Which one of the following statements is not true?
1. | Concentration of dissolved oxygen below 5 ppm is good for the growth of fish. |
2. | Clean water would have a BOD value of less than 5 ppm. |
3. | Oxides of sulphur, nitrogen, and carbon are the most widespread air pollutant. |
4. | pH of drinking water should be between 6.5-8.5. |
The major source of BOD in the river Ganga is
(1) Leaf litter
(2) Fishes
(3) Human waste
(4) Aquatic plants
B.O.D is-
1. | The amount of O2 utilized by organisms in the water. |
2. | The amount of O2 utilized by microorganisms for decomposition. |
3. | The total amount of O2 present in water. |
4. | All of the above |
Which of the following is absent in polluted water
1. Hydrilla
2. Water hyacinth
3. Larva of stone fly
4. Blue green algae
B.O.D is connected with
(1) Organic matter
(2) Microbes
(3) Both
(4) None
Incorrect statement among the following is:
1. Oxides of sulphur, nitrogen, and carbon are the most widespread air pollutant.
2. pH of drinking water should be between 6.5 and 8.5.
3. Concentration of dissolved oxygen below 6 ppm is good for the growth of fish.
4. Clean water would have a BOD value of less than 5 ppm.
Biochemical oxygen Demand value less than 5 ppm indicates a water sample to be :
1. Highly polluted.
2. Poor in dissolved oxygen.
3. Rich in dissolved oxygen.
4. Not suitable for aquatic life.
Phytoplanktons kill the fish because :
1. | Phytoplanktons decrease the BOD level that causes the death of fish. |
2. | Phytoplanktons increase the BOD level that causes the death of fish. |
3. | Phytoplanktons reduce the amount of dissolved CO2. |
4. | None of the above. |
Biochemical Oxygen Demand (BOD) is-
1. | Amount of oxygen required by bacteria to decompose organic matter in a certain volume of a sample of water. |
2. | Amount of CO2 required by bacteria to decompose organic matter in a certain volume of a sample of water. |
3. | Amount of O3 required by bacteria to decompose organic matter in a certain volume of a sample of water. |
4. | None of the above |
A student collected samples from two water bodies A and B in a metro city. The biochemical oxygen demand for 'A' is 3 ppm while for B is found to be 18 ppm. Which one of the following is true?
1. Both A and B are clean
2. Both A and B are polluted
3. A is clean but B is polluted
4. A is polluted but B is clean