Wastewater Treatment and Design (Practice Test MCQs)

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1. The primary objective of wastewater treatment is:
(A) To remove all water from sewage
(B) To make wastewater reusable or safe for disposal
(C) To generate electricity only
(D) To separate sludge for construction

2. The main source of domestic wastewater is:
(A) Factories
(B) Households
(C) Storm runoff
(D) Industrial effluents only

3. The first step in wastewater treatment is:
(A) Secondary treatment
(B) Screening and grit removal
(C) Sludge digestion
(D) Tertiary treatment

4. The unit used for sedimentation of grit is called:
(A) Septic tank
(B) Aeration tank
(C) Grit chamber
(D) Trickling filter

5. BOD stands for:
(A) Biological Oxygen Demand
(B) Biochemical Organic Demand
(C) Biotic Oxygen Delivery
(D) Basic Oxygen Determination

6. The typical BOD removal efficiency in primary treatment is:
(A) 10–20%
(B) 25–40%
(C) 50–70%
(D) 80–90%

7. Secondary treatment primarily removes:
(A) Suspended solids only
(B) Organic matter using biological processes
(C) Heavy metals
(D) Oils and grease only

8. Activated sludge process is an example of:
(A) Physical treatment
(B) Chemical treatment
(C) Biological treatment
(D) Tertiary treatment

9. The sludge age in an activated sludge process refers to:
(A) Time for sludge digestion
(B) Average time solids stay in the system
(C) Time for sedimentation
(D) Time for sludge disposal

10. Which gas is mainly produced in anaerobic sludge digestion?
(A) Oxygen
(B) Carbon monoxide
(C) Methane
(D) Ozone

11. Trickling filters are based on:
(A) Filtration of sand
(B) Fixed-film biological treatment
(C) Chemical oxidation
(D) Membrane filtration

12. The typical detention period for a septic tank is:
(A) 1–2 hours
(B) 6–8 hours
(C) 12–24 hours
(D) 2–3 days

13. Tertiary treatment is mainly for:
(A) Removal of fine suspended solids, nutrients, and pathogens
(B) Screening
(C) Grit removal
(D) Coarse sedimentation only

14. Chlorination in wastewater treatment is used for:
(A) Aeration
(B) Disinfection
(C) Sludge stabilization
(D) Odor removal only

15. The design of a grit chamber is based on:
(A) Flow velocity
(B) Temperature
(C) Chlorine dose
(D) BOD concentration only

16. The main function of primary clarifiers is:
(A) Remove dissolved salts
(B) Remove settleable solids and floating materials
(C) Remove heavy metals
(D) Provide disinfection

17. Sludge thickening is done to:
(A) Increase moisture content
(B) Reduce volume of sludge
(C) Increase BOD
(D) Neutralize pH

18. In the activated sludge process, F/M ratio refers to:
(A) Flow/Manhole ratio
(B) Food to microorganism ratio
(C) Filter media ratio
(D) Flow to mass ratio

19. Imhoff tank combines:
(A) Screening and chlorination
(B) Sedimentation and sludge digestion
(C) Grit removal and aeration
(D) Filtration and disinfection

20. The purpose of equalization tanks is to:
(A) Increase BOD
(B) Balance fluctuations in flow and load
(C) Neutralize chlorine
(D) Digest sludge

21. Typical pH for efficient biological treatment is:
(A) 3–5
(B) 5–6
(C) 6.5–8.5
(D) 9–10

22. Which of the following is a tertiary treatment method?
(A) Activated sludge
(B) Trickling filter
(C) Sand filtration
(D) Septic tank

23. Sludge dewatering is generally done by:
(A) Gravity thickener only
(B) Belt filter press, centrifuge, or drying beds
(C) Chlorination
(D) Activated sludge process

24. Aeration in wastewater treatment helps to:
(A) Remove heavy metals
(B) Increase dissolved oxygen for microorganisms
(C) Reduce temperature
(D) Increase alkalinity

25. Which of the following is NOT a unit of secondary treatment?
(A) Trickling filter
(B) Activated sludge tank
(C) Oxidation pond
(D) Bar screen

26. The term “MLSS” in wastewater treatment refers to:
(A) Mixed Liquor Suspended Solids
(B) Medium Level Sludge Sediment
(C) Minimum Lime Slurry Solution
(D) Maximum Lime Sediment Solids

