Submerged Anaerobic Membrane Bioreactor Research Articles

Inorganic fouling of an anaerobic membrane bioreactor treating leachate from the organic fraction of municipal solid waste (OFMSW) and a polishing aerobic membrane bioreactor

The treatment of leachate (Average TCOD=11.97g/L, 14.4% soluble) from the organic fraction of municipal solid waste was investigated using a Submerged Anaerobic Membrane BioReactor (SAMBR), followed by an aerobic membrane bioreactor (AMBR) to polish this effluent. This paper investigated the exact nature and composition of the inorganic precipitate in each of the reactors in the process. The flux decreased due to precipitation of calcium as monohydrocalcite (CaCO3·H2O) containing traces of metals onto the SAMBR membrane because of high CO2 partial pressures. Precipitation of calcium in the AMBR was also observed due to a higher pH. In this case, phosphorus also precipitated with calcium in two different phases: the background layer contained calcium, oxygen, carbon and small amounts of phosphorus (2–6.7%), while flakes containing calcium, oxygen and higher amounts of phosphorus (10–17%) were probably hydroxyapatite (Ca5(PO4)3OH).

Effect of sparging rate on permeate quality in a submerged anaerobic membrane bioreactor (SAMBR) treating leachate from the organic fraction of municipal solid waste (OFMSW)

This paper focuses on the treatment of leachate from the organic fraction of municipal solid waste (OFMSW) in a submerged anaerobic membrane bioreactor (SAMBR). Operation of the SAMBR for this type of high strength wastewater was shown to be feasible at 5 days hydraulic retention time (HRT), 10 L min−1 (LPM) biogas sparging rate and membrane fluxes in the range of 3–7 L m−2 hr−1 (LMH). Under these conditions, more than 90% COD removal was achieved during 4 months of operation without chemical cleaning the membrane. When the sparging rate was reduced to 2 LPM, the transmembrane pressure increased dramatically and the bulk soluble COD concentration increased due to a thicker fouling layer, while permeate soluble COD remained constant. Permeate soluble COD concentration increased by 20% when the sparging rate increased to 10 LPM.

A novel configuration for an anaerobic submerged membrane bioreactor (AnSMBR). Long-term treatment of municipal wastewater under psychrophilic conditions

A novel design for a pilot scale anaerobic submerged membrane bioreactor (AnSMBR) equipped with an ultrafiltration unit, treating municipal wastewater at 18±2°C, and inoculated with a mesophilic inoculum without acclimation, was implemented and evaluated over 3years of stable operation. The AnSMBR operated with a volumetric loading rate between 1.6 to 2.0kgCOD/m3UASBd, 12.8 to 14.2h hydraulic retention time, and reached a tCOD removal efficiency of around 90%. Biosolid production was between 0.05 and 0.083gVS/gCODremoved. Dissolved methane oversaturation in the effluent was observed, reaching average values of 19.1±0.84mgCH4/L. The permeate flow rate ranged from 10 to 14L/m2h with trans-membrane pressure (TMP) values of 400–550mbar, using cycles of 30s backwash, 7.5min filtration, and continuous biogas sparging (9–16m/h). During the three years of continuous operation, the membrane was not physically or chemically cleaned.

Modeling of hydrodynamics and mixing in a submerged membrane bioreactor

This work deals with the optimization of mixing in an anaerobic submerged membrane bioreactor (AnMBR) devoted to the production of biohydrogen as a 2nd generation biofuel using the dark fermentation process from lignocellulosic waste. The AnMBR consists of an unbaffled mechanically-stirred tank equipped with a two-stage radial impeller which is coupled to an external hollow fibre membrane module placed in a forced circulation loop with permeate suction. In the tank, mixing conditions must enable the suspension of solid waste, homogenize local concentrations, and enhance hydrogen desorption simultaneously. For optimizing reactor design, mixing was investigated both experimentally and numerically. The computational strategy consisted in the combination of 1D and 3D methodologies including single-phase and two-fluid CFD models. The experimental approach encompassed RTD and mixing time measurements, the analysis of vortex formation and the description of solid suspension using straw as waste. The results showed that a laminar flow pattern prevailed in the recirculation loop and the membrane unit, while turbulent flow was observed in the stirred tank in which mixing time was far smaller than residence time in single-phase flow. A compromise was defined using CFD, which prevented vortex formation and promoted homogeneous suspension, by optimizing impeller position and rotation speed. The positions of the inlet and the outlet of the forced circulation loop in the tank were deduced from CFD simulations and validated by experimental data. Finally, this work confirms the potential interest of AnMBR for biohydrogen production and the applicability of CFD for the optimization of abiotic factors.

