You can make a water filter using simple, low-tech materials available locally. There are various easy to set up filtration systems you can make within a short period, such as biofilters. The type of water filter you make will depend on the budget, time, availability of materials, capacity, and water condition.
What We Aim to Filter Out From the Water
You need to understand what impurities you are filtering out. Some contaminants will demand unique ways to purify. For instance, you may filter tap water differently from dirty water.
Water filter science aims to eliminate harmful contaminants such as chemicals, pesticides, and pathogens. At the same time, we aim to retain beneficial mineral ions such as magnesium which are useful to our health.
If possible, get a test kit from the local store and test your water supply. The test result will inform you of the water composition and what you need to filter out.
Homemade Water Filter
You can filter water at home using all sorts of simple items like funnels, water bottles, a coffee filter, and sand. Some of the popular homemade water filters include activated charcoal and sand filter and bio-sand filters. These are simple filters that can purify drinking water, water for gardening, or household use.
DIY Water Filtration – Activated Charcoal and Sand
Activated charcoal filters remove contaminants and improve the taste of the water. It is possible to use water sources from lakes and wells.
It is convenient and simple to construct with readily available materials. Your setup will depend on how much water you need to purify.
This would be a great science school project to do with students:
Cost: If you decide to buy all the items in the setup, costs may be less than $50.
Time is taken to assemble the setup: 1hr-2hr.
- Activated charcoal (crushed)
- A clean cloth, cotton balls, or coffee filter to act as a strainer
- Two-liter plastic bottle
- Sand and gravel
- A water container, e.g., bucket or vase
- For a small setup, you first need to fashion a suitable funnel. This can be done by cutting the two-liter bottle at the base using the knife to make the funnel.
- Make a small poke on the bottle cap. This is where filtered water will flow.
- Flip the funnel and line up the cloth or coffee filter at the bottom of the funnel. This first layer should be one or two inches in thickness.
- Place your funnel onto your vase or bucket.
- Start filling the funnel with crushed charcoal. You can use cooled charcoal from your grill because you require about an inch of the charcoal for a small setup.
- For the third layer, add about two inches of gravel.
- Next, fill the setup with about 4 inches of clean sand.
- About an inch or half an inch of the funnel will be left unfilled with materials.
- Your homemade water filter is now ready. Try with a cup of dirty water and check the filtered water that comes out.
- Repeat the filtering process until you get the desired results.
Testing the Water
- Testing the effectiveness of your DIY water filter requires a pre-filter water sample and a post-filter sample.
- Contaminate the prefilter sample with detergents, dirt, oils, or pesticides.
- Pour some of it into the purifier and collect the water. This is the post-filtered water.
- Use a standard water test kit to test the two water samples. You can also collect some clean water to compare the results.
How It All Works
Water purification, in this instance, works via chemical absorption. There are 4 layers that work to filter out impurities—the sand and gravel work to trap sediments. The activated charcoal traps chemicals and removes any bad taste in the water. For bigger capacity, you can get a bigger funnel.
DIY Biosand Water Filtration System
A bio-sand water filter guarantees effectiveness against viruses, pathogens, and some chemical pollutants. It is inexpensive to construct and simple to use.
The 2 students from India in the video below show how simple and important it is to have easy access to water filtrations systems in rural areas. Water filters do not have to be expensive.
This water purifier system utilizes biological processes, mechanical processes, es, and natural elimination. Materials used for this filter are available in any local store or hardware.
Time is taken to assemble the setup: 6hr-12hr.
Cost: At least $70
- Filter container made of concrete or food-grade plastic.
- Diffuser (A plastic or metal plate containing small holes)
- Filtration sand
- Separation gravel
- Drainage gravel
- Food grade safe water storage
- Pipe outlet
- Make an outlet at the bottom of the filter container.
- Add the piping outlet to the setup.
- The drainage gravel is the first layer.
- The separation gravel comes in second.
- Next, add the filtration layer.
- Add the biolayer.
- Leave some 2 inches above the biolayer and insert the diffuser.
- Add the lid to protect your setup from dust.
How it Works
You can use this setup to filter rivers, well, tap or rainwater. The system consists of layers of gravel and sand. The filtration system can filter drinking water for a household of 10.
When dirty water is poured over the water filter, the diffuser plate spreads the water over the sand biolayer. The water then travels through the layers of gravel and collects at the bottom. It is piped to the storage container. The lid prevents dust from getting into the filter.
The biolayer may contain bacteria that live on its top, which eat pathogens. The water filtered is odorless and safe for drinking.
DIY Emergency Water Filter
Making water filters in emergency situations is critical for anyone who loves activities such as camping and biking. Out there, you may not get any bottled water from the store.
Now, if you find yourself in an emergency situation and you have access to some kind of natural water source, you can use a method known as solar disinfection (SODIS). What does SODIS mean? This short video will explain the easiest and cheapest emergency water filtration method we know:
All you need is a plastic water bottle. It is a simple method as it requires you to bottle your water and expose it to sunlight for at least 6 hours. The UV rays will kill pathogens. Sediments will also settle at the bottom.