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This set of Water and Wastewater Engineering Multiple Choice Questions & Answers (MCQs) focuses on Water And Wastewater Engineering Set 3
Q1 | The normal value of over flow rates for plain primary sedimentation tanks, ranges between
- 25,000 to 35,000 litres/sqm/day
- 40,000 to 50,000 litres/sqm/day
- 50,000 to 60,000 litres/sqm/day
- 80,000 to 100,000 litres/sqm/day
Q2 | Which one of the following statements regarding septic tanks is wrong?
- A gap of 7.5 cm between the bottom of the covering slab and the top level of scum is provided
- The outlet invert level is kept 5 to 7.5 cm below the inlet invert level
- The minimum width of septic level is 90 cm
- The depth of tank is kept equal to its width
Q3 | In areas where rainy season is limited to a few months, the type of sewerage systemrecommended is
- Combined system
- Partially separate system
- Separate system
- None of these
Q4 | The rate of accumulation of sludge in septic tanks is recommended as
- 30 litres/person/year
- 25 litres/person/year
- 30 litres/person/month
- 25 litres/person/month
Q5 | Dried sewage after treatment is used as
- Fertilizer
- Building material
- Chemical for lowering B.O.D.
- Base material for paints
Q6 | For drains up to 15 cumecs, the depth “d” and “B” width are related by
- d = 0.2
- d = 0.5 B
- B = 0.2 d
- B = 0.5 d
Q7 | In areas where light rains are uniformly distributed throughout the year, the type of seweragesystem to be adopted is
- Separate system
- Combined system
- Partially combined system
- None of these
Q8 | Self-cleansing velocity is
- Velocity at dry weather flow
- Velocity of water at flushing
- Velocity at which no accumulation remains in the drains
- Velocity of water in a pressure filter
Q9 | 5 days-biochemical oxygen demand (BOD5) is taken at a temperature of
- 0°C
- 15°C
- 20°C
- 25°C
Q10 | A well oxidized sewage contains nitrogen mainly as
- Nitrates
- Nitrites
- Free ammonia
- None of these
Q11 | In a sludge tank, the gas mainly produced, is
- Oxygen
- Nitrogen
- Hydrogen
- Carbon dioxide
Q12 | If “D” is the diameter of upper circular portion, the overall depth of New Egg shaped sewersection, is
- 1.250 D
- 1.350 D
- 1.425 D
- 1.625 D
Q13 | In normal conditions, the period for sludge digestion, is
- 10 days
- 20 days
- 30 days
- 60 days
Q14 | For evaporation and measurement of settable solids, the apparatus used, is
- A jar
- A breaker
- A test tube
- An Imhoff cone
Q15 | In trickling filter, B.O.D. is reduced to
- 30 to 40%
- 40 to 60%
- 60 to 80%
- 80 to 90%
Q16 | For design of sewers, percentage of sewage discharge is assumed
- 65 to 70
- 70 to 75%
- 75 to 80%
- 85%
Q17 | The grit chambers of sewage treatment plants, are generally cleaned after
- 2 days
- 7 days
- 12 days
- 14 days
Q18 | Maximum permissible velocity 1.5 m/sec, is adopted in drains
- With beds of rocks and gravels
- Lined with stones
- Both (a) and (b)
- Neither (a) nor (b)
Q19 | The average temperature of sewage in India, is
- 10°C (B) (C) (D)
- 15°C
- 20°C
- 25°C
Q20 | Pick up the in-correct statement from the following:
- Manholes are provided in sewer pipes at suitable intervals
- Catch basins are generally provided in sewers for carrying drainage discharge
- Inlets are generally provided in all sewers
- None of these
Q21 | The moisture content of sludge is reduced from 90% to 80% in a sludge digestion tank. Thepercentage decrease in the volume of sludge, is
- 25 % (B) (C) (D)
- 50%
- 10%
- 5%
Q22 | If ‘D’ is the diameter of upper circular portion, the overall depth of New Egg shaped sewersection, is
- 1.250 D
- 1.350 D
- 1.425 D
- 1.625 D
Q23 | In trickling filter, B.O.D. is reduced to
- 30 to 40% (B) (C) (D)
- 40 to 60%
- 60 to 80%
- 80 to 90%
Q24 | For design of sewers, percentage of sewage discharge is assumed
- 65 to 70% (B) (C) (D)
- 70 to 75%
- 75 to 80%
- 85%
Q25 | The grit chambers of sewage treatment plants, are generally cleaned after
- 2 days (B) (C) (D)
- 7 days
- 12 days
- 14 days