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Grit is usually removed from sewage flow just prior to treatment by some type of grit chamber, often little more than a wide channel with a depressed trough to trap the grit. Three shapes of grit chamber troughs were studied in a model to determine which was the most efficient for the selective capture of grit. The model was constructed of wood, with plastic, interchangeable troughs, and was six inches wide by about ten feet long, including a three foot approach channel to the chamber. The three troughs were six inches deep with 2:1, side slopes and differed, therefore, only in bottom length. Trough 1 tapered to a point, Trough 2 had a four inch bottom length, and Trough 3 had an eight inch bottom length. Water from a town main was run through the apparatus at velocities varying from 0.11. to 0.8 fps and depths from 0.1 to 0.33 feet. Grit was added, as the flow entered the approach channel, through a funnel. Ordinary construction sand was used as grit after being sieved to obtain 0.1 and 0.2 mm diameter particles. When all the grit had been added the flow was stopped and all grit which had not passed the trough was removed and measured. This measurement when compared with the known amount of grit which was added produced a value of per cant grit passing the trough for each run. Trough 2, the medium length trough, was found to be relatively most efficient for the selective capture of grit. / Master of Science

The quality of healthcare in low-resource countries is often limited by the environment, lack of funds, staff availability, electricity availability, and more. In the words of a Malawian physician, medicine can feel like improvisation, wherein one must make due with available resources rather than desired resources. One prevalent problem among low-resource hospitals is the functionality and longevity of medical equipment. A large percentage of all medical equipment in Malawian hospitals is donated, resulting in a wide spectrum of models, necessary spare parts, and functionality. These machines can break quickly due to heavy use prior to donation, missing user and maintenance manuals, and a lack of replacement parts. Thus, finding necessary life-saving equipment in Malawian hospital wards can be a challenge. One such piece of equipment is the oxygen concentrator, necessary for treatment of respiratory disease, use with CPAP machines, and in the administration of surgical anesthesia. This device fills many roles in low-resource hospitals, but in many Malawian hospitals it is the most frequently malfunctioning piece of equipment. A survey administered to medical personnel and maintenance personnel in hospitals in Malawi’s Central and Southern Regions isolated some common causes of oxygen concentrator malfunction. Prominent among these were poor oxygen concentrator ventilation and the lack of consumable replacement parts such as the intake bacterial filter. A stand made from locally-sourced materials was developed to encourage better oxygen concentrator exhaust and raise the device out of dust and cleaning fluids on ward floors. Intake bacterial filter alternatives were researched, designed, constructed, and tested, manufactured from housing materials and filter media available in Malawi or continental Africa. A primary source of difficulty for low-resource hospitals is lack of autonomy, requiring aid from affluent nations to supply equipment and consumable materials. This work suggests that sustainable innovations, such as allowing consumables to be produced in-country, can replace aid with development and create more accessible materials to hospital maintenance personnel. Collaboration with material suppliers and engineers in Malawi can provide sustainable designs and systems to help hospitals access the supplies they need to service oxygen concentrators and other equipment. / Master of Science / The quality of healthcare in low-resource countries is often limited by the environment, lack of funds, staff availability, electricity availability, and more. In the words of a Malawian physician, medicine can feel like improvisation, wherein one must make due with available resources rather than desired resources. One prevalent problem among low-resource hospitals is the functionality and longevity of medical equipment. A large percentage of all medical equipment in Malawian hospitals is donated, resulting in a wide spectrum of models, necessary spare parts, and functionality. These machines can break quickly due to heavy use prior to donation, missing user and maintenance manuals, and a lack of replacement parts. Thus, finding necessary life-saving equipment in Malawian hospital wards can be a challenge. One such piece of equipment is the oxygen concentrator. This device fills many roles in low-resource hospitals, but in many Malawian hospitals it is the most frequently malfunctioning piece of equipment. A survey was used in hospitals in Malawi’s Central and Southern Regions to collect information on why oxygen concentrators malfunction. Common reported causes of malfunction were oxygen concentrators overheating due to clogged exhaust vents, and the unavailability of necessary disposable filters. A stand made from locally-available materials was developed to improve oxygen concentrator ventilation. Replaceable filter alternatives were researched, designed, constructed, and tested, made from housing materials and filter materials available in Malawi or continental Africa. A primary source of difficulty for low-resource hospitals is dependence on more developed nations for supplies and aid. This work suggests that designing materials from locally-available materials can lessen this dependency and make necessary medical materials more accessible. Collaboration with material suppliers and engineers in Malawi can provide sustainable designs and systems to help hospitals access the supplies they need to service oxygen concentrators and other equipment.

