Membrane bioreactors activated sludge process

Among several techniques used, the advantages offered by membrane bioreactor (MBR) technology have been recognized for some time. An MBR comprises a conventional activated sludge process coupled with membrane separation to retain the biomass. Since the effective pore size is generally below 0.1 pm, the MBR effectively produces a clarified and substantially disinfected effluent. In addition, it concentrates up the biomass and, in doing so, reduces the necessary tank size and also increases the efficiency of the biotreatment process [1]. 

Santos, A. Judd, S. (2010) The fate of metals in wastewater treated by the activated sludge process and membrane bioreactors a brief review. Journal of Environmental Monitoring, 12,110-118. 

Membrane bioreactors combine the activated sludge process for wastewater treatment with biomass separation from the mixed liquor by ultra- or microfiltration membranes. Advantages are the superior effluent quality characterized by complete solids removal and disinfection, the small footprint of the plant resulting from more compact aeration tanks, the absence of a secondary sedimentation tank, and the modular construction. 

Typical schematic representation of activated sludge process (a) membrane bioreactor (b) conventional activated sludge process. 

Dufresne R, LavaUee HC, Lebrun RE, and Lo SN, Comparison of performance between membrane bioreactor and activated sludge system for the treatment of pulping process wastewaters. Tappi J. 1998 81(4) 131-135. 

Figure 3.53 Membrane bloreactor (MBR) system process flow schematic. MBR combines biological degradation with membrane separation. Raw municipal water flows to an aerated bioreactor where the organic components are oxidised by the activated sludge. The aqueous sludge then passes through a MF or UF membrane filtration unit, separating water from the sludge. The sludge flows back to the bioreactor while the membrane permeate is discharged or reused. Source USFilter.

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