Dewatering of Scenedesmus obliquus Cultivation Substrate with Microfiltration:Potential and Challenges for Water Reuse and Effective Harvesting

In the microalgae harvesting process,which includes a step for dewatering the algal suspension,directly reusing extracted water in situ would decrease the freshwater footprint of cultivation systems.Among various algae harvesting techniques,membrane-based filtration has shown numerous advantages.This study evaluated the reuse of permeate streams derived from Scenedesmus obliquus(S.obliquus)biomass filtration under bench-scale and pilot-scale conditions.In particular,this study identified a series of challenges and mechanisms that influence the water reuse potential and the robustness of the membrane harvesting system.In a preliminary phase of this investigation,the health status of the initial biomass was found to have important implications for the harvesting performance and quality of the permeate stream to be reused;healthy biomass ensured better dewatering performance(i.e.,higher water fluxes)and higher quality of the permeate water streams.A series of bench-scale filtration experiments with different combinations of cross-flow velocity and pressure values were performed to identify the operative conditions that would maximize water productivity.The selected conditions,2.4 m·s^(-1)and 1.4 bar(1 bar=105 Pa),respectively,were then applied to drive pilot-scale microfiltration tests to reuse the collected permeate as a new cultivation medium for S.obliquus growth in a pilot-scale photobioreactor.The investigation revealed key differences between the behavior of the membrane systems at the two scales(bench and pilot).It indicated the potential for beneficial reuse of the permeate stream as the pilot-scale experiments ensured high harvesting performance and growth rates of biomass in permeate water that were highly similar to those recorded in the ideal cultivation medium.Finally,different nutrient reintegration protocols were investigated,revealing that both macro-and micro-nutrient levels are critical for the success of the reuse approach.

Flow-Induced Clogging in Microfiltration Membranes: Numerical Modeling and Parametric Study

Microfiltration membrane technology has been widely used in various industries for solid-liquid separation. However, pore clogging remains a persistent challenge. This study employs (CFD) and discrete element method (DEM) models to enhance our understanding of microfiltration membrane clogging. The models were validated by comparing them to experimental data, demonstrating reasonable consistency. Subsequently, a parametric study was conducted on a cross-flow model, exploring the influence of key parameters on clogging. Findings show that clogging is a complex phenomenon affected by various factors. The mean inlet velocity and transmembrane flux were found to directly impact clogging, while the confinement ratio and cosine of the membrane pore entrance angle had an inverse relationship with it. Two clog types were identified: internal (inside the pore) and external (arching at the pore entrance), with the confinement ratio determining the type. This study introduced a dimensionless number as a quantitative clogging indicator based on transmembrane flux, Reynolds number, filtration time, entrance angle cosine, and confinement ratio. While this hypothesis held true in simulations, future studies should explore variations in clogging indicators, and improved modeling of clogging characteristics. Calibration between numerical and physical times and consideration of particle volume fraction will enhance understanding.

Evaluation of Four Measurement Operation Modes of Streaming Potential for Microfiltration and Ultrafiltration Membranes

Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were investigated in this study, and among the four modes, the steady mode with pressure stepped downward was considered the best one. Experimental results showed that the effects of compaction on the streaming potential measurement for a microfiltration membrane was more obvious than that for a ultrafiltration membrane. Both feed pH and presoaking could affect the measurement of streaming potential.

Preparation and Characterization of the Modified Polyvinylidene Fluoride (PVDF) Hollow Fibre Microfiltration Membrane

A novel thermally induced graft polymerization technique was used to modify a polyvinylidene fluoride （PVDF） hollow fibre microfiltration membrane. An artificial neural network （ANN） was applied to optimize the prepared condition of the membrane. The optimized dosing of acrylic acid （AA）, acrylamide （AM）, N, N＇- methylenebisacrylamide （NMBA） and potassium persulphate （KSP） designed by ANN was that AA was 40.63 ml/L; AM acted as 6.25 g/L; NMBA was 1.72 g/L and KSP was 1.5 g/L, respectively. The thermal stability of the PVDF modified hollow fibre membrane （PVDF-PAA） was investigated by thermogravimetric （TG） and differential scanning calorimetry （DSC） analysis. The polycrystallinity of the PVDF-PAA membrane was evaluated by X-ray diffraction （XRD） analysis. The complex formation of the modified membrane was ascertained by Fourier transform infrared spectroscopy （FTIR）. The morphology of the PVDF-PAA membrane was studied by environmental scanning electron microscopy （ESEM）. The surface compositions of the membrane were analyzed by X-ray photoelectron spectroscopy （XPS）. The adsorption capacity of Cu^2＋ ion on the PVDF-PAA hollow fibre membrane was also investigated.

