MA Wastewater Operator Certification Grade 2 Study Guide Questions and Correct Answers Exam 2026

Wastewater MA Wastewater Operator Certification Grade 2 Study Guide Questions and Correct Answers Exam 2026 What is the methane content in a properly operating anaerobic digester? a. 30 to 35% by volume b. 1 to 2% by volume c. 65 to 70% by volume d. 15 to 20 % by volume - ANS-c What will the addition of chlorine gas do to the pH of wastewater? a. Moderately increase the pH b. pH will not be affected c. Significantly increase the pH d. Decrease the pH - ANS-d What is the purpose of a Parshall flume? a. Measure turbidity b. Measure flowrate c. Measure settling rate d. Measure solids content - ANS-b What is the typical removal efficiency of settleable solids in a primary clarifier? a. 95 to 99% b. 40 to 60% C. 20 to 50% d. 10 to 15% - ANS-a Which of the following is true about pumping scum from a primary clarifier? a. Pumping scum is less problematic during cold weather b. Scum rarely leads to plugged pipelines due to its viscous nature c. Scum causes more piping problems than other substances pumped at a wastewater treatment plant. d. Scum causes the least amount of piping problems among all the substances pumped at a wastewater treatment plant pumped at a wastewater treatment plant - ANS-c Wastewater Wastewater What might cause thick billows of white sudsy foam in the aeration tank? a. MLSS is too high b. Temperature in the aeration tank is too low c. Old sludge d. MLSS is too low - ANS-d What does the "M" in F/M ratio represent? a. MLSS in the aeration tank b. The influent BOD loading rate into the aeration tank c. The mixed liquor volatile suspended solids in the aeration tank d. The mass of inorganic solids in the aeration tank - ANS-c In general- how will warmer temperature affect the settling rate of solids in a clarifier? a. Decrease the settling rate b. Increase the settling rate c. Temperature will not affect the settling rate d. Worsens the settling rate - ANS-b What could happen if the digester gas is mixed with air (85 TO 95% by volume)? a. Cause an explosion b. Improve efficiency of digestion c. The bacteria will become aerobic and increase VSR d. The digester becomes safer to operate due to less toxic gas in the system. - ANS-a How will algae impact the chlorine demand in the pond effluent? a. Slightly decreases chlorine demand b. Does not affect chlorine demand c. Significantly decreases chlorine demand d. Increases chlorine demand - ANS-d Which of the following is true about a positive displacement pump? a. It is a type of centrifugal pump b. Suction valve should be closed when the pump is started c. It must never be started with the discharge valve closed d. Adds head to liquid using several impellers - ANS-c What is true about the F/M ratio? a. MLVSS data is not required to determine the F/M ratio Wastewater Wastewater Wastewater b. Volume of the secondary clarifier is not needed to determine the F/M ratio c. The amount of COD or BOD entering the aeration tank does not have to be known to calculate the F/M ratio d. The amount of organisms in the aeration tank is not needed to calculate the F /M ratio - ANS-b Which of the following is one of the basic rules of laboratory work? a. Do not leave keys in equipment or vehicles at any time b. Patrol the facilities frequently and look for suspicious activity or behavior c. Never pipet hazardous material with your mouth even if the pi pet has been sterilized d. Lock out and tag out relevant mechanical and electrical equipment before starting any maintenance activity - ANS-c What is the recirculation ratio for a trickling filter? a. Qr/Q b. Q/Qr c. Q/ Qr+Q d. Qr+Q/Q - ANS-a Which of the following is true about COD and BOD? a. They are direct measurements of the organic content in the influent b. They measure the inorganic content of the influent c. They represent the amount of filamentous bacteria in the influent d. They are indirect measurements of the organic content in the influent - ANS-d What is the purpose of the grit channel? a. Remove dissolved and non-settleable organics b. Remove heavy inorganic wastes. c. To allow activated sludge to settle d. Remove substances that float and readily settle from the wastewater as part of primary treatment. - ANS-b Which of the following is true about the extended aeration process? a. Bugs get more food b. Wasting is not necessary c. It does not produce as much waste sludge as other processes. d. It is very different from the conventional activated sludge process - ANS-c What is the correct formula for solids in raw wastewater? a. Non-volatile solids + Suspended solids = Total solids in the influent Wastewater Wastewater b. Dissolved solids + Settleable solids = Total suspended solids c. Colloids + dissolved solids = total suspended solids d. Non-settleable solids + Settleable solids = Total suspended solids. - ANS-d What is "freeboard" in a waste stabilization pond? a. Operational depth of the pond b. Wooden inlet and outlet structures c. Wooden baffles d. Vertical distance from normal water surface to the top of the levee. - ANS-d What is one of the requirements for a BOD test? a. The BOD bottle should be completely filled to the top. b. The BOD bottles must be 100-mL in size c. Sample bottles should be incubated at 30 degrees Celsius d. Stoppers should not be installed on the bottles to ensure proper air flow to the samples - ANS-a What should be scheduled every 3 months for a flamer arrester in an anaerobic digester? a. Replacement b. Maintenance c. Flow test d. Temperature test - ANS-b What is common practice in an activated sludge process? a. Waste all activated sludge b. Sludge age of 14 days for conventional system c. Recirculate activated sludge d. limiting DO to increase microorganism population - ANS-c Prior to entering a permit-required confined space what should you verify? a. A standby person should be at the entrance to the confined space. An additional person is not required b. A standby person should be within 30 feet of the confined space. c. A standby person should be within 50 feet of the confined space. d. A standby person should be located outside the entrance to the confined space while another person should be within sight or call of the standby person. - ANS-d What is a common way to determine the organic strength of wastes in the influent? a. Test for the biochemical oxygen demand Wastewater b. Test for the biological oxygen demand c. Test for the volatile solids reduction d. Test for the carbon and hydrogen concentrations - ANS-a What should you do if you are mildly exposed to chlorine gas? a. Breathe heavily to inhale clean air b. Cough to release chlorine from lungs c. Immediately evacuate the contaminated area- remain calm- keep warm- breathe lightly- and avoid coughing d. Keep your body as cool as possible - ANS-c What are the main sources of domestic sewage in the collection system? a. Canals b. Surface flow c. Ocean outfall d. Households and commercial establishments - ANS-d Why is it important to maintain a horizontal weir in a clarifier? a. Prevent sludge bulking b. Prevent short-circuiting c. Prevent gasification d. Prevent excessive slime growth - ANS-b What are mostly removed in the grit channel? a. Biomass b. Organics c. Dissolved solids d. Sand- eggshells- cinders- and heavier particulate matter - ANS-d How often should an anaerobic digester be fed? a. Several times a day b. Once a day c. Twice a week 4. Five times per week - ANS-a What is the health effect of carbon dioxide? a. Vomiting b. Migraine c. Can lead to asphyxiation d. Rapid heart beat - ANS-c Wastewater Wastewater Which of