Diss. (sammanfattning) Linköping Univ. / Härtill 7 uppsatser.

Call number: LD2668 .T4 1955 Y36 / Master of Science

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Water as a route of opportunistic bacterial disease transmission has not been well established. The use of epidemiological evidence linking drinking water bacterial contamination to health effects in a population is lacking and very costly to obtain. Also, the significance of exposure to low-level contamination is difficult to determine epidemiologically. This makes it difficult to estimate the impact on a community. The use of risk assessment approach allows an understanding of low-level exposure; and to define it in a more quantitative fashion. Microbial risk assessment was employed to determine the risks associated with exposure to selected opportunistic bacterial pathogens (Aeromonas hydrophila and Pseudomonas aeruginosa) present in drinking water from various sources. An extensive analysis was conducted on drinking water obtained from various sources including point-of-use (POU)-treated water, tap water with POUconnection, tap water, bottled water, and water from vending machines and storage tanks. Enumerated bacteria included: A. hydrophila, heterotrophic plate count (HPC) bacteria, Mycobacteriuni spp., Plesiomonas shigelloides, P. aeruginosa, and total and fecal coliforms. It was found that opportunistic pathogens were present in small numbers in drinking water. Neither fecal coliforms nor P. shigelloides were found in the drinking water samples. The annual risks of colonization based on the consumption of 2L/day/person for drinking water were determined to be as high as 7.9x10⁻⁵ and 9.9x10⁻⁴ for A. hydrophila and P. aeruginosa, respectively at exposure levels ranging from 90 to 10 CFliimL. respectively. The results obtained indicates that the risk of colonization is a transient process, and the probability of infection may be very but could result in the most vulnerable (very young, the elderly and immunocompromised). More studies are needed on the occurrence of opportunistic pathogens in drinking water from various sources and animal andjor human feeding studies to better define dose-response in both healthy and immunocomprimised individuals. There is no doubt that the greatest need for microbial risk assessment is the occurrence data. Therefore, national surveys in drinking water from various sources will help in the developing of microbial risk assessment for opportunistic bacterial pathogens. The use of conventional methods as well as molecular approaches are recommended in order to obtain a more accurate identification of waterborne bacterial pathogens.

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Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1974. / Bibliography: leaves 156-160. / x, 160 leaves ill., maps

M. Tech. Biomedical Technology. / In most rural areas of developing countries, people use untreated water sources for consumption and sanitation purposes. The current health-related water quality testing techniques only determine the presence of indicator organisms and may not adequately predict the potential of water to result in adverse physiological effects after ingestion. The possibility of using an accurate and reliable in vitro bioassay that could directly predict the potential of water to cause an infection after ingestion was investigated in this study.

Many determinations have been made of the dielectric constant of water, and of its variations caused by temperature and frequency. The dielectric constant of water has a relatively high value as compared with those of many other substances with which water is commonly associated. Consequently, measurements of the dielectric constant (or of the electrical capacitance) of materials such as soil, cereal and grain have been used as indications of their moisture contents. This study was undertaken to determine whether or not a capacitance method can be used to measure sediment concentrations in water. Laboratory measurements were made of varying concentrations of several individual artificial sediments, natural sediments, and pure salts in distilled water. A flow-through-type conductivity cell was used in which the capacitor plates are fixed in relation to each other. The equation for capacitance of the flow through cell can be written as C = kD where C capacitance in farads, k = a constant determined by the physical configuration of the cell, D = dielectric constant, and it is seen that C varies directly as D. Typical values of salt and sediment concentrations existing in natural streams in the United States were determined from the literature. Conclusions of the study are summarized as follows: 1. The capacitance method of measuring concentrations of sediment in natural streams is not practical for the following reasons. The presence of even small quantities of conducting and/or magnetic sediments in the measured samples invalidates the measurements. Concentrations of sediments in most streams in the United States are too low during most of the year to be sensed by the capacitance method. Concentrations of dissolved solids in many streams in the United States are high enough during at least part of the year to render capacitance measurements inaccurate. The surface chemistry of clay-size particles prevents their being reliably measured with the capacitance method. 2. The capacitance method of measurement may be applicable for particular or specialized uses, such as the determination in the laboratory of concentrations of mixtures of known nonconducting and nonmagnetic particulate matter. Such measurements are not noticeably affected by the salts used in this study until their concentrations exceed about 10 meq/l. It is recommended that further efforts to adapt the capacitance method to the measurement of stream sediments be discontinued.

Currently it is common practice to conduct the environmental analysis of river water on randomly collected samples. Since rivers are considered to be continuously mixing, these waters are assumed to be homogeneous and therefore, the samples representative. This sampling parameter study was established to test that assumption.Three proximal points were established on the White River at Muncie, Indiana and sampled daily for twenty-five days. The samples were monitored for twenty-one different constituents: Alkalinity, chloride, color, calcium hardness, magnesium hardness, total hardness, total iron, ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, dissolved oxygen, pH, orthophosphate, total phosphate, specific conductance, sulfate, turbidity, and temperature, using the Hach DR/EL-2 water analysis kit.The results indicated that thorough mixing is present and that homogeneity does exist for some constituents. However, the data also indicate that for some constituents homogeneity within the river does not exist. The significance of sampling frequency and the correlation of some of the interrelated chemical changes which occurred during the study are also discussed.