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Membrane Technologies for Oil–Water Separation 653
The quality of permeate obtained by the application of an ultrafiltration and nanofiltration
integrated membrane system allows the direct reuse of treated water for fresh emulsion top up.
3.6. Membrane Bioreactor
Membrane bioreactor is usually referred to as a bioreactor integrated to a membrane
module system. This technology has been developed over 30 years ago (67) and it is mostly
applied to treat industrial wastewater, domestic wastewater, and specific municipal wastewater,
where a few small work appears in treatment of water (68).
In general, membrane bioreactors consist of two compartments, the biological unit and the
membrane module (69). The biodegradation of the compounds occurs in the biological unit,
while the physical separation of the treated water from mixed liquor takes place in the
membrane module. Membrane bioreactor systems can be classified into two groups:
integrated or submerged membrane bioreactors, and external or recirculated membrane
bioreactors (69). The first group, integrated membrane bioreactors, involves the outer skin
membranes that are internal to the bioreactor as shown in Fig. 15.5. The driving forces across
the membrane is achieved by pressurizing the bioreactor or creating negative pressure on the
permeate side (69–72). A diffuser is provided for mixing and facilitating the filtration surface
scouring. The second type, external or recirculated membrane bioreactors, involves of the
recirculation of the mixed liquor through a membrane module that is outside the bioreactor
(72). The driving force is the pressure created by high cross-flow velocity along the membrane
surface (73, 74). A schematic of this system is shown in Fig. 15.6.
Types and configurations of membrane used in membrane bioreactor applications include
tubular, plate and frame, rotary disk, hollow fiber, organic (polyethylene, polyethersulfone,
polysulfone, polyolefin, etc.), metallic, and inorganic (ceramic) microfiltration and ultrafiltration
membranes (75). The pore size of membranes used ranged from 0.01 to 0.4 mm(69).
O 2 /air
Wastewater
Process
control
Membrane
unit
Vacuum
pump
Pump
Mixing + aeration +
membrane scouring
Fig. 15.5. Schematic of integrated membrane bioreactors (69).
Treated
water