Characterization and preservation techniques of plant xylem as low cost membrane filtration devices

Abstract

Safe drinking water remains inaccessible for roughly 1.1 billion people in the world.³⁴ As a result, 400 children under the age of 5 die every hour from biological contamination of drinking water.³⁴ Studies have been done to show that plant xylem from the sapwood of coniferous trees is capable of rejecting 99.99% of bacteria from feed solutions.16 Additionally, 4 L/d of water can be filtered with a ~ 1 cm² filter area using a transmembrane pressure of 5 psi, an amount sufficient to meet the drinking needs of one person. However, the main drawback of xylem is that its permeability drops by a factor of 100 or more after being left out to dry for only a few hours. This paper seeks to characterize the performance of the xylem as a filter, determine the minimum length at which the xylem is effective for filtering bacteria, and increase the xylem's ability to rewet (retaining its permeability and rejective capabilities) after drying through the use of polymer coatings. Finally, potential techniques for decreasing the minimum particulate size the xylem can filter are discussed, with the aim of allowing the membrane to filter viruses.