Water Treatment Class 3

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Water Treatment Class 3 - Quiz

Welcome to the Water Treatment Quiz for class 3! Water treatment is a vital process that ensures access to clean and safe water for various purposes. This quiz will test your knowledge about the fascinating world of water treatment and the techniques involved in purifying water.
Water treatment, but also gain a deeper understanding of the critical role it plays in public health and environmental sustainability. So, dive into the world of water treatment and see how well you know the processes that make our water clean, safe, and suitable for consumption! If you like this quiz, share it with Read moreyour friends.


Questions and Answers
  • 1. 

    The filter rate and backwash rate of each filter shall be determined and recordedonce each

    • A.

      Week

    • B.

      Month

    • C.

      Quarter

    • D.

      Year

    Correct Answer
    B. Month
    Explanation
    The filter rate and backwash rate of each filter should be determined and recorded once each month. This frequency allows for regular monitoring and maintenance of the filters to ensure their optimal performance. Checking the rates on a monthly basis allows for timely identification of any issues or deviations from the desired levels, enabling prompt corrective actions to be taken. It also provides a reasonable balance between frequent monitoring and the practicality of the task.

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  • 2. 

    The culture media used in the presumptive test is of

    • A.

      Agar

    • B.

      A brilliant green lactose bile broth

    • C.

      A lactose or lauryl tryptose broth

    • D.

      A nutrient agar

    Correct Answer
    C. A lactose or lauryl tryptose broth
    Explanation
    The presumptive test is used to detect the presence of coliform bacteria in a sample. Coliform bacteria are a group of bacteria that are commonly found in the intestines of warm-blooded animals and are used as indicators of fecal contamination. The culture media used in the presumptive test should be selective for coliform bacteria, meaning it should inhibit the growth of other bacteria. A lactose or lauryl tryptose broth is commonly used as it contains specific ingredients that promote the growth of coliform bacteria while inhibiting the growth of other bacteria. This allows for the detection and isolation of coliform bacteria in the sample.

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  • 3. 

    Fish eyes are

    • A.

      Undissolved clumps in solution

    • B.

      The primary cause of floc carryover

    • C.

      Spots of coagulant attaching to the sides of the basin.

    • D.

      An unavoidable operating problem associated with solution tanks

    Correct Answer
    A. Undissolved clumps in solution
    Explanation
    Fish eyes are undissolved clumps in solution. This means that when a solution is prepared, there may be small particles or aggregates that do not fully dissolve and remain as clumps. These undissolved clumps can affect the quality and appearance of the solution, as well as potentially impact its functionality. It is important to properly mix and dissolve the components of a solution to avoid the presence of fish eyes.

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  • 4. 

    Water may be aerated by several methods, almost all of which involve

    • A.

      Covering the storage facilities

    • B.

      Exposing a large surface area to the atmosphere

    • C.

      Increasing the pressure

    • D.

      Reducing its temperature

    Correct Answer
    B. Exposing a large surface area to the atmosphere
    Explanation
    Exposing a large surface area to the atmosphere is a method of aerating water. When water is exposed to the atmosphere, it allows for the exchange of gases, particularly oxygen, between the air and water. This process helps to increase the dissolved oxygen levels in the water, which is essential for aquatic organisms to survive. By increasing the surface area of water in contact with the air, more oxygen can be absorbed, improving the overall quality and health of the water.

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  • 5. 

    All chlorine cylinders are required to contain at least one fusible metal safety device (plug) designed to melt at between _____ Degrees F

    • A.

      98 - 105

    • B.

      120 - 150

    • C.

      158 - 165

    • D.

      200 - 212

    Correct Answer
    C. 158 - 165
    Explanation
    Chlorine cylinders are required to have a fusible metal safety device (plug) that is designed to melt at a specific temperature range. The correct answer is 158 - 165 degrees Fahrenheit. This means that the plug will melt if the temperature inside the cylinder reaches this range, allowing the pressure to be released and preventing the cylinder from exploding.

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  • 6. 

    What is the amount of chlorine required to treat 5 mil gal of water to provide a 0.8 ppm residual and satisfy 2.4 ppm chlorine demand?

    • A.

      33.33 lb

    • B.

      66.67 lb

    • C.

      100.00 lb

    • D.

