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    Technical Engines
    for pure Water.

Water treatment

Under ArbStättV (German Workplace Ordinance) and Betriebssicherheitsverordnung (German Industrial Safety Ordinance), operators are responsible for the hygienic operation of an air humidifier. VDI 6022/1 07/2011 and the operating instructions for the air humidifier provide important information in this regard. These stipulate that air humidifiers must be operated, in principle, in a way that prevents any proliferation of microorganisms.

The wet areas within the air humidifier encourage microbial proliferation.

To prevent the total colony count increasing above the limit value set out in VDI 6022/1 07/2011, we recommend water sterilisation in addition to regular cleaning.

Using a sterilisation unit obviates the need to drain the tank and water-bearing components. Under VDI 6022, adherence to hygiene requirements must be ensured and recorded by means of regular reviews (hygiene controls/inspections).

Special requirements are therefore placed on these system components:

  1. Supplied water must meet the microbiological requirements of the Trinkwasserverordnung (German Drinking Water Ordinance)
  2. Good accessibility of areas exposed to water
  3. If there is no request for humidification for more than 48 hours, the water present in the humidifier and components must be completely drained. 
  4. The total colony count in the humidifier water must be below 1,000 cfu/ml

The following systems, which can also be used in combination depending on the bacterial load of the supply air, are available:

  • Elutriation
  • Physical water sterilisation
  • Chemical water sterilisation


Pure water is chemically withdrawn from a washer’s water supply due to water evaporation, with the salts and hardness components contained in the water and the contaminants input via the air being left behind. If only the evaporated water portion is therefore offset by the constant subsequent supply of fresh water, these substances accumulate in the water supply, increasing the tendency towards corrosion and the formation of deposits. To counter this “thickening” of the circulating water, part of the water must be discharged on a regular basis and replaced by fresh water. This process is called elutriation or desalination. A washer’s overall water consumption, without allowing for the upstream water treatment, consists of the evaporated water quantity and the elutriated water quantity. In order to ensure that the quality of the circulating water remains constant, the elutriated water portion also needs to be increased as water evaporation increases. The ratio of elutriated water quantity to evaporated water quantity is constant and is referred to as elutriation rate d. The following guide values result for the elutriation rate, depending on the quality of the replenishment water:



Demineralised water, d=0.5, elutriation of 0.5 times the evaporated water quantity


Municipal water, d=2, elutriation of twice the evaporated water quantity


The elutriated water flow is either set manually via a ball valve - manual elutriation - or via a motor-driven ball valve in line with the measured guide value - automatic elutriation.

Physical water sterilisation

UV-C radiation of wavelength 254nm has the special effect of altering the DNA of bacteria and viruses such that reproduction is no longer possible. In contrast to chemical disinfection methods, microorganisms do not develop any resistance to UV light. Furthermore, UV light cannot be overdosed. A distinction is drawn between UV immersion emitters and UV reactors.

Chemical water sterilisation

Using chemical water sterilisation is the “last resort” for ensuring hygiene requirements. Alternative measures such as UV systems should be used first. Chemical water sterilisation should therefore always be used as a supplement to these systems.


There are many ways of increasing humidity in the air, but there is only one optimum solution for your humidification task.

We will work this out, together with our specialists. The diversity of our products and the know-how of our experienced specialists will open up new possible solutions.

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