Intermediate Study Questions Provided By RoyCEU.com

A Tank is 50 feet in length and 18 feet wide. The tank is 15 feet deep on one end but then tapers off to 12 feet deep on the other end.
What is the volume of the tank in ft³?
1. 10,800 ft³
2. 12,150 ft³
3. 13,500 ft³
4. 24,300 ft³
When Sampling for Nocardia, where would you get the best representative sample that has the bacteria?
1. MLSS
2. Primary Effluent
3. Foam
4. WAS line
Which preservative do you need for an ammonia nitrogen sample?
1. 6 Degrees C with NHO₃
2. 6 Degrees C with Na₂H₂O₄
3. 4 Degrees C with H₂SO₄
4. 4 Degrees C with ZN (OCCI) and HNO₃
After getting a fecal coliform sample, how long can you wait until you test the sample?
1. 4 hours
2. 8 hours
3. 24 hours
4. 48 hours
The chlorine residual is falling, and inspection of the 150 pound cylinder and chlorine feed equipment shows ice forming on the chlorine regulator and feed lines.
The BEST method to fix the falling chlorine residual is________________?
1. Switch over to sodium hypochlorite solution
2. Place a second chlorine cylinder on line
3. Roll the cylinder so liquid is feeding instead of gas
4. Place a 1500 Watt space heater next to the cylinder to thaw the ice
Throughout the week, you notice these changes in the settleometer at the wastewater treatment plant.
What is the reason for the slower settling times?

10/30/2021
MIN .... MLSS
5 .......... 550
10 ........ 500
15 ........ 460
20 ........ 430
25 ........ 390
30 ........ 380

11/05/2021
MIN ..... MLSS
5 ......... 960
10 ....... 890
15 ....... 760
20 ....... 700
25 ....... 620
30 ....... 540
1. Excessive amounts of filaments
2. Too much MLSS in system
3. RAS flow is too low
4. RAS flow is too high
A Parshall flume is a great measuring device to record flow rates.ul>Where does the Parshall flume read the measurements?
1. Upstream, 2/3 the length of the converging wall
2. Downstream, 1/3 the length after the throat
3. Upstream, 1/6 the length before the throat
4. When the wastewater hits the throat
You notice that your chlorine residual is dropping. The DT is right in the contactor and there is no solids build up on the tank. The chlorine supplies are not the issue.
What is the cause of the residual drop?
1. Excessive ammonia in the effluent
2. Excessive nitrite in the effluent
3. Excessive nitrate in the effluent
4. Excessive phosphorus in the effluent
When using a pneumatic pump, these conditions are critical for proper performance of the pump.
1. Submerged
2. Primed
3. Wet environment with very little air
4. Dry environment with little to no water
In a chlorine gas system, what would happen in the system if the vacuum was lost?
1. The diaphragm would slam shut
2. The gas pressure would drop
3. More liquid carry over would happen, potentially ruining the chlorinator
4. Gas pressure will increase, potentially melting the fusible plug
What does an SVI of 180 mean in a settleometer?
1. Very old sludge that settles very slowly
2. Old sludge with lots of red worms and rotifers, typically settles very quick
3. Moderately aged sludge, typically settles more slowly but has better capture efficiency
4. Young sludge with lots of free swimmers that typically settles faster with smaller floc
Electronic resistance is measured in_____________.
1. Ohms
2. Volts
3. Watts
4. Amps
An anaerobic digester should be adjusted _________________.
1. By 1 degree C per day
2. By 1 degree F per day
3. By 10 degrees C per day
4. By 10% per day
An operator does a BOD test of 3 mL, 5 mL, and 10 mL. For some reason, the higher BOD samples are getting a higher oxygen uptake reading. If the operator did all the quality control requirements correctly, what is the problem with the higher OUR readings?
1. The operator switched up the labels
2. The operator didn’t incubate the sample right
3. The operator didn’t make the dilation water right
4. There was a toxic substance in the sample
How many times heavier is chlorine gas than air?
1. 1.5
2. 2.5
3. 3.5
4. 4.5
What are the vector attraction reduction requirements for lime stabilization to accomplish class B stabilization standards?
