What are Coliforms?
Coliforms are a group of bacteria that are always present in the digestive tracts of animals, including humans, and are found in their wastes. They are also found in plant and soil material.
Most coliform bacteria will not cause illness. However, these bacteria are indicators in water tests because their presence indicates that disease-causing organisms (pathogens) could also be in the water. Coliforms come from the same sources as potentially dangerous pathogenic organisms. Faeces and sewage wastes are usually the source of the disease-causing organisms.
Testing for all disease causing organisms is extremely time consuming and expensive, thus we test coliforms to give an indication of the presence of pathogens, so that corrective action can be taken. Total coliform bacteria is a standard to determine bacterial safety of water.
Each of these groups of bacteria has a different concentration of risk, starting with the broadest group:
1. Total Coliforms are most the commonly found group.
- Found in the environment – eg. in soil, water and waste. This is the most basic test and gives a general indication of the sanitary condition of a water supply.
- Found in the intestines and faeces of animals. They are a more accurate indication of faecal or sewage contamination and the possible presence of pathogens.
- Found in great quantities in the intestines. Some strains, however, can cause illness. It is considered the best indicator of faecal pollution and the possible presence of pathogens.
Sources of Bacteria in Drinking Water:
Human and animal wastes – from animal pastures, seepage from septic tanks or sewage facilities, natural soil / plant bacteria. Wells that are not well sealed, open or old are especially vulnerable. Spring / floods often precipitate high levels, too.
Potential Health Effects:
Most coliform bacteria do not cause disease. Other pathogenic organisms can cause diarrhoea and vomiting, dysentery, hepatitis, typhoid fever, cholera and other illnesses.
Rare strains of E.Coli can cause serious illness, but are more commonly found in food, such as under-cooked hamburger.
Testing for Bacteria in Water:
Bacterial contamination cannot be detected by sight, smell or taste. It needs to be tested regularly – at least once a year for well owners and more often for public water supplies.
The South African Requirements and WHO Guidelines are 0 Faecal Coliforms per 100 ml water.
Bacterial testing in water most commonly requires a sample to be incubated for approximately 24 – 48 hours at a warm temperature and then viewed under a UV light (for E.Coli). See more info on Lovibond® Coliform / E.coli Test Kits.
Quicker, but less accurate, dip-and-read tests strips are also available. These are ideal for making fast decisions in real-time, then if more detailed and quantifiable info is needed, more lengthy and involved tests can be carried out. See more info on Quick 15 Minute Bacteria in Water Test.
What to do if the test is Positive for Bacteria:
- Do not drink the water
- Boil the water at a rolling boil for 5 – 10 minutes to kill the bacteria or disinfect the water with chlorine or other disinfection method
- Identify and eliminate the source of contamination
- Retest the water before use
Updated Feb. 2018