      133.33 lb

    Correct Answer
    D. 133.33 lb
    Explanation
    To calculate the amount of chlorine required, we need to consider both the desired residual chlorine concentration and the chlorine demand of the water.
    First, let's determine the amount of chlorine required to satisfy the chlorine demand: Chlorine required for demand = Demand × Volume of water = 2.4 ppm × 5 million gallons = 12 million ppm-gallons
    Next, let's calculate the amount of chlorine needed to provide the desired residual concentration: Chlorine required for residual = Residual × Volume of water = 0.8 ppm × 5 million gallons = 4 million ppm-gallons
    Finally, add the chlorine required for demand and residual to get the total chlorine required: Total chlorine required = Chlorine required for demand + Chlorine required for residual = 12 million ppm-gallons + 4 million ppm-gallons = 16 million ppm-gallons

    Using the conversion factor: 1 ppm-gallon of liquid chlorine = 8.34 × 10^-6 pounds (lb)
    Now, let's calculate the amount of chlorine required in pounds (lb):
    Total chlorine required (in ppm-gallons) = 16,000,000 ppm-gallons
    Total chlorine required (in pounds) = 16,000,000 ppm-gallons × 8.34 × 10^-6 lb/ppm-gallon
    Total chlorine required ≈ 133.44 pounds (lb)

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  • 7. 

    The detention time usually required in a conventional straight-flow sedimentationbasin is _______ h.

    • A.

      0.5 - 1

    • B.

      2 - 6

    • C.

      10 - 12

    • D.

      24

    Correct Answer
    B. 2 - 6
    Explanation
    The detention time required in a conventional straight-flow sedimentation basin is typically between 2 to 6 hours. This is because the sedimentation process involves allowing the water to flow slowly through the basin, allowing enough time for the suspended particles to settle at the bottom. A detention time of 2 to 6 hours ensures that there is sufficient time for the settling process to occur effectively, resulting in clearer water.

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  • 8. 

    Air binding is a condition that may occur as a result of

    • A.

      Filter-bed compaction

    • B.

      Gravel displacement

    • C.

      Negative head.

    • D.

      Reaching terminal head loss.

    Correct Answer
    C. Negative head.
    Explanation
    Air binding is a condition that may occur as a result of negative head. Negative head refers to a situation where the pressure in a system drops below atmospheric pressure, causing air to be drawn into the system. In the context of the given options, filter-bed compaction, gravel displacement, and reaching terminal head loss do not directly cause negative head. However, negative head can occur as a result of these factors, leading to air binding.

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  • 9. 

    A program for the control of algae should be instituted

    • A.

      On a routine, periodic schedule, but not to exceed two applications per year

    • B.

      On a seasonal basis

    • C.

      After trend information has been established and adequate monitoring is practiced.

    • D.

      During extended periods of warm water temperatures

    Correct Answer
    C. After trend information has been established and adequate monitoring is practiced.
    Explanation
    The correct answer suggests that before implementing a program for algae control, it is important to gather trend information and practice adequate monitoring. This implies that a thorough understanding of the algae growth patterns and the effectiveness of control measures is necessary before taking any action. This approach ensures that the program is based on reliable data and is more likely to be successful in controlling algae growth.

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  • 10. 

    With the coming of winter, the water temperature drops. A likely operational problem at a filtration plant with coagulation is

    • A.

      Floc carryover from the sedimentation system

    • B.

      High alkalinity

    • C.

      High chlorine residual

    • D.

      Odor.

    Correct Answer
    A. Floc carryover from the sedimentation system
    Explanation
    During winter, the water temperature drops, which can lead to a decrease in the efficiency of the coagulation process at a filtration plant. Coagulation is the process of adding chemicals to the water to form flocs, which help in the removal of impurities. If the water temperature drops too low, the flocs may not form properly or may break apart, resulting in floc carryover from the sedimentation system. This means that the flocs are not settling properly and are carried over into the filtered water, leading to reduced water quality.

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  • 11. 

    A fluoride saturator

    • A.

      Can only be used by large treatment facilities

    • B.

      Eliminates the need for a metering pump

    • C.

      Eliminates the need for chemical handling.

    • D.

      Is suitable for small water systems

    Correct Answer
    D. Is suitable for small water systems
    Explanation
    The correct answer is "is suitable for small water systems." This means that a fluoride saturator is designed to be used specifically by small water systems. It implies that it is not recommended or necessary for large treatment facilities to use a fluoride saturator.

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  • 12. 

    The most desirable place to feed activated carbon in a lime-soda ash softening plant is

    • A.

      After lime feed.

    • B.

      In the clearwell

    • C.

      To raw water at earliest stage possible.

    • D.

      With lime feed

    Correct Answer
    C. To raw water at earliest stage possible.
    Explanation
    The most desirable place to feed activated carbon in a lime-soda ash softening plant is to the raw water at the earliest stage possible. This is because activated carbon is used to remove organic compounds, taste, and odor from the water. By adding it at the earliest stage, it ensures that these impurities are effectively removed before the water goes through the lime-soda ash softening process. Adding activated carbon after lime feed or in the clearwell may not be as effective in removing these impurities, leading to lower water quality.

