Colorado WW Operator D Exam ACTUAL EXAM QUESTIONS WITH
Colorado WW Operator D Exam
COMPLETE SOLUTION GUIDE (A+ GRADED 100% VERIFIED) LATEST
Study online at https://quizlet.com/_a77etr
VERSION 2025!!
1. ______ = BOD, lbs/day / MLVSS, lbs F/M ratio
2. In a conventional activated sludge plant, oxygen de- At the head end of the tank
mand is highest
3. Air requirements in an activated sludge tank are gov- BOD and the desired re-
erned by moval efficiency, Volatile
suspended solids concen-
tration in the aerator, Sus-
pended solids concentra-
tions of the primary effluent
4. It is not necessary to be a skilled microbiologist or to Filamentous bacteria, ro-
be able to identify or count individual species. Rather tifers, protozoa
the operator needs only to recognize major groups
of organisms such as:
5. In addition to high energy costs, excess DO levels can Damage to floc particles
cause due to turbulence
6. Which of the following are key factors in activated MCRT, Alkalinity and pH,
sludge nitrification? Check all that apply. Temperature, DO, TKN
loading
7. An activated sludge that settles poorly and has an SVI Bulking
> 250 mL/g is described as what?
8. Which of the following is a modification of the activat- All of these answers are
ed sludge process? correct
9. Taking samples at different locations along the Proper mixing in the tank
length and the width of a reactor (aeration tank) as
well as at different depths and analyzing them for
, Colorado WW Operator D Exam
Study online at https://quizlet.com/_a77etr
solids concentration will verify whether or not you
have....?
10. CCSS stands for: Clarifier core suspended
solids
11. Because nitrifiers grow slower than other bacteria, 5 days
sludge ages longer than ____ days are often needed.
12. During plant rounds, an operator notices that the Check the dissolved oxygen
secondary effluent is cloudy. The operator should: level in the aeration tank
13. Given the following data, determine the excess solids 11,467 lb
(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
14. Conditions in which oxygen is absent but nitrate is Anoxic
present are referred to as what?
15. What characteristics are associated with quality acti- Brown color, some dis-
vated sludge? solved oxygen content, and
good settling
16. The activated sludge process removes soluble BOD Absorption
from wastewater by
17. Why is the sludge returned from the secondary clar- To provide microorganisms
ifier to the aeration tank in activated sludge used for
nitrification?
18. Mildly agitated, partially
covered with light foam
, Colorado WW Operator D Exam
Study online at https://quizlet.com/_a77etr
If fine-bubble diffusers are used to introduce air into
a biological reactor, the surface of the tank will typi-
cally have what type of appearance?
19. In an anoxic activated sludge process, oxygen for Nitrate, NO3
facultative bacteria is provided by...?
20. A small area of dark gray/black sludge in an aeration The introduction of a septic
tank can be due to aeration equipment failure or ____. sidestream
21. When doing a 30-minute activated sludge settleabili- FALSE
ty test, a 1000ml Imhoff cone should be used.
22. In a conventional activated sludge process, how 0.8 to 1.2 lb oxygen /lb
much oxygen is required per lb. of BOD removed? BOD
23. Which of the following conditions would least likely Clarifier hydraulic loading
contribute to rising sludge in secondary clarifiers?
24. In an activated sludge process bacteria release chem- Enzymes
icals called ________ that break down the food particles
that are adsorbed to the cell wall so that they can be
absorbed by the microorganism.
25. Acids should never be added to chlorine solutions Cause chlorine gas to be
because they released
26. Chloramines are ____? Combined chlorine
27. What are the characteristics for chlorine as used in Chlorine gas is toxic, corro-
pollution control? sive, and heavier than air
28. Chlorine applied minus ____ equals chlorine residual Chlorine demand
, Colorado WW Operator D Exam
Study online at https://quizlet.com/_a77etr
29. Unlike chlorine, UV does not leave what in treated A residual
water?
30. Coliform bacteria are: Indicators
31. A _____ residual is attained after breakpoint chlorina- Free
tion.
32. If you need a chlorine residual of 1 mg/l, how many 334 lb/d
pounds of chlorine must be applied each day if the
flow is 2.5 mgd and the chlorine demand is 15 mg/l?
33. A total residual is also referred to as a ______ residual. Combined
34. Total and fecal coliform are pathogenic. FALSE
35. _________ = flow, mgd x chlorine dosage, mg/L x 8.34 Feed Rate/Dose (lbs/day)
lb/gal.
36. Sodium hypochlorite is manufactured by the reac- Sodium hypochlorite
tion of gaseous or liquid chlorine with a solution
of _________ _________ to produce a liquid containing
NaOCl.
37. At concentrations less than _____, chlorine gas is not 1 ppm
detectable by the human sense of smell.
38. A treatment plant uses sulfur dioxide to dechlorinate 100 lb/day
effluent. An operator needs to adjust the sulfonator
so that the dosing concentration is 1.5 mg/l more
than the chlorine residual. Based on the following
information, what should the sulfonator feed rate be:
design flow = 5 mgd; chlorine dosage rate = 4 mg/l;
chlorine residual = 0.9 mg/l
Colorado WW Operator D Exam
COMPLETE SOLUTION GUIDE (A+ GRADED 100% VERIFIED) LATEST
Study online at https://quizlet.com/_a77etr
VERSION 2025!!
