Electrochemical Membrane Bioreactor Research Articles

The preparation of electrically-enhanced and hydrophilic CNTs-PVDF composite hollow fiber membranes for fouling resistance

The anaerobic membrane bioreactor has great potentials to treat the wastewater with high organic matter due to the efficient anaerobic digestion process and high biomass retention. However, the existence of membrane fouling significantly increases the maintenance cost, and always requires frequent and complex cleaning process to recover the membrane performance. Thus, it is significant to fabricate a membrane with excellent anti-fouling performance for the application in membrane bioreactors. Herein, we prepared the CNTs-PVDF hollow fiber membrane with fouling resistance via loading the conductive CNTs coating on the surface of commercial PVDF membrane by a simple cross-linking reaction with hydrophilic polyvinyl alcohol and succinic acid. “Dual defense” was constructed by the combination of the hydrophilic surface and conductive CNTs coating, which lifted the anti-fouling performance of this membrane. In the assistance of electrical effect, the permeance of the membrane with −1.2 V bias could be recovered to 95 % of original state by simple hydraulic cleaning, while that of the membrane without bias was only 58 % after filtrating the sludge of 2000 mg/L. Furthermore, this membrane also exhibited the superior stability and fouling resistance in the operation of anaerobic electrochemical membrane bioreactor, which was promising for the advanced water treatment.

Polyamidoamine-based graphene oxide nanoparticles as adsorbent for mitigation of fouling in electrochemical membrane bioreactor

Polyamidoamine-based graphene oxide nanoparticles as adsorbent for mitigation of fouling in electrochemical membrane bioreactor

Biogas upgrading and membrane anti-fouling mechanisms in electrochemical anaerobic membrane bioreactor (EC-AnMBR): Focusing on spatio-temporal distribution of metabolic functionality of microorganisms

Electrochemical anaerobic membrane bioreactor (EC-AnMBR) by integrating a composite anodic membrane (CAM), represents an effective method for promoting methanogenic performance and mitigating membrane fouling. However, the development and formation of electroactive biofilm on CAM, and the spatio-temporal distribution of key functional microorganisms, especially the degradation mechanism of organic pollutants in metabolic pathways were not well documented. In this work, two AnMBR systems (EC-AnMBR and traditional AnMBR) were constructed and operated to identify the role of CAM in metabolic pathway on biogas upgrading and mitigation of membrane fouling. The methane yield of EC-AnMBR at HRT of 20 days was 217.1 ± 25.6 mL-CH4/g COD, about 32.1 % higher compared to the traditional AnMBR. The 16S rRNA analysis revealed that the EC-AnMBR significantly promoted the growth of hydrolysis bacteria (Lactobacillus and SJA-15) and methanogenic archaea (Methanosaeta and Methanobacterium). Metagenomic analysis revealed that the EC-AnMBR promotes the upregulation of functional genes involved in carbohydrate metabolism (gap and kor) and methane metabolism (mtr, mcr, and hdr), improving the degradation of soluble microbial products (SMPs)/extracellular polymeric substances (EPS) on the CAM and enhancing the methanogens activity on the cathode. Moreover, CAM biofilm exhibits heterogeneity in the degradation of organic pollutants along its vertical depth. The bacteria with high hydrolyzing ability accumulated in the upper part, driving the feedstock degradation for higher starch, sucrose and galactose metabolism. A three-dimensional mesh-like cake structure with larger pores was formed as a biofilter in the middle and lower part of CAM, where the electroactive Geobacter sulfurreducens had high capabilities to directly store and transfer electrons for the degradation of organic pollutants. This outcome will further contribute to the comprehension of the metabolic mechanisms of CAM module on membrane fouling control and organic solid waste treatment and disposal.

