This article describes the Vortex Generator by Sweden's Watreco that uses vortex motion to purify water. Watreco has commercialized a device that removes air and impurities from water used in artificial ice rinks, reducing energy consumption and improving ice quality.
A similar filtration technique that currently removes impurities of 5 microns or larger is being developed by Palo Alto Research Center. The technology has the potential to capture particles as small as 1 micron. If volume and reliability targets can be met, the approach would be more energy efficient and smaller than existing membrane/filter-based systems.
Other companies such as Novozymes, Aquaporin and Danfoss are developing filtration systems based on synthetic versions of the protein aquaporin. Aquaporins are proteins found in cell membrane pores that allow passage of water molecules while blocking ions and other solutes. It is hoped that membranes based on these proteins will require 1/5 the pressure currently required by reverse osmisis and increase flow five-fold.