Cross-flow Ultrafiltration Research Articles

Anaerobic membrane bioreactor (AnMBR) with external ultrafiltration membrane for the treatment of sugar beet vinasse.

Vinasse, a by-product of ethanol production, is generated at significant rates. While rich in nutrients such as calcium, magnesium, and potassium, its high solids, organic matter, acidity, and sulfate content pose challenges when disposed directly on soil, necessitating treatment. Anaerobic digestion is a viable solution, reducing organic pollution while recovering energy in the form of biogas, aligning with the biorefinery concept. Traditionally, sludge bed reactors and anaerobic contact reactors are utilized for vinasse processing, with sludge granulation being vital for treatment success. However, challenges such as sludge wash-out due to recalcitrant compounds, high solids concentration in the influent, low pH, salinity, and temperature hinder granule formation. Anaerobic membrane bioreactors (AnMBR) offer an alternative, simplifying treatment by integrating intensified pre- and post-treatment units. Due to complete sludge retention, AnMBRs achieve high COD removal efficiencies, yielding a suspended solids-free and largely disinfected effluent. Therefore, AnMBRs show promise for vinasse treatment, eliminating the need for sludge granulation and producing nutrient-rich effluent with minimal residual organics and suspended solids. In this study, an AnMBR equipped with an inside-out external crossflow ultrafiltration membrane was proposed for the treatment of vinasse. The AnMBR reached a COD removal efficiency of 95% ± 2.6% and produced 0.3 CH4 L.g COD removed -1 working at organic loading rates of 8g COD. L-1 d-1 and membrane fluxes of 10 LMH. At organic loading rates of 10g COD. L-1 d-1 and fluxes of 12 and 14 LMH, the COD removal efficiency decreased to 77% ± 11% and 73% ± 7.9%, respectively. The AnMBR technology represents an innovation for wastewater treatment, however, more research using the cross-flow configuration and different types of effluents is needed. Literature studies that address the treatment of sugar beet or sugarcane vinasse using AnMBR are still scarce. This study explored the potentials of AnMBR technology for vinasse treatment and contributes to the dissemination of this technology, opening new possibilities for vinasse processing.

Treatment of sugarcane vinasse in AnMBR and UASB: process performance and microbial community comparison.

Vinasse is a by-product of sugarcane processing which is often used in fertigation; however, the direct use of vinasse harms the environment and reduces soil productivity due to its physicochemical properties. Anaerobic digestion (AD) offers an alternative to mitigate part of the negative effects. Anaerobic high-rate reactors, which mainly rely on sludge granulation, are mostly used in AD of vinasse wastewater. However, the composition of vinasse such as high concentration of solids and organic matter, high salinity, low pH, and high concentrations of sulfate, affect granule formation, leading to sludge washout. Anaerobic membrane bioreactors (AnMBR) present an alternative for vinasse treatment, eliminating the need for sludge granulation and producing a nutrient-rich effluent with minimal residual organics and no suspended solids. Research on sugarcane vinasse treatment using AnMBRs is limited. Most studies have employed submerged internal membrane modules, highlighting the need for further research with different reactor configurations to enhance process performance. In this study, an AnMBR equipped with an external inside-out crossflow ultrafiltration membrane was compared to an upflow anaerobic sludge blanket (UASB) reactor for the treatment of sugarcane vinasse. At a volumetric organic loading rate of up to 6g COD. L-1.d-1, the UASB reactor reached 75% ± 7% of COD removal efficiency whereas the AnMBR generated a solids-free effluent and reached 88% ± 2% of COD removal efficiency. Microorganisms such as Clostridia, Bacteroidia, Mesotaga, Syner-01, Dehalococcoidia, Bacteroidia-DMER64, and Methanolinea were found as the most abundant. The results highlight the AnMBR potential as an effective alternative for treating sugarcane vinasse while overcoming the challenges posed by unsatisfactory sludge granulation.

