Anaerobic Fluidized Bed Membrane Bioreactor Research Articles

Understanding key factors determining the effect of particle scouring efficiency on membrane fouling mitigation in AnFMBRs: Correlation analysis via machine learning

Particle scouring methods offer several advantages, including low energy consumption, ease of operation, and effective fouling control. The anaerobic fluidized bed membrane bioreactor is considered to be the most efficient wastewater treatment method with zero energy consumption, as it produces bioenergy and has lower energy requirements compared to conventional processes. However, membrane fouling in AnFMBRs can be affected by various factors such as fluidized particle hydrodynamics, particle properties, and operating conditions. To identify the primary factors affecting membrane fouling control in AnFMBRs, machine learning methods were utilized. Analysis of datasets from previous studies revealed several key findings. The location of the membrane in the reactor, particle momentum, and particle size were identified as the major parameters that govern membrane fouling reduction. Additionally, the optimal condition for AnFMBRs was determined to involve a membrane height-to-reactor height ratio of ≤0.5 and the use of particles with diameters of 1.5–3.0 mm. Furthermore, the use of smaller fluidized particles was shown to decrease particle scouring efficacy, making it less cost-effective. Machine learning models were successfully established to predict fouling, thus providing a comprehensive understanding of the dominant factors influencing membrane fouling control in AnFMBRs and offering an efficient method for optimizing fouling mitigation.

Membrane fouling, methane production and microbial community under fluidization of biocarrier with conductive surface in anaerobic fluidized bed membrane bioreactor for greywater treatment

A comparative study of organic removal efficiency, fouling control, and methane production from synthetic greywater was performed operating three anaerobic fluidized bed membrane bioreactors (AFMBRs). Granular activated carbon (GAC) particles, polyaniline-coated polyethylene terephthalate (PET) beads, and uncoated PET beads were added as scouring agent to control fouling through each AFMBR. The use of PET spherical beads coated with polyaniline as a fluidized medium improved both fouling reduction and methane production kinetics. Although the GAC particles showed the highest organic removal efficiency in AFMBR due to adsorption capability, their progressive fragmentation reduced the methanogenic population and accelerated fouling rate. Microbial activity was adversely affected when the bulk biomass was exposed to the surfactant in the synthetic greywater. Microbiome analysis showed that the methanogenic archaeal population in the GAC bulk biomass reduced significantly from 10 to 0.5%, which corroborates the decrease in methane production rate. The methanogens on the PET beads shifted gradually from acetoclastic Methanosaeta to hydrogenotrophic Methanospirillum presumably because of the detachment of the biofilm that suppressed the slow-growing Methanosaeta. In addition, the key exoelectrogenic microbes were related to Desulfovibrio and Geobacter, which may be associated with direct interspecies electron transfer with the methanogens.

Anaerobic Fluidized-Bed Membrane Bioreactor for Treatment of Liquid Fraction of Sludge Digestate: Performance and Agricultural Reuse Analysis

The treatment of sludge digestion liquid is a big challenge in wastewater treatment. If treated as normal wastewater, large amounts of nitrogen and phosphorus present in the sludge digestion liquid might be wasted when they could be reused in agricultural irrigation and reduce the consumption of artificial fertilizers. Thus, it is of utmost importance to deliver a simple and feasible strategy to treat sludge digestion liquid for agricultural reuse. In this study, a novel type of anaerobic fluidized bed membrane bioreactor system (US-AnFMBR) was developed by combining an ultrasonic processing unit and biochar in AnFMBR. The improvement of sludge properties, removal of pollutants performance and membrane fouling mitigation were achieved in this novel system. The optimal dose of BC (biochar) was 2.5 g·L−1, and the optimal ultrasonic treatment conditions were 30 min at 26 W. The main contribution of ultrasound was to improve the activity of sludge microorganisms to adsorb and degrade more organic matter present in sewage. The system achieved the removal efficiencies of COD, NH4+-N and PO43−-P up to 89.41%, 49.29% and 54.83%, respectively, and had a better mitigation effect in terms of membrane fouling. On the one hand, the biochar addition for COD removal performance was mainly manifested in membrane rejection performance. On the other hand, the combination of low-cost biochar and AnFMBR can also provide new ideas for the recycling of agricultural waste for biochar production. However, regarding the removal efficiency of NH4+-N and PO43−-P, the US-AnFMBR system promoted the activity of starved sludge to preferentially absorb NH4+-N compared with PO43−-P by statistical analysis. The US-AnFMBR can reduce the viscosity of sludge and release more small molecular substances, thus better mitigating membrane fouling. Long-term operation performance also revealed the excellent stability of the sludge digestion liquid treatment. The US-AnFMBR system achieves the recovery of nitrogen and phosphorus resources for subsequent agricultural recycling, and avoids the eutrophication of water ecosystems. Reclaimed water meets the nutrient requirements of typical crops during the growing season. To a certain extent, carbon emission reductions in agriculture can be achieved.

