1. | Clean water would have a BOD value of 5 ppm. |
2. | Fluoride deficiency in drinking water is harmful. Soluble fluoride is often used to bring its concentration upto 1 ppm. |
3. | When the pH of rainwater is higher than 6.5, it is called acid rain. |
4. | Dissolved Oxygen (DO) in cold water can reach a concentration upto 10 ppm. |