I. The importance of using swimming pool disinfectants
As a public entertainment and fitness venue, the water quality safety of swimming pools is directly related to the health of swimmers. Water without proper treatment may become a breeding ground for bacteria, viruses and other pathogens, leading to the spread of pink eye, skin diseases, gastrointestinal diseases and even more serious infectious diseases.
Disinfection is the most critical link in the swimming pool water treatment system, and its main purposes include:
Killing pathogenic microorganisms in the water.
Preventing algae growth.
Oxidizing organic pollutants.
Keeping the water clear and transparent.
II. Common swimming pool disinfectant types and characteristics
Chlorine disinfectant
Chloride disinfectant is the most traditional and widely used disinfection method for swimming pools.
Liquid chlorine: strong disinfection effect, low cost, but high storage and use risks.
Sodium hypochlorite (bleaching powder): easy to use, but poor stability, need to be added frequently.
Calcium hypochlorite: solid form, easy to transport and store, but may increase water hardness.
Sodium dichloroisocyanurate SDIC and trichloroisocyanuric acid TCCA: sustained-release chlorine preparations with good stability, high chlorine content, reliable effect, and continuous disinfection ability.
Bromine disinfectants
Bromides (such as bromochlorohydantoin, sodium bromide) are used as disinfectants to replace chlorine.
Excellent characteristics:
Still maintain good sterilization effect at higher pH values.
The disinfection by-products produced are less irritating.
Particularly suitable for high-temperature environments such as hot spring spas.
Ozone disinfection
Ozone O₃ is a strong oxidant with an oxidizing capacity 1.5 times that of chlorine.
Advantages:
It has a fast sterilization speed and high efficiency, and does not produce chlorine odor.
It can effectively degrade organic pollutants and reduce the generation of disinfection by-products.
Disadvantages:
It has no continuous disinfection ability and needs to be used in conjunction with chlorine or bromine.
The system investment and operating costs are high.
Excessive ozone is harmful to the human body and needs to be strictly controlled.
UV disinfection
Ultraviolet light (especially UV-C band) is a physical disinfection solution that does not produce chemical byproducts. It is particularly effective against chlorine-resistant pathogens such as Cryptosporidium. However, it needs to be used in combination with other disinfectants to provide residual disinfection capacity.
Metal ion disinfection (silver/copper ions)
Silver ions have a long-lasting bactericidal effect, and copper ions can effectively inhibit algae growth. Metal ion disinfection is usually used in combination with low-dose chlorine or other oxidants. This method has high equipment investment but low operating costs.
Comparative analysis of four common used chlorine-based disinfectants
Sodium hypochlorite NaClO(liquid chlorine)
Bactericidal mechanism:
Hydrolysis to generate hypochlorous acid (HOCl), destroying the cell structure of microorganisms.
Advantages:
The lowest price, fast dissolution, suitable for emergency chlorine supplementation, and suitable for automated dosing systems.
Disadvantages:
Easy to decompose during storage, and loses 10-15% of effective chlorine per month.
Strong irritation, may produce chlorine odor.
Applicable scenarios: large public swimming pools, water treatment plants.
Calcium hypochlorite Ca(ClO)₂
Bactericidal mechanism:
Hydrolysis to produce hypochlorous acid and calcium hydroxide.
Advantages:
Better stability than liquid chlorine, powder can be stored for 6-12 months.
Calcium content will increase water hardness appropriately, suitable for use in soft water.
Disadvantages:
It will increase pH and calcium hardness, which may cause scaling.
There is precipitation after dissolution, and filtration needs to be strengthened.
Applicable scenarios: outdoor swimming pools, areas with low hardness
Trichloroisocyanuric acid TCCA 90
Bactericidal mechanism:
Slow release of hypochlorous acid and isocyanuric acid.
Advantages:
The highest chlorine content (90%), long-term sustained release of up to 3-7 days.
Tablets can be directly put into skimmers or floats.
It can lower pH and reduce the need for acid adjustment.
Disadvantages:
Isocyanuric acid (CYA) will accumulate, and when it is greater than 50ppm, it will inhibit the activity of chlorine.
It is necessary to change the water regularly or use a chlorine-free oxidant (such as potassium persulfate) to break CYA.
Applicable scenarios: small and medium-sized commercial swimming pools, private swimming pools.
Sodium dichloroisocyanurate NaDCC
Bactericidal mechanism:
Rapid release of hypochlorous acid, with a small amount of residual isocyanuric acid.
Advantages:
The dissolution rate is faster than TCCA, suitable for rapid increase of residual chlorine.
At the same time, the accumulation rate of isocyanuric acid is slow.
Disadvantages:
The price is higher than TCCA.
Applicable scenarios: occasions where rapid disinfection is required.
Key considerations for the selection of disinfectants
Bactericidal efficacy. Killing effect on different pathogens.
Continuous disinfection ability. Whether it can maintain long-term disinfection in water.
Safety. Impact on the skin, eyes and respiratory system of swimmers.
By-product risk. Harmful substances generated during the disinfection process.
Operational convenience. The difficulty of addition, monitoring and control.
Economic efficiency. Initial investment and long-term operating costs.
Influence of water quality parameters. Impact on pH, alkalinity, hardness, etc.
Environmental friendliness. Impact on the environment after discharge.