Harvesting of microalgal biomass using MF membrane: Kinetic model, CDE model and extended DLVO theory

Impact of sandwich-type composite anodic membrane on membrane fouling and methane recovery from sewage sludge and food waste via electrochemical anaerobic membrane bioreactor

Membrane fouling presents a big challenge for the real-world implementation of anaerobic membrane bioreactors (AnMBRs) in digesting high-solid biowastes. In this study, an electrochemical anaerobic membrane bioreactor (EC-AnMBR) with a novel sandwich-type composite anodic membrane was designed and constructed for controlling membrane fouling whilst improving the energy recovery. The results showed that EC-AnMBR produced a higher methane yield of 358.5 ± 74.8 mL/d, rising by 12.8% compared to the AnMBR without applied voltage. Integration of composite anodic membrane induced a stable membrane flux and low transmembrane pressure through forming an anodic biofilm while total coliforms removal reached 97.9%. The microbial community analysis further provided compelling evidence that EC-AnMBR enriched the relative abundance of hydrolyzing (Chryseobacterium 2.6%) bacteria and methane-producing (Methanobacterium 32.8%) archaea. These findings offered new insights into anti-biofouling performance and provided significant implications for municipal organic waste treatment and energy recovery in the new EC-AnMBR.

Microalgae biomass concentration and reuse of water as new cultivation medium using ceramic membrane filtration

The aim of this study is to advance means for microalgae dewatering with the simultaneous reuse of water as new cultivation medium, specifically through ceramic membrane filtration. Three algae, namely, Spirulina platensis, Scenedesmus obliquus, and Chlorella sorokiniana were tested by filtering suspensions with four ceramic membranes having nominal pore sizes of 0.8 μm, 0.14 μm, 300 kDa, 15 kDa. The observed flux values and organic matter removal rates were related to the membrane pore size and cake layer properties, with some differences in productivity between algae types, likely due to cell size and shape. Interestingly, similar near steady-state fluxes (70-120 L m^-2h^-1) were measured using membranes with nominal pore size above 15 kDa, suggesting the dominance of cake layer filtration independently of the initial flux. Virtually complete algae cells rejections and high nutrient passage (>75%) were observed in all combinations. When the permeate streams were used as media for new growth cycles of the various algae, no or little growth was observed with Spirulina p., while Chlorella s. (permeate from 300 kDa membrane) and especially Scenedesmus o. (permeate from 0.14 μm membrane) showed the fastest growth rates, almost comparable to those observed with ideal fresh media.

A Study of the Mechanism and Separation of Structurally Similar Phenolic Acids by Commercial Polymeric Ultrafiltration Membranes

This study examined the behavior and penetration mechanisms of typical phenolic (benzoic) acids, which determine their observed penetration rates during membrane separation, focusing on the influence of electrostatic and hydrophobic solute/membrane interactions. To understand the effects of hydrophobicity and electrostatic interaction on membrane filtration, the observed penetration of five structurally similar phenolic acids was compared with regenerated cellulose (RC) and polyamide (PA) membranes at different solute concentrations and solution pHs. Variation partitioning analysis (VPA) was performed to calculate the relative contributions of electrostatic and hydrophobic effects. The penetration of phenolic acids was mainly influenced by the electrostatic interaction, with salicylic acid having the highest penetration. Penetration of phenolic acids through the PA membrane decreased from 98% at pH 3.0 to 30–50% at pH 7.4, indicating the dominance of the electrostatic interaction. Moreover, based on its hydrophobicity and greater surface charge, the PA membrane could separate binary mixtures of protocatechuic/salicylic acid and 4-hydroxybenzoic/salicylic acid at pH 9.0, with separation factors of 1.81 and 1.78, respectively. These results provide a greater understanding of solute/membrane interactions and their effect on the penetration of phenolic acids through polymeric ultrafiltration membranes.

Evaluation of the performance of different membrane materials for microalgae cultivation on attached biofilm reactors

Attached microalgae production in wastewater is a promising method to further develop biofilm reactors by reducing economic costs associated with biomass separation and harvesting. However, the reliability of materials to support such adherence needs further investigation. Five common microfiltration membranes were evaluated in this study to assess their influence on the efficacy of harvesting Chlorella pyrenoidosa. The material-to-material, algae-to-algae, and algae-to-material interactions were studied based on the Extended Derjaguin, Landau, Verwey, Overbeek (XDLVO) theory. The results showed that Chlorella pyrenoidosa was hydrophobic and that the algae particles derived from this algae type tended to agglomerate. Furthermore, the algae–membrane adhesion free energy further validated the accumulation of biomass in the experiments — the cellulose acetate nitrate (CACN) membrane and the cellulose acetate (CA) membrane obtained an optical biomass production of 59.93 and 51.27 g m⁻². The presence of these interactions promoted the adhesion of more microalgae particles to the membrane. Moreover, the relationship between the algae–membrane and the distance at which the microalgae approached the membrane surface was simulated. The study indicated that the XDLVO theory could be successfully applied to the mechanism for the adhesion of the attached culture of Chlorella pyrenoidosa to the membrane material.

Attached microalgae production in wastewater is a promising method to further develop biofilm reactors by reducing economic costs associated with biomass separation and harvesting.

Effect of the modified dispersing agent and milling time on the properties and particle size distribution of inkjet ink formulation for textile printing

Purpose

This paper aims to study the effect of the new modified dispersing agent, milling time of the properties and particle size distribution (PSD) of inkjet ink formulation for polyester fabric printing.

Design/methodology/approach

The study’s methods include preparation of different formulations of textile inkjet inks based on different types of dispersing agents, then applying and evaluating the prepared formulations on the polyester fabric. The properties of the prepared ink formulations were analyzed by measuring viscosity, surface tension and particle size. The current work is including the study of the effect of using different doses of different dispersing agents and the milling time on their characteristics. Also, the study was extended to evaluate the printed polyester by using the prepared inks according to light fastness, washing fastness, alkali perspiration fastness and crock fastness.

Findings

The results showed that the used dispersing agents and the different milling time enhanced the viscosity and dynamic surface tension in the accepted range, but it was largely cleared in the PSD which tends to perform the inks on the printhead and prevent clogging of nozzles. Light fastness, washing fastness, alkali perspiration fastness and crock fastness gave good results in agreement with this type of inkjet inks for textile printing.

Research limitations/implications

In this work, good results were obtained with this type of dispersing agent for inkjet ink formulations, but for other dispersing agents, other tests could be performed. The inkjet ink could also be formulated with other additives to prevent clogging of nozzles on the printhead.

Practical implications

These ink formulations could be used for printing on polyester fabric by the inkjet printing.

Originality/value

Recently, there was a considerable interest in the study of the effect of PSD on the inkjet inks to prevent clogging of nozzles on the printhead and to improve the print quality on the textile fiber.

Real-time fouling monitoring and membrane autopsy analysis in forward osmosis for wastewater reuse

Forward osmosis process in emerging technology which can applicable in wastewater reuse and desalination simultaneously. In this study, the development of fouling on the FO membrane surface was monitored in real-time. The investigation of fouling layer physical and chemical characteristics was assessed by performance evaluation and in-depth analysis of fouling layer. Non-invasive visual monitoring and in-depth autopsy, combined with the performance and image analyses provided a better understanding of fouling phenomena. The relative roughness of the fouling layer was correlated with water flux decrease while the fouling layer thickness decreased rapidly when fouling was stabilized. From 66-day operation using the primary wastewater as the feed, membrane fouling development was classified into 4 phases: virgin performance, initial deposition, stabilization and aggregation. With the growing fouling layer and with aggregation, the removal rate of organic matter was reduced from 99 to 70%. Conversely, the removal rate of inorganic matter was maintained at a level higher than 90%. The fractionation of physical and chemical extraction had the following characteristics: TPI>HPI>HPO and HPI>TPI>HPO respectively. Also, low molecular weight and building blocks like organic matter were observed with a high composition ratio of fouling layer. Through the correlation between the process performance, real-time monitoring of fouling layer formation and deep-layer fouling analysis, it was possible to identify the major membrane contaminants and propose process optimization guidelines.

