Microbes in Sewage Treatment Questions in English

(C) Biological oxygen demand $(BOD)$ is the method of determining the amount of oxygen required by micro-organisms to decompose the organic waste present in a water supply. If the quantity of organic waste is high,the number of decomposing bacteria increases,leading to a higher $BOD$ value.
Therefore,a higher $BOD$ value indicates higher pollution. Comparing the given values: $400\, mg/L$ (Sample $C$) > $20\, mg/L$ (Sample $A$) > $8\, mg/L$ (Sample $B$).
$1$. Sample $C$ $(400\, mg/L)$ is the most polluted,representing untreated sewage water.
$2$. Sample $A$ $(20\, mg/L)$ represents secondary effluent from a sewage treatment plant.
$3$. Sample $B$ $(8\, mg/L)$ is the cleanest,representing river water.

Label	Sample Type
$A$	Secondary effluent $(20\, mg/L)$
$B$	River water $(8\, mg/L)$
$C$	Untreated sewage $(400\, mg/L)$

(N/A) Large quantities of wastewater are generated every day in cities and towns. $A$ major component of this wastewater is human excreta. This municipal wastewater is called sewage.
It contains a large amount of organic matter and microbes,many of which are pathogenic.
This urban wastewater cannot be discharged directly into natural water bodies like rivers and streams.
Sewage is treated in sewage treatment plants $(STPs)$ to make it less polluting.
The treatment of wastewater is carried out by heterotrophic microbes that are naturally present in the sewage.

(N/A) Sewage treatment is carried out in two main stages:
$1$. Primary Treatment: This stage involves the physical removal of large and small particles from sewage through filtration and sedimentation.
- Initially,floating debris is removed by sequential filtration.
- Then,grit (soil and small pebbles) is removed by sedimentation.
- All solids that settle form the 'primary sludge',and the supernatant forms the 'effluent'.
$2$. Secondary Treatment or Biological Treatment: The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it.
- This allows for the vigorous growth of useful aerobic microbes into 'flocs' (masses of bacteria associated with fungal filaments to form mesh-like structures).
- While growing,these microbes consume the major part of the organic matter in the effluent,which significantly reduces the $BOD$ (Biochemical Oxygen Demand) of the effluent.
- $BOD$ refers to the amount of oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
- The greater the $BOD$ of wastewater,the more is its polluting potential.
- Once the $BOD$ is reduced significantly,the effluent is passed into a settling tank where the bacterial flocs are allowed to sediment. This sediment is called 'activated sludge'.
- $A$ small part of the activated sludge is pumped back into the aeration tank to serve as an inoculum.
- The remaining major part of the sludge is pumped into large tanks called 'anaerobic sludge digesters'.
- Here,anaerobic bacteria digest the bacteria and fungi in the sludge,producing gases such as methane,hydrogen sulfide,and carbon dioxide,which form 'biogas'.
- The effluent from the secondary treatment plant is generally released into natural water bodies like rivers and streams.

(N/A) Secondary wastewater treatment is referred to as biological treatment because it primarily relies on the activity of living organisms,such as aerobic and anaerobic bacteria and fungi,to decompose and mineralize the organic matter present in the sewage. These microorganisms consume the organic waste as their food source,thereby significantly reducing the Biological Oxygen Demand $(BOD)$ of the effluent.

(B) Secondary treatment or biological treatment: The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it.
This allows the vigorous growth of useful aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh-like structures).
While growing,these microbes consume the major part of the organic matter in the effluent.
This significantly reduces the $BOD$ (Biochemical Oxygen Demand) of the effluent,thereby cleaning the water.

