Class 3 Wastewater Collection System Exam Prep (50 Questions)

1. What is the primary purpose of a wastewater collection system?

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To collect and transport wastewater to a treatment facility.

2. What is infiltration in a collection system?

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Groundwater entering sewers through cracks, joints, or defects.

3. What is inflow in a collection system?

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Stormwater entering the sewer from direct connections like downspouts or manholes.

4. What is the difference between a combined sewer and a sanitary sewer?

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Combined sewers carry both wastewater and stormwater; sanitary sewers carry only wastewater.

5. What is a force main?

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A pressurized pipe that conveys wastewater under pressure, typically from a pump station.

6. What is the function of a lift station?

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To pump wastewater from lower to higher elevations when gravity flow is not possible.

7. What are manholes used for in collection systems?

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They provide access for inspection, cleaning, and maintenance of sewer lines.

8. What is a sewer surcharge?

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When the hydraulic grade line rises above the crown of the sewer pipe, causing pressurized flow.

9. What type of gas is commonly found in sewers and poses an explosion hazard?

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Methane (CH₄).

10. What gas in sewers has a rotten egg smell and is highly toxic?

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Hydrogen sulfide (H₂S).

11. What is the main cause of hydrogen sulfide formation in sewers?

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Anaerobic conditions that allow sulfate-reducing bacteria to thrive.

12. What is the typical slope of a gravity sewer?

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0.5% to 2% depending on pipe size and design standards.

13. What is the purpose of an air release valve in force mains?

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To release trapped air pockets and maintain hydraulic efficiency.

14. What is the main disadvantage of combined sewers?

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They can cause combined sewer overflows (CSOs) during heavy rainfall.

15. What is the primary purpose of CCTV inspection in sewers?

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To assess pipe condition and identify defects like cracks, blockages, or root intrusion.

16. What is the purpose of a drop manhole?

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To allow sewers of different elevations to connect without excessive turbulence.

17. What type of pump is commonly used in lift stations?

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Centrifugal pumps.

18. What is inflow and infiltration (I/I)?

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The total of groundwater infiltration and stormwater inflow entering the system.

19. Why is it important to control I/I in a collection system?

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Excess flow can overload treatment plants and cause sanitary sewer overflows.

20. What is the purpose of odor control in collection systems?

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To reduce complaints, corrosion, and health hazards from sewer gases.

21. What does SCADA stand for in collection system monitoring?

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Supervisory Control and Data Acquisition.

22. What is the function of grease traps in collection systems?

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To capture fats, oils, and grease (FOG) before they enter the sewer system.

23. What does HGL stand for?

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Hydraulic Grade Line.

24. What is a common method of root control in sewers?

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Chemical root foaming or mechanical root cutting.

25. What does a smoke test help identify in a sewer system?

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Leaks, cross-connections, and inflow sources.

26. What type of flow occurs when the sewer is flowing full under pressure?

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Surcharged flow.

27. What is a wet well?

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A chamber in a lift station where wastewater collects before being pumped.

28. What is the main cause of sewer corrosion?

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Hydrogen sulfide gas converting to sulfuric acid in moist conditions.

29. What is a siphon in a collection system?

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A pipeline crossing under an obstacle where wastewater flows under pressure.

30. What is the main purpose of grit removal in pump stations?

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To protect pumps and equipment from abrasion and damage.

31. What is a confined space hazard in sewer entry?

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Low oxygen levels, toxic gases, and engulfment risks.

32. What is the minimum oxygen level considered safe for sewer entry?

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19.5% oxygen.

33. What PPE is typically required for sewer entry?

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Gas detector, harness, respirator if needed, hard hat, gloves, safety boots.

34. What is the function of bar screens at the head of a pump station?

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To remove large debris that could damage pumps.

35. What does CCTV stand for in sewer inspections?

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Closed Circuit Television.

36. What type of sewer cleaning uses high-pressure water jets?

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Hydro jetting.

37. What type of pipe material is most resistant to corrosion?

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PVC or HDPE.

38. What is a vacuum truck used for in sewer maintenance?

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Removing debris, sludge, and blockages from sewers.

39. What is the purpose of by-pass pumping during sewer repairs?

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To maintain flow while a section of sewer is taken out of service for repair.

40. What does SCBA stand for in confined space entry?

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Self-Contained Breathing Apparatus.

41. What is the recommended maximum lift for a wastewater pump?

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Generally 25–30 feet for suction lift (depends on pump type).

42. What is a force main surge tank used for?

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To absorb pressure surges (water hammer) in pressurized pipelines.

43. What does I/I stand for in sewer systems?

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Infiltration and Inflow.

44. What is the recommended spacing of manholes in gravity sewers?

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Typically every 300–500 feet, or at changes in direction, grade, or diameter.

45. What is the function of an odor control scrubber?

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To remove H₂S and other odorous gases using chemical or biological treatment.

46. What is the primary health risk of raw sewage exposure?

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Pathogenic bacteria, viruses, and parasites causing disease.

47. What is the purpose of a grinder pump in collection systems?

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To grind solids and pump wastewater through small-diameter force mains.

48. What is a sewer lateral?

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The pipe connecting a building’s plumbing to the public sewer.

49. What is the typical velocity range in gravity sewers to prevent settling?

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2–10 feet per second.

50. What is the purpose of sewer mapping and GIS in collection systems?

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To maintain accurate records of sewer assets for planning, maintenance, and emergency response.

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