A review of the potential of conventional and advanced membrane technology in the removal of pathogens from wastewater.

Consumption of pathogenic contaminated water has claimed the lives of many people. Hence, this scenario has emphasized the urgent need for research methods to avoid, treat and eliminate harmful pathogens in wastewater. Therefore, effective water treatment has become a matter of utmost importance. Membrane technology offers purer, cleaner, and pathogen-free water through the water separation method via a permeable membrane. Advanced membrane technology such as nanocomposite membrane, membrane distillation, membrane bioreactor, and photocatalytic membrane reactor can offer synergistic effects in removing pathogen through the integration of additional functionality and filtration in a single chamber. This paper also comprehensively discussed the application, challenges, and future perspective of the advanced membrane technology as a promising alternative in battling pathogenic microbial contaminants, which will also be beneficial and valuable in managing pandemics in the future as well as protecting human health and the environment. In addition, the potential of membrane technology in battling the ongoing global pandemic of coronavirus disease 2019 (COVID-19) was also discussed briefly.

Recent progress in integrated fixed-film activated sludge process for wastewater treatment: A review.

Integrated fixed-film activated sludge (IFAS) process is considered as one of the leading-edge processes that provides a sustainable solution for wastewater treatment. IFAS was introduced as an advancement of the moving bed biofilm reactor by integrating the attached and the suspended growth systems. IFAS offers advantages over the conventional activated sludge process such as reduced footprint, enhanced nutrient removal, complete nitrification, longer solids retention time and better removal of anthropogenic composites. IFAS has been recognized as an attractive option as stated from the results of many pilot and full scales studies. Generally, IFAS achieves >90% removals for combined chemical oxygen demand and ammonia, improves sludge settling properties and enhances operational stability. Recently developed IFAS reactors incorporate frameworks for either methane production, energy generation through algae, or microbial fuel cells. This review details the recent development in IFAS with the focus on the pilot and full-scale applications. The microbial community analyses of IFAS biofilm and floc are underlined along with the special emphasis on organics and nitrogen removals, as well as the future research perspectives.

Hybrid Membrane Distillation and Wet Scrubber for Simultaneous Recovery of Heat and Water from Flue Gas.

Flue gas contains high amount of low-grade heat and water vapor that are attractive for recovery. This study assesses performance of a hybrid of water scrubber and membrane distillation (MD) to recover both heat and water from a simulated flue gas. The former help to condense the water vapor to form a hot liquid flow which later used as the feed for the MD unit. The system simultaneously recovers water and heat through the MD permeate. Results show that the system performance is dictated by the MD performance since most heat and water can be recovered by the scrubber unit. The scrubber achieved nearly complete water and heat recovery because the flue gas flows were supersaturated with steam condensed in the water scrubber unit. The recovered water and heat in the scrubber contains in the hot liquid used as the feed for the MD unit. The MD performance is affected by both the temperature and the flow rate of the flue gas. The MD fluxes increases at higher flue gas temperatures and higher flow rates because of higher enthalpy of the flue gas inputs. The maximum obtained water and heat fluxes of 12 kg m-2 h-1 and 2505 kJm-2 h-1 respectively, obtained at flue gas temperature of 99 °C and at flow rate of 5.56 L min-1. The MD flux was also found stable over the testing period at this optimum condition. Further study on assessing a more realistic flue gas composition is required to capture complexity of the process, particularly to address the impacts of particulates and acid gases.

Development of novel hydrophilic ionic liquid membranes for the recovery of biobutanol through pervaporation.

