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Wastewater Treatment Exam Questions and Answers: Class B Wastewater Textbook, Exams of Water and Wastewater Engineering

A series of true/false questions and answers related to odor control in wastewater treatment systems. It covers topics such as hydrogen sulfide generation, odor control methods, and safety precautions. Suitable for students studying wastewater treatment or environmental engineering.

Typology: Exams

2024/2025

Available from 12/09/2024

Estrelia
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Download Wastewater Treatment Exam Questions and Answers: Class B Wastewater Textbook and more Exams Water and Wastewater Engineering in PDF only on Docsity!

EXAM QUESTIONS AND ANSWERS

100% PASS

If wastewater contains dissolved oxygen, the biological breakdown will reduce sulfate to sulfide. T or F - - - correct answer ✅False At a pH below 5, all sulfide is present in the gaseous h2s form and most of it can be released from wastewater. T or F - - - correct answer ✅True In order to control odors effectively, the operator should know where odors originate and the cause. T or F - - - correct answer ✅True Chlorination is one of the oldest and least effective methods of controlling odors. T or F - - - correct answer ✅False- it is one of the oldest & most effective The reaction of chlorine with certain chemicals can cause a more odorous gas.

EXAM QUESTIONS AND ANSWERS

100% PASS

T or F - - - correct answer ✅True Decreasing the pH of wastewater is an effective odor control method for hydrogen sulfide. T or F - - - correct answer ✅False- Increasing is an effective method Odor control towers must have a biomass established on the filter media in order to remove odors. T or F - - - correct answer ✅True The hazard classification of the spent carbon from odor control must be established when considering disposal. T or F - - - correct answer ✅True Regeneration of activated carbon temporarily eliminates any concerns about hazardous waste disposal. T or F - - - correct answer ✅True

EXAM QUESTIONS AND ANSWERS

100% PASS

Hydrogen sulfide gas combines with moisture to form sulfuric acid, which is very corrosive. T or F - - - correct answer ✅True Which factor causes increased odor and corrosion problems in wastewater treatment plants? - - - correct answer ✅Increased travel times for wastewater to reach treatment plants What is the principle source of odor generation in wastewater collection systems and treatment processes? - - - correct answer ✅Production of inorganic and organic gases by microorganisms What is the main cause of most odors in wastewater systems? - - - correct answer ✅Hydrogen sulfide What is the most common source of sulfide in wastewater? - - - correct answer ✅Biological activity in the collection sewer or treatment plant

EXAM QUESTIONS AND ANSWERS

100% PASS

Why is the temperature of the wastewater system an important factor in the production of hydrogen sulfide gas? - - - correct answer ✅The rate of bacterial metabolism is related to temperature Why does ozone have limited use in controlling odors? - - - correct answer ✅Because an effective concentration may be too costly to use at large treatment plants What is the problem with using combustion to remove odors from wastewater treatment plant gases? - - - correct answer ✅The combustibility of the gases is so low that fuel costs are high How can cathode scale be removed from an electrolytic chemical scrubber unit? - - - correct answer ✅Flush the system with dilute nitric acid What is the adsorption odor removal process? The process in which odorous components are removed from a a gas through - - - correct answer ✅Adherence to a solid surface

EXAM QUESTIONS AND ANSWERS

100% PASS

What is the best solution to odor problems? - - - correct answer ✅Prevent odors from ever developing How are odors generated in wastewater collection systems and treatment plants? - - - correct answer ✅-Biological generation -Hydrogen sulfide generation -Hydrogen transfer schemes Which problems are created by hydrogen sulfide gas? - - - correct answer ✅-corrosion or deterioration of concrete sewer structures -explosive gas mixtures -hazards to the respiratory system to persons working in confined or close spaces -rotten egg odor Which items are facts that can help in odor classification? - - - correct answer ✅-individuals respond differently to the same odor -odors travel great distances with the direction of the wind

