Question

A water treatment process of removing suspended solids by destabilizing the suspended particles in water solutions is

• A. Clarks process
• B. Screening
• C. Coagulation
• D. Disinfection

Hint:

\textbf{Coagulation} is a water treatment process that destabilizes fine suspended and colloidal particles.
Coagulants (chemicals like alum) are added to neutralize particle charges, allowing them to aggregate into larger flocs.
These flocs can then be removed by settling (sedimentation) and filtration.
Screening removes large solids. Clarks process is for water softening. Disinfection kills pathogens.

Answer 1

The Correct Option is C

The question describes a water treatment process for removing suspended solids by destabilizing them. Many fine suspended solids (colloidal particles) in water are stable due to small size and surface charges (often negative), which cause them to repel each other and remain dispersed. Let's analyze the options:
(a) Clarks process: This is a water softening process used to remove temporary hardness (calcium bicarbonate) by adding slaked lime (calcium hydroxide). It causes precipitation of calcium carbonate. While it removes solids (precipitated hardness), its primary purpose is softening, not removal of general suspended solids by destabilization of existing particles.
(b) Screening: This is a physical process that removes larger floating or suspended solids from water by passing it through screens of various mesh sizes. It doesn't involve destabilizing fine particles.
(c) Coagulation: This is a chemical water treatment process used to remove fine suspended and colloidal particles that are too small to settle out or be filtered easily. It involves adding chemicals called coagulants (e.g., alum, ferric chloride, polyelectrolytes). These coagulants neutralize or reduce the surface charges of the colloidal particles, destabilizing them. This allows the particles to come together (agglomerate) to form larger, heavier flocs. These flocs can then be removed by subsequent processes like sedimentation (settling) and filtration. This matches the description perfectly.
(d) Disinfection: This process kills or inactivates pathogenic microorganisms in water to make it safe for drinking. Common methods include chlorination, UV irradiation, ozonation. It does not primarily remove suspended solids. The process of removing suspended solids by destabilizing the suspended particles is Coagulation. This is often followed by flocculation (gentle mixing to promote floc growth), sedimentation, and filtration. \[ \boxed{\text{Coagulation}} \]