Development and testing of a fully gravitational submerged anaerobic membrane bioreactor for wastewater treatment

A gravity-operated submerged anaerobic membrane bioreactor (SAnMBR) was set up in order to test its principle of operation as an alternative to conventional pumped permeation of the membrane. This operating mode allowed the membrane flux rate to be measured accurately whilst maintaining a constant transmembrane pressure (TMP), and allowed small transient variations in the flux rate to be observed. The reactor was operated at 36°C for a period of 115 days using a nutrient-balanced synthetic substrate with a high suspended solids concentration. Membrane cleaning was in situ by a gas scouring system using recirculation of headspace biogas. With an initial TMP of 7.0 kPa, the membrane flux slowly decreased due to membrane fouling and had not reached a constant value by day 71. The results indicated that the system was still acclimatizing up to 50 days after start-up; but from that point onwards, performance parameters became much more stable. A constant flux of 2.2 L m−2 h−1 was achieved over the last 45 days after the TMP was reduced to 2.3 kPa. The stable flux was maintained over this period and the loading raised to 1 g COD L−1 d−1 by increasing the influent strength. Under these conditions, the average chemical oxygen demand removal efficiency was 96% and the specific methane potential was 0.31 L CH4 g−1 COD removed.

Modelling wastewater treatment in a submerged anaerobic membrane bioreactor

Mathematical modelling has been widely applied to membrane bioreactor (MBRs) processes. However, to date, very few studies have reported on the application of the anaerobic digestion model N.1 (ADM1) to anaerobic membrane processes. The aim of this study was to evaluate the applicability of the ADM1 to a submerged anaerobic MBR (SAMBR) treating simulated industrial wastewater composed of cheese whey and sucrose. This study demonstrated that the biological processes involved in SAMBRs can be modelled by using the ADM1. Moreover, the results showed that very few modifications of the parameters describing the ADM1 were required to reasonably fit the experimental data. In particular, adaptation to the specific conditions of the coefficients describing the wastewater characterisation and the reduction of the hydrolysis rate of particulate carbohydrate (khyd,ch) from 0.25 d-1 (as suggested by the ADM1 for high-rate mesophilic reactors) to 0.13 d-1 were required to fit the experimental data.

Performance of a Submerged Anaerobic Membrane Bioreactor (SAnMBR) for Food Wastewater Treatment: Treatment Efficiency and Membrane Fouling

Performance of a Submerged Anaerobic Membrane Bioreactor (SAnMBR) for Food Wastewater Treatment: Treatment Efficiency and Membrane Fouling

EPS and SMP dynamics at different heights of a submerged anaerobic membrane bioreactor (SAMBR)

Membrane bioreactors (MBR) technology for wastewater offers many advantages over conventional technologies such as high effluent quality, less footprint and others. The main disadvantage of membrane bioreactors (MBR) is related to membrane fouling, which is mainly caused by extracellular polymeric substance (EPS) and soluble microbial products (SMP). This research studied EPS and SMP dynamics at different heights of a submerged anaerobic membrane bioreactor (SAMBR). The SAMBR was operated under two organic loading rates (OLR) (0.79 and 1.56kg/m3d) and was fed with synthetic wastewater with glucose as the carbon source. The results showed percentages of chemical oxygen demand (COD) removal above 95% and the highest COD removal rates were observed at the bottom of the reactor (>83%) for both OLR. The EPS showed a stratification with highest quantities in the supernatant. For the SMP the highest concentration was in the bottom of SAMBR where utilization predominated associated products whereas in the SAMBR supernatant predominated biomass associated products. The OLR change led to a significant increase in SMP accumulation but not in EPS. These facts showed that EPS and SMP dynamic in the SAMBR seemed to be mainly influenced by biological activity, total suspended solids concentration and substrate composition.

