Commonly used swimming pool water treatment chemicals

I. Swimming pool water treatment is divided into two parts: physical and chemical processes.

The physical process is the purification of water through the filtration of swimming pool water by circulating water treatment equipment. The chemical process refers to the disinfection, flocculation, and algae removal treatment by adding chemicals while the pool water is circulating. Only when these two processes are carried out simultaneously can the water quality of the pool water meet national standards.

II. Swimming pool water treatment chemicals

(I) Types and names of swimming pool water treatment chemicals

1. Disinfectants - mainly using chlorine disinfection, the disinfectants currently used in China mainly include: Trichloroisocyanuric acid (Trichloroisocyanuric acid), chlorine-containing disinfectants (TCCA), bleaching powder, sodium hypochlorite, liquid chlorine, bromine chlorine, etc.

2. Precipitants - mainly divided into alkaline coagulants and acidic coagulants. Coagulants currently used in China include: polyaluminum chloride, alum, aluminum sulfate, etc.

3. PH adjusters - mainly divided into alkaline drugs and acidic drugs. There are mainly: caustic soda (alkaline), hydrochloric acid (acidic), soda (PH neutral), etc.

4. Algaecides - generally use copper sulfate, blue crystals, easily soluble in water. It can kill insects, algae, and inhibit the growth of microorganisms, and can also make the swimming pool water appear sea blue.

(II) Color and dosage of swimming pool water treatment chemicals

A. Disinfectants

1. Chlorine-containing disinfectants (swimming pools in the Pearl River Delta region all use trichloroisocyanuric acid) - divided into flake and powder forms, which are almost entirely present in the form of sodium hypochlorite after dissolving in water. It is a neutral molecule that can diffuse to the surface of negatively charged bacteria, penetrate the bacterial cell membrane into the bacteria, produce chlorination, destroy some systems of bacteria, and eventually lead to bacterial death. High effective chlorine content. Double the initial medication, and then add the daily dose. (Recommended to use this product)

2. Sodium hypochlorite (bleach, used more in the 1980s, rarely used now) - the liquid is yellow, containing 10-15% effective chlorine, which produces hypochlorous acid (HOCl) after dissolving in water. Under the action of light, the sterilization effect is good, easy to use, the pool water has no residue, and the lasting effect is good. The disadvantages are that storage and transportation are inconvenient, and the cost is high. Approximately 40-50 kg is required for 1000 cubic meters of water.

3. Bleaching powder (this medicine is not used in swimming pools now) - white powder, the main component is calcium hypochlorite Ca(OCl)2, which produces calcium oxide precipitate and hydrochloric acid after dissolving in water, and produces nascent oxygen to kill bacteria, with strong bactericidal power. The disadvantages are that storage and transportation are inconvenient, and the pool water has residue. Approximately 20-30 kg of bleaching powder is required for 1000 cubic meters of water.

B. Precipitants

1. Polyaluminum chloride - grayish yellow (powder), transparent (liquid), polyaluminum chloride is actually a mixture of aluminum oxide and aluminum chloride, its precipitation effect is mainly aluminum hydroxide Al(OH)3 precipitate, which is a colloid that can wrap impurities in water inside or attach to its surface, gradually settling down to clarify the water. The dosage for 1000 cubic meters of water is about 10-15 kg for liquid and 8-10 kg for solid. (Recommended to use this product)

2. Alum - white solid, alum actually belongs to aluminum salt coagulant, its PH value is slightly acidic, alum in water is the same as aluminum chloride, both are used for precipitation to clarify water quality, its dosage is about 20-25 kg/1000 cubic meters of water.

C. PH adjusters

1. Caustic soda - Caustic soda is alkaline. When the tested water quality PH value is lower than 6.8, an appropriate amount of caustic soda can be added, and the dosage should be determined according to the actual test results. (Recommended to use this product)

2. Hydrochloric acid - Hydrochloric acid is acidic. When the tested water quality PH value is higher than 8.2, an appropriate amount of hydrochloric acid can be added, and the dosage should be determined according to the actual test results. For example: PH value = 8.2, 5-10 kg/1000 cubic meters of water can be added to restore the PH value to 7.6-7.8. (Hydrochloric acid is highly corrosive and should be diluted evenly before use)

3. Soda - The PH value of soda is relatively neutral. When the PH value is too high or too low, an appropriate amount of soda can be added to adjust the PH value to the normal range, and the dosage is also determined according to the actual test results. (10-15 kg of soda powder can be added per 1000 cubic meters of water)

D. Algaecides

Copper sulfate - blue, slightly smelly, the usual dosage is 0.5-1 kg per 1000 cubic meters of water, but the number of uses should not be too much, 1-2 times per month is enough. (Recommended to use this product)

(III) Frequency, dosage, order of swimming pool water treatment chemicals, and new water treatment process:

1. Disinfectants: When using trichloroisocyanuric acid for disinfection, during the normal use of the swimming pool, it should be added once a day, with a dosage of 2-3 kg per 1000 cubic meters of water. The method of application is to directly and evenly add it to the swimming pool (when no one is swimming). When the number of swimmers increases in summer, it should be added once in the morning and once in the evening.

2. Coagulants: When using polyaluminum chloride to purify water quality, the turbidity of the water (no more than 5 degrees, or the bottom of the 2.5-meter swimming lane can be seen from both sides of a 25-meter-wide swimming pool) can be used to determine whether to add it. If it does not meet the standard, polyaluminum chloride should be added, with a dosage of 8-10 kg per 1000 cubic meters of water. The method of application is to dilute the polyaluminum chloride after sunset and add it with an automatic dosing pump, or sprinkle it evenly on the water surface. It is best to stir the water for 30 minutes. When using, pay attention to the PH value of the water. If the PH value is too low, add the PH neutralizer soda first, with a dosage of 10-15 kg/1000 cubic meters of water.

3. Algaecides: Use copper sulfate, with a dosage of 1-2 kg per 1000 cubic meters of water. Note that the number of applications should not be too much, 1-2 times per month is enough. (Or use when algae are found.)

4. After introducing the commonly used chemical drugs for swimming pool water quality, the medication situation is briefly summarized.

(1) For regularly open swimming pools, disinfectants should be added daily on cloudy days or after sunset. The amount of trichloroisocyanuric acid should be 2-3 kg per 1000 cubic meters of water. In spring, when there are no guests swimming, disinfectants can be used every other day, and the amount can be slightly reduced, but attention should be paid to the growth of moss. It is best to add copper sulfate once every half month, at a dosage of 1-2 kg per 1000 cubic meters of water.

(2) For normally open swimming pools, attention should be paid to the maintenance of equipment in the pump room and the handover of equipment operation procedures, and all equipment in the swimming pool and pump room should be inspected frequently.

(3) Water quality should be tested multiple times daily, including PH value and residual chlorine content. Water quality standards are: residual chlorine (combined = 1-1.5, free = 0.3-0.5) normal, PH value = 7.6-8.0 is optimal. However, the residual chlorine content is unstable, and the indicators will vary under different water temperature and weather conditions. The residual chlorine value is highest in the morning and evening, reaching more than 1.0; the residual chlorine value is lowest at noon, about 0.2, and these situations are all normal.