Class 3 Water Treatment Exam Prep – 50 Questions
1. What is the main purpose of coagulation in water treatment?
To destabilize and aggregate particles for removal.
2. Which chemical is most commonly used as a coagulant in water treatment?
Aluminum sulfate (alum).
3. What does CT mean in water disinfection?
Concentration × Time – the product of disinfectant concentration and contact time.
4. What unit is turbidity measured in?
NTU (Nephelometric Turbidity Units).
5. What is breakpoint chlorination?
The point where chlorine demand is met and a free chlorine residual begins to appear.
6. What is the minimum free chlorine residual required in Ontario distribution systems?
0.05 mg/L.
7. What is the purpose of flocculation?
To gently mix water so particles collide and form larger flocs.
8. What process removes suspended solids after flocculation?
Sedimentation (clarification).
9. What is the purpose of filter backwashing?
To clean and restore filter media by removing trapped solids.
10. What chemical is commonly used to raise pH in water treatment?
Lime.
11. What is the purpose of fluoride addition?
To prevent dental cavities.
12. What is the primary purpose of aeration in water treatment?
To remove dissolved gases (like CO₂, H₂S) and add oxygen.
13. What is the main purpose of disinfection?
To inactivate pathogenic organisms.
14. Which organisms are indicators of fecal contamination?
E. coli (coliform bacteria).
15. What does alkalinity represent in water?
The buffering capacity of water to resist pH changes.
16. What is the optimal pH range for coagulation with alum?
5.5–7.5.
17. What is the purpose of clearwells in water treatment?
To provide contact time for disinfection.
18. What does SCADA stand for?
Supervisory Control and Data Acquisition.
19. What is cavitation in pumps?
Formation and collapse of vapor bubbles causing damage to pump parts.
20. What unit is used for measuring pressure in water systems?
kPa (kilopascals).
21. What is the difference between raw water and finished water?
Raw water is untreated source water; finished water is treated and ready for distribution.
22. What is the main purpose of reservoirs in distribution systems?
To provide storage, maintain pressure, and meet demand fluctuations.
23. What does TDS stand for?
Total Dissolved Solids.
24. Which type of filtration is used in membrane plants?
Microfiltration, ultrafiltration, nanofiltration, or reverse osmosis.
25. What is the purpose of secondary disinfection?
To maintain a disinfectant residual in the distribution system.
26. What is the standard unit for water hardness?
mg/L as CaCO₃.
27. What does DO stand for in water quality testing?
Dissolved Oxygen.
28. What type of pump is most common in water treatment plants?
Centrifugal pump.
29. What does SOP stand for in operations?
Standard Operating Procedure.
30. What does SOP ensure?
Consistency and safety in operations.
31. What is the purpose of jar testing?
To determine the optimum coagulant dosage.
32. What does NTU stand for?
Nephelometric Turbidity Unit.
33. What is the function of sedimentation basins?
To allow floc particles to settle before filtration.
34. What is the main purpose of baffles in clearwells?
To improve mixing and increase contact time.
35. What is the maximum allowable turbidity in filtered water in Ontario?
0.3 NTU (95% of the time).
36. What is the primary purpose of chlorine contact tanks?
To provide adequate contact time for disinfection.
37. What is the typical chlorine dosage for primary disinfection?
1–5 mg/L depending on water quality.
38. What is chloramine used for?
As a secondary disinfectant in distribution systems.
39. What is a cross-connection?
A physical link between a potable water system and a source of contamination.
40. What is the purpose of cross-connection control?
To prevent backflow contamination.
41. What is the function of activated carbon in treatment?
To remove taste, odor, and organic compounds.
42. What is the difference between free chlorine and combined chlorine?
Free chlorine is active disinfectant; combined chlorine is chlorine bound with ammonia or organics.
43. What does THM stand for?
Trihalomethanes – disinfection byproducts.
44. What does HPC stand for in microbiology?
Heterotrophic Plate Count.
45. What is the purpose of sodium hypochlorite in treatment?
It is a liquid form of chlorine used for disinfection.
46. What is the main risk of low pH in treated water?
Corrosion of pipes and leaching of metals.
47. What does Langelier Index measure?
The corrosivity or scaling potential of water.
48. What is the purpose of manganese greensand filters?
To remove iron and manganese.
49. What is the main advantage of membrane filtration?
It can remove very small particles, including bacteria and viruses.
50. Which Ontario regulation governs drinking water systems?
O. Reg. 170/03 under the Safe Drinking Water Act.
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