Food waste in the waste stream is becoming an important aspect of integrated waste management systems. Current efforts are composting and animal feeding. However, these food waste disposal practices rely on slow thermodynamic processes of composting or finding farmers with domestic animals capable of consuming the food wastes. Bioconversion, a potential alternative, is a waste management practice that converts food waste to insect larval biomass and organic residue. This project uses a native and common non-pest insect in Texas, the black soldier fly, which processes large quantities of food wastes, as well as animal wastes and sewage in its larval stage. The goal of this research is to facilitate the identification and development of the practical parameters of bioconversion methods at a large cafeteria. Three major factors were selected to evaluate the practicality of a bioconversion system: (1) the biological constraints on the species; (2) the economic costs and benefits for the local community; (3) the perception of and interaction between the public and management agencies with respect to the bioconversion process. Results indicate that bioconversion is feasible on all levels. Larvae tolerate and consume food waste as well as used cooking grease, reducing the overall waste volume by 30-70% in a series of experiments, with an average reduction of 50%. The economical benefits are reduced collection costs and profit from the sale of pupae as a feedstuff, which could amount to as much as $1,200 per month under optimal conditions. Social acceptance is possible, but requires education of the public, specifically targeting school children. Potential impediments to social acceptance include historical attitudes and ignorance, which could be overcome through effective educational efforts.

This research presents the results on an experimental investigation to identify the effects of rebar temperature, fly ash and water to cement ratio on concrete porosity in continuously reinforced concrete pavements (CRCP). Samples were cast and analyzed using pullout tests. Water to cement ratio (w/c) and rebar temperature had a significant influence on the rebar-concrete bond strength. The 28-day shear strength measurements showed an increase in rebar-concrete bond strength as the water to cement ratio (w/c) was reduced from 0.50 to 0.40 for both fly ash containing and non fly ash control samples. There was a reduction in the peak pullout load as the rebar surface temperature increased from 77o F to 150o F for the cast samples. A heated rebar experiment was performed simulating a rebar exposed to hot summer days and the rebar cooling curves were plotted for the rebar temperatures of 180o F - 120o F. Fourier transform infrared spectroscopy was performed to show the moisture content of cement samples at the rebar-concrete interface. Mercury intrusion porosimetry test results on one batch of samples were used for pore size distribution analysis. An in-depth analysis of the morphological characteristics of the rebar-concrete interface and the observation of pores using the scanning electron microscope (SEM) was done.

>Magister Scientiae - MSc / Fly ash is the major waste material produced by power plants in the combustion of coal to generate electricity. The main constituents of fly ash are Si, Al, Fe and Ca with smaller amount of S, Mn, Na, K, and traces of many other elements such as Co, Cd, As, Se, Zn, Mo, Pb, B, Cu and Ni. Fly ash is usually disposed either by dry or wet disposal methods. These disposal methods have raised major environmental concerns due to the potential leaching of chemical species from the ash heap by ingress of rainfall and brine used to transport the fly ash to the dam. This study focuses on the changes in chemical composition, morphology and mineral phases due to weathering, of coal fly ash co-disposed with brine over 20 years at Sasol Secunda ash dump in Mpumalanga Province, South Africa. The design and operation of the Secunda ash dump presupposes that the ash dump may act as a sink for the salts which originated from chemicals used for normal operation in the plants. The majority of these salts come from the brines generated during desalination and raw water regeneration. The aim of this study is to ascertain if the ash dump could serve as a sustainable salt sink.Samples were drawn along the depth of two drilled cores (S1 and S3) from the weathered Secunda ash dump and analysed in conjunction with the fresh (unweathered) Secunda fly ash taken from the fly ash hoppers for comparative analysis. Scanning electron microscopy (SEM), X-ray diffractive (XRD) and X-ray fluorescence (XRF) spectrometry were employed to obtain a detailed morphological, mineralogical and bulk chemical composition of all the samples. Pore water analysis was used to determine the pH, EC and moisture content of fly ash samples. A five step sequential chemical extraction procedure was used to establish the geochemical association of particular elements with various mineral phases. The total acid digestion test was also used to determine the total elemental compositions of the Secunda fly ash samples. The SEM