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  • 13. 

    Activated alumina is used effectively for the removal of

    • A.

      Certain inorganic elements

    • B.

      Herbicides and pesticides

    • C.

      Humic substances

    • D.

      Oxidized precipitates

    Correct Answer
    A. Certain inorganic elements
    Explanation
    Activated alumina is a highly porous material that has a strong affinity for certain inorganic elements. It works by adsorbing these elements onto its surface, effectively removing them from a solution. This makes activated alumina an effective tool for water treatment, as it can remove contaminants such as fluoride, arsenic, and selenium. Therefore, the correct answer is that activated alumina is used effectively for the removal of certain inorganic elements.

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  • 14. 

    Four milligrams per litre of chlorine is added continuously to a water flow thataverages 5 mgd. How much chlorine will be used in 30 days?

    • A.

      1500 lb

    • B.

      3000 lb

    • C.

      5000 lb

    • D.

      15,000 lb

    Correct Answer
    C. 5000 lb
    Explanation
    In order to find the amount of chlorine used in 30 days, we need to calculate the total amount of chlorine added to the water flow over that period. The water flow averages 5 mgd (milligrams per day), so in 30 days, the total amount of water flow would be 5 mgd * 30 days = 150 mg. Since 4 milligrams per litre of chlorine is added continuously, we need to convert the total amount of water flow from milligrams to litres. Assuming 1 litre of water weighs 1 kilogram, we can convert the total amount of water flow to litres by dividing it by 1000. Therefore, the total amount of chlorine used in 30 days would be 150 mg / 1000 = 0.15 litres. Finally, we can convert litres to pounds by multiplying by the density of chlorine, which is approximately 33.8 pounds per litre. Thus, the amount of chlorine used in 30 days would be 0.15 litres * 33.8 pounds per litre = 5.07 pounds, which can be rounded to 5000 lb.

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  • 15. 

    Harvesting, dewatering, dredging, shading, and lining are all methods for controlling rooted aquatic plants

    • A.

      Without much effort

    • B.

      Physically

    • C.

      Chemically.

    • D.

      Biologically

    Correct Answer
    B. Physically
    Explanation
    Physically controlling rooted aquatic plants involves methods such as harvesting, dewatering, dredging, shading, and lining. These methods require physical intervention to remove or restrict the growth of aquatic plants. Harvesting involves manually cutting or removing the plants from the water. Dewatering involves reducing the water level to expose and dry out the plants. Dredging involves removing the plants by scooping or suctioning them from the water. Shading involves blocking sunlight to prevent plant growth. Lining involves placing physical barriers to restrict the spread of plants. These methods do not involve chemical or biological means of control.

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  • 16. 

    Sodium hydroxide (NaOH) is often used as the base in acid-base titrations. It has a molecular weight of 40 (23 + 16 + 1 = 40). How many grams of NaOH are in 1 L of a 1N (normal) solution?

    • A.

      20

    • B.

      40

    • C.

      60

    • D.

      80

    Correct Answer
    B. 40
    Explanation
    In a normal solution, the concentration is expressed in terms of normality (N), which is the number of equivalents of a solute per liter of solution. Sodium hydroxide (NaOH) has a molecular weight of 40 g/mol, meaning that 1 mole of NaOH weighs 40 grams. Since the normality of the solution is 1N, it means that there is 1 equivalent of NaOH in 1 liter of the solution. Therefore, there are 40 grams of NaOH in 1 liter of a 1N solution.

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  • 17. 

    When using the multiple-tube fermentation test method and coliform organismsoccur in six out of ten of the 10-mL portions of a single standard sample, then

    • A.

      Customers should be told to boil their water

    • B.

      The system must collect a set of repeat samples within 24 h.

    • C.

      The chlorine residual should be increased to 1.0 mg/L

    • D.

      The water main should be flushed for 24 h.

    Correct Answer
    B. The system must collect a set of repeat samples within 24 h.
    Explanation
    When coliform organisms occur in six out of ten of the 10-mL portions of a single standard sample using the multiple-tube fermentation test method, it indicates a potential contamination issue. In such cases, it is necessary for the system to collect a set of repeat samples within 24 hours. This is important to confirm the presence of coliform organisms and to assess the extent of the contamination. Collecting repeat samples helps ensure the accuracy of the test results and allows for appropriate actions to be taken to address the issue and protect the customers' health.

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  • 18. 

    Fire fighting may cause low pressure in an area of a distribution system. The lowpressure might lead to

    • A.

      Contamination of the system by backsiphonage

    • B.

      Ice formation in the pipes

    • C.

      Loss of chlorine residual

    • D.

      Muddy water.