the following enters the headworks of a treatment plant? a. Effluent b. Supernatant c. WAS d. Influent - ANS-d Which gas diminishes your sense of smell? a. Hydrogen b. Hydrogen sulfide c. Nitrogen d. Ethane - ANS-b What type of microorganism can use nitrate as a source of oxygen? a. Aerobic bacteria b. Anaerobic bacteria c. Facultative bacteria d. Zoogleal - ANS-c What is the equivalent of 1 mg/L? a. 1 ppb b. 10 ppm c. 10 ppb d. 1 ppm - ANS-d Select the most accurate statement about extended aeration. a. The bugs are retained in the aeration tank much shorter than the conventional activated sludge system b. Extended aeration produces the most waste sludge compared to other activated sludge processes c. An oxidation ditch is usually operated in extended aeration mode and is used for small flows d. Extended aeration is the least common type of package plant treatment process - ANS-c What is equivalent to organic solids? a. Volatile solids b. Fixed solids c. Suspended d. Colloids - ANS-a Wastewater Wastewater What should be done if a large amount of organic matter is found in the grit channel? a. Decrease the velocity of wastewater b. Inject sodium hydroxide at the headworks c. Raise the pH d. Increase the velocity of wastewater - ANS-d Which flowrate should you use to calculate the hydraulic loading to a trickling filter? a. Plant inflow b. Plant inflow minus recirculated flow c. Plant Inflow plus recirculated flow d. Recirculated flow - ANS-c What is the difference between the sludge from a primary clarifier and secondary clarifier? a. Secondary sludge is denser than primary sludge b. Primary sludge is denser than secondary sludge c. Specific gravity of secondary sludge is larger than that of primary sludge d. Primary sludge has a smaller specific weight than secondary sludge - ANS-b Which process includes a blower? a. Trickling filter b. Waste stabilization pond c. Chlorine contact tank d. Activated sludge - ANS-d How does an activated sludge system remove waste from wastewater? a. Physical treatment b. Chemical treatment c. Biological treatment d. Radiological treatment - ANS-c Which of the following best describes pre-chlorination? a. Mainly used for disinfection and requires a large amount of chlorine residual in the wastewater at the chlorine contact chamber b. Addition of chlorine to wastewater at the entrance to the plant and used for odor control- BOD reduction- grease removal- and aid sedimentation c. Injected on a well-clarified effluent d. Describes a type of chlorination to address sludge bulking - ANS-b Wastewater Wastewater When would you expect reduced algae population and less oxygen released into a pond? a. Fall and winter when the weather is cool and sunlight is reduced b. Summer when there is abundant sunlight c. Spring when the weather transitions from cool to warm d. When photosynthesis is very effective and at its peak - ANS-a What is the first step of the lockout/tagout procedure? a. Shut down the equipment if it is operating b. Operate the energy isolating device so that the equipment is isolated from its energy source c. Lockout the equipment with assigned lock or tag d. Notify all affected employees that a lockout or tagged system is going to be used and the reason why - ANS-d What type of process is the activated sludge system? a. Anaerobic b. Anoxic c. Aerobic d. Jonie - ANS-c What will happen if too much raw sludge is added to the digester? a. pH will increase due to increase in sodium hydroxide b. Acid fermenters will predominate and lower the pH c. pH will not be affected d. Methane fermenters will thrive - ANS-b What might cause sludge to rise in a clarifier? a. Gasification from aging sludge b. pH is too high c. Sludge withdrawal rate is too high d. Photosynthesis - ANS-a What happens when carbon dioxide is removed from a pond? a. Decreases pH b. pH is not affected c. Increases pH d. Sudden increase in H2S - ANS-c Wastewater Wastewater How much dissolved oxygen should be in a conventional activated sludge system if good effluent is being produced? a. 6 to 8 mg/L b. 0.5 to 1 mg/L c. 4 to 6 mg/L d. 2 to 4 mg/L - ANS-d What is the typical concentration of mixed liquor suspended solids in a conventional activated sludge process? a. 50 to 1000 mg/L b. 1000 to 4500 mg/L c. 4500 to 5500 mg/L d. 5500 to 6500 mg/L - ANS-b The temperature of the plant influent is: a. Slightly warmer than tap water b. Slightly cooler than tap water c. Much cooler than tap water d. Much warmer than tap water - ANS-a The purpose of disinfection is to: a. Kill all microorganisms in the wastewater b. Stabilize the pH c. Destruction or inactivation of pathogenic bacteria d. Oxidize the minerals in the effluent - ANS-c What must you do before entering a room with harmful concentration of chlorine gas in the air? a. Read the O&M manual b. Wear self-contained breathing apparatus (SCBA) c. Prepare the fire extinguishers d. Cover your mouth and spray aqueous ammonia in the room - ANS-b What does black sludge at the bottom of a secondary clarifier located downstream of a trickling filter signify? a. Pumping rate is excessive b. Pumping duration is too long c. Detention time is too short d. Sludge has stayed in the secondary clarifier too long - ANS-d Wastewater Wastewater Wastewater If the lab results show that the plant influent sample has a COD of 100 mg/Land a BOD of 300 mg/l- which of the following is most likely true? a. Lab results appear incorrect b. Carbon concentration is very high c. Organic content is unusually high d. COD seems excessive - ANS-a If a primary clarifier is placed out-of-service then how should a plant with at least two trickling filters operate the system? a. Operate the filters in parallel b. Divert the influent to several trickling filters c. Operate the filters in series d. Maintain existing operation without changing filter arrangement - ANS-c What is the main reason for preventing a direct connection between a potable water pipe and a stuffing box (packings) of a wastewater pump? a. Wears out the glands quicker b. Glands should not be wet c. Potable water will rapidly destroy the stuffing box d. Cross connection - ANS-d Which of the following is true about algae in a pond? a. During the daytime the algae will release carbon dioxide b. During the daytime the algae will release oxygen for the aerobic bacteria in the pond c. Algae uses sunlight to produce hydrogen sulfide d. Photosynthesis helps algae create carbon monoxide - ANS-b Which of the following is not true about hydrogen sulfide? a. Hydrogen sulfide is flammable b. Hydrogen sulfide is explosive under certain conditions c. Hydrogen sulfide is lighter than air d. Hydrogen sulfide is toxic - ANS-c What type of treatment is primarily used to thicken sludge instead of dewater the sludge? a. DAF b. Sludge drying bed c. Centrifuge d. Vacuum filters - ANS-a Wastewater Wastewater Why should sludge at the bottom of a clarifier be removed in a timely manner? a. To improve the performance of the grit channel b. To maintain a consistent volume of sludge in the drying bed c. To minimize the formation of chloramines d. To prevent sludge gasification which causes the sludge to float - ANS-d What is the purpose of sludge digestion? a. Convert primary and secondary sludge to mostly hydrogen sulfide b. Increase efficiency of the OAF c. Reduce the volume of the sludge and stabilize the solids d. Increase solids volume - ANS-c Which of the following is true about trickling filters? a. It is mostly an anaerobic process b. The three main parts of a trickling filter are media distribution system and underdrain c. In computing BOD loading it is standard practice