27. The main disadvantage of oxidation ponds is:
(A) High energy consumption
(B) Large area requirement
(C) Poor BOD removal
(D) High operational complexity

28. Which pathogen is commonly used as an indicator of contamination in wastewater?
(A) Salmonella
(B) E. coli
(C) Vibrio cholerae
(D) Staphylococcus aureus

29. Chemical coagulation in wastewater treatment is used to:
(A) Increase pH
(B) Remove fine suspended particles
(C) Decrease chlorine demand
(D) Generate methane gas

30. Dissolved air flotation (DAF) removes:
(A) Settleable solids
(B) Oil, grease, and fine suspended solids
(C) Heavy metals
(D) Pathogenic bacteria

31. Sludge digestion is mainly a:
(A) Physical process
(B) Biological process
(C) Chemical process
(D) Mechanical process

32. Which is the most common method for wastewater disinfection?
(A) UV radiation
(B) Chlorination
(C) Ozonation
(D) Electrocoagulation

33. The term “SRT” in activated sludge refers to:
(A) Sludge Recycling Time
(B) Solids Retention Time
(C) Sludge Reduction Technique
(D) Solids Recirculation Treatment

34. Greywater refers to:
(A) Industrial wastewater only
(B) Sewage containing human waste
(C) Wastewater from bathrooms, kitchens, and laundries
(D) Stormwater

35. The major component of wastewater is:
(A) Solids
(B) Water
(C) Bacteria
(D) Gases

36. Which process is used in tertiary treatment for nutrient removal?
(A) Chlorination
(B) Nitrification and denitrification
(C) Grit removal
(D) Screening

37. The detention time for primary sedimentation tanks is usually:
(A) 15–30 min
(B) 2–3 hours
(C) 6–8 hours
(D) 12–24 hours

38. Anaerobic treatment is preferred when:
(A) Wastewater has very low organic load
(B) Wastewater has high organic load and limited oxygen supply
(C) Only inorganic matter is present
(D) High chlorine demand exists

39. Wastewater recycling for irrigation is an example of:
(A) Primary treatment
(B) Advanced treatment
(C) Direct reuse
(D) Sludge stabilization

40. The standard BOD of domestic sewage is approximately:
(A) 10 mg/L
(B) 50 mg/L
(C) 200 mg/L
(D) 1000 mg/L

41. COD stands for:
(A) Chemical Organic Demand
(B) Chemical Oxygen Demand
(C) Carbonate Oxygen Demand
(D) Chemical Oxidation Dose

42. Which is faster: BOD or COD test?
(A) BOD
(B) COD
(C) Both are equal
(D) Cannot be determined

43. Typical DO (dissolved oxygen) level in a healthy river is:
(A) 0–2 mg/L
(B) 4–6 mg/L
(C) 8–10 mg/L
44. Waste stabilization ponds rely on:
(A) Mechanical aeration
(B) Natural processes (algae-bacteria symbiosis)
(C) High chemical doses
(D) Pressure filtration

45. The sludge volume index (SVI) indicates:
(A) Chlorine demand
(B) Settleability of sludge
(C) BOD removal efficiency
(D) pH stability

46. Odor in wastewater is mainly due to:
(A) Methane
(B) Hydrogen sulfide (H₂S)
(C) Carbon dioxide
(D) Oxygen deficiency

47. Which is a physical method of wastewater treatment?
(A) Coagulation
(B) Screening
(C) Biological oxidation
(D) Chlorination

48. The term “effluent” refers to:
(A) Raw sewage
(B) Treated wastewater discharged from a treatment plant
(C) Sludge residue
(D) Stormwater runoff

49. Which is used to measure turbidity in wastewater?
(A) BOD test
(B) Turbidimeter or Nephelometer
(C) COD test
(D) pH meter

50. The ultimate aim of wastewater treatment is to:
(A) Discharge untreated sewage
(B) Protect environment and human health
(C) Increase population
(D) Produce sludge

Wastewater Treatment and Design (Practice Test MCQs)

1. Basic/Foundation Subjects

2. Core Civil Engineering Subjects

3. Advanced/Applied Subjects

4. Management and Planning

5. Environmental & Sustainable Development