---
title: "Removal of taste and odour"
subject: "Water Supply Engineering"
chapter: 6
key: "semester_5/water_supply_engineering:taste-odour-removal"
source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/taste-odour-removal
site: BCT Engineering
---

# Removal of taste and odour

Water Supply Engineering · Chapter 6: Water Treatment

- Asked in: 2080 Bhadra, 5 marks
- Video: [CE 405 - EE 1 | Module 5 - Lecture 4 | Colour, Taste & Odour Removal  in the Treatment of Water](https://www.youtube.com/watch?v=VxHiMUK9lEM) — Alex -E Academy
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/water_supply_engineering/taste-odour-removal
- Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-6

## Question

Describe briefly the methods of removal of tastes and odour in water.

## Short answer

Taste and odour are removed by aeration (volatile gases), activated carbon adsorption (most effective for organics), break-point chlorination or ozone/permanganate oxidation, copper sulphate for algae, and coagulation–filtration.

## Answer

Taste and odour in water are caused by dissolved gases (H$_2$S, CO$_2$), decaying vegetation and algae, industrial wastes, phenols, and iron, manganese and chlorine compounds. The methods of removal are as follows.

1. **Aeration**: the water is exposed to air (cascade, spray, diffusion), which drives out H$_2$S, CO$_2$ and volatile organics and oxidises Fe and Mn.
2. **Activated carbon adsorption**: powdered activated carbon (PAC) 5 to 50 mg/l is added before the filters, or granular (GAC) is used in a filter bed. It adsorbs organic compounds, phenols and chlorine tastes. It is the most effective method.
3. **Chlorination**: break-point chlorination and chlorine dioxide oxidise organic compounds and ammonia, and destroy taste-causing algae and bacteria.
4. **Oxidation by potassium permanganate or ozone**: ozone and KMnO$_4$ destroy odour-producing organic substances.
5. **Copper sulphate (CuSO$_4$) dosing** (0.3 to 0.5 mg/l) in storage reservoirs to kill algae which cause the taste and odour.
6. **Coagulation, sedimentation and filtration**: remove colloids and algae together with the floc; micro-straining removes algae.
7. **Prevention at source**: protect the catchment from pollution and avoid stagnant, stratified water.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which method is described as the most effective for taste and odour?
   A. Plain sedimentation
   B. Activated carbon adsorption (PAC or GAC)
   C. Ion exchange
   D. Alum coagulation alone
   Answer: B. Activated carbon adsorbs organics, phenols and chlorine tastes. (Key point: Most effective method)

2. How is algae-caused taste and odour controlled in storage reservoirs?
   A. Dosing 50 mg/l of lime
   B. Adding brine
   C. Dosing copper sulphate at about 0.3 to 0.5 mg/l
   D. Raising the water level
   Answer: C. CuSO4 kills algae that produce taste and odour. (Key point: Algae control)

3. What does aeration do for taste and odour?
   A. It adds chlorine to the water
   B. It adsorbs phenols
   C. It softens the water
   D. It drives out H2S, CO2 and volatile organics and oxidises Fe and Mn
   Answer: D. Aeration strips dissolved gases and volatiles. (Key point: Aeration role)

## Related in Water Supply Engineering

- [Causes of taste and odour in water](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Ataste-odour-causes) — Water Supply Engineering, chapter 4