Texas Wastewater Operator Certification Exam Review with
Answers and Rationales | 100% Pass Guaranteed | Graded
A+
1. The primary purpose of preliminary treatment is to remove:
A. Dissolved solids
B. Pathogens
C. Large debris and grit
D. Nutrients
Preliminary treatment protects equipment by removing large solids, rags,
and grit.
2. Screening removes:
A. Dissolved organics
B. Bacteria
C. Rags and large solids
D. Ammonia
Screens physically remove large floating and suspended debris.
3. Grit removal is important because grit:
A. Increases BOD
B. Causes odor
C. Abrades pumps and equipment
D. Adds nutrients
Sand and gravel cause excessive wear on mechanical equipment.
4. Primary clarifiers remove solids mainly by:
A. Filtration
B. Chemical reaction
C. Gravity settling
D. Aeration
Primary treatment relies on sedimentation.
, 5. Typical primary treatment removes approximately:
A. 10% BOD
B. 25–35% BOD
C. 70% BOD
D. 95% BOD
Primary clarifiers remove about one-third of BOD.
Activated Sludge
6. The main purpose of aeration is to:
A. Remove grit
B. Supply oxygen for microorganisms
C. Kill pathogens
D. Remove phosphorus
Microorganisms require oxygen to break down organic matter.
7. MLSS stands for:
A. Maximum Liquid Suspended Solids
B. Mixed Liquor Suspended Solids
C. Minimum Level Settled Solids
D. Mixed Loading Sludge System
MLSS measures biomass concentration in aeration.
8. If DO in the aeration tank drops below 1.0 mg/L, the likely result is:
A. Excess nitrification
B. Poor treatment and odors
C. Increased settling
D. Reduced sludge production
Low oxygen leads to septic conditions.
9. Sludge age is also called:
A. F/M ratio
B. Solids Retention Time (SRT)
C. Hydraulic detention time
, D. Return rate
SRT measures how long biomass remains in the system.
10.Bulking sludge is commonly caused by:
A. High DO
B. Filamentous bacteria
C. Excess chlorine
D. Low temperature
Filamentous organisms prevent proper settling.
Secondary Clarification
11.Rising sludge in a clarifier is usually caused by:
A. Low flow
B. Denitrification
C. High chlorine
D. Excess grit
Nitrogen gas forms and lifts sludge.
12.A sludge blanket that becomes too high may cause:
A. Better settling
B. Solids washout
C. Higher DO
D. Reduced flow
High blankets reduce settling capacity.
13.The purpose of RAS is to:
A. Waste solids
B. Remove scum
C. Return microorganisms to aeration
D. Add oxygen
RAS maintains biomass concentration.
Answers and Rationales | 100% Pass Guaranteed | Graded
A+
1. The primary purpose of preliminary treatment is to remove:
A. Dissolved solids
B. Pathogens
C. Large debris and grit
D. Nutrients
Preliminary treatment protects equipment by removing large solids, rags,
and grit.
2. Screening removes:
A. Dissolved organics
B. Bacteria
C. Rags and large solids
D. Ammonia
Screens physically remove large floating and suspended debris.
3. Grit removal is important because grit:
A. Increases BOD
B. Causes odor
C. Abrades pumps and equipment
D. Adds nutrients
Sand and gravel cause excessive wear on mechanical equipment.
4. Primary clarifiers remove solids mainly by:
A. Filtration
B. Chemical reaction
C. Gravity settling
D. Aeration
Primary treatment relies on sedimentation.
, 5. Typical primary treatment removes approximately:
A. 10% BOD
B. 25–35% BOD
C. 70% BOD
D. 95% BOD
Primary clarifiers remove about one-third of BOD.
Activated Sludge
6. The main purpose of aeration is to:
A. Remove grit
B. Supply oxygen for microorganisms
C. Kill pathogens
D. Remove phosphorus
Microorganisms require oxygen to break down organic matter.
7. MLSS stands for:
A. Maximum Liquid Suspended Solids
B. Mixed Liquor Suspended Solids
C. Minimum Level Settled Solids
D. Mixed Loading Sludge System
MLSS measures biomass concentration in aeration.
8. If DO in the aeration tank drops below 1.0 mg/L, the likely result is:
A. Excess nitrification
B. Poor treatment and odors
C. Increased settling
D. Reduced sludge production
Low oxygen leads to septic conditions.
9. Sludge age is also called:
A. F/M ratio
B. Solids Retention Time (SRT)
C. Hydraulic detention time
, D. Return rate
SRT measures how long biomass remains in the system.
10.Bulking sludge is commonly caused by:
A. High DO
B. Filamentous bacteria
C. Excess chlorine
D. Low temperature
Filamentous organisms prevent proper settling.
Secondary Clarification
11.Rising sludge in a clarifier is usually caused by:
A. Low flow
B. Denitrification
C. High chlorine
D. Excess grit
Nitrogen gas forms and lifts sludge.
12.A sludge blanket that becomes too high may cause:
A. Better settling
B. Solids washout
C. Higher DO
D. Reduced flow
High blankets reduce settling capacity.
13.The purpose of RAS is to:
A. Waste solids
B. Remove scum
C. Return microorganisms to aeration
D. Add oxygen
RAS maintains biomass concentration.
