GATE ES kind:question PYQs & Answers — Page 39 — Exam Papers

Questions 381–390 of 390. Imported answers require independent review unless marked reviewed.

Topic practice 390 questionsPage 39 of 39

In a field test of a geological formation of permeable soil (porosity = 20 %), the hydraulic gradient was found to be 2 %. The actual seepage velocity of the flow was found to be 0.0025 m/s. Assume that the flow is in the laminar regime. The permeability (K) of the aquifer is ______ m/s (rounded off to three decimal places).

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An underground hazardous waste storage tank is leaking. The contaminant concentration directly beneath the site is 0.5 mg/L. The contaminant is travelling at an effective rate of 0.4 m per day towards a water well which is 2 km away. Assume that the degradation of the contaminant follows a first order reaction, and the initial concentration of the contaminant becomes half in 10 years. In this case, the contaminant concentration expected at the well under steady state conditions is ______ mg/L (rounded off to two decimal places).

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The net profit expected from a manufacturing unit is ₹ 6000 per year. The operational life of the unit is 15 years. Assuming a fixed discount rate of 8 % per annum, the net present worth of the profit earned over the operational life is ₹ ______ (answer in integer).

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A 900 mm internal diameter sewer is laid at a slope of 0.004 and has an actual flow of 0.15 m³/s. Assuming Manning’s roughness coefficient to be 0.013, the ratio of the actual flow to the flow when the sewer is running full is ______ (rounded off to two decimal places). Take

.

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A 10 million litres per day (MLD) sewage treatment plant (STP) is based on the Activated Sludge Process (ASP). First, the sewage undergoes primary treatment and the resulting treated sewage has BOD₅ of 140 mg/L concentration. This is further passed through a 1500 m³ capacity aeration tank (in ASP), where the mixed liquor volatile suspended solids (MLVSS) concentration is maintained at 300 mg/L. The concentration of BOD₅ of the treated sewage is 5 mg/L. The Food to Microorganism ratio (F/M) of the ASP is ______ day⁻¹ (rounded off to two decimal places).

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The municipal solid waste (MSW) generated in a community (population = 10000) is disposed on a 12×10⁴ m² landfill site, which can be filled to a total depth of 25 m (including soil cover). Assume that MSW is generated at a rate of 2.5 kg per person per day and its compacted density is 800 kg/m³. If the volumetric ratio of MSW and soil cover is 5:1, the useful life of the landfill site is ______ years (rounded off to the nearest integer).

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A mechanized stationary container system is proposed for waste collection from a commercial area. The container unloading time is 0.1 hours per container. There are two containers at each location and the drive time between the two locations is 0.2 hours. The maximum waste ‘pick-up time’ is 2.4 hours per trip. The ‘pick-up time’ starts at the instant the truck arrives at the first pick-up location and ends when the last container on the route is emptied. The maximum number of locations which can be covered in a trip by the collection vehicle are ______ (answer in integer).

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The molar concentrations (M, i.e. mol/L) of some ionic species in a water sample were estimated as follows: Na⁺ = 0.25 M; Ca²⁺ = 0.12 M; Cl⁻ = 0.32 M; HCO₃⁻ = 0.05 M. The ionic strength of this water sample is ______ M (correct up to two decimal places).

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Excess amount of solid calcium sulfate (CaSO₄) was added to a pure water sample (pH = 7) so that some solids remain undissolved at the equilibrium. The solubility product of CaSO₄ is 2×10⁻⁵ mol²/L². The molar concentration of SO₄²⁻ in this water sample at equilibrium will be ______ mol/L (rounded off to three decimal places).

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A facultative pond system for sewage treatment consists of two ponds in series. The hydraulic retention time (HRT) of each pond is 6 days. The total BOD₅ reduction through the entire pond system is 90 %. If the ponds are considered to be completely mixed, then the rate constant describing the BOD₅ removal is ______ day⁻¹ (rounded off to two decimal points). Assume that the rate constant is same for both the ponds.

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