results showed that the fly ashes consist of irregular and numerous spherically shaped particles. Changes (encrustations, etchings and corrosion) in the morphologies of the weathered ash particles were also observed. The XRD results revealed quartz, mullite, lime and calcite as the major mineral phases. Other minerals identified in very minor quantities in the drilled Secunda ash core that were dried prior to analysis were halite, kaolinite, nitratine, bassanite, microline. and hydrophitte. These phases may have formed during sample handling. XRF investigation revealed that the major oxides present in the dumped ash samples were SiO₂, A₂2O₃, CaO, Fe₂O₃, MgO, Na₂O, TiO₂ and the minor elements present were K₂O, P₂O₅, SO₃ and MnO. The sum of the mean values of the % composition of SiO₂, Al₂O₃, and Fe₂O₃ was 70.19 %, and 72.94 % for the two drilled ash core samples (S1 and S3) respectively, and 78.67 % for the fresh ash which shows the significant alteration of the Si, Al and Fe content in the ash matrix over time. The fly ash is classified as Class F using the ASTM C 618 standards. The loss on ignition (LOI) which is an indication of unburned carbon or organic content was 4.78 %, 13.45 % and 8.32 % for the fresh ash, drilled ash cores S1 and S3 respectively. The high LOI values for the drilled ash cores could indicate high hydrocarbon content in the ash dump because of co-disposal practises where hydrocarbon waste are included in the brine stream for disposal on the ash. While the ash samples from the surface appeared dry, moisture content (MC) analysis showed that there is considerable water entrained in the fly ash dump. The fresh ash MC was 1.8 % while core S1 ranged from 41.4 – 73.2 %; core S3 ranged from 21.7 – 76.4 %. The variations in the MC values can be attributed to uneven flow paths due to inconsistent placement conditions or variations in ambient weather conditions during placement. The fresh fly ash (n=3) had a pH of 12.38±0.15, EC value of 4.98±0.03 mS/cm and TDS value of 2.68±0.03 g/L, the pH of the drilled ash core S1 (n=35) was 10.04 ±0.50, the EC value was 1.08±0.14 mS/cm and the TDS value was 0.64 ±0.08 g/L. Core S3 (n=66) had pH of 11.04±0.09; EC was 0.99 ±0.03 and TDS was 0.57 ± 0.01. The changes in pH values can be attributed to the dissolution and flushing out from the dump basic alkaline oxides like CaO and MgO These variations in pH values shows that the fly ash is acidifying over time and metal mobility can be expected under these conditions. The large decrease of EC in the drilled ash cores S1 and S3 compared to the fresh ash indicated a major loss of ionic species over time in the ash dump. The sequential extraction scheme revealed that the elements Al, Si, Ca, Mg, Ba, Sr, Fe, Mn, Na, K, As, Pb, Cr, Mo, Cu, Ni and Zn are present in Secunda fresh and weathered fly ash and are partitioned between the water soluble, exchangeable, carbonate, iron and manganese, and residual fractions of the coal fly ash. It also showed that the trace elements As, Pb, Cr, Mo, Cu, Ni and Zn do not show permanent association with particular mineral phases as a continuous partitioning between different mineral phases was observed in the weathered drilled core. Generally, all the elements had the highest concentration in the residual fraction. But it was evident that the labile phase (water soluble, exchangeable and carbonate fractions) had fairly high concentrations of Si (± 6.5 %), Al (± 6.5 %), Ca (±10 %), Mg (± 5.5 %), Ba (± 7.5 %),Sr (± 7.5 %), Na (± 12 %) and K (± 12 %) for the Secunda drilled ash core (S1 and S3) and fresh fly ash samples. This indicates that these species can leach easily upon water ingress and could pose a danger to the environment. Na and K had the highest concentrations leached out in the labile phase in all the ash samples. The amount of Na leached out of the drilled Secunda ash core in the labile phase was 13.21 % of 18584.26 mg/kg in the five geochemical phases of core S1; and 9.59 % of 11600.17 mg/kg in the five geochemical phases of core S3 while the fresh Secunda fly ash leached out 11.28 % of 16306.30 mg/kg of Na in the five geochemical phases. This study provided significant insight into the pore water chemistry, morphology, mineralogy and chemical composition and the elemental distribution pattern of the major and trace elements in the Secunda fly ash and weathered drilled Secunda ashm core S1 and S3. Though results from XRF analysis and the sequential extraction scheme shows that Na, K, S, Ca and Mg were slightly captured from the co-disposed brine by the Secunda fly ash, these species were however released in the labile phase. Hence there was no significant retention of these species in the ash dump. The amount of these species retained in the weathered ash were (0.26 % and 0.55 %) for Na, (0.02 % and 0.34 %) for K, (0.08 % and 0.06 %) for S, (0.94 % and 0.01 %) for Ca and (0.37 % and 0.96 %) for Mg in drilled ash cores S1 and S3 respectively. This poor retention of Na K, S, Ca and Mg which are major components of Sasol Secunda brine in the drilled ash cores S1 and S3 clearly shows the unsustainability of the Secunda fly ash dump as a salt sink.