(N/A) Secondary treatment or biological treatment is essential for large volumes of wastewater because aerobic microbes are highly efficient at breaking down organic matter.
$1$. In aeration tanks,constant agitation and air supply promote the growth of aerobic microbes into 'flocs' (masses of bacteria associated with fungal filaments).
$2$. These microbes consume the major part of the organic matter,which significantly reduces the $BOD$ (Biochemical Oxygen Demand) of the effluent.
$3$. $BOD$ is a measure of the organic matter present in the water; the greater the $BOD$,the higher the polluting potential.
$4$. Aerobic degradation is faster and more effective at reducing high levels of organic pollutants compared to anaerobic processes,which are typically used later for sludge digestion.
$5$. Once $BOD$ is reduced,the effluent is passed into a settling tank where flocs sediment as 'activated sludge'.
$6$. The remaining sludge is then treated in anaerobic sludge digesters to produce biogas (methane,hydrogen sulphide,and carbon dioxide),which serves as an energy source.

(N/A) Due to increasing urbanization,sewage is being produced in much larger quantities than ever before. However,the number of sewage treatment plants has not increased enough to treat such large quantities. Consequently,untreated sewage is often discharged directly into rivers,leading to severe water pollution and an increase in water-borne diseases.
$(b)$ Once the $BOD$ (Biochemical Oxygen Demand) of sewage or wastewater is reduced significantly,the effluent is passed into a settling tank where the bacterial 'flocs' are allowed to sediment. This sediment is called activated sludge. $A$ small part of the activated sludge is pumped back into the aeration tank to serve as an inoculum. The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters. Here,anaerobic bacteria digest the bacteria and fungi present in the sludge. During this process,these bacteria produce a mixture of gases such as methane $(CH_4)$,hydrogen sulphide $(H_2S)$,and carbon dioxide $(CO_2)$. These gases form biogas,which is inflammable and can be used as a source of energy.

(B) During secondary treatment,the sewage is constantly agitated and air is forced into it. This promotes the rapid growth of aerobic microbes into flocs (masses of bacteria associated with fungal filaments). During their growth,these microbes consume the major part of the organic matter in the effluent. This significantly reduces the $BOD$ (Biochemical Oxygen Demand) of the effluent.

(A) During sewage treatment,the sediment from the primary settling tank is called primary sludge. The sediment from the secondary treatment (biological treatment) is called activated sludge. $A$ small part of the activated sludge is pumped back into the aeration tank as inoculum,while the remaining major part of the activated sludge is pumped into large tanks called anaerobic sludge digesters. In these digesters,other kinds of bacteria,which grow anaerobically,digest the bacteria and the fungi in the sludge.

(A) In the process of sewage treatment,the primary sludge obtained from the primary settling tank is sent to anaerobic sludge digesters. In these digesters,anaerobic bacteria digest the organic matter present in the sludge,producing gases like methane,hydrogen sulfide,and carbon dioxide. Therefore,the correct option is $A$.

(A) Municipal wastewater,also known as sewage,contains large amounts of organic matter and pathogenic microbes.
To prevent water pollution,it is mandatory to treat this wastewater before releasing it into natural water bodies.
This treatment is carried out in $STPs$ (Sewage Treatment Plants),where microbes play a crucial role in reducing the Biological Oxygen Demand $(BOD)$ of the wastewater.

(D) $STPs$ stands for $Sewage$ $Treatment$ $Plants$. These are facilities designed to treat wastewater (sewage) to remove contaminants and produce environmentally safe treated wastewater (or treated effluent) and a solid waste (sludge) suitable for disposal or reuse. Microbes play a crucial role in the secondary treatment phase of these plants.

(B) Sewage treatment in $STPs$ (Sewage Treatment Plants) is carried out in two main stages:
$1$. Primary treatment: This involves physical removal of particles through filtration and sedimentation.
$2$. Secondary treatment (Biological treatment): This involves the use of aerobic and anaerobic microbes to digest the organic matter present in the effluent.
Therefore,the correct answer is $B$.

(A) Primary treatment of sewage involves physical removal of particles (large and small) from the sewage through filtration and sedimentation.
$1$. Filtration: Floating debris is removed by sequential filtration.
$2$. Sedimentation: Grit (soil and small pebbles) is removed by sedimentation.
All solids that settle form the primary sludge,and the supernatant forms the effluent.

