Conventional Membrane Filtration Research Articles

Integrated electroflocculation-membrane process for pre-concentration of domestic wastewater: Filtration performance, organics recovery and membrane fouling characteristics

A novel electroflocculation-membrane (EFM) reactor for pre-concentrating domestic wastewater (DWW) is proposed in this study, using a conventional direct membrane filtration (DMF) reactor as a control. The results showed that under the operating conditions of a current density of 5 A/m2, an electrolysis time of 2.5 h and an inter-electrode distance of 25 mm, an obviously higher organics recovery efficiency of 72.92 % can be achieved in EFM, while only 55.14 % was obtained in DMF. Concentrate with chemical oxygen demand (COD) concentration of 4391.50 mg/L and 3322.88 mg/L was finally got by EFM and DMF, respectively. The higher retention effect of the dissolved organics remained key to the enhanced organics recovery capability of the EFM. Membrane fouling was also mitigated with EFM in continuous operation, with transmembrane pressure (TMP) increasing rate of 0.15 kPa/h (1.27 kPa/h for DMF). The loose and porous floc structure and small size distribution of the supernatant in EFM were the main contributors for reducing the resistance of the cake layer to mitigate membrane fouling. This study provides a new perspective on future wastewater resource recovery.

Alkaline treatment of antifoulant PVB/SA-grafted ε-MnO2 adsorptive nanocomposite membrane for synchronous separation of pollutants from pharmaceutical effluents

Conventional membrane filtration processes suffer from severe fouling and permeance decrement due to the accumulation of co-existing pharmaceutical pollutants in pores and valleys of the surface of membranes. Adsorptive nanocomposite (ANC) membranes possess a double function of adsorption and filtration for synchronous separation of pollutants, nevertheless, nano-leaching is a considerable challenge for their applications. Herein, a new high-performance alkali-treated PVB/SA-grafted ε-MnO2 ANC membrane was fabricated through a facile phase inversion technique, and used for synchronous separation of Cd(II) ions and tetracycline (TC) from aqueous solutions. The chemical structure, elemental characteristic, surface and cross-section morphology, surface hydrophilicity, and surface topography of the fabricated alkali-treated ANC membrane (OH-PVB/SA-ε-MnO2) were respectively investigated through FTIR, XPS, FE-SEM, water contact angle and AFM techniques. The alkaline treatment enhanced the pure water flux from 311.54 to 394.62 L/m2.h.bar, which was much higher than that for the pristine PVB membrane. The rejection rates of Cd(II) and TC by the OH-PVB/SA-ε-MnO2 membrane were respectively 98.55 and 98.73 % at pH = 6. The flux recovery ratio of 99.04, 98.66 and 97.61 % was obtained after the first, second and third successive cycles respectively. This verified the excellent antifouling performance of OH-PVB/SA-ε-MnO2 membrane that was originated from the enhancement of hydroxyl group content.

Simulation and experiment of turbulent particle motions in a hydrocyclone membrane filtration cell optimized for low-fouling water filtration

Particle-laden source waters are ubiquitously present in the natural environment and engineered systems. The demand for facile and energy-efficient treatment of these waters is increasing due to global water shortage aggravated by climate change. Therefore, a hydrocyclone membrane filtration cell (HMFC) enabled by 3D-printing technology was developed in this study and examined for its capability and mechanisms for pretreatment- and backwash-free filtration of inorganic and organic particle suspensions. Computational fluid dynamics simulation results indicate that the particles in the HMFC are subject to a strong swirling and turbulent flow field with turbulent kinetic energy ranging from 0.02-2.42 m2/s2 and shear strain from 104-105 s−1, 106 and 100 times higher than those obtained with conventional membrane filtration systems, respectively. This unique flow condition leads to centrifugal/centripetal, revolving, and rotational particle motions and turbulent-induced diffusion. The experimental results revealed that these particle motions effectively eliminated particle deposition on a porous microfiltration membrane and completely alleviated membrane fouling that were serious in traditional filtration modes. These findings shed light on the development of novel membrane filtration systems with enhanced fluid dynamics, for energy-efficient harvesting of clean water from particle-laden water resources.

Ultra-Low-Pressure Membrane Filtration for Simultaneous Recovery of Detergent and Water from Laundry Wastewater.

