How to determine the size of the ozone disinfection system for swimming pool water

Design a swimming pool water treatment plan

1. Based on relevant foreign materials, introduce how to determine the size of the ozone disinfection system for swimming pool water.

The CT value is the main design parameter of the ozone disinfection system, where C represents the ozone concentration in mg/L; T represents the contact time, measured in minutes; The CT value of the product 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 4 minutes, the CT value is equal to 1.6. The higher the water temperature, the shorter the reaction time, and the lower the required CT value.

The United States Environmental Protection Agency (EPA) and Occupational Safety and Health Administration (OSHA) have published a CT value of 1.6 for the ozone disinfection system of drinking water based on experimental results. The CT value in the swimming pool water standard issued by European countries and Canadian governments also adopts 1.6.

But swimming pool water is different from drinking water:

(1) Swimming pool water is closed loop, with a minimum of 4 cycles per day, while drinking water is direct flow.

(2) As the number of swimmers increases, the amount of oxidation required for the pool water also increases.

(3) The temperature of swimming pool water is generally between 25 ℃ and 40 ℃, while the temperature of drinking water is generally between 0.5 ℃ and 25 ℃.

(4) Chlorine is also added to the swimming pool water as an auxiliary disinfectant.

(5) The circulating water in the swimming pool is filtered and disinfected with ozone. Therefore, using a CT value of 1.6 to determine the size of the ozone disinfection system for swimming pool water is relatively safe. Some regions adopt low CT values of 0.8, ozone concentrations ranging from 0.2mg/L to 0.25mg/L, and contact times ranging from 3.5min to 4min. At this time, the amount of chlorine added as an auxiliary disinfection can be reduced by 65%. When chlorine is used as the main disinfectant and ozone is used as the precision treatment disinfectant, the CT value can be less than 0.8, the ozone concentration can be less than 0.5mg/L, and the contact time can be less than 1 minute.

Usually, ozone is introduced into water using a jet device installed on a side flow pipe. To ensure the inlet pressure of the jet device, a pipeline pump is installed on the side flow pipe to pressurize.

The mixture of water and ozone behind the jet enters the reaction tank from the top side and comes into full contact with the circulating water main pipe of the swimming pool from the bottom side.

The water in the bypass pipe is disinfected at 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 rate of the bypass pipe is 5% to 15% of the main flow rate of the circulating water. This ensures that ozone has sufficient mass transfer efficiency and sufficient contact time before entering the main line.

Process flow

1. Good water treatment effect: Ozone can quickly kill algae and microorganisms (bacteria and viruses) in water, and can decolorize and remove odors. After ozone treatment, swimming pool water is clear and transparent, showing a blue color.

2. High system safety: Ozone is an internationally recognized green and environmentally friendly disinfectant that does not produce secondary pollution or residues, avoiding skin irritation after chlorine disinfection, and avoiding accidents such as chlorine gas leakage or exceeding standards during operation.

3. Reduce operating costs: Ozone is generated using air as the raw material, and swimming pool water can be recycled and reused, significantly reducing operating costs.

Several suggestions on ozone treatment of swimming pool water

When ozone disinfection is used in the swimming pool, a countercurrent circulating water distribution method should be used.

In this case, the influent containing ozone can be quickly mixed with the pool water, and there may be no need to add other chemicals such as chlorine, flocculants, pH regulators, etc.

In actual operation, the other benefits brought by the countercurrent water distribution method can only be truly realized by the swimming pool manager, such as easy removal of floating objects on the water surface, water-saving and energy-saving The cleaning workload of the pool is small, etc.

When ozone disinfection is used for swimming pool water, it is not necessary and should not remove the remaining ozone, as the remaining ozone in the water will not reach a concentration that can cause harm to humans.

When using a countercurrent circulation without removing ozone, if the pool water can be circulated according to specifications, and under normal passenger flow, the ozone dosage of 0.5mg/l can meet the disinfection needs, but the design should consider leaving a margin.

4. ORP controllers can be used to monitor the ozone concentration in the water. When the ozone concentration in the return water of the pool is too high (greater than 0.15ppm), the ozone generator can be turned off.

5. Filtration plays a decisive role in water quality. When the particle size of the filter material is between 0.6 and 1.0mm, if the thickness of the filter layer (excluding the thickness of the support layer) can reach 900mm, the amount of ozone added can be reduced.

Otherwise, no amount of ozone added can meet the design requirements.6. Almost all the data in Almost all are about avoiding too much ozone from entering the lungs of swimmers and pool people. The so-called “excessive” refers to the situation where the ozone concentration in the air that a person breathes within 8 hours is above 0.1ppm, which is a unified regulation by European and American authorities.

Theoretical analysis and practical applications indicate that a typical ozone generator designed for a swimming pool will never reach this concentration.

If chlorine preparations need to be added, disinfection needs can be met when the residual chlorine reaches 0.1ppm.

8. If activated carbon is used, it can be used as a biological filter material to degrade organic matter and ammonia nitrogen in water. At this time, long-term fungicides should not be added to prevent it from killing microorganisms on the activated carbon, and a small amount of ozonated water should be passed through the activated carbon tank.

In this case, the purpose of ozonation is twofold: one is disinfection, and the other is to decompose difficult to biodegradable organic matter into biodegradable organic matter, improving the ability to degrade organic matter.