Modeling of Continuous Cross-flow Microfiltration Process in an Airlift External-loop Slurry Reactor

New modified combination mathematical models including the pores blocking models and the cake layer models were developed to describe the continuous cross-flow microfiltration in an airlift external loop slurry reactor. The pores blocking models were created based on the standard blocking law and the intermediate blocking law, and then the cake layer models were developed based on the hydrodynamic theory in which the calculation method of porosity of cake layer was newly corrected. The Air-Water-FCC equilibrium catalysts cold model experiment was used to verify the relevant models.Results showed that the calculated values fitted well with experimental data with a relative error of less than 10%.

Treatment of phosphate-containing oily wastewater by coagulation and microfiltration

The oily wastewater generated from pretreatment unit of electrocoating industry contains oils, phosphate, organic solvents, and surfactants. In order to improve the removal efficiencies of phosphate and oils, to mitigate the membrane fouling, coagulation for ceramic membrane microfiltration of oily wastewater was performed. The results of filtration tests show that the membrane fouling decreased and the permeate flux and quality increased with coagulation as pretreatment. At the coagulant Ca （OH）2 dosage of 900 mg/L, the removal efficiency of phosphate was increased from 46.4% without coagulation to 99.6%; the removal of COD and oils were 97.0% and 99.8%, respectively. And the permeate flux was about 70% greater than that when Ca（OH）2 was not used. The permeate obtained from coagulation and microfiltration can be reused as make-up water, and the recommended operation conditions for pilot and industrial application are transmembrane pressure of 0.10 MPa and cross-flow velocity of 5 m/s. The comparison results show that 0.2 μm ZrO2 microfilter with coagulation could be used to perform the filtration rather than conventional ultrafilter, with very substantial gain in flux and removal efficiency of phosphate.

Purifying chylous plasma by precluding triglyceride via carboxylated polyethersulfone microfiltration membrane

Precluding the excessive lipoproteins from plasma rapidly and effectively is highly needed for biomedical detection and reducing plasma product scrap in blood donation stations.The current centrifugation procedure is high-cost and time-consuming.Herein,we fabricated an anionic microfiltration polyethersulfone(PES)membrane modified by interface swelling and implanting of acrylic acid(AA)for screening out large particle lipoprotein chylomicron(CM)and adsorbing cationic very low-density lipoproteins(VLDL).To improve the separation efficiency,a two-stage filtration through carboxylated polyethersulfone microfiltration membranes with the mean pore size of 0.45 and 0.22μm respectively were conducted.Attenuated total reflection Fourier transform infrared technique(ATR-FTIR),water contact angle(WCA),Zeta potential and scanning electron microscope(SEM)were employed to characterize the modified membrane.To test the effectiveness of this membrane,plasma flux and concentration variation of plasma components were examined to study the purification effectiveness.Furthermore,the hemocompatibility of modified membranes was tested to confirm its practicability on bloodcontacting materials.The carboxylated polyethersulfone microfiltration membrane shows its promising potential application to purify chylous plasma.

Study on Separation of Water and Alumina Fine Particles by Cross-Flow Microfiltration

A cross-flow microfiltration process had been developed to separate alumina fine particles from the suspension using a stainless steel membrane tube with a pore size of 10 μm. The influence of cross-flow velocity and trans-membrane pressure on the permeate flux and the solid holdup in permeate had been investigated. It was found that both the permeate flux and the solid holdup in permeate decreased with time. Moreover, the permeate flux increased with an increasing transmembrane pressure but the influence of cross-flow velocity on the permeate flux was quite complex. Both the permeate flux and the solid holdup in permeate in long term filtration had been studied. The operation of cross-flow microfiltration could be carried out stably for 10 hours with the permeate flux values ranging from 520.5 to 936 L/(m^2·h) at rs=1%, while it could continue in 10 hours with the permeate flux values ranging from 226 to 432 L/(m^2·h) at rs=5%. The solid holdup in permeate had been less than 10 mg/L during the whole operating cycle.

Experimental Study on Revolving Cross-flow Microfiltration of Highly Viscous Liquids

Experimental investigation of the microfiltration （MF） using a revolving cross-flow membrane filter was performed under the condition of constant pressure difference, and different flat membranes made of polyvinylidene fluoride （PVDF, 0.1 μm）, cellulose acetate （CA, 0.22 μm）, sulfonated polyethersulfone （SPES, 0.22 μm） and polyamide （PA, 0.45 μm）, respectively, were used in filtration experiments. The dependence of the filtrate mass of the cross-flow MF on time was measured on-line. The experimental results showed that the effect of the cross-flow on high viscosity medium was more significant than that on the low viscosity one.

