Match List-I (Biological System) with List-II (Type of Growth / Configuration) and select the correct code:

Question

Match List-I (Biological System) with List-II (Type of Growth / Configuration) and select the correct code:

List-I

i. Activated Sludge

ii. Trickling Filter

iii. RBC

iv. UASB

List-II

a. Attached (rotating)

b. Attached (stationary)

c. Suspended (aeration+clarifier)

d. Anaerobic granular bed

Choose the correct match:

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

Correct Answer

Option A — i-c, ii-b, iii-a, iv-d

Detailed Solution & Explanation

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

Key Points

• The four systems classify by where the biomass sits and whether oxygen is present:
  • i. Activated Sludge - c. Suspended growth. Biomass floats freely as floc in the mixed liquor.
  • ii. Trickling Filter - b. Attached, stationary. Biofilm grows on a fixed bed of media over which wastewater trickles.
  • iii. RBC - a. Attached, rotating. Biofilm grows on discs that rotate through the wastewater.
  • iv. UASB - d. Anaerobic, with a granular sludge blanket and no aeration at all.

Additional Information

• The neat discriminator between the two attached-growth systems is what moves. In a trickling filter the wastewater moves past stationary media; in an RBC the media move through relatively still wastewater.
• The UASB is the only anaerobic unit of the four, which changes its economics entirely: no aeration energy, far less sludge, and recoverable biogas, at the cost of poorer effluent quality needing post-treatment.
• Suspended-growth systems need return activated sludge to hold their biomass inventory; attached-growth systems do not, because the biomass is anchored.
• Loading is expressed differently for each family — F/M ratio and MLSS for suspended growth, hydraulic and organic loading per unit media volume for attached growth.