Total Fouling Research Articles

Novel Ultrafiltration Polyethersulfone Membranes Blended with Carrageenan

The development of ultrafiltration (UF) polymeric membranes with high flux and enhanced antifouling properties bridges a critical gap in the polymeric membrane fabrication research field. In the present work, the preparation of novel PES membranes incorporated with carrageenan (CAR), which is a natural polymer derived from edible red seaweed, is reported for the first time. The PES/CAR membranes were prepared by using the nonsolvent-induced phase separation (NIPS) method at 0.1–4.0 wt.% CAR loadings in the casting solutions. The use of dimethylsulfoxide (DMSO), which is a bio-based and low-toxic solvent, is reported. Scanning electron microscopy, atomic force microscopy, water contact angle, porosity, and zeta potential measurements were used to evaluate the surface morphology, structure, pore size, hydrophilicity, and surface charge of the prepared membranes. The filtration performance of PES/CAR membranes was tested with bovine serum albumin (BSA) solutions. It was shown that CAR incorporation in the casting solutions notably increased hydrophilicity, porosity, pore size, surface charge, and fouling resistance of the prepared membranes compared with plain PES membranes due to the hydrophilic nature and pore-forming properties of CAR. The PES/CAR membranes showed a significant reduction in irreversible and total fouling during filtration of BSA solutions by 38% and 32%, respectively, an enhancement in the flux recovery ratio by 20–40%, and an improvement in mechanical properties by 1.5-fold when compared with plain PES membranes. The findings of the present study indicate that CAR can be used as a promising additive for the development of PES UF membranes with enhanced properties and performance for water treatment applications.

Modification of blend reverse osmosis membranes using ZrO2 for desalination process purposes

Desalination of water is a crucial step in the process of obtaining potable water. One of the main challenges for the researchers is its efficient application and affordable preparation. It was planned to prepare the flat sheet membranes using cellulose acetate as a base polymer, and polyvinyl alcohol (PVA) as an additive with dosing of (0.1, 0.3, 0.5, and 0.7 wt%) from zirconium oxide (ZrO2) nanoparticle. SEM, TEM, and XRD analyses were used to characterize the generated ZrO2 nanoparticle in order to confirm its nano-size and crystal structure. The surface morphologies and existence of the dense layer, which is the typical property of the RO membrane capable of salt separation, were identified on the manufactured RO membranes by SEM. Membranes prepared by embedding 0.5 wt%ZrO2 with PVA/CA proved efficient as RO membranes using 2000 ppm NaCl and exhibited high salt rejection of 97% and water permeability of 12.5 LMH. Also, there is a decrease in the NaCl removal tendency was observed with the excessive dosages of ZrO2 with 0.7 wt%, which was due to the concentration polarization, which blocks the pores on the surfaces of the membranes. The antifouling behavior of the prepared membranes was tested using bovine serum albumin (BSA), the results indicate the low irreversible resistance, total fouling resistance, and high flux recovery ratio compared to the neat membrane. The prepared membranes have a stable salt rejection and water productivity even after demonstrating with chlorine (25–100 mg l−1 of NaOCl for 120 min).

Innovation of poly(ionic liquid)-stabilized TiO2 for membrane-based dye waste remediation

Organic–inorganic nanohybrids based membrane materials are reported for separation applications. In the present study, poly(ionic liquid)-stabilized TiO2/polysulfone-based mixed matrix membranes are produced using a phase separation technique induced by a nonsolvent. The presence of PIL-stabilized TiO2 nanohybrids and the hydrophilic nature of PIL enhance the overall hydrophilicity of the PSf membrane, reaching an impressive water flux of 158 LMH at an operating pressure of 6 bar. Further, membranes were characterized through, Field emission scanning electron microscopy, X-ray diffraction, Atomic force microscopy, Thermogravimetry, and Zeta potential. The synergistic effect of positively charged PIL and TiO2 nanohybrids enhances the membrane's anionic dye retention capability, achieving retention rates of nearly 90.83% for Methyl Blue, 94.28% for Congo red, 65.89% for Evan's blue, and 30.98% for Methyl orange with respect to dye size. However hydrophilic membrane showed outstanding antifouling property of the M2 membrane achieved ∼77% of flux recovery ratio with minimal of ∼37% total fouling for 1000 ppm of Bovine Serum Albumin as a foulant. Highly efficient nanocomposite membranes exhibit significant potential for dye removal and addressing water contamination issues, making them attractive solutions for sustainable fouling resilient water treatment processes.

