La prolifération grandissante des épisodes de fleurs d’eau de cyanobactéries toxiques dans les plans d'eau potable et dans les usines de traitement d'eau potable est une préoccupation mondiale. L’utilisation de sondes in vivo, permettant la détection de la phycocyanine des cyanobactéries par fluorescence, est une technologie innovante, de plus en plus couramment utilisée. Néanmoins, pour favoriser son implémentation à grande échelle, elle doit être validée scientifiquement. De nombreuses sources d’interférences dans ces sondes sont à l’origine de biais de lecture. Les objectifs de cette recherche sont :1. La caractérisation des espèces dominantes et la succession des espèces de cyanobactéries dans deux grands lacs utilisés pour la production de l’eau potable2. L’analyse de la variabilité des espèces de cyanobactéries et d’autres groupes de phytoplancton en fonction de la température et des nutriments3. La validation du suivi des cyanobactéries par sonde fluorométriques aux sources d’eau potable en corrigeant le signal pour les interférences d’autres groupes de phytoplanctonLes résultats de ce travail de recherche ont montré qu’il existe de nombreses sources d’interférences aux sondes à fluoresence YSI, mais qu’il était possible de développer un facteur de correction afin d’éviter de surestimer les cyanobactéries. Suite à la validation de la sonde, celle-ci a été utilisée pour comprendre la dynamique des cyanobactéries à la baie Missisquoi afin de caractériser les espèces dominantes et de mieux comprendre la succession phytoplanctonique de la baie afin d’aider les opérateurs de l’usine de traitement d’eau potable à planifier les traitements en fonction de la qualité biologique de la baie. Parmi les résultats les plus intéressants, notons l’apparition précoce, de plus en plus marquée à travers les années, des blooms de Microcystis sp. et le développement de bloom co-dominés par des Chroococcales et des Nostocales. Le développement de fleurs d’eau dominées par Aphanizomenon sp. ou Dolichospermum sp. est généralement précédé d’une période où le milieu est limité en N ce qui favorise le développement de ces espèces fixatrices d’azote atmosphérique / The increase of toxic cyanobacterial blooms in source waters that can lead to breakthrough into drinking water treatments plants is a worldwide concern. The use of in situ probes allows for the detection of cyanobacterial phycocyanin through fluorescence. It is an innovative technology becoming more widely used. However, to facilitate the implementation of this technology, it must be validated. Several sources of interferences can lead to biases in their application. The objectives of this research are to :1. characterize the dominant species and cyanobacterial succession in two large lakes used for drinking water production2. analyse the variability of cyanobacterial species as well as other groups of phytoplankton as a function of temperature and nutrients3. validate cyanobacterial monitoring by fluorometric probe in drinking water sources by correcting the signal for other groups of phytoplanktonThe results of this research have shown that there are many sources of interference in fluorescence probes, but that a correction factor can be used to prevent the overestimation of cyanobacteria. Following the validation of the probe, it was used to improve our understanding of the dynamics of phytoplankton succession in Missisquoi Bay in order to characterize the dominant species and succession to improve the operation of drinking water treatment at Missisquoi Bay. Among the interesting findings was the earlier apparition of cyanobacteria throughout the years, Micocystis sp. blooms and blooms co-dominated by Chroococcales and Nostocales. The development of cyanobacterial blooms dominated by Aphanizomenon sp. or Dolichospermum sp. was generally preceded by a period where the water body was limited in nitrogen, which favours the development of these species capable of fixing nitrogen

>Magister Scientiae - MSc / South Africa is facing a problem of many municipal waste water treatment works (WWTW) not working efficiently. The environmental impacts of poorly treated effluents on receiving water bodies have required special attention from researchers. In this study, the relationships between water quality variables in the Baths River in the Western Cape province of South Africa were evaluated upstream, at the source and downstream of the Caledon wastewater treatment works between March 2013 to March 2016. The assumption has been tested that water quality is deteriorating downstream of the Caledon Waste Water Treatment Works (WWTW) discharge point in the Baths River and are affected by this change in water quality. / 2023

No description available.

