Pressurized system or pressure-vessel configuration:
TMP (transmembrane pressure) is generated in the feed by a pump, while the permeate stays at atmospheric pressure.
Pressure-vessels are generally standardized, allowing the design of membrane systems to proceed independently of the characteristics of specific membrane elements.

Immersed system:
Membranes are suspended in basins containing the feed and open to the atmosphere.
Pressure on the influent side is limited to the pressure provided by the feed column.
TMP is generated by a pump that develops suction on the permeate side.
Ultrafiltration, like other filtration methods can be run as a continuous or batch process