GATE ES area:environmental-engineering PYQs & Answers — Page 5

Questions 41–50 of 55. Imported answers require independent review unless marked reviewed.

A sewage treatment plant with a capacity of 10 million litres per day (MLD) is treating the sewage through an aerobic biological process. The inlet and outlet BOD are measured as 100 and 30 mg/l, respectively. If the mixed microbial culture has an observed biomass yield of 0.5 g Volatile Suspended Solids (VSS)/g BOD, the sludge production rate (in kg per day, rounded off to one decimal place) when the plant is operating at 80% capacity will be __________.

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A centrifuge is processing 1000 litres per hour of water containing 2 g per litre of suspended solids. The thickened slurry coming out of the centrifuge has solids concentration of 20 g per 100 ml. If the centrifuge has 99% efficiency based on solids separation, the flow rate (in litres per hour, rounded off to one decimal place) of the supernatant stream will be __________.

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A sample of air is collected in the morning at an ambient temperature of 25 °C. The concentration of carbon monoxide (CO) in this sample is 30 ppm (ppm by volume). The same sample is analysed later in the afternoon when the sample temperature is 35 °C. The analysis results will show the CO concentration as __________.

Your answerChoose one option.

< 29 ppm

30 ppm

= 30 ppm

= 29 ppm

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In fluid statics, the line of action of the buoyant force always acts through the ____________________.

Your answerChoose one option.

centre of gravity of any submerged body

centroid of the volume of any floating body

centroid of the displaced volume of fluid by the body

centroid of the volume of fluid vertically above the body

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Which of the following causes ‘Type-I’ settling in a sedimentation tank?

Your answerChoose one option.

Agglomeration

Compression

Force of gravity

Charge neutralization

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Chlorine is most effective as a water disinfectant at a pH of __________.

Your answerChoose one option.

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A flocculation tank used for water treatment has a velocity gradient (G) of 800 s⁻¹. The volume of the tank is 40 m³. The dynamic viscosity of water is 9×10⁻⁴ N·s/m². The theoretical power required to maintain the given velocity gradient is __________ kW (rounded off to the nearest integer).

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A water jet discharging from a 4 cm diameter orifice has a diameter of 3.5 cm at its vena contracta. The coefficient of velocity is defined as the ratio of the actual velocity of the jet at vena contracta to the theoretical velocity of the jet. If the coefficient of velocity is 0.98, the coefficient of discharge for the orifice will be __________ (rounded off to two decimal places).

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A sewage treatment plant (STP) receives sewage at a flow rate of 20000 m³ per day. The sewage has 200 mg/L of suspended solids. Assume 60 % suspended solids are removed in the primary clarifier. The underflow (i.e. sludge) removed from the clarifier contains 5 % solids (by weight).

The daily volume of the sludge generated will be ______ m³ per day.

Assume sludge density = 1000 kg/m³.

Your answerChoose one option.

480

800

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In air pollution, which of the following is/are classified as primary pollutants?

Your answerSelect all correct options. You can choose more than one.

Carbon monoxide (CO)

Sulphur dioxide (SO₂)

Ozone (O₃)

Nitrogen dioxide (NO₂)

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GATE ES area:environmental-engineering PYQs

Question 62

Question 63

Question 4

Question 5

Question 9

Question 15

Question 23

Question 25

Question 32

Question 37