New technologies are needed to address the removal of contaminants to increase the safety and realization of wastewater reuse practices for urban water sustainability. The AIMS Lab will employ surface chemistry analysis, advanced analytical tools and water chemistry techniques in the conceptualization, design, characterization and application of novel materials to examine creative solutions to water security challenges. Specifically, the AIMS Lab is currently investigating:
1. Low-cost media for stormwater treatment
One of the challenges facing urban water sustainability is reduced replenishment of groundwater. In rural cities, there is more stormwater infiltration to restore groundwater in aquifers. This is not the case in urban cities like Seattle, San Francisco, etc. due to large areas of impervious surface coverage.
Stormwater runoff is a major component of the urban water cycle, yet it is a highly under-utilized resource. In fact, it is often viewed as a waste or a nuisance causing street flooding. Instead of discharging runoff, a more practical solution would be to convey surface runoff to rain gardens or bioswales to promote groundwater recharge and decrease street flooding. Additionally, urban stormwater could be captured and harvested for use during landscape irrigation.
Despite its potential for augmenting water supplies, particularly in urban cities that are prone to drought, urban stormwater contains elevated concentrations of trace contaminants that pose risks to human and aquatic ecosystems.
Our group is interested in the development and application of low-cost reactive media to remove contaminants in urban stormwater. Researchers will be investigating urban stormwater contaminant fate and transport where reactive media are employed in existing stormwater infrastructure (e.g., rain gardens, green roofs, bioswales).
2. Selective removal of per- and polyfluoroalkyl substances (PFAS) in wastes
While media generated for urban stormwater treatment should be able to remove a broad suite of contaminants, these materials may not be appropriate for more toxic, persistent contaminants. For example, PFAS are organofluoro compounds that are extremely stable and resist chemical and biological degradation. Their applications as flame retardants and in water-resistant industrial products are resulting in the widespread presence of PFAS in wastewater and drinking water sources.
Granular activated carbon, an inexpensive and commercially available adsorbent is typically applied to remove PFAS in water. However, PFAS typically exist in low concentrations and in the presence of co-contaminants. In addition to PFAS, activated carbon is a highly efficient adsorbent for other trace organic compounds, trace metals, and other aqueous species. Therefore, PFAS removal by activated carbon may become ineffective due to lack of selectivity and competition for adsorption sites.
Our group will investigate the synthesis of PFAS selective polymer composites. By incorporating the target compound during synthesis, the resulting polymer operates in a lock-and-key mechanism for selective adsorption. We will examine composite affinity and selectivity for PFAS compared to existing technologies to treat complex, waste streams to increase the safety of wastewater and drinking water. We will also explore opportunities to release adsorbed PFAS and regenerate our selective polymers for multiple cycles of treatment.
3. Substrate-facilitated degradation of PFAS
Selective removal is only one half of the solution for complete remediation of toxic and recalcitrant contaminants like PFAS. Typical chemical oxidants used to degrade trace organic compounds during wastewater treatment are not powerful enough to completely oxidize PFAS. Furthermore, PFAS cannot be naturally degraded by microorganisms.
New reductive technologies are being examined to chemically breakdown PFAS into benign species. Literature suggests that specific conditions are needed to reduce PFAS including high pH and anoxic conditions. no oxygen present. To increase the feasibility of reductive treatments, we are probing the use of nanocomposites for heterogeneous PFAS reduction. Our group will identify the reduction mechanisms via formation of reactive oxygen species, the formation of transformation products and characterize the evolution of the nanocomposites during treatment.