Treatment of a submerged anaerobic membrane bioreactor (SAnMBR) effluent by an activated sludge system: The role of sulphide and thiosulphate in the process

This work studies the use of a well-known and spread activated sludge system (UCT configuration) to treat the effluent of a submerged anaerobic membrane bioreactor (SAnMBR) treating domestic wastewater. Ammonia, phosphate, dissolved methane and sulphide concentrations in the SAnMBR effluent were around 55 mg NH4–N L−1, 7 mg PO4–P L−1, 30 mg non-methane biodegradable COD L−1, and 105 mg S2− L−1 respectively. The results showed a nitrification inhibition caused by the presence of sulphur compounds at any of the solids retention time (SRT) studied (15, 20 and 25 days). This inhibition could be overcome increasing the hydraulic retention time (HRT) from 13 to 26 h. Among the sulphur compounds, sulphide was identified as the substance which caused the nitrification inhibition. When the nitrification was well established, removal rates of nitrogen and phosphorus of 56% and 45% were reached respectively. The sulphide present in the influent was completely oxidised to sulphate, contributing this oxidation to the denitrification process. Moreover, the presence of methanotrophic bacteria, detected by FISH technique, could also contribute to the denitrification.

Effect of solids retention time on membrane fouling intensity in two-stage submerged anaerobic membrane bioreactors treating palm oil mill effluent

Submerged anaerobic membrane bioreactors (SAnMBRs) treating palm oil mill effluent were analysed in terms of membrane fouling dynamics when working at three different sludge retention times (SRTs of 15, 30 and 60 d). The average permeate flux was fixed at 2.4 L·m−2·h−1. During operation, the membrane was regenerated by using two steps: membrane wiping during each experiment as soon as trans-membrane pressure reached 125–130 mbars, and complete membrane cleaning including backwash and chemical cleaning at the end of each experiment when analysing the membrane surface and foulant material. Whatever the SRT, the cake formation was the dominant effect on membrane fouling dynamics. The concentration of suspended solids in the SAnMBRs, depending on the SRT, was then a determining criterion. Scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, Fourier transform infrared spectroscopy indicated that fouled membrane surfaces were covered with a cake layer containing organic and inorganic elements whose concentrations were higher when working at a higher SRT; the higher concentrations of such elements gave to the cake layer a denser and more compact structure. In these experiments, the soluble fractions played a secondary role because of the dominant effect of cake layer structuring.

Anammox granules formation and performance in a submerged anaerobic membrane bioreactor

Abstract Anaerobic ammonium oxidation (Anammox) granules with the maximum specific Anammox activity (SAA) of 2.14 kg N/kgVSS d, the short doubling time of 6.9 days and the maximum endurable NO2−-N concentration of 130 mg/L were successfully formed in a continuously fed and completely mixing submerged anaerobic membrane bioreactor (SAnMBR). With specific input power ranging from 0.08 to 0.02 kW/m3, mean particle size (volume-weighted mean) of the Anammox flocs did not change a lot. With a specific input power of 0.003 kW/m3, the mean particle size increased rapidly from 180 μm of the flocs to 863 μm of the formed granules in 90 days. With maximum influent total nitrogen (TN) up to 4.1 g/L, a stable nitrogen removal efficiency of 88% was accomplished by the formed granules. The nitrite degradation kinetics was also investigated and it showed that the formed Anammox granules reached its maximum activity at 30 mg NO2−-N/L but was strongly inhibited at 150 mg NO2−-N/L. With granule size increasing from 287 to 896 μm, the membrane operation circle prolonged by 2–2.3 times due to the relief of membrane fouling. The cultivated Anammox granules with high activity and shock resistance capacity, fast growth rate and relieved membrane fouling shows the appealing potential of the Anammox-SAnMBR in treating high-strength nitrogen wastewaters.

Impacts of Different Membrane Module Designs in Anaerobic Submerged Membrane Bioreactors

In this study, the anaerobic submerged membrane bioreactors (AnSMBR) was designed to use in different membrane modules. Furthermore, their treatment performance was investigated. Water quality parameters such as chemical oxygen demand (COD), total organic carbon (TOC), suspended solids, alkalinity, and volatile fatty acids were analyzed. Total system performance was examined by determining biogas generation and composition. The permeate flux and membrane total fouling resistances were measured and efficiencies in AnSMBR system were identified. TOC and COD removal efficiencies did not change in the different membrane modules. However, in sulfate removal rate the cylinder module was more effective compared to other modules. The biogas production is higher in AnSMBRs compared to conventional anaerobic systems. Methane production was determined as 0.35–0.38 L CH4/g CODremoved. When trans‐membrane pressure was set at 170 ± 3 mbar, the flux of permeates decreased through the whole operation of the AnSMBR system. The efficiency rank is a cylinder, funnel‐shaped and U‐shaped module, as membrane modules were compared in terms of providing high permeates fluxes.

