Development and permeability of a dynamic membrane for anaerobic wastewater treatment

Mechanistic insights into different illumination positions control algae production in anaerobic dynamic membrane filtration (AnDM) during decentralized wastewater treatment

Sunlight illumination has the potential to control the stability and sustainability of dynamic membrane (DM) systems. In this study, an up-flow anaerobic sludge blanket (UASB) reactor was combined with DM under different illumination positions (direct, indirect and no illumination) to treat wastewater. Results indicated that the UASB achieved a COD removal up to 87.05 % with an average methane production of 0.28 L/d. Following treatment by the UASB, it was found that under illumination, the removal of organic substances by DM exhibited poor performance due to algal proliferation. However, the DM systems demonstrated efficient removal of ammonia nitrogen, ranging from 96.21 % to 97.67 % after stabilization. Total phosphorus removal was 45.72 %, and membrane flux remained stable when directly illuminated. Conversely, the DM system subjected to indirect illumination showed unstable membrane flux and severe fouling resistance. These findings offer valuable insights into optimizing illumination positions in DM systems under anaerobic conditions.

A Review on Opportunities and Limitations of Membrane Bioreactor Configuration in Biofuel Production

Biofuels are a clean and renewable source of energy that has gained more attention in recent years; however, high energy input and processing cost during the production and recovery process restricted its progress. Membrane technology offers a range of energy-saving separation for product recovery and purification in biorefining along with biofuel production processes. Membrane separation techniques in combination with different biological processes increase cell concentration in the bioreactor, reduce product inhibition, decrease chemical consumption, reduce energy requirements, and further increase product concentration and productivity. Certain membrane bioreactors have evolved with the ability to deal with different biological production and separation processes to make them cost-effective, but there are certain limitations. The present review describes the advantages and limitations of membrane bioreactors to produce different biofuels with the ability to simplify upstream and downstream processes in terms of sustainability and economics.

Development and performance of a dynamic membrane for anaerobic wastewater treatment - an analysis with different mesh pore sizes and configurations

Recent studies have focused on proposing materials with larger pores and lower cost to replace conventional membranes. This study aims to investigate the performance of an anaerobic dynamic membrane bioreactor (AnDMBR) at pilot scale, acting as a post-treatment for an Upflow Anaerobic Sludge Blanket (UASB) reactor treating sewage, for the removal of complementary organic matter, focusing on the module design, dynamic layer formation and process performance. The configurations tested on this study were: UASB followed by stone filter and three AnDMBRs in series with polyester pore sizes of 100 μm, 50 μm, and 5 μm; UASB followed by disc filter and the three AnDMBRs in series; UASB followed by the three AnDMBRs in series; and UASB reactor with only one AnDMBR module. Regarding the studied configurations, high removals of total suspended solids, chemical oxygen demand, and turbidity were achieved in all experimental setups. The use of stone and disc filters did not bring clear benefits to the system concerning the direct application of filtration with dynamic membranes, therefore, their removal in the system was favorable. The dynamic membrane formation was faster in the 50 μm mesh, and only a few hours were necessary to obtain a permeate quality with a total suspended solids concentration and a turbidity lower than 15 mg·L^-1 and 30 NTU, respectively. Thus, the dynamic membrane technology proved to be a potential solution in the post-treatment of UASB reactor effluents.

Dynamic anaerobic membrane bioreactor coupled with sulfate reduction (SrDMBR) for saline wastewater treatment

This study investigated organic removal performance, characteristics of the membrane dynamics, membrane fouling and the effects of biological sulfate reduction during high-salinity (1.0%) and high-sulfate (150 mgSO₄^2--S/L) wastewater treatment using a laboratory-scale upflow anaerobic sludge bed reactor integrated with cross-flow dynamic membrane modules. Throughout the operational period, dynamic membrane was formed rapidly (within 5-10 min) following each backwashing cycle (21-16 days), and the permeate turbidity of <5-7 NTU was achieved with relatively high specific organic conversion (70-100 gTOC/kgVSS·d) and specific sulfate reduction (50-70 gSO₄^2--S/kgVSS·d) rates. The sulfide from sulfate reduction can be reused for downstream autotrophic denitrification. 16S rRNA gene amplicon sequencing revealed that the microbial communities enriched in the sludge were different than those accumulated on the dynamic layer. Overall, this study demonstrates that the anaerobic dynamic membrane bioreactor coupled with sulfate reduction (SrDMBR) shows promising applicability in saline wastewater treatment.

