There are three broad categories in water purification systems: mechanical, biological, and chemical. Each of them has a different function and sometimes they can be used in combination. In any case, it’s not the same to purify water for human consumption, as it is to purify water for the maintenance of aquarium habitats, or for its recreational use in swimming pools and other leisure facilities. On this occasion, we’re going to assess mechanical filtration systems, as they’re used in most swimming pools, water parks and other facilities for bathing and recreational uses.
The main difference between mechanical filtration systems is found in the type of filter media they use, that is, the material that the filters have inside. To assess the different filter media available on the market, it’s necessary to compare three fundamental factors: their ability to retain solid particles, their degree of adsorption (or ability to attract and retain molecules or ions present in water), and the tendency of the medium of coagulation and flocculation (that is, the formation of lumps and channels through which the water passes without being purified).
There are four main types of filter media: silica sand, zeolite or diatom sand, glass and the most modern, expanded perlite.
– Silica sand: this is the most traditional filter medium and today it is still the most used in domestic pools. Made up of porous and irregular grains, by passing water through it, the sand retains dirt and suspended particles of up to 8 microns. However, it has two drawbacks. Firstly, it is a favourable medium for the proliferation of bacteria and microorganisms. Consequently, its second drawback is a high tendency to coagulation and flocculation and, therefore, to the formation of preferential channels that reduce its efficiency. However, the disadvantage of its biological aptitude is neutralized with the washing of the sand and the chemical treatment of the water.
-Diatomaceous and zeolite sands: diatomaceous sands come from marine fossil deposits of single-celled algae, of which some 20,000 different species still live in the seas. Zeolite, on the other hand, is a microporous mineral. They are capable of retaining particles of up to 4 and 5 microns respectively and both also represent a favourable medium for biological proliferation. In the case of diatomaceous sands, they cannot be used in traditional filters due to their physical characteristics and their application, which prevents washing.
– Glass: this filter medium is made of crushed glass or in the form of spherical balls. The more effective of the two, according to all studies, is crushed glass. It’s recycled glass and a wide variety of treatments are available, depending on the manufacturers. The most efficient is the treatment that gives crushed glass a strong negative charge that guarantees its adsorption capacity, in addition to preventing the proliferation of bacteria and microorganisms. It is capable of retaining particles of up to 4.5 microns.
-Expanded Perlite: Perlite is a volcanic mineral that is subjected to high temperatures for drying. The resulting expanded perlite is crushed to obtain a material that forms useful microscopic channels for filtering the water. Technical studies indicate that this filter medium is capable of retaining up to 56.5% of 1-micron particles.
The matter is complex and technical, so here we have only offered you a brief summary, as a guide. In any case, Amusement Logic carefully studies the needs of each aquatic installation and provides the appropriate filtering solution for them.
Sources: Piscinas AOP, Wikipedia (1, 2), Zootecnia Doméstica, Tu and Co, La Web de las Piscinas, Directorioshoy.