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171.

Rapid sand filter can remove turbidity from water upto an extent of

A.	15 to 25 ppm	B.	25 to 35 ppm
C.	35 to 40 ppm	D.	40 to 50 ppm

172.

Rapid sand filters are cheap and economical as compared to slow sand filters.

True

False

173.

Pressure filters are not used for treating municipal water supplies, because

A.	the rate of filteration is high	B.	the overall plant capacity is small
C.	they are inefficient in the removal of turbidity and bacterias	D.	they are more costly

174.

In presure filters, water is forced at a pressure

A.	equal to	B.	less than
C.	greater than

175.

Pressure filters are best suited for

A.	swimming pools	B.	railway stations
C.	individual industries	D.	all of these

176.

The process of killing pathogenic bacterias from water is called

A.	sedimentation	B.	filteration
C.	coagulation	D.	disinfection

177.

The most commonly used disinfectant for drinking water throughout the world is

A.	alum	B.	nitorgen
C.	lime	D.	chlorine

178.

The ideal method of disinfection of swimming pool water is by

A.	chlorination	B.	lime treatment
C.	ozonisation	D.	ultra-violet rays

179.

The amount of residual chlorine in treated water is determined by the

A.	Orthotolodine test	B.	Iodemetric test
C.	Amperometric test	D.	all of these

180.

The time of contact for chlorination should be at least

A.	5 minutes	B.	20 minutes
C.	1 hour	D.	2 hours