Standard Blocking Research Articles

Improved ultrafiltration performance through dielectric barrier discharge/sulfite pretreatment: Effects of water matrices and mechanistic insights

The feasibility of utilizing a dielectric barrier discharge (DBD)/sulfite-ultrafiltration system was investigated in various real water bodies, aiming to clarify the mechanism behind alleviating membrane fouling while synchronously degrading perfluorooctanoic acid (PFOA) during the treatment process of Yangtze River water. The results demonstrated that the DBD/sulfite pretreatment exhibited remarkable rates of membrane flux mitigation (>84.10%) and efficient degradation rates of PFOA (>85.13%), which decreased with increasing pH from 3.0 to 11.0. The presence of anions, cations, and natural organic matter slightly hindered the membrane fouling mitigation and PFOA degradation by quenching free radicals; however, the addition of SO42− had a negligible impact. The mitigation of membrane fouling was attributed to the significant involvement of various radicals, including hydroxyl radical (•OH), sulfate radical (SO4•−), electron (e−/eaq−), su-peroxide anion radicals (•O2−), and other radicals such as SO3•−, exhibiting respective contributions of 33.25%, 28.49%, 20.56%, 11.32%, and 6.39% in a synergistic redox effect. The pretreatment effectively reduced standard blocking and cake filtration fouling mechanisms by creating a sparse fouling layer on the membrane surface while increasing its roughness. Additionally, the main active species that played a significant role in the degradation of PFOA were identified as SO4•−, •OH, and eaq−. These species contributed approximately 43.63%, 24.39%, and 20.65% respectively to the degradation process. By employing mass spectrometry and density functional theory, a proposed pathway for PFOA degradation was established, effectively reducing the toxicity associated with its degradation byproducts. This study provides innovative insights into membrane-based water treatment technologies that effectively tackle both membrane fouling mitigation and PFOA degradation.

Fabrication and application of highly permeable ceramic membranes: Membrane-forming mechanism, pore structure, separation performance and fouling mechanism analyses

High separation efficiency and satisfactory economic benefits are of great importance for ceramic membranes in the field of water treatment. Herein, microfiltration ceramic membrane with high permeability and selectivity was prepared in one-step (dip-coating and sintering) by sacrificial-interlayer method. The membrane-forming mechanism, effect of temperature on the morphology and pore structure, separation performance, fouling mechanism, and regeneration performance of the ceramic membranes were systematically investigated. The results show that membrane-forming mechanism of the membranes largely depends on film-coating filtration. The membrane with a mixture of nanocellulose crystals and graphene oxide as sacrificial interlayer (C1G1) and sintered at 1100–1300 °C possessed smooth surface. The open porosity and average pore size increased, and the pore size distribution became broader as the temperature increased. Moreover, the sacrificial-interlayer membrane sintered at 1300 °C (mA4S-C1G1) possessed suitable porosity (53.4%) and average pore size (200 nm), high permeance (4828 L·m−2·h−1·bar−1), which was larger than that of the membrane without sacrificial interlayer, manifesting that C1G1 could prevent the penetration of membrane-forming particles into support. The final fouling mechanism of mA4S-C1G1 was cake filtration, although complete pore blocking, standard pore blocking, intermediate pore blocking also involved in the initial stage. In addition, the oil rejection rate (∼97%) and steady-state feed flux (810–1154 L·m−2·h−1) of mA4S-C1G1 was high, and it also possessed good regeneration performance.

Dynamic behavior and mechanistic analysis in filtration of dilute particulate suspensions through nanofibrous membrane

Nanofibrous membranes have garnered significant interest in membrane filtration due to their high porosity, small pore sizes, and complex interconnected pore structures. Although many studies focus on size exclusion in surface filtration, the filtration behavior and mechanisms for particles smaller than the pore size have been relatively underexplored. In this study, membrane filtration using nanofibrous membranes was employed to elucidate the filtration behavior and mechanisms for polystyrene latex suspensions with particles smaller than the pore size. The results indicated that reducing fiber diameter decreases the pore size and enhances particle rejection, with particle retention occurring within the intricate three-dimensional nanofiber pore network. In contrast, the effect of the membrane’s basis weight was less significant compared to fiber diameter. This observation can be attributed to the concept of effective thickness; once this thickness is exceeded, particles are prevented from penetrating deeper into the membrane. The filtration model was analyzed using Hermans-Bredée blockage filtration theory and cake filtration theory, considering the mass of trapped particles within the membranes. The model characterizes the filtration process as initially following standard blocking, progressing to cake filtration once a sufficient number of pores become clogged.