1. Raise the sludge pH to no more than 11.0
2. Raise the sludge pH to at least 12 for the first 2 hours, and then at least 12.5 for the next 24 hours
3. Raise the sludge pH to between 10.0 and 10.5
4. Raise the sludge pH to at least 12.0 for the first 2 hours, and then at least 11.5 for the next 22 hours
A wet well that uses a bubbler tube system is empty and the pumps are running at 100%. The pressure is HIHI and the pumps are in auto.
What is the problem with the wet well system?
1. The tank is full of solids
2. The bubbler tube is clogged
3. The pumps are running in hand
4. The HMI system needs to be hard reset
A town that has a population of 2,286 people has an industry that puts 300 pounds of BOD into the plant. What percent of total BOD does the industry contribute to?
1. 32%
2. 38%
3. 44%
4. 56%
There are two pumps in a wet well. What capacity should each pump be able to operate at?
1. 50% of the average flow
2. 100% of the max flow
3. 25% of the max flow
4. 75% of the average flow
What type of filament is associated with very old sludge that denitrifies, bulks up, and has lots of red worms, water bears, and rotifers?
1. Beggiatoa
2. Thiothrix
3. Type 1-1038
4. Type 0914
How will low water flow affect the vacuum created in a gas injector?
1. It will create a high vacuum condition
2. It will create a low vacuum condition
3. Water flow does not affect injector vacuum
4. It will create a high pressure in the system
A 150 lb chlorine container should be restrained _________________.
1. 1/4 of the way from the top
2. 1/3 of the way from the bottom
3. 1/2 the length of the bottle
4. 1/3 of the way down from the top
Which type of self-contained breathing apparatus should be used in oxygen deficient areas?
1. Negative pressure
2. Positive pressure
3. 1/2 the length of the bottle
4. 1/3 of the way down from the top
What is an example of predictive maintenance?
1. Lubricating a chain and changing the oil monthly
2. Monitoring vibration levels, oil analysis and checking circuits
3. Replacing an impeller and tightening connections
4. Unclogging the step screen auger
Which emergency repair kit is used for ton containers?
1. Kit A
2. Kit B
3. Kit C
4. Kit T
Which type of valve would be best to use in throttling flow situations?
1. Gate
2. Ball
3. Check
4. Butterfly
A common BOD to nitrogen to phosphorus ratio is ________________.
1. 100:5:1
2. 150:15:6
3. 100:30:30
4. 50:50:50
A wastewater treatment plant normally runs very well with an F/M ratio of 0.4 to 0.5. The lab test shows that the F/M ratio is 0.2.
What is the best action to take to permanently increase the F/M ratio?
1. Decrease WAS
2. Increase RAS
3. Increase WAS
4. Decrease RAS
Water is pumped through a 12 inch main at a rate of 300 gallons per minute.
What is the velocity of the flow?
1. 0.5 ft/s
2. 0.66 ft/s
3. 0.85 ft/s
4. 1.01 ft/s
Large amounts of solids are rising in a secondary clarifier and going over the weir followed by large gas bubbles.
What is the best action to take to fix the rising solids?
1. Increase the WAS and decrease the DO
2. Decrease the RAS and increase the DO
3. Decrease the WAS and increase the
4. Increase the RAS and Increase the DO
What is the correct flow pattern in a Bardenpho process?
1. Mix flow/Static flow/Mix react
2. Mix react/Mix flow/Static flow
3. Static flow/Mix flow/Mix react
4. Mix flow/Mix react/Static flow
Boilers are used to heat up 2 anaerobic digesters and run on both methane gas and natural gas purchased by the city. When the boilers have used up all the methane gas, they switch over to natural gas. The boilers use 175,000 units of gas per day. Other data is shown below

• 25,000 pounds of solids added per day
• Solids are 57% volatile
• 7.9 cubic feet of gas/ pound of volatile solids added

The natural gas is sold by 1,000 units each. Given the following data, how many units of natural gas must be purchased per day by the city to keep the digesters heated?
1. 60 units
2. 70 units
3. 80 units
4. 90 units
The pressure on a mechanical blower is high and the blowers keep kicking on and off.
What is most likely the problem?
1. The oil has water condensation in it
2. There was a power outage
3. The VFD needs to be recalibrated
4. The valves to the aeration basin are stuck closed
Which type of chlorine is the strongest?
