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Pseudomonas in Building Water Systems


Pseudomonas, a microbiological organism found in water, can lead to problems in building water systems, be they drinking water, sealed heating or chilled water, or even in cooling tower systems. It may be provided free of charge by your local water company (!) in the incoming mains, and, while there, may cause a variety of problems.

The Problems

The presence of the Pseudomonas bacteria in drinking water may affect the colour, turbidity, taste and odour of the water, leading to complaints. Often there is an accompanying growth of slime within the pipe work, especially where warming or reductions in flow are occurring. In hospitals, the presence of this bacterium may be a problem as it is an opportunist pathogen and therefore a danger to immuno-compromised persons who may be infected. In the food and catering industry, taste and odour problems are undesirable results of the bacteria’s presence.

Sealed heating and chilled water systems in buildings are another area where the bacteria may become a problem. Reduction in flow through pipework and warming of the system water may lead to slime formation. This in turn may further reduce water flow and form sludges which block small bore pipe work and prevent the system working correctly. The slime may also harbour other undesirable bacteria, such as sulphate-reducing and Nitrate-reducing bacteria, which can cause system corrosion, and reduction in the efficacy of water treatment chemicals. Chilled water systems are more likely to present these kinds of problems than heating systems, and new buildings may be particularly prone to bacterial growth if the system becomes fouled during construction.

The Pseudomonas bacteria can also contaminate cooling systems, especially if the water treatment regime is not controlled successfully. In extreme cases, the cooling tower pack and pipework may become fouled with slime, and prevent free flow of water to the pond. The cooling capacity of the tower may be reduced, and thus the process being cooled may be compromised. The bacteria may also harbour Legionella, seeding it back into the system water at any time and thus causing a considerable health risk.

The Answers

Pseudomonas may enter a building’s water systems from time to time from the incoming mains, but it is the design of the system, and its operation, which will determine whether or not the bacteria becomes a problem. What is certain is that, once the bacterium has started to grow in the system, it may be very difficult indeed to remove.

Domestic water systems may be chlorinated on an annual basis as part of an annual maintenance regime, but this rarely includes the incoming mains and drinking water pipe work. Should a taste and odour problem manifest itself in the drinking water system, it may be chlorinated and flushed to remove the contamination. Routine future sampling should be carried out to monitor the drinking water, highlighting any reoccurrence of bacterial growth before complaints are received.

Chilled water and heating systems can be protected from bacterial growth initially by correct flushing and treatment programs as soon as the pipe work is installed. The treatment should be ongoing, with regular maintenance checks of the treatment regime to ensure the correct amount of inhibitor is present and that there is no corrosion taking place. Regular dosing with a suitable biocide is advised. Once contaminated, thorough flushing and chemical treatment may be used with varying degrees of success to treat a sealed water system. The program will vary between systems, and can only be recommended after a site inspection and possibly the taking of pertinent water samples.

Under L8 Legionnaires’ disease. The control of legionella bacteria in water systems – Approved Code of Practice & Guidance Health and Safety Approved Code of Practice and Guidelines, cooling systems already require a suitable and sufficient water treatment regime to control bacterial growth. Should a regime get out of control for any reason, the cause for this should be remedied and rectified. Pseudomonas growth in the system may require an alternative or additional treatment to that already in use. In cooling systems it is essential that bacterial growth be under control, so any treatment of the Pseudomonas bacteria should be carried out as a matter of some urgency. Again, future sampling for the bacteria may give prior warning of an impending problem, and will allow treatment to occur before the bacteria becomes a major problem.

Rainbow Water Services Ltd. is fully equipped to provide both the expertise and resources required to prevent or combat any of the above problems. Please contact us by telephone or by e-mail if you require further information or wish us to attend your site and discuss your requirements.

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