    Correct Answer
    A. Contamination of the system by backsiphonage
    Explanation
    When fire fighting causes low pressure in a distribution system, it creates a potential for backsiphonage. Backsiphonage occurs when there is a sudden drop in pressure, causing water to flow backward from a contaminated source into the distribution system. This can lead to the contamination of the system, as the water from the contaminated source mixes with the clean water in the distribution system. Therefore, the low pressure caused by fire fighting can result in the system being contaminated by backsiphonage.

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  • 19. 

    Pinpoint floc is a condition associated with

    • A.

      Flash mixing

    • B.

      Low turbidity

    • C.

      The type of chemical selected.

    • D.

      Water temperature

    Correct Answer
    A. Flash mixing
    Explanation
    Pinpoint floc is a condition associated with flash mixing. Flash mixing refers to the rapid and intense mixing of chemicals with water to promote coagulation and flocculation. During flash mixing, the chemicals are added quickly and mixed vigorously to create small, dense floc particles. Pinpoint floc refers to the formation of small, compact floc particles that are highly effective in removing suspended solids and impurities from water. Therefore, flash mixing is the correct answer as it is directly related to the formation of pinpoint floc.

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  • 20. 

    Sedimentation can be improved by

    • A.

      Lowering the water temperature after flocculation.

    • B.

      Maintaining a uniform, horizontal, low-velocity flow across the basin

    • C.

      Maintaining a uniform sludge blanket

    • D.

      Reducing the detention time

    Correct Answer
    B. Maintaining a uniform, horizontal, low-velocity flow across the basin
    Explanation
    Maintaining a uniform, horizontal, low-velocity flow across the basin can improve sedimentation. This is because it helps to prevent the re-suspension of settled particles, allowing them to settle and accumulate at the bottom of the basin more effectively. By ensuring a uniform flow, the particles are less likely to be disturbed and remain settled, resulting in improved sedimentation. Additionally, a low-velocity flow helps to minimize turbulence, which can also prevent the re-suspension of particles and promote better settling.

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  • 21. 

    A carbon dosage of 20 mg/L is required for the removal of taste and odors. With aflow of 5560 gpm, how many pounds of carbon should be fed per hour?

    • A.

      27.8 lb

    • B.

      49.9 lb

    • C.

      55.6 lb

    • D.

      668.0 lb

    Correct Answer
    C. 55.6 lb
    Explanation
    To calculate the amount of carbon that should be fed per hour, we need to convert the flow rate from gallons per minute (gpm) to pounds per hour (lb/hr). Since 1 gallon of water weighs 8.34 pounds, we can multiply the flow rate of 5560 gpm by 8.34 to get the flow rate in pounds per minute. Then, we multiply the result by 60 to convert it to pounds per hour. The calculation would be: 5560 gpm * 8.34 lb/gal * 60 min/hr = 2,769,864 lb/hr. Therefore, the correct answer is 55.6 lb.

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  • 22. 

    If a filter has been out of service and allowed to go dry, which filter control valveshould be used to refill it with water?

    • A.

      Effluent valve

    • B.

      Influent valve

    • C.

      Rewash valve

    • D.

      Backwash inlet valve

    Correct Answer
    D. Backwash inlet valve
    Explanation
    When a filter has been out of service and allowed to go dry, the backwash inlet valve should be used to refill it with water. The backwash inlet valve is responsible for allowing water to enter the filter during the backwashing process, which helps to clean and remove any accumulated debris. In this case, since the filter has been out of service and needs to be refilled with water, the backwash inlet valve would be the appropriate choice to ensure water flow into the filter.

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  • 23. 

    A liquid has a specific gravity of 1.16. How much would 300 gallons of this liquid weigh?

    • A.

      158

    • B.

      348

    • C.

      2902

    • D.

      2899

    Correct Answer
    C. 2902
  • 24. 

    Polyelectrolytes are

    • A.

      Coagulants

    • B.

      Coagulant aids

    • C.

      Used for hardness reduction

    • D.

      Used for pH adjustment

    Correct Answer
    B. Coagulant aids
    Explanation
    Polyelectrolytes are substances that are used in water treatment processes to aid in the coagulation of suspended particles. They work by neutralizing the charges on the particles, allowing them to come together and form larger flocs that can be easily removed from the water. While coagulants are substances that directly cause the particles to come together, polyelectrolytes act as coagulant aids, enhancing the effectiveness of the coagulants. Therefore, the correct answer is "coagulant aids".

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  • 25. 

    Which of the following processes in water treatment involves the removal of suspended solids by allowing water to pass through a porous medium?

    • A.

      Coagulation

    • B.

      Sedimentation

    • C.

      Filtration

    • D.