1. Hypochlorous acid
2. Hydrochloric acid
3. Monochloramine
4. Hypochlorite ion
Given the following information, what is the volatile solids concentration of this sample?
• Weight of Crucible= 21.0256 g
• Weight of Crucible and Dry solids= 21.0301 g
• Weight of Crucible and Ash= 21.0263 g
• Volume of Sample Filtered= 50 mL
1. 52 mg/L
2. 69 mg/L
3. 76 mg/L
4. 90mg/L
Aeration blowers at a wastewater treatment plant have VFDs on them that will adjust the blowers if an issue is detected. If there is too much ammonia in the basins, the VFDs will
1. Increase the DO
2. Decrease the DO
3. Increase the RAS
4. Decrease the WAS
Which type of washer needs to go between a chlorinator and the cylinder to insure a good tight seal?
1. Lead
2. Copper
3. Anti-corrosive
4. Lock washer
A wastewater treatment plant has 2 large bubble compressors. For some reason the compressors keep switching over to the other over and over again.
What is the best solution to fix the problem?
1. Change the oil
2. Change the seal on the pressure relief valve
3. Monitor the operating hours on each compressor
4. Switch out the air filters on both compressor
150 pound chlorine cylinders should always be stored and moved in what position?
1. Vertically
2. Horizontally
3. Rolled
4. Carried
A chlorine leak has developed in the chlorine gas system. The best way to check for this leak is to use
1. Water
2. Alcohol
3. Ammonia fumes
4. Black clouds
An operator connects a chlorine line to the bottom valve of a 1 ton container expecting to remove liquid chlorine. Instead, chlorine gas comes out through the lower valve. They switch the line to the upper valve, but still pull gas instead of liquid.
What is the most likely reason for both valves to produce gas?
1. Eductor tube has broken off within the container
2. Container is positioned so both valves are below the liquid level
3. Container is less than 50% full of liquid chlorine
4. Excessive heat has converted all of the liquid chlorine to gas
An anaerobic digester is receives an MLSS that is 7,000 mg/L. The MLSS contains 80% volatile suspended solids. The digester has solids that are 1.82%. The solids that get loaded on the trucks and sent to farm lands contain 67% volatile solids.
What is the volatile solids reduction of this anaerobic digestion system?
1. 49%
2. 52%
3. 56%
4. 60%
Which parameter is the best to use as a control for anaerobic digestion?
1. pH
2. Temperature
3. Volatile acid/Alkalinity ratio
4. Organic loading
You are viewing past data for your anaerobic digesters. The temperature looks great but the volatile acid to alkalinity ratio has increased from 0.1 to 0.3.
What is the best action to take to fix this problem?
1. Increase the sludge feed rate
2. Increase the sludge withdraw rate
3. Increase the detention time in the tank
4. Decrease the sludge feed
The chlorine residual concentration, and ability to disinfect, are lowest _______________.
1. To the left of the break point
2. At the hump, before combined residual destruction
3. At the breakpoint
4. To the right of the break point
Which of the following chemical species will not be measured in the total chlorine residual?
1. Hypochlorous acid
2. Hypochlorite ion
3. Chloride ion
4. Monochloramine
Chlorine and hypochlorites break down in water to form _________________.
1. Hypochlorous acid and hypochlorite ion
2. Hypochlorous acid and hydrochloric acid
3. Hypochlorite ion and hydrogen ion
4. Hydrochloric acid and chloride ion
How many fusible plugs does a one-ton chlorine container have?
1. 1 fusible plug
2. 3 fusible plugs
3. 6 fusible plugs
4. 9 fusible plugs
It is best practice to only open a chlorine cylinder by ______________.
1. 1/8 of a turn
2. ¼ of a turn
3. 1/3 of a turn
4. ½ of a turn
Fusible plugs will melt at _____________.
1. 70 to 74 degrees C
2. 158 to 165 degrees C
3. 165 to 172 degrees F
4. 170 to 175 degrees F
By law, chlorine cylinders and containers are filled to a maximum of _____________.
1. 70%
2. 80%
3. 90%
4. 100%
What happens to the activity rate of activated sludge microorganisms as the temperature increases by 10 degrees C?
1. It is cut in half
2. It doubles
3. It remains the same
4. It triples
A pump is rated at 120 volts and it takes 1.5 KW to run it. How many amps will be used with a power factor of 1:1?
