As per BIS 10500-2012, Total hardness (as CaCO₃) in drinking water should not exceed
- A200 mg / litCorrect
- B300 mg / lit
- C500 mg / lit
- D600 mg / lit
Solution
Concept
Total hardness limit
Formula
Acceptable 200 mg/L; permissible 600 mg/L
Step-by-step solution
1. IS 10500:2012: total hardness acceptable limit 200 mg/L, permissible limit (no alternate source) 600 mg/L. 2. "Should not exceed" is taken as the desirable (acceptable) limit: 200 mg/L.
Explanation
Acceptable limit = 200 mg/L.
Why the other options are wrong
600 mg/L is the permissible limit in the absence of alternate sources.
Shortcut
Hardness: 200 / 600.
Correct answer: A) 200 mg / lit