      Disinfection

    Correct Answer
    C. Filtration
    Explanation
    Filtration is a water treatment process that involves the removal of suspended solids, such as dirt, sand, and other particles, from water by allowing it to pass through a porous medium, such as sand, gravel, or activated carbon. This process helps to improve the clarity and quality of the water by physically straining out impurities.

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  • 26. 

    What is total hardness of water in mg/L CaCO3 when magnesium (Mg) is 10 mg/L and calcium (Ca) is 20 mg/L?

    • A.

      100.09

    • B.

      30.8

    • C.

      91.09

    • D.

      107.33

    Correct Answer
    C. 91.09
    Explanation
    To find the total hardness of water in mg/L CaCO3 (calcium carbonate) when both magnesium (Mg) and calcium (Ca) concentrations are given, you can use the following formula:
    Total Hardness (as CaCO3) = (2.497 × Mg concentration in mg/L) + (4.118 × Ca concentration in mg/L)
    In this case:
    Mg concentration = 10 mg/L
    Ca concentration = 20 mg/L
    Now, plug these values into the formula:
    Total Hardness (mg/L CaCO3) = 2.497 × Ca (mg/L) + 4.115 × Mg (mg/L)
    Total Hardness = 2.497 × 20 mg/L (Ca) + 4.115 × 10 mg/L (Mg)
    Total Hardness = 49.94 mg/L CaCO3 + 41.15 mg/L CaCO3
    Total Hardness = 91.09 mg/L CaCO3
    So, the total hardness of the water is approximately 91.09 mg/L CaCO3.

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  • 27. 

    One function of aeration is the removal of ______ from water prior to the lime-soda ash softening process.

    • A.

      Carbon dioxide

    • B.

      Chlorine

    • C.

      Inorganic material

    • D.

      Oxygen

    Correct Answer
    A. Carbon dioxide
    Explanation
    Aeration helps in removing carbon dioxide from water before the lime-soda ash softening process. This is because carbon dioxide can react with lime to form calcium carbonate, which can cause scaling and reduce the effectiveness of the softening process. By removing carbon dioxide through aeration, the water can undergo the softening process more efficiently.

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  • 28. 

    Calcium carbonate stability refers to

    • A.

      A condition where calcium carbonate, pH, and alkalinity are in equilibrium

    • B.

      A condition where water will neither dissolve nor deposit calcium carbonate

    • C.

      A theoretical property of water.

    • D.

      Water in equilibrium where the measured pH is equal to the Langelier index

    Correct Answer
    B. A condition where water will neither dissolve nor deposit calcium carbonate
    Explanation
    The correct answer is "a condition where water will neither dissolve nor deposit calcium carbonate." This means that in a stable condition, the water is in balance and does not have the ability to either dissolve or deposit calcium carbonate. This equilibrium is important because it helps to prevent the formation of scale or deposits of calcium carbonate in water systems.

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  • 29. 

    A condition that tends to increase the corrosiveness of water on metals is

    • A.

      High dissolved oxygen content

    • B.

      High fluoride concentration

    • C.

      Low dissolved oxygen content

    • D.

      Low total dissolved solids

    Correct Answer
    A. High dissolved oxygen content
    Explanation
    High dissolved oxygen content tends to increase the corrosiveness of water on metals because oxygen is a strong oxidizing agent. When oxygen dissolves in water, it can react with the metal surface, leading to the formation of metal oxides or hydroxides. These compounds can corrode the metal, causing it to deteriorate over time. Therefore, water with high dissolved oxygen content is more likely to accelerate the corrosion process on metals.

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  • 30. 

    Adsorption operates on the principle of

    • A.

      Adhesion

    • B.

      Chance collision

    • C.

      Gravity

    • D.

      Magnetic polarization

    Correct Answer
    A. Adhesion
    Explanation
    Adsorption operates on the principle of adhesion, which refers to the attraction between molecules of different substances. In adsorption, molecules from a gas or liquid adhere to the surface of a solid material. This occurs because the attractive forces between the molecules of the gas or liquid and the solid surface are stronger than the cohesive forces between the molecules of the gas or liquid. As a result, the molecules adhere to the solid surface, forming a thin film or layer. Adhesion is the fundamental principle behind adsorption processes.

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  • 31. 

    When both chlorine and polyphosphate are added to a well, which should be fedfirst?

    • A.

      Chlorine

    • B.

      Polyphosphate

    • C.

      Both added simultaneously

    • D.

      Either may be added first

    Correct Answer
    B. Polyphosphate
    Explanation
    Polyphosphate should be fed first because it helps to prevent the formation of scale and corrosion in the well. By adding polyphosphate first, it forms a protective layer on the surfaces of the well and pipes, which helps to inhibit the build-up of mineral deposits and reduces the risk of corrosion. Once the polyphosphate has been added, chlorine can then be added to disinfect the water and kill any bacteria or pathogens that may be present. This sequential addition ensures that both the prevention of scale and corrosion and the disinfection of the water are effectively achieved.