A assimetria de cinco estruturas corporais da mosca-das-frutas Ceratitis capitata foi analisada para uma avaliação se poderiam ser utilizadas como bioindicadores. As análises foram feitas em amostras de uma população natural e de uma população de laboratório. Adicionalmente, em amostras obtidas da população de laboratório, os índices de assimetria foram avaliados após a submissão das diferentes amostras à diferentes temperaturas. No estágio de pupa, as amostras foram tratadas nas temperaturas de 17, 20, 25 e 30oC. As estruturas analisadas, em machos e fêmeas foram as cerdas frontais (FO), orbitais (OB), pós-oculares (PO), o comprimento e largura das asas. Nos machos, além dessas estruturas, foi incluída a análise do comprimento de uma das cerdas orbitais, a supra-fronto-orbital (SFO), que apresenta dimorfismo sexual. A variação numérica das cerdas FO e OB foi muito baixa em todas as amostras, não permitindo uma análise da assimetria. A assimetria das demais características, tanto merísticas como métricas, mostrou ser compatível com o modelo da assimetria flutuante (AF). O grau de assimetria de cada estrutura não diferiu entre machos e fêmeas, mas foi significativamente mais alto na amostra da população de laboratório do que na amostra da população natural. No entanto, a assimetria holística (somatória da AF das diferentes estruturas) não mostrou diferenças entre as duas amostras. Nas amostras submetidas a diferentes temperaturas foram observadas alterações significativas no grau de assimetria das estruturas, mas nenhuma alteração no tipo de assimetria que continuou sendo caracterizada como flutuante. Essas análises mostraram não haver diferenças entre os sexos, nem interações entre sexo e temperatura, mas apenas diferenças significativas entre as temperaturas. A assimetria flutuante das cerdas pós-oculares aumenta com o elevação da temperatura, a AF do comprimento das asas e da cerda SFO (nos machos) não mostra correlação com as temperaturas e os resultados indicam que a AF da largura das asas é mais elevada nas temperaturas extremas que nas intermediárias. A comparação da assimetria holística entre as amostras das diferentes temperaturas mostrou que as diferenças não foram significativas. Os resultados indicam que a assimetria das 52 cerdas pós-oculares e das medidas do largura das asas apresentam potencial para evidenciar eventuais estresses durante o desenvolvimento desses insetos. Indicam, também, que a utilização de uma assimetria holísitca pode mascarar possíveis diferenças da assimetria flutuante de estruturas individuais. / Asymmetry of five traits of the fruit fly Ceratitis capitata, an introduced insect pest in Brazil, was analysed in order to evaluate if they present potencial to be used as bioindicators of the \"quality\" of these insects. Samples from a natural population and from a laboratory colony were studied. Moreover, asymmetry was measured in samples from the laboratory colony maintained during the pupal stage, in the temperatures of 17, 20, 25 and 30oC. The analysed traits of males and females, were the frontal, the orbital and the postocular bristles, measurement of the length and cross diameter of the wings and the length of the supra-frontoorbital bristles in the males that show a pronounced sexual dimorphism. Since the numerical variation of the frontal and orbital bristles was very low in all samples it was not possible to analyse the variation in terms of asymmetry. For all other traits, meristic or metric, asymmetry was characterized as following the fluctuating asymmetry (AF) model. AF of the different traits does not differ between sexes, but was significantly higher in the laboratory sample than in the sample from the natural population. No significant differences, however, were found in the holistic asymmetry (sum of AF of different traits) between the two samples. In relation to the experiments conducted in different temperatures, no variations in AF levels were observed between sexes, nor interactions between sex and temperatures. However, significant differences were observed among the samples submitted to different temperatures. AF of the postocular bristles increases proportionaly to the increment of the temperature, while AF of wings and supra-fronto-orbital bristles (in males) lengths showed no correlations with the temperatures, and AF of the cross diameter of wings seems to be higher at the extreme temperatures than at the intermediate ones. When a holistic AF was applied, no significant differences among the temperature samples were observed. The results indicate that asymmetry of the postocular bristles and the length of the wings are parameters showing potencial use as indicators of stresses during development of these insects. They also indicate that a holistic asymmetry may mask variations in the asymmetry of individual traits.

