This set of Environmental Engineering Interview Questions and Answers for freshers focuses on “Removal of Iron, Manganese, Colour, Odour and Taste”.
1. Iron and Manganese are generally present in water supplies as ____________
a) Suspension
b) Solution
c) Colloidal particles
d) Either suspension or solution
View Answer
Explanation: Iron and Manganese are generally present in water supplies in the form of hydrated oxide as suspension and bicarbonates as a solution.
2. What concentration of iron and manganese will cause unpleasant taste and odor of water?
a) 1ppm
b) 2ppm
c) 3ppm
d) >3ppm
View Answer
Explanation: When the concentration of iron and manganese is greater than 3, it will result in unpleasant taste and odor, unwanted precipitation and difficulties in manufacturing processes.
3. The presence of Sulfate iron in the water results in ____________
a) Odorless water
b) Acidity in water
c) Colorless water
d) Growth of crenothrix in water mains
View Answer
Explanation: The presence of Sulfate iron in the water results in acidity in water and corrosiveness on iron and brass.
4. The reddish tinge in the water is due to the presence of ____________
a) Zinc
b) Copper
c) Iron
d) Manganese
View Answer
Explanation: The reddish tinge in the water is due to the presence of iron. Water contains iron by the reaction of CO2 in contact with iron ore forming soluble ferrous bicarbonate.
5. The brown tinge in the water is due to the presence of ____________
a) Zinc
b) Copper
c) Iron
d) Manganese
View Answer
Explanation: The brown tinge in the water is due to the presence of manganese, which occurs when it is present in an amount greater than 0.3ppm.
6. By aeration process, dissolved iron is oxidized into ____________
a) Ferrous oxide
b) Ferric oxide
c) Ferrous hydroxide
d) Ferric hydroxide
View Answer
Explanation: By aeration process, dissolved iron is oxidized into ferric oxide, which is insoluble in water.
7. By which process dissolved manganese compounds can be converted into insoluble manganese compounds?
a) Aeration
b) Coagulation
c) Sedimentation
d) Flocculation
View Answer
Explanation: The dissolved manganese compounds can be converted into insoluble manganese compounds by aeration The precipitated floc can be settled down in settling tanks.
8. For removal of iron from water ________ mg of oxygen is required.
a) 0.14
b) 0.50
c) 1
d) 1.5
View Answer
Explanation: The reaction for removal of iron from water is – 4Fe + O2 + 10H2O = 4Fe (OH)3 + 8H
1mg of Fe requires 0.14 mg of O2.
9. For removal of manganese from water ________ mg of oxygen is required.
a) 0.14
b) 0.50
c) 0.29
d) 0.90
View Answer
Explanation: The reaction for removal of manganese from water is – 4Mn + 3O2 + 6H2O = 6MnO2 + 12H
1mg of Mn requires 0.29 mg of O2.
10. Removal of manganese from water takes place at a pH of ______
a) 1.5
b) 3
c) 6
d) 9.4
View Answer
Explanation: Removal of manganese from water takes place at a pH between 9.4 to 9.6. Pre- chlorination up to 0.7 to 1 mg/l affect the oxidation and precipitation of manganese.
11. When small amounts of iron and manganese are present in water, they are removed by ____________
a) Aeration
b) Coagulation
c) Manganese zeolite
d) Filtration
View Answer
Explanation: When small amounts of iron and manganese are present in water, they are removed by manganese zeolite where iron and manganese are oxidized to insoluble hydrated oxides which are removed by filtration action of zeolite bed.
12. Removal of iron from water takes place at a pH of ______
a) 1.5
b) 3
c) 8.2
d) 9.4
View Answer
Explanation: Removal of iron from water takes place at a pH of 8.2. It can be removed in an oxidized condition by softening water by the excess lime process.
13. The taste produced by a microorganism, can be controlled by ____________
a) Potassium per-manganate
b) Potassium dichromate
c) Sodium chloride
d) Iodine
View Answer
Explanation: The taste produced by a microorganism, can be controlled by potassium per-manganate. It can be controlled alone or in combination with chlorine.
14. Which of the following regarding ozonation is incorrect?
a) Improves the appearance of water
b) Removes traces of color
c) Remove odor
d) Remove phenolic and algae taste
View Answer
Explanation: Ozonation improves the appearance of water, removes traces of color, remove odor and is also effective against earthy and moldy tastes and odor.
Sanfoundry Global Education & Learning Series – Environmental Engineering.
To practice all areas of Environmental Engineering for Interviews, here is complete set of 1000+ Multiple Choice Questions and Answers.
If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]
- Apply for 1st Year Engineering Internship
- Check Environmental Engineering Books
- Practice Mining Engineering MCQs
- Check Mining Engineering Books
