Match List (treatment of liquid waste) with its brief description:
List I
i.Primary treatment
ii.Secondary treatment
iii.Tertiary treatment
List II
a.Use of anaerobic bacteria to degrade the biodegradable matter
b.Disinfecting process for removal of bacteria and any dissolved organic solids
c.To separate the solids
Ai-c, ii-b, iii-a
Bi-c, ii-a, iii-b ✓ Correct
Ci-b, ii-c, iii-a
Di-a, ii-b, iii-c
Correct answer: (B) i-c, ii-a, iii-b
Explanation
Primary treatment pairs with separating the solids from the liquid waste.
Secondary treatment pairs with using anaerobic bacteria to degrade the biodegradable matter.
Tertiary treatment pairs with the disinfecting process that removes bacteria and dissolved organic solids.
Primary is physical settling, secondary is biological breakdown and tertiary is final polishing.
The stages run in this order so each removes what the previous one left.
Tertiary-treated water can be clean enough for reuse in irrigation.
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