In order to guarantee the hygienic condition of the water under all circumstances, pool users have a wide range of options for water treatment. The average person carries about 1010, that is about 10 billion germs on the skin!!! Most of these germs are harmless or even useful for the human organism. However, enough pathogenic germs remain which can cause the creation and development of a disease. Therefore, the first step towards hygiene is a thorough shower before visiting the swimming pool. Bacteria, viruses and fungi that are not introduced into the water do not represent a health risk.
Which established methods of water treatment should be preferred? The following overview provides you with the most important information and may help you to make a decision.
Disinfection
Chlorine is still the most common method for killing germs. Correctly dosed, it is capable of killing almost all micro-organisms in the water within approx. 30 seconds or inert, i.e. deactivating them. The dosage form is of secondary importance. Chlorine is offered in liquid form (sodium hypochlorite solution), solid chlorine as granules or compressed into tablets (calcium hypochlorite), or in situ, i.e. generated directly on site using the electrolysis process.
An alternative to chlorination is bromine. Unlike the bound chlorine (chloramines), the corresponding bromamines are odourless, do not irritate the mucous membranes and have an undiminished disinfection power. The disadvantage, however, is the generally lower oxidation effect and the higher price.
Silver has no oxidation effect and kills microorganisms relatively slowly. Various commercially available preparations contain small amounts of silver or silver compounds for supporting effect.
Oxygen-releasing compounds, such as hydrogen peroxide or persulphate, are used as oxidation and disinfection agents. However, it is not molecular oxygen (O2), as it is contained in the air we breathe, but an oxygen radical that has an oxidising or disinfecting effect. As this oxygen radical recombines to molecular oxygen, i.e. forms the oxygen in the air we breathe, the disinfecting and oxidising effect only exists shortly after the agent has been used. The term "oxygen method" is therefore somewhat misleading, since here too, as with all other disinfection methods, a chemical is added to the water and not just oxygen. The depot effect is only present to a limited extent.
Biguanides are only a partial substitute for chlorine in terms of their spectrum of activity, as algae formation is difficult to control with biguanides. Furthermore, biguanides are not oxidising agents, so that organic contaminants such as urine and sweat are not degraded.
Summary
“…when properly handled, chlorination is still an excellent treatment and disinfection method which is certainly not easily replaced and may not need to be replaced at any cost…”
Quote: Dr. D. Eichelsdörfer /et al: Archive of the Bathing Industry 29,9 - 13 (1976)
This quotation is still justified today, since, for example, only chlorine is used in public swimming pools.
Algicide
In addition to the common disinfection procedures, you should also pay attention to the prevention of algae formation.
Particularly when operating outdoor pools that are directly exposed to sunlight and UV radiation, algae growth can occur in the water despite maintaining the disinfectant, for example during muggy weather and thunderstorms. So-called quats (quaternary ammonium compounds), which are effective even in very low concentrations, are suitable for preventing algae infestation. As a rule, quats are characterised by their surface activity and, at higher application concentrations, favour the formation of foam in the pool water. Modern quats are low-foaming or foam-free.
pH value
All of the treatment processes shown do not work or only work to a very limited extent if the pH value of the water is not adjusted around the neutral value 7.0. Adherence to the pH range of 6.5 - 7.5 is essential in order to be able to carry out the various treatment measures optimally on the one hand and not to impair the well-being of the bathers on the other. It is also important to avoid pH-related corrosion and lime deposits.
In principle, a swimming pool is not a closed circuit. Depending on the visitor load and environmental factors, regular filter backwashing is recommended to remove undissolved pollutants. The water consumed in this way is usually replaced by fresh water, which has a diluting effect so that the water care products in the pool cannot accumulate.
Please do not confuse clear water with hygienically safe water. The microbiology is only a few micrometres in size and therefore not visible to the human eye.
Finally, a practical note - preferably use treatment agents that can also be detected analytically. Pool testers for visual determination or an electronic pool tester that works on the photometric principle and displays the measured values digitally are particularly suitable for this purpose.