Osmotic Membrane Bioreactor Research Articles

Mathematical modeling of osmotic membrane bioreactor process for oily wastewater treatment

ABSTRACT To evaluate the disposal effluent from the Aldura refinery in Iraq, which comprises oily wastewater, a mathematical model has been developed for both forward osmosis (FO) and osmotic membrane bioreactor (OsMBR). The procedure is explained mathematically, accounting for both the concentration and polarization aspects. As a result of mathematical modeling, the water flux was determined by the osmotic pressure, the concentration, and the polarization of the feed and draw solutions. Based on traditional methods of predicting water flux using external and internal concentration polarizations, it is determined that water flux will occur in the first model (Model-1). To increase the accuracy of Model-1, the resistivity (K) of the solute has been modified to be independent of the diffusivity of the solute. The old model (Model-1) and the updated model (Model-2) overestimated water flux by 17 and 25%, respectively. It was possible to make a valid comparison between the experiment and theory based on the results of both experiments.

A comparative study on UASB MF-OMBR and AnMF-OMBR treating slaughterhouse wastewater: Process performance, struvite precipitation, and economic evaluation

Up-flow anaerobic sludge blanket microfiltration osmotic membrane bioreactor (UASB MF-OMBR) is a cutting-edge technology derived from the anaerobic osmotic membrane bioreactor (AnOMBR). This study investigated long-term performance of an UASB MF-OMBR and an anaerobic microfiltration osmotic membrane bioreactor (AnMF-OMBR) comparatively focusing on process performance, membrane fouling, microbial community shift, struvite precipitation, and economic evaluation for the treatment of synthetic and real slaughterhouse wastewater (SSW and RSW). The UASB MF-OMBR achieved higher process performance regarding chemical oxygen demand (COD) removal (70 ± 1 %), methane yield (0.24 ± 0.03 L CH4 g−1 CODremoved) and NH4+-N rejection (85 ± 3 %). On the other hand, high COD and PO43−-P rejections were observed in both systems (>92 % and ∼98 %, respectively). The impact of the salinity build-up in the UASB MF-OMBR was the lower due to the bioreactor configuration. In addition, compared to the AnMF-OMBR, the better water fluxes were obtained in the UASB MF-OMBR, which can be attributed to the less membrane fouling. The results of precipitation modelling and Mg2+ measurement in the sludge of both bioreactors demonstrated that the struvite precipitation occurred during the forward osmosis (FO) operation was more often and in higher amounts in the AnMF-OMBR. The economic evaluation indicated that the specific produced permeate cost (SPC) with revenue was slightly lower for the UASB MF-OMBR than that of the AnMF-OMBR.

Determination of the critical draw solution concentration for anaerobic microfiltration osmotic membrane bioreactors

Anaerobic microfiltration osmotic membrane bioreactors (AnMF-OMBRs) have the advantages of resource recovery such as energy, water, and nutrients, but they have some drawbacks of low flux and severe membrane fouling. The concentration of draw solution (DS) is effective on the flux and fouling of FO membrane, and microbial inhibition. The aim of this study is to determine the critical DS concentration in AnMF-OMBR and up-flow anaerobic sludge blanket microfiltration osmotic membrane bioreactor (UASB MF-OMBR) systems operated with DS concentrations of 0.47, 1, and 1.5 M. The analytical hierarchical process (AHP) was applied to determine the critical DS concentration considering the criteria of forward osmosis (FO) performance, anaerobic performance, water recovery, microbial inhibition and operation time. The results demonstrated that the DS concentration of 0.47 M showed a better system performance, by causing less membrane fouling and microbial inhibition than that of the 1 and 1.5 M, and higher methane yield was obtained with 0.47 M in both bioreactors. The membrane autopsy analyses verified that the membrane fouling was severe with increasing DS concentration. Microbial community structure was affected by salinity build-up, high free ammonia (FA), and low organic loading rate (OLR). The relative abundance of Synergistota, a syntrophic acetate oxidizer, showed a parallel trend with Methanobacterium, a hydrogenotrophic methanogen in the conditions of high FA and salinity build-up due to the FO operation. Consequently, the critical DS concentration was determined as 0.47 M MgCl2.

