Wastewater Treatment Class 2 Final Exam Questions with Answers 100% Guaranteed Pass
A supervisor notices that solids exiting the dewatering facility has increased in dryness by 1.2% after
changing to a new cationic polymer. The next sample taken a week later shows a reduction in dryness by
7%. Organic loadings have increased in the plant while weather conditions have been unusually cold.
What is the best correct course of action to return the higher quality sludge? - Answers Perform jar
testing to estimate proper dosage of polymer while also adjusting temperature of sludge
Which of the following is not considered a hazardous gas if exposed to over the course of a shift?
-Diatomic oxygen
-Hydrogen sulfide
-Carbon dioxide
-Methane - Answers Diatomic oxygen
You work at a plant that has a daily flow of 10.5 MGD. Currently organic loading is normal. All clarifiers
contain excessive floating sludge. Alkalinity has been steadily decreasing over the last week and in the
operator notes, there is mention of low pH in the basins. What is occurring and what should be done to
correct it? - Answers Nitrification is consuming the alkalinity causing a drop in pH while solids are being
held too long in the clarifier causing denitrification
If all process control adjustments have been made to your DAFT, but solids are escaping out to the
effluent, what is the most likely cause? - Answers The unit is overloaded and needs to be upgraded
Which has the least effect on the ability of water to contain sufficient DO? - Answers Color
What can be done to prevent the binding of a belt in a belt filter press? - Answers Proper polymer
dosage and regular cleaning
When pumping sludge to be wasted, what is the most important to consider? - Answers Solids % from
start to finish
Baffles in a contact chamber are primarily in place to increase detention time. Which condition will
prevent a long contact time from resulting in adequate disinfection? - Answers Reducing compounds
such as nitrite and sulfites
A centrifugal pump that is operating against a closed discharge valve temporarily will exhibit what? -
Answers Begin to heat up but will evaporate the water contained in the volute preventing overheating
Which of the following would most likely indicate an anaerobic digester is upset?
-Lack of a flame when attempting to burn
-68% methane
, -Temperatures maintaining between 95-100 degrees F - Answers Lack of a flame when attempting to
burn
The purpose of a foot valve on a pump system is what? - Answers To prevent the pump from losing
prime
The bacteria responsible for nitrification are: - Answers Nitrosomonas and nitrobacter
Which organisms are most responsible for the oxidation of dissolved organics in wastewater? - Answers
Bacteria
Filamentous bacteria that may cause excessive foam, specifically nocardia, are compounded by what
conditions? - Answers Low dissolved oxygen and high FOG in a warm environment
In an anoxic zone, which organisms will be most prevalent? - Answers Facultative
Your plant uses anaerobic digesters. The plant flow has increased by 45% over the last month, increasing
organics by 34% relative to average annual flow. Alkalinity is being supplied at a constant rate to buffer
pH in the digesters. If all conditions stay the same, what operational changes will most likely have to be
made to maintain plant health? - Answers Solids wasting will need to be increased
An operator notes that blanket levels in the final clarifiers are rising at a level of 1 foot per hour. Plant
flow is normal while TSS is 10% higher than normal. RAS and WAS values have been adjusted to
compensate for the increase in solids being introduced to the plant. After 4 hours the operator sees that
the blanket has not responded and is still rising, however, only 0.5 foot per hour. What is the most likely
cause? - Answers RAS pumps have a flow restriction and are not able to pump the sludge
An operator notes that COD values have been steadily increasing. BOD dilutions that are regularly within
QA/QC range are beginning to fall out of limits. What should be done to correct this? - Answers
Increased COD values should alert the operator that BOD will also increase by 0.5/1 ratio indicating the
need for more dilutions
The operator notices that the shear pin in the bar screen is continually failing. Flow to the plant has been
150% of normal flow. What is the best action to take? - Answers Divert a portion of the flow to the EQ
pond
What is most likely the cause of excessive vibration in a pump assembly? - Answers Misalignment
What is the holding time for an ammonia sample? - Answers 28 days if properly sampled and preserved
with sulfuric acid and cooled to < 6 degrees Celsius
What is the proper holding time and storage temperature for BOD? - Answers 48 hours and <6 degrees
Celsius
What does not have an effect on the rate of nitrification? - Answers Ciliates
Which would most likely result in a -250 ORP? - Answers Nitrite
A supervisor notices that solids exiting the dewatering facility has increased in dryness by 1.2% after
changing to a new cationic polymer. The next sample taken a week later shows a reduction in dryness by
7%. Organic loadings have increased in the plant while weather conditions have been unusually cold.
