Microbes in Sewage Treatment Questions in English

(C) The presence of $E. coli$ bacteria indicates possible sewage contamination of water.
$E. coli$ is found exclusively in the mammalian intestinal tract,including that of humans.
These bacteria belong to the coliform group.
Coliforms found in mammals are specifically referred to as faecal coliforms.
Since most coliforms in this context are $E. coli$,tests for $E. coli$ are widely used as a standard indicator for faecal contamination from sewage.

(C) Biochemical Oxygen Demand $(BOD)$ is a measure of the amount of dissolved oxygen required by aerobic microorganisms to break down the organic matter present in a given volume of water.
$BOD$ is directly related to the amount of organic matter in the water sample.
Microbes (aerobic bacteria) consume oxygen to decompose this organic matter.
Therefore,$BOD$ is concerned with both microbes and organic matter,as the demand for oxygen is created by the microbial decomposition of organic pollutants.

(C) Biological Oxygen Demand $(BOD)$ is a measure of the amount of dissolved oxygen required by aerobic microorganisms to break down the organic material present in a given water sample at a specific temperature over a specific time period.
$BOD$ is directly proportional to the amount of organic matter present in the water.
Therefore,it is primarily used to estimate the level of organic pollution in sewage water.
Higher $BOD$ values indicate higher levels of organic pollution.

(C) The 'activated sludge system' is a biological wastewater treatment process.
In this process,a portion of the sludge (which contains a high concentration of aerobic decomposer bacteria) is recycled back into the aeration tank.
This recycled sludge acts as an inoculum,providing a large population of metabolizing bacteria,yeasts,molds,and protozoa to the incoming raw sewage.
These microorganisms form flocculent masses called 'flocs' and oxidize the organic matter present in the sewage into $CO_2$ and water.
Therefore,the process of recycling these bacteria is a defining characteristic of the activated sludge treatment.

(D) $E. coli$ (Escherichia coli) is a bacterium commonly found in the lower intestine of warm-blooded organisms. Its presence in water samples is a standard indicator of faecal contamination,as it suggests that the water has been exposed to sewage or animal waste.

(A) Primary treatment in sewage treatment is essentially a physical process.
It involves the 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) Secondary treatment,also known as biological treatment,is a process where aerobic microbes (bacteria and fungi) are used to decompose the organic matter present in the primary effluent.
$1$. Primary treatment is a physical process involving filtration and sedimentation.
$2$. Secondary treatment is a biological process where microorganisms consume the organic waste,thereby reducing the Biological Oxygen Demand $(BOD)$ of the effluent.
$3$. Therefore,the correct answer is $C$ (Biological).

(B) In the process of sewage treatment,the primary treatment involves the physical removal of particles from the sewage through filtration and sedimentation.
Initially,floating debris is removed by sequential filtration.
Then,the grit (soil and small pebbles) is removed by sedimentation.
All solids that settle down form the primary sludge,while the supernatant forms the effluent.

(C) 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 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.
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'.

(B) The image shows an aeration tank,which is a key component of secondary treatment (biological treatment) in a sewage treatment plant.
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 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 $(BOD)$.

(A) The sewage treatment process involves several steps:
$1$. Primary treatment involves physical removal of particles through filtration and sedimentation.
$2$. The effluent from primary treatment is then taken for secondary or biological treatment,where aerobic microbes consume organic matter.
$3$. Finally,the activated sludge is sent to anaerobic sludge digesters,where anaerobic bacteria digest the remaining organic matter to produce biogas.

(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,thereby reducing the Biological Oxygen Demand $(BOD)$.

(D) In sewage treatment,the primary treatment involves physical removal of particles from the sewage through filtration and sedimentation.
$1$. Filtration is used to remove floating debris.
$2$. Sedimentation is used to remove grit (soil and small pebbles).
Since both processes are part of the physical removal phase,the correct answer is $D$.

(B) $E. coli$ (Escherichia coli) is a bacterium commonly found in the lower intestine of warm-blooded organisms.
Its presence in water bodies is a standard indicator of fecal contamination.
Since sewage contains human and animal waste,a high concentration of $E. coli$ in water is a direct indicator of sewage pollution.
Therefore,the correct option is $B$.

(B) In sewage treatment,the process is divided into two main stages:
$1$. Primary treatment: This is a physical process involving filtration and sedimentation to remove large and small particles.
$2$. Secondary treatment (Biological treatment): This process involves the use of aerobic and anaerobic microbes to digest the organic matter present in the sewage.
Therefore,the biological process is carried out during the secondary treatment phase.

(C) The correct sequence of sewage treatment is as follows:
$1$. Wastewater screening $(ii)$: Large debris is removed by filtration.
$2$. Grit settling $(v)$: Grit (sand,pebbles) is removed by sedimentation.
$3$. Primary treatment $(i)$: Removal of suspended solid particles by sedimentation.
$4$. Treatment by flocs in aeration tank $(iv)$: Secondary treatment where aerobic microbes (flocs) consume organic matter.
$5$. Anaerobic digestion of activated sludge $(iii)$: Anaerobic bacteria digest the sludge produced during secondary treatment.
Therefore,the sequence is $ii \longrightarrow v \longrightarrow i \longrightarrow iv \longrightarrow iii$.

(B) In sewage treatment,the removal of suspended,floating,coarse,and solid particles is primarily achieved through physical processes such as filtration and sedimentation.
This stage is known as $Preliminary$ or $Primary$ treatment.
$Preliminary$ treatment involves the removal of large debris using screens and grit chambers,while $Primary$ treatment involves the sedimentation of solid particles to form sludge.
Therefore,the correct answer is $Preliminary$ treatment.