Harvesting of Rhodotorula glutinis via Polyaluminum Chloride or Cationic Polyacrylamide Using the Extended DLVO Theory

Polyaluminum chloride (PAC) and cationic polyacrylamide (CPAM) play a crucial role for separating microorganisms from bulk media. However, the mechanism of adsorption between cells and flocculants remain to be further defined to improve the flocculation efficiency (FE) in extreme conditions. This study conducted the flocculation process of Rhodotorula glutinis induced by PAC and CPAM, firstly. The result demonstrated that CPAM possessed more efficient harvesting ability for R. glutinis compared to PAC. The difference of flocculation capacity was then thermodynamically explained by the extended DLVO (eDLVO) theory; it turned out that the poor harvesting efficiency of PAC was attributed to lacking of binding sites as well as low adsorption force within particles. Based on this, the FE of PAC to R. glutinis was mechanically enhanced to 99.84% from 32.89% with 0.2 g/L CPAM modification at an optimum pH of 9. Also, the paper will play a guiding role in the treatment of inorganic salt ions and organic matters in wastewater.

Harvesting microalgal biomass using negatively charged polysulfone patterned membranes: Influence of pattern shapes and mechanism of fouling mitigation

Membranes have a lot of potential for harvesting microalgae, but membrane fouling is hampering their breakthrough. In this study, the effects of charge and corrugated surface on membrane filtration performance were investigated. The clean water permeance (CWP), the microalgae harvesting efficiency and the membrane flux for a microalgal broth were determined using patterned polysulfone (PSf) membranes with different shapes of the surface patterns and containing different charge densities by blending sulfonated polysulfone (sPSf). The flow behavior near the patterned membrane surface, as well as the interaction energy between membrane and microalgae were investigated using computational fluid dynamics (CFD) simulation and the improved extended "Derjaguin, Landau, Verwey, Overbeek" (XDLVO) theory, respectively. Membrane charge and pattern shape significantly improve the membrane performance. The critical pressures of all sPSf blend patterned membranes were higher than 2.5 bar. A 4.5w% sPSf blend patterned membranes with wave patterns showed the highest CWP (2300 L/m² h bar) and membrane flux in the microalgal broth (1000 L/m² h bar) with 100% harvesting efficiency. XDLVO analysis showed that sPSf blend patterned membranes prepared obtained the lowest interaction energy and highest energy barrier for microalgal attachment. CFD simulation showed a higher velocity and wall shear on the pattern apexes.

Thermodynamic prediction and experimental investigation of short-term dynamic membrane formation in dynamic membrane bioreactors: Effects of sludge properties

In dynamic membrane bioreactors (DMBRs), a dynamic membrane (DM) forms on a support material to act as the separation membrane for solids and liquids. In this study, batch filtration tests were carried out in a DMBR using nylon mesh (25 μm) as support material to filtrate sludge suspensions of variable properties from three different sources to evaluate the effects on the short-term DM formation process (within 240 min). Furthermore, the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory was applied to analyze the sludge adhesion and cohesion behaviors on the mesh surface to predict quantitative parameters of the short-term DM formation process (including initial formation and maturation stage). The filtration results showed that the order of the initial DM formation time (permeate turbidity <1 NTU as an indicator) was as follows: sludge with poor settleability and dewaterability < normal sludge < sludge with poor flocculability. Moreover, normal sludge (regarding settleability, dewaterability, flocculability, and extracellular polymeric substance) showed a more acceptable DM formation performance (short DM formation time, low permeate turbidity, and high permeate flux) than sludge with poor settleability, dewaterability and flocculability. The influence of sludge properties on the initial DM formation time corroborates the prediction of sludge adhesion behaviors by XDLVO theory. Additionally, the XDLVO calculation results showed that acid-based interaction, energy barrier, and secondary energy minimum were important determinants of the sludge adhesion and cohesion behaviors. Therefore, short-term DM formation process may be enhanced to achieve stable long-term DMBR operation through positive modification of the sludge properties.