Evaluating performance of nano-Fe3O4 modified granular activated carbon assisted wastewater treatment in anaerobic fluidized membrane bioreactor

Magnetic granular activated carbon (MGAC), a nano-Fe3O4 modified granular activated carbon, was used as the carrier in an anaerobic fluidized-bed membrane bioreactor (AFMBR) to promote domestic wastewater treatment efficiency and alleviate membrane biofouling. Chemical oxygen demand (COD) removal reached 89 ± 2.6% with the effluent concentration of 20 ± 3.9 mg/L in the MGAC-AFMBR, while it was 28 ± 5.2 mg/L in AFMBR at hydraulic retention time (HRT) of 4 h. Total nitrogen (TN) removal was also enhanced by 4.0% with MGAC. An increased proportion of Chloroflexi and Bacteroidetes in the sludge may be responsible for improved treatment performance. MGAC reduced the protein and polysaccharide content in extracellular polymeric substances (EPS) by 9.8% and 8.1%, respectively. Besides, Bacteroidetes and Proteobacteria abundance decreased by 4.0% and 16.6% in the membrane cake layer with MGAC addition. Therefore, the high-quality effluent and low membrane biofouling of AFMBR was sustained by MGAC.

Dissolved Methane Recovery and Trace Contaminant Fate Following Mainstream Anaerobic Treatment of Municipal Wastewater.

Anaerobic treatment of municipal wastewater with the staged anaerobic fluidized bed membrane bioreactor (SAF-MBR) shows promise to transform secondary wastewater treatment into an energy-positive process. However, the dissolved methane in SAF-MBR effluent needs to be recovered to reach net energy positive. To recover this methane for energy generation, an air stripping system was constructed downstream of a pilot-scale SAF-MBR facility and operated for over 80 days. The process removed 98% of effluent dissolved methane, and with the addition of intermittent disinfection recovered an average of 90% of the dissolved methane. The exit gas from air-stripping comprised 1.5-2.5% methane and could be utilized by blending with biogas produced from primary solids digestion and the SAF-MBR in an on-site combustion process. The direct energy costs for air stripping methane are <1% of the energy recoverable from the dissolved methane, not accounting for siloxane or sulfide scrubbing. Only siloxanes were observed at levels impacting combustion in this study, with 1.6 mg Si/m3 present in the blended biogas and air stripping mixture. The fate of a subset of trace organic contaminants was examined across the air stripping unit to check for aerobic degradation by methanotrophs or other opportunistic aerobes. Only 1,4-dioxane and benzotriazole showed statistically significant removal among 17 compounds screened, with 0.53 ± 0.13 and 0.34 ± 0.15 fraction removal, respectively. Our results indicate that air stripping is an energy efficient and robust technology for dissolved methane removal and onsite utilization for heat and electricity generation from anaerobic treatment of municipal wastewater.

