® Cooling Tower Maintenance Legionella Awareness 3 rd Installment

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Cooling Tower Maintenance Legionella Awareness

Cooling Tower Maintenance Legionella Awareness

3rd Installment

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CTM/Ashland PresentationsCTM/Ashland Presentations

Legionella Awareness – 2003 Filtration of Cooling Waters – 2005 Legionella Risk Management – 2006 Legionella Proactive Protocol – 2008 Literature References

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Legionella Proactive ProtocolLegionella 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

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Legionella Proactive ProtocolLegionella 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.

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Refresher InformationRefresher Information

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Legionella BacteriaLegionella Bacteria

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

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Factors Determining the Risk of Contracting the Disease

Factors Determining the Risk of Contracting the Disease

A source of Legionella

Favorable growth conditions

Aqueous aerosol

Sufficient organisms to cause

infection

Susceptible individual

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Total System Approach:Five Areas of Activity and Performance

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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Preventive ActionsPreventive Actions

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

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Field Study on Biofilm GrowthField 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)

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

1600

<10

10

<10

1,000,000

No

Yes

Basin Sludge 3,500,000 20 1,000,000 Yes

Dead Head (off) Plate/Frame XER

400 <10 10,000 Yes

Slip Stream By-pass (10%) Plate/Frame

<10 <10 <10 No

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Action LevelsAction 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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Oxidant FeedrateOxidant Feedrate

00.5

11.5

22.5

33.5

44.5

5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Time to satisfy System Demand

Ff

tBreakthrough

system biofilm demand

Oxidant Feedrate

Time

raw water demand0.5 ppm oxidant residual

Fi

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Monitoring and InspectionMonitoring and Inspection

Inspection for visible slime or sludge's

– Decks

– Mist eliminators

– Fill

– Sumps

– Corrosion or biofilm coupons

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Monitoring and InspectionMonitoring 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

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Systems That May Harbour LegionellaSystems That May Harbour Legionella

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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

Systems Promoting GrowthSystems Promoting Growth

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Potable Water Supply (AWWA)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 SystemsPotable Water Systems

Emergency Water Systems

– Stagnant/Idle

– Ideal Temperatures – Reach Room Temp

Eye Wash/Showers (Low to no Atomization)

Fire Systems

Periodically Flush

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Potable Water SystemsPotable 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

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Legionnella and Water Temperature

Legionnella and Water Temperature

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SPASSPAS

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

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Other Water SystemsOther 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 CATEGORYRISK CATEGORY

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Influence Risk Associated With LegionellaInfluence Risk Associated With Legionella

Dutch Frequency of Legionella Testing MinimumDutch Frequency of Legionella Testing Minimum

Risk Category Frequency

1. 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

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Dutch Risk CategoryDutch Risk Category1. Highest Risk – Cooling Towers < 200 meters from

Hospital, Nursing Home or Health Care Facility where Occupants maybe immunologically compromised

2. Cooling Tower < 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 > 600 metres Away from a Residential Area.

Survey of Process RiskSurvey 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

>⅛″ - ¼″

Non-Visible

Temperature

35ºC (95ºF)

To 46ºC (115ºF)

<20ºC (68ºF)

>50ºC (124ºF)

Biological Activity

>104 CFU/ml

>105 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

Factors Contributing to Legionella Health Risks in Cooling Systems

BiofilmTemperature

and pHOrganic

ContaminationAerosols

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

TABLE 2 – COOLING SYSTEM SUSCEPTIBILITY TO LEGIONELLA RISKSTABLE 2 – COOLING SYSTEM SUSCEPTIBILITY TO LEGIONELLA RISKS

ISSUE CONDITION CORRECTIVE MEASURE

COOLING TOWER (C.T.) LOCATION GROUND LEVEL AND/OR DIRECT EXPOSURE TO POPULATIONC.T. AIR DISCHARGE NEAR BUILDING FRESH AIR INTAKEC.T. AIR DISCHARGE NEAR WINDOWS IN BUILDINGTHAT OPEN

NONE A DESIGN CONSTRAINSNONE, A DESIGN CONSTRAINT, USE THERMOGRAPHY TO DETECT DISTANCE OF AIR TRAVEL WRT INTAKE LOCATIONNONE, 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 EXCAVATIONLACK OF GROUND COVER

TEMPORARY, STEP-UP BIO TREATMENT APPLICATIONS, USE SIDE STREAM FILTRATIONCOVER 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 > 1 MONTHROTATE EQUIPMENT WEEKLY WITH MILD STERILIZATION (5 PPM FAH, 6 HOURS) UPON RESTARTSINSTALL 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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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 DAYSLOOP 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 INLEAKAGEEXHAUSTING 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 PROGRAMSREDIRECT EXHAUSTING AIR/GASES

DIRECT SUNLIGHT ABSORPTION BY COOLING TOWER

BASINUPPER DISTRIBUTION DECK

NONE, A DESIGN CONSTRAINTENCLOSE WETTED EXPOSED AREAS WITH HINGED COVERS THAT ALLOW FOR ACCESS AND INSPECTION

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HIGH DRIFT AND AEROSOLS IN COOLING TOWER AIR EXHAUST

DRIFT ELIMINATORS MISSING OR IMPROPERLY INSTALLEDOLD, LOW EFFICIENCY DRIFT

ELIMINATORS PRESENT

CHECK DRIFT ELIMINATORS FOR PRESENCE AND CORRECT INSTALLATION. REFIT REPLACE BROKEN ELIMINATORSUPGRADE TO HIGHER EFFICIENCY DRIFT ELIMINATORS

COOLING TOWER INSPECTION OF FILL, ELIMINATORS, BASIN, DISTRIBUTION DECK

VISIBLE BIOFILMS, ALGAE, SLUDGE, DEBRISANAEROBIC/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)>105 CFU/ML H.B.C.> 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

Site Survey Pretreatment/Precleaning Need AssessmentSite Survey Pretreatment/Precleaning Need Assessment

Question/Observations/Analytical Results Yes No CFU/ml > 105 - 106, SRB’s, IRB’s, Mold Fungi: Present > 1 inch of sludge in Cooling Tower Distribution Decks, spray nozzle header dead ends blow off points and/or basin.