Access to clean water is one of the world's greatest concerns. Because 97% of global water resources are seawater, desalination via reverse osmosis (RO) membrane process has become a vital technology to obtain drinkable water. At the same time, the discharge of industrial waste effluents containing heavy metal ions to the available water resources (seawater and brackish water) without adequate pre-treatment is a major cause of water pollution. Heavy metal rejection using nanofiltration (NF) membrane process is a recognized water treatment methodology. Thin-film nanocomposite (TFN) membranes have shown vast performance enhancement using both RO and NF processes. However, TFN membrane fabrication has been limited due to poor dispersion of the nanoparticles in the polyamide (PA) layer of the membrane, and the leaching of the often-hazardous nanoparticles from the TFN membranes. For various reasons such as their dispersibility in aqueous media, safety, high aspect ratio, and functionality, cellulose nanocrystals (CNCs) are an ideal nanoparticle for inclusion in TFN membranes. Because of their hydrophilicity, CNCs have more commonly been dispersed in the aqueous monomer solution during PA interfacial polymerization. In this thesis, we investigated two different CNC modification routes to improve CNC dispersion within the trimesoyl chloride (TMC)/n-hexane (non-aqueous) monomer solution. In one case, we acetylated the CNCs (ACNCs) using a straightforward, efficient, solvent-free method to achieve a more uniform CNC dispersion in the PA layer. The resulting ACNCs were less hydrophilic, which allowed increased nanoparticle loading and improved dispersion in the PA layer. In an RO desalination process, compared to unmodified CNC-TFN membranes, the NaCl rejection of the ACNC-TFN membranes remained stable (at 98-99%) up to a 0.4 wt% loading, while water permeability increased by up to 40%. For the second case, we synthesized L-cysteine functionalized CNCs (CysCNCs) and incorporated them into the PA layer for testing in an NF wastewater treatment process. The amine functional groups of L-cysteine covalently bonded with the acyl chloride groups of the TMC monomer. This resulted in improved nanoparticle dispersion but could also have prevented nanoparticle leaching. Moreover, because L-cysteine contains strong chelating groups, their inclusion in the PA layer led to improved heavy metal rejection. A loading of 0.1 wt% CysCNCs in the TFN membranes provided high rejection of both copper and lead ions, 98.1 and 95.2%, respectively. The CysCNCs were also evaluated in an NF desalination process resulting in a 40% increase in water permeability with almost no decline in Na₂SO₄ (97-98%), MgCl₂ and NaCl rejection. The modified CNCs enabled us to overcome the water permeability/selectivity trade-off in CNC-TFN membranes for both RO and NF membrane desalination. Finally, we developed an experimental protocol to investigate the effect of the adsorption of heavy metal ions (if any) on the performance of thin film composite (TFC) and TFN membranes in NF. We confirmed that adsorption occurred, and the equilibrium capacity of the membranes was reached after 8 - 12 h of the experiment. Despite reaching the equilibrium capacity, the water permeability and heavy metal rejection remained at their highest values. This led to the conclusion that the adsorbed heavy metals altered the membrane surface, thereby improving the performance of both TFC and TFN membranes. The ability to modify CNCs enables one to achieve a controlled range of hydrophilicity/ hydrophobicity. This allows one to fine-tune CNC compatibility with the TMC/n-hexane non-aqueous monomer solution and enable improved dispersion in the PA layer, eventually leading to improved TFN membrane performance for both RO and NF processes.