Enhanced performance of aerobic granular sludge-membrane system through the utilization of different iron-based nano-metal oxides for mitigating membrane fouling

Fe3O4, γ-Fe2O3, and α-Fe2O3 nanoparticles play a crucial role in influencing the adsorption capacity and pretreatment efficacy as iron-based nano-metal oxides due to their distinct structural and physicochemical properties. However, the impact of these adsorbents on membrane filtration efficiency remains unexplored. This study aimed to investigate the influence of these three adsorbents on membrane fouling in an aerobic granular sludge–membrane system (AGSMS) used for municipal wastewater reuse treatment. The results demonstrated that under optimal conditions, γ-Fe2O3 exhibited superior effectiveness in removing low and medium molecular weight contaminants from wastewater, resulting in a higher normalized flux (0.59) and reduced total fouling resistance (2.66 × 1011 m−1). It also showed the highest removal rate for organic matter and suspended solids, making it particularly effective in mitigating AGSMS membrane fouling. However, excessive addition (2 g/L) of Fe3O4, γ-Fe2O3, and α-Fe2O3 could potentially hinder the proper operation of the AGSMS. Pre-adsorption facilitated the formation of a porous cake layer while inhibiting standard blocking behavior. Additionally, the extended Derjaguin–Landau–Verwey–Overbeek theory analysis revealed a substantial energy barrier between membrane-foulant interactions (125.65 kT) as well as foulant-foulant interactions (62.06 kT) within the γ-Fe2O3 system, confirming its exceptional antifouling characteristics. This study offers valuable insights into the selection of iron oxide adsorbents for membrane fouling mitigation and wastewater reuse.

In situ polymerization of a poly(3,4-ethylenedioxythiophene):poly(sodium–styrennesulfonate) conductive layer for electro-assisted ultrafiltration and fouling mitigation

Electrification can enhance the antifouling performance of ultrafiltration membranes and improve the sustainability of membrane technologies. The design of high-performance conductive membrane materials remains one of the core technologies in electro-assisted ultrafiltration. Here, conductive PVDF/PEDOT:PSS composite membranes were prepared via in situ chemical oxidation polymerization on a PVDF surface. The PVDF/PEDOT:PSS membranes were subsequently used for electro-filtration to study the effect of the applied potential on humic acid fouling. When a voltage of 3 V was applied, the PVDF/PEDOT:PSS20 membrane was continuously polluted for 5 cycles. The results showed that after simple hydraulic cleaning, the membrane flux recovery rate reached 91 %. Compared with that of the PVDF membrane, the irreversible fouling of the PVDF/PEDOT:PSS20 membrane decreased by 65 %. The modified Poisson Boltzmann equation indicates that applying cathodic potential on the surface of PEDOT:PSS conductive layer increases the cumulative concentration of counter ions on the membrane surface and the thickness of the charged layer, thereby promoting the migration of peak forces on the membrane surface to the bulk solution, changing the fouling behaviour of HA from cake filtration to standard blocking.

A three-mechanism (intermediate pore blocking, standard pore blocking and cake filtration) model considering correction of effective filtration area

