Wastewater Treatment Plant Operations, Exams of Water and Wastewater Engineering

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What is the typical BOD removal efficiency in a primary clarifier? A) 10 to 15% B) 40 to 60% C) 20 to 50% D) 95 to 99% C) 20 to 50% (v.1 pg 129) 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 D) The food for the microorganisms flowing into the aeration tank, in lbs/day (v.2 pg 58) 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 B) Brown with a moderate amount of crisp, white foam What is used to control filamentous organisms? A) Polymer B) Sulfur Dioxide C) Coagulant D) Chlorine

D) Chlorine (v.1 pg 399) 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 C) Flow and chlorine residual (v.1 pg 356) Which toxic gas is commonly found in septic wastewater and smells like rotten eggs? A) Hydrogen Sulfide B) Carbon monoxide C) Hydrogen D) Carbon Dioxide A) Hydrogen Sulfide (v.2 pg 299) What is the permissible exposure limit for chlorine gas vapor during a normal 8 hour workday and a 40 hour work week? A) 0.1 ppm B) 0.5 ppm C) 1 ppm D) 15 ppm B) 0.5 ppm (v.2 pg 268) What is a vulnerability assessment? A) Assesses the impact of hydrogen sulfide to a concrete structure B) Analyzes the impact of flow 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

D) Contingency planning to determine the vulnerability of the utility during various types of emergencies and identify corrective actions to reduce the risks (v.2 pg 722) 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 C) Activated sludge settles slower than raw sludge (v.1 pg 109) What should be mostly found in healthy activated sludge? A) Tiny flagellates B) Amoeboids C) Short Filaments D) Free swimmers and stalked ciliates D) Free swimmers and stalked ciliates (v.2 pg 120,124) One to two percent of the digester gas in an anaerobic consists of A) Hydrogen, Nitrogen, Hydrogen sulfide, and other gases B) Methane C) Carbon Dioxide D) CH_ A) Hydrogen, Nitrogen, Hydrogen sulfide, and other gases (v.2 pg 158) What is true during the colder winter months? 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 B) Modify operations to increase solids under aeration to provide more microorganisms to treat the BOD (v.2 pg 71) What type of sludge would you expect in an aeration tank if the content is dark and has low DO? A) Sludge that is heavy B) Chlorinated Sludge C) Septic Sludge D) Healthy Sludge C) Septic Sludge (v.2 pg 75) What could have 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 D) Carbon dioxide content in the digester gas will increase (v.2 pg 191) What are screenings? A) Colloids B) TDS C) Pieces of wood, roots, rags, and other large debris D) COD C) Pieces of wood, roots, rags, and other large debris (v.1 pg 41) 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 takes place B) More oxygen is required in the aeration tank (v.2 pg 19) What impact does temperature have on the reaction rate of microorganisms in wastewater? A) Reaction rate doubles with every 18 degree Fahrenheit increase in temperature until higher temperature inhibits biological activity B) Reaction rate decreases by 20% with every 10 degree Fahrenheit increase in temperature C) Reaction rate of microorganism is not impacted by temperature D) Reaction rate goes to zero A) Reaction rate doubles with every 18 degree Fahrenheit increase in temperature until higher What is commonly used to control the odor of hydrogen sulfide? A) Carbon Dioxide B) Methane C) Chlorine D) Hydrogen C) Chlorine (v.1 pg 398) 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) D) Mixed Liquor Volatile Suspended Solids (MLVSS) (v.2 pg 58) 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 C) Gas production could increase the internal pressure and cause the line to fail D) The aerobic condition will cause Zoolgleal mass to grow in large numbers. C) Gas production could increase the internal pressure and cause the line to fail (v.2 pg 152) 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) It is 1.5 times lighter than air B) it is 2.5 times heavier than air (v.1 pg 375) Which of the following is typically treated by biological processes? A) Roots and rags B) Sand and eggshells C) Cinders

D) Dissolved and non settable organic material D) Dissolved and non settable organic material (v.1 pg 46) 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 C) Chain of Custody form (v.2 pg 498) What could cause a sudden drop in pH of the influent? 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 A) Acidic chemical in the influent (v.2 pg 579) What is the 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 walls, floor and equipment inside the clarifiers D) Inspect chains, sprockets, and flights. D) Inspect chains, sprockets, and flights (v.1 pg 118)

