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Pool maintenance

Bio or chemistry: Which water treatment is right for my pool?

Whether you treat your pool water biologically or chemically is primarily a matter of taste. Do you want a natural pool that is cleaned by microorganisms similar to a swimming lake, or do you want disinfected water similar to a swimming pool? Both types of water treatment have their advantages. Both are possible in prefabricated swimming pools with biological water treatment. The actual swimming pool is preceded by a planted filter zone, which can be located directly next to the swimming pool or a few metres away. Therefore, the natural pool is divided into a swimming area and a cleaning area - about 90 percent of the area is available for swimming. The filter zone occupies about 10 percent of the area. It consists of gravel, granules, and aquatic plants. With the aid of a pump, pool water continuously flows through the filter zone. The nutrients of the pool water are stored in the filter substrate and decomposed by the biomass. Microorganisms reliably and naturally clean the water and permanently keep it in balance. Water in natural pools is drinking water quality and is particularly soft and pleasant on the skin. Depending on the design, a heated pool can also be combined with biofiltration. Slow heating is recommended so that the microorganisms can adjust to the temperatures. In chemical water treatment, the addition of inorganic chlorine is the most common form because it kills germs quickly, reliably and economically. Chlorine has an odour and can cause skin and eye irritations, something you may know from the outdoor swimming pools of one’s childhood. These occur when there is too little free and effective chlorine in the swimming pool water. Then, for example, chlorine nitrogen compounds are formed, which cause the unpleasant side effects. If the value of free and effective chlorine is around 0.3 mg per litre, these side effects are not an issue. Additionally, it is important to add enough fresh water and to have a perfectly functioning filtration system. Then chlorine is the first choice for disinfection.

An alternative is water treatment with so-called active oxygen. Hydrogen peroxide (H2O2) is added to the water. In the water, the peroxide breaks down into water (H2O) and bivalent oxygen (O2). It has a good disinfecting effect. There are no side effects, even if the dosage is insufficient. Overall, however, the disinfecting effect is considerably weaker compared to chlorine.

Ozone can also be used for water treatment. However, since the process technology required here is very complex, the actual use of ozone is reserved for public swimming pools. However, various systems on the market use the word ozone in their type designation. Usually, these are electrolysis of common salt.

In addition to the processes mentioned above, the electrolysis of sodium chloride is often used as a so-called disinfection or water treatment process. Sodium chloride (NaCl) is added to the pool water and broken down into sodium hydroxide solution and chlorine by an electrolysis cell. So this is nothing more than disinfection with chlorine. The only difference is that the chlorine is produced on-site in the pool water.

Generally applies: the more thoroughly you shower before bathing and the more you remove dirt, cosmetics, and sunscreen, the cleaner the pool water remains.