Water treatment facilities commonly reduce soluble contaminants, such as soluble manganese (Mn2+), in water by oxidation and subsequent filtration. Previous studies have shown that conventional porous filter system removes Mn2+ from drinking water by developing Mn-oxides (MnOx(s)) bearing coating layers on the surface of filter media. Multiple models have been developed to explain this Mn2+ removal process and the formation mechanism of MnOx(s) coatings. Both, experimental and theoretical studies to date have been largely focused on the micrometer to millimeter scale range; whereas, coating layers are composed of nanoscale particles and films. Hence, understanding the nanoscale particle and film formation mechanisms is essential to comprehend the complexity of soluble contaminant removal processes. The primary objective of this study was to understand the initial MnOx(s) coating formation mechanisms and evaluate the influence of filter media characteristics on these processes. We pursued this objective by characterizing at the micro and nanoscale MnOx(s) coatings developed on different filter media by bench-scale column tests with simulating inorganic aqueous chemistry of a typical coagulation fresh water treatment plant, where free chlorine is present across filter bed. Analytical SEM and TEM, powder and synchrotron-based XRD, XPS, and ICPMS were used for characterization of coatings, filter media and water solution elemental chemistry. A secondary objective was to model how surface coating formation occurred and its correlation with experimentally observed physical characteristics. This modeling exercise indicates that surface roughness and morphology of filtering media are the major contributing factors in surface coating formation process. Contrary to previous models that assumed a uniform distribution and growth of surface coating, the experimental results showed that greater amounts of coating were developed in rougher areas. At the very early stage of coating formation, unevenly distributed thin films and/or particle aggregates were observed, which provided active sites for further surface coating growth. The predominant MnOx(s) phase in the surface coatings was identified to be poorly crystalline birnessite having scavenging activity by intercalation and/or sorption. This would explain the enhancement of efficiency in removing soluble manganese and other contaminants during water filtration. Moreover, the increased Mn2+ removal effect of having aluminum (Al) in pre-treated water is explained. These results indicate that the surface roughness and morphology need to be incorporated into particle capture models to more precisely describe the soluble manganese removal process. / Ph. D.

Water utilities can experience problems from bubble formation during conventional treatment, including impaired particle settling, filter air binding, and measurement as false turbidity in filter effluent. Coagulation processes can cause supersaturation and bubble formation by converting bicarbonate alkalinity to carbon dioxide by acidification. A model was developed to predict the extent of bubble formation during coagulation which proved accurate, using an apparatus designed to physically measure the actual volume of bubble formation. Alum acted similar to hydrochloric acid for initializing bubble formation, and higher initial alkalinity, lower final solution pH, and increased mixing rate tended to increase bubble formation. Lastly, the protocol outlined in Standard Methods for predicting the degree of supersaturation was examined, and when compared to this work, the Standard Methods approach produces an error up to 16% for conditions found in water treatment. Air entrainment and ozonation are the key causes of dissolved gas supersaturation and eventual bubble formation in water treatment plants. Total dissolved gas probes (TDGP) are now available to directly measure supersaturation and have many advantages compared to conventional techniques. Bubble formation during coagulation-flocculation hindered particle sedimentation, producing settled turbidities double that of solutions without dissolved gases. In a filtration study, run time to one half of initial flow was decreased by 54% when the source water was increased from 0.1 to 0.2 atm supersaturation. Indeed, even at 0.05 atm supersaturation, run length was only 21 hours in solutions without added particulate matter. A case study confirmed that bubble formation can interfere with coagulation and filtration processes at conventional treatment plants. / Master of Science

Optimum feed ration was determined for riffleshell mussels (Epioblasma spp.) held in captivity. Mussels were fed one of four rations (0.49, 0.72, 1.28, or 1.73 mg dry wt/l) of algae Neochloris oleoabundans for 2-h trials in spring, summer, fall, and winter. The test ration resulting in the most feed absorbed per hour (net absorption rate, mg/h) was determined to be the optimum feed ration. Mussels absorbed the greatest amount of food when fed the highest ration. Suggested feed rations for captive adult Epioblasma species are 1.73 mg/l when held at moderate temperatures (i.e., 15-19C), and 1.28 mg/l when held at cool temperatures (i.e., near 11C). Seasonal utilization of protein by oyster mussel (E. capsaeformis) and rainbow mussel (V. iris) was examined with O:N ratios. Ratios were determined for mussels fed a low or high-protein diet (0.11, or 0.31 mg protein/mg dry algal feed), and for mussels held in a hatchery or in the Clinch River, in spring, summer, and winter. Significant differences in O:N ratios were not observed between mussels fed a low or high-protein diet (p > 0.05). The O:N ratios were significantly highest in spring and summer, and lowest in winter (p < 0.05). Mussels primarily utilized protein in spring and summer, and conserved protein in winter. A diet high in energy was suggested in spring and summer, and a diet high in protein was suggested in winter. / Master of Science