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 C) Excessive organic loading (v.1 pg 192) What could happen if the dissolved oxygen content in the aeration tank is too low? A) Pinpoint floc will develop B) Filamentous organisms could thrive and prevent the sludge sludge floc from settling properly in the secondary clarifier C) Settling will improve in the secondary clarifier D) Sludge bulking will be eliminated B) Filamentous organisms could thrive and prevent the sludge sludge floc from settling properly in the secondary clarifier (v.1 pg 254) 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% D) Mostly between 70 to 80% (v.1 pg 317)

What is a 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. C) Combined chlorine- a chemical that is formed when chlorine reacts with ammonia (v.1 pg

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 gastrification 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 A) When mixed liquor solids settle slowly and compact to a limited extent (v.2 pg 71) 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 C) Excess acid formation (v.2 pg 148) What is the only reliable method of detecting hydrogen sulfide?

A) Sense of smell B) Atmospheric monitoring C) Color titration D) Lab test B) Atmospheric monitoring (v.2 pg 271) What is sludge age? A) An expression of the average time that a microorganism will spend in the activated sludge process, and calculated using 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 any given flowrate D) A rough indicator of the length of time a pound of solids is maintained under aeration D) A rough indicator of the length of time a pound of solids is maintained under aeration (v.2 pg 519) 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 C) Shorter test period (v.2 pg 541) 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 D) 1.5 to 2 hours (v.1 pg 43) If you are testing the pH of a wastewater sample, what is the maximum recommended holding time? A) 5 days B) It must be tested immediately C) 24 hours D) 36 hours B) It must be tested immediately (v.2 pg 502) What could cause short circuiting in a clarifier? A) Sludge composition B) Reduction in flowrate C) Uneven weir settings D) Broken sludge pump C) Uneven weir settings (v.1 pg 125) 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 A) It could indicate solids or organic overloading (v.1 pg 228) What is an air gap? A) A distance between blowers in an activated sludge system B) The vertical distance between the surface of wastewater and the top of basin C) Backflow prevention D) Type of aeration equipment C) Backflow prevention (v.1 pg 503) Which is true about chlorine demand? A) Chlorine demand= Chlorine residual + Chlorine dose B) Chlorine demand= Chlorine does x Chlorine residual C) Chlorine demand= Chlorine residual - Chlorine dose D) Chlorine demand= Chlorine dose - Chlorine residual D) Chlorine demand= Chlorine dose - Chlorine residual (v.1 pg 352) What is accomplished by the activated sludge process? A) Anaerobic bacteria use SO_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

B) Remove soluble or finely divided suspended materials (v.2 pg 16) 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 C) 30 to 35% by volume (v.2 pg 158) Which of the following is a collection of individual samples obtained at regular intervals? A) Grab B) Culmination C) Comprehensive D) Composite D) Composite (v.2 pg 499) 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 A) Beaker(v.2 pg 479)

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 D) Very small, finely divided solids that remain dispersed in a liquid for a long time (v.1 pg 22,144) What is the most common type of grit collector? A) Deflectors B) Weirs C) Chain driven scrapers called "flights" D) Parshall flume C) Chain driven scrapers called "flights" (v.1 pg 87) 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 D) They are directly related to flow (v.1 pg 118) What is the slime growth on a trickling filter called?

A) Filamentous bacteria B) Zoogleal film C) Stalked ciliate D) Acid formers B) Zoogleal film (v.1 pg 169) What should be done if you observe a small, steady stream of water leakage from the pump packings? A) tighten the packings until they are water tight B) Replace the packing C) Do nothing. The leakage is required to cool and lubricate the dynamic surface D) Replace the pump C) Do nothing. The leakage is required to cool and lubricate the dynamic surface (v.2 pg 344) What should be done if the 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 levels is very low in the aeration tank C) Decrease MLSS and sludge age D) Chlorinate the return activated sludge D) Chlorinate the return activated sludge (v.2 pg 60) When is confined space considered oxygen deficient?

