What is microbiological contamination?

Microbiological contamination occurs when water contains harmful microorganisms such as bacteria, viruses, or protozoa.
These organisms are invisible to the naked eye and may not affect the appearance of water, but they can impact safety if untreated.

Microorganisms are microscopic living organisms that cannot be seen without magnification.

In water, the most relevant types include:

• Bacteria (e.g. E. coli, coliforms)

• Viruses

• Protozoa (e.g. Giardia, Cryptosporidium)

• Etc. etc.

Some microorganisms are harmless. Others may cause illness if consumed in sufficient quantities.

Water can become contaminated through:

• Surface runoff

• Failing municipal infrastructure

• Well or borehole exposure

• Storage tank contamination

• Pipe leaks or cross-connections

In tropical or developing regions, microbiological variability can be more common due to climate and infrastructure differences.

Clear water does not necessarily mean safe water.

Microorganisms:

• Do not change colour

• Do not change taste

• Do not always produce odour

The only reliable way to confirm microbiological safety is laboratory testing.

Potential signs of microbiological risk include:

• Irregular municipal supply

• Frequent water shut-offs

• Use of private wells

• Surface water sources

• Poorly maintained storage tanks

However, contamination is not always visible or obvious.

Treatment methods include:

• Ultrafiltration (physical membrane separation)

• UV sterilisation

• Reverse osmosis (in certain configurations)

• Chemical disinfection

Each method addresses different aspects of contamination.

If microbiological contamination is suspected, laboratory testing should include:

• Total coliform

• E. coli

• Turbidity

• General bacterial indicators

Testing before and after treatment confirms system suitability and performance.

Microbiological contamination is different from:

• Hardness

• Dissolved salts (TDS)

• Chemical contaminants

Each water issue requires a different treatment approach.