41. The small sewers are cleaned by____________________? A. Flushing B. Cane rodding C. Wooden pills D. None of these ✅ The correct answer is option A.
42. A well oxidized sewage contains nitrogen mainly as___________________? A. Nitrates B. Nitrites C. Free ammonia D. None of these ✅ The correct answer is option A.
43. For pipes, laminar flow occurs when Roynolds number is__________________? A. less than 2000 B. between 2000 and 4000 C. more than 4000 D. less than 4000 ✅ The correct answer is option A.
44. 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 ✅ The correct answer is option A.
45. The first stage of neutral process of sludge digestion, is__________________? A. Acid fermentation B. Acid regressio C. Alkaline fermentation D. None of these ✅ The correct answer is option A.
46. Surface tension _____________________? A. acts in the plane of the interface normal to any line in the surface B. is also known as capillarity C. is a function of the curvature of the interface D. decreases with fall in temperature ✅ The correct answer is option A.
47. The detention period for plain sedimentation water tanks, is usually____________________? A. 4 to 8 hours B. 8 to 16 hours C. 16 to 24 hours D. 24 to 36 hours ✅ The correct answer is option A.
48. The sewerage system originates from__________________? A. House sewers B. Lateral sewers C. Branch sewers D. Main sewers ✅ The correct answer is option A.
49. hydraulically equivalent, the relationship which holds good, is _______________? A. D8/3 = 4 b8/3 B. D3/8 = 4 b3/8 C. D2/3 = 4 b2/3 D. D3/2 = 4 b3/2 ✅ The correct answer is option A.
50. The coagulant which is generally not used for treating the sewage, is__________________? A. Alum B. Ferric chloride C. Ferric sulphate D. Chlorinated copperas ✅ The correct answer is option A.