Waste Water Engineering Online Test – Multiple Choice Questions and Answers 1. If the depletion of oxygen is found to be 2.5 mg/litre after incubating 2.5 ml of sewage diluted to 250 ml for 5 days at 20°C, B.O.D. of the sewage is 100 mg/l 150 mg/l 2000 mg/l 250 mg/l 2. The digested sludge from septic tanks, is removed after a maximum period of 3yrs 4yrs 5yrs 6yrs 3. The amount of oxygen consumed by the aerobic bacterias which cause the aerobic biological decomposition of sewage, is known Dissolved Oxygen (D.O.) Chemical Oxygen Demand (C.O.D.) Bio-Chemical Oxygen Demand (B.O.D.) None of these 4. The standard B.O.D. of water is taken for 1 day 2 day 3 day 5 day 5. For providing an Indian type W.C., the R.C.C. slabs in the toilet portion should be kept 20 cm above the adjacent portion should be sunk by 50 cm should be sunk by 20 cm need not be sunk 6. To prevent settling down of sewage both at the bottom and on the sides of a large sewer, self-cleaning velocity recommended for Indian conditions, is 0.50 m/sec 0.60 m/sec 0.70 m/sec 0.75 m/sec 7. The detention period for plain sedimentation water tanks, is usually 4 to 8 hours 8 to 16 hours 16 to 24 hours 24 to 36 hours 8. Rate of flow of sewage is generally assumed equal to the rate of water supply less than the rate of water supply more than the rate of water supply at 150 litres per capita 9. A manhole is classified as shallow if its depth is between 0.5 to 0.7 m 0.4 to 0.5 m 0.9 to 1.20 m 0.7 to 0.9 m 10. A drop manhole is provided if a lamp is inserted to check obstruction a branch sewer joins the main sewer at higher level a sewer drops from a height none of these Loading … Question 1 of 10
