TEXAS ENVIRONMENTAL OPERATOR
LICENSING LEVEL IV QUESTIONS AND
CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALES 2026 Q&A | INSTANT
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1. Which parameter is MOST critical for controlling nitrification in an
activated sludge system?
A. pH
B. Temperature
C. Dissolved oxygen
D. Sludge age
Answer: D
Sludge age determines how long nitrifying bacteria remain in the
system to fully develop.
2. Excessive filamentous growth in activated sludge is commonly
associated with:
A. High DO levels
B. High F/M ratio
C. Low nutrient levels
D. High pH
Answer: C
Filaments often dominate when nutrients like nitrogen or phosphorus
are limited.
,3. Chlorine gas leaking from a cylinder should FIRST be addressed by:
A. Spraying with water
B. Using a repair kit
C. Evacuating the area
D. Ventilating the room
Answer: C
Safety requires immediate evacuation before attempting repairs.
4. The BEST method to remove hydrogen sulfide from wastewater is:
A. Aeration
B. Chlorination
C. Filtration
D. UV disinfection
Answer: A
Aeration easily strips volatile gases like H₂S.
5. Sludge bulking is often diagnosed by measuring:
A. MCRT
B. SVI
C. F/M ratio
D. DO levels
Answer: B
SVI directly indicates settling characteristics of sludge.
6. A clarifier operating at excessive surface overflow rates will MOST
likely result in:
,A. Better settling
B. Increased solids carryover
C. Reduced return flows
D. Increased DO
Answer: B
High overflow rates push solids out with the effluent.
7. The most effective process for removing ammonia is:
A. Coagulation
B. Nitrification
C. Filtration
D. UV treatment
Answer: B
Nitrifying bacteria convert ammonia to nitrite and nitrate.
8. The main purpose of performing jar tests is to:
A. Measure DO
B. Optimize chemical dosages
C. Detect pathogens
D. Increase alkalinity
Answer: B
Jar tests simulate coagulation/flocculation to determine best chemical
doses.
9. A wastewater plant using anaerobic digestion should maintain
mesophilic temperatures around:
, A. 20°C
B. 30°C
C. 35°C
D. 45°C
Answer: C
Mesophilic digestion typically occurs near 35°C.
10. A drop in alkalinity during nitrification occurs because:
A. Metals form precipitates
B. Carbon dioxide is absorbed
C. Hydrogen ions are produced
D. Organic matter decreases
Answer: C
Nitrification releases H⁺ ions, reducing alkalinity.
11. Excessive chlorine demand is often caused by:
A. High DO
B. Low turbidity
C. High organic content
D. High alkalinity
Answer: C
Organics consume chlorine before disinfection occurs.
12. The most accurate method for determining sludge concentration
is:
A. Settleometer test
B. TSS analysis
LICENSING LEVEL IV QUESTIONS AND
CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALES 2026 Q&A | INSTANT
DOWNLOAD PDF
1. Which parameter is MOST critical for controlling nitrification in an
activated sludge system?
A. pH
B. Temperature
C. Dissolved oxygen
D. Sludge age
Answer: D
Sludge age determines how long nitrifying bacteria remain in the
system to fully develop.
2. Excessive filamentous growth in activated sludge is commonly
associated with:
A. High DO levels
B. High F/M ratio
C. Low nutrient levels
D. High pH
Answer: C
Filaments often dominate when nutrients like nitrogen or phosphorus
are limited.
,3. Chlorine gas leaking from a cylinder should FIRST be addressed by:
A. Spraying with water
B. Using a repair kit
C. Evacuating the area
D. Ventilating the room
Answer: C
Safety requires immediate evacuation before attempting repairs.
4. The BEST method to remove hydrogen sulfide from wastewater is:
A. Aeration
B. Chlorination
C. Filtration
D. UV disinfection
Answer: A
Aeration easily strips volatile gases like H₂S.
5. Sludge bulking is often diagnosed by measuring:
A. MCRT
B. SVI
C. F/M ratio
D. DO levels
Answer: B
SVI directly indicates settling characteristics of sludge.
6. A clarifier operating at excessive surface overflow rates will MOST
likely result in:
,A. Better settling
B. Increased solids carryover
C. Reduced return flows
D. Increased DO
Answer: B
High overflow rates push solids out with the effluent.
7. The most effective process for removing ammonia is:
A. Coagulation
B. Nitrification
C. Filtration
D. UV treatment
Answer: B
Nitrifying bacteria convert ammonia to nitrite and nitrate.
8. The main purpose of performing jar tests is to:
A. Measure DO
B. Optimize chemical dosages
C. Detect pathogens
D. Increase alkalinity
Answer: B
Jar tests simulate coagulation/flocculation to determine best chemical
doses.
9. A wastewater plant using anaerobic digestion should maintain
mesophilic temperatures around:
, A. 20°C
B. 30°C
C. 35°C
D. 45°C
Answer: C
Mesophilic digestion typically occurs near 35°C.
10. A drop in alkalinity during nitrification occurs because:
A. Metals form precipitates
B. Carbon dioxide is absorbed
C. Hydrogen ions are produced
D. Organic matter decreases
Answer: C
Nitrification releases H⁺ ions, reducing alkalinity.
11. Excessive chlorine demand is often caused by:
A. High DO
B. Low turbidity
C. High organic content
D. High alkalinity
Answer: C
Organics consume chlorine before disinfection occurs.
12. The most accurate method for determining sludge concentration
is:
A. Settleometer test
B. TSS analysis