Reusing water and excess detergent from the laundry industry has become an attractive method to combat water shortages. Membrane filtration is considered an advanced technique and highly attractive due to its excellent advantages. However, the conventional membrane filtration method suffers from membrane fouling, which restricts its performance and diminishes its economic viability. This study assesses the preliminary performance of submerged, gravity-driven membrane filtration—under ultra-low trans-membrane pressure (△P) of <0.1 bar—to combat membrane fouling issues for detergent and water recovery from laundry wastewater. The results show that even under ultra-low pressure, the membrane suffered from compaction that lowered its permeability by 14% under △P of 6 and 10 kPa, with corresponding permeabilities of 2085 ± 259 and 1791 ± 42 L/(m2 h bar). Filtration of a detergent solution also led to up to 8% permeability loss due to membrane fouling. During the filtration of laundry wastewater, 80–91% permeability loss was observed, leading to the lowest flux of 15.6 L/(m2·h) at △P of 10 kPa, 38% lower than △P of 6 kPa (of 25.2 L/(m2·h)). High △P led to both the membrane and the foulant compaction inflating the filtration resistance. The system could recover 83.6% of excess residual detergent, while most micelles were rejected (ascribed from 71% of COD removal). The TDS content could not be retained, disallowing maximum resource recovery. A gravity-driven filtration system can be self-sustained with minimum supervision in residential and industrial laundries. Nevertheless, a detailed study on long-term filtration performance and multiple cleaning cycles is still required in the future.

Integrated microdevice with a windmill-like hole array for the clog-free, efficient, and self-mixing enrichment of circulating tumor cells

Circulating tumor cells (CTCs) have tremendous potential to indicate disease progression and monitor therapeutic response using minimally invasive approaches. Considering the limitations of affinity strategies based on their cost, effectiveness, and simplicity, size-based enrichment methods that involve low-cost, label-free, and relatively simple protocols have been further promoted. Nevertheless, the key challenges of these methods are clogging issues and cell aggregation, which reduce the recovery rates and purity. Inspired by the natural phenomenon that the airflow around a windmill is disturbed, in this study, a windmill-like hole array on the SU-8 membrane was designed to perturb the fluid such that cells in a fluid would be able to self-mix and that the pressure acting on cells or the membrane would be dispersed to allow a greater velocity. In addition, based on the advantages of fluid coatings, a lipid coating was used to modify the membrane surface to prevent cell aggregation and clogging of the holes. Under the optimal conditions, recovery rates of 93% and 90% were found for A549 and HeLa cells in a clinical simulation test of our platform with a CTC concentration of 20–100 cells per milliliter of blood. The white blood cell (WBC) depletion rate was 98.7% (n = 15), and the CTC detection limit was less than 10 cells per milliliter of blood (n = 6). Moreover, compared with conventional membrane filtration, the advantages of the proposed device for the rapid (2 mL/min) and efficient enrichment of CTCs without clogging were shown both experimentally and theoretically. Due to its advantages in the efficient, rapid, uniform, and clog-free enrichment of CTCs, our platform offers great potential for metastatic detection and therapy analyses.

Copper doped Fe-N-C as an excellent Fenton-like catalyst for membrane fouling mitigation against natural organic matters at neutral pH

The presence of humic substances as a component of natural organic matter (NOM) may cause inefficiency towards drinking water treatment processes, especially the membrane fouling during filtration process. Therefore, to enhance the efficiency of the conventional membrane filtration process, several copper doped Fe-N-C bimetallic heterogeneous Fenton-like catalysts (Cux@FeNC) were prepared and evaluated by executing their catalytic degradation performance against NOM. Results indicated that humic acid (HA, 10 mg/L) could be significantly degraded (95%) within 30 min application of Cu5p@FeNC-Fenton under neutral pH, which was relatively higher than of FeNC-Fenton (70%) under identical conditions. The macromolecular organic matters in NOM could be destroyed more effectively while the overall mineralization degree also became relatively higher. Meanwhile, a lower membrane fouling of UF (PES 20 kDa)/NF (DOW 270) and highest flux recovery after backwash were observed with Cu5p@FeNC-Fenton treatments. Characterization and chemical analysis further explored the introduction of Cux in FeNC was responsible for the rapid reactive oxygen species (ROS) generation and efficient degradation of NOM. Additionally, a possible copper-iron synergetic mechanism in Fenton-like system was proposed. This work gives a deep insight into the potential NOM degradation using Fenton-like Cux@FeNC catalysts and ensures the membrane fouling mitigation for effective water treatment processes.