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  • 32. 

    Practicing breakpoint chlorination involves chlorine addition until

    • A.

      Taste and odor characteristics of a swimming pool have dissipated

    • B.

      Combined chlorine residual reaches its highest point of disinfection

    • C.

      Chloroorganics and chloramines have formed

    • D.

      Chloroorganics and chloramines are destroyed and free available chlorine residual is formed.

    Correct Answer
    D. Chloroorganics and chloramines are destroyed and free available chlorine residual is formed.
    Explanation
    Practicing breakpoint chlorination involves adding chlorine until chloroorganics and chloramines are destroyed and free available chlorine residual is formed. This process is necessary to ensure effective disinfection of the swimming pool. Chloroorganics and chloramines can cause unpleasant taste and odor in the pool, so it is important to eliminate them. By reaching the breakpoint, the chlorine is able to break down these compounds and create a residual of free available chlorine, which is crucial for maintaining a safe and clean swimming environment.

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  • 33. 

    If a water supply exceeds a maximum contaminant level, whose responsibility is it to notify the consumer?

    • A.

      EPA

    • B.

      Laboratory

    • C.

      State

    • D.

      Water supplier

    Correct Answer
    D. Water supplier
    Explanation
    The responsibility to notify the consumer if a water supply exceeds a maximum contaminant level lies with the water supplier. As the entity responsible for providing safe and clean drinking water to consumers, it is their duty to inform the consumers if the water supply becomes contaminated beyond the acceptable limit. This ensures that the consumers are aware of any potential health risks and can take appropriate measures to protect themselves.

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  • 34. 

    Coagulation usually

    • A.

      Occurs in seconds

    • B.

      Occurs in minutes

    • C.

      Occurs in hours

    • D.

      Depends on coagulant and mixing rates

    Correct Answer
    A. Occurs in seconds
    Explanation
    Coagulation refers to the process of clumping together of particles in a liquid to form larger, heavier particles. This process typically happens very quickly, usually within seconds. The coagulant, which is a substance added to the liquid to facilitate coagulation, along with the mixing rates, play a role in determining the speed at which coagulation occurs. However, regardless of these factors, coagulation is generally a rapid process that happens within seconds.

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  • 35. 

    Which chemical is considered most effective for removing or destroying the effect of phenols in water?

    • A.

      Activated carbon

    • B.

      Cl2

    • C.

      ClO2

    • D.

      KMnO4

    Correct Answer
    A. Activated carbon
    Explanation
    Activated carbon is the most effective chemical for removing or neutralizing phenols in water due to its high adsorption capacity. It traps organic compounds within its porous structure, reducing their presence in the water and eliminating their harmful effects. This method is widely used in water treatment processes to ensure that potentially hazardous organic materials like phenols are removed efficiently, contributing to cleaner and safer water.

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  • 36. 

    Treated water is always used for backwashing

    • A.

      Because of its availability

    • B.

      Because the use of untreated water is more costly.

    • C.

      To avoid contamination of the filter bed.

    • D.

      To lessen sludge disposal problems.

    Correct Answer
    C. To avoid contamination of the filter bed.
    Explanation
    The correct answer is to avoid contamination of the filter bed. Using treated water for backwashing helps prevent any potential contamination of the filter bed, ensuring that the water being filtered remains clean and safe for use. Using untreated water could introduce impurities or contaminants into the filter bed, compromising its effectiveness in removing pollutants from the water. Therefore, using treated water is essential to maintain the integrity and efficiency of the filtration process.

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  • 37. 

    A water treatment plant produces 850,000 gpd. On one day 24,526 gal was used for backwashing the filters. What was the net production for this day?

    • A.

      406,740 gal

    • B.

      604,740 gal

    • C.

      476,604 gal

    • D.

      825,474 gal

    Correct Answer
    D. 825,474 gal
    Explanation
    The net production for the day can be calculated by subtracting the amount of water used for backwashing the filters from the total production. In this case, the total production is 850,000 gpd and the amount used for backwashing is 24,526 gal. Therefore, the net production for the day is 850,000 - 24,526 = 825,474 gal.

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  • 38. 

    The nephelometric method of measuring turbidity is based on the

    • A.

      Transmission of light

    • B.

      Scattering of light.

    • C.

      Passage of light.

    • D.

      Adsorption of light.

    Correct Answer
    B. Scattering of light.
    Explanation
    The nephelometric method of measuring turbidity is based on the scattering of light. Turbidity refers to the cloudiness or haziness of a liquid caused by suspended particles. In this method, a light source is directed into the liquid, and the scattered light is measured at a specific angle. The amount of scattering is directly related to the concentration of particles in the liquid, allowing for the determination of turbidity. Therefore, the correct answer is scattering of light.

