The GATE Grind

GATE 2025 CE (CE2) – Question 17

Water and Waste Water Quality and Treatment · Sewerage system design and quantity of domestic wastewater · 1 mark · Multiple choice

The bacteria mainly responsible for crown corrosion in a sewer is ______.

  1. Methanogenic bacteria
  2. Denitrifying bacteria
  3. Sulphur reducing bacteria
  4. Pseudomonas bacteria

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Show answer and explanation

Correct answer: (C) Sulphur reducing bacteria

Explanation

Sulphate-reducing bacteria in the slime of the sewer produce hydrogen sulphide. The H₂S escapes into the air above the flow and is oxidised to sulphuric acid on the crown of the pipe, which corrodes the concrete.