Chapter 2 - Fundamentals

Abstract

This chapter provides the fundamentals of membrane bioreactor (MBR) technology. Membrane separation processes applied to it have conventionally been limited to microfiltration and ultrafiltration for separation of the permeate product from the bioreactor mixed liquor suspended solid. Other processes, in which the membrane is used to support a biomass and facilitate gas transfer into the biofilm or extract ions or water through transmembrane osmotic/vapor pressure differences, have not reached the commercial stage of development. Membrane module configurations employed for biomass separation are limited to flat sheet and hollow fiber for immersed processes (where the membrane is placed in the tank), and mainly multitubular (where it is placed outside the biotank). The latter provide shear mainly through pumping, although more recent processes also employ airlift, whereas immersed processes rely entirely upon aeration to provide airlift and shear. Shear enhancement is critical in promoting permeate flux through the membrane and suppressing membrane fouling and clogging, but generating shear also demands energy. There is a presence of cross-disciplinary issues in the area of membrane fouling. Little interconnection exists between foulant analysis in wastewater and potable applications and between membrane cleaning in the industrial process and municipal water and wastewater sectors.