A general three-mechanism (intermediate pore blocking, standard pore blocking and cake filtration) model considering correction of the effective filtration area based on Darcy's law, Hagen-Poiseuille equation and Hermes’ law was firstly developed to describe the variation of trans-membrane pressure (∆p(t)) in the constant flowrate cross-flow filtration mode by using EPS model solutions (bovine serum albumin (BSA), sodium alginate (SA) and humic acid (HA)). Results showed that the model predictions fitted well with the experimental data (the single EPS model solution (R2≥0.904), the binary EPS model solution (R2≥0.910) and the ternary EPS model solution (R2≥0.878)). For all model solution, the domination mechanism in the first stage was intermediate pore blocking, while that in the second stage was cake filtration. Meanwhile, higher flux or concentration would led to the transition point appear earlier, while higher cross-flow velocity made it appear later. Moreover, the predictive accuracy of the proposed model improved by 1.25 % compared with that without considering the correction of the effective filtration area. Also, the proposed model was also validated using other membranes (polyvinylidene fluoride (PVDF) and polyether sulfone (PES) membranes) (R2≥0.953) and other feed suspensions (yeast, kaolin and activated sludge suspensions) (R2≥0.981).

Innovative ceramic membrane plate filtration system for sustainable semiconductor industry wastewater treatment: A pilot scale study

Conventional methods of coagulation and flocculation are used to treat semiconductor industry wastewater, but they often fail to recover valuable silica particles and result in resource wastage and environmental risks. Despite the potential of membrane filtration for silica recovery, limited research is available on scaling up the process beyond laboratory scale. Therefore, this study aims to develop and evaluate the feasibility of pilot-scale ceramic membrane plate filtration system for treatment of diluted back grinding wastewater (DBGW) from the semiconductor industry. Specific objectives include assessing permeate quality in terms of rejection and benchmarking it to established standards, identifying fouling mechanisms, characterising sludge constituents and conducting life cycle assessment (LCA) to evaluate the environmental impacts of the ceramic membrane plate filtration system compared with conventional treatment. The pilot membrane plate filtration system demonstrated significant reductions of 85.71 % in chemical oxygen demand, 67.31 % in total suspended solid, 75 % in nitrate–nitrogen (NO3-N), 33.33 % in ammonia nitrogen (NH3-N), 74.07 % in colour and 98.37 % in turbidity. Effective mitigation of irreversible fouling during DBGW filtration was achieved using 0.1 M NaOCl, resulting in a flux recovery ratio of 95.35 %. The retained silica on the membrane exhibited a purity of 64 wt%, as confirmed by EDX analysis. The treated wastewater met various regulatory standards including Malaysia Industrial Effluent Discharge (Standard A and Standard B), restricted USEPA standard, NWQS Class IIA, IIB, III, IV and V, and Singapore’s greywater standards. The fouling mechanism of silica on the ceramic membrane was well represented by the standard blocking model with an R2 value of 0.92. Furthermore, LCA confirmed that the utilisation of the ceramic membrane plate filtration system exhibited fewer environmental impacts than conventional coagulation–flocculation methods. This study represents a significant breakthrough in wastewater treatment in the semiconductor industry in terms of concurrent recovery and reuse of silica to address environmental and resource sustainability concerns.

Investigating the Fouling Models of the Microfiltration Mixed Matrix Membranes-Based Oxide Nanoparticles Applied for Oil-in-Water Emulsion Separation

Membrane fouling is a major problem encountered in the use of microfiltration (MF) processes to separate the emulsified oil from water. This work involves assessing the efficacy of removing oil-in-water emulsion (O/W emulsion), and evaluating fouling resistance by studying the membrane morphology before and after fouling, and after washing with different cleaning solutions via field emission scanning electron microscopy (FESEM) analysis. Also, the fundamental mechanism involved in the flux drop during crossflow MF has been assessed using models such as the Hermia blocking models and the modified model by Field. The standard and intermediate pore blocking models provided the best prediction for experimental behavior when analyzing the decay in the flux with time for the bio silicon oxide/polyvinylchloride (B-SiO2/PVC) membrane and the stannic oxide/polyvinylchloride (SnO2/PVC) membrane. This research established regression equations of the flux for both membranes in which these equations are highly correlated with R2 of 98.33% for B-SiO2/PVC and R2 of 99.52% for SnO2/PVC using the surface response methodology (RSM). The high flux recovery ratio (FRR) is indicative of the improved antifouling feature of the manufactured membranes where it was 96.8% for B-SiO2/PVC and 94.6% for SnO2/PVC. The results obtained by Hermia and Field were in good agreement with RSM analysis supporting the standard pore-blocking mechanism.