Polyaniline-coated conductive media promotes direct interspecies electrons transfer (DIET) and kinetics enhancement of low-strength wastewater treatment in anaerobic fluidized bed membrane bioreactor (AFMBR)

Polyaniline (PANI) was applied as coating materials to develop conductive surface on polyethylene terephthalate (PET) bead and polyvinylidene fluoride (PVDF) pellet termed as C-PET and C-PVDF as fluidized media in anaerobic fluidized bed membrane bioreactor (AFMBR). Parallel operation with AFMBRs showed that the fouling rate was lower for the C-PET and C-PVDF media than uncoated ones to scour membrane, and this was more pronounced as the organic loading rate was higher. Methane production rate was about 50% faster for the C-PET and C-PVDF media, and their use in the AFMBR system promoted methane yield by 14 to 190% higher than uncoated ones. 16S rRNA gene analysis revealed predictable results for methanogenic archaeal community structure (high abundance in Methanothrix), in line with the reactor performance observed, and suggestive of known Direct Interspecies Electron Transfer (DIET) metabolism. The bacterial analysis revealed common syntrophic species typically seen in anaerobic reactors, however, few known DIET species were also found, suggesting that more works are needed to elucidate pathways and syntrophies which may be activated by the PANI coating. Our results supported that conductive polymeric fluidized media should have great potential to promote kinetic enhancement in AFMBR treating low-strength wastewater.

Wastewater Treatment Using Anaerobic Fluidized Bed Membrane Bioreactor Coupled with Microbial Fuel Cells for Circular Economy

Wastewater treatment has been a problem in modern society due to negligence. It has led to the depletion of freshwater resources for human consumption and it is inevitable to search for ways to treat the wastewater effectively and economically. Domestic and industrial wastewaters are not treated well before letting into the freshwater sources. The freshwater gets polluted due to the presence of organic and inorganic substances that are known to be mutagenic, carcinogenic, and harmful to the environment. The conventional wastewater treatment systems are energy-intensive and inefficient. The use of membrane bioreactors is one of the breakthroughs in the field of wastewater treatment, where microorganisms are used to produce energy from the biomass present in the wastewater and utilize it as a substrate for their growth and development. The metabolic cycles of these microbes produce electrons/ions that are utilized in electricity/energy generation respectively. Wastewater usage to produce energy promotes circular economy, but this method alone is not very effective in treating the wastewater. Anaerobic fluidized bed membrane bioreactor with suspended granular activated carbon serves the purpose of a bio sorbent that facilitates the adsorption of low concentration pollutants and reduce the COD levels making it suitable for release into the freshwater resources. Coupling these two methods together seems to be effective and can be scaled up. This review article concentrates on coupling the two mechanisms to promote circular economy.

Long-term performance evaluation of granular activated carbon fluidization and biogas sparging in anaerobic fluidized bed membrane bioreactor: Membrane fouling and micropollutant removal

In this study, fluidization of granular activated carbon (GAC) by the recirculation of a bulk suspension through an anaerobic fluidized bed membrane bioreactor (AFMBR) and biogas sparging from the bottom of an anaerobic membrane bioreactor (G-AnMBR) for treating low-strength wastewater were compared to investigate organic removal and fouling rate. The chemical oxygen demand (COD) removal efficiency obtained by both the AFMBR and G-AnMBR exceeded 90 %, and the proportion of methane in the biogas produced was 60 % at the same hydraulic retention time (HRT). In the AFMBR, the transmembrane pressure (TMP) gradually increased, but a rapid TMP jump was not observed during operational period. In the G-AnMBR, the TMP increased rapidly as the biogas flowrate was 2 and 3 L/min (LPM) at 8 h of HRT while the TMP below 0.1 bar was maintained over 90 d at 4 LPM. Our results also indicated that organic micropollutants, such as Bisphenol A (BPA), Sulfamethoxazole (SMX), and Methylparaben (MeP), were removed by AFMBR almost completely. However, the G-AnMBR showed relatively low SMX and MeP removal efficiencies of 47.6 % and 74.9 %, respectively. The estimated energy required to operate the G-AnMBR was 1.37 kW h/m3, while it was only 0.06 kW h/m3 for AFMBR.

