E.Coli – The Canary in Drinking Water Systems
Waterborne diseases never sleep. They often make a tragic comeback in the event of a natural disaster, like the earthquake in Haiti. In that case, cholera devastated the small island nation long after the tremors ceased. But the cholera bacterium is not the only disease-causing microbe that lurks in untreated or mistreated water: There are over 100 different types of waterborne pathogens, including various types of bacteria, parasites and viruses. In water microbiology we only test specifically for some of these, but we can also test water to understand the contamination level and potential for waterborne disease.
Escherichia coli (abbreviated to “E. coli”) are a large and diverse group of bacteria which are always found in the intestines of warm blooded animals, humans, mammals and birds, and in their excrement. Almost all pathogens of human illness are also found in large numbers in the intestinal tracts and excrement of animals infected with the respective disease, but many, if not most of them, are difficult and expensive to detect. E. coli is relatively easy and inexpensive to detect and enumerate, so it is used as a marker for water contamination and threat of disease around the world. You might hear, for example, of E. coli being found in recreational waters or drinking waters, indicating the water is contaminated. While not always harmful, there are certain strains of E.coli that can make you sick because they carry extra DNA that causes various illnesses, such as diarrhea, gastroenteritis, urinary tract infections, intestinal hemorrhage, and kidney failure, and may even result in death.
Accounts of E. coli in drinking water are numerous, and its detection is often accompanied by an advisory that urges people to boil their water. My recent Google search of “E.coli” and “boil order” yielded over 11,000 results. In one recent incident in northeast Pennsylvania, employees and residents of Tobyhanna Army Depot were advised to boil drinking water after routine testing found abnormal amounts of E. coli in the tap water (source: Pocono Record,).
Wherever there is water, animals and people, one can find E.coli in the water, but there is often no information on whether the water contains benign or far more dangerous microbes or whether dangerous microbes are present at levels of concern. That’s why the U.S. Centers for Disease Control and Prevention recommends that people avoid swallowing water in lakes, ponds, streams, and even swimming pools, and backyard “kiddie” pools.
Sewage discharges, septage, animal farm waste, and wildlife excretions are all sources of E. coli and other waterborne pathogens, which will always find their way into water. In order to prevent waterborne disease, a multiple barrier approach works best, including adequate treatment of drinking water (filtration and chlorination) as well as treatment and disinfection of wastewaters and fecal wastes, which helps protect natural waters and the sources for drinking water.
(Joan Rose, PhD, is the Homer Nowlin Chair in Water Research at Michigan State University and a member of the Water Quality and Health Council)