A hybrid anaerobic osmotic membrane bioreactor - membrane distillation for water reclamation: aquatic toxicity, membrane fouling characterization, and economic assessment

The incomplete removal of pharmaceutically active compounds (PhACs) by conventional wastewater treatment has been challenging due to their ecological implications. Therefore, advanced technologies are necessary to remove PhACs efficiently. In the present study, an anaerobic osmotic membrane bioreactor - membrane distillation (AnOMBR-MD), aiming to remove seven PhACs, was evaluated by an integrated approach, considering the environmental toxicity, fouling characterization, and economic assessment. PhACs removal was evaluated using liquid chromatography coupled with mass spectrometry. Besides, organic matter and nutrient removal were evaluated. The FO and MD membrane fouling was characterized with scanning electron microscopy and energy dispersive spectroscopy. Toxic effects were analyzed for Aliivibrio fischeri, Daphnia similis, and Raphidocelis subcapitata. Furthermore, a preliminary economic assessment was carried out using capital and operating expenditures. The results showed a DOC, N-NH4+, and P-PO43- removal of 92%, 97%, and 99.9%, respectively, while removal of PhACs was >96%. However, the distillate was classified as very toxic forR. subcapitata, and a strong correlation was found between toxicity and the Mg2+ originating from the draw solution (DS). This result showed the importance of including toxicity tests in the selection of DS. The economic evaluation indicated that the higher cost is related to the membrane replacement due to the decrease in the permeate flux, pointing out the need for future studies that address cleaning strategies to solve the organic and inorganic fouling on the membrane's surface. In this sense, this study promoted an improvement in understanding the AnOMBR-MD technical-economic viability aiming at full-scale application.

Impacts of draw solutes on the fate of tetracycline in an osmotic membrane bioreactor: Role of the combination between membrane fouling and microorganisms

Osmotic membrane bioreactors (OMBRs) are considered a suitable technology for treating wastewater containing tetracycline due to their high rejection and biodegradation efficiency. However, the impact of membrane fouling layer (i.e., chemical composition, microbial composition, and formation) on the filtration and biodegradation of tetracycline is still unclear. Herein, the effects of draw solute concentration and type on the formation of a membrane fouling layer for tetracycline filtration and its relationship with microbial activity were investigated. The results showed that over 99% of tetracycline was retained on the feed side by membrane rejection, and the fouling layer played an important role in tetracycline filtration. Specifically, membrane foulants resulted in a more hydrophilic membrane facilitating tetracycline filtration, while the tetracycline-degrading genera from the fouled membrane promoted tetracycline degradation. The structure equation model showed that tetracycline filtration dominated by electrostatic repulsion between tetracycline and the fouled membrane was more important than tetracycline degradation for tetracycline removal (path coefficient of 0.655 vs. 0.395). This study provided insights into the combined effect of membrane foulants and microorganisms on tetracycline removal.

A Comprehensive Review on Wastewater Nitrogen Removal and Its Recovery Processes

Discharging large amounts of domestic and industrial wastewater drastically increases the reactive nitrogen content in aquatic ecosystems, which causes severe ecological stress and biodiversity loss. This paper reviews three common types of denitrification processes, including physical, chemical, and biological processes, and mainly focuses on the membrane technology for nitrogen recovery. The applicable conditions and effects of various treatment methods, as well as the advantages, disadvantages, and influencing factors of membrane technologies, are summarized. Finally, it is proposed that developing effective combinations of different treatment methods and researching new processes with high efficiency, economy, and energy savings, such as microbial fuel cells and anaerobic osmotic membrane bioreactors, are the research and development directions of wastewater treatment processes.

