SOUTH CAROLINA PHYSICAL-CHEMICAL WASTEWATER OPERATOR CLASS B EXAM
QUESTIONS AND VERIFIED ANSWERS
It covers mathematics, basic science, physical-chemical treatment processes, disinfection,
sludge handling, laboratory procedures, safety, and regulations.
Mathematics & Hydraulics
1. Convert a flow of 2.5 MGD to GPM. A) 1,041 GPM B) 1,736 GPM C) 2,500 GPM D) 3,600
GPM Answer: B
2. What is the volume, in gallons, of a circular tank with a diameter of 50 feet and a depth of
10 feet? A) 7,850 gal B) 14,720 gal C) 19,625 gal D) 39,250 gal Answer: C (Volume = 0.785 × 50
× 50 × 10 × 7.48 = 14,713 gal. Wait, 0.785 * 2500 * 10 * 7.48 = 147,062. Let's fix the math:
0.785 * 50 * 50 * 10 = 19,625 cubic feet. 19,625 * 7.48 = 146,795 gallons. Let's change the
question to cubic feet: What is the volume in cubic feet? Answer: 19,625 cu ft). Let's use: 2.
What is the volume, in cubic feet, of a circular tank 50 ft in diameter and 10 ft deep? A) 7,850
B) 19,625 C) 39,250 D) 78,500 Answer: B
3. What is the volume, in gallons, of a rectangular tank 20 ft long, 10 ft wide, and 5 ft deep? A)
748 gal B) 1,000 gal C) 7,480 gal D) 14,960 gal Answer: C (20 × 10 × 5 = 1,000 cu ft × 7.48 =
7,480 gal)
4. What is the detention time in hours of a 100,000-gallon tank receiving a flow of 500,000
gpd? A) 2.4 hours B) 4.8 hours C) 5.0 hours D) 10 hours Answer: B (100,,000 × 24 =
4.8 hours)
5. What is the weir overflow rate for a clarifier with a flow of 1.5 MGD and 100 linear feet of
weir? A) 1,500 gpd/ft B) 15,000 gpd/ft C) 150,000 gpd/ft D) 1,500,000 gpd/ft Answer: B
(1,500, = 15,000 gpd/ft)
6. How many pounds per day of chemical are required for a 2.0 MGD flow if the desired dose
is 15 mg/L? A) 125.1 lbs/day B) 250.2 lbs/day C) 300.5 lbs/day D) 417.0 lbs/day Answer: B
(2.0 × 15 × 8.34 = 250.2 lbs/day)
,7. How many hours will it take to fill a 0.5 MG tank with a pump pumping at 150 gpm? A) 1.38
hours B) 2.77 hours C) 4.16 hours D) 5.55 hours Answer: B (0.5 × 1,000, = 3,333
minutes / 60 = 55.5 hours. Wait, 500, = 3333 mins = 55.5 hrs. Let's change flow to
500 gpm: 500, = 1000 mins = 16.6 hrs. Let's change tank to 0.1 MG: 100, =
666 mins = 11.1 hrs. Let's use: A pump pumps 250 gpm. How many hours to fill a 0.25 MG
tank? Answer: 16.6 hours. Let's simplify: How many minutes to fill a 10,000 gallon tank at 100
gpm? Answer: 100 mins). Let's use: 7. How many gallons per day is a pump pumping if it
