Coliform Bacteria

Definition - What does Coliform Bacteria mean?

Coliform bacteria are rod-shaped, non-spore microorganisms found in soil, water and aquatic environments, as well as in the feces of humans and warm-blooded animals.

Coliform bacteria in water distribution systems may be caused by maintenance issues, presence of nutrients in the system, through leakages and defects caused by corrosion or other system quality factors. Detection is critical and leads to further tests to identify any likelihood of dangerous contaminations that could lead to waterborne disease outbreaks and health risks.

Corrosionpedia explains Coliform Bacteria

The coliform family is made up of several groups, described based on origin or characteristics. The two most common types are the total and fecal coliform.

Total coliform bacteria gets into distribution systems when three conditions occur simultaneously:

  • Source of bacteria
  • Pathway into the system
  • Suitable mechanism enabling the bacteria to be transported into the distribution system, or that allows bacteria within sediments, biofilms or corrosion tubercles to enter the water

The distribution system includes storage tanks, pipes, pipe laterals and appurtenances that comprise the delivery system. Pathways that breach the system are either external, such as main breaks, intrusion and cross connection, or internal such as biofilms, corrosion and leaching.

Sources of total coliform include:

  • Water and soil surrounding pipes
  • Corrosion tubercles
  • Biofilm and microbial growth
  • Sediments
  • Weather-related events

The pathways through which they can enter distribution systems include:

  • Finished water storage facilities
  • Intrusion and main breaks
  • Cross connections and backflow

Mechanisms that allow bacteria to enter a distribution system are:

  • Hydraulic conditions
  • Operations
  • Retention times
  • Maintenance practices
  • Presence of nutrients

Stagnant water causes suspended articles to settle in pipe sediments, giving rise to biofilm development and accelerating biological meditated corrosion.

Since fecal materials are generally present in rivers and lakes, it is expected to be part of the environment. Therefore, the presence of coliform bacteria serves as an indication of failure in the water distribution system, and can guide in identifying the system's control and repair requirements.

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