E. coli

Escherichia coli (E. coli) is a bacterium found in the intestines of humans and animals. While most strains are harmless, its detection in drinking water indicates faecal contamination and the possible presence of disease-causing organisms.

Why it matters

The ADWG requires 0 E. coli per 100 mL — any detection is a failure that triggers immediate investigation and corrective action.

E. coli is the most important microbiological indicator because:

• It is reliably associated with faecal contamination
• Its detection methods are well-established and rapid
• Its presence suggests the potential for more dangerous pathogens like Cryptosporidium and Giardia

Australian compliance

Australia’s urban water utilities achieve >99% E. coli compliance. Detections are rare and typically trigger boil-water alerts, increased chlorination, and system flushing.

Private water supplies

Rainwater tanks and bore water are not routinely disinfected and may contain E. coli. Regular testing is recommended for private supplies.