WasteWater Operator Certification Final Grade 1 Exam
2025/2026 Accurate Actual Exam Questions and Verified
Correct Answers | Guaranteed Pass.
RATED
Question. What is the most common reason for a wastewater to contain intermittent large
amounts of sand, gravel, and grit?
a. groundwater infiltration
b. storm events
c. cement company discharges
d. refinery discharges - Correct Ans ✓✓ storm events
Question. Combined wastewater is defined as
a. domestic wastewater and industrial wastewater
b. sanitary wastewater
c. domestic wastewater and stormwater runoff
d. sanitary wastewater and stormwater runoff - Correct Ans ✓✓ sanitary wastewater and stormwater runoff
Question. In general, the solids content in wastewater is about
a. 0.1%
b. 0.6%
c. 1%
d. 2.5% - Correct Ans ✓✓ 0.1%
Question. In general, what is the percentage of suspended solids in the total amount of solids?
a. 30%
b. 35%
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,c. 45%
d. 55% - Correct Ans ✓✓ 30%
Question. Generally, the percentage of dissolved solids in the amount of total solids is about
a. 45%
b. 55%
c. 65%
d. 70% - Correct Ans ✓✓ 70%
Question. Which type of organisms would most probably be associated with poor treatment or young
biomass?
a. amoebas
b. free-swimming ciliates
c. rotifers
d. stalked ciliates - Correct Ans ✓✓ amoebas
Question. Which type of organisms would most probably be associated with very clear plant effluent, low
biochemical oxygen demand (BOD), and low amounts of suspended solids?
a. free-swimming ciliates
b. stalked ciliates
c. amoebas
d. rotifers - Correct Ans ✓✓ stalked ciliates
Question. Aerobic bacteria will reproduce and live in an environment that contains only
a. hydrogen sulfide
b. oxygen
c. water
d. methane - Correct Ans ✓✓ oxygen
Question. Anaerobic bacteria will reproduce and live only in an environment that completely
lacks
a. free or dissolved nitrates
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,b. dissolved methane
c. dissolved hydrogen sulfide
d. free or dissolved oxygen (DO) - Correct Ans ✓✓ free or dissolved oxygen (DO)
Question. The biochemical oxygen demand (BOD) test usually has a specific time of
a. 2 days
b. 3 days
c. 5 days
d. 10 days - Correct Ans ✓✓ 5 days
Question. An Imhoff cone measures
a. volume of settleable solids
b. how fast sludge water will filter through a membrane
c. depth of transparency in a digester
d. sludge carry-over from a digester - Correct Ans ✓✓ volume of settleable solids
Question. Septic conditions are caused by
a. fungi
b. molds
c. anaerobic bacteria
d. hydrogen sulfide accumulation - Correct Ans ✓✓ anaerobic bacteria
Question. Scum is usually removed in the _______ treatment stage.
a. primary
b. secondary
c. biological
d. chemical - Correct Ans ✓✓ primary
Question. When domestic wastewater enters natural waters, what species deplete most of the oxygen?
a. anaerobic bacteria
b. aerobic bacteria
3|Page
, c. protozoans
d. rotifers - Correct Ans ✓✓ aerobic bacteria
Question. Once the oxygen is depleted in a natural body of water, which organisms take over?
a. flagellates
b. sporozoans
c. anaerobic bacteria
d. coliform bacteria - Correct Ans ✓✓ anaerobic bacteria
Question. The major gas produced by anaerobic decomposition is
a. methane
b. carbon dioxide
c. nitrogen
d. hydrogen sulfide - Correct Ans ✓✓ methane
Question. Another name for primary treatment is
a. chemical treatment
b. sedimentation
c. grit removal
d. biological treatment - Correct Ans ✓✓ sedimentation
Question. Digester gas is _______ when mixed with air in the proper proportions.
a. extremely toxic and moderately explosive
b. extremely explosive
c. slightly toxic and explosive
d. slightly explosive when there is an ignition source and - Correct Ans ✓✓ extremely explosive
Question. A pond that is used to treat raw wastewater is called
a. an oxidation pond
b. a facultative pond
c. a waste stabilization pond
4|Page
2025/2026 Accurate Actual Exam Questions and Verified
Correct Answers | Guaranteed Pass.
