NPTEL Wastewater Treatment And Recycling Week 8 Assignment Solutions
NPTEL Wastewater Treatment And Recycling Week 8 Assignment Answer 2023
1. Settleable inorganic and organic solids removed from raw wastewater, are components of:
a. Screenings
b. Primary Sludge
c. Secondary Sludge
d. Digested Sludge
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2. The sludge produced from the secondary clarifier of a conventional STP is known as:
a. Screenings and Grit
b. Primary sludge
c. Digested sludge
d. Waste activated sludge
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3.
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4. Increasing the solid content of the sludge through mechanical or gravity thickeners, leads to:
a. No change in the total volume of sludge
b. Increase in the total volume of sludge
c. Decrease in the total volume of sludge
d. Fluctuations in the total volume of the sludge
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5. Which of the followings are examples of mechanical sludge thickening systems?
a. Filter Press. and Belt Press
b. Screw Press, and Rotary Drums
c. Centrifuges
d. All of the above
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6. In the process of anaerobic sludge digestion, organic matter is converted to:
a. COz
b. CHa
c. New bacterial cells
d. All of the above
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7. A sludge digestion process usually leads to:
a. Less water content in the sludge
b. Less total mass of solids in the sludge
c. Higher total mass of solids in the sludge
d. Digestion process does not alter liquid or solid mass in the sludge
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8. Coagulants such as ferric chloride, alum or organic polymers may be added to wastewater sludge for:
a. Sludge stabilization
b. Sludge thickening
c. Sludge conditioning
d. Sludge hygienisation
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10. Identify the correct statements regarding sludge dewatering:
Statement I: Sludge Drying Beds are one of the simplest methods of dewatering, but they have large land footprint.
Statement II: Dewatered sludge essentially have zero or near zero water content.
a. Statement I is correct, while statement II is incorrect
b. Statement II is correct. while statement I is incorrect
c. Both. statements I and II are correct
d. Both. statements I and II are incorrect
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11. Water content of a 6400 kg/d wet sludge was reduced from 98.5 % to 96 % using a sludge thickening unit. What’s the net change in the total quantity of dry solids present in the sludge through this thickening process:
a. 0 % No change)
b. Increased by 2.5 %
c. Decreased by 2.5 %
d. Increased by 250 %
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12. A thickened sludge is having the ratio of volatile to total solids (VS/IS) as 0.75. The sludge is further digested where 72% of the organic (volatile) fraction is converted to liquid and gaseous products. Neglecting any loss in inorganic (non-volatile) fraction of solids during digestion process, the VS/TS ratio of the digested sludge would be:
a. 0.93
b. 0.68
c. 0.54
d. 0.32
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13. The total amount of dry solids in the thickened sludge is (in kg/d):
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14. The total volume of sludge produced after sludge thickening is (in m3/d):
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15. Assuming no reduction in the inorganic fraction of solids during the digestion, the percentage reduction in the organic fraction of solids during the digestion process is (in %):
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