Modeling and fouling control in a hybrid membrane process using CuO-catalytic membrane coupled to ozone

Membrane filtration methods are prone to significant fouling, which lowers the efficiency of the operation. Hybrid techniques combining ozone and membrane filtration are promising for removing dissolved contaminants and reducing membrane fouling. However, a detailed knowledge of fouling processes is necessary to incorporate these technologies in large-scale water and wastewater treatment plants. Although fouling models for conventional membrane filtration systems are well established in the literature, modeling data for hybrid systems (combining membrane/advanced oxidative processes) with antifouling features are scarce. Therefore, a ceramic α-Al2O3/ZrO2 commercial membrane with a molecular weight cut off of 10 kDa was functionalized applying layer-by-layer deposition of CuO for application in a hybrid system (membrane/catalytic ozonation) to treat contaminated surface water. The findings show that CuO-membranes can mitigate membrane fouling during hybrid processes, enhancing total filtration efficiency in the treatment of surface water. A fitting model that incorporated Hermia’s law as well as surface and bulk reactions that contribute to fouling removal is proposed and was successfully applied. The model allowed parameters to be estimated for the coated and uncoated membranes in the presence or absence of ozone. Membrane reusability was also investigated.

Evaluation of BACTECTM FX Blood Culture System for Rapid Sterility Testing of Human Medicinal Solutions for Infusion

Human medicinal products for infusion should be tested for sterility at various stages of manufacturing including the final step before marketing. Conventional sterility methods recommended in pharmacopeia need a 14 days incubation period in order to get reliable analytical results. However, rapid alternative methods based on automated detection of microbial growth have the advantage of taking only 5 days for sterility testing of medicinal products which can be very important especially during pandemics and emergency conditions. The aim of the present study is to evaluate the microbial detection potential and capacity of the BACTEC FX system for the rapid sterility testing of Paracerol, a 10 mg/mL paracetamol containing pediatric medicine for infusion, and to specify time required for the detection of a variety of microorganisms. Accordingly, the results showed that there were no significant differences between the BACTEC and conventional membrane filtration methods for detecting contamination. All positive/negative controls and all samples intentionally contaminated with microorganisms were determined correctly by using both methods. BACTEC FX system detected all microorganisms including slow growers significantly faster than the membrane filtration method (p<0.05). This system can be considered as a rapid alternative over conventional sterility methods for the release of human medicinal products for infusion to the markets especially under emergency conditions. However, for each particular products, validation steps should be executed according to European Pharmacopoeia by using a broad range of microorganisms.

Miniature auto-perfusion bioreactor system with spiral microfluidic cell retention device.

Medium perfusion is critical in maintaining high cell concentration in cultures. The conventional membrane filtration method for medium exchange has been challenged by the fouling and clogging of the membrane filters in long-term cultures. In this study, we present a miniature auto-perfusion system that can be operated inside a common-size laboratory incubator. The system is equipped with a spiral microfluidic chip for cell retention to replace conventional membrane filters, which fundamentally overcomes the clogging and fouling problem. We showed that the system supported continuous perfusion culture of Chinese hamster ovary (CHO) cells in suspension up to 14 days without cell retention chip replacement. Compared to daily manual medium change, 25% higher CHO cell concentration can be maintained at an average auto-perfusion rate of 196 ml/day in spinner flask at 70 ml working volume (2.8 VVD). The auto-perfusion system also resulted in better cell quality at high concentrations, in terms of higher viability, more uniform and regular morphology, and fewer aggregates. We also demonstrated the potential application of the system for culturing mesenchymal stem cells on microcarriers. This miniature auto-perfusion system provides an excellent solution to maintain cell-favorable conditions and high cell concentration in small-scale cultures for research and clinical uses.

Development of an Electrochemical Ceramic Membrane Bioreactor for the Removal of PPCPs from Wastewater

The removal of pharmaceutical and personal care products (PPCPs) from water and wastewater is of great significance for eco-system safety. In this study, an electrochemical ceramic membrane bioreactor (ECMBR) was developed for removing seven groups (24 kinds in total) of PPCPs from real wastewater. In the presence of an electric field (2 V/cm), the ECMBR could enhance the removal efficiencies for most targeted PPCPs without having adverse impacts on conventional pollutant removal and membrane filtration. The ECMBR achieved higher removal efficiencies for fluoroquinolones (82.8%), β-blockers (24.6%), and sulfonamides (41.0%) compared to the control (CMBR) (52.9%, 4.6%, and 36.4%). For trimethoprim, ECMBR also significantly increased the removal to 66.5% compared to 15.6% in CMBR. Furthermore, the exertion of an electric field did not cause significant changes in microbial communities, suggesting that the enhanced removal of PPCPs should be attributed to the electrochemical oxidation of the built-in electrodes in the ECMBR.

