What is the role of ultraviolet (UV) radiation in the water purification systems? 1. It inactivates/kills the harmful microorganisms in water. 2. It removes all the undesirable odours from the water. 3. It quickens the sedimentation of solid particles, removes turbidity and improves the clarity of water. Which of the statements given above is/are correct?

1. Statement 1 is correct. Ultraviolet (UV) radiation, specifically UV-C light (wavelength 200-280 nm), damages the genetic material (DNA/RNA) of harmful microorganisms like bacteria, viruses, and protozoa. This damage prevents them from reproducing, effectively inactivating or killing them. This is the primary mechanism by which UV is used for water purification (a method of disinfection). 2. Statement 2 is incorrect. UV radiation does not typically remove undesirable odours from water. Odour removal usually requires processes like adsorption (e.g., using activated carbon) or oxidation. 3. Statement 3 is incorrect. UV radiation is a disinfection process and does not affect the physical properties of water like turbidity or suspended solid particles. It does not quicken sedimentation or improve the physical clarity of water. These are typically addressed by filtration and sedimentation processes *before* UV treatment, as high turbidity can shield microorganisms from UV light.