Application of low pressure membranes in drinking water treatment, including both microfiltration (MF) and ultrafiltration (UF), have witnessed a rapid increase in the past decades. Low pressure membranes are considered a good technology in retrofitting existing conventional drinking water treatment plants or in newly constructed plants to meet the stringent regulations for drinking water treatment that aim at preventing health risks of waterborne diseases. Enteric viruses are one of the major types of waterborne pathogens, and they can be commonly found and are persistent in the environment. Both the United States and Canada require a 99.99% (4-log) removal of viruses during the drinking water treatment train. Unlike MF membranes, UF membranes have a very good potential for removing enteric viruses from the water due to their smaller pores comparable to the size of viruses. Drinking water regulations/guidelines in both the United States and Canada do not grant UF membranes any removal credit for viruses by default; however they have the provision that, in certain cases, virus removal credit may be granted based on pilot scale challenge testing. A better understanding of the interaction between the UF membranes and virus rejection can help to establish a removal credit for UF membranes. An essential part of this will be the effect of the membrane operation on the rejection of viruses to determine if UF membranes can offer a consistent removal of viruses. Membrane fouling is one of the major problems in membrane operation and it can affect the rejection characteristics of the membrane and improve its performance. The aim of this study was to investigate the removal of virus surrogates (MS2 and φX174 bacteriophage) using a commercial UF membrane under different conditions, to obtain information about the removal mechanisms of viruses. The experimental filtration unit was designed to have similar conditions like the full scale membrane treatment plants. The UF membrane used in this study provided very good removal of both MS2 and φX174 bacteriophage. The obtained results were consistent and in agreement with the expected removals based on the membrane characterization results and types of virus surrogate. As part of this work, a detailed study to improve methods for characterizing the pore size distribution of membranes was conducted. In the second part of the study, two different types of surface waters were used to study the effect of membrane fouling on virus removal. It was found that mainly hydraulically irreversible fouling could significantly improve the virus removal by UF membranes. Different cleaning regimes that are used in treatment plants had varying effects on virus removal. After maintenance cleaning, virus removal remained higher than that of clean membranes, and only chemical cleaning was effective for completely removing membrane foulants and returning virus removal back to base levels. Advanced analytical techniques were used to define the nature of the fouling layer on the membrane surface and how the foulants affected the rejection of viruses. Finally, our study showed that UF membranes are a robust treatment technology for removing different types of enteric virus surrogates from water under different operational conditions. Close monitoring of the UF unit performance and direct integrity testing can possibly detect membrane problems that can affect the rejection of viruses. Based on the virus physical characteristics and a detailed study of the membrane surface characteristics, especially the pore size distribution of the membrane, the removal of the specific virus can be closely estimated.

Ziel der Arbeit ist die Beschreibung des Membranverhaltens bzw. der Membraneigenschaften bei der Regeneration von Extraktionsmitteln der Metallextraktion durch Trennung von beladenen und unbeladenen Extraktionsmitteln mittels Ultrafiltration. Dazu wurden die Trennleistungen als Funktion von Druck, Temperatur und Solventzusammensetzung für verschiedene Membranmaterialien und -typen untersucht. Anhand von Sorptionsversuchen konnte die Löslichkeit der Komponenten der organischen Phase in den verschiedenen Polymermatrizen von Membranen aus regenerierter Cellulose bzw. Polyethersulfon und die adsorptive Gelschichtbildung als Funktion der Solventzusammensetzung, der Temperatur und des Membranmaterials aufgezeigt werden. Der Einfluss der Sorption, des Quellens und Kompaktierens auf das Materialverhalten konnte mittels einer Hochdruckmikrowaage und eines Laserscanner-Messstandes ermittelt werden. Die durch Veresterung und Wasserstoffbrückenbindung entstehende Gelschicht auf der Membranoberfläche, die letztendlich für die Rückgewinnung von unbeladenem Extraktionsmittel ausschlaggebend ist, kann mit Hilfe der Röntgenphotoelektronenspektroskopie, Rasterelektronen- und Rasterkraftmikroskopie nachgewiesen werden.

