Class C Wastewater Treatment Plant



Class C Wastewater Treatment Plant

Operator Sample Questions

1. As the operator of a primary clarifier, you notice black and odorous septic wastewater leaving the clarifier. What is the probable cause?

a. Withdrawing sludge too frequently

b. Improper sludge removal

c. Excessive I&I entering the WWTP

d. Excessive oil and grease entering the WWTP

2. A fire has started in the maintenance shop due to an ignition of petroleum oil. Which type of fire extinguisher should NOT be used to fight the fire?

a. CO2

b. Purple K

c. Pressurized water

d. Dry chemical

3. Chlorine gas is how many times heavier than air?

a. 1 times

b. 2.5 times

c. 7 times

d. 25 times

4. The combination of methane and ______________ can be very combustible?

a. Carbon monoxide

b. Carbon dioxide

c. Carbon tetrazzini

d. Oxygen

PLANT PROBLEM: Plant effluent coliform count fails to meet required standards for disinfection. Chlorine residual is normal. Disinfectant supplies are not a problem.

5. Probable cause:

a. Capacity of chlorinator too low

b. Too little solids in effluent

c. Contact time too short

d. Chlorine demand too high

6. A fixed sample is

a. Not broken

b. A sample purposely ‘spiked’ by the lab technician for QA/QC

c. A series of composite samples

d. A sample preserved in the field upon collection

7. PROBLEM:

Classic sludge bulking occurring in the final clarifier of a conventional activated sludge plant. Indicators include solids pouring over the weirs, excessive floc observed at the surface, and a homogenous sludge blanket appearing throughout the clarifier. Sludge in settling test settles slowly leaving a cloudy supernatant. What is the MOST probable cause?

a. Over-oxidized sludge

b. Hydraulic washout

c. Young sludge

d. SVI too low

8. How many fusible plugs can be found on a one-ton chlorine container?

a. 1

b. 2

c. 6

d. There are no fusible plugs on a one-ton container

PROBLEM:

Operational data is given below for a primary clarifier:

Influent flow: 2.5 mgd

Primary tank volume: 41,310 cubic feet

9. Calculate the primary clarifier detention time in hours.

a. 0.3 hours

b. 3.0 hours

c. 13.0 hours

d. 16.8 hours

PROBLEM:

Good settling in the 30-minute settleability test. Excessive floc billowing in the clarifier and washing out. Sludge scrapers and RAS system appear normal.

10. What is the BEST solution to fix the problem?

a. Lower aeration tank effluent weirs

b. Increase RAS

c. Add chlorine to RAS

d. Reduce clarifier hydraulic loading rates

11. The first step in anaerobic digestion is called

a. Acid formation

b. Stabilization

c. Methane formation

d. Alkalinity formation

12. According to FDEP Chapter 62-602 FAC, an operator could have his/her license permanently revoked for

a. Falsified or misrepresented reports, logs or lab sheets

b. Cheating on an exam

c. Incompetence in operation of a wastewater treatment plant

d. Submitting false data on license application

13. What process do the bacteria perform in the stabilization (re-aeration) tank in the contact-stabilization process?

a. Adsorption of the activated floc

b. Adsorption of waste material by microorganisms

c. Agglomeration of the activated floc

d. Absorption and digestion of the waste material they collected

14. A screenings dumpster at the headworks of the treatment plant is full at the end of the day. The dumpster is 6 ft tall, 10 feet long and 8 feet wide. How many cubic yards of screenings must be disposed of in a 30-day month?

a. 18

b. 129

c. 480

d. 533

15. According to Chapter 62-620 FAC, Wastewater Permitting, plant records must be maintained on-site for how many years?

a. One year

b. Three years

c. Five years

d. Forever

16. When properly adjusted, the rope packing on a centrifugal pump is designed to leak how much?

a. One drip per second

b. One drip per hour

c. A steady, pencil-sized stream should flow at all times

d. There should be NO leaks from a rope packing

17. A confined space is defined as having a space large enough to bodily enter and perform work, has limited entry and egress and is _________________?

a. Not designed to perform strenuous computer calculations

b. Designed for state exam prep classes

c. Not designed for continuous occupancy

d. Designed as a long-term hurricane and tornado shelter

18. F/M Ratio can be BEST be described as:

a. The loading of solids to a trickling filter

b. The amount of influent TSS applied to the aeration tank

c. The pounds of CBOD applied to a pound of MLVSS

d. The amount of soluble CBOD fed to an RBC

19. The preservative used for transport of the fecal coliform sample is

a. 0.2% sulfuric acid

b. 0.5% hydrochloric acid

c. Ice to 4°C

d. Ice the sample for no less than 6 hours minimum

20. What is the removal efficiency of the solids contact/trickling filter process if the influent TSS is 439 mg/L and the plant effluent TSS is 4.0 mg/L?

a. 4%

b. 40%

c. 89%

d. 99%

PROBLEM:

Classic sludge bulking occurring in the final clarifier of a conventional activated sludge plant. Indicators include solids pouring over the weirs, excessive floc observed at the surface, and a homogenous sludge blanket appearing throughout the clarifier. Sludge in the settling test settles slowly leaving a cloudy supernatant. What is the necessary check to confirm the cause?

