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MBR building blocks

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An image of yellow lego bricks scattered on the right hand side of a bright blue background.

MBR building blocks

As with a conventional biological wastewater treatment process, an MBR is a combination of tanks, pipework, pumps and blowers, with the addition of the membrane differentiating it from classical processes.

A simple design of a small MBR has been provided by Lo et al (2015). This is a general design for a municipal wastewater treatment based on an immersed membrane and an MLE (modified LudzackEttinger) process. The specifications of the individual pieces of equipment (power, flow and/or pressure ratings) then depend on the application and assumptions made.

Most MBR installations must also include a control system for regulating flows and pressures.

Fig. 1. Components of an MBR plant
Fig. 1. Components of an MBR plant
A graphic of the components of an MBR, including (not in sequence) raw water tank, primary sedimentation tank, equalisation tank, rotary fine screen, sludge holding tank, membrane tank, aeration tank, anoxic tank, treated water tank.
Table 1. MBR plant components and design basis
Category Component(s) ID Description/purpose
TanksRaw waterT1Storage tank for inlet wastewater
Primary sedimentationT2Removal of gross, settleable solids
Equalisation (EQ)T3Equalisation of flow
Anoxic (Ax)T4Denitrification
Aeration (Ae)T5Nitrification and biological oxidation
MembraneT6Membrane separation
Treated waterT7Storage of permeate water
SludgeT8Storage of wasted sludge
Chemicals storageT9, T10
PumpsSettled sludge transferP1Submerged, settled sludge to sludge storage tank
FeedP2EQ tank through rotary screen
PermeateP3Self-priming, membrane suction filtration
Sludge return/dischargeP4Submerged, sludge recirculation and excess
Sludge transferP5WAS to dewatering
ChemicalsP6, P7Cleaning chemicals transfer to membrane, x2
BlowerProcessB1Biological process aeration
MembraneB2Membrane scouring
MixerEQ tank mixerX1High speed, equalisation tank
Ax tank mixerX2Low speed, anoxic tank
ScreenRotary screenS1Fine screening of feed
MembraneMembrane moduleM1FS membrane plus frame with built-in aerator
DiffusersFine bubble diffuserD1Process aeration
Coarse bubble diffuserD2Membrane aeration


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Lo, C.-H., McAdam, E., and Judd, S. (2015). The cost of a small membrane bioreactor, Water Sci Technol 72(10) 17391746.

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'MBR building blocks' was written by Simon Judd

This page was last updated on 24 August 2021


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