Aerobic Membrane Bioreactor Research Articles

Removal of azo dye acid orange 7 using aerobic membrane bioreactor

A laboratory scale aerobic membrane bioreactor (MBR) using a submerged microfiltration (MF); hollow-fiber membrane was used for treating wastewater polluted with azo dye acid orange 7 (AO7). Initial dye concentrations studied were from 50 to 400 mg/l with a COD ranging from 95 to 550 mg O 2/l and hydraulic retention times (HRT) 4, 6, 8 and 24 h. Results showed that the biological process was responsible for almost 60–80% of COD removal and almost all the removal of AO7 color. Membrane microfiltration merely balanced the unstable biological treatment of COD and demonstrated almost no contribution to AO7 color removal. Trans-membrane pressure (TMP) increased with time, and with the increase of dye concentration reaching a maximum of 4.175 psi. Scanning electron microscope (SEM) images of the membrane’s filament were taken and compared with a SEM image of a virgin membrane; clear deformation in membrane’s pore structure could be noticed as well as scale formation on the outer surface of filaments, foulants were determined using the energy dispersive X-ray analysis (EDX).

Linking microbial community structure to membrane biofouling associated with varying dissolved oxygen concentrations

In order to elucidate how dissolved oxygen (DO) concentration influenced the generation of extracellular polymeric substance (EPS) and soluble microbial products (SMP) in mixed liquor and biocake, 16S rDNA fingerprinting analyses were performed to investigate the variation of the microbial community in an aerobic membrane bioreactor (MBR). The function of microbial community structure was proved to be ultimately responsible for biofouling. Obvious microbial community succession from the subphylum of Betaproteobacteria to Deltaproteobacteria was observed in biocake. High concentration of EPS in biocake under the low DO concentration (0.5 mg L −1) caused severe biofouling. The correlation coefficient of membrane fouling rate with EPS content in biocake (0.9941–0.9964) was much higher than that in mixed liquor (0.6689–0.8004).

Bioaugmented membrane bioreactor (MBR) with a GAC-packed zone for high rate textile wastewater treatment

The long-term performance of a bioaugmented membrane bioreactor (MBR) containing a GAC-packed anaerobic zone for treatment of textile wastewater containing structurally different azo dyes was observed. A unique feeding strategy, consistent with the mode of evolution of separate waste streams in textile plants, was adopted to make the best use of the GAC-zone for dye removal. Dye was introduced through the GAC-zone while the rest of the colorless media was simultaneously fed through the aerobic zone. Preliminary experiments confirmed the importance of coupling the GAC-amended anaerobic zone to the aerobic MBR and also evidenced the efficacy of the adopted feeding strategy. Following this, the robustness of the process under gradually increasing dye-loading was tested. The respective average dye concentrations (mg/L) in the sample from GAC-zone and the membrane-permeate under dye-loadings of 0.1 and 1 g/L.d were as follows: GAC-zone (3, 105), permeate (0, 5). TOC concentration in membrane-permeate for the aforementioned loadings were 3 and 54 mg/L, respectively. Stable decoloration along with significant TOC removal during a period of over 7 months under extremely high dye-loadings demonstrated the superiority of the proposed hybrid process.

Microbial community analysis of an aerobic nitrifying-denitrifying MBR treating ABS resin wastewater

A two-stage aerobic membrane bioreactor (MBR) system for treating acrylonitrile butadiene styrene (ABS) resin wastewater was carried out in this study to evaluate the system performance on nitrification. The results showed that nitrification of the aerobic MBR system was significant and the highest TKN removal of approximately 90% was obtained at hydraulic retention time (HRT) 18 h. In addition, the result of nitrogen mass balance revealed that the percentage of TN removal due to denitrification was in the range of 8.7–19.8%. Microbial community analysis based on 16s rDNA molecular approach indicated that the dominant ammonia oxidizing bacteria (AOB) group in the system was a β-class ammonia oxidizer which was identified as uncultured sludge bacterium ( AF234732). A heterotrophic aerobic denitrifier identified as Thauera mechernichensis was found in the system. The results indicated that a sole aerobic MBR system for simultaneous removals of carbon and nitrogen can be designed and operated for neglect with an anaerobic unit.