Fabrication and assessment of performance of clay based ceramic membranes impregnated with CNTs in dye removal

In this research, flat disk clay-based ceramic membranes were fabricated and optimized for use in the treatment of wastewater contaminated with dye. The properties of the fabricated membranes were assessed to optimize the fabrication conditions, namely, the firing temperature (1150 °C, 1200 °C, and 1250 °C), soaking time (30 min and 60 min) and zeolite percentage (0%, 10%, and 20%). On the other hand, the rejection of methylene blue dye (MB) and acid fuchsin dye (AF) was studied. The surface of the optimal membrane support was modified using functionalized COOH-carbon nanotubes to increase the dye removal percentage. The fabricated membranes were characterized using FTIR, XRD, and XRF. The optimum membrane support was fabricated at 1150 °C, after 30 min of soaking and with 0% zeolite. The most suitable membrane support was found to be AF, as its rejection percentages reached 42% and 95% without and after surface modification, respectively. The surface of the membrane was examined via SEM, which revealed normally distributed pores. The average pore size of the final membrane was found to be 0.076 micrometers using a mercury porosimeter; thus, the produced membranes can be used in ultrafiltration applications. Finally, the fouling properties showed that the total fouling reached 72.8%, of which only 2.1% was irreversible.

The Application of TiO2/ZrO2-Modified Nanocomposite PES Membrane for Improved Permeability of Textile Dye in Water.

This study investigates the modification of polyethersulfone (PES) membranes with 1 wt% titanium dioxide (TiO2), zirconium dioxide (ZrO2) and a nanocomposite of TiO2/ZrO2. The aim was to efficiently remove Rhodamine B (RhB) from water using a threefold approach of adsorption, filtration and photodegradation. Among the modified membranes (TiO2, ZrO2 and TiO2/ZrO2), the TiO2/ZrO2-PES nanocomposite membrane showed a better performance in rejection of RhB than other membranes with the rejection efficiency of 96.5%. The TiO2/ZrO2-PES membrane was found to possess a thicker selective layer and reduced mean pore radius, which contributed to its improved rejection. The TiO2/ZrO2 nanocomposite membrane also showed high bulk porosity and a slightly lower contact angle of 69.88° compared to pristine PES with a value of 73°, indicating an improvement in hydrophilicity. Additionally, the TiO2/ZrO2-PES nanocomposite membrane demonstrated a relatively lower surface roughness (Sa) of 8.53 nm, which offers the membrane antifouling properties. The TiO2/ZrO2-PES membrane showed flux recovery ratio (FRR), total fouling (Rt), reversible fouling (Rr) and irreversible fouling (Rir) of 48.0%, 88.7%, 36,8% and 52.9%, respectively. For the photocatalytic degradation performance, the removal efficiency of RhB followed this order TiO2 > TiO2/ZrO2 > ZrO2 (87.6%, 85.7%, 67.8%). The tensile strength and elongation were found to be compromised with the addition of nanoparticles and nanocomposites. This indicates the necessity to further modify and optimise membrane fabrication to achieve improved mechanical strength of the membranes. At low pressure, the overall findings suggest that the TiO2/ZrO2 nanocomposite has the potential to offer significant improvements in membrane performance (water flux) compared to other modifications.