Exploration of the dynamic osmotic membrane bioreactor in low-speed rolling motion for membrane fouling mitigation

A specific dynamic osmotic membrane bioreactor (DR-OMBR) in low-speed rolling motion was designed to alleviate membrane fouling. Using a low rotation speed (2 rpm) together with the cross-flow velocity in this designed DR-OMBR, the shear stress (−1.57 × 10−4 N/m2) and the centrifugal force (1.31 × 10−4 N) were generated to reduce the attachment of foulant to the membrane surface and achieve a relatively stable water flux. A parallel experiment indicated that the water flux of the conventional OMBR (without rotation) was 10% lower than that of the DR-OMBR, and total organic carbon and phosphate removals still achieved 99.9 and 97.0%, respectively. The ammonium rejection was slightly lower as a result of the Donna effect. Furthermore, compared to rotation speeds (0–5 rpm), the rotation speed of 2 rpm achieved better water flux (6.4 LMH) and lower reversal salt diffusion (3.7 gMH) because the centrifugal force had a positive effect on the reversal salt flux and a negative impact on the water flux, and a higher rotation speed could generate a considerable centrifugal force to limit the water flux and increase the reverse salt flux. Furthermore, the mitigation of membrane fouling was further confirmed by the relatively low amount of extracellular polymeric substances (EPS) and soluble microbial products (SMP) on the membrane surface of the DR-OMBR.

Enhanced understanding of osmotic membrane bioreactors through machine learning modeling of water flux and salinity.

Mathematical modeling can be helpful to understand and optimize osmotic membrane bioreactors (OMBR), a promising technology for sustainable wastewater treatment with simultaneous water recovery. Herein, seven machine learning (ML) algorithms were employed to model both water flux and salinity of a lab-scale OMBR. Through the optimum hyperparameters tuning and 5-fold cross-validation, the ML models have achieved more accurate results without obvious overfitting and bias. The median R2 scores of water flux modeling were all over the 0.95 and the most of median R2 scores from total dissolved solids (TDS) modeling were higher than 0.90. During model testing, random forest (RF) algorithm presented the highest R2 score of 0.987 with the lowest root mean square error (RMSE = 0.044) for the water flux modeling, and extreme gradient boosting (XGB) algorithm exhibited the best results (R2 = 0.97; RMSE = 0.234) in the TDS modeling. The Shapley Additive exPlanations (SHAP) analysis found that the phosphorus concentration was a critical input feature for both water flux and TDS modeling. Finally, the selected ML models were used to predict water flux and salinity affected by two input features and the predication results confirmed the importance of the phosphate concentration. The results of this study have demonstrated the promise of ML modeling for investigating OMBR systems.

High−saline and long−term treatability of industrial wastewater by AnOMBR using organic and inorganic draw solutions

Less costly to AnMBR, anaerobic osmotic membrane bioreactor (AnOMBR) proceeds water and energy−efficient progresses within green and cleaner technologies. Long−term effectively operation of AnOMBR in high salinities due to salt accumulation is of the greatest priority, accompanied with a cost−performance efficient and non−inhibitory draw solution (DS) usage. Operational stability of AnOMBR in industrial wastewater treatment was studied at 30 mS/cm using the most favorable organic and inorganic DS within 29 DSs in our prior work, namely HCOONa and CaCl2. Osmotic and microbial yields during unintervented operations were lost due to severe salt stress and membrane biofouling. With a virgin membrane replacement, removal efficiencies, water and salt flux selectivity were partially restored, but the AnOMBRs turned towards collapse due to microbial activity lost. Therefore, sludge inoculation was applied and improved all AnOMBR performances to levels so close to before losses with 78 ± 3 % COD and 98.3 ± 0.6 % PO43-–P, 0.44 ± 0.2 L CH4/d excluding NH4+–N of 44 ± 10 %. It was designated that reverse salt passage for both the DS was responsible for approximately two-thirds of in-reactor salt build-up during stable AnOMBR operations. Statistical analysis results of the AnOMBR system for HCOONa and CaCl2 showed that statistical significances of performances in treatments with both DSs were from moderate to strong evidence levels. Microbial diversity increased by salt accumulation, and archaeal community differentiated. HCOONa promoted hydrogenotrophic halotolerant methanogenic archaeas, but not by CaCl2. Biofilm formed predominantly by biomass, Na+/Ca2+−bound biopolimers and inorganic precipitates provided bioactively better C, N, and P exhaustions in more porous and thicker secondary membrane layer by HCOONa. Beyond a virgin membrane replacement and sludge inoculation, an AnOMBR can be efficiently operated by sludge acclimation to high salinities, finest membrane clean-up, and even fabrication of FO membrane with the integrated nano-structured novel membranes such as including silver, nanofibers, graphene oxides etc.

