How to Remove Giardia From Water

Giardia infection is common in regions where the water supply houses the giardia parasites. To make your water supply safe for human consumption, we present multiple treatment methods that are effective and affordable. Read on to learn how to remove giardia from the water.

giardia contaminated glass of water

4 Effective Ways of Removing Giardia from water

Untreated water is the leading reason for the increasing giardiasis infections worldwide. Following are some of the water treatment options available if you suspect that the water supplies to your household harbor the giardia parasites:

1. Boiling Water

Bring contaminated water to a rolling boil for three minutes in a clean pot to make it safe to drink. The boiled water should be cool down and stored in a clean, sanitized container with a tight cover. Refrigeration is recommended if the boiled water is to be used for several days. Proper storage after boiling is a prerequisite for safe drinking water.

2. Reverse Osmosis

A point of use filter with reverse osmosis (RO) feature can be installed at sources of drinking water for cyst removal. These filters must have a semi-permeable membrane with an absolute pore size of less than or equal to 1 micron to withhold the giardia cysts.

3. Conventional Disinfection With chlorine

Chlorine is a widely employed chemical disinfectant. Various studies show that chlorine is effective in limiting giardia spread in drinking water supplies and swimming pools. Contact time of the microscopic parasite and the giardia cysts with the agent determines the effectiveness. Prolonged treatment times are recommended, especially in water supplies in areas where giardia outbreaks are an epidemic.

4. Alternative Disinfection Methods

Apart from chlorine, you can also use the following disinfectants for the removal of giardia. 

giardia contamination

A. Chlorine dioxide

Chlorine dioxide is usually used as a gaseous chemical disinfectant to treat giardia-contaminated water. It has high effectiveness against the adult parasite and moderate utility against giardia cysts.

B. Ozone

Ozone is a powerful oxidizing gas that can be used to eradicate giardia lamblia and its cysts along with other microscopic parasites.

C. Ultraviolet light

Ultraviolet light chambers can be installed to remove Giardia cysts from drinking water supplies in homes.

What is Giardia?

Giardia is a microscopic parasite that causes a waterborne disease called giardiasis. The parasite and its cysts are most commonly found in surface water, shallow wells, and soils that have been contaminated by excreta from an infected human.

Campers are most likely to get infected with giardia when they resort to pond water, lakes, and shallow wells as sources of drinking water.

How Does Giardia Get Into Contaminated Drinking Water?

The most common cause of giardiasis is the direct ingestion of water and food contaminated by Giardia lamblia. Touching surfaces of public toilets or living in close vicinity with someone infected by the disease can lead to gastrointestinal illness. Swimming pools also contribute to the spread of giardiasis.

Drinking water sources are contaminated by human feces containing the parasite. When the same water is used for drinking or irrigating meal crops, the contaminated water, and agricultural runoff act as vehicles for the transmission of the giardia parasites.

swimming pool contaminated with giardia parasite

Signs and Symptoms of Giardia Contamination

Giardiasis is a gastrointestinal disease. Like other infections, it is accompanied by high fever, malaise, and lethargy. Following are some of the grave signs of a giardiasis infection:

Diarrhea: Foul-smelling diarrhea accompanied by abdominal pain is a tell-tale sign of giardia infection. The stools are watery and are at times intercepted by slimy stools in between. If unchecked, diarrhea can lead to severe dehydration and electrolyte imbalance in the patient. This may prompt hospitalization and continuous monitoring to prevent life-threatening deterioration.

Extreme abdominal cramps: Severe abdominal cramps during a giardia infection can hinder routine life. The pain starts within a few minutes of contaminated water or meal consumption. Patients may at first complain of a feeling of flatulence that they may mistake as gas. With passing time and the onset of other usual symptoms, the cramping gets worse, and the patient may retire to their bed because of the excruciating stomach pain.

Weight loss: A giardiasis patient will lose drastic weight over the course of the disease. Anorexia, abdominal pain, diarrhea, and discomforting flatulence can all contribute to it. When the small intestine is affected, absorption is disrupted and the patient cannot fully derive the nutrients he needs.

Can Water Filters Remove Giardia From the Drinking Water?

Filters with appropriate absolute pore size and the correct complementary chemical disinfectant can effectively remove giardia parasites from the water supplies.

Many water treatment plants are installed to filter giardia cysts from the primary water sources, but they may not provide adequate protection. Private wells and domestic water supplies may still require efficient water treatment systems at the point of use to limit giardia spread.

Filters installed in homes for drinking water can also prevent direct contamination that may take place on a domestic level, such as from agricultural runoffs or improper sanitation facilities.

Filters are an effective and affordable means of protection against giardia infections.

Best Water Filters For Removal of Giardia

Various filters can remove giardia from your water supply; these include backpacking filters, gravity water filters, whole house filters, etc. 

Backpacking Filter

As mentioned in the previous section, campers and backpackers are more likely to suffer from giardia infection. A backpacking water filter is designed to be compact, easy to carry, and effective. They adequately remove giardia parasites, cysts, and most of the other microorganisms commonly encountered in outdoor drinking water sources.

The filter comes with a pipe that can be used as a straw to directly drink water from a lake, pond, or shallow well. The pore size of the filter installed in the straw is the main functioning component. Another variant comes with a tank-shaped bottle that can store filtered drinking water.

backpacking water filter that can remove giardia parasite from drinking water

Whole House Filtration

If the water supplies to the entire house seem to be contaminated with giardia, then a whole house water filtration system is the most effective option. To prevent giardia infections in such a household, you can install this filter at the site of entry of the main water supply.

Its functioning is dependent on a multi-stage operation involving multiple carbon filters and an additional layer of UV filtration. These filters effectively filter and eradicate the giardia cysts from the entire domestic water supply. The ultraviolet light as the last stage of the whole house filtration ensures that the parasite is killed after being filtered by the pre-filter and carbon filters.

Faucet Mounted Filter

In the event that the main source of giardiasis is the drinking water from the tap, then a faucet-mounted filter should suffice. Its compact design and easy installation make it a go-to filter option for most homeowners.

The filter pores are 0.5 microns small, being adequate when it comes to filtering giardia cysts from the drinking water supply. The most attractive feature of this filter is that it is functional against cyst removal without the need for extra pipe installation or any drilling procedures. Contaminated drinking water can be treated simply by twisting the faucet on.

Under Sink Water Filter

This filter is specific to treating drinking water. It is inconspicuous as it is installed within the cabin. It is easy to set up and can be easily cleaned periodically for greater longevity.

For drinking water treatment, the under sink water filter uses a membrane with a pore size as small as 0.0001. This effectively filters the giardia cysts so that the drinking water is made fit for human consumption. Some models come with as many as seven different filters to ensure that no microorganism or unwanted particles enter the drinking water.

FAQs on How to Remove Giardia From Water

Does Water softener remove giardia?

No. A water softener is used in areas with hard and heavy water. They basically target the heavy metals that are responsible for the problem. These filters have no tested efficacy against removing giardia parasites or cysts.

How do I know if my house is contaminated with giardia?

A water test known as the coliform test can be undertaken to detect the presence of the microorganism in the water source and supply. This is particularly important in areas that receive much of the agricultural runoff that needs to undergo the same test.

Does PUR remove giardia?

It is important to note that not all filters are able to sieve giardia, including PUR. As mentioned in the previous section, the filter needs to have an absolute pore size of no more than 1 micron to entrap the cysts. PUR has filters with larger pore sizes.


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We wrote this article with the sole purpose of increasing awareness about giardiasis and the means of minimizing its spread through the population.

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