LEGIONELLA & Cooling Towers. Mark Lewis Occupational Hygiene & Noise Control Team WorkSafe WA

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1 LEGIONELLA & Cooling Towers Mark Lewis Occupational Hygiene & Noise Control Team WorkSafe WA

2 Legionella present in water supply WHY AM I TALKING TO YOU TODAY? During workplace inspections I ve found many Cooling Towers / Evaporative Condensors Not approved by LGA No water treatment No inspection No maintenance / monitoring / testing Poor condition

3 Adopt AS/NZS 3666 parts 1-3 Part 1: Design, installation and commissioning; Part 2: Operation and maintenance; Part 3: Performance-based maintenance

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5 Transient worker contracts deadly Legionnaires disease MARCH 2014

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9 Cooling Tower Sump

10 Legionella bacterium Flagellum = motile µm (can swim ) Gram Negative Aerobic Bacillus (rod shaped) Over 40 species with many subspecies Ubiquitous in Aquatic Environments

11 Other Properties of Legionella bacteria Non-spore forming but. Cyst-Like Form Metabolically dormant Highly resistant / resilient in environment May be resistant to disinfectants (eg: chlorine) VNC - ( Viable Non Culturable ) state: Laboratory culture tests negative Remains alive & dormant can produce infection

12 Where do Legionella Come from It all Starts with a microbial Biofilm Micro-organisms present in aquatic environments Colonise surfaces Secrete polysaccharides (slime) to adhere to surfaces & protect themselves Multiply to Large numbers Protozoa (amoebae) feed on bacteria in biofilm

13 Protozoa - Natural Hosts of Legionella Legionella parasitise (infect) amoebae & other protozoa ie: intracellular pathogens of protozoa Legionella multiply to large numbers inside protozoa

14 If Humans Inhale Legionella bacteria Similar process occurs in Lung Macrophages Vacuole - Secrete proteins & enzymes into macrophage switches off normal cell functions - Create vacuole multiplies in vacuole - Large numbers released from cell

15 COOLING TOWERS Function: Cool Water Using: Fan-Forced Evaporative Cooling process Have a Reservoir / Sump of Water and produce. AEROSOLS

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20 COOLING TOWER FILL MATERIAL CORRUGATED PLASTIC

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25 WHY ARE COOLING TOWERS A RISK Spray drift / aerosols can travel ~ km (W.H.O.) (? Up to 11km - potential to expose many persons) Warm Water Recycled Water tower acts as an air scrubber (collects dust/dirt from air in water) Installed Outdoors -> sunlight -> algal growth -> BIOFILM! Intermittent Use Stagnant areas

26 KEY REQUIREMENTS Design of Cooling Tower Appropriate Installation Provision of Information: Operator Manuals (tower & water treatment system) Site specific operational procedures Site specific decontamination procedures Regular inspection / maintenance / cleaning Regular water sampling

27 DESIGN Water treatment systems (automatic) Corrosion-resistant Resistant to Regular Cleaning & Disinfectants Readily Cleanable (smooth) Impervious Surfaces (don t support microbial growth) All components able to be drained / cleaned No dead legs Sump/Pond screened Drift minimised (drift eliminators 2 or 3 pass)

28 Water Treatment Systems Cooling Tower Water Treatment Systems Generally have no chemical monitoring can and DO FAIL REQUIRE REGULAR CHECKING / INSPECTION

29 INSTALLATION SUITABLE LOCATION Intake - away from other sources of contamination: Kitchen Ventilation Outlets Other Cooling Towers Exhaust discharge away from: Occupied areas Pedestrian thoroughfares Air intakes (including lift vents) Building openings Areas of traffic movement Prevailing Wind Direction Height & Design of Adjacent Structures Future Planned Developments

30 Cooling tower next to building air intake grills Potential for Legionella droplets to enter the building via air intakes

31 COOLING TOWER AEROSOLS CAN TRAVEL 1.6 KM Cooling tower next to residential building.

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33 MANUALS & RECORDS Drawings / Diagrams of equipment, systems & pipework Manufacturer s instructions / Owners Manual Service / Maintenance Records Water Treatment Reports & Records Microbiological reports & records Roles & Responsibilities WHO IS RESPONSIBLE Awareness Training Records Risk Assessment & System-Specific Management Plan

34 OPERATION & MAINTENANCE INSPECTION At least monthly EFFECTIVE THOROUGH CLEANING At least 6 monthly WATER TREATMENT Disinfection & Scale Control MICROBIOLOGICAL MONITORING AS 3666 / WorkSafe Code: (HPC & Legionella)

35 INSPECTIONS At least monthly (? More frequently) Should include: Tower generally fan, water pumps, etc. Cleanliness esp. sump & packing/fill Water treatment system Water testing Operation & flushing of drainage systems Review pump & fan operating conditions

36 CLEANING At least 6 monthly more frequently if inspection / micro results indicate Include: Physical cleaning of Cooling Tower High-pressure blasting of internal wetted surfaces Particularly Sumps & Packing / Fill Disinfection ALL PARTS incl. storage & makeup tanks, filter systems Draining ENTIRE water system OSH Precautions Required for Cleaning -> Aerosol Control Disinfect (eg: chlorinate) system prior to cleaning Switch off tower during cleaning Workers should wear PPE / RPE

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39 New direct testing processes being developed (DNA PCR based & others) MICROBIOLOGICAL WATER TESTING USA CDC do not recommend testing Traditional testing methods do not always detect Legionella Results take 7-10 days (..what happens in the meantime?) If results are positive exposure has already occurred HPC (total bacterial counts) are useful indication

40 Inappropriate Installation & Inadequate Maintenance

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55 Biofilm! Before Cleaning After Cleaning

56 THANK YOU