Mitigation of fouling problem and optimization of treatment effect in the polyvinylidene fluoride (PVDF) based electrochemical membrane bioreactor (EMBR)

The hydrophobic polyvinylidene fluoride (PVDF) membrane is one of the most widely used membrane material in the treatment of domestic sewage, while it still endures the fouling problem. Many studies have focused on the fouling control, among which the electrochemical membrane bioreactor (EMBR) is promising because of its chemical-free nature, but the specific influence of applied electric field on the mitigation of membrane fouling and the treatment effect are unclear and need further exploration. In this work, the influence and interaction of operation parameters (operation voltage, electrode spacing, power-on mode, and hydraulic retention time) on fouling development and pollutants removals in a PVDF based EMBR were carefully explored for the optimal operating conditions. Results showed that the run time of EMBR system under optimal conditions was 23.4 % longer than that of the MBR system without a weak electric field, indicating that the membrane fouling problem was well alleviated. In addition, the effluent quality of EMBR was also improved than that treated by the MBR system. The removal rates of chemical oxygen demand, ammonia nitrogen, total phosphorus, and total nitrogen were increased by 2.25 %, 2.64 %, 9.02 %, and 12.1 %, respectively, revealing the improvement of this EMBR system in sewage treatment. This work shows that introduction of a weak electric field in MBR system not only effectively controls membrane fouling, but also increases the effluent quality, and thus endows EMBR as a candidate for sustainable and green technique in sewage treatment.

Electroactive biocake layer-driven advanced removal of dissolved organic matter at membrane interface of anaerobic electrochemical membrane bioreactor

The bio-cake layer is one of the most negative effects during water and wastewater filtration, but its potential behoof of biodegradation is poorly understood. In this study, we activated and reconstructed the bio-cake by using the carbon nanotube membrane (25 cm2 area, 17 LMH flux) as the anode in an anaerobic membrane bioreactor (AnMBR), and investigated its positive role in advanced removal of dissolved organic matter from up-flow anaerobic sludge bed unit (3 L/d) when treating synthetic municipal wastewater. At the anodic membrane interface, the enhanced biodegradation was proved to dominate the DOM reduction (contribution >40%), controlling the effluent COD as low as 19.2 ± 2.5 mg/L. Bio-cake characterizations suggested that the positive potential induced electroactive improvement, cell viability boost, and metabolic optimization. Metatranscriptomic analyses revealed that anode respiratory out-compete methanogenesis, forwarding a synergetic metabolism between enriched fermenters like Proteiniphilum sp. and exoelectrogens like Geobacter sp. Thus, electroactive bio-cake not only accelerated the decomposition of inside foulants to maintain the high flux, but also efficiently intercepted flow-through DOM due to reduced mass-transfer limitations and enhanced metabolic activity. An ordered, non-clogging, and potentially functional “cell filter” was established to achieve a win-win situation between fouling control and effluent improvement, which is promising to upgrade the AnMBR technology for maximizing the sustainable regeneration in future wastewater treatment.

Enhanced Anaerobic Digestion Effluent Treatment by an Electrochemical Membrane Bioreactor: Synergistic Roles of Forward Osmosis and Microbial Electrosynthesis

Enhanced Anaerobic Digestion Effluent Treatment by an Electrochemical Membrane Bioreactor: Synergistic Roles of Forward Osmosis and Microbial Electrosynthesis

Techno-economic and environmental sustainability assessment of succinic acid production from municipal biowaste using an electrochemical membrane bioreactor

The techno-economic and environmental performance of succinic acid (SA) production by an engineering Yarrowia lipolytica strain has been evaluated in a process using the organic fraction of municipal solid waste (OFMSW) as feedstock and a novel electrochemical membrane bioreactor (EMB) for simultaneous SA production and extraction. The minimum selling price (MSP) of SA ($2.70–3.71/kg) considering 50,000 tSA/year production capacity using the EMB-based process was slightly lower than the conventional bioprocess depending on OFMSW management fees ($0–35/tOFMSW). Life Cycle Assessment was carried out for the EMB-based bioprocess and the conventional bioprocess considering either conventional electricity production mix (grid) or renewable electricity production from photovoltaics. The use of renewable electricity in the EMB-based bioprocess led to lower Global Warming Potential (0.81 kg CO2-eq/kgSA), Abiotic Depletion Potential (15.71 MJ/kgSA), Acidification Potential (1.87 kg SO2-eq/kgSA) and Eutrophication Potential (0.25 kg PO4-eq/kgSA) than the conventional bioprocess when renewable electricity was used, while higher Human Toxicity Potential (0.29 kg DCB-eq/kgSA) was observed due to the raw materials (e.g. heavy metals) and utilities (e.g. electricity) used in photovoltaics production. It has been demonstrated that the EMB-based system could improve the sustainability of SA production.

