment
34
Precleaning Determination
DEPOSIT ANALYSIS

lt10 LOI lt40 MOISTURE lt104 CFU/CM2 lt105 CFU/GM NO SRBS, IRBS, MOLD COUPONS TUBERCLATED WITH HARD SINTERED CORROSION PRODUCT AND SHINY SILVER TUBERCLE BASE HIGH IRON
gt10 LOI gt40 MOISTURE gt105 CFU/CM2 gt106 CFU/GM POSITIVE SRBS, IRBS MOLD COUPONS AND SURFACES NOT SEVERELY TUBERCULATED, BASE NOT SHINY SILVER
gt10 LOI gt40 MOISTURE gt105 CFU/CM2 gt106 CFU/GM POSITIVE SRBS, IRBS, MOLD
COUPONS/SURFACES HIGHLY TUBERCULATED AND SHINY
SILVER BASE
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
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Breakdown of Bacteria Often Found in Cooling Water
Organism Action
Total Aerobic Bacteria Multiple Actions
Clostridium Slime Formers, Gas Producers, Corrosion
Pseudomonas Slime Formers, Denitrifying, Deposits
Achromobacter Deposits, Denitrifying
Iron Related Bacteria Deposits, Corrosion
Sulfate Reducing Bacteria (Anaerobic) H2S Producers, Deposits Corrosion
Acid Producers (Aerobic. Faculative) Corrosion, Deposits
Algae Slime, Corrosion, Fouling, Odour, Deposits
Mold/Fungi Slime, Fouling, Soft/Brown/White Rot, Corrosion, Deposits
Protozoa Fouling, Slime
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Legionella Testing Requirements
37
Survey Summary Requirements For Legionella Testing
Country Testing Required Frequency Offline Cleaning And Disinfection
Aust./NZ Yes Monthly 2 Consecutive 1000 CFU/ml
EU Yes Quarterly 100,000 CFU/L
France Yes Monthly 100,000 CFU/L
Spain Yes Monthly 100,000 CFU/L
Italy Yes Not Specified 10,000 CFU/L
Netherlands Yes Quarterly (Monthly to Yearly Risk Based) 100,000 CFU/L
Switzerland No Quarterly 10,000,000 CFU/ml HPC
Singapore Yes Quarterly 1,000,000 CFU/L
Japan Yes Not Specified 1,000,000 CFU/L
UK Yes Quarterly gt 1,000 CFU/ml
USA No Not Specified Not Specified
Canada No Not Specified Not Specified
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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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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

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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

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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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Actions Levels/AssociatedCleaning Disinfection
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OSHA Technical Manual (Section III Chapter 7)
Legionella Counts Legionella Counts Legionella Counts Legionella Counts
Action Level Cooling Tower CFU/ml Domestic Water CFU/ml Humidifier CFU/ml
1 100 10 1
2 1000 100 10
Where - AL1 Online Cleaning and/or Biocide Treatment Improvement Required - AL2 Immediate Online Cleaning and/or Biocide Improvement Where - AL1 Online Cleaning and/or Biocide Treatment Improvement Required - AL2 Immediate Online Cleaning and/or Biocide Improvement Where - AL1 Online Cleaning and/or Biocide Treatment Improvement Required - AL2 Immediate Online Cleaning and/or Biocide Improvement Where - AL1 Online Cleaning and/or Biocide Treatment Improvement Required - AL2 Immediate Online Cleaning and/or Biocide Improvement
(Note If Online Approach Does not Eradicate, then Off Line is Required) (Note If Online Approach Does not Eradicate, then Off Line is Required) (Note If Online Approach Does not Eradicate, then Off Line is Required) (Note If Online Approach Does not Eradicate, then Off Line is Required)
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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 Bioaerosol 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 Bioaerosol 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 Bioaerosol 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 Bioaerosol 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, Pantheon Laboratories, Pathogen Control Associates Inc. 1998, Pantheon Laboratories, Pathogen Control Associates Inc. 1998, Pantheon Laboratories, Pathogen Control Associates Inc. 1998, Pantheon Laboratories, Pathogen Control Associates Inc.
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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 1 per 2 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 6 Hours
• 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

51
OSHA/Wisconsin Protocol

• Confirmed Cooling Tower Source of Outbreak
• 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.

52
OSHA/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
• Note test monthly
• Legionella 10 CFU/ml
• HPC 105 CFU/ml

53
Action Levels of One JCAHO Facility Cooling Tower
Upwind from Building Air Intakes
Legionella (CFU/ml) Action Level
lt 10 1
10 - 30 2
gt30 - 100 3
gt100 - 200 4
gt200 5
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Cooling Tower DesignBest Practices
55
C.T.I. Cooling Tower Design Best Practices

• Use High Efficiency Drift Eliminators and Operate
  within Design Air Velocities
• Plenums to be Sealed to Avoid Local Elevated
  Velocities within the Drift Eliminators
• Water Distribution Design to Minimize the
  Creation of Very Fine Droplets at the Louver or
  Eliminator Locations to Avoid Air Seal By-Pass
• Air Inlet and Rain Zone Design to Minimize Splash
  out and Aerosol Creation

56
C.T.I. Cooling Tower Design Best Practice

• Fill Selection to Minimize
• Drift and Splash Out
• Poor Water Distribution
• Fouling
• Fan Cylinder Seal to Avoid Extraneous Water
  Intake to the Fan
• Cooling Tower Not to Located Near Building Air
  Intakes
• No Dead Flow Locations in Tower Basin
• Ensure Equalization Piping are Not Stagnant
• Side Stream Filtration

