Explain the effect on the characteristics of a river when urban sewage is discharged in to it.

Explanation

### Step-by-Step Solution:

1. **Definition of Urban Sewage**:
- Urban sewage refers to wastewater generated from urban areas, which includes sewage from households, hospitals, and industries.

2. **Components of Urban Sewage**:
- **Household Sewage**: Contains organic matter, nutrients, and potentially pathogenic bacteria.
- **Hospital Sewage**: May contain pathogens, pharmaceuticals, and other hazardous materials.
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