Wastewater Class C Exam Questions and Answers, Exams of Water and Wastewater Engineering

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WASTEWATER CLASS C EXAM

QUESTIONS WITH THE LATEST

AND UPDATED SCORE.

1. Industrial waste materials which are usually not compatible with municipal treatment plants include: A. chemical oxygen demand B. Heavy metals. C. petroleum fats , oils and greases D. nitrogen and phosphorus compounds. E. B and C -- Correct Answer ✔✔ B. Heavy metals.
2. Sludge is observed to accumulate in the final clarifier. This may be caused by : A. plugged sludge collectors return pumps or waste pumps B. too high a return rate. C. excessive solids wasting. D. hydraulically overloaded clarifier E. All of the above. -- Correct Answer ✔✔ A. plugged sludge collectors return pumps or waste pumps
3. What is the relationship between the F/M ratio and the MCRT sludge age for a particular plant when the aerator detention time is a constant value. A. these to control parameters are unrelated. B. When one increases the other increases. C. When one increases the other decreases. D. it is a direct relationship

E. The F/M ratio is one tenth of the MCRT (Sludge Age) -- Correct Answer ✔✔ C. When one increases the other decreases.

4. Using results only from the settle-ability test and MLSS test of activated sludge solids the operator will be able to A. calculate the F/M ratio B. Set the doge for chlorinating the return activated sludge C. Calculate the MCRT D. Calculate the SVI E. A and C -- Correct Answer ✔✔ D. Calculate the SVI
5. Which of the following F/M ratios would be in the proper rage for a contact stabilization activated sludge plant? A. 0. B. 0. C. 0. D. 0. E. 1.25 -- Correct Answer ✔✔ C. 0.
6. Short circuiting in a final sedimentation process: A. is probably caused by mechanical failures. B. usually represents a hydraulic deficiency of design or operation C. Increases efficiency by facilitating rapid movement of treatment plant effluent D. has no effect on plant performance. E. All of the above. -- Correct Answer ✔✔ B. usually represents a hydraulic deficiency of design or operation
7. An old, over oxidized sludge at an underloaded plant produces mixed liquor solids that A. settle slowly but produce a clear effluent

B. Settle rapidly leaving a turbid supernatant. C. Cannot nitrify but turn septic readily in the final clarifier D. All the above E. None of the above. -- Correct Answer ✔✔ B. Settle rapidly leaving a turbid supernatant.

8. The Correct operational response to a gently settling sludge which stays in the bottom two feet of the clarifier and produces a clear final effluent is to A. Increase return sludge flow rate B. Decrease return sludge flow rate C. Increase sludge wasting D. Decrease sludge wasting E. continue with past operating practices. -- Correct Answer ✔✔ E. continue with past operating practices.
9. The Activated Sludge Process: A. requires pre aeration B. requires Activated Carbon C. is an aerobic biological process. D. Usually precedes primary sedimentation. E. Requires 50% by volume old sludge to work effectively. -- Correct Answer ✔✔ C. Is an Aerobic biological process
10. A complete mix activated sludge plant has a fast settling sludge and high amounts of pin floc leaving the clarifier. One way to correct this problem is to : A. Increase the RAS Flow B. Reduce Wasting Rates C. Increase dissolved oxygen levels. D. Increase the F/M ratio by wasting more E. Increase the sludge age by wasting less. -- Correct Answer ✔✔ D. Increase the F/M Ratio by Wasting More

11. Who can sign the effluent Discharge Monitoring Report? -- Correct Answer ✔✔ Operator with signature authorization and an executive or official of the permittee
12. True or False: Chlorine disinfection works better at a PH of 9 rather than 6 -- Correct Answer ✔✔ False
13. Pooling on a trickling filter can be caused by -- Correct Answer ✔✔ Increased BOD strength entering the plant
14. If the disinfection residual after 20 min is between 1mg/l and 4 mg/l but E.coli is exceeding the permitted value what could be the cause -- Correct Answer ✔✔ Bacteria and algae sloughing off of the clarifier weirs
15. Granular HTH is explosive or flammable when mixed with what? -- Correct Answer ✔✔ Petroleum products
16. When working on an open channel uv system one should? -- Correct Answer ✔✔ Use Lock Out/ Tag Out procedures before beginning work
17. What must you do before placing a pump back into service that has been locked out -- Correct Answer ✔✔ Find the person that applied the LOTO and have him remove it once the pump is ready
18. Which of the following flow rates should be measured if the operator is to control plant properly? A. Aeration rate or resulting dissolved oxygen level. B. Influent or effluent. C. return sludge D. waste sludge E. all the above -- Correct Answer ✔✔ E. all the above