Permeability is the Critical Factor Governing the Life Cycle Environmental Performance of Drinking Water Treatment Using Living Filtration Membranes.

Living Filtration Membranes (LFMs) are a water filtration technology that was recently developed in the lab (Technology Readiness Level 4). LFMs have shown filtration performance comparable with that of ultrafiltration, far better fouling resistance than conventional polymer membranes, and good healing capabilities. These properties give LFMs promise to address two significant issues in conventional membrane filtration: fouling and membrane damage. To integrate environmental considerations into future technology development (i.e., Ecodesign), this study assesses the life cycle environmental performance of drinking water treatment using LFMs under likely design and operation conditions. It also quantitatively ranks the engineering design and operation factors governing the further optimization of LFM environmental performance using a global sensitivity analysis. The results suggest that LFMs' superior fouling resistance will reduce the life cycle environmental impacts of ultrafiltration by 25% compared to those of a conventional polymer membrane in most impact categories (e.g., acidification, global warming potential, and carcinogenics). The only exception is the eutrophication impact, where the need for growth medium and membrane regeneration offsets the benefits of LFMs' fouling resistance. Permeability is the most important factor that should be prioritized in future R&D to further improve the life cycle environmental performance of LFMs. A 1% improvement in the permeability will lead to a ∼0.7% improvement in LFMs' environmental performance in all the impact categories, whereas the same change in the other parameters investigated (e.g., LFM lifespan and regeneration frequency) typically only leads to a <0.2% improvement.

The Influence of Composition and Manufacturing Approach on the Physical and Rehydration Properties of Milk Protein Concentrate Powders.

This study investigated the physical and rehydration properties of milk protein concentrate (MPC) powders with five different protein contents (i.e., 38.9, 53.7, 63.6, 74.1, and 84.7%, w/w) prepared by recombining the ultrafiltration (UF) retentate and UF permeate of skim milk. Powder density and flowability increased, while the powder particle size decreased with decreasing powder protein content. The amount of non-wetting MPC powder decreased with decreasing protein content, demonstrating greater wettability for lower protein powders. At protein contents >65% (w/w), the dispersibility and solubility of the powders decreased significantly, likely due to the greater hydrophobic interactions between casein proteins and a lower concentration of lactose. Therefore, as the protein content of the MPC powders was decreased, their rehydration properties improved. The results obtained in this study provide novel insights into the relationship between the composition of recombined UF retentate and UF permeate streams on the subsequent powder particle size, density, and rehydration properties, and demonstrate that such powders possess similar properties to those prepared using conventional direct membrane filtration.

Pre-coagulation coupled with sponge-membrane filtration for organic matter removal and membrane fouling control during drinking water treatment

A new hybrid system was developed in this study for the treatment of drinking water consisting of pre-coagulation using polyaluminium chloride (PACl) and membrane filtration (MF) with sponge cubes acting as biomass carriers (P-SMF). When compared to a conventional MF (CMF) and a MF after coagulation by utilizing PACl (P-MF), better removal of nutrients, UV254 and dissolved organic carbon (DOC) (>65%) was obtained from the P-SMF. The accumulation of biopolymers (including polysaccharides and proteins), humic substances, hydrophilic organics, and other small molecular weight (MW) organic matter in the CMF led to the most severe membrane fouling coupled with the highest pore blocking and cake resistance. Pre-coagulation was ineffective in eliminating small MW and hydrophilic organic matter. Conversely, the larger MW organics (i.e. biopolymers and humic substances), small MW organics and hydrophilic organic compounds could be removed in significantly larger quantities in the P-SMF by PACl coagulation. This was achieved via adsorption and the biodegradation by attached biomass on these sponges and by the suspended sludge. Further analyses of the microbial community indicated that the combined addition of PACl and sponges generated a high enrichment of Zoolgloea, Amaricoccus and Reyranella leading to the reduction of biopolymers, and Flexibacter and Sphingobium were linked to the degradation of humic substances. Moreover, some members of Alphaproteobacteria in the P-SMF may be responsible for the removal of low MW organics. These results suggest that the pre-coagulation process coupled with adding sponge in the MF system is a promising technology for mitigating membrane fouling.

