Treatment of Sewage · Environmental Engineering · GATE CE
Marks 2
A community generates 1 million litres/day (MLD) of wastewater. This wastewater is treated using activated sludge process (ASP). The working volume of the aeration tank of the ASP is $250 \mathrm{~m}^3$, and the biomass concentration in the tank is $3000 \mathrm{mg} / \mathrm{L}$. Analyses results showed that a biomass concentration of $10 \mathrm{mg} / \mathrm{L}$ is present in the treated effluent from the secondary sedimentation tank of the ASP. Sludge wastage from the system is at a rate of $5000 \mathrm{~L} /$ day with a biomass concentration of $10000 \mathrm{mg} / \mathrm{L}$. The system is in steady state condition.
The biological sludge residence time (BSRT) of the system (in days) is _________ (round off to one decimal place).
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 |
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)
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)
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)