Legionella removed out of a water-system


The problem

  Due to extremely high Legionella values (>100.000 CFU/100ml), the health authority shut down the sanitary equipment in a nursing home. The nursing home was built in the 1970s in three phases of construction, with a total of almost 300 apartments. The water system was always only extended without calculating the risk of getting microbiological problems, like biofouling later on. The management of the home has to take appropriate action and performed repeated decontamination by means of heat sanitisation. Doing this requires heating the circulated water to a temperature, that each part of the water will have 80°C temperature. This is an extremely complex task, it has not only the water to be heated, it has as well to be assured that during the period of hot water is circulated no tap point is opened by accident.
After this decontamination, the legionella contamination increased again very quickly and reached the former values. The costs: several ten thousands of EURO.

The solution

At first, Pursanova TM was only installed at the 2 city water inlets into the building and as well behind the hot water boilers, in the circulation line of the hot water.

The checking

Shortly after the installation was completed, the CFU - values of the Legionella dropped by about 80%. After three more months the numbers dropped even further everywhere with the exemption of a little-used sector, in which compared to the first measuring slightly increased numbers were detected. Pursanova TM retrofitted Pursanova TM there in order to get an optimum of performance. About one year later the water in this sector also conformed to the compulsory limit value of 100 CFU/100ml, whereas the other sectors had reached this value after only six months. Today, this building is considered to be free of Legionella and no longer is on the watch list of the health authority.