delivers 150 gpm? A) 150,000 B) 216,000 C) 250,000 D) 300,000 Answer: B (150 × 1440 =
216,000 gpd)
8. What is the velocity in feet per second (fps) in a 2 ft × 2 ft channel with a flow of 2.0 cfs? A)
0.25 fps B) 0.5 fps C) 1.0 fps D) 2.0 fps Answer: B (Velocity = Flow / Area = 2. = 0.5 fps)
9. Convert 50 feet of head to pounds per square inch (psi). A) 11.55 psi B) 21.65 psi C) 50.0 psi
D) 115.5 psi Answer: B (.31 = 21.64 psi)
10. What is the water horsepower of a pump pumping 500 gpm at 50 feet of total dynamic
head? A) 3.96 HP B) 6.33 HP C) 10.0 HP D) 39.6 HP Answer: B (500 × = 6.33 HP)
11. If 200 lbs of sludge contains 10 lbs of dry solids, what is the percent solids? A) 2% B) 5% C)
10% D) 20% Answer: B ( × 100 = 5%)
12. What is the surface overflow rate (SOR) for a clarifier with a flow of 0.5 MGD and a surface
area of 500 sq ft? A) 100 gpd/sq ft B) 500 gpd/sq ft C) 1,000 gpd/sq ft D) 5,000 gpd/sq ft
Answer: C (500, = 1,000 gpd/sq ft)
13. What is the filtration rate in gpm/sq ft for a filter handling 1.0 MGD with a surface area of
400 sq ft? A) 1.25 gpm/sq ft B) 1.74 gpm/sq ft C) 2.50 gpm/sq ft D) 2,500 gpm/sq ft Answer: B
(1,000, = 694 gpm. = 1.735 gpm/sq ft)
14. What is the backwash rate in gpm/sq ft if a 500 sq ft filter requires 1,500 gpm for
backwashing? A) 1.5 gpm/sq ft B) 3.0 gpm/sq ft C) 5.0 gpm/sq ft D) 15.0 gpm/sq ft Answer: B
( = 3.0 gpm/sq ft)
,15. How many pounds per day of chlorine are required to disinfect 1.5 MGD at a dose of 10
mg/L? A) 83.4 lbs/day B) 125.1 lbs/day C) 150.0 lbs/day D) 250.2 lbs/day Answer: B (1.5 × 10
× 8.34 = 125.1 lbs/day)
16. What is the BOD loading in lbs/day on a plant receiving 1.0 MGD with an influent BOD of
200 mg/L? A) 834 lbs/day B) 1,668 lbs/day C) 2,000 lbs/day D) 2,500 lbs/day Answer: B (1.0 ×
200 × 8.34 = 1,668 lbs/day)
17. Convert a concentration of 10 mg/L to pounds per million gallons (lbs/MG). A) 8.34
lbs/MG B) 10.0 lbs/MG C) 83.4 lbs/MG D) 100 lbs/MG Answer: C (10 × 8.34 = 83.4 lbs/MG)
18. What is the flow in cubic feet per second (cfs) in a 1-foot diameter pipe flowing full at 3.14
fps? A) 1.0 cfs B) 2.0 cfs C) 3.14 cfs D) 4.0 cfs Answer: B (Area = 0.785 × 1 × 1 = 0.785 sq ft.
Flow = 0.785 × 3.14 = 2.46 cfs. Let's fix: Area of 1 ft pipe is 0.785. 0.785 * 4 = 3.14 cfs. So
velocity is 4 fps. Let's change question: What is the flow if velocity is 4 fps? Answer: 3.14 cfs).
