May 11, 2020

Do Water Filters Remove Bacteria?

The first thing to note when discussing water filters is that this is a generic term, there are many different types of water filter on the market.

The short answer to do water filters remove bacteria is yes and no. Certain types will and others won’t, it depends on what they are designed to remove.

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How Water Filters Work
All water filters create a barrier that traps dirt or bacteria. In effect, there is a membrane inside the filter that allows water through but not all other substances.

The speed at which the water flows through is dependent on the size of the homes in the filter. The finer the holes the slower the water flow. A clogged filter will also reduce flow.

Filters That Remove Bacteria
Bacteria are generally removed from tap water by adding chlorine. This is very effective at killing almost any bacteria. The treatment plant will have large filters to remove debris and adds chlorine to kill bacteria.

However, the water can pick up new bacteria as it travels through miles of pipes between the treatment plant and your home. Tiny splits in the pipes will allow bacteria in and can go undetected.
Bacteria are also a concern if you have private water, such as a well in your yard.

At the moment the only filter that can effectively remove bacteria is one that uses reverse osmosis.

This process pushes water through a semi-permeable membrane. This works in the same way as a screen door, which allows air through but not pests. In the case of reverse osmosis, it allows water through but not bacteria. The water must be pushed through with more force than it normally has.

This ensures the water passes through the membrane but minerals and bacteria can’t. They are collected and directed out of the filter through a different route. This allows the bacteria-filled water to be diluted and sent back to the water plant or even around in a circle to go through the filter system again.

Re-directing is important to ensure there is not a bacterial buildup by the filter.

It is worth noting that reverse osmosis is also effective at removing chemicals in the water but it won’t remove hydrogen sulphide, that’s the gas that smells like rotten eggs.

Ultraviolet Radiation
Ultraviolet rays can also kill bacteria in water. A simple way of doing this is to fill a clear bottle with water and leave it in the sun for at least a day. The UV rays from the sun will kill harmful bacteria.

It is possible to buy this type of filter that directs a pulse of UV light through water. Coupled with a pre-filter it can be effective at removing bacteria.

However, as with any of these filters, the key is to ensure the filtration material is cleaned and maintained regularly. If it isn’t bacteria can build up and breed. This can clog the filter and may even lead to bacteria getting back into your water.

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