Thesis (Ph. D.)--University of New South Wales, 2005. / Also available online.

In this PhD thesis, seawater desalination by Membrane Distillation (MD) has been explored from the perspective of process and membrane. Regarding the process, an innovative, energy efficient, and environmentally friendly Zero Thermal Input Membrane Distillation (ZTIMD) process was proposed. ZTIMD uses thermal energy stored in seawater, which makes the process sustainable by being independent of the external sources of thermal energy, which is one of the major contributors to the cost and energy consumption of conventional MD desalination processes. Economic feasibility study was carried out for the ZTIMD process, and it was demonstrated that drinking water could be produced with a cost of $0.28/m3, which is approximately half of the cost of conventional desalination processes. Regarding the membrane, novel MD membranes were developed through incorporation of nanomaterials in polyvinylidene fluoride (PVDF). Different nanomaterials including superhydrophobic SiO2, amine modified hydrophilic SiO2, CuO, and CaCO3 were used for this purpose. It was shown that membrane structure and consequently its performance could be affected by the nanoparticle properties, concentration, presence of backing material, PVDF blend ratio, and penetration time. In a best membrane developed in this work, almost 2500% increase was observed in the Vacuum Membrane Distillation (VMD) flux over that of the neat PVDF membrane at a feed temperature of 27.5 °C and vacuum pressure of 1.2 kPa, when 7.0 wt.% hydrophilic SiO2 nanoparticles were added into a PVDF membrane supported with Non-Woven Fabric (NWF) polyester. The membrane possessed near perfect selectivity.

<p>Membrane filtration is widely used to biomedical and analytical applications. Compared to other techniques available membrane filtration provides fast processing time, easy availability, robust performance and relatively low cost. These advantages make ultrafiltration and microfiltration well integrated into bioseparation, purification of biomedical materials and downstream polishing. Apart from the advatanges, there are certain drawbacks with microfiltration and ultrafiltration. While perceived negative in many scenarios, the effects does not necessarily counteract the purpose of the process and could find some useful applications if treated from a different perspective.</p> <p>By the virtue of fast processing of membrane filtrations, applications were made in processing biomedical materials and developing analytical methods. Poly(<em>N</em>-isopropylacrylamide) microgels are of potential in many biomedical applications. Microfiltration and ultrafiltration of such microgels for fast purification were explored. Meanwhile, the environmental responsive behaviours of such microgels bring about opportunity and challenge. Investigations were made on the salt-responsive transmission behaviours of microgels in microfiltrations. A hypothesis was raised and verified. Implications of applications <em>in vivo</em> were drawn based on experimental results. Many techniques for analysis of protein-drug binding have been under development. A new alternative utilizing pulsed tangential flow ultrafiltration was developed in this study and used to obtain binding data between aspirin and BSA under different conditions. The performance of the systems was assessed under different parameter settings. Possibility of further automation was discussed. On account of the fouling and concentration polarization, a new perspective was taken with the effort of developing such effects into potential applications. Patterned fouling was introduced and the fouled membrane was used to filter coloured feed to reveal the patterns transferred. Concentration polarization in ultrafiltrations with different levels of fixation of membranes was visualized by dyed particles. The possible flow modes under these conditions were suggested. A hypothesis was attempted from a fluidics point of view.</p> / Master of Applied Science (MASc)