VUV coupled with low-dose H2O2 as pretreatment prior to UF: Performance, mechanisms, DBPs formation and toxicity evaluation

Ultrafiltration (UF) is widely used in drinking water plants; however, membrane fouling is unavoidable. Natural organic matter (NOM) is commonly considered as an important pollutant that causes membrane fouling. Herein, we proposed VUV/H2O2 as a UF pretreatment and used UV/H2O2 for comparison. Compared to UV/H2O2, the VUV/H2O2 system presented superior NOM removal. In the VUV/H2O2 system, the steady-state concentration of HO• was approximately twice that in the UV/H2O2 system, which was ascribed to the promoting effect of the 185 nm photons. Specifically, 185 nm photons promoted HO• generation by decomposing mainly H2O at a low H2O2 dose or by decomposing mainly H2O2 at a high H2O2 dose. The VUV/H2O2 pretreatment also demonstrated better membrane fouling mitigation performance than did UV/H2O2. An increase in the H2O2 dose promoted HO• generation, thereby enhancing the performance of NOM degradation and membrane fouling alleviation and shifting the major membrane fouling mechanism from cake filtration to standard blocking. The VUV/H2O2 (0.60 mM) pretreatment effectively reduced disinfection byproducts (DBPs) formation during chlorine disinfection. Additionally, the oxidant H2O2 affected the membrane surface morphology and performance but had no evident effect on the mechanical properties. In actual water treatment, the VUV/H2O2 pretreatment exhibited better performance than the UV/H2O2 pretreatment in easing membrane fouling, ameliorating water quality, and reducing DBPs formation and acute toxicity.

Enhanced performance and mechanism of adsorption pretreatment for alleviating membrane fouling in AGMBR: Impact of structural variations in carbon adsorbents

The structural variances of adsorbents play a crucial role in determining the number of effective adsorption sites and pretreatment performance. However, there is still a gap in comprehending the impact of different carbon structural adsorbents on membrane fouling. Therefore, this study aimed to compare the efficacy of granular activated carbon (GAC), powdered activated carbon (PAC), and activated carbon fiber (ACF) in mitigating membrane fouling during municipal sewage reclamation using an aerobic granular sludge membrane bioreactor (AGMBR). The results demonstrated that the utilization of PAC significantly enhanced the normalized flux and reduced fouling resistance in comparison to GAC and ACF systems. PAC effectively adsorbed low and medium-molecular-weight pollutants present in raw sewage, resulting in an increase in average particle size and a decrease in foulant content on the membrane surface. The Hermia model indicated that adsorption pretreatment minimized standard blocking while promoting the formation of a sparse and porous cake layer. Moreover, according to the extended Derjaguin–Landau–Verwey–Overbeek theory, PAC has been demonstrated as the optimal antifouling system owing to its enhanced repulsion between membrane-foulant and foulant-foulant interactions. Correlation analysis revealed that the exceptional antifouling performance of the PAC system was due to its high removal rates of chemical oxygen demand (~78 %) and suspended solids (~97 %). This research offers valuable insights into the mitigation of membrane fouling through the utilization of adsorbents featuring diverse carbon structures.

Sulfite-activated permanganate pre-oxidation coupled ultrafiltration for treating algae-laden water: Role of calcium ions and in-situ formed MnO2

