Figure 3 further demonstrates that a critical crossflow velocity is necessary to achieve maximum separation. It can also be seen that above a certain velocity there is little benefit. Note this is true even for non-fouling dissolved salts. This graph is based on Full-Fit data but the principle applies to all sepralators, at least with standard mesh spacers. A wrap or more of mesh spacer may also be applied over an FRP outer cover to act as a partially restricting seal.
All designs give subtle performance differences.
The choice for these will depend on the application and on the manufacturer's viewpoint. The membrane is usually the compatibility-limiting component of a sepralator. Membrane choice is often governed by compatibility considerations rather than separation performance and flux-related characteristics. Both homogeneous and thin-film composite polyamide membranes followed to provide wider pH range, improved separation and biological degradation resistance. Since these are more expensive and less tolerant of oxidizing agents than the cellulosics, they have not replaced CA but closely rival it for total use.