Homogeneous CaAlg/PES hybrid ultrafiltration membranes prepared with in situ ionic crosslinking and phase inversion method

Calcium alginate hydrogel/polyethersulfone (CaAlg/PES) hybrid membranes were synthesized via combining in situ ion crosslinking with phase conversion method. Once the Sodium alginate (NaAlg) uniformly dispersed in the casting solution contacted with Ca2+ dissolved in coagulation bath solution in the phase conversion membrane formation process, nanoscale CaAlg hydrogel was in situ formed through ion exchange and evenly dispersed in the membrane matrix. FT-IR and XPS were adopted to confirm the formation of CaAlg hydrogel distributed in PES membrane matrix. SEM, AFM, BET analysis and contact Angle analyzer were all used to characterize the surface changes of morphology, roughness and hydrophilicity in detail. Specific separation performance was also evaluated and compared by cross-flow ultrafiltration tests. Comprehensive analysis of the measured properties of all obtained membranes, when the content of NaAlg was 1.5 wt%, the CaAlg/PES hydrogel membrane M32 had the most excellent performance. The pure water flux increased from 1967 to 2193 L/m2hMPa, rejection rate of BSA was up to 99.87 %, and RFR value was almost 76.83 % after 4 cycles BSA filtration. XPS characterization of the membrane after filtration for 72 hours showed that the retention rate of Ca (2 P) reached 95 %, which further proved the stability of the membrane operation.

Hydrolysis and cross-flow ultrafiltration as an alternative process to isolate fucoidans from edible seaweed Nizamuddinia zarnardinii with enhanced immunostimulatory efficacy

In the present investigation, fucoidan isolated from Nizamuddinia zanardinii was hydrolysed using 0.01 N HCl at boiling temperature for 10, 20, 40 and 60 min. Native and hydrolysed fucoidans contained a close chemical compositions, most importantly constituted of sulfates and uronic acids as well as fucose, galactose and mannose. Hydrolysis and cross-flow ultrafiltration produced fucoidan hydrolysates having different weight average molecular weights. The FH20 fucoidan was the most potent polysaccharide hydrolysate to stimulate NO-release from RAW264.7 macrophage cells. After cross-flow ultrafiltration of FH20, 100 < kDa fucoidan, polysaccharide with high branching degree consisting mainly of (1 → 2)-Fucp, (1 → 2,3)-Fucp, (1 → 3)-Galp, (1 → 2,3)-Galp, (1 → 2)-Manp and (1 → 3)-Manp residues, exerted the highest stimulation effect on RAW264.7 macrophage cells, secreting considerable NO, TNF-α, IL-1β, IL-6 and IL-12 proinflammatory mediators. Also, 100 < kDa fucoidan activated NK-92 cells to release TNF-α, INF-γ, granzyme-B, perforin, NKG2D and FasL. Both RAW264.7 and NK-92 cells were activated through NF-κB and MAPKs signalling pathways and the degree of stimulation capacity in fucoidan from N. zanardinii was in close correlation with the molecular weight.

Catalytic Ozonation of Pharmaceuticals Using CeO2-CeTiOx-Doped Crossflow Ultrafiltration Ceramic Membranes.

The removal of persistent organic micropollutants (OMPs) from secondary effluent in wastewater treatment plants is critical for meeting water reuse standards. Traditional treatment methods often fail to adequately degrade these contaminants. This study explored the efficacy of a hybrid ozonation membrane filtration (HOMF) process using CeO2 and CeTiOx-doped ceramic crossflow ultrafiltration ceramic membranes for the degradation of OMPs. Hollow ceramic membranes (CM) with a 300 kDa molecular weight cut-off (MWCO) were modified to serve as substrates for catalytic nanosized metal oxides in a crossflow and inside-out operational configuration. Three types of depositions were tested: a single layer of CeO2, a single layer of CeTiOx, and a combined layer of CeO2 + CeTiOx. These catalytic nanoparticles were distributed uniformly using a solution-based method supported by vacuum infiltration to ensure high-throughput deposition. The results demonstrated successful infiltration of the metal oxides, although the yield permeability and transmembrane flow varied, following this order: pristine > CeTiOx > CeO2 > CeO2 + CeTiOx. Four OMPs were examined: two easily degraded by ozone (carbamazepine and diclofenac) and two recalcitrant (ibuprofen and pCBA). The highest OMP degradation was observed in demineralized water, particularly with the CeO2 + CeTiOx modification, suggesting O3 decomposition to hydroxyl radicals. The increased resistance in the modified membranes contributed to the adsorption phenomena. The degradation efficiency decreased in secondary effluent due to competition with the organic and inorganic load, highlighting the challenges in complex water matrices.