This paper aims to develop novel hydrophilic ionic liquid membranes using pervaporation for the recovery of biobutanol. Multiple polyvinyl alcohol (PVA) membranes based on three commercial ionic liquids with different loading were prepared for various experimental trials. The ionic liquids selected for the study include tributyl (tetradecyl) phosphonium chloride ([TBTDP][Cl]), tetrabutyl phosphonium bromide ([TBP][Br]) and tributyl methyl phosphonium methylsulphate ([TBMP][MS]). The synthesized membranes were characterized and tested in a custom-built pervaporation set-up. All ionic liquid membranes showed better results with total flux of 1.58 kg/m2h, 1.43 kg/m2h, 1.38 kg/m2h at 30% loading of [TBP][Br], [TBMP][MS] and [TBTDP][Cl] respectively. The comparison of ionic liquid membranes revealed that by incorporating [TBMP]MS to PVA matrix resulted in a maximum separation factor of 147 at 30 wt% loading combined with a relatively higher total flux of 1.43 kg/m2h. Density functional theory (DFT) calculations were also carried out to evaluate the experimental observations along with theoretical studies. The improved permeation properties make these phosphonium based ionic liquid a promising additive in PVA matrix for butanol-water separation under varying temperature conditions.

Improving Water Permeability of Hydrophilic PVDF Membrane Prepared via Blending with Organic and Inorganic Additives for Humic Acid Separation.

The removal of impurities from water or wastewater by the membrane filtration process has become more reliable due to good hydraulic performance and high permeate quality. The filterability of the membrane can be improved by having a material with a specific pore structure and good hydrophilic properties. This work aims at preparing a polyvinylidene fluoride (PVDF) membrane incorporated with phospholipid in the form of a 2-methacryloyloxyethyl phosphorylcholine, polymeric additive in the form of polyvinylpyrrolidone, and its combination with inorganic nanosilica from a renewable source derived from bagasse. The resulting membrane morphologies were analyzed by using scanning electron microscopy. Furthermore, atomic force microscopy was performed to analyze the membrane surface roughness. The chemical compositions of the resulting membranes were identified using Fourier transform infrared. A lab-scale cross-flow filtration system module was used to evaluate the membrane's hydraulic and separation performance by the filtration of humic acid (HA) solution as the model contaminant. Results showed that the additives improved the membrane surface hydrophilicity. All modified membranes also showed up to five times higher water permeability than the pristine PVDF, thanks to the improved structure. Additionally, all membrane samples showed HA rejections of 75-90%.

Optimization of operational parameters using RSM, ANN, and SVM in membrane integrated with rotating biological contactor.

Membrane fouling is a critical bottleneck to the widespread adoption of membrane separation processes. It diminishes the membrane permeability and results in high operational energy costs. The current study presents optimizing the operating parameters of a novel rotating biological contactor (RBC) integrated with an external membrane (RBC + ME) that combines membrane technology with an RBC. In the RBC + ME, the membrane panel is placed external to the bioreactor. Response surface methodology (RSM) is applied to optimize the membrane permeability through three operating parameters (hydraulic retention time (HRT), rotational disk speed, and sludge retention time (SRT)). The artificial neural networks (ANN) and support vector machine (SVM) are implemented to depict the statistical modelling approach using experimental data sets. The results showed that all three operating parameters contribute significantly to the performance of the bioreactor. RSM revealed an optimum value of 40.7 rpm disk rotational speed, 18 h HRT and 12.4 d SRT, respectively. An ANN model with ten hidden layers provides the highest R2 value, while the SVM model with the Bayesian optimizer provides the highest R2. RSM, ANN, and SVM models reveal the highest R-square values of 0.97, 0.99, and 0.99, respectively. Machine learning techniques help predict the model based on the experimental results and training data sets.

Enhancing Water Purification by Integrating Titanium Dioxide Nanotubes into Polyethersulfone Membranes for Improved Hydrophilicity and Anti-Fouling Performance.