The applications of membrane technologies have dramatically increased during the last few decades due to technology improvement and cost reduction. Membrane applications can be found in water and wastewater treatment, pharmaceutical industry, chemical processing industry, food industry, etc. However, the membrane technology faces two major challenges: membrane fouling and membrane lifetime. During the membrane filtration process, membrane fouling caused by natural organic matter (NOM) is an inevitable phenomenon, and physical cleaning or chemical cleaning are required for recovering the performance of membrane. As a result of these cleaning processes, membrane lifetime is shortened. For this reason, it is necessary to improve membrane's fouling resistance and lifetime in order to apply membrane technology in large-scale facilities. This dissertation focuses on improving the fouling resistance and flux performance of polyvinyl chloride (PVC) membrane and polyvinylidene fluoride (PVDF) membrane. Specifically, it is comprised of four parts. First, I prepared PVC membranes by adding different amounts of amphiphilic copolymer (Pluronic F 127) into PVC casting solutions. I optimized the performance of PVC membranes by changing the amount of Pluronic F127 used in the casting solution. The results show that with the increase of Pluronic F 127 content, the pore size and pore density both decrease. Moreover, the membrane surface becomes more hydrophilic as indicated by lower contact angles. In addition, the PVC membrane exhibits remarkable antifouling characteristics after adding Pluronic F 127. Second, I synthesized PVDF membranes by adding PVDF graft poly(ethylene glycol) methyl ether methacrylate (PEGMA) (PVDF-g-PEGMA) as additive in casting solutions via the phase inversion method. The synthesized PVDF membranes have unique pillar-like structures on surfaces, which gives the PVDF membrane a defect-free feature and allows it to generate high flux under low pressure. Third, I investigated the forming mechanism of the pillar-like structure from aspects of solvent and additive. Finally, I investigated the influence of PEGMA dose on the performance of PVDF membranes. I changed the amount of PEGMA used in the casting solution and compared the performance of the synthesized PVDF membranes. To summarize, this dissertation has deepened our understanding of how to improve the fouling resistance and flux performance of PVC membranes and PVDF membranes by using amphiphilic copolymer. In addition, the PVDF membrane I synthesized has unique pillar-like structures that give it defect-free and high flux properties. Overall, the results of this study provide valuable information for PVC and PVDF membrane synthesis for large-scale production.

Chlorine is the most widely used disinfectant for drinking water treatment. Chlorine canreact with natural organic matter (NOM) in water sources resulting in the formation of potentially carcinogenic disinfection by-products (DBPs). The most common DBPs measured in chlorinated drinking water distribution systems are trihalomethanes (THMs) and haloacetic acids (HAAs). In 2005, the City of Kamloops, British Columbia upgraded the drinking water treatment system to ultrafiltration membrane treatment. The objective of this study was to determine the extent to which upgrades to a drinking water treatment system, specifically, implementation of an ultrafiltration treatment process, impacted DBP formation within a distribution system. This study used a two-phase research approach. Phase I of the study was a distribution system monitoring program that collected water samples and physical and chemical information using data loggers at five sampling sites within the distribution system. Phase II of the study used bench-scale simulations that modeled DBP formation using a flow-through reactor system, the material-specific simulated distribution system (MS-SDS), constructed of pipe material resurrected from the City of Kamloops distribution system. Phase I results suggested that implementation of the ultrafiltration treatment process and accompanying treatment system upgrade was not effective at reducing the concentration of DBPs delivered to consumers. Concentrations of THMs remained relatively constant at sampling sites, while concentrations of HAAs increased following implementation of the ultrafiltration treatment process. The increase in HAA formation was likely due to an increase in retention time of the water within the distribution system following implementation of the ultrafiltration treatment process, rather than due to the treatment process itself. The results of this study are consistent with previous work on South Thompson River water DBP precursors, which suggested that THM and HAA precursors of this source water are small and hydrophilic, and therefore cannot be removed by ultrafiltration processes. Phase II results showed that the MS-SDS was more representative of distribution system c onditions than traditional glass bottles to estimate DBP formation. It is recommended that the MS-SDS be used in parallel with a simultaneous distribution system monitoring program to estimate distribution system retention times from THM and HAA concentrations.

