Municipal Solid Waste Management

01

PYQ 2022

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water-wastewater-treatment-and-management ID: gate-es-

For effluents generated by a molasses-based distillery and wood-based pulp and paper industry, which of the following statement(s) is/are NOT correct?

1

Both the effluents have dark colour.

2

Both the effluents have high toxicity.

3

Both the effluents generally have BOD greater than 15{,}000 ppm.

4

Both the effluents have high pH.

02

PYQ 2022

medium

water-wastewater-treatment-and-management ID: gate-es-

Clean water is passed through a bed of uniform spherical sand at a filtration velocity of 0.002 m/s. Sand grains are 0.4 mm diameter, specific gravity 2.65, bed depth = 0.67 m, porosity . Water density = 998.2 kg/m, viscosity = Pa\cdots. Friction factor: where is Reynolds number. The headloss (in m, rounded off to three decimal places) using the Carman-Kozeny equation is __________.}

Official Solution

Correct Option: (1)

$Sand grain diameter: Filtration velocity: Reynolds number: Friction factor: Headloss from Carman-Kozeny equation: Substitute values: Compute stepwise: Final answer:$

03

PYQ 2022

medium

water-wastewater-treatment-and-management ID: gate-es-

$Which of the following statement(s) is/are NOT correct while comparing continuously stirred tank reactor (CSTR) and plug flow reactor (PFR)?$

1

$CSTR and PFR are normally operated under steady state condition.$

2

$There is complete homogeneity in the CSTR while there are concentration variations within the PFR.$

3

$The overall reaction carried out in a PFR is always higher than that in a CSTR for the same total volume.$

4

$Reaction kinetics do not play any role in choosing between a CSTR and PFR.$

Official Solution

Correct Option: (3)

$Statement (A) is correct because both CSTR and PFR typically operate under steady state conditions. Statement (B) is correct because CSTR is perfectly mixed while PFR has axial concentration gradients. Statement (C) is NOT correct: a PFR is only more efficient for reactions of order . For zero-order or first-order reactions, performance may be equal; hence it is not “always” higher. Statement (D) is NOT correct: reaction kinetics play a crucial role in selecting between CSTR and PFR, especially the reaction order and rate. Final Answer: (C), (D)$

04

PYQ 2022

medium

water-wastewater-treatment-and-management ID: gate-es-

$Which one of the following statements is NOT correct with respect to a batch reactor?$

1

$No reactant is added after the reactor has started operation.$

2

$No product is withdrawn during the course of the reactor operation.$

3

$The reactor operates under steady state.$

4

$The reactor operation is carried out for a pre-specified duration.$

Official Solution

Correct Option: (1)

$Step 1: Understand batch reactor fundamentals. A batch reactor is a closed system in which all reactants are charged at the beginning. No reactant enters and no product leaves during operation. The mass inside the reactor remains fixed during the process. Step 2: Check each statement. (A) True — no reactant is added after start-up. This is a defining feature of batch reactors. (B) True — no product is removed until the reaction is complete. (C) False — batch reactors do \emph{not} operate at steady state. Conditions (concentration, temperature, reaction rate) vary continuously with time. (D) True — batch reactors run for a fixed or predetermined reaction time. Thus the only incorrect statement is (C). Final Answer: (C)$

05

PYQ 2023

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water-wastewater-treatment-and-management ID: gate-es-

$Ultimate analysis of an MSW sample (mass fractions, % by weight): C = 48, H = 6, O = 35, N = 6, Ash = 5. For burning 1 kg of this MSW (air contains only O and N ), the maximum CO emitted is ________________ (in kg, rounded off to three decimals).$

Official Solution

Correct Option: (1)

$Step 1: Determine available carbon in 1 kg waste. Mass of carbon . Moles of C . Step 2: ``Maximum CO '' assumption. All C CO (no CO/soot). So moles of CO moles of C kmol. Step 3: Convert moles of CO to mass. Mass CO . Final Answer:\fbox{1.760 kg}$

06

PYQ 2023

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water-wastewater-treatment-and-management ID: gate-es-