Effect of low dissolved oxygen on simultaneous nitrification and denitrification in a membrane bioreactor treating black water

Effect of low dissolved oxygen on simultaneous nitrification and denitrification was evaluated in a membrane bioreactor treating black water. A fully aerobic membrane bioreactor was operated at a sludge age of 60 days under three low dissolved oxygen (DO) levels below 0.5 mg/L. It sustained effective simultaneous nitrification/denitrification for the entire observation period. Nitrification was incomplete due to adverse effects of a number of factors such as low DO level, SMPs inhibition, alkalinity limitation, etc. DO impact was more significant on denitrification: Nitrate was fully removed at low DO level but the removal was gradually reduced as DO was increased to 0.5 mg/L. Nitrogen removal remained optimal within the DO range of 0.15–0.35 mg/L. Experimental results were calibrated and simulated by model evaluation with the same model coefficients. The model defined improved mass transfer with lower affinity coefficients for oxygen and nitrate as compared to conventional activated sludge.

Simultaneous methane production and wastewater reuse by a membrane-based process: Evaluation with raw domestic wastewater

In this study, a membrane-based process was applied to simultaneously reclaim methane and generate reused water from raw domestic wastewater. The system was comprised of up-flow anaerobic sludge fixed bed (UAFB), anoxic sink (AS) and aerobic membrane bioreactor (MBR). The hydraulic retention time of UAFB (HRTU) was gradually shortened from 8h to 6h, 3h and to 1h, while the HRT of AS and MBR kept at 8h. It is found that HRTU of 3h was more suitable for the balancing production of biogas and volatile fatty acids (VFAs), and the VFAs served as carbon source for denitrification. The trans-membrane pressure (TMP) of the MBR kept lower than 0.04MPa without wash or change of membrane sheet, however, the scanning electron microscopy (SEM) analysis indicated that microbes attached to the inner-surface of membrane, causing irreversible fouling after 133-day operation. The denaturing gradient gel electrophoresis (DGGE) profiles of amplified 16S rDNA gene fragments proved that more functional bacteria and higher microbial diversity emerged at HRTU of 3h and 1h. Most bacteria belonged to Betaproteobacteria and were responsible for carbon and nitrogen removal.

Treatment of a simulated textile wastewater containing the azo-dye reactive orange 16 in an anaerobic-biofilm anoxic–aerobic membrane bioreactor

This study evaluated the treatability of simulated textile wastewaters in a bench-scale experimental system, comprising an anaerobic biofilter, an anoxic reactor and an aerobic membrane bioreactor. The Reactive Orange 16 (RO16) was used as model of azo dye. The proposed system was demonstrated to be effective in the treatment of the synthetic wastewater under the operating conditions applied in the study. The results demonstrate that neither the azo dye, nor the aromatic amines formed by the anaerobic azo-bond cleavage seem to significantly affect the COD and nitrogen removal under the operating conditions applied. Although aromatic amines are considered easily degradable under aerobic conditions, the results confirms that at least the sulfonated aromatic amines formed under anaerobic conditions from the RO16 are recalcitrant to biodegradation and therefore aromatic amines are still a matter of concern for the biological treatment of textile wastewater.

Visualizing Fouling Layer in Membrane Bioreactor

The membrane fouling layer in the combined aerobic granular membrane bioreactor (AGMBR) process and the conventional MBR process was probed in this study using the multiple staining and confocal laser scanning microscope (CLSM) technique. The fouling layer built up outside and inside the membrane was principally composed of live cells embedded in a matrix of proteins and polysaccharides. The fouling layer presented outside the membrane is noted denser in structure than that inside the membrane.

Influence of Internal Biofilm Growth on Residual Permeability Loss in Aerobic Granular Membrane Bioreactors

Membrane fouling results in flux decline or transmembrane pressure drop increase during membrane bioreactor (MBR) operation. Physical and chemical cleanings are essential to keep an MBR operating at an appropriate membrane flux. Considerable residual membrane permeability loss that cannot be removed by conventional cleaning requires membrane replacement. This study demonstrates that an internal biofilm can develop inside a hollow-fiber membrane and can probably account for up to 58.9 and 81.3% of total membrane resistance for aerobic granular MBR operated in sequencing batch reactor (SBR) mode or continuous-fed mode, respectively. The Arthrobacter sp. (accession no. AM900505 in GenBank) corresponded to internal biofilm development by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis and the agar-plating technique. This study also identifies a single strain, Arthrobacter sp., generates the internal biofilm. The Arthrobacter sp. is a rod-shaped bacterium with a size close to that of membrane pores, and can secrete excess bound proteins, hence can penetrate and attach itself inside the membrane and grow. Internal biofilm growth could contribute significantly to membrane resistance during long-term MBR operation.