Evaluation of Four Measurement Operation Modes of Streaming Potential for Microfiltration and Ultrafiltration Membranes

Surface charge characteristics of a membrane can be determined by the streaming potential. In order to obtain more accurate streaming potential value during the measurement, four measurement operation modes were investigated in this study, and among the four modes, the steady mode with pressure stepped downward was con- sidered the best one. Experimental results showed that the effects of compaction on the streaming potential meas- urement for a microfiltration membrane was more obvious than that for a ultrafiltration membrane. Both feed pH and presoaking could affect the measurement of streaming potential.

Membrane Microfiltration Fermentation of Glucose Oxidase with Cell Recycling

Membrane microfiltration fermentation (MMF) with cell recycling was successfully applied to the production of glucose oxidase (GOD). A plate microfiltration module was found suitable for such purpose. By feeding whole medium in MMF, the productivity of GOD was much higher than that by feeding glucose alone. With increasing dilution rate the enzyme productivity increased and average enzyme activity decreased. The enzyme productivity of MMF under D = 0.12h-1 and 0.20h-1 were 3871 and 3945U·h-1 respectively, which was about 3 times as that of batch fermentation (BF) and the average enzyme activity was still as high as STU·mL-1 under D = 0.12h-1. The relative efficiency of MMF applied to low yield strain was higher than that applied to high yield strain.

Investigation of organic fouling of microfiltration membrane

Because the natural organic matters (NOMs) and proteins are the principal foulants of microfiltration membranes in drinking water, the primary aim of this paper is to obtain a better understanding of the interactions between those foulants and the microfiltration membrane from a novel view of coagulation. Based on reviewed literature and our own analysis, the authors consider that the behaviors of NOMs in the fouling of microfiltration membrane are like a form of crystal growth, and we recognize that the extent of the membrane hydrophobicity plays an essential role in NOMs fouling. However, proteins’ fouling is more affected by intermolecular interaction. Additionally, the effect of membrane surface chemistry is not as essential as it is in the situation of NOMs.

Removal of endocrine disrupting chemicals from water through urethane functionalization of microfiltration membranes via electron beam irradiation

Polyethersulphone(PES)membranes modified with urethane functional groups were prepared through an interfacial reaction using electron beam irradiation.The removal of eight endocrine disrupting chemicals(EDCs)was studied using both pristine and functionalized PES membranes.The prepared membranes underwent characterization using several techniques,including attenuated total reflectance-Fourier transform infrared(ATR-FTIR)spectroscopy,scanning electron microscopy,contact angle analysis,and measurements of pure water flux.Furthermore,dynamic adsorption experiments were conducted to evaluate the adsorption mechanism of the prepared membrane toward the eight EDCs.The urethane functionalized membranes were hydrophilic(52°contact angle)and maintained a high permeate flux(26000 L/h m^(2) bar)throughout the filtration process.Dynamic adsorption results demonstrated that the introduction of urethane functional groups on the membranes significantly enhanced the removal efficiency of 17β-estradiol,estriol,bisphenol A,estrone,ethinylestradiol,and equilin.The adsorption loading of 17β-estradiol on the functionalized PES membrane was 6.7±0.7 mg/m^(2),exhibiting a 5-fold increase compared to the unmodified PES membrane.The membranes were successfully regenerated and reused for three adsorption cycles without experiencing any loss of adsorption capacity.

膜技术在生态环境治理中的应用

在生态环境治理工作中,膜技术是具有先进性和应用适宜性的一种高效的环境治理技术,在生态环境治理和保护中有非常重要的作用。本文重点针对微滤膜技术、超滤膜技术和纳滤膜技术进行分析,并且进一步研究其在生态环境治理中的实际应用策略。通过本文分析可知,微滤膜技术可主要应用在饮用水工业废水和农业灌溉水处理中,而超滤膜技术则主要用在地表水海水食品饮料用水处理中。纳滤膜技术则主要应用在饮用水的深度净化地下水处理和制药领域中.由此可见,不同类型的膜技术可在生态环境治理中有针对性的发挥作用,只要技术人员合理选择模技术,在不同的治理背景下有效应用即可。

Polyaniline-poly(vinylidene fluoride) blend microfiltration membrane and its spontaneous gold recovery application

