Download Texas Wastewater Class B | Questions with 100% Correct Answers | Verified | Latest Update and more Exams Water and Wastewater Engineering in PDF only on Docsity!
Texas Wastewater Class B | Questions with 100% Correct
Answers | Verified | Latest Update 2025
Texas Wastewater Class B Practice Questions โ Verified 2025
1. What is the primary purpose of an activated sludge process? A. Chlorination B. Removal of organic matter C. Sand filtration D. pH adjustment Activated sludge promotes biological degradation of organic material in wastewater. 2. What is the minimum chlorine contact time required by TCEQ rules when disinfecting wastewater effluent? A. 10 minutes B. 15 minutes C. 30 minutes D. 60 minutes TCEQ requires a minimum of 30 minutes contact time at peak flow for effective disinfection. 3. Which lab test best indicates the strength of wastewater? A. pH B. BOD C. TSS D. DO
Biochemical Oxygen Demand (BOD) reflects the amount of organic material present.
4. What is the typical range of pH for treated wastewater discharge? A. 5.0 - 6. B. 6.0 - 9. C. 7.5 - 10. D. 4.0 - 6. TCEQ requires pH of treated effluent to be within 6.0 to 9.0. 5. What type of bacteria thrives in the activated sludge process? A. Anaerobic B. Facultative C. Aerobic D. Pathogenic Aerobic bacteria dominate in the activated sludge system, using oxygen to break down waste. 6. What is the main cause of filamentous bulking in an aeration basin? A. High chlorine levels B. Low dissolved oxygen levels C. High alkalinity D. Excessive pH Low DO promotes filamentous bacteria growth, leading to poor settling sludge. 7. What is the typical MLSS concentration range for extended aeration systems? A. 500โ1,000 mg/L B. 2,000โ3,000 mg/L
11. What is the primary cause of septic conditions in a collection system? A. High velocity B. Low flow and lack of oxygen C. Excessive chlorine D. Alkalinity increase Low flow and lack of aeration lead to anaerobic (septic) conditions. 12. Which of the following is used to measure flow in open channels? A. Pitot tube B. Parshall flume C. Rotameter D. Venturi meter Parshall flumes are widely used in wastewater to measure flow in open channels. 13. What does a high SVI (Sludge Volume Index) typically indicate? A. Good sludge settling B. High BOD C. Poor settling and filamentous bulking D. Proper sludge age High SVI indicates the sludge is not settling well, possibly due to filamentous bacteria. 14. What is the recommended DO (dissolved oxygen) level in the aeration basin? A. 0.5โ1.0 mg/L
B. 2.0โ3.0 mg/L C. 4.0โ5.0 mg/L D. 6.0โ7.0 mg/L DO levels of 2.0โ3.0 mg/L support healthy aerobic biological activity.
15. What does the term โRBCโ stand for in wastewater treatment? A. Return BOD Concentration B. Rotating Biological Contactor C. Recirculating Bio Chamber D. Reduced Biological Carbon RBCs are fixed-film biological treatment systems that rotate slowly to expose biofilm to air and wastewater. 16. What should be done if sludge blanket levels in the secondary clarifier rise excessively? A. Increase aeration B. Increase sludge wasting rate C. Increase flow rate D. Add chlorine Excess sludge must be removed to prevent solids carryover into effluent. 17. What is the purpose of the digester in wastewater treatment? A. Chlorinate effluent B. Stabilize sludge through biological decomposition C. Remove grit D. Aerate the water Digesters reduce the volume and stabilize organic matter in sludge.
D. Raw wastewater Supernatant is the clarified liquid found above sludge in tanks.
22. Which condition may result from over-aerating an activated sludge system? A. Septic conditions B. Foaming C. Odor D. Nitrification Extended aeration may lead to nitrification, converting ammonia to nitrate. 23. What is a common symptom of a toxic shock to an activated sludge system? A. Increased BOD B. High pH C. Sudden loss of biological activity D. Increased MLSS Toxic materials can kill beneficial microorganisms, disrupting treatment. 24. What is a common cause of low pH in digesters? A. Acid formation during initial digestion B. Excessive aeration C. Chlorine overdose D. High sludge age Volatile acids accumulate in the early anaerobic digestion phase, lowering pH. 25. What is a manhole used for in a collection system? A. Bypass flow B. Metering wastewater C. Access for inspection and maintenance
D. Odor control Manholes allow entry into the sewer for maintenance or emergency response.
26. What is the primary gas produced during anaerobic digestion? A. Oxygen B. Methane C. Nitrogen D. Ammonia Methane is the primary byproduct of anaerobic digestion. 27. What happens if sludge is returned too rapidly from the clarifier to the aeration tank? A. Increased nitrification B. Overloading of aeration basin C. Septic conditions D. Loss of MLSS Returning too much sludge may overwhelm the aeration system. 28. What is the most common cause of foaming in an aeration basin? A. High chlorine B. Nocardia or filamentous bacteria C. Low pH D. High temperature Certain bacteria like Nocardia create stable foams. 29. What instrument is used to measure TSS (Total Suspended Solids)? A. DO probe B. Spectrophotometer
33. Which type of pump is commonly used to move sludge? A. Submersible pump B. Positive displacement pump C. Jet pump D. Centrifugal pump Sludge requires pumps that handle thick materials; PD pumps are ideal. 34. What is the first step in troubleshooting low DO in aeration basins? A. Add chlorine B. Check blower operation C. Increase MLSS D. Raise temperature A malfunctioning blower or low airflow causes low DO. 35. What is the minimum retention time for an aerobic digester? A. 1 hour B. 20 days C. 2 days D. 5 hours TCEQ recommends 20+ days for proper aerobic digestion. 36. What chemical is used to raise pH in wastewater? A. Alum B. Ferric chloride C. Lime D. Polymer Lime is commonly used to raise pH and reduce odor.