Microbial Electrochemical Systems and Membrane Bioreactor Technology for Wastewater Treatment

AbstractMembrane bioreactors (MBRs) and microbial electrochemical systems (MESs) are promising technologies for wastewater treatment and generation of electricity from organic matter. The application of MBRs is limited due to membrane fouling and high energy consumption. The novel design of the coupling system of microbial fuel cell and membrane bioreactor (MFC‐MBR), which efficiently combines microbial degradation in MFCs and uses the microelectric field to reduce and mitigate membrane fouling in MBR. The fundamentals of extracellular electron transport, the performance of MFCs, different types of MBR systems, and the novelty of the MFC‐MBR coupling system for wastewater treatment are reviewed.

Impact of sandwich-type composite anodic membrane on membrane fouling and methane recovery from sewage sludge and food waste via electrochemical anaerobic membrane bioreactor

Membrane fouling presents a big challenge for the real-world implementation of anaerobic membrane bioreactors (AnMBRs) in digesting high-solid biowastes. In this study, an electrochemical anaerobic membrane bioreactor (EC-AnMBR) with a novel sandwich-type composite anodic membrane was designed and constructed for controlling membrane fouling whilst improving the energy recovery. The results showed that EC-AnMBR produced a higher methane yield of 358.5 ± 74.8 mL/d, rising by 12.8% compared to the AnMBR without applied voltage. Integration of composite anodic membrane induced a stable membrane flux and low transmembrane pressure through forming an anodic biofilm while total coliforms removal reached 97.9%. The microbial community analysis further provided compelling evidence that EC-AnMBR enriched the relative abundance of hydrolyzing (Chryseobacterium 2.6%) bacteria and methane-producing (Methanobacterium 32.8%) archaea. These findings offered new insights into anti-biofouling performance and provided significant implications for municipal organic waste treatment and energy recovery in the new EC-AnMBR.

Development of an electrochemical membrane bioreactor for succinic acid production and in situ separation with engineered Yarrowia lipolytica cultivated on municipal biowaste hydrolysate

A novel electrochemical membrane bioreactor (EMB) integrating succinic acid (SA) production and in situ separation in the anode compartment through an anion exchange membrane was employed in fed-batch fermentations with Y. lipolytica PSA02004 using hydrolysates from the organic fraction of municipal solid waste (OFMSW) as feedstock. The initiation of electrolysis cell operation and the reduction of pH from 6 to 5.5 at 30 h in a 6.7 L bioreactor improved the SA production efficiency, resulting in 66.7 gSA/L, 0.51 g/g yield, 0.78 g/(L·h) productivity, high coulombic efficiency (66.2%) and relatively low electricity consumption for SA separation (2.6 kWh/kgSA). The recirculation of the fermentation broth in the cathode compartment and the OH– produced by water reduction reduced NaOH consumption (35.4%) for pH control during fermentation. The fermentation was efficiently replicated in a 30 L bioreactor with a low membrane surface area (100 cm2) electrolysis cell, but it failed with a higher membrane surface area (702 cm2) electrolysis cell indicating that yeast cell viability, cell design and EMB configuration are important aspects for process scale-up. SA crystals were purified, at 99.95% purity and 95% yield, from the anolyte solution via activated carbon treatment, evaporation, crystallization and drying. Cell removal via centrifugation and acidification stages were not required as in conventional SA purification processes. The produced SA crystals were suitable for the production of polyester polyols for polyurethane urea dispersions applications.