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  • 39. 

    A hydrofluosilicic acid (H2SiF6) chemical feed pump is feeding a 30 percent by weight solution (specific gravity = 1.26) at the rate of .025 gpm in a plant operating at 12 mgd. The resulting fluoride dosage is _____ mg/L.

    • A.

      1.4

    • B.

      1.13

    • C.

      0.90

    • D.

      0.71

    Correct Answer
    B. 1.13
    Explanation
    The resulting fluoride dosage can be calculated by first finding the total amount of hydrofluosilicic acid being fed into the plant per day. This can be calculated by multiplying the flow rate (0.025 gpm) by the number of minutes in a day (1440 minutes). Then, the total amount of hydrofluosilicic acid in pounds can be found by multiplying the total amount fed per day by the specific gravity (1.26). Finally, the fluoride dosage in mg/L can be calculated by dividing the total amount of hydrofluosilicic acid in mg by the flow rate of the plant (12 mgd). The resulting value is 1.13 mg/L.

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  • 40. 

    Hydrogen sulfide in water may be effectively controlled by

    • A.

      Aeration.

    • B.

      Filtration.

    • C.

      Fluoridation

    • D.

      Sedimentation.

    Correct Answer
    A. Aeration.
    Explanation
    Hydrogen sulfide is a gas that can dissolve in water, causing an unpleasant odor and taste. Aeration is the process of introducing air into the water, which helps to oxidize and remove hydrogen sulfide. This is achieved by exposing the water to air, allowing the gas to escape and reducing its concentration. Filtration, fluoridation, and sedimentation are not effective methods for controlling hydrogen sulfide in water.

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  • 41. 

    In general, a properly operated presedimentation facility should remove

    • A.

      90 percent of all suspended matter.

    • B.

      At least 60 percent of the settleable matter.

    • C.

      All the algae and floating debris

    • D.

      None of the above.

    Correct Answer
    B. At least 60 percent of the settleable matter.
    Explanation
    A properly operated presedimentation facility is designed to remove settleable matter, which refers to the larger particles that can settle at the bottom of a water body. The answer states that the facility should remove at least 60 percent of settleable matter, indicating that it is effective in removing a significant portion of these particles. This ensures that the water is cleaner and reduces the risk of clogging or damaging downstream treatment processes. However, it does not mention the removal of suspended matter, algae, or floating debris, indicating that the facility may not be effective in removing these types of contaminants.

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  • 42. 

    Trihalomethanes are formed when

    • A.

      The water contains organic chemicals

    • B.

      The water contains large concentrations of inorganic chemicals

    • C.

      The filters are backwashed

    • D.

      Chlorine reacts with humic and fulvic acids in water

    Correct Answer
    D. Chlorine reacts with humic and fulvic acids in water
    Explanation
    Trihalomethanes are formed when chlorine reacts with humic and fulvic acids in water. Humic and fulvic acids are organic chemicals that are naturally present in water sources. When chlorine, which is often used as a disinfectant in water treatment, reacts with these organic acids, it forms trihalomethanes. Trihalomethanes are a group of chemical compounds that can be harmful to human health when consumed in large concentrations. Therefore, it is important to monitor and control the levels of trihalomethanes in drinking water.

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  • 43. 

    The most severe symptom of fluorosis is teeth that

    • A.

      Show signs of pitting.

    • B.

      Darken, turning shades of gray to black

    • C.

      Are mottled in appearance

    • D.

      Are less susceptible to cavities and erosion.

    Correct Answer
    A. Show signs of pitting.
    Explanation
    Fluorosis is a condition caused by excessive fluoride intake, which affects the appearance and health of teeth. The most severe symptom of fluorosis is teeth that show signs of pitting. This means that the teeth develop small, shallow holes or depressions on their surface. This is a significant indicator of fluorosis and can affect the aesthetic appearance of the teeth. Darkening or turning shades of gray to black, mottled appearance, and being less susceptible to cavities and erosion are not the most severe symptoms associated with fluorosis.

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  • 44. 

    To ensure that operating parameters are effectively monitored during aeration, surface water should be sampled and tested

    • A.

      Daily, at a minimum.

    • B.

      More frequently as seasonal temperatures rise and less frequently when temperatures drop.

    • C.

      Only as needed since monitoring is not as critical with aeration as with other treatment processes.

    • D.

      To the extent required to detect and evaluate all significant changes in water quality.

