Water Core 4 Pre-Q questions

How does inactivation of pathogens differ from removal of pathogens in wastewater treatment?

 

Inactivation physically removes pathogens from the wastewater.

 

Inactivation kills or renders pathogens inactive without removing them from the wastewater.

 

Inactivation involves chemical treatment to enhance pathogen removal.

 

Inactivation increases the volume of wastewater to dilute pathogens.

Inactivation kills or renders pathogens inactive without removing them from the wastewater.

Which of the following is an example of a pathogen removal process in wastewater treatment?

 

Aeration tanks

 

Chlorination

 

Filtration

 

Clarifiers

Filtration

How can the presence of ammonia affect chlorination processes in water treatment?

 

Ammonia has no impact on the chlorination process.

 

Ammonia enhances the disinfectant properties of chlorine.

 

Ammonia reacts with chlorine to form chloramines, which are less effective as disinfectants and can lead to breakthrough chlorination.

 

Ammonia stabilizes chlorine, increasing its oxidation potential.

Ammonia reacts with chlorine to form chloramines, which are less effective as disinfectants and can lead to breakthrough chlorination.

How can the formation of chloramines affect water treatment efficiency?

 

Chloramines improve the oxidation potential of disinfectants.

 

Chloramines are less effective than free chlorine in killing pathogens and can lead to breakthrough chlorination.

 

Chloramines completely eliminate the need for additional disinfection.

 

Chloramines enhance the taste and odor of the treated water.

Chloramines are less effective than free chlorine in killing pathogens and can lead to breakthrough chlorination.

What is a common cause of breakthrough chlorination in water treatment systems?

 

Excessive use of other disinfectants alongside chlorine.

 

High concentrations of organic matter or ammonia that consume chlorine before it can disinfect effectively.

 

Low levels of chlorine applied to the water.

 

Insufficient water flow through the chlorination system.

High concentrations of organic matter or ammonia that consume chlorine before it can disinfect effectively.

If a water treatment system has a CT value of 100 mg·min/L, what does this mean?

 

The system needs a concentration of disinfectant of 100 mg/L for 1 minute to achieve the desired disinfection.

 

The system must maintain a concentration of 100 mg/L for 100 minutes.

 

The system must achieve 100% pathogen removal in 1 minute.

 

The system requires a total of 100 liters of disinfectant for disinfection.

The system needs a concentration of disinfectant of 100 mg/L for 1 minute to achieve the desired disinfection.

How does increasing the concentration of a disinfectant affect the CT value?

 

It has no effect on the CT value.

 

It increases the required contact time to maintain effectiveness.

 

It reduces the required contact time to achieve the same level of disinfection.

 

It decreases the effectiveness of disinfection.

It reduces the required contact time to achieve the same level of disinfection.

How does temperature affect the CT value in disinfection processes?

 

Temperature does not influence the CT value.

 

Temperature directly affects the concentration of disinfectant used.

 

Lower temperatures generally reduce the CT value needed for disinfection.

 

Higher temperatures generally reduce the CT value required for effective disinfection.

Higher temperatures generally reduce the CT value required for effective disinfection.

What is the primary factor that can influence the required CT value for chlorine disinfection?

 

The type of water source.

 

The type of the pathogen being targeted.

 

Temperature

 

pH

The type of the pathogen being targeted.

Greywater is typically less contaminated than blackwater because it does not contain:

 

Fecal matter

 

Organic food particles

 

Household chemicals

 

Soaps and detergents

 

Fecal matter

Which is not the primary target in secondary and tertiary wastewater treatment processes to minimize its environmental impact?

 

Carbon

 

Sodium

 

Phosphorous

 

Nitrogen

Sodium

If a WWTP is not functioning correctly, what is the most likely immediate effect?

 

Faster water flow in the river

 

The river will become more acidic

 

Increased sedimentation in the river

 

The oxygen level will decrease.

The oxygen level will decrease.

Which of the following elements is most abundant in bacterial cells?

 

Nitrogen

 

Hydrogen

 

Oxygen

 

Carbon

Carbon

During which phase of the bacterial growth curve do bacteria multiply at their maximum rate?

 

Log phase

 

Stationary phase

 

Death phase

 

Lag phase

Log phase

What is the primary characteristic of the lag phase in the bacterial growth curve?

