Features - Membrane operation

At what cost? MBR capital and operating expenditure − the impact of labour

It is most often assumed that the main cost associated with operating a membrane separation plant relates to the energy consumption, followed by the membrane replacement. Consequently, considerable efforts have been devoted to fouling control and mitigation, with more than one fifth of all MBR research literature publications devoted to this topic (Judd, 2017).

view feature

Membrane operation | Feasibility, optimisation and costs

Channel clogging in membrane bioreactors

Clogging can take place within MBR module channels as a thick deposit which fills the channel (‘sludging’ or ‘localised dewatering’). Sometimes long rags or braids can develop in the tank itself which wrap around the membrane tank infrastructure (‘ragging’ or ‘braiding’). Chemical cleans are largely ineffective since they can only attack the foulants on the membrane surface, so leaving the clogged material filling the membrane channels largely unaltered. Cranfield University and Qatar University have completed work on this largely neglected research area.

view feature

Membrane operation

The disinfection capability of MBRs: credit where credit’s due

Disinfection by MBRs. Unlike regular physical membrane filtration, virus removal by MBRs is not limited to simple size exclusion. Adsorption onto the sludge solids and the membrane cake layer (as well as the membrane itself) represent important removal mechanisms, as well as removal by predation (the feeding on the pathogens by other higher organisms).

view feature

Membrane operation | Process biology | Water quality and treatability

The impact of biofouling on surface membrane properties in MBRs

MBR membranes are prone to fouling generally, and biofouling in particular, by organic matter originating from the microbial cells. These biofoulants vary in concentration with the activated sludge characteristics, such as the mixed liquor suspended solids (MLSS) concentration and solids retention time (SRT) (and so the food/microorganism (F/M) ratio), as well as the feedwater chemistry.

view feature

Membrane operation | Process biology

Reducing process aeration energy consumption in MBRs

MBRs use more energy compared with classical activated sludge (CAS) because the aeration requirements are greater. Aeration is needed both for the biological and membrane tanks for degrading the organics and scouring the membrane respectively. Typically, aeration energy consumption accounts for 70–80% of total energy used for the municipal wastewater treatment process, with 40–60% consumed by the process biology.

view feature

Membrane operation | Process biology | Feasibility, optimisation and costs