TEXAS CLASS C WASTEWATER TREATMENT LICENSE EXAM
QUESTIONS WITH VERIFIED ANSWERS 2025.
1) What activated sludge process parameters can an operator change directly? --
_ _ _ _ _ _ _ _ _ _ _
Answer ✔✔ aeration rates, waste rates, and return sludge rates
_ _ _ _ _ _ _ _ _
2) What happens when the return sludge rate is too low? -- Answer ✔✔ there will be
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
insufficient organisms to treat the waste load entering the aeration basin and the
_ _ _ _ _ _ _ _ _ _ _ _ _
sludge blanket in the secondary clarifier could become too high
_ _ _ _ _ _ _ _ _
3) Physical causes of sludge bulking are... -- Answer ✔✔ excessive hydraulic loading,
_ _ _ _ _ _ _ _ _ _ _ _
settled sludge that is not promptly removed from the clarifier, inadequate weir
_ _ _ _ _ _ _ _ _ _ _ _
lengths and improper ratio of depth to surface area of the final clarifier
_ _ _ _ _ _ _ _ _ _ _ _
4) Preliminary Treatment -- Answer ✔✔ the 1st stage of sewage treatment where large
_ _ _ _ _ _ _ _ _ _ _ _ _
debris, such as sticks, grit, and rags pas through a screen followed by a grit chamber,
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
where the flow of water is slowed enough to allow for sedimentation.
_ _ _ _ _ _ _ _ _ _ _
5) What are major surface waters classified as for the purposes of water quality
_ _ _ _ _ _ _ _ _ _ _ _ _
management and designation of site-specific standards? -- Answer ✔✔ segments
_ _ _ _ _ _ _ _ _
6) Inflow -- Answer ✔✔ direct discharges of storm water or surface water into a
_ _ _ _ _ _ _ _ _ _ _ _ _ _
wastewater collection system (storm drains, roof gutters, yard drains, basement
_ _ _ _ _ _ _ _ _ _
sump pumps and broken manholes and wastewater lines).
_ _ _ _ _ _ _
7) How many gallons per day will each person contribute to the wastewater treatment
_ _ _ _ _ _ _ _ _ _ _ _ _
plant? -- Answer ✔✔ 100
_ _ _ _
8) How much BOD will each person contribute to the wastewater treatment plant each
_ _ _ _ _ _ _ _ _ _ _ _
day? -- Answer ✔✔ 0.17
_ _ _ _ _
,9) Cause of septic wastewater -- Answer ✔✔ bacterial action
_ _ _ _ _ _ _ _
10) Classifications of solids in wastewater -- Answer ✔✔ fixed/ash, suspended/dissolved,
_ _ _ _ _ _ _ _ _ _
organic/inorganic
11) Organic compounds in wastewater include -- Answer ✔✔ carbon, hydrogen and
_ _ _ _ _ _ _ _ _ _ _
oxygen (animal and vegetable in nature)
_ _ _ _ _
12) Type of organic matter present in wastewater -- Answer ✔✔ proteins
_ _ _ _ _ _ _ _ _ _
13) BOD is a measure of what? -- Answer ✔✔ oxygen used up
_ _ _ _ _ _ _ _ _ _ _
14) Ways that oxygen can be depleted in streams -- Answer ✔✔ untreated waste
_ _ _ _ _ _ _ _ _ _ _ _ _
discharges, algae masses at night, and high BOD in the effluent
_ _ _ _ _ _ _ _ _ _
15) A gas found in treatment systems that is NOT dangerous -- Answer ✔✔ dissolved
_ _ _ _ _ _ _ _ _ _ _ _ _ _
oxygen
16) Cycles of decay include -- Answer ✔✔ carbon, nitrogen and sulfur
_ _ _ _ _ _ _ _ _ _
17) A flow totalizer is required when the plant design flow is more than -- Answer ✔✔
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
0.5 MGD
_
18) Non-hazardous wastes include -- Answer ✔✔ chlorides, alkalinity, color, _ _ _ _ _ _ _ _ _
phosphorous and iron _ _
19) Hazardous wastes include -- Answer ✔✔ cyanide, sulfides, organics and gasoline
_ _ _ _ _ _ _ _ _ _
20) Synergistic Effect -- Answer ✔✔ reaction between waste streams
_ _ _ _ _ _ _ _
21) How many cubic feet of screenings per million gallons of wastewater will coarse
_ _ _ _ _ _ _ _ _ _ _ _ _
screens remove? -- Answer ✔✔ 0.5 to 6.0
_ _ _ _ _ _ _
