What is sludge? Explain how it is treated.

Explanation

**Step-by-Step Solution:**

1. **Definition of Sludge:**
- Sludge is a semi-solid waste that is produced during the treatment of wastewater. It primarily consists of human feces and other organic materials that settle down during the wastewater treatment process.

2. **Collection of Sludge:**
- After the wastewater treatment process, the sludge that has settled at the bottom is scraped and collected. This is an important step as it separates the solid waste from the liquid waste.

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