Oxidation plays an important role in the basic processes of life, such as the production of energy and phagocytosis employed by the immune system. However, when an imbalance between oxidants and antioxidants exists in vivo, oxidation can become uncontrolled and result in diseases such as arthritis, cancer, artherosclerosis, and Alzheimer’s Disease. Dietary antioxidants including polyphenolic compounds, proteins, and peptides have been identified as being physiologically functional foods capable of contributing to the restoration of this oxidant-antioxidant balance. The objective of this study was to explore the production of antioxidant soy peptides from a commercially available soy protein isolate (SPI) by enzymatic hydrolysis in a process similar to that occurring in the human digestive tract. In this study Archer-Daniels Midland SPI PRO-FAM 974 was used as a raw material for the production of antioxidant soy peptides. The digestion consisted of enzymatic digestion of the SPI (3.12 wt %) with pepsin (37ºC, pH 1.5) and/or pancreatin (40ºC, pH 7.8) either individually or sequentially. The enzyme concentration and digestion time for each enzyme was optimized using a 2^4 factorial experimental design to produce the greatest concentration of peptides quantified in PheGly equivalents by the OPA assay. A maximum peptide concentration of approximately 65 mM PheGly equivalents was achieved in the follow-up digests resulting from this factorial design model, using pepsin (0.15 g/L, 15 minutes) and pancreatin (4.5 g/L, 120 minutes) sequentially to digest the SPI. Fractionation of the peptides by sequential dead-end membrane ultrafiltration with molecular weight cut-offs (MWCO) of 3 kDa and 1 kDa was performed to produce peptide fractions with increased antioxidant capacity. The permeate flux as a function of time was fit to empirical models, revealing that the membrane fouling resulting in the permeate flux decline is largely reversible and most likely the result of cake filtration. Antioxidant capacity was quantified by the DPPH, FCR, and ORAC assays to determine the electron-donating and proton-donating capacities of the soy peptides. The electron-donating DPPH assay was not suitable to quantify the antioxidant capacity of the soy peptides due to poor peptide solubility in the assay media and sensitivity. The electron-donating FCR assay and the proton-donating ORAC assay were used to distinguish between the ultrafiltration and digestion conditions employed to produce the soy peptides and the antioxidant capacity was quantified in equivalence to the standard antioxidant Trolox. The soy peptide fraction with the greatest antioxidant capacity was produced by enzymatic digestion with pancreatin (4.5 g/L, 120 minutes) alone and had a molecular weight cut-off of between 3 kDa and 1 kDa. This fraction had an equivalent antioxidant capacity of approximately 190 mg Trolox/g sample in the ORAC assay and approximately 180 mg Trolox/g sample in the FCR assay. A preliminary linear model for the optimum digestion and ultrafiltration conditions for the production of antioxidant peptides with the greatest ORAC antioxidant capacity was also developed. The model includes a positive pancreatin digestion time term and a negative pepsin digestion time term. No ultrafiltration terms were found to be significant in this preliminary model, but a large constant term persisted. In conclusion, the enzymatic digestion of commercially available SPI with pancreatin and fractionated by ultrafiltration successfully produced a soy peptide fraction with increased antioxidant capacity.

Membrane filtration is growing in popularity as a viable technology for drinking water treatment to meet high demand and regulatory requirements. While many improvements have been made to the technology in the past decade, fouling continues to be one of the major operational challenges associated with membranes as it increases operating costs and reduces membrane life. Fouling control typically requires some form of pre-treatment. Biofiltration is a ???green??? technique that can minimize chemical usage and waste during water treatment and is a relatively new application as a pre-treatment for membranes. Proteins and polysaccharides (biopolymers) have been found to contribute most to fouling of low pressure polymeric membranes. Biofiltration has recently been demonstrated as an effective pre-treatment method for reducing biopolymer-associated fouling of this type of membrane (Hall?? et al., 2009). Given that the concentration and composition of organic matter in water is variable, there is an opportunity to explore the applicability of this robust technology for different water types. The primary goals of this research were to assess the effectiveness of direct biofiltration in minimizing ultrafiltration polymeric (PVDF) membrane fouling and at the same time evaluate the biofilter development, biofilter performance based on organics removal potential, and the effect of phosphorus addition (as a nutrient) to the biofilter influent. A pilot-scale treatment train was constructed at the Technology Demonstration Facility at the Walkerton Clean Water Centre. It included two parallel dual media (sand/anthracite) biological filters (preceded by roughing filters), followed by an ultrafiltration membrane unit. Experiments were conducted using water from the Saugeen River (Ontario, Canada) whose primary form of carbon is humic material. The biofilters were allowed to acclimate and biofilter performance and organics removal were tested over a fourteen month period, the last four months of which were dedicated to phosphorus enhancement experiments. The membrane fouling experiments started seven months following the start-up of the biofilters, after confirmation of steady-state operation. Biofilter water samples were analyzed for natural organic matter constituents along with other water quality parameters, and biomass quantity and activity in the media were measured. Biomass activity in the biofilter media and biopolymer removal through the biofilter indicated a rapid acclimation period, and also demonstrated similar performance of the parallel biofilters during start-up and steady-state operation. The biofilters achieved 21% removal of the biopolymers on average following acclimation, while reduction of the humic fractions was not observed. A linear relationship between biopolymer removal and its concentration in the river water was observed (first-order process). Membrane fouling experiments were conducted using both untreated and biofiltered river water. The fouling rates were computed by monitoring changes in transmembrane pressure over time. Analysis of the samples with liquid chromatography-organic carbon detection confirmed the significant contribution of biopolymers to irreversible and reversible membrane fouling rates even when only present at low concentrations. During the phosphorus enhancement phase, two different phosphorus doses were fed into the influent of one of the parallel biofilters in order to achieve a target C:N:P ratio of roughly 100:10:1. Although initially (first month of the dosing period) an increase in the removal of dissolved organic carbon and ultraviolet-absorbance was observed in the phosphorus-enhanced biofilter, this was not sustained. Phosphorus addition did not affect biopolymer removal or biomass quantity and activity in the biofilter, and the membrane fouling experiments during this period did not show any significant effect of phosphorus addition.

