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Transcript of ® Cooling Tower Maintenance Legionella Awareness 3 rd Installment.
®
Cooling Tower Maintenance Legionella Awareness
Cooling Tower Maintenance Legionella Awareness
3rd Installment
®
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
®
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
®
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
®
Preventive ActionsPreventive Actions
Inspect and Test– Domestic Waters– Fountains– Spas– Air Handling Units– Humidifying/Dehumidifying Equipment/Coils– Cooling Towers
®
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
®
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
®
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
®
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
®
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
®
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
®
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
®
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
®
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
®
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).
®
TABLE 2 – COOLING SYSTEM SUSCEPTIBILITY TO LEGIONELLA RISKSTABLE 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 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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TABLE 2 – COOLING SYSTEM SUSCEPTIBILITY TO LEGIONELLA RISKSTABLE 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 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
Frequency of Cleaning/Disinfection
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Frequency of Cleaning/Disinfection
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
®
Frequency of Cleaning/Disinfection
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
®
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.
®
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
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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Implications of the Need for Biocide Improvements
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
®
Implications of the Need for Biocide Improvement
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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Implications of the Need for Biocide Improvement
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 – 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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Implications of the Need for Biocide Improvement
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 Off-line Cleans as Previous Suppressed Bioflims, Sludge and Muds have now been Conditioned/ Loosened for Release to the Bulk Water
®
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
®
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
®
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
®
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
®
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
®
C.T.I. Maintenance ConsiderationsC.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
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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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C.T.I. Maintenance ConsiderationsC.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 ConsiderationsC.T.I. Maintenance Considerations
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