Natural swimming pool and pool cleaning
Principle
A 100% natural swimming pool is cleaned by plants, with no chemicals or physical process based on ultra-violet radiation or ozone.
The principal of organic bathing mimics the water cleansing process that occurs naturally in the mountains.
Technical principle: in natural settings water is polluted primarily by organic matter (leaves, pollen, dead animals, etc.) This organic matter, which at this stage cannot be assimilated by plants, is "mineralised" by bacteria. The mineralised matter is consumed by plants as they grow, thus cleansing the water of elements that are harmful to animals and humans. The water becomes potable. The pool purification process uses this natural cycle. The water "polluted" by swimmers passes through a substrate colonised by inoffensive bacteria that are found everywhere in our daily surroundings. Here the mineralisation occurs, and then the water flows to a "purification" tank planted with aquatic species that have strong purification qualities (iris, carex, scirpes, rushes, etc.) and are nourished by this transformed pollution. The fully purified water is pumped from this tank and sent back to the swimming area.
Explanations
1. Pool banks: They integrate the pool into the landscape, and may disappear altogether in a modern design, or for lack of space
2. Bathing pool
3. Mineralisation tank: The water overflows from the bathing pool into this invisible tank, large particles removed and oxygen added in the process, and here organic matter is mineralised, the first stage of the purification process
4. Purification basin: The mineralised elements are consumed by growing plants, a process known as "phytoextraction", the final purification phase. 5. Filtration circuit: The water is pumped from the purification basin and sent back to the banks or the bathing pool via waterfall, stream, gargoyles, water tears or other type of water spray that oxygenates the water
6. Mixing circuit: To avoid the creation of "dead water" zones water is sucked through a bottom drain in the bathing pool and reinjected into the same pool through immersed inlets.
Implementation
The ratio of bathing water to total water surface area varies from 1.5 to 3, depending on processes used.
Benefits
• A conventional swimming pool can be transformed into a natural pool, but more space is need for the complementary lagoon tanks.
• A truly natural and sustainable alternative to the conventional swimming pool.
• Natural pools are more readily integrated into the landscape.
• Natural pools need no chemicals, eliminating chlorine, among others.
• Natural swimming pools are not taxed (in France).
• Once installed, the advantage of natural pools is that they are easier to maintain than conventional swimming pools.
Constraints
• Higher water consumption: Given the greater water surface area, there is much more evaporation. The aeration waterfall also causes evaporation.
• Higher electricity consumption: The natural swimming pool requires continuous water circulation to refresh water, and so pumps must operate all the time, unlike in conventional pools. Electricity use is much higher, an estimated 5,000 kWh/year.
• Chemical sunscreen lotions are to be prohibited; mineral-based lotions are recommended.
• Risk of excess algae growth: the vegetation area should b placed in a shady area, not in the full sun. Falling leaves must be kept out of the pools at all costs, to avoid eutrophication. In some cases it may be necessary to install netting.
• The swimming water temperature is limited to 24°C, to avoid excess proliferation of bacteria.