Application of low pressure membranes in drinking water treatment, including both microfiltration (MF) and ultrafiltration (UF), have witnessed a rapid increase in the past decades. Low pressure membranes are considered a good technology in retrofitting existing conventional drinking water treatment plants or in newly constructed plants to meet the stringent regulations for drinking water treatment that aim at preventing health risks of waterborne diseases. Enteric viruses are one of the major types of waterborne pathogens, and they can be commonly found and are persistent in the environment. Both the United States and Canada require a 99.99% (4-log) removal of viruses during the drinking water treatment train. Unlike MF membranes, UF membranes have a very good potential for removing enteric viruses from the water due to their smaller pores comparable to the size of viruses. Drinking water regulations/guidelines in both the United States and Canada do not grant UF membranes any removal credit for viruses by default; however they have the provision that, in certain cases, virus removal credit may be granted based on pilot scale challenge testing. A better understanding of the interaction between the UF membranes and virus rejection can help to establish a removal credit for UF membranes. An essential part of this will be the effect of the membrane operation on the rejection of viruses to determine if UF membranes can offer a consistent removal of viruses. Membrane fouling is one of the major problems in membrane operation and it can affect the rejection characteristics of the membrane and improve its performance. The aim of this study was to investigate the removal of virus surrogates (MS2 and φX174 bacteriophage) using a commercial UF membrane under different conditions, to obtain information about the removal mechanisms of viruses. The experimental filtration unit was designed to have similar conditions like the full scale membrane treatment plants. The UF membrane used in this study provided very good removal of both MS2 and φX174 bacteriophage. The obtained results were consistent and in agreement with the expected removals based on the membrane characterization results and types of virus surrogate. As part of this work, a detailed study to improve methods for characterizing the pore size distribution of membranes was conducted. In the second part of the study, two different types of surface waters were used to study the effect of membrane fouling on virus removal. It was found that mainly hydraulically irreversible fouling could significantly improve the virus removal by UF membranes. Different cleaning regimes that are used in treatment plants had varying effects on virus removal. After maintenance cleaning, virus removal remained higher than that of clean membranes, and only chemical cleaning was effective for completely removing membrane foulants and returning virus removal back to base levels. Advanced analytical techniques were used to define the nature of the fouling layer on the membrane surface and how the foulants affected the rejection of viruses. Finally, our study showed that UF membranes are a robust treatment technology for removing different types of enteric virus surrogates from water under different operational conditions. Close monitoring of the UF unit performance and direct integrity testing can possibly detect membrane problems that can affect the rejection of viruses. Based on the virus physical characteristics and a detailed study of the membrane surface characteristics, especially the pore size distribution of the membrane, the removal of the specific virus can be closely estimated.

