Does Reverse Osmosis Remove E Coli?

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If you are looking for a water filtration system to remove E coli from your drinking water, you can never go wrong with a reverse osmosis system.

According to the Center for Disease Control and Prevention (CDC), RO systems are considered effective in getting rid of bacteria, especially E coli.

What is E.coli?

E.coli is a bacteria that resides in human and animal intestines.

There are several types of E.coli, some harmless and others extremely dangerous. The latter produces a highly potent toxin that causes health complications if ingested in food or water.

How Does E.coli Get into Drinking Water?

E.coli is found within coliform bacteria (a larger set of bacteria), which exists in the intestines of cows and sheep.

The bacteria is an important factor in the nutrition of these animals and is usually found in high concentrations in their waste.

E.coli gets in water due to animal waste getting into water sources such as lakes, rivers and groundwater before decomposition.

This results in drinking water with toxic levels of E.coli bacteria.

How Can You Determine Whether Your Water is Contaminated with E.coli?

Check your water for discoloration or debris

Fill a clear glass with water and look closely to see whether the water appears color-tinted. Are there any visible particles floating in the water?

Even if present, it does not mean that your water has E.coli. Remember that E.coli is not visible to the naked eye.

However, signs of discoloration or particles indicate that the water is most likely contaminated with a nasty bacteria or E.coli.

Watch out for E.coli symptoms

Some of E.coli symptoms include nausea, vomiting and diarrhea. If you experience these digestive upsets 3 to 4 days after drinking contaminated water, chances are, your water has E.coli.

Additionally, if you start feeling excessively weak and can’t stop vomiting, it could be the result of drinking polluted water. Seek medical help.

Also, seek professional help if your diarrhea appears bloody.

Send a sample of your water to a certified water testing laboratory

Sending a sample of your water to a certified water-testing laboratory in your area will grant you the peace of mind you deserve.

But first, you need to verify whether the lab tests for E.coli, otherwise you will not get the results you are looking for.

If you have a private well, send the water for testing at least once every year since the contaminants can return.

How Does Reverse Osmosis Remove E.coli?

Reverse osmosis filter water through multiple filtration stages.

The water passes through several filters, including a sediment filter, a carbon filter and a post-filter. However, these filters cannot handle E.coli.


The filters have a bigger pore size (1-5 microns), and since the bacteria is smaller than this, it slips through the cracks with the tiny water molecules.

The reverse osmosis membrane filter makes RO systems the best option for removing bacteria from water. It is semi-permeable and boasts tiny pores of about 0.0001 microns.

This membrane effectively blocks contaminants of all sizes, E.coli included.

Only water molecules pass through to the other side.

It is, however, important to note that reverse osmosis technology does not kill bacteria; it only filters them out, so you end up with pure water.

If you are looking forward to destroying the DNA of these microorganisms and killing them, try UV treatment.

How Much E.coli Does Reverse Osmosis Remove?

Reverse osmosis is highly effective in removing E.coli and other bacteria from drinking water.

A high-quality RO system can eliminate up to 99.9% of E.coli, Salmonella, Shigella and Campylobacter from your water.

In What Other Ways Can You Remove E.coli from Water?

Other alternatives to reverse osmosis for E.coli removal include:

  • Ultraviolet systems – Kill the bacteria with ultraviolet light. They are incredibly effective.
  • Distillation systems – These boil water and recollect the steam, free of bacteria.
  • Ultrafiltration filter – These filters have ultrafine pores that block the bacteria from passing through.
  • Nanofiltration filter – The filter has nano-sized pores that filter the bacteria from water. They are highly effective as well.

    What is not removed by reverse osmosis?

    Reverse osmosis does not remove chlorine by-products, most organic compounds or dissolved gases like methane, carbon dioxide and radon.
    Additionally, the technology does not remove some common contaminants like pesticides, herbicides, fungicides and dissolved gases like hydrogen sulphide.
    This is simply because these contaminants are molecularly smaller than water.

    Can E.coli be filtered out of water?

    Yes, E.coli can be filtered out of the water through reverse osmosis.

    How do you get E.coli out of water?

    You can remove E.coli from drinking water by:
    1. Reverse osmosis,
    2. Boiling the water for a minute at maximum temperature. If at an altitude higher than 65d6 ft., boil the water for a minimum of 3 minutes.
    3. Using bleach containing between 5.25 to 6 percent of sodium hypochlorite.
    4. Using paper strips soaked in sugar to kill the bacteria.

    What kills E.coli in well water?

    Pouring chlorine or bleach down the well kills E.coli in the water. Leave the bleach or chlorine in the well for about 12 hours before using the water from the well.

    How Does E.coli Affect Health?

    Individuals infected with E.coli develop health complications like abdominal cramps, fever, vomiting, nausea and watery or bloody diarrhea.
    The illnesses can be mild, severe or life-threatening.
    Kids infected with E.coli are at a higher risk of developing severe complications like hemolytic uremic syndrome – a type of kidney failure.

    What other contaminants does reverse osmosis remove from water?

    Aside from E.coli and other microorganisms, reverse osmosis can remove 99.9% of total dissolved solids in water(TDS), heavy metals such as lead and arsenic, hardness minerals like magnesium and calcium and other impurities like nitrates, fluoride etc.


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    Dr. Peter Gleick

    Dr. Peter Gleick is an experienced water filtration engineer and technical writer for He is an expert in water purification and filtration, focusing on helping people get clean, safe, and healthy water for domestic use. He has more than 10 years of writing experience and has numerously contributed to leading publications in this field.

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