to include the BOD of the re circulated effluent d. Filter ponding is usually due to inadequate organic loading - ANS-b Which of the following could cause foaming in an anaerobic digester? a. Temperature is kept constant b. Feeding sludge at regular short interval c. Digester is well-mixed d. Organic overload - ANS-d Which of the following parameters should be monitored several times a week in a pond? a. TDS b. MLSS c. Dissolved oxygen- temperature- and pH d. MLVSS - ANS-c Which is true about the temperature in an anaerobic digester? a. Temperature in a digester should not be changed by more than 1 degree Fahrenheit per day b. Temperature must be changed significantly according to sludge loading rate c. Temperature at the bottom should be higher than at the top of the digester Wastewater d. Mesophilic digestion requires a temperature between 105 to 108 degrees Fahrenheit - ANS-a The effectiveness of disinfection is determined by: a. The chlorine residual concentration b. The chlorine demand c. The chloramine concentration in the effluent d. The coliform concentration in the effluent - ANS-d An increase in the acid/alkalinity ratio for an anaerobic digester means: a. The digester ls in an ideal condition b. The carbon dioxide content is decreasing c. Acid concentration is increasing or alkalinity is decreasing d. pH of the sludge in the digester is increasing - ANS-c Which of the following will not cause short-circuiting in a clarifier? a. Uneven weir settings b. Flow line of launder is low c. Damaged or missing inlet line baffles d. Velocity of wastewater is greater in some sections than in others - ANS-b A grab sample is most suited for these constituents. a. BOD b. TSS c. Suspended solids concentration d. Residual chlorine - ANS-d The organic loading to a trickling filter is expressed as: a. lbs BOD/day/1000 ft3 b. lbs BOD/day/1000 ft2 c. lbs BOD/day/ft2 d. lbs BOD/1000 gallon - ANS-a How often should the sludge at the bottom of a clarifier be pumped? a. Once a week b. Bi-weekly c. Frequently throughout the day d. Once every three days - ANS-c Which of the following will not affect settling characteristics in a clarifier? Wastewater Wastewater a. Temperature b. Short circuit c. Detention time d. Depth of launder - ANS-d The best way to evaluate the effluent TSS concentration from a plant is to: a. Check the grab sample at peak flow b. Check the composite sample of TSS c. Check the grab sample at low flow d. Check the grab sample during average flow - ANS-b Which of the following is not associated with an aeration tank? a. RAS b. WAS c. RBC d. MCRT - ANS-c What creates hydrogen sulfide? a. Excessive aeration b. Surface active agents c. Organic matter under aerobic condition d. Decomposing organic matter under anaerobic condition - ANS-d A pond with a detention time of less than three days will perform similar to: a. Sedimentation tank b. Aeration tank c. Trickling filter d. RBC - ANS-a Which type of bacteria is used for a trickling filter? a. Anaerobic bacteria b. Anoxic bacteria c. Aerobic bacteria d. Facultative bacteria - ANS-c Which of the following is not associated with a trickling filter? a. Media b. Filamentous bacteria c. Zoogleal film Wastewater Wastewater d. Recirculation - ANS-b What is an MCRT? a. A calculation that indicates the tendency of activated sludge solids to thicken b. A measure of food provided to bacteria in an aeration tank c. The amount of volatile suspended solids in the mixed liquor-of an aeration tank d. An expression of the average time a microorganism will spend in an activated sludge process - ANS-d What is the typical BOD removal efficiency in a primary clarifier? a. 10 to 15% b. 40to 60% c. 20 to 50% d. 95 to 99% - ANS-c What does the "F" in F/M ratio represent? a. The microorganism population in the aeration tank b. The amount of filamentous bacteria in the activated sludge process c. The MLVSS in the aeration tank d. The food for the microorganisms flowing into the aeration tank in lbs/day - ANS-d Which of the following describes the appearance of healthy activated sludge? a. Thick greasy dark tan foam b. Brown with a moderate amount of crisp white foam c. Clear liquid with clear foam d. Gray liquid with no foam - ANS-b What is used to control filamentous organisms? a. Polymer b. Sulfur dioxide c. Coagulant d. Chlorine - ANS-d What are commonly used to control chlorine feed rate for disinfection? a. BOD and MLVSS b. pH and temperature c. Flow and chlorine residual d. DO and TSS - ANS-c Which toxic gas is commonly found in septic wastewater and smells like rotten eggs? Wastewater Wastewater a. Hydrogen sulfide b. Carbon monoxide c. Hydrogen d. Carbon dioxide - ANS-a What is the permissible exposure limit for chlorine gas vapor during a normal 8-hour workday and a 40-hour workweek? a. 0.1 ppm b. 0.5 ppm c. 1 ppm d. 15 ppm - ANS-b What is a vulnerability assessment? a. Assesses the impact of hydrogen sulfide to a concrete structure b. Analyzes the impact of inflow and infiltration problem to the plant hydraulics c. Estimates the vulnerability of aquatic wildlife to excessive algae growth d. Contingency planning to determine the vulnerability of the utility during various types of emergencies and identify corrective actions to reduce the risks - ANS-d What is the difference between the settling rate of activated sludge and raw sludge? a. Activated sludge settles slightly faster than raw sludge b. Activated sludge settles at the same rate as raw sludge c. Activated sludge settles slower than raw sludge d. Activated sludge settles much faster than raw sludge - ANS-c What should be mostly found in healthy activated sludge? a. Tiny flagellates b. Amoeboids c. Short filaments d. Free-swimming and stalked ciliates - ANS-d One to two percent of the digester gas in an anaerobic digester consists of: a. Hydrogen nitrogen hydrogen sulfide and other gases b. Methane c. Carbon dioxide d. CH4 - ANS-a What is true during the colder winter months? Wastewater Wastewater Wastewater a. Modify operations to decrease solids under aeration to provide less microorganisms to treat the BOD b. Modify operations to increase solids under aeration to provide more microorganisms to treat the BOD c. Biological activity will increase which results in more overall sludge production d. Microorganisms become more active - ANS-b What type of sludge would you expect in an aeration tank if the content is dark and has low DO? a. Sludge that is heavily mixed b. Chlorinated sludge c. Septic sludge d. Healthy sludge - ANS-c What could happen if the volatile acid/alkalinity ratio starts to increase and corrective action is not taken immediately? a. Carbon dioxide content in the digester gas will decrease b. Carbon monoxide content in the digester gas will fluctuate c. pH of the digester sludge will increase d. Carbon dioxide content in the digester gas will increase - ANS-d What are screenings? a. Colloids b. TDS c. Pieces of wood roots rags and other large debris d. COD - ANS-c What happens when there is more food in the influent to the aeration tank? a. Less oxygen is required in the aeration tank b. More oxygen is required in the aeration tank c. Less organism activity takes place d. Less oxidation occurs - ANS-b What impact does temperature have on the reaction rate of microorganisms in wastewater? a. Reaction rate doubles with every 18° Fahrenheit increase in temperature until higher temperature inhibits biological activity b. Reaction rate decreases by 20% with every 10° Fahrenheit increase in temperature c. Reaction rate of microorganism is not impacted by temperature d. Reaction rate goes to zero - ANS-a Wastewater What