According to the Department of Water Affairs (DWAF, 2004 p.15), South Africa’s water resources are scarce and extremely limited and much of this precious resource is utilised and consumed in our industries. Treatment and re-use of effluent generated is, in some cases, preferred over use of alternate water resources (Du Plessis, 2008 p.3). The volume of effluent generated in treatment processes like ultra-filtration (UF) and reverse osmosis (RO) units is determined by the feed water quality, with high water loss through effluent generation at poor feed water quality. Current UF and RO applications require an increased UF production capacity due to the use of UF filtrate for periodic backwashing of the UF membrane units. This results in loss of water and decreases overall recovery. The need therefore exists to increase the overall recovery of product water from the raw water stream by reducing the amount of effluent generated. This would be possible to achieve by using RO brine to backwash the UF unit. The study was conducted to provide a modelling tool, assisting management to optimise the use of RO brine as backwash water on the UF system at the Medupi power station. The secondary objective of this study was the development of a modelling tool that can be used for other projects, new or existing, as a measure and indication of the usability of RO brine as backwash water on UF systems. By successfully applying this newly developed model, the viability of utilising the RO brine as backwash water for the UF was investigated. This modification would lead to utilizing smaller UF units than previously envisioned, which in turn leads to reducing capital cost with 11.07% and operating expenditure with 9.98% at the Medupi power station. This also has a positive environmental impact by reducing the amount of raw water used monthly by 10.34% (108 000 m3/month). / MIng (Development and Management Engineering), North-West University, Potchefstroom Campus, 2014

Gravity-driven membrane (GDM) filtration is one of the promising membrane bioreactor (MBR) technologies. It operates at a low pressure by gravity, requiring a minimal energy. Thus, it exhibits a great potential for a decentralized system, conducting household in developing and transition countries. Biofouling is a universal problem in almost all membrane filtration applications, leading to the decrease in flux or the increase in transmembrane pressure depending on different operation mode. Air scoring or regular membrane cleaning has been utilized for fouling mitigation, which requires increased energy consumption as well as complicated operations. Besides, repeating cleaning will trigger the deterioration of membranes and shorten their lifetime, elevating cost expenditures accordingly. In this way, GDM filtration stands out from conventional MBR technologies in a long-term operation with relative stable flux, which has been observed in many studies. The objective of this study was to monitor the biofilm development on a flat sheet membrane submerged in a GDM reactor with constant gravitational pressure. Morphology of biofilm layer in a fixed position was acquired by an in-situ and on-line OCT (optical coherence tomography) scanning at regular intervals for both visual investigation and structure analysis. The calculated thickness and roughness were compared to the variation of flux, fouling resistance and permeate quality, showing expected consistency. At the end of experiment, the morphology of entire membrane surface was scanned and recorded by OCT. Membrane autopsy was carried out for biofilm composition analysis by total organic carbon (TOC) and liquid chromatography with organic carbon detection (LC-OCD). In addition, biomass concentration was obtained by flow cytometer and adenosine tri-phosphate (ATP) method. The data of biofilm components indicated a homogeneous biofilm structure formed after a long-term running of the GDM system, based on the morphology observation by OCT images. The superiority of GDM in both flux maintaining and long-term operation with production of high quality effluent was demonstrated, as well as the suitability of OCT for biofouling monitoring was emphasized.

Esta tesis doctoral se encuentra dentro del ámbito de estudio de la Fraseología y su relación con la enseñanza de Español como Lengua Extranjera (ELE). Si bien existen estudios relacionados, no se ha estudiado mucho sobre la didáctica de las unidades fraseológicas (UF) teniendo en cuenta su variedad diatópica y, mucho menos, las UF del español rioplatense hablado en Argentina. Esta investigación buscó: (1) analizar las estrategias de enseñanza e inclusión de UF utilizadas en los manuales de ELE de España, México y Argentina; (2) establecer el grado de conocimiento de UF generales y del español rioplatense que tenía un grupo de estudiantes de ELE de la Universidad Adventista del Plata entre 2016 y 2017; y (3) proponer una estrategia didáctica de integración transversal que permita incluir UF diatópicas en la clase de ELE que se apoye en la lengua materna de los estudiantes y en estrategias básicas de traducción y documentación.