(A) Statement $I$ is incorrect because the sediment in the settling tank (after secondary treatment) is called activated sludge,while flocs are masses of bacteria associated with fungal filaments formed during aeration.
Statement $II$ is incorrect because sewage is first passed through screens to remove large debris,and then it is passed through the grit chamber to remove grit and small pebbles.

(D) During secondary treatment (biological treatment),aerobic microbes grow into flocs and consume the major part of the organic matter present in the effluent.
As the organic matter is consumed,the $BOD$ (Biochemical Oxygen Demand) of the effluent decreases significantly.
Therefore,Statement $I$ is incorrect because the $BOD$ decreases,not increases.
Statement $II$ is correct because flocs of bacteria are responsible for the degradation of organic matter.

(D) Statement $I$ is incorrect because activated sludge is formed in the settling tank (secondary treatment) after aeration,not in the grit chamber.
Statement $II$ is correct because a small part of the activated sludge is pumped back into the aeration tank as an inoculum,while the major part is pumped into large tanks called anaerobic sludge digesters where anaerobic bacteria digest the organic matter.

(A) In 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 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. 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'.

(C) During the secondary treatment of sewage in a $STP$ (Sewage Treatment Plant),the primary effluent is passed into large aeration tanks.
Here,it is constantly agitated mechanically and air is pumped into it.
This allows vigorous growth of useful aerobic microbes into masses of bacteria associated with fungal filaments to form mesh-like structures.
These structures are known as $flocs$.

(C) In sewage treatment,primary treatment involves physical removal of particles through filtration and sedimentation. Secondary treatment is a biological process where aerobic microbes consume organic matter,which significantly reduces the Biochemical Oxygen Demand $(BOD)$ of the effluent. Therefore,the statement that $BOD$ increases after secondary treatment is incorrect. Additionally,anaerobic sludge digesters are typically used for the treatment of sludge collected from primary and secondary processes,not as a standard tertiary treatment step.

(A) $BOD$ stands for Biochemical Oxygen Demand.
It 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.
Therefore,$BOD$ is a measure of the amount of biodegradable organic matter present in a water sample.
Higher $BOD$ indicates higher pollution levels due to organic waste.

(A) The correct sequence in a $\text{Sewage Treatment Plant}$ $(\text{STP})$ is as follows:
$1$. $\text{Primary sludge}$ is the solid waste settled during primary treatment.
$2$. The supernatant liquid is called the $\text{effluent}$,which is passed into aeration tanks.
$3$. In aeration tanks,aerobic microbes grow into masses called $\text{flocs}$.
$4$. Finally,the $\text{flocs}$ are digested by anaerobic bacteria in an $\text{anaerobic sludge digester}$,resulting in $\text{anaerobic sludge}$.
Therefore,the sequence is: $\text{Primary sludge} \rightarrow \text{effluent} \rightarrow \text{flocs} \rightarrow \text{anaerobic sludge}$.

(A) The first step of sewage treatment is the primary treatment,which involves the physical removal of large and small particles from the sewage through filtration and sedimentation.
$1$. Filtration is used to remove floating debris.
$2$. Sedimentation is used to remove grit (soil and small pebbles).
Therefore,the correct option is $A$.

(A) In a Sewage Treatment Plant $(STP)$, the primary treatment involves the physical removal of particles through filtration and sedimentation.
The sediment that settles at the bottom during this process is known as primary sludge.
The supernatant liquid that remains above the primary sludge is called the primary effluent.
This primary effluent is then taken for secondary treatment (biological treatment), where it is passed into large aeration tanks.
Therefore, the primary effluent is the key substance that acts as the link between primary and secondary treatment.

(C) Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures.
These structures are known as flocs.
They are formed during the secondary treatment of sewage,where aerobic microbes consume the organic matter in the effluent.
Therefore,flocs consist of fungi mycelium and microbes.

(D) The correct statement is $D$. Activated sludge in sediment tanks is a rich source of aerobic bacteria.
$A$ is incorrect because $Methanobacterium$ is an anaerobic bacterium.
$B$ is incorrect because biogas is produced by the activity of anaerobic bacteria,not aerobic bacteria.
$C$ is incorrect because biogas is a mixture of gases (primarily $CH_4$,$CO_2$,and $H_2S$),not pure methane.

(C) is the correct answer. Secondary treatment is highly significant because it reduces the $BOD$ level of sewage.
Primary treatment involves the physical removal of large and small particles through filtration and sedimentation.
The effluent from primary treatment is then passed into large aeration tanks for secondary treatment (biological treatment).
In these tanks,aerobic microbes consume the major part of the organic matter present in the effluent.
This significant reduction in organic matter leads to a decrease in the Biochemical Oxygen Demand $(BOD)$ of the sewage,making it safer to discharge into water bodies.

(B) The correct answer is $B$.
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 microorganisms consume the major part of the organic matter in the effluent,thereby significantly reducing the $BOD$ (Biochemical Oxygen Demand) of the sewage.

(B) $BOD$ stands for Biochemical Oxygen Demand.
It is defined as the amount of oxygen that would be consumed if all the organic matter in $1000 \ mL$ ($1$ litre) of water were oxidised by bacteria.
It is a measure of the organic matter present in the water sample; higher $BOD$ indicates higher pollution levels.

(D) filtration and sedimentation.
Primary sewage water treatment entails the physical removal of particles through filtration and sedimentation of solid waste present in the water.
The purpose of primary treatment is to settle down large and small particles by gravity,removing floatable debris and grit,which reduces the pollution load to ease the subsequent secondary treatment process.

(A) is the correct answer.
In a sewage treatment plant,during secondary treatment,a large number of aerobic heterotrophic microbes grow in the aeration tank.
These microbes include bacteria and some filamentous fungi and yeasts,which form $Flocs$.
$Flocs$ are mesh-like structures formed by the interweaving of fungal filaments and bacterial cells.