Physiologically, the inside of nonflowering trees such as ginkgo and pine is such to draw water up through the trunk and branches. In fact, the interiors contains sapwood lined up with conduits known as xylem, which has a straw like appearance. Interestingly, the xylem conduits are interconnected by means of thin membranes that work as natural sieves to filter bubbles from sap and water.
To understand this thoroughly, research initiatives undertaken by MIT engineers has been involving examining of the natural filtering ability of sapwood. Previously, the team of engineers fabricated simple filters from the peeled cross-sections of branches of sapwood, thereby demonstrating that low-tech designs effectively filter out bacteria.
With advancement of the technology, the same team has demonstrated that sapwood work as filters in real-world situations. For this, the team fabricated new xylem filters that can sieve pathogens such as rotavirus and E.coli in lab tests, and showcased that the filter can separate bacteria from contaminated tap, spring, and groundwater. In addition, the research team also developed simple techniques to expand the shelf-life of filters, thereby enabling the woody disks to filter water after being stored in dry state for at least two years.
To validate this, the team of engineers took the techniques developed by them to India. While investigating the technique in India, the xylem filters were made from native trees and the filters tried with local users. Based on the feedback of local users, the team developed a prototype of a simple filtration system equipped with changeable xylem filters that purified water at one liter per hour.