What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.

Explanation

### Step-by-Step Solution

1. **Definition of Sewage**:
- Sewage is a type of wastewater that contains both solid and liquid waste. It is produced by human activities and comes from various sources such as households, industries, hospitals, and offices.

2. **Components of Sewage**:
- Sewage contains contaminants, which are substances that can pollute water. These contaminants include disease-causing bacteria and other harmful microbes.

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