The GATE Grind

GATE 2025 CE (CE1) – Question 32

Water and Waste Water Quality and Treatment · Water requirement, distribution system and drinking water treatment · 1 mark · Multiple select

Aeration is employed as a treatment option for the removal of several pollutants from contaminated water.

Identify the pollutant(s), where aeration is employed as a part of their removal:

  1. Iron
  2. Cadmium
  3. Manganese
  4. Zinc

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Show answer and explanation

Correct answer: (A) Iron; (C) Manganese

Explanation

Dissolved iron and manganese are present in their reduced, soluble forms. Aeration supplies oxygen, which oxidises them to insoluble ferric hydroxide and manganese dioxide that can then be removed by settling and filtration. Cadmium and zinc are not oxidised in this way, and they are removed by precipitation or other methods.