Wastewater Treatment MCQ with answer and solution

Concept

In one classification of treatment operations, chlorination, liming and recarbonation come under solute stabilization.

Step-by-step solution

1. Recall the functional groups of unit operations: ion transfer, solute stabilization, solids transfer, solids concentration, etc. 2. Ion transfer covers coagulation, precipitation, ion exchange and adsorption. 3. Solids transfer covers screening, sedimentation, flotation and filtration. 4. Solids concentration covers thickening, centrifugation and drying. 5. Solute stabilization covers chlorination, liming, recarbonation and superchlorination. 6. So the answer is (B).

Explanation

Chlorination, liming and recarbonation change dissolved substances into a stable, harmless form. They do not remove solids or exchange ions. So they are grouped under solute stabilization.

Why the other options are wrong

A: Ion transfer is coagulation, precipitation, ion exchange and adsorption. C: Solid transfer is screening, sedimentation, flotation and filtration. D: Solid concentration is thickening, centrifugation and sludge drying.

Shortcut

Chemicals that stabilise dissolved matter (chlorine, lime, CO2) = solute stabilization.

Common mistake

Choosing ion transfer because lime and chlorine are chemicals that react with ions.