However, this odor is not caused by the process itself, but by the evaporation of water and some of the substances contained within, which are released into the air, where we can then inhale and smell them.

Closed-system wastewater treatment is usually not a realistic option because of the large volumes and considerable extra costs involved. Thus, the easiest way to reduce unpleasant odors is to reduce evaporation, which can be practically achieved by covering the surface of the water.

However, since active processes continue to be carried out in the clarifiers and basins – adding and removing water, continuous mixing, introducing and filtering out various substances, etc. – a contiguous film cover is not a viable option. Firstly, film covers are not very resistant to long-term outdoor use, as they can easily be damaged by storms or strong winds. Secondly, they can hinder the movement of mixing arms, or cause problems during the aeration of wastewater.

Cover balls offer a solution to this problem, as they can easily withstand UV radiation and stormy winds, as well as all the chemical effects occurring during the treatment process. Floating on the surface, these balls do not interfere with the aforementioned technological and chemical processes, while still covering 91% of the surface, thereby reducing evaporation and thus the formation of odors. The balls follow changes in water level, and are also excellent thermal insulators. The latter is important because the biological processes taking place during clarification require a specific temperature range, which the balls can also help maintain: they prevent the risk of freezing in winter, and protect against overheating in summer.