A pilot-scale, two-stage (carbon oxidation stage one, ammonia oxidation stage two) fixed film biological aerated filter (BAF) process was operated on-site at a domestic wastewater treatment plant. Over the study period, hydraulic loadings to the system were varied, generating a range of organic and ammonia loading conditions. Nitrification was monitored along the length of the filters by measuring chemical nitrogen species and activity levels of ammonia oxidizing bacteria (AOB). During the first phase of the study, nitrification performance was characterized during the wintertime and compared with oligonucleotide probing results using an ammonia-oxidizer specific probe. Overall nitrification efficiency for wintertime conditions (average temperature 12.4 ± 0.1°C) was greater than 90 percent when ammonia-N loadings to the second stage were 0.6 kg/m3-day or less. Nitrification efficiency started to deteriorate at loadings beyond this point. Biofilm and liquid samples were collected along the distance of the two columns at high and low ammonia loadings. The degree of activity observed by ammonia oxidizing bacteria in the biofilm corresponded with the disappearance of ammonia and the generation of nitrate as water passed through the columns. During the second phase of the study, the probing methods were investigated and results of two approaches of analysis were compared to chemical nitrogen profiles. It was found that probe signals normalized to mass of total bacterial nucleic acid corresponded better with chemical profiles than using a novel method of standardizing against known nucleic acid mass standards. During both phases of the study, zones of ammonia oxidizing activity progressed along the length of the columns as organic and ammonia loadings to the system increased. The oligonucleotide probe data suggest that this shift in the location of the nitrifier population is due to higher BOD loads to the second stage, which supported higher levels of heterotrophic growth in the second stage of the system. It was concluded that the strongest influence on nitrification performance in this type of BAF system is likely to be competition between heterotrophs and autotrophs. / Master of Science

The objective of this project was to develop a suitable procedure for the design, control and optimisation of the Tubular Filter Press. To this end, the following objectives were defined for this study: • To extend or improve upon the constant pressure compressible cake filtration model, predictive solution procedure, and standard laboratory characterisation techniques requlred to obtain the empirical model parameters, presented in Rencken (1992). A new generalised area contact constant pressure compressible cake filtration model was developed for both the internal cylindrical and planar filtration geometries. The model utilises a heuristically developed area contact function which relates the interparticle contact area to the solids compressive pressure within the cake. If the area contact is zero, the model reduces to the conventional point contact model as presented in Rencken ( 1992). The sludge used in this investigation was found to exhibit a negligible degree of area contact. A new pseudo variable pressure solution procedure was developed, that is an extension of the constant pressure solution procedure, to account for the initial variable pressure stage of the Tubular Filter Press operation. The pseudo variable pressure solution procedure was found to account accurately for the initial filtration behaviour observed during the pressurisation period of the Tubular Filter Press. However for the normal operation of the Tubular Filter Press. the difference between the output of the pseudo variable pressure and constant pressure solution procedures, was found to be insignificant. Wall friction in compression-permeability (C-P) cell tests was identified as a main source of error. The significance of wall friction was investigated using a specially constructed C-P cell. that enabled the transmitted pressure through the cake sample to be measured. The accuracy of the characterisation which had been corrected for the effects of wall friction, was found to improve the prediction of the filtration behaviour of the sludge significantly. The direct shear test was identified and documented as a feasible experimental procedure to determine the coefficient of earth pressure at rest. The coefficient of earth pressure is unique to the non-planar filtration geometries. The coefficient of earth pressure at rest was determined for the sludge used in this investigation. • To incorporate the constant pressure compressible cake filtration model and the associated predictive solution procedures into a user-friendly computer programme that will facilitate the design and optimisation of full-scale plants. The predictive solution procedures were incorporated into the Windows 95 computer programme, COMPRESS, that can be used for any constant pressure compressible cake dead-end filtration application where the filtration geometry is planar or internal cylindrical. A control and optimisation strategy for the continuous operation of the Tubular Filter Press has been proposed. To develop a regressive solution procedure, and incorporate this procedure into a user-friendly computer progranune, that will enable the empirical model parameters. normally obtained from standard laboratory-scale tests, to be obtained from actual filtration data. A regressive solution procedure was developed that utilises a direct search optimisation technique that is an extension of the COMPLEX method. The regressive solution procedure was incorporated into the Windows 95 program, REGRESS. The program utilises filtration data from any dead-end constant pressure filtration application of either planar or internal cylindrical geometry. REGRESS provides an effective means for determining the true physical or plant specific filtration characteristics of the sludge. The regressive solution procedure also enables the parameters specific to the new area contact model to be determined. The sludge characterisation obtained from regressing on filtration data was found to be a significant improvement in predicting the filtration behaviour, than the characterisation obtained from the standard non-filtration laboratory-scale methods, even after the C-P cell data had been corrected for the effects of wall friction. The programs COMPRESS and REGRESS should greatly assist in the design. control and optimisation of the Tubular Filter Press process. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2000.

