Activated sludge should have the ability to settle quickly so that it can

Options

A. be rapidly pumped back from sedimentation tank to aeration tank
B. absorb pathogenic bacteria present in watewater while sinking to the botton of the settling tank
C. be discarded and anaerobically digested
D. absorb colloidal organic matter

Explanation

To answer the question about why activated sludge should have the ability to settle quickly, we can break it down into a step-by-step explanation:

### Step-by-Step Solution:

1. **Understanding Activated Sludge**: Activated sludge is a mixture of microorganisms (mainly bacteria) and organic matter that is used in the treatment of wastewater. It plays a crucial role in the biological treatment process.

2. **Formation of Activated Sludge**: Activated sludge is formed in the primary settling tank during the sedimentation process. Here, the solid waste settles down, and the remaining liquid contains the activated sludge.

3. **Transfer to Aerobic Tanks**: After the primary settling tank, the activated sludge needs to be transferred to aerobic tanks for further treatment. This transfer is essential for the aerobic digestion of organic matter.

4. **Importance of Settling Ability**: For the activated sludge to be efficiently transferred from the sedimentation tank to the aerobic tanks, it must have the ability to settle quickly. If the sludge does not settle well, it would be difficult to separate it from the treated water.

5. **Rapid Pumping Back**: The ability to settle quickly allows the activated sludge to be rapidly pumped back from the sedimentation tank to the aeration tank. This is crucial for maintaining the efficiency of the wastewater treatment process.

6. **Conclusion**: Therefore, the correct answer to the question is that activated sludge should have the ability to settle quickly so that it can be rapidly pumped back from the sedimentation tank to the aeration tank.