List of top Water & Wastewater Treatment and Management Questions on Municipal solid waste management asked in 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$_2$ and N$_2$), the maximum CO$_2$ emitted is ________________ (in kg, rounded off to three decimals).

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).

An industry with an effective stack height of 80 m emits 1200 g/h of CO. The windrose indicates wind speed $u=3$ m/s. At a downwind distance of 2 km (plume centerline), the dispersion coefficients $(\sigma_y,\sigma_z)$ 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/m³, 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

Ms. Anita uses a BS-IV two-wheeler petrol scooter (mileage $=50$ km/L) to travel $30$ km every day. She exchanges this with an electric scooter that consumes electricity at $0.1$ kWh per $10$ km (i.e., $0.01$ kWh/km). Petrol and electricity prices are Rs. $90$/L and Rs. $3.5$/kWh, respectively. Maintenance costs of both are negligible. The \emph{operational cost saved in a year} is __________________ (in Rs., in integer).

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 $\eta = 0.35$. Water density = 998.2 kg/m$^3$, viscosity = $1.002\times10^{-3$ Pa·s. Friction factor: \[ f = 1.75 + \frac{150(1-\eta)}{Re}, \] where $Re$ is Reynolds number. The headloss (in m, rounded off to three decimal places) using the Carman–Kozeny equation is __________.}

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

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

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?