The correct answer is D. All the above.
Detritus tanks are a type of sedimentation tank used in wastewater treatment. They are designed to remove suspended solids and organic matter from the wastewater. The flow velocity in a detritus tank is kept at 0.09 m/sec to allow the solids to settle out. The detention period is kept at 3 to 4 minutes to ensure that all of the solids have time to settle out. Organic and inorganic materials are separated in a detritus tank by the difference in their densities. The organic materials, which are lighter, float to the surface and are skimmed off, while the inorganic materials, which are heavier, sink to the bottom and are removed by sludge pumps.
Here is a more detailed explanation of each option:
- Option A: The flow velocity in a detritus tank is kept at 0.09 m/sec to allow the solids to settle out. If the flow velocity is too high, the solids will not have time to settle out and will be carried out of the tank with the wastewater. If the flow velocity is too low, the solids will settle out too quickly and will not be able to be removed from the tank.
- Option B: The detention period in a detritus tank is kept at 3 to 4 minutes to ensure that all of the solids have time to settle out. If the detention period is too short, some of the solids will not have time to settle out and will be carried out of the tank with the wastewater. If the detention period is too long, the solids will start to decompose and release harmful gases.
- Option C: Organic and inorganic materials are separated in a detritus tank by the difference in their densities. The organic materials, which are lighter, float to the surface and are skimmed off, while the inorganic materials, which are heavier, sink to the bottom and are removed by sludge pumps.
I hope this information is helpful. Please let me know if you have any other questions.