Explanation:

- Option 1: Sewage

- Sewage refers to waste water and excrement conveyed in sewers.

- It encompasses both waste from domestic, industrial, and stormwater sources.

- The process of treating this is indeed called sewage treatment.

- Correct Answer

- Option 2: Microbe

- Microbes are microscopic organisms, such as bacteria, fungi, and viruses.

- They play a key role in breaking down organic matter during wastewater treatment but don't describe the treatment process itself.

- Option 3: Bacteria

- Bacteria are a type of microbe.

- They assist in decomposing organic substances in sewage during treatment.

- However, they aren't synonymous with the treatment process.

- Option 4: Pollutant

- Pollutants refer to substances that contaminate water or the environment.

- Wastewater contains pollutants that need to be treated, but this isn't a name for the treatment process.