21.The maximum permissible turbidity for domestic supplies, on silica scale is ?
- 5 to 10 ppm
- 10 to 20 ppm
- 20 to 30 ppm
- 30 to 40 ppm
22.The water mains should be designed for .......... of the average daily water requirement ?
- 100%
- 150%
- 225%
- 250 %
23.The quantity of water available from an infiltration gallery depends upon the ?
- size of gallery
- nature of soil
- yield of source
- all of these
24.The yield of a surface stream may be obtained by ?
- cross-section velocity method
- stream gauging
- chemical method
- all of these
25.The commercial osmoscope is graduated with po values from ?
- 0 to 5
- 5 to 10
- 10 to 15
- 15 to 20
26.The presence of .................causes red colour in water ?
- iron
- manganese
- sodium fluoride
- calcium carbonate
27.The yield of the well depends upon the ?
- permeability of the soil
- position of water table
- depth of well in impervious layer
- all of these
28.Low turbidity of water can be determined by ?
- turbidity tube
- Jacksons turbidimeter
- Baylis turbidimeter
- Hellipe turbidimeter
29.The sodium carbonate in water ?
- causes bad taste
- softens the water
- increases hardness of water
- stops epidemic
30.The yield of the well is measured in ?
- cum/h
- litres/h
- either (a) or (b)
- none of these.
31.The maximum permissible chlorine content for public supplies should be between ?
- 0.1 to 0.2 ppm
- 0.3 to 0.4 ppm
- 1.2 to 4 ppm
- 6.5 to 8 ppm
32.Run-off is the water which flows ?
- in infiltration galleries
- in sewer pipes
- due to leakage of pipes
- in rivers
33.The maximum permissible quantity of iron and manganese in water for domestic purposes should be ?
- 0.1 ppm
- 0.3 ppm
- 0.6 ppm
- 0.8 ppm
34.The layers such as lime stone and sand stone which do not allow the water to pass through them are known as ?
- aquifers
- aquiclude
- aquifuge
- none of these
35.Suspended impurities consist of ?
- iron
- chlorine
- bacteria
- all of these
36.The maximum permissible total solid content in water for domestic purposes should not exceed ?
- 300 ppm
- 400 ppm
- 500 ppm
- 1000 ppm
37.Which of the following statement is correct ?
- The rate of silting in a reservoir is more in the beginning and less in the end
- At the economical height of a dam, its cost per million cubic metre of storage is minimum
- The percentage of water required for public use amounts to about 10% of the total water requirements
- all of the above
38.The alkalinity in water is caused by ?
- sodium carbonate
- potassium carbonate
- calcium hydroxide
- all of these
39.An artesian spring is formed ?
- when an aquifer gets exposed in a valley against a vertical cut
- due to continuous fault in a rock through which water under pressure comes out
- when a porous strata gets enclosed between two impervious strata
- none of the above.
40.Which of the following statement is wrong ?
- The quality of tube well water is better than that of surface sources
- The discharge of tube well is more than that of an open well
- The tube well should not derive water from the first previous strata
- none of the above.
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