Treatment of metalworking fluids using a submerged anaerobic membrane bioreactor (SAMBR)

AbstractBACKGROUNDThe role of biodegradation and physical–chemical mechanisms involved in the treatment of metal working fluids (MWFs) using a submerged anaerobic membrane bioreactor (SAMBR) was assessed in this research. Two SAMBRs were employed in series, with the second SAMBR being fed the permeate from the first bioreactor.RESULTSResults showed a low biodegradability of the MWF both in batch tests (bioconversion efficiency ≤ 3%), and operating the bioreactors continuously (bioconversion efficiency ∼0%). Among the physical–chemical removal mechanisms identified, it was found that bio‐adhesion was the most important in MWF removal (removal rate of 96.0 ± 1.64%), whereas membrane rejection was not significant (removal rate of 0.2 ± 0.18%). However, it is expected that membrane separation will play an important role in removal after bio‐adhesion has been saturated.CONCLUSIONThe inhibition of the hydrolytic/heteroacetogenic biomass was the most problematic aspect in anaerobic digestion, resulting in the need for bioaugmentation of specific microorganisms to degrade MWFs. In the case of non‐adaptation during long‐term operation, the bio‐adhesive propensity of MWFs could be used as a potential method for removing spent MWFs from wastewater streams. © 2014 Society of Chemical Industry

Pollutant removal and membrane fouling in an anaerobic submerged membrane bioreactor for real sewage treatment.

Real sewage was continuously treated by a laboratory-scale anaerobic submerged membrane bioreactor (AnSMBR) for over 160 days. Results showed that around 90% of chemical oxygen demand, and 99% of turbidity and total suspended solids in the sewage could be removed by the AnSMBR system. Membrane flux sustained at 11 L/(m(2) h) was realized with biogas sparging. Small flocs from sludge deflocculation in the early operational period caused a high membrane fouling rate, and the high specific filtration resistance of the cake layer appeared mostly attributable to the osmotic pressure effect. The performance results were also compared with those in the literature for upflow anaerobic sludge blanket reactors and aerobic membrane bioreactors for sewage treatment, demonstrating that AnSMBR could provide a desirable alternative for sewage treatment.

Effect of biogas sparging with different membrane modules on membrane fouling in anaerobic submerged membrane bioreactor (AnSMBR)

This study focused on the effect of biogas sparging and different membrane modules such as cylinder shaped, funnel-shaped, and U-shaped on the membrane fouling behavior in a lab-scale submerged anaerobic membrane bioreactor (AnSMBR) which was operated for over 60 days. In order to investigate the membrane fouling behavior, a series of analysis such as SMP, EPS, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), particle size distribution, and filtration resistances were performed. Although the rapid generation of cake layer took placed in case of the absence of biogas sparging, the membrane module design mostly influenced the membrane resistance when biogas sparging was applied. Total resistance was the highest for U-shaped module. The permeate fluxes with biogas sparging were higher about one half and two times than those without biogas sparging. Cylinder-shaped module had the lowest SMP and EPS concentrations followed by U-shaped and funnel-shaped modules under both cases with and without biogas sparging. The total resistances of all membrane modules without biogas sparging were found to be very high compared the pore blocking resistances (Rp).

Membrane fouling control in anaerobic submerged membrane bioreactor

In this study, the aim was to assess the impact of different membrane modules such as cylinder-shaped, funnel-shaped, and U-shaped on the membrane fouling behavior in a laboratory-scale submerged anaerobic membrane bioreactor (AnSMBR) treating the synthetic wastewater for over 124 days. A series of analysis, including soluble microbial products (SMP), extracellular polymeric substances (EPSs), scanning electron microscopy, energy dispersive X-ray spectroscopy, particle size distribution, and filtration resistances, was performed by considering all membrane modules. The results showed that difference between COD and TOC removals was negligible in membrane modules designed at different forms. However, the priority of the membrane modules in terms of providing high permeate fluxes was found to be cylinder-shaped ##xgt; funnel-shaped ##xgt; U-shaped bundle. Both SMP and EPS within cake formed on the fibers in the cylinder-shaped module were lower than those in the U-shaped and funnel-shaped modules. The particles in the U-shaped module were smaller than those in other modules while they were coarse in the cylinder-shaped module. The results demonstrate that cylinder-shaped module was the most suitable module of hollow fiber to control the membrane fouling in a AnSMBR.

