Karnataka Board PUCPUC Science 2nd PUC Class 12

Describe how do 'flocs' and 'activated sludge' help in Sewage Treatment. - Biology


Describe how do 'flocs' and 'activated sludge' help in Sewage Treatment.



After the primary treatment, the primary effluent is taken for secondary treatment where it is passed into large aeration tanks and is constantly agitated and air is pumped into it. This leads to the vigorous growth of useful aerobic microbes into flocs. Flocs are masses of bacteria associated with fungal filaments to form mesh like structures. These microbes in the flocs consume the major part of the organic matter in the effluent and reduces the BOD (biological oxygen demand) of the effluent. Less BOD means that the waste water is less polluted.

After this, the effluent is passed into a settling tank where the flocs are allowed to settle and this sediment is called activated sludge. A small part of the activated sludge is pumped back to serve as the inoculum. Inoculum is the small amount of a material containing microbes that can start a new culture. This way same microbial culture is recycled and reused to start a new culture for the treatment.

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2016-2017 (March) Delhi Set 1

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Explain the different steps involved during primary treatment phase of sewage.

Explain the process of sewage water treatment before it can be discharged into natural water bodies.

What is the key difference between primary and secondary sewage treatment?

Find out the role of microbes in the following

Single cell protein (SCP)

What is primary treatment of sewage?

Answer the following question.
What are ‘flocs’, formed during secondary treatment of sewage?

Answer the following question.
Secondary treatment of the sewage is also called Biological treatment. Justify this statement and explain the process.

Removal of large pieces of floating debris, oily substances, etc. during sewage treatment is called _______________.

One of the free-living anaerobic nitrogen-fixer is _________.

Why is this sewage water treatment essential?

Name the chamber in which the suspended objects are filtered and removed during sewage treatment?

Name the tank to which the sewage water is passed after the preliminary treatment?

What are flocs with respect to sewage treatment?

Small part of activated sludge is passed back into primary sedimentation tank.

If the above statement is correct then rewrite as it is and in case it is incorrect then reframe it.

Rearrange the names of tanks used in sewage treatment as per the flow of procedure.

  1. settling tank
  2. Grit Chamber
  3. aeration tanks 
  4. primary sedimentation tank.

The purpose of biological treatment of waste water is to ______.

In which of the following microbial digestion of organic wastes of sewage takes place?

Due to which of the following reason/s sewage water cannot be discharged directly into river?

Which of the following is/are found in discharge from industrial waste?

Which of the following occurs during secondary treatment?

______ refers to the organic matter which settles down after physical treatment of sewage.

During tertiary treatment, the bacterial floes sediment in the sedimentation tank, this sediment is called ____________.

After which of the following treatment BOD of the effluent is significantly reduced?

Which of the following process is a part of preliminary treatment of sewage?

In the process of sewage treatment, the activated sludge is digested by ______

Nitrogen fixation by organisms requires conditions that are:

During sewage, treatment biogas is produced wits which include:

Which of the following is put into Anaerobic sludge disaster for further sewage treatment?

Methanogenic bacteria are not found in ______.

In a sewage treatment plant, all of the following processes belong to secondary treatment except: 

In which of the following step large and small particles are removed from sewage through sequential filtration and sedimentation?

Activated sludge should have the ability to settle quickly so that it can ______.

Why do we prefer to call secondary waste water treatment as biological treatment?

What is the group of bacteria found in both the rumen of cattle and shidge of sewage treatment?

Given below is the flowchart of sewage treatment. Identify A, B, C, D and E and select the correct option.

The aeration tank of a sewage treatment plant is not functioning properly. Explain in detail the impact of this on the treatment of sewage and BOD of the effluent.


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