309. In the activated sludge process
A. aeration is continued till stability
B. aeration is done with an admixture of previously aerated sludge
C. sludge is activated by constant stirring
D. water is removed by centrifugal action.
310. Drop manholes are the manholes
A. without entry ladders
B. without manhole covers
C. with depths more than 3.5 m
D. having drains at different levels.
311. Skimming tanks are
A. used to remove the grease and oil
B. those from which sludge is skimmed out
C. tanks provided with self-cleansing screens
D. improved version of grit chambers.
312. Traps
A. are water seals which prevent the entry of foul gases
B. are used to trap the rats entering sewers
C. dissolve the foul gases
D. create syphonic action to increase the quick disposal of sewerage.
313. For providing an Indian type W.C., the R.C.C. slabs in the toilet portion
A. should be sunk by 20 cm
B. should be kept 20 cm above the adjacent portion
C. should be sunk by 50 cm
D. need not be sunk.
314. Lead caulked joints are used for laying
A. stone ware pipes
B. earthern ware pipes
C. C.I. pipes
D. G.I. pipes.
315. The minimum recommended diameter of sewers, is
A. 5 cm
B. 10 cm,
C. 15 cm
D. 20 cm,
Page 45 of 52