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Ohio Water and Wastewater Operator Certification Exams
Environmental Protection Agency (EPA) Questions And Correct
Answers (Verified Answers) Plus Rationales.
- What is the primary purpose of coagulation in water treatment? A. Increase pH B. Remove odor C. Destabilize particles D. Add chlorine Coagulation destabilizes suspended particles, allowing them to clump for removal.
- Which of the following is a secondary standard under the Safe Drinking Water Act? A. Lead B. Iron C. Arsenic D. Nitrate Secondary standards affect aesthetics like color, taste, and odor, and iron is one such parameter.
- What does NTU stand for in turbidity measurement? A. Normal Turbidity Units B. Nephelometric Turbidity Units
C. Non-Threshold Units D. Non-thermal Units Turbidity is measured in Nephelometric Turbidity Units using light scattering techniques.
- The process of reducing the biological oxygen demand in wastewater involves: A. Aeration B. Chlorination C. Filtration D. Disinfection Aeration promotes microbial digestion of organic matter, reducing BOD.
- What is the main purpose of a trickling filter in wastewater treatment? A. Disinfection B. Grit removal C. Biological treatment D. Sludge thickening Trickling filters promote biological degradation of organics by microbial biofilms.
- The chlorine demand of water is defined as: A. The total chlorine added B. The chlorine remaining after disinfection C. The amount of chlorine consumed D. The chlorine added minus total coliforms
B. 2 hours C. 12 hours D. 24 hours Primary clarifiers typically operate with 1-2 hour detention times. 11.What does SCADA stand for? A. Supervisory Central Algae Discharge Automation B. Supervisory Control And Data Acquisition C. Secure Control and Digital Access D. System Control of Aqueous Data SCADA systems monitor and control infrastructure systems like water plants remotely. 12.Which is considered a pathogenic organism? A. Giardia lamblia B. Diatoms C. Nematodes D. Zooplankton Giardia is a protozoan that causes waterborne diseases. 13.What does MCL mean under EPA regulations? A. Maximum Chlorine Level B. Maximum Contaminant Level C. Minimum Compliance Limit D. Maximum Control Limit MCLs are legally enforceable limits for contaminants in drinking water.
14.What is the standard pH range for treated drinking water? A. 2- 4 B. 5- 6 C. 6.5-8. D. 9- 11 EPA recommends a pH of 6.5 to 8.5 for aesthetic and operational reasons. 15.The term "sludge age" refers to: A. Time for sludge to settle B. Average time solids remain in the aeration basin C. Time before sludge is disposed D. Age of biosolids storage Sludge age is the average time microorganisms are kept in the system. 16.What is a common cause of high chlorine demand in water? A. Iron B. Turbidity C. Organic material D. Ammonia Organic compounds react with chlorine, increasing its consumption. 17.What does D.O. stand for in wastewater? A. Digested Organics B. Dissolved Oxygen C. Denatured Organisms D. Dissolved Organisms
21.What is the typical temperature range for optimal biological activity in wastewater treatment? A. 0โ5ยฐC B. 15โ30ยฐC C. 40โ50ยฐC D. 60โ70ยฐC Biological treatment processes are most effective between 15โ30ยฐC. 22.What is the primary function of a grit chamber? A. Remove heavy inorganic solids B. Settle organic solids C. Aerate wastewater D. Disinfect wastewater Grit chambers prevent damage to equipment by removing sand and small stones. 23.What is backwashing? A. Adding disinfectant B. Reversing flow to clean filters C. Pumping sludge D. Sampling influent Backwashing cleans filters by reversing flow and removing trapped particles. 24.In lab analysis, TSS stands for: A. Total Soil Solids B. Total Suspended Solids
C. Total Salt Solutions D. Tertiary Settled Solids TSS indicates the concentration of solids suspended in water. 25.A weir is commonly used to: A. Disinfect water B. Add chemicals C. Measure flow D. Settle sludge Weirs are flow-measuring devices based on water level over a notch. 26.The term โlagoonโ in wastewater treatment refers to: A. Large pond for biological treatment B. Clarifier C. Filtration tank D. Grit basin Lagoons treat wastewater using natural processes in large basins or ponds. 27.What color is typically associated with fresh wastewater? A. Brown B. Gray C. Black D. Yellow Fresh wastewater usually has a grayish appearance before becoming septic.