Degradation of a model azo dye in submerged anaerobic membrane bioreactor (SAMBR) operated with powdered activated carbon (PAC)

This work investigated the anaerobic degradation of the model azo dye Remazol Yellow Gold RNL in an upflow anaerobic sludge blanket reactor (UASB) and two submerged anaerobic membrane (SAMBR) bioreactors, one of which (SAMBR-1) was operated with powdered activated carbon (PAC) in its interior. The reactors were operated at 35 °C with a hydraulic retention time of 24 h in three operational phases, aimed to assess the effect of external sources of carbon (glucose) or redox mediator (yeast extract) on the removal or color and organic matter. The results showed that removal efficiencies of COD (73–94%) and color (90–94%) were higher for SAMBR-1 when compared to SAMBR-2 (operated without PAC) and UASB reactors. In addition, the presence of PAC in SAMBR-1 increased reactor stability, thereby leading to a lower accumulation of volatile fatty acids (VFA). The microfiltration membrane was responsible for an additional removal of ∼50% of soluble residual COD in the form of VFA, thus improving permeate quality. On its turn, PAC exhibited the ability to adsorb byproducts (aromatic amines) of azo dye degradation as well as to act as source of immobilized redox mediator (quinone groups on its surface), thereby enhancing color removal.

Influence of relaxation frequency on membrane fouling control in submerged anaerobic membrane bioreactor (SAnMBR)

The effect of different intermittent filtration modes on membrane fouling was investigated in a submerged anaerobic membrane bioreactor treating palm oil mill effluent. The filtration was operated at the range of supra critical conditions (permeate flux equal to 20 L m−2 h−1), and the submersed membranes were continuously cleaned by gas injection and intermittent periods of relaxation. Four conditions of relaxation (S1: 240 s filtration/30 s relaxation, S2: 480 s filtration/30 s relaxation, S3: 720 s filtration/30 s relaxation, and S4: 960 s filtration/30 s relaxation) were analyzed by comparing the trans-membrane pressure evolution rates, the main fouling origins, and the content of membrane cleaning solutions in terms of proteins and carbohydrates. Results showed (i) the dominant effect of the cake deposit (50% of the total hydraulic resistance) whatever the relaxation frequency, (ii) the equivalent importance of pore blocking and adsorption, and (iii) the clear interest of working with the highest relaxation frequencies to limit the specific hydraulic resistance (50 times lower in comparison with low relaxation frequencies). Moreover, the presence of SMP and EPS was found in the different cleaning solutions confirming their determining role in fouling mechanisms.

Performance of submerged anaerobic membrane bioreactor at different SRTs for domestic wastewater treatment

Three submerged anaerobic membrane bioreactors (SAnMBR) with solids retention times (SRTs) of 30, 60 and 90d were set up for domestic wastewater treatment. Total COD removal rates higher than 83% were achieved. Maximum biogas production was 0.5L CH4d−1 (0.010L CH4 (gMLVSS)−1d−1; MLVSS: mixed liquor volatile suspended solids) at a SRT of 90d. A longer SRT benefited biomass accumulation and biogas production due to enhanced dominancy of methanogens. With the SRT increasing from 30 to 90d, enhancement of hydrolysis from 35 to 56% was identified as the major reason for the better efficient acidification and methanogenesis observed. Best treatment performance and membrane fouling control were observed for the SAnMBR operated at a SRT of 60d. Soluble microbial products or specific soluble microbial products that accumulated with SRT decrease from 60 to 30d led to a faster membrane fouling. With an increase of SRT from 60 to 90d, higher mixed liquor suspended solids concentration caused more particle deposition on the membrane surface, while more soluble microbial products or specific soluble microbial products was attributed to more metabolism products generation.

Microalgae cultivation in wastewater: Nutrient removal from anaerobic membrane bioreactor effluent

This study investigated the removal of nitrogen and phosphorus from the effluent of a submerged anaerobic membrane bioreactor (SAnMBR) by means of a lab-scale photobioreactor in which algae biomass was cultured in a semi-continuous mode for a period of 42days. Solids retention time was 2days and a stable pH value in the system was maintained by adding CO2. Nitrogen and phosphorus concentrations in the SAnMBR effluent fluctuated according to the operating performance of the bioreactor and the properties of its actual wastewater load. Despite these variations, the anaerobic effluent proved to be a suitable growth medium for microalgae (mean biomass productivity was 234mgl−1d−1), achieving a nutrient removal efficiency of 67.2% for ammonium (NH4+–N) and 97.8% for phosphate (PO4−3–P). When conditions were optimum, excellent water quality with very low ammonium and phosphate concentrations was obtained.