UPSC Prelims 2012·GS1·science-and-technology·science and technology

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?

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Last updated 23 May 2026, 3:31 pm IST
  1. A1 onlyCorrect
  2. B2 and 3 only
  3. C1 and 3 only
  4. D1, 2 and 3

Explanation

The correct answer is A because ultraviolet radiation works solely as a disinfectant. Regarding Statement 1: UV radiation penetrates the cells of harmful microorganisms like bacteria, viruses, and cysts, damaging their DNA or RNA. This process inactivates them and prevents them from reproducing, effectively making the water safe for consumption. Regarding Statement 2: UV radiation is a physical process, not a chemical one. It does not remove dissolved gases, chemicals, or organic compounds that cause bad odors or tastes. Technologies like activated carbon filters are required for this purpose. Regarding Statement 3: UV light has no impact on the physical particles suspended in water. It cannot cause sedimentation or reduce turbidity. In fact, for a UV system to work effectively, the water must already be clear, as suspended particles can shield microorganisms from the UV rays. Processes like coagulation and filtration are used to improve clarity and remove solids. Therefore, only the first statement is a correct function of UV radiation in water purification.
science-and-technology: What is the role of ultraviolet (UV) radiation in the water purification systems? 1. It inactivates/kills the harmful mi
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