How to Remove Bacteria from Drinking Water?


Water – the elixir of life. We all know its importance, yet the quality of the water we drink can sometimes be overlooked. In Ireland, where a significant portion of the population relies on private wells, the presence of bacteria and other microorganisms can pose a real health risk.  This is why prioritizing water quality and taking steps to remove bacteria from your drinking water is essential.

This blog post is your guide to achieving peace of mind! We’ll explore how bacteria and other microorganisms can enter your drinking water, the health risks they pose, and most importantly, effective methods for removing them from your home’s water supply.

How Does Bacteria Infiltrate Our Drinking Water?

While water treatment plants work tirelessly to deliver safe drinking water, bacteria can still find sneaky ways to hitch a ride into your home. Here’s a breakdown of the common culprits:

  • Natural Sources: Even the most pristine lakes and rivers harbour bacteria. These microbes can be present in the environment naturally, washing into waterways from soil and decaying organic matter.
  • Runoff from Land: Animal waste, or decaying organic matter can seep into water sources. This runoff can introduce harmful bacteria into the water supply, especially if agricultural practices or improper waste disposal are prevalent near water sources.
  • Faulty Pipes: Over time, cracks or leaks can develop in older pipes. These breaches can create an entry point for bacteria to infiltrate the system and contaminate your drinking water. Regular maintenance and replacement of aging pipes are crucial to prevent such contamination.
  • Well Water: Private wells are more susceptible to contamination compared to public water. Nearby septic systems, agricultural activities, or natural runoff can increase the risk of bacteria entering your well water. Regular testing and proper well maintenance are essential for homeowners who rely on private wells.

It’s important to remember that contamination isn’t always obvious. Even clear water can contain harmful bacteria, making regular testing and treatment crucial for ensuring your drinking water’s safety.

Dangerous Microorganisms in Drinking Water

While most bacteria in your drinking water are unlikely to cause harm, some can trigger a range of unpleasant and even dangerous health problems. Here, we’ll delve deeper into a few of the most commonly found disease causing microorganisms in water supplies:

Coliform Bacteria

This umbrella term encompasses a group of bacteria naturally present in soil and the intestines of humans and animals. While not inherently harmful themselves, their presence in drinking water indicates potential faecal contamination.

This is particularly concerning because faecal matter can harbour a variety of other harmful pathogens, posing a significant health risk.  E. coli, a specific type of coliform bacteria, is a prime example. Its presence is a red flag for possible contamination with sewage or animal waste.

E. coli

E coli is a strain of Escherichia coli, bacteria that are found in the intestines of healthy people and animals around the world. While almost all E. coli bacteria are completely harmless, there are a small number of vicious strains that can cause serious illness if consumed. The strain (named O157:H7) is found in the intestines of cattle.

Young children and the elderly are especially vulnerable to the harmful effects of E. coli O157:H7.  Contaminated water sources, such as those susceptible to runoff from improperly managed livestock farms, can increase the risk of exposure to this dangerous strain.


Legionella are pathogenic bacteria that thrive in warmer temperature waters and are found naturally in freshwater streams, lakes, and other surface waters. It thrives in warm and stagnant water and often found in poorly maintained plumbing systems.

If inhaled, Legionella causes a pneumonia-like illness known as a Legionnaires disease. It is also responsible for a disease called Pontiac Fever, a mild flu-like sickness.

Giardia lamblia

Giardia is a microscopic parasite. If infected by Giardia, the parasite will dwell in your intestines and cause a condition known as giardiasis. Giardia causes diarrhoea, bloating, nausea, and painful stomach cramps.

Wells near farms are especially prone to Giardia infestations, as agricultural runoff from sheep or cows can expose the water to the parasite.


Cryptosporidium, often referred to as Crypto, is a waterborne microscopic parasite. Cryptosporidium bacteria will reside in the intestine of a human, causing a condition known as cryptosporidiosis. This mild gastrointestinal illness causes diarrhoea, dehydration, fever, nausea, and weight loss.

Crypto can survive for long periods of time in the water, and it is typically resistant to chlorine treatments. Well water can become contaminated with Crypto when it comes in contact with wastewater that contains faeces from an infected person or animal.