Biofouling effect of different landfill leachates on high-density polyethylene pipe material

Pipelines used for collecting and transporting landfill leachates may be affected by biofouling, subsequently posing environmental risks. This study investigates the surface biofouling on high-density polyethylene (HDPE) pipes immersed in leachates acquired from operating (MSW-1) and closed (MSW-2) landfills and from a landfill containing incinerated bottom ash and municipal waste (MSW-3). Water quality monitoring, material characterization, and microbial high-throughput sequencing analysis were conducted to analyze the biofouling effects of different landfill leachates on HPDE pipes. The total fouling masses in the MSW-1, MSW-2, and MSW-3 leachates were 29.2 %, 35.2 %, and 24.5 %, respectively; MSW-2 depicted severe biofouling. The biofouling mass was dominated by living mycobacterial cells (69.93 % of the total biovolume). Proteobacteria was the dominant phylum (30.43 %) and the key bacteria group to cause biofouling. The leachates had a significant impact on the microbial community structure, with Castellaniella and Luteibacter being the endemic genera in MSW-3 and norank_f__Rhodothermaceae being the endemic genera in MSW-1 and MSW-2. Furthermore, Ca2+ was the dominant water-quality parameter to affect the distribution of microbial communities. This study provides valuable insights for pipeline disinfection and sterilization to mitigate bio-clogging in HDPE pipes.

Fabrication of nanocomposite membranes containing Ag/GO nanohybrid for phycocyanin concentration

In this research, silver/graphene oxide (Ag/GO) nanohybrid was first synthesized and used in production of polysulfone (PSF) ultrafiltration (UF) membranes via phase inversion method for concentrating phycocyanin (PC) and treating methylene blue (MB) dye effluent. Designing the experiment (DOE) using Box-Behnken method by Design Expert software helped to calculate the optimal values of the variables under study. The studied variables included PSF polymer concentration, polyvinyl pyrrolidone (PVP) pore-former concentration and Ag/GO nanohybrid content, which were investigated for their effects on pure water flux (PWF) and MB pigment rejection. According to the results of the DOE, the membrane containing 19.485 wt% PSF, 0.043 wt% PVP and 0.987 wt% Ag/GO was selected as the optimal membrane. Due to the high price of PC as drug, and the importance of removing MB pigment from the effluent of dyeing and textile industries, the membranes were first optimized with MB pigment and then the optimal membrane was used for concentrating PC. The results showed that PWF reaches from 40.05 L.m− 2.h− 1 (LMH) for the neat membrane to 156.73 LMH for the optimized membrane, which shows about 4 times improvement. Compared to the neat membrane, flux recovery ratio (FRR) of the optimized membrane increased by about 20% and its total fouling (Rt) decreased by about 10%. Also, the results showed that the optimized membrane can remove 81.6% of MB, as well as to reject 93.8% of PC.

A numerical investigation on the dynamics of particle deposition and fouling on a vertical falling film pipe

The zero liquid discharge process is designed to eliminate the discharge of industrial wastewater into the environment, addressing significant environmental concerns that have emerged in recent decades. Falling film evaporator is one of the primary technologies employed in these systems. As observed, there is a noticeable lack of research numerically simulating these phenomena in a vertical pipe including falling film flow. In the present study, an effort has been made to address the existing research gap by conducting numerical simulation of particles deposition and fouling phenomena in a falling film flow in a three-dimensional vertical pipe using computational fluid dynamics. Continuous phases which contain two non-penetrating fluids, i.e., air and water, are simulated using volume of fluid multiphase model and the large eddy simulation turbulence model. Meanwhile, particles motion has been tracked utilizing discrete phase model. Water film enters the pipe with a thickness of 3.7 mm and an inlet velocity of 1 m/s, and particles with a density of 3110 kg/m3 are injected through the water inlet surface in various cases, each with different diameters. As observed, with an increase in particles diameter from 5 to 15 μm, the asymptotic total fouling mass has increased over 14 times, reaching from 0.016 to 0.18 kg/m2, and the total number of deposited particles has also increased. By increasing the fluids inlet velocity from 1 to 1.5 m/s, the total number of deposited particles has decreased throughout the pipe wall, and the total fouling mass has experienced a reduction of 55.8 %.

