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प्रश्न
Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20 mg/L, 8 mg/L and 400 mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each, assuming the river water is relatively clean?
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उत्तर
Biological oxygen demand (BOD) is the method of determining the amount of oxygen required by micro-organisms to decompose the waste present in the water supply. If the quantity of organic waste in the water supply is high, then the number of decomposing bacteria present in the water will also be high. As a result, the BOD value will increase.
Therefore, it can be concluded that if the water supply is more polluted, then it will have a higher BOD value. Out of the above three samples, sample C is the most polluted since it has the maximum BOD value of 400 mg/L. After untreated sewage water, secondary effluent discharge from a sewage treatment plant is most polluted. Thus, sample A is secondary effluent discharge from a sewage treatment plant and has the BOD value of 20 mg/L, while sample B is river water and has the BOD value of 8 mg/L.
Hence, the correct label for each sample is:
| Label | BOD value | Sample |
| A | 20 mg/L | Secondary effluent discharge from a sewage treatment plant |
| B | 8 mg/L | River water |
| C | 400 mg/L | Untreated sewage water |
APPEARS IN
संबंधित प्रश्न
Distinguish between the roles of flocs and anaerobic sludge digesters in sewage treatments.
Answer the following question.
What are ‘flocs’, formed during secondary 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.
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 the procedure.
- Settling tank
- Grit Chamber
- Aeration tanks
- Primary sedimentation tank.
Due to which of the following reason/s sewage water cannot be discharged directly into river?
After which of the following process effluents from anaerobic sludge digesters are released in natural water bodies?
In the process of biogas production which of the following anaerobic bacteria are used?
Identify the type of microorganisms involved in floe formation during sewage treatment.
Identify the INCORRECT statement with respect to sewage treatment.
What happens during the course of sewage decomposition?
During tertiary treatment, the bacterial floes sediment in the sedimentation tank, this sediment is called ____________.
Study the following statements regarding tertiary treatment of sewage and choose the correct option.
i. It produces methane gas.
ii. The effluents formed from these plants undergo chlorination.
iii. BOD is significantly increased at this step.
iv. It includes screening and passage of effluent through grit chamber.
Which of the following is TRUE regarding 'Flocs'?
Nitrogen fixation by organisms requires conditions that are:
In which of the following step large and small particles are removed from sewage through sequential filtration and sedimentation?
The primary treatment of waste water involves the removal of ______.
What would happen if oxygen availability to activated sludge flocs is reduced?
Discuss about the major programs that the Ministry of Environment and Forests, Government of India, has initiated for saving major Indian rivers from pollution.
Study the given diagram of the Sewage Treatment Plant (S.T.P.) and answer the question that follows:
- Which one of the two 'S.T.P.' (A) or (B) will be more effective in treating the human excreta in municipal waste?
- Write the steps followed in carrying the treatment of the sewage in step (Z), once the BOD of sewage is reduced significantly till it is passed on to the "anaerobic sludge digesters".
Which one is wrongly matched?
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.