This study aims to compare the strength of bonding joint and bonding quality depending on the proportion of violations. The first part contains a research of various types of adhesives. Based on the research, two types of adhesive were chosen - the PVAC and UF adhesives. These adhesives are used directly in manufacturing of solid wood panels. Our test samples were made of beech wood and oak wood using both types of adhesive, four groups of samples altogether. The thesis contains an analysis of the requirements for bonding strength as well as production of samples from solid wood panel. According to current standards, the tests were performed to determine the density, moisture content, strength of bonding joint, the bonding quality and proportion of violations.

In this project, urea-formaldehyde (UF) resins were produced and investigated. UF resins are commonly used indoors as wood adhesives in, e.g. particle boards, in different furniture applications and flooring. UF resins are produced by alternating methylolation and condensation reactions, thus reacting urea and formaldehyde with each other and creating longer polymeric chains. The number of alternations, i.e. number of condensation reactions can be varied. The focus laid on the effect of the formaldehyde/urea molar ratio during synthesis. This includes the effect of the molar ratio on both the composition and structure and in turn their effect on the properties of the resin. UF resin was synthesized via two different methods. In method one, a reference adhesive was synthesized, this adhesive was produced using three condensation reactions. In method one, another resin was also produced using only two condensation reactions but with the same F/U molar ratios. In method two, only two condensations reactions were performed for each resin. In the start of the reaction, the F/U-molar ratio was varied in three different values. Towards the end, however, different amounts of urea were added to make sure that the final F/U-molar ration was kept constant. The results showed that the F/U molar ratio during synthesis will have an effect on both the composition of the resin and the structures being formed. With less urea added in the beginning as in the case with a high starting molar ratio, more dimethyl ether bridges and methylol groups, but less methylene bridges were formed in the end-product. This was formed together with a more branched UF structure with a higher polydispersity index. The reason for this probably originates from the more highly substituted amino groups formed due to the lower amount of urea in the beginning in the sample with a high F/U molar ratio. The composition and structure of the resin with a higher F/U molar ratio also seem to favor a stronger tensile strength. The increased amount of methylol groups and the increased PDI are thought to have a larger effect on the increased tensile strength. The shelf life of the finished resin also showed dependency with the F/U molar ratio, since resins produced with a low molar ratio gelled within 24h compared the two other variations of F/U ratios, where it took about 90 days to gel at the same temperature.

Wood waste containing formaldehyde based resins are generated yearly and disposed in landfills or burned. No regulations exist in most states and no studies have been conducted to address formaldehyde emission from wood waste buried in landfills. The objective of this study was to: a) determine the amount of formaldehyde released into air and leachate from MDF disposed in a simulated landfill, b) analyze the environmental impacts of leachate containing formaldehyde, and c) investigate change in chemical and morphological properties of disposed MDF. Sampling of MDF, soil and leachate were conducted for determination of formaldehyde weekly for 56 days by HPLC. Environmental impacts of leachate was determined by BOD, COD, and toxicity. Changes in the chemical composition and morphological structures were also determined. No detectable formaldehyde was observed in MDF, soil or leachate after 28 days. The BOD and COD levels indicated the leachate was not suitable for drinking.

Anthropogenically generated antibiotic resistance genes (ARGs) are considered emerging contaminants, as they are associated with a critical human health challenge, are persist independent of a bacterial host, are subject to transfer between bacteria, and are present at amplified levels in human-impacted environments. Given the gravity of the problem, there is growing interest in advancing water treatment processes capable of limiting ARG dissemination. This study examined the potential for membrane treatment of microconstituent ARGs, and the effect of wastewater colloids on their removal. Native and spiked extracellular vanA (vancomycin resistance) and blaTEM (β-lactam resistance) ARGs were tracked by quantitative polymerase chain reaction through a cascade of membrane filtration steps. To gain insight into potential associations occurring between ARGs and colloidal material, the wastewater colloids were characterized by scanning electron microscopy, as well as in their protein, polysaccharide, and total organic carbon content. The results suggest that extracellular DNA (eDNA) containing ARGs interacts with wastewater colloids, and can both be protected against degradation and be removed more efficiently in the presence of wastewater colloidal material. Thus, ARG removal may be achievable in sustainable water reuse scenarios using lower cost membranes than would have been selected based on molecular size alone. As membranes are likely to play a vital role in water sustainability, the results of this study enable consideration of ARG removal as part of a comprehensive strategy to manage emerging contaminants and to minimize overall public health risks. / Master of Science

