26. Permanent hardness of water may be removed by the addition of

A. lime
B. soda ash
C. potassium permanganate
D. sodium bicarbonate

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27. Both temporary and permanent hardness of water can be removed on boiling water with

A. calcium hydroxide
B. sodium carbonate
C. calcium oxide
D. calcium carbonate

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28. Lagoons may be characterized as

A. anaerobic
B. facultative
C. aerated
D. all of these

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29. Temporary hardness of water may be removed by adding

A. calcium hydroxide
B. calcium carbonate
C. calcium chloride
D. sodium bicarbonate

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30. The maximum desirable limit (BIS of mercury in the drinking water is

A. 0.05 mg/l
B. 0.9 mg/l
C. 0.1 mg/l
D. 0.001 mg/l

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