The swimming pool disinfectant is one of the crucial factors in maintaining the cleanliness and safety of pool water. Among various disinfection methods, choosing the right disinfectant and using the correct methods are essential for ensuring the hygiene of pool water. This article will explore the main types of swimming pool disinfectants, their methods of use, and their key roles in maintaining water quality.
Common Methods of Swimming Pool Disinfection
I. Pure Chemical Agent Disinfection Method
In the treatment of pool water, the pure chemical agent disinfection method is a common approach, typically employing chlorine-based disinfectants. Some commonly used chlorine-based disinfectants include:
- Liquid Chlorine
- Advantages: Contains 100% effective chlorine, strong bactericidal power, and has lasting bactericidal and algae, odor, and taste removal capabilities. Widely used with mature technological processes and relatively low investment and operating costs, commonly used in water treatment plants.
- Disadvantages: Generally ineffective against viruses, pathogens, and complex compounds like general insecticides. Vulnerable to pH fluctuations and can generate unpleasant chlorine odor during reactions. The use of liquid chlorine poses risks to human health and the environment, requiring special safety precautions. The acidic nature of liquid chlorine needs substantial alkali addition for pH adjustment, leading to its decreasing use in modern swimming pools.
- Calcium Hypochlorite (Bleaching Powder)
- Advantages: Widely used, mainly composed of calcium hypochlorite [Ca(OCl)2], containing 25%-30% effective chlorine. Effective against various microorganisms, especially powerful in acidic conditions and high concentrations can kill spores.
- Disadvantages: Unstable in nature, prone to decomposition by light, heat, humidity, and CO2, requiring sealed storage in a dark and dry place for up to one year. Corrosive and bleaching effects limit its use on metal instruments and colored textiles. Residues and potential pipeline blockages may occur after reactions.
- Sodium Hypochlorite (Efficient Bleaching Powder, Liquid Chlorine)
- Advantages: Also known as efficient bleaching powder. The main component is sodium hypochlorite [NaOCl], appearing as white powder or gray-green crystals. It is unstable in the air. Sodium hypochlorite has a chlorine odor, can dissolve in water, and forms an alkaline solution. The pH of the emulsion can reach 12, and as the dilution of the water solution increases, the pH can drop to 7-9. It is unstable and decomposes rapidly when heated. It has bleaching and corrosive effects on items.
- Disadvantages: The effective chlorine content is generally between 10%-12%, lower in danger compared to liquid chlorine, with good disinfection effects. The chlorine content in sodium hypochlorite is extremely unstable. It gradually decreases due to factors such as the environment, temperature, humidity, light, and storage time. Because of its rapid attenuation, it cannot be stored on-site for an extended period. It is corrosive, making storage and operation difficult. Sodium hypochlorite significantly increases the pH value of pool water, requiring a large amount of acid for adjustment.
- Trichloroisocyanuric Acid (TCCA – Strong Chlorine Tablets)
- Advantages: TCCA, commonly known as strong chlorine tablets, with a molecular formula of C3N3O3Cl3, is an excellent disinfectant with a high effective chlorine content of up to 90%. It is mainly granular or tablet-shaped, demonstrating strong bactericidal power.
- Disadvantages: Slow dissolution, may lag behind the chlorine consumption rate in heavily loaded pools, leading to reduced disinfection capacity. The pH is relatively low, requiring a significant amount of alkali adjustment. TCCA contains a stabilizer, cyanuric acid, which is stable under ultraviolet light, making it suitable for outdoor pool use. However, using TCCA indoors may lead to over-stabilization issues. The use of TCCA also inevitably produces harmful chlorine by-products, a common drawback of chlorine-based chemicals.
Precautions When Using Disinfectants in Swimming Pools
- Gradual Application: It is recommended to apply swimming pool disinfectants in two stages, once after the pool closes each day and another 1-2 hours before opening. This method helps maintain the efficacy of the disinfectant during cooler, sunless nights, ensuring a more thorough and effective disinfection of the pool water.
- Volatile Disinfectants: Disinfectants containing trichloroisocyanuric acid, a chlorine-based compound, are volatile. The rate of volatilization is directly related to sunlight and temperature. During hot summer days with intense sunlight, the disinfectant may evaporate rapidly. Applying the disinfectant at night helps preserve its effectiveness.
- Chlorine Testing: Testing the chlorine residual 1-2 hours before opening ensures that the chlorine level is within sanitary requirements. If the residual chlorine is too low, supplementing with an appropriate amount of disinfectant is recommended to meet the necessary chlorine levels.
- Choice of Disinfectants: Trichloroisocyanuric acid and its series of disinfectants are commonly used due to their efficiency, low toxicity, broad spectrum, and rapid bactericidal properties. They are widely applied in industrial circulating water treatment, drinking water treatment, wastewater treatment, and swimming pool treatment. These disinfectants effectively eliminate various bacteria, fungi, spores, molds, and cholera bacteria.
- Characteristics of Disinfectants:
- Available in various forms such as white powder, granules, flakes, blocks, tablets, liquid packaging, etc.
- Applicable to multiple areas, including industrial circulating water treatment, drinking water treatment, wastewater treatment, swimming pool treatment, industrial bleaching, public places, hospitals, homes, seeds, aquaculture disinfection, and wool anti-shrinkage.
- Effective against fungi, bacteria, viruses, and spores.
- Solid formulation, convenient and safe for storage, transportation, and use, representing one of the most widely used swimming pool water treatment disinfectants globally.
- Timing for Disinfectant Supplement: The timing for disinfectant supplementation should align with the opening hours of each swimming pool. Testing chlorine residual 1-2 hours before opening helps avoid early application, preventing rapid evaporation and ensuring that the chlorine residual meets the standard at opening time.
- Other Agent Supply: Provision of other water maintenance agents, including emergency treatment for green pool water, dealing with excessive urea levels, eliminating chlorine odor, killing green algae and water parasites, improving water color and turbidity, and solving groundwater metal ion issues. These measures are essential to restore water quality to its original health and enhance the vivid blue color of pool water.
In conclusion, the choice and proper use of swimming pool disinfectants are crucial for maintaining the cleanliness and safety of pool water. Whether opting for conventional chlorine disinfection or advanced disinfection technologies, wise decisions based on specific pool needs and conditions are necessary. Through the scientific and rational use of disinfectants, we can ensure excellent water quality in swimming pools, providing a fresh and safe aquatic recreational environment for swimmers.