This set of Waste Water Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Sludge Treatment Process – 2”.
1. Out of the following methods which provide uniform dewatering?
a) Belt filter press
b) Filter press
c) Sludge bed
d) Centrifuge
View Answer
Explanation: Belt filter press results in uniform dewatering. This prevents clogging of the solids. This also prevents warping of rollers.
2. The usage of which type of pump results in less wear and tear while pumping the sludge?
a) Vertical turbine pumps
b) Submersible pump
c) Progressive cavity pump
d) Non-clog pump
View Answer
Explanation: By using progressive cavity pumps to pump the sludge wear and tear can be reduced. This is also one method to reduce the clogging of solids. Thus mostly progressive cavity pumps are preferred over other pumps in order to pump sludge.
3. The cyclone gritter removes the grit particles based on which of the below mentioned phenomenon?
a) Centrifugal force
b) Gravity
c) Brownian motion
d) Sedimentation
View Answer
Explanation: The cyclone gritter removes grit particles based on centrifugal force. The heavier particles move to the outside of the cylinder section. These are then discharged through the conical section.
4. Primary sludge constitutes which of the following?
a) Chemical sludge
b) Settlable solids
c) Biological solids
d) Biological and settlable solids
View Answer
Explanation: Primary Sludge constitutes of settleable solids. This is mostly returned to the primary clarifier. This is done in order to carry out mixing to provide a uniform mixture.
5. Secondary sludge constitutes which of the following?
a) Chemical sludge
b) Settlable solids
c) Biological solids
d) Biological and settlable solids
View Answer
Explanation: The secondary sludge constitutes biological sludge. This also constitutes settleable solids. The secondary sludge is sent to the primary clarifier, where mixing is carried out in order to provide an uniformity.
6. Advanced waste water sludge constitutes which of the following?
a) Chemical sludge
b) Settlable solids
c) Biological solids
d) Chemical and biological solids
View Answer
Explanation: The advanced waste water sludge constitutes biological sludge. This also constitutes chemical sludge. The advanced waste water sludge is sent to the primary clarifier, where mixing is carried out in order to provide an uniformity to the mixture.
7. To remove 1% primary sludge which of the following size of mesh of a cyclone gritter is used?
a) 150
b) 100
c) 300
d) 50
View Answer
Explanation: To remove the 1% primary sludge usually a 150 sized mesh of the cyclone degritter is used. In these cyclone degritters the sludge is fed tangentially. This is the most effective way to degrit sludge.
8. To remove 2% primary sludge which of the following size of mesh of a cyclone gritter is used?
a) 150
b) 100
c) 65
d) 28-35
View Answer
Explanation: To remove the 2% primary sludge usually a 100 sized mesh of the cyclone degritter is used. Prior to thickening of sludge, degritting should be carried out. After degritting the sludge is stored before it is subjected to thickening.
9. To remove 3% primary sludge which of the following size of mesh of a cyclone gritter is used?
a) 100
b) 150
c) 65
d) 28-35
View Answer
Explanation: To remove the 3% primary sludge usually a 65 sized mesh is used. After degritting, the sludge is stored for not more than 4-5 hours. Then the sludge is thickened using a centrifuge, gravity belt etc.
10. Which of the following methods is used for stabilization of the sludge?
a) Anaerobic digestion
b) Sludge drying bed
c) Centrifuge
d) Filter press
View Answer
Explanation: The sludge is stabilized by anaerobic digestion. Lime conditioning and aerobic digestion are the other methods in order to bring about stabilization. The sludge is stabilized before it is subjected to conditioning.
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