cpmx show 140320_2040320-final
TRANSCRIPT
LEGIONELLA UPDATE Québec 2012:
Learned, Done & to DoAlain Trahan,
P.Eng. 20th of March
2014
Cooling towers are the outside heat sinks that exhaust the heat carried by the air conditioning cooling water circuit used in buildings HVAC systems.
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What is a cooling tower?
Pump
HVAC Air
conditioning
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What is a cooling tower?
Step 1:
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How it works
Step 2:
Magic of evaporation
Liquid water + energy Water vapor (with less energy remaining in the liquid)
Evaporative cooling
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How it works (in a bio-clean world !)
Dry air
Humid air (evaporated water)+
Water loss (drift)
Dry air
Warm water from AC
Cool water to AC
Demister
Water distributor
Fill
Fan
Water make-up
Typically between 85 and 95 °F.
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In the real “dirty” world…
Dry air Dry air
WindBuilding “fresh
air” intake louvers
Building “fresh air” intake louvers
Simple definition:
An ubiquitous aquatic organism that causes Pontiac Fever and Legionnaires’ disease (lung infection) if inhaled.
Thrives in temperatures between 77 and 122 °F.
Travels from infected water source through aerosolized water droplets.
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Legionella pneumophila
In the United States…• 10,000 to 20,000 people get infected by legionella every year. • Various studies have shown that some 40 to 60% of tested cooling towers contained Legionella.• Legionnaires’ disease mortality rate: 10 to 15% of those infected.
Cooling tower drift
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Biofilms
• Form on surfaces in aquatic systems. • Often resistant to biocides.• Monitoring is difficult.• Release organisms into bulk fluid.• Cost the US nation billions of dollars yearly in equipment damage, product contamination, energy losses and medical infections.
Bacteria
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The old way
Make-up
Warm water
Cool waterBlow-down
CHEMICAL$$$(transport, storage, handling)
Québec 2012: Source?
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Québec 2012: 11 km!
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24% had Lp sp1!
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Before: ASHRAE 62.1-2010
• Specifies minimum distances between CTs vs Air Intakes & Kitchen exhausts.
• Not frequently applied especially by architect.
• Mitigation :• UVGI of fresh Air: always when high risk
occupants• Project the CT plume higher• Prevent food particles from reaching the CT.
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Before: Pesticide Regulatory System
• Pesticides need to be approved by HC for each use with application guidelines.
• Sellers & applicators need certification.
• Reality :• Provincial application.• No processes for CT biocides!• >75% non compliance in commercial blds for
concentration, contact time or hydraulics.
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Before: Guidelines not Standards
• ASHRAE 12-2000• AWT 2003 (2008)• CTI WTB-148 (2008)• CDC
• Reality :• Contradict each other.• Incomplete.• Control is left to water treatment as a last step
in general.• Voluntary: doesn’t work.
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Before: Guide for Hospitals in 2005
Very Generic
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During
• ‘Hopes’ of official that situation would go away by itself…
• High dose oxidizing biocide only.• CDC protocol ASSumes surfaces are clean &
circulation in whole system.• Plan created during crisis.• Localisation & owners unknown.• No early public communication.
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Lessons : Emergency planning
• Have a plan of action:• If this then that, etc.• What, Where, How, When, Who.• Work upstream of Legionella.• Do not ASSume or ‘Hope-away’.• Legislate.
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Lessons : Immediate steps
• Stop the fans!• Ultra High Efficiency drift eliminators• Decontamination:
• Clean first to remove deposits.• Circulate in whole system.• Fast acting biocide that keeps its efficiency
throughout the system.• Know system volume.• Analyze biocide concentration
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Lessons : Involve outside experts
Interview with an official from the health agency DSP followed by one with the building code agency, RBQ
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Lessons : Involve outside experts
Interview with an official the RBQ – Building Code Agency
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After: Québec Law 2013, phase I of III
• The Excellent:• Mandatory documentation of
actions & tests results.• Schematics of system.• Mandatory maintenance plan
signed by at least one professional.
• 40 inspectors actually going to each site.
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2013 Law: Form signed by Owner!
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4 Dimensions of Risk Management
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Interrelation of the 4 dimensions
Law DescriptionWater
TreatmentHydraulic Solids Drift
402.1 Overwintering X X X X
402.2 Operational stops X X
402.3 Decontamination X X X X
402.4Corrosion, Scale,
OrganicsX X X
402.5 Schematics X X X
402.6 Water treatment quality X X X
402.7 Chemicals X
402.8 Mechanical Verification X X
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Law 2013, Phase I : the Good
• Any law is great.• Well made technical guide &
training sessions• Inspectors systematically
validate backflows & existence of signed documentation
• Tickets with 7 days to comply.• Inspectors take pictures.• Indicators & Lp analysis with
action levels
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Law 2013, phase I: the Good
LevelResult
(logs/L)Action
Normal < 4
Intervene 4 - 6 Identify causes. Validate efficiency of new measures.
