The branch filter developed by MIT engineers has been proven to be effective in providing clean drinking water in India.
Photo credit: NR Fuller, Sayo Studio
The filter developed by MIT engineers has been proven effective in filtering Escherichia coli Rotavirus is the most common cause of diarrhoeal disease. In tests conducted in India, they removed more than 99% of both pollutants.
Filter base made of tree branches
In the sapling part of the wood (sapwood) (corresponding to the last annual rings of the tree), the pipes that transport the sap (xylem) are connected to each other to form a dense membrane. This structure is an effective filter, which can filter impurities in the water.
The interior of unflowered trees (such as pine and ginkgo) has a real grid in the sapwood, which is formed by conduits that extract water from the ground and distribute it to the rest of the tree. The xylem pipes are connected to each other by membranes that act as natural screens to filter out air bubbles from the water and sap.
Pores are much smaller than various pollutants in the water (such as dust, bacteria and protozoa).
These ducts are connected to each other by holes present in their side walls. The size of these holes ranges from a few nanometers in angiosperms to a few hundred nanometers in gymnosperms. They are much smaller than the various pollutants (such as dust, bacteria and protozoa) present in the water.
MIT engineers studied the natural filtering capacity of sapwood and made a simple filter from the cross section of the peeled young branches.
They show that they can filter out pathogens such as Escherichia coli And rotavirus are tested in the laboratory, and they can effectively remove bacteria from contaminated spring water, taps and groundwater.
Wood filters can purify water after being stored in a dry form for at least two years.
This is how they are done:
caveat: Make sure the tree is not poisonous! For example, yew is toxic and should not be used. Please follow safety precautions when cutting. Unless proper quality control measures are taken and safety standards are met, it is not recommended to use self-made filters for drinking water.
Ensure that the filter is made of green wood and kept moist throughout the experiment
- Branches of non-flowering trees (such as pine, cedar, etc.), at least 0.5 cm thick
2. Hose/pipe installation branch pipe
3. Clamp to seal the branch inside the hose/pipe
4. Feed the filter test solution (you can use dirty water or create your own feeding solution by adding powder to clean water, diluting yogurt, etc.)
This video shows how to create a filter and also demonstrates a demo activity.More information Code page MIT is open.
Tested in India
The researchers brought their technology to India, where they made xylem filters from local trees and tested them with local users. The system purifies water at a rate of one liter per hour.
Their results have been published in Nature Communications.
The co-authors of the Karnik study are the lead authors Krithika Ramchander and Luda Wang of the MIT Department of Mechanical Engineering, and Megha Hegde, Anish Antony, Kendra Leith and Amy Smith of MIT D-Lab.
How to make the filter more durable
Put the branches in hot water. Then add ethanol. Finally, heat it in the microwave for a few minutes and you will get a filter for water.
In previous studies on xylem, Karnik and his colleagues found that the natural filtering capacity of wood materials also has some natural limitations. As the wood dries, the sieve-like membrane of the branches begins to adhere to the wall, reducing the filter’s permeability or the ability to let water flow through. The filter also seems to “self-lock” over time, accumulating sawdust that clogged the pipe.
Surprisingly, two simple treatments overcome these two limitations. By immersing a small section of the small sapwood in hot water for an hour, then immersing it in ethanol and allowing it to dry, Ramchander found that the material maintained its permeability, effectively filtering the water without clogging. The filtering effect can also be improved by adjusting the thickness of the filter according to the type of tree.
Researchers cut small pieces of white pine trees from the branches around the Massachusetts Institute of Technology campus and processed them. The results showed that even if stored for up to two years, the resulting filter can still maintain the same level as commercial filters. Considerable permeability, which greatly extends the shelf life of the filter. .
The researchers also tested the filter’s ability to remove contaminants, such as Escherichia coli Rotavirus is the most common cause of diarrhoeal disease. The treated filter removed more than 99% of the two pollutants, reaching the ” Comprehensive two-star protection “Established by the World Health Organization.
In India, they used local pine trees to make filters and tested them with filters made from American ginkgo trees and used local drinking water. These tests confirmed that the filter can effectively remove bacteria found in local water.
They used the opinions of more than 1,000 potential users from all over India to design a prototype of a simple filtration system with a container on the top of the system that users can fill with water. The water flows through a 1-meter tube, through the xylem filter, and then flows out through a valve-controlled spout. The xylem filter can be replaced daily or weekly, depending on the needs of the house.
The team is exploring ways to use locally available resources to produce xylem filters on a large scale. This method will encourage people to make water purification a part of their daily lives, such as providing replacement filters at a low price. When you go.
He said: “Xylem filters are made of cheap and widely available materials and can be bought in local stores. People can buy what they need here without the initial investment like other water filter cartridges.” So far, we have proven that xylem filters can provide realistic performance.”