    Correct Answer
    D. To the extent required to detect and evaluate all significant changes in water quality.
    Explanation
    The correct answer suggests that surface water should be sampled and tested to the extent required to detect and evaluate all significant changes in water quality. This implies that monitoring the operating parameters during aeration is crucial for maintaining water quality. Sampling and testing the water regularly allows for the detection of any significant changes that may occur, ensuring that appropriate actions can be taken to maintain the desired water quality standards.

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  • 45. 

    In-plant sampling points following filtration are normally selected to monitor for

    • A.

      Turbidity removal

    • B.

      Reduction in turbidity, taste and odor, and bacteria

    • C.

      Reduction in sediment load and bacteria

    • D.

      Bacteria and turbidity removal

    Correct Answer
    D. Bacteria and turbidity removal
    Explanation
    In-plant sampling points following filtration are normally selected to monitor for bacteria and turbidity removal. This is because filtration is an important process in water treatment plants that helps remove suspended particles and microorganisms from the water. By monitoring for bacteria and turbidity removal at sampling points after filtration, water treatment plants can ensure that the water is clean and safe for consumption.

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  • 46. 

    The chemical formula for ferric oxide is

    • A.

      FO

    • B.

      FeO

    • C.

      FeO2.

    • D.

      Fe2O3.

    Correct Answer
    D. Fe2O3.
    Explanation
    The correct answer is Fe2O3. Ferric oxide is a compound composed of iron (Fe) and oxygen (O). The subscript "2" indicates that there are two iron atoms, and the subscript "3" indicates that there are three oxygen atoms. Therefore, the chemical formula Fe2O3 represents ferric oxide.

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  • 47. 

    Sedimentation is improved by

    • A.

      A sludge blanket

    • B.

      Reducing the detention period in the basin

    • C.

      Short circuiting

    • D.

      Uniform, horizontal, low-velocity flow across the basin.

    Correct Answer
    D. Uniform, horizontal, low-velocity flow across the basin.
    Explanation
    Uniform, horizontal, low-velocity flow across the basin improves sedimentation because it allows for the settling of suspended particles in the water. When the flow is uniform and horizontal, it prevents the formation of dead zones or areas of high velocity, which can disrupt the settling process. Low velocity ensures that particles have enough time to settle, while a uniform and horizontal flow helps to evenly distribute the particles across the basin, increasing the efficiency of sedimentation.

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  • 48. 

    When calculating carbonate hardness, the following would be included:

    • A.

      Calcium chloride

    • B.

      Calcium sulfate

    • C.

      Magnesium bicarbonate.

    • D.

      Magnesium chloride.

    Correct Answer
    C. Magnesium bicarbonate.
    Explanation
    When calculating carbonate hardness, magnesium bicarbonate would be included because it is a compound that contributes to the overall carbonate hardness. Calcium chloride, calcium sulfate, and magnesium chloride do not contain carbonate ions and therefore would not be included in the calculation.

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  • 49. 

    An important reason for analyzing raw-water samples for color is

    • A.

      To improve customer relations.

    • B.

      To comply with the Secondary Drinking Water Regulations

    • C.

      Because the test data is a good baseline indicator for treatment plant efficiency.

    • D.

      Because it may indicate high levels of organic compounds, which may produce trihalomethanes upon contact with chlorine.

    Correct Answer
    D. Because it may indicate high levels of organic compounds, which may produce trihalomethanes upon contact with chlorine.
    Explanation
    Analyzing raw-water samples for color is important because it may indicate high levels of organic compounds, which may produce trihalomethanes upon contact with chlorine. Trihalomethanes are potentially harmful compounds that can form when chlorine reacts with organic matter in water. Therefore, monitoring the color of raw-water samples can serve as an early warning sign for the presence of organic compounds and help ensure the safety and quality of drinking water.

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  • 50. 

    Objectives for a preventive maintenance program include

    • A.

      Eliminate parts inventory

    • B.

      Get organized to unstop overflowing manholes quickly

    • C.

      Increase use of standby equipment.

    • D.

      Reduce emergency repairs and maintenance.

    Correct Answer
    D. Reduce emergency repairs and maintenance.
    Explanation
    The correct answer is "reduce emergency repairs and maintenance." This objective is important for a preventive maintenance program because it aims to minimize unexpected breakdowns and repairs, which can be costly and disruptive. By implementing regular maintenance procedures and inspections, potential issues can be identified and addressed before they escalate into emergencies, leading to a more efficient and cost-effective maintenance program.

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Quiz Review Timeline +

Our quizzes are rigorously reviewed, monitored and continuously updated by our expert board to maintain accuracy, relevance, and timeliness.

  • Current Version
  • May 15, 2024
    Quiz Edited by
    ProProfs Editorial Team
  • Aug 04, 2015
    Quiz Created by
    Brandon.gebhart1
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