Project Details
Projekt
FreeSpace: Fundamental research to exploit hydrodynamic effects to reduce membrane fouling by introducing special arrangements of novel feed spacer geometries in combination with non-regular membrane surface-pattern
Subject Area
Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 499318495
Reverse osmosis (RO) and nanofiltration membranes (NF) are known for their high selectivity towards dissolved substances and emerging pollutants present in different types of water. Spiral wound membrane modules are the most frequently employed membrane configuration in RO / NF installations. They consist of thin-film composite (TFC) membrane flat sheets (also called envelopes), a permeate tube, in addition to permeate and feed spacers. Feed spacers offer inter-membrane spacing, consequently, they create a flow channel between two adjacent membrane sheets with the intent to establish proper fluid mixing and mass transfer. They have a substantial role in determining fluid characteristics inside feed flow channels, and consequently, influencing crossflow velocity and pressure drop. Crossflow velocity is affecting membrane fouling, while pressure drop is influencing energy consumption and operational costs. Generally, feed spacers are beneficial for enhancing mass transport, fluid mixing and shear stress, which should mitigate concentration polarization (i.e., accumulation of retained solutes in a boundary layer near membrane surface) and scaling. Nevertheless, they are also found to result in localized regions with poor mass transport along the feed channel where particulate fouling and biofouling often occur. Utilization of synergetic influences of surface micro-patterning (regular micro- or nanometer-scale pattern on the active side) as well as feed spacer design and orientation can potentially promote fluid mixing that will improve shear stress on membrane surface and feed spacer structures, which can mitigate significantly adhesion of particles and biofoulants, reduce concentration polarization, and therefore, increase average permeate flux and critical flux for the onset of fouling. Up to now, the particle deposition behavior and the tendency to biofouling in spacer-filled channels of surface-structured TFC membranes have not been investigated in theoretical (simulation) or experimental studies. The proposed research will promote the understanding of fundamental design and operational aspects. Based on experimentally determined spatial distributions of particles and biofoulants in feed-spacers, the topography of the membrane surface shall be adapted to the geometry of the feed-spacers and specifically designed. Ultimately, this will lead to a new generation of tailor-designed non-regular surface-patterned membrane-feed spacer assemblies exhibiting superior separation performance and antifouling properties. This new development concept is believed to better allow managing process efficiency, module lifespan, and energy consumption towards more sustainable and cost-effective water purification processes.
DFG Programme
Research Grants
Co-Investigators
Dr. Ibrahim Elsherbiny; Dr.-Ing. Thomas Lippert
