---
title: "Causes of taste and odour in water"
subject: "Water Supply Engineering"
chapter: 4
key: "semester_5/water_supply_engineering:taste-odour-causes"
source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/taste-odour-causes
site: BCT Engineering
---

# Causes of taste and odour in water

Water Supply Engineering · Chapter 4: Quality of Water

- Asked in: 2080 Bhadra, 3 marks
- Video: [TASTE, ODOUR AND COLOUR CONTROL OF WATER, PART 23, ENVIRONMENTAL ENGINERING](https://www.youtube.com/watch?v=eGYGc7cZ1_0) — Vidhya Focus-2020
- 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-causes
- Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-4

## Question

What are the causes of tastes and odour in water from various sources?

## Short answer

Tastes and odours arise from algae, decaying organic matter, dissolved gases like hydrogen sulphide, minerals (iron, manganese), sewage, industrial chemicals, and chlorine compounds. Removal uses aeration, activated carbon, or oxidation.

## Answer

Taste and odour in water arise from the following causes:

1. **Algae and other micro-organisms:** blue-green algae, diatoms and actinomycetes give fishy, grassy, earthy or musty smells, especially in lakes and reservoirs in warm weather.
2. **Decaying organic matter:** decomposing leaves, vegetation and animal matter give musty or swampy taste and odour.
3. **Dissolved gases:** hydrogen sulphide (rotten egg smell) in ground water, and methane.
4. **Dissolved minerals and salts:** iron and manganese (metallic taste), sodium chloride (salty), magnesium and sulphate (bitter taste), high TDS.
5. **Sewage and industrial wastes:** phenols, oils, chemicals, pesticides, and detergents.
6. **Chlorine and its compounds:** excess chlorine or chlorophenols from disinfection of water that has phenols.
7. **Pipes and storage:** corrosion of iron or copper pipes, bacterial growth in dead ends, and stagnant water.

Removal methods include aeration, activated carbon, chlorination or ozonation, and protecting the source.

## Check yourself

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

1. Rotten egg smell in ground water is due to:
   A. hydrogen sulphide
   B. methane only
   C. chlorine
   D. fluoride
   Answer: A. Dissolved gases cause odour. (Key point: H2S)

2. Metallic taste is caused by:
   A. sodium chloride
   B. iron and manganese
   C. algae
   D. detergents
   Answer: B. Salty taste is from sodium chloride. (Key point: Metallic taste)

3. Earthy, musty, fishy smells in reservoirs come mainly from:
   A. pure H2O
   B. calcium carbonate
   C. algae and actinomycetes
   D. nitrate
   Answer: C. Especially in warm weather. (Key point: Algae)

## Related in Water Supply Engineering

- [Removal of taste and odour](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Ataste-odour-removal) — Water Supply Engineering, chapter 6
- [Water sources: quality and quantity](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Asources-quality-quantity) — Water Supply Engineering, chapter 2, asked 3×

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