Thesis (PhD)--Stellenbosch University, 2002. / Some digitised pages may appear illegible due to the condition of the original hard copy. / ENGLISH ABSTRACT: Membrane fouling is universally accepted as one of the most critical problems limiting the wider application of membranes in liquid separations. The development and utilization of a suitable non-invasive technique for the on-line monitoring of fouling in industrial and laboratory applications may enable the effectiveness of fouling remediation and cleaning strategies to be quantified. The overall objective of this research is to develop ultrasonic time-domain reflectometry (UTDR) and its use as an analytical tool for the real-time study of inorganic-, organic- and protein- fouling of various types of membranes including nylon, polysulfone (PSU) and polyethersulfone (PESU) and modules, including flatsheet and tubular types. Different separation systems including microfiltration (MF) and ultrafiltration (UF), flat-sheet and tubular modules, and suitable ultrasonic probes were used in this study. Results of this study show a good correlation between the UTDR signal response and the development of a fouling layer on a membrane surface. UTDR effectively detected the appearance, growth and movement of a fouling layer echo as fouling proceeded. Cake (fouling)-layer compressibility was observed by UTDR. The structure and compaction of an asymmetric PSU membrane could be detected by UTDR. UTDR was also successfully used for monitoring membrane cleaning and evaluating the cleaning effectiveness o f various cleaning methods. UTDR results corroborated the flux measurements and SEM analyses. The ultrasonic unit is a programmed microprocessor, and can be used to compare reference and test signals to produce a differential signal (a fouling layer echo). A differential signal indicates the state and progress o f a fouling layer on the membrane surface in actual operations. Both amplitude and arrival time of differential signals as a function of operation time provide useful quantitative information, i.e. changes in thickness and density of a fouling layer, on the fouling processes. A predictive modelling program, ultrasonic reflection modelling (URM), was developed to describe the processes of ultrasonic testing related to the deposition of fouling layers on membrane surfaces. The mathematical model could substantiate changes in the densities of the fouling layer as well as the thickness. This is important as deposit resistance to flow is related to both thickness and density (compressibility). The predicted results of cake layer deposition are in good agreement with the actual UTDR measurements obtained in MF and UF. Furthermore, protein fouling was successfully detected in tubular UF by UTDR. Ultrasonic frequency spectra could be used as an additional tool for fouling detection. / AFRIKAANSE OPSOMMING: Membraan-aanvuiling of -verstopping is die grootste struikelblok wat die meer algemene aanwending van membrane vir verskillende watersuiweringsprosesse beinvloed. Die ontwikkeling en gebruik van ‘n geskikte nie-inmengende tegniek vir die in-lyn meting van aanvuiling van membrane in laboratorium-en nywerheidstoepassings mag ‘n geleentheid bied vir die kwantifisering van die verwydering van aanvuiling en skoonmaakstrategiee. Die hoofdoel van hierdie studie was die ontwikkeling van ultrasoniese tydgebiedsweerkaatsing (Eng: ultrasonic time-domain reflectometry, UTDR) en die gebruik daarvan as ‘n analitiese metode vir die studie van anorganiese-, organiese- en bio-besoedeling op verskeie tips membrane, insluitend nylon, polisufoon (PSU) en polietersulfoon (PESU), in beide platvel- en buismodules. Verskeie skeidingsisteme, insluitend mikrofiltrasie (MF) en ultrafiltrasie (UF) is ontwerp en gebruik in hierdie studie. Eksperimentele resultate het goeie ooreenstemming tussen die UTDR seinrespons en die ontwikkeling van ‘n aanvuilingslaag op die membraanoppervlakte bewys. Die ultrasoniese tegniek kon die vorming, groei en beweging van ‘n bevuilingslaagterugkaartsing waarneem namate bevuiling vorder. Aanvuilingslaagsamepersing is deur UTDR waargeneem. Die struktuur en samepersing van ‘n asimmetriese PSU membraan is ook deur UTDR gesien. UTDR is verder suksesvol gebruik om die skoonmaak van membrane te monitor en om die skoonmaakgeskiktheid (cleaning effectiveness) van verskeie skoonmaakmetodes te bepaal. UTDR resultate het permeaatvloeimetings en SEM analyses bevestig. Die ultrasoniese eenheid is ‘n geprogrameerde mikroverwerker, en kan gebruik word om verwysings- en toetsseine te vergelyk, en dan ‘n differensiaalsein te gee (‘n aanvuilingslaagweerklank). ‘n Differensiaalsein dui die toestand en vordering van ‘n aanvuilingslaag op die membraanoppervlakte gedurende gebruik aan. Beide amplitude asook aankomstyd van differensiaalseine as funksies van gebruikstyd verskaf bruikbare kwantatiewe inligting, dws. Veranderings in die dikte en digtheid van ‘n aanvuilingslaag, op die aanvuilingsproses. ‘n Voorspellingsmodelleringprogram - ultrasonieseweerkaatsingsmodellering (Eng: ultrasonic reflection modeling, URM) is ontwikkel om die proses van ultrasoniese toetsing by die deponering van aanvuilingslae op membraanoppervlaktes beter te beskryf. Veranderings in die digtheid en dikte van die aanvuilingslaag teenvloei is verwant aan dikte en digtheid (saampersbaarheid). Die voorspelde resultate van aanvuilingslaagdeponering stem goed ooreen met die werklike UTDR-metings wat in MF en UF gemaak is. Bio-aanvuiling is suksesvol waargeneem deur UTDR in buisvormige UF membrane. Ultrasoniese frekwensiespektra kan dus as ‘n bykomende metode gebruik word vir die waarneming van aanvuiling op skeidingsmembrane.

