Which one of the following impuritites is easiest to remove from wastewater ?

Options

A. Bacteria
B. Colloids
C. Dissolved solids
D. Suspended solids

Answer

To solve the question "Which one of the following impurities is easiest to remove from wastewater?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Types of Impurities**:
- Wastewater can contain various types of impurities including suspended solids, bacteria, colloids, and dissolved solids.

2. **Identify the Treatment Process**:
- The treatment of wastewater typically involves several steps: filtration, sedimentation, and sometimes biological treatment.

3. **Filtration Step**:
- In the filtration step, suspended solids (which include larger particles and debris) are removed from the wastewater. This is the first step in the treatment process.

4. **Sedimentation Step**:
- After filtration, sedimentation occurs where heavier materials settle at the bottom, and lighter materials may float to the top.

5. **Evaluate the Options**:
- **Bacteria**: These are microorganisms and are not easily removed in the initial stages of treatment.
- **Colloids**: These are fine particles that remain suspended in the liquid and are also difficult to remove.
- **Dissolved Solids**: These are substances that are completely dissolved in water and require advanced treatment methods to remove.
- **Suspended Solids**: These are larger particles that can be easily filtered out during the initial treatment process.

6. **Conclusion**:
- Among the options provided, suspended solids are the easiest to remove from wastewater due to the filtration process. Therefore, the correct answer is **suspended solids**.

### Final Answer:
The easiest impurity to remove from wastewater is **suspended solids**.

---