EXAM QUESTIONS AND ANSWERS

100% PASS

-small concentrations of odors can be offensive -some odors are objectionable and others are pleasant -the human nose rapidly becomes fatigued (insensitive) to odors Investigations in the neighborhood near the location of an odor complaint may reveal that the odors are coming from which possible nearby sources? - - - correct answer ✅-dead animal -home plumbing problem -sewer -storm drain -trash pile Which items are possible solutions operators can use to control odors? - - - correct answer ✅-changing or enforcing sewer-use ordinances -immediately removing floating scum/solids -maintaining dissolved oxygen in the wastewater -minimizing hydraulic detention times in pipes and wet wells -routinely and frequently disposing of screenings and grit

EXAM QUESTIONS AND ANSWERS

100% PASS

How does chlorine control odors? - - - correct answer ✅-destroys bacteria that convert sulfate to sulfide -destroys hydrogen sulfide at the point of application -inhibits the growth of slime layers in sewers How does hydrogen peroxide control odors? - - - correct answer ✅-by killing sulfate-reducing bacteria -by oxidant action -by producing oxygen What are the advantages of using hydrogen peroxide to control odors? - - - correct answer ✅-ability to inhibit the regeneration of sulfate- reducing microorganisms -effectiveness as an oxidant -lack of toxic by-products Which odorous gases can be removed by absorption by a hypochlorite process? - - - correct answer ✅-ammonia

EXAM QUESTIONS AND ANSWERS

100% PASS

-hydrogen sulfide -mercaptans -organic gases -sulfur dioxide To ensure optimal odor removal efficiency of a chemical mist odor control system, which tasks should be performed daily? - - - correct answer ✅-check chemical feed pumps -check chemical tank levels -check outlet hydrogen sulfide concentration -check water flow rate and pressure Which safety precautions should be taken when working with or installing a chemical mist odor control system? - - - correct answer ✅-provide an emergency eye wash/deluge shower in an easily accessible location near the installation -provide secondary containment for the chemical storage tanks -routinely inspect the system for leaks -use proper lockout/blockout procedures when working on equipment -wear PPE when handling process chemicals

EXAM QUESTIONS AND ANSWERS

100% PASS

What are the advantages of using activated carbon adsorption to control odors? - - - correct answer ✅-ability to increase adsorbent capability by the use of additive compounds -accommodation of high gas flow rates by the use of multiple units -fairly consistent reliability -simple operation Which safety precautions should be taken when working with or installing activated carbon odor control units? - - - correct answer ✅-adequately ground carbon treatment systems -implement engineering controls to eliminate dust inhalation -make available in the work area an emergency eye wash/deluge shower and washing facilities -prevent contact between carbon and strong oxidizing agents -use approved confined space procedures for vessel entry What are possible solutions to odor problems in the primary sedimentation area of a wastewater treatment plant? - - - correct answer ✅-air stream treatment

EXAM QUESTIONS AND ANSWERS

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-chemical addition -chemical addition at headworks -cover tanks, vent odors, and treat -remove sludge faster Equipment and instruments must be available in enclosed spaces to detect what kinds of conditions? - - - correct answer ✅-explosive conditions -hydrogen sulfide -oxygen concentration The pure oxygen activated sludge system is a modification of the air activated sludge process. T or F - - - correct answer ✅true The PSA Oxygen Generating Systems are usually installed in larger plants. T or F - - - correct answer ✅false- usually in smaller plants

EXAM QUESTIONS AND ANSWERS

100% PASS

All types of hydrocarbon and other flammable materials may be allowed to mix with oxygen. T or F - - - correct answer ✅false To operate the activated sludge process efficiently, a properly settling mixed liquor must be achieved and maintained. T or F - - - correct answer ✅true The RAS makes it possible for the microorganisms to be in the treatment system shorter than the flowing wastewater. T or F - - - correct answer ✅false- RAS keeps the microorganisms in the system longer than the wastewater The SVI values that indicated good operation in one plant will always apply to good operation in other plants. T or F - - - correct answer ✅false

EXAM QUESTIONS AND ANSWERS

100% PASS

Operation by or calculations of the F/M ratio should be based on daily tests to reflect rapidly changing conditions. - - - correct answer ✅false-calculations/operation should use 7-day average Cyanide combines with acid wastes to form the extremely toxic gas HCN. T or F - - - correct answer ✅true Frequently, the most economical method of treating toxic or undesirable wastes is at the source. T or F - - - correct answer ✅true Frequently, industrial wastes lack the proper nutrients for healthy microorganism growth and reproduction in the activated sludge process. T or F - - - correct answer ✅true

