Cwea collections Grade 1| 28 QUESTIONS
Course
Cwea
1. What is the primary function of a sewer collection system?
A. To store wastewater
B. To treat wastewater
C. To transport wastewater to a treatment facility
D. To remove sludge from wastewater
Correct Answer: C. To transport wastewater to a treatment facility
Rationale:
A sewer collection system is designed to convey wastewater from homes, businesses, and
industries to a wastewater treatment plant for proper processing. It does not store or treat
wastewater but merely transports it efficiently.
2. What is the typical slope required for gravity sewer lines to ensure proper
flow?
A. 0.1%
B. 0.5%
,C. 1.0%
D. 2.0%
Correct Answer: B. 0.5%
Rationale:
Gravity sewer lines rely on proper slope (grade) to allow wastewater to flow efficiently without
excessive velocity or stagnation. The standard slope varies by pipe size, but 0.5% (or 0.005 ft/ft)
is a common minimum slope to prevent blockages.
3. What is the primary cause of hydrogen sulfide (H₂S) buildup in sewer
systems?
A. Excessive aeration
B. Stagnant wastewater in anaerobic conditions
C. High chlorine levels
D. Presence of ammonia
Correct Answer: B. Stagnant wastewater in anaerobic conditions
Rationale:
Hydrogen sulfide gas is formed when organic matter decomposes in the absence of oxygen
(anaerobic conditions). It is a major cause of odor issues and corrosion in sewer pipes,
particularly in areas with low flow.
, 4. Which type of sewer pipe is most resistant to corrosion from hydrogen sulfide?
A. Concrete
B. Ductile iron
C. PVC
D. Clay
Correct Answer: C. PVC
Rationale:
PVC (Polyvinyl Chloride) is highly resistant to chemical corrosion, making it ideal for sewer
lines exposed to hydrogen sulfide and acidic conditions. In contrast, concrete and ductile iron
are prone to deterioration in high H₂S environments.
5. What is the main purpose of manholes in a sewer collection system?
A. To store wastewater during peak flow
B. To provide maintenance access to sewer pipes
C. To filter debris before treatment
D. To measure flow rate in the system
Correct Answer: B. To provide maintenance access to sewer pipes
Course
Cwea
1. What is the primary function of a sewer collection system?
A. To store wastewater
B. To treat wastewater
C. To transport wastewater to a treatment facility
D. To remove sludge from wastewater
Correct Answer: C. To transport wastewater to a treatment facility
Rationale:
A sewer collection system is designed to convey wastewater from homes, businesses, and
industries to a wastewater treatment plant for proper processing. It does not store or treat
wastewater but merely transports it efficiently.
2. What is the typical slope required for gravity sewer lines to ensure proper
flow?
A. 0.1%
B. 0.5%
,C. 1.0%
D. 2.0%
Correct Answer: B. 0.5%
Rationale:
Gravity sewer lines rely on proper slope (grade) to allow wastewater to flow efficiently without
excessive velocity or stagnation. The standard slope varies by pipe size, but 0.5% (or 0.005 ft/ft)
is a common minimum slope to prevent blockages.
3. What is the primary cause of hydrogen sulfide (H₂S) buildup in sewer
systems?
A. Excessive aeration
B. Stagnant wastewater in anaerobic conditions
C. High chlorine levels
D. Presence of ammonia
Correct Answer: B. Stagnant wastewater in anaerobic conditions
Rationale:
Hydrogen sulfide gas is formed when organic matter decomposes in the absence of oxygen
(anaerobic conditions). It is a major cause of odor issues and corrosion in sewer pipes,
particularly in areas with low flow.
, 4. Which type of sewer pipe is most resistant to corrosion from hydrogen sulfide?
A. Concrete
B. Ductile iron
C. PVC
D. Clay
Correct Answer: C. PVC
Rationale:
PVC (Polyvinyl Chloride) is highly resistant to chemical corrosion, making it ideal for sewer
lines exposed to hydrogen sulfide and acidic conditions. In contrast, concrete and ductile iron
are prone to deterioration in high H₂S environments.
5. What is the main purpose of manholes in a sewer collection system?
A. To store wastewater during peak flow
B. To provide maintenance access to sewer pipes
C. To filter debris before treatment
D. To measure flow rate in the system
Correct Answer: B. To provide maintenance access to sewer pipes
