Waste Water Engineering

21. An inverted siphon is designed generally for

  1. One pipe
  2. Two pipes
  3. Three pipes
  4. Four pipes

Correct answer: (C)
Three pipes

22. Antisyphonage pipe is fitted

  1. At the end of septic tanks
  2. On manholes
  3. With a W.C. trap
  4. At the beginning of sewer line

Correct answer: (C)
With a W.C. trap

23. As compared to fresh river water, sea water contains oxygen

  1. 10% less
  2. 20% less
  3. 10% more
  4. 20% more

Correct answer: (B)
20% less

24. Assertion (A) : Discharging the effluents from the oxidation ponds just up stream of lakes or reservoirs is undesirable. Reason (R) : The discharged algae get settled in the reservoirs and cause anaerobic decomposition and other water qualities.

  1. Both A and R are true and R is the correct explanation of A
  2. Both A and R are true but R is not a correct explanation of A
  3. A is true but R is false
  4. A is false but R is true

Correct answer: (A)
Both A and R are true and R is the correct explanation of A

25. Assertion (A): A free board of 0.3 m is provided above the top sewage line in septic tanks. Reason (R): It helps to accommodate the scum in the septic tank.

  1. Both A and R is true and R is the correct explanation of A
  2. Both A and R is true but R is not a correct explanation of A
  3. A is true but R is false
  4. A is false but R is true

Correct answer: (A)
Both A and R is true and R is the correct explanation of A

26. Assertion (A): The determination of pH value of sewerage is important. Reason (R): The efficiency of certain treatment methods depends upon the availability of pH value.

  1. Both A and R are true and R is the correct explanation of A
  2. Both A and R are true but R is not a correct explanation of A
  3. A is true but R is false
  4. A is false but R is true

Correct answer: (A)
Both A and R are true and R is the correct explanation of A

27. Assertion (A): The minimum self cleansing velocity in the sewer, at least once a day, must be generated. Reason (R): If certain deposition takes place and is not removed, it obstructs free flow and causes further deposition leading to complete blocking of the sewer.

  1. Both A and R are true and R is the correct explanation of A
  2. Both A and R are true but R is not a correct explanation of A
  3. A is true but R is false
  4. A is false but R is true

Correct answer: (A)
Both A and R are true and R is the correct explanation of A

28. At the junction of sewers

  1. Top of smaller sewer is kept lower
  2. Top of larger sewer is kept lower
  3. Tops of both the sewers are at the same level
  4. None of these

Correct answer: (D)
None of these

29. Before discharging the foul sewage into rivers, it is generally treated by

  1. Screening
  2. Sedimentation
  3. Oxidation
  4. All the above

Correct answer: (D)
All the above

30. Bio-chemical oxygen demand (BOD) for the first 20 days in generally referred to

  1. Initial demand
  2. First stage demand
  3. Carbonaceous demand
  4. All of these

Correct answer: (D)
All of these

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