1. ______ = BOD, lbs/day / MLVSS, lbs F/M ratio
2. In a conventional activated sludge plant, oxygen de- At the head end of the tank
mand is highest
3. Air requirements in an activated sludge tank are gov- BOD and the desired re-
erned by moval efficiency, Volatile
suspended solids concen-
tration in the aerator, Sus-
pended solids concentra-
tions of the primary effluent
4. It is not necessary to be a skilled microbiologist or to Filamentous bacteria, ro-
be able to identify or count individual species. Rather tifers, protozoa
the operator needs only to recognize major groups
of organisms such as:
5. In addition to high energy costs, excess DO levels can Damage to floc particles
cause due to turbulence
6. Which of the following are key factors in activated MCRT, Alkalinity and pH,
sludge nitrification? Check all that apply. Temperature, DO, TKN
loading
7. An activated sludge that settles poorly and has an SVI Bulking
> 250 mL/g is described as what?
8. Which of the following is a modification of the activat- All of these answers are
ed sludge process? correct
9. Taking samples at different locations along the Proper mixing in the tank
length and the width of a reactor (aeration tank) as
well as at different depths and analyzing them for
, Colorado WW Operator D Exam
Study online at https://quizlet.com/_a77etr
solids concentration will verify whether or not you
have....?
10. CCSS stands for: Clarifier core suspended
solids
11. Because nitrifiers grow slower than other bacteria, 5 days
sludge ages longer than ____ days are often needed.
12. During plant rounds, an operator notices that the Check the dissolved oxygen
secondary effluent is cloudy. The operator should: level in the aeration tank
13. Given the following data, determine the excess solids 11,467 lb
(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
14. Conditions in which oxygen is absent but nitrate is Anoxic
present are referred to as what?
15. What characteristics are associated with quality acti- Brown color, some dis-
vated sludge? solved oxygen content, and
good settling
16. The activated sludge process removes soluble BOD Absorption
from wastewater by
17. Why is the sludge returned from the secondary clar- To provide microorganisms
ifier to the aeration tank in activated sludge used for
nitrification?
18. Mildly agitated, partially
covered with light foam
, Colorado WW Operator D Exam
Study online at https://quizlet.com/_a77etr
If fine-bubble diffusers are used to introduce air into
a biological reactor, the surface of the tank will typi-
cally have what type of appearance?
19. In an anoxic activated sludge process, oxygen for Nitrate, NO3
facultative bacteria is provided by...?
20. A small area of dark gray/black sludge in an aeration The introduction of a septic
tank can be due to aeration equipment failure or ____. sidestream
21. When doing a 30-minute activated sludge settleabili- FALSE
ty test, a 1000ml Imhoff cone should be used.
22. In a conventional activated sludge process, how 0.8 to 1.2 lb oxygen /lb
much oxygen is required per lb. of BOD removed? BOD
23. Which of the following conditions would least likely Clarifier hydraulic loading
contribute to rising sludge in secondary clarifiers?
24. In an activated sludge process bacteria release chem- Enzymes
icals called ________ that break down the food particles
that are adsorbed to the cell wall so that they can be
absorbed by the microorganism.
25. Acids should never be added to chlorine solutions Cause chlorine gas to be
because they released
26. Chloramines are ____? Combined chlorine
27. What are the characteristics for chlorine as used in Chlorine gas is toxic, corro-
pollution control? sive, and heavier than air
28. Chlorine applied minus ____ equals chlorine residual Chlorine demand
, Colorado WW Operator D Exam
Study online at https://quizlet.com/_a77etr
29. Unlike chlorine, UV does not leave what in treated A residual
water?
30. Coliform bacteria are: Indicators
31. A _____ residual is attained after breakpoint chlorina- Free
tion.
32. If you need a chlorine residual of 1 mg/l, how many 334 lb/d
pounds of chlorine must be applied each day if the
flow is 2.5 mgd and the chlorine demand is 15 mg/l?
33. A total residual is also referred to as a ______ residual. Combined
34. Total and fecal coliform are pathogenic. FALSE
35. _________ = flow, mgd x chlorine dosage, mg/L x 8.34 Feed Rate/Dose (lbs/day)
lb/gal.
36. Sodium hypochlorite is manufactured by the reac- Sodium hypochlorite
tion of gaseous or liquid chlorine with a solution
of _________ _________ to produce a liquid containing
NaOCl.
37. At concentrations less than _____, chlorine gas is not 1 ppm
detectable by the human sense of smell.
38. A treatment plant uses sulfur dioxide to dechlorinate 100 lb/day
effluent. An operator needs to adjust the sulfonator
so that the dosing concentration is 1.5 mg/l more
than the chlorine residual. Based on the following
information, what should the sulfonator feed rate be:
design flow = 5 mgd; chlorine dosage rate = 4 mg/l;
chlorine residual = 0.9 mg/l
