Membrane terms

Terms for the individual components of a membrane technology are used inconsistently for membrane bioreactors.

An ‘element’ can be considered to be the smallest replaceable component of the membrane technology. The term ‘module’ normally applies to a single element for a rectangular hollow fibre technology, but usually to a collection of elements in the case of flat sheets.  The term ‘stack’ can be considered to apply generally to a collection of elements, though the terms ‘rack’, ‘unit’, ‘cassette’ and ‘skid’ are also used.  A collection of immersed stacks is usually called a ‘train’, and the train may include the biological tank.

Terminology for MBR membrane products and technologies:

Component Flat sheet (FS) Hollow Fibre (HF)
rectangular panel
Hollow Fibre (HF)
cylindrical bundle; Multitube (MT)
Element Panel, element, sheet, cartridge Module, sub-unit Module
Collection of elements Module, cassette, unit Rack, cassette, cartridge, module Skid
Stack, frame


Abbreviations for membrane polymeric materials are:

PAN Polyacrylonitrile
(HD)PE (High density) polyethylene
PES Polyethylsulphone
PS Polysulphone
PTFE Polytetrafluoroethylene
PVDF Polyvinylidine difluoride


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