Page 1 of 105
Wastewater Treatment Operator Certification
Exam ACTUAL QUESTIONS AND ANSWERS LATEST
UPDATE THIS YEAR
Wastewater Treatment Operator Certification Exam
Summary of High-Yield Exam Topics
Based on TCEQ and industry standards , the following topics are most relevant for wastewater operator
certification (Grade 1-4 levels):
• Preliminary Treatment – Bar screens, comminutors, grit removal (purpose and operation),
protection of downstream equipment
• Primary Treatment – Sedimentation, settling of solids by gravity, detention time (typically 2
hours), scum removal
• Secondary Treatment – Activated sludge process, trickling filters, RBCs, BOD removal via
microorganisms, aeration
• Tertiary/Advanced Treatment – Filtration, disinfection (chlorine, UV), nutrient removal
(nitrogen, phosphorus), effluent polishing
• Activated Sludge Process – Aeration tanks, MLSS, RAS, WAS, F/M ratio, SVI, settling
characteristics, DO range (1.5-3.0 mg/L)
• Ponds & Lagoons – Facultative ponds, oxidation ponds, aerobic/anaerobic zones, DO patterns
• Disinfection – Chlorination (purpose, dosage, residual, hazards), dechlorination, UV disinfection
• Solids/Sludge Handling – Thickening, digestion (aerobic/anaerobic), dewatering (drying beds,
belt presses, centrifuges), composting
• Nutrient Removal – Nitrification (ammonia → nitrate), denitrification (nitrate → nitrogen gas),
chemical phosphorus precipitation
• Laboratory & Testing – BOD5 (5-day test), TSS, pH, DO, settleable solids (Imhoff cone), sampling
procedures, holding times
• Safety – Confined space entry (3-person rule), trench safety (5 feet requires shoring, ladder
every 25 ft), H₂S (anaerobic odor), chlorine safety
• Maintenance & Equipment – Pumps (centrifugal, positive displacement), motors, EMV, amps,
volts, electrical safety, fire classes
• Regulations – Clean Water Act, NPDES permits, secondary treatment standards (30 mg/L BOD &
TSS), effluent limits
• Math & Calculations – Flow rates (Q=A×V), detention time (HRT), organic loading, F/M ratio,
SVI, removal efficiency, area/volume
, Page 2 of 105
1. What is the main purpose of primary treatment in a wastewater plant?
A) Biological removal of organics
B) Settling of solids by gravity
C) Disinfection of wastewater
D) Removal of nutrients
Answer: B – Primary treatment uses sedimentation to remove settleable solids and floating materials by
gravity .
2. The primary goal of secondary treatment is to:
A) Remove grit and large debris
B) Remove dissolved and suspended organic matter via biological processes
C) Disinfect effluent
D) Thicken sludge
Answer: B – Secondary treatment uses microorganisms to break down organic pollutants (e.g., activated
sludge, trickling filters) .
, Page 3 of 105
3. Tertiary treatment is primarily used to:
A) Remove grit
B) Settle solids
C) Further polish effluent for reuse or strict discharge limits
D) Thicken sludge
Answer: C – Tertiary processes (filtration, disinfection) remove remaining contaminants like nutrients
and pathogens .
4. If influent wastewater has a pH of 6.0, the operator should:
A) Add chlorine
B) Adjust pH to 6.5–8.5 for optimal microbial activity
C) Increase aeration
D) Reduce sludge wasting
Answer: B – Acidic pH (below 6.5) inhibits microbial growth; optimal range for biological treatment is
6.5–8.5 .
, Page 4 of 105
5. Biochemical Oxygen Demand (BOD) measures:
A) The amount of dissolved oxygen in water
B) The oxygen required by microorganisms to break down organic matter
C) The total suspended solids in wastewater
D) The pH level of wastewater
Answer: B – BOD indicates organic pollution level; high BOD = more oxygen consumed by microbes .
6. Total Suspended Solids (TSS) measures:
A) Dissolved organic matter
B) Solids retained on a filter during testing
C) Microbial population
D) Chemical oxygen demand
Answer: B – TSS quantifies non-dissolved solids in wastewater by filtering and weighing retained solids .
7. What is the most common reason for wastewater to contain intermittent large amounts of sand,
gravel, and grit?