is commonly used to control the odor of hydrogen sulfide? a. Carbon dioxide b. Methane c. Chlorine d. Hydrogen - ANS-c What is used to determine the amount of microorganisms in the aeration tank? a. Mixed liquor suspended solids (MLSS) b. Influent TSS c. BOD d. Mixed liquor volatile suspended solids (MLVSS) - ANS-d What could happen if the sludge line is isolated by closing the valves on each end for several days? a. It could result in water hammer b. Cavitation could occur c. Gas production could increase the internal pressure and cause the line to fail d. The aerobic condition will cause Zoogleal mass to grow in large numbers - ANS-c Which is true about chlorine gas? a. It is 2.5 times lighter than air b. It is 2.5 times heavier than air c. It is 1.5 times heavier than air d. lt is 1.5 times lighter than air - ANS-b Which of the following is typically treated by biological processes? a. Roots and rags b. Sand and eggshells c. Cinders d. Dissolved and non-settleable organic material - ANS-d Which document is a written record that accurately traces the custody of wastewater samples through all phases of a monitoring program? a. Wastewater Lab Analysis form b. NEPA c. Chain of Custody form d. Diagnostic form - ANS-c What could cause a sudden drop in pH of the influent? Wastewater Wastewater Wastewater a. Acidic chemical in the influent b. A strong base was dumped into the collection system c. Ammonia from a factory was discharged into the sewer d. The influent contained sodium hydroxide - ANS-a What is a recommended daily maintenance activity for a clarifier? a. Dewater the clarifier by draining the wastewater b. Repaint metal surfaces that have lost their protective coating c. Hose down the walls floor and equipment inside the clarifiers d. Inspect the chains sprockets and flights - ANS-d Which of the following could be the cause of ponding in a trickling filter? a. Hydraulic loading is too low b. Clogging of distributor orifices c. Excessive organic loading d. Denitrification - ANS-c What could happen if the dissolved oxygen content in the aeration tank is too low? a. Pinpoint flocs will develop b. Filamentous organisms could thrive and prevent the sludge floc from settling properly in the secondary clarifier c. Settling will improve in the secondary clarifier d. Sludge bulking will be eliminated - ANS-b What is the expected BOD removal efficiency in a facultative pond? a. Mostly between 40 to 50% b. Mostly between 30 to 40% c. Mostly between 20 to 30% d. Mostly between 70 to 80% - ANS-d What is chloramine? a. Free chlorine b. A chemical that is formed when chlorine reacts with iron c. Combined chlorine-a chemical that is formed when chlorine reacts with ammonia d. A chemical that is formed when chlorine reacts with air - ANS-c What is sludge bulking in an activated sludge process? a. When mixed liquor solids settle slowly and compact to a limited extent b. When old sludge denitrify and cause sludge to rise as a result of gasification Wastewater Wastewater c. When sludge form large aggregates and cause sludge to settle quickly d. When compaction in the secondary clarifier is improved due to chemical injection - ANS-a What is the most common imbalance in an anaerobic digester? a. Excess methane formation b. Excess nitrogen formation c. Excess acid formation d. Excess carbon dioxide formation - ANS-c What is the only reliable method of detecting hydrogen sulfide? a. Sense of smell b. Atmospheric monitoring c. Color titration d. Lab test - ANS-b What is sludge age? a. An expression of the average time that a microorganism will spend in the activated sludge process and calculated using the total suspended solids removed from the process b. A measure of food provided to bacteria in an aeration tank c. The theoretical time required for water to pass through a tank at a given flowrate d. A rough indicator of the length of time a pound of solids is maintained under aeration - ANS-d What is one of the benefits of a COD test over a BOD test? a. COD test does not require any chemicals to perform the test b. COD test will easily predict the effects of an effluent on the DO in receiving waters c. Shorter test period d. COD test is capable of measuring the biodegradability of matter - ANS-c What is the typical detention time for a primary clarifier? a. 3 to 4 hours b. 30 minutes c. 6 hours d. 1.5 to 2 hours - ANS-d If you are testing the pH of a wastewater sample what is the maximum recommended holding time? a. 5 days Wastewater b. It must be tested immediately c. 24 hours d. 36 hours - ANS-b What could cause short-circuiting in a clarifier? a. Sludge decomposition b. Reduction in flowrate c. Uneven weir settings d. Broken sludge pump - ANS-c What could cause the slime growth on a rotating biological contactor to appear black? a. It could indicate solids or organic overloading b. High DO in the plant effluent c. Lack of BOD in the influent to the rotating biological contactor d. Low hydraulic loading - ANS-a What is an air gap? a. Distance between blowers in an activated sludge system b. The vertical distance between the surface of wastewater and top of basin c. Backflow prevention d. Type of aeration equipment - ANS-c Which is true about chlorine demand? a. Chlorine demand= chlorine residual+ chlorine dose b. Chlorine demand= chlorine dose x chlorine residual c. Chlorine demand= chlorine residual - chlorine dose d. Chlorine demand = chlorine dose - chlorine residual - ANS-d What is accomplished by the activated sludge process? a. Anaerobic bacteria use 50 4 to eat incoming volatile solids b. Remove soluble or finely divided suspended materials c. Anoxic microorganisms destroy incoming BOD d. Zoogleal breaks down influent organics - ANS-b What is the carbon dioxide content of a properly functioning anaerobic digester? a. 65 to 70% by volume b. 1 to 2% by volume c. 30 to 35% by volume d. 40 to 60% by volume - ANS-c Wastewater Wastewater Which of the following is a collection of individual samples obtained at regular intervals? a. Grab b. Culmination c. Comprehensive d. Composite - ANS-d What is the most common piece of laboratory equipment which is used mainly to mix chemicals and measure approximate volumes? a. Beaker b. Graduated cylinder c. Pipet d. Flask - ANS-a What are colloids? a. Solids that settle rapidly b. Dissolved solids c. Solids found in the grit channel d. Very small finely divided solids that remain dispersed in a liquid for a long time - ANS d What is a common type of grit collector? a. Deflectors b. Weirs c. Chain-driven scrapers called "flights" d. Parshall flume - ANS-c What is true-about surface loading and detention time? a. They stay fairly constant throughout the day b. They are impacted by the influent BOD c. They are indirectly related to flow d. They are directly related to flow - ANS-d What is the slime growth on a trickling filter called? a. Filamentous bacteria b. Zoogleal film c. Stalked ciliate d. Acid formers - ANS-b What should be done if you observe a small 1 steady stream of water leakage from the pump packings? Wastewater Wastewater Wastewater a. Tighten the packings until they are water-tight b. Replace the packings c. Do nothing. The leakage is required to cool and lubricate the dynamic surface. d. Replace the pump - ANS-c What should be done if SVI is high and there is an excess of normal filamentous microorganisms in the activated sludge process? a. Inject hydrogen peroxide in the secondary effluent b. Make sure DO level is very low in the aeration tank c. Decrease MLSS and sludge age d. Chlorinate the return activated sludge - ANS-d When is a confined space considered oxygen-deficient? a. In