What is the maximum permissible limit of turbidity in potable water as per the Bureau of Indian Standards (BIS) (IS-10500 : 2012)?
- A.5 NTU
- B.1 NTU
- C.3 NTU
- D.7 NTU
Correct answer
Explanation
The correct answer is A, 5 NTU. Under the Bureau of Indian Standards specification for drinking water, IS 10500:2012, turbidity has an acceptable limit of 1 NTU and a maximum permissible limit of 5 NTU in the absence of any alternate source. Turbidity is the cloudiness of water caused by suspended clay, silt and organic matter, and it is measured in nephelometric turbidity units by how much light a sample scatters sideways. It is kept low because suspended particles shelter bacteria and viruses from chlorine and make disinfection less effective. Option B is wrong because 1 NTU is the acceptable limit, not the maximum permissible one. Option C is wrong because 3 NTU appears in neither column of the standard. Option D is wrong because 7 NTU is above what the standard allows in any circumstance. Exam tip: for IS 10500:2012 remember the pair — turbidity acceptable 1 NTU and permissible 5 NTU, with pH held between 6.5 and 8.5.
Practice Questions
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- C.Lead
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- D.It is bound by the procedures laid down under the Code of Civil Procedure, 1908.
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3. The NWAP has ten components.
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- A.1 only
- B.1 and 2 only
- C.2 and 3 only
- D.1, 2 and 3
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- A.Rooftop recharge pit
- B.Recharge wells
- C.Gully plug
- D.Recharge trench
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- A.Colombia
- B.Venezuela
- C.Brazil
- D.Guyana
Show answer
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