Colorado WW Operator D Exam Ques ons and answers
With complete solu on RATED A+ NEW EDITION 100%
VERIFIED CORRECT
______ = BOD, lbs/day / MLVSS, lbs - Ans F/M ra o
In a conven onal ac vated sludge plant, oxygen demand is highest - Ans At the head end of
the tank
Air requirements in an ac vated sludge tank are governed by - Ans BOD and the desired
removal efficiency, Vola le suspended solids concentra on in the aerator, Suspended solids
concentra ons of the primary effluent
It is not necessary to be a skilled microbiologist or to be able to iden fy or count individual
species. Rather the operator needs only to recognize major groups of organisms such as: - Ans
Filamentous bacteria, ro fers, protozoa
In addi on to high energy costs, excess DO levels can cause - Ans Damage to floc par cles due
to turbulence
Which of the following are key factors in ac vated sludge nitrifica on? Check all that apply. -
Ans MCRT, Alkalinity and pH, Temperature, DO, TKN loading
An ac vated sludge that se:les poorly and has an SVI > 250 mL/g is described as what? - Ans
Bulking
Which of the following is a modifica on of the ac vated sludge process? - Ans All of these
answers are correct
,Taking samples at different loca ons along the length and the width of a reactor (aera on tank)
as well as at different depths and analyzing them for solids concentra on will verify whether or
not you have....? - Ans Proper mixing in the tank
CCSS stands for: - Ans Clarifier core suspended solids
Because nitrifiers grow slower than other bacteria, sludge ages longer than ____ days are oCen
needed. - Ans 5 days
During plant rounds, an operator no ces that the secondary effluent is cloudy. The operator
should: - Ans Check the dissolved oxygen level in the aera on tank
Given the following data, determine the excess solids (in lbs) that should be wasted from this
ac vated sludge system. Target F:M = 0.6 per day, MLVSS = 2500 mg/L, BOD loading= 18,140
lb/day, Volume of aera on basin = 2 million gallons - Ans 11,467 lb
Condi ons in which oxygen is absent but nitrate is present are referred to as what? - Ans
Anoxic
What characteris cs are associated with quality ac vated sludge? - Ans Brown color, some
dissolved oxygen content, and good se:ling
The ac vated sludge process removes soluble BOD from wastewater by - Ans Absorp on
Why is the sludge returned from the secondary clarifier to the aera on tank in ac vated sludge
used for nitrifica on? - Ans 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? - Ans Mildly agitated, par ally covered with light
foam
In an anoxic ac vated sludge process, oxygen for faculta ve bacteria is provided by...? - Ans
Nitrate, NO3
A small area of dark gray/black sludge in an aera on tank can be due to aera on equipment
failure or ____. - Ans The introduc on of a sep c sidestream
When doing a 30-minute ac vated sludge se:leability test, a 1000ml Imhoff cone should be
used. - Ans FALSE
In a conven onal ac vated sludge process, how much oxygen is required per lb. of BOD
removed? - Ans 0.8 to 1.2 lb oxygen /lb BOD
Which of the following condi ons would least likely contribute to rising sludge in secondary
clarifiers? - Ans Clarifier hydraulic loading
In an ac vated sludge process bacteria release chemicals called ________ that break down the
food par cles that are adsorbed to the cell wall so that they can be absorbed by the
microorganism. - Ans Enzymes
Acids should never be added to chlorine solu ons because they - Ans Cause chlorine gas to be
released
Chloramines are ____? - Ans Combined chlorine
, What are the characteris cs for chlorine as used in pollu on control? - Ans Chlorine gas is
toxic, corrosive, and heavier than air
Chlorine applied minus ____ equals chlorine residual - Ans Chlorine demand
Unlike chlorine, UV does not leave what in treated water? - Ans A residual
Coliform bacteria are: - Ans Indicators
A _____ residual is a:ained aCer breakpoint chlorina on. - Ans 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? - Ans 334 lb/d
A total residual is also referred to as a ______ residual. - Ans Combined
Total and fecal coliform are pathogenic. - Ans FALSE
_________ = flow, mgd x chlorine dosage, mg/L x 8.34 lb/gal. - Ans Feed Rate/Dose (lbs/day)
Sodium hypochlorite is manufactured by the reac on of gaseous or liquid chlorine with a
solu on of _________ _________ to produce a liquid containing NaOCl. - Ans Sodium
hypochlorite
At concentra ons less than _____, chlorine gas is not detectable by the human sense of smell. -