Investigation of the Distribution and Binding Affinity of Copper to Size-Fractioned Dissolved Organic Matter (DOM) in a Constructed Wetland

This study investigated the distribution and binding affinity of dissolved copper (Cu) and organic carbon (OC) in size-fractioned dissolved organic matter (DOM) in a constructed wetland (CW). Two sites were studied: one at the inflow (P-1) and one within the wetland (P-2). The DOMs (&lt;0.45 μm) were separated into six size fractions using a cross-flow ultrafiltration system. In the wetland (P-2), the concentrations of dissolved organic carbon (DOC) increased while the concentrations of Cu decreased. The high molecular weight fraction (1 kDa–0.45 μm, HMW) contained most of the OC mass (57.4–71.2% averages). On the other hand, Cu was almost equally distributed in HMW and low molecular weight fractions (&lt;1 kDa, LMW) with mean HMW percentages of 50.3–51.3%. The mean Cu binding affinity to DOM ratios (CuBADOM) was 74.9 ± 24.0 μmol/g-C at site P-1 and 17.3 ± 2.6 μmol/g-C at site P-2. The CuBADOM ratios were decreased in wetlands of bulk and size-fractioned DOM (p &lt; 0.001 to p = 0.073). The SUVA254 values for bulk DOM solution were 2.54 ± 0.15 and 1.68 ± 0.18 L/mg-C/m, and humidification index (HIX) values were 1.74 ± 0.16 and 2.09 ± 0.19 for sites P-1 and P-2, respectively. Optical indicators suggested that the wetland process decreased aromaticity but increased the humification degree of DOM. Furthermore, the CuBADOM ratios positively correlated with SUVA254 and HIX within the constructed wetland DOM but not in the influent DOM. Understanding the Cu distribution and binding affinity to size-fractioned DOM makes it possible to develop strategies to mitigate the potential effects of copper pollution in wetlands.

Copper Distribution and Binding Affinity to Size-Fractioned Dissolved and Particulate Organic Matter in River Sediment

This study investigated the distribution of copper in sediment dissolved and particulate organic matter (DOM and POM) based on their size. The DOM and alkaline extracted POM (AEOM) were separated into five size fractions using a cross-flow ultrafiltration (CFUF) system. The results showed that Cu mass was mainly distributed in the low molecular weight (&lt;1 kDa, LMW) fraction of the DOM with an average range of 78.1–83.1%. Conversely, the high molecular weight (1 kDa–0.45 μm, HMW) AEOM fraction had a higher distribution of Cu mass with an average range of 92.6–93.3%. The Cu and AEOM binding affinity ratios (CuBAAEOM) ranged from 17.0 to 149.6 μmol/g-C in site-1 and from 20.6 to 143.7 μmol/g-C in site-2. The HMW CuBAAEOM ratios were significantly higher than the LMW ratios. The Cu and DOM binding affinity ratios (CuBADOM) ranged from 5.6 to 358.6 μmol/g-C and 17.2 to 126.6 μmol/g-C in site-1 and site-2, respectively. However, the LMW CuBADOM ratios were significantly higher than the HMW ratios. Optical indices suggested that the AEOM had more aromaticity and terrestrial and allochthonous contributions than the DOM. The optical indices were significantly correlated with the CuBAAEOM ratios but weakly correlated with the CuBADOM ratios. Sediment exchange between POM and DOM may affect copper distribution. DOM has a low-molecular-weight composition, while POM retains high-molecular-weight organic matter.

