E. Coli in Drinking Water
E. coli is a dangerous bacteria that can cause serious and life threatening illness in humans. E. coli is part of a larger group of bacteria called coliform bacteria. Coliform bacteria are found in the guts of ruminant animals such as sheep and cattle. In the guts of these animals they play a beneficial role in the nutrition of the animal. However, the waste of these animals also contains a high concentration of these bacteria. This isn't a problem as natural decomposition processes will break down the waste and the bacteria it contains. However, when animal waster is allowed to enter natural waterways or to pollute groundwater sources before it has a chance to be decomposed, the result can be drinking water with dangerous levels of e. coli bacteria. This can have devastating results.
Biology of E. coli
The full name of E. coli is Escherichia coli. It is a gram negative, rod shaped bacteria that lives in the lower guts of warm blooded ruminant animals. Sheep and cattle are examples. E. coii is also found in the gut of humans. The normal strains of E.coli that inhabit the guts of these animals are beneficial. They help the animal to produce vitamin K2 and they also help to prevent disease-causing microbes from establishing. But some strains of E. coli such as the infamous 0157:H7 strain are very dangerous. If water or food containing this strain of E. coli is ingested, serious illness and death can occur. E. coli is unique in that it can survive outside the body of it's host for an extended period, making it an excellent choice as an indicator organism for the presence of animal waste in the environment
E. coli as an Indicator Organism
Because E. coli is found only in the guts of animals and in their waste, it's presence in the environment is a sign of pollution. Anytime that E. coli is found in water it is a clear indication that the water supply has been contaminated with animal waste. E. coli can be used as an indicator organism because it can live outside of it's host for an extended period. In most areas of North America a bacterial water sample analysis consists of a test for coliform bacteria and a test for E. coli. If any E. coli is found in a water sample the water source is deemed unfit to consume.
How Water Becomes Contaminated with E. coli?
As mentioned above, E. coli has only one source - animal waste. A water source becomes contaminated with E. coli when animal waste makes its way into the water. This can happen in many different ways. Let's first look at how a well water source might become contaminated with e. coli bacteria. There are two common ways that this occurs. The most common source of e. coli in a well is from septic system discharge. Sometimes a well is situation too close to a septic weeping bed. If the well casing is cracked some septic discharge, which is rich in e. coli will end up in the well water. Even if the well casing is not cracked, if the well is in very porous material, septic discharge may percolate through the ground and enter the well through the water table. Well water may also become contaminated from surface water. This most commonly occurs when the well head is below the level of the ground. When it rains surface water picks up traces of animal waste and this runs into the well cap from the surface. Even if the well cap is above grade, if the fill material around the well casing is not of the correct material, or if it has been disturbed, surface water this is contaminated with e. coli can run down the outside of the casing and make its way into the water table and ultimately the well water.
How Can I Protect My Water Supply from E. coli?
Thankfully, E. coli and most other bacteria are not all that difficult to kill. In a residential application where bacterial contamination is proven or suspected there are two common technologies used to handle the problem. Chlorine is one approach that can be taken. Typically a dosing pump is used to inject chlorine into the drinking water lines. The chlorine is a disinfectant that kills the bacteria. The most popular approach to killing bacteria in residential drinking water applications is the use of a UV system. A UV system is plumbed in line with the home water main. Water passing through the UV system is blasted with bacteria-killing UV rays. UV systems are popular because there are no chemicals to handle and no chemicals are added to the water. UV systems are easy to maintain and highly effective at killing not only E. coli and other bacteria but a range of other viruses and waterborne parasites.