Membrane fouling caused by algal-derived foulants severely impedes the widespread application of ultrafiltration (UF). Herein, two sulfites (Na2SO3 and CaSO3, S(IV)) were used to activate potassium permanganate (Mn(VII)) as pretreatment to enhance the performance of UF in treating algae-laden water. The results showed that the Mn(VII)/S(IV) system produced MnO2 with abundant hydroxyl groups, which was advantageous for adsorbing algal pollutants. Compared with Mn(VII)/Na2SO3, Mn(VII)/CaSO3 process further increased the aggregation tendency of algal cells, which was due to the Ca2+ bridging effect that promoted the aggregation of MnO2 and algal foulants. S(IV) can activate Mn(VII) to produce free radical (OH and SO4−), and enhance removal of dissolved organic carbon (DOC) and fluorescent organics in coordination with the adsorption of in-situ MnO2. Moreover, the presence of Ca2+ ensured compliance with residual manganese in the treated water. Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory suggested that the Mn(VII)/S(IV) strategy weakened the attractive forces between pollutants and the membrane. FTIR analysis further confirmed that the combined process reduced the accumulation of protein organics on the membrane surface. As a result, the reversible fouling was reduced by 65.3 % and 92.2 %. The in-situ formed manganese oxide altered the structure of the cake layer and delayed the formation of the cake filtration mechanism. Mn(VII)/CaSO3 pretreatment produced a looser cake layer, resulting in a shift of the fouling mechanism towards a single standard blocking. In summary, the novel integrated process can ensure the efficient operation of UF in the purification of algae-laden water.

Investigation of membrane fouling behaviors triggered by different characteristics of anaerobic digestion effluent in membrane distillation

This study investigated the membrane fouling behaviors triggered by different characteristics of anaerobic digestion (AD) effluents in the operation of 851-h membrane distillation (MD). The AD effluents with different concentration factors (CF) were used as the feed separately. Results illustrated a stable normalized water flux in the treatment of raw AD effluent (CF = 1) over the 851-h MD experiment, showing negligible membrane fouling. While the sharp decreases in normalized water flux occurred when treating the concentrated AD effluents. The membrane fouling mechanism tended to change from inorganic scaling to organic fouling when the CF value increased from 1 to 3, while the combination of organic and inorganic fouling dominated the membrane fouling when CF was 5. Inorganic fouling was further intensified when the CF value increased to 10. The regression analysis demonstrated that the complete blocking model was the dominant development mechanism for CF = 3 treatment. The membrane fouling mechanism of CF = 5 treatment switched from the cake filtration model in the intermediate phase to the standard blocking model in the final phase. Additionally, there was a transition from the complete blocking model to the standard blocking model for CF = 10 treatment. The study may provide an in-depth knowledge of membrane fouling control during the actual AD effluent concentrating process.

Abstract 2744: Exploring the role of the MSLN/MUC16 interaction in cancer progression via the in situ proximity ligation technique

Abstract Introduction: Mesothelin (MSLN) is a glycoprotein present on the surface of mesothelial cells, sometimes used as a tumor marker. Its overexpression in various cancers, including mesothelioma, ovarian, pancreatic, and lung, is linked to increased tumor aggressiveness, evasion of apoptosis, metastasis, and resistance to treatments. Mucin16 (MUC16) belongs to a family of proteins that play a crucial role in cell adhesion, signaling, and immune responses. In cancer, alterations in mucin expression and structure may contribute to tumor progression and metastasis by enhancing cell survival and immune evasion. Mesothelin is known to interact with mucins, influencing tumor cell behavior and metastatic potential. More specifically, the MSLN/MUC16 interaction facilitates tumor cell invasion and peritoneal spread in ovarian cancer. However, reliable molecular tools to study protein interactions have been scarce. Here, we relied on the Naveni® in situ proximity ligation technology to identify MSLN/MUC16 in various cancer samples. The method detects proteins located within interaction range (<40 nm) by means of antibodies conjugated to oligonucleotides that create amplified fluorescent signal. Since the technique does not compromise the structural integrity of tissues, communication between proteins can be studied in their native environment. Materials & Methods: Human FFPE tissue microarrays (TMA) with ovarian primary carcinoma and matched metastatic cancer (80 cores) and ovarian cancer tissue with normal tissue (100 cores) were deparaffinized and subjected to standard heat-induced antigen retrieval and blocking. Staining against the MSLN/MUC16 interaction was performed with the NaveniFlex Tissue MR Atto647N kit (Navinci Diagnostics). Co-staining antibodies against pan-Cytokeratin and Ki67 were included in the detection mix. Immunofluorescence (IF), using the same MSLN and MUC1 primary antibodies, was completed on an additional slide of each TMA, and then secondary antibodies conjugated to Alexa Fluor™ 488 and 594 were used for detection. Imaging was performed on an Olympus scanner VS200. Results & Discussion: In this study, we showed that the interaction is abundant in ovarian cancer, with a distinguishable difference in the signal presence between cancerous and normal adjacent tissue. Furthermore, the additional tumor marker co-stainings give insights into the tumor invasion and growth. When comparing the Naveni® signal of MSLN/MUC16 against IF staining of each, the Naveni® signal shows true interactions, as opposed to expression patterns. Understanding the roles of mesothelin and mucin in cancer, both individually and in interaction, is crucial for developing targeted therapies and diagnostic tools. Further research on their interaction and specific molecular pathways triggered by it is essential for devising effective strategies to combat cancer progression. Citation Format: Sara Bodbin, Doroteya Raykova, Agata Zieba-Wicher. Exploring the role of the MSLN/MUC16 interaction in cancer progression via the in situ proximity ligation technique [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2744.