Deterministic mathematical modeling, sensitivity analysis, and dynamic optimization of cross-flow ultrafiltration systems for concentration of monoclonal antibody solutions

This manuscript proposes a general new framework for mathematical modeling, extended sensitivity analysis and dynamic optimization of tangential flow filtration (TFF) systems for concentration of monoclonal antibody (mAb) products and, potentially, other biologics. This framework is comprised of four major components: (I) a new first-principles-inspired TFF model; (II) dedicated parameter estimation strategies for automated model training; (III) new extended sensitivity analysis techniques for enhancing TFF phenomenological understanding and providing general guidance on TFF process development; and (IV) novel mono-objective and multi-objective dynamic optimization strategies for optimal TFF design and operation. The application of this framework to Bovine immunoglobulin γ (IgG) – a mAb analog in terms of physicochemical properties – shows the potential benefits it may offer in terms of overall TFF performance and rapid TFF development for new mAb candidates, compared to the current state of the art.

Efficient recovery of TiO2 and Pt-doped TiO2 photocatalysts in wastewater treatment using a pilot-scale cross-flow ultrafiltration membrane system

Despite the high efficacy of photocatalysts in wastewater treatment, their pilot plant and industrial-scale applications are scanty. The photocatalysts must be recovered for their reuse to minimize the treatment cost and also to avoid secondary water pollution due to the presence of catalyst particles. Herein, we have studied the recovery of TiO2 and Pt-doped TiO2 (Pt/TiO2) photocatalysts using a pilot scale cross-flow ultrafiltration (CF-UF) membrane system with a nominal area of 2 m2 and pore size of 75 kDa. The photocatalysts recovery was conducted at a 0.032–0.105 m s−1 cross flow velocity (CFV) and transmembrane pressure (TMP) drop of 0.6–1.05 kg cm−2. The wettability studies revealed that the membrane is more hydrophilic from the inside (water contact angle, θ = 54.1°) than the outer surface (θ = 77.3°) with an inner diameter of 0.78 mm and a thickness of 0.21 mm. Pure water flux (PWF), permeate flux, and catalyst recovery (%) decreased with increased pH and catalyst concentration. The flux was reduced from 11.12 ± 0.15 to 10.56 ± 0.17 and 10.37 ± 0.19 L m−2 h−1 during the recovery of TiO2 and Pt/TiO2 (50 mg/L), respectively. The recovery of about 99.74 ± 0.13 and 99.41 ± 0.29 % of TiO2 and Pt/TiO2 (50 mg/L), respectively, was achieved at the optimized pH 5. Membrane fouling and flux recovery studies revealed excellent antifouling properties of the membrane with a maximum of 9.86 ± 0.04 % reversible fouling and a minimum of 98.78 ± 0.20 % flux recovery. The hydrodynamic diameters of both catalyst particles increased in the reject and backflush streams with right-tailed lognormal distribution.

Effect of Flowrate and Pressure on the Crossflow Filtration in Textile Wastewater Treatment by Commercial UF Membrane

Textile industries are one of the greatest wastewater producers as they require a significant amount of water to be used in the dyeing and finishing processes of textile manufacturing. The number of unit operations in the technological process, the product range, the bath ratio, the mass of fiber in relation to the bath volume, and the finishing machine are some variables that will affect water consumption in the textile industry. As a result, generally, a typical textile plant may consume a volume of water between 100,000 and 300,000 m3 annually. As textiles address a substantial portion of human requirements, it is predicted that by 2050, there will be 160 million metric tonnes, three times as much clothing as there is today. Membrane technology in wastewater treatment is a recent interest arising technique and garnering the industrial application’s interest, owing to its ease of setup and low energy requirement. Crossflow membrane filtration is commonly used in the industry, attributed to its tangential flow across the membrane mechanism, leading to low fouling. This study investigated the textile wastewater’s effluents using crossflow ultrafiltration (UF) membrane filtration. The effect of the operating parameter in terms of pressure and flowrate of the crossflow system were performed to evaluate it permeate flux performance. The study’s outcome reveals pressure increases from 2 bar to 4 bar, the water flux enhances dramatically from 156.26 L/m2hr to 591.98 L/m2hr, and the water flux further increases constantly from 4 bar to 10 bar. On the other hand, the flowrate positively affects the permeate flux, where the flux was enhanced from 651.01 L/m2hr to 726.08 L/m2hr when adjusting the flow rate from 2 LPM to 6 LPM. The results from this study suggested that crossflow membrane filtration system could be commercially feasible due to its permeate flux performance.