Improving biological removal of pharmaceutical active compounds and estrogenic activity in a mesophilic anaerobic osmotic membrane bioreactor treating municipal sewage.

The contamination of water sources by pharmaceutically active compounds (PhACs) and their effect on aquatic communities and human health have become an environmental concern worldwide. Membrane bioreactors (MBRs) are an alternative to improve biological removal of recalcitrant organic compounds from municipal sewage. Their efficiency can be increased by using high retention membranes such as forward osmosis (FO) and membrane distillation (MD). Thus, this research aimed to evaluate the performance of an anaerobic osmotic MBR coupled with MD (OMBR-MD) in the treatment of municipal sewage containing PhACs and estrogenic activity. A submerged hybrid FO-MD module was integrated into the bioreactor. PhACs removal was higher than 96% due to biological degradation, biosorption and membrane retention. Biological removal of the PhACs was affected by the salinity build-up in the bioreactor, with reduction in biodegradation after 32d. However, salinity increment had little or no effect on biosorption removal. The anaerobic OMBR-MD removed >99.9% of estrogenic activity, resulting in a distillate with 0.14ngL-1 E2-eq, after 22d, and 0.04ngL-1 E2-eq, after 32d. OMBR-MD treatment promoted reduction in environmental and human health risks from high to low, except for ketoprofen, which led to medium acute environmental and human health risks. Carcinogenic risks were reduced from unacceptable to negligible, regarding estrogenic activity. Thus, the hybrid anaerobic OMBR-MD demonstrated strong performance in reducing risks, even when human health is considered.

Insight into the role of microbial community interactions on nitrogen removal facilitated by a bioelectrochemical system in an osmotic membrane bioreactor

Insufficient nitrogen removal is a key challenge for the application of an osmotic membrane bioreactor (OMBR). The integration of a bioelectrochemical system (BES) and an OMBR was constructed to enhance nitrogen removal.To optimize the operation, five aeration intensities and three draw solutes (DSs) were applied in the proposed system. The results showed that the proposed system obtained the highest nitrogen removal efficiency of 77.36 ± 3.55 % with an aeration intensity of 0.6 L/min, and it was further increased to 94.99 ± 2.83 % and 99.92 ± 0.14 %with the NaOAc DS and the glucose DS, respectively.The analysis ofmetabolic pathways implied that species interactions existed,andthe following different mechanisms of enhanced nitrogen removal for the two organic DSs were proposed. The growth of denitrifying bacteria was enhanced by using reverse-fluxed organic NaOAc DS as a carbon source;glucoseDS stimulated electron transfer system activity to accelerate denitrification.

Fabrication and characterization of inner selective antibiofouling forward osmosis hollow fiber membranes for simultaneous wastewater treatment and desalination