RATED
Question. What is the most common reason for a wastewater to contain intermittent large
amounts of sand, gravel, and grit?
a. groundwater infiltration
b. storm events
c. cement company discharges
d. refinery discharges - Correct Ans ✓✓ storm events
Question. Combined wastewater is defined as
a. domestic wastewater and industrial wastewater
b. sanitary wastewater
c. domestic wastewater and stormwater runoff
d. sanitary wastewater and stormwater runoff - Correct Ans ✓✓ sanitary wastewater and stormwater runoff
Question. In general, the solids content in wastewater is about
a. 0.1%
b. 0.6%
c. 1%
d. 2.5% - Correct Ans ✓✓ 0.1%
Question. In general, what is the percentage of suspended solids in the total amount of solids?
a. 30%
b. 35%
1|Page
,c. 45%
d. 55% - Correct Ans ✓✓ 30%
Question. Generally, the percentage of dissolved solids in the amount of total solids is about
a. 45%
b. 55%
c. 65%
d. 70% - Correct Ans ✓✓ 70%
Question. Which type of organisms would most probably be associated with poor treatment or young
biomass?
a. amoebas
b. free-swimming ciliates
c. rotifers
d. stalked ciliates - Correct Ans ✓✓ amoebas
Question. Which type of organisms would most probably be associated with very clear plant effluent, low
biochemical oxygen demand (BOD), and low amounts of suspended solids?
a. free-swimming ciliates
b. stalked ciliates
c. amoebas
d. rotifers - Correct Ans ✓✓ stalked ciliates
Question. Aerobic bacteria will reproduce and live in an environment that contains only
a. hydrogen sulfide
b. oxygen
c. water
d. methane - Correct Ans ✓✓ oxygen
Question. Anaerobic bacteria will reproduce and live only in an environment that completely
lacks
a. free or dissolved nitrates
2|Page
,b. dissolved methane
c. dissolved hydrogen sulfide
d. free or dissolved oxygen (DO) - Correct Ans ✓✓ free or dissolved oxygen (DO)
Question. The biochemical oxygen demand (BOD) test usually has a specific time of
a. 2 days
b. 3 days
c. 5 days
d. 10 days - Correct Ans ✓✓ 5 days
Question. An Imhoff cone measures
a. volume of settleable solids
b. how fast sludge water will filter through a membrane
c. depth of transparency in a digester
d. sludge carry-over from a digester - Correct Ans ✓✓ volume of settleable solids
Question. Septic conditions are caused by
a. fungi
b. molds
c. anaerobic bacteria
d. hydrogen sulfide accumulation - Correct Ans ✓✓ anaerobic bacteria
Question. Scum is usually removed in the _______ treatment stage.
a. primary
b. secondary
c. biological
d. chemical - Correct Ans ✓✓ primary
Question. When domestic wastewater enters natural waters, what species deplete most of the oxygen?
a. anaerobic bacteria
b. aerobic bacteria
3|Page
, c. protozoans
d. rotifers - Correct Ans ✓✓ aerobic bacteria
Question. Once the oxygen is depleted in a natural body of water, which organisms take over?
a. flagellates
b. sporozoans
c. anaerobic bacteria
d. coliform bacteria - Correct Ans ✓✓ anaerobic bacteria
Question. The major gas produced by anaerobic decomposition is
a. methane
b. carbon dioxide
c. nitrogen
d. hydrogen sulfide - Correct Ans ✓✓ methane
Question. Another name for primary treatment is
a. chemical treatment
b. sedimentation
c. grit removal
d. biological treatment - Correct Ans ✓✓ sedimentation
Question. Digester gas is _______ when mixed with air in the proper proportions.
a. extremely toxic and moderately explosive
b. extremely explosive
c. slightly toxic and explosive
d. slightly explosive when there is an ignition source and - Correct Ans ✓✓ extremely explosive
Question. A pond that is used to treat raw wastewater is called
a. an oxidation pond
b. a facultative pond
c. a waste stabilization pond
4|Page