A direct comparison amongst different technologies (aerobic granular sludge, SBR and MBR) for the treatment of wastewater contaminated by 4-chlorophenol

Environmental concern on chlorinated phenols is rising due to their extreme toxicity even at low concentrations and their persistency in water and soils. Since the high amount of published data often lacks in terms of uniformity, direct comparisons amongst different treatment technologies are very difficult, or even impossible. In this study, granular sludge developed in an acetate-fed Granular sludge Sequencing Batch Reactor (GSBR) was used for the aerobic degradation of low chlorinated 4-chlorophenol (4CP), with readily biodegradable sodium acetate (NaAc) as growth substrate. A conventional Sequencing Batch Reactor (SBR) and a Membrane BioReactor (MBR) were operated in parallel under the same 4CP influent concentrations and/or 4CP volumetric organic loading rates as the GSBR, in order to carry out a direct comparison in terms of 4CP removal efficiencies and specific removal rates, effluent quality, waste sludge production, system simplicity, land area requirement, start-up times, NaAc dosage as growth substrate and maximum applied 4CP volumetric organic loading rate. A decision matrix was built to define the best technology to suit different scenarios: the GSBR was proved to be the most suitable technology when system simplicity, low land area requirement and short start-up times were considered as critical parameters for decision making.

Biodegradation of the endogenous residue of activated sludge

This study evaluated the potential biodegradability of the endogenous residue in activated sludge subjected to batch digestion under either non-aerated or alternating aerated and non-aerated conditions. Mixed liquor for the tests was generated in a 200 L pilot-scale aerobic membrane bioreactor (MBR) operated at a 5.2 days SRT. The MBR system was fed a soluble and completely biodegradable synthetic influent composed of sodium acetate as the sole carbon source. This influent, which contained no influent unbiodegradable organic or inorganic materials, allowed to generate sludge composed of essentially two fractions: a heterotrophic biomass X H and an endogenous residue X E, the nitrifying biomass being negligible (less than 2%). The endogenous decay rate and the active biomass fraction of the MBR sludge were determined in 21-day aerobic digestion batch tests by monitoring the VSS and OUR responses. Fractions of X H and X E: 68% and 32% were obtained, respectively, at a 5.2 days SRT. To assess the biodegradability of X E, two batch digestion units operated at 35 °C were run for 90 days using thickened sludge from the MBR system. In the first unit, anaerobic conditions were maintained while in the second unit, alternating aerated and non-aerated conditions were applied. Data for both units showed apparent partial biodegradation of the endogenous residue. Modeling the batch tests indicated endogenous residue decay rates of 0.005 d −1 and 0.012 d −1 for the anaerobic unit and the alternating aerated and non-aerated conditions, respectively.

Performance of a three-stage membrane bioprocess treating the Organic Fraction of Municipal Solid Waste and evolution of its archaeal and bacterial ecology

A novel three-stage bioprocess achieved 75% volatile solids (VS) removal at an organic loading rate (OLR) of 4 g VS L −1 day, a solids retention time (SRT) of 66 days, a hydraulic retention time (HRT) of 20 days, at a temperature of 35 °C. The bioprocess consisted of an anaerobic hydrolytic reactor (HR) where the solids and liquid fractions of the Organic Fraction of the Municipal Solid Waste (OFMSW) were separated with a mesh. The leachate was pumped to a Submerged Anaerobic Membrane Bioreactor (SAMBR) and the treated permeate was polished in an Aerobic Membrane Bioreactor (AMBR). Denaturing Gradient Gel Electrophoresis (DGGE) and DNA sequencing analyses indicated that the increase in methane content in the HR caused by the excess sludge recycle from the SAMBR was associated with an increase in the number of hydrogenotrophic species, mainly Methanobrevibacter sp., Methanobacterium formicicum and Methanosarcina sp. At 20 °C VS removal dropped to 50% in the HR and some DGGE bands disappeared when compared to 35 °C samples, while some bands such as the one corresponding to Ruminococcus flavefaciens were reduced in intensity. The species associated with the COD-polishing properties of the AMBR correspond to the genera Pseudomonas, Hyphomonas and Hyphomicrobiaceae. These results highlight the positive effect of recycling the excess sludge from the SAMBR to re-inoculate the HR with hydrogenotrophic species.