Forward osmosis (FO) hollow-fiber membranes were prepared by in situ thin layer assembly of polyethyleneimine (PEI) on antifouling PES-based porous nanocomposite membranes during membrane formation by spinning and phase inversion, via incorporation of surface-modified silver nanoparticles (NPs) in the dope solution and addition of PEI in the bore liquid; after cross-linking with glutaraldehyde the FO selective layer was obtained at the lumen surface while the shell surface had ultrafilter (UF) properties. This design enabled the utilization of the FO membranes in active layer facing draw solution (DS) orientation to employ maximum effective osmotic pressure, while the UF layer in combination with the antibacterial NPs was supposed to reduce fouling by the wastewater used as feed solution (FS). The quality of the active layer assembly was characterized using atomic force microscopy and scanning electron microscopy analyses, as well as salt rejection, structural parameter (S), and molecular weight cut-off (MWCO) measurements. The separation performance of these membranes was evaluated in an osmotic membrane bioreactor (OMBR) system, showing for the best FO nanocomposite membranes less than 10% fouling and flux reduction over 5 cycles of operation over a total period of 5 days. The best-suited membrane showed promising separation performance in the OMBR system by providing 43.4 LMH water flux and only around 0.2 g/l specific reverse salt flux (SRSF) with 1 M NaCl and DI water serving as DS and feed, respectively. This study focused also on distinctive performance criteria in combined FO and OMBR systems, such as the membrane’s potential in a pretreatment step of brine streams (used as DS) to provide proper feed composition for RO units and introduced a new specific performance index (SPI) for better characterization of FO membranes which summarizes all essential characteristics of the membrane application, instead of using existing structural parameter equations for membrane characterization. The best-suited FO membrane offered an SPI of 778.2 gl−1 m−2 h−1, meaning 778.2 g/l reduction of TDS in DS per unit membrane surface area per hour.

Methane production improvement in an osmotic membrane bioreactor for sludge anaerobic digestion: pretreatment optimization and long-term performance.

Hydrolysis is the first step and also rate-limiting step of anaerobic digestion which recovers energy from waste sludge. In order to accelerate the reaction rate of the hydrolysis, many pretreatment conditions had been taken into account. In this study, thermal pretreatment and alkaline pretreatment were combined with each other, serving as a thermal-alkaline pretreatment approach. Firstly, an orthogonal designed batch experiment was conducted to evaluate the pretreatment conditions, and then the optimal conditions were applied to an osmotic membrane bioreactor for a long-term investigation. Based on batch experiments, sludge treated by NaOH at pH 9 or 10 showed a better effect in cell solubilization. Sludge treated by Ca(OH)2 at pH 9, and sludge treated by NaOH at pH 9 or 10 showed advantages in methane production. Ultimately, sludge treated by NaOH at pH 9 and then heated at 90 °C for 60 min was selected as the optimal pretreatment condition. During the long-term operation of osmotic membrane bioreactor for sludge anaerobic digestion, the volume methane production of the sludge treated by thermal-alkaline was maintained at around 200-300 mL/L/d, which was 2-3 times of the sludge treated by ultrasound.

Enhancing selectivity of novel outer-selective hollow fiber forward osmosis membrane by polymer nanostructures

An ideal forward osmosis (FO) membrane module for osmotic membrane bioreactor (OMBR) application would have high packing density, low reverse solute flux and low fouling propensity. Recently, an outer-selective hollow fiber forward osmosis (HFFO) membrane has been developed to simultaneously improve packing density and reduce fouling propensity. However, a high reverse solute flux of the HFFO membrane still generates a salinity build-up in the reactor and remains the main challenge of this technology. To tackle this problem, we successfully improved the selectivity of an outer-selective HFFO membrane by incorporating a prior developed formulation based on Pluronic® nanostructures containing water selective proteins into the active layer of the membrane. The assimilation of these nanostructures in the membrane resulted in a significant decrease of the specific reverse solute flux from 0.36 ± 0.01 gL-1 to 0.12 ± 0.02 gL-1 with no significant decrease in water flux. Also, urea was selected as a challenging solute to investigate the selectivity of the developed membranes. In comparison with the pristine membranes, membranes containing nanostructures presented a superior rejection of urea from 87.7 ± 2.0 % to 95.2 ± 0.9 %. The developed membranes are able to be used for future OMBR application tests to prove feasibility of the process. Thus, this study can lead to the development of new membranes suitable for efficient and long-term operation in OMBR configurations. Additionally, the nanostructures investigated here can be used for different thin-film composite membranes as an additive to improve membrane selectivity.

