The low-rate trickling filter is the most common biological treatment process used in small and medium sized sewage works in the UK. It produces an inconsistent effluent quality, which has traditionally been related to seasonal changes in solids accumulation, grazing activity and sloughing of microbial film. The final effluent solids and, organic matter content is then too high for discharge or reuse. Given the increasingly stringent effluent standards, both in terms of quality and consistency, tertiary treatment is often required. This study was designed to investigate the key parameters affecting the performance of low-rate trickling filters and the characteristics of their effluents in terms of contaminant size, which might influence the efficiency of crossflow filtration as a tertiary treatment for the trickling filter.

Clean and spiked sediment formulations of various silt sand and clay sand ratios were tested for toxicity using a bioassay that utilizes bioluminescent bacteria Measured toxicities of clean and copper sulfate–spiked sediments were negatively but nonlinearly related with percent silt and percent clay, but no significant relationship existed between measured toxicity and sediment composition for methyl parathion–spiked formulations Results suggest that solid phase sediment bioassays using bioluminescent bacteria may be useful for testing the toxicities of single contaminants in formulated artificial sediments of known particle size composition, and for repeated samples collected from the same site However, extreme caution must be taken when testing sediments of varying composition or which may be differentially contaminated or contain a suite of contaminants.

The study investigates the surface controls of major dust emissions and determines the patial distribution of major dust source in South Africa. This study follows a multi-disciplinary approach where primary and secondary data were used. The main objective of the study is to determine the spatial distribution of South Africa's Major Dust Sources. Meteosat Second Generation (MSG) satellite imagery, land use and land cover maps were used to achieve the first and the second objectives of the study. Primary data involved sampling 30 soil samples in the field in order to achieve the third objective of the study. The crust, soil moisture, soil texture and grain size are all controls of dust emission. This investigation is however focused predominantly on grain size characteristics. GIS methods were also used to determine soil type from the African soil map. Soil samples in both provinces were then collected to assess the Particle Size Distribution (PSD) of the soils. The particle size was determined based on a sieve analysis for grain sizes that were greater than 2mm and laser diffractometry, MasterSizer (Malvern) was used to achieve this. The results from the Malvern were later put to R Statistics where they were clustered into eight clusters to determine similarities and difference of the grain size. Because there is no uniqueness in the soil types found in the study area, there were no solid conclusions made based in them. The results show that the soil types are found across South Africa but not the same amount of dust activity was detected in the other parts of the country. Previous studies show that global significant dust sources are natural sources such as lakes, pans and depressions. However, results demonstrate that South African dust sources are anthropogenic sources resulting from commercial agriculture in semi-arid regions. This study has demonstrated that surface sediments suitable for dust production are a mixture of fine material, silt (50µm) and coarse material, sand (2000µm) and it appears that all clusters in this study all contained both mixtures and all have potential to emit dust.

No description available.

<p> Powder Metallurgy (P/M) offers a very efficient method to produce high volume, high throughput steel parts. The two most important property issues affecting P/M steels are: (I) possessing high mechanical properties despite having inherent internal porosity; (2) maintaining very tight dimensional tolerances during processing (sintering). Researchers are continually looking at ways to improve these two properties while keeping costs down. As in wrought and cast steels, in most applications P/M steels are alloyed; in P/M processing, alloys are typically added to Fe + C powder mixes as elemental powders. The entire mix of Fe+ C +elemental alloying additives are then consolidated under high pressure and sintered at high temperatures to strengthen the compact. The current work deals mainly with the the most commonly used alloying additives in P/M steels, Ni and Cu. </p> <p> While it is well-known that Ni and Cu do indeed improve the mechanical performance of steels and do affect the dimensional change of P/M parts in specific ways, for over 50 years the same standard Ni and Cu powders have been used in the industry. With new breakthroughs in the production of extra-fine metal powders (- 1-2 urn) P/M researchers now must examine the effect of particle size of alloying additions on the performance of sintered steels. Prior to the current work, significant documented work investigating the effect of particle size of Ni and Cu on the performance of P/M steels was very limited. </p> <p> The current work examined: (I) Ni powder particle size effects in P/M Ni steels; (2) Ni powder particle size effects in P/M Ni-Cu steels; (3) Ni and Cu powder particle size effects in P/M Ni-Cu-Mo steels. </p> <p> Specific focus was on determining the effects of particle sizes on the dimensional control and mechanical peformance of P/M steels. With both Ni and Cu, the finer the powder addition the better the dimensional control and mechanical performance of the steels. In steels containing both Ni and Cu, finer Ni also improved the distribution and diffusion of Cu. This suggested that there was a significant interaction between Ni and Cu during sintering which could be tailored to improve properties. The effect of changing Ni particle size on overall steel properties was significantly greater than the effect of changing Cu particle size. </p> <p> Mechanistic analyses via optical microscopy, SEM-EDX and E-SEM investigation, dilatometry, and differential thermal analysis were carried out to explain the results. Mathematical models were also developed to show the effect of Ni and Cu particle size on diffusion into the Fe matrix during sintering. </p> / Thesis / Master of Applied Science (MASc)