37. What does TCEQ require before discharging effluent into waters of the state? A. City approval B. Federal consent C. Valid discharge permit (TPDES) D. Public vote TPDES permits regulate discharge to ensure compliance with environmental laws. 38. Whatโs the best way to determine sludge age (solids retention time)? A. Flow readings B. pH trends C. Temperature logs D. Calculating from MLSS and sludge wasting rates Sludge age is calculated based on solids inventory and wasting. 39. What can be added to reduce phosphorus in wastewater? A. Chlorine B. Soda ash C. Alum D. Ammonia Alum (aluminum sulfate) binds phosphorus, aiding in its removal. 40. What is the primary purpose of tertiary treatment? A. Solids removal B. Advanced polishing (nutrients, pathogens) C. Screening
B. 250โ300 mL/g C. 80โ150 mL/g D. 300โ400 mL/g SVI in this range indicates efficient settling in secondary clarifiers.
45. What is the abbreviation MCRT used for? A. Maximum Chlorine Residual Test B. Mean Cell Residence Time C. Mechanical Clarifier Rotation Time D. Microbial Carbon Reuse Threshold MCRT is the average time microorganisms remain in the system. 46. What is the purpose of scum removal in clarifiers? A. Increase pH B. Reduce odors C. Remove floatable solids and grease D. Eliminate chlorine Scum is skimmed off to prevent accumulation of grease and debris. 47. What parameter is used to control the return sludge rate? A. BOD B. Sludge blanket depth C. Temperature D. SVI Operators monitor the sludge blanket to adjust return rates. 48. What is the purpose of effluent filters in small plants? A. Aeration
B. Clarification C. Tertiary solids removal D. pH adjustment Effluent filters trap fine solids before discharge.
49. What is the function of polymer in sludge treatment? A. Kill pathogens B. Aid in coagulation and dewatering C. Increase pH D. Break down solids Polymers help bind particles together to improve sludge settling. 50. What is the most likely cause of a rotten egg smell at a wastewater plant? A. Ammonia B. Hydrogen sulfide C. Chlorine gas D. Methane Hydrogen sulfide (HโS) smells like rotten eggs and forms under anaerobic conditions. 51. What type of valve is most suitable for throttling flow in wastewater systems? A. Gate valve B. Globe valve C. Check valve
C. 85โ95%
D. 99%
Secondary treatment removes most BOD through biological action.
56. What happens if the return activated sludge (RAS) rate is too low? A. Low effluent BOD B. Sludge washout from the clarifier C. Higher MLSS D. Reduced aeration Low RAS can cause insufficient sludge return and poor settling. 57. What is the purpose of an air relief valve in a wastewater system? A. Increase pressure B. Release trapped air from pipelines C. Prevent leaks D. Add oxygen Air relief valves prevent air lock in pressurized systems. 58. What instrument is used to measure chlorine residual? A. Turbidimeter B. DPD colorimeter C. pH meter D. DO probe The DPD (diethyl-p-phenylenediamine) method is standard for chlorine measurement. 59. What is the typical detention time for an aeration basin in extended aeration systems?
A. 1โ2 hours B. 3โ5 hours C. 18โ30 hours D. 40โ50 hours Extended aeration systems run longer detention times for complete digestion.
60. What is the most probable cause of rising effluent BOD? A. High alkalinity B. Insufficient aeration or microbial activity C. High chlorine D. Too much DO If microbes arenโt functioning properly, BOD wonโt be removed efficiently. 61. What effect does high temperature have on biological treatment? A. Slows down activity B. No effect C. Speeds up microbial metabolism D. Causes foaming Higher temperatures can enhance microbial growth up to a point. 62. What is the proper storage procedure for liquid chlorine containers? A. Store in direct sunlight B. Store in a well-ventilated, dry area away from heat C. Keep them upside down D. Store near fuel tanks Chlorine is hazardous and must be kept in controlled, ventilated environments.
D. Doubles Oxygen solubility decreases as temperature rises.
67. What is a cause of excessive foam in anaerobic digesters? A. High DO B. Overloading with volatile solids C. Nitrification D. Low temperature Overfeeding volatile solids can lead to foaming and gas release. 68. What is the typical range of percent solids in digested sludge? A. 0.1%โ0.3% B. 1%โ2% C. 2%โ6% D. 10%โ15% Digested sludge generally contains 2%โ6% solids before dewatering. 69. What is the purpose of the vent on a force main? A. Drain the line B. Release trapped air C. Increase flow D. Maintain pressure Air vents help prevent vapor lock in pressurized wastewater lines. 70. What are the main gases produced in anaerobic digestion? A. Hydrogen & oxygen B. Ammonia & oxygen C. Methane & carbon dioxide
D. CO2 & nitrogen These gases result from decomposition of organic matter in anaerobic conditions.
71. Whatโs the acceptable range for chlorine residual in wastewater effluent per TCEQ standards? A. 0.5โ1.0 mg/L B. 0.1โ4.0 mg/L C. 5โ10 mg/L D. 10โ15 mg/L Residual chlorine must be high enough to disinfect but low enough to avoid toxicity. 72. What causes filamentous bacteria to dominate in the activated sludge process? A. High DO B. Low DO or nutrient imbalance C. High pH D. Warm temperatures Unfavorable conditions for floc-forming bacteria allow filamentous bacteria to dominate. 73. What is the purpose of an effluent weir being level in a clarifier? A. Reduce flow B. Ensure even distribution of effluent flow C. Allow sludge return
