WATER TREATMENT OIT TEST 300 PRACTICE
QUESTIONS WITH DETAILED EXPLANATIONS
2026
◉ Combined wastewater is defined as:
Answer: sanitary wastewater and stormwater runoff
◉ In general, the total solids content in wastewater is about
Answer: 0.1%
◉ The percentage of suspended solids in wastewater which can be
filtered out of is
Answer: 30%
◉ The percentage of total dissolved solids in wastewater which
cannot be filtered out is
Answer: 70%
◉ Which type of organisms would most probably be associated with
poor treatment or young biomass:
Answer: amoebas
,◉ 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?
Answer: stalked ciliates
◉ Aerobic bacteria will reproduce and live in an environment that
contains only:
Answer: oxygen
◉ Anaerobic bacteria will produce and live only in an environment
that completely lacks:
Answer: free or dissolved oxygen (DO)
◉ The biochemical oxygen demand (BOD) test usually has a specific
time of:
Answer: 5 days
◉ An Imhoff cone measures
Answer: volume of settleable solids
◉ Septic conditions are caused by:
Answer: anaerobic bacteria
, ◉ Scum is usually removed in the ___ treatment stage.
Answer: primary
◉ When domestic wastewater enters natural waters, what species
deplete most of the oxygen?
Answer: aerobic bacteria
◉ Once the oxygen is depleted in a naturally body of water, which
organisms take over?
Answer: anaerobic bacteria
◉ The major gas produced by anaerobic decomposition is
Answer: methane
◉ Another name for primary treatment is:
Answer: sedimentation
◉ Digester gas is ___ when mixed with air in the proper proportions.
Answer: extremely explosive
◉ A pond that is used to treat raw wastewater is called:
Answer: a waste stabilization pond
QUESTIONS WITH DETAILED EXPLANATIONS
2026
◉ Combined wastewater is defined as:
Answer: sanitary wastewater and stormwater runoff
◉ In general, the total solids content in wastewater is about
Answer: 0.1%
◉ The percentage of suspended solids in wastewater which can be
filtered out of is
Answer: 30%
◉ The percentage of total dissolved solids in wastewater which
cannot be filtered out is
Answer: 70%
◉ Which type of organisms would most probably be associated with
poor treatment or young biomass:
Answer: amoebas
,◉ 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?
Answer: stalked ciliates
◉ Aerobic bacteria will reproduce and live in an environment that
contains only:
Answer: oxygen
◉ Anaerobic bacteria will produce and live only in an environment
that completely lacks:
Answer: free or dissolved oxygen (DO)
◉ The biochemical oxygen demand (BOD) test usually has a specific
time of:
Answer: 5 days
◉ An Imhoff cone measures
Answer: volume of settleable solids
◉ Septic conditions are caused by:
Answer: anaerobic bacteria
, ◉ Scum is usually removed in the ___ treatment stage.
Answer: primary
◉ When domestic wastewater enters natural waters, what species
deplete most of the oxygen?
Answer: aerobic bacteria
◉ Once the oxygen is depleted in a naturally body of water, which
organisms take over?
Answer: anaerobic bacteria
◉ The major gas produced by anaerobic decomposition is
Answer: methane
◉ Another name for primary treatment is:
Answer: sedimentation
◉ Digester gas is ___ when mixed with air in the proper proportions.
Answer: extremely explosive
◉ A pond that is used to treat raw wastewater is called:
Answer: a waste stabilization pond