Enhanced co-digestion of sewage sludge and food waste using novel electrochemical anaerobic membrane bioreactor (EC-AnMBR)

Membrane fouling remains a big challenge hindering the wide-application of anaerobic membrane bioreactor (AnMBR) technology. In this study, an electrochemical anaerobic membrane bioreactor (EC-AnMBR) was developed by coupling electrochemical regulation to enhance co-digestion of sewage sludge and food waste and mitigate membrane fouling. The highest methane production (0.12 ± 0.02 L/Lreactor/day) and net energy recovery (31.82 kJ/day) were achieved under the optimum conditions of 0.8 V, hydraulic retention time of 10 days and solids retention time of 50 days. Electrochemical regulation accelerated the mineralization of high-molecular-weight organics and reinforced the membrane antifouling ability by inducing electrostatic repulsive force and electrochemical oxidation. Besides, symbiotic relationships among functional microorganisms (Spirochaetes, Methanolinea, etc.) were enhanced, improving the hydrolysis and methanogenesis processes of complex organics and the long-term stability. This study confirms the technical feasibility of EC-AnMBR in treating high-solid biowastes, and provides the fundamental data to support its application in real-world scenarios.

Progress on the Development of Techniques to Remove Contaminants from Wastewater: A Review

The continuous depletion of fresh drinking water resources throughout the world has increased the necessity for the development of new techniques for wastewater treatment and recycling process. Domestic, industrial and agricultural wastes are major sources of aquatic contamination all over the world. Before discharging wastewater into natural water bodies, it must be treated. Apart from primary, secondary and tertiary treatment, membrane separation techniques and electrochemical membrane bioreactors for wastewater treatment have all been studied in this review paper. The electrochemical membrane bioreactor (EMBR) system has a lot of potential for treatment of wastewater and energy recovery. These novel EMBR techniques give feasible solutions for renewable treatment of wastewater and resource resumption.

Low-maintenance anti-fouling and phosphorus removal of an electro-MBR with Fe anode-cathodic membrane

Frequent membrane cleaning and chemical phosphorus removal increase the maintenance burden of membrane bioreactors (MBRs), greatly limiting their application in decentralized wastewater treatment. Herein, an electrochemical MBR (electro-MBR) integrating a Fe anode and a membrane cathode was constructed to simultaneously alleviate membrane fouling and enhance phosphorus removal using a low-maintenance method. Compared with conventional MBR, coagulation by Fe ions released from the sacrificial anode coupled with electrostatic repulsion from the cathodic membrane significantly mitigated membrane fouling in the electro-MBR. The coagulation significantly increased the sludge floc size, favoring the generation of a porous cake layer, and enhanced phosphorus removal by 69.0% without the addition of chemicals. The electrostatic repulsion impeded the adhesion of foulants, particularly extracellular polymeric substances (EPS), onto the conductive membrane. The EPS deposited onto the membrane surface declined by 31.5% under the synergistic effect of coagulation and electrostatic repulsion. Additionally, the applied electric fields increased microbial species diversity and enhanced the adaptability of biochemical systems to water quality variations. The service life of the membrane module in the electro-MBR was extended by 3 times, and the dosing coagulant was replaced by a sacrificial Fe anode with a working life of 600 d, resulting in 66.7% decrease in maintenance costs. This study suggests a low-maintenance method to achieve anti-fouling and phosphorus removal and promotes the development and application of MBRs.

Reduction of Contaminants from Municipal Wastewater of Salori Sewage Treatment Plant Using Electrochemical Membrane Bioreactor and Bioelectricity Generation

Reduction of Contaminants from Municipal Wastewater of Salori Sewage Treatment Plant Using Electrochemical Membrane Bioreactor and Bioelectricity Generation

Adopting the circular model: opportunities and challenges of transforming wastewater treatment plants into resource recovery factories in Saudi Arabia

