Water treatment practice: To remove foul odour and unpleasant taste from drinking water, which treatment chemical or medium is most effective under standard plant conditions?

Introduction / Context:
Taste and odour episodes in potable water often stem from natural organics, algae by-products, or industrial contaminants. Utilities need a robust, economical method to polish water after clarification and disinfection so that consumers perceive it as clean and palatable. This question targets the best-practice solution for removing offensive tastes and odours.

Given Data / Assumptions:

• Finished water requires polishing for taste and odour.
• Conventional treatment steps (coagulation, sedimentation, filtration, disinfection) are in place.
• Operations prefer proven methods compatible with large-scale plants.

Concept / Approach:
Activated carbon—either powdered (PAC) dosed into the process or granular (GAC) in fixed beds—adsorbs a wide spectrum of organics responsible for taste and odour, including geosmin and MIB from algal blooms. Alum is a coagulant used to remove turbidity and some organics by enmeshment, but it is not optimized for odour-causing compounds. Bleaching powder (chlorine) disinfects but can form chlorinated by-products that may worsen taste if overdosed. Copper sulphate is an algicide for source water control, not a direct taste-and-odour adsorbent in finished water.

Step-by-Step Solution:
Identify target contaminants: trace organics causing taste/odour.Match unit process: adsorption on high-surface-area carbon removes these molecules efficiently.Select activated carbon as the appropriate solution.

Verification / Alternative check:
Industry guidance documents recommend PAC during seasonal events and GAC filters for continuous control. Pilot tests typically confirm sharp reductions in taste/odour compounds with carbon dosing or bed contactors.

Why Other Options Are Wrong:
Alum: Primarily a coagulant; limited impact on taste compounds alone.Bleaching powder: Disinfects but may create chlorinous taste.Copper sulphate: Controls algae in reservoirs; not a finishing adsorbent.

Common Pitfalls:

• Attempting to “mask” odour with higher chlorine doses, which often worsens palatability.
• Misapplying coagulants instead of adsorption when organics are dissolved.

Final Answer:
activated carbon