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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