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Do you know what’s growing
in your wet cooling system?
Legionnaires' Disease - Outbreaks
linked to poor management of wet cooling systems still
occur; often leading to prosecutions by HSE, eg in the
West Midlands and Cumbria. Indeed August 2006 saw 127
reported cases of Legionnaire’s
disease, a twofold increase on the figure for August
2005. Although such a seasonal increase is normal, not
so many of these were associated with foreign travel
as would be expected. In addition up to the end of August
2006, there were 273 reported cases as opposed to 205
for the corresponding period in 2005.
During 2003-2005, HSE inspected wet cooling systems
at 22 Midlands chemical manufacturing sites. At up to
a quarter of those sites, the following conditions were
found:
- build-up of slime, algae, scale, and corrosion;
- poorly-covered ponds exposed to light and fouling;
- broken and damaged equipment.
The legionella bacterium can thrive on the warmth and
nutrients provided by poor conditions in wet cooling
towers and evaporative condensers. At chemical sites,
such equipment is often used intensively and round the
clock. The bacterium can survive in wind-borne water
droplets which can be carried up to 2 km away from its
source. Outbreaks linked to poor management of wet cooling
systems still occur; often leading to prosecutions by
HSE, eg in the West Midlands and Cumbria.
Water treatment. Do you:
- use up-to-date, appropriate disinfection techniques?
- check water quality regularly?
- incubate dipslides properly?
- record your remedial actions?
Cleaning and disinfection. Do you:
- clean and disinfect every 6-12 months?
- remove the pack for cleaning?
- fully drain during long shutdowns?
- protect everyone in the area during cleaning?
- ensure that cleaning procedures are site-specific
and cover all risks?
Have you got the main elements
of control covered?
Risk assessments. Are they:
- suitable and sufficient?
- reviewed regularly?
- developed with employee consultation?
Roles and responsibilities. Are:
- duties clearly defined for employees and contractors?
Routine checks and maintenance. Do you:
- carry out full inspections?
- regularly calibrate dosing pumps?
- maintain items such as drift eliminators?
HSE’s Hazardous Installations Directorate will
continue this intervention programme in all regions
in 2007/2008. Guidance on managing wet cooling systems
can be found in the HSE publication Legionnaires’
disease: The control of Legionella bacteria in water
systems. Approved Code of Practice and guidance. Where
dutyholders are found to be in breach of the legislation,
HSE will explore all options, including enforcement,
to ensure that the duty holder does prevent or control
risks.
Conditions often found by HSE in wet cooling systems:
Examples of scale deposits, rust, biofilm and algal
growth on packing and cooling tower interiors
This document contains notes on good practice which
are not compulsory but which you may find helpful in
considering what you need to do.
© Crown copyright – Published
12/06
Additional Information & Expert Assistance
For further information and expert assistance please
call us on +44 (0) 161 877 0586 or
email info@legionellacontrol.com.
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