MnO2@CS modified catalytic membrane for simultaneous organics removal and membrane fouling mitigation via peroxymonosulfate activation

The integration of advanced oxidation process and ultrafiltration membrane has been regarded as an effective method to improve pollutants removal and mitigate membrane fouling simultaneously in the field of wastewater treatment. Hence, a novel catalytic membrane microreactor, referred to as MnO2@CS-UF, was synthesized via coupling MnO2 modified carbon spheres (MnO2@CS) with membrane. The mesoporous structure of MnO2@CS guaranteed adequate water transfer channels and also contributed to more exposure of active sites. With MnO2@CS uniformly dispersed, the MnO2@CS-UF membrane showed increased hydrophilicity, higher permeability and superior peroxymonosulfate (PMS)-activation capability. With synergistic effect of pore interception and catalytic degradation, MnO2@CS-UF showed excellent organic pollutants removal (MB removal of about 100 % in 5 min), and had a prominent mitigation effect on membrane fouling caused by model NOM. In addition, MnO2@CS-UF/PMS system showed excellent catalytic filtration performance in the treatment of actual secondary effluent (SE). MnO2@CS-UF/PMS system could effectively remove fluorescent organics, and the removal rates of I-V region were 36.3 %, 72.3 %, 67.7 %, 73.5 % and 71.4 %, respectively. The permeance decline of MnO2@CS-UF was also effectively alleviated, with irreversible and reversible resistances reduced by 61.0 % and 23.2 % than UF membranes, individually. High-valent manganese-oxo species and singlet oxygen played a leading role in contaminants elimination, whereas radical oxidation acted as auxiliary contributors. Standard blocking became the dominant fouling pattern for MnO2@CS-UF/PMS, demonstrating that the MnO2@CS catalytic layer ensured the synthesis of vast active substances, prevented foulant adhesion on pore walls and alleviated the growth of cake layer. These results illustrated that the integration of MnO2@CS catalytic degradation and membrane filtration was feasible to improve the permeate quality and mitigate membrane fouling in wastewater reclamation.

Reclamation of acid with electrodialysis process: Influence of selective ion-exchange membranes

Electrodialysis (ED) could concentrate salt solutions, but the leakage of H+ ions across the anion-exchange membrane (AEM) obstructed their application in waste acid recovery. Selective electrodialysis (SED) with acid blocking AEM and monovalent selective cation-exchange membrane (CEM) has the ability of reclaiming acid with high concentration efficiently. This study investigated the individual effect of the two selective ion-exchange membranes by comparing the acid reclamation performance of configurations with standard AEM and CEM (A-C), acid blocking AEM and standard CEM (SA-C) and acid blocking AEM and monovalent selective CEM (SA-SC) for etching solution treatment after diffusion dialysis. Substituting acid blocking AEMs for the standard ones could significantly increase the recovered acid concentration. An acid concentration plateau was reached quickly, but Cu2+ ions transfer through the CEMs continuously due to the low H+/Cu2+ ratio in the dilute of SA-C configuration. The monovalent selective CEM obstructed the migration of Cu2+ through the CEM and broke the balance of H+ migration into and out of the dilute through CEM and selective AEM individually. The configuration of SA-SC has the highest current efficiency and the configuration of A-C has the lowest. The utilization of selective membranes increased the purity of the recovered acid, and decreased the specific energy consumption simultaneously. The acid concentration could be further improved by higher current or enlarged dilute volume in SA-SC configuration. During the ED process, H+ concentration difference between the concentrate and the dilute plays a crucial role on the current efficiency for acid recovery.

