The escalating global demand for freshwater, driven by diverse applications, places increasing stress on finite water resources

The Cooperative Agreement award R24AC00497, totaling $419,450.08, was provided by the U.S. Department of the Interior Bureau of Reclamation under the Water Desalination Research and Development Program (CFDA 15.506). The project, led by Professor Sergio Garcia-Segura at Arizona State University, aims to develop a chemical-free solution using gas nanobubbles to prevent scaling and biofouling issues in reverse osmosis desalination. The research will evaluate the impact of water composition on bubble attributes, determine the ideal gas and bubble size for fouling prevention, and demonstrate the cost-effectiveness of the nanobubble approach at a pilot scale. The ultimate goal is to unravel the mechanisms and identify the most effective bubble type for preventing and cleaning membrane fouling, which can potentially extend the application to other membrane-based water treatment processes. This innovative research aligns with the program's objectives of developing cost-effective, energy-efficient, and environmentally friendly desalination technologies.

To ensure future water security, exploring alternative sources like seawater, groundwater, and wastewater is imperative. However, these sources often contain salts and contaminants, requiring removal for safe use. Reverse osmosis dominates desalination, producing approximately 50% of global desalinated water. Despite its effectiveness, reverse osmosis faces a critical challenge: membrane fouling. This phenomenon, marked by the accumulation of particles and microorganisms on the membrane, results in diminished operational efficiency, elevated costs, and environmental concern, with scaling and biofouling emerging as particularly pervasive issues within this context. IT is estimated that the associated costs represent approximately 24% of operating expenses. Scaling results from inorganic mineral ION precipitation, while biofouling involves living microorganisms adhering to the membrane. Current strategies, including chemical additives and disinfection methods, have drawbacks. The project entitled nanobubbles as a chemical-free fouling and scale control strategy for reverse osmosis, led by professor sergio garcia-segura at arizona state university, proposes a chemical-free solution using gas nanobubbles for scaling and biofouling control during brackish water desalination. Preliminary results indicate that air microbubbles, larger and presumably less effective than nanobubbles, diminish membrane scaling during reverse osmosis treatment due to turbulence. Nanobubbles also act as coagulants, anti-scalants, oxidizers, and disinfectants, offering a dual solution without introducing additional chemicals. To establish nanobubbles as a competitive solution, several research questions must be addressed, including (1) the impact of water matrix composition on bubble attributes, (2) the influence of bubble size and gas type on fouling prevention, and (3) the cost-effectiveness compared to conventional methods. This project aims to fill these knowledge gaps by evaluating bubble generation in different water matrices, determining the ideal gas and bubble size for fouling prevention, and demonstrating cost-effectiveness at a pilot scale. The ultimate goal is to unravel mechanisms and identify the most effective bubble type for preventing and cleaning membrane fouling. While the focus is on reverse osmosis desalination, successful application of nanobubbles can be extended to other membrane-based processes, contributing to the overall advancement of desalination technologies. The proposed research aligns with the objectives of notice of funding opportunity R24AS00016 by developing or improving process or approaches to reduce the cost, energy consumption, feasibility, and or environmental impacts of desalination and water treatment as well as improving existing membrane technologies, including reverse osmosis, electrodialysis, nanofiltration, membrane filtration, and pretreatment processes. By advancing a potential chemical-free scaling and biofouling control strategy, the proposed research will also help develop cost-effective approaches for concentrate management that minimize potential environmental impacts. This innovative approach has the potential to substantially reduce reliance on anti-fouling chemicals and disinfectants, also addressing the critical environmental concern associated with the limited lifespan of membranes.