Visible biofilms in Cooling Tower, fill, basins, coupons, heat exchangers (tubing, head box)

Deposits Greater than 10% LOI, 40% Moisture, 106 CFU/gm aerobic, 104 anaerobic, or SRB’s, IRB’s, mold/fungi present

Surface films contain tanish brown coloration upon drying or begin to curl up, like potatoe chips upon dehydration, > 106 CFU/cm2aerobic, > 102 CFU/cm2 anaerobic, or SRB’s, IRB’s, Mold/Fungi present

CFU/ml, SRB’s, IRB’s or Mold, /fungi increase 4-6 hours after biodispersant added.

Periodic spike increase in CFU/ml when no biocide is added. System has experienced process inleakage presently or in the past.

Addition of HCI to deposits release H2S Addition of HCI to surfaces release fluffy coagulated cellulytic materials

Legionella control has been poor or sporadic

DEPOSIT ANALYSIS

Precleaning DeterminationPrecleaning Determination

<10% LOI<40% MOISTURE<104 CFU/CM2

<105 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>105 CFU/CM2

>106 CFU/GM POSITIVE SRB’S,

IRB’S, MOLD

COUPONS/SURFACES HIGHLY TUBERCULATED AND SHINY SILVER BASE

>10% LOI>40% MOISTURE>105 CFU/CM2

>106 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

Breakdown of Bacteria Often Found in Cooling Water

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

Legionella Testing Requirements

Survey Summary Requirements For Legionella TestingSurvey Summary Requirements For Legionella Testing

Country Testing Required FrequencyOffline 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 > 1,000 CFU/ml

USA No Not Specified Not Specified

Canada No Not Specified Not Specified

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Direct Testing of LegionellaDirect 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


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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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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 OnlySterilization 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

Actions Levels/AssociatedCleaning Disinfection

OSHA Technical Manual (Section III: Chapter 7)

OSHA Technical Manual (Section III: Chapter 7)

Legionella Counts

Action LevelCooling 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

(Note: If Online Approach Does not Eradicate, then Off Line is Required)

Suggested Legionella Remedial Action CriteriaSuggested Legionella Remedial Action Criteria

Legionalla

(CFU/ml)

Cooling/Tower

Evaporative Condenser

Potable Water Humidifier/Fogger

Detectable;<1 1 2 3

1-9 2 3 4

10-99 3 4 5

100-999 4 5 5

>1000 5 5 5

Actions –

1. Review Maintenance

2. Follow-up Analysis and Implement Action 1

3. 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 One 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, Pantheon Laboratories, Pathogen Control Associates Inc.

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

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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

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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

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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 – 8.0

2. 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

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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 Off-line Cleans as Previous Suppressed Bioflims, Sludge and Muds have now been Conditioned/ Loosened for Release to the Bulk Water

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OSHA/Wisconsin ProtocolOSHA/Wisconsin Protocol

Confirmed Cooling Tower Source of Outbreak1. 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 2 - 4

6. Inspect for biofilms. If present, drain and mechanically clean.

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OSHA/Wisconsin ProtocolOSHA/Wisconsin Protocol

7. Refill system and operate for 1 hour at 10 ppm FAC

8. Flush system

9. 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

Action Levels of One JCAHO Facility Cooling Tower Upwind from Building Air Intakes

Action Levels of One JCAHO Facility Cooling Tower Upwind from Building Air Intakes

Legionella

(CFU/ml)Action Level

< 10 1

10 - 30 2

>30 - 100 3

>100 - 200 4

>200 5

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Cooling Tower DesignBest Practices

Cooling Tower DesignBest Practices

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C.T.I. Cooling Tower Design Best PracticesC.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

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C.T.I. Cooling Tower Design Best Practice

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

Sand Filtration 5 Micron MediaSand Filtration 5 Micron MediaParticle

Size Microns

Percent

Of

Total

Before

FiltrationAfter

FiltrationPercent

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 - >50 Micron

Diatoms - >20 Micron

Algae - >100 Micron

•1 Micron = 0.00004 (4 x 10) Inches

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Considerations for FiltrationConsiderations 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

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Suspended Solids Control Target(First Case Approximation)

Suspended Solids Control Target(First Case Approximation)

As per Tower Fill Manufacturers Recommendations

Tower Sump Sludge < 1"

Tower Distribution Deck/Lateral Sludge <⅛" - 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 FiltrationHow 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

Maintenance Considerations

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C.T.I. Maintenance ConsiderationsC.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

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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

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C.T.I. Maintenance ConsiderationsC.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

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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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Filtration Equipment

– Periodic Media Cleaning and Disinfection

- Once per Year

- CFU/ml Counts Outlet > 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

Documents

® Cooling Tower Maintenance Legionella Awareness 3 rd Installment