Optimization of a Water Purification Process

Water Filtering Diagram of photoreactions catalyzed by titanium dioxide (TiO2)
Water Filtering Diagram of photoreactions catalyzed by titanium dioxide (TiO2).

May 10, 2010

Portland, Ore. — The Oregon Health & Science University (OHSU) has received a research grant from the Oregon Nanoscience and Microtechnologies Institute (ONAMI) to identify improvements to a water purification process based on photocatalysis. The process was developed by Puralytics, an early stage business based in Beaverton, Oregon.

The project's principal investigator is Paul Tratnyek, a Professor in Division of Environmental and Biomolecular Systems at OHSU's Institute of Environmental Health. His research concerns the chemical processes involved in contaminant degradation in a wide range of environments. The photocatalytic process developed by Puralytics is closely related to processes Tratnyek has studied previously.

The Puralytics process uses a proprietary combination of ultraviolet light-emitting diodes (LEDs) and photocatalyst-coated fiber filters to degrade organic contaminants, sequester heavy metals, and inactivate pathogens in water. The ability to treat all three of these categories of contaminants simultaneously is a distinguishing advantage of the Puralytics process.

Organic contaminants that are degraded by the Puralytics process include pesticides, herbicides, solvents, petrochemicals, pharmaceuticals, and personal care products. Metals that can be removed by this process include lead, mercury, arsenic, and selenium. Pathogens that can be inactived include viruses, bacteria, protozoa, and cysts.

The Puralytics process works mainly by photoreactions catalyzed by titanium dioxide (TiO2). This chemistry is well established, with major features summarized in the adjacent figure. Puralytics' version of this process is distinguished by the particular selection of light source, catalyst material, and operating regime.

A specific goal of the research to be performed at OHSU is to identify ways of modifying the photocatalyst to give more efficient degradation of contaminants. For this, Tratnyek expects they will be able to draw from the large body of recent research by others on surface modification of nano-particulate semi-conductor photocatalysts. "This is not the place to be reinventing the wheel." Tratnyek says. "there is so much information out there that we have many promising options to select from."

Testing modifications of the photocatalyst and other operating parameters (e.g., flow rate) will be performed on a range of contaminants. A multi-variate experimental design will be used to identify process operating conditions that produce optimal overall performance. A simple plug flow model of the system performance will be developed to help interpret the results and to assist with reoptimization of the system for future applications.

The experimental and modeling work will be done by OHSU Masters student Amanda Mather. Amanda has a B.S. in Mechanical Engineering from Oregon State University and experience working as an engineer for Tektronix. To begin applying her engineering skills to environmental improvement, Amanda choose OHSU's graduate program in Environmental Science and Engineering. Amanda's background is perfect for this project says Tratnyek.

The project will focus mainly on optimization of the product Puralytics calls "The Shield" which is intended for small to medium flow rate situations, such as private drinking water supply wells, ultrapure water for commercial and industrial processes, greywater recycling, etc. A variation on their technology is sunlight activated for use in remote locations or emergency response situations. "The ONAMI grant with OHSU gives Puralytics the opportunity to optimize the Shield system, and to validate the system on a variety of contaminants that are difficult to measure without the sophisticated equipment and staff such as those at OHSU. Both the test results and the optimization will be essential for commercializing this innovative development," said Mark Owen, CEO of Puralytics.

In addition to helping a local, early stagebusiness get established in the highly competitive water treatment sector, Tratnyek hopes that this project will spark new interest at OHSU into the environmental health aspects of water treatment. "The Puralytics process should be very effective at removing water-borne pathogens like Cryptosporidium, for example, and the consequences of Cryptosporidium outbreaks have aspects that are relevant to many parts of OHSU, including the programs in Public Health, Global Health, etc.," says Tratnyek.

Another benefit of this project is that it is one of the first competitive grants from ONAMI to support research at OHSU on human health aspects of nanotechnology. Skip Rung, President and Executive Director of ONAMI, says "The ONAMI gap fund, advised by leading venture capital partners active in the Pacific Northwest, sees this project as an opportunity for OHSU research to advance Puralytics as both an attractive investment and an Oregon growth company."

ONAMI is the first of several "Signature Research Centers" created by the Oregon Innovation Council to cultivate Oregon-based research and commercialization in strategic economic sectors. ONAMI promotes the nanoscience and microtechnology sectors in Oregon by funding fundamental and applied research, and other cooperative ventures, at universities and businesses in the Pacific Northwest.

Update (11.22.2010). Puralytics won the 2010 "CleanTech Open" for their water purification technology.