The discharge of poorly treated wastewater containing persistent organic contaminants, such as phenol, into water bodies is a major contributor to water pollution. This is of great concern as it poses health threats to human beings, aquatic species and the ecosystem as a whole. Amongst the water treatment technologies available, adsorption is highly recommended because of its ease of operation, simple design and economic viability. Commercial activated carbon (CAC) has previously been utilised as an adsorbent for remediation of recalcitrant pollutants from wastewater. However, high costs and the complexity of regenerating spent carbon has resulted in the need for economically viable adsorbents. The current research focused on the use of layered double hydroxide (LDH) clays for removal of phenol from contaminated water. The work is divided into two sections whereby the initial phase focuses on the use of commercial LDH clays, while the second phase is based on the in-house synthesised LDH clays guided by the performance of the commercial clays. Six commercial clays were sourced from different suppliers for the first phase, namely: DHT ̵ 4A and Alcamizer 1 from Kisuma Chemicals (Netherlands), Sorbacid 944, Sorbacid 911 and Hycite 713 from Clariant (Germany) and GF ̵ 450 from Greenfield additives (South Africa). Sorbacid 944 was the only clay which had three metallic constituents, magnesium Mg), zinc (Zn) and aluminium (Al) and was quantified to be 100% hydrotalcite; other clays had a substantial amount of impurities, such as calcite, boehmite and silica. Screening tests on the commercial clays were done by contacting 10 g L-1 of each clay with 40 mg L-1 synthetic phenol solution over 108 h. All the clays produced an adsorption efficiency of less than 10%. However, three clays which showed better adsorption efficiencies, namely: GF ̵ 450 (9%), Sorbacid (6%) and DHT ̵ 4A (3%) were utilised for further assessment. The three clays were thermally treated at 500°C for 4 h to produce mixed metal oxides (MMO), which are known to be good adsorbents. Calcination of the clays resulted in an increase in phenol adsorption efficiency over 24 h on Sorbacid 944 (87%) and DHT ̵ 4A (52%) while GF ̵ 450 remained below 10%. Having produced a higher adsorption efficiency, Sorbacid 944 was further assessed for optimisation of phenol removal process. The initial pH of the solution was established to have an inverse proportionality relationship with phenol adsorption. Elevated pH resulted in an increase in the concentration of hydroxyl ions (OH-) which increased the reformation rate of calcined LDH (CLDH) and reduced the adsorption efficiency, while acidic pH was not evaluated as it is known to cause dissolution of LDH. Neutral pH was established to be the optimum pH for phenol adsorption. An increase in operational temperature resulted in a faster phenol adsorption rate from 2 x 10-4 g mg-1min-1 at 25 °C to 3.8 x 10-3 g mg-1min-1at 65 °C. The optimum clay loading was 10 g L-1 and the clay proved to be effective over three cycles. The Freundlich equilibrium isotherm best fitted the phenol adsorption equilibrium data, with a maximum adsorption capacity of 16.6 mg g-1. The change in enthalpy of the adsorption process was determined to be ca.20 kJ mol-1 indicating an endothermic process dominated by physical adsorption. The changes in Gibbs free energy over the evaluated temperatures ranged between -12 kJ mol-1 and -16 kJ mol-1. This showed that the adsorption process was spontaneous irrespective of the operating temperature. The second phase of the study involved the synthesis of eight LDH clays containing varying compositions of Mg, Zn and Al with a carbonate interlayer anion. The clay which contained molar ratios of Mg (60%), Zn (20%) and Al (20%) (Mg0.6Zn0.2Al0.2) was found to possess higher adsorption efficiencies upon calcination at 450 °C for 4 h. Clays which had a Zn/Mg molar ratio greater than 1, Mg0.4Zn0.4Al0.2, Mg0.25Zn0.5Al0.25 and Zn0.75Al0.25 showed lower phenol adsorption efficiencies of 63%, 65% and 50% respectively. Clays with a Zn/Mg ratio less than 1, Mg0.6Zn0.2Al0.2 and Mg0.5Zn0.25Al0.25 showed optimal ratio of acidic and basic sites hence higher phenol adsorption efficiencies of 89% and 80% respectively. A higher aluminium content in the clay increased the spinel content (MgAl2O4) upon calcination resulting in a decrease in phenol adsorption. Phenol adsorption equilibrium data and kinetics for clay Mg0.6Zn0.2Al0.2 were comparable with those of Sorbacid 944. Column reactor configurations should be investigated for industrial applications. Furthermore, real wastewater matrices containing multi-contaminants should be used instead of synthetic wastewater with a few pollutants. This will provide insight in the applicability of LDH for impurity removal from wastewater on an industrial scale. / Dissertation (MEng (Water Utilisation))--University of Pretoria, 2021. / Technology and Human Resources for Industrial Support (THRIP) / Chemical Engineering / MEng (Water Utilisation) / Unrestricted

