TABLE 11-1 Membrane Terminology (Continued) Term Definition Differential pressure A pressure drop across a membrane element or module from the feed inlet to concentrate outlet Feed Input stream to the membrane array Flux The throughput of a membrane process expressed as a mass (mL 2t-)or volume (Lt-)rate of transfer through a membrane surface Fouling Deposition of solid material from the feed stream onto the membrane surface or within a porous membrane structure that restricts the passage of water decreasing productivity High-recovery array Array where the concentrate stream from one array becomes feed to a succeeding array to increase recovery Hollow fiber membrane A geometry in which the membrane material is configured into a very small diameter and mounted in a housing or pressure vessel,or submerged in a basin Instantaneous flux The flux that occurs in a MF or UF membrane when the unit is operating between backwash operations and is generally the highest flux reported for a system,as it does not account for system downtime or filtrate losses during treatment Lumen The center or bore of a hollow fiber membrane Mass transfer coefficient (RO.NF). Mass or volume unit transfer through a membrane based on or specific flux (MF,UF) driving force expressed in volume per unit area per unit time Membrane element A single membrane unit containing a bound group of SW or HFF membranes to provide a nominal surface area Module or cartridge The smallest component of a MF or UF membrane unit where the membranes are placed in a housing device with a filtrate outlet structureTongji University