Ans 1 ppm
With complete solu on RATED A+ NEW EDITION 100%
VERIFIED CORRECT
______ = BOD, lbs/day / MLVSS, lbs - Ans F/M ra o
In a conven onal ac vated sludge plant, oxygen demand is highest - Ans At the head end of
the tank
Air requirements in an ac vated sludge tank are governed by - Ans BOD and the desired
removal efficiency, Vola le suspended solids concentra on in the aerator, Suspended solids
concentra ons of the primary effluent
It is not necessary to be a skilled microbiologist or to be able to iden fy or count individual
species. Rather the operator needs only to recognize major groups of organisms such as: - Ans
Filamentous bacteria, ro fers, protozoa
In addi on to high energy costs, excess DO levels can cause - Ans Damage to floc par cles due
to turbulence
Which of the following are key factors in ac vated sludge nitrifica on? Check all that apply. -
Ans MCRT, Alkalinity and pH, Temperature, DO, TKN loading
An ac vated sludge that se:les poorly and has an SVI > 250 mL/g is described as what? - Ans
Bulking
Which of the following is a modifica on of the ac vated sludge process? - Ans All of these
answers are correct
,Taking samples at different loca ons along the length and the width of a reactor (aera on tank)
as well as at different depths and analyzing them for solids concentra on will verify whether or
not you have....? - Ans Proper mixing in the tank
CCSS stands for: - Ans Clarifier core suspended solids
Because nitrifiers grow slower than other bacteria, sludge ages longer than ____ days are oCen
needed. - Ans 5 days
During plant rounds, an operator no ces that the secondary effluent is cloudy. The operator
should: - Ans Check the dissolved oxygen level in the aera on tank
Given the following data, determine the excess solids (in lbs) that should be wasted from this
ac vated sludge system. Target F:M = 0.6 per day, MLVSS = 2500 mg/L, BOD loading= 18,140
lb/day, Volume of aera on basin = 2 million gallons - Ans 11,467 lb
Condi ons in which oxygen is absent but nitrate is present are referred to as what? - Ans
Anoxic
What characteris cs are associated with quality ac vated sludge? - Ans Brown color, some
dissolved oxygen content, and good se:ling
The ac vated sludge process removes soluble BOD from wastewater by - Ans Absorp on
Why is the sludge returned from the secondary clarifier to the aera on tank in ac vated sludge
used for nitrifica on? - Ans 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? - Ans Mildly agitated, par ally covered with light
foam
In an anoxic ac vated sludge process, oxygen for faculta ve bacteria is provided by...? - Ans
Nitrate, NO3
A small area of dark gray/black sludge in an aera on tank can be due to aera on equipment
failure or ____. - Ans The introduc on of a sep c sidestream
When doing a 30-minute ac vated sludge se:leability test, a 1000ml Imhoff cone should be
used. - Ans FALSE
In a conven onal ac vated sludge process, how much oxygen is required per lb. of BOD
removed? - Ans 0.8 to 1.2 lb oxygen /lb BOD
Which of the following condi ons would least likely contribute to rising sludge in secondary
clarifiers? - Ans Clarifier hydraulic loading
In an ac vated sludge process bacteria release chemicals called ________ that break down the
food par cles that are adsorbed to the cell wall so that they can be absorbed by the
microorganism. - Ans Enzymes
Acids should never be added to chlorine solu ons because they - Ans Cause chlorine gas to be
released
Chloramines are ____? - Ans Combined chlorine
, What are the characteris cs for chlorine as used in pollu on control? - Ans Chlorine gas is
toxic, corrosive, and heavier than air
Chlorine applied minus ____ equals chlorine residual - Ans Chlorine demand
Unlike chlorine, UV does not leave what in treated water? - Ans A residual
Coliform bacteria are: - Ans Indicators
A _____ residual is a:ained aCer breakpoint chlorina on. - Ans 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? - Ans 334 lb/d
A total residual is also referred to as a ______ residual. - Ans Combined
Total and fecal coliform are pathogenic. - Ans FALSE
_________ = flow, mgd x chlorine dosage, mg/L x 8.34 lb/gal. - Ans Feed Rate/Dose (lbs/day)
Sodium hypochlorite is manufactured by the reac on of gaseous or liquid chlorine with a
solu on of _________ _________ to produce a liquid containing NaOCl. - Ans Sodium
hypochlorite
At concentra ons less than _____, chlorine gas is not detectable by the human sense of smell. -
Ans 1 ppm
