Chemical disinfection
The water purification in a swimming pond and natural pool is based on a purely mechanical-biological purification and copies the mechanisms of nature. With the help of the food chain and the continuous extraction of nutrients, healthy and "pure" water is achieved.
This is in stark contrast to the chemical disinfection in the classic chlorine pool or in the "hybrid pool".
Chemical chlorine disinfection.
The standard method of keeping pool water clean is chemical disinfection, mainly with chlorine. This can be added to the water in the form of gas, liquid, powder or tablets. However, it can also be obtained by electrolysis in the pool water cycle, often referred to as "salt water pool".
Chlorine and other disinfectants are toxic and aim to kill all life in the water. Bacteria and algae have a very large surface area and a fast metabolism and therefore die very quickly. But our skin, eyes and mucous membranes are also attacked.
For chlorine to develop its deadly effect, the pH value must be adjusted in the range of 7.2-7.6. This is done automatically in the saltwater pool by adding hydrochloric acid.
For example, chlorine reacts with nitrogen from sun creams, skin particles and urine to form carcinogenic compounds.
Especially at high temperatures and intensive use, the disinfectant effect is often too weak to reliably prevent algae. It requires the use of algaecides, usually copper-based, so that it is necessary to add even more poison. After a Saharan rain, the water becomes cloudy and the dust is so fine that it cannot be trapped by the filter. Now a chemical flocculant must be used.
You can no longer see the nutrients, but the impurities stay in the water and accumulate there.
By the way, chlorine is an odorless gas. The typical "chlorine smell" in swimming pools is caused by the reaction products of chlorine.
Since all these reaction products and toxins accumulate in the pool water, the water has to be partially replaced constantly. Therefore, public swimming pools have to change 5% of the total water volume every day!
Chemically disinfected water does not mean clean water, it only means DEAD WATER. As soon as the disinfectant is missing or the pH value goes out of the necessary range, algae and bacteria start to multiply exponentially, the water turns green and shows its degree of contamination. The picture shows the same pool 7 days before (blue, clear) and after disinfection failure (green and cloudy).
Chemical disinfection in the "hybrid pool" (often mistakenly sold as a biological or ecological pool).
Hybrid pools use a different form of disinfection that allows some resistant aquatic organisms to survive. This allows the use of hardy riparian plants to create a natural appearance. But biology is not the basis of water purification, as the physical and chemical techniques used kill most of the microscopic living things responsible for bio-purification. Plants are only decoration.
The physical and chemical disinfection techniques commonly used in "hybrid pools" are:
Ultraviolet light: part of natural sunlight that strongly affects living tissues. It causes sunburn and the death of viruses, bacteria and algae. UV lamps are used in ponds to avoid cloudy green water caused by small algae. In aquariums or aquaculture with large numbers of fish, UV can be used to reduce pathogen pressure. In nature, this only occurs in the first few centimeters of the surface, while pathogens and algae in the lower water layers are eaten by zooplankton. Ultraviolet light also kills zooplankton.... the entire food chain and biological purification is interrupted. Ultraviolet light does not reduce or fix nutrients. Nutrients fixed in the biomass of algae, bacteria and zooplankton are released again and instead promote the growth of filamentous algae. Ultraviolet light leaves no chemicals in the water and does not kill life outside the lamp. Therefore, it is acceptable for use in an exceptional situation of disruption of the biological system, and for temporary use (FLL, German standards for the planning, construction and maintenance of NSPs and basis for several other national standards). The energy consumption of UV lamps is relatively high, on average higher than the total energy consumption in a biological pool.
Copper: essential for life in small amounts, rapidly toxic in higher concentrations. Most algae removers for pools and ponds are copper-based. It can be added as a salt (e.g. CuSO4) or by electrolysis. Copper destroys the structure of algae, both planktonic and sessile, so it is also effective against filamentous algae. It also kills many bacteria and other microorganisms in the water and biofilm (filter), aquatic snails, larvae and sensitive fish. Copper remains in the water and accumulates in sediments. In countries with more restrictive legislation, copper is strictly forbidden in public swimming pools (both natural and chemical). Copper is not allowed in a natural pond/pool. However, tall riparian plants are much more resistant to copper, which allows them to be used as a decorative element in hybrid tanks, giving them the visual appearance of a biological system.
Silver: Silver, like copper, is a heavy metal with lethal effects on small organisms. It is also used in the form of electrolysis. Absolute no-go in biological purification.
Salt hydrolysis: This is the technique used in "salt water pools". An electric field creates "radicals" of chloride ions from the salt dissolved in the water. At higher voltages, the splitting of the water molecule can even produce oxygen and hydrogen radicals. The radicals are extremely aggressive to all surfaces and quickly kill small forms of life. Chloride reacts with nitrogen (from skin, hair, urine, all biomass) and generates carcinogenic by-products such as trichloramine which accumulates in pool water.
There is much more reactive biomass and nitrogen present in a hybrid pool than in a chlorine disinfected pool, resulting in an even higher production of these dangerous by-products! Absolutely forbidden for biological water treatment.
pH control with hydrochloric acid, as in a saltwater pool, to ensure the disinfection effect.
A hybrid pool is neither a NBS (nature-based solution) nor a swimming pond or a natural pool. All poisons that can be used in a hybrid pool are legal for private use. In terms of water treatment, the hybrid pool is very similar to a classic swimming pool, although the appearance may resemble that of a biological swimming pond. It is an alternative to Cl and NSP disinfection.
It is completely wrong: selling a hybrid pool as a swimming pond/natural pool! This is greenwashing and unfair competition.