The following units are included in a sewage treatment plant.
1. Screening
2. Grit removal
3. Secondary sedimentation
4. Aeration
5. Primary sedimentation
The correct sequence of these units is:
1
1, 2, 3, 4, 5
2
1, 2, 5, 4, 3
3
2, 1, 4, 5, 3
4
2, 1, 4, 3, 5
5
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