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GATE CE 2022: Environmental Engineering Quiz #5

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Question 1

Domestic sewage of the town was tested for total solids and following results were obtained :
Weight of sample of sewage = 1000 gm
Weight of solids after evaporation of liquid = 0.952 gm
Weight of dry residue after ignition = 0.516 gm
Determine volatile solids

Question 2

Determine the critical deficit (in ppm) of dissolved oxygen when the stream flowing at a rate of 210 cumec with saturated dissolved oxygen limit of 10.6ppm is diluted with a sewage flowing at the rate of 1.35 cumec. Assume the Dissolved oxygen limit of waste water as 4ppm.

Question 3

If the BOD2 of a waste water sample is 62 mg/L and reaction rate constant K (base e) is 0.322 per day, the amount of BOD remaining in the given sample after 10 days is

Question 4

250 cumecs of sewage of Varanasi city containing no dissolved oxygen (DO) is discharged into the Ganga river which is fully saturated with oxygen and flowing at a rate of 2000 cumecs with a minimum velocity of 0.15 m/sec. The 5 day BOD of sewage is 350 mg/litre. The value of critical Do (in mg/l) deficit is
[Assume coefficient of purification of river is 3.0, coefficient of deoxygenation is 0.12, the ultimate BOD is 150% of the 5 day BOD and sarurated DO of river is 12 mg/litre]

Question 5

A reactor has an inflow of sewage 180 liters/min. The influent COD is 1000 mg/l and the effluent COD is 250 mg/l. The waste water contains 50% of biodegradable waste. The volume of methane gas produced per day is _____ m3.

Question 6

If in a district of area 30 hectare has density of population 300 per hectare and quota for water supply is 130 litre then Average rate of sewage produced? (Sewage discharge is 80% of water supplied) (2 Mark)
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