134.  During preliminary treatment of a sewage
A. Oil and grease are removed from skimming tanks
B. Floating materials are removed by screening
C. Girt and sand are removed by girt chambers
D. All the above.

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135.  Primary treatment of sewage consists of removal of
A. large suspended organic solids
B. oil and grease
C. sand and girt
D. floating materials

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136. For treating the sewage of a large city, you will recommend
A. a sedimentation tank and an activated sludge treatment plant
B. a plant consisting of Imhoff tanks with low rate trickling filters
C. sedimentation tanks with high rate trickling filters
D. none of these.

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137.  The spacing of bars for perforations in coarse screens used for the treatment of sewage, is
A. 20 mm
B. 30 mm
C. 40 mm
D. 50 mm

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138.  The spacing of bars of perforations of fine screens used for the treatment of sewage, is
A. 2 to 3 mm
B. 3 to 5 mm
C. 5 to 8 mm
D. 8 to 10 mm.

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139.  The screens are fixed
A. perpendicular to the direction of flow
B. parallel to the direction of flow
C. at an angle 30? to 60? to the direction of flow
D. none of these.

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140.  The use of coarse screens for the disposal of sewage, may be dispensed with by
A. comminutor
B. shredder
C. both A and B
D. neither A nor B.

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