MCQ
During primary treatment, all solids that settle forms __$A$__ and the supernatant forms __$B$__.
- ✓$A$ - Primary sludge; $B$ - effluent
- B$A $ - Primary sludge; $B$ - secondary effluent
- C$A$ - Activated sludge; $B$ - clarified effluent
- D$A$ - Activated sludge; $B$ - effluent