Water pollution remains a critical concern, one necessitated by rapidly increasing industrialization and urbanization. Among the various strategies for water purification, membrane technology stands out, with polyethersulfone (PES) often being the material of choice due to its robust mechanical properties, thermal stability, and chemical resistance. However, PES-based membranes tend to exhibit low hydrophilicity, leading to reduced flux and poor anti-fouling performance. This study addresses these limitations by incorporating titanium dioxide nanotubes (TiO2NTs) into PES nanofiltration membranes to enhance their hydrophilic properties. The TiO2NTs, characterized through FTIR, XRD, BET, and SEM, were embedded in PES at varying concentrations using a non-solvent induced phase inversion (NIPS) method. The fabricated mixed matrix membranes (MMMs) were subjected to testing for water permeability and solute rejection capabilities. Remarkably, membranes with a 1 wt% TiO2NT loading displayed a significant increase in pure water flux, from 36 to 72 L m2 h-1 bar-1, a 300-fold increase in selectivity compared to the pristine sample, and a dye rejection of 99%. Furthermore, long-term stability tests showed only a slight reduction in permeate flux over a time of 36 h, while dye removal efficiency was maintained, thus confirming the membrane's stability. Anti-fouling tests revealed a 93% flux recovery ratio, indicating excellent resistance to fouling. These results suggest that the inclusion of TiO2 NTs offers a promising avenue for the development of efficient and stable anti-fouling PES-based membranes for water purification.

Kinetic model derived from machine learning for accurate prediction of microalgal hydrogen production via conversion from low thermally pre-treated palm kernel expeller waste.

The depletion of fossil fuel sources and increase in energy demands have increased the need for a sustainable alternative energy source. The ability to produce hydrogen from microalgae is generating a lot of attention in both academia and industry. Due to complex production procedures, the commercial production of microalgal biohydrogen is not yet practical. Developing the most optimum microalgal hydrogen production process is also very laborious and expensive as proven from the experimental measurement. Therefore, this research project intended to analyse the random time series dataset collected during microalgal hydrogen productions while using various low thermally pre-treated palm kernel expeller (PKE) waste via machine learning (ML) approach. The analysis of collected dataset allowed the derivation of an enhanced kinetic model based on the Gompertz model amidst the dark fermentative hydrogen production that integrated thermal pre-treatment duration as a function within the model. The optimum microalgal hydrogen production attained with the enhanced kinetic model was 387.1 mL/g microalgae after 6 days with 1 h thermally pre-treated PKE waste at 90 °C. The enhanced model also had better accuracy (R2 = 0.9556) and net energy ratio (NER) value (0.71) than previous studies. Finally, the NER could be further improved to 0.91 when the microalgal culture was reused, heralding the potential application of ML in optimizing the microalgal hydrogen production process.

Bio-Nanocomposite Based on Edible Gelatin Film as Active Packaging from Clarias gariepinus Fish Skin with the Addition of Cellulose Nanocrystalline and Nanopropolis.

This study develops bio-nano composite gelatin-based edible film (NEF) by combining nanogelatin, cellulose nanocrystal (CNC), and nanopropolis (NP) fillers to improve the resulting film characteristics. The NEF was characterized in terms of thickness, swelling, pH, water content, solubility, vapor and oxygen permeability, mechanical properties, heat resistance, morphology, transparency, and color. The results showed that the thickness and swelling increased significantly, whilst the pH did not significantly differ in each treatment. The water content and the water solubility also showed no significant changes with loadings of both fillers. At the same time, vapor and oxygen permeability decreased with addition of the fillers but were not significantly affected by the loading amounts. The heat resistance properties increased with the filler addition. Tensile strength and Young's modulus increased for the films loaded with >3% CNC. The elongation at break showed a significant difference together with transparency and color change. The greater the CNC concentration and NP loading were, the darker the resulting transparency and the color of the NEF. Overall results show a considerable improvement in the properties of the resulting NEFs with the incorporation of CNC and NP fillers.

Optimization of Biocomposite Film Based on Whey Protein Isolate and Nanocrystalline Cellulose from Pineapple Crown Leaf Using Response Surface Methodology.