Ultrahigh-throughput cross-flow filtration of solution-processed 2D materials enabled by porous ceramic membranes.

Printed electronics is a disruptive technology in multiple applications including environmental and biological sensors, flexible displays, and wearable diagnostic devices. With superlative electronic, optical, mechanical, and chemical properties, two-dimensional (2D) materials are promising candidates for printable electronic inks. While liquid-phase exfoliation (LPE) methods can produce electronic-grade 2D materials, conventional batch separation processes typically rely on centrifugation, which requires significant time and effort to remove incompletely exfoliated bulk powders, hindering the scale-up of 2D ink manufacturing. While cross-flow filtration (CFF) has emerged as a promising continuous flow separation method for solution-processed 2D nanosheets, previously demonstrated polymer CFF membranes necessitate low 2D nanosheet concentrations to avoid fouling, which ultimately limits mass throughput. Here, we demonstrate a fully flow-based, exfoliation-to-ink system for electronic-grade 2D materials using an integrated cross-flow separation and concentration system. To overcome the relatively low-throughput processing concentrations of incumbent polymer CFF membranes, we employ porous ceramic CFF membranes that are tolerant to 10-fold higher nanosheet concentrations and flow rates without compromising separation efficiency. Furthermore, we demonstrate a concentration method via cross-flow ultrafiltration, where the retentate can be directly formulated into printable inks with electronic-grade performance that meets or exceeds centrifugally produced inks. Life cycle assessment and technoeconomic analysis quantitatively confirm the advantages of ceramic versus polymer CFF membranes including reductions of 97%, 96%, 94%, and 93% for greenhouse gas emissions, water consumption, fossil fuel consumption, and specific production costs, respectively. Overall, this work presents an environmentally sustainable and cost-effective solution for the fabrication, separation, and printing of electronic-grade 2D materials.

Ultrafiltration Harvesting of Microalgae Culture Cultivated in a WRRF: Long-Term Performance and Techno-Economic and Carbon Footprint Assessment

A cross-flow ultrafiltration harvesting system for a pre-concentrated microalgae culture was tested in an innovative anaerobic-based WRRF. The microalgae culture was cultivated in a membrane photobioreactor fed with effluent from an anaerobic membrane bioreactor treating sewage. These harvested microalgae biomasses were then anaerobically co-digested with primary and secondary sludge from the water line. Depending on the needs of this anaerobic co-digestion, the filtration harvesting process was evaluated intermittently over a period of 212 days for different operating conditions, mainly the total amount of microalgae biomass harvested and the desired final total solids concentration (up to 15.9 g·L−1 with an average of 9.7 g·L−1). Concentration ratios of 15–27 were obtained with average transmembrane fluxes ranging from 5 to 28 L·m−2·h−1. Regarding membrane cleaning, both backflushing and chemical cleaning resulted in transmembrane flux recoveries that were, on average, 21% higher than those achieved with backflushing alone. The carbon footprint assessment shows promising results, as the GHG emissions associated with the cross-flow ultrafiltration harvesting process could be less than the emissions savings associated with the energy recovered from biogas production from the anaerobic valorisation of the harvested microalgae.

Effect of Metal Cations on Colloids-Microcystin-LR Interaction.

Colloidal particles, mixture with continuous molecular weight distribution and multiple organic components, is widespread in lake and have significant impact on the retention, migration, transportation, and fate of contaminants in lake ecosystems. Here we extract sedimentary colloids from algal growth dominant area (AD) in Taihu Lake and further separated into four different particle size ranges by cross-flow ultra-filtration (CFUF). The interaction mechanism between colloids and Microcystin-LR (MC-LR) was investigated under different cation conditions by dialysis equilibrium experiment method. Adsorption kinetics research shows the adsorption of MC-LR by colloids follows second-order kinetics and can be simulated by Freundlich isotherms. The effects of different cations on colloids-MC-LR interaction shows the addition of Mg(II) decreased colloids-MC-LR interaction, while Cu(II) increased colloids-MC-LR binding. MC-LR also increased Cu(II) binding to colloids, while MC-LR decreased Mg(II) binding. Therefore, different effect of cations to colloids-MC-LR interaction was proposed.