 

Rapid cell division

 

Equal rates of growth and death

 

Adaptation to new environment

 

Cell death exceeds cell growth

Adaptation to new environment

What typically happens to the bacterial population during the stationary phase?

 

Cells begin to sporulate

 

Cell metabolism ceases entirely

 

Cells continue to grow exponentially

 

Nutrient depletion slows down the growth rate

Nutrient depletion slows down the growth rate

Which of the following is NOT a characteristic of suspended growth processes?

 

Microorganisms are freely suspended in the wastewater

 

Microorganisms grow on solid media

 

Aeration is often required to maintain oxygen levels

 

Commonly used in activated sludge systems

Microorganisms grow on solid media

Which of the following statements about BOD and COD is true?

 

COD is a more comprehensive measure because it includes biodegradable and non-biodegradable substances

 

COD only measures biodegradable organic matter

 

BOD measures both biodegradable and non-biodegradable organic matter

 

BOD is faster to measure than COD

COD is a more comprehensive measure because it includes biodegradable and non-biodegradable substances

Why is COD often used instead of BOD in wastewater treatment analysis?

 

COD is less expensive to measure

 

COD provides results faster than BOD

 

BOD is not affected by the presence of toxic substances

 

BOD is more sensitive to temperature changes

COD provides results faster than BOD

What does the observed cell yield (Y_obs) represent in wastewater treatment?

 

The concentration of pathogens in the wastewater

 

The ratio of biomass produced to the substrate consumed

 

The total amount of suspended solids in the system

 

The amount of oxygen required to oxidize organic material

The ratio of biomass produced to the substrate consumed

What is the typical unit used to express cell yield in wastewater treatment?

 

gVSS/gCOD removed

 

mg/L

 

gO2/L

 

gCOD/L

gVSS/gCOD removed

Which of the following statements about oxygen demand is true?

 

It increases with the concentration of biodegradable organic matter

 

It is only relevant in chemical oxidation processes

 

It is higher in anaerobic processes compared to aerobic processes

 

It remains constant regardless of the substrate concentration

It increases with the concentration of biodegradable organic matter

In an aerobic wastewater treatment system, what would likely happen if the oxygen demand exceeds the available oxygen supply?

 

Complete substrate degradation

 

Decreased microbial activity and potential system failure

 

Increased cell yield

 

Reduced production of carbon dioxide

Decreased microbial activity and potential system failure

In the context of thermodynamics, which statement best describes the energy yield in bacterial respiration?

 

The energy yield is determined by the Gibbs free energy change, which should be negative for the process to be spontaneous.

 

The energy yield is solely determined by the electron donors used.

 

The energy yield is unrelated to Gibbs free energy and only depends on the type of bacteria.

 

The energy yield is always positive, regardless of the Gibbs free energy change.

The energy yield is determined by the Gibbs free energy change, which should be negative for the process to be spontaneous.

In anaerobic respiration, how does the use of nitrate as an electron acceptor compare to oxygen in terms of thermodynamic energy production?

 

Nitrate produces more energy than oxygen because it is a more efficient electron acceptor.

 

Nitrate and oxygen produce the same amount of energy in anaerobic respiration.

 

Nitrate as an electron acceptor typically produces less energy compared to oxygen due to its lower reduction potential.

 

Nitrate’s role as an electron acceptor does not impact thermodynamic energy production.

Nitrate as an electron acceptor typically produces less energy compared to oxygen due to its lower reduction potential.

How does pyruvate contribute to the biosynthesis of amino acids in aerobic bacteria?

 

Pyruvate is used only for energy production, not for amino acid synthesis.

 

Pyruvate is converted into glucose, which then synthesizes amino acids.

 

Pyruvate serves as a precursor for several amino acids, including alanine, valine, and leucine, through various transamination reactions.

 

Pyruvate directly incorporates nitrogen into amino acids.

Pyruvate serves as a precursor for several amino acids, including alanine, valine, and leucine, through various transamination reactions.

Why do aerobic bacteria convert other forms of nitrogen into ammonia for synthesis purposes?

 

Ammonia is the most readily assimilated form of nitrogen for incorporation into amino acids and other nitrogenous compounds.

 

Ammonia is less toxic than other forms of nitrogen and does not need further conversion.

 

Converting other forms of nitrogen into ammonia is unnecessary as they are directly usable.

 

Other forms of nitrogen are already in the correct form for immediate use in synthesis.

