In 1996, Statistics Canada stated that 8.9 million Canadians relied on ground water as their main source of household water(1). Usually this ground water is clean and safe for drinking because soil acts as a natural filter for disease-causing organisms such as bacteria.
What is Bacteria
Bacteria (or the singular bacterium) are microscopic organisms that are so small it would take about 25,000 lined up to make a line 1 inch long. All natural water contains micro-organisms, but not all are bacteria, and not all bacteria are harmful. In fact some types of bacteria are even beneficial, acting as natural decomposers.
Sometimes ground water can become contaminated by domestic sewage, feedlots and surface runoff, or other pollution sources, which contain harmful bacteria. When this happens, people drinking well water from these sources can become ill, sometimes very ill.
The most likely to be affected are the young, the very old and those with a weakened immune system.
Possibly the worst tragedy from contaminated water in recent history happened in Walkerton Ontario in May 2000 when the water supply became contaminated from a deadly strain of E. coli from farm runoff into a nearby well.
Nearly 2000 people experienced blood diarrhea, gastrointestinal infections and other symptoms of E. coli infection, and at least 7 people died(2). Sadly, this tragedy could have been avoided since water testing had shown there was evidence of contamination.
Well Construction and Maintenance
Wells should not be located downhill from any contamination source. Inspect well caps regularly to ensure they are closed tightly and there are no cracks. Inspect pipes and pumps regularly and investigate any change in water quality.
Health Canada recommends new wells be disinfected and then tested for micro-organisms, and existing wells be tested 2 or 3 times a year or when any change in water clarity, color, odor or taste is noticed(3). The best time to test an existing well is when the probability of contamination is highest. This is in spring, after extended dry periods, after heavy rains or when a well has been unused for some time.
How to Conduct Well Water Testing For Bacteria
Contact your local provincial health laboratory or a certified private laboratory for a clean sterilized sample bottle and instructions. Collect your water sample, refrigerate it immediately and transport it to your laboratory of choice within 24 hours.
The lab will look for total coliform bacteria, which may indicate fecal contamination, and E. coli, which definitely indicates fecal contamination.
Interpreting Water Testing Results
If your well water test shows a total coliform bacteria count greater than 10 per 100ml of water, you may be asked to resample. If the second test also indicates more than 10 total coliform bacteria per 100ml or water, immediate action should be taken to find the source of the contamination, remove it, and correct the condition.
If fewer than 10 coliform bacteria per 100ml of water is found, you may still need to resample your well water, and corrective action should be taken.
Any E. coli present indicates recent fecal contamination and the possibility of disease-causing bacteria. Water contaminated with E. coli is unsafe to drink and corrective measures should be taken immediately.
References For Well Water Testing For Bacteria:
(1) Statistics Canada, 1996, Quarterly Estimates of the Population of Canada, the Provinces and the Territories, 11-3, Catalogue no. 91-001, Ottawa.