Potable water vs legionella 20131127

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presented at CWWA Ottawa on the 27th of November 2013

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  • LeChevallier
  • Michelle Prévost
  • Venne diagram: Interaction of the four dimensions of the Maintenance Plan
  • & a lot more…. 
  • source Gulf news June 2005 and Statistics provided by US GBC’s LEED for Product Manufacturers presentation, ©2005Statistics provided by US Department of Energy: Buildings info and components
  • Potable water vs legionella 20131127

    1. 1. Potable Water vs Atypical Pneumonia Risk Management & Bionebulisation CWWA, Ottawa 27th of November 2013
    2. 2. Transferable Approaches TOC & Phosphorus : • High levels increase tendency to form Biofilm. • Concentration in CTs will be 3 to 6 times higher
    3. 3. Transferable Approaches Stale or slow moving water: • Risk №1 demonstrated to cause outbreaks Disinfectants: • negative synergies, half life, Minimal Effective Concentration, Corrosion, Contact time, Temperature & pH effects.
    4. 4. Transferable Approaches • Cyst control vs Amoeba & Protozoa • Outbreak much more likely if water source is from surface water • Giardia & Crypto reduction may reduce risk • Potable technologies difficult to transfer to CTs • Zero risk does not exist. • Risk = Probability x Consequences
    5. 5. Transferable Approaches • • • • • Reservoir hydraulics Last in, last out reservoirs Cross connections Back-flow preventers IRBs : SRBs & Ferrogineous
    6. 6. Transferable Approaches • Risk management: Critical control points, Gradated risk management, Audits, Check lists, Maintenance plan, Documentation & Tests history, Training. • Multiple barriers approach • Use of indicators : fast drop in HOCl, Aerobes levels, Turbidity • Algae management-reduction • Chemical pumps, controllers, sensors, on-site chemical tests
    7. 7. Transferable Approaches • ≠ Materials = Different tendencies for biofilm. • Biofilm media: PVC high surface area • CTs use exactly the same in cooling towers! Coated to reduce surface tension? No. Impregnated with silver ions-zeolite? No • No kidding, no joke.
    8. 8. Counterintuitive & Different • • • • Fecal microorganisms vs water-borne Oral vs Inhalation Planktonic Vs Sessile Indicators in potable water allow validation. NOT in CTs. There is no definitive validation in CTs with a test. • Finished water quality control vs Process QC
    9. 9. Counterintuitive & Different • In CTs same bug (DNA) can be mostly innocuous or highly pathogenic! • Potable water can contain 3 logs of Legionella that are non-cultivable but viable & infectious. • You do it right nobody gets sick. In CTs we are never sure. • You can get away with important deposits & biofilm. Not in CTs.
    10. 10. Counterintuitive & Different Cleaning: • Flushing does not work • High levels of disinfectant do not work
    11. 11. Québec 2012: lessons • Do not disinfect without having clean surfaces. Remove the deposits 1st. • Install high efficiency drift eliminators at the onset : very low implementation • Validate biocide concentration, contact time & circulation at time of injection: >75% wrong. • Involve external pros & a chemist (please)!
    12. 12. Québec 2012: lessons • • • • • Have a plan of action. If this then that, etc. What, Where, How, When, Whom. Priorities. Work upstream of Legionella pneumophila. Do not ASSume.
    13. 13. Québec Law : the Excellent • Mandatory documentation of actions & test results. • Schematics of the CT system.
    14. 14. Québec Law : the Excellent • Maintenance plan signed by a professional with an ethic’s code to be revised after: 1. Over limit Legionella result 2. Change to the equipment or systems 3. Changes vs the Maintenance plan
    15. 15. Québec Law : the Excellent • Maintenance plan covers: 1. 2. 3. 4. CT layout & start-up CT operational stops & starts. Decontamination Normal operation
    16. 16. Québec Law : the Excellent
    17. 17. Québec Law : the Excellent
    18. 18. Québec Law – Interpretation - Who
    19. 19. Québec Law : the Good • Law: any law is great. • List of CTs, owners, localisation, tons. • 40 inspectors actually visiting every CT!!! – Systematic validation of back-flows, existence of required signed documentation. Issuance of ‘tickets’ with 7 days to comply! Pictures. • Technical guide & training sessions.
    20. 20. Québec Guide : the Good • • • • • • Iron as a virulence & amplification factor. Relationship between biofilm, amoeba & Lp. Association between deposits & Lp. Indicators & Lp analysis w/ action levels. Personalised planning. Hydraulic management.
    21. 21. Québec Law : the Missing • • • • ASHRAE 188, 62.1 Penalties & Responsabilisation. Content of the plans & documentation. Not specific as to the actors: Eng, Chemist, Water treat, Mechanics, Control cie., Chiller & CT maintenance cies. • Reducing agents as microbiostat –cide • Risk analysis framework.
    22. 22. Québec Guide : the Bad • False information: 1. Non oxidizing biocides can be measured with test kits on site or off-site (GC).
    23. 23. Consumption Implications
    24. 24. Reduced consumption • When risk is perceived as hard to control then managers replace CTs with Air-cooled units. • ~ 2x more energy consumption • HVAC: 40-60% of the bld energy consumption. • Buildings = 39% of total energy consumption. • Island heat effect amplified. In Paris over 3°C. • Ex. L’Oréal
    25. 25. Increased Consumption • Fastest way to reduce risk is to reduce cycles of concentration • Also improves energy efficiency • Increases water consumption. Usually 2nd biggest after toilets & urinals. • Increases proportion of water returned to drain. • Reduces water gas thus reducing Island heat.
    26. 26. District Cooling – Water2Water • • • • • • Ex. Toronto, Morocco. No potable water or net water use. Energy & GHG savings. No island heat effect. Less smog. Increased floor space & competitiveness. Less city hollowing. • NO LEGIONELLA RISK
    27. 27. Quantitative Microbiology Case: 1000 tons CT, 35% in operation, Lp within guidelines at 3 logs Drift eliminators at 0.5% vs 0.0005% efficiency 20 000 vs 20 cfu Lp/minute Material cost of about 300$/CT CTI’s 1st recommendation is for validation of drift control. Never followed.
    28. 28. Questions, Comments ?

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