Name two inorganic impurities present in sewage.

Explanation

**Step-by-Step Solution:**

1. **Understanding Sewage**: Sewage is a type of wastewater that includes human excreta and other liquid waste from households, shops, offices, and institutions. It is carried through sewers.

2. **Identifying Impurities**: Sewage contains various impurities, which can be categorized into organic and inorganic impurities. Inorganic impurities are those that do not contain carbon.

3. **Listing Inorganic Impurities**: Two common inorganic impurities found in sewage are:
- **Nitrates**: These are compounds that can come from fertilizers and are often found in wastewater.
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