Water Treatment for Taste and Odour Removal | Civil Engineering Optional Notes for UPSC PDF Download

Introduction

• Presence of organic matter, algae, dissolved hydrogen sulfide, industrial wastes like phenol, excessive chlorine, dissolved iron and manganese salts impart color, odor and taste to water.
• Several water treatment methods are employed to remove color, taste and odor.

Aeration Treatment

•   Aeration is the process of bringing water in intimate contact with air to absorb oxygen.
•   Removes iron, manganese, CO₂, H₂S and oxidizes certain organic impurities.
•   To a certain extent, bacteria are also killed.
•   Can remove only up to 10% of CO₂, residue of 3-5 mg/liter always remains.

Note: Excessive aeration should be avoided as it increases water's corrosive characteristics, may require de-aeration.

Aeration Treatment

Activated Carbon Treatment

• Activated carbon is obtained by charring wood or sawdust at 500°C in a closed vessel to expel hydrocarbons.
• Available in granular or powdered form.
• Highly porous and possesses free valencies, providing high adsorption capacity.
• Widely used for removing tastes and odors from public water supplies due to excellent properties of attracting gases, finely divided solid particles, and phenol-type impurities.
• Added to water either before or after coagulation with sedimentation, but always before filtration.

Advantages:

• Increases coagulation power of the process.
• Reduces chlorine demand.
• Excessive dose is not harmful.
• Simple process, requires nearly no skill.
• High efficiency in removing color, odor, and taste.

• Copper sulfate (CuSO₄.5H₂O) solution is applied with a dose of 0.5 to 0.75 mg/liter to treated water before distribution in mains.
• Can also be added to lakes or reservoirs.
• Helps in removing odors, tastes, and colors from water.
• Main advantage: Checks the growth of algae, even before production, and kills some bacteria.