ONE . Swimming pool water ozone disinfection process
Initial hair filtration-pressurized water pump-sand filter tank-pressurized water pump-ozone generator (dosing via jet)-reaction tank-carbon Filter tank-heat exchanger-back to the pool
TWO. Features of ozone sterilization for swimming pool water
- Ozone is an extremely strong oxidant, which can effectively decompose the humus in the water, oxidize the iron and manganese ions in the water, and decompose the tiny organisms that scatter light in the water. It can greatly improve the clarity of the water and make the water appear beautiful blue. The preparation has no such effect. In order to make the water blue, the swimming pool using chlorine preparations often need to add copper sulfate, which is extremely harmful to the human body.
- Ozone has a strong bactericidal and virus inactivation effect, which can effectively prevent the spread of infectious diseases. Experiments have shown that the same concentration of ozone is 600-3000 times more effective than chlorine in killing bacteria and viruses. When the ozone concentration is 1 mg/l, the inactivation of fecal E. coli only takes 5 seconds, and it takes 15,000 seconds to achieve the same effect with the same concentration of chlorine.
- Ozone is an internationally recognized environmentally friendly green bactericide, which will not cause any secondary pollution to the environment, and chlorine preparations will react with organic matter in the water to generate a variety of chlorinated organic compounds, such as chloroform, chloroform, etc., these substances All are recognized as carcinogenic mutagen. When a person swims, these toxic substances are absorbed by the body (the body can absorb 500 ml of water per hour in water). Chlorinated organic compounds in water can also irritate people’s eyes and skin, causing red eyes and skin rashes.
- The chlorinated organic compounds and chlorine and other toxic gases that evaporate from the water gather at the top of the swimming pool and are not easy to disperse, damage people’s respiratory organs, and seriously affect people’s health. However, the use of ozone will not cause such problems at all.
- The hypochlorous acid and its derivatives produced by chlorination seriously corrode the water treatment system and the equipment and structures in the hall, such as grids and heating pipes.
- After adding chlorine preparation, it will inevitably lead to the change of the pH value of the water, which makes people feel uncomfortable. Therefore, it is necessary to add alkaline or acidic substances to neutralize. However, ozone is a neutral substance and will not cause such problems.
THREE, swimming pool water ozone disinfection system design reference
- CT value is the main design parameter of ozone disinfection system
Where C represents the ozone concentration, measured in mg/L; T represents the contact time, measured in minutes; the product CT value of the two represents the effectiveness of the disinfection process.
For example, when the ozone concentration is 0.4mg/L and the contact time is 4min, the CT value is equal to 1.6. Swimming pool water and drinking water are different:
The swimming pool water is closed and circulates at least 4 times a day, and the drinking water is direct; (2) As the number of swimmers increases, the amount of oxidation required in the pool water also increases; (3) The temperature of the pool water is generally 25～ 40. The temperature of drinking water is generally 0.5-25; (4) The swimming pool water should be chlorinated as an auxiliary disinfectant; (5) The circulating water of the swimming pool should be disinfected with ozone after filtration;
Therefore, it is safer to use a CT value of 1.6 to determine the size of the swimming pool water ozone disinfection system. Some areas use a low CT value of 0.8, the ozone concentration is 0.2mg/L～0.25mg/L, and the contact time is 3.5min～4min. At this time, the amount of chlorination used as an auxiliary disinfection can be reduced by 65%. When chlorine is used as the main disinfectant and ozone is used as the refined disinfectant, the CT value can be less than 0.8, the ozone concentration is less than 0.5 mg/L, and the contact time is less than 1 min.
Oxidation reaction of mixing ozone and water
Usually, ozone is introduced into the water with an ejector installed on the bypass pipe. In order to ensure the water inlet pressure of the ejector, a pipeline pump is installed on the bypass pipe to increase pressure. The mixed liquid of water and ozone after the ejector enters the reaction tank from the upper side and is fully in contact with the water from the lower side to connect with the circulating water main pipe of the swimming pool. The water in the bypass pipe is disinfected under high ozone concentration and then mixed with the water in the main pipe to produce an oxidation reaction. The water circulation cycle of commercial swimming pools is 6 hours, and the water flow of the bypass pipe is 15% to 25% of the flow of the circulating water main pipe, which can ensure that the ozone has sufficient mass transfer efficiency and sufficient contact time before entering the main pipe.
- How to determine the size of the ozone generator
Ozone generator output (g/h) = circulating water flow rate (m3/h) × ozone concentration (0.5-1g)
The reaction tank is used to oxidize the inorganic and organic pollutants in the water by dissolved ozone and perform disinfection and sterilization. The exhaust valve on the upper part of the reaction tank should be connected with an ozone destruction device to remove undissolved ozone before entering the atmosphere.
The volume of the reaction tank is determined by the following formula:
Reaction tank volume (m3) = circulating water flow rate (m3/h) × by-pass water percentage (%) × reaction time (h).
Within the swimming pool water temperature range, the saturated concentration of dissolved ozone in the pool follows Henry’s law. The higher the concentration of ozone in the gas produced by the ozone generator, the higher the saturated concentration in the water, the higher the mass transfer equilibrium concentration of dissolved ozone, and the better the disinfection performance. it is good. This should be taken into consideration when choosing an ozone generator.
Five, some suggestions of ozone for swimming pool water treatment
- When the swimming pool adopts ozone disinfection, the counter-current circulating water method should be adopted. In this case, the influent water containing ozone can be quickly mixed with the pool water, and there may be no need to add other chemical agents, such as chlorine, flocculants, and pH adjustment.剂 etc. In actual operation, other benefits brought by the counter-current water distribution method include: easy removal of floating objects on the water surface, water saving and energy saving, and small pool cleaning workload;
- When the swimming pool water is disinfected with ozone, it is not necessary and should not remove the remaining ozone. The remaining ozone in the water will not reach a concentration that causes harm to people;
- Adopt the counter-current circulating water method. If the pool water can be circulated according to the specifications, under the normal passenger flow, when the ozone dosage is 0.5mg/l, it can meet the disinfection needs, but the design should consider leaving a margin;
- Ozone concentration monitoring — The ORP controller is used to monitor the ozone concentration in the water. When the ozone concentration in the backwater of the pool is too high (greater than 0.15ppm), turn off the ozone generator;
- Filtration plays a decisive role in water quality. When the particle size of the filter material is 0.6-1.0mm, if the thickness of the filter layer (not including the thickness of the supporting layer) can reach 900mm, the dosage of ozone can be reduced, otherwise, No amount of ozone can meet the design requirements;
- Many sources talk about avoiding too much ozone to enter the lungs of swimmers and poolsiders. The so-called “excessive” refers to the situation where the ozone concentration in the air that a person breathes is above 0.1ppm within 8 hours;
- If activated carbon is used, it can be used as a biological filter to degrade organic matter and ammonia nitrogen in the water. At this time, long-acting fungicides should not be added to prevent it from killing microorganisms on the activated carbon, and a small amount of ozone The chemical water passes through the activated carbon tank. In this case, the purpose of ozone oxidation is twofold: one is to disinfect, and the other is to decompose hard-to-degrade organic matter into degradable biological organic matter and improve the ability of biodegradable organic matter.