$Ms. Anita uses a BS-IV two-wheeler petrol scooter (mileage km/L) to travel km every day. She exchanges this with an electric scooter that consumes electricity at kWh per km (i.e., kWh/km). Petrol and electricity prices are Rs. /L and Rs. /kWh, respectively. Maintenance costs of both are negligible. The \emph{operational cost saved in a year} is __________________ (in Rs., in integer).$

Official Solution

Correct Option: (1)

$Step 1: Convert all given performance numbers to ``per km'' costs. Petrol scooter: Mileage km/L fuel per km L/km. Cost per km . Electric scooter: Use kWh/10 km kWh/km. Cost per km . Step 2: Daily operating cost for 30 km. Petrol: . Electric: . Step 3: Daily savings and annual savings (assuming 365 days). Saving/day . Saving/year Report as integer . Final Answer:\fbox{19{,}327 Rs.}$

07

PYQ 2023

medium

water-wastewater-treatment-and-management ID: gate-es-

$A city generates on average 1000 metric tonnes/day (t/d) of municipal solid waste and follows an integrated waste management system. 15% of the total waste is recycled, 40% used to produce compost, 25% converted to refuse derived fuel (RDF) with 80% efficiency, and the remaining disposed in a sanitary landfill. The calorific value of the RDF is 15 MJ/kg. The electrical energy that could be generated from the RDF with a thermal-to-electrical conversion efficiency of 20% is ____________________ (in MWh/d, rounded off to two decimal places).$

Official Solution

Correct Option: (1)

$Step 1: Mass of waste routed to RDF. Fraction to RDF of 1000 t/d t/d of feed to the RDF process. Process efficiency RDF actually produced t/d. Step 2: Daily thermal energy in the RDF. Step 3: Convert thermal energy to electrical energy (20% efficiency). Step 4: Convert MJ to MWh. . Hence, Final Answer:$

08

PYQ 2023

medium

water-wastewater-treatment-and-management ID: gate-es-

$An industry with an effective stack height of 80 m emits 1200 g/h of CO. The windrose indicates wind speed m/s. At a downwind distance of 2 km (plume centerline), the dispersion coefficients depend on wind direction as per the table below. Air Pollution Concentration Calculation During the maximum duration of the year (i.e., the most frequent wind direction from the windrose), the ground-level PM 2.5 concentration is to be computed at the plume centerline at 2 km. Find the concentration (in μg/m 3, rounded off to two decimal places). Dispersion Coefficients (in m) Wind Direction Dispersion Coefficients (in m) Northeast Crosswind: 50, Vertical: 20 North Crosswind: 45, Vertical: 30 Northwest Crosswind: 40, Vertical: 35 East Crosswind: 45, Vertical: 30 Southeast Crosswind: 55, Vertical: 35 South Crosswind: 60, Vertical: 40 Southwest Crosswind: 65, Vertical: 45 West Crosswind: 70, Vertical: 50 Table 1: Dispersion coefficients based on wind direction$

Official Solution

Correct Option: (1)

$Step 1: Identify the most frequent wind direction and corresponding . From the windrose, the Northwest direction has the maximum frequency. From the table (for 2 km):, . Step 2: Convert source strength to consistent units. Emission rate . Step 3: Use the centerline ground-level Gaussian plume formula (with image reflection). For a completely mixed atmosphere and ground reflection, centerline, ground level : where is the effective stack height and . Step 4: Evaluate the exponential term. Step 5: Compute the denominator . Step 6: Calculate concentration. Final Answer:$

High-Yield Trend

Chapter Questions
8 MCQs

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Wind Direction	Dispersion Coefficients (in m)
Northeast	Crosswind: 50, Vertical: 20
North	Crosswind: 45, Vertical: 30
Northwest	Crosswind: 40, Vertical: 35
East	Crosswind: 45, Vertical: 30
Southeast	Crosswind: 55, Vertical: 35
South	Crosswind: 60, Vertical: 40
Southwest	Crosswind: 65, Vertical: 45
West	Crosswind: 70, Vertical: 50

Municipal Solid Waste Management

High-Yield Trend

Chapter Questions 8 MCQs

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Chapter Questions
8 MCQs