Inkjet Printable and Self-Curable Disperse Dyes/P(St-BA-MAA) Nanosphere Inks for Both Hydrophilic and Hydrophobic Fabrics

Low-water-soluble disperse dyes possess a broad color gamut and good durability, but they need chemical or physical modification before being used in inks and can only be applied to several kinds of hydrophobic fabrics. In this work, disperse dyes/P(St-BA-MAA) nanospheres (known as DPN) absorbed by sodium nitrilotriacetate (known as NTA@DPN) were prepared and applied into ink formulations, which exhibited high dye fixation, long-term stability and self-curable ability without addition of any binder. Transmission electron microscopy (TEM) images showed the nanospheres have homogeneous core-shell spherical shape and the average diameter increased by 20.6 nm after coloration. X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), and differential scanning calorimetry (DSC) measurements illustrated the interaction between dyes and nanospheres and indicated that the colored nanospheres contained both dye molecules and crystalline dyes. The Zeta potential and particle size measurements demonstrated that the dispersion stability was improved when sodium nitrilotriacetate (NTA) was absorbed onto DPN. The rheological behavior of the NTA@DPN inks was Newtonian and desired droplet formation was achieved at the viscosity of 4.23 mPa·s. Both hydrophilic cotton and hydrophobic polyester fabrics were cationic modified before used, which had an excellent image quality and desired rubbing fastness after inkjet printing. Scanning electron microscope (SEM) images showed NTA@DPN formed stable deposits on the surface of modified fibers and could self-cure to form continuous film coating on the fiber surface after being baked at 150 °C without addition of any binder.

The filtration and fouling performance of membranes with different pore sizes in algae harvesting

In this study, ultrafiltration membranes with three different pore sizes were applied for algae harvesting to investigate filtration performance. The critical fluxes (J_C) increased as the pore size increased, and the J_C of 0.03-, 0.05- and 0.1-μm membranes were 20.0, 25.0 and 42.0Lm^-2h^-1, respectively. During continuous filtration, 0.7J_C was selected as the operation flux and the 0.1-μm membrane had the highest initial flux and final flux. It also had the highest flux decline rate, and therefore, the 0.1-μm membrane was more appropriate for algae separation compared to the 0.03- and 0.05-μm membrane. The mechanism by which pore size influenced filtration performance and membrane fouling was presented from the viewpoint of permeate drag force (F_D). A lower F_D retarded the velocity of algae cells towards the membrane, which could decelerate the deposition of particles on the membrane and thus reduce the membrane fouling rate. As the pore size increased, the membrane hydraulic resistance (R_m) decreased, which led to a decrease of F_D.

Comparison of axial vibration membrane and submerged aeration membrane in microalgae harvesting

The submerged aeration membrane (SAM) system and axial vibration membrane (AVM) system can mitigate membrane fouling. In this study, both systems were investigated to compare the performance of filtration and the membrane fouling in algae filtration. In 5-h filtration, the transmembrane pressure (TMP) of SAM reached to 70.0 kPa, while there was almost no increase in TMP for AVM. After continuous filtration, it could be found that there was hardly any algae cells on the membrane of AVM (0.11 g/m(2)), which was about 32.4 times less than that of SAM (3.56 g/m(2)). Compared with the SAM system, AVM had a lesser membrane fouling, regardless of the reversible fouling or irreversible fouling. By SEM, FTIR and EEM, it could be found there was less irreversible extracellular organic matter (EOM) on the membrane of AVM. By MW distribution, it could be observed that less EOM with high-MW adhered to membrane of AVM.