22) Pre aeration benefits -- Answer ✔✔ freshen wastewater, scour gases and remove
_ _ _ _ _ _ _ _ _ _ _ _
grease
, 23) Main purpose of sedimentation tank -- Answer ✔✔ allow scum to rise and solids to
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _
settle under quiescent (low velocity) conditions
_ _ _ _ _
24) What stage of treatment is grit removal usually accomplished in? -- Answer ✔✔
_ _ _ _ _ _ _ _ _ _ _ _ _
preliminary treatment _
25) Rotating Biological Contactor -- Answer ✔✔ a type of biological secondary treatment
_ _ _ _ _ _ _ _ _ _ _
_process
26) Digester trouble signs include... -- Answer ✔✔ an increase in CO2 content and a
_ _ _ _ _ _ _ _ _ _ _ _ _ _
decrease in volatile solids reduction _ _ _ _
27) Since the majority of _______ digesters are open tanks, digester liquid temperatures
_ _ _ _ _ _ _ _ _ _ _ _
are dependent on weather conditions and can fluctuate extensively. -- Answer ✔✔
_ _ _ _ _ _ _ _ _ _ _ _
aerobic
28) A minimum value of _________ of oxygen should be maintained in the aerobic
_ _ _ _ _ _ _ _ _ _ _ _ _
digester at all times. -- Answer ✔✔ 1.0 mg/L
_ _ _ _ _ _ _ _
29) The following processes are used to dewater sewage sludge: -- Answer ✔✔ vacuum
_ _ _ _ _ _ _ _ _ _ _ _ _
filters, filter presses and centrifuges
_ _ _ _
30) Sludge drying time is affected most by... -- Answer ✔✔ degree of digestion
_ _ _ _ _ _ _ _ _ _ _ _
31) The depth of sludge drawn to a drying bed should be... -- Answer ✔✔ about 9 inches
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
32) The moisture content of sludge transported to a municipal landfill should be less than
_ _ _ _ _ _ _ _ _ _ _ _ _ _
__________. -- Answer ✔✔ 80% _ _ _ _
33) The most expensive method for the final disposal of sludge is... -- Answer ✔✔
_ _ _ _ _ _ _ _ _ _ _ _ _ _
incineration
34) Disinfection may also be accomplished by... -- Answer ✔✔ ozone, bromine and
_ _ _ _ _ _ _ _ _ _ _ _
ultraviolet radiation _
QUESTIONS WITH VERIFIED ANSWERS 2025.
1) What activated sludge process parameters can an operator change directly? --
_ _ _ _ _ _ _ _ _ _ _
Answer ✔✔ aeration rates, waste rates, and return sludge rates
_ _ _ _ _ _ _ _ _
2) What happens when the return sludge rate is too low? -- Answer ✔✔ there will be
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
insufficient organisms to treat the waste load entering the aeration basin and the
_ _ _ _ _ _ _ _ _ _ _ _ _
sludge blanket in the secondary clarifier could become too high
_ _ _ _ _ _ _ _ _
3) Physical causes of sludge bulking are... -- Answer ✔✔ excessive hydraulic loading,
_ _ _ _ _ _ _ _ _ _ _ _
settled sludge that is not promptly removed from the clarifier, inadequate weir
_ _ _ _ _ _ _ _ _ _ _ _
lengths and improper ratio of depth to surface area of the final clarifier
_ _ _ _ _ _ _ _ _ _ _ _
4) Preliminary Treatment -- Answer ✔✔ the 1st stage of sewage treatment where large
_ _ _ _ _ _ _ _ _ _ _ _ _
debris, such as sticks, grit, and rags pas through a screen followed by a grit chamber,
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
where the flow of water is slowed enough to allow for sedimentation.
_ _ _ _ _ _ _ _ _ _ _
5) What are major surface waters classified as for the purposes of water quality
_ _ _ _ _ _ _ _ _ _ _ _ _
management and designation of site-specific standards? -- Answer ✔✔ segments
_ _ _ _ _ _ _ _ _
6) Inflow -- Answer ✔✔ direct discharges of storm water or surface water into a
_ _ _ _ _ _ _ _ _ _ _ _ _ _
wastewater collection system (storm drains, roof gutters, yard drains, basement
_ _ _ _ _ _ _ _ _ _
sump pumps and broken manholes and wastewater lines).
