What reagent is used for water treatment?

Various reagents are used in water treatment to remove contaminants, disinfect, and improve water quality. Some of the common reagents include:

1. Chlorine (Cl₂) and Chlorine Compounds: Used as disinfectants to kill bacteria, viruses, and other pathogens in water.

2. Alum (Aluminum Sulfate): A coagulant used to remove suspended solids by causing them to clump together and settle out of the water.

3. Ferric Chloride or Ferric Sulfate: Another coagulant used for removing turbidity, organic matter, and phosphates.

4. Sodium Hypochlorite (NaClO): Used for disinfection, similar to chlorine, but in liquid form.

5. Lime (Calcium Hydroxide): Used to adjust pH levels and for water softening by removing hardness-causing minerals like calcium and magnesium.

6. Ozone (O₃): A powerful oxidizing agent used for disinfection and the breakdown of organic contaminants.

7. Activated Carbon: Though not a reagent in the strict sense, it’s used in granular or powdered form to adsorb organic compounds, chlorine, and taste/odor-causing substances.

8. Sodium Bisulfite: Used to neutralize excess chlorine after disinfection in some cases.

9. Polymer Coagulants: Synthetic organic compounds that aid in flocculation by helping particles combine and settle.

10. Hydrogen Peroxide (H₂O₂): Sometimes used for oxidation of organic compounds and disinfection.

Each reagent is selected based on the specific treatment needs, such as removing particular contaminants, adjusting pH, or ensuring safe disinfection levels.