A família Tephritidae congrega várias espécies de moscas-das-frutas que utilizam frutos como substrato alimentar no estágio larval, adquirindo o status de inseto-praga quando esses frutos são de valor comercial. O gênero Anastrepha é endêmico do Continente Americano e compreende cerca de 212 espécies descritas, das quais 109 ocorrem no Brasil. A espécie nominal Anastrepha fraterculus representa um complexo de espécies crípticas e se encontra distribuída pela Região Neotropical e sul dos Estados Unidos. No Brasil, através do estudo de diversas características biológicas e do marcador molecular ITS-1 (espaçador ribossômico nuclear), identificou-se a existência de três espécies crípticas no complexo fraterculus, a Anastrepha sp.1 affinis fraterculus, A. sp.2 aff. fraterculus e A. sp.3 aff. fraterculus. Marcadores gênicos presentes no DNA mitocondrial, como o gene cytochrome oxidase I (COI), são ferramentas amplamente utilizadas em análises filogenéticas, pois esta molécula apresenta características distintas do DNA nuclear, como o fato de possuir herança predominantemente materna, apresentar ausência ou baixíssima taxa de recombinação na maioria dos táxons, além de altas taxas mutacionais. Estas características possibilitam a obtenção de dados importantes na interpretação das relações entre as espécies. Amostras do complexo fraterculus (A. sp.1, A. sp.2, A. sp.3) de 14 localidades (média de 5 indivíduos / localidade) no sudeste do Brasil, uma amostra de A sp.4 do Equador e dois grupos externos (A. grandis e A. striata) foram utilizados. Fragmentos de 1139bp do gene COI foram amplificados e sequenciados, 45 haplótipos foram identificados: 30 em A. sp.1, 5 em A. sp.2 e 17 em A. sp.3. A distância média entre as espécies foi de 0,021 e o Fst médio foi 0,347 indicando estruturação populacional muito alta e pequena distância entre os haplótipos, que não apresentaram diferenças fixadas entre as espécies. Os testes de desvio de neutralidade apresentaram valores significativamente negativos. Os testes de seleção evidenciaram a atuação de seleção purificadora com baixos valores de Ka/Ks e significância no Z-teste de seleção. A análise filogenética mostrou fortes evidências de introgressão e não separou as diferentes entidades em clados distintos. Houve a formação de dois ramos principais, um constituído quase que exclusivamente por amostras de A. sp.1, e apenas duas amostras de A. sp.3, e outro que reuniu todas as espécies do complexo. Os dois principais grupos de haplótipos também foram visualizados na rede de haplótipos que mostrou indícios de expansão populacional. Quando somado ao estudo sequências depositadas em bancos de dados por outros autores, a espécie nominal A. fraterculus apresentou em sua distribuição 5 grupos de haplótipos mitocondriais. Dois deles ocorrem no Brasil, um com amostras do México e Costa Rica, um na Guatemala e Venezuela (baixa latitude) e um com indivíduos da Colômbia e Venezuela (alta latitude), sendo que os grupos Brasileiros também reuniram amostras da Argentina e do Equador. Assim, as sequências de COI não permitem a caracterização das entidades do complexo fraterculus apesar de indicar a estruturação populacional e a hipótese mais provável é a de que tenha havido introgressão da molécula mitocondrial entre as espécies do complexo com posterior expansão / The Tephritidae family comprises fruit flies species whose larvae feed and develop in fruits, many of which are commercial varieties and thus the species assume economic significance. Anastrepha genus is distributed throughout the Neotropical region and Southern United States. Analyses of biological characteristics and of the internal transcribed spacer (ITS-1) of the nuclear ribosomal DNA allowed the characterization of three cryptic species of the fraterculus complex in Brazil: Anastrepha sp.1 affinis fraterculus, Anastrepha sp.2 aff. fraterculus and Anastrepha sp.3 aff. fraterculus. Mitochondrial markers as gene cytochrome oxidase I (COI) are largely used in phylogenetic analyses because they have maternal inheritance, none or low recombination and high mutation rates compared to the nuclear DNA. Hence, analyses of the complex based in this marker will offer a