Potable water vs legionella 20131127

Potable Water vs Atypical Pneumonia Risk Management &

Bionebulisation

CWWA, Ottawa 27th of November 2013

Transferable Approaches

TOC & Phosphorus :• High levels increase tendency to form Biofilm.• Concentration in CTs will be 3 to 6 times

higher


Stale or slow moving water:• Risk №1 demonstrated to cause outbreaksDisinfectants:• negative synergies, half life, Minimal Effective

Concentration, Corrosion, Contact time, Temperature & pH effects.


• 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


• Reservoir hydraulics• Last in, last out reservoirs• Cross connections• Back-flow preventers• IRBs : SRBs & Ferrogineous


• 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


• ≠ 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.

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


• 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.


Cleaning:• Flushing does not work• High levels of disinfectant do not work

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)!

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.

Québec Law : the Excellent

• Mandatory documentation of actions & test results.

• Schematics of the CT system.


• Maintenance plan signed by a professional with an ethic’s code to be revised after:1. Over limit Legionella result2. Change to the equipment or systems3. Changes vs the Maintenance plan


• Maintenance plan covers:1. CT layout & start-up2. CT operational stops & starts.3. Decontamination4. Normal operation

Québec Law – Interpretation - Who

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.

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.

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.

Québec Guide : the Bad

• False information:1. Non oxidizing biocides can be measured with test

kits on site or off-site (GC).

Consumption Implications

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

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.

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

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/minuteMaterial cost of about 300$/CTCTI’s 1st recommendation is for validation of drift

control. Never followed.

Questions, Comments ?

Potable water vs legionella 20131127

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