1. 4.0 amps
2. 14.7 amps
3. 22.5 amps
4. 12.5 amps
A single piston pump delivers 2.5 gallons and reciprocates at 40 strokes per minute. How long will the pump take to pump 3,500 pounds of sludge at 5% solids?
1. 50 minutes
2. 67 minutes
3. 78 minutes
4. 84 minutes
When a chlorine gas leak is identified, what color will it turn?
1. Yellow green
2. Amber
3. White
4. Yellow
How much alkalinity was consumed, using the standard 7.2 pounds of alkalinity consumed per pound of ammonia converted, given the effluent NH₃ value in the data?
1. 30 Pounds
2. 1,932 Pounds
3. 13,908 Pounds
4. 14,012 Pounds
Which noise level in the workplace does OSHA require implementation of a hearing protection program?
1. 120 decibels, 2 hours, time weighted average
2. 90 decibels, 16 hours, time weighted average
3. 85 decibels, 8 hours, time weighted average
4. 14,012 Pounds
An operator wants to figure out the SVI on the sludge blankets on the secondary clarifiers. The settleometer at 30 minutes was 325 ml/L and the MLSS was 3,500 mg/L at 74% volatile solids. Giving the following data, what is the SVI of this mixed liquor?
1. 93
2. 125
3. 186
4. 251
What is the main advantage of having an egg shaped anaerobic digester than a cylinder shaped digester?
1. More gas production
2. Less scum production
3. Less construction costs
4. More surface area
An activated sludge basin holds 3.0 million gallons of MLSS with a concentration of 2,500 mg/L. The plant is set to waste at 80 gallons per minute. The WAS/RAS concentration is 8,000 mg/L. What is the SRT of this treatment plant?
1. 8 days
2. 11 days
3. 14 days
4. 16 days
Which chemical is most commonly used to convert H₂S gas in a wet scrubber tower?
1. Sodium hydroxide
2. Sodium bicarbonate
3. Potassium chloride
4. dLime
A river that flows upstream and downstream of a wastewater treatment plant typically has a fecal coliform number of 15 MPN upstream and 25 MPN downstream. One day, you take a look at lab data and notice an MPN of 275 upstream and 319 downstream.
What is the most likely reason for the increased fecal coliform number?
1. A storm happened last night, increasing the amount of toxins in the river
2. A digester spill has happened and the sludge went into the river
3. I&I has entered the river from a collection sewer overflow
4. Someone illegally discharged sodium hydroxide to the river
Nametags on shirts, city logos on trucks and ID badges are all part of which control department?
1. Human Resources
2. Risk Management
3. Civilian Acknowledgment and Awareness
4. Reward System
A BOD bottle can be removed from the incubator at 5 days plus or minus __________.
1. 1 hour
2. 2 hours
3. 3 hours
4. 4 hours
Fecal coliform tests are reported as MPN per 100 mL. The fecal coliform to sample volume ratio is 5:10.
How will you express this reading?
1. 5 MPN/10mL
2. 50 MPN/100mL
3. 500 MPN/1000mL
4. 50,000 MPN/10,000mL
Filamentous bulking of activated sludge may be controlled temporarily by ________________.
1. Adding more air to the aeration tank
2. Spraying water on the aeration tank surface
3. Chlorinating the return sludge or mixed liquor
4. Aeration to the final settling tank
The best operation strategy for feeding primary sludge to an anaerobic digester is to feed ________________.
1. Several times a day
2. Large quantities once or twice a day
3. Once a day
4. When the volatile solids drop below 60%
The best way to give your employees an ideal plan is to _________________.
1. Say they will be responsible for the whole outcome of the plan
2. Fire them if they don’t do the ideal plan
3. Tell them that the employee who does the least work on the plan will be fired
4. Give the employee who works the hardest on the plan a reward
Which repair kit is used with a 150 pound cylinder of chlorine?
1. Kit A
2. Kit B
3. Kit C
4. Kit T
Using the breakpoint chlorination method of ammonia removal, how many parts of chlorine are needed to remove one part of ammonia?
1. 2 parts
2. 5 parts
3. 10 parts
4. 25 parts
What pipe material is needed to transport chlorine under pressure from one ton containers to downstream equipment components?