Thesis advisor: David R. Burgess / Cytokinesis is the final step in cell division, culminating in the formation of two daughter cells from a single mother cell. Previous studies from our lab have shown that lipid rafts are dynamic during cytokinesis in sea urchin embryos, migrating into the ingressing cleavage furrow then moving back outwards towards the poles prior to abscission. Here, I quantitated the mobility of GM1, a ganglioside enriched in lipid rafts, using cholera toxin subunit B (CTB). Despite previous observations of raft movement during cell division, I have found lipid rafts to be immobile throughout the cell cycle. Lipid raft stability is dependent on the activity of myosin light chain kinase (MLCK), most likely due to the dramatic reorganization of actin filaments upon MLCK inhibition. While further investigating the immobility of lipid rafts during cytokinesis using confocal microscopy, I have found that new membrane is added to the cell poles during anaphase, causing the plasma membrane to expand coincident with the constriction of the contractile ring. This membrane addition is dependent on actin and astral microtubules and occurs significantly earlier during mitosis than membrane addition at the furrow. The membrane that is added at the polar regions is compositionally distinct from the original cell membrane in that it is devoid of GM1, a component of lipid rafts. I also found that Rab11 vesicles are trafficked to the polar plasma membrane during the time of this new membrane event, suggesting that the growth of the plasma membrane at the cell poles during cell division is not due to stretching as previously thought, but due to the addition of new membrane through exocytosis. / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Biology.

The mechanism of how pulsatile flow affects flux behaviour in crossflow micro-filtration was investigated. The effects of pulsatile flow were sub-divided into shear effects and backflushing effects. A servo-valve hydraulic piston pump was applied to generate pulsatile flows in the membrane module with particular waveforms. Four types of fluid pulsation with specific flow-rate and pressure waveforms were produced for experimental tests. Two parameters, /dVcf\dt/ maxand Pmin, were examined independently for their effect during pulsatile flow, which was estimated by comparing the cake resistance during steady flow and pulsatile flow at the same mean crossflow velocity, trans-membrane pressure and membrane resistance. Filtration tests for all the pulsatile flows with clean water confirmed that pulsatility only affects cake depositions. Without particles, no flux improvement was obtained. The results for the microfiltration of 0.5g/1 silica suspension showed that for pulsatile flows without backflushing (i.e. no negative transmembrane pressure peak), the fluid pulsation decreased cake resistance when the shear related parameter /dVcf\dt/max exceeded a critical value for each given waveform. When the instantaneous transmembrane pressure reached negative values, i.e. back-flushing occurred, the cake resistance was reduced for all pressure waves tested. Cake resistance was reduced more for more negative P min. With two of the waveforms tested, the cake resistance was almost completely eliminated. In contrast, the shear affected cake resistance reduction differently for each waveform. Comparing cake reduction results for different pulsatile waveforms, it was found that, for the square wave, the cake resistance reduction was higher for both shear and backflushing effect tests, while for the short spike waveform, the cake resistance reduction was lower. The flux waveforms were seen to follow the variations in transmembrane pressure. The flux response time was longer than the time required for the pressure changes, but was not dependent on the direction of the pressure change.

The membrane bioreactor (MBR) is becoming increasingly popular for wastewater treatment, mainly due to its capability of producing high quality effluent with a relatively small footprint. However, high plant maintenance and operating costs due to membrane fouling limit the wide spread application of MBRs. Membrane fouling generally depends on the interactions between the membrane and, the activated sludge mixed liquor, which in turn, are affected by the chosen operating conditions. The present research study aimed to explore the process performance and membrane fouling in the membrane enhanced biological phosphorus removal (MEBPR) process under different operating conditions by, (1) comparing two MEBPRs operated in parallel, one with constant inflow and another with a variable inflow, and by, (2) operating the MEBPRs with different solids retention times (SRT). On-line filtration experiments were conducted simultaneously in both MEBPR systems by using test membrane modules. From the transmembrane pressure (TMP) data of the test membrane modules, it was revealed that fouling propensities of the MEBPR mixed liquors were similar in both parallel reactors under the operating conditions applied, although the fouling propensity of the aerobic mixed liquors of both reactors increased when the SRT of the reactors was reduced. Routinely monitored reactor performance data suggest that an MEBPR process with a varying inflow (dynamic operating condition) performs similarly to an MEBPR process with steady operating conditions at SRTs of 10 days and 20 days. Mixed liquor characterization tests were conducted, including critical flux, capillary suction time (CST), time to filter (TTF) and, bound and soluble extracellular polymeric substances (EPS) were quantified, to evaluate their role on membrane fouling. The tests results suggest that the inflow variation in an MEBPR process did not make a significant difference in any of the measured parameters. With decreased SRT, an increase in the concentrations of EPS was observed, especially the bound protein, and the bound and soluble humic-like substances. This suggests that these components of activated sludge mixed liquors may be related to membrane fouling. No clear relationship was observed between membrane fouling and other measured parameters, including critical flux, normalized CST and normalized TTF.