EXAM QUESTIONS AND ANSWERS

100% PASS

Emergency spill tanks should normally be operated full so their capacity is available during an emergency. T or F - - - correct answer ✅false A good source reduction program will save money in both production and waste treatment operation. T or F - - - correct answer ✅true The rate of nitrification will vary significantly with temperature and pH. T or F - - - correct answer ✅true Acid is produced by nitrification. T or F - - - correct answer ✅true What is an advantage of pure oxygen activated sludge systems over air activated sludge systems? - - - correct answer ✅they use smaller aeration (reactor) tanks

EXAM QUESTIONS AND ANSWERS

100% PASS

What is the function of the activated sludge process? - - - correct answer ✅to remove suspended and dissolved solids Under what conditions should the reactor vent gas purity valve be "fine tuned"? - - - correct answer ✅when there is a drastic change in either the quantity or strength of the wastewater entering the plant What does the settleability method of calculating the RAS flow rate assume? - - - correct answer ✅that measurements made with a laboratory settling cylinder will accurately reflect the settling in a clarifier What is the purpose of the Respiration Rate for activated sludge test? To give some insight into the - - - correct answer ✅health of the microorganisms in the activated sludge What can an operator expect of an activated sludge that has excessive filamentous organisms? - - - correct answer ✅poor settling

EXAM QUESTIONS AND ANSWERS

100% PASS

When establishing an industrial waste monitoring program, what is one of the first tasks? - - - correct answer ✅an examination of the wastewater characteristics of each industry that discharges to the collection system. what does the BOD test measure? - - - correct answer ✅the rate of oxygen uptake from the wastewater by microorganisms in biochemical reactions what are the major nutrients of concern in the activated sludge process? - - - correct answer ✅nitrogen and phosphorus how can more nitrogen be added to industrial wastewater? more nitrogen can be added in the form of - - - correct answer ✅ammonia how can more phosphorus be added to industrial wastewater? more phosphorus can be added in the form of - - - correct answer ✅phosphoric acid

EXAM QUESTIONS AND ANSWERS

100% PASS

what is a bioassay test? - - - correct answer ✅a method of determining toxic effects of industrial wastes using live test organisms such as fish what happens when brewery wastewaters first come in contact with activated sludge organisms? - - - correct answer ✅there is a sudden demand for oxygen by the activated sludge organisms what is the major cause of pH fluctuations in dairy plant effluent? -

correct answer ✅cleaning and sanitizing operations what could be the cause of rising sludge in clarifiers? - - - correct answer ✅denitrification potentially explosive or flammable conditions can be present when pure oxygen is mixed with which items? - - - correct answer ✅-fuel oil -gasoline -lubricating oil

EXAM QUESTIONS AND ANSWERS

100% PASS

which special safety rules must be applied when operating and maintaining pure oxygen systems? - - - correct answer ✅-clean, insulated gloves that can be easily removed are recommended -cuffless trousers should be worn outside boots or over shoes to shed spilled liquid oxygen -long shirt sleeves for arm protection are recommended -safety goggles or a face shield should be worn if liquid oxygen releases or splashing may occur which precautions are intended to eliminate the possibility of combustion and explosions caused by pure oxygen? - - - correct answer ✅-flammable materials must be kept far away from oxygen systems and storage tanks -grease and oil must be removed from tools and equipment by use of an approved solvent for the material to be cleaned -smoking and open flames are prohibited near oxygen systems and storage tanks -special non-hydrocarbon lubricants should be used for equipment in contact with oxygen -tools and equipment must be specially designed to be compatible for use in oxygen service

EXAM QUESTIONS AND ANSWERS

100% PASS

which basic approaches can be used to control the RAS flow rate? -

correct answer ✅-as a constant percentage of the influent flow -independently of the influent flow the amount of waste activated sludge (WAS) removed from the process affects which of the following items? - - - correct answer ✅-effluent quality -growth rate of the microorganisms -mixed liquor settleability -occurrence of foaming/frothing -oxygen consumption the objective of the activated sludge process control is to approach a particular "steady state" by controlling any one or a combination of which of the following control guidelines? - - - correct answer ✅-F/M food to microorganism ratio -MCRT, mean cell resident time -MLVSS concentration -sludge age

