Question

Activated carbon is added to water treatment for removing

• A. colour
• B. tastes and odours
• C. turbidity
• D. corrosiveness

Hint:

Activated carbon's high porosity and large surface area make it an excellent adsorbent. This property is particularly effective for removing dissolved organic compounds, which are often responsible for undesirable tastes, odours, and colours in water. It is a tertiary treatment step often used for polishing water quality.

Answer 1

The Correct Option is B

Step 1: Understand Activated Carbon in Water Treatment.
Activated carbon is a form of carbon that has been processed to have small, low-volume pores that increase the surface area available for adsorption or chemical reactions. It is widely used in water treatment.
Step 2: Analyze the primary functions of activated carbon in water treatment.
Activated carbon works primarily through adsorption. Adsorption is the process where molecules adhere to the surface of a solid. Activated carbon is particularly effective at adsorbing organic molecules. Common uses include:

• Removal of tastes and odours: Organic compounds are often responsible for undesirable tastes and odours in water (e.g., from algal blooms, decaying vegetation, industrial wastes). Activated carbon effectively adsorbs these compounds.
• Removal of dissolved organic matter: This can include natural organic matter (NOM), synthetic organic chemicals (SOCs) like pesticides, herbicides, and industrial solvents.
• Removal of colour: Many colour-causing compounds in water are organic and can be adsorbed by activated carbon. While activated carbon can remove colour, its most significant and widely recognized application is for tastes and odours.
• Removal of chlorine and chloramines: Activated carbon can remove residual disinfectants.

Step 3: Evaluate the given options in the context of activated carbon's primary role.

• (1) colour: Activated carbon can remove colour, but it's not its most prominent or primary use, especially when compared to tastes and odours.
• (2) tastes and odours: This is a major and widely recognized application of activated carbon in water treatment.
• (3) turbidity: Turbidity is caused by suspended solids. Activated carbon is an adsorbent, not primarily a filter for large suspended particles. While it can contribute to a slight reduction in very fine suspended solids, its main role is not turbidity removal, which is typically achieved through coagulation, flocculation, sedimentation, and filtration.
• (4) corrosiveness: Corrosiveness of water is related to its chemical properties (e.g., pH, alkalinity, dissolved oxygen, mineral content) that lead to corrosion of pipes. Activated carbon does not directly treat corrosiveness.

Step 4: Select the correct option.
Among the given options, the most significant and common purpose for which activated carbon is added to water treatment is for removing tastes and odours. $$\boxed{\text{tastes and odours}}$$