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.

Manifestation of UiO-66-Zr MOF-enabled photocatalytic membranes for successive separation and degradation of dye mixtures in water remediation

The use of metal-organic framework (MOF) nanoparticles both as a separation-enhancer and as a photocatalyst has been demonstrated by suitably embedding them into polysulfone (PSU) membranes. These MOF-nanoparticles with Zr-metal and 2-aminoterephthalic-ligand, namely UiO-66-NH2, are synthesized via solvothermal and embedded into the PSU-membranes via solvent-casting process, confirmed via XRD and IR analysis. The skin-deep presence of MOFs and enhancements in the depth of pore-channels within membrane are confirmed through FESEM images. A favorable surface-charge and hydrophilic nature of the MOF-membrane are confirmed via zeta-surface potential and water contact angle analysis, respectively. Consequently, the water-flux efficacy of the optimized MOF-embedded membrane is estimated to be ∼59 L/m2h, while it is ∼20 L/m2h for pristine-membrane. The flux of MOF-membrane against the dye solutions containing rhodamine B (RhB), Congo red (CR), and their mixtures (RhB+CR) is estimated to be ∼39.9, 42.7 and 28.8 L/m2h, which is ∼3.6 times more than the pristine-membrane. Correspondingly, a rejection of ∼81.6, 77.6, and (87.2+79.2%) is estimated for RhB, CR and RhB+CR, respectively, which is ∼2.3 times higher the pristine-membrane. Furthermore, under sunlight irradiation, the MOF-membrane degrades ∼10.1, 7.1 and (7.3+4.2%) of RhB, CR and (RhB+CR) dyes, respectively. The parameters indicating regenerative efficiency, such as flux recovery ratio, reversible, irreversible, and total fouling are found to be enhanced for MOF-membranes compared to pristine-membrane. Overall, the incorporation of MOFs as additives enhances both separation and regeneration efficiency of membranes through photocatalytic process. This process holds promise as a reliable strategy for developing smart-membranes for energy-efficient real-time water treatment applications.

Ultrafiltration polyanionic poly (3‐sulfopropyl methacrylate) membranes with enhanced antifouling and water flux

AbstractPolyethersulfone (PES) membranes are prevalent in the field of water treatment owing to their exceptional separation efficiency, robust mechanical properties, and resistance to chemical degradation. Nevertheless, these membranes are prone to fouling, resulting in a decrease in both flux and ultrafiltration efficiency. In the present study, PES membranes are blended with poly (3‐Sulfopropyl Methacrylate) (PSPMA) in various weight percentages (0%–3%) to improve their antifouling and ultrafiltration properties. The physicochemical properties of the blended membranes, including surface morphology, contact angle, hydrophilicity and surface energy are evaluated. The findings indicate that incorporation PSPMA results in an enhancement of the hydrophilic properties and surface charge of the PES membranes, assessed by employing Bovine Serum Albumin (BSA) as a representative protein. Modified blended membranes display greater Flux Recovery Ratio (FRR%) and exhibit superior fouling resistance. Under the same experimental conditions (0.2 MPa applied pressure), a pure water flux of 154.18 L·m−2·h−1 for PES/PSPMA membrane found substantially greater than pure PES membrane (103.52 L·m−2·h−1) along with Total Fouling Ratio (TFR) of 36% and 64.9% respectively. Exceptional antimicrobial efficacy for modified membranes is revealed against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) using disc diffusion technique rendering them well‐suited for water treatment applications.

