If totally chlorine free?

   Often... very often the happy owners of swimming-pools have a question ”Is it possible if water is totally chlorine free?” It goes without saying, the question of water disinfection is meant by this. The answer is obvious – certainly, it is possible. Surely, it leads to unforeseen troubles and more intensive expenses, but the lengths you have to go to calm down or even to ensure yourself. It is well known that chloride interaction products with organic things are rather dangerous. There are a lot of not only harmful, but also those that are able to induce a mutation of cells, substances that irritate the skin and carcinogenic compounds among them.

   When it comes to chlorine-free water treatment in swimming pools, we recall the active oxygen first of all. Indeed, this is one of the main alternative water treatment methods to chlorine one. But what is the active oxygen? How does it work? How does it happen?

   Oxygen is absolutely essential for all organisms, and for human life in particular. Just a few minutes without oxygen lead to irreversible brain damage. The human brain, constituting only 2% of the weight of the body, consumes about 20% of the oxygen produced by the body. A person can live without food for up to 40 days, without water - no more than 5 days and without air - just a few minutes. Hence, the role of two simple substances - oxygen and water in sustaining life is more important than hundreds of much more complex molecules contained in food - proteins, fats, carbohydrates, vitamins, and others. Of course, full life is impossible without the last ones, but it is still based on water and oxygen.

   The ancient people compared life with the candle flame. A candle burnes, if there is enough oxygen in the air, and if there is anything to burn. But for the flame to kindle, one necessarily needs a spark. Oxygen, being not excited and active, does not react with the pairs of wax, as a spark makes oxygen from inactive to active. Once the flame kindles, its energy, released not only in the form of heat, but also in the form of light, activates all of the new oxygen molecule, and the flame does not slake. If for some reason, the flame slakes, and the combustible material continues to smolder, the additional activation of oxygen in some way allows the flame to flare up again. There is enough combustible material in the candle, it stands at the air, where oxygen is sufficient, but a pair of spontaneously wax is unlikely to burn. This requires activation of the oxygen near the wick in some way.

   Oxygen is unique among the important molecules for life. It contains two unpaired electrons in the valence orbitals. These particles have a much greater amount of energy than the molecules in the ground state, when all their electrons are paired. O2 can become active, only if it receives a considerable amount of energy. The excess energy of O2 (180 kcal / mol) releases when it reduces to 2 water molecules, having become four electrons with hydrogen atoms, that completely balance the electron shells of both atoms of oxygen.

   Despite the large excess energy, O2 hardly reacts with oxidizable substances to them. If oxygen acquires an extra electron in some way, it can get the next one easy. On the way of one-electron reduction of O2 the formation of intermediate compounds occures, that are called the reactive oxygen species (ROS), due to their high chemical activity. After receiving the first electron, O2 turns into superoxide anion radical O2-á. Addition of a second electron (with two protons) turns the latter into hydrogen peroxide, H2O2. Peroxide, being not radical, but unstable molecule that can easily get a third electron, becoming a highly active hydroxyl radical, HOá, which easily takes up all the organic molecules of hydrogen atom, turning into the water.

   May it be too difficult to understand all this "by ear"? Then, let's try to find out more.

   In contrast to conventional molecular reactions of free radicals - particles with an odd number of electrons - generate a chain reaction, which snaps only with radical recombination. Free radicals are molecules different from normal not only with high chemical activity, but that they give rise to chain reactions. "Once removed" available electron from a molecule which was near, the radical turnes into a molecule, and electron donor – turnes into the radical, which may continue on the circuit (Figure). Indeed, when free-radical reactions develope in the solutions of bio-organic compounds, the few sources of free radicals can cause damage to the vast number of biomolecules. That is why the ROS is traditionally considered in the biochemical literature as an extremely aggressive particles. Do not be afraid, it is not for us, but for the microorganisms to protozoa, viruses, spores, germs, etc.

   Where do we take these same ROS, which destroy all organics in the pool water?

  • First, we use products containing active oxygen. They are usually two-component. The second component is always used as algaecides and activator. But the main active ingredient in them is almost always the peroxides, through which a chain mechanism of super active particles runs.
  • Second, we use water ozonation systems. Ozone, in the way of turning into oxygen, forms a free radical superoxide anion, triggering the processes described above. Therefore it is proud of its outstanding oxidizing ability.
  • And third, we use installations of ultraviolet water treatment. Not only ultraviolet rays are detrimental to the cells, spores, and the micelles, they also provoke a reaction of photooxidation, as they transform an ordinary oxygen dissolved in water in the active forms of it. In other words, the ultraviolet radiation is the spark that ignites the flame of the wax candle.

   And finally, a few words about the most progressive method of UV + O3. In the process of ozone / UV, one of the advanced oxidation processes (Advanced Oxidation Processes, AOP), clearly increases the benefits of ozone and ultraviolet radiation. By irradiation of water containing dissolved ozone, there is an effective appearance of hydroxyl radicals, and also it runs a complete decomposition of ozone. OH – radicals – are the particles, characterized by extremely short period of life, in the order of microseconds, but at the same time, they are the strongest known oxidants. Through their influence the process of high-performance disinfection and oxidation of the substances present in water takes place. The organic material is oxidized to harmless carbon dioxide, water and inorganic salts.