Abstract With the ever-growing population, water, energy, and resources need to be used carefully, reused, and renewed. There is an increasing global interest in resource recovery from ‘waste’, which is driven by sustainability and environmental concerns and motivated by the potential for economic benefits. A new era in waste (water) management is being realized where wastewater treatment is becoming part of the circular economy by integrating the production of reusable water with energy and resource recovery. In this new perspective, wastewater is no longer seen as a waste to be treated with energy expenditure but rather as a valuable source of freshwater, energy, nutrients (nitrogen and phosphorous), and materials (e.g., bioplastics, cellulose fibres, and alginate). In this review paper, the conversion of wastewater treatment plants (WWTPs) into resource recovery factories (RRFs) is presented as one of the ways forward to achieve a circular economy in the water sector for the Kingdom of Saudi Arabia (KSA). The advanced technologies, some highlighted in the article, can be installed, integrated, or retrofitted into existing WWTPs to create RRFs enabling the recovery of freshwater, cellulose, alginate-like exopolymers (bio-ALE), and biogas from municipal wastewater achieving climate neutrality, decarbonization, and production of new and promising resources. The article highlights the need for modular, adaptive, and/or decentralized approaches using sustainable technologies such as aerobic granular sludge (AGS)-gravity-driven membrane (AGS-GDM), anaerobic electrochemical membrane bioreactor (AnEMBR), and anaerobic membrane bioreactor (AnMBR) for conducive localized water reuse. The increase in reuse will reduce the pressure on non-renewable water resources and decrease dependency on the energy-intensive desalination process. This article also outlines the water challenges that are arising in KSA and what are the major water research programmes/themes undertaken to address these major challenges.

Anaerobic electrochemical membrane bioreactor effectively mitigates antibiotic resistance genes proliferation under high antibiotic selection pressure.

The spread of antibiotics and antibiotic resistance genes (ARGs) in environments has posed potential threats to public health. Unfortunately, conventional biological wastewater treatment technologies generally show insufficient removal of antibiotics and ARGs. Bioelectrochemical systems, which can effectively degrade refractory organic pollutants via enhancing microbial metabolisms through electrochemical redox reaction, may provide an alternative for the control of antibiotics and ARGs. Herein, an anaerobic electrochemical membrane bioreactor (AnEMBR) was conducted by combining bioelectrochemical system and anaerobic membrane bioreactor to treat antibiotic-containing wastewater. The AnEMBR at open circuit showed stable CH4 production and high removal of COD and chlortetracycline (CTC) in treating 2.5-15mg/L CTC. However, increasing CTC to 45mg/L completely inhibited the methanogenesis of AnEMBR at open circuit. After applying external voltage in AnEMBR, the performances of AnEMBR were significantly improved (e.g., increased CH4 production and CTC removal). Moreover, CTC exposure significantly increased the relative abundances of ARGs in sludge, supernatant, and effluent in AnEMBR at open circuit. Applying voltage greatly attenuated the total relative abundances of ARGs in the supernatant and effluent of AnEMBR compared to those at open circuit. This could be attributed to the enrichment of tetracycline degradation gene tetX, which greatly enhanced the removal of CTC by the AnEMBR and thus reduced the selective pressure of CTC on the microorganisms in supernatant and effluent for ARGs proliferation. These results would provide an effective wastewater treatment technology for treating high-level antibiotic-containing wastewater to mitigate the potential risk of ARGs and antibiotics spread in receiving water body.

Improvement of sludge characteristics and mitigation of membrane fouling in the treatment of pesticide wastewater by electrochemical anaerobic membrane bioreactor

Electrochemical anaerobic membrane bioreactor attracted attention due to stable treatment quality with low footprint, and draw solute has significant effect on the sludge characteristics and membrane fouling performance. In this pilot-scale study, an electrochemical anaerobic membrane bioreactor (E-AnMBR) was proposed for treating pesticide wastewater at different hydraulic retention times (HRTs), demonstrating that E-AnMBR was superior on improvement of sludge characteristics and mitigation of membrane fouling, compared with the conventional anaerobic membrane bioreactor (C-AnMBR). E-AnMBR reduced sludge yield by 41.2 ± 6.7% and the SVI was significantly decreased by 32.5±13.8%. The accumulation of VFA in E-AnMBR was slighter than that of C-AnMBR, and the minimum average VFA was 255±6 mg/L. The methane yield of E-AnMBR (0.22–0.29 L CH4/g CODremoved) was 1.2–1.4 times than that of C-AnMBR. The EPS contents in suspended and attached sludge of E-AnMBR were significantly reduced by 41.8 ± 3.3% and 77.4 ± 14.5% than that of C-AnMBR, respectively. These results suggested that E-AnMBR has lower sludge disposal pressure, higher stability and methane recovery potential. Not only that, E-AnMBR successfully reduced membrane resistance, delaying the fouling rate by 31.0–38.5%. Finally, the linear relationship between EPS characteristics and membrane pollution was determined.