Combined Effect of Activated Carbon Particles and Non-Adsorptive Spherical Beads as Fluidized Media on Fouling, Organic Removal and Microbial Communities in Anaerobic Membrane Bioreactor.

The combined effect of acrylonitrile butadiene styrene (ABS) spherical beads and granular activated carbon (GAC) particles as fluidized media on the performance of anaerobic fluidized bed membrane bioreactor (AFMBR) was investigated. GAC particles and ABS beads were fluidized together in a single AFMBR to investigate membrane fouling and organic removal efficiency as well as energy consumption. The density difference between these two similarly sized media caused the stratified bed layer where ABS beads are fluidized above the GAC along the membrane. Membrane relaxation was effective to reduce the fouling and trans-membrane pressure (TMP) below 0.25 bar could be achieved at 6 h of hydraulic retention time (HRT). More than 90% of soluble chemical oxygen demand (SCOD) was removed after 80 d operation. Biogas consisting of 65% of methane was produced by AFMBR, suggesting that combined use of GAC and ABS beads did not have any adverse effect on methane production during the operational period. Scanning Electron Microscope (SEM) examinations showed the adherence of microbes to both media. However, 16S rRNA results revealed that fewer microbes attached to ABS beads than GAC. There were also compositional differences between the ABS and GAC microbial communities. The abundance of the syntrophs and exoelectrogens population on ABS beads was relatively low compared to that of GAC. Our result implied that syntrophic synergy and possible occurrence of direct interspecies electron transfer (DIET) might be facilitated in AFMBR by GAC, while traditional methanogenic pathways were dominant in ABS beads. The electrical energy required was 0.02 kWh/m3, and it was only about 13% of that produced by AFMBR.

Microbial fuel cells for municipal wastewater treatment: From technology fundamentals to full-scale development

Microbial fuel cells (MFCs) in municipal wastewater treatment plants (M-WWTPs) have garnered increasing interest in terms of attaining energy self-sufficiency due to their theoretical superiority to conventional M-WWTP processes. Despite being widely studied, pertaining literature primarily focuses on the fundamentals and configurations of the MFCs while overlooking their targeted application niche. Therefore, the adoption of MFCs in many niches (i.e., M-WWTPs) has not been adequately reviewed yet. This study aims to critically review the adoption of MFCs for carbon handling in the liquid stream of M-WWTPs with an emphasis on MFC's scalability, use of municipal wastewater (M-WW) as the substrate, and MFC's capital cost. The review includes the scaled-up results and other efforts to engineer MFCs. Three key challenges stymie MFC's adoption in M-WWTPs: low power generation, wide range of reported carbon removal efficiencies, and high capital cost. Accordingly, MFCs should be adopted in M-WWTPs with the goal of energy neutrality, not extra electricity production. To meet the effluent discharge standards, MFCs should be preceded by primary treatment, followed by an anaerobic fluidized bed membrane bioreactor. However, breakthroughs are still required to make this technology cost-efficient and energy-efficient. These efforts should take into consideration the multivariate nature of the MFCs. Additionally, the development of bioelectrochemically assisted anaerobic technologies has shown great prominence as an alternative technology that can be integrated into M-WWTPs. However, validation based on larger-scale applications, cost, and energy estimations is still needed.

Use of polymeric scouring agent as fluidized media in anaerobic fluidized bed membrane bioreactor for wastewater treatment: System performance and microbial community

