Capillary hollow fiber nanofiltration membranes

Spiral-wound modules generally have high packing densities, low costs, but require extensive feedwater pretreatment and have a high fouling potential. Tubular membrane modules have beneficial fouling properties, can be backflushed, but have low packing densities and are expensive. Both module types exist for the nanofiltration process. However, the membrane module type combining the superior properties of both types, namely capillary hollow fiber membrane modules, have not been developed yet. This paper presents the flux and retention performance data of new developed nanofiltration capillary hollow fiber membrane modules. The new modules show retention performances comparable with those of best-performing spiral-wound modules. They can typically be applied for water softening and decoloring. Continuous experiments on surface water and nanofiltration whey permeate demonstrate that the fouling behavior of the new capillary modules is indeed better than the spiral-wound modules due to its well-defined feed channel geometry.