COLORADO WW OPERATOR D EXAM ACTUAL EXAM QUESTIONS WITH
COMPLETE SOLUTION GUIDE (A+ GRADED 100% VERIFIED) LATEST VERSION
2025!!
______ = BOD, lbs/day / MLVSS, lbs - (Correct Answer)-F/M ratio
In a conventional activated sludge plant, oxygen demand is highest - (Correct Answer)-At the
head end of the tank
Air requirements in an activated sludge tank are governed by - (Correct Answer)-BOD and the
desired removal efficiency, Volatile suspended solids concentration in the aerator, Suspended
solids concentrations of the primary effluent
It is not necessary to be a skilled microbiologist or to be able to identify or count individual
species. Rather the operator needs only to recognize major groups of organisms such as: -
(Correct Answer)-Filamentous bacteria, rotifers, protozoa
In addition to high energy costs, excess DO levels can cause - (Correct Answer)-Damage to floc
particles due to turbulence
Which of the following are key factors in activated sludge nitrification? Check all that apply. -
(Correct Answer)-MCRT, Alkalinity and pH, Temperature, DO, TKN loading
An activated sludge that settles poorly and has an SVI > 250 mL/g is described as what? -
(Correct Answer)-Bulking
Which of the following is a modification of the activated sludge process? - (Correct Answer)-All
of these answers are correct
, 2
Taking samples at different locations along the length and the width of a reactor (aeration tank)
as well as at different depths and analyzing them for solids concentration will verify whether or
not you have....? - (Correct Answer)-Proper mixing in the tank
CCSS stands for: - (Correct Answer)-Clarifier core suspended solids
Because nitrifiers grow slower than other bacteria, sludge ages longer than ____ days are often
needed. - (Correct Answer)-5 days
During plant rounds, an operator notices that the secondary effluent is cloudy. The operator
should: - (Correct 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 - (Correct Answer)-11,467 lb
Conditions in which oxygen is absent but nitrate is present are referred to as what? - (Correct
Answer)-Anoxic
What characteristics are associated with quality activated sludge? - (Correct Answer)-Brown
color, some dissolved oxygen content, and good settling
The activated sludge process removes soluble BOD from wastewater by - (Correct Answer)-
Absorption
, 3
Why is the sludge returned from the secondary clarifier to the aeration tank in activated sludge
used for nitrification? - (Correct 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? - (Correct Answer)-Mildly agitated, partially
covered with light foam
In an anoxic activated sludge process, oxygen for facultative bacteria is provided by...? - (Correct
Answer)-Nitrate, NO3
A small area of dark gray/black sludge in an aeration tank can be due to aeration equipment
failure or ____. - (Correct Answer)-The introduction of a septic sidestream
When doing a 30-minute activated sludge settleability test, a 1000ml Imhoff cone should be
used. - (Correct Answer)-FALSE
In a conventional activated sludge process, how much oxygen is required per lb. of BOD
removed? - (Correct 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? - (Correct Answer)-Clarifier hydraulic loading
, 4
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. - (Correct Answer)-Enzymes
Acids should never be added to chlorine solutions because they - (Correct Answer)-Cause
chlorine gas to be released
Chloramines are ____? - (Correct Answer)-Combined chlorine
What are the characteristics for chlorine as used in pollution control? - (Correct Answer)-
Chlorine gas is toxic, corrosive, and heavier than air
Chlorine applied minus ____ equals chlorine residual - (Correct Answer)-Chlorine demand
Unlike chlorine, UV does not leave what in treated water? - (Correct Answer)-A residual
Coliform bacteria are: - (Correct Answer)-Indicators
A _____ residual is attained after breakpoint chlorination. - (Correct 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? - (Correct Answer)-334 lb/d
COMPLETE SOLUTION GUIDE (A+ GRADED 100% VERIFIED) LATEST VERSION
2025!!
______ = BOD, lbs/day / MLVSS, lbs - (Correct Answer)-F/M ratio
In a conventional activated sludge plant, oxygen demand is highest - (Correct Answer)-At the
head end of the tank
Air requirements in an activated sludge tank are governed by - (Correct Answer)-BOD and the
desired removal efficiency, Volatile suspended solids concentration in the aerator, Suspended
solids concentrations of the primary effluent
It is not necessary to be a skilled microbiologist or to be able to identify or count individual
species. Rather the operator needs only to recognize major groups of organisms such as: -
(Correct Answer)-Filamentous bacteria, rotifers, protozoa
In addition to high energy costs, excess DO levels can cause - (Correct Answer)-Damage to floc
particles due to turbulence
Which of the following are key factors in activated sludge nitrification? Check all that apply. -
(Correct Answer)-MCRT, Alkalinity and pH, Temperature, DO, TKN loading
An activated sludge that settles poorly and has an SVI > 250 mL/g is described as what? -
(Correct Answer)-Bulking
Which of the following is a modification of the activated sludge process? - (Correct Answer)-All
of these answers are correct
, 2
Taking samples at different locations along the length and the width of a reactor (aeration tank)
as well as at different depths and analyzing them for solids concentration will verify whether or
not you have....? - (Correct Answer)-Proper mixing in the tank
CCSS stands for: - (Correct Answer)-Clarifier core suspended solids
Because nitrifiers grow slower than other bacteria, sludge ages longer than ____ days are often
needed. - (Correct Answer)-5 days
During plant rounds, an operator notices that the secondary effluent is cloudy. The operator
should: - (Correct 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 - (Correct Answer)-11,467 lb
Conditions in which oxygen is absent but nitrate is present are referred to as what? - (Correct
Answer)-Anoxic
What characteristics are associated with quality activated sludge? - (Correct Answer)-Brown
color, some dissolved oxygen content, and good settling
The activated sludge process removes soluble BOD from wastewater by - (Correct Answer)-
Absorption
, 3
Why is the sludge returned from the secondary clarifier to the aeration tank in activated sludge
used for nitrification? - (Correct 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? - (Correct Answer)-Mildly agitated, partially
covered with light foam
In an anoxic activated sludge process, oxygen for facultative bacteria is provided by...? - (Correct
Answer)-Nitrate, NO3
A small area of dark gray/black sludge in an aeration tank can be due to aeration equipment
failure or ____. - (Correct Answer)-The introduction of a septic sidestream
When doing a 30-minute activated sludge settleability test, a 1000ml Imhoff cone should be
used. - (Correct Answer)-FALSE
In a conventional activated sludge process, how much oxygen is required per lb. of BOD
removed? - (Correct 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? - (Correct Answer)-Clarifier hydraulic loading
, 4
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. - (Correct Answer)-Enzymes
Acids should never be added to chlorine solutions because they - (Correct Answer)-Cause
chlorine gas to be released
Chloramines are ____? - (Correct Answer)-Combined chlorine
What are the characteristics for chlorine as used in pollution control? - (Correct Answer)-
Chlorine gas is toxic, corrosive, and heavier than air
Chlorine applied minus ____ equals chlorine residual - (Correct Answer)-Chlorine demand
Unlike chlorine, UV does not leave what in treated water? - (Correct Answer)-A residual
Coliform bacteria are: - (Correct Answer)-Indicators
A _____ residual is attained after breakpoint chlorination. - (Correct 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? - (Correct Answer)-334 lb/d