divergent perspective from nuclear DNA for inferences on the evolutive relationships between different species. Samples from the fraterculus complex (A. sp.1, A. sp.2, A. sp.3) from 15 localities (average of 5 individuals/ locality) in southeastern Brazil, one sample of A. sp.4 from Ecuador and two outgroups (A. grandis and A. striata) were employed and COI sequences of 1139bp were amplified and analyzed. We identified 45 haplotypes: 30 in A. sp.1, 5 in A.sp.2 and 17 in A. sp.3. The mean distance between the haplotypes was 0.021 and mean Fst 0.347, indicating high population structure and low mitochondrial distance. The neutrality tests had significantly neutral values. The selection tests revealed the action of purifying selection with low values of Ka/Ks and significance in the Z-test selection. Phylogenetic analysis showed strong evidences of introgression and did not separate the various entities in distinct clades grouping the three species in a single branch; there was also the formation of another main branch formed almost exclusively by strains of A. sp.1 and only two samples of A. sp.3. The two main groups of haplotypes were also seen in the haplotype network that showed evidence of population expansion. The analysis of the philogenetic tree based on mitochondrial COI showed strong evidence for introgression. No fixed differences between species were found though mtDNA marker shows a lot of polymorphism. When added sequences deposited in databases by other authors the nominal species A. fraterculus presented in its distribution five groups of mitochondrial haplotypes, two of them in Brazil, one with samples from Mexico and Costa Rica, one in Guatemala and Venezuela and one with individuals from Colombia. The Brazilian groups also collected samples from Argentina and Ecuador. Therefore, the COI sequences do not allow the characterization of the entities of the fraterculus complex, although structure among the species is shown. The most likely hypothesis is that introgression has happened in the mitochondrial molecule among the species with further expansion

The house fly, Musca domestica can transmit human pathogens including Escherichia coli O157:H7 through regurgitation of ingested bacteria from the crop which is a foregut organ of house fly and stores the excess ingested nutrients. Interactions between the ingested bacteria and the crop have a direct influence on bacteria persistence, survival and ultimately fly vector competence. In this research, in situ crop vessel assay was developed to investigate bacterial growth within fly crops up to 48 hours post-ingestion. Flies were fasted for 12 h prior to feeding E. coli O157:H7 pEGFP and then fed bacteria with red food color which was added to confirm that flies had consumed the bacteria. After feeding, flies with red abdomens were aseptically dissected and crops were removed and maintained in sterile phosphate buffered saline in microtiter plates held at 32˚C. For each time point (0, 24 and 48 hours post-ingestion), five crops were homogenized individually using a tissue grinder and bacterial levels (CFU/crop) were monitored using plate counts. Confocal microscopy of intact crops was used to monitor biofilm development. There was no statistical difference in cell numbers (CFU/crop) over the 48 h incubation period. Microscopy showed that upon prolonged incubation, GFP-expressing E. coli within the crop produced biofilms. This method showed greater reproducibility in studying crop bacteria level than using a live fly feeding study. But this system was not recommended to study the interaction between bacteria and the crop of housefly.

The aim of this diploma thesis is to design flying rotary shears for metal cutting at high speed. The shears are a part of a rolling mill where they are used to cut faces and ends of the simple sections, i.e. rounds or squares. In case of the malfunction of the rolling mill, the shears can be used for scrapping the simple sections. A technical report with function destription of the machine as well as machine design according to specified parameters and control calculations are an integral part of the thesis. The required design documentation is included.

