An opportunity to monitor the performance of reverse osmosis membranes and quickly detect conditions that would undermine water desalination efficiency has been engineered by University of Colorado researchers. Stimulated Raman scattering (SRS) enables the real-time detection of membrane fouling, a process where salts, minerals and other unwanted materials accumulate on filtration membranes.

The laser-based imaging technology relies on changes in the wavelength of scattered light to indicate the status of the membrane’s molecular structure and composition. The researchers used SRS to observe crystal growth on membranes in reverse osmosis desalination flow cells, documenting how the molecules vibrated and revealing the chemical makeup of the material.

As reported in Environmental Science & Technology, the chemical scalants were identified as calcium sulfate and calcium bicarbonate, ions commonly found in seawater. SRS provided both high-speed imaging and chemical identification, which can enhance process efficiency, improve cleaning strategies and reduce maintenance and operational costs.

Such real-time sensing of membrane condition can also lend itself to the analysis of more complex mixtures of organic, inorganic and biological materials that contribute to fouling in both seawater and brackish water systems.