Sodium metabisulfite is used in water primarily for its ability to remove chlorine and chloramines. Here are the main reasons why it’s used:

1. Chlorine Removal: Sodium metabisulfite reacts with chlorine (Cl₂) present in water, converting it into chloride ions (Cl⁻) and releasing sulfur dioxide gas (SO₂). This reaction effectively dechlorinates the water, which is important in various industrial processes where chlorine can interfere with reactions or damage equipment.

2. Chloramine Removal: In some water treatment processes, chloramines (compounds formed by combining chlorine with ammonia) are used as disinfectants. Sodium metabisulfite also reacts with chloramines, breaking them down into harmless by-products, ammonia, and sulfur dioxide.

Why Is Sodium Metabisulfite Used In Water

3. Dechlorination: In municipal water treatment, dechlorination may be necessary before discharge into the environment to minimize the environmental impact of chlorine.

4. Water Quality Control: Removing chlorine and chloramines helps improve water quality by eliminating their taste and odor, making the water more palatable for consumption.

Overall, sodium metabisulfite plays a crucial role in water treatment processes where the presence of chlorine or chloramines needs to be controlled or removed to meet specific quality standards or process requirements.