Application of a hybrid gravity-driven membrane filtration and dissolved ozone flotation (MDOF) process for wastewater reclamation and membrane fouling mitigation

This study proposed a novel membrane filtration and dissolved ozone flotation integrated (MDOF) process and tested it at pilot scale. Membrane filtration in the MDOF process was operated in gravity-driven mode, and required no backwashing, flushing, or chemical cleaning. Because ozone was added in the MDOF process, ozonation, coagulation, and membrane filtration could occur in a single reactor. Moreover, in situ ozonation occurred in the MDOF process, which differs from the conventional pre-ozonation membrane filtration process. Significant enhancement of turbidity removal was further achieved through the addition of membrane filtration. Membrane fouling was mitigated in the MDOF process compared to the MDAF process. In situ ozonation in the MDOF process decreased the fluorescence intensity and transformed the high MW dissolved organics into small MW compounds. For the fouling layer, the extracellular polymeric substance (EPS) contents and cake layer morphology were analyzed. The results indicated that the contents of EPS decreased. Furthermore, a thinner and more loosely structured cake layer formed in the MDOF process. Because coagulation and ozonation occurred simultaneously in a single reactor, the generation of hydroxyl radicals was enhanced through the catalytic effect of Al-based coagulants on ozone decomposition, which further alleviated membrane fouling in the MDOF process.

Beer microfiltration with static turbulence promoter: Sum of ranking differences comparison

AbstractThe challenges of beer microfiltration are fouling and to get decent quality. These problems can be partially eliminated with the use of Static Turbulence Promoter (STP). In this study, STP (pitch diameter ratio of 2, 13.2 mm pitch length, 6.5 mm diameter, 241 mm length, and 1.2 mm thickness), Pall Membralox T1‐70 membrane, and lager beer were used for the filtrations. Experiments were performed with combinations of different parameters, such as usage of STP (No/Yes), Transmembrane Pressure (TMP) (0.4–1.2 bar), and Retentate Flow Rate (Q) (50–200 L hr−1). Experiments were ranked with Sum of Ranking Differences based on the analytical properties, hydrodynamic and separation characteristics parameters. The best conditions were the following: STP = Yes, TMP = 0.4 bar, Q = 50 L hr−1; STP = No, TMP = 0.4 bar, Q = 200 L hr−1; STP = Yes, TMP = 1.2 bar, Q = 200 L hr−1.Practical applicationsClarification of rough beer is important because of eliminating yeast and colloidal particles responsible for haze and ensuring the microbiological stability of beer. Our research has several practical applications as mentioned below. First clarification of rough beer by crossflow microfiltration is more sustainable technology than conventional clarification with Kieselguhr, because of lower carbon footprint, lower solid waste stream, less beer loss, and less health and safety concerns. In addition, the shelf life of the microfiltered beer is longer, because there is no iron pickup. Furthermore, according to the results better beer quality can be achieved with the application of novel Static Turbulence Promoter (STP) compared to the conventional (without STP) membrane filtration. It is important because product quality is partly responsible for consumer satisfaction. Finally, it has been proven that usage of STP can improve filtration throughput that means lower production cost.

Hybrid membrane filtration-advanced oxidation processes for removal of pharmaceutical residue

Reports of pharmaceuticals exist in surface water and drinking water around the world, indicate they are ineffectively remove from water and wastewater using conventional treatment technologies. The potential of adverse effect of these pharmaceuticals on public health and aquatic life, also their continuos accumulation have raised the development of water treatment technologies. Hybrid treatment processes like membrane filtration and advance oxidation processes (AOPs) are likely to give rise to efficient simultaneous degradation and separation mechanisms. Conventional membrane filtration techniques can remove the majority of contaminants, but the smallest, undegraded, and stabilized pharmaceutical wastes persist in the treated water. After some 20 years, researchers have recognized the important role of AOPs in the treatment of pharmaceutical wastewater because these technologies are capable of oxidizing recalcitrant, toxic, and non-biodigradable compounds into numerous by-products and finally, inert end-products via the intermediacy of hydroxyl and other radicals. Evidently, membranes are subjected to the fouling phenomenon by the contaminants in wastewater, hence resulting in a reduction of clean water flux and increase in energy demand. In such situations, these membrane hybrid AOPs exert a complementary effect in the elimination of membrane fouling, thus enhancing the performance of the membrane. Therefore, in this review, we describe the basic aspects of the removal and transformation of certain pharmaceuticals via membranes and AOPs. In addition, information and evidences on membrane hybrid AOPs in the field of pharmaceutical wastewater treatment is also presented.

