Analysis of backwashing efficiency in dead-end hollow-fibre ultrafiltration of anaerobic suspensions

Vera, Luisa; Cabrera, E; Ruigómez, Ignacio; Gómez, José Ignacio González; Delgado, S.

doi:10.1007/s11356-015-4857-0

Cited by 19 publications

(13 citation statements)

References 29 publications

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“…was used for the dead-end regime ( Table 2). This is higher than compared with typical fluxes of 5-12 L m -2 h -1 reported in the AnMBR literature [5,31] and is equivalent to or higher than the critical flux recorded for the suspension (Figure 3). This is consistent with earlier studies of dead-end gas sparging for MBR where sustained operation was demonstrated at fluxes exceeding the critical flux [31,32].…”

Section: Discussioncontrasting

confidence: 52%

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Identification of gas sparging regimes for granular anaerobic membrane bioreactor to enable energy neutral municipal wastewater treatment

Wang

Cingolani

Eusebi

et al. 2018

Journal of Membrane Science

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In this study, conventional and novel gas sparging regimes have been evaluated for a municipal wastewater granular anaerobic MBR to identify how best to achieve high sustainable fluxes whilst simultaneously conserving energy demand. Using continuous gas sparging in combination with continuous filtration, flux was strongly dependent upon shear rate, which imposed a considerable energy demand. Intermittent gas sparging was subsequently evaluated to reduce energy demand whilst delivering an analogous shear rate. For a flux of 5 L m-2 h-1 , a fouling rate below 1 mbar h-1 was sustained with low gas sparging frequency and gas sparging rates. However, to sustain low fouling rates for fluxes above 10 L m-2 h-1 , a gas sparging frequency of 50 % (i.e. 10 s on/10 s off) and an increase in gas sparging rate is needed, indicating the importance of shear rate and gas sparging frequency. An alternative gas sparging regime was subsequently tested in which filtration was conducted without gas sparging, followed by membrane relaxation for a short period coupled with gas sparging, to create a pseudo dead-end filtration cycle. Fouling characterisation evidenced considerable cake fouling rates of 200-250 mbar h-1 within each filtration cycle. However, long term fouling transient analysis demonstrated low residual fouling resistance, suggesting the cake formed during filtration was almost completely reversible, despite operating at a flux of 15 L m-2 h-1 , which was equivalent or higher than the critical flux of the suspension. It is therefore asserted that by operating filtration in the absence of shear, fouling is less dependent upon the preferential migration of the submicron particle fraction and is instead governed by the compressibility of the heterogeneous cake formed, which enables higher operational fluxes to be achieved. Comparison of energy demand for the three gas sparging regimes to the energy recovered from municipal wastewater AnMBR demonstrated that only by using dead-end filtration can energy neutral wastewater treatment be realised which is the ultimate ambition for the technology.

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Section: Discussioncontrasting

confidence: 52%

“…Dead-end filtration cycle analysis was undertaken using three profile characteristics [31]. The initial TMP for each filtration cycle (TMP i ) which is related to the resistance provided by the clean membrane (R m ) and the internal residual fouling resistance (R if ) which is not removed by physical cleaning:…”

Section: Anaerobic Mbr Pilot Plantmentioning

confidence: 99%

Identification of gas sparging regimes for granular anaerobic membrane bioreactor to enable energy neutral municipal wastewater treatment

Wang

Cingolani

Eusebi

et al. 2018

Journal of Membrane Science

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“…However, it is important to recognise that the maximum TMP reached increased with peak length, reaching a maximum of around 300 mbar following operation for 8 h at peak flow (Figure 9), which is above the operating TMP ordinarily adopted at full-scale. Several authors have adopted reactive maintenance philosophies where a TMP set-point initiates automated backwash/relaxation, rather than temporal cycling [20,35]. For example, Hirani et al [4] applied shorter filtration cycles, longer backwash durations or higher backwash fluxes during peak flow and evidenced only modest permeability reduction after several days of peak-flow assessment for aerobic MBR.…”

Section: Discussionmentioning

confidence: 99%

“…In AnMBR, the bulk sludge matrix is considerably more complex than in conventional aerobic MBR, leading to significantly higher membrane fouling [7,19]. As such, the reported flux for AnMBR is ordinarily between 5-12 L m -2 h -1 [1,20], which is considerably below the flux of 20-30 L m -2 h -1 typically specified for full-scale aerobic MBR [7]. The membrane area required for AnMBR will therefore be greater than for aerobic MBR, with the membrane cost inevitably increasing when membrane area is specified to sustain average flux at peak flow.…”

Section: Introductionmentioning

confidence: 99%

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

Wang

Jefferson

Soares

et al. 2018

Journal of Membrane Science

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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.

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“…The AnMBR was equipped with a ZeeWeed hollow‐fibre module with an average pore size of 0.04 µm (ZW‐1, GE Water & Process Technologies, USA). Further details of the experimental unit can be found in a previous work . The main characteristics of the AnMBR effluent are shown in Table .…”

Section: Methodsmentioning

confidence: 99%

Critical assessment of the nanofiltration for reusing brackish effluent from an anaerobic membrane bioreactor

Cabrera

Ruigómez

Gómez

et al. 2017

Env Prog and Sustain Energy

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In this study, a saline effluent from an anaerobic membrane bioreactor was treated by nanofiltration in order to allow its agricultural reuse. Short-term tests were conducted to investigate membrane fouling and selective rejection of ions and emerging organic contaminants (EOCs). The study has been conducted with a negatively charged commercial thin-film composite membrane (DK, GE Osmonics). The effect of operating pressure (5-20 bar) and cross-flow velocity (0.12-0.37 m/s) on membrane performance have been researched. Dimensional analysis of steady permeate flux indicated that the gel layer or the polarization layer can be completely removed at critical cross-flow velocity. At a subcritical velocity, membrane autopsies by scanning electron microscopy (SEM) and energy dispersive X-Ray spectroscopy revealed a complex mixture of organic matter, phosphates and colloidal silica over the membranes surface. Since the rejection of monovalent cations (76-88%) was lower than that of multivalent cations (above 96%), the treated effluent was characterized by a very high levels of sodium adsorption ratio and ammonium. In addition, moderate rejection of low molecular weight EOCs (clofibric acid and caffeine) was observed. Therefore, the treated effluent did not achieve enough quality to be reused for agricultural irrigation. V C 2017 American Institute of Chemical Engineers Environ Prog, 37: 383-390, 2018 During the last decade, interest in the application of nanofiltration in wastewater treatment has grown in response to stringent water quality standards and increasing concern about the presence of emerging organic contaminants (EOCs). Nevertheless, information remains scarce about membrane fouling and EOCs rejection. The current research addresses these issues during its application to a brackish effluent from an anaerobic membrane bioreactor to be reused for agricultural irrigation. Dimensional analysis has allowed establishing the optimum operation conditions in terms fouling control. As regard of EOCs rejection, low molecular weight compounds were not completely retained by the membrane.

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Analysis of backwashing efficiency in dead-end hollow-fibre ultrafiltration of anaerobic suspensions

Cited by 19 publications

References 29 publications

Identification of gas sparging regimes for granular anaerobic membrane bioreactor to enable energy neutral municipal wastewater treatment

Identification of gas sparging regimes for granular anaerobic membrane bioreactor to enable energy neutral municipal wastewater treatment

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

Critical assessment of the nanofiltration for reusing brackish effluent from an anaerobic membrane bioreactor

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