Efficient Methods to Remove Bacteria from Water

There are several effective ways to remove bacteria from your drinking water, depending on your needs and budget. Here are some popular methods:


Boiling water has been passed down from generation to generation as a way to ensure that water is safe to drink.  Boiling water can effectively kill microorganisms, including bacteria, viruses and protozoans. Microorganisms are sensitive to heat, and bacteria are typically inactivated the fastest when boiled. While boiling is reliable, it can be inconvenient and leave your water with a flat taste.

How to boil water

If this is your only option, here’s how you boil tap water to help purify it according to the CDC:

  • Bring tap water to a solid boil. Once the water is steadily boiling, continue to boil for one full minute. Allow to cool. Store water in a clean container (not washed in contaminated water), cover with a tight lid.
  • If the water is cloudy, filter it through clean clothes or allow it to settle, and draw off the clear water for boiling.
  • This includes water used for brushing teeth, making ice, washing raw foods, preparation of drinks, and water for pets.


Chlorination is a widely used and effective method for disinfecting water by adding chlorine. Using or drinking water with small amounts of chlorine does not cause harmful health effects and provides protection against waterborne disease outbreaks. Water treatment plants treat water supplies with chlorine before it is supplied to homes.

Chlorine inactivates a microorganism by damaging its cell membrane. Once the cell membrane is weakened, the chlorine can enter the cell and disrupt cell respiration and DNA activity (two processes that are necessary for cell survival).

In many instances, the positive bacteria tests from a private well are the result of a less serious, one-time contamination incident. For example, bacteria may be introduced when a new submersible pump is installed in a well. Shock chlorination is a simple and inexpensive process that can be used to disinfect water supplies that have been contaminated as a result of these one-time contamination incidents. When done properly, shock chlorination will kill all the bacteria existing in a well.

It is important to note that treating water with chlorine usually introduces a chemical like taste to water making it unpleasant to drink.

UV Disinfection

UV disinfection is one of the most effective method to treat microbiologically unsafe water as it eliminates a wide range of bacteria, including E. coli, Giardia, and Cryptosporidium. It utilizes ultraviolet light, a specific wavelength of light invisible to the human eye, to eliminate bacteria and other microorganisms from water.  This technology disrupts the DNA of these harmful organisms, rendering them inactive and unable to reproduce.

UV water filters typically involve prefiltering the water. Any suspended particles in the water can make UV disinfection less effective.

Unlike chlorination, UV disinfection does not alter the taste or odour of your water. You can enjoy the natural taste of your well water without any chemical aftertaste.

UV disinfection is an eco-friendly option as it doesn’t involve the use or storage of harsh chemicals. The initial cost of a UV disinfection system can be higher compared to some chlorination methods. However, the long-term operational costs are typically lower, and the benefits of chemical-free disinfection may outweigh the initial investment for many homeowners.

Can Reverse Osmosis Systems Remove Bacteria?

Reverse Osmosis (RO) is a filtration technology that utilizes a semi-permeable membrane to remove a wide range of contaminants from water, including dissolved solids, chlorine, fluoride, heavy metals, and more.

While RO systems can significantly reduce bacterial levels, it is not recommended as the sole method for treating microbiologically unsafe water. The possibility of some bacteria bypassing the membrane or breaches in the membrane itself necessitates additional disinfection methods like chlorination or UV light for guaranteed bacterial elimination. Indeed, all reverse osmosis systems will specify in their specs sheets that they are only to be used on potable and microbiologically safe water.

Over time bacteria can build up in the system including the storage tank and pre-filters. This bacterial haven can serve as a breeding ground for contaminants, potentially multiplying and contaminating your filtered water.

It is therefore, not a standalone solution to treat microbiologically contaminated water. It must be always accompanied with a UV water filter.

Enjoy Nothing But Safe Drinking Water

Ensuring access to clean, bacteria-free drinking water is paramount to your health and well-being.  For many private well owners in Ireland, this requires taking proactive steps to safeguard their water source. EPA (Environment Protection Agency) recommends testing domestic wells once a year to check for water quality.

The ideal water treatment solution for your private well depends on several factors, including your water quality test results, budget, and desired level of filtration.  Consider consulting with a water treatment professional to assess your specific needs and recommend the most suitable method or combination of methods for achieving bacteria-free drinking water.

Hydrotech Water Services is a leading water treatment company specializing in treating private well for over 20 years. Get in touch for a free consultation.

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