The correct answer is C. 3 minutes.
A grit chamber is a type of sedimentation tank that is used to remove coarse solids, such as sand and gravel, from wastewater. The detention period is the amount of time that the wastewater stays in the tank. The recommended detention period for grit chambers is 3 minutes. This is because it takes about 3 minutes for the coarse solids to settle out of the wastewater.
If the detention period is too short, the coarse solids will not have enough time to settle out and they will be discharged with the treated wastewater. This can cause problems downstream, such as clogging of pipes and equipment.
If the detention period is too long, the wastewater will spend too much time in the tank. This can lead to problems such as the growth of algae and bacteria.
Therefore, the recommended detention period for grit chambers is 3 minutes. This will ensure that the coarse solids are removed from the wastewater while minimizing the risk of problems downstream.
Here is a brief explanation of each option:
- Option A: 1 minute. This is too short a detention period. The coarse solids will not have enough time to settle out of the wastewater and they will be discharged with the treated wastewater. This can cause problems downstream, such as clogging of pipes and equipment.
- Option B: 2 minutes. This is a bit longer than the recommended detention period, but it is still not long enough to ensure that all of the coarse solids are removed from the wastewater.
- Option C: 3 minutes. This is the recommended detention period. It is long enough to ensure that all of the coarse solids are removed from the wastewater, but it is not so long that it causes problems downstream.
- Option D: 5 minutes. This is too long a detention period. The wastewater will spend too much time in the tank. This can lead to problems such as the growth of algae and bacteria.