Hydrophobic microporous membranes have been widely used in water and wastewater treatment by microfiltration, ultrafiltration and membrane distillation. Poly(vinylidene fluoride) (PVDF) materials are one of the most popular polymeric membrane materials because of their high mechanical strength, excellent thermal and chemical stabilities, and ease of fabrication into asymmetric hollow fiber membranes. In this work, specialty PVDF materials (Kynar 741, 761, 461, 2851, RC-10186 and RC10214) newly developed by Arkema Inc. were used to develop hollow fiber membranes via the dry/wet phase inversion. These materials were evaluated from thermodynamic and kinetic perspectives. The thermodynamic analysis was performed by measuring the cloud points of the PVDF solution systems. The experimental results showed that the thermodynamic stability of the PVDF solution system was affected by the type of polymer and the addition of additive (LiCl); and the effects of the additive (LiCl) depended on the type of polymer. The kinetic experiments were carried out by determining the solvent evaporation rate in the “dry” step and the small molecules (solvent, additive) diffusion rate in the “wet step”. Solvent evaporation in the early stage could be expressed quantitatively. In the “wet” step, the concentrations of solvent and additive had a linear relationship with respect to the square root of time (t1/2) at the early stage of polymer precipitation, indicating that the mass-transfer for solvent-nonsolvent exchange and additive LiCl leaching was diffusion controlled. The kinetic analysis also showed that the slope of this linear relationship could be used as an index to evaluate the polymer precipitation rate (solvent-nonsolvent exchange rate and LiCl leaching rate). The extrusion of hollow fiber membranes was explored, and the effects of various fabrication parameters (such as dope extrusion rate, internal coagulant flow velocity and take-up speed) on the structure and morphology of the hollow fiber membranes were also investigated. The properties of the hollow fiber membranes were characterized by gas permeation method and gas-liquid displacement method. The morphology of the hollow fibers was examined by scanning electron microscope (SEM). It was found that Kynar 741 and 2851 were the best among the PVDF polymers studied here for the fabrication of hollow fiber membranes. In order to reduce the problems associated with the hydrophobicity of PVDF on hollow fiber module assembly, such as tubesheet leaking through problem and fouling problem, amine treatment was used to modify PVDF membranes. Contact angle measurements and filtration experiments were performed. Fourier-transform infrared (FT-IR) spectroscopy and energy dispersive x-ray analysis (EDAX) were used to analyze the modified polymer. It was revealed that the hydrophilicity of the modified membrane was improved by amine treatment and conjugated C=C and C=O double bonds appeared along the polymer backbone of modified PVDF. Hollow fiber membranes fabricated from Kynar 741 were tested for water desalination by vacuum membrane distillation (VMD). An increase in temperature would increase the water productivity remarkably. Concentration polarization occurred in desalination, and its effect on VMD could be reduced by increasing the feed flowrate. The permeate pressure build-up was also investigated by experiments and parametric analysis, and the results will be important to the design of hollow fiber modules for VMD in water desalination.

