UPSC CSE Prelims 2012
Ultraviolet (UV) radiation plays a crucial role in water purification primarily through disinfection. It inactivates or kills harmful microorganisms such as bacteria, viruses, and protozoa by damaging their DNA or RNA, thereby preventing their reproduction and infectivity. This process effectively controls pathogens in water without adding chemicals. Therefore, statement 1 is correct.
Statement 2 is incorrect. UV radiation does not remove undesirable odours from water. Odour removal typically involves physical adsorption processes, such as activated carbon filtration, or chemical oxidation methods like ozonation.
Statement 3 is incorrect. UV treatment has no impact on the sedimentation of solid particles, the removal of turbidity, or the improvement of water clarity. These processes are achieved through physical methods like coagulation, flocculation, and filtration, which separate suspended solids from water.