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Pseudomonas is a bacteria commonly found in closed circuit water systems, a problem that until recent years was largely confined to London. As Pseudomonas increasingly finds a home in buildings throughout the UK, its spread must be stopped to ensure the safety and efficiency of pipework and associated HVAC systems.
While Pseudomonas can be harmful to health, in a closed system, humans are rarely exposed, so the main issue is the damage it does to HVAC equipment. In order to prevent Pseudomonas, care must be taken in a water systems design, pre-commissioning cleaning is essential and ongoing maintenance must be planned and fit for purpose.
Any stagnant or low flowing water will give Pseudomonas the perfect conditions to grow and multiply leading to biofilm formation and other problems, such as corrosion and the rise of Sulphate Reducing Bacteria (SRBs).
SRBs: SRB’s metabolise naturally occurring sulphate in the water to produce sulphide under clumps of bacteria, depolarising the metal surface, resulting in localised pitting corrosion and eventual perforation.
Biofilm: In general, bacterial build-up in the water, especially in stagnant areas, can create a microbial biofilm layer on pipe and heat exchanger surfaces, causing a reduction in efficiency and flow restrictions. Preventing biofilm from forming in the first place is essential; once biofilms start to form, the bacteria that reside within them can be thousands of times more resistant to biocides than that found free floating in the water.
Pseudomonas can be particularly problematic in modern buildings with the small-bore pipework and small orifices associated with control valves. The biofilm reduces water flow and provides a habitat for other corrosion inducing bacteria that will lead to pitting and leaking pipework. The net result of Pseudomonas in heating and chilled water systems is a decrease in their efficiency and increase down time and costs from repairing leaks.
Preventing Pseudomonas begins with how a water system is designed. Cutting corners at this crucial stage will lead to problems further down the line. Design problems can include dead legs and capped pipes, added to allow for further expansion, but creating the ideal stagnant conditions for Pseudomonas to grow. If unavoidable, these must be looped out and circulated regularly.
Once installed, new water systems must undergo pre-commissioning cleaning, in-line with BSRIA guidelines. By making sure a water system is clean from the outset unnecessary maintenance and repairs can be avoided. Remediation cleaning is possible, but it will never render a system ‘as new’.
Chemicals flush out the system and then provide ongoing water treatment, with regular ‘dosing’ the normal course of action. While biocides are effective, they should be used with caution and only where necessary. Potentially harmful to maintenance operatives and pipework, a bespoke approach is always best, with a water system continually monitored so dosing is based on actual requirements, rather than a one-size-fits-all approach.
If possible, non-chemical alternatives should be explored, which can be installed when a water system is being built, acting as a gate keeper to mains water, or retrofitted to existing systems. Our version, Wallenius AOT, has been proven to kill 100% of Pseudomonas bacteria, harnessng a specific frequency of light and photocatalytic surfaces to create free radicals that break down harmful micro-organisms. Extremely low energy, AOT allows buildings to cut down or eliminate their reliance on dosing, which contributes to improving water hygiene’s ‘green’ credentials and reduces chemical and maintenance costs.
What’s key is that an approach to water hygiene is an integrated one. By taking the right steps at design and construction stages, followed by fit for purpose pre-commissioning cleaning and on-going water treatment, Pseudomonas can be kept at bay. Exploring solutions such as AOT will save money long-term, reducing chemical usage and on-going maintenance requirements.
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