Broiler nutrition can be affected by many different factors, and diets can be made up of a wide variety of components. Feed enzymes, different Ca sources, and various ingredient particle sizes all contribute to broiler nutritional status and need to be investigated to determine their full effects on the bird. The objective of the first study was to evaluate various Ca sources and microbial phytases using an in vitro assay to simulate broiler digestion. The trial measured total Ca and P, soluble Ca and P, and pH. It involved limestone, dicalcium phosphate, highly soluble Ca (HSC), whey, and a control with no added Ca. Each diet was supplemented with 0 or 500 FTU/kg of phytase 1 or phytase 2. Diets were analyzed for total Ca and P and then were subjected to a gastric phase digestion, including the addition of HCl and pepsin, with incubation times of 5, 10, or 20 min. They were also subjected to a gastric phase and a SI phase digestion, including the addition of HCl, pepsin, NaHCO3, and pancreatin with incubation times of 5, 10, 20, or 60 min. The objective of the second study was to evaluate various particle sizes, Ca sources, and source locations using the same in vitro assay. Large, medium, and fine particle sizes, as well as limestone from 4 different locations and HSC were subjected to the same assays and conditions as in the first trial. These studies suggest that HSC is a highly soluble Ca source, phytase improves P solubility in vitro, fine particle size is more soluble than large particle size in vitro, and location from which the Ca source is obtained can affect Ca and P solubility. The in vitro assay utilized in this study is a fast and cost efficient technique for evaluating and comparing parameters of broiler diets to make recommendations for commercial poultry nutrition. / Master of Science

As part of a risk assessment study of the Leading Creek Watershed in Ohio, a prior Virginia Tech researcher collected pavement and subpavement sediment samples at 17 sites using the hybrid areal sampling technique with a clay adhesive. The watershed, which is heavily impacted by mining and agricultural activities, suffers from low pH, high concentrations of metals and sediment in the water column, and excessively silted streambeds. The current work presents the results of the particle size analyses performed on the hybrid samples in the context of evaluating the effectiveness of the technique itself and as a tool in future watershed/ecological studies, as well as examining possible relationships between siltation and indicators of ecological health in Leading Creek. By combining clay grid and adhesive sampling methods, the hybrid technique consistently achieved an effective particle size sampling range of 0.05 mm (1.97 x 10-3 in) to over 300 mm (11.8 in), thereby reducing the common problem of trunction. However, the overlap of the clay adhesive and natural sediment distributions and atypical sediment loading from surrounding abandoned and reclaimed mine lands obscured expected trends such as downstream fining and hindered the analysis of materials finer than 0.125 mm (4.93 x 10-3 in). Volumetric conversion of areal samples using the Modified Cube Model with a traditional exponent of -1 for clay was complicated by the large amount of fines in the Leading Creek samples. Further investigation into a more appropriate conversion technique for the evaluation of fine sediment samples is warranted. / Master of Science

Master of Science / Food Science Institute / Fadi M. Aramouni / Jeffrey A. Gwirtz / In order to improve the quality of products available for consumers who require a gluten-free diet, this study examined the effects of sorghum flour composition and particle size on functionality in gluten-free batter bread. White, food-grade sorghum was milled to flour of varying extraction rates (60%, 80%, 100%), and was subsequently pin-milled at different speeds (no pin-milling, low- speed, and high-speed) to create flours of both variable composition and particle size. Two commercially-milled sorghum flour samples (AF and TV) were included in the study and subjected to the same pin-milling treatments. Characterization of each flour included measurements of flour composition, total starch content, particle size distribution, damaged starch, and water absorption. Bread characterization included measurement of specific volume, crumb properties, and crumb firmness through the use of digital imaging and texture profile analysis. Significant differences were found (p<0.05) in the composition of sorghum flours of varying extraction rate, most notably for fiber and total starch contents. Flour particle size and starch damage were significantly impacted by extraction rate and speed of pin milling (p<0.05). With the exception of the commercial flour samples, water absorption increased significantly with increasing extraction rate and speed of pin-milling speed (p<0.05). Within all treatments, breads produced from 60% extraction flour had significantly higher specific volumes, better crumb properties, and lower crumb firmness when compared to all other extractions and flour types. These measured bread characteristics were significantly impacted by flour properties, specifically particle size, starch damage, and fiber content (p<0.0001). The commercial flours studied produced breads of low specific volume, poor crumb properties, and dense textures. These results can assist millers and product developers in advancing the quality of sorghum-based gluten-free foods for the consumers that require them. Further research is necessary to better understand the extent to which particle size, and therefore starch damage, can improve sorghum-based gluten-free breads.

published_or_final_version / abstract / Physics / Doctoral / Doctor of Philosophy

This study focuses on the effect that particle properties (size, density and shape) have on fluidized bed hydrodynamics and entrainment rate. The experimental work was carried out using two Plexiglas columns having internal diameters of 0.05 m and 0.14 m respectively and a total height of 6 m from the gas distributor. The particle density was in the range 1300 to 4600 kg/m3, the Sauter mean diameter was in the range 23 to 60 um and the fines content (% < 22 um) was in the range 1 to 29 %. Particle shapes, which ranged from angular to spherical, were characterized by image analysis of SEM photographs. Air was used, as the fluidizing gas and the superficial velocity was kept constant at 0.38 m/s in the 0.05 m column. In the 0.14 m column it was varied in the range 0 to 0.8 m/s. The dense-phase voidage, bubble fraction and entrainment rate of the powders were measured at ambient conditions. In general it was found that the bubble fraction and entrainment rate increased with an increase in the superficial gas velocity. The dense phase voidage was found to increase with an increase in the fines content of the powder and it was only a weak function of the superficial gas velocity. Most importantly, it was found that angular-shaped particles had a higher dense phase voidage, a lower bubble fraction and a lower entrainment rate when compared to spherical-shaped particles having similar particle density and size. Possible reasons for the lower entrainment rate for the angular-shaped particles are given. The measured dense phase voidage, bubble fraction and entrainment flux was compared with predictions from published correlations and it was found that none of the correlations provided a good fit to the data obtained in this work and that different correlations predicted widely different entrainment rates for the same system. It is therefore recommended that literature correlations should be used with caution in the absence of experimental data. Empirical correlations for the dense phase voidage and bubble fraction are developed. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2007.