Zugl.: Giessen, Univ., Diss., 2009

Thesis (M.S.)--University of Wisconsin--Madison, 1961. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 53-55).

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010. / Full text also available online. Scroll down for electronic link.

Techn. Universiẗat, Diss., 2005--Hamburg.

A slow sand filter system was developed which was suitable both for experimental purposes and full scale community water supply. The performance of the system was enhanced by the incorporation of pretreatments such as gravel prefiltration, sub-sand prefiltration and direct protection of filters by the incorporation of synthetic fabric layers. The system was used to examine aspects of the biological and physico-chemical nature of Slow Sand Filtration with particular reference to the removal of Rotavirus and a variety of bacterial and viral indicators. The results of the developmental phase and experiments conducted with operational filters and in the laboratory confirmed the importance of biological mechanisms, in particular adsorption to biological surfaces present in the upper horizons of slow sand filters. It was observed that both the efficiency and pattern of removal of Rotavirus in Slow Sand Filtration were similar to those observed for faecal indicator bacteria, bacteriophage and turbidity ie colloidal clay and other particles. Thus it was concluded that negatively charged particulate colloidal entities appear to behave similarly despite differences in size and surface characteristics and that Rotavirus is no more or less likely to pass through slow sand filters than any other particle. Thus, a well operated slow sand filter may be expected to achieve a reduction in Rotavirus densities of 2 log10 orders of magnitude. The principal mechanisms of removal of Rotavirus in the upper horizons would appear to be transportation by diffusion and adsorption to biofilms and biomass. Microbial predation is not likely to play a dominant role in the removal of Rotavirus from the aqueous phase but may be important in inactivation. A detailed examination of the incidence, prevalence and seasonal occurrence of rotaviral and other diarrhoeas in less developed countries led to the observation that unlike some of the bacterial pathogens, transmission of Rotavirus does not have a strong association with water quality. Hence. The case for low level waterborne transmission and thereby maintenance of endemicity in the community remains entirely theoretical. Moreover, bearing in mind the likelihood that slow sand filters will be operated sub-optimally in many cases, a moderate reduction in Rotavirus densities eg 1 - 2 log10 units may not be significant in terms of diarrhoeal disease risk, particularly for children and especially in the rural sector. In view of these observations and other factors eg the low infective dose of the virus and the undoubted pre-eminence of person-to-person spread, it was concluded that as a single process, Slow Sand Filtration is probably not capable of significantly reducing the incidence of rotaviral diarrhoea in less developed countries.

No description available.

Most eye drops are dispensed in multi-dose containers, hence protection should be given against microbial contamination during use. To remain sterile during it's use, the solution should contain a preservative in such concentration so that it kills micro-organisms in a short time. It has been stated in the literature that the instillation of contaminated eye drops constitutes a greater danger than the intravenous injection of a contaminated solution since the cornea is nonvascular and lacks the normal antimicrobial defences of the blood stream. Amongst the preservatives used, those included in the official formulations for eye drops are Chlorhexidine Acetate, Phenyl Mercuric Nitrate, Benzalkonium Chloride, and to some extent Phenylethanol, which may be used in combination with Benzalkonium Chloride. The main purpose of this investigation has been to determine the adsorption of these preservatives by different filters during sterilization by filtration. Part 1, p. 2.

