Water scarcity will be a defining characteristic of our lifetime - 2.5 billion people are expected to live under water stress by 2050 - and will be exacerbated by rapid urbanization and energy scarcity. It is projected that majority of future population growth will be concentrated in cities, resulting in more people drawing water from the same, already-stressed water resources. The energy intensity of water treatment and distribution further complicates the issue: distribution of water in California accounts for nearly 20% of the state's energy budget; treatment represents nearly 3% of United States power output. This energy-water nexus will be centered on cities, and drive scarcity to more extreme heights. The proposed technology has the potential to turn these drivers of scarcity into opportunities for innovation. The proposed system uses photocatalysis via nanostructured titanium dioxide (TiO2) and sunlight to destroy pollutants and pathogens of concern in water, all in an envelope that integrates directly into the building façade. This team's key innovation lies in the integration of photocatalytic water treatment into the building envelope, affording low-footprint, low-energy water treatment. The team believes that a wide range of stakeholders - from city planners to water engineers to building designers - will have a strong interest in seeing the proposed research come to market.
The proposed work will explore the viability of a building façade-integrated solar photocatalytic water treatment system as a deployed technology and as commercial product. In laboratory and real solar conditions, this I-Corps team has demonstrated promising solar photocatalytic treatment of water (as proxied by an organic probe compound) at a representative sub-pilot scale - reactors of 0.5m x 0.5m. Thus, the scope of this research is to understand the customer requirements of various sectors - e.g. residential buildings, municipal buildings, industrial users - while establishing how our technology can achieve those targets, be it in its current state, or through significant redesign. Technically, the methods in the proposed research will involve redesign, development and treatment characterization of prototype reactor systems, with the aim of demonstration studies using real and synthetic greywater. As described by California Title 22 Regulations, this team aims to demonstrate a reduction of pathogen load and organic pollutants (as represented by chemical oxygen demand). This will be demonstrated through experimental characterization of scale prototypes developed through the course of the I-Corps program. First, this work advances the field of environmental engineering by describing solar photocatalytic treatment of real and synthetic greywaters, which has thus far been demonstrated only with energy-intensive UV lamps. Second, this work advances the field of building science by exploring integration of water treatment systems into the building façade, an area that has received little attention from the field. Finally this team aims to contribute its insights as best-practices of the innovation process applied to the water sector - a sector that has historically embraced new technologies reluctantly, but given today's crisis, must adapt to pursue innovation vigorously.
