Ultrafiltration
(UF) - Design Criteria
UF modules are designed with high
circulation velocities up to 18 feet/second to create a
turbulent flow, which minimizes the build up of solids on the
membrane surface. Individual modules may be arranged in
parallel or in series. A combination of both is also
possible. Parallel configurations have the lowest pressure
drop, the highest flux, and the highest transmembrane
pressure (TMP). Additional recirculation flows result in a
pressure drop in each module and an increase in energy
requirements. Series arrangements decrease TMP in subsequent
elements, resulting in a reduced flow. Even though the feed
pumps are smaller in a series arrangement, more modules are
required.
UF membranes require only a coarse pretreatment to improve
its filterability. This benefit is realized as a result of
the flow channels in A3's UF tubular membranes.
Narrow-flow-channel flat sheet (spiral wound) or small
diameter capillary membranes (hollow fiber) require a more
thorough pretreatment. Additionally, using a ceramic membrane
offers superior chemical, mechanical, and thermal stability
over hollow fiber UF membranes.