Hydrophobic microporous membranes have been widely used in water and wastewater treatment by microfiltration, ultrafiltration and membrane distillation. Poly(vinylidene fluoride) (PVDF) materials are one of the most popular polymeric membrane materials because of their high mechanical strength, excellent thermal and chemical stabilities, and ease of fabrication into asymmetric hollow fiber membranes. In this work, specialty PVDF materials (Kynar 741, 761, 461, 2851, RC-10186 and RC10214) newly developed by Arkema Inc. were used to develop hollow fiber membranes via the dry/wet phase inversion. These materials were evaluated from thermodynamic and kinetic perspectives. The thermodynamic analysis was performed by measuring the cloud points of the PVDF solution systems. The experimental results showed that the thermodynamic stability of the PVDF solution system was affected by the type of polymer and the addition of additive (LiCl); and the effects of the additive (LiCl) depended on the type of polymer. The kinetic experiments were carried out by determining the solvent evaporation rate in the “dry” step and the small molecules (solvent, additive) diffusion rate in the “wet step”. Solvent evaporation in the early stage could be expressed quantitatively. In the “wet” step, the concentrations of solvent and additive had a linear relationship with respect to the square root of time (t1/2) at the early stage of polymer precipitation, indicating that the mass-transfer for solvent-nonsolvent exchange and additive LiCl leaching was diffusion controlled. The kinetic analysis also showed that the slope of this linear relationship could be used as an index to evaluate the polymer precipitation rate (solvent-nonsolvent exchange rate and LiCl leaching rate). The extrusion of hollow fiber membranes was explored, and the effects of various fabrication parameters (such as dope extrusion rate, internal coagulant flow velocity and take-up speed) on the structure and morphology of the hollow fiber membranes were also investigated. The properties of the hollow fiber membranes were characterized by gas permeation method and gas-liquid displacement method. The morphology of the hollow fibers was examined by scanning electron microscope (SEM). It was found that Kynar 741 and 2851 were the best among the PVDF polymers studied here for the fabrication of hollow fiber membranes. In order to reduce the problems associated with the hydrophobicity of PVDF on hollow fiber module assembly, such as tubesheet leaking through problem and fouling problem, amine treatment was used to modify PVDF membranes. Contact angle measurements and filtration experiments were performed. Fourier-transform infrared (FT-IR) spectroscopy and energy dispersive x-ray analysis (EDAX) were used to analyze the modified polymer. It was revealed that the hydrophilicity of the modified membrane was improved by amine treatment and conjugated C=C and C=O double bonds appeared along the polymer backbone of modified PVDF. Hollow fiber membranes fabricated from Kynar 741 were tested for water desalination by vacuum membrane distillation (VMD). An increase in temperature would increase the water productivity remarkably. Concentration polarization occurred in desalination, and its effect on VMD could be reduced by increasing the feed flowrate. The permeate pressure build-up was also investigated by experiments and parametric analysis, and the results will be important to the design of hollow fiber modules for VMD in water desalination.

The membrane bioreactor (MBR) is becoming increasingly popular for wastewater treatment, mainly due to its capability of producing high quality effluent with a relatively small footprint. However, high plant maintenance and operating costs due to membrane fouling limit the wide spread application of MBRs. Membrane fouling generally depends on the interactions between the membrane and, the activated sludge mixed liquor, which in turn, are affected by the chosen operating conditions. The present research study aimed to explore the process performance and membrane fouling in the membrane enhanced biological phosphorus removal (MEBPR) process under different operating conditions by, (1) comparing two MEBPRs operated in parallel, one with constant inflow and another with a variable inflow, and by, (2) operating the MEBPRs with different solids retention times (SRT). On-line filtration experiments were conducted simultaneously in both MEBPR systems by using test membrane modules. From the transmembrane pressure (TMP) data of the test membrane modules, it was revealed that fouling propensities of the MEBPR mixed liquors were similar in both parallel reactors under the operating conditions applied, although the fouling propensity of the aerobic mixed liquors of both reactors increased when the SRT of the reactors was reduced. Routinely monitored reactor performance data suggest that an MEBPR process with a varying inflow (dynamic operating condition) performs similarly to an MEBPR process with steady operating conditions at SRTs of 10 days and 20 days. Mixed liquor characterization tests were conducted, including critical flux, capillary suction time (CST), time to filter (TTF) and, bound and soluble extracellular polymeric substances (EPS) were quantified, to evaluate their role on membrane fouling. The tests results suggest that the inflow variation in an MEBPR process did not make a significant difference in any of the measured parameters. With decreased SRT, an increase in the concentrations of EPS was observed, especially the bound protein, and the bound and soluble humic-like substances. This suggests that these components of activated sludge mixed liquors may be related to membrane fouling. No clear relationship was observed between membrane fouling and other measured parameters, including critical flux, normalized CST and normalized TTF.