On the rejection and reversibility of fouling in ultrafiltration as assessed by hydraulic impedance spectroscopy

The manifestation of critical fluxes in membrane filtration has typically served to set an upper value above which detrimental fouling events and a substantial increase of membrane resistance occurs. Despite the usefulness of critical flux concepts for conducting sustainable membrane processes, the specific phenomena causing them cannot be easily identified via conventional membrane filtration modes. Usually arbitrary fouling rates are selected to delimit the boundary between under- and over-critical flux operation. Timescales respective for colloidal matter accumulation are overlooked.Frequency response analysis of transmembrane pressures has been recently presented as a highly-sensitive method to track fouling in ultrafiltration. This hydraulic impedance spectroscopy method allows not only measuring membrane resistances but also corresponding time constants related to colloidal matter accumulation. In this work, hydraulic impedance spectra are gained for the ultrafiltration of different model foulants to assess the origin of critical fluxes for two different membranes. A correlation among characteristic impedance features and the type of fouling could be established: the evolution of phase shift between flux and pressure at increasing fluxes allows identifying the formation of external fouling layers, while registering of hysteresis loops at reversed frequency sequences signals the development of irreversible internal fouling. The hydraulic impedance method emerges as a precise and more sensitive monitoring tool to diagnose the beginning and nature of critical fouling.

Anti-fouling characteristic of carbon nanotubes hollow fiber membranes by filtering natural organic pollutants

Membrane fouling is a universal problem for conventional membrane filtration that usually causes a deterioration in membrane performance. We used electro-assisted carbon nanotubes hollow fiber membranes (CNTs-HFMs) to investigate the anti-fouling properties using natural organic pollutants. Benefiting from the electro-assistance, the permeation flux of humic acid solution using CNTs-HFMs was 190.20 L/(m2·h·bar), which was about 1.5- and 4.4-times higher than those of CNTs-HFMs without electro-assistance and traditional polyvinylidene fluoride hollow-fiber membranes (PVDF-HFMs). And the permeation fluxes of bovine serum albumin, sodium alginate and supernatant of anaerobic bioreactor also presented similar results. The average COD removal rate of CNTs-HFMs (66.8%) at −1.0 V was higher than that of CNTs-HFMs without electro-assistance and PVDF-HFMs, which can be attributed to the formation of electrostatic repulsive force. It could reduce the deposition of pollutants on membrane surface under electroassistance.

Performance evaluation of attached growth membrane bioreactor for treating polluted surface water

Attached growth membrane bioreactor (aMBR) process was investigated for treating polluted surface water with CODMn around 10mg/L of raw water. Lab scale reactors, aMBR with 15% PVA-gel as carrier and conventional membrane filtration reactor (MF) were tested in parallel. aMBR achieved two times higher CODMn removal than MF system. Ammonia removal occurred almost completely in both MF and aMBR system – around 94% and 96%, respectively. Permeate turbidity was almost totally removed while UV254 removal was around 15% in MF and 20% in aMBR system. aMBR system largely mitigated membrane fouling and prolonged the system operation time. Results showed 2h hydraulic retention time provided relatively higher removal efficiency and stable operation performance. Modified Stover Kincannon model was able to match the aMBR system.

The role of innovative technologies in achieving energy-neutral wastewater treatment

A new flowsheet is proposed to achieve energy-neutral wastewater treatment (even better, electricity-neutral) while removing nitrogen using the proven nitrification-denitrification metabolic pathway. It is compatible with solid-liquid separation by conventional clarification or membrane filtration. The new flowsheet is based on a hybrid membrane-aerated biofilm reactor process which uses hollow fiber membranes arranged in modules and cassettes deployed in a way similar to immersed hollow fiber filtration membranes used for MBR (e.g., the ZeeWeed1 500 product). Atmospheric air is fed down the lumen of hollow fibers and oxygen is transferred to the biofilm growing on the outer surface of the membrane without the formation of bubbles. The new energy-neutral flowsheet is compared to a conventional activated sludge (CAS) flowsheet including complete wastewater and sludge treatment with anaerobic digestion and combined heat and power energy recovery. The new flowsheet has an electricity consumption 40% lower and energy production 18% higher as compared to the CAS flowsheet and is overall electricity-neutral.