(C) Primary treatment of sewage involves the physical removal of particles from the sewage through filtration and sedimentation.
$1$. Filtration: Floating debris is removed by sequential filtration.
$2$. Sedimentation: Grit (soil and small pebbles) is removed by sedimentation.
All solids that settle form the primary sludge,and the supernatant forms the effluent.
Therefore,primary treatment is essentially a physical process that removes physical particles.

(C) In sewage treatment plants,the primary treatment involves physical removal of particles from the sewage through filtration and sedimentation.
$1$. Floating debris is removed by sequential filtration (using screens).
$2$. Grit (soil and small pebbles) is removed by sedimentation (in settling tanks).
Therefore,floating debris is removed by filtration and grit is removed by sedimentation.

(B) In the process of sewage treatment,the primary treatment involves the physical removal of particles from the sewage through filtration and sedimentation.
$1$. Filtration removes large debris.
$2$. Sedimentation allows the grit (soil and small pebbles) and all solids that settle to form the primary sludge.
Therefore,sedimentation is the key process responsible for the formation of sludge.

(A) Secondary treatment of sewage is primarily a biological process.
It involves the use of aerobic and anaerobic microbes to decompose the organic matter present in the primary effluent.
Physical treatment (filtration and sedimentation) is part of primary treatment.
Therefore,secondary treatment is correctly identified as biological treatment.

(B) In the biological treatment (secondary treatment) of sewage,the primary effluent is passed into large aeration tanks.
In these tanks,the effluent is constantly agitated mechanically and air is pumped into it.
This allows vigorous growth of aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh-like structures).
These microbes consume the major part of the organic matter in the effluent,thereby significantly reducing the Biochemical Oxygen Demand $(BOD)$.

(D) Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures.
These are formed during the secondary treatment of sewage (biological treatment).
During this process,aerobic bacteria grow rapidly and form flocs,which consume the major part of the organic matter in the effluent,thereby significantly reducing the Biochemical Oxygen Demand $(BOD)$.

(D) Secondary treatment is a biological process that primarily involves the use of aerobic and anaerobic microbes.
During this process,the primary effluent is passed into large aeration tanks where it is constantly agitated and air is pumped into it.
This allows vigorous growth of useful aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh-like structures).
While growing,these microbes consume the major part of the organic matter in the effluent.
This significantly reduces the Biochemical Oxygen Demand $(BOD)$ of the effluent.

(B) The aeration tank is a critical component of the secondary treatment (biological treatment) in a sewage treatment plant. In this tank,the effluent from the primary settling tank is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh-like structures). These microbes consume the major part of the organic matter in the effluent,significantly reducing the Biochemical Oxygen Demand $(BOD)$.

(B) Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures.
These flocs are formed in the $Aeration \text{ } tank$ during the secondary treatment of sewage.
In the $Aeration \text{ } tank$, the effluent is constantly agitated mechanically and air is pumped into it, which allows vigorous growth of aerobic microbes into flocs.
These microbes consume the major part of the organic matter in the effluent, thereby reducing the $BOD$ (Biochemical Oxygen Demand).

(D) In the process of sewage treatment,the primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh-like structures). When the sewage is passed into the settling tank,the bacterial flocs are allowed to sediment. This sediment is called activated sludge.

(C) In the process of sewage treatment,the activated sludge is pumped into large tanks called anaerobic sludge digesters.
In these tanks,other kinds of bacteria,which grow anaerobically,digest the bacteria and the fungi in the sludge.
During this digestion,bacteria produce a mixture of gases such as methane,hydrogen sulfide,and carbon dioxide.
These gases form biogas,which can be used as a source of energy.
Therefore,the anaerobic sludge digester is also known as a digester tank.

(A) In the process of sewage treatment,the primary sludge and the supernatant from the settling tanks are passed into large tanks called anaerobic sludge digesters.
In these tanks,other kinds of bacteria,which grow anaerobically,digest the bacteria and the fungi in the sludge.
During this digestion,bacteria produce a mixture of gases such as methane,hydrogen sulphide,and carbon dioxide,which form biogas.

(A) During sewage treatment,the activated sludge is pumped into large tanks called anaerobic sludge digesters.
In these tanks,other kinds of bacteria,which grow anaerobically,digest the bacteria and the fungi in the sludge.
During this digestion,bacteria produce a mixture of gases such as methane,hydrogen sulphide,and carbon dioxide.
These gases form biogas,which can be used as a source of energy as it is inflammable.

(A) $1$. $BOD$ (Biochemical Oxygen Demand) refers to the amount of oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
$2$. $A$ higher $BOD$ indicates a higher amount of organic matter,meaning the water is more polluted. Conversely,a low $BOD$ indicates less organic matter.
$3$. Therefore,the statement 'If the $BOD$ of a water sample is low,it contains a high amount of organic matter' is incorrect.
$4$. Dissolved oxygen is inversely proportional to $BOD$; thus,high dissolved oxygen implies low $BOD$.
$5$. Wastewater treatment involves primary (physical) and secondary (biological) treatment.
$6$. During biological treatment,aerobic microbes grow into flocs (masses of bacteria associated with fungal filaments).

(D) In a sewage treatment plant,the secondary treatment involves the use of aerobic microbes to reduce the Biological Oxygen Demand $(BOD)$.
After this,the sediment is passed into a large tank called an anaerobic sludge digester.
In this tank,other kinds of bacteria,which grow anaerobically,digest the bacteria and the fungi in the sludge.
During this digestion,bacteria produce a mixture of gases such as methane,hydrogen sulfide,and carbon dioxide,which form biogas.
These bacteria are known as methanogens.

(C) $BOD$ stands for Biochemical Oxygen Demand. It is a measure of the amount of dissolved oxygen that would be consumed if all the biodegradable organic matter in one liter of water were oxidized by bacteria. Therefore,the greater the $BOD$ of wastewater,the more is its polluting potential.

(B) The biologists from Humboldt State University,in collaboration with the city of Arcata,California,developed an integrated wastewater treatment process. This process was carried out in two main stages:
$1$. Conventional sedimentation,filtering,and chlorine treatments.
$2$. The development of a series of six connected marshes over $60$ hectares of marshland,where appropriate plants,algae,fungi,and bacteria were seeded to neutralize,absorb,and assimilate the pollutants.

(A) Primary treatment is the physical removal of large and small particles from sewage through filtration and sedimentation.
These processes involve the removal of floating debris by sequential filtration and the removal of grit (soil and small pebbles) by sedimentation.
All solids that settle form the primary sludge,and the supernatant forms the effluent.

(C) Primary or physical treatment of sewage involves the physical removal of large and small particles from sewage.
First,floating debris is removed by sequential filtration using wire mesh screens.
Then,grit (soil and small pebbles) is removed by sedimentation in a settling tank.
The sediment that settles down is called primary sludge,and the supernatant liquid is known as the effluent.

(A) The biological treatment of wastewater involves the use of aerobic and anaerobic microbes. These microbes consume the organic matter present in the sewage. As the organic matter is broken down,the amount of oxygen required by bacteria to decompose the remaining organic waste decreases,which effectively reduces the Biochemical Oxygen Demand $(BOD)$.

(C) During the biological treatment of sewage,useful aerobic microbes grow rapidly to form flocs.
Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures.
These growing microbes consume the major part of the organic matter in the sewage,which significantly reduces the Biochemical Oxygen Demand $(BOD)$ of the effluent.

(A) Primary treatment of sewage is a physical process that involves the removal of large and small particles from sewage through filtration and sedimentation.
It is primarily a mechanical process that does not involve biological activity.

(A) In sewage treatment,once the Biochemical Oxygen Demand $(BOD)$ of the sewage is significantly reduced,the effluent is passed into a settling tank. In this tank,the bacterial flocs are allowed to settle down. This sediment is known as activated sludge.

(B) The sewage treatment process in which a portion of the activated sludge (containing decomposer bacteria) is pumped back into the aeration tank to serve as an inoculum is known as the activated sludge treatment. This recycled portion is referred to as the 'activated sludge'.