Mathematical modeling of aerobic membrane bioreactor (MBR) using activated sludge model no. 1 (ASM1)

Abstract Activated sludge model no. 1 (ASM1) was applied to an aerobic membrane bioreactor (MBR) treating dilute municipal wastewater. The model for the aerobic MBR was calibrated using the data collected from a lab-scale aerobic MBR using AQUASIM 2.0. The performance of MBR process in terms of chemical oxygen demand (COD) removal and ammonia nitrogen (SNH) nitrification was studied at different operating conditions such as hydraulic retention time (HRT), solid retention time (SRT) and mixed liquor suspended solids (MLSS) concentrations. The characteristics of influent wastewater, pre-settled primary effluent from a wastewater treatment plant (City of Elmhurst WWTP, Elmhurst, IL, USA), were determined in the laboratory and used for the calibration of the model. The results from the simulations provided a better understanding of the mechanisms and kinetics of the MBR process including sludge removal.

Filterability in a submerged anaerobic membrane bioreactor

Studies on anaerobic membrane bioreactor (AMBR) show high variability about filterability. Therefore, in this study, a laboratory-scale submerged AMBR (SAMBR) was operated with the aim of identifying operational conditions and sludge characteristics that influence the membrane flux. Short-term experiments applying the flux-step method resulted in values of the critical flux (Jc) variable depending on the operational condition applied in the SAMBR. The application of different parameters for the identification of Jc gave comparable results. Although the plant was operated applying different operational conditions, a rapid membrane fouling was usually observed. The applicable fluxes were between 2 and 5 L/(m 2 h) depending on operational conditions. Therefore, the results confirm the much lower sludge filterability in anaerobic than aerobic MBRs. Multiple regression analysis showed that the supernatant composition plays the most important role in membrane fouling.

Potential for reuse of high cellulose containing wastewater after membrane bioreactor treatment

It is difficult to adequately treat wastewater with a high cellulose content with the traditional anaerobic and aerobic activated sludge processes. In this study we used microfiltration (MF) and reverse osmosis (RO) membranes combined with an anaerobic or aerobic activated sludge process to treat high cellulose containing wastewater for different hydraulic retention times (HRTs). The potential target applications for reuse of the treated wastewater are also compared. Six bioreactors, which were configured as anaerobic sequencing batch reactor (ANSBR), aerobic sequencing batch reactor (ASBR), aerobic membrane bioreactor (AMBR), AMBR plus RO (AMBR/RO), anaerobic activated sludge plus aerobic MBR (AOMBR), and AOMBR plus RO (AOMBR/RO), was operated in this study. The experiment results showed that, as expected, no effluents from the ASBR or the ANSBR could meet the Taiwan EPA criteria for effluent and wastewater reuse, no matter what the HRT was. However when the HRT was 12 h or more, the effluent from the AMBR and AOMBR processes did meet the criteria for effluent, but still did not meet the treated wastewater reuse criteria , primarily due to the color, total alkalinity, and total dissolved solid parameters. Finally, the effluents from the AMBR/RO and AOMBR/RO processes did meet the Taiwan criteria for both effluent and treated wastewater reuse when the HRT for the AOMBR/RO and AMBR/RO processes was equal to or longer than 12 h and 8 h, respectively. For the HRT of 4 h for both the AOMBR/RO and AMBR/RO process, and an HRT of 8 h for the AOMBR/RO process, neither the effluent criteria nor the treated wastewater reuse criteria were met.

Biodiversity in aerobic granule membrane bioreactor at high organic loading rates

The aerobic granular sludge process and the membrane bioreactor process are promising, novel environmental bioprocesses for the reclamation of industrial and municipal wastewaters. They are practical and have attracted much research interest. The combination of these two processes in the aerobic granular membrane bioreactor (AGMBR), yields reclaimed water of high quality in a compact reactor. Information on the microbial community in an AGMBR operated at a high organic loading rate is lacking. This study elucidates the microbial dynamics in acetate-fed AGMBR operated in sequencing batch reactor mode. The structure of the microbial community revealed by denaturing gradient gel electrophoresis, demonstrates the dominance of the denitrifying microbial community, which is affiliated with members of the families Comamonadaceae and Alcaligenaceae, of the class Betaproteobacteria. The role of the predominant strains in the AGMBR is discussed.

