How to Remove Bacteria from Drinking Water


Water can contain germs such as bacteria and viruses which can be harmful and make you unwell. More than 11% of households in Ireland rely on private water sources such as wells which are not regulated. As a result, the quality of water could be compromised especially during wet weather. Removing or inactivating bacteria in water can be done in a variety of ways, depending on the water source, level of bacteria and inorganic matter, and resources available. In this blog, we talk about various methods that can be successfully used to make water biologically safe to drink.

Common Sources of Bacteria in Water

Bacteria is everywhere, including lakes, rivers, streams, and groundwater. Water is the universal solvent, collecting everything from dissolved salts to organic matter and mineral content as it makes its journey from rainwater through the earth to aquifers. Most of these bacteria are harmless to humans; however, certain bacteria, some of which normally inhabit the intestinal tract of warm-blooded animals, have the potential to cause sickness and disease in humans. High numbers of these harmless bacteria often indicate high numbers of harmful bacteria as well as other disease-causing organisms such as viruses and protozoans. The problem is that you cannot smell, taste or see bacteria in water. Bacteria cannot be detected without performing a water test.

Some of the common bacteria that may be found in water are:

  • Cryptosporidium
  • Giardia Lamblia
  • Coliforms
  • Coli
  • Salmonella

Bacteria may be found in water sources such as private wells that have been contaminated with faeces from infected humans or animals. Water can be contaminated through sewage overflows, sewage systems that are not working properly, polluted stormwater runoff, and agricultural runoff. Wells may be more vulnerable to such contamination after flooding, particularly if the wells are shallow, have been dug or bored, or have been submerged by floodwater for long periods.

Best Ways to Remove Bacteria from Water

When there are bacteria in water, it must be treated before use, especially for drinking. There are several ways to make water safe for use. Some are more effective than others. The method you use will depend on: How contaminated the water is and which method is going to be most practical and easy for you to use.

1. Boiling

Boiling water is a recommended method to disinfect water, and it has been used for thousands of years. By boiling water, you kill any microbes lurking in the water and prevent them from causing any illness to you. Boil the drinking water by bringing it to a vigorous, rolling boil, for example with an electric kettle. In order to be sure that you’ve killed pathogenic bacteria that may be present in water, it is recommended to follow this process:

  • If the water is cloudy, either let it settle or filter it through a coffee filter or a clean piece of cloth before you boil it.
  • Bring the water to a rolling boil. This is the point where the water is boiling very vigorously with lots of bubbles.
  • Allow the water to boil like this for at least 1 minute.
  • Remove the water from the heat source and allow it to cool down.
  • Once the water has cooled, store it in a clean, tightly secured container.

2. Chemical Disinfection

Another commonly used method of killing bacteria is the application of chemicals. Among the chemicals, chlorine remains the most widely used and is in some cases recommended by government agencies. When chlorine comes in contact with bacteria, it breaks down the chemical bonds on a molecular level. Shock chlorination is the most widely recommended means of treating bacterial contamination in water. The term “shock” indicates the addition of a strong dose of a concentrated chlorine solution. Shock chlorination is recommended:

  • Upon completion of a new well or when an unused well is returned to service
  • If annual water test results indicate the presence of bacteria
  • If a well system is opened for any installation, repair or maintenance
  • Whenever the well is surrounded by floodwater (standing water around or covering the well casing)
  • If well water becomes muddy or cloudy after a rain
  • If a well has been left stagnant or unused for a long period of time

While chlorine does impart a chemical aftertaste to water, the water’s taste can be easily improved by a carbon filter.

3. UV Disinfection

UV water filters are gaining immense popularity amongst well owners who are looking to remove bacteria from their water supply. UV sterilisers are highly effective, safe and cost-effective methods of disinfecting water. UV filters use ultraviolet light at a specific wavelength (254 nanometers) which neutralises the DNA of bacteria, preventing them from reproducing in the water. This renders the bacteria harmless. Unlike chlorine, UV disinfection does not use any chemical additives to treat water and hence, does not change the colour and taste of water.

Some of the benefits of UV water filters include:
  • Cost-effective method to treat water
  • Does not waste water
  • Environmentally friendly as no by-products are produced in the process
  • Does not change the colour and taste of the water

UV systems are ideal for a wide array of homes and applications. Houses that rely on well water, small cottages, vacation homes, and beach houses that draw water from wells all utilise UV disinfection systems to great effect. Read More: How do UV Water Filters Work?

Is Reverse Osmosis Effective in Removing Bacteria?

The membrane on RO systems is small enough to eliminate more than 99% of commonly found contaminants in water including chemicals, chlorine, fluoride, heavy metals and even micro-organisms. However, reverse osmosis systems should not be used as a primary method of removing bacteria from water. They are designed to be used to treat microbiologically safe water. Bacteria in water can proliferate on the membrane leading to possible contamination and reduced performance of the filters. The O-rings within a residential reverse osmosis system are also not designed to prevent bacteria from migrating, meaning there is a risk of bacteria being reintroduced into your water supply. We usually recommend a UV filter to remove bacteria before it reaches the RO system. This prolongs the life of the RO system and membrane, as well as ensures a safe supply of drinking water.

Keep Your Water Supply Safe

Removing bacteria from drinking water is critical to ensure you and your family are using only safe water for every use. If you use a private water supply such as a private well, we highly recommend getting it tested every year. All the water testing should be done by an INAB-accredited laboratory. In instances where well water quality has been compromised, it is best to take professional help. Celtic Water Solutions is a market leader in Ireland when it comes to good treatment. We have nearly 20 years of experience treating private wells and have helped several families in Ireland improve their well quality. Contact our team for a free consultation.

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