MBR features

Search our in-depth feature articles on MBRs. Practitioners with experience of operating membrane bioreactor technology and academics researching this specialist area share their expertise.

About MBRs

A membrane bioreactor (MBR) is a wastewater treatment process where a perm-selective membrane is integrated with a biological process – a suspended growth bioreactor.

A membrane bioreactor is essentially a version of the conventional activated sludge (CAS) system. Whereas the CAS process uses a secondary clarifier or settlement tank for solid/liquid separation, an MBR uses a membrane. This provides a number of advantages relating to process control and product water quality.

Municipal & industrial treatment

There is no significant difference in the design of the MBR technology for a process treating industrial rather than municipal wastewater. The key differences between the two applications are that, for industrial effluents, there are:

• higher concentrations of organic matter
• more temporal variation in the concentrations of pollutants (seasonally and diurnally)
• very significant variations across different industrial sectors, the most biorefactory effluents being from landfill leachate applications
• no requirement for the removal of pathogenic micro-organisms, unless the effluent is combined with a sewage stream.

MBR costs

A full needs analysis is required before selecting a membrane bioreactor system, first of all to confirm that an MBR will be the most cost effective solution for a particular requirement, taking everything into account. Secondly, to ensure an MBR is the most appropriate choice of technology for the circumstances.

Design and Operation

Operation and maintenance (O&M) parameters for an MBR include:

• membrane side − flux, pressure, permeability, recovery, membrane aeration rate, and physical and chemical cleaning cycle times and protocols, and
• biological side − hydraulic and solids retention time, and sludge recycle rate(s).