Fate, elimination, and simulation of low-molecular-weight micropollutants in an integrated activated carbon-fertiliser drawn osmotic membrane bioreactor

This study investigated the behaviour and simulation of low-molecular-weight (low-MW) micropollutants (MPs) in a powdered activated carbon (PAC)–assisted fertiliser-drawn OMBR. 10% increase in water recovery and two times thinner fouling layer were observed in OMBR with addition of 100 mg-PAC/g-MLSS. This amount of PAC also boosted the richness and diversity in microbial community (Chao1 and Shannon index increased 1.5 times). Nearly 100% low-MW MPs were eliminated in PAC-OMBR, while 2–80% was achieved with traditional OMBR. This reduced the pathway of low-MW MPs into diluted fertiliser from 47% to < 1% of the total influent mass. Hydrophilicity played the crucial role in the removal of low-MW MPs, especially acetaminophen and nonylphenol. Neural network was suitable for the simulation of MP behaviour with high accuracy (R = 0.98, RMSE = 4.7%). The findings support safer and cleaner use of the diluted fertiliser and promote a cost-effective tool for real-time analysis of MP behaviour.

Engineering pressure retarded osmosis membrane bioreactor (PRO-MBR) for simultaneous water and energy recovery from municipal wastewater

Osmotic membrane bioreactors (OMBR) have gained increasing interest in wastewater treatment and reclamation due to their high product water quality and fouling resistance. However, high energy consumption (mostly by draw solution recovery) restricted the wider application of OMBR. Herein, we propose a novel pressure retarded osmosis membrane bioreactor (PRO-MBR) for improving the economic feasibility. In comparison with conventional FO-MBR, PRO-MBR exhibited similar excellent contaminants removal performance and comparable water flux. More importantly, a considerable amount of energy can be recovered by PRO-MBR (4.1 kWh/100 m2·d), as a result of which, 10.02% of the specific energy consumption (SEC) for water recovery was reduced as compared with FO-MBR (from 1.42 kWh/m3 to 1.28 kWh/m3). Membrane orientation largely determined the performance of PRO-MBR, higher power density was achieved in AL-DS orientation (peak value of 3.4 W/m2) than that in AL-FS orientation (peak value of 1.4 W/m2). However, PRO-MBR suffered more severe and complex membrane fouling when operated in AL-DS orientation, because the porous support layer was facing sludge mixed liquor. Further investigation revealed fouling was mostly reversible for PRO-MBR, it exhibited similar flux recoverability (92.4%) to that in FO-MBR (95.1%) after osmotic backwash. Nevertheless, flux decline due to membrane fouling is still a restricting factor to power generation of PRO-MBR, its power density was decreased by 38.2% in the first 60 min due to the formation of fouling. Overall, in perspective of technoeconomic feasibility, the PRO-MBR demonstrates better potential than FO-MBR in wastewater treatment and reclamation and deserves more research attention in the future.

Fertilizer draw solution index in osmotic membrane bioreactor for simultaneous wastewater treatment and sustainable agriculture

This study investigated the feasibility of applying a novel protocol for constructing a fertilizer draw solution (DS) index used in osmotic membrane bioreactor (OMBR) for simultaneous wastewater treatment and sustainable fertigation. The results indicated that system performance (i.e., water flux, reverse salt flux, contaminant removal) varied critically under different fertilizers. In which, the highest water recovery (∼60%) was observed with potassium chloride (KCl), whereas the lowest value (∼20%) was observed with ammonium nitrate (NH4NO3), which corresponded to the highest reverse salt flux. With all fertilizers, the membrane fouling layer thickness was in the range of 15.7–45.7 μm. The foulant were mostly irreversible and hydrophilic, with protein and polysaccharides were the dominant compounds. NH4NO3 and NH4H2PO4 (MAP) fertilizers caused the highest and lowest fouling resistances, respectively. Based on the matrix of performance aspects, the very first DSI was constructed for the assessment of fertilizer suitability. Principal component analysis (PCA) showed that fouling resistance played a pivotal role in the total variation of the system. The multi-criteria decision analysis (MCDA) suggested MAP as the most appropriate fertilizer with the highest fertilizer DS index (0.90), followed by KH2PO4 (0.67), KCl (0.65), NaNO3 (0.58), and NH4NO3 (0.16). A numerical simulation using an artificial intelligence-based technique revealed that MAP is also capable of maintaining high performance during long-term operations.