atmospheres where the oxygen content is less than 19.5% by volume b. In atmospheres where the oxygen content is less than 23.5% by volume c. In atmospheres where the oxygen content is more than 23.5% by volume d. In atmospheres where the oxygen content is less than 29.5% by volume - ANS-a Which of the following is not true about chlorine gas? a. 2.5 times heavier than air b. Extremely toxic c. Common chlorine gas concentration at treatment plants is 12.5% d. Corrosive in moist atmosphere - ANS-c What is a "dead spot" in an activated sludge process? a. An area in the secondary clarifier with rising sludge b. An area in the aeration tank that has insufficient mixing c. An area in the aeration tank that has high concentration of DO d. An area in the secondary clarifier with many dead viruses - ANS-b Which of the following is an improper way to control an anaerobic digester? a. Control the loading rate or food supply b. Control the volatile acid/ alkalinity relationship c. Control mixing d. Control the acid formation so that it is larger than the methane formation - ANS-d Which of the following is not true about permitted confined space entry? a. Wear an approved harness with an attached line. b. If the entry is made through a top opening use a hoisting device with a Wastewater harness that suspends a person in an upright position. c. Testing for atmospheric hazards is not required as long as a blower is in use. d. Wear protective clothing when entering a confined space that contains corrosive substances or other substances harmful to the skin. - ANS-c What is an MSDS? a. A federal law that is designed to protect the health and safety of workers b. A condition in which a person's nose is no longer able to detect odor from a chemical c. A document that contains important information about a chemical such as safe exposure level flammability rating and first-aid procedures d. A publication written by the federal government that contains all regulations including those that affect safety and the environment - ANS-c How often should grit be removed from the grit channel? a. Weekly b. Monthly c. Bi-weekly d. Daily - ANS-d What is the typical removal efficiency for bacteria in a primary clarifier? a. 0-5% b. 25-75% c. 5-10% d. 10-20% - ANS-b What problem could most likely cause a centrifugal pump to discharge at a reduced rate? a. Damaged impeller b. Slight water leak at the packings c. Pumping against less resistance d. Seal water is dripping slowly - ANS-a What are the two categories of coliform bacteria? a. Lactose and lauryl tryptose b. Primary and secondary c. Free swimming and stalked d. Total and fecal - ANS-d Which of the following is true about the extended aeration process? a. Wasting is not necessary to maintain proper control of the process Wastewater Wastewater Wastewater b. It produces more waste than conventional activated sludge process c. It has low F/M ratio d. It has low MLSS concentration - ANS-c What type of disinfection is gaining in popularity and expected to become a practical alternative to chlorination? a. Sulfur dioxide b. Ultraviolet (UV) disinfection c. Aqueous ammonia d. Caustic soda - ANS-b Where is the proper sampling location for an effluent from a wastewater treatment plant? a. Next to the chlorinator equipment b. At the end of a solids handling facility c. Prior to discharge into receiving waters d. At the head of a chlorine contact chamber - ANS-c What is true if the F/M ratio increases? a. Less DO is required b. Less BOD is available c. DO will not be affected by an increase in F/M ratio d. More DO is needed - ANS-d Who must be included in a hearing conservation program to prevent hearing loss? a. Employees whose normal noise exposure equals or exceeds 65 decibels b. Employees whose normal noise exposure equals or exceeds an 8-hour time-weighted average of 85 decibels c. Employees whose normal noise exposure exceeds 45 decibels at any time d. Employees whose normal noise exposure exceeds an 8-hour timeweighted average of 25 decibels - ANS-b What is a major cause of repeated sludge bulking? a. High pH b. High DO c. High food-to-microorganism loading rates d. High nutrient concentration - ANS-c How can the efficiency of a trickling filter be improved? a. Raise the distributor arm Wastewater Wastewater b. Reduce the size of the ventilation ports c. Decrease the amount of the filter media d. Add recirculation - ANS-d During the day what typically happens to a pond as a result of the algae? a. Algae uses carbon dioxide which raises pH b. Algae produce carbon dioxide which lowers pH c. Algae consumes carbon dioxide which lowers pH d. Algae releases carbon dioxide which raises pH - ANS-a What should be done to find a small chlorine leak? a. Spray hydrochloric acid near the suspected leak b. Tie a rag on a stick dip the rag in a strong ammonia solution and hold the rag near the suspected points c. Release carbon dioxide to trace the leak d. Apply a small quantity of citric acid near the leak - ANS-b What should you do if there is thick dark foam on the surface of an aeration tank? a. Increase sludge wasting b. Decrease sludge wasting c. Maintain current MLSS concentration d. Increase the microorganism population - ANS-a Why is mixing important in an anaerobic digester? a. Increases the build-up of grit b. Speeds up digestion rate c. Achieves heterogeneous content in the digester d. Forms scum blanket - ANS-b Where is the correct location for a vent inside a room storing chlorine gas? a. 12 inches below the ceiling b. At nose level c. Within 12 inches of the floor d. At the highest point in the room - ANS-c What is the purpose of the seal water at the stuffing box in a pump? a. Increases the discharge flowrate of the pump b. Minimizes cavitation c. Increases brake horsepower d. lubricates the packing - ANS-d Wastewater What is the incubation period for the BOD test? a. Five days+/- 3 hours b. Five days +/-1 hour c. Five days+/- 4 hours d. Five days+/- 2 hours - ANS-a What could happen if you are exposed to very high concentration of hydrogen sulfide? a. Swelling of hand b. Numbness of legs c. It could quickly lead to death d. Develop skin rash - ANS-c What causes primary effluent to become black and odorous? a. Excessive sludge pumping b. Oil leak from sludge pump c. Crack ln the launder d. Improper sludge removal from the clarifier - ANS-d What is a biomass? a. Bacteria that change ammonia into oxidized nitrogen b. Organisms that grow in a thread or filamentous form c. A mass of organic material consisting of living organisms that feed on the wastes in sewage d. Wastes such as sand salt and calcium that are present in the plant influent - ANS-c What is the color of a pond that is operating properly? a. Brown b. Deep green color c. Clear d. Tan - ANS-b What does healthy activated sludge smell like? a. Chlorine b. Raw sewage c. Rotten eggs d. Earthy - ANS-d Which law regulates wastewater discharge to receiving waters? Wastewater Wastewater Wastewater a. Wastewater Act b. Clean Water Act c. National Discharge Act d. Federal Effluent Act - ANS-b The typical suspended solids removal rate in the primary clarifier is 5 to 10% a. True b. False - ANS-b Over-greasing a pump motor can lead to damage. a. True b. False - ANS-a A healthy digester gas consists mostly of hydrogen sulfide. a. True b. False - ANS-b Coliform results are reported as MPN/100 ml. a. True b. False - ANS-a Increased concentrations of volatile acids and decreased alkalinity are signs that the anaerobic digestion is in an ideal state. a. True b. False - ANS-b Breakpoint chlorination is the addition of chlorine to wastewater until the chlorine