Synergistic roles of oxidation and self-aggregation in efficient ultrafiltration membrane fouling alleviation using a flow-through Sb-SnO2 anode during wastewater reclamation

The application of ultrafiltration (UF) in wastewater reclamation alleviates the demand for limited water supplies. However, the membrane fouling caused by the effluent organic matter (EfOM) becomes a major obstacle for UF application. In this study, a pre-oxidation strategy for UF using a Sb-SnO2 (ATO) anode in flow-through mode was proposed with the hopes to improve the performance of UF during wastewater reclamation. The results indicated that this flow-through ATO (FA) anode significantly outperformed a boron-doped diamond (BDD) anode in terms of EfOM degradation and membrane fouling control. It is noteworthy that apart from oxidation, the self-aggregation behavior of foulants was also involved in the mechanisms of membrane fouling mitigation. On the one hand, FA pre-oxidation relieved the burden of membrane fouling by decomposing the macromolecular EfOM into small molecular organic matter, and even mineralizing it. The effective destruction of unsaturated EfOM by FA pre-oxidation made a remarkable contribution to fouling mitigation due to the strong correlation between the total fouling index and UV254. On the other hand, the surface morphology of membrane and interface properties of foulants revealed the self-aggregation behavior of foulants. FA pre-oxidation made the foulants aggregate spontaneously and reduced the potential of forming a dense cake layer on the membrane surface, which was conductive for water permeation. Overall, FA pre-oxidation proved to be a feasible and chemical-free option for UF pretreatment to simultaneously produce high-quality reused water and alleviate membrane fouling during wastewater reclamation.

Effect of organic loading rates on the performance of membrane bioreactor for wastewater treatment behaviours, fouling, and economic cost

Although submerged membrane bioreactor (MBR) are widely used in treating municipal wastewater and recovery of potential resources, membrane operational parameters and membrane fouling control remain debated issues. In this study, the treatment of municipal wastewater by MBR at high-biomass sludge (MLSS (g/L) ranging from 5.4 g/L to 16.1 g/L) was assessed at an organic loading rates (OLRs) ranging from 0.86 to 3.7 kg COD/m3d. The correlation between trans-membrane pressure and total fouling resistance was thoroughly investigated in this study. According to the findings, greater OLRs of 0.86 to 3.7 kg COD/m3d caused a decrease in COD, BOD, and NH4–N removal efficiency, and higher OLRs of 3.7 kg COD/m3d resulted in a higher increase in total fouling resistance (Rt). The economic study of using the MBR system proved that for a designed flow rate of 20 m3/d, the payback period from using the treated wastewater will be 7.98 years, which confirms the economic benefits of using this MBR for treating municipal wastewater. In general, understanding the challenges facing the efficiency of MBR would improve its performance and, consequently, the sustainability of wastewater reclamation.

Acrylonitrile-Acrylic Acid Copolymer Ultrafiltration Membranes for Selective Asphaltene Removal from Crude Oil.

In this study, ultrafiltration membranes were developed via a nonsolvent-induced phase separation method for the removal of asphaltenes from crude oil. Polyacrylonitrile (PAN) and acrylonitrile copolymers with acrylic acid were used as membrane materials. Copolymerizing acrylonitrile with acrylic acid resulted in an improvement in the fouling resistance of the membranes. The addition of 10% of acrylic acid to the polymer chain decreases the water contact angle from 71° to 43°, reducing both the total fouling and irreversible fouling compared to membranes made from a PAN homopolymer. The obtained membranes with a pore size of 32-55 nm demonstrated a pure toluene permeance of 84.8-130.4 L/(m2·h·bar) and asphaltene rejection from oil/toluene solutions (100 g/L) of 33-95%. An analysis of the asphaltene rejection values revealed that the addition of acrylic acid increases the rejection values in comparison to PAN membranes with the same pore size. Our results suggest that the acrylonitrile-acrylic acid copolymer ultrafiltration membranes have promising potential for the efficient removal of asphaltenes from crude oil.