Anaerobic Membrane Bioreactors for Municipal Wastewater Treatment: A Literature Review

Currently, there is growing scientific interest in the development of more economic, efficient and environmentally friendly municipal wastewater treatment technologies. Laboratory and pilot-scale surveys have revealed that the anaerobic membrane bioreactor (AnMBR) is a promising alternative for municipal wastewater treatment. Anaerobic membrane bioreactor technology combines the advantages of anaerobic processes and membrane technology. Membranes retain colloidal and suspended solids and provide complete solid–liquid separation. The slow-growing anaerobic microorganisms in the bioreactor degrade the soluble organic matter, producing biogas. The low amount of produced sludge and the production of biogas makes AnMBRs favorable over conventional biological treatment technologies. However, the AnMBR is not yet fully mature and challenging issues remain. This work focuses on fundamental aspects of AnMBRs in the treatment of municipal wastewater. The important parameters for AnMBR operation, such as pH, temperature, alkalinity, volatile fatty acids, organic loading rate, hydraulic retention time and solids retention time, are discussed. Moreover, through a comprehensive literature survey of recent applications from 2009 to 2021, the current state of AnMBR technology is assessed and its limitations are highlighted. Finally, the need for further laboratory, pilot- and full-scale research is addressed.

Anaerobic self-forming dynamic membrane bioreactors (AnSFDMBRs) for wastewater treatment - Recent advances, process optimization and perspectives

Recently, anaerobic self-forming dynamic membrane bioreactors (AnSFDMBRs) have attracted increasing attention, and are considered as an alternative to conventional anaerobic membrane bioreactors (AnMBRs). The key advantages of AnSFDMBRs include high flux, low propensity towards fouling, and low capital and operational costs. Although there have been several reviews on AnMBRs, very few reviews on AnSFDMBR system. Previous AnSFDMBR studies have focused on lab-scale to investigate the long-term flux, methods to improve performance and the associated mechanisms. Microbial analysis showed that the phyla namely Proteobacteria, Bacteroidetes and Firmicutes are dominant in both bulk sludge and cake biofilm, but their abundance is low in biocake. This review critically examines the fundamentals of AnSFDMBRs, operational conditions, process optimization and applications. Moreover, the current knowledge gaps (e.g., dynamic membrane module optimization, membrane surface modification and functional microbes enrichment) that should be studied in future to design an efficient AnSFDMBR system for treatment of diverse wastewaters.

Self-forming dynamic membrane bioreactor for textile industry wastewater treatment

The robustness of anaerobic dynamic membrane bioreactor (AnDMBR) for synthetic textile wastewater treatment was investigated. Textile wastewater may contain high concentrations of NaCl and sulfate, hence their impact on the AnDMBR performance was investigated in detail. A dynamic membrane was formed on a 20-μm pore sized nylon support layer at a constant flux of around 8 LMH. In the absence of sulfate addition, total and filtered (soluble) COD averaged 96 ± 49 mg/L (91% removal) and 75 ± 35 mg/L (93% removal), respectively. Sulfate addition increased total COD in the permeate to 222 ± 68 mg/L (79% removal). Average SS concentration was lower than 30 mg/L in the permeate although its concentration in the bioreactor reached 10 g/L. Throughout the AnDMBR operation dye removal averaged >97%. Sludge filterability, which was assessed by specific resistance to filtration, supernatant filtration, capillary suction time and viscosity, decreased after sulfate addition. Organic and inorganic matters in the dynamic layer were characterized by SEM-EDS and FTIR analyses.

