As freshwater shortages worsen around the world, desalination—turning seawater into drinkable water—is becoming increasingly important.
But the technology that powers most desalination plants has a persistent problem: membranes that slowly clog with salts, minerals, and microorganisms.
Now, engineers at University of Colorado Boulder have developed a new imaging method that lets scientists watch this clogging process happen in real time, offering a powerful tool to make desalination more efficient and sustainable.
The research, published in Environmental Science & Technology, introduces the use of stimulated Raman scattering, or SRS, to monitor membrane fouling as it develops.
Fouling occurs when unwanted materials build up on the thin polymer membranes used in reverse osmosis systems, reducing how well they filter water and increasing energy use and operating costs.
Reverse osmosis plants account for about 80% of desalination facilities worldwide. These systems push seawater through membranes that block salt and other impurities, leaving fresh water behind.
Over time, however, minerals and biological material stick to the membranes, making it harder for water to pass through. Detecting this buildup early has long been one of the biggest challenges for plant operators.
“SRS allows us to monitor membranes and provide early warning when fouling begins,” said Juliet Gopinath, a professor of electrical, computer and energy engineering and physics at CU Boulder.
Instead of waiting until membranes are badly clogged, operators could potentially intervene sooner, improving efficiency and extending membrane life.
The new method works by shining laser light onto the membrane surface and analyzing the light that scatters back. This process is based on Raman scattering, a technique that reveals the molecular structure of materials by how their molecules vibrate when exposed to light. Stimulated Raman scattering takes this a step further, allowing for faster imaging with greater sensitivity.
Postdoctoral researcher Jasmine Andersen explained that different types of light reveal different information. With SRS, the team can not only see where material is forming on a membrane, but also identify exactly what that material is. This is a major advance over existing tools, which typically provide either visual information or chemical identification, but not both at the same time.
To test the technique, the researchers observed the formation of calcium sulfate and calcium bicarbonate crystals, two common contributors to membrane fouling in seawater desalination. Using SRS, they were able to track crystal growth as it happened, capturing three-dimensional images while simultaneously identifying the chemical composition of the deposits.
“Watching these crystals form in real time and knowing exactly what they’re made of is incredibly valuable,” Andersen said. “This is insight that current industry tools simply can’t provide.”
Experts say this level of detail could help desalination plants operate more efficiently. By understanding what materials are clogging membranes and how quickly they form, operators can fine-tune cleaning schedules and reduce unnecessary shutdowns. Professor Emeritus Alan Greenberg, a specialist in membrane performance, noted that reducing fouling and improving cleaning efficiency can significantly lower costs and boost water production.
Looking ahead, the team believes SRS could be used to study even more complex fouling, including organic and biological material found in both seawater and brackish water systems. As global water scarcity grows—already affecting more than half the world’s population for part of the year—tools like this could play a key role in ensuring reliable access to clean water.
By making the invisible visible, real-time membrane imaging may help desalination plants run smarter, cleaner, and more sustainably in the decades to come.