Studiens syfte är att undersöka lärares upplevelse av att använda organisationen Ung Företagsamhets koncept; UF-företagande i sin undervisning. De frågeställningar som studien ska besvara är; Vilka möjligheter och utmaningar upplever lärare när de använder UF-företagande i sin undervisning? Hur resonerar lärare kring bedömning och betygsunderlag när de använder UF-företagande i sin undervisning?  För att besvara studiens frågeställningar har en kvalitativ metod med semistrukturerade intervjuer använts. Urvalet har bestått av sex lärare som har erfarenhet av att använda konceptet UF-företagande i kursen Entreprenörskap och företagande.   Resultatet visar att de främsta möjligheterna som lärarna upplever är ett välfungerande koncept, naturliga samarbeten, motiverade elever och verklighetsbaserat lärande – på riktigt. De utmaningar de upplever är tidsbegränsning, konflikthantering och att centralt innehåll inte ryms i konceptet. När lärarna resonerar kring bedömning och betygsunderlag upplever de det som en utmaning, men lyfter metoder som de upplever som framgångsrika. Lärarna använder dokumentation, sambedömning, självvärdering och teoretiska moment för att styrka sin bedömning.

Reverse osmosis (RO) and ultrafiltration (UF) retentates were ultra-high temperature (UHT) processed and compared for storage life at room temperature. Viscosity studies indicated that UHT-treated, RO retentate delayed age gelation longer than UF retentate at the same total solids level (26% TS). When compared at 6.4% protein level (2x RO vs 2.7x UF where x=ratio of the feed volume to concentrate volume), the storage life for both RO and UF retentates was about 6 to 8 months. Sodium hexametaphosphate (SHMP) and disodium phosphate (DSP) at 1, 3, 5, 10, and 20 mM concentrations were incorporated prior to UHT processing of each sample to improve the shelf life. SHMP at 1 and 3 mM concentrations was effective in delaying age gelation, whereas all levels of DSP accelerated gelation. However, SHMP accelerated age gelation at concentrations of 10 and 20 mM. SHMP at 1 mM in RO retentate was more effective in delaying age gelation than the same SHMP level in two UF samples (22 and 26% TS). Analysis showed that RO/UHT-treated samples had higher soluble calcium and ionic calcium than did UF/UHT-treated samples. The coefficient of determination (R2) was .80 between soluble calcium-to-protein ratio and shelf life.

Les technologies à membranes sont en plein développement ; toutefois, les problèmes de colmatage limitent cette expansion. Les acides humiques présents dans les eaux naturelles induisent des chutes de production des membranes et sont à l'origine de fortes diminutions des durées de vie des matériaux filtrants. L'objectif principal de ce travail a été de développer une approche originale du colmatage de membranes basses pression d'ultrafiltration (UF). L'originalité de ce travail est de proposer plusieurs outils d'autopsie de membranes à deux échelles, l'une macroscopique (par des mesures de perméabilité hydraulique, dont sont déduites les résistances de colmatage et l'indice de colmatage MFI-UF) et l'autre microscopique (par la détermination de la dimension fractale des particules d'acides humiques et leurs agrégats déposés à la surface de la membrane). En utilisant une combinaison de ces outils macroscopiques, microscopiques et in situ, nous avons développé une nouvelle méthodologie pour l'analyse d'un gâteau d'acides humiques sur une membrane et ainsi permis d'évaluer plus finement que jusqu'ici la nature, les mécanismes, et les conséquences du colmatage de membranes basses pression. Cette méthode a été appliquée aux fibres creuses (vierge et colmaté par l'eau de surface naturelle), combinées avec l'autopsie de membrane. De plus, un nouvel appareillage semi-automatique de la mesure du potentiel d'écoulement, mise au point par nos soins, a permis de réaliser des investigations à l'intérieur de la structure de la membrane afin d'y déceler le cas échéant la présence de matière organiques naturelles (MON). La dernière partie est consacrée à une étude du prétraitement d'une solution d'acides humiques en présence de.bentonite modifiée (dénommée mont-Al-CTAB) afin de tenter de limiter le colmatage par les MON. La méthode de prétraitement employant la bentonite s'est avérée efficace en réduisant la résistance totale du gâteau d'acides humiques, en particulier en provoquant la diminution de la dimension fractale du gâteau formé en présence de bentonite.