Visible Light Activated Photocatalytic Water Polishing System, Phase I

This proposal targets development of a LED light activated photocatalytic water polishing system that enables reduction of organic impurities (TOC and microorganisms) in the processed water to levels less than 0.25 ppm for NASA?s future long duration mission. The proposed photocatalytic oxidation reactor is novel in two ways: 1) Strongly oxidative nanostructured TiON photocatalysts under visible light activation, which enables miniaturized water treatment devices utilizing energy efficient LEDs and/or solar radiation in space; and 2) A novel catalyst support approach that enables optimization of the structure to maximize exposed surface area and induce turbulent water flow for very high mass transfer rates. Rapid decomposition of organic contaminants in the water stream translates into a low energy, low volume, and lightweight method of polishing reclaimed water on manned spacecraft. In Phase I, TiON coated reticulated structures will be fabricated and evaluated in a test cell spiked with organic contaminants similar to those in process wastewater streams on board spacecraft using LEDs. Contaminant destruction rates will be compared for using different purification system such as photolysing and photocatalysis using titania and UV light. Phase I results will be used to design a pilot scale treatment system in Phase II.