19. During start up your aeration tank produces excessive amounts of billowing white foam. This can be corrected by: A. Doing nothing, it will go away in a few hours B. Increasing the sludge wasting rate C. Seeding the process with sufficient good quality sludge D. Spraying water on the foam until it is gone E. Taking a weeks vacation -- Correct Answer ✔✔ C. Seeding the process with sufficient good quality sludge
20. In solving an operational problem at a treatment plant: A. there is almost always a good technical solution. It may require considerable experience and time to learn whaat it is. B. Human errors have to be corrected since the operator is at fault. C. don't let the laboratory personnel influence you're judgement as to what the best solution is. D. standard textbooks in sanitary engineering are the best source of information. E. It is best to do nothing until the TNRCCC sends a violation notice. -- Correct Answer ✔✔ A. there is almost always a good technical solution. It may require considerable experience and time to learn whaat it is.
21. When the return sludge rate is too low, what happens? A. the aeration tank will not fill B. There will be insufficient organisms to treat the waste load entering the aeration basin C. the activated sludge in the aerator will starve. D. the sludge blanket in the secondary clarifier could become too high. E. B and D -- Correct Answer ✔✔ E. B and D

22. What factors affect how well the mixed liquor suspended solids settle in the final clarifier? A. flow velocity and or turbulence B. temperature C. quality of the mixed liquor solids D. Short circuiting E. All of the above -- Correct Answer ✔✔ E. All of the above
23. The Active sludge process parameters which n operator can change directly are: A. aeration rates. B. waste rates. C. the ratio of free swimming to stalked ciliates. D. Return sludge rates. E. All the above except C. -- Correct Answer ✔✔ E. All the above except C.
24. Which of the following would you use to increase the degree of nitrification in an activated sludge plant? A. increase the waste rates B. increase dissolved oxygen levels and increase the sludge age C. Remove excess alkalinity from the wastewater D. Maintain a thicker sludge blanket n the clarifier E. Inhibit the growth of the nitrifying bacteria with chemicals. -- Correct Answer ✔✔ B. increase dissolved oxygen levels and increase the sludge age
25. The Maximum change in the sludge wasting rates to maintain uniform operating conditions should be about A. 10- 20 % per day B. 20-40 % per day C. 40-60 % per day

D. 60-80 % per day E. 100% per day -- Correct Answer ✔✔ A. 10- 20 % per day

26. When operating an activated sludge plant, Which TSS concentration is most important for process control? A. Primary effluent B. Aeration tank mixed liquor. C. Return Sludge D. Digester. E. Plant influent -- Correct Answer ✔✔ B. Aeration tank mixed liquor.
27. How many aeration tanks does a contact stabilization plant have? A. one, like all the others B. Four: contact, mix, reaeration and stabilization C. Two if you count the digester as an aeration tank D. a contact tank and a reaeration tank E. none of this makes any sense to me. -- Correct Answer ✔✔ D. a contact tank and a reaeration tank
28. Reducing the return sludge flow rate for an activated sludge system which has a good settling sludge will. A. Decrease the hydraulic detention time in the aeration basin B. Increase the solids concentration in the aeration basin C. cause the return sludge concentration to decrease D. have no effect on process performance. E. increase the RAS concentration and the clarifier blanket thickness. -- Correct Answer ✔✔ E. increase the RAS concentration and the clarifier blanket thickness.
29. What items would you check if an activated sludge plant becomes upset?

A. Influent temperature. B. Monthly average flow rates C. BOD loadings MLSS sludge settle-ability D.O. and oxygen uptake rate D. digester operation. E. Chlorinator settings. -- Correct Answer ✔✔ C. BOD loadings MLSS sludge settle-ability D.O. and oxygen uptake rate

30. Causes of sludge bulking include: A. Low DO and presence of sulfides B. Air supply too low C. organic loading rate too high D. nutrient imbalance. E. All the above can cause bulking. -- Correct Answer ✔✔ E. All the above can cause bulking.
31. Certain violations at a WWTP require written notice within 5 days to the Executive Director of the TCEQ. What would be a reason? A. Exceed the permitted limit by more than 40% B. Endangers human health C. Operator bypasses treatment without prior authorization D. All of the above -- Correct Answer ✔✔ D. All of the above
32. Effluent should be Neutralized so it does not adversely affect the aquatic life. What should the PH be A. 2 B. 4 C. 7 D. 10 E. 12 -- Correct Answer ✔✔ C. 7
33. A centrifugal pump running at 100% with restricted flow is registering 40 amps. If the pump is changed to run at 50% and

the restriction is removed causing increased flow. What happens to the number of amps? A. Increase B. Decrease C. Stays the same D. Does not Change -- Correct Answer ✔✔ B. Decrease