1. Black iron pipe
2. PVC pipe
3. Ductile clay pipe
4. Pre-stressed concrete pipe
A secondary clarifier has a 25 foot radius and is 17.5 feet deep. There are 1,736 gallons per minute going through the clarifier. What is the detention time in hours?
1. 0.62 hours
2. 3.0 hours
3. 2.0 hours
4. 2.5 hours
BOD tests were done at a wastewater treatment plant. The initial DO of the sample was 7.5 mg/L. After 5 days, the sample had a DO of 3.0 mg/L. If the operator used 50 mL of sample, what is the BOD result of this sample?
1. 21.5 mg/L
2. 24.6 mg/L
3. 25.3 mg/L
4. 27.0 mg/L
A wastewater treatment plant has a total aeration volume of 2.12 million gallons. The MLSS in the aeration basins is 3,112 mg/L and the return activated sludge has a concentration of 4,572 mg/L. The plant has a total influent flow of 6.5 MGD and the effluent has a TSS concentration of 12 mg/L.
Given the following data, how many gallons per minute should this wastewater treatment plant waste if the target SRT is 10 days?
1. 50 gpm
2. 75 gpm
3. 100 gpm
4. 125 gpm
75. Liquid chlorine is backflowing into the tank and the tank level is rising, even though the chlorinator is still trying to pump chlorine.
What is the best solution to solve the issue?
1. Replace the chlorinator with a new one
2. going down toward the contact point toward the contact point
3. Clean the chlorinator with trivalent chromium
4. Replace the injection check valve
How long can a BOD sample be preserved before running the test?
1. 24 hours at 6^o C
2. 48 hours at 4^o C
3. 12 hours at 4^oC
4. 36 hours at 6^o C
The utility is preparing to implement a new emergency response plan. This plan is meant to be used during various types of emergency situations. This plan is also known as ____________.
1. Contingency plan
2. Mitigation master plan
3. Preparedness objective
4. Predisposition assessment
What is the only acceptable piece of equipment that should be stored in a chlorine cylinder gas feed room?
1. Self-Contained Breathing Apparatus
2. Eye wash station
3. Repair kit tools
4. Empty chlorine tanks
Where is the pressure relief valve located in a chlorine or sulfur dioxide evaporator?
1. Inside the tank
2. Upstream of the gas outlet
3. Downstream of the gas outlet
4. Between the metal to metal seal
A chlorine evaporator is equipped with catholic protection to help prevent corrosion from happening.
What is it also equipped with to help prevent corrosion?
1. 6% Moly coating on the inside of the tank
2. Anodic protection
3. Ozone treated water with no minerals
4. 4 magnesium-anode rods
The preservative used for transport of the fecal coliform sample is ___________.
1. 0.2% sulfuric acid
2. 0.5% nitric acid
3. Ice to 4 degrees C
4. Ice the sample for no less than 6 hours minimum
As denitrification occurs in the anoxic tank, what is the expected effect on the parameters listed below?
1. Alkalinity: No change pH: Increase Ammonia: Decrease Nitrate: Decrease
2. Alkalinity: Decrease pH: Increase Ammonia: Decrease Nitrate: Increase
3. Alkalinity: Increase pH: Increase Ammonia: No change Nitrate: Decrease
4. Alkalinity: Decrease pH: Decrease Ammonia: Decrease Nitrate: Increase
Chlorine residual can be measured in several ways, including the use of DPD reagent, spectrophotometers, and iodometric titration. Which of the following is also an approved method?
1. Meg-ohm method
2. Amperometric titration
3. Winkler method
4. Standard titration method
If the sludge concentration coming off the gravity belt thickener is too low, which adjustment will the operator most likely make?
1. Increase the polymer dose
2. Decrease the belt speed
3. Increase the belt speed
4. Decrease the polymer dose
If you have a static head of 20 feet, a friction loss of 16 feet, and a static lift of 40 feet, what is the total dynamic head?
1. 4 ft TDH
2. 76 ft TDH
3. 87 ft TDH
4. 108 ft TDH
Chlorine gas is used to disinfect the final effluent. If the effluent flow is 2.5 MGD and 281 pounds of chlorine is used each day, what should the dose be set at?