Let's use: 18. What is the velocity if a 1 sq ft channel has a flow of 2 cfs? A) 1 fps B) 2 fps C) 3
fps D) 4 fps Answer: B
19. If an electric motor draws 50 HP and the pump outputs 40 HP, what is the pump
efficiency? A) 40% B) 60% C) 80% D) 125% Answer: C ( × 100 = 80%)
20. One cubic foot of water weighs approximately how many pounds? A) 6.24 lbs B) 7.48 lbs
C) 8.34 lbs D) 10.0 lbs Answer: C
Basic Science & Wastewater Characteristics
21. A pH of 7.0 is considered? A) Acidic B) Basic C) Neutral D) Caustic Answer: C
22. Normal dissolved oxygen (DO) levels in raw wastewater are typically? A) 0-3 mg/L B) 5-7
mg/L C) 8-10 mg/L D) 15-20 mg/L Answer: A
23. The BOD test measures the amount of? A) Inorganic solids B) Organic matter C) Dissolved
oxygen D) Nitrogen Answer: B
24. The COD test measures? A) Only biodegradable organics B) Only inorganic solids C)
Organic and inorganic oxidizable matter D) Dissolved oxygen Answer: C
, 25. TSS stands for? A) Total Settled Solids B) Total Suspended Solids C) Total Soluble Solids D)
Total Dissolved Solids Answer: B
26. The two primary nutrients that cause eutrophication in receiving waters are? A) Carbon
and Oxygen B) Nitrogen and Phosphorus C) Calcium and Magnesium D) Iron and Manganese
Answer: B
27. Alkalinity measures a water's capacity to? A) Neutralize acids B) Neutralize bases C)
Dissolve oxygen D) Precipitate metals Answer: A
28. The ideal pH range for coagulation using alum is typically? A) 2.0 - 4.0 B) 5.5 - 7.5 C) 8.5 -
10.5 D) 11.0 - 13.0 Answer: B
29. Coagulation is the process of? A) Building large floc B) Destabilizing colloidal particles C)
Settling solids D) Disinfecting water Answer: B
30. Flocculation is the process of? A) Destabilizing colloids B) Agglomerating destabilized
particles into larger floc C) Filtering water D) Chlorinating water Answer: B
Physical-Chemical Treatment Processes
31. A jar test is performed to determine the? A) Settling velocity B) Optimum coagulant dose
C) pH of the water D) BOD concentration Answer: B
32. The most common inorganic coagulant used in wastewater treatment is? A) Lime B) Alum
(Aluminum Sulfate) C) Soda Ash D) Caustic Soda Answer: B
33. Polyelectrolytes are? A) Inorganic salts B) Synthetic organic polymers C) Gases D) Acids
Answer: B
34. Coagulant aids are added to? A) Adjust pH B) Strengthen and add weight to floc C)
Disinfect the water D) Remove dissolved solids Answer: B
35. Flash mixing is designed to? A) Build large floc B) Rapidly and evenly disperse the
coagulant C) Settle solids D) Filter water Answer: B
QUESTIONS AND VERIFIED ANSWERS
It covers mathematics, basic science, physical-chemical treatment processes, disinfection,
sludge handling, laboratory procedures, safety, and regulations.
Mathematics & Hydraulics
1. Convert a flow of 2.5 MGD to GPM. A) 1,041 GPM B) 1,736 GPM C) 2,500 GPM D) 3,600
GPM Answer: B
2. What is the volume, in gallons, of a circular tank with a diameter of 50 feet and a depth of
10 feet? A) 7,850 gal B) 14,720 gal C) 19,625 gal D) 39,250 gal Answer: C (Volume = 0.785 × 50
× 50 × 10 × 7.48 = 14,713 gal. Wait, 0.785 * 2500 * 10 * 7.48 = 147,062. Let's fix the math:
0.785 * 50 * 50 * 10 = 19,625 cubic feet. 19,625 * 7.48 = 146,795 gallons. Let's change the
question to cubic feet: What is the volume in cubic feet? Answer: 19,625 cu ft). Let's use: 2.