34. The chlorine room is required to have two air vents. One is a forced air fan at the top where should the vent on the opposite wall be placed? A. At the top B. Half way up the wall C. At the Bottom -- Correct Answer ✔✔ C. At the Bottom
35. Carbon Dioxide is hazardous in a closed environment In an activated sludge plant this could -- Correct Answer ✔✔ Makes up 3-4% of normal sludge gas
36. The required detention time for a chlorine contact chamber is how many minutes? A. 5 B. 10 C. 15 D. 20 E. 25 -- Correct Answer ✔✔ D. 20
37. If a treatment plant has a high air flow rate and it is not overloaded with BOD, what could be the cause of low dissolved oxygen. -- Correct Answer ✔✔ Leaks in the air lines, and plugged diffusers
38. The influent BOD is not high but the plant appears to be overloaded. What could be causing the problem?

A. High solids from thickeners to digester B. High solids in belt press C. Supernatant from digester to aeration D. RAS too high -- Correct Answer ✔✔ D. RAS too high

39. What are some of the disadvantages of a manual bar screen? -- Correct Answer ✔✔ Must be cleaned often
40. Grease and oil can pass through a plant and cause? -- Correct Answer ✔✔ Pumps too clog, collect on weirs, pass through the facility and endanger aquatic life.
41. After collecting a 30 Min. set, what characteristics of a true bulking sludge would show? A. Settles fast with a cloudy supernatant B. Settles slowly with only a few milliliters of clear liquid at the top C. Sludge in bottom 1/3 with clear supernate D. Settles slowly with fluffy sludge E. Settles fast with clear supernate and pin floc -- Correct Answer ✔✔ B. Settles slowly with only a few milliliters of clear liquid at the top
42. Ponds should be designed to A. always be 10 feet deep B. Have an influent pipe with multiple outlets C. Maintain lots of vegetation on slopes D. Have trees to provide shade -- Correct Answer ✔✔ B. Have an influent pipe with multiple outlets
43. The most accurate samples showing conditions through the day are? Samples collected at even intervals throughout the day i called a ____________ Sample -- Correct Answer ✔✔ Flow weighted composite

44. When collecting E. Coli samples, one should? A. Not collect on rainy or windy days B. Do not touch the inside of the lid or bottle C. Use bottles sterilized in a laboratory D. Collect directly into the bottle when possible E. All the above -- Correct Answer ✔✔ E. All the above
45. Analysis of dissolved oxygen must be performed how soon after collection? -- Correct Answer ✔✔ Immediately
46. Flow measuring devices must be calibrated where? -- Correct Answer ✔✔ The 0" reading is at the bottom of the v-notch
47. To improve accuracy of a flow measuring device one could? -- Correct Answer ✔✔ Clear algae or growth from sides to provide for even flow.
48. What helps the process by removing small bits of bacteria and organics from the clarifier? -- Correct Answer ✔✔ Protozoa
49. Using alternating controls on lift pumps allows the operator to -- Correct Answer ✔✔ Evenly wear pumps so they are ready for use.
50. Floats in a lift station are designed to -- Correct Answer ✔✔ Measure liquid levels and trigger pump controls
51. Primary clarifiers can have a higher surface loading rate than secondary clarifiers because -- Correct Answer ✔✔ The particles are heavier so they settle faster
52. Treated sludge that is land applied is beneficial to the soil by adding -- Correct Answer ✔✔ Nutrients
53. When installing pipe underground which way should the bel be installed -- Correct Answer ✔✔ Uphill

54. What hazards would you find in an aeration tank? A. Hazardous/Toxic gases B. Drowning due to lack of buoyancy C. Waterborne diseases D. All of the above -- Correct Answer ✔✔ D. All of the above
55. The grit removal of inorganic from a wastewater plant helps with maintenance. What effects would they have on the plant -- Correct Answer ✔✔ Oil and grease and clog pumps
56. If a centrifugal pumps 100 gallons using 100 mps with a good impeller, what happens to the amps when a pump has a worn impeller? A. Amps increase B. Amps decrease C. Amps stay the same D. Amps can increase or decrease -- Correct Answer ✔✔ A. Amps increase
57. What causes corrosion in a collection system -- Correct Answer ✔✔ Hydrogen sulfide
58. The water in a wastewater collection line is septic, what are the characteristics -- Correct Answer ✔✔ More gases than fresh raw wastewater
59. A pump has a worn impeller the energy cost would be A. More B. Less C. The same -- Correct Answer ✔✔ A. More