Sanitary Risk > 6Apply Decontamination. Identify root causes & correct maintenance plan.Validate efficiency of new measures.
Test for Legionella pneumophila.
Legionella pneumophila Test concentration & Action Levels
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2013 Phase I: Lessons
• Plans : ‘copy-paste’• Schematics have or are:
• Not up-to-date• No flow speed or materials of
construction• No zones of stand-by operation
• Inspectors have no powers.
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After: Coroner’s report, 2013-09
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After: Public Health Report
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After: Media reports
• Radio-Canada (CBC) had a 30 minutes piece that showed delayed actions by officials.
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After: Worker’s Health & Safety
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Graduated Risk Management
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After: Sampling Guide
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After: Very Good CT Guide
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After: Excellent Full Day Training
Michelle Merchat, Climespace
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Law 2014, phase II: the Excellent
• Specific cleaning step independant from decontamination
• Stop the fans if log 6 or more• Identification of sampling
points
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Law 2014, phase II: the Good
• Mandatory testing for Legionella p. every 30 days at most.
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Interrelation of the 4 dimensions
Law DescriptionWater
TreatmentHydraulic Solids Drift
402.7a Sampling Points X
402.8 Chemicals X
402.9 Mechanical Verification X X
406 Log book X X X
407+408
Sampling procedures X X
417 4-6 logs Action Plan X X X X
418 Interfering flora X x
419 >6 logs, Action Plan X X X X
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Interrelation of the 4 dimensions
Law DescriptionWater
TreatmentHydraulic Solids Drift
402.1 Overwintering X X X X
402.2 Operational stops X X
402.3 Decontamination X X X X
402.4+402.9
Preventive Cleaning X X X X
402.5Corrosion, Scale,
OrganicsX X X
402.6 Schematics X X X
402.7 Water treatment quality X X X
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Beyond: What we do
• Guidelines, Standards & Regulations are a minimum
• ASHRAE 188 methodology• Zero risk does not exist.• Risk = Probability x Consequences
• Multiple barriers: if one fails we avoid an outbreak
• Non-oxydising biocide measurement
• On-site one hour Legionella measurement!
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Risk Assessment: beyond 62.1
• Risk = concentration x duration.• Occupants: long exposition.• High riks by Common Sense :
– Close to ground, next to parking, bld entrance.
– Next to roof terrasse, balconies.– Adjacent to open windows.
• Mitigation: UHE eliminator, lower °C, continuous or low tox or permanent biocide. Ex: Cu/Ag ionisation
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Beyond: Flow Speed
• Higher flow speed = less biofilm• 5+ fps up to 10 fps especially for horizontal lines.
• No dead legs: mitigation approach
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Vulnerability of CT
Contamination MitigationInsects from
waterway Intake screens
Pollen, leaves, etc
screens, basin sweep, filters,
continuous biocide, etc.
Algea Sunlight shade, Cu ionization
Dust filter, basin sweep
Vulnerability vs environment thru seasons?
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Beyond: Deposits & Corrosion
• Variable speed motors to avoid:–Total evaporation deposits–Stray current corrosion.
• Mechanical action to remove deposits.
• Zinc coatings are subject to white rust corrosion.
• Copper to steel surface ratio.• Is it clean?
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Back-Flow Preventer
• Biocide means ‘kill the biological’
• Some are banned from hospitals!
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Water Meter & Level Control
• Towers purge water but take no make-up?!?
• No moving parts Water meter.• Convert from continuous water
MU to ON-OFF.
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Green & Bio Chemicals
• Feels good to use these, doesn’t it?
• Banning zinc? used in baby cream with 20%+ ZnO.
• No area in Canada has too much Zinc. Zinc is essential to life. No Zn in the environment means no Zn in our food.
• Life-cycle approach rather than Bio
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Local Control: Very bad
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Local Control: Average
• Most common currently• °T compensated conductivity by dual carbon probes
• Flow switch, Pre-bleed, Bleed block, Water meter input, permanent program.
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Probe
•Toroidal Conductivity : deposits & chem.
Valve
•Ball valve, not solenoid : plugging.
Meter
•No moving parts & low flow range.
Level
•Chem inventory, water MU control.
Wireless
•Meter, valve, level, etc.
pH+ORP
•Oxydizing biocides dosing.
Record
•Conductivity, °T, Meter, etc.
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Local Control: Best
• Internet accessible PLC.• Continuous inhibitor measurement• Change µS depending on operating
mode• Increase cooling capacity without
changing the system.
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Beyond: Internal Tank
• Last in, last out: hydraulic factor closer to 1
• PE instead of steel• Easy to access• Bottom does not favor accumulation
• Affects biocide selection & risk strategy
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District Cooling
• No, ZERO Legionella risk• No island effect, less smog• Energy & GHG savings• No potable or net water use
Thank you!Alain Trahan, ing.
(514) 943-9044Prepared with
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Copper - Silver Ionization
Input: 110-240VAC 50/60HzOutput to electrodes: 0 to 42V