Write the missing correlated terms.
Electrostatic precipitators: Air pollution :: Sewage treatment: _________

Explanation

To solve the question, we need to identify the relationship between the first pair of terms: "Electrostatic precipitators" and "Air pollution."

1. **Understanding the first pair**:
- Electrostatic precipitators are devices used to remove particles from the air, thus they are directly related to controlling air pollution.

2. **Identifying the second pair**:
- We need to find a term that correlates with "Sewage treatment" in a similar way that "Air pollution" correlates with "Electrostatic precipitators."

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