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Legionella and its prevention

Legionella pneumophile is one of the bacteria present in the aquatic environment that, if they encounter favorable conditions for growth, can contribute to real health risks for humans.

It is true that Legionella can be found in many freshwater reservoirs (less frequently in seawater) – but it does not necessarily become “problematic.” In order to cause the dangerous Legionellosis (Legionnaires’ disease or Pontiac fever), the bacterium first of all needs a convenient temperature (between approx. 20 and 50°C). The optimal temperature is around 40°C, but this does not mean that Legionella will not be able to survive in extreme temperature conditions – so it can be found in cool water (around 5°C) as well as in water reaching over 60°C.

Legionella “likes” humid and warm environments. Ideal conditions for its development prevail in outdated, inadequately protected, rarely used and contaminated water installations. It is also necessary to pay particular attention to the presence of this type of bacteria in all systems that heat water, air conditioning and ventilation systems. Hot tubs and even showers may also be at risk. Legionella can also show up in industrial cooling towers and fountains.

As can be seen – it is difficult to hope for its “freedom” – but you in fact it is possible to effectively counteract the potentially dangerous multiplication. The most effective agent used today is chlorine dioxide, which has a much more universal, precise and prolonged effect, compared to previously applied agents, such as chlorine.

In order to effectively prevent the development of Legionella colonies, it is necessary to combat the occurrence of biofilm, which contains, among others, amoebae that are extremely valuable for Legionella, as the bacterium has the ability to reproduce inside these organisms (which makes it difficult to combat Legionella with biocides).

Chlorine dioxide – an effective weapon against Legionella

Chlorine dioxide not only deals with the resistant biofilm in which Legionella is found, but it is also highly effective against other bacteria in the aquatic environment.
It eliminates biofilm and prevents its formation during the further operation of water installations. Compared to other disinfectants, chlorine dioxide, which is used for a long time, is not resistant to its active agents – small doses of this gas dissolved in water are enough to free various types of water installations from unwanted Legionella.

The use of chlorine dioxide does not contribute to corrosion (to the extent that it does with chlorine). It is also much healthier because chlorine dioxide has no association with THM carcinogens and negligible association with AOX agents (unlike chlorine).

Chlorine dioxide also has a more selective effect than chlorine alone and is more temperature resistant.

Small doses of chlorine dioxide (as opposed to chlorine and/or bromine) are also sufficient to combat algae and viruses.

As there is no need for shock concentrations, chlorine dioxide in water does not affect the quality of drinking water (the water does not have an unpleasant “chlorine” smell) and does not cause dermatological irritations.

Chlorine dioxide is particularly useful in areas where other products cannot cope, e.g. with high pH-value water.

These are just some of the advantages of using CIO2. Chlorine dioxide optimizes the operation of equipment in contact with water, e.g. by increasing the water flow and reducing calcium deposits. The process of CIO2 application is not expensive either.

For this purpose, two methods are used: chlorine dioxide application with a dosing pump or the use of a chlorine dioxide generator

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Chlorine dioxide generators

This method of introducing chlorine dioxide is now being increasingly used. The generators produce chlorine dioxide of a high purity class and modern measuring methods not only monitor the level of chlorine dioxide, but also of by-products (chlorite). This ensures that the safety of chlorine dioxide is optimized (in line with the current drinking water regulations).

Chlorine dioxide in generators (such as the popular Oxiperm Pro OCD-162 from Grundfos, which we work with) is produced from dilute solutions of sodium chlorite and hydrochloric acid. Four versions of the system are available (making it effective for different water environments).

Such generators as Pro OCD-162 are recommended especially for discontinuous disinfection. It is an ideal solution for water in public facilities (hospitals, schools, kindergartens, sports facilities, hotels, etc.). The chlorine dioxide generator is also perfect as a device treating water: tap water, process water or cooling water.

Dosing of CIO2 from generators can take place in different modes: constant, variable and proportional to water movement.

Interest in this method of water disinfection is influenced not only by its high efficiency, but also to the easiness in using generators – from their selection (Granimex provides professional advice in this area), through installation, to the flexibility of adjusting to individual investment conditions.

Generators are small in size, simple and robust in design and easy to operate.