Identification of Membrane Fouling with Greywater Filtration by Porous Membranes: Combined Effect of Membrane Pore Size and Applied Pressure.

Membrane fouling caused by complex greywater synthesized by personal care products and detergents commercially available for household applications was investigated using dead-end microfiltration (MF) and analyzed systematically by a multistage Hermia blocking model as a first attempt. The highest flux decline was associated with the smallest pore size of the membrane (0.03 μm). This effectiveness was more pronounced at higher applied pressures to the membrane. A cake layer was formed on the membrane consisting mainly of silica particles present as ingredients in greywater. Although organic rejection was low by the porous MF membrane, the organic compound contributed to membrane fouling in the filtration stage. With a 0.03 μm pore size of the membrane, dominant fouling mechanisms were classified into three stages as applied pressure increased, such as complete pore blocking, intermediate pore blocking, and cake layer formation. Specifically, during the early stage of membrane filtration at 1.5 bar, membrane fouling was determined by complete pore blocking in the 0.10 μm pore size of the membrane. However, the later stage of membrane fouling was controlled mainly by intermediate pore blocking. Regardless of the applied pressure, pore constriction or standard blocking played an important role in the fouling rate with a 0.45 μm pore size of the membrane. Our results also support that complex formation can occur due to the concentration of organic and inorganic species present in simulated greywater. Thus, strategic approaches such as periodic, chemically enhanced backwashing need to be developed and tailored to remove both organic and inorganic fouling from MF membranes treating greywater.

Chalcopyrite functionalized ceramic membrane for micropollutants removal and membrane fouling control via peroxymonosulfate activation: The synergy of nanoconfinement effect and interface interaction

This work developed a novel chalcopyrite (CuFeS2) incorporated catalytic ceramic membrane (CFSCM), and comprehensively evaluated the oxidation-filtration efficiency and mechanism of CFSCM/peroxymonosulfate (PMS) for organics removal and membrane fouling mitigation. Results showed that PMS activation was more efficient in the confined membrane pore structure. The CFSCM50/PMS filtration achieved almost complete removal of 4-Hydroxybenzoic acid (4-HBA) under the following conditions: pH = 6.0, CPMS = 0.5 mM, and C4-HBA = 10 mg/L. Meanwhile, the membrane showed good stability after multiple uses. During the reaction, SO4•− and •OH were generated in the CFSCM50/PMS system, and SO4•− was considered to be the dominant reactive species for pollutant removal. The roles of copper, iron, and sulfur species, as well as the possible catalytic mechanism were also clarified. Besides, the CFSCM50/PMS catalytic filtration exhibited excellent antifouling properties against NOM with reduced reversible and irreversible fouling resistances. The Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory analysis showed an increased in repulsive energy at the membrane-foulant interface in the CFSCM50/PMS system. Membrane fouling model analysis indicated that standard blocking was the dominant fouling pattern for CFSCM50/PMS filtration. Overall, this work demonstrates an efficient catalytic filtration process for foulants removal and outlines the synergy of catalytic oxidation and interface interaction.

Chemical-free vacuum ultraviolet irradiation as ultrafiltration membrane pretreatment technique: Performance, mechanisms and DBPs formation

