Potable Water vs Legionella_20131127.pptx

8/12/2019 Potable Water vs Legionella_20131127.pptx

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Potable Water vs AtypicalPneumonia Risk Management &

Bionebulisation

CWWA, Ottawa27th of November 2013


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Transferable Approaches

TOC & Phosphorus :

High levels increase tendency to form Biofilm.

Concentration in CTs will be 3 to 6 timeshigher


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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.


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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


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Reservoir hydraulics

Last in, last out reservoirs

Cross connections Back-flow preventers

IRBs : SRBs & Ferrogineous


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Risk management: Critical control points,Gradated risk management, Audits, Check lists,Maintenance plan, Documentation & Testshistory, Training.

Multiple barriers approach Use of indicators: fast drop in HOCl, Aerobes

levels, Turbidity

Algae management-reduction

Chemical pumps, controllers, sensors, on-sitechemical tests


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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.


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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


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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.


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Cleaning:

Flushing does not work

High levels of disinfectant do not work


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Qubec 2012: lessons

Do not disinfect without having clean surfaces.

Remove the deposits 1st.

Install high efficiency drift eliminators at theonset : very low implementation

Validate biocide concentration, contact time &

circulation at time of injection: >75% wrong. Involve external pros & a chemist (please)!


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Qubec 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.


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Qubec Law : the Excellent

Mandatory documentation of actions & test

results.

Schematics of the CT system.


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Maintenance plan signed by a professional

with an ethics code to be revised after:

1. Over limit Legionella result

2. Change to the equipment or systems

3. Changes vs the Maintenance plan


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Maintenance plan covers:

1. CT layout & start-up

2. CT operational stops & starts.

3. Decontamination

4. Normal operation


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Qubec LawInterpretation - Who


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Qubec 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.


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Qubec 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.


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Qubec 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 microbiostatcide

Risk analysis framework.


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Qubec Guide : the Bad

False information:

1. Non oxidizing biocides can be measured with test

kits on site or off-site (GC).


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Consumption Implications


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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 3C. Ex. LOral


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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.


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District CoolingWater2Water

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


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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

CTIs 1strecommendation is for validation ofdrift control. Never followed.


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Questions, Comments ?

Potable Water vs Legionella_20131127.pptx

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