Treatment processes (primary, secondary, tertiary) MCQs Civil

1. Primary treatment in wastewater mainly removes:
(A) Suspended solids through sedimentation
(B) Dissolved salts
(C) Pathogens
(D) Nitrogen and phosphorus

2. The main purpose of secondary treatment is:
(A) Remove large solids
(B) Remove heavy metals
(C) Remove biodegradable organic matter
(D) Remove oils and grease

3. Tertiary treatment is designed to:
(A) Reduce BOD only
(B) Settle suspended solids
(C) Remove grit
(D) Remove remaining nutrients, pathogens, or pollutants

4. Which of the following is a primary treatment process?
(A) Trickling filter
(B) Sedimentation tank
(C) Activated sludge
(D) Sand filtration

5. Which process uses microorganisms to degrade organic matter?
(A) Secondary biological treatment
(B) Primary screening
(C) Sedimentation
(D) Chemical precipitation

6. The activated sludge process is a type of:
(A) Primary treatment
(B) Tertiary treatment
(C) Secondary treatment
(D) Physical treatment

7. Trickling filters are:
(A) Primary sedimentation units
(B) Biological treatment systems
(C) Chemical treatment units
(D) Disinfection units

8. Coagulation and flocculation are usually part of:
(A) Primary treatment
(B) Secondary treatment
(C) Tertiary treatment
(D) Screening

9. Chlorination is commonly used in:
(A) Primary treatment
(B) Secondary treatment
(C) Sedimentation
(D) Tertiary treatment / disinfection

10. Screens and grit chambers are used in:
(A) Secondary treatment
(B) Primary treatment
(C) Tertiary treatment
(D) Nutrient removal

11. The main unit in secondary treatment is:
(A) Grit chamber
(B) Sedimentation tank
(C) Biological reactor (like aeration tank)
(D) Sand filter

12. Primary treatment removes approximately:
(A) 10–30% BOD
(B) 70–90% BOD
(C) 90–99% BOD
(D) 100% BOD

13. Secondary treatment can remove up to:
(A) 20–40% BOD
(B) 60–90% BOD
(C) 100% BOD
(D) Only solids

14. Tertiary treatment is sometimes called:
(A) Settling stage
(B) Screening stage
(C) Polishing stage
(D) Grit removal stage

15. Biological nutrient removal (BNR) targets:
(A) BOD only
(B) Nitrogen and phosphorus
(C) Suspended solids only
(D) Heavy metals

16. Anaerobic treatment is commonly used for:
(A) High-strength industrial wastewater
(B) Domestic wastewater only
(C) Stormwater
(D) Tertiary treatment

17. The clarifier in a treatment plant is part of:
(A) Primary or secondary treatment
(B) Tertiary treatment only
(C) Screening process
(D) Disinfection

18. Sand filtration is considered:
(A) Primary treatment
(B) Secondary treatment
(C) Tertiary treatment
(D) Screening

19. Sludge produced in primary treatment is:
(A) Mainly organic matter
(B) Mainly sand and grit
(C) Pathogens
(D) Nutrients

20. Activated sludge process requires:
(A) High oxygen supply
(B) No aeration
(C) Only gravity
(D) Chemical addition only

21. Disinfection in tertiary treatment can be done by:
(A) Chlorine, ozone, or UV radiation
(B) Sedimentation only
(C) Screening
(D) Grit removal

22. Membrane filtration belongs to:
(A) Primary treatment
(B) Secondary treatment
(C) Tertiary treatment
(D) Aeration

23. Organic removal in secondary treatment is mainly done by:
(A) Physical settling
(B) Biological oxidation
(C) Chemical precipitation
(D) Sand filtration

24. Primary treatment does not remove:
(A) Large solids
(B) Suspended solids
(C) Grit
(D) Dissolved organics

25. Sludge recirculation is associated with:
(A) Primary sedimentation
(B) Tertiary treatment
(C) Activated sludge process
(D) Screening

26. Constructed wetlands can be used as:
(A) Primary treatment
(B) Secondary or tertiary treatment
(C) Screening
(D) Grit removal

27. Dissolved air flotation (DAF) is used to:
(A) Remove oils and grease
(B) Remove heavy solids
(C) Settle grit
(D) Screen large objects

28. Biological aerated filters (BAF) are part of:
(A) Primary treatment
(B) Secondary or tertiary treatment
(C) Screening
(D) Disinfection only

29. Sludge digestion is typically done:
(A) Before primary treatment
(B) During tertiary treatment
(C) After primary or secondary treatment
(D) At screening

30. The main goal of tertiary treatment is to:
(A) Remove settleable solids
(B) Aerate wastewater
(C) Remove coarse debris
(D) Meet high effluent quality standards