Effective adsorbents for polyfluorinated compounds (PFCs) were obtained and successfully tested in adsorption of perfluorooctanoic and perfluorooctanesulfonic acids. Bridged silsesquioxanes containing secondary and tertiary amino groups were synthesized by sol-gel condensation of bis[3-(trimethoxysilyl)propyl]amine and N-methyl-3,3′-bis(trimethoxysilyl)dipropylamine in acidic media in the presence of surfactants. Obtained materials were mesoporous with high BET surface area. They combine high structural stability with high concentration of surface amino groups serving as adsorption sites. Batch adsorption tests demonstrated their high adsorption capacity on PFCs: in some experiments it reached up to 88% of the adsorbent weight. Adsorption of PFCs changed the surfaces of the adsorbent nanoparticles from hydrophilic to hydrophobic thus providing their agglomeration and floatability. Column tests showed fast adsorption of PFCs even at high concentrations and high flow rates. Obtained results can be used in the development of an effective filtration device for clean-up of water contaminated by PFCs.

No description available.

The first two chapters of this dissertation focus on the child health outcomes in brief, child diarrheal incidence in India, and child growth measures in Rwanda. The third chapter examines the determinants of timely access to health care in emergency departments in the United States. All three essays are different in their area of interest, data sources, and methodology.ESSAY 1 India has recorded the highest number of child diarrheal deaths at the global level. Oral Rehydration Therapy (ORT) would just provide hydration and few mineral supplements for infected children. However, their malnutrition and weakened immune system cannot be reversed. Malnutrition affects child growth, and causes stunting, and makes them susceptible to other forms of infections. The rotavirus vaccine provides a pseudo-sense of protection from non-rotaviral diarrhea. Preventing diarrhea right away from the source of the infection would be a better solution. Since most diarrheal pathogens are water borne, disinfection treatment of drinking water at the point of use could prevent diarrheal incidence of children and adults as well. Household data from the National Family and Health Survey and their estimators viz., Propensity Score Matching (PSM), and Inverse Probability Weights Regression Adjustment (IPWRA) have been employed to examine the effects of water treatment techniques in households. This chapter attempted a novel approach in studying all the popularly used water treatment techniques currently practiced in India in one study. They have been ranked for multi-value treatment effects model. Water filters with ceramic candles are more effective than other point-of-use water treatment techniques, followed by chlorination, water purifiers, and boiling. ESSAY 2 Rwanda is a sub-Sahara African country affected by genocide with a patriarchal family structure system. Higher poverty and gender imbalance were not alleviated by gender equality being on the political agenda. Despite the highest female representation in the parliament in the world, gender equality and liberty are confined to elite women. Additionally, flawed laws for women's equality made women's empowerment a paradoxical phenomenon. Women at the gross root levels, i.e., community and household, are still dependent or interdependent on men (husband/father). This has been confirmed by the findings in Chapter 3, that is, for most decisions, women are taken jointly with their partners. A minimal percentage of women are autonomous in their decisions and in their home. This study made an attempt to examine the mother’s autonomy in Rwanda and its impact on child health. Mother’s autonomy is negatively related to child’s height and weight for their age. Although the expected association between mother’s autonomy and child height/weight is positive, it would also depend on the historical and cultural context of the country of interest. Instrumental variable analysis is used to study women’s autonomy due to its complex and endogenous nature. Spousal educational difference and marriage-to-birth interval are valid instruments but weakly identified. ESSAY 3 An increasing burden on emergency services that exceeded its resources led to congestion in the emergency department (ED), with patients waiting for physicians on the examination bed and for inpatient bed transfer. This creates a blockage between access to healthcare and emergent patients. ED measures adopted to reduce ED congestion, boarding, and waiting times, such as ambulance diversion management, fast tracking of patients with low acuity, and bed coordination do not effectively control waiting time and boarding. ED crowding is a patient flow, but not necessarily a hospital resource deficiency. This is evident from the findings that even EDs with new treatment spaces still keep patients waiting for an inpatient bed, however, they reported a shorter wait time for the physician. Optimal utilization of nurses by floating them to needy units is effective in timely transfers of patients to inpatient beds compared to EDs without floating nurses.

Research interest in Additive Manufacturing (AM) as an enabling technology for customizable parts is rapidly expanding. While much AM research focus is on high performance feedstocks and process optimization to obtain parts with improved mechanical properties, interest in the environmental applications of AM has recently increased. The lower cost and greater accessibility AM is leading to novel environmental research solutions in wastewater treatment and toxicity reduction by capitalizing on the increased affordability and accessibility of 3D printing (3DP) technologies for customizable, high surface area structures. The novelty and focus of this dissertation is exploration of Material Extrusion (MatEx) based Fused Filament Fabrication (FFF) of filled polymer composites as a disruptive technology enabler for deployable and retrievable structures in environmental media for adsorption, destruction and toxicity reduction of harmful chemicals. This dissertation addresses research questions that generally answer, "why AM for environmental applications?". The inherent layer-by-layer design provides larger surface area structures for interaction with contaminated media. Polylactic acid (PLA) was selected due to its green sources and biocompatibility relative to synthetic polymers and its wide processing window allowing shear thinning and "printability" despite the elevated viscosity and modulus of highly filled composites. The filler selected for contaminant adsorption was microporous zeolite, which has affinity for ammonia, radionuclides and Per- and Polyfluorinated Substances (PFAS). The filler selected for contaminant destruction was photocatalytic TiO2 nanoparticles which can degrade organic chemicals, harmful algal bloom toxins and PFAS. A preliminary research hurdle was overcome by demonstrating that immobilization of zeolite and TiO2 in a PLA binder matrix did not prevent adsorption or free radical release, respectively. The first major research objective involved investigation of high surface area printed PLA-zeolite geometries with different zeolite loadings and found that while ammonia was reduced, there were diminishing returns with increased loading in terms of mass standardized adsorptive performance due to insufficiently exposed zeolite. The research solution leveraged AM print process parameters to increase the macroporosity of the printed composite structure to create voids and channels allowing water infiltration and chemical adsorption to zeolite. Faster printing of larger roadways generated macrostructural voids that were maintained by extrusion at lower temperature for rapid solidification. The second research objective involved compounding different loadings and dispersion states of TiO2 in PLA to demonstrate immobilization of TiO2 closer to UV-light penetration water improves photocatalysis. Higher 32% w/w TiO2 loadings were heavily agglomerated and more difficult to print process due to high viscosity, rapid liquid-solid transition (G'>G") and particle network recovery during printer retractions, leading to nozzle clogging. Lower 20% w/w loading was more conducive to larger production printing due to lower viscosity, longer viscosity recovery times for retractions and thus generally a wider processing window. While altering twin screw processing parameters reduced TiO2 agglomerates in filaments, leading to increases in crystallinity (due to seeding effects and chain scission) and lower viscosity recovery, photocatalytic performance was not significantly improved. Evidence presented showed that larger particle agglomerates were more toward the inside of printed surfaces and thus less available to UV-light irradiation. This location of larger particles is supported by previous theoretical and empirical investigations showing larger particles migrate at a faster velocity away from the outer walls of confined extrudates within non-Newtonian flow fields due to normal forces, leaving more smaller particles toward outer surfaces. This research provided novel contributions to the environmental and AM research communities and pioneered a convergence of these fields into an interdisciplinary community of practice focused on better characterization and processing in environmental applications to improve structure-environmental property relationships. Future research should build on these findings