Abundance of colloidal organic phosphorus in the Taiwan Strait

The Taiwan Strait is a coastal sea with dynamic hydrologic condition and dissolved organic matter (DOM) cycling. To better understand its phosphorus (P) transformation, phosphate and bulk dissolved organic phosphorus (DOP) concentrations were determined in the surface water of the Taiwan Strait during 2010 and 2011 summers. The bulk DOP was further fractionated into the low molecular weight (LMW) DOP and colloidal organic phosphorus (COP) with the application of the cross-flow ultrafiltration technique at a size cut-off of 10 kDa. The surface water in the Taiwan Strait generally showed higher bulk DOP concentration than phosphate excluding estuarine stations. This is similar to the surface waters in the subtropical gyres, implying a P-deficient condition in the Taiwan Strait. The LMW-DOP followed a constant permeation behavior in the ultrafiltration experiments, allowing the quantification of LMW-DOP and COP concentrations with the ultrafiltration permeation model. The average COP concentration was 0.044 ± 0.022 μmol/L and 0.042 ± 0.027 μmol/L during 2010 and 2011 summers, respectively. Accordingly, COP accounted for 35 ± 13% and 34 ± 16% of bulk DOP during 2010 and 2011 summers, respectively, suggesting a substantial occurrence of organic phosphorus in the colloidal fraction. The C/P ratio decreased from LMW-DOM to bulk DOM and to colloidal organic matter (COM), supporting the degradation pathway of bulk DOM from colloidal to LMW fractions and the lability of COP in the Taiwan Strait. The fractionation of C/P ratio between bulk DOM and COM in the Taiwan Strait, denoted by the fractionation factor (FC/D), was comparable to the open oceans, but significantly stronger than rivers and estuaries. It might indicate an autochthonous input and rapid turnover of bulk DOP pool in the Taiwan Strait in the context of low phosphate concentration. The FC/D also showed a spatial variability in the Taiwan Strait, high in the South China Sea Warm Current and upwelling occupied stations and low in inshore areas influenced by terrestrial input. This further supports the FC/D as an indicator of bulk DOM sources besides its application to decipher the diagenetic status of bulk DOM and biogeochemical cycles of bulk DOP in the coastal oceans.

Enrichment of Lactoferrin and Immunoglobulin G from Acid Whey by Cross-Flow Filtration.

The production of cream cheese, curd, high-protein yogurt, or caseinate results in large amounts of acid whey as a by-product. So far acid whey is often disposed as animal feed or organic fertilizer. However, these approaches ignore the valorization potential that arises from the unique composition of the whey protein fraction. Whey contains the biofunctional proteins lactoferrin and immunoglobulin G, which possess immune-supporting, antibacterial, antiviral, and numerous further health-promoting functions. However, the concentration of these proteins in bovine milk or whey is below a physiologically relevant level. Based on literature research we specified a daily intake of 200 mg lactoferrin as the minimal functional dose. By means of cross-flow ultrafiltration, an attempt was made to increase the concentration of biofunctional proteins. Therefore, a membrane for the selective retention of lactoferrin and immunoglobulin G was identified, and the process parameters were optimized. Finally, a concentration experiment was conducted, whereby the concentration of biofunctional proteins was increased up to factor 30. The biofunctionality was assessed in a microbiological assay. Surprisingly, the antimicrobial growth inhibition of the produced concentrate was even higher than in pure lactoferrin. The presented approach offers a strategy to convert an abundant but underutilized by-product into valuable products for human nutrition.