L’objectif de la thèse a été la construction d’un pilote de filtration horizontale en République Centrafricaine, pays dont les besoins en eaux potables sont criants. Le pilote devait permettre un traitement simple de l’eau de rivière, nécessitant un minimum d’énergie et de produits de traitement. La filtration lente sur sable qui apparaît comme une réplique des processus naturels dans le sol répond à ces exigences. Après avoir effectué un bilan de la pluviométrie, nous avons pu montrer que si les eaux souterraines étaient de bonne qualité, les aquifères superficiels sont par contre contaminés par le manque d’assainissement. Après examen de la qualité des eaux et sédiments en différents sites du fleuve Oubangui, un pilote a été construit selon les recommandations des «Eaux de Paris» à Bangui et alimenté avec de l’eau de l’Oubangui. Le suivi des performances et de la qualité des eaux produites a montré que ce pilote avec une production de 400l/h respectait les normes exigées pour une eau brute avant javellisation Des essais de la modélisation du transit des eaux dans le pilote ont été entrepris par l’utilisation du modèle MODFLOW. L’emploi du traceur «fluorescéine» a permis de calibrer le modèle .Les propriétés adsorbantes des différents sables du pilote ont été étudiées grâce à l’utilisation conjointe des techniques : MEB/EDS; BET; ICP/AES; CHNS; UV/Visible. Par comparaison avec les sables originels ayant été utilisés dans la conception du pilote, la capacité d’adsorption des sables est améliorée en raison de modifications de surface et de dépôts d’argile et oxydes/hydroxydes de fer dans les interstices et fissures produits par effet d’érosion dû à l’écoulement des eaux. / The objective of this thesis concerned the elaboration of a horizontal flow filtration pilot in Central African Republic because of a lack of potable waters in this country. In the conception of this pilot, treatment processes which should be chosen for riverine water purification, have to be low energy cost and easy to be implemented. Taking into account these considerations, we decided to employ the low-filtration method with the sand as the adsorbent. Indeed, this latter is known to behave as a natural adsorbent through hydrogeological processes in sols. After itemizing pluviometric data. it was shown that ground-waters possessed good water quality, whereas aquifers in low depths were found to be instead contaminated. A pilot was built by respecting the recommendations established by Eaux de Paris located at Bangui Performances and quality of treated waters were followed up, and the data obtained during the running were found to be in good accordance first with potable-water criteria with a water production of 400L/h and second with water-quality norms which were usually recommended for a raw water before its chlorination. Modelisation tests on the transit of water in the pilot were carried out using MODFLOW. For model calibration, it was used the dye Fluorescein as a tracer. The adsorption properties of sand in this pilot were studied owing to the combined use of the techniques:SEM/EDS;BET;ICP-AES;CHNS;UV/visible. In comparison with the starting sand used in the construction of the pilot, all the data showed clearly that the adsorption capacity of this sand increases with time owing to surface modifications and clays and iron oxides / hydroxides depositions in cracks.

No description available.

The adsorption of low concentrations of heavy metals, such as zinc, copper, lead and mercury, by various British Columbia coals was investigated. Five British Columbia coals were used as adsorbents for the four heavy metals described above. Batch tests were run on all five coals, namely, Hat Creek Oxidised, Hat Creek Unoxidised, Cominco Oxidised, Cominco Ash Waste and Cominco Production Coal. The optimum contact time for batch tests was found to be 60 mins. Batch tests provided a quick comparison of the adsorptive capacities of the five coals. Based on the batch tests data, the best performing coal from each of the Hat Creek and Cominco groups, namely, Hat Creek Oxidised and Cominco Ash Waste were chosen for further investigatory work using column tests. For the column tests, the influent concentrations were 2 mg/ℓ and less for zinc, copper and lead. Column work with mercury was carried out with influent concentrations of 5 μg/ℓ and less. Column tests showed the following:- a) Varying the cross-sectional area of the coal column from .001 ft² to .002 ft² has no significant influence on the adsorptive capacity. Both columns have diameters more than 10 times that of the average coal particle. b) The most crucial factor affecting adsorptive capacity is the pH of the influent. There is a definite decrease in capacity with decreasing pH. c) The capacity decreases with increasing flow rate, but the relationship is not linear. The decrease in capacity due to a flow rate increase from 1 to 3 Igpm/ft² is much greater than the decrease in capacity due to an increase from 3 to 5 Igpm/ft². d) Comparing the adsorptive affinities of zinc, copper and lead, it is seen that lead displayed the greatest affinity with copper second and zinc third. At 10% breakthrough concentration, the capacities displayed by Cominco Ash Waste coal for lead, copper and zinc were in the ratio of 12:6:1. The influent pH and initial concentrations involved were 4.0 and 2 mg/ℓ respectively, and the flow rate was 1 Igpm/ft². e) Using influents containing a mixture of zinc, copper and lead results in smaller individual capacities for Zn, Cu and Pb than would be achieved with single solute influents. But the total overall capacity of the coal for heavy metals is greater with mixed influents than with any single solute influent. f) Tests with mercury influents show that deterioration of the concentration of the mercury solution occurs at concentration of 5 μg/ℓ and less. g) Of the two coals chosen for column test work, Hat Creek Oxidised is the superior coal with regard to the adsorptive capacity of heavy metals. Tests run at an influent pH of 4.0 and influent concentrations of 2 mg/£ of each metal, showed the ratio of capacities of Hat Creek Oxidised: Darco activated carbon: Cominco Ash Waste for Zn to be 12.1 : 1.2 : 1.0, for Cu to be 11.9 : 1.7 : 1.0 and for Pb to be 3.8 : 0.7 : 1.0. An attempt was made to correlate the column effluent pH with the effluent metal concentration. It was found that this correlation is more pronounced at lower influent pH values. During the course of the column work, a growth of fungus was observed at the top of the coal columns. It is possible that adsorptive capacities were affected by this fungus. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate