Which of the following techniques is used to remove fluorides from the water bodies?

(a) Osmosis

(b) Ion exchange

(c) Lime softening

(d) Both b and c

(d) Both b and c

Both ion exchange and lime softening are established techniques used to remove excess fluorides from water.

• Ion Exchange: This method uses special materials called anion exchange resins.As water passes through the resin, the fluoride ions in the water are attracted to the resin and are exchanged for harmless ions like chloride, effectively removing the fluoride from the water.
• Lime Softening (Nalgonda Technique): This is a chemical precipitation method widely used for defluoridation, particularly in India. The process, known as the Nalgonda Technique, involves adding lime and alum (an aluminum salt) to the water. These chemicals cause the fluoride to clump together (flocculate) and settle down, allowing it to be easily removed.

Other common methods for removing fluoride include reverse osmosis and adsorption using activated alumina.