Treatment of synthetic wastewater and cheese whey by the anaerobic dynamic membrane bioreactor

The aim of this study was to develop a laboratory-scale anaerobic dynamic membrane bioreactor (AnDMBR) for the treatment of high-strength synthetic and real cheese whey wastewater. We determined the appropriate pore size for a convenient type of support material (nylon mesh) to optimize cake layer formation. The performance of the AnDMBRs was measured in terms of chemical oxygen demand (COD) and solids removal efficiencies. During high-strength synthetic wastewater treatment, the 70-μm pore size AnDMBR achieved COD removal efficiencies of 78% and 96% with COD loading rates of 4.03 and 2.34 kg m^-3 day^-1, respectively, while the 10-μm pore size AnDMBR achieved 66% and 92% COD removal efficiencies at COD loading rates of 5.02 and 3.16 kg m^-3 day^-1. The 10 μm pore size AnDMBR was operated in two periods: first period and second period (before and after physical cleaning) during high-strength synthetic wastewater treatment. The 10-μm pore size AnDMBR removed 83% and 88% of suspended solids during period 1 and period 2, respectively. Furthermore, using a pore size of 10 μm retained 72% of solids (973 mg L^-1) in the reactor outlet. The 10-μm pore size AnDMBR performed better than the 70-μm pore size AnDMBR in terms of cake layer formation. The 10-μm pore size AnDMBR was used to treat real cheese whey wastewater, resulting in COD removal efficiencies ranging from 59% (4.32 kg m^-3 day^-1) to 97% (5.22 kg m^-3 day^-1). In addition, 85% of suspended solids were removed from real cheese whey wastewater after treatment. The results show that dynamic membrane technology using a pore size of 10 μm can be used to treat real industrial wastewater.

Exploring dynamic membrane as an alternative for conventional membrane for the treatment of old landfill leachate

This study compares the performance of a lab-scale pre-anoxic and post-aerobic submerged dynamic membrane bioreactor (DMBR) with similar studies on conventional membrane bioreactors (MBRs) for the treatment of old landfill leachate (LFL) while presenting a strategy to achieve stable DMBR operation. The results suggested that DMBR performed similar, or in some cases, better than MBRs. Like conventional MBRs treating LFL, DMBR can also accommodate large variations in operating parameters including influent feed composition and loading rates and thus, it can guarantee long term stable bioreactor operation (total nitrogen removal up to 98%) with acceptable effluent quality (Turbidity < 10 NTU). The results also demonstrated that gradual increment in influent LFL concentration was found to be effective for a stable DMBR operation however, it significantly deteriorated dynamic membrane (DM) filtration performance (p < 10E-7), resulting in higher fouling rate and deteriorated effluent quality. Nonetheless, poor DM performance and higher fouling rate were effectively controlled by using lower mesh porosity (52 μm instead of 200 μm) and increase in DM effective filtration area.

Anaerobic membrane bioreactors for wastewater treatment: Novel configurations, fouling control and energy considerations

Water shortage, public health and environmental protection are key motives to treat wastewater. The widespread adoption of wastewater as a resource depends upon development of an energy-efficient technology. Anaerobic membrane bioreactor (AnMBR) technology has gained increasing popularity due to their ability to offset the disadvantages of conventional treatment technologies. However there are several hurdles, yet to climb over, for wider spread and scale-up of the technology. This paper reviews fundamental aspects of anaerobic digestion of wastewater, and identifies the challenges and opportunities to the further development of AnMBRs. Membrane fouling and its implications are discussed, and strategies to control membrane fouling are proposed. Novel AnMBR configurations are discussed as an integrated approach to overcome technology limitations. Energy demand and recovery in AnMBRs is analyzed. Finally key issues that require urgent attention to facilitate global penetration of AnMBR technology are highlighted.

Dynamic membrane bioreactor (DMBR) for the treatment of landfill leachate; bioreactor's performance and metagenomic insights into microbial community evolution

The use of dynamic membranes as a low-cost alternative for conventional membrane for the treatment of landfill leachate (LFL) was investigated in this study. For this purpose a lab-scale, submerged pre-anoxic and post-aerobic bioreactor configuration was used with nylon mesh as dynamic membrane support. The study was conducted at ambient temperature and LFL was fed to the bioreactor in gradually increasing concentration mixed with tap water (from 20% to 100%). The results of this study demonstrated that lower mesh pore size of 52 μm achieved better results in terms of solid-liquid separation performance (turbidity <10 NTU) of the formed dynamic membrane layer as compared to 200 and 85 μm meshes while treating LFL. Consistently high NH₄⁺-N conversion efficiency of more than 98% was achieved under all nitrogen loading conditions, showing effectiveness of the formed dynamic membrane in retaining slow growing nitrifying species. Total nitrogen removal reached more than 90% however, the denitrification activity showed a fluctuating profile and found to be inhibited by elevated concentrations of free nitrous acid and NO₂^--N at low pH values inside the anoxic bioreactor. A detailed metagenomic analysis allowed a taxonomic investigation over time and revealed the potential biochemical pathways involved in NH₄⁺-N conversion. This study led to the identification of a dynamic system in which nitrite concentration is determined by the contribution of NH₄⁺ oxidizers (Nitrosomonas), and by a competition between nitrite oxidizers (Nitrospira and Nitrobacter) and reducers (Thauera).

Application of anaerobic dynamic membrane bioreactor (AnDMBR) for the successful enrichment of Anammox bacteria using mixed anaerobic and aerobic seed sludge

This study investigated a novel bioreactor configuration coupled with a side-stream dynamic membrane (DM) for Anammox enrichment as an alternative for conventional membrane. Bioreactor was fed with synthetic feed and seeded with a mix of anaerobic and aerobic sludge. In situ mechanical cleaning was employed for DM cleaning. DM development and performance was analysed over two polyamide-nylon meshes (200 and 52 µm). Solid-liquid separation of 52 µm mesh outperformed 200 µm with an average effluent turbidity of 2.4 ± 0.1 NTU. The system was operated at a maximum nitrogen loading rate of 696 mg-N L^-1 d^-1 and achieved a maximum nitrogen removal rate of 611.6 mg-N L^-1 d^-1. At steady state, the average ammonium, nitrite and total nitrogen removal efficiencies were 87 ± 0.6%, 98.5 ± 0.15% and 87.5 ± 0.56% respectively. Digital realtime PCRSequence analysis showed that Planctomycetales belonging to ascertained Anammox-specific genera progressively increased their presence in the reactor consistently with its nitrogen removal performance.

Assessment of dynamic membrane filtration for biological treatment of old landfill leachate

This study investigated the behaviour of dynamic membrane (DM) filtration for the treatment of stabilised landfill leachate in a bench-scale pre-anoxic and aerobic submerged dynamic membrane bioreactor (DMBR). Four meshes with different openings (10, 52, 85 and 200 μm) were tested to support the development of DM. Differences were observed among the meshes in supporting the development of the cake layer constituting the DM. The treatment of landfill leachate had an impact on sludge characteristics resulting in deteriorated filtration performance of the DM. Effluent turbidity was often higher than 100 NTU for larger mesh pore size (85 and 200 μm). Low effluent turbidity was achieved with meshes with 10 and 52 μm (13 ± 2 and 26 ± 4 NTU, respectively) although at membrane fluxes lower than 10 L m^{- 2} h^-1. The bioreactor exhibited a moderate organics removal of 50-60% and an ammonia oxidation between 80 and 90%. Incomplete nitrification was observed due to increased concentrations of free ammonia and free nitrous acid, with nitrite effluent concentrations up to 1062 mgNO₂^--N L^-1. Due to the large presence of refractory organic matter in landfill leachate, denitrification was limited resulting in a total nitrogen removal of approximately 20%.

