Subject :NSO Class : Class 7
Given are five processes in the treatment of sewage.
Arrange the processes in the correct order and select
the correct option.
(i) In the digester tank, many anaerobic bacteria
decompose the organic matter present in sludge
to produce biogas.
(ii) Solids are separated from liquids by using screens.
(iii) The clarified water is passed into aeration tank
that contains aerobic bacteria.
(iv) Impurities settle to the bottom of the tank in the
form of sludge in sand and grit chambers.
(v) Suspended microbes settle down at the bottom as
activated sludge and water is discharged into water
bodies.
A (iii) → (iv) → (v) → (i) → (ii)
B (ii) → (iv) → (i) → (iii) → (v)
C (i) → (iv) → (ii) → (v) → (iii)
D (ii) → (iii) → (iv) → (v) → (i)