Membrane processes are now being used for many environmental applications such as drinking water and wastewater treatment. They are also used in indirect potable reuse and desalination plants. One of the single biggest issues is membrane fouling which increases the operational and maintenance cost. This project uses ultraviolet radioluminescence, a potentially transformative tool for membrane biofouling prevention, with many theoretical advantages over chemical antimicrobial strategies currently being researched.
The concept, conceived by the PI, involves incorporation of inorganic phosphor materials within reverse osmosis or nanofiltration membrane module feed channels, which emit germicidal ultraviolet radiation when excited by X-rays. The penetrating ability of high-energy X-rays could thus allow controllable ultraviolet treatment within the typically inaccessible confines of spiral-wound modules by employing externally-situated X-ray sources to excite the phosphors within. This approach is attractive in theory, but its predicted feasibility currently relies on cursory simulations involving simplified scenarios and approximate values of X-ray attenuation, phosphor efficiency, and microbial UVC dose response from the literature. In order to predict if RL membrane biofouling control (RMBC) can become a viable technology in the future, the PI proposes to conduct exploratory research involving simplified proof-of-concept experiments to probe internal microbial inactivation rates. This data will then be assessed with regards to conventional X-ray sources and emerging high-efficiency flat panel sources. Before full-scale research efforts are expended, it should also be demonstrated that the expected X-ray and UVC doses required to adequately curtail fouling are not high enough to significantly impact the working lifetimes of membranes. The PIs propose 10 months of experiments to explore these factors and reveal the feasibility of RMBC without requiring intensive prototype development. The approach being proposed is; (1) the first known method of achieving UV inactivation of bacteria within small spaces confined by UV-opaque materials, and, (2) the first use of UV radiation in directly deterring biofouling within modules. While the individual phenomena of X-ray transmission, RL, and UVC microbial inactivation are qualitatively well-understood - though in disparate contexts - this project will be the first to demonstrate how they perform in succession and to quantify the outcome. The research will thus support the PI's goals of instilling greater interaction between students in these two fields in order to encourage advancement of transformative sustainable technologies. The PIs have also developed a plan to include undergraduate summer interns of underrepresented minorities in future embodiments of this research.
