Sustaining membrane permeability during unsteady-state operation of anaerobic membrane bioreactors for municipal wastewater treatment following peak-flow

Abstract

Key highlights Peak flow characteristics (size, duration and frequency) are examined for AnMBR  Increasing gas flow rate during peak flow improves recovery  Supra-critical fluxes can be sustained for short durations  Specifying average flux below critical flux improves recoverability  Membrane area should be based on average flow, reducing capital cost AbstractIn this study, the impact of peak flow on anaerobic membrane bioreactor operation is investigated to establish how system perturbation induced by diurnal peaks and storm water flows will influence membrane permeability. Good permeability recovery was attained through increasing gas sparging during peak flow, which was explained by the transition in critical flux of the suspension at higher shear rates. However, supra-critical fluxes could also be sustained, provided peak flow was for a short duration. We suggest longer durations of supra-critical operation could be sustained through introduction of reactive fouling control strategies (e.g. TMP set-point control). An initial flux below the critical flux, prior to the introduction of peak flow, was advantageous to permeability recovery, suggesting membrane 'conditioning' is important in governing recoverability following peak flow. The importance of conditioning was confirmed through analysis of multiple peak flow events in which the loss of permeability following each peak-flow event was increasingly negligible, and can be ascribed to the arrival of a steady-state in membrane surface deposition. Whilst responding to peak flow with increased gas sparging has been shown effective, the energy demand is considerable, and as such a pseudo dead-end filtration strategy was also evaluated, which required only 0.04 kWh m -3 of energy for gas sparging. Comparison of both filtration modes identified comparable fouling rates, and the feasibility of a low energy gas sparging method for peak flow management that has successfully enabled supra-critical fluxes to be achieved over long-periods in other MBR applications. Importantly, membrane . Please refer to any applicable publisher terms of use.2 area provides the highest contribution toward capital cost of AnMBR. The potential to turnup flux in response to peak-flow has been identified in this study, which suggests membrane area can be specified based on average flow rather than peak flow, providing substantive reduction in the capital cost of AnMBR for municipal wastewater treatment.

Long-term operation of a pilot-scale anaerobic membrane bioreactor (AnMBR) treating high salinity low loaded municipal wastewater in real environment

“…The TMP of AnMBRs is highly dependent on the critical flux and the sparging rate together with other environmental and operating conditions [35]. Furthermore, an initial flux below the critical flux, prior to the introduction of peak flow, is reported to be advantageous to permeability recovery [36]. In the study of Muñoz Sierra et al [18], increased salt concentration was found to affect the TMP negatively (350 mbar at a flux of 4.0 Lm 2. h -1 ).…”

Hydrolysis and Methanogenesis in UASB-AnMBR Treating Municipal Wastewater Under Psychrophilic Conditions: Importance of Reactor Configuration and Inoculum

“…The granular 42.5 L reactor (G-AnMBR) was inoculated with 16 L granular sludge from a mesophilic UASB used for pulp and paper industry. Both inoculums had a previous acclimation of 3 years treating the same wastewater and had been left without feeding for 5 months (Wang et al, 2018b). During the previous acclimation period, the effect on membrane permeability of peak flow was assessed.…”

Membrane processes

“…The impact of diurnal peak flow and stormwater flows on the permeability of MBR was investigated by Wang, Soares, Soares, Jefferson, and McAdam (2018) to determine if the design of the MBR surface area can be based on the average flows instead of the peak flows. A granular UASB (G‐UASB) AnMBR, pilot plant study, indicated that the membrane design could be based on average flows, and the membranes can be operated at peak.…”