Performance and dye-degrading bacteria isolation of a hybrid membrane process

Textile dyeing wastewater contains harmful compounds, which are toxic to both marine organisms and human beings if it discharged into an aquatic environmental without suitable treatment. In this study, the wastewater containing the azo dye, Reactive Black 5 (RB5), was partially treated in an anaerobic sequencing batch reactor which was further treated either in an aerobic membrane bioreactors (AOMBR) or in combined aerobic membrane bioreactor/reverse osmosis (AOMBR/RO) process. The results showed that in the anaerobic sequencing batch reactor the RB5 dye was degraded to form aromatic amine intermediate metabolites, which were further mineralized in the AOMBR. It was also observed that although all effluents from the AOMBR and AOMBR/RO processes met the Taiwan EPA's effluent criteria, irrespective of which membranes were used in the aerobic tank, the effluent from the AOMBR/RO process met the criteria for reuse for toilet flushing, landscaping, irrigation, and cooling water purposes, where as the AOMBR effluent only met the criteria for cooling water due to incomplete color removal. Five anaerobic high dye-degrading bacteria were isolated, which were identified to be the same species of Lactococcus lactis by 16S rRNA sequencing. The L. lactis showed complete degradation of RB5 and further studies showed that it can also able to degrade Reactive Red 120 and Reactive Yellow 84 efficiently within 6 h.

Application of combined membrane biological reactor and electro-oxidation processes for the treatment of landfill leachates

Landfill leachate (LFL) is a very complex wastewater that poses considerable hazards to local communities and the environment. With this concern in mind, the present study was undertaken to investigate the performance of an aerobic membrane bioreactor treating raw LFL from Djebel Chekir (Tunisia) discharge. The LFL samples collected from this site were found to be highly loaded with organic matter, ammonia, salts, greases, phenols and hydrocarbons. Important removals of chemical oxygen demand (COD) and NH4+-N were attained after 44 days of treatment at optimum conditions for the membrane and with organic loading rates (OLR) of 1.9 and 2.7 grams COD per litter and day. This treatment allowed for an important detoxification of the landfill leachates and a significant elimination of the microorganisms. Electrochemical oxidation using Pi/Ti was applied as a post-treatment and after the biological process in order to reduce the residual ammonia and COD. At a pH value of 9, current density of 4 A dm(-2) and electrolysis time of 60 minutes, COD and ammonia nitrogen were reduced to 1,000 mg L(-1) and 27 mg L(-1), respectively. COD and NH4+-N removals were accompanied by significant detoxification.

Effect of Recirculation Ratio on Simultaneous Methanogenesis and Nitrogen Removal Using a Combined Up-Flow Anaerobic Sludge Blanket–Membrane Bioreactor

Abstract Simultaneous methanogenesis and nitrogen removal using a combined system consisting of an up-flow anaerobic sludge blanket (UASB) and aerobic membrane bioreactor (MBR) was investigated for treating synthetic municipal wastewater. A more reliable effluent quality of above 98.0% total organic carbon (TOC) and 98.0% NH4+-N removal was achieved consistently throughout the experiments. Total nitrogen (TN) removal of up to 82.8% could also be achieved when the recycling ratio was increased from 0 to 800%. Analysis of the biogas composition showed that the degradation of NOX−-N through denitrification did not have any obvious effect on the total methane production up to a recycling ratio of 400%. A higher recycling ratio of 800% resulted in an increase of CO2 and a decrease of CH4, due to more sludge being washed out from the UASB into the MBR and recycled back into the UASB, which resulted in a higher dissolved oxygen (DO) concentration in the UASB. Hence, an optimal recycling ratio of 400% was suggest...

Anaerobic decolorization bacteria for the treatment of azo dye in a sequential anaerobic and aerobic membrane bioreactor

Textile dyeing wastewater is harmful to both marine organisms and human beings. This study focused on the treatment of wastewater containing an azo dye, Reactive Black 5 (RB5), using an anaerobic sequencing batch reactor (SBR) combined with an aerobic membrane bioreactor (aerobic MBR). In addition the anaerobic RB5 degrading bacteria were isolated and their individual performance were tested separately. Nearly 92.3 and 5.2% of COD removal and 74.6 and 9.1% of true color removal was achieved using the anaerobic SBR and the aerobic MBR respectively. Five types of high RB5 degrading bacteria isolated were sequenced to be different subspecies of Lactococcus lactis, which could degrade more than 99% of the RB5 within 5.5 h. Twenty types of medium RB5 degrading isolation were observed to be different subspecies of Lactobacillus casei, which could degrade more than 99% of the RB5 within 36 h. Finally, the experiments also showed that the RB5 degradation performance of the L. casei was improved by the suitable addition of carbon and nitrogen source in the medium.