Total Coliforms

Total coliforms are a family of bacteria commonly found in soil, vegetation, and the intestines of warm-blooded animals. While not all coliforms cause illness, their presence in treated water indicates a breakdown in treatment or contamination entering the distribution system.

Why it matters

The ADWG requires 0 total coliforms per 100 mL in treated drinking water. Detection triggers investigation because:

• It may indicate inadequate disinfection
• It suggests possible contamination entry points in the pipe network
• Some coliforms (like E. coli) are specifically associated with faecal contamination

Difference from E. coli

Total coliforms is the broader group. E. coli is a subset that specifically indicates faecal contamination. A sample can test positive for total coliforms but negative for E. coli — this is less serious but still requires investigation.