Ammonia is the most readily assimilated form of nitrogen for incorporation into amino acids and other nitrogenous compounds.

What is the best electron donor for maximizing energy production?

Methanol 

Glucose

Ethanol

Formate

formate

Choose the equations from the table above that are necessary to determine the balanced reactions for the microbe utilizing ethanol (as the electron donor) and nitrate (as the electron acceptor for both energy production and cell synthesis). Note that you should reverse one of the equations to represent the electron donor.

Finally, sum the selected equation numbers for your answer. For example, if you choose equations 1, 5, and -10, then -4 should be the final result.

-9

There are two microbial species, A and B. Microbe A uses nitrate as the electron acceptor for energy production, while Microbe B uses sulfate. If the electron acceptors for cell synthesis and the electron donors are the same for both Microbe A and Microbe B, which one would have the higher fe value?

 

Microbe B

 

Microbe A

 

Insufficient information

 

The same fe values for both Microbes

 

Microbe B

For the same microbes A and B, which one would grow faster? 

 

The same fe values for both Microbes

 

Microbe A

 

Insufficient information

 

Microbe B

 

Microbe A

Which of the following best describes the role of microorganisms in the activated sludge process?

 

Microorganisms physically remove solids from the wastewater.

 

Microorganisms consume organic pollutants in the wastewater, converting them into biomass and simpler compounds.

 

Microorganisms produce chemicals that neutralize toxins in the wastewater.

 

Microorganisms increase the temperature of the wastewater to aid in sedimentation.

Microorganisms consume organic pollutants in the wastewater, converting them into biomass and simpler compounds.

In the activated sludge process, what happens in the secondary clarifier?

 

The secondary clarifier introduces air to increase microbial activity.

 

The secondary clarifier heats the wastewater to speed up the biological reactions.

 

The secondary clarifier allows the settled sludge (activated sludge) to be separated from the treated wastewater, which then flows out as clarified effluent.

 

The secondary clarifier adds chemicals to enhance the growth of microorganisms.

The secondary clarifier allows the settled sludge (activated sludge) to be separated from the treated wastewater, which then flows out as clarified effluent.

What is the purpose of returning activated sludge to the aeration tank?

 

To increase the volume of wastewater in the aeration tank.

 

To maintain an adequate concentration of microorganisms in the aeration tank for effective treatment.

 

To adjust the pH of the wastewater before further treatment.

 

To remove excess sludge from the system.

To maintain an adequate concentration of microorganisms in the aeration tank for effective treatment.

How is the excess sludge managed in the activated sludge process?

 

Excess sludge is removed from the system and treated further through processes like digestion, dewatering, or incineration.

 

Excess sludge is added back to the aeration tank to increase microbial activity.

 

Excess sludge is converted into chemical additives for other processes.

 

Excess sludge is diluted with clean water and discharged.

Excess sludge is removed from the system and treated further through processes like digestion, dewatering, or incineration.

What does Hydraulic Retention Time (HRT) represent in a wastewater treatment plant?

 

The average time that wastewater spends in a treatment unit or process before exiting.

 

The duration of the aeration period in the aeration tank.

 

The time required for microorganisms to degrade organic matter.

 

The time it takes for sludge to be removed from the system.

The average time that wastewater spends in a treatment unit or process before exiting.

What does Sludge Retention Time (SRT) refer to in a wastewater treatment plant?

 

The average time that microorganisms (sludge) remain in the treatment system before being removed.

 

The duration of the chemical dosing in the treatment process.

 

The time it takes for wastewater to pass through the aeration tank.

 

The time required for the treated effluent to exit the secondary clarifier.

The average time that microorganisms (sludge) remain in the treatment system before being removed.

What is the impact of a longer Sludge Retention Time (SRT) on the performance of a wastewater treatment plant?

 

It improves the removal of organic matter and allows for better stabilization of sludge.

 

It reduces the efficiency of biological treatment.

 

It decreases the concentration of microorganisms in the aeration tank.

 

It shortens the time required for wastewater to pass through the treatment plant.

It improves the removal of organic matter and allows for better stabilization of sludge.

What role do inorganic materials play in sludge composition?

 

They include residual chemicals and particulate matter that do not decompose biologically.

 

They help in the chemical precipitation of pollutants.

 

They are primarily responsible for the biological activity in the sludge.

 

They provide nutrients for microorganism growth.

They include residual chemicals and particulate matter that do not decompose biologically.