What is the best correct course of action to return the higher quality sludge? - Answers Perform jar
testing to estimate proper dosage of polymer while also adjusting temperature of sludge
Which of the following is not considered a hazardous gas if exposed to over the course of a shift?
-Diatomic oxygen
-Hydrogen sulfide
-Carbon dioxide
-Methane - Answers Diatomic oxygen
You work at a plant that has a daily flow of 10.5 MGD. Currently organic loading is normal. All clarifiers
contain excessive floating sludge. Alkalinity has been steadily decreasing over the last week and in the
operator notes, there is mention of low pH in the basins. What is occurring and what should be done to
correct it? - Answers Nitrification is consuming the alkalinity causing a drop in pH while solids are being
held too long in the clarifier causing denitrification
If all process control adjustments have been made to your DAFT, but solids are escaping out to the
effluent, what is the most likely cause? - Answers The unit is overloaded and needs to be upgraded
Which has the least effect on the ability of water to contain sufficient DO? - Answers Color
What can be done to prevent the binding of a belt in a belt filter press? - Answers Proper polymer
dosage and regular cleaning
When pumping sludge to be wasted, what is the most important to consider? - Answers Solids % from
start to finish
Baffles in a contact chamber are primarily in place to increase detention time. Which condition will
prevent a long contact time from resulting in adequate disinfection? - Answers Reducing compounds
such as nitrite and sulfites
A centrifugal pump that is operating against a closed discharge valve temporarily will exhibit what? -
Answers Begin to heat up but will evaporate the water contained in the volute preventing overheating
Which of the following would most likely indicate an anaerobic digester is upset?
-Lack of a flame when attempting to burn
-68% methane
, -Temperatures maintaining between 95-100 degrees F - Answers Lack of a flame when attempting to
burn
The purpose of a foot valve on a pump system is what? - Answers To prevent the pump from losing
prime
The bacteria responsible for nitrification are: - Answers Nitrosomonas and nitrobacter
Which organisms are most responsible for the oxidation of dissolved organics in wastewater? - Answers
Bacteria
Filamentous bacteria that may cause excessive foam, specifically nocardia, are compounded by what
conditions? - Answers Low dissolved oxygen and high FOG in a warm environment
In an anoxic zone, which organisms will be most prevalent? - Answers Facultative
Your plant uses anaerobic digesters. The plant flow has increased by 45% over the last month, increasing
organics by 34% relative to average annual flow. Alkalinity is being supplied at a constant rate to buffer
pH in the digesters. If all conditions stay the same, what operational changes will most likely have to be
made to maintain plant health? - Answers Solids wasting will need to be increased
An operator notes that blanket levels in the final clarifiers are rising at a level of 1 foot per hour. Plant
flow is normal while TSS is 10% higher than normal. RAS and WAS values have been adjusted to
compensate for the increase in solids being introduced to the plant. After 4 hours the operator sees that
the blanket has not responded and is still rising, however, only 0.5 foot per hour. What is the most likely
cause? - Answers RAS pumps have a flow restriction and are not able to pump the sludge
An operator notes that COD values have been steadily increasing. BOD dilutions that are regularly within
QA/QC range are beginning to fall out of limits. What should be done to correct this? - Answers
Increased COD values should alert the operator that BOD will also increase by 0.5/1 ratio indicating the
need for more dilutions
The operator notices that the shear pin in the bar screen is continually failing. Flow to the plant has been
150% of normal flow. What is the best action to take? - Answers Divert a portion of the flow to the EQ
pond
What is most likely the cause of excessive vibration in a pump assembly? - Answers Misalignment
What is the holding time for an ammonia sample? - Answers 28 days if properly sampled and preserved
with sulfuric acid and cooled to < 6 degrees Celsius
What is the proper holding time and storage temperature for BOD? - Answers 48 hours and <6 degrees
Celsius
What does not have an effect on the rate of nitrification? - Answers Ciliates
Which would most likely result in a -250 ORP? - Answers Nitrite