Exosomen aus Zellen nehmen eine immer größere Rolle in aktuellen Erkenntnissen zu Tumorwachstum und Metastasierung ein. Die Funktionen dieser circa 40-100 nm großen, aktiv sezernierten Vesikel sind bisher noch weitesgehend ungeklärt. Für die Untersuchung von Exosomen sind optimierte und schonende Isolierungsmethoden notwendig. Zur Zeit gibt es jedoch weder eine standardisierte Methode zur routinemäßigen Isolation von Exosomen noch zur Isolation von funktionell intakten Exosomen für die anschließende Funktionsanalyse. Ziel dieser Arbeit war es, eine vereinfachte, größenbasierte und standardisierbare Methode zur Isolation von funktionell intakten Exosomen zu entwickeln und die isolierten Exosomen qualitativ und quantitativ zu charakterisieren. Die Ergebnisse dieser Arbeit konnten in einer internationalen Fachzeitschrift publiziert werden. Die Publikation liegt dieser Arbeit bei (Heinemann et al. 2014).

The problem of filtration of liquid aerosols by both wettable and nonwettable filters has been extensively studied and the results of the theoretical calculations together with the experimental results are presented. More realistic models of filtration by both wettable and nonwettable filters have been developed and verified experimentally. A new instrument has been developed, and used in the experiments, for the measurement of the absolute concentration of aerosols in the gas stream. This instrument is based on the measurement of the initial vapour content of the gas stream simultaneously with the measurement of the vapour content after the total evaporation of aerosol. The concentration of the aerosol is calculated as the difference between these two values. The instrument was developed to provide fast and accurate measurements of aerosol concentration. The main advantages of the instrument are: high accuracy, simplicity of measurement, possibility of use for a wide range of substances, perfect suitability of operation for automatic monitoring technologies, etc. All rights for this instrument have been reserved and the fully automatic version will be available in the near future. It was found that the efficiency of filtration of aerosol on the wettable filter depends on the thickness of the liquid film on the fibre. This parameter was taken into account in the development of a theoretical model of filtration on wettable fibrous filters. The particle breakthrough problem has been solved by the optimisation of the aspect ratio (the ratio of the height by width) of the wettable filter. On this basis, industrial devices have been developed, patented, and implemented in industry. These devices provide a stable operating efficiency of higher than 99%. It was found experimentally that the efficiency of filtration of aerosol on the nonwettable filter depends on the diameter of the drop suspended on the filter, and on the area of the filter blocked by drops: this influences the velocity of filtration. All these parameters were taken into account in the development of a theoretical model of filtration on nonwettable fibrous filters. On the basis of this model, satisfactorily verified by the experiments, an industrial device has been developed. The harnessing of atomisers makes it possible to maintain the efficiency of filtration higher than 99%, even with a relatively high velocity of filtration of 2.7m/s. The new technology is tackling the problem of handling huge amounts of exhaust gases and this is particularly important for cramped installations when the space available for the air pollution control technology is quite limited. A highly efficient gas cleaning technology has been developed. This technology is based on combining two stages (wet scrubber and filter) of currently utilised air pollution control devices by submerging the fibrous filter into the liquid on the plate. The new device provides an effective division of the main gas stream into ultra-small bubbles which increase the contact area between the gas and liquid phases. It was estimated theoretically and verified experimentally that the efficiency of the proposed 'combined' technology, is 45% higher than the efficiency of the two stages technology. The technology has been patented and will be offered for industrial implementation in the near future.