New attempts using polymeric media with a tubular shape consisting of polyvinylidene fluoride (PVDF) were made as fluidized agent for anaerobic fluidized bed membrane bioreactor (AFMBR) in wastewater treatment. The AFMBR added with PVDF media was operated at room temperature and hydraulic retention time (HRT) from 4 to 16 h to investigate membrane fouling, organic removal efficiency, and microbial structure. Results showed that the PVDF media reduced membrane fouling effectively due to their scouring actions to clean the membrane. Transmembrane pressure (TMP) was maintained less than 0.1 bar during the operational period. More than 90% of chemical oxygen demand (COD) removal was achieved, yielding 10 mg/L of COD in membrane permeate. The energy required to operate the AFMBR using PVDF media was only 1.09×10−2 kWh/m3. The electrical energy produced by AFMBR was 0.246 kWh/m3, which is much higher than that required for system operation. Microbial community analysis based on 16S rRNA gene sequencing showed that the microbial community on PVDF biofilm was distinct from that in the suspended microbes. Importantly, it was found that dominant propionate-catabolizing bacteria on PVDF media include Desulfobulbus and syntroph Syntrophobacter while the key methanogenic player shifted from hydrogenotrophic Methanolinea to acetoclastic Methanothrix during the operation.

Integration of an anaerobic fluidized-bed membrane bioreactor (MBR) with zeolite adsorption and reverse osmosis (RO) for municipal wastewater reclamation: Comparison with an anoxic-aerobic MBR coupled with RO.

This study compared the performance of an anaerobic fluidized bed membrane bioreactor (AFMBR)-zeolite adsorption-reverse osmosis (RO) system and an anoxic-aerobic MBR-RO system for municipal wastewater reclamation. Both MBR-RO systems were operated in parallel with the same operating conditions. The results showed that the MBR systems achieved excellent organic removals (>95%) and the anoxic-aerobic MBR could also remove ∼57% of soluble total nitrogen. Compared to the aerobic MBR, the AFMBR displayed better membrane performance with less energy consumption, attributed to effective membrane scouring by liquid-fluidized GAC particles. Furthermore, a zeolite column was employed to remove ammonia in the AFMBR permeate, which ensured comparable organic and nitrogen levels in the feeds to RO units in the two processes. Although less organic substances and microbial cells were accumulated on the RO membrane fed with AFMBR-zeolite column effluent, its fouling rate (∼6.5±2.2bar/day) was significantly greater than that fed with anoxic-aerobic MBR permeate (∼1.1±1.5bar/day). This may be associated with more severe inorganic colloidal fouling on the RO membrane, illustrated by an electrical impedance spectroscopy fouling monitoring system.

CFD-DEM study of geometry changes in an AnFMBR towards particle momentum

An anaerobic fluidized bed membrane bioreactor (AnFMBR) with granular activated carbon (GAC) particles as a scouring material was numerically investigated with the use of a CFD-DEM approach. After validation of the numerical solver, two different shapes of impediments, i.e., linear decreasing of the gap and linear de-/increasing of the gap, with variable impediment lengths were introduced to the geometry. The effects of built-in impediments, different fluid inlet velocities and particle sizes on the hydrodynamics, resulting particle momentum and required power input were evaluated and compared to the reactor geometry without an impediment. The disadvantage of reactor geometry without an impediment, i.e., the non-uniform distribution of particle momentum across the height, can be compensated with the use of built-in impediments depending on the fluid inlet velocity, particle diameter and impediment lengths. Furthermore, with the introduction of impediments the maximum achievable particle momentum can be increased or the optimum of particle momentum in regards to the power input can be shifted towards lower power inputs. The latter case is especially important for collisional- and scouring-sensitive membranes. The most promising effect towards particle momentum in terms of uniform distribution and magnitude was observed with small scouring particles (1.25 and 1.55 mm) for both impediments.

Biological treatment of DMSO-containing wastewater from semiconductor industry under aerobic and methanogenic conditions

