STUDIES ON MECHANICAL AERATORS

Abstract

For those of man's activities which result in the widespread distribution of natural and synthetic organic compounds, degradation and recycling depend on natural processes. Some these waste products are collected for disposal and treatment whereas others are dispensed so widely in theA. environment that, once distributed their ultimate fate depends on factors beyond man's capacity for intervention. Although the activity or microorganisms is not• the only mechanism involved in recycling it makes a major contribution in many cases; a combination or physicochemical and biological degradation may be important with both dispersed and collected chemicals. For these wastes which can be collected and which are recycled by breakdown to the constituent elements a microbiological approaCh through a designed process is often the method of choice, mainly for reasons of economy including energy conservation. This applies particularly to purification of wastewater where microbial processes are effective at the concentrations'of dissolved compounds which would generally be too low for economic physicochemical treatment.. Application of microbiological waste treatment processes provides the basis for what is probably the single largest economic' contribution of biotechnology. In the present study, the pattern (d. COt) reduction untie r• varying impeller speeds and submergences in a cylindrical batch reactor was observed, For COt) reductiinn, fermentation of synthetic wastewater (dilute molasses solution) was done. Impeller speeds used for experiments were 90 rpm, 120 rpm, 150 rpm and 1R0 rpm. The majority of fermentation processes are aerobic and therefore, require the provision of oxygen. If the stoichometry of respiration is considered, then oxidation of glucose may be represented as : C6H1206 + 602 = 61120 + 6C02 Thus, 192 grams of oxygen are required for the complete oxidation of 180 grams of glucose. However, both components must be in solution before they are available to a micro organism and oxygen is approximately 6000 times less soluble in water than is glucose. Thus, it is not possible to provide a microbial culture with all the oxygen it will need for the complete respiration of glucose (or any other carbon source) in one addition. Therefore, a microbial culture must be supplied with oxygen during growth at a rate sufficