Microbes in Sewage Treatment Questions in English

(A) In 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,which form biogas.

(D) During the sewage treatment process,specifically in the anaerobic sludge digesters,bacteria produce a mixture of gases.
These bacteria break down the organic matter present in the sludge.
The gases produced during this anaerobic digestion process include $CH_4$ (Methane),$H_2S$ (Hydrogen sulfide),and $CO_2$ (Carbon dioxide).
These gases form what is known as biogas,which can be used as a source of energy.

(D) Assertion $(S)$ is false because flocs are associations of aerobic bacteria with fungal filaments to form mesh-like structures,and they consume organic matter,not inorganic substances.
Reason $(R)$ is true because Sewage Treatment Plants $(STPs)$ are essential for treating wastewater to reduce its biological oxygen demand $(BOD)$ before it is released into water bodies,thereby preventing water pollution.
Therefore,$S$ is false and $R$ is true.

(A) Primary treatment of sewage involves the physical removal of large and small particles from the sewage through filtration and sedimentation.
$1$. Filtration: Sequential filtration is used to remove floating debris.
$2$. Sedimentation: Grit (soil and small pebbles) is removed by sedimentation.
Both statements are correct,and the reason $R$ correctly explains the process mentioned in statement $S$.

(D) In the process of sewage treatment,the primary treatment involves physical removal of particles through filtration and sedimentation.
$1$. Filtration removes floating debris.
$2$. Sedimentation removes grit and small pebbles.
$3$. The solid material that settles down is called primary sludge,while the supernatant liquid is called the effluent.
Therefore,option $D$ is mismatched because primary sludge refers to the solid settled material,not the liquid effluent.

(D) In sewage treatment,the primary treatment involves physical removal of particles through filtration and sedimentation,resulting in 'primary sludge'.
'Flocs' are masses of bacteria associated with fungal filaments,which are formed during the secondary (biological) treatment process.
Therefore,'Primary sludge – Flocs' is a mismatched pair because primary sludge consists of solid waste settled during primary treatment,whereas flocs are a characteristic feature of the secondary biological treatment.

(C) The removal of physical particulate matter from sewage is primarily achieved through physical processes.
$1$. Filtration is used to remove large floating debris.
$2$. Sedimentation is used to remove grit (soil and small pebbles) and other solid particles that settle down.
These steps are collectively known as primary treatment.

(C) In the primary treatment of sewage,the removal of floating debris is done by sequential filtration.
After this,the grit (soil and small pebbles) is removed by sedimentation.
These processes are physical and do not involve biological or chemical agents.

(A) Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures. These are formed during the secondary treatment of sewage,also known as biological treatment. In the aeration tank,aerobic microbes grow vigorously into flocs,which consume the major part of the organic matter in the sewage,thereby reducing the Biochemical Oxygen Demand $(BOD)$.

(C) Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures. During sewage treatment,these flocs grow in the aeration tank and consume the major part of the organic matter in the sewage,thereby reducing the Biochemical Oxygen Demand $(BOD)$.

(D) Sewage treatment involves several stages:
$1$. Primary treatment involves physical removal of particles through filtration and sedimentation. Floating debris is removed by sequential filtration,and grit is removed by sedimentation.
$2$. Secondary treatment or biological treatment involves the growth of aerobic microbes into flocs (masses of bacteria associated with fungal filaments).
$3$. The primary objective of sewage treatment is to reduce the $BOD$ of the wastewater. $BOD$ refers to the amount of oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria. During the treatment process,microbes consume the organic matter,thereby significantly decreasing the $BOD$ of the effluent before it is released into water bodies.
$4$. Therefore,the statement that $BOD$ increases during treatment is incorrect.

(B) Statement $P$ is false because the reduction of organic matter in water (especially in sewage treatment) is primarily a biological process,not a chemical one. Microbes like bacteria and fungi break down organic matter during the secondary treatment phase.
Statement $Q$ is true because microorganisms,particularly aerobic and anaerobic bacteria,are responsible for the decomposition of organic matter in water bodies and sewage treatment plants.
Therefore,Statement $P$ is false and Statement $Q$ is true.

(D) The correct statement is $D$.
$A$ is incorrect because biogas is produced by anaerobic bacteria (methanogens).
$B$ is incorrect because Methanobacterium are anaerobic,not aerobic.
$C$ is incorrect because biogas is a mixture of gases (primarily methane,$CO_2$,and $H_2$),not pure methane.
$D$ is correct because during secondary treatment,the activated sludge in the settling tank is rich in aerobic bacteria which are used to digest organic matter.

(B) Sewage water contains a large amount of organic matter and excreta. This environment is highly conducive to the growth of various microorganisms,including bacteria,viruses,protozoa,and fungi. Many of these microorganisms are pathogenic,meaning they are capable of causing diseases such as cholera,typhoid,and dysentery in humans and animals. Therefore,sewage water is considered a major source of waterborne diseases.

(C) Sewage treatment involves the use of microorganisms to break down organic matter present in wastewater.
Specifically,heterotrophic bacteria are used in the secondary treatment (biological treatment) phase.
These bacteria grow rapidly and form flocs (masses of bacteria associated with fungal filaments to form mesh-like structures) which consume the major part of the organic matter in the effluent,thereby reducing the Biological Oxygen Demand $(BOD)$ of the sewage.

(A) The first stage of sewage treatment is known as primary treatment.
This process involves the physical removal of large and small particles from the sewage through two main steps:
$1$. Sequential filtration: This removes floating debris.
$2$. Sedimentation: This allows grit (soil and small pebbles) to settle down.
These materials are collectively referred to as physical particulate matter.
Secondary treatment involves biological processes using bacteria and fungi.

(C) In the process of primary sewage treatment,the sewage is passed through filtration and sedimentation.
During sedimentation,all solids that settle form the primary sludge.
The supernatant liquid (the free water) that remains above the primary sludge is referred to as the effluent.
Therefore,both 'Effluent water' and 'Effluent' refer to the same liquid component in this context.

(B) In the secondary treatment of sewage,the primary effluent is passed into large aeration tanks.
Mechanical agitation allows for the constant pumping of air into this effluent.
This vigorous aeration promotes the rapid growth of aerobic microbes into flocs (masses of bacteria associated with fungal filaments).
These aerobic bacteria consume the major part of the organic matter in the effluent,thereby significantly reducing the Biological Oxygen Demand $(BOD)$.

(C) In the process of sewage treatment,the primary sludge is passed into large tanks called anaerobic sludge digesters.
Inside these tanks,anaerobic bacteria digest the bacteria and fungi present in the sludge.
During this digestion,these bacteria produce a mixture of gases such as methane,hydrogen sulfide,and carbon dioxide,which form biogas.

(D) Assertion $(A)$ is false because the reduction of organic matter in sewage treatment is primarily a biological process,not a chemical one. Bacteria and other microorganisms consume the organic matter during the secondary treatment (biological treatment) phase.
Reason $(R)$ is true because microorganisms,specifically aerobic and anaerobic bacteria,are responsible for breaking down the organic matter present in sewage,thereby reducing the Biological Oxygen Demand $(BOD)$.

(B) Assertion $(A)$ is true because the increasing human population generates a massive amount of sewage,necessitating more $STPs$ to prevent water pollution.
Reason $(R)$ is true because during the secondary treatment of sewage,anaerobic sludge digesters are used where anaerobic bacteria digest the organic matter,producing gases like methane,hydrogen sulfide,and carbon dioxide,which constitute biogas.
However,the production of biogas in $STPs$ is a beneficial byproduct of the treatment process,not the primary reason why we need more $STPs$ (the primary reason is the need to treat the increasing volume of waste to protect the environment). Therefore,$R$ is not the correct explanation of $A$.

(A) Assertion $(A)$ is true because $STPs$ (Sewage Treatment Plants) utilize heterotrophic microbes (like bacteria and fungi) in the secondary treatment phase to digest organic matter.
Reason $(R)$ is true because the primary purpose of $STPs$ is to reduce the $BOD$ (Biochemical Oxygen Demand) of sewage water before it is released into water bodies,thereby preventing water pollution.
Since the use of microbes is the fundamental mechanism by which $STPs$ achieve the goal of preventing water pollution,$R$ is the correct explanation of $A$.

(B) In sewage treatment,the process of primary treatment involves two main steps:
$1$. Filtration: This removes floating debris.
$2$. Sedimentation: This process allows grit (soil and small pebbles) to settle down at the bottom of the tank.
Therefore,sedimentation is used to remove soil and small pebbles from the sewage.

(A) Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures.
These flocs are formed during the secondary treatment (biological treatment) of sewage.
They consume the major part of the organic matter in the sewage,thereby reducing the $BOD$ (Biochemical Oxygen Demand) of the effluent.

(C) The process of sewage treatment involves several stages:
$1$. Primary treatment: This involves physical removal of particles through filtration (sequential filtration) and sedimentation (grit removal).
$2$. Secondary treatment (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 vigorous growth of useful aerobic microbes into flocs.
$3$. After aerobic treatment,the effluent is passed into a settling tank where the bacterial 'flocs' are allowed to sediment. This sediment is called activated sludge.
$4$. $A$ small part of the activated sludge is pumped back into the aeration tank,and the remaining major part is pumped into large tanks called anaerobic sludge digesters,where anaerobic bacteria digest the bacteria and fungi in the sludge.
Therefore,the correct sequence is Filtration $\to$ Sedimentation $\to$ Aerobic bacteria $\to$ Anaerobic bacteria.

(B) : Primary or physical treatment is the process of removal of small and large,floating and suspended solids from sewage through two processes of filtration and sedimentation.

(B) The correct answer is $B$.
During the process of sewage treatment,anaerobic sludge digesters are used to decompose organic matter.
Microbial activity in these digesters depends on the specific microbes and the organic substrates present.
Methanogens are a group of anaerobic bacteria that act on cellulosic material to produce large amounts of methane $(CH_4)$ along with carbon dioxide $(CO_2)$.
Additionally,other anaerobic bacteria present in the sludge produce gases such as hydrogen sulphide $(H_2S)$ and ammonia $(NH_3)$.
Therefore,the mixture of gases produced in anaerobic sludge digesters typically includes methane,hydrogen sulphide,and carbon dioxide.

(B) : Sewage water can be purified by passing it through sewage treatment plants with the action of heterotrophic microorganisms. There are three stages of this treatment - primary,secondary,and tertiary. Primary treatment removes floating and suspended solids from sewage through two processes of filtration and sedimentation. First,floating matter is removed through sequential filtration. The filtrate is kept in large open settling tanks where grit settles down. The sediment is called primary sludge,while the supernatant is called effluent. In secondary treatment,the primary effluent is taken to aeration tanks. $A$ large number of aerobic heterotrophic microbes grow in the aeration tank and form flocs. The microbes digest a lot of organic matter,reducing the $BOD$ of the waste. The sediment of the settling tank is called activated sludge. The remaining is passed into a large tank called an anaerobic sludge digester,where anaerobic microbes digest the organic mass and produce gases like methane,$H_2S$,and $CO_2$.

(D) Secondary sewage treatment,also known as biological treatment,primarily involves the use of aerobic and anaerobic microorganisms to decompose organic matter present in the sewage.
In this process,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 useful 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 Biological Oxygen Demand $(BOD)$.
Therefore,it is essentially a biological process.

(D) : Sewage water can be purified by passing it through sewage treatment plants with the action of heterotrophic microorganisms. There are three stages of this treatment: primary,secondary,and tertiary. Primary treatment removes floating and suspended solids from sewage through two processes of filtration and sedimentation. First,floating matter is removed through sequential filtration. The filtrate is kept in large open settling tanks where grit settles down. The sediment is called primary sludge,while the supernatant is called effluent. The primary sludge traps a lot of microbes and debris. In secondary treatment,the primary effluent is taken to aeration tanks. $A$ large number of aerobic heterotrophic microbes grow in the aeration tank. They form flocs. Flocs are masses of bacteria held together by slime and fungal filaments to form mesh-like structures. The microbes digest a lot of organic matter,converting it into microbial biomass and releasing a lot of minerals. As the $BOD$ of the waste matter is reduced to $10-15\%$ of raw sewage,it is passed into a settling tank. Thus,secondary treatment is more or less biological. The sediment of the settling tank is called activated sludge. The remaining is passed into a large tank called an anaerobic sludge digester. It is designed for continuous operation. The aerobic microbes present in the sludge get killed. Anaerobic microbes digest the organic mass as well as aerobic microbes of the sludge. They are of two types: non-methanogenic and methanogenic. Methanogenic bacteria produce a mixture of gases containing methane,$H_2S$,and $CO_2$.

(A) : Biochemical oxygen demand $(BOD)$ is the amount of dissolved oxygen required by aerobic microorganisms to break down the organic matter present in a given volume of water sample.
It serves as a direct indicator of the level of organic pollution in water bodies.
Higher $(BOD)$ values indicate higher levels of organic pollution,making it a standard method for estimating the amount of organic matter in sewage water.

(A) Activated sludge refers to the sedimented bacterial flocs that are produced during the secondary treatment of sewage.
In the aeration tank,aerobic microbes grow rapidly to form flocs (masses of bacteria associated with fungal filaments).
These flocs consume the major part of the organic matter in the sewage.
Once the $BOD$ (Biochemical Oxygen Demand) of the sewage is significantly reduced,the effluent is passed into a settling tank where the bacterial flocs are allowed to sediment.
This sediment is called 'activated sludge'.

(A) Primary treatment of sewage involves the physical removal of large and small 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.
This process does not involve any biological or chemical treatment.

(A) During the secondary treatment of sewage,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 useful aerobic microbes into flocs. Flocs are 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.

(B) Statement $X$ is True: Sewage treatment involves two main phases: Primary treatment (physical removal of particles) and Secondary treatment (biological treatment).
Statement $Y$ is True: Microbes play a crucial role in the secondary treatment phase,where aerobic and anaerobic microbes decompose organic matter present in the sewage.
Therefore,both statements $X$ and $Y$ are true.

(D) Assertion $(A)$ is correct because $STP$s are designed to treat wastewater by removing contaminants through physical,chemical,and biological processes.
Reason $(R)$ is incorrect because,at the end of the $STP$ process (specifically after secondary treatment),the water is treated to remove flocs (masses of bacteria associated with fungal filaments). The treated effluent,which is released into water bodies,is largely free of these flocs. Therefore,the water does not 'possess' flocs at the end of the process; rather,flocs are removed during the sedimentation phase.

(C) Sewage waste primarily consists of organic matter,such as human excreta,food scraps,and other biological materials.
Because these materials are derived from living organisms,they can be broken down by microorganisms like bacteria and fungi into simpler substances.
Therefore,sewage waste is classified as biodegradable.

(A) $BOD$ (Biochemical Oxygen Demand) refers to the amount of dissolved oxygen required by aerobic microorganisms to break down the organic matter present in a given volume of water at a specific temperature.
$1$. $BOD$ is directly proportional to the amount of organic pollutants in the water.
$2$. Pond water typically contains a significant amount of organic matter,such as decaying plants,animal waste,and microorganisms,leading to a higher $BOD$.
$3$. Bisleri water,soda,and mineral water are processed or treated to be free from organic pollutants,resulting in a very low or negligible $BOD$.
Therefore,pond water has the highest $BOD$ among the given options.

(C) Bacteria play a crucial role in the carbon cycle primarily through the process of decomposition.
They break down complex organic matter (dead plants and animals) into simpler inorganic substances like $CO_2$.
This process releases carbon back into the atmosphere or soil,making it available for reuse by producers.
Therefore,the digestion or decomposition of organic compounds is their most significant contribution to the carbon cycle.

(D) $1$. Biogas is produced by anaerobic bacteria,not aerobic bacteria,from animal excreta.
$2$. Methanobacterium is an anaerobic bacterium,not aerobic,found in the rumen of cattle.
$3$. Biogas is a mixture of gases (mainly methane,$CO_2$,and $H_2$),not pure methane.
$4$. In a sewage treatment plant,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 useful aerobic microbes into flocs (masses of bacteria associated with fungal filaments to form mesh-like structures). These flocs consume the major part of the organic matter in the effluent,significantly reducing the $BOD$. This mixture is then passed into a settling tank where the bacterial flocs are allowed to sediment. This sediment is called activated sludge.

(B) During the process of sewage treatment,specifically in the anaerobic sludge digesters,anaerobic bacteria (methanogens) act on the organic matter present in the sludge.
These bacteria produce a mixture of gases,which is known as biogas.
The primary components of this biogas are $CH_4$ (Methane),$H_2S$ (Hydrogen sulfide),and $CO_2$ (Carbon dioxide).
Therefore,the correct combination is Methane,Hydrogen sulfide,and Carbon dioxide.

(B) During the secondary treatment of sewage,the sediment of 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 $(CH_4)$,hydrogen sulfide $(H_2S)$,and carbon dioxide $(CO_2)$.
These gases form biogas and can be used as a source of energy.

(C) Primary treatment in sewage plants involves physical removal of particles from the sewage through filtration and sedimentation.
These stages remove floating debris by sequential filtration and grit (soil and small pebbles) by sedimentation.
All solids that settle form the primary sludge,and the supernatant forms the effluent.

(A) Biochemical Oxygen Demand $(BOD)$ refers to the amount of dissolved oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
When a large amount of sewage (organic waste) is discharged into a river,the population of decomposer bacteria increases to break down this organic matter.
These bacteria consume a large amount of dissolved oxygen from the water for the process of decomposition.
Consequently,the $BOD$ of the river water increases significantly as the demand for oxygen by microorganisms rises.

(C) In the sewage treatment process,the secondary treatment is also known as biological treatment.
During this process,the effluent from the primary settling tank is passed into large aeration tanks where it is constantly agitated mechanically 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.
Once the $BOD$ of sewage or wastewater is reduced significantly,the effluent is then 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 the inoculum. This is known as recycling of bacteria.

(C) Secondary sewage treatment,also known as biological treatment,involves the use of aerobic and anaerobic microorganisms to decompose organic matter present in sewage.
Primary treatment is a physical process involving filtration and sedimentation.
Secondary treatment relies on the metabolic activities of microbes to reduce the Biological Oxygen Demand $(BOD)$ of the effluent.
Therefore,it is primarily a biological process.

(A) Domestic sewage in large cities is characterized by high organic content.
$1$. $BOD$ (Biochemical Oxygen Demand) is a measure of the organic matter present in water.
$2$. Domestic sewage contains a large amount of biodegradable organic matter,which serves as food for microorganisms like aerobic and anaerobic bacteria.
$3$. As these microorganisms decompose the organic matter,they consume dissolved oxygen,leading to a high $BOD$ value.
$4$. Therefore,domestic sewage is characterized by high $BOD$ due to the presence of high organic load and associated microbial activity.

(B) In the secondary treatment of sewage,activated sludge flocs consist of masses of bacteria associated with fungal filaments to form a mesh-like structure.
These flocs require a constant supply of oxygen for the aerobic decomposition of organic matter.
If the oxygen availability is reduced,the oxygen cannot diffuse into the interior of the flocs.
Consequently,the centre of the flocs becomes anoxic (lacking oxygen).
This leads to the death of the aerobic bacteria residing in the centre,which eventually causes the structural integrity of the flocs to fail,leading to their breakage.

(N/A) Sewage is the municipal waste matter that is carried away in sewers and drains. It includes both liquid and solid wastes,rich in organic matter and microbes.
Many of these microbes are pathogenic and can cause several water-borne diseases such as cholera,typhoid,and dysentery.
Sewage water is a major cause of polluting drinking water sources.
Hence,it is essential that sewage water is properly collected,treated,and disposed of to prevent environmental and health hazards.

(B)

Primary Sewage Treatment	Secondary Sewage Treatment
$1$. It is a physical/mechanical process involving the removal of large and small particles through filtration and sedimentation.	$1$. It is a biological process involving the action of aerobic and anaerobic microbes to decompose organic matter.
$2$. It is relatively inexpensive and less complex.	$2$. It is a more expensive and complex process requiring aeration and microbial management.