The aim of this work was to develop an alkali activated matrix based mainly on fly ash, to determine the ability to fix lead in these matrices, the impact of added lead on mechanical properties and to reveal the way of lead fixation in these matrices. The matrices consisted mainly of fly ash (four from fluidized bed combustion, one pulverized coal combustion) with an admixture of blast furnace slag and sodium silicate as an activator. Lechates were prepared on the basis of the ČSN EN - 12457-4 standard, lead concentrations in them were measured using an atomic emission spectrometer with inductively coupled plasma. The strengths of the samples were measured after 28 days. Images, element maps and element spectra were taken to determine the structure using a scanning electron microscope with an electron dispersion spectrometer, the samples were analyzed on an infrared spectrometer with a Furier transform, X-ray diffraction analysis and electron spectroscopy for chemical analysis were also used. The individual measurements showed that lead is accumulated in the form of hydroxide. The impact of lead doping on strength of the matrix was different for individual samples. Matrices from both types of fly ash released minimal amounts of lead into leachates, so it is possible to use them to fixate lead.

No description available.

In South Africa, as much as 33 million tons of ash, a waste product of burning coal, are produced per year. Of the total ash produced, just over 8% is sold for utilisation, the remainder of which is disposed of in landfills or ash lagoons. Countries like the UK, USA, Germany, Poland and Russia are producing Lightweight Aggregates (LWAs) commercially by using fly ash and clay, however, this technology is not available in many developing countries. The opportunity to utilise the fly ash produced in South Africa for the production of coarse LWA for use in structural concrete has therefore been identified and investigated in this dissertation. This dissertation consists of two phases, firstly to determine a suitable method for the manufacture of a high quality LWA, and secondly to determine the manufactured aggregate’s performance and potential for use in structural concrete. In the first phase, different LWA batches were produced using fly ash as the main constituent and kaolin clay, in contents of 0%, 10%, 20% and 30% by mass, as a binder. Green aggregate particles were produced in a disc granulator and then hardened using sintering at 1200°C for one hour. It was found that the LWA batch containing 20% kaolin produced LWA with the most suitable mechanical properties for use in concrete, and was therefore mass produced for further aggregate testing and for the production of concrete specimens for concrete testing. The final LWA produced was found to have an apparent density of 1600 kg/m3 and 24 hour water absorption of 12% by mass. The produced LWA was also found to have an Aggregate Crushing Value (ACV) and 10% FACT of 24.4% and 185 kN, respectively, which indicated that it would be suitable for use in High Strength Concrete (HSC). The sintering process was found to induce liquid phase sintering and the formation of new phases, mainly mullite, which contributed to the relatively high strengths of the aggregates. In the second phase of this dissertation, the manufactured LWA was then used to produce HSC and Normal Strength Concrete (NSC) specimens for concrete testing, which were compared to control mixes made with normal weight dolomite aggregate. In the HSC testing, concrete with a density of 2300 kg/m3 and compressive strength of 90 MPa was produced with the LWA. In HSC, it was found that internal curing was improved when up to 50% of the normal weight coarse aggregate was replaced by saturated LWA for this specific concrete mix. By using different stiffness relationship models between the concrete constituents, it was found that the manufactured LWA modulus of elasticity was between 8-23 GPa, and had a compressive strength of between 49-60 MPa. The Interface Transition Zone (ITZ) in concrete produced with the LWA was found to be stronger than the LWA as a result of the impregnation of the cement paste within the aggregate, and that the LWA was reactive in an alkaline environment. This resulted in an improved early age strength development, as well as caused the concrete failure surface to occur through the LWA particles rather than at the ITZ. Finally, Lightweight Concrete (LWC), having a dry density below 2000 kg/m3, was produced with the manufactured LWA. The LWC, produced with a water-to-cement ratio of 0.75, 28 day compressive strength of 24 MPa, modulus of elasticity of 21 GPa and dry density of 1800 kg/m3, was found to be suitable for use as structural concrete when assessed in terms of EN 1992-1-1 (2004). / Dissertation (MEng (Structural Engineering))--University of Pretoria, 2020. / Civil Engineering / MEng (Structural Engineering) / Restricted