Adsorption behaviors and influencing factors of antibiotic norfloxacin on natural kaolinite-humic composite colloids in aquatic environment

Particles are ubiquitous and abundant in natural waters and play a crucial role in the fate and bioavailability of organic pollution. In the present study, natural mineral (kaolinites, KL), organic (humic/fulvic acid, HA/FA) and their composite particles were further separated into particles fractions (PFs, >1 μm) and colloidal fractions (CFs, 1 kDa-1 μm) by cross-flow ultrafiltration (CFUF). This research demonstrated the role of kaolinite-humic composite colloids on the adsorption of fluoroquinolone norfloxacin (NOR). The Freundlich model satisfactory described adsorption curves, showing strong affinity of NOR to CFs, with sorption capacity (KF) between 8975.50 and 16638.13 for NOR. The adsorption capacities of NOR decreased with the particle size increasing from CFs to PFs. In addition, composite CFs showed excellent adsorption capacity, which was mainly attributed to the larger specific surface area of composite CFs and electronegativity and numerous oxygen-containing functional groups on the surfaces of the complexes, and electrostatic attraction, hydrogen bond and cation exchange could dominate the NOR adsorption onto the composite CFs. The best pH value under adsorption condition of composite CFs varied from weakly acidic to neutral with the increase of load amount of humic and fulvic acids on the surface of inorganic particles. The adsorption decreased with higher cation strength, larger cation radius and higher cation valence, which depended on the surface charge of colloids and the molecular shape of NOR. These results provided insight into the interfacial behaviors of NOR on the surfaces of natural colloids and promoted the understanding of the migration and transport of antibiotics in environmental systems.

Application of Artificial Neural Networks for Modelling and Control of Flux Decline in Cross-Flow Whey Ultrafiltration

This study is part of the re-valorisation of the dairy waste industry through the use of membrane ultrafiltration (UF), in order to recover whey proteins and remove as much water as possible from the permeate. This study aimed to predict and control the permeate flux decline in cross-flow whey UF through a step procedure, and to compare different Artificial Neural Networks (ANNs), followed by a genetic algorithm (GA), as the optimization strategy. Models were developed in Matlab® Neural Network Toolbox. ANNs of one or two hidden layers were trained and simulated. A trial-and-error procedure identified the best network based on its performance values. The networks were trained through a selected set of experimental data obtained for lab-scale hollow-fibre membrane modules used to re-value scotta, the final waste of the dairy industry. The operating conditions considered as the input of the ANN were: operating time (top), sampling time (tsample), cross-flow velocity (CFV) and transmembrane pressure (TMP), while the output of the network was exclusively the normalized permeate flux (Jn). GA optimization was carried out to the following range of operating conditions to reach the best performances and to manage the fouling effect: 225 &lt; top &lt; 300 min, 8.33 &lt; tsample &lt; 15.9 min, 6.25 &lt; CFV &lt; 8.33 L/min, and TMP equal to 1.33 bar, otherwise it can be ignored. In fact, it has been noted that the networks with only three inputs, without TMP, predict and control Jn output better. Moreover, considering the normalized flux, it was possible to ignore some other important operating conditions, such as the membrane geometry. Consequently, the proposed general solution could also be used for other kinds of membrane applications. Finally, a hybrid approach among the ANN networks and a theoretical model was also used to better predict the resistance trend. It also returned more evident correspondence results than the ANN simulation alone, especially in the initial drop of Jn. The use of the theoretical part in the hybrid approach acts as a filter and returned the following order of significance of the operational input conditions on the resistance: top, tsample, CFV and TMP.

