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MBR membranes generally have one of three module configurations: flat sheet (FS) hollow fibre (HF) and multitube or multichannel (MT/MC). The choice of membrane configuration can depend on the applications.
The MBR process can be configured either as immersed or sidestream, with the governing microbiology predominantly aerobic but most often including an anoxic stage and sometimes an anaerobic step.
Flat sheet and hollow fibre membranes are used almost exclusively in immersed MBRs for both municipal and industrial applications. Multitube and multichannel systems tend to be used for treating smaller flows of more highly concentrated industrial effluents.
Flat sheet (FS) membranes normally comprise flat, rectangular sheets either as individual panels (or rigid plates) or sandwiched together in a multi-layer module. They are designed to be immersed in the membrane tank and scoured with air delivered from aerators to maintain the flow of sludge through the membrane channels.
HF membranes are nearly always vertically oriented with the aerators either integrated with the membrane module or fitted to the frame. They are normally immersed in the membrane tank and scoured with air to keep the membrane channels clear of sludge solids.
Multitube and multichannel membrane configurations are currently the only MBR membrane products which are provided in standardised module diameters − most often 200 mm. In MBR technologies, these products are used exclusively in sidestream MBRs.
Membrane materials can be either polymeric or ceramic, with the polymeric membranes being more established and widespread in use. Membranes generally comprise a thin surface layer which provides the required perm-selectivity on top of a more open, thicker porous support which provides mechanical stability.
MBR processes are configured with the membrane either submerged in a tank (the 'immersed' configuration or 'iMBR'), or placed outside of it ('sidestream' or 'sMBR').
For iMBRs the permeate is produced either under vacuum on the permeate side or from the hydrostatic head in the membrane tank. For sMBRs it is produced by pumping sludge through the membrane channels.
The governing biochemistry by which contaminants are removed in a biological process depends on whether or not oxygen is present, and in what form. Biotreatment processes may be aerobic (oxygen present), anaerobic (oxygen absent) or anoxic (oxygen present predominantly as oxyanions, such as nitrate).