demand has been met. a. True b. False - ANS-a Zero calibration accuracy for DO probes and meters should be checked with an absolute zero solution (sodium sulfite). a. True b. False - ANS-a Temperature pH and dissolved oxygen do not have to be analyzed immediately because they can be preserved. a. True b. False - ANS-b Sterilization is the goal of most wastewater treatment plants. a. True b. False - ANS-b One of the most common types of package plants is extended aeration. Wastewater Wastewater a. True b. False - ANS-a NPDES permits are issued by the EPA or the state. a. True b. False - ANS-a Hypochlorination will raise the pH of wastewater being treated. a. True b. False - ANS-a Denitrification does not cause sludge to rise in a secondary clarifier. a. True b. False - ANS-b The sludge digester can be either aerobic or anaerobic. a. True b. False - ANS-a In order to protect your family from infectious disease you should not wear your work clothes home. a. True b. False - ANS-a One application of centrifugal pumps is to lift raw wastewater. a. True b. False - ANS-a BOD and suspended solids are measured using grab samples. a. True b. False - ANS-b Algae uses carbon dioxide in the pond to produce free oxygen for the aerobic bacteria. a. True b. False - ANS-a The purpose of a scraper in a clarifier is to collect the settled wastewater flowing over the weirs and convey it from the clarifier. a. True b. False - ANS-b An oxidation ditch is typically used for small communities. a. True b. False - ANS-a Wastewater Wastewater If there is white foam on the surface of the aeration tank increase the sludge wasting rate. a. True b. False - ANS-b Feeding the digester once a month helps maintain better condition in the clarifiers. a. True b. False - ANS-b Hydrogen sulfide is heavier than air and typically flows towards a lower elevation. a. True b. False - ANS-a A solution with a pH of 13 is a strong base. a. True b. False - ANS-a Positive displacement pumps are not used to pump sludge and chemicals. a. True b. False - ANS-b The velocity through a grit channel should be lower than the collection system. a. True b. False - ANS-a Septic sludge in a clarifier has low pH. a. True b. False - ANS-a A trickling filter is a type of activated sludge process usually operated in the extended aeration mode. a. True b. False - ANS-b Chlorine residual is the chlorine concentration in the wastewater after the chlorine demand has been met. a. True b. False - ANS-a If the DO is too low in the activated sludge process pinpoint flocs will develop which will not be removed in the secondary clarifiers. a. True b. False - ANS-b When foam is observed in the supernatant from a single stage anaerobic digester it could mean that it has experienced organic overload. Wastewater Wastewater a. True b. False - ANS-a Non-sparking tools must be used when working around digesters or in confined spaces that may contain flammable gas. a. True b. False - ANS-a Higher MCRT values are used during warmer weather. a. True b. False - ANS-b Alkalinity is the capacity of a liquid to neutralize acid. a. True b. False - ANS-a Sludge from a secondary clarifier is usually darker than the sludge from a primary clarifier. a. True b. False - ANS-a The temperature in an anaerobic digester should be changed by more than 1° Fahrenheit daily. a. True b. False - ANS-b A common range for the pH of raw domestic wastewater is 6.8 to 8.0. a. True b. False - ANS-a All microorganisms cause disease. a. True b. False - ANS-b V-notch openings are commonly found on weirs. a. True b. False - ANS-a An MPN test is considered positive when there are gas bubbles in the tube. a. True b. False - ANS-a A gear pump is a common type of positive displacement pump. a. True b. False - ANS-a Wastewater Wastewater Short-circuiting in a clarifier can be prevented with baffles. a. True b. False - ANS-a The preliminary treatment system mainly removes larger solids such as rocks debris and grit. a. True b. False - ANS-a Vacuum filtration is one method to settle solids in primary treatment. a. True b. False - ANS-b Land application is one type of disposal method for sludge. a. True b. False - ANS-a F/M ratio is a control method for the activated sludge process. a. True b. False - ANS-a The drive unit in a circular clarifier rotates the sludge collector. a. True b. False - ANS-a Oxygen deficiency is most likely to occur at the high point within an aboveground structure. a. True b. False - ANS-b Chlorine demand concentration is often determined using the DPD test. a. True b. False - ANS-b When algae consumes carbon dioxide from a waste stabilization pond the pH of the wastewater in the pond will increase. a. True b. False - ANS-a Which of the following is true about coliform bacteria? a. The Most Probable Number method is not applicable for analyzing wastewater for coliform but it is frequently used to determine the ciliate concentration b. Multiple tube coliform test is not frequently used to determine coliform bacteria due to its complexity c. Coliform bacteria are considered harmless but their presence may indicate the presence of pathogens Wastewater Wastewater d. Test for coliform bacteria cannot be used by an operator at a treatment plant as a guide to achieve a desired degree of treatment - ANS-c What is the typical removal efficiency of total suspended solids in the primary clarifier? a. 95 to 99% b. 20 to 50% c. 10 to 15% d. 40 to 60% - ANS-d Which of the following is the most abundant in an anaerobic digester? a. Carbon dioxide b. Nitrogen c. Methane d. Hydrogen sulfide - ANS-c What might cause brown or black scum to appear on the surface of a pond? a. Low BOD loading b. Pond is overloaded (BOD) c. Storm d. Periods of high run-off - ANS-b What is the purpose of air input for an aerated grit chamber? a. Helps remove TDS b. Air improves the disinfection process c. Freshens wastewater and helps separate grit and other solids d. Addresses denitrification - ANS-c What happens when there are many air bubbles in the water of an operating pump? a. Water hammer b. Cavitation c. Less noise generated by the pump d. More efficient pumping - ANS-b Which are the common characteristics of COD? a. COD is typically larger than B0D5 and COD test results are available sooner than BODs b. COD is typically smaller than B005 c. COD is usually equal to B0D5 d. COD results are available after 4 days of testing - ANS-a What happens when free chlorine reacts with ammonia? a. Forms chlorine dioxide b. Forms hydrogen sulfide c. Forms ozone d. Forms chloramine - ANS-d Wastewater Wastewater What should be done if you see sludge rising in the primary clarifier? a. Reduce frequency of sludge pumping b. Adjust the MCRT c. Remove sludge more frequently d. Fix uneven weir setting - ANS-c Which of the following is true about trickling filters? a. It's mostly an anaerobic process b. It's mostly an anoxic process c. Photosynthesis is an important part of the trickling filter d. It's mostly an aerobic process - ANS-d How does temperature affect the activity of microorganisms in an aeration tank? a. low microorganism growth rate as temperature increases b. Rapid microorganism growth rate as temperature increases c. Does not affect activity of microorganisms d. Decrease in temperature will result in more biological activity - ANS-b What change would most likely be made to an activated sludge process during the winter? a. Decrease solids under aeration b. Increase pH c. Increase solids under aeration d. Add chlorine to the influent of the aeration tank - ANS-c If the influent solids loading rate to an activated sludge system increases what should be