Anaerobic dynamic membrane bioreactor (AnDMBR) for wastewater treatment: A review

Recently, an increasing level of attention has focused on the emerging technology of anaerobic dynamic membrane bioreactors (AnDMBRs), owing to its merits such as low membrane module cost, easy control of membrane fouling, low energy consumption and sludge production, as well as biogas production. As research on AnDMBRs is still in the nascent stage, an introduction of bioreactor configurations, dynamic membrane (DM) module, and DM layer formation and cleaning is firstly presented. The process performance of the AnDMBR for wastewater treatment is then reviewed with regard to pollutant removal, DM filterability, biogas production, and potential advantages over the conventional anaerobic membrane bioreactor (AnMBR). In addition, the important parameters affecting process performance are briefly discussed. Lastly, the challenges encountered and perspectives regarding the future development of the AnDMBR process to promote its practical applications are presented.

Rapid establishment of phenol- and quinoline-degrading consortia driven by the scoured cake layer in an anaerobic baffled ceramic membrane bioreactor

Although toxic and refractory organics, such as phenol and quinoline, are decomposed by anaerobic bacteria, the establishment of specific degrading consortia is a relatively slow process. An anaerobic membrane bioreactor allows for complete biomass retention that can aid the establishment of phenol- and quinoline-degrading consortia. In this study, the anaerobic digestion of phenol (500 mg L^-1) and quinoline (50 mg L^-1) was investigated using an anaerobic baffled ceramic membrane bioreactor (ABCMBR). The results showed that, within 30 days, 99% of phenol, 98% of quinoline and 88% of chemical oxygen demand (COD) were removed. The substrate utilisation rates of the cake layer for phenol and quinoline, and specific methanogenic activity of the cake layer, were 7.58 mg phenol g^-1 mixed liquor volatile suspended solids (MLVSS) day^-1, 8.23 mg quinoline g^-1 MLVSS day^-1 and 0.55 g COD_CH4 g^-1 MLVSS day^-1, respectively. The contribution of the cake layer to the removals of phenol and quinoline was extremely underestimated because the uncounted scoured cake layer was disregarded. Syntrophus was the key population for phenol and quinoline degradation, and it was more abundant in the cake layer than in the bulk sludge. The highly active scattered cake layer sped up the establishment of phenol- and quinoline-degrading consortia in the ABCMBR.

Effects of coupling a UF membrane with a mesh screen and elevating temperature in the methanogenic digester of a two-phased anaerobic system

This study was conducted to investigate coupling of UF with a mesh screen under thermophilic temperatures and compare the effectiveness of membrane filtration and temperature change in the methanogenic digester. A two-phased anaerobic digester coupled with an ultrafiltration (UF) membrane system was used for anaerobic sludge digestion. The overall average chemical oxygen demand (COD) removal efficiency achieved in the two-phased anaerobic digester coupled with the UF membrane system was 97.9 ± 0.8%. In the methanogenic digester, 10.5% improvement of methane production rate was obtained by the increased microbial population and metabolic activity due to coupling with a UF membrane and a mesh screen and elevating the temperature from mesophilic to thermophilic conditions. The average methane production per VS loading and unit volume (m³) was 477.14 ± 31.5 and 567.15 ± 43.3 mL CH₄g^-1 VS before and after elevating the temperature, respectively. The optimal operating pressure for the UF membrane system was less than 3 kg_f cm^-2, and the mesh screen saved 19.0% of the operating cost and 17.3% of energy consumption. As a result, the UF membrane system enhanced the digestion of sewage sludge, where the elevation of temperature improved the methane production rate in the thermophilic methanogenic digester.

Dynamic membrane-assisted fermentation of food wastes for enhancing lactic acid production

A dynamic membrane (DM) module was inserted into a fermentation reactor to separate soluble products from the fermented mixture to increase lactic acid (LA) production from food wastes under acidogenic conditions (uncontrolled pH, pH 4 and 5). With a high total suspended solid content (20-40g/L) in the fermenter, a stable DM could be maintained through regular backwashing. By effectively intercepting suspended solids and lactic acid bacteria (LAB), the fermenter was able to increase microbial activity and largely promote LA yield. Hydrolysis and acidogenesis rates increased with pH, and the highest LA yield (as high as 0.57g/g-TS) was obtained at pH 4. The microbial community analysis showed that the relative abundance of Lactobacillus increased to 96.4% at pH 4, but decreased to 43.3% at pH 5. In addition, the DM could be easily recovered by intercepting larger particles in less than 2h after each cycle of periodic backwashing.

