Anaerobic membrane bioreactors: Are membranes really necessary?

Abstract

Membranes themselves represent a significant cost for the full scale application of anaerobic membrane bioreactors (AnMBR). The possibility of operating an AnMBR with a self-forming dynamic membrane generated by the substances present in the reactor liquor would translate into an important saving. A selfforming dynamic membrane only requires a support material over which a cake layer is formed, which determines the rejection properties of the system. The present research studies the application of self-forming dynamic membranes in AnMBRs. An AnMBR was operated under thermophilic and mesophilic conditions, using woven and non woven materials as support for the dynamic membranes. Results showed that the formation of a cake layer over the support materials enables the retention of more than 99% of the solids present in the reactor. However, only low levels of flux were achieved, up to 3 L/m 2 x h, and reactor operation was unstable, with sudden increases in filtration resistance, due to excessive cake layer formation. Further fine-tuning of the proposed technology involves looking for conditions that can control effectively cake layer formation.

Anaerobic membrane bioreactors—a mini review with emphasis on industrial wastewater treatment: applications, limitations and perspectives

“…Dynamic membranes appear to be a promising approach for solving problems associated with high membrane cost, rapid membrane fouling and low membrane flux as such membranes exhibit low cost with high permeation at low transmembrane pressure [112]. Moreover, dynamic membranes can also improve the effluent quality [112][113][114].…”

“…The performance of dynamic membrane, therefore, depends upon various characteristics and process conditions used, with resulting differences in cake density and cake characteristics, playing a key role in the membrane's permeability. Creation of dynamic membranes, however, differs both between AnMBRs and aerobic MBR system [109,113].…”

“…While searching the literature database for this mini review, only few studies [26,113] could be found regarding use of a dynamic membrane in an AnMBR and, as with the studies focused on low cost and alternative membrane materials, this was performed under laboratory-scale conditions only. Hence, there is a clear need for further studies regarding conditions in the dynamic membrane's active layer and on identifying the optimal operational conditions to ensure middle-to long-term operation of such membranes under pilot-or full-scale conditions.…”

Analysis of fouling development under dynamic membrane filtration operation

“…[4][5][6][7][8]. Meshes of different porosity ranging from 10 to 500 µm have been reported in literature as a suitable support material for developing DMs [7][8][9][10]. The filtration mechanism of DMs is quite different to conventional MF/UF membranes in a way that, after the formation of DM layer, the filtration resistance is exclusively caused by the cake layer [7].…”

Characteristics and role of dynamic membrane layer in anaerobic membrane bioreactors

“…They found that the best effluent quality and sludge retention efficiency were achieved with a pore size of 100 μm. On the other hand, Jeison et al () showed that pore sizes of over 60–70 μm were not suitable for cake layer accumulation. Thus, smaller pore sizes should be selected for anaerobic dynamic membrane applications.…”