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Subject :NSO    Class : Class 7

Read the following statements regarding waste-water treatment plant with one or two blanks. Select the option that correctly completes any two statements.
(i) ________ process allows settling of sand in the chambers.
(ii) The solid waste called _______settles down and lighter waste called ________ floats on the surface.
(iii) Secondary treatment involves use of_______.
(iv) ________ and ________ are used in tertiary treatment.

A (ii) sluge, scum; (iii) chemicals
B (iii) grit removal; (iv) chlorine, UV rays
C (ii) scum, sludge; (iii) bacteria
D (i) screening; (iv) aerobic, anaerobic bacteria

What is the answer for the fourth statement?

Ans 1:

Class : Class 9
chlorine and UV rays are tertiary treatment

Ans 2:

Class : Class 8

Ans 3:

Class : Class 7

Ans 4:

Class : Class 8
yeah...sludge settles and scum floats.

Ans 5:

Class : Class 8

Ans 6:

Class : Class 8
Sludge settles down while scum stays up

Ans 7:

Class : Class 9
Sludge settles while scum floats .you are right

Ans 8:

Class : Class 8

Ans 9:

Class : Class 7

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