Optimizing anaerobic technology by using electrochemistry and membrane module for treating pesticide wastewater: Chemical oxygen demand components and fractions distribution, membrane fouling, effluent toxicity and economic analysis

Optimization in performance and membrane fouling of an electrochemical anaerobic membrane bioreactor (R1) for treating pesticide wastewater was investigated and compared with a conventional anaerobic membrane bioreactor (R2). The maximum COD removal efficiency of R2 was 80.1%, 80.0%, 67.4%, 61.1% with HRT of 96, 72, 48 and 24 h, which of R1 was enhanced to 84.7%, 84.3%, 82.0% and 66.3%. These results demonstrated that the optimum HRT of R1 was shortened to 48 h, which of R2 required 72 h. R1 reduced the contents of particulate and colloidal COD, and the fraction of COD converted to sludge was 5.0–8.2% lower than that of R2. The fouling rate was 0.99–1.44 kPa/d and reduced by 31.0%-38.5% compared with R2. Detoxification was enhanced by 7.8–47.7% with the assistance of bio-electrochemistry. Ultimately, ensuring similar performance, R1 achieved a 65.6% improvement in environmental benefit, a 26.3% and 38.9% reduction in unit capital and operating costs.

Pollutant removal, electricity generation and microbial community in an electrochemical membrane bioreactor during co-treatment of sewage and landfill leachate

A three-chamber electrochemical membrane bioreactor (EMBR) with a microbial fuel cell (MFC) was employed to co-treat synthetic wastewater and 20% landfill leachate (LFL) and produce electrical energy. We observed the following removal rates: 98 ± 1% of BOD5,20, 86 ± 5% of COD, 79 ± 2% of N-NH4+, 72 ± 6% of DOC and 43 ± 3% of N-total, while voltage generation was 463 ± 41 mV. The EMBR compartments showed distinct microbial communities and inferred metabolic pathways. Acinetobacter spp. was the most abundant bacteria in the anodic biofilm and has an important role in energy generation, as noted elsewhere. Meanwhile, the high abundance of Nitrospira spp. in the cathodic biofilm indicated its importance in the nitrification process in this system, essential for treating matrices with high-nitrogen content, such as LFL. Important abundant metabolic pathways inferred in the EMBR also included aerobic chemoheterotrophs, fermenters, degraders of aromatic compounds/hydrocarbon, and denitrifiers. Clearly, metabolic groups showed that microbial communities developed in the EMBR can degrade organic matter and remove toxic compounds (e.g., aromatic compounds) and nitrogen from LFL while producing energy. Furthermore, this study indicated that a MBR coupled with MFC create a great system for the co-treatment of LFL with wastewater, achieving both pollutant removal and electrical energy generation.

Evaluating the effect of gradient applied voltages on antibiotic resistance genes proliferation and biogas production in anaerobic electrochemical membrane bioreactor

Anaerobic biological treatment technologies are one of the major hotspots of antibiotic resistance genes (ARGs). Previous studies have applied the electrochemical process to improve biogas production, however, it was challenged that high voltages might promote membrane permeability and reactive oxygen species overproduction to promote ARGs proliferation. Herein, the biogas production and ARGs proliferation in an anaerobic electrochemical membrane bioreactor (AnEMBR) were investigated at the gradient voltages of 0–0.9 V. Results show the reactor performances (average CH4 production and current generation) were distinctly improved with the increase of applied voltage, and reached the optimum at 0.9 V. However, long-term application (>30 day) of 0.9 V deteriorated the reactor performances. Meanwhile, the relative abundances of most target ARGs in the supernatant and effluent of AnEMBR at 0.9 V increased by 0.68–1.55 and 0.42–1.26 logs compared to those before applying voltage, respectively. After disconnecting the circuit, these ARGs abundances all decreased to the original level. Significant correlations between intlI and ARGs (e.g., tetA, tetQ, sulI, and sulII) were observed, indicating horizontal gene transfer may contribute to the increased ARGs. Moreover, the shift of microbial communities caused by the applied voltage enriched potential ARGs-hosts (e.g., Tolumonas), contributing to the proliferation of ARGs.