Closed-circuit RO membrane coupled with vacuum UV enhances pharmaceutical degradation via molecular uncoupling in soluble fractions

Trace pharmaceuticals in water pose environmental and health risks that conventional water treatment struggles to address. Reverse osmosis (RO) rejects a broad range of these compounds, but shifts them from the bulk stream to the concentrate, requiring further treatment. Ultraviolet (UV)-based advanced oxidation processes (AOPs), such as vacuum UV (VUV), are capable of degrading persistent compounds, yet their high energy demand can make application economically challenging, particularly in matrices with high radical scavenging capacity. This study presents an innovative treatment strategy based on the concept of physical decoupling of RO permeate and retentate molecules subjected to differential VUV doses. This innovative treatment approach leverages the membrane system as a separation process to enable “decoupling” of two soluble fractions (controlled by the membrane weight cut off (MWCO)), providing process intensification and more compact reactor design. A pilot-scale hybrid RO-VUV system was used to treat tap water, spiked with acetaminophen (ACE), caffeine (CAF), carbamazepine (CBZ), and sulfamethoxazole (SMX)as model contaminants. Benchmarking against RO alone and VUV alone configurations, the integrated system demonstrated superior degradation efficiency and faster reaction rates within the same treatment time. Specifically, the same performance with VUV alone required more than twice the treatment time and energy. The integrated approach required 3.7 kWh per order versus 3.1 for RO alone, adding ∼0.066 CAD m−3, while VUV alone showed higher EEO due to slower kinetics. Permeate from the integrated system had the lowest concentration of pharmaceuticals, generating the highest quality product when compared to RO/VUV alone.