Membrane fouling induced by natural organic matter (NOM) has seriously affected the further extensive application of ultrafiltration (UF). Herein, a simple, green and robust vacuum ultraviolet (VUV) technology was adopted as pretreatment before UF and ultraviolet (UV) technology was used for comparison. The results showed that control effect of VUV pretreatment on membrane fouling was better than that of UV pretreatment, as evidenced by the increase of normalized flux from 0.27 to 0.38 and 0.73 after 30 min UV or VUV pretreatment, respectively. This is related to the fact that VUV pretreatment exhibited stronger NOM degradation ability than UV pretreatment owing to the formation of HO•. The steady-state concentration of HO• was calculated as 3.04 × 10−13 M and the cumulative exposure of HO• reached 5.52 × 10−10 M s after 30 min of VUV irradiation. And the second-order rate constant between NOM and HO• was determined as 1.36 × 104 L mg−1 s−1. Furthermore, fluorescence EEM could be applied to predict membrane fouling induced by humic-enriched water. Standard blocking and cake filtration were major fouling mechanisms. Moreover, extension of UV pretreatment time increased the disinfection by-products (DBPs) formation, the DBPs concentration was enhanced from 322.36 to 1187.80 μg/L after 210 min pretreatment. However, VUV pretreatment for 150 min reduced DBPs content to 282.57 μg/L, and DBPs content continued to decrease with the extension of pretreatment time, revealing that VUV pretreatment achieved effective control of DBPs. The variation trend of cytotoxicity and health risk of DBPs was similar to that of DBPs concentration. In summary, VUV pretreatment exhibited excellent effect on membrane fouling alleviation, NOM degradation and DBPs control under a certain pretreatment time.

MECHANISM OF MEMBRANE FOULING IN HYBRID MEMBRANE PHOTOCATALYTIC REACTOR FOR PALM OIL MILL SECONDARY EFFLUENT TREATMENT

Palm oil mill secondary effluent (POMSE) is a byproduct of the biological treatment of palm oil mill effluent. This research aims to investigate the mechanism of membrane fouling in the treatment of POMSE using a hybrid membrane photocatalytic reactor (MPR). The effectiveness of MPR in POMSE treatment is currently limited due to membrane fouling on the membrane surface. This study focuses on understanding the various mechanisms of membrane fouling, including complete blocking, intermediate blocking, standard blocking, and cake filtration. The determination of each fouling mechanism is achieved through an analysis of normalized flux data employing the Wiesner and Aptel equation. The results demonstrate a high degree of model fitness (R2 = 0.9576) for MPR Run 3, confirming its effectiveness. Based on the (R2) values and the fitted parameter (Ks^(-1)), it is evident that, under varying pH levels, catalyst types, catalyst loading, and initial POMSE concentrations, the cake formation fouling mechanism prevails in MPR Run. In conclusion, this research holds promising potential for implementation in the wastewater treatment industry while ensuring compliance with environmental regulations.

Biofouling metallic membranes in algae-laden water treatment: Performance, mechanism, and the role of the pre-coated layer

Biofouling is the primary factor limiting the performance of ultrafiltration membrane systems in drinking water treatment. This study systematically investigated the application effect and biofouling behavior of metallic membranes in the treatment of algae-laden water and evaluated the mitigation effect and mechanism of the pre-coated layer on biofouling. The findings demonstrate that the metallic membrane can almost completely remove algal cells (>99.99 %) and macromolecular organics in EOM (Extracellular Organic Matter) but has limited effects on micromolecules, such as humic acid and fulvic acid, in EOM (47.29 % and 17.72 % for TOC (Total Organic Carbon) and UV254, respectively). During direct filtration, algal cells can form a cake layer in front of the metallic membrane to reduce the membrane flux, whereas the presence of EOM makes the cake layer denser and hastens the decline in flux. In addition, irreversible membrane fouling is exasperated in acidic or Ca2+-rich solutions, whereas an increase in algal cell particles exacerbates reversible membrane fouling, causing a faster decline in flux. According to the membrane mechanism analysis, the fouling mechanism ranges from complete pore blocking to standard and intermediate blocking throughout the direct filtration process. In contrast, the application of a pre-coated kaolin layer significantly decreases membrane fouling compared with direct filtration. The pre-coated layer can prevent direct contact between the foulants and the membrane surface during the early stages of filtration, resulting in a delayed complete pore blockage stage. On the other hand, XDLVO (Derjaguin-Landau-Verwey-Overbeek) data reveals that the force between kaolinite and algae (−102.323 mJ/m2) is greater than that between kaolinite and metallic membranes (−61.424 mJ/m2), resulting in better backwashing efficacy. These findings support the use of metallic membranes in drinking water treatment.