Total Coliforms
Cities measured
87
Detected in
11 / 87
Elevated / alert
2
Highest
68 CFU/100mL — Beirut
Overview
Total coliforms are a broad group of bacteria that include E. coli and non-faecal environmental coliforms. Their presence indicates either faecal contamination OR biofilm regrowth in distribution pipes. Distinguishing the two sources is critical for risk assessment.
Health Relevance
Total coliforms are not reliable direct health indicators — many are environmental organisms. Their regulatory value is as a distribution system integrity monitor: unexpected growth signals treatment failure or pipe contamination.
Regulatory Limits
Drinking Water Directive 2020/2184
0 per 100 mL.
Controversy & Contested Science
A 2019 review found biofilm-embedded coliforms in distribution pipes are a persistent source of exceedances in European systems, particularly after low-flow periods (weekends, seasonal shutdowns). The response — flushing and shock chlorination — provides temporary relief without addressing the underlying biofilm. Pipe replacement is the only durable solution but is prohibitively expensive at city scale. Critics argue utilities routinely manage coliform exceedances administratively rather than resolving the underlying infrastructure failure.