Novel research has proven that filters made from xylem in trees can be used to remove bacteria and pathogens from drinking water, leading to a possible solution for the worldwide E.coli crisis.
Nonflowering trees, such as pine and ginkgo, contain sapwood lined with straw-like conduits known as xylem. Xylem is a vascular tissue found in plants that provides structural integrity and carries water and minerals from the roots to the rest of the plant. Xylem tissue is made of specialized cells which are water-conducting, allowing for the water molecules to adhere to its tissue as it is being pulled up the plant. Water passes through Xylem’s conduits which are interconnected via thin membranes that act as natural sieves, filtering out bubbles from water and sap. Inspired by this natural phenomenon, a study published by the Massachusetts Institute of Technology engineered a filter made of xylem that successfully removes E. coli from drinking water.
“Two Birds With One Stone”
One major problem that the engineers ran into was dryness and its effect on the xylem’s permeance: as the wood dried, the branches’ sieve-like membranes began to stick to the walls, reducing the filter’s permeance, or ability to allow water to flow through. Another problem found was that the filters would erode and degrade with use, causing a build-up of woody matter which clogged its passageways. The engineers were able to solve both of these problems by cutting the xylem into small cross-sections, soaking them in hot water and then in ethanol, and letting them dry. Now, the filters were ready to be used.
The engineers quickly sprang into action and brought their invention to India for testing; India holds the highest mortality rate due to water-borne disease in the world, where safe and reliable drinking water is inaccessible to more than 160 million people. Their trials in India provided them with beneficial feedback regarding replacement frequency and the comfortability of the product being natural and recognizable. With this criticism and assurance in mind, they crafted a new prototype and are now hoping to produce these on a massive scale so that all can have access to clean water.
A study published by the International Journal of Environmental Research and Public Health concluded that safe drinking water for all is one of the major challenges of the 21st century and that microbiological control of drinking water should be the norm everywhere. E. coli infections cause approximately 265,000 illnesses and about 100 deaths in the US and greater than 300 million illnesses and nearly 200,000 deaths are caused by diarrheagenic E. coli globally each year worldwide. It is imperative that this filter be mass-produced and utilized nationally in order to prevent further deaths and guarantee clean water to everyone across the globe.
Relation to AP Bio
This topic is closely related to the adhesive and cohesive properties of water. In plants, water adheres to the xylem as it is brought up from the roots and dispersed throughout the plant. Water also coheres to itself, allowing for more than one molecule to move up at a time and therefore causing a cascade of molecules to follow in one’s path. If it were not for this property of water, plants would not have evolved xylem and therefore this filtration innovation would not exist.
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