This study employed response surface methodology to optimize the preparation of biocomposites based on whey protein isolate, glycerol, and nanocrystalline cellulose from pineapple crown leaf. The effects of different concentrations of nanocrystalline cellulose as a filler and glycerol as a plasticizer on the thickness, the tensile strength, and the elongation at break on the resulting biocomposite films were investigated. The central composite design was used to determine the optimum preparation conditions for biocomposite films with optimum properties. The regression of a second-order polynomial model resulted in an optimum composition consisting of 4% glycerol and 3.5% nanocrystalline cellulose concentrations, which showed a desirability of 92.7%. The prediction of the regression model was validated by characterizing the biocomposite film prepared based on the optimum composition, at which the thickness, tensile strength, and elongation at break of the biocomposite film were 0.13 mm, 7.16 MPa, and 39.10%, respectively. This optimum composition can be obtained in range concentrations of glycerol (4-8%) and nanocrystalline cellulose (3-7%). Scanning electron microscope images showed that nanocrystalline cellulose dispersed well in the pure whey protein isolate, and the films had a relatively smooth surface. In comparison, a rough and uneven surface results in more porous biocomposite films. Fourier transform infrared spectroscopy revealed that nanocrystalline cellulose and glycerol showed good compatibility with WPI film by forming hydrogen bonds. The addition of nanocrystalline cellulose as a filler also decreased the transparency, solubility, and water vapor permeability and increased the crystallinity index of the resulting biocomposite film.

Confounding Effect of Wetting, Compaction, and Fouling in an Ultra-Low-Pressure Membrane Filtration: A Review.

Ultra-low-pressure membrane (ULPM) filtration has emerged as a promising decentralized water and wastewater treatment method. It has been proven effective in long-term filtration under stable flux without requiring physical or chemical cleaning, despite operating at considerably lower flux. The use of ultra-low pressure, often simply by hydrostatic force (often called gravity-driven membrane (GDM) filtration), makes it fall into the uncharted territory of common pressure-driven membrane filtration. The applied polymeric membrane is sensitive to compaction, wetting, and fouling. This paper reviews recent studies on membrane compaction, wetting, and fouling. The scope of this review includes studies on those phenomena in the ULPM and how they affect the overall performance of the system. The performance of GDM systems for water and wastewater treatment is also evaluated. Finally, perspectives on the future research direction of ULPM filtration are also detailed.

Thermophysical Properties of Nanofluid in Two-Phase Fluid Flow through a Porous Rectangular Medium for Enhanced Oil Recovery.

It is necessary to sustain energy from an external reservoir or employ advanced technologies to enhance oil recovery. A greater volume of oil may be recovered by employing nanofluid flooding. In this study, we investigated oil extraction in a two-phase incompressible fluid in a two-dimensional rectangular porous homogenous area filled with oil and having no capillary pressure. The governing equations that were derived from Darcy's law and the mass conservation law were solved using the finite element method. Compared to earlier research, a more efficient numerical model is proposed here. The proposed model allows for the cost-effective study of heating-based inlet fluid in enhanced oil recovery (EOR) and uses the empirical correlations of the nanofluid thermophysical properties on the relative permeability equations of the nanofluid and oil, so it is more accurate than other models to determine the higher recovery factor of one nanoparticle compared to other nanoparticles. Next, the effect of nanoparticle volume fraction on flooding was evaluated. EOR via nanofluid flooding processes and the effect of the intake temperatures (300 and 350 K) were also simulated by comparing three nanoparticles: SiO2, Al2O3, and CuO. The results show that adding nanoparticles (<5 v%) to a base fluid enhanced the oil recovery by more than 20%. Increasing the inlet temperature enhanced the oil recovery due to changes in viscosity and density of oil. Increasing the relative permeability of nanofluid while simultaneously reducing the relative permeability of oil due to the presence of nanoparticles was the primary reason for EOR.

Long-Term Performance and Stability of Interlayer-Free Mesoporous Silica Membranes for Wetland Saline Water Pervaporation.

