Test: Types Of Screens And Aerators - Civil Engineering (CE) MCQ

Explanation: Screens are used as a pretreatment process for purification of water to avoid large size suspended materials from water.

Explanation: Coarse screens are used in the form of bars of 25mm diameter size and are spaced at 75 to 100mm centers.

Explanation: The coarse screen is inclined at 450-600 so that they can be easily cleaned with a rake. Moreover, it reduces the flow velocity which also helps in cleaning the screen

Explanation: The head loss through the screen is given by, h=B (w/b) 4/3h1*sinx Where h=head loss, h1=approach velocity head, b=minimum width, x=angle of rack, B=shape factor. It also depends on the nature of their construction.

Explanation: The shape factor rectangular bar with sharp edges is 2.42, for semicircular face is 1.83 and for circular rod is 1.79.

Explanation: Aeration reduces the carbon dioxide content and corrosiveness of water and hence, raises the pH value of water.

Explanation:Cascade aerators are the gravity aerators in which water falls from 1-3m height such that it comes in contact with air and reduces carbon dioxide content to 50-60%.

Explanation: In Cascade aerator, the flow of water is divided into fine streams and small droplets such that they come in contact with air in their trajectories and reduces CO2 by 70-90%.

Answer: b
Explanation: t = 1sec, g = 9.8
Elapsed time, t = (2h/g) 1/2 in a single descent.
Height of fall, H = t2g/2 = 1*1*9.8/2= 4.9m.

Explanation: Automatic strainers are self cleaning devices which remove solids from the flowing liquid continuously and help in fine screen so that it do not get clogged up.