done? a. Increase sludge wasting rate b. Decrease MLSS c. Decrease temperature of aeration tank d. Reduce wasting rate of the sludge - ANS-d What could happen if a valve is closed too quickly? a. Water hammer b. Cavitation c. Tuberculation d. Gasification - ANS-a Which part of a facultative pond would you most likely find abundant algae growth? a. Middle layer b. lower layer c. Upper layer d. Algae grows evenly in every layer - ANS-c What is the main purpose of primary treatment? Wastewater Wastewater a. Convert dissolved or suspended solids into a form more readily separated from wastewater b. To remove substances that readily settle or float c. To remove debris and trash such as wood roots and rags d. To remove heavy inorganic material such as sand eggshells gravel and cinders - ANS-b What may be the problem if solids in the secondary clarifier are settling very slowly? a. Denitrification b. Nitrification c. Sludge bulking d. Excessive sludge pumping - ANS-c What will happen if the influent BOD increases in an activated sludge system? a. Less oxygen will be required in the aeration tank b. Hydrogen sulfide production will increase during normal operation c. Temperature in the secondary clarifier will decrease d. More oxygen will be required in the aeration tank - ANS-d Which of the following is the most likely cause of oxygen depletion in the receiving waters downstream of a wastewater treatment plant? a. Dissolved solids b. Bacteria decomposing dead algae c. Manganese d. Carbon dioxide - ANS-b What is located below the media in a trickling filter? a. Distributor arm b. Underdrain system c. Distributor bearings d. Splash plates - ANS-b What may be the probable cause of pin flocs in the secondary clarifier overflow? a. Over-oxidized sludge b. Low MCRT c. Excessive sludge wasting d. Warm temperature - ANS-a What would be a sign of an aeration tank with low MLSS concentration? a. Rising sludge in clarifier b. Thick billows of white sudsy foam in aeration tank c. Dark tan foam d. No foam - ANS-b What is static head? a. A part of an electrical panel Wastewater Wastewater b. Headworks of a plant c. Electrical energy d. Vertical distance from a reference point to the water surface - ANS-d ln an anaerobic digester what are some common end-products after digestion has taken place? a. Hydrogen peroxide b. Humus c. Gases (methane and carbon dioxide) d. Sodium hypochlorite - ANS-c What is a facultative bacteria? a. Bacteria that requires dissolved oxygen to survive b. Bacteria that obtain their oxygen by breaking down chemical compounds such as sulfate c. Bacteria that use chemically bound oxygen from nitrate to survive d. Bacteria that can use dissolved oxygen or oxygen obtained from food materials such as sulfate or nitrate ions - ANS-d What would most likely cause septic sludge in an aeration tank? a. Low solids loading rate b. Excessive mixing c. Insufficient air rates that are not keeping the aeration tank completely mixed d. Excessive sludge pumping - ANS-c When is a confined space considered oxygen-deficient? a. Oxygen is less than 22.5% by volume b. Oxygen is less than 19.5% by volume c. Oxygen is greater than 23.5% by volume d. Oxygen is less than 24% by volume - ANS-b What is the first reaction that occurs when sludge enters an anaerobic digester? a. Methane fermenters convert volatile acids to methane gas b. Carbon monoxide is initially produced in large quantity c. Volatile acids are created by methane fermenters d. Volatile matter is converted to volatile acids by acid formers - ANS-d What happens to the settling rate in a clarifier when the water temperature increases? a. Settling rate decreases b. Unaffected c. Settling velocity becomes negligible d. Settling rate increases - ANS-d What should be done before repairing an equipment that starts automatically? a. Check MSDS b. Fill-out Chain of Custody form Wastewater Wastewater c. Lock out and tag out d. Wear SCBA - ANS-c 1 mg/L is the same as 1 part per billion (ppb). a. True b. False - ANS-b A SCADA system is capable of monitoring and controlling equipment from a remote location. a. True b. False - ANS-a A Discharge Monitoring Report is typically submitted to the regulatory agency on a daily basis. a. True b. False - ANS-b A mechanical seal is used to prevent leaks between the pump casing and shaft. a. True b. False - ANS-a Alkalinity is the capacity of a liquid to neutralize base. a. True b. False - ANS-b Typical mixed liquor suspended solids concentration is 1000 to 4500 mg/L a. True b. False - ANS-a Turbidity is caused by suspended matters. a. True b. False - ANS-a Algae is not essential to the successful operation of both aerobic and facultative ponds. a. True b. False - ANS-b The addition of acid and CO2 will lower the pH of wastewater. a. True b. False - ANS-a Hydrogen sulfide will deteriorate concrete structures. a. True b. False - ANS-a The higher the pH the better the disinfection. Wastewater Wastewater a. True b. False - ANS-b Maintain a dissolved oxygen concentration of 12 to 14 mg/L in the aeration tank. a. True b. False - ANS-b When the velocity of the wastewater in a clarifier is greater in some sections than others it will lead to short-circuiting. a. True b. False - ANS-a The F/M ratio will decrease when the microorganism population in the aeration tank increases. a. True b. False - ANS-a Algae growth will be faster when there is less sunlight. a. True b. False - ANS-b The higher the temperature the more rapid the rate of disinfection. a. True b. False - ANS-a One of the benefits of recirculation for a trickling filter is that it decreases the contact time of the wastewater with the biological film. a. True b. False - ANS-b Maintaining a constant temperature in an anaerobic digester is one way to prevent foaming from recurring. a. True b. False - ANS-a Preventative maintenance is a proactive programmed and systematic approach to maintenance. a. True b. False - ANS-a Abnormal operation in a pond will not occur if it is overloaded with BOD. a. True b. False - ANS-b Anaerobic decomposition of sewage will release hydrogen sulfide. a. True Wastewater Wastewater b. False - ANS-a Always pour water into acid and never the other way around. a. True b. False - ANS-b Scum escaping in the clarifier effluent could be caused by hydraulic overload. a. True b. False - ANS-a Operate an activated sludge system at low MCRT if you have limited aeration capacity. a. True b. False - ANS-a Chlorine gas ls brown in color. a. True b. False - ANS-b Typical suspended solids concentration of domestic influent wastewater is 150 to 400 mg/L. a. True b. False - ANS-a Poor ventilation of a trickling filter could lead to odor problems. a. True b. False - ANS-a Sulfur dioxide is used to dechlorinate the effluent prior to discharge to protect aquatic organisms in the receiving waters. a. True b. False - ANS-a MCRT describes the average residence time of the activated sludge particle in the return sludge pipe. a. True b. False - ANS-b Free chlorine combines with water to form hypochlorous and hydrochloric acids. a. True b. False - ANS-a The trickling filter can be controlled by changing the loadings based on sludge age F/M ratio or MCRT. a. True b. False - ANS-b Wastewater Wastewater The MPN test for coliform does not test for individual pathogenic microorganism but uses coliform as an indicator organism to estimate the microorganism population. a. True b. False - ANS-a Mixed liquor volatile suspended solids (MLVSS) is used to determine the amount of microorganisms in the aeration tank to treat the incoming waste. a. True b. False - ANS-a A manhole sump or vault can be entered without