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Sand Filtration 5 Micron Media
Particle Size Microns Percent Of Total Before Filtration After Filtration Percent Reduction
1 5 86.3 44,879,400 346,760 99.2
5 10 10.7 5,588,600 36,920 99.3
10 25 2.7 1,410,600 24,060 98.3
25 0.3 126,800 8,760 93.1
Totals 99.0 52,005,400 416,500 99.2
Finer the Size, more Surface Area and Nutrient Value Typical Size of Bacteria 0.2 0.45 Micron Spores 0.1 Micron Protozoa - gt50 Micron Diatoms - gt20 Micron Algae - gt100 Micron 1 Micron 0.00004 (4 x 10 -5) Inches Finer the Size, more Surface Area and Nutrient Value Typical Size of Bacteria 0.2 0.45 Micron Spores 0.1 Micron Protozoa - gt50 Micron Diatoms - gt20 Micron Algae - gt100 Micron 1 Micron 0.00004 (4 x 10 -5) Inches Finer the Size, more Surface Area and Nutrient Value Typical Size of Bacteria 0.2 0.45 Micron Spores 0.1 Micron Protozoa - gt50 Micron Diatoms - gt20 Micron Algae - gt100 Micron 1 Micron 0.00004 (4 x 10 -5) Inches Finer the Size, more Surface Area and Nutrient Value Typical Size of Bacteria 0.2 0.45 Micron Spores 0.1 Micron Protozoa - gt50 Micron Diatoms - gt20 Micron Algae - gt100 Micron 1 Micron 0.00004 (4 x 10 -5) Inches Finer the Size, more Surface Area and Nutrient Value Typical Size of Bacteria 0.2 0.45 Micron Spores 0.1 Micron Protozoa - gt50 Micron Diatoms - gt20 Micron Algae - gt100 Micron 1 Micron 0.00004 (4 x 10 -5) Inches
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Considerations for Filtration

• Total Suspended Solids Leading to
• UDC
• Loss of Biofilm Control or High Biocide Demands
  for Bulk Water Biocontrol
• Mass Balance Verification of Scale and/or
  Corrosion Inhibitor Adsorption Losses
• Settled Solids Harboring Bioactivity, Higher Life
  Forms
• Periodic Biocount Spikes for No Apparent Reason
• Presence of Visual Biofilms and Agglomerates

59
Suspended Solids Control Target(First Case
Approximation)

• As per Tower Fill Manufacturers Recommendations
• Tower Sump Sludge lt 1"
• Tower Distribution Deck/Lateral Sludge lt?" - ¼"
• Tower Fill Deposit Loadings 0.00187
  lbs./ft3/day
• Filtration or Chemical Dispersants for TSS Values
  Greater than 10 ppm in the Cooling Tower Water
• Ensure Cost Effective Biocontrol is Practiced
• Planktonic - 103 CFU/ml
• Sessile - 105 CFU/cm2

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How to Size and Apply Filtration

• Side Stream with Distribution and Collection
  Laterals
• Laterals Operated at 10 15 ft./sec.
• Jet Nozzle Enhancements Increasing the Area of
  Influence
• Worked Example Given for Application Design

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Maintenance Considerations
65
C.T.I. Maintenance Considerations

• Louvers All in Place, Correctly positioned,
  Free of Biomass and Deposits
• Piping Dead Legs Remove or Loop Recirculate, or
  Bleed/Flush Frequently (Also Applies to
  Equalization Lines)
• Cold Water Basin Any Significant Accumulation
  of Organic Matter, Dirt and Debris to Be Removed.
  If Cleaning Requirements are Frequent Consider
  Filtration

66
C.T.I. Maintenance Considerations

• Cross Flow - Hot Water Basin
• Leakage Corrected to Avoid Entrained Water into
  Air Stream
• Missing/Broken Nozzles to be Replaced
• Overflowing Water to be Corrected
• Cover Against Sunlight and Wind blow Debris
  Instruction
• Counter Flow - Spray System
• Free of Fouling and Properly Positioned
• Avoidance of Water Passage into Eliminators
• Misaligned Spray Nozzles Corrected
• Leakage of Pipe Joints or Corrected Nozzle

67
C.T.I. Maintenance Considerations

• Eliminators
• Free of Organic/Inorganic Debris
• Replace Damaged or Missing Eliminators
• Correct Gaps Between Eliminators, Casing,
  Structural Elements, Air Seals, and Plenum
  Framework
• Fill
• Replace Damaged or Deteriorated
• Presence of Fouling, then Review/Inspect
• Water Distribution/Spray Nozzles
• Louvers
• Air Seals
• Water Treatment Program and Control

68
C.T.I. Maintenance Considerations

• Leakage Corrected to Avoid Entrained Water into
  Air Stream
• Missing/Broken Nozzles to be Replaced
• Overflowing Water to be Corrected
• Cover Against Sunlight and Windblown Debris
  Intrusion.
• Counter Flow Spray System
• Free of Fouling and Properly positioned
• Avoidance of Water Passage into Eliminators
• Misaligned Spray Nozzles Corrected
• Leakage of Pipe Joints or Corrected Nozzles

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C.T.I. Maintenance Considerations

• Filtration Equipment
• Periodic Media Cleaning and Disinfection
• Once per Year
• CFU/ml Counts Outlet gt Inlet After Backwash
• Alkaline Detergent Air Lance/Bubble Mixing for 2
  to 4 Hours Backwash
• Chlorination at 100 ppm FAC Air Lance/Bubble
  Mixing for 2 to 3 Hours - Backwash