EXAM QUESTIONS AND ANSWERS

100% PASS

-volatile solids inventory the respiration rate for activated sludge test can be used to alert operators to required changes in which operating guidelines? - - - correct answer ✅-aeration tank detention times -quantity of oxygen needed -return sludge flow rates -waste sludge flow rates what information can be gained by calculating the oxygen uptake rate (OUR) value? you can obtain a fairly good estimate of - - - correct answer ✅-effluent quality -food quality -food strength which microorganisms are important indicators in the activated sludge process? - - - correct answer ✅-filamentous organisms -protozoa -rotifers

EXAM QUESTIONS AND ANSWERS

100% PASS

automatic devices are commonly used to monitor which items? - - - correct answer ✅-dissolved oxygen (DO) -flow -oxidation potential (conductivity) -pH what are the most common causes of industrial wastewater toxicity? excessive amounts of - - - correct answer ✅-biocides -detergents -free ammonia -heavy metals -solvents how can toxic materials enter the wastestream? - - - correct answer ✅-accidental spills -improper handling of toxic materials -indiscriminate dumping -leaking vessels and pipes

EXAM QUESTIONS AND ANSWERS

100% PASS

why should grit, soil, grease and oil be removed from industrial wastes? to prevent - - - correct answer ✅-accelerated equipment wear -accumulation in the treatment system -creation of odors -settling in pipes which conditions have been found to cause the disappearance of the higher forms of activated sludge bacteria (ciliates and rotifers)?


correct answer ✅-DO levels below 3 to 4 mg/l -high organic loadings -lack of pH control -nutrient deficiencies -toxic substances what are the goals for shutdowns/startups for industrial wastewater treatment plants using the activated sludge process? - -

correct answer ✅-cost optimization -maintain constant environment (temperature, pH, DO)

EXAM QUESTIONS AND ANSWERS

100% PASS

-maintain hydraulic loading -maintain nutrient balance (N, P, metals) -protect receiving stream which items could be causes of filamentous bulking in the activated sludge process? - - - correct answer ✅-a lack of adequate nutrients in the influent -large fluctuations in the plant influent organic loading -low DO levels in aeration basins and secondary clarifiers -low F/M levels in aeration system -the presence of high level sulfur in the influent which types of toxins are often found in dairy effluents? - - - correct answer ✅-detergents -lubricants -refrigerants -sanitizers

EXAM QUESTIONS AND ANSWERS

100% PASS

which items are potential adverse impacts of a dairy pretreater on the municipal wastewater treatment facility? - - - correct answer ✅-blockages in the collection system -effluent BOD violations caused by organic overloads -floating solids in the municipal effluent -spills of high organic strength wastes/toxins which main compounds found in petroleum wastewater can be treated very effectively by the activated sludge process? - - - correct answer ✅-ammonia -phenols -sulfide which items should the operational staff check when reviewing the plans and specifications for a pure oxygen activated sludge plant? -

correct answer ✅-oxygen generation equipment -oxygen safety and process instrumentation -physical plant layout -preventative maintenance program -reactor basins (aeration tanks)

EXAM QUESTIONS AND ANSWERS

100% PASS

minimum sludge thickening should always be attempted in the sedimentation tank before using a separate sludge thickener. T or F - - - correct answer ✅false the primary function of sludge thickening is to increase the sludge volume to be handled in subsequent processes. T or F - - - correct answer ✅false the quantity of air introduced and dissolved into the recycle or waste stream is critical to the operation of flotation thickeners. T or F - - - correct answer ✅true close visual monitoring of a centrifuge is the operator's best indication of operational problems. T or F - - - correct answer ✅true

EXAM QUESTIONS AND ANSWERS

100% PASS

the ideal operating gravity belt thickener belt speed is the fastest the operator can maintain without washing out the belt. T or F - - - correct answer ✅false gravity belt thickener blinding often develops because of polymer underdosing. T or F - - - correct answer ✅false the sludge feed to aerobic digesters should be as continuous and consistent as possible. T or F - - - correct answer ✅true the addition of lime to stabilize sludge significantly reduces the quantity of solids that ultimately must be disposed of. T or F - - - correct answer ✅false