The primary treatement of wastewater involves the removal of

Options

A. dissolved impurities
B. stable particles
C. toxic substances
D. harmful bacteria

Explanation

**Step-by-Step Solution:**

1. **Understanding Primary Treatment of Wastewater:**
- The primary treatment of wastewater focuses on the initial stage of wastewater management, which primarily involves physical processes.

2. **Physical Removal of Particles:**
- The primary treatment involves the physical removal of both large and small particles from sewage. This is achieved through two main processes: filtration and sedimentation.

3. **Sequential Filtration:**
- Initially, floating debris, which includes larger materials, is removed through sequential filtration. This step ensures that larger objects do not interfere with subsequent treatment processes.

4. **Sedimentation of Grit:**
- After the floating debris is removed, the next step involves the removal of grit, which consists of solid particles and small pebbles. This is done through sedimentation, where these heavier particles settle at the bottom.

5. **Formation of Primary Sludge and Effluent:**
- The solids that settle during sedimentation form what is known as primary sludge. The liquid that remains above the settled solids is referred to as supernatant, which is the effluent that will move on to secondary treatment.

6. **Limitations of Primary Treatment:**
- It is important to note that primary treatment does not remove dissolved impurities, toxic substances, or harmful bacteria. These contaminants are addressed in the secondary treatment phase.

7. **Conclusion:**
- Based on the processes involved in primary treatment, the correct answer to the question regarding what is removed during this stage is stable particles (option 2).

**Final Answer:**
The primary treatment of wastewater involves the removal of stable particles.

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