Deformation-induced cleaning of organically fouled membranes: Fundamentals and techno-economic assessment for spiral-wound membranes

Abstract

Membrane fouling is a ubiquitous challenge in water treatment and desalination systems. Current reverse osmosis (RO) membrane cleaning technology relies on chemical processes, incurring considerable costs and generating waste streams. Here, we present a novel chemical-free membrane cleaning method applicable to commercially existing RO spiral-wound membrane modules. The method employs controlled membrane deformation through pressure modulation, which induces shear stresses at the foulant-membrane interface that lead to detachment and removal of the foulants. To investigate the effectiveness of the method, experiments on organic fouling by alginate are conducted on a flat-sheet membrane coupon followed by tests on a commercial spiral-wound module with feeds of varying fouling propensities. Cleaning durations are six-fold lower, and the experimental results demonstrate flux recoveries and cleaning efficiencies comparable to those of chemical cleaning. The experiments on the spiral-wound module indicate that this method will have applicability in industrially-relevant settings. To elucidate the underlying cleaning mechanisms, membrane deformation experiments with no flow are conducted, and in situ visualization techniques are employed for both the flat-sheet and spiral-wound modules. The results show that cleaning is caused by a reduction in shear strength at the foulant-membrane interface after cycles of repeated loading, a behavior typical of fatigue. By enabling more frequent cleanings, deformation-induced cleaning is shown to considerably lower operating costs in an economic case study while offering a more sustainable and environmentally sound solution to membrane cleaning and antifouling in desalination.