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Environmental (41-60)

Updated: Apr 9, 2020

41.The detention period and overflow rate respectively for plain sedimentation as

compared to sedimentation with coagulation are generally more and less


42. The amount of coagulant needed for coagulation of water increases with

increase in turbidity of water,decrease in temperature of water


43. Alum as a coagulant is found to be most effective when pH range of water is

6 to 8


44. The detention period in coagulation tanks is usually kept as 2 to 6 hour


45. The alum, when added as a coagulant in water decreases pH value of water


46. The chemical most commonly used to increase speed of sedimentation of sewage is lime


47. In water treatment, rapid gravity filters are adopted to remove bacteria and colloidal solids


48. The rate of filtration in slow sand filters in million litres per day per hectare is

about 50 to 60


49. The effective size of sand particles used in slow sand filters is 0.25 to 0.35mm


50. As compared to rapid sand filters, slow sand filters give slower filtration rate,higher efficiency in removal of bacteria


51.Assertion A: Slow sand filters are more efficient in removal of bacteria than rapid sand filters.

Reason R : The sand used in slow sand filters is finer than that in rapid sand



52. Air binding phenomena in rapid sand filters occur due to excessive negative head


53. The percentage of filtered water, which is used for backwashing in rapid sand filters, is about 2 to 4


54. Period of cleaning of slow sand filters is about 2-3 month


55. The rate of Alteration of pressure filters is greater than that of rapid sand filters


56. Double filtration is used to increase the filtration capacity of slow sand filters


57. Cleaning is done by scraping and removal in slow sand filters,back washing in rapid sand filters


58. Disinfection of water results in killing of disease bacteria


59. The disinfection efficiency of chlorine increases by increasing the temperature of water


60. Chlorine demand of water is equal to difference of applied and residual


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