Question

Given below are two statements:
Statement I: If BOD value is 4 ppm and dissolved oxygen is 8 ppm, it is a good quality water.
Statement II: If the concentration of zinc and nitrate is 5 ppm, then it can be used as good quality water.

• A. Statement I is correct but statement II is incorrect
• B. Statement I is incorrect but statement II is correct
• C. Both statements I and II are incorrect
• D. Both statements I and II are correct

Hint:

When evaluating water quality, check for parameters like BOD, dissolved oxygen, and concentrations of hazardous elements such as zinc and nitrates.

Answer 1

The Correct Option is D

To determine the correctness of the given statements, let's assess each one based on water quality standards.

1. Statement I: If BOD value is 4 ppm and dissolved oxygen is 8 ppm, it is a good quality water.
   • BOD (Biochemical Oxygen Demand): BOD measures the amount of oxygen required by microorganisms to decompose organic matter in water. A lower BOD indicates less organic pollution.
   • In general, a BOD of 4 ppm is considered acceptable for good quality water. It suggests moderate levels of organic pollution which are typically manageable in natural water systems.
   • Dissolved Oxygen (DO): Dissolved oxygen is crucial for aquatic life. A DO level of 8 ppm is quite good, indicating that the water can support a healthy aquatic environment.
   • Given these values, the water quality is indeed good. Thus, Statement I is correct.
2. Statement II: If the concentration of zinc and nitrate is 5 ppm, then it can be used as good quality water.
   • Zinc Concentration: The permissible limit for zinc in drinking water, according to many standards, is around 5 ppm. Therefore, a zinc concentration of 5 ppm is at the upper limit but generally considered acceptable.
   • Nitrate Concentration: For drinking water, the acceptable limit for nitrate is typically around 45 ppm. A concentration of 5 ppm nitrate is well below this threshold, indicating very good water quality regarding nitrate content.
   • Thus, the presence of zinc and nitrate at 5 ppm would not disqualify the water from being of good quality. Therefore, Statement II is also correct.

In conclusion, both Statement I and Statement II are correct concerning water quality criteria. Thus, the correct answer is: Both statements I and II are correct.