Oregon Collection System Operator
Exam Practice Questions And Correct
Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant Download
Pdf.
1. What is the primary purpose of a wastewater collection system?
A. To disinfect wastewater before treatment
B. To collect and transport wastewater to a treatment facility or
designated treatment point
C. To remove dissolved nutrients from wastewater
D. To produce potable water
A wastewater collection system conveys domestic, commercial, and
permitted industrial wastewater from points of generation to a treatment
facility for appropriate treatment and disposal.
2. Which type of sewer is designed to carry sanitary wastewater while
excluding stormwater under normal conditions?
A. Combined sewer
B. Sanitary sewer
C. Storm drain
D. Irrigation canal
,A sanitary sewer is designed primarily to collect wastewater from homes,
businesses, and other permitted sources without intentionally conveying
stormwater.
3. What is a combined sewer designed to convey?
A. Drinking water and groundwater
B. Industrial wastewater only
C. Sanitary wastewater and stormwater in the same pipe
D. Treated effluent and drinking water
Combined sewers convey sanitary wastewater and stormwater together,
which can create substantially different hydraulic conditions during
rainfall.
4. What is the primary purpose of a sewer manhole?
A. To disinfect wastewater
B. To increase wastewater temperature
C. To provide access for inspection, maintenance, cleaning, and changes in
sewer alignment or elevation
D. To remove all suspended solids
Manholes provide personnel and equipment access to collection-system
piping and are commonly installed at changes in direction, grade, size, or
junctions.
5. Why should manhole covers be maintained in good condition?
A. To increase wastewater BOD
B. To reduce sewer pipe diameter
C. To protect public safety and limit unauthorized or excessive inflow into
the collection system
D. To increase infiltration
Properly maintained covers reduce hazards to the public and help prevent
stormwater, debris, and other unwanted material from entering the sewer.
, 6. What is infiltration in a wastewater collection system?
A. Intentional addition of drinking water
B. Groundwater entering the sewer through defects, joints, cracks, or
other openings
C. Stormwater entering through a roof drain
D. Wastewater leaking from a treatment basin
Infiltration is groundwater that enters a sewer through structural defects,
faulty joints, cracks, manholes, or other pathways below or near the
groundwater table.
7. What is inflow?
A. Groundwater entering through pipe cracks below the water table
B. Treated effluent entering a sewer
C. Water entering a collection system through direct or indirect
connections such as roof drains, catch basins, or improperly connected
stormwater sources
D. Wastewater leaving a lift station
Inflow enters the collection system through relatively direct connections or
openings that can convey rainfall or surface water rapidly into the sewer.
8. Why are infiltration and inflow undesirable?
A. They always improve biological treatment
B. They reduce hydraulic loading
C. They increase flows, consume collection and treatment capacity, and
can contribute to overflows
D. They eliminate pump operation
Excessive I/I increases hydraulic loading and can exceed the capacity of
pipes, lift stations, treatment facilities, or receiving systems.
9. Which event is most likely to produce a rapid increase in collection-
system flow?
, A. Extended dry weather
B. A decrease in groundwater elevation
C. Heavy rainfall entering through inflow sources
D. Reduced customer water use
Rainfall can rapidly increase wastewater flows when stormwater enters
sanitary sewers through direct or indirect inflow pathways.
10. What is the primary purpose of an infiltration and inflow
investigation?
A. To increase groundwater infiltration
B. To reduce sewer inspection activities
C. To identify and correct sources of unnecessary water entering the
collection system
D. To increase wastewater dilution intentionally
I/I investigations identify sources of excess water so corrective measures
can reduce hydraulic loading and improve system capacity.
11. Which observation may indicate significant infiltration into a
sanitary sewer?
A. Flow remaining constant during and after dry weather
B. Decreasing groundwater levels with no flow change
C. Elevated nighttime or base flows during periods of high groundwater
D. Reduced sewer depth after rainfall
Persistent elevated flows during periods of high groundwater can indicate
groundwater entering the sewer through infiltration pathways.
12. What is the primary purpose of sewer flow monitoring?
A. To determine drinking-water chlorine residual
B. To measure treatment-plant sludge age
C. To quantify wastewater flow patterns and identify hydraulic conditions
Exam Practice Questions And Correct
Answers (Verified Answers) Plus
Rationale 2027 Q&A| Instant Download
Pdf.
