2.4.3  Physical tests

Turbidity (cloudiness due to a large number of very tiny particles), colour, taste and odour (smell), whether of natural or other origin, affect people’s perceptions of water. As you know water should be free of tastes and odours that would be unpleasant to the majority of people. In extreme cases, people may avoid water that does not look or taste good – even if it is otherwise safe – in favour of more pleasant-looking and tasting water that may actually be contaminated.

Colour in drinking water occurs due to the presence of dissolved organic matter and metals such as iron and manganese. Colour can come from industrial pollution such as from dyes used in textile manufacture. Odour in water is due mainly to the presence of organic substances. Taste is the combined perception of substances detected by the senses of taste and smell. Changes in the normal taste of a piped water supply can be important as they may signal changes in the quality of the raw water source or deficiencies in the treatment process.

2.4.2  Chemical tests

Summary of Study Session 2