Using Fe(II)/Fe(VI) activated peracetic acid as pretreatment of ultrafiltration for secondary effluent treatment: Water quality improvement and membrane fouling mitigation

Ultrafiltration (UF) is a technology commonly used to treat secondary effluents in wastewater reuse; however, it faces two main challenges: 1) membrane fouling and 2) inadequate nitrogen (N), phosphorus (P), and organic micropollutants (OMPs) removal. To address these two issues, in this study, we applied peracetic acid (PAA), Fe(VI)/PAA, and Fe(II)/PAA as UF pretreatments. The results showed that the most effective pretreatment was Fe(II)/200 μM PAA, which reduced the total fouling resistance by 90.2%. In comparison, the reduction was only 29.7% with 200 μM PAA alone and 64.3% with Fe(VI)/200 μM PAA. Fe(II)/200 μM PAA could effectively remove fluorescent components and hydrophobic organics in effluent organic matter (EfOM), and enhance the repulsive force between foulants and membrane (according to XDLVO analysis), and consequently, mitigate pore blocking and delay cake layer formation. Regarding pollutant removal, Fe(II)/200 μM PAA effectively degraded OMPs (>85%) and improved P removal by 58.2% via in-situ Fe(Ⅲ) co-precipitation. The quencher and probe experiments indicated that FeIVO2+, •OH, and CH3C(O)OO•/CH3C(O)O• all played important roles in micropollutant degradation with Fe(II)/PAA. Interestingly, PAA oxidation produced highly biodegradable products such as acetic acid, which significantly elevated the BOD5 level and increased the BOD5/total nitrogen (BOD5/TN) ratio from 0.8 to 8.6, benefiting N removal with subsequent denitrification. Overall, the Fe(II)/PAA process exhibits great potential as a UF pretreatment to control membrane fouling and improve water quality during secondary effluent treatment.

Long-term operational performance and membrane fouling mechanisms of AGMBR treating municipal wastewater under different superficial air velocities

The granulation and stability of aerobic granular sludge (AGS) as well as membrane fouling in AGS-membrane bioreactor (AGMBR) are significantly influenced by superficial air velocity (SAV). However, there is a lack of relevant research on this topic. Therefore, this study aims to investigate the specific impacts of SAV on AGMBR performance and membrane fouling. The results showed that the experimental SAVs (1.6, 2.1, and 2.6 cm/s) were found to provide sufficient dissolved oxygen for the removal of organics and ammonium nitrogen at efficiencies exceeding 94.50% and 99.40%, respectively. The larger SAV also extended the overall lifespan of the AGMBR, while altering both the content of foulants on fouled membranes and their associated microbial community structure. Moreover, the cake layer exhibiting the highest degree of porosity was observed at an SAV of 2.6 cm/s, which corresponded to the largest pore blocking fouling resistance (28.81% of the total fouling resistance) and the presence of fluorine on the fouled membrane. Additionally, the results from extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory were consistent with the increase in transmembrane pressure. Polysaccharides (PS) played a more significant role than proteins in membrane fouling, and the PS present in soluble microbial products exhibited a strong correlation with fouling resistance distribution. This study aims to optimize the treatment performance and minimize membrane fouling in AGMBR, thereby establishing a mutually beneficial scenario that is essential for the practical implementation of wastewater reuse in engineering.

Statistical evaluation of the coagulation-flocculation process by using Moringa oleifera seeds extract to reduce dairy industry wastewater turbidity

The use of coagulant aqueous extract obtained from M. oleifera seeds in the integration of coagulation/flocculation processes and membrane separation proved to be an environmentally friendly alternative for wastewater treatment from the dairy industry. Three saline solutions, KCl, MgCl2 and CaCl2, were tested to extract the active component from Moringa seeds. The greatest statistical effect on turbidity removal was attributed to the initial pH of the effluent, according to the t-Student at the 5 % significance level. The maximized turbidity and color removals were 96.8 and 90.3 %, respectively, at pH 11 and 300 mg L−1 of the coagulant extracted with CaCl2 0.9 mol L−1. Nanofiltration indicated that previously flocculated organic matter particles were reversibly retained by the membrane. Total fouling was only 35 %, resulting in 98 % recovery of the initial water flow, and a reduction in color, turbidity, COD, calcium, and hardness of 99.5; 98.9; 89.1; 85.5 and 85 %, respectively.

