A membrane supported
biofilm reactor uses modules having fine, hollow fibres, for example, made from melt spun
thermoplastic polymers treated after
spinning to increase their permeability to
oxygen, used, for example, in tows or formed into a fabric. In one module, one or more sheets of the fabric are potted into a module to enable
oxygen containing gas to be supplied to the lumens of the hollow fibres. Various reactors and processes, for example to treat
wastewater, using such modules are described. In one process,
oxygen travels through fibers, optionally through an attached
biofilm, to
oxygenate surrounding water. Mechanical, chemical and biological methods, for example
endogenous respiration, are used to control the thickness of the
biofilm.