The amount of residual chlorine left in public water supply for safety against pathogenic bacteria is about______________?

Question: Fresh sewage is __________ in nature.
[A].

acidic

[B].

neutral

[C].

alkaline

[D].

highly acidic

Answer: Option C

Explanation:

No answer description available for this question.

Question: Corrosion in boilers can be prevented by
[A].

deaeration of feed water.

[B].

enhancing pH of feed water by adding alkali.

[C].

feeding sodium sulphite or hydrazine phosphate to the boilers, which combines with oxygen and prevents corrosion.

[D].

all (a), (b) and (c).

Answer: Option D

Explanation:

No answer description available for this question.

Question: Fresh domestic sewage is __________ in color.
[A].

grey

[B].

dark brown

[C].

red

[D].

black

Answer: Option A

Explanation:

No answer description available for this question.

Question: For existence of aquatic life in water, the dissolved oxygen content in it, should not be less than __________ ppm.
[A].

10000

[B].

5

[C].

500

[D].

1000

Answer: Option B

Explanation:

No answer description available for this question.