Membrane bioreactors − multitube configurations
Multitube and multichannel membrane configurations are the third major category of configuration for membrane bioreactor technology. Multitube (MT) membranes are currently the only MBR membrane products which are standardised, and − for MBR technologies − are only used for sidestream configurations.
A module comprises a bundle of tubes within a standard-sized cylindrical casing − most often 8″ (200 mm) in diameter − and the water flows from inside to outside the membrane tubes.
For pumped systems, the modules are placed in series to provide a high conversion, with one individual stream comprising a number of horizontal 'loops' (normally 2−4 in all) in a serpentine arrangement.
For air-lift sidestream systems, the modules are discrete, vertically-oriented and generally longer than those used for the pumped type.
The pumped systems are often favoured for treating small effluent flows from industrial installations on the basis of their robustness, reduced footprint and/or operational flexibility and control. Recently multi-channel ceramic membranes have been introduced for some niche sidestream MBR applications.
The air-lift MT type competes with FS and HF immersed systems, having a similar energy demand for the membrane separation component.
Examples of multitube reference installations are Kanes Foods (pumped) and Ootmarsum (air-lift).