Recirculating water supply systems for swimming poolsбует

Nonchemical systems of purification and decontamination of recirculated water in the pools

Any recirculating water treatment system for swimming pools should include three important elements: mechanical filtration of suspended and colloidal particles, removing of dissolved organic compounds and disinfection. A traditional treatment and decontamination solution involves filtering of water through the mechanical filters with sand filling and application of the chlorine-containing chemicals, coagulants and flocculants. These time-proved technical solutions, in fact, have a substantial and apparent drawbacks.

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The main problem of traditional technology is the use of chlorine-containing chemicals for water decontamination. If water contains а dissolved organic substances, chlorine reacts with them and forms the organochlorines. Reaction takes most of the chlorine, and only a small residue (a few percent) is in a free state and produces a useful effect of decontamination. In the process of operation of pool, organochlorine compounds accumulate quickly. That organochlorine compounds give the water an unforgettable harsh smell, which is well known to all visitors of the swimming pools and irritates the conjunctiva. Besides, organochlorine substances are extremely toxic and carcinogenic. As one of them, for example, a famous dioxin (the most poisonous substances known). And because of that, carcinogenic effect of organochlorine compounds is the main motivation for seeking an alternative solutions in water treatment systems for swimming pools. The utilization of ozone in the recirculating water treatment systems in a swimming pools is an alternative technology, which has long proved its efficiency. The idea of ozone utilization is clear. Ozone is a much more powerful oxidizer and disinfectant compared to chlorine. In addition, ozone is an active form of oxygen and the products of its reaction with organic compounds are usual and familiar oxygen-containing organic substances (aldehydes, alcohols, acids), which are always present in any cleanest open ponds.  Oxygen-containing products are incomparably less toxic than organochlorine substances and end-products of the oxidation of organic compounds, as a matter of fact, are carbon dioxide and water. Thus, the ozone utilization not only provides a safe and reliable water decontamination, but also gradually reduces the overall level of dissolved organic compounds in the pool, solving the second important task in recirculating water treatment systems. By the way, this circumstance opens the possibility of the combined use of ozone and chlorine-containing reagents. In such systems, ozone is used as a primary agent for disinfection and oxidation of the dissolved organic compounds, whereas chlorine-contained reagent is added just before supplying back the water into the pool as a long-lived disinfectant of durable action for decontamination of water directly in the pool. After ozonization the amount of dissolved organic compounds rapidly drops and chlorine becomes nothing to react to. In this case, all the chlorine is in a free state and required for decontamination doze reduces tenfold. In addition, the toxic and carcinogenic organochlorine compounds are not formed and such technology, when used properly, is quite safe.  

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In general, it can be said that approach to the combined use of ozone and chlorine-containing reagents (usually hypochlorite) is quickly becoming the most popular for the recirculating water treatment systems in modern swimming pools for communal use. Thus, it's clear that the result is only achievable with the proper selection of design and ozone technology, which can provide the dose of ozone sufficient to purge dissolved organic compounds in the water of the pool during its operation. Unfortunately, as it often happens, the popularity of ozonizing technology has played a negative role as well. Sometimes, for promotional purposes, they add into the scheme an ozonizer with insignificantly small performance and positioning the system as a full-blown, which leads to the result that only a small part of the water flow is ozonized. Thus, the desired effect is not achievable and the presented dose of chlorine remains high, with all the consequences that described above. When designing the system, it is essential to consider not only the capacity and the parameters of the pool and the water turnover rate, but the water temperature as well, because with an increase of its temperature the solubility of ozone falls rapidly. This is particularly important when designing children's pools, where the water temperature should be maintained above 30°C, and the water turnover rate is very high. For such cases, the calculated efficiency of ozonizer becomes very high, which stimulates interest for application of more complex schemes in which ozone is combined with other technologies of water treatment.

The most promising solution is the use of ozonizing along with ultraviolet irradiation. Such installation is called a module of intensive oxidation. Ozone decays under ultraviolet radiation with formation of OH active substance. In contrast to the ozone, OH reacts almost instantaneously and does not quits out the reaction zone. Organic compounds are completely oxidized (to carbon dioxide and water) without the accumulation of intermediate compounds. The system is compact and durable. There is no need to maintain the level and gassing, because ozone decays straight within the reaction zone. In this case, the time required for water decontamination and impurities oxidation is less on one or two orders, which is very important for the system operation in case of a high temperature and a turnover rate of the water.                                 

Description of the water purification technological process using the module of intensive oxidation.

During the water treatment process an oxidation of the dissolved organic and organochlorine compounds and decontamination by ozonization simultaneously with ultraviolet irradiation is taking place.

Part of the water flow is fed into the reaction chamber through the ejector that inhausts the mixture of ozone and air from the discharge chamber of ozonizer. The content of the contact tank is irradiated by compact UV-lamp, which is installed at the top of the tank. Absorbing the ultraviolet radiation, the ozone molecule decays with formation of OH active particle, which instantly reacts with organic compounds dissolved in water. The surface of the protective housing of the lamp is treated by ultrasound, which prevents formation of deposits.

The installation does not require maintenance and application of reagents.

The family of modules of intensive oxidation show in the table below. Please, consider that besides the pool's deck volume, during the selection of an optimal model of the module for a particular swimming pool, you need to take into account other factors such as water temperature, attendance, type of pool, etc.

Model Pool capacity, m3 Ozonizer output, g/hour
EcoPool - 10 treatment system 10 1
EcoPool - 30 treatment system 30 1,5
EcoPool - 50 treatment system 50 2
EcoPool - 100 treatment system 100 10
EcoPool - 150 treatment system 150 20
EcoPool - 200 treatment system 200 30
EcoPool - 300 treatment system 300 50
EcoPool - 500 treatment system 500 100
EcoPool - 1000 treatment system 1000 200
EcoPool - 1500 treatment system 1500 300
EcoPool - 2000 treatment system 2000 400