Grundlagen und Optimierung der Sauerstoffzufuhr und des Sauerstoffertrags beim Belebungsverfahren mit Aufwuchskoerpern Schlussbericht

In the first part of the report the influence of plastic media modules with regard to oxygen transfer in clean water was investigated. Different types of plastic media modules were fixed within the aeration tank of a common fine bubble aeration systems above the diffusers. The height of the media modules and the distance between diffusers and the lower border of the media modules were important experimental variables with respect to the modules configuration. During all oxygen uptake runs the oxygen transfer rate, the diameter and velocity of bubbles, and the movement velocity of the water were determined. On the basis of extensive experiments the influence of the type of plastic media modules, of the distance between diffusers and modules, of the arrangement of the modules and the diffusers in the tank (single and double spiral flow) and of the air flow rate on the oxygen transfer rate, on the diameter and velocity of the bubbles and on the water velocity was determined. In the second part of the report the influence of surfactants on the oxygen transfer rate in clean water was examined in order to simulate the reducing influence of surfactants in activated sludge plants on the rate of oxygen transfer of fine bubble aeration. After characterizing the different types of surfactants and their concentrations in typical wastewater their influence on the properties of water is discussed. Based on the fundamentals of oxygen transfer, the present knowledge of the properties and behaviour of air bubbles in water with and without surfactants is compiled, mainly with respect to those parameters that influence the rate of oxygen transfer. The influence of type and concentration of surfactants is extensively investigated varying the properties of the applied pure water (content of electrolytes, hardness). On the basis of the experimental results it is shown that the well known hypotheses describing the influence of surfactants on the coalescence of bubbles and the corresponding inhibition of oxygen transfer are incorrect. A new hypothesis could not be formulated, however. Finally, suggestions are made for improving the technique of measuring the rate of oxygen transfer essentially. These results can be applied in practice directly. (orig.)SIGLEAvailable from TIB Hannover: F93B737 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman