Natural organic matter (NOM), a complex mixture of organic compounds, influences drinking water quality and water treatment processes. The presence of NOM is unaesthetic in terms of colour, taste and odour, and may lead to the production of potentially carcinogenic disinfection by-products (DBPs), as well as biofilm formation in drinking water distribution systems. Some NOM removal processes such as coagulation, magnetic ion exchange resin (MIEXTM) and membrane filtration produce sludge and residuals. These concentrated NOM-containing sludges from alum precipitation, membrane treatment plants and MIEX regeneration must therefore be treated prior to disposal. The white-rot fungi possess a non-specific extracellular oxidative enzyme system composed of lignin peroxidase (LiP), manganese-dependent peroxidase (MnP) and laccase (Lac) that allows these organisms to mineralise lignin and a broad range of intractable aromatic xenobiotics. Rojek (2003) has shown the capabi lity of Phanerochaete chrysosporium ATCC 34541 to remove 40-50% NOM from solution, however, this was found to be mainly due to adsorption and to be a partially metabolically linked activity. Consequently, the bioremediation of NOM wastes by selected white-rot fungi was further investigated in the present study. The P. chrysosporium seemed to preferentially remove the very hydrophobic acid (VHA) fraction, and so was most effective for a NOM preparation with a high proportion of hydrophobic content (and so high in colour and specific UV absorbance (SUVA)). The extent of NOM decolourisation by P. chrysosporium in three growth media with different C:N ratios followed the trends: Waksman (C:N = 6) > Fahy (C:N = 76) > Fujita medium (C:N = 114), such that the lower the C:N ratio, the greater NOM removal. This was consistent with the findings of Rojek (2003), who used a different NOM preparation and demonstrated that the removal of NOM increased with decreased C:N ratio (1.58-15.81). As removals of NOM with P. c hrysosporium ATCC 34541 were low, and little biodegradation occurred, this organism was compared with P. chrysosporium strain ATCC 24725, Trametes versicolor ATCC 7731, and three strains of yeast (Saccharomyces species arbitrarily denoted 1, 2 and 3). T. versicolor gave the greatest removal (59%) which was attributed largely to degradation, whereas the NOM removal by the two strains of P. chrysosporium (37%) and the yeast was predominantly due to adsorption as indicated by the deep brown colouration of the biomass. Saccharomyces sp. 1, 2 and 3 removed 12%, 61% and 23% of the colour, respectively. Although Saccharomyces sp. 2 had similar high colour reduction to T. versicolor, the specific removal values differed markedly: 0.055 compared to 0.089 mg NOM/mg biomass, respectively. The low level of the ligninolytic enzymes secreted by both strains of P. chrysosporium corresponded with the low degree of NOM removal by biodegradation as shown by high performance size exclusion chromatography (HPSEC). The high NOM removal attained by T. versicolor was attributed to the activities of the ligninolytic enzymes, especially laccase. The NOM removal was attributed to the breakdown of the high molecular weight compounds to form a pool of low molecular weight materials, which were then most likely utilised by the T. versicolor. Growth of T. versicolor cultures at 36oC caused inhibition or denaturation of the activity of the phenoloxidase enzymes compared to those grown at 30oC. The low activity of LiP in both cultures suggested that this enzyme may not play much of a role in NOM removal. The higher levels of MnP and Lac activities at 30oC were responsible for the greater NOM removal (73% vs. 59%) and thus the cleavage of aromatic rings, conjugated and C-Cβ αbonds in phenolic moieties, as well as catalysing alkyl-aryl cleavage in the NOM structures. T. versicolor cultured in Waksman medium with higher initial glucose (5 g/L cf. 2 g/L) led to lower ligninolytic enzyme activities and a lower degree of NOM removal (25% less colour reduction), probably due to preferential use of glucose over NOM as carbon source. NOM removal (mg removed) increased linearly with NOM concentration up to 600 mg C/L (62 mg (A446); 31 mg (A254)), above which removal decreased markedly. This trend coincided with increasing total ligninolytic enzyme activity, where the level of Lac increased up to 600 mg C/L NOM although MnP decreased gradually across the range while LiP was only detected for 100 and 300 mg C/L NOM. Hence, the removal of NOM from solution by T. versicolor was associated with high oxidative enzyme activity, particularly of laccase. Laccase was the major extracellular enzyme secreted by T. versicolor and by deduction, played a major role in NOM removal. The optimum temperature for Lac activity secreted by T. versicolor cultured in Waksman medium supplemented with 4.5 g/L wheat bran plus 0.5% Tween 80 was determined to be 50oC. The optimum pH for the Lac activity for guaiacol and NOM was identified as pH 4.0-4.5. Although the optimum enzyme activity occurred at 50oC, 30oC was recommended for enzymatic removal of NOM as the phenoloxidase enzyme activity may be denatured if the NOM removal process were considered to run for long period at high temperature. Although agitation led to apparent enzyme denaturation, fermentations with continuous agitation promoted enzyme activity faster than those with occasional agitation (agitated every 6 hours for 30 minutes at 130 rpm and 30oC) as it provides better mass transfer. However, it seemed that continuous agitation had an adverse effect on the fungal growth and enzyme production over extended fermentation periods. Addition of 4.5 g/L wheat bran to modified Waksman medium in the absence of NOM led to high production of Lac activity compared with LiP and MnP activities, showing its great potential as a laccase inducer. Addition of Tween 80 alone to the cultures led to a small improvement in Lac activity; however, with the presence of wheat bran it caused marked increases in LiP, MnP and Lac activit ies. When NOM was added to cultures of T. versicolor with the two supplements, it led to markedly reduced Lac activity, but increased LiP and MnP activities, and no improvement in NOM removal compared with the cultures in the absence of supplements (12 mg (or 61%) cf. 15 mg (or 73%) for 100 mg C/L after corrected for colour from and adsorption by wheat bran).

Multiple metal-gill modelling based on the toxic unit concept suggests that metals with the same toxic actions (e.g. Pb and Cd interacting at Ca-gill channels) will exhibit strictly additive binding at the gills of fish if the concentrations of the two metals sum to one toxic unit. Due to the non-linear nature in which metals bind to fish gills, the metal mixture will be more than additive below one toxic unit and less than additive above one toxic unit. This research tested the models by exposing rainbow trout to mixtures of Cd and Pb to investigate the metal-gill binding of these two metals when present in mixtures with fish. The relationship between Cd and Pb in mixtures was also investigated when natural organic matter (NOM) was added to the treatment solutions. Juvenile rainbow trout (5 g) were exposed to equal mixtures of Cd and Pb at 0.75, 1.5, 2.25 and 3.0 µM each. The high gill-Pb accumulation in relation to gill-Cd was unexpected and suggested an additional gill-binding site for Pb aside from the apical Ca channels on the gill. 96 h toxicity experiments revealed that Cd and Pb in mixtures were more toxic than either Cd or Pb alone. The bioaccumulation and partitioning of Cd and Pb within the body of 50 g rainbow trout was investigated when these fish were exposed to mixtures of Cd and Pb. The accumulation of metals within the trout body did not change between the single metal and mixture exposures. To investigate how Pb affects Cd binding to fish gills, and how these metals exert toxicity when present in mixtures, trout (2 g) were exposed to a range of Cd concentrations (0.75, 1.5, 2.25 and 3.0 µM) while maintaining constant Pb concentrations over the same concentration range. Gill binding results revealed that Pb reduced or inhibited gill-Cd binding. With the addition of NOM, this inhibition was lost. LT50 results for fish exposed to metal mixtures for 96 h revealed that without NOM, the mixture toxicity was dependent on Pb concentration. With the addition of NOM, mixture toxicity decreased with increasing Pb.

Multiple metal-gill modelling based on the toxic unit concept suggests that metals with the same toxic actions (e.g. Pb and Cd interacting at Ca-gill channels) will exhibit strictly additive binding at the gills of fish if the concentrations of the two metals sum to one toxic unit. Due to the non-linear nature in which metals bind to fish gills, the metal mixture will be more than additive below one toxic unit and less than additive above one toxic unit. This research tested the models by exposing rainbow trout to mixtures of Cd and Pb to investigate the metal-gill binding of these two metals when present in mixtures with fish. The relationship between Cd and Pb in mixtures was also investigated when natural organic matter (NOM) was added to the treatment solutions. Juvenile rainbow trout (5 g) were exposed to equal mixtures of Cd and Pb at 0.75, 1.5, 2.25 and 3.0 µM each. The high gill-Pb accumulation in relation to gill-Cd was unexpected and suggested an additional gill-binding site for Pb aside from the apical Ca channels on the gill. 96 h toxicity experiments revealed that Cd and Pb in mixtures were more toxic than either Cd or Pb alone. The bioaccumulation and partitioning of Cd and Pb within the body of 50 g rainbow trout was investigated when these fish were exposed to mixtures of Cd and Pb. The accumulation of metals within the trout body did not change between the single metal and mixture exposures. To investigate how Pb affects Cd binding to fish gills, and how these metals exert toxicity when present in mixtures, trout (2 g) were exposed to a range of Cd concentrations (0.75, 1.5, 2.25 and 3.0 µM) while maintaining constant Pb concentrations over the same concentration range. Gill binding results revealed that Pb reduced or inhibited gill-Cd binding. With the addition of NOM, this inhibition was lost. LT50 results for fish exposed to metal mixtures for 96 h revealed that without NOM, the mixture toxicity was dependent on Pb concentration. With the addition of NOM, mixture toxicity decreased with increasing Pb.

Some community water systems using sources containing elevated levels of fluoride, in the United States and worldwide, struggle to treat their drinking water to healthy fluoride concentrations. Many treatment plants in the U.S. currently use aluminum based salts, such as aluminum sulfate and polyaluminium chloride, as coagulants during conventional treatment for removal of particles from drinking water sources. Moreover, enhanced aluminum sulfate, or alum, coagulation requires higher concentrations of aluminum added to the process and has been shown to be effective for removal of disinfectant byproduct precursors, i.e., natural organic matter (NOM). The presence of fluoride may interfere with the formation of aluminum hydroxide precipitates, and interrelationships among NOM, aluminum precipitation and fluoride removal are not well understood. A fundamental understanding of how fluoride alters the properties of aluminum precipitates and how fluoride and NOM molecules compete as ligands interacting with soluble aluminum species is lacking. As a result, the development of guidelines for implementation and optimization of a treatment scheme that uses aluminum in the presence of fluoride requires a multi-faceted approach in which the development of a mechanistic understanding of these interactions is conducted in concert with macroscopic experiments to identify optimum conditions for simultaneous removal of fluoride and NOM. To date, little research has looked at the efficiency of removing both fluoride and organics from the perspective of the precipitation process. To provide a foundation for revising treatment techniques, this research evaluated the effect of co-precipitating aluminum in the presence of fluoride, organics, and in multi-ligand systems to characterize the solid precipitate and removal competition. This research verified the formation of a co-precipitate in the presence of fluoride and certain low molecular weight organics. Co-precipitation from organics and fluoride competes for removal, especially at low alum coagulant doses, complicating treatment for resource limited areas. / text

Seasonal periods of high rainfall have led to difficulties in removing sufficient natural organic matter (NOM) to meet trihalomethane (THM) standards, and hence better or alternative treatments are required. Typically bulk water parameters such as dissolved organic carbon (DOC) and UV absorbance at 254nm (UV254) are used to optimise treatment processes. Here the isolated fraction character and molecular weight (MW) distribution was used in conjunction with bulk water parameters to tailor process options for the treatment of humic rich waters. Three options for the removal of NOM were proposed. A staged coagulation based on the optimisation of isolated fractions. The results showed that although no significant reduction in DOC or UV254 was observed filter breakthrough was significantly reduced. Secondly a novel magnetic ion exchange process (MIEX®) for the removal of NOM was evaluated. The results showed that a combination of MIEX® and ferric reduced the THM formation potential (THMFP) by more than 50% and lower MW compounds that are known to be untreated by conventional coagulation were reduced. This option was also shown to be the most robust option for the treatment of waters with differing quality caused by seasonal changes and different catchments. Finally the addition of a range of adsorbents including carbons, hydroxides and clays to both the raw water and the isolated low MW fractions showed that an increase in DOC and UV254 removal was achievable. This was proposed as a post coagulation option during times of high organic loading. All processes provide viable options for the treatment of humic rich waters during times when current processes are being challenged and having difficulty meeting THM standards.

No description available.

This research evaluated natural organic matter (NOM) dissolved-solid phase separation resulting from alum coagulation under the following sourcewater conditions: pH, initial NOM concentration, initial turbidity, and temperature. The solid phase was partitioned into two operationally defined size fractions; colloidal matter was defined as organic carbon (OC) retained by a 30 kilodalton ultrafiltration membrane, and particulate matter was defined as OC retained by a 1μm glass-fiber filter. Coagulation pH had a considerable impact on residual OC colloid formation, signified by more colloids formed as a function of alum dose at pH 6.8 as compared to pH 5.8. Initial NOM concentration strongly influenced the alum dose range over which OC colloid formation occurred and was found to be a proportional relationship. The presence of bentonite clay (used as the initial turbidity source) somewhat affected OC colloid formation by exerting some amount of coagulant demand, signified by decreasing OC colloid formation with increasing initial turbidity. Coagulation temperature had a considerable impact on particulate matter formation, as there was an increase in the dose at which particle formation first occurred at 4 ºC when compared to 25 ºC. Phase separation of OC from dissolved to colloidal matter was very similar at both 4 ºC and 25 ºC. The ability for low doses of polymers to replace a large portion of alum in order to further aggregate colloids during flocculation was unsuccessfully investigated. OC phase separation resulting from alum and iron sulfate coagulation was compared on a molar coagulant metal basis. The amount of residual OC associated with colloidal matter was similar, while the critical coagulant dose at which particulate matter formed was shifted to a much higher dose for iron. / Master of Science

Fluoride naturally occurs in some ground and surface waters at high concentrations all around the world. Due to increasing health concerns about over-exposure to fluoride in drinking water, the United States Environmental Protection Agency (USEPA) has begun to review fluoride as a drinking water contaminant. Should the USEPA decide to lower the fluoride maximum contaminant limit (MCL), many water systems in addition to those already struggling to meet the fluoride MCL will require defluoridation as part of their drinking water treatment process. Alum coagulation was investigated as a defluoridation treatment strategy in this research project. Surface and blended (ground/surface) drinking water sources with high fluoride concentrations pose a unique challenge to defluoridation by alum coagulation because of the presence of both natural organic matter (NOM) and fluoride. Defluoridation of synthetic and natural waters using jar tests elucidated interactions of fluoride, NOM, and aluminum during alum coagulation. Alum coagulation was able to remove 80% of fluoride from natural waters with a 500 mg/L alum dose; however, 50% fluoride removal was observed to be possible with an alum dose of 150-170 mg/L. The optimum pH for fluoride removal in synthetic and natural waters was observed to be approximately 6.5 and was found to be an important factor in determining the overall performance of alum coagulation. The presence of fluoride during alum coagulation was found to reduce the removal of three low molecular weight (LMW) organics, acting as surrogates for NOM, to different extents depending on their functionality. The presence of LMW organic acids in synthetic waters did not impact the removal of fluoride; however, increasing NOM concentrations in the natural waters likely accounted for decreasing fluoride removals observed in the natural waters. Additional jar tests with natural waters revealed that pH adjustment was unnecessary for defluoridation of high pH and high alkalinity waters and that an enhanced precipitation effect occurred at low alum doses when no pH adjustment was made during alum coagulation. The enhanced precipitation effect caused comparable or enhanced removals of fluoride and NOM to be observed despite system pH values being higher than the optimal defluoridation pH of 6.5. Lower aluminum residuals were also observed as part of the enhanced precipitation effect, suggesting that when precipitation begins under high pH conditions, fluoride interference does not occur and therefore promotes more precipitate formation with greater available surface area for adsorption. However, as precipitation occurs, pH drops, and fluoride increasingly interacts with the aluminum precipitate resulting in greater overall fluoride removals. / text

Supported lipid bilayers (SLBs) are one of the most common model membranes used in the field of cell membrane biology as they provide a well-defined model membrane platform for determination of molecular-level interactions between different biomolecules (e.g. proteins, peptides) and lipid membrane. Compared to model organisms, the use of SLB is preferable since it mimics cell plasma membrane in a very simple and well-controlled way. Therefore, molecular structure of membrane and experimental conditions (e.g. solution chemistry, temperature, and pH) can be easily adjusted to the required conditions of any systematic research. In addition, SLBs are typically easy to form, cheap and very reproducible and they are compatible with different surface characterization techniques, such as quartz crystal microbalance with dissipation (QCM-D), ellipsometry and atomic force microscopy (AFM). This study demonstrates that QCM-D analysis of SLBs serve as powerful tool to investigate and characterize the mechanisms of interactions between lipid membrane and gold nanoparticles (NPs), environmentally relevant polymers, and disease-inducing peptides. Due to many critical applications of gold NPs in drug delivery and diagnostics, understanding of membrane-NP interactions is crucial especially for determination of NPs cytotoxicity. In this study we focus on membrane disruption as one of the different mechanisms by which metal NPs induce cytotoxicity. The use of SLB is beneficial for this goal as it elucidates the unique mechanism of membrane disruption without interference of other mechanisms taking place simultaneously in biological cells. For NP-membrane interaction studies, a SLB composed of L-α-phosphatidylcholine (egg PC) was formed on a SiO2-coated crystal and QCM-D analysis was performed to obtain information about mass and viscoelastic changes of SLB resulting from interactions with gold NPs. For better understanding of the mechanisms of NP-membrane interactions, we systematically changed the NPs properties and the experimental conditions. In order to understand the effect of NP size, gold NPs with diameters of 2,5,10, and 40 nm were tested and compared to each other. NPs were tested in their citric acid-stabilized state as well as in the presence of poly (methacrylic acid) (PMAA), representing an organic coating that could become associated with NPs in the environment. The results indicated that when dissolved in water, gold NPs with the dimeters of 2, 5, 10, and 40 nm did not perturb the membrane, but in the presence of environmentally relevant polymer, the larger nanoparticles were found to disrupt the membrane. In order to elucidate the effect of surface chemistry, 10 nm - gold NPs with various functionalizations (i.e. anionic, cationic and non-ionic ligands) were tested. Control experiments were designed to test the effect of NPs in the absence of humic substances which means the NPs were dissolved in water. In these cases, regardless of the type of NP functionalization, no substantial bilayer mass changes were observed. This suggests that the charge and chemistry of the ligands had a minor effect on NP-membrane interactions. Furthermore, in both the control and humic acid experiments, there were small dissipation changes (less than 1 unit) indicating that the overall membrane structure was not perturbed. In order to mimic environmentally-relevant conditions, mass and viscoelasticity of SLB was characterized in the presence of four different natural polymers, also known as natural organic materials (NOMs): Fulvic and humic acids extracted from Suwannee River (SRFA and SRHA), which had relatively lower molecular weights and a commercial humic acid (HA) and the humic acid extracted from Elliott soil (ESHA) with higher molecular weight. The results showed that NOMs with lower molecular weights, adsorbed to the bilayer, while higher molecular weight components, did not induce any changes to the bilayers. In addition, the NPs in SRFA and SRHA increased the mass of the bilayer by 20-30 ng, while the NPs in HA and ESHA changed the mass of the bilayer by < 10 ng. It was concluded that the presence of humic substances as well as their physical and chemical properties exert a direct impact on the interactions between cell membrane and the nanoparticles. In addition to the field of NP toxicity, SLBs play a pivotal role in the field of neurodegenerative diseases, such as Alzheimer’s disease (AD), in which the pathological cascade of events starts from interactions of a misfolded peptide with cell membrane. In this thesis, we confirm the validity of QCM-D analysis of SLB as an important platform for investigation of amyloid β (the peptide associated with AD) interactions with lipid membrane. Adsorption of Aβ peptide to cell membrane is known to take place on the so-called “lipid raftâ€� which are membrane microdomains enriched with cholesterol, sphingomyelin and ganglioside. The formation of SLBs containing lipid rafts is not only important for the field of AD research, but also it is important for other in vitro studies of cell biology as the lipid rafts are responsible for a variety of biological functions such as association of some membrane proteins and cellular signaling. However, the presence of lipid raft components such as sphingomyelin and cholesterol makes the formation of the bilayer more challenging which leads to adsorption of intact vesicles on the substrate without formation of the bilayer. In this study, the formation of lipid bilayer composed of 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-dioleoyl- sn-glycero-3-phospho-L-serine (DOPS), cholesterol (Chol), sphingomyelin (SM), and ganglioside (GM) was investigated using QCM-D. A challenge was that the raft-containing vesicles remained intact on the SiO2 crystal. Therefore, different experimental conditions were tested to induce vesicle fusion, such as pH, temperature, osmotic pressure, and vesicle size. The key parameter in forming the bilayer was found to be applying osmotic pressure to the vesicles by having the vesicles exterior concentration of NaCl higher than interior concentration. When this concentration gradient was applied to the vesicles before flowing them on the substrate, vesicle rupture was favored and formation of a complete bilayer could occur. Here, we report the effects of each tested variable on the adsorption and fusion of the raft-containing vesicles, and the results are discussed based on the mechanisms of vesicle-vesicle and vesicle-substrate interactions.After developing the robust method for formation of SLB with lipid rafts, we used that as a template to characterize the mechanism of interactions between Aβ peptide and cell membrane which leads to onset of AD. The mechanism of Aβ toxicity leading to AD has not fully discovered yet, due to the complexity of the process including several steps of Aβ peptide adsorption on membrane, conformational change from disordered in solution to a membrane-bound α-helix structure and then formation of β-sheet aggregates that serve as fibrillation seeds. In this study, we showed that QCM-D technique as a promising tool to conduct systematic studies on the mechanism of interactions between Aβ peptide with lipid membrane. To our knowledge, this was the first time QCM-D was utilized for characterization of Aβ fibrillation starting from monomer states until formation of mature fibrils. The data indicated that peptide-membrane interactions follow a two-step kinetic pathway starting with the adsorption of small (low-n) oligomers until covering all the adsorption sites on the surface. In the second step, the membrane structure is destabilized as the result of interaction with oligomers which leads to lipid loss from the surface. Consistency of the results with the data obtained via other techniques substantiates QCM-D technique as a robust approach to answer the remaining unanswered questions in the field of Alzheimer’s disease.

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.