following confined space entry procedures if it appears safe. a. True b. False - ANS-b An increase in the volatile acids/alkalinity ratio in an anaerobic digester indicates that a problem is developing. a. True b. False - ANS-a Chain-driven scrapers called "flights" are commonly used as mechanical grit collectors. a. True b. False - ANS-a A facultative bacteria is capable of living under an aerobic condition but not in an anaerobic condition. a. True b. False - ANS-b An impeller is an important part of a centrifugal pump that spins the liquid at high speed. a. True b. False - ANS-a Hot bearings in a blower could be caused by defective bearings. a. True b. False - ANS-a Class A fire extinguisher should be used for an electrical fire. a. True b. False - ANS-b Scum from primary clarifiers consists mainly of grease and other floatable materials. a. True b. False - ANS-a Wastewater Wastewater One of the ways to resolve an increase in the volatile acid/alkalinity ratio in an anaerobic digester is to decrease raw sludge feed rates. a. True b. False - ANS-b Sludge will not become septic when it remains in a channel or basin for an extended period of time. a. True b. False - ANS-b Shallow ponds that are used to treat wastewater are typically 3 to 5 feet deep. a. True b. False - ANS-a A slight seal leakage should be observed when a pump is operating to keep the packings cool. a. True b. False - ANS-a Total solids= volatile solids+ suspended solids a. True b. False - ANS-b The purpose of sludge wasting in an activated sludge process is to control the amount of solids in the primary treatment process. a. True b. False - ANS-b Chlorine gas is not flammable. a. True b. False - ANS-a Screening is a part of the pretreatment process that removes larger debris such as rocks cans and bottles. a. True b. False - ANS-a The best velocity through a grit channel is 3 foot per second. a. True b. False - ANS-b What is the main purpose of the activated sludge process? a. Removal of sand and pebbles b. Removal of settleable solids and floating scum c. Organic solids are liquefied and the solids volume is reduced Wastewater Wastewater d. Removal of soluble or finely divided suspended materials that were not removed by previous treatment - ANS-d Where is the primary sludge typically pumped to? a. Grit classifier b. Centrifuge c. Sludge digester d. Sludge drying bed - ANS-c What problem is caused by denitrification? a. Excessive settling of solids b. Rising sludge in secondary clarifier c. Very short detention time d. Conversion of ammonia to oxidized nitrogen - ANS-b What condition is necessary to perform a BOD test? a. 5 days at 20 degrees Celsius b. 5 days at 25 degrees Celsius c. 5 days at 30 degrees Celsius d. 5 days at 35 degrees Celsius - ANS-a What is a fusible plug? a. A plug on the bottom of a valve to drain sludge during maintenance b. A plug that can be fused to a diffuser in an aeration tank to permanently seal the outlet c. A safety device used to prevent build-up of excessive pressure in a chlorine cylinder d. A plug used to seal a leak on a polymer storage tank - ANS-c What is usually the last indicator to change in an anaerobic digester that is becoming sour? a. Volatile acid/alkalinity ratio b. Temperature c. Color d. pH - ANS-d What information is needed to calculate the F/M ratio? a. BOD and MLSS b. BOD and MLVSS c. TSS and MLSS d. MLSS and Settled sludge volume - ANS-b Which chemical is commonly used to control hydrogen sulfide gas? a. Chlorine b. Ammonia c. Carbon dioxide d. Sodium dioxide - ANS-a Wastewater Wastewater What would cause a trickling filter to operate less effectively? a. Blower inefficiency b. Recirculation c. Plastic media d. Ponding - ANS-d What is MPN? a. A type of surfactant found in wastewater b. A clump of organic material c. Most Probable Number of coliform group organisms per unit volume of sample water d. A number that indicates the tendency of activated sludge solids to thicken - ANS-c What is true regarding dissolved solids? a. They will get caught on a filter b. They are often called colloidal particles c. They will pass through a filter d. They are all inorganic solids - ANS-c Why is chlorine sometimes added at the headworks of the plant? a. To address denitrification b. Control odor c. To address sludge bulking d. Control fly problems - ANS-b What is the purpose of a launder in a primary clarifier? a. Collects the primary effluent that flows over the weir and conveys it towards the next treatment process b. A pipe that conveys wastewater to the influent of the clarifier c. Blades that scrape sludge from the bottom of the clarifier to the sump d. A power unit that rotates the collector - ANS-a What is the best way to communicate important information to employees? a. Memo b. Meeting in person c. Bulletin board in break room d. Send an email - ANS-b What problem might arise from tightening a gland in a pump? a. Excessive leakage b. Water hammer c. Wear on shaft or shaft sleeve d. Cavitation - ANS-c What could the Oxygen Uptake Rate test be used for? a. Determine SVI Wastewater Wastewater b. Obtain the F/M ratio c. Obtain pH of the wastewater d. Detect toxicity in the activated sludge process - ANS-d What does anaerobic bacteria require for metabolism? a. Dissolved oxygen b. Oxygen from nitrate c. They obtain oxygen by breaking down chemical compounds that contain oxygen such as sulfate d. Carbon - ANS-c Which of the following is used to dewater sludge? a. All choices (bcd) b. Drying bed c. Centrifuge d. Vacuum filter - ANS-a Which of the following is true about algae in a pond? a. During the day it consumes oxygen and releases CO2 for the bacteria in the pond h. During the day it consumes H2S and releases oxygen for the anaerobic bacteria in the pond c. During the day it consumes H2S and releases CO2 for the anaerobic bacteria d. During the day it consumes CO2 and releases oxygen for the aerobic bacteria in the pond - ANS-d What is the typical BOD in the secondary effluent? a. Between 50 to 100 mg/L b. Between 120 to 300 mg/L c. Between 5 to 30 mg/L d. Between 300 to 350 mg/L - ANS-c What should be done to a chlorine container if liquid chlorine is leaking? a. Turn it over so that the leaking side is on the bottom to seal the leak b. Turn it to the side c. Apply water on the chlorine leak to slow down the leakage d. Turn it over so that the leaking side is on top - ANS-d ln a domestic wastewater system how many pounds of oxygen are used each day by the microorganisms for each person using the system? a. 1.3 lbs/day/person b. 0.17 lb/day/person (roughly equal to 0.2 lb/day/person) c. 2.4 lbs/day/person d. 3.5 lbs/day/person - ANS-b What terminology indicates the time required to fill a basin at a given flowrate? a. Detention time Wastewater Wastewater b. Short-circuiting c. Hydraulic loading rate d. Weir overflow rate - ANS-a What could happen if the intake of a progressing cavity pump is not kept wet? a. Increase in head b. Damage to pump c. Slight decrease in flowrate d. Incremental increase in pressure - ANS-b How should you operate an anaerobic digester? a. The rate of acid formation is more than the methane formation b. The rate of acid formation is less than the methane formation c. The rate of acid formation and methane formation are approximately equal d. The rate of acid formation is predominant and methane formation is negligible - ANS c What is the purpose of a check valve? a. To isolate a clarifier for maintenance b. To stop flow from entering the headworks c. To throttle flow by turning the nut d. Prevent liquid from flowing in the reverse direction - ANS-d Which of the following is the best