Test: Quality & Characteristics of Sewage - 2 - Civil Engineering (CE) MCQ

Complete thorough treatment should generally be given to sewage before its disposal in a stream if the dilution factor available is:

• If the dilution factor is less than 350, thorough treatment is necessary.
• For a dilution factor below 250, the need for treatment becomes even more critical.
• When the dilution factor is less than 150, immediate and comprehensive treatment is essential to prevent environmental harm.

Thus, the correct answer is C: less than 150.

Algae dies out, though fish life may survive, in a river zone, known as

• Zone of degradation: This area is characterised by a decline in algae, yet fish may still be present.

• Zone of active decomposition: This zone is where organic matter breaks down, potentially affecting fish life.

• Zone of recovery: In this region, ecosystems begin to heal, allowing for regrowth of algae and fish.

• Zone of clear water: This area typically features healthy water quality, supporting both fish and algae.

The correct term for the river zone where algae dies but fish may survive is the zone of degradation.