Today, we protect ourselves against harmful Legionella bacteria – which can cause Legionnaires’ disease and Pontiac fever – by supplying buildings with hot water at a temperature of at least 55°C. Wallenius Water has been invited in a unique pilot project, to verify if Wallenius AOT purifiers can be used instead of heat. The project might change current regulations.
In January, a pilot project was initiated by Teknikmarknad, a system integrator within environmental technology that cooperates with Swedish Institute for Communicable Diseases, Swedish Energy Agency, Swedish National Board of Housing, Building and Planning and Swedish Chemicals Agency. Teknikmarknad invited Wallenius Water to participate and install Wallenius AOT 5 purifiers in ten buildings all over Sweden. The idea is to use the purifiers rather than heat as a microbiological barrier.
The current solution used in Sweden is to keep the tap water in buildings at least 55°C, since Legionella bacteria are believed to die at about 45-50°C. This often means that the hot water leaving substations is 65-70°C, despite the fact that the water we use for showering and washing our hands seldom is hotter than 38°C, and that for washing dishes about 43°C. The hot water lead into the building is mixed with cold water to get the right temperature. This results in major energy losses. The method is also debated, as Legionella bacteria can be found in heat-resistant amoebae. These amoebae have been seen to survive for several minutes in temperatures of 80°C.
If Wallenius AOT purifiers are proven efficient in this project, a maximum hot water temperature of 45°C would be sufficient for tap water. A 10°C reduction in the temperature of the incoming water would reduce the energy requirements for heating the water, but there are considerably more advantages. Alternative energy sources, such as solar power and different types of heat pumps, then become viable and interesting, as a solar thermal collector cannot heat the water enough with current requirements. The project might even result in a change of the current regulations from the National Board of Housing, Building and Planning.
The buildings chosen for this project – residential properties, offices and hospitals – maintain the normal water temperature for a couple of months, after which the temperature is reduced in two stages. Each month, samples are taken to test for Legionella, to ensure that no bacteria are growing. The pilot project will run until autumn 2011.
A presentation on the project will be held at the Real Estate Fair in Gothenburg on September 8 at 1-1.25 p.m. at the learnShops stage.
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Facts about Legionella
Legionella bacteria are enriched in standing water and easily multiply at temperatures between +18°C and +45°C. They can grow in regular water pipes, air conditioning systems, showers and jacuzzis. Growth is favoured by the biofilm that almost always lines the insides of water tanks, water pipes and shower hoses.
Legionnaires’ disease is a type of pneumonia caused by Legionella bacteria. The disease is contracted by breathing contaminated water in aerosol form, small water droplets. Legionella bacteria can also cause Pontiac fever, an illness similar to the flu.
Legionella bacteria are generally considered quite harmless. In order to become ill, you generally need to inhale the bacteria while also suffering from an impaired immune system. Infection does not spread from person to person, and people cannot become chronic carriers of Legionella.
Under the Swedish Act on Infectious Diseases, Legionella infection must be reported, and all cases are reported to the county medical officer of communicable disease control and the Swedish Institute for Infectious Disease Control (SMI). Some 100 to 150 cases are reported each year in Sweden, with almost half of patients contracting the illness overseas.
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