(C) Sewage or municipal waste should not be directly passed into rivers,streams,and other water bodies because it contains human excreta and other organic waste,as well as a large number of pathogenic microbes.
These wastes increase the Biological Oxygen Demand $(BOD)$ of the water body,leading to the death of aquatic organisms.
Therefore,it is made less polluting by passing it through Sewage Treatment Plants $(STPs)$ before discharge.

(A) The correct statement is that activated sludge sediment in settlement tanks of sewage treatment plants is a rich source of aerobic bacteria.
In an activated sludge system,the primary effluent is passed into an aeration tank.
Inside the aeration tank,vigorous growth of aerobic microbes (bacteria,protozoa,micro-fungi,and micro-algae) occurs,which consume a major part of the organic matter present in the sewage.
Option $B$ is incorrect because biogas is produced by anaerobic bacteria.
Option $C$ is incorrect because $Methanobacterium$ is an anaerobic bacterium.
Option $D$ is incorrect because biogas is a mixture of gases (primarily methane,$CO_2$,and $H_2S$),not pure methane.

(D) In sewage treatment,the effluent from the primary settling tank is passed into large aeration tanks $(A)$ where it is constantly agitated mechanically $(B)$ and air is pumped into it.
This allows vigorous growth of aerobic microbes into flocs,which consume the major part of the organic matter in the effluent,thereby significantly reducing the $BOD$ $(C)$.
Once the $BOD$ of sewage or wastewater is reduced significantly,the effluent is passed into a settling tank where the bacterial 'flocs' are allowed to sediment. This sediment is called activated sludge $(D)$.
$A$ small part of the activated sludge is pumped back into the aeration tank to serve as the inoculum. The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters $(E)$.
In these digesters,other kinds of bacteria,which grow anaerobically,digest the bacteria and the fungi in the sludge,producing gases like methane,hydrogen sulphide,and carbon dioxide,which form biogas.

(C) The treatment of waste-water (sewage) is primarily carried out by heterotrophic microbes. These microorganisms are naturally present in the sewage and are utilized in the secondary treatment process (biological treatment). They consume the organic matter present in the sewage,thereby reducing the Biological Oxygen Demand $(BOD)$ of the effluent.

(B) Primary treatment in a sewage treatment plant is a physical process. It involves two main steps:
$1$. Sequential filtration to remove floating debris.
$2$. Sedimentation to remove grit (soil and small pebbles) and other solid particles to form primary sludge.

(A) Primary treatment of sewage involves physical removal of particles through filtration and sedimentation.
All solids that settle down during this process are known as primary sludge.
The supernatant liquid that remains above the settled solids is called the effluent.

(D) Flocs are defined as masses of aerobic bacteria associated with fungal filaments to form mesh-like structures.
These structures play a vital role in the secondary treatment of sewage,where they consume the major part of the organic matter in the effluent,thereby significantly reducing the Biochemical Oxygen Demand $(BOD)$.

(B) The image shows an aeration tank,which is a key component of the secondary treatment of sewage. In this stage,the primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh-like structures). These microbes consume the major part of the organic matter in the effluent,significantly reducing the Biochemical Oxygen Demand $(BOD)$.

(C) small part of the activated sludge is pumped back into the aeration tank to serve as inoculum (seed).
The major part of the activated sludge is pumped into large tanks called anaerobic sludge digesters,where anaerobic bacteria digest the bacteria and fungi in the sludge,producing gases like methane,hydrogen sulfide,and carbon dioxide.

(D) Secondary treatment of sewage,also known as biological treatment,involves the microbial digestion of organic matter. During this process,aerobic microbes consume the organic waste present in the sewage,significantly reducing the Biological Oxygen Demand $(BOD)$.

(A) The removal of floating and suspended solids from sewage through filtration and sedimentation is known as primary treatment.
This process involves physical removal of particles through sequential filtration and sedimentation.

(A) Sewage is defined as municipal waste water that contains large amounts of organic matter and microbes. Its major component is human excreta. It cannot be discharged directly into natural water bodies because it contains pathogenic microbes and high organic content,which would lead to pollution. Therefore,option $A$ is the most accurate description of its composition.