GATE CE Water and Waste Water Quality and Treatment PYQs & Answers — Page 8

Questions 71–80 of 81. Imported answers require independent review unless marked reviewed.

At a small water treatment plant which has 4 filters, the rates of filtration and backwashing are 200 m

/d/m

and 1000 m

/d/m

, respectively. Backwashing is done for 15 min per day. The maturation, which occurs initially as the filter is put back into service after cleaning, takes 30 min. It is proposed to recover the water being wasted during backwashing and maturation. The percentage increase in the filtered water produced (up to two decimal places) would be _____

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A schematic flow diagram of a completely mixed biological reactor with provision for recycling of solids is shown in the figure.

Diagram for Civil Engineering question 52

S₀, S = readily biodegradable soluble BOD, mg/L Q, Qᵣ, Qw = flow rates, m

/d X₀, X, Xₑ, Xᵤ = microorganism concentrations (mixed-liquor volatile suspended solids or MLSS), mg/L

The mean cell residence time (in days, up to one decimal place) is _____

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The most important type of species involved in the degradation of organic matter in the case of activated sludge process is

Your answerChoose one option.

autotrophs

heterotrophs

protrophs

photo-autotrophs

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The reaction rate involving reactants

and

is given by

. Which one of the following statements is valid for the reaction to be a first-order reaction?

Your answerChoose one option.

and

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The wastewater from a city, containing a high concentration of biodegradable organics, is being steadily discharged into a flowing river at a location S. If the rate of aeration of the river water is lower than the rate of degradation of the organics, then the dissolved oxygen of the river water

Your answerChoose one option.

is lowest at the location S.

is lowest at a point upstream of the location S.

remains constant all along the length of the river.

is lowest at a point downstream of the location S.

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For a given water sample, the ratio between BOD

and the ultimate BOD is 0.68. The value of the reaction rate constant

(on base

) (in day

, up to two decimal places) is

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A municipal corporation is required to treat 1000 m

/day of water. It is found that an overflow rate of 20 m/day will produce a satisfactory removal of the discrete suspended particles at a depth of 3 m. The diameter (in meters, rounded to the nearest integer) of a circular settling tank designed for the removal of these particles would be

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The spherical grit particles, having a radius of 0.01 mm and specific gravity of 3.0, need to be separated in a settling chamber. It is given that • g = 9.81 m/s² • the density of the liquid in the settling chamber = 1000 kg/m³ • the kinematic viscosity of the liquid in the settling chamber = 10⁻⁶ m²/s Assuming laminar conditions, the settling velocity (in mm/s, up to one decimal place) is ______.

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The analysis of a water sample produces the following results:

Ion	milligram per milli-equivalent for the ion	Concentration (mg/L)
Ca	20.0	60
Mg	12.2	36.6
Na	23.0	92
K	39.1	78.2
Cl	35.5	71
SO	48.0	72
HCO	61.0	122

The total hardness (in mg/L as CaCO

) of the water sample is

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Two wastewater streams A and B, having an identical ultimate BOD are getting mixed to form the stream C. The temperature of the stream A is 20°C and the temperature of the stream C is 10°C. It is given that • the 5-day BOD of the stream A measured at 20°C = 50 mg/l • BOD rate constant (base 10) at 20°C = 0.115 per day • temperature coefficient = 1.135 The 5-day BOD (in mg/l, up to one decimal place) of the stream C, calculated at 10°C, is ______.

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GATE CE Water and Waste Water Quality and Treatment PYQs

Question 51

Question 52

Question 10

Question 13

Question 14

Question 51

Question 52

Question 53

Question 53

Question 54