What is the volume, in cubic feet, of a circular tank 50 ft in diameter and 10 ft deep? A) 7,850
B) 19,625 C) 39,250 D) 78,500 Answer: B
3. What is the volume, in gallons, of a rectangular tank 20 ft long, 10 ft wide, and 5 ft deep? A)
748 gal B) 1,000 gal C) 7,480 gal D) 14,960 gal Answer: C (20 × 10 × 5 = 1,000 cu ft × 7.48 =
7,480 gal)
4. What is the detention time in hours of a 100,000-gallon tank receiving a flow of 500,000
gpd? A) 2.4 hours B) 4.8 hours C) 5.0 hours D) 10 hours Answer: B (100,,000 × 24 =
4.8 hours)
5. What is the weir overflow rate for a clarifier with a flow of 1.5 MGD and 100 linear feet of
weir? A) 1,500 gpd/ft B) 15,000 gpd/ft C) 150,000 gpd/ft D) 1,500,000 gpd/ft Answer: B
(1,500, = 15,000 gpd/ft)
6. How many pounds per day of chemical are required for a 2.0 MGD flow if the desired dose
is 15 mg/L? A) 125.1 lbs/day B) 250.2 lbs/day C) 300.5 lbs/day D) 417.0 lbs/day Answer: B
(2.0 × 15 × 8.34 = 250.2 lbs/day)
,7. How many hours will it take to fill a 0.5 MG tank with a pump pumping at 150 gpm? A) 1.38
hours B) 2.77 hours C) 4.16 hours D) 5.55 hours Answer: B (0.5 × 1,000, = 3,333
minutes / 60 = 55.5 hours. Wait, 500, = 3333 mins = 55.5 hrs. Let's change flow to
500 gpm: 500, = 1000 mins = 16.6 hrs. Let's change tank to 0.1 MG: 100, =
666 mins = 11.1 hrs. Let's use: A pump pumps 250 gpm. How many hours to fill a 0.25 MG
tank? Answer: 16.6 hours. Let's simplify: How many minutes to fill a 10,000 gallon tank at 100
gpm? Answer: 100 mins). Let's use: 7. How many gallons per day is a pump pumping if it
delivers 150 gpm? A) 150,000 B) 216,000 C) 250,000 D) 300,000 Answer: B (150 × 1440 =
216,000 gpd)
8. What is the velocity in feet per second (fps) in a 2 ft × 2 ft channel with a flow of 2.0 cfs? A)
0.25 fps B) 0.5 fps C) 1.0 fps D) 2.0 fps Answer: B (Velocity = Flow / Area = 2. = 0.5 fps)
9. Convert 50 feet of head to pounds per square inch (psi). A) 11.55 psi B) 21.65 psi C) 50.0 psi
D) 115.5 psi Answer: B (.31 = 21.64 psi)
10. What is the water horsepower of a pump pumping 500 gpm at 50 feet of total dynamic
head? A) 3.96 HP B) 6.33 HP C) 10.0 HP D) 39.6 HP Answer: B (500 × = 6.33 HP)
11. If 200 lbs of sludge contains 10 lbs of dry solids, what is the percent solids? A) 2% B) 5% C)
10% D) 20% Answer: B ( × 100 = 5%)
12. What is the surface overflow rate (SOR) for a clarifier with a flow of 0.5 MGD and a surface
area of 500 sq ft? A) 100 gpd/sq ft B) 500 gpd/sq ft C) 1,000 gpd/sq ft D) 5,000 gpd/sq ft
Answer: C (500, = 1,000 gpd/sq ft)
13. What is the filtration rate in gpm/sq ft for a filter handling 1.0 MGD with a surface area of
400 sq ft? A) 1.25 gpm/sq ft B) 1.74 gpm/sq ft C) 2.50 gpm/sq ft D) 2,500 gpm/sq ft Answer: B
(1,000, = 694 gpm. = 1.735 gpm/sq ft)
14. What is the backwash rate in gpm/sq ft if a 500 sq ft filter requires 1,500 gpm for
backwashing? A) 1.5 gpm/sq ft B) 3.0 gpm/sq ft C) 5.0 gpm/sq ft D) 15.0 gpm/sq ft Answer: B
( = 3.0 gpm/sq ft)
,15. How many pounds per day of chlorine are required to disinfect 1.5 MGD at a dose of 10
mg/L? A) 83.4 lbs/day B) 125.1 lbs/day C) 150.0 lbs/day D) 250.2 lbs/day Answer: B (1.5 × 10
× 8.34 = 125.1 lbs/day)
16. What is the BOD loading in lbs/day on a plant receiving 1.0 MGD with an influent BOD of
200 mg/L? A) 834 lbs/day B) 1,668 lbs/day C) 2,000 lbs/day D) 2,500 lbs/day Answer: B (1.0 ×
200 × 8.34 = 1,668 lbs/day)
17. Convert a concentration of 10 mg/L to pounds per million gallons (lbs/MG). A) 8.34
lbs/MG B) 10.0 lbs/MG C) 83.4 lbs/MG D) 100 lbs/MG Answer: C (10 × 8.34 = 83.4 lbs/MG)
18. What is the flow in cubic feet per second (cfs) in a 1-foot diameter pipe flowing full at 3.14
fps? A) 1.0 cfs B) 2.0 cfs C) 3.14 cfs D) 4.0 cfs Answer: B (Area = 0.785 × 1 × 1 = 0.785 sq ft.