Mitigation of salinity buildup in hybrid flow-electrode capacitive deionization-osmotic membrane bioreactor for sludge anaerobic digestion

Osmotic membrane bioreactors (OMBRs) for anaerobic digestion of waste sludge have many advantages, but salt accumulation in the feed solution is a major problem. In this study, the feasibility of using flow-electrode capacitive deionization (FCDI) to mitigate salinity buildup was investigated. Three types of carbon materials, i.e., activated carbon (AC), carbon black (CB), and carbon nanotubes (CNTs), were tested as flow-electrode materials in desalination via FCDI. The results showed that, the salt removal efficiency (SRE) of CNTs was 110% higher than that of AC. Addition of CB and CNTs to 5.0 wt% AC as conductive additives at concentrations of 0.5 or 1.0 wt% synergistically enhanced the FCDI desalination performance. Cyclic voltammetry, galvanostatic charge–discharge, and electrical impendence spectroscopy showed that use of a combination of 5.0 wt% AC and 1.0 wt% CNTs gave an excellent capacitive performance, and the highest SRE, fastest average salt adsorption rate (0.84 μg cm−2 s−1), and the highest charge efficiency (85.0%) were achieved. The optimal voltage and sludge flow rate for FCDI of real OMBR sludge were 1.5 V and 80 mL min−1, respectively. In comparison with a control OMBR, a hybrid FCDI-OMBR system showed many advantages such as slower salinity buildup, alleviation of inhibition by ammonia, lower production of soluble microbial products, greater volumetric methane production, and higher net energy gains. The proposed hybrid FCDI-OMBR system provides a novel and cost-effective approach to recovering resources and energy from waste sludge or other types of biomass.

The trade-off between nitrogen removal and current generation in an air-cathode bioelectrochemically assisted osmotic membrane bioreactor

One of the key challenges for the application of an osmotic membrane bioreactor (OMBR) is low nitrogen removal efficiency. Herein, a novel integrated configuration by combining a single-chamber air-cathode bioelectrochemical system (BES) with an OMBR was proposed to facilitate nitrogen removal due to simultaneous nitrification and denitrification in the bioreactor, and carbon source trade-off between nitrogen removal and current generation were also investigated under different hydraulic retention times (HRTs) and draw solute (DS) concentrations. By applying sodium acetate as DS, the supplementary carbon source from reverse-fluxed solute promoted nitrogen removal (i.e., total nitrogen removal efficiency of 93.08 ± 0.93%) and current generation (i.e., current density of 110.67 ± 4.99 A/m3). Sequencing analyses revealed that nitrifying bacteria (62.7%), denitrifying bacteria (33.82%), and electrochemically-active bacteria (EAB, 4.31%) were abundant in the bioreactor. Both a long HRT or a high DS concentration improved nitrogen removal, but promoted the carbon source competition among denitrifying bacteria, EAB, and other heterotrophic bacteria. Cost balance of 0.32–1.13 $USD/kgCOD or 3.60–9.03 $USD/kgN was obtained, and a lower DS concentration was more cost-saving for the system operation. Those results have demonstrated that the proposed system could be an alternative approach for simultaneous enhancement of nitrogen removal and current generation.

Fate, Elimination, and Simulation of Low-Molecular-Weight Micropollutants in Powdered Activated Carbon–Assisted Fertiliser-Drawn Osmotic Membrane Bioreactor

Fate, Elimination, and Simulation of Low-Molecular-Weight Micropollutants in Powdered Activated Carbon–Assisted Fertiliser-Drawn Osmotic Membrane Bioreactor