Coliform Bacteria

Cathal Walsh
Environmental Blogger
Friday, 14th June 2019
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Table of Contents

Maximum amount allowed in water:


What is it?

These are a diverse group of gram-negative non-sporing rod-shaped bacteria, some of which are of faecal origin (e.g. E. coli). There are many species of coliform bacteria however that occur naturally in the environment and are not harmful to humans.


How does it get into water?

Many species of coliform bacteria occur naturally in water and as a result would be present in water from the source.  Coliform bacteria may also indicate faecal contamination of water. This may happen in a few ways. It could be that the disinfection processes in place in the municipal water treatment plant are insufficient. It could also indicate that there is a leak or fault in the pipeline system leaking sediment into the clean water supply. Lastly it could indicate contamination or seeping from the soil or surrounding area at the source.


Do they pose a risk to health?

Coliform bacteria themselves are mostly inert however if they are detected in the water it indicates that other more harmful bacteria such as E-Coli may be present. In this way they are not a risk in themselves but more of an indicator of risk.


How do I check for them?

Firstly one should check the disinfection system for the water to make sure it is working correctly. If this system is working correctly then the overwhelming odds are that Coliform bacteria will not be present in the end stage. You should still check the water at the end stage however; a test for coliform bacteria may be purchased from an accredited lab, such as one that may be purchased here.


What do I do if I detect it?

First of all you should do your best to examine the whole water system to ensure that there is no contamination at some point or that there is nothing leaking into the system. Scouring

will be required following a confirmed contamination of the network or a section of the

network. After that one should ensure that the disinfection systems are in place and working correctly.


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