A) In atmosphere where oxygen content is less than 19.5% by volume B) In atmosphere where oxygen content is less than 23.5% by volume C) In atmosphere where oxygen content is less more than 23.5% by volume D) In atmosphere where oxygen content is less than 29.5% by volume A) In atmosphere where oxygen content is less than 19.5% by volume (v.2 pg 267) 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 the treatment plants is 12.5% D) Corrosive in moist atmosphere C) Common chlorine gas concentration at the treatment plants is 12.5% (v.1 pg 375) 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 may dead viruses B) An area in the aeration tank that has insufficient mixing 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 D) Control the acid formation so that it is larger than the methane formation (v.2 pg 148) 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 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 C) Testing for atmospheric hazards is not required as long as a blower is in use (v.2 pg 270) What is a MSDS? A) A federal law that is designed to protect the health and safety of workers B) A condition in which a persons 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 C) A document that contains important information about a chemical, such as safe exposure level, flammability rating, and first aid procedures (v.2 pg 728) How often should grit be removed from the grit channel? A) Weekly

B) Monthly C) Bi-weekly D) Daily D) Daily (v.1 pg 87) What is the typical removal efficiency from bacteria in a primary clarifier? A) 0 - 5% B) 25 - 75% C) 5 - 10% D) 10 - 20% B) 25 - 75% (v.1 pg 129) 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 A) Damaged impeller (v.1 pg 182) What is the two categories of coliform bacteria? A) Lactose and lauryl tryptose B) Primary and secondary C) Free swimming and stalked

D) Total and Fecal D) Total and Fecal (v.2 pg 552) Which of the following is true about the extended aeration process? A) Wasting is not necessary to maintain proper control of the process B) It produces more waste than conventional activated sludge process C) It has low F/M ratio D) It has low MLSS concentration C) It has low F/M ratio (v.1 pg 257) What type of disinfection is gaining popularity, and expected to become a practical alternative to chlorination? A) Sulfur dioxide B) Ultraviolet (UV) disinfection C) Aqueous ammonia D) Caustic soda B) Ultraviolet (UV) disinfection (v.1 pg 303) 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 C) Prior to discharge into receiving waters

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 D) More DO is needed (v.2 pg 53) 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 and 8 hour time weighted average of 25 decibels B) Employees whose normal noise exposure equals or exceeds an 8 hour time weighted average of 85 decibels (v.2 pg 277) What is a major cause of repeated sludge bulk? A) High pH B) High DO C) High food to mircoorganism loading rates D) High nutrient concentration C) High food to mircoorganism loading rates (v.2 pg 71)

How can the efficiency of a trickling filter be improved? A) Raise the distributor arm B) Reduce the size of the ventilation ports C) Decrease the amount of the filter media D) Add recirculation D) Add recirculation (v.1 pg 175) 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 produces carbon dioxide, which lowers pH C) Algae consumes carbon dioxide, which lower pH D) Algae releases carbon dioxide, which raises pH A) Algae uses carbon dioxide, which raises pH (v.1 pg 299) What should be done to find a small chlorine leak? A) Spray hypocloric 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 B) Tie a rag on a stick, dip the rag in a strong ammonia solution, and hold the rag near the suspected points (v.1 pg 386)

What should you do if there is a thick, dark foam on the surface of an aeration tank? A) Increase the sludge wasting B) Decrease sludge wasting C) Maintain current MLSS concentration D) Increase the mircoorganism population A) Increase the sludge wasting (v.2 pg 53) 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 a scum blanket B) Speeds up digestion rate (v.2 pg 176) 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 C) Within 12 inches of the floor (v.1 pg 396) What is the purpose of the seal 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 D) Lubricates the packing (v.2 pg 344) What is the incubation period for the BOD test? A) Five days +/- 3 hours B) Five days +/- 1 hours C) Five days +/- 4 hours D) Five days +/- 2 hours A) Five days +/- 3 hours (v.2 pg 574) What could happen if you are exposed to very high concentration of hydrogen sulfide? A) Swelling of the hand B) Numbness of the legs C) It could quickly lead to death D) Develop skin rash C) It could quickly lead to death (v.2 pg 268) What causes primary effluent to become black and odorous? A) Excessive sludge pumping

B) Oil leak from the sludge pump C) Crack in the launder D) Improper sludge removal from the clarifier D) Improper sludge removal from the clarifier (v.1 pg 123) 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 C) A mass of organic material consisting of living organisms that feed on the wastes in sewage (v.2 pg 816) What is the color of a pond that is operating properly? A) Brown B) Deep green color C) Clear D) Tan B) Deep green color (v.1 pg 309) What does healthy activated sludge smell like? A) Chlorine B) Raw sewage

C) Rotten eggs D) Earthy D) Earthy Which law regulates wastewater discharge to receiving water? A) Wastewater Act B) Clean Water Act C) National Discharge Act D) Federal Effluent Act B) Clean Water Act