Treatment of Sewage · Environmental Engineering · GATE CE

Marks 2

In the following table, identify the correct set of associations between the entries in Column - 1 and Column-2.

Column-1	Column-2
P: Reverse Osmosis	III: Concentration Polarization
Q: Trickling Filter	I: Ponding
R: Coagulation	IV: Charge Neutralization
S: Adsorption	II: Freundlich Isotherm

GATE CE 2023 Set 1

The wastewater inflow to an activated sludge plant is 0.5 m3/s, and the plant is to be operated with a food to microorganism ratio of 0.2 mg/mg-d. The concentration of influent biodegradable organic matter of the wastewater to the plant (after primary settling) is 150 mg/L, and the mixed liquor volatile suspended solids concentration to be maintained in the plant is 2000 mg/L. Assuming that complete removal of biodegradable organic matter in the tank, the volume of aeration tank (in m3, in integer) required for the plant is _________.

GATE CE 2023 Set 1

In a city, the chemical formula of biodegradable fraction of municipal solid waste (MSW) is C₁₀₀H₂₅₀O₈₀N. The waste has to be treated by forced-aeration composting process for which air requirement has to be estimated.

Assume oxygen in air (by weight) = 23% and density of air = 1.3 kg/m³. Atomic mass : C = 12, H = 1, O = 16, N = 14.

C and H are oxidized completely whereas N is converted only into NH₃ during oxidation.

For oxidative degradation of 1 tonne of the waste, the required theoretical volume of air (in m³/tonne) will be (round off the nearest integer)

GATE CE 2022 Set 2

A sewage treatment plant receives sewage at a flow rate of 5000 m³/day. The total suspended solids (TSS) concentration in the sewage at the inlet of primary clarifier is 200 mg/L. After the primary treatment, the TSS concentration in sewage is reduced by 60%. The sludge from the primary clarifier contains 2% solids concentration. Subsequently, the sludge is subjected to gravity thickening process to achieve a solids concentration of 6%. Assume that the density of sludge, before and after thickening, is 1000 kg/m³. The daily volume of the thickened sludge (in m³/day) will be _________. (round off to the nearest integer)

GATE CE 2022 Set 2

A wastewater sample contains two nitrogen species, namely ammonia and nitrate. Consider the atomic weight of N, H, and O as 14 g/mol, 1 g/mol, and 16 g/mol, respectively. In this wastewater, the concentration of ammonia is 34 mg NH₃/liter and that of nitrate is 6.2 mg NO$$_3^ - $$/liter. The total nitrogen concentration in this wastewater is _________ milligram nitrogen per liter.

(round off to one decimal place)

GATE CE 2022 Set 1