GATE CE area:environmental-engineering PYQs & Answers — Page 8

Questions 71–80 of 110. Imported answers require independent review unless marked reviewed.

A river has a flow of 1000 million litres per day (MLD), BOD₅ of 5 mg/litre and Dissolved Oxygen (DO) level of 8 mg/litre before receiving the wastewater discharge at a location. For the existing environmental conditions, the saturation DO level is 10 mg/litre in the river. Wastewater discharge of 100 MLD with the BOD₅ of 200 mg/litre and DO level of 2 mg/litre falls at that location. Assuming complete mixing of wastewater and river water, the immediate DO deficit (in mg/litre, round off to two decimal places), is ________.

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Two identically sized primary settling tanks receive water for Type-I settling (discrete particles in dilute suspension) under laminar flow conditions. The Surface Overflow Rate (SOR) maintained in the two tanks are 30 m

.d and 15 m

.d. The lowest diameters of the particles, which shall be settled out completely under SORs of 30 m

.d and 15 m

.d are designated as

and

, respectively. The ratio

(round off to two decimal places) is ____________.

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A water supply scheme transports 10 MLD (Million Litres per Day) water through a 450 mm diameter pipeline for a distance of 2.5 km. A chlorine dose of 3.50 mg/litre is applied at the starting point of the pipeline to attain a certain level of disinfection at the downstream end. It is decided to increase the flow rate from 10 MLD to 13 MLD in the pipeline. Assume exponent for concentration, n = 0.86. With this increased flow, in order to attain the same level of disinfection, the chlorine dose (in mg/litre) to be applied at the starting point should be

Your answerChoose one option.

3.95

4.40

4.75

5.55

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Alkalinity of water, in equivalent/litre (eq/litre), is given by

Where, represents concentration in mol/litre. For a water sample, the concentrations of HCO₃⁻ = 2×10⁻³ mol/litre, CO₃²⁻ = 3.0 × 10⁻⁴ mol/litre and the pH of water = 9.0. The atomic weights are: Ca = 40; C = 12; and O = 16. If the concentration of OH⁻ and H⁺ are NEGLECTED, the alkalinity of the water sample (in mg/litre as CaCO₃), is

Your answerChoose one option.

130.4

100.0

50.0

65.2

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Surface Overflow Rate (SOR) of a primary settling tank (discrete settling) is 2000 litre/m

per day. Kinematic viscosity of water in the tank is 1.01×10

/s. Specific gravity of the settling particles is 2.64. Acceleration due to gravity is 9.81 m/s

. The minimum diameter (in μm, round off to one decimal place) of the particles that will be removed with 80% efficiency in the tank, is _____.

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The ion product of water (pK_w) is 14. If a rain water sample has a pH of 5.6, the concentration of OH⁻ in the same (in 10⁻⁹ mol/litre, round off to one decimal place), is ________.

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A gaseous chemical has a concentration of 41.6 μmol/m

in air at 1 atm pressure and temperature 293 K. The universal gas constant

is 82.05×10

atm)/(mol K). Assuming that ideal gas law is valid, the concentration of the gaseous chemical (in ppm, round off to one decimal place), is _____.

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A sample of water contains an organic compound C₈H₁₆O₈ at a concentration of 10⁻³ mol/litre. Given that the atomic weight of C = 12 g/mol, H = 1 g/mol, and O = 16 g/mol, the theoretical oxygen demand of water (in g of O₂ per litre, round off to two decimal places), is ________.

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Which one of the following options contains ONLY primary air pollutants?

Your answerChoose one option.

Hydrocarbons and nitrogen oxides

Hydrocarbons and ozone

Ozone and peroxyacetyl nitrate

Nitrogen oxides and peroxyacetyl nitrate

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Analysis of a water sample revealed that the sample contains the following species. CO₃²⁻, Na⁺, H⁺, PO₄³⁻, Al³⁺, H₂CO₃, Cl⁻, Ca²⁺, Mg²⁺, HCO₃⁻, Fe²⁺, OH⁻ Concentrations of which of the species will be required to compute alkalinity?

Your answerChoose one option.

CO₃²⁻, H⁺, HCO₃⁻, OH⁻

CO₃²⁻, H⁺, H₂CO₃, HCO₃⁻

CO₃²⁻, H₂CO₃, HCO₃⁻, OH⁻

H⁺, H₂CO₃, HCO₃⁻, OH⁻

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GATE CE area:environmental-engineering PYQs

Question 25

Question 25

Question 37

Question 37

Question 52

Question 52

Question 53

Question 54

Question 9

Question 10