Performance of an anaerobic membrane bioreactor in which granular sludge and dynamic filtration are integrated

To alleviate the fouling of a filter, simple substrates, dynamic filtration, and granular sludge were applied in an anaerobic membrane bioreactor (AnMBR). The results showed that under a transmembrane pressure < 20 kPa, the filter flux ranged between 15 and 20 l (m^-2 h)^-1 for a period of 30 days. The flux was higher than the typical flux of AnMBRs with conventional membranes and most current dynamic filters. In addition, the low cost of the filter avoided the need for a higher flux. Moreover, a stable granular sludge bed, which consumed all volatile fatty acids, was maintained. A compact fouling/filtration layer formed on the filter, which contributed to low effluent chemical oxygen demand concentrations and turbidity. In addition, substrate scarcity in the filtration zone resulted in the evolution of diverse bacteria on the filter.

Influence of air scouring on the performance of a Self Forming Dynamic Membrane BioReactor (SFD MBR) for municipal wastewater treatment

The Membrane BioReactor (MBR) is a well-established filtration-based technology for wastewater treatment. Despite the high quality of the effluent produced, one of the main drawbacks of the MBR is membrane fouling. In this context, a possible evolution towards systems having potentially lower installation and operating costs is the Self Forming Dynamic Membrane BioReactor (SFD MBR). Key of this technology is the self-formation of a biological filtering layer on a support of inert material. In this work, a lab-scale aerobic SFD MBR equipped with a nylon mesh was operated at approximately 95Lm^-2h^-1. Two mesh pore sizes (20 and 50μm) and three air scouring flow rates (150, 250, and 500mL_airmin^-1) were tested at steady state. Under all the tested conditions, the SFD MBR effectively treated real municipal wastewater. The quality of the produced effluent increased for lower mesh size and lower air scouring intensity.

Characterization of a hybrid powdered activated carbon-dynamic membrane bioreactor (PAC-DMBR) process with high flux by gravity flow: Operational performance and sludge properties

Three PAC-DMBRs were developed for wastewater treatment under different PAC dosages with biomass concentrations averaged at 2.5, 3.5 and 5.0g/L. The DMBRs could be continuously operated at 40-100L/m²h, while higher fluxes were obtained within the PAC-DMBRs with hydraulic retention times varying in 4-10h. A dose of 1g/L PAC brought about obvious improvement in the sludge particle size distribution, settling, flocculating and dewatering properties due to the formation of biological PAC, and the sludge properties were further improved at a higher PAC dose (3g/L). The addition of PAC notably shortened the DM formation time after air backwashing and enhanced pollutant removal. Moreover, under a long solid retention time (approximately 150d), the concentrations of both soluble and bound extracellular polymeric substances (EPS) decreased substantially because of the adsorption and biodegradation effects of the biological PAC. No obvious impact on biomass activity was observed with PAC addition.

Effect of filtration flux on the development and operation of a dynamic membrane for anaerobic wastewater treatment

Dynamic membrane represents a cost effective alternative to conventional membranes by employing fouling as a means of solid-liquid separation. This study evaluated the effects of initial flux on both development rate of dynamic membrane and bioreactor performance during two consecutive experiments. The dynamic membrane was developed over a 200 μm mesh and the reactor was operated under anaerobic conditions. It was found that the effect of an initial higher applied flux on dynamic membrane development was more pronounced than mixed liquor suspended solid concentration inside the bioreactor. The development of the dynamic membrane was therefore positively associated with the applied flux. The rapid development of the dynamic membrane during the second experimental run at high initial fluxes and lower MLSS concentrations also affected the performance of the bioreactor in terms of more efficient COD removal and biogas production. A major shortcoming of applying higher initial applied flux was the formation of a denser and robust dynamic membrane layer that was resistant to applied hydraulic shear to control desired permeability and thus represented an obstacle in maintaining a long term operation with sustainable flux at lower transmembrane pressure (TMP).