21.

a. Weir overflow rate

b. Determine effluent suspended solids concentration

c. Calculate the sludge age

d. DO in aeration tank

22. According to FDEP chapter 62-600.440 (4)(c) 4, basic level disinfection, any ONE sample may not exceed how many colonies per 100 ml sample?

a. 100

b. 200

c. 500

d. 800

23. Mixing dry granular chlorine with petroleum products will

a. Create anhydrous chlorine dioxide

b. Create an explosive condition

c. Create hydrogen dioxide

d. Create a white cloud

24. In a lab, a dilute acid solution must be prepared for titration in the alkalinity test. The proper procedure for making the weak acid is to:

a. Add the water slowly to the concentrated acid to begin dilution.

b. Add the water quickly to the acid to begin dilution.

c. Add the acid directly to the sample without dilution.

d. Add the acid slowly to the dilution water.

25. What is the dosage of chlorine, in mg/L, if the flow being treated is 85,000 gpd and 3 pounds of chlorine are used per day?

a. 0.42 mg/L

b. 1.4 mg/L

c. 2.3 mg/L

d. 4.2 mg/L

26. PROBLEM:

Upon arriving at the package treatment plant serving a small community, you find a uniform sludge blanket rising throughout the clarifier. A settleability test reveals a very slow-settling sludge leaving a clear supernatant. MLSS test results are normal, but a calculation of the SVI shows a high sludge volume index. What is the MOST likely cause of the high sludge blanket?

a. The operator has wasted too much sludge, causing a young sludge condition.

b. An extreme rain event washed out the majority of the solids.

c. Filamentous bacteria are causing the slow settling.

d. An overdose of chlorine has killed the floc forming and filament bacteria.

27. PROBLEM:

Solids are washing out of the secondary clarifier of the activated sludge plant. Plant personnel increase the return activated sludge (RAS) flow rate, which slows the problem temporarily, but gets worse after 30 minutes. What is the cause of the plant problem?

a. increasing the RAS increased the detention time in the clarifier

b. increasing the RAS decreased the detention time in the clarifier

c. increasing the RAS increased the detention time in the aeration tank

d. Increasing the RAS caused the DO in the aeration

28. PROBLEM:

The chlorine residual is falling, and inspection of the 150-lb. 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 to:

a. switch over to sodium hypochlorite solution.

b. place a second chlorine cylinder on-line.

c. roll the cylinder so liquid is feeding instead of gas.

d. place a 1500W space heater next to the cylinder to thaw the ice.

29. According to FDEP chapter 62-601, FAC, a composite sample shall be used for which test?

a. Total chlorine residual

b. Effluent CBOD

c. Effluent pH

d. Effluent fecal coliform

30. According to FDEP chapter 62-604.550 (a) FAC, a wastewater spill shall be verbally reported to the state warning point no later than:

a. 8 hours from discovery

b. 12 hours from discovery

c. 24 hours from discovery

d. 72 hours from discovery

31. According to FDEP chapter 62-600.440 (4)(b), basic disinfection is described as:

a. A chlorine residual of 0.5 mg/L for 30 minutes at peak hourly flow

b. A chlorine residual of 1.0 mg/L for 15 minutes at peak hourly flow

c. A chlorine residual of 0.5 mg/L for 15 minutes at peak hourly flow

d. A chlorine residual of 0.5 mg/L for 30 minutes at average daily flow

32. pH is the measure of the

a. Amount of an acid

b. Intensity of the basic or acidic condition of a liquid

c. Acidity

d. Alkalinity

33. The most important adjustments to the activated sludge process are made by adjusting

a. Aeration, pH and RAS

b. Aeration, pH and WAS

c. RAS, WAS and aeration

d. pH, RAS and WAS

PROBLEM:

Excessive white, billowing foam in the aeration tank surface.

34. What is the MOST probable cause?

a. pH too high

b. MLSS too low

c. Waste temperature too high

d. WAS too low

35. In an activated sludge plant, if the DO in the aeration tank suddenly decreases and the aerators are not the problem, what is the most probable cause?

a. F/M Ratio decreased

b. Increased organic load into tank

c. Denitrification occurring

d. MCRT too long

36. Operational data is given below for a conventional activated sludge treatment plant:

Influent flow: 5.0 mgd

Aeration tank volume: 3.5 MG

MLSS: 4200 mg/L

WASSS: 12,600 mg/L

WAS flow: 75,000 gpd

Effluent TSS: 45 mg/L

Calculate the MCRT.

a. 9.3 days

b. 12.6 days

c. 17.9 days

d. 25.7 days

37. A waste treatment pond that is aerobic in the upper portion while the bottom layer is anaerobic is called

a. Anaerobic pond

b. Aerobic pond

c. Photosynthetic pond

d. Facultative pond

38. If a pump takes 30 seconds to fill a 5-gallon bucket, what is the pumping rate in gpm?

a. 5 gpm

b. 10 gpm

c. 15 gpm

d. 10 gph

39. What is the most beneficial process control tool in the operation of an anaerobic digester?

a. pH

b. Alkalinity

c. Volatile acid

d. Volatile acid to Alkalinity ratio

40. pH is measured on a scale of

a. 0 – 20

b. 0 – 14

c. 1 – 14

d. 0 -100

Answer Key To

Class C Wastewater Treatment Plant

Operator Sample Questions

1. B

2. C

3. B

4. D

5. C

6. D

7. C

8. C

9. B

10. D

11. A

12. A

13. D

14. D

15. B

16. A

17. C

18. C

19. C

20. D

21. C

22. D

23. B

24. D

25. D

26. C

27. B

28. B

29. B

30. C

31. C

32. B

33. C

34. B

35. B

36. B

37. D

38. B

39. D

40. B

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