HVAC water treatment in HVAC systems: definition, purpose, risks
In principle, HVAC water treatment is necessary for all installations that treat the room air in any way. This may involve ventilation, heating, cooling, filtering, humidifying, dedusting or various combinations of these tasks.
While dry indoor air treatments such as heating or filtering/dedusting do not pose major risks to the users’ health, wet systems such as humidifiers, air washers or air conditioning systems (condensation) are a different matter entirely. As soon as air, dirt and water are combined, large numbers of microbes will always be present within a very short time. Either the microbes themselves, or the toxins they produce, may then be released into the air as aerosols. In order to reduce the risk of contamination with mould, legionellae or pseudomonads, the water must be treated or disinfected.
Water treatment for ventilation systems: air washers
In most HVAC air washers, water is atomised via a nozzle before coming into contact with the air flow and partially evaporating. At the same time, some of the dust particles in the air are precipitated, washed out and collected in a reservoir. Unless the water is rigorously treated using disinfectant, and especially if it is circulated, it will soon become contaminated.
If contamination has already occurred, the entire system must first be thoroughly cleaned with alkaline detergent and, if necessary, a descaling agent, and then thoroughly flushed. All lines, nozzles, pipes, etc. must be shock-disinfected with a disinfectant solution. Subsequently, a small amount of disinfectant, for example Sanosil S015 or Super 25, should be added to the fresh water by means of an automatic dosing system to ensure continuous HVAC water treatment. While this effectively prevents repeated, rapid microbial contamination, it does not prevent the system from being contaminated with dust, etc. during normal operation. Regular cleaning is therefore essential.
Water disinfection for HVAC systems: air humidifiers
Humidifiers and air washers often have a very similar structure in terms of the ventilation technology they contain. The fundamental difference is that humidifiers operate with smaller amounts of water (usually demineralised), which is completely evaporated.
However, many customers believe that HVAC water treatment, for example, via osmosis, which removes limescale and minerals from the water, is a form of “sterilisation”. Of course, this is not the case. Even treated osmosis water, as well as the tank and pipes, are exposed to the risk of contamination. It is therefore important to adequately condition the water after desalination, and to protect it against microbial growth. Here again, the air humidifiers or air washers water treatment can be carried out by means of an automatic proportional dosing system and an air humidifier water disinfectant Sanosil S015 or Super 25.
HVAC water treatment in water-bearing systems: open adiabatic coolers / adiabatic air conditioning systems
In adiabatic coolers, water is atomised and evaporated, thus depriving the target process of heat. This principle is applied in both large wet cooling towers and adiabatic air conditioning systems. The only difference is that air that is drawn over a heat exchanger can be cooled down. These systems are becoming increasingly popular because they can not only be operated relatively easily and efficiently (compared to conventional air conditioning systems), but can also be run “dry” in winter.
However, due to the small size of these systems, it is often forgotten that legionellae and other microbes can multiply just as easily in a water tank on the roof of a building as they can in large cooling towers. Whereas operators of large refrigeration systems use a technical service to ensure adequate HVAC water treatment and water disinfection in ventilation systems, this is often overlooked with adiabatic air conditioners. Despite the automatic water exchange, an enormous level of microbial contamination occurs in warm conditions. The possibility of water treatment to combat the spread of legionellae should therefore be discussed in advance. By disinfecting the tank or the water itself in adiabatic coolers with Sanosil S015 or Super 25, you can easily ensure compliance with the statutory operating conditions to combat the spread of legionellae.
Water treatment in air conditioning systems (water-bearing HVAC systems)
Although no actual HVAC water treatment occurs, for the sake of completeness we should also mention water disinfection in air-conditioning systems in which water unintentionally (but regularly) appears as condensation due to physics. It is no secret that poorly maintained/cleaned air conditioners are excellent germ spreaders. This is because, on the one hand, water and dust/dirt present an ideal breeding ground for mould and bacteria, and on the other, the ventilation system blows large quantities of spores and bacteria into the room air.
This means that operators of such air-conditioning systems should not only always ensure that the condensation water is continuously discharged, but also regularly clean and subsequently disinfect the entire ventilation system (including the heat exchanger). In particular, the presence of mould should never be tolerated.