to enhance performance through multi-functional materials that adsorb and destroy contaminants. The reactive surface area should be further increased through by high surface area designs and print parameter optimized porous structures providing a continuum of meso- to microporosity as confirmed by chemical flux and mass transfer studies for additional AM technologies (e.g., Direct Ink Write). / Doctor of Philosophy / Engineers and hobbies alike have great interest in Additive Manufacturing (AM), or 3D Printing, to customize parts and new designs. More recently, environmental scientists and engineers have turned to 3D printing to solve environmental problems due to the lower cost and user-friendliness of desktop machines. This research dissertation focuses on how 3D printing can allow for iterative improvements in customizable, high surface area structures to reduce chemical concentrations in water by either adsorbing or destroying the chemicals. Water is clearly a critical resource for ecosystems, recreation and drinking supplies as national security, human and ecosystem health are tied to clean water. This research addresses why 3D printing is interesting and effective for environmental solutions. Briefly the layer-by-layer design provides larger surface area structures for interaction with contaminated media. The common 3D printer feedstock Polylactic Acid (PLA) was selected since it is non-toxic and can be relatively easy to print even if modified by adding rigid filler particles for research. Micron-scale (zeolite) and nano-scale (Titanium Dioxide) particles were mixed with the polymer to make printable filaments to adsorb and destroy contaminants, respectively. This research demonstrated the proof-of-concept by removing ammonia, methylene blue dye and a harmful algal toxin from water. The materials produced are also applicable to both conventional organic pollutants and emerging contaminants of concern in the popular news such as Per- and Polyfluorinated Substances (PFAS), which were used as flame retardants and non-stick surfaces. This research ties the material properties of the experimental micro- and nano-composite filaments to how the materials extrude and solidify during 3D printing and how well the resulting printed structures work for reducing contaminant levels in water. Altering the parameters and conditions at which these materials are processed and 3D printed can significantly change their structure, density, porosity and distribution of particles and in turn increase effectiveness. The results provide new contributions to both the environmental and AM research communities and pioneers interdisciplinary collaborative ideas for these different subject matter experts to work together to better understand how handling and processing of these materials can improve their performance in environmental applications. New work should leverage the ideas and principles presented here to further improve performance, ease of production and scale-up of multifunctional material structures for multiple classes of chemicals that are of concern in surface and drinking water.

This research presents a critical evaluation of chitin- and chitosan-based materials as innovative treatment alternatives for water contaminated with insensitive munitions (IMs) compounds. Specifically, chitin, chitosan, amineunctionalized chitin (AFC) were evaluated for adsorptive removal of these compounds. Cellulose and cellulose triacetate were evaluated for adsorptive performance for comparison. Chitosan-graphene oxide (CSGO) composite membranes were evaluated for removal via adsorption and filtration and compared against nanofiltration and reverse osmosis membranes in the current market. Insensitive munitions evaluated include nitrotriazolone (NTO), nitroguanidine (NQ), and 2,4-dinitroanisole (DNAN); 2,4,6-trinitrotoluene (TNT) was also studied as a traditional munition for comparison. AFC is an effective adsorbent for NTO, DNAN, and TNT. Cellulose triacetate was the only commercially available biopolymer adsorbent effective at removing munitions compounds from solution; only DNAN and TNT were removed. CSGO membranes effectively removed NTO, DNAN, and TNT, but removal performance degraded with time. Overall, this research shows that the materials studied are viable options for removing IM and traditional munitions from water.