1. 10.23 mg/L
2. 11.87 mg/L
3. 12.55 mg/L
4. 13.47 mg/L
You are walking past the non-potable water pumping room and you hear a loud banging noise. You go in the room to investigate the loud sound and you see the piping is having terrible water hammer issues and the pumps are running at 100%. What is the most likely cause of this problem?
1. The pumps were shut off and got started too quickly
2. The non-potable water filter did not get put back into service resulting in too many solids for the pumps
3. There is a high demand for the non-potable water, resulting in the water flowing too quickly
4. The lines are dry and the pumps are pumping air
The volatile acid to alkalinity ratio of a properly operating anaerobic digester is ___________________.
1. 0.1 parts acid to one part alkalinity
2. 0.3 parts acid to one part alkalinity
3. 0.8 parts acid to one part alkalinity
4. 1.0 parts acid to one part alkalinity
A pump is discharging 5.0 MGD against a total head of 15 feet. The pump runs at 70% efficiency and the motor runs at 90% efficiency. What is the motor horsepower?
1. 5.48 BHP
2. 10.66 BHP
3. 17.22 BHP
4. 20.87 BHP
MLSS with a concentration of 1800 mg/L was placed into a settleometer and allowed to settle for 30 minutes. The initial sludge volume was 2000 mL and the 30 minute sludge volume was 280 mL.
IWhat is the SSC?
1. 6,429 mg/L
2. 7,143 mg/L
3. 12,857 mg/L
4. 14,286 mg/L
Which wavelength of UV light is needed for proper disinfection of bacteria?
1. 190 nanometers
2. 254 nanometers
3. 336 nanometers
4. 480 nanometers
A wastewater treatment plant uses ultraviolet light to disinfect effluent going into the river. How does the ultraviolet light allow for proper disinfection?
1. The UV light kills the bacteria almost immediately after being exposed to it due to UV radiation
2. The UV light heats up the wastewater enough so that bacteria cannot survive
3. UV rays penetrate harmful pathogens by attacking their genetic core (DNA)
4. UV rays oxidize harmful substances (ammonia, nitrite, phosphorus) and sanitizes bacteria
A centrifugal pump has just been put back into service but is not delivering properly. What is the problem with the pump?
1. Barings are misaligned
2. There is water condensation in the oil reservoir
3. The pump has cavitation problems
4. There is a clog in the outlet line
What would be the anticipated result of increasing the belt speed in a gravity belt thickener?
1. The solids content will increase
2. The volatile solids content will increase
3. The belt may blind
4. The solids content will decrease
An operator notices that the nitrate levels in the Bardenpho process are higher than normal. The operator needs to make an adjustment soon because the treatment plant will be undergoing bio-monitoring in a few weeks.
Which adjustment will decrease the nitrate levels in the Bardenpho process?
1. Increase the internal recycle rate
2. Decrease the internal recycle rate
3. Increase the DO
4. Decrease the RAS
A wastewater treatment plant that uses HTH has a flow of 9 MGD and a set dose of 8.0 mg/L. If the HTH is only at 15% strength, how many pounds of HTH will be used per day?
1. 90 Lbs/day
2. 601 Lbs/day
3. 900 Lbs/day
4. 4,003 Lbs/day
When performing an MPN, the sample dilution is considered positive when _______________.
1. The Durham tube is found upside down
2. The sample turns color from amber to brown
3. No bubbles are found in the Durham tube
4. Gas bubbles are found in the Durham tube
Given the following data, what is the most likely cause of the up-flow, continuous backwash, deep bed sand filter problem?
1. Effluent valve open too much
2. Reject/washwater flow rate too low
3. Too many filters on-line
4. Influent valve open too much
A wastewater treatment plant has two anaerobic digesters. These digesters create gases that are further used to heat boilers on site.
What does the gas pressure normally read?
1. 6 to 8 inches above the static water level
2. 2 to 4 inches above the static water level
3. 6 to 8 PSI
4. 8 to 10 inches of water column
An advantage of a continuous backwash, up flow, deep bed, sand filter is ___________.
1. Filters do not need to be taken out of service for backwashing
2. Filters do not need coagulants
3. Filter backwash does not need to be returned to the plant for treatment
4. Filters do not need routine maintenance

Intermediate Study Questions Provided By RoyCEU.com

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