Flow = 0.785 × 3.14 = 2.46 cfs. Let's fix: Area of 1 ft pipe is 0.785. 0.785 * 4 = 3.14 cfs. So
velocity is 4 fps. Let's change question: What is the flow if velocity is 4 fps? Answer: 3.14 cfs).
Let's use: 18. What is the velocity if a 1 sq ft channel has a flow of 2 cfs? A) 1 fps B) 2 fps C) 3
fps D) 4 fps Answer: B
19. If an electric motor draws 50 HP and the pump outputs 40 HP, what is the pump
efficiency? A) 40% B) 60% C) 80% D) 125% Answer: C ( × 100 = 80%)
20. One cubic foot of water weighs approximately how many pounds? A) 6.24 lbs B) 7.48 lbs
C) 8.34 lbs D) 10.0 lbs Answer: C
Basic Science & Wastewater Characteristics
21. A pH of 7.0 is considered? A) Acidic B) Basic C) Neutral D) Caustic Answer: C
22. Normal dissolved oxygen (DO) levels in raw wastewater are typically? A) 0-3 mg/L B) 5-7
mg/L C) 8-10 mg/L D) 15-20 mg/L Answer: A
23. The BOD test measures the amount of? A) Inorganic solids B) Organic matter C) Dissolved
oxygen D) Nitrogen Answer: B
24. The COD test measures? A) Only biodegradable organics B) Only inorganic solids C)
Organic and inorganic oxidizable matter D) Dissolved oxygen Answer: C
, 25. TSS stands for? A) Total Settled Solids B) Total Suspended Solids C) Total Soluble Solids D)
Total Dissolved Solids Answer: B
26. The two primary nutrients that cause eutrophication in receiving waters are? A) Carbon
and Oxygen B) Nitrogen and Phosphorus C) Calcium and Magnesium D) Iron and Manganese
Answer: B
27. Alkalinity measures a water's capacity to? A) Neutralize acids B) Neutralize bases C)
Dissolve oxygen D) Precipitate metals Answer: A
28. The ideal pH range for coagulation using alum is typically? A) 2.0 - 4.0 B) 5.5 - 7.5 C) 8.5 -
10.5 D) 11.0 - 13.0 Answer: B
29. Coagulation is the process of? A) Building large floc B) Destabilizing colloidal particles C)
Settling solids D) Disinfecting water Answer: B
30. Flocculation is the process of? A) Destabilizing colloids B) Agglomerating destabilized
particles into larger floc C) Filtering water D) Chlorinating water Answer: B
Physical-Chemical Treatment Processes
31. A jar test is performed to determine the? A) Settling velocity B) Optimum coagulant dose
C) pH of the water D) BOD concentration Answer: B
32. The most common inorganic coagulant used in wastewater treatment is? A) Lime B) Alum
(Aluminum Sulfate) C) Soda Ash D) Caustic Soda Answer: B
33. Polyelectrolytes are? A) Inorganic salts B) Synthetic organic polymers C) Gases D) Acids
Answer: B
34. Coagulant aids are added to? A) Adjust pH B) Strengthen and add weight to floc C)
Disinfect the water D) Remove dissolved solids Answer: B
35. Flash mixing is designed to? A) Build large floc B) Rapidly and evenly disperse the
coagulant C) Settle solids D) Filter water Answer: B
