15.  Which of the following chemical is sometime added in the process of coagulation and flocculation?
A.Aluminum sulphate
B.Aluminum oxide
C.Calcium chloride
D.None of these

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16.  Which of the following physical method is used as germicidal in modern time for the treatment of drinking water?
A.Chlorination
B.Treating with potassium permagnate
C.UV radiation
D.Treating with bleaching powder

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17. Sanitizer used specifically for vitreous enamel are
A.strong alkalis
B.strong acids
C.weak alkali with sodium silicate
D.none of these

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18. The common methods used for disinfection in waste water treatment plants are
A.chlorination
B.UV light
C.both (a) and (b)
D.Phenolic solvent

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19. Inhibitors are used along with sanitizer to
A.improve their action
B.to prevent corrosion
C.both (a) and (b)
D.none of these

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20. Sanitizers used for rubber made equipments are
A.strong acids
B.strong alkalis
C.combination of both
D.none of these

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21. Which of the following substances are commonly used in a filter?
A.Charcoal
B.Sand
C.Both (a) and (b)
D.Aluminum chloride

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