Improvement of MBBR-MBR Performance by the Addition of Commercial and 3D-Printed Biocarriers.

Moving bed biofilm reactor combined with membrane bioreactor (MBBR-MBR) constitute a highly effective wastewater treatment technology. The aim of this research work was to study the effect of commercial K1 biocarriers (MBBR-MBR K1 unit) and 3D-printed biocarriers fabricated from 13X and Halloysite (MBBR-MBR 13X-H unit), on the efficiency and the fouling rate of an MBBR-MBR unit during wastewater treatment. Various physicochemical parameters and trans-membrane pressure were measured. It was observed that in the MBBR-MBR K1 unit, membrane filtration improved reaching total membrane fouling at 43d, while in the MBBR-MBR 13X-H and in the control MBBR-MBR total fouling took place at about 32d. This is attributed to the large production of soluble microbial products (SMP) in the MBBR-MBR 13X-H, which resulted from a large amount of biofilm created in the 13X-H biocarriers. An optimal biodegradation of the organic load was concluded, and nitrification and denitrification processes were improved at the MBBR-MBR K1 and MBBR-MBR 13X-H units. The dry mass produced on the 13X-H biocarriers ranged at 4980-5711 mg, three orders of magnitude larger than that produced on the K1, which ranged at 2.9-4.6 mg. Finally, it was observed that mostly extracellular polymeric substances were produced in the biofilm of K1 biocarriers while in 13X-H mostly SMP.

Interfacial polymerization layer with CNT providing fast water channels under electric field for efficient desalination of nanofiltration membranes

In order to solve the contradiction between permeability flux and selectivity in nanofiltration membrane desalination technology, a novel interfacial polymerization layer structure was designed. In this structure, the hydrophilic modified carbon nanotubes (CNT) untangled and protruded the PA layer under the electric field, resulting in the generation of microporous water channels between CNT and polyamide molecules. Thanks to this unique membrane surface structure, the permeability of the nanofiltration membrane was significantly enhanced, reaching 24.4 L·m−2·h−1·bar−1, in which the rejection of MgCl2 and Na2SO4 were also maintained at 96.1 % and 97.3 %, respectively. At the same time, the surface of the nanofiltration membrane remained intact in the chlorine resistance test, and the total fouling rate caused by lysozyme (LYZ) protein solution was only 2.89 %, demonstrating excellent chlorine resistance and pollution resistance. The design of changing surface structure through electric field-assisted nanomaterials provides a new innovative strategy for the development of separation membrane.

Integrating gravity-driven ceramic membrane filtration with hydroponic system for nutrient recovery from primary municipal wastewater

In this study, a gravity-driven membrane (GDM) filtration system and hydroponic system (cultivating basil and lettuce) were combined for nutrient recovery from primary municipal wastewater. The GDM system was optimized by increasing the periodic air sparging flow rate from 1 to 2 L/min (∼15 hr per 3–4 days), resulting in a ∼52% reduction of irreversible fouling. However, the total fouling was not alleviated, and the water productivity remained comparable. The GDM-filtrated water was then delivered to hydroponic systems, and the effects of hydroponic operation conditions on plant growth and heavy metal uptake were evaluated, with fertilizer- and tap water-based hydroponic systems and soil cultivation system (with tap water) for comparison. It was found that (i) the hydroponic system under batch mode facilitated to promote vegetable growth with higher nutrient uptake rates compared to that under flow-through feed mode; (ii) a shift in nutrient levels in the hydroponic system could impact plant growth (such as plant height and leaf length), especially in the early stages. Nevertheless, the plants cultivated with the GDM-treated water had comparable growth profiles to those with commercial fertilizer or in soils. Furthermore, the targeted hazard quotient levels of all heavy metals for the plants in the hydroponic system with the treated water were greatly lower than those with the commercial fertilizer. Especially, compared to the lettuce, the basil had a lower heavy metal uptake capability and displayed a negligible impact on long-term human health risk, when the treated water was employed for the hydroponic system.