Chlorine is the most widely used disinfectant for drinking water treatment. Chlorine canreact with natural organic matter (NOM) in water sources resulting in the formation of potentially carcinogenic disinfection by-products (DBPs). The most common DBPs measured in chlorinated drinking water distribution systems are trihalomethanes (THMs) and haloacetic acids (HAAs). In 2005, the City of Kamloops, British Columbia upgraded the drinking water treatment system to ultrafiltration membrane treatment. The objective of this study was to determine the extent to which upgrades to a drinking water treatment system, specifically, implementation of an ultrafiltration treatment process, impacted DBP formation within a distribution system. This study used a two-phase research approach. Phase I of the study was a distribution system monitoring program that collected water samples and physical and chemical information using data loggers at five sampling sites within the distribution system. Phase II of the study used bench-scale simulations that modeled DBP formation using a flow-through reactor system, the material-specific simulated distribution system (MS-SDS), constructed of pipe material resurrected from the City of Kamloops distribution system. Phase I results suggested that implementation of the ultrafiltration treatment process and accompanying treatment system upgrade was not effective at reducing the concentration of DBPs delivered to consumers. Concentrations of THMs remained relatively constant at sampling sites, while concentrations of HAAs increased following implementation of the ultrafiltration treatment process. The increase in HAA formation was likely due to an increase in retention time of the water within the distribution system following implementation of the ultrafiltration treatment process, rather than due to the treatment process itself. The results of this study are consistent with previous work on South Thompson River water DBP precursors, which suggested that THM and HAA precursors of this source water are small and hydrophilic, and therefore cannot be removed by ultrafiltration processes. Phase II results showed that the MS-SDS was more representative of distribution system c onditions than traditional glass bottles to estimate DBP formation. It is recommended that the MS-SDS be used in parallel with a simultaneous distribution system monitoring program to estimate distribution system retention times from THM and HAA concentrations.

Membrane processes have found increasing industrial applications worldwide. For membrane processes to deliver their desired performances and mitigate the effect of disturbances, automatic controllers must be installed. Before the installation of controllers, operability analysis is a crucial step to evaluate how well the processes can be controlled, and to determine how process design can be improved for better control. However, existing applications of operability analysis in membrane processes are limited. This thesis extends the application of operability analysis to a multiple-stage membrane process, exemplified by a detailed case study of a 12-stage industrial whey ultrafiltration (UF) process. Process dynamic models are determined to describe the transient behaviour of process performance caused by disturbances and long-term fouling. Steady-state nonlinear operability analysis is conducted to identify inherent limitations of the process. Using the process dynamic models, dynamic operability analysis is performed to determine the effects of dynamic behaviour on process and controller design. Steady-state operability analysis shows that the whey UF process is not able to mitigate the effects of high concentrations of true protein in the fresh whey feed. The ability of the process to mitigate the effects of disturbances is also adversely affected by long-term membrane fouling. Mid-run washing is therefore necessary to restore control performance after long periods of operation. Besides demonstrating the adverse effects of long-term membrane fouling on operability, dynamic operability analysis identifies the manipulated variables that can deliver the best control performance. It also indicates that control performance can be improved by installing equipment (e.g. buffer tanks) upstream of the process. Dynamic operability analysis shows that recycling of the retentate stream has a profound effect on the plant-wide dynamics and reduces significantly the achievable speed of process response under automatic control. However, retentate recycling is essential during operation to minimize membrane fouling. Although reducing the number of stages in the whey UF process can improve the achievable speed of process response under automatic control, process performance will fluctuate significantly from its desired level. A trade-off therefore exists between process performance and control performance that should be addressed during process and controller design.

Membrane processes are increasingly used in water treatment. Experiments were performed using stirred cell equipment, polymeric membranes and synthetic surface water containing natural organics, inorganic colloids and their aggregates, and cations. All processes could remove a significant amount of natural organics. Pretreatment with ferric chloride was required to achieve significant organic removal with MF and high MWCO UF. Additionally, fouling mechanisms for the three processes were investigated. Crucial parameters were aggregate characteristics (fractal structure, stability, organic-colloid interactions), solubility of organics and calcium, and hydrodynamics. In MF, fouling by pore plugging was most severe. Variations in solution chemistry changed the aggregation state of the colloids and/or natural organic matter and dramatically affected rejection and fouling behaviour. UF membrane fouling was mainly influenced by pore adsorption and could improve natural organics rejection significantly. Coagulant addition shifted fouling mechanism from pore adsorption to cake formation. Aggregate structure was most significant for flux decline. In NF, rejection of natural organics involved both size and charge exclusion. Fouling was caused by precipitation of a calcium-organic complex. Fouling could be avoided by pretreatment with metal salt coagulants. Thorough chemical characterisation of the organics used demonstrated that only size and aromaticity can be related to fouling. The study is concluded with a process comparison based on a water quality parameter and a cost comparison. Treatment cost of microfiltration with chemical pretreatment was similar to that of nanofiltration at a comparable natural organics rejection.