Structural regular polyaniline was synthesized via a modified-chemical oxidative polymerization reaction. Highly hydrophilic polyaniline(PANi) and polyaniline-poly(vinylidene fluoride) blend(PANi-PVDF) membranes were prepared by solution casting and phase inversion techniques. Both of the mechanical and filtration properties of the membranes depend on the polymer composition and doping level of the blends. The elasticity of the membrane is greatly improved upon introducing poly(vinylidene fluoride) into the blend. The water permeability of the blend membranes is further enhanced when the membranes are doped with hydrochloric acid. The PANi-PVDF blend membranes are capable of recovering metallic gold from the acid/halide leaching streams spontaneous and sustainably, and are promising candidates for wastewater treatments in electronic industries.

Roles of membrane and organic fouling layers on the removal of endocrine disrupting chemicals in microfiltration

To understand the adsorption behavior of endocrine disrupting chemicals（EDCs） is important for enhancing the treatment performance and preventing potential secondary pollution caused by EDCs desorption in a microfiltration system. The dynamic adsorption of four representative EDCs, namely estriol（E3）, 17β-estradiol（E2）, 17α-ethynylestradiol（EE2）, and 4-nonylphenol（4-NP） in a microfiltration system was investigated using the Thomas＇ model.The product of the equilibrium constant and the total adsorption capacity of the membrane,Ka, for E3, E2, EE2, and 4-NP were 4.91, 9.78, 15.6, and 826, respectively, strongly correlating with the compound octanol–water partition coefficient（KOW）. Adsorption appeared to be enhanced when organic fouling formed on the surface of membrane, indicating the role of an additional adsorption column for EDCs acted by a fouling layer in microfiltration. Results of a comparison between the Ka values for clean membrane and fouled membrane illustrated that the significant contribution made by fouling layers may be attributed to the foulant layer＇s hydrophobicity（in the case of calcium humate layer） and thickness（in the case of calcium alginate layer）. This study provided a novel perspective to quantitatively analyze the dynamic adsorption behavior of trace pollutants in membrane process.

Bisphenol A removal from synthetic municipal wastewater by a bioreactor coupled with either a forward osmotic membrane or a microfiltration membrane unit

Forward osmotic membrane bioreactor is an emerging technology that combines the advantages of forward osmosis and conventional membrane bioreactor. In this paper, bisphenol A removal by using a forward osmotic membrane bioreactor and a conventional mem- brane bioreactor that shared one biologic reactor was studied. The total removal rate of bisphenol A by the conventional membrane bioreactor and forward osmotic membrane bioreactor was as high as 93.9% and 98%, respectively. Biodegradation plays a dominant role in the total removal of bisphenol A in both processes. In comparison of membrane rejection, the forward osmosis membrane can remove approximately 70% bisphenol A from the feed, much higher than that of the microfiltration membrane （below 10%）. Forward osmosis membrane bioreactor should be operated with its BPA loading rate under 0.08 mg. g-1. d-1 to guarantee the effluent bisphenol A concentration less thanlO μg·L-1.

Membrane Fouling in Microfiltration used for Cell Harvesting

In the present study the membrane fouling in microfiltraiton used for cell harvesting in a deadend system has been investigated. Experimental results were analysed in terms of existing membrane filtration models and membrane resistances. The cake filtration model (CFM) and standard blocking model (SBM) have been considered in this study.Various membrane resistances were determined at different processing time, feed concentration and stirring speed. Resistances to permeation in this system include filter medium, pore blocking, adsorption, cake layer and concentration polarization.

反渗透预处理及膜清洗方法

基于预处理和膜清洗对于反渗透RO(reverseosmosis)长期稳定运行的重要性 ,介绍了常规预处理方法及其改进、膜法预处理等预处理方法 ,以及各种新型的物理、化学膜清洗方法 .

Experimental and CFD Study on the Role of Fluid Flow Pattern on Membrane Permeate Flux

This paper reports a study on the role of fluid flow pattern and dynamic pressure on the permeate flux through a micro filtration membrane in laboratory scale.For this purpose,a dead-end membrane cell equipped with a marine type impeller was used.The impeller was set to rotate in the clockwise and counter clockwise directions with the same angular velocities in order to illustrate the effect of rotation direction on permeate flux.Consequently, permeate fluxes were measured at various impeller rotational speeds.The computational fluid dynamics（CFD）predicted dynamic pressure was related to the fluxes obtained in the experiments.Using the CFD modeling,it is proven that the change in dynamic pressure upon the membrane surface has direct effect on the permeate flux.