D. Pressure Larger particles settle faster due to greater weight and lower resistance. 32.Which device is used to measure flow rate in a pipe? A. Turbidimeter B. Flow meter C. Manometer D. Barometer Flow meters quantify the rate of flow in pipes or open channels. 33.Which chemical is commonly used to remove hardness? A. Lime B. Chlorine C. Alum D. Fluoride Lime softening removes calcium and magnesium ions responsible for hardness. 34.Chlorine residual in drinking water must be: A. Nonexistent B. Detectable C. Above 5.0 mg/L D. At 0.0 mg/L A detectable residual ensures continued disinfection throughout the system. 35.The abbreviation TDS stands for: A. Total Digested Solids
B. Total Dissolved Solids C. Turbidity Dissipation Standard D. Time-Diluted Sample TDS refers to all inorganic and organic substances dissolved in water. 36.What is the correct order of steps in conventional drinking water treatment? A. Coagulation โ Filtration โ Flocculation โ Disinfection B. Coagulation โ Flocculation โ Sedimentation โ Filtration โ Disinfection C. Aeration โ Coagulation โ Sedimentation โ Filtration D. Flocculation โ Disinfection โ Filtration โ Coagulation This sequence is standard for effective removal of particles and pathogens. 37.The presence of which gas indicates anaerobic digestion? A. COโ only B. Methane C. Oxygen D. Ozone Methane is produced during anaerobic digestion. 38.Which form of chlorine is most effective for disinfection? A. Hypochlorite ion B. Chloride C. Hypochlorous acid
D. Weir Pumps move water through the distribution system at necessary pressure. 43.What type of valve prevents backflow? A. Gate valve B. Check valve C. Globe valve D. Butterfly valve Check valves allow flow in only one direction to prevent backflow. 44.Why are manholes used in collection systems? A. To access sewer lines for maintenance B. To control odor C. To pump sewage D. To filter influent Manholes allow entry for inspection, cleaning, and repair. 45.What is the main source of phosphorus in wastewater? A. Grit B. Oil C. Detergents D. Heavy metals Phosphorus often comes from household detergents and cleaning agents. 46.In water treatment, which of the following is considered a flocculant? A. Chlorine B. Alum C. UV light
D. Ferric nitrate Alum (aluminum sulfate) is a common coagulant/flocculant. 47.What does UV disinfection do? A. Adds chemicals B. Inactivates microorganisms with light C. Removes metals D. Settles particles UV disrupts DNA in microorganisms, preventing reproduction. 48.What causes nitrification in distribution systems? A. Excess chlorine B. Ammonia and low residuals C. High pH D. Low turbidity Ammonia in the presence of low chlorine can allow bacteria to convert ammonia to nitrites/nitrates. 49.What is the purpose of a blower in activated sludge systems? A. Supply oxygen B. Remove grit C. Add chlorine D. Reduce solids Blowers supply air to maintain aerobic conditions for microbial activity. 50.A permit required to discharge treated wastewater is called: A. CWA license B. Water treatment license
Septicity occurs under anaerobic conditions, usually due to low DO and long detention times. 54.What device measures the depth of sludge in a clarifier? A. Pressure gauge B. Conductivity meter C. Sludge judge D. Flow meter A sludge judge is a clear sampling tube used to visually measure settled sludge depth. 55.What type of pump is most commonly used for sludge transfer? A. Submersible pump B. Positive displacement pump C. Jet pump D. Centrifugal pump Positive displacement pumps handle thick, viscous fluids like sludge efficiently. 56.What is the recommended range for chlorine residual in distribution systems? A. 0.0โ0.2 mg/L B. 0.2โ4.0 mg/L C. 4.5โ10 mg/L D. 10โ20 mg/L Regulations require a detectable residual, typically maintained between 0.2 and 4.0 mg/L.
57.Which of the following is a common source of ammonia in wastewater? A. Nitrates B. Human waste C. Sulfates D. Phosphates Ammonia is primarily introduced from urea in human waste. 58.What happens if the F/M ratio is too low in an activated sludge system? A. Sludge bulking B. Starved microorganisms C. Excess foaming D. High BOD in effluent Low F/M means low food relative to microbes, potentially causing endogenous respiration and sludge issues. 59.Which chemical is often added to wastewater to aid phosphorus removal? A. Chlorine B. Lime C. Ferric chloride D. Carbon dioxide Ferric chloride precipitates phosphorus into solids that can be settled and removed. 60.What is the term for wastewater that enters the collection system through cracks or holes? A. Infiltration B. Inflow
64.Which best defines a grab sample? A. A single sample taken at a specific time B. Composite of multiple samples C. Filtered influent D. Sludge sample only Grab samples reflect the water quality at one moment in time. 65.What is the function of a flow equalization basin? A. Increase chlorine contact B. Regulate inflow variations C. Remove suspended solids D. Reduce odors Equalization basins stabilize flow rates, minimizing system surges. 66.In laboratory analysis, what does MLSS stand for? A. Mean Level Solids Sample B. Mixed Liquor Suspended Solids C. Maximum Limit of Suspended Solids D. Mixed Lime Sample Solids MLSS is a measure of the solids concentration in the aeration tank. 67.What is the correct order of nitrogen transformation during nitrification? A. Ammonia โ Nitrate โ Nitrite B. Nitrite โ Ammonia โ Nitrate C. Ammonia โ Nitrite โ Nitrate D. Nitrate โ Nitrite โ Ammonia Nitrifying bacteria first convert ammonia to nitrite, then to nitrate.
68.What is the term for the volume of air needed to keep solids in suspension in an aeration tank? A. Air demand B. Pressure loss C. Head loss D. Oxygen transfer efficiency Air demand ensures oxygenation and mixing to support microbial digestion. 69.Why is dechlorination used before effluent discharge? A. To protect aquatic life B. To increase pH C. To enhance nitrification D. To reduce TSS Chlorine can harm aquatic ecosystems, so it must be removed or neutralized. 70.The presence of grease in a lift station often results in: A. Clogging and equipment damage B. Improved flow C. Lower BOD D. pH reduction Grease accumulates, causing blockages and pump failures. 71.Which of the following is most responsible for taste and odor complaints in drinking water? A. Chloride
