1. The sedimentation basin should be made as deep as possible.
a) True
b) False
Explanation: The particle settling efficiency is independent of the depth of the basin and should be made as shallow as possible
2. What is formed when coagulant is added to water?
a) Scum
b) Soap
c) Bubbles
d) Floc
Explanation: When coagulant is added to water, then white gelatinous precipitate is formed called floc.
3. The chemical composition of Alum is _____________
a) Al2 (SO4)3.18H2O
b) Al2 (SO4)2.18H2O
c) Al3 (SO4)2.18H2O
d) Al4 (SO4)3.18H2O
Explanation: Alum is the most common and universal coagulant used in water treatment having chemical composition Al2 (SO4) 3.18H2O.
4. The chemical compound which is insoluble in water, formed when alum is added to water is _____________
a) Al (OH)3
b) CaSO4
c) CO2
d) Ca (OH)3
Explanation: Al2 (SO4)3.18H2O + 3Ca (HCO3)2 = 2Al (OH)3 + 3CaSO4 + 18H2O + CO2
Where Al (OH)3 is insoluble in water.
5. Which gas is released when alum is added to water?
a) Al (OH)3
b) CaSO4
c) CO2
d) Ca (OH)3
Explanation: Carbon dioxide gas is released when alum is added to water, which is corrosive to metals.
6. What indicates the permanent hardness when alum is added to water?
a) Al (OH)3
b) CaSO4
c) CO2
d) Ca (OH)3
Explanation: The presence of calcium sulfate indicates the permanent hardness in water when alum is added to water
7. Alum is effective when pH of water is between ____
a) 8-10
b) 6-8
c) 6.5-8.5
d) 7-9
Explanation: Alum is effective when pH of water is between 6.5-8.5. Its dose depends on turbidity, color, taste, pH and temperature of water
8. Why Alum is preferred over other coagulants?
a) It is easy to dewater the sludge formed
b) It imparts corrosiveness to water
c) It reduces taste and odor in addition to turbidity
d) The time required for floc formation is less
Explanation: Alum is preferred over other coagulants because it reduces the taste and odor in addition to turbidity and produce lighter flocs that can be broken easily.
9. The chemical composition of Chlorinated Copperas is __________
a) Fe2 (SO4)3 + FeCl3
b) FeSO4.9H2O
c) FeSO4.18H2O
d) Fe2 (SO4)3
Explanation: 6FeSO4.7H2O2 +3Cl2 = 2Fe2(SO4) 3 + 2FeCl3 + 7H2O
The ferric sulfate and ferric chloride so formed are called as Chlorinated Copperas.
10. Ferric chloride is effective over a pH range of __________
a) 3.5-6
b) 6.5-8
c) 3.5-6.5
d) 2-5
Explanation: Ferric chloride is effective over a pH range of 3.5-6.5 and above 8.5 whereas if Ferric sulfate is used then, it is effective over a pH range of 4-7 and above 9