NPTEL Wastewater Treatment and Recycling Week 5 Anssignment Answers 2024

1. Identify the correct statements regarding primary treatment of wastewaters:
Statement I: Primary treatment of wastewater typically aims for removal of dissolved organic matter.
Statement II: Primary treatment processes mainly rely of gravity settling for removal of solids.

a. Statement I is correct, while statement II is incorrect
b. Statement Il is correct, while statement I is incorrect
c. Both, statements I and Il are correct
d. Both, statements I and II are incorrect

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2. Which of the followings appear as appropriate velocity through screens:

a. 0.2 m/s
b. 0.8 m/s
c. 2.0 m/s
d. 5.0 m/s

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3. Gravel and cinders in the wastewater are typically removed in:

a. Grit Chamber
b. Bar Racks
c. Primary Sedimentation
d. Comminuting device

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4. Which of the following units are used for balancing variations in the flowrate and fluctuating pollutant load in the influent?

a. Screens
b. Gravity wells
c. Equalization tank
d. Sedimentation tank

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5. The real settling basins used for primary sedimentation usually have:

a. Discrete particle settling
b. Flocculent settling
c. Hindered settling
d. Compression settling

Answer :-

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7. As per CPHEEO, bottom slope in a rectangular settling basin is typically kept as:

a. 1 % towards inlet
b. 5 % towards center
c. 8 % towards outlet
d. 25 % towards sides

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8. For designing an ideal settling basin, overflow rate of settling basin is considered equal to the settling velocity of:

a. Smallest dia particle intended to be removed
b. Largest dia particle intended to be removed
c. Average dia particle intended to be removed
d. None of the above

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9. For treating 1 MLD wastewater, which of the following settling units would require least area, for the same settling efficiency?

a. Conventional Rectangular Settling Tank
b. Conventional Circular Settling Tank
c. Inclined Tube Settlers
d. Squire Settling Basin

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10. A spherical particle of dia 0.02 mm, and specific gravity 2.6 is settling in water of density 1000 kg/m’ and dynamic viscosity 1.002 × 10-3 Ns/m?. The terminal settling velocity of the particle would be:

a. 7 mm/s
b. 3.5 mm/s
c. 0.7 mm/s
d. 0.35 mm/s

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11. For ensuring head loss below 0.05 m, the maximum velocity through the bar screen having an approach velocity of 0.8 m/s should be:

a. 3.80 m/s
b. 2.27 m/s
c. 1.15 m/s
d. 0.64 m/s

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12. A 15 m long grit chamber is treating 12 MLD wastewater flow, with a flow through velocity of 0.25 m/s. The detention time for the grit chamber is:

a. 60 sec
b. 45 sec
c. 30 sec
d. 20 sec

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13. A 3.5 m deep circular sedimentation tank is treating 6000 m’/day wastewater flow at an overflow rate of 40 m/day. The approximate detention time of wastewater in the tank would be:

a. 3.0 hrs
b. 2.1 hrs
c. 1.6 hrs
d. 1.2 hrs