This study evaluated biological treatment of dimethyl sulfoxide (DMSO)-containing wastewater from semiconductor industry under aerobic and anaerobic conditions. DMSO concentration as higher as 1.5 g/L did not inhibit DMSO degradation efficiency in aerobic membrane bioreactor (MBR), while specific DMSO degradation rate at different initial DMSO-to-biomass (S0/X0) ratios from batch tests seemed to follow the Haldane-type kinetics. According to the microbial community analysis, Proteobacteria decreased from 88.2% to 26% as influent DMSO concentration increased, while Bacteroidetes, Parcubacteria, Saccharibacteria increased. Within the Bacteroidetes class, Flavobacterium and Laribacter genus significantly increased from less than 0.05%–26.8% and 13.4%, respectively, which might both be related to the DMS degradation. Hyphomicrobium and Thiobacillus, known as aerobic DMSO and DMS degraders, instead, decreased at higher DMSO conditions. Under methanogenic conditions, batch results implied DMSO concentrations higher than 3 g/L could be inhibitory, while DMSO and COD removal achieved 100% and 93%, respectively, using a pilot-scale anaerobic fluidized bed membrane bioreactor (AFMBR) with influent DMSO below 1.5 g/L. Results of terminal restriction fragment length polymorphism (TRFLP) analysis targeting on mcrA functional gene revealed that Methanomethylovorans sp. was dominant in AFMBR after 54 days of operation, indicating its importance on degrading DMS and mathanethiol (MT).

Membrane distillation as post-treatment for anaerobic fluidized bed membrane bioreactor for organic and nitrogen removal

To observe feasibility of membrane distillation (MD) as post-treatment for anaerobic fluidized bed membrane bioreactor (AFMBR), removals of organic and total nitrogen were investigated by using the commercial polyvinylidene difluoride (PVDF) membrane for direct contact membrane distillation (DCMD) at various operational conditions. Test solutions for MD experiments were permeate produced by staged AFMBR (SAF-MBR), permeate from single AFMBR and synthetic wastewater fed to both reactors. Increasing in feed temperature improved permeate flux through PVDF membrane, but it decreased total nitrogen (TN) removal efficiency. Effect of chemical oxygen demand (COD) concentrations in feed solutions for DCMD on TN removal efficiency was almost negligible. However, the COD removal efficiency was lower at lower feed concentration in DCMD operation. At constant feed temperature, TN removal efficiency was improved by increasing a recirculation flow rate on PVDF membrane across DCMD system. Both organic and inorganic fouling were observed on PVDF membrane surface and pore matrix after conducting DCMD operation. The organic fouling on PVDF membrane consisted mainly of protein and fatty acids, supporting that the permeate produced by AFMBR should have potentials to foul the membrane applied in DCMD system as post-treatment.

Removals of micropollutants in staged anaerobic fluidized bed membrane bioreactor for low-strength wastewater treatment

This study applied a laboratory-scaled, staged anaerobic fluidized bed membrane bioreactor (SAF-MBR) added with granular activated carbon (GAC) as fluidized media to treat a synthetic wastewater containing 0.1 mg/L of three different pharmaceutical micropollutants. Diclofenac, ibuprofen, and sulfamethoxazole were selected as target micropollutants to investigate their removal efficiency during SAF-MBR operation. More than 96% of overall COD removal efficiency was achieved at 8.7 h of total HRT with 288 mg/L of bulk VSS concentration. Transmembrane pressure (TMP) from membrane remained less than 0.3 bar during operational period. After the SAF-MBR was introduced with the micropollutants at 5 Lm−2 h−1 of permeate flux, they were removed completely within 3 days of operation. Our batch experiments supported that the removal of micropollutants in reactor bulk was immensely pronounced by adsorption to GACs, sorption and biodegradation due to the biofilm formed on GACs fluidized in SAF-MBR system.

Experimental Study on Removal of Organics from Landfill Leachate by Stage Aeration AFMBR Process

This paper used a stage aeration anaerobic fluidized bed membrane bioreactor (AFMBR), combined the advantages of membrane bioreactor (MBR) and anaerobic fluidized bed bioreactor (AFBR), put forward to add granular activated carbon (GAC) to make up for the deficiency of AFMBR process, and explored its impact on the process effect. At the same time, it was proposed to utilize the stage aeration to enhance the membrane flux, and to increase the residence time of organic pollutants in the facultative environment through the fluidized bed membrane bioreactor to improve the removal characteristics of organic pollutants in landfill leachate. The influence of aeration rate on the process effect was also investigated. Finally, the relationship between temperature and AFMBR treatment effect was briefly analyzed.