Wetland water is an alternative water resource around wetland areas. However, it is typically saline due to seawater intrusion and contains high natural organic matter (NOM) that is challenging to treat. This study evaluated the stability of interlayer-free mesoporous silica matrix membranes employing a dual acid-base catalyzed sol-gel process for treatment of saline wetland water. The silica sols were prepared under a low silanol concentration, dip-coated in 4 layers, and calcined using the rapid thermal processing method. The membrane performance was initially evaluated through pervaporation under various temperatures (25-60 °C) using various feeds. Next, the long-term stability (up to 400 h) of wetland saline water desalination was evaluated. Results show that the water flux increased at higher temperatures up to 6.9 and 6.5 kg·m-2·h-1 at the highest temperature of 60 °C for the seawater and the wetland saline water feeds, respectively. The long-term stability demonstrated a stable performance without flux and rejection decline up to 170 h operation, beyond which slow declines in water flux and rejection were observed due to fouling by NOM and membrane wetting. The overall findings suggest that an interlayer-free mesoporous silica membrane offers excellent performance and high salt rejection (80-99%) for wetland saline water treatments.

The Combined Effects of the Membrane and Flow Channel Development on the Performance and Energy Footprint of Oil/Water Emulsion Filtration.

Membrane filtration is a promising technology for oil/water emulsion filtration due to its excellent removal efficiency of microdroplets of oil in water. However, its performance is highly limited due to the fouling-prone nature of oil droplets on hydrophobic membranes. Membrane filtration typically suffers from a low flux and high pumping energy. This study reports a combined approach to tackling the membrane fouling challenge in oil/water emulsion filtration via a membrane and a flow channel development. Two polysulfone (PSF)-based lab-made membranes, namely PSF- PSF-Nonsolvent induced phase separation (NIPS) and PSF-Vapor-induced phase separation (VIPS), were selected, and the flow channel was modified into a wavy path. They were assessed for the filtration of a synthetic oil/water emulsion. The results showed that the combined membrane and flow channel developments enhanced the clean water permeability with a combined increment of 105%, of which 34% was attributed to the increased effective filtration area due to the wavy flow channel. When evaluated for the filtration of an oil/water emulsion, a 355% permeability increment was achieved from 43 for the PSF-NIPS in the straight flow channel to 198 L m-2 h-1 bar-1 for the PSF-VIPS in the wavy flow channel. This remarkable performance increment was achieved thanks to the antifouling attribute of the developed membrane and enhanced local mixing by the wavy flow channel to limit the membrane fouling. The increase in the filtration performance was translated into up to 78.4% (0.00133 vs. 0.00615 kWh m-3) lower in pumping energy. The overall findings demonstrate a significant improvement by adopting multi-pronged approaches in tackling the challenge of membrane fouling for oil/water emulsion filtration, suggesting the potential of this approach to be applied for other feeds.

Compaction of a Polymeric Membrane in Ultra-Low-Pressure Water Filtration.

Applications of ultra-low-pressure filtration systems are increasing as they offer enhanced sustainability due to lower energy input, almost no use of chemicals, and minimum operational expenditure. In many cases, they operate as a decentralized system using a gravity-driven membrane (GDM) filtration process. These applications are relatively new; hence, the fundamental knowledge of the process is still limited. In this study, we investigated the phenomenon of polymeric membrane compaction under an ultra-low-pressure system. The compaction phenomenon is well-recognized in the traditional pressure-driven system operating at high transmembrane pressures (ΔPs > 200 kPa), but it is less documented in ultra-low-pressure systems (ΔP < 10 kPa). A simple GDM filtration setup operated under a constant-pressure system was employed to investigate the compaction phenomena in a polymeric hollow fiber membrane for clean water filtration. Firstly, a short-term pressure stepping test was performed to investigate the occurrence of instantaneous compaction in the ΔP range of 1−10 kPa. The slow compaction was later investigated. Finally, the compaction dynamic was assessed under alternating high and low ΔP and relaxation in between the filtrations. The findings demonstrated the prominence of membrane compaction, as shown by the decreasing trend in clean water permeability at higher ΔPs (i.e., 3240 and 2401 L m−2 h−1 bar−1 at ΔPs of 1 and 10 kPa, respectively). We also found that the intrinsic permeability of the applied polymeric membrane was significantly higher than the apparent one (4351 vs. 2401 L m−2 h−1 bar−1), demonstrating >50% loss due to compaction. The compaction was mainly instantaneous, which occurred when the ΔP was changed, whereas only minor changes in permeability occurred over time when operating at a constant ΔP. The compaction was highly reversible and could be restored (i.e., decompaction) through relaxation by temporarily stopping the filtration. A small fraction of irreversible compaction could be detected by operating alternating filtrations under ΔPs of 1 and 10 kPa. The overall findings are essential to support emerging GDM filtration applications, in which membrane compaction has been ignored and confounded with membrane fouling. The role of compaction is more prominent for high-flux GDM filtration systems treating less-fouling-prone feed (i.e., rainwater, river water) and involving membrane cleaning (i.e., relaxation) in which both reversible and irreversible compaction occurred simultaneously.

