Question

Which one of the following impurities is easiest to remove from wastewater?

• A. Colloids
  
• B. Bacteria
  
• C. Suspended solids
• D. Dissolved solids
  

Answer 1

The correct option is C Suspended solids

Bacteria

Bacteria are microorganisms that can cause disease in plants, animals and humans. Chlorination is used to kill these bacteria. It is a chemical method.

Colloids

Colloids are small particles that don’t settle on standing and impart turbidity and colour to the wastewater. Coagulation-flocculation processes are used to remove colloids as they sediment slowly. These are done by addition of coagulants like alum.

Dissolved solids

Dissolved organic solids are removed by biological treatment and the dissolved inorganic solids are removed by precipitation. These involve treatments which require sophisticated techniques.


Suspended solids

Suspended solids are the fine particles present in the wastewater which usually settle down on standing. These particles are removed easily by sedimentation and filtration.

Final answer
d. Suspended solids