Coliforms / Coliformes /

What are coliforms?

Coliform bacteria are micro-organisms that can be found everywhere in our environment. As an entire group, coliforms are referred to as total coliforms. However, some types of coliform bacteria occur in the feces of warm-blooded animals, and these are referred to as fecal coliforms. Escherichia coli (or E. coli) is the most well-known member of this group. E. Coli is naturally present in the intestines of warm-blooded animals, including humans. Because of the abundance of this bacterium in the intestines, fecal contamination of water is cannot occur without E. coli also being present in the water. Consequently, the presence of E. coli in water is an indication that it has been contaminated by fecal matter.

What are the consequences for public health?

Coliforms are not normally dangerous, but they can coexist with other bacteria, viruses, protozoa that are considered pathogens.  Coliforms are thus indicators of pathogens in the water.

Despite being harmless in most cases, certain strains of E. Coli can cause illnesses such as gastroenteritis and dysentery.

What factors cause coliform populations to vary?

Certain coliform bacteria are found naturally in the soil and water. However, large numbers of fecal coliforms may occur in waterways if:

• sanitary sewers (or storm sewers during heavy rains) flow directly into a waterway,
• rainfall runs off of farmland that has been fertilized with animal excrement,
• animals (wild or domesticated) defecate on the shores of or directly into a waterway.

How are coliforms measured?

For the Adopt a River protocol, participants simply fill the wells of a ColiPlate™ with the water to be tested and incubate it at 35°C for 24 hours. During incubation, a blue colour develops in wells that contain total coliforms. Using a UV lamp, the blue wells are then checked for fluorescence, which indicates the presence of E. coli. Then, with the help of a probability table, one may infer the quantity of total coliforms and E. coli from the number of blue and fluorescent wells.
 
Other methods, such as using a filtering membrane or incubating in a tube containing agar  can also be employed.

The unit used in Adopt a River is Colony Forming Units per 100 ml (CFU/100ml).

What are the standards?

Depending on the use of the water, its coliform content must not exceed certain levels. Water used for: