Match List-I (Unit Process) with List-II (Primary Purpose) and select the correct code:

Question

Match List-I (Unit Process) with List-II (Primary Purpose) and select the correct code:

List-I

i. Equalization

ii. Aeration

iii. Adsorption

iv. Disinfection

List-II

a. Pathogen removal

b. Reduction of variations

c. Supply oxygen

d. Removal of color/odour

Choose the correct match:

1. A. i-b, ii-c, iii-d, iv-a (Correct answer)
2. B. i-c, ii-b, iii-a, iv-d
3. C. i-b, ii-a, iii-d, iv-c
4. D. i-d, ii-c, iii-b, iv-a

Correct Answer

Option A — i-b, ii-c, iii-d, iv-a

Detailed Solution & Explanation

The correct answer is i-b, ii-c, iii-d, iv-a.

Key Points

• Each unit process exists to solve one specific problem:
  • i. Equalization - b. Reduction of variations. A holding basin evens out swings in flow, strength and pH so that downstream units see a steady load.
  • ii. Aeration - c. Supply oxygen. Air is transferred to the liquid to sustain aerobic micro-organisms, and it also strips volatile compounds and oxidises iron and manganese.
  • iii. Adsorption - d. Dissolved organics, colour, taste and odour are held on the surface of a medium, typically activated carbon.
  • iv. Disinfection - a. Pathogen removal. The final barrier, killing or inactivating pathogenic organisms.

Additional Information

• Equalization is the one most often undervalued. Industrial effluent arrives in batches of wildly different strength, and biological systems fail on shock loads, so an equalization tank is frequently what makes the rest of the plant workable at all.
• Adsorption is a surface phenomenon and so depends on surface area — which is why activated carbon, with an internal area of several hundred square metres per gram, is the standard medium. It is distinct from absorption, where the substance penetrates the bulk.
• Disinfection is not sterilisation: it targets pathogens, not all organisms. Chlorine, chloramines, ozone and UV are the usual agents, chlorine alone leaving a protective residual in the distribution system.
• In match questions of this kind, secure the two unambiguous pairings — here aeration and disinfection — and the rest follows by elimination.