Temporary hardness in water is caused by the presence of

 

(A) chlorides of Ca and Mg

 

(B) bicarbonate of Ca and Mg

 

(C) sulphates of Ca and Mg

 

(D) nitrates of Ca and Mg

Bacteria that need oxygen to live are known as

(A) pathogenic bacteria

(B) facultative bacteria

(C) anaerobic bacteria

(D) aerobic bacteria

Suspended impurities in water is

(A) algae

(B) bacteria

(C) silts

(D) all of these

A timber dam is a

(A) detention dam

(B) rigid dam

(C) non-rigid dam

(D) non-overflow dam

Stone ware pipes are

(A) specially suited to pressure pipes

(B) hydraulically efficient because of their smooth interior surface

(C) highly impervious

(D) highly resistant to sulphide corrosion

Process of killing pathogenic bacteria from water is known as

(A) sedimentation

(B) disinfection

(C) coagulation

(D) filtration

Bacteria that survive in the absence of oxygen are known as

(A) anaerobic bacteria

(B) aerobic bacteria

(C) facultative bacteria

(D) pathogenic bacteria

A pipe sunk into the well to tap underground water is called

(A) artesian well

(B) open well

(C) infiltration well

(D) tube well

Dry water flow in a combined sewer, is

(A) storm water

(B) inclusive of domestic and industrial sewage but excludes storm water

(C) industrial sewage

(D) domestic sewage

Aerosol is

(A) diffused liquid particles

(B) carbon particles of microscopic size

(C) dispersion of small solid or liquid particles in gaseous media

(D) finely divided particles of ash

All major and important gravity dams are nowadays constructed with

(A) concrete

(B) earth and rock fill

(C) brick masonry

(D) stone masonry