1. What is the primary purpose of a wastewater collection system?
A. To disinfect wastewater before treatment
B. To collect and transport wastewater to a treatment facility or
designated treatment point
C. To remove dissolved nutrients from wastewater
D. To produce potable water
A wastewater collection system conveys domestic, commercial, and
permitted industrial wastewater from points of generation to a treatment
facility for appropriate treatment and disposal.
2. Which type of sewer is designed to carry sanitary wastewater while
excluding stormwater under normal conditions?
A. Combined sewer
B. Sanitary sewer
C. Storm drain
D. Irrigation canal
,A sanitary sewer is designed primarily to collect wastewater from homes,
businesses, and other permitted sources without intentionally conveying
stormwater.
3. What is a combined sewer designed to convey?
A. Drinking water and groundwater
B. Industrial wastewater only
C. Sanitary wastewater and stormwater in the same pipe
D. Treated effluent and drinking water
Combined sewers convey sanitary wastewater and stormwater together,
which can create substantially different hydraulic conditions during
rainfall.
4. What is the primary purpose of a sewer manhole?
A. To disinfect wastewater
B. To increase wastewater temperature
C. To provide access for inspection, maintenance, cleaning, and changes in
sewer alignment or elevation
D. To remove all suspended solids
Manholes provide personnel and equipment access to collection-system
piping and are commonly installed at changes in direction, grade, size, or
junctions.
5. Why should manhole covers be maintained in good condition?
A. To increase wastewater BOD
B. To reduce sewer pipe diameter
C. To protect public safety and limit unauthorized or excessive inflow into
the collection system
D. To increase infiltration
Properly maintained covers reduce hazards to the public and help prevent
stormwater, debris, and other unwanted material from entering the sewer.
, 6. What is infiltration in a wastewater collection system?
A. Intentional addition of drinking water
B. Groundwater entering the sewer through defects, joints, cracks, or
other openings
C. Stormwater entering through a roof drain
D. Wastewater leaking from a treatment basin
Infiltration is groundwater that enters a sewer through structural defects,
faulty joints, cracks, manholes, or other pathways below or near the
groundwater table.
7. What is inflow?
A. Groundwater entering through pipe cracks below the water table
B. Treated effluent entering a sewer
C. Water entering a collection system through direct or indirect
connections such as roof drains, catch basins, or improperly connected
stormwater sources
D. Wastewater leaving a lift station
Inflow enters the collection system through relatively direct connections or
openings that can convey rainfall or surface water rapidly into the sewer.
8. Why are infiltration and inflow undesirable?
A. They always improve biological treatment
B. They reduce hydraulic loading
C. They increase flows, consume collection and treatment capacity, and
can contribute to overflows
D. They eliminate pump operation
Excessive I/I increases hydraulic loading and can exceed the capacity of
pipes, lift stations, treatment facilities, or receiving systems.
9. Which event is most likely to produce a rapid increase in collection-
system flow?
, A. Extended dry weather
B. A decrease in groundwater elevation
C. Heavy rainfall entering through inflow sources
D. Reduced customer water use
Rainfall can rapidly increase wastewater flows when stormwater enters
sanitary sewers through direct or indirect inflow pathways.
10. What is the primary purpose of an infiltration and inflow
investigation?
A. To increase groundwater infiltration
B. To reduce sewer inspection activities
C. To identify and correct sources of unnecessary water entering the
collection system
D. To increase wastewater dilution intentionally
I/I investigations identify sources of excess water so corrective measures
can reduce hydraulic loading and improve system capacity.
11. Which observation may indicate significant infiltration into a
sanitary sewer?
A. Flow remaining constant during and after dry weather
B. Decreasing groundwater levels with no flow change
C. Elevated nighttime or base flows during periods of high groundwater
D. Reduced sewer depth after rainfall
Persistent elevated flows during periods of high groundwater can indicate
groundwater entering the sewer through infiltration pathways.
12. What is the primary purpose of sewer flow monitoring?
A. To determine drinking-water chlorine residual
B. To measure treatment-plant sludge age
C. To quantify wastewater flow patterns and identify hydraulic conditions