A) Industrial discharge
Wastewater Treatment Operator Certification
Exam ACTUAL QUESTIONS AND ANSWERS LATEST
UPDATE THIS YEAR
Wastewater Treatment Operator Certification Exam
Summary of High-Yield Exam Topics
Based on TCEQ and industry standards , the following topics are most relevant for wastewater operator
certification (Grade 1-4 levels):
• Preliminary Treatment – Bar screens, comminutors, grit removal (purpose and operation),
protection of downstream equipment
• Primary Treatment – Sedimentation, settling of solids by gravity, detention time (typically 2
hours), scum removal
• Secondary Treatment – Activated sludge process, trickling filters, RBCs, BOD removal via
microorganisms, aeration
• Tertiary/Advanced Treatment – Filtration, disinfection (chlorine, UV), nutrient removal
(nitrogen, phosphorus), effluent polishing
• Activated Sludge Process – Aeration tanks, MLSS, RAS, WAS, F/M ratio, SVI, settling
characteristics, DO range (1.5-3.0 mg/L)
• Ponds & Lagoons – Facultative ponds, oxidation ponds, aerobic/anaerobic zones, DO patterns
• Disinfection – Chlorination (purpose, dosage, residual, hazards), dechlorination, UV disinfection
• Solids/Sludge Handling – Thickening, digestion (aerobic/anaerobic), dewatering (drying beds,
belt presses, centrifuges), composting
• Nutrient Removal – Nitrification (ammonia → nitrate), denitrification (nitrate → nitrogen gas),
chemical phosphorus precipitation
• Laboratory & Testing – BOD5 (5-day test), TSS, pH, DO, settleable solids (Imhoff cone), sampling
procedures, holding times
• Safety – Confined space entry (3-person rule), trench safety (5 feet requires shoring, ladder
every 25 ft), H₂S (anaerobic odor), chlorine safety
• Maintenance & Equipment – Pumps (centrifugal, positive displacement), motors, EMV, amps,
volts, electrical safety, fire classes
• Regulations – Clean Water Act, NPDES permits, secondary treatment standards (30 mg/L BOD &
TSS), effluent limits
• Math & Calculations – Flow rates (Q=A×V), detention time (HRT), organic loading, F/M ratio,
SVI, removal efficiency, area/volume
, Page 2 of 105
1. What is the main purpose of primary treatment in a wastewater plant?
A) Biological removal of organics
B) Settling of solids by gravity
C) Disinfection of wastewater
D) Removal of nutrients
Answer: B – Primary treatment uses sedimentation to remove settleable solids and floating materials by
gravity .
2. The primary goal of secondary treatment is to:
A) Remove grit and large debris
B) Remove dissolved and suspended organic matter via biological processes
C) Disinfect effluent
D) Thicken sludge
Answer: B – Secondary treatment uses microorganisms to break down organic pollutants (e.g., activated
sludge, trickling filters) .
, Page 3 of 105
3. Tertiary treatment is primarily used to:
A) Remove grit
B) Settle solids
C) Further polish effluent for reuse or strict discharge limits
D) Thicken sludge
Answer: C – Tertiary processes (filtration, disinfection) remove remaining contaminants like nutrients
and pathogens .
4. If influent wastewater has a pH of 6.0, the operator should:
A) Add chlorine
B) Adjust pH to 6.5–8.5 for optimal microbial activity
C) Increase aeration
D) Reduce sludge wasting
Answer: B – Acidic pH (below 6.5) inhibits microbial growth; optimal range for biological treatment is
6.5–8.5 .
, Page 4 of 105
5. Biochemical Oxygen Demand (BOD) measures:
A) The amount of dissolved oxygen in water
B) The oxygen required by microorganisms to break down organic matter
C) The total suspended solids in wastewater
D) The pH level of wastewater
Answer: B – BOD indicates organic pollution level; high BOD = more oxygen consumed by microbes .
6. Total Suspended Solids (TSS) measures:
A) Dissolved organic matter
B) Solids retained on a filter during testing
C) Microbial population
D) Chemical oxygen demand
Answer: B – TSS quantifies non-dissolved solids in wastewater by filtering and weighing retained solids .
7. What is the most common reason for wastewater to contain intermittent large amounts of sand,
gravel, and grit?
A) Industrial discharge
