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Colorado WW Operator D EXAM 2026/2027 ACTUAL
COMPLETE REAL VERIFIED EXAM QUESTIONS WITH
COMPLETE VERIFIED SOLUTION GUIDE (A+ GRADED
100% CORRECT ANSWERS) NEWEST VERSION!!
During plant rounds, an operator notices that the
secondary effluent is cloudy. The operator should: -
Answer-Check the dissolved oxygen level in the aeration
tank
Given the following data, determine the excess solids (in
lbs) that should be wasted from this activated sludge
system. Target F:M = 0.6 per day, MLVSS = 2500 mg/L,
BOD loading= 18,140 lb/day, Volume of aeration basin = 2
million gallons - Answer-11,467 lb
Conditions in which oxygen is absent but nitrate is present
are referred to as what? - Answer-Anoxic
What characteristics are associated with quality activated
sludge? - Answer-Brown color, some dissolved oxygen
content, and good settling
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The activated sludge process removes soluble BOD from
wastewater by - Answer-Absorption
Why is the sludge returned from the secondary clarifier to
the aeration tank in activated sludge used for nitrification?
- Answer-To provide microorganisms
If fine-bubble diffusers are used to introduce air into a
biological reactor, the surface of the tank will typically have
what type of appearance? - Answer-Mildly agitated,
partially covered with light foam
In an anoxic activated sludge process, oxygen for
facultative bacteria is provided by...? - Answer-Nitrate,
NO3
A small area of dark gray/black sludge in an aeration tank
can be due to aeration equipment failure or ____. -
Answer-The introduction of a septic sidestream
When doing a 30-minute activated sludge settleability test,
a 1000ml Imhoff cone should be used. - Answer-FALSE
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In a conventional activated sludge process, how much
oxygen is required per lb. of BOD removed? - Answer-0.8
to 1.2 lb oxygen /lb BOD
Which of the following conditions would least likely
contribute to rising sludge in secondary clarifiers? -
Answer-Clarifier hydraulic loading
In an activated sludge process bacteria release chemicals
called ________ that break down the food particles that
are adsorbed to the cell wall so that they can be absorbed
by the microorganism. - Answer-Enzymes
Acids should never be added to chlorine solutions
because they - Answer-Cause chlorine gas to be released
Chloramines are ____? - Answer-Combined chlorine
What are the characteristics for chlorine as used in
pollution control? - Answer-Chlorine gas is toxic, corrosive,
and heavier than air
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Chlorine applied minus ____ equals chlorine residual -
Answer-Chlorine demand
Unlike chlorine, UV does not leave what in treated water?
- Answer-A residual
Coliform bacteria are: - Answer-Indicators
A _____ residual is attained after breakpoint chlorination. -
Answer-Free
If you need a chlorine residual of 1 mg/l, how many
pounds of chlorine must be applied each day if the flow is
2.5 mgd and the chlorine demand is 15 mg/l? - Answer-
334 lb/d
A total residual is also referred to as a ______ residual. -
Answer-Combined
Total and fecal coliform are pathogenic. - Answer-FALSE
Colorado WW Operator D EXAM 2026/2027 ACTUAL
COMPLETE REAL VERIFIED EXAM QUESTIONS WITH
COMPLETE VERIFIED SOLUTION GUIDE (A+ GRADED
100% CORRECT ANSWERS) NEWEST VERSION!!
During plant rounds, an operator notices that the
secondary effluent is cloudy. The operator should: -
Answer-Check the dissolved oxygen level in the aeration
tank
Given the following data, determine the excess solids (in
lbs) that should be wasted from this activated sludge
system. Target F:M = 0.6 per day, MLVSS = 2500 mg/L,
BOD loading= 18,140 lb/day, Volume of aeration basin = 2
million gallons - Answer-11,467 lb
Conditions in which oxygen is absent but nitrate is present
are referred to as what? - Answer-Anoxic
What characteristics are associated with quality activated
sludge? - Answer-Brown color, some dissolved oxygen
content, and good settling
,2|Page
The activated sludge process removes soluble BOD from
wastewater by - Answer-Absorption
Why is the sludge returned from the secondary clarifier to
the aeration tank in activated sludge used for nitrification?
- Answer-To provide microorganisms
If fine-bubble diffusers are used to introduce air into a
biological reactor, the surface of the tank will typically have
what type of appearance? - Answer-Mildly agitated,
partially covered with light foam
In an anoxic activated sludge process, oxygen for
facultative bacteria is provided by...? - Answer-Nitrate,
NO3
A small area of dark gray/black sludge in an aeration tank
can be due to aeration equipment failure or ____. -
Answer-The introduction of a septic sidestream
When doing a 30-minute activated sludge settleability test,
a 1000ml Imhoff cone should be used. - Answer-FALSE
,3|Page
In a conventional activated sludge process, how much
oxygen is required per lb. of BOD removed? - Answer-0.8
to 1.2 lb oxygen /lb BOD
Which of the following conditions would least likely
contribute to rising sludge in secondary clarifiers? -
Answer-Clarifier hydraulic loading
In an activated sludge process bacteria release chemicals
called ________ that break down the food particles that
are adsorbed to the cell wall so that they can be absorbed
by the microorganism. - Answer-Enzymes
Acids should never be added to chlorine solutions
because they - Answer-Cause chlorine gas to be released
Chloramines are ____? - Answer-Combined chlorine
What are the characteristics for chlorine as used in
pollution control? - Answer-Chlorine gas is toxic, corrosive,
and heavier than air
, 4|Page
Chlorine applied minus ____ equals chlorine residual -
Answer-Chlorine demand
Unlike chlorine, UV does not leave what in treated water?
- Answer-A residual
Coliform bacteria are: - Answer-Indicators
A _____ residual is attained after breakpoint chlorination. -
Answer-Free
If you need a chlorine residual of 1 mg/l, how many
pounds of chlorine must be applied each day if the flow is
2.5 mgd and the chlorine demand is 15 mg/l? - Answer-
334 lb/d
A total residual is also referred to as a ______ residual. -
Answer-Combined
Total and fecal coliform are pathogenic. - Answer-FALSE