Updated review on microplastics in water, their occurrence, detection, measurement, environmental pollution, and the need for regulatory standards.

The gravity of the impending threats posed by microplastics (MPs) pollution in the environment cannot be over-emphasized. Several research studies continue to stress how important it is to curb the proliferation of these small plastic particles with different physical and chemical properties, especially in aquatic environments. While several works on how to monitor, detect and remove MPs from the aquatic environment have been published, there is still a lack of explicit regulatory framework for mitigation of MPs globally. A critical review that summarizes recent advances in MPs research and emphasizes the need for regulatory frameworks devoted to MPs is presented in this paper. These frameworks suggested in this paper may be useful for reducing the proliferation of MPs in the environment. Based on all reviewed studies related to MPs research, we discussed the occurrence of MPs by identifying the major types and sources of MPs in water bodies; examined the recent ways of detecting, monitoring, and measuring MPs routinely to minimize projected risks; and proposed recommendations for consensus regulatory actions that will be effective for MPs mitigation.

Fabrication of Polyvinylidene Difluoride Membrane with Enhanced Pore and Filtration Properties by Using Tannic Acid as an Additive.

Potential use of tannic acid (TA) as an additive for fabrication of polyvinylidene difluoride (PVDF) membrane was investigated. The TA was introduced by blending into the dope solution with varying concentrations of 0, 1, 1.5, and 2 wt%. The prepared membranes were characterized and evaluated for filtration of humic acid (HA) solution. The stability of the membrane under harsh treatment was also evaluated by one-week exposure to acid and alkaline conditions. The results show that TA loadings enhanced the resulting membrane properties. It increased the bulk porosity, water uptake, and hydrophilicity, which translated into improved clean water flux from 15.4 L/m2.h for the pristine PVDF membrane up to 3.3× for the TA-modified membranes with the 2 wt% TA loading. The flux recovery ratio (FRR) of the TA-modified membranes (FRRs = 78-83%) was higher than the pristine one (FRR = 58.54%), with suitable chemical stability too. The improved antifouling property for the TA-modified membranes was attributed to their enhanced hydrophilicity thanks to improved morphology and residual TA in the membrane matric.

Functionalization of PEG-AgNPs Hybrid Material to Alleviate Biofouling Tendency of Polyethersulfone Membrane.