Effect of Temperature on the Performance and Microbial Community Structure in an Integrated Anaerobic Fluidized-bed Membrane Bioreactor Treating Benzothiazole Wastewater

An integrated anaerobic fluidized-bed membrane bioreactor (IAFMBR) was applied to treat synthetic high-strength benzothiazole wastewater. This study investigated the effect of temperature on the performance, membrane fouling and microbial community structure of IAFMBR. The results showed that decreasing temperature had an adverse effect on the performance and the cycle of membrane fouling. When temperature declined from 35℃ to 15℃, the COD efficiency dropped 7.4%, benzothiazole removal efficiency dropped 49.2%, the accumulation of total VFAs increased 225.66 mg·L-1, and methane yield (in CH4/CODremoved) dropped 0.118 m3·kg-1. The membrane fouling cycle shortened from 5.2 d to 2.5 d. For cake layer, the concentration of soluble microbial product (SMP) increased from 42.47 mg·L-1 to 70.62 mg·L-1, and the extracellular polymeric substance (EPS) content (in VSS) increased from 46.30 mg·g-1 to 82.22 mg·g-1 when the TMP was 15 kPa. For mixed liquor, the concentration of SMP increased from 36.46 mg·L-1 to 69.35 mg·L-1 and the EPS content increased from 47.47 mg·g-1 to 81.63 mg·g-1. Protein was the main component of EPS and SMP, and occurred in proportion of 80%.The microbial community structure showed that the dominant phyla were Firmicutes and Chloroflexi, which accounted for 42.6%-61.0% of the total relative abundance. The genera Clostridium (13.7%), Levilinea (15.2%), and Lactococus (17.9%) dominated with decreasing temperatures. The dominant methanogen was Methanosaeta.

Particle-sparged anaerobic membrane bioreactor with fluidized polyethylene terephthalate beads for domestic wastewater treatment: Modelling approach and fouling control

The study presents a mathematical model developed to better understand and control membrane fouling in a single-staged, anaerobic fluidized bed membrane bioreactor (AFMBR) using polyethylene terephthalate (PET) beads as scouring media. The model was based on combining the anaerobic biological model AM2b and a fouling model applied in membrane filtration. The presented model was validated using experimental data obtained by a laboratory scaled AFMBR reactor run during 250 d under various operational conditions. The combined AM2b and fouling model was able to simulate volatile suspended solids, soluble COD concentration, soluble microbial products concentrations and the methane production rate at steady-state condition with R2 of 95% as well as the trans-membrane pressure with R2 of 99%. The model was able to predict dominant fouling mechanism by assessing fouling resistances caused by cake formation and pore blocking separately.

Dynamics of Archaeal and Bacterial Communities in Response to Variations of Hydraulic Retention Time in an Integrated Anaerobic Fluidized-Bed Membrane Bioreactor Treating Benzothiazole Wastewater.

An integrated anaerobic fluidized-bed membrane bioreactor (IAFMBR) was investigated to treat synthetic high-strength benzothiazole wastewater (50 mg/L) at a hydraulic retention time (HRT) of 24, 18, and 12 h. The chemical oxygen demand (COD) removal efficiency (from 93.6% to 90.9%), the methane percentage (from 70.9% to 69.27%), and the methane yield (from 0.309 m3 CH4/kg·CODremoved to 0.316 m3 CH4/kg·CODremoved) were not affected by decreasing HRTs. However, it had an adverse effect on membrane fouling (decreasing service period from 5.3 d to 3.2 d) and benzothiazole removal efficiency (reducing it from 97.5% to 82.3%). Three sludge samples that were collected on day 185, day 240, and day 297 were analyzed using an Illumina® MiSeq platform. It is striking that the dominant genus of archaea was always Methanosaeta despite of HRTs. The proportions of Methanosaeta were 80.6% (HRT 24), 91.9% (HRT 18), and 91.2% (HRT 12). The dominant bacterial genera were Clostridium in proportions of 23.9% (HRT 24), 16.4% (HRT 18), and 15.3% (HRT 12), respectively.