THE OBTAINING OF THE RECOMBINANT CAMEL CHYMOSIN BY SUBMERGE FERMENTATION IN THE PILOT BIOREACTOR

In the cheese making industry, chymosin is used as a milk-clotting enzyme. With its high specific activity against κ-casein, chymosin better than other proteolytic enzymes. Bactrian camel chymosin has a milk-clotting activity higher than calf chymosin. A scheme for obtaining a milk-clotting preparation based on recombinant camel chymosin is proposed. Submerge fermentation of recombinant yeast Pichia pastoris was carried out in a 50-liter bioreactor and recombinant camel chymosin was obtained. The activity of chymosin in the yeast culture was 174.5 U/mL. Chymosin was concentrated 5.6-fold by cross-flow ultrafiltration with 10 kDa cut-off membrane, and chymosin was purified by ion exchange chromatography. The activity of purified chymosin was 4700 U/mL. By sublimation drying with casein peptone, the powder chymosin was obtained with an activity of 36,000 U/g. The proposed scheme for obtaining a milk-clotting drug based on recombinant camel chymosin using submerge fermentation of recombinant yeast has the prospect of being used at biotechnological enterprises.

Ag@BiOBr/PVDF photocatalytic membrane for remarkable BSA anti-fouling performance and insight of mechanism

Membrane technologies offer great potential in desalination and wastewater treatment. However, the serious issue of membrane fouling results in the unsatisfactory sustainability and reusability for treating wastewater containing high level of organic foulants. In this work, a photocatalytic membrane reactor system combining Ag@BiOBr photocatalyst and polyvinylidene fluoride (PVDF) ultrafiltration with remarkable anti-fouling property was constructed. The integrated Ag@BiOBr/PVDF photocatalytic ultrafiltration membranes were prepared by blending Ag@BiOBr nanoparticles (NPs) into PVDF membrane via phase inversion method. The membrane separation performance and fouling resistance were studied in a cross-flow ultrafiltration system using bovine serum albumin (BSA) as the model foulants. Compared with the pristine PVDF membrane, the hydrophilicity and surface smoothness of composite membranes were promoted by photocatalyst-incorporation, the Ag@BiOBr/PVDF membrane with the optimal Ag@BiOBr blending content of 2.0 wt% achieved both enhanced water flux and higher BSA rejection efficiency. More importantly, the mechanism of anti-fouling and self-cleaning performances were further studied, the photocatalysis process based on Ag@BiOBr/PVDF membrane effectively decomposed the BSA foulant into broken protein with induced change of carbonyl, ionic bond and hydrogen bond contents in BSA foulants via the active radicals, weakened the intermolecular force of BSA foulants to prevent membrane pore blockage. Meanwhile, the broken protein peptide chains with more negative charges could result in the strength of electrostatic repulsive forces between BSA molecules and membrane. As a result, the BSA foulant could be stably removed in the Ag@BiOBr/PVDF photocatalytic ultrafiltration system under visible light irradiation, achieving the excellent anti-fouling performance by preventing the membrane pore blockage and foulant adhesion. We believe the Ag@BiOBr/PVDF photocatalytic membrane presented in this study will be one example among many photocatalyst-membrane combinations that can be further pursued for organic pollutants removal. In particular, we expect the theoretical support can present a great opportunity to design novel photocatalytic membranes with sustainable anti-fouling performance.

Pilot-scale crossflow ultrafiltration of four different cell-sized marine microalgae to assess the ultrafiltration performance and energy requirements

Four marine microalgae (e.g., Tetraselmis, Picochlorum, Dunaliella, and Synechococcus) with different cell sizes were harvested using pilot-scale ultrafiltration. Average permeate fluxes were 16.75, 19, 25.35, and 33.75 L/m2h at 60 min for Synechococcus, Dunaliella, Picochlorum, and Tetraselmis, respectively. The concentrating factors for Synechococcus, Picochlorum, Dunaliella, and Tetraselmis were 46.6, 42, 39.2, and 39.5, respectively. The highest and lowest microalgal biomass retention was 47.1 and 41.7% for Tetraselmis and Synechococcus, respectively. Due to higher microalgal biomass retention, initial crossflow velocities of 0.16 to 0.18 m/s were reduced to 0.02 to 0.05 m/s for Tetraselmis and Dunaliella sp. The total harvesting energy requirement by membrane and centrifuge was 16.44 – 28.48 GJ/tonne biomass; the smaller the cell size, the lower the energy requirement. The optimum biomass concentrating factor by the membrane filtration process also depended on size; for optimum total energy requirement, tangential flow filtration (TFF) could concentrate a smaller strain more than a larger strain.