Membrane-based processes are a promising technology in water and wastewater treatments, to supply clean and secure water. However, during membrane filtration, biofouling phenomena severely hamper the performance, leading to permanent detrimental impacts. Moreover, regular chemical cleaning is ineffective in the long-run for overcoming biofouling, because it weakens the membrane structure. Therefore, the development of a membrane material with superior anti-biofouling performance is seen as an attractive option. Hydrophilic-anti-bacterial precursor polyethylene glycol-silver nanoparticles (PEG-AgNPs) were synthesized in this study, using a sol-gel method, to mitigate biofouling on the polyethersulfone (PES) membrane surface. The functionalization of the PEG-AgNP hybrid material on a PES membrane was achieved through a simple blending technique. The PES/PEG-AgNP membrane was manufactured via the non-solvent induced phase separation method. The anti-biofouling performance was experimentally measured as the flux recovery ratio (FRR) of the prepared membrane, before and after incubation in E. coli culture for 48 h. Nanomaterial characterization confirmed that the PEG-AgNPs had hydrophilic-anti-bacterial properties. The substantial improvements in membrane performance after adding PEG-AgNPs were evaluated in terms of the water flux and FRR after the membranes experienced biofouling. The results showed that the PEG-AgNPs significantly increased the water flux of the PES membrane, from 2.87 L·m-2·h-1 to 172.84 L·m-2·h-1. The anti-biofouling performance of the PES pristine membrane used as a benchmark showed only 1% FRR, due to severe biofouling. In contrast, the incorporation of PEG-AgNPs in the PES membrane decreased live bacteria by 98%. It enhanced the FRR of anti-biofouling up to 79%, higher than the PES/PEG and PES/Ag membranes.

Response Surface Methodology for Optimization of Rotating Biological Contactor Combined with External Membrane Filtration for Wastewater Treatment.

A large amount of wastewater is directly discharged into water bodies without treatment, causing surface water contamination. A rotating biological contactor (RBC) is an attached biological wastewater treatment process that offers a low energy footprint. However, its unstable removal efficiency makes it less popular. This study optimized operating parameters in RBC combined with external membrane filtration (RBC-ME), in which the latter acted as a post-treatment step to stabilize the biological performance. Response surface methodology (RSM) was employed to optimize the biological and filtration performance by exploiting three parameters, namely disk rotation, hydraulic retention time (HRT), and sludge retention time (SRT). Results show that the RBC-ME exhibited superior biological treatment capacity and higher effluent quality compared to stand-alone RBC. It attained 87.9 ± 3.2% of chemical oxygen demand, 45.2 ± 0.7% total nitrogen, 97.9 ± 0.1% turbidity, and 98.9 ± 1.1% ammonia removals. The RSM showed a good agreement between the model and the experimental data. The maximum permeability of 144.6 L/m2 h bar could be achieved under the optimum parameters of 36.1 rpm disk rotation, 18 h HRT, and 14.9 d SRT. This work demonstrated the effective use of statistical modeling to enhance RBC-ME system performance to obtain a sustainable and energy-efficient condition.

A Rotary Spacer System for Energy-Efficient Membrane Fouling Control in Oil/Water Emulsion Filtration.

Membrane fouling deteriorates membrane filtration performances. Hence, mitigating membrane fouling is the key factor in sustaining the membrane process, particularly when treating fouling-prone feed, such as oil/water emulsions. The use of spacers has been expanded in the membrane module system, including for membrane fouling control. This study proposed a rotating spacer system to ameliorate membrane fouling issues when treating an oil/water emulsion. The system's effectiveness was assessed by investigating the effect of rotating speed and membrane-to-disk gap on the hydraulic performance and the energy input and through computational fluid dynamics (CFD) simulation. The results showed that the newly developed rotary spacer system was effective and energy-efficient for fouling control. The CFD simulation results proved that the spacer rotations induced secondary flow near the membrane surface and imposed shear rate and lift force to exert fouling control. Increasing the rotation speed to an average linear velocity of 0.44 m/s increased the permeability from 126.8 ± 2.1 to 175.5 ± 2.7 Lm-2h-1bar-1. The system showed better performance at a lower spacer-to-membrane gap, in which increasing the gap from 0.5 to 2.0 cm lowered the permeability from 175.5 ± 2.7 to 126.7 ± 2.0 Lm-2h-1bar-1. Interestingly, the rotary system showed a low energy input of 1.08 to 4.08 × 10-3 kWhm-3 permeate when run at linear velocities of 0.27 to 0.44 ms-1. Overall, the findings suggest the competitiveness of the rotary spacer system as a method for membrane fouling control.