_ _ _ _ _ _ _
7) How many gallons per day will each person contribute to the wastewater treatment
_ _ _ _ _ _ _ _ _ _ _ _ _
plant? -- Answer ✔✔ 100
_ _ _ _
8) How much BOD will each person contribute to the wastewater treatment plant each
_ _ _ _ _ _ _ _ _ _ _ _
day? -- Answer ✔✔ 0.17
_ _ _ _ _
,9) Cause of septic wastewater -- Answer ✔✔ bacterial action
_ _ _ _ _ _ _ _
10) Classifications of solids in wastewater -- Answer ✔✔ fixed/ash, suspended/dissolved,
_ _ _ _ _ _ _ _ _ _
organic/inorganic
11) Organic compounds in wastewater include -- Answer ✔✔ carbon, hydrogen and
_ _ _ _ _ _ _ _ _ _ _
oxygen (animal and vegetable in nature)
_ _ _ _ _
12) Type of organic matter present in wastewater -- Answer ✔✔ proteins
_ _ _ _ _ _ _ _ _ _
13) BOD is a measure of what? -- Answer ✔✔ oxygen used up
_ _ _ _ _ _ _ _ _ _ _
14) Ways that oxygen can be depleted in streams -- Answer ✔✔ untreated waste
_ _ _ _ _ _ _ _ _ _ _ _ _
discharges, algae masses at night, and high BOD in the effluent
_ _ _ _ _ _ _ _ _ _
15) A gas found in treatment systems that is NOT dangerous -- Answer ✔✔ dissolved
_ _ _ _ _ _ _ _ _ _ _ _ _ _
oxygen
16) Cycles of decay include -- Answer ✔✔ carbon, nitrogen and sulfur
_ _ _ _ _ _ _ _ _ _
17) A flow totalizer is required when the plant design flow is more than -- Answer ✔✔
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
0.5 MGD
_
18) Non-hazardous wastes include -- Answer ✔✔ chlorides, alkalinity, color, _ _ _ _ _ _ _ _ _
phosphorous and iron _ _
19) Hazardous wastes include -- Answer ✔✔ cyanide, sulfides, organics and gasoline
_ _ _ _ _ _ _ _ _ _
20) Synergistic Effect -- Answer ✔✔ reaction between waste streams
_ _ _ _ _ _ _ _
21) How many cubic feet of screenings per million gallons of wastewater will coarse
_ _ _ _ _ _ _ _ _ _ _ _ _
screens remove? -- Answer ✔✔ 0.5 to 6.0
_ _ _ _ _ _ _
22) Pre aeration benefits -- Answer ✔✔ freshen wastewater, scour gases and remove
_ _ _ _ _ _ _ _ _ _ _ _
grease
, 23) Main purpose of sedimentation tank -- Answer ✔✔ allow scum to rise and solids to
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _
settle under quiescent (low velocity) conditions
_ _ _ _ _
24) What stage of treatment is grit removal usually accomplished in? -- Answer ✔✔
_ _ _ _ _ _ _ _ _ _ _ _ _
preliminary treatment _
25) Rotating Biological Contactor -- Answer ✔✔ a type of biological secondary treatment
_ _ _ _ _ _ _ _ _ _ _
_process
26) Digester trouble signs include... -- Answer ✔✔ an increase in CO2 content and a
_ _ _ _ _ _ _ _ _ _ _ _ _ _
decrease in volatile solids reduction _ _ _ _
27) Since the majority of _______ digesters are open tanks, digester liquid temperatures
_ _ _ _ _ _ _ _ _ _ _ _
are dependent on weather conditions and can fluctuate extensively. -- Answer ✔✔
_ _ _ _ _ _ _ _ _ _ _ _
aerobic
28) A minimum value of _________ of oxygen should be maintained in the aerobic
_ _ _ _ _ _ _ _ _ _ _ _ _
digester at all times. -- Answer ✔✔ 1.0 mg/L
_ _ _ _ _ _ _ _
29) The following processes are used to dewater sewage sludge: -- Answer ✔✔ vacuum
_ _ _ _ _ _ _ _ _ _ _ _ _
filters, filter presses and centrifuges
_ _ _ _
30) Sludge drying time is affected most by... -- Answer ✔✔ degree of digestion
_ _ _ _ _ _ _ _ _ _ _ _
31) The depth of sludge drawn to a drying bed should be... -- Answer ✔✔ about 9 inches
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
32) The moisture content of sludge transported to a municipal landfill should be less than
_ _ _ _ _ _ _ _ _ _ _ _ _ _
__________. -- Answer ✔✔ 80% _ _ _ _
33) The most expensive method for the final disposal of sludge is... -- Answer ✔✔
_ _ _ _ _ _ _ _ _ _ _ _ _ _
incineration
34) Disinfection may also be accomplished by... -- Answer ✔✔ ozone, bromine and
_ _ _ _ _ _ _ _ _ _ _ _
ultraviolet radiation _
