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131.

The efficiency of sedimentation tank for a given discharge, can be increased by

A.	increasing the depth of tank	B.	decreasing the depth of tank
C.	increasing the surface area of tank	D.	decreasing the surface area of tank

132.

Which of the following statement is correct?

A.	Screens are inclined to increase the opening area.	B.	Plain sdimentation is useful as a process preliminary to further treatments.
C.	Ratio of the volume of the basin of sedimentation tank to the rate of flow is called detention period	D.	all of the above

133.

The most common coagulant is

A.	magnesium sulphate	B.	alum
C.	chlorine	D.	bleaching powder

134.

When turbidity of water exceeds about 45 ppm, coagulation

should be

should not be

135.

In dry feeding type of coagulants, the dose of coagulant is controlled by

A.	scrapers	B.	worm wheel
C.	paddles	D.	none of these

136.

Which of the following is not a coagulating agent?

A.	Ferric sulphate	B.	Ferric chloride
C.	Aluminium sulphate	D.	Copper sulphate

137.

The alum when mixed with water as a coagulant,

A.	does not effect pH value of water	B.	decreases pH value of water
C.	increases pH value of water	D.	none of these

138.

Coagulation is required when the particles are of

fine

coarse

139.

Aluminium sulphate may be used for coagulation.

Correct

Incorrect

140.

The volume of a settling basin is large due to

A.	large volumes of floc added for coagulation	B.	large amount of water entrapped into it
C.	greater amount of suspended solids to be removed	D.	none of the above