Engineering Questions with Answers - Multiple Choice Questions

# Environmental Engineering MCQ – High Rate Trickling Filter and Secondary Clarifier

1 - Question

The maximum removal of suspended and dissolved impurities from the sewage is?
a) 65
b) 70
c) 92
d) 99

Explanation: The maximum and minimum removal of suspended and dissolved impurities from the sewage is 92% and 65% respectively.

2 - Question

The color of the secondary sludge produced from the high rate trickling filter is ___________
a) Gray
b) Black
c) Brown
d) Green

Explanation: The color of the secondary sludge produced from the high rate trickling filter is brown and the secondary sludge obtained is partially oxidized.

3 - Question

_______ is the ratio of volume of recirculated sewage to the raw sewage.
a) Recirculation factor
b) Recirculation ratio
c) Food to mass ratio
d) BOD

Explanation: Recirculation ratio is the ratio of volume of recirculated sewage to the raw sewage. It is denoted by R/I where, ‘R’ is the recirculated sewage and I is the volume of raw sewage.

4 - Question

The range of organic loading in kg/hectare metre/ day in a high rate trickling filter is ___________
a) 6000-18000
b) 10000-20000
c) 5000-10000
d) 900-2200

Explanation: The range of organic loading in high rate trickling filter lies between 6000 to 18000 kg of 5 days BOD per hectare metre of filter media per day.

5 - Question

The expression of the recirculation factor F is given by ___________
a) F = 1 / (1+0.1 (R/I))2
b) F = (1+ R) / (1+0.1 (R/I))2
c) F = (1+ I/R) / (1+0.1(R/I))2
d) F = (1+ R/I) / (1+0.1(R/I))2

Explanation: The expression of the recirculation factor F is given by
F = (1+ R/I) / (1+0.1 (R/I))2 where, R/I represents the recirculation ratio.

6 - Question

The size of filter media in a high rate trickling filter is ___________
a) 10-20mm
b) 34-68mm
c) 25-60mm
d) 20-50mm

Explanation: The size of filter media in a high rate trickling filter is 25-60mm and it can be a rock, slag or any synthetic material.

7 - Question

Recirculation increases the efficiency of high rate trickling filters.
a) True
b) False

Explanation: Recirculation reduces the loading in high rate trickling filter and thus, increase the efficiency infiltration process.

8 - Question

a) 1000
b) 10000
c) 20000
d) 40000

Explanation: The range of surface loading rate of a secondary clarifier lies between 40,000 litres/m2/day to 70,000 litres/m2/day.

9 - Question

The detention period of a secondary clarifier is ___________
a) 30 minutes
b) 1 hour
c) 2 hours
d) 4 hours

Explanation: The detention period of a secondary clarifier is between 1.5 hours to 2 hours.

10 - Question

Which of the following is the cause of rising sludge?
a) Sedimentation
b) Denitrification
c) Chlorination
d) Flocculation

Explanation: When nitrogen is formed in the sludge, the rise of the sludge mass takes place. These phenomena is called as rising sludge.

11 - Question

a) 125000
b) 50000
c) 10000
d) 20000

Explanation: The minimum and maximum weir loading rate of primary clarifier is 125000 and 500000 m3/m/day respectively.

12 - Question

Hopper bottom vertical flow type tank is _____ in shape.
a) Circular
b) Triangular
c) Rectangular
d) Elliptical