How is Sodium Chlorite 31% Used in Swimming Pools?

Sodium chlorite (NaClO₂) is a strong oxidizing agent, and a 31% concentration solution is commonly used in pool water treatment, mainly as a disinfectant or auxiliary oxidizing agent. The following are its specific application methods and precautions:

1. Principle of action

Oxidation disinfection: Sodium chlorite decomposes in water to produce chlorine dioxide (ClO₂), which can effectively kill bacteria, viruses, algae, and even degrade organic pollutants (such as urea and ammonia nitrogen).

Chlorine-free byproducts: Unlike chlorine-containing disinfectants (such as sodium hypochlorite), the sodium chlorite disinfection process does not produce carcinogenic trihalomethanes (THMs) and is suitable for chlorine-sensitive scenarios.

2. Usage method

(1) Direct addition

After dilution: Dilute 31% of sodium chlorite solution proportionally (usually 1:10 to 1:100), slowly pour into the water inlet of the pool circulation system or evenly sprinkle in the pool.

Dosage calculation:

Generally, the initial dosage is 0.5 to 2 ppm (mg/L) (measured in available chlorine, which needs to be adjusted according to water quality).

For example: 1000 tons of water swimming pool, need to add 31% sodium chlorite about 1.6~6.5 kg (specific need to be converted according to the target concentration and purity).

(2) Use after activation

With acid activator: Sodium chlorite needs to be converted to chlorine dioxide under acidic conditions (pH 2.5~3.5). Common activators:

Citric acid or hydrochloric acid: Mix in a 1:1 ratio of sodium chlorite mass, leave for 10 minutes to activate and then add.

Note: The activation process releases toxic gases and should be operated in a ventilated place.

(3) Continuous maintenance

The diluted solution is continuously injected into the circulating system through an automatic dosing pump to maintain the residual chlorine dioxide concentration of 0.1 to 0.5 ppm.

3. Precautions

pH control: The optimal pH range is 6.5~7.5, which needs to be adjusted with sodium carbonate or sulfuric acid.

Avoid mixed hazards:

It is strictly prohibited to mix with strong acids (such as concentrated hydrochloric acid) directly, which may cause violent reactions and even explosions.

Do not mix with chlorine-containing disinfectants (such as bleach powder), it will produce toxic chlorine gas.

Safety protection: Wear gloves and goggles during operation to avoid contact with skin or inhalation of gas.

Residue monitoring: Regular detection of chlorine dioxide residue, exceeding the limit (> 0.5ppm) may irritate the skin and mucosa.

4: Pros and cons

Pros:

High bactericidal efficiency, especially against chlorine-resistant pathogens such as cryptosporidium.

No chlorine odor, improve pool air quality.

Cons:

The cost is high, and the dosage needs to be precisely controlled.

The activation procedure is complex, and improper operation has security risks.

5. Synergies with other agents

Combined with ozone or ultraviolet: can reduce the amount of sodium chlorite, improve the disinfection effect.

In combination with sustained-release chlorine preparations, such as trichloroisocyanuric acid for long-term maintenance disinfection.

Sum up

31% sodium chlorite is suitable for swimming pools with high water quality requirements, chlorine sensitivity or large organic load, but safe operating procedures must be strictly followed. It is recommended to test on a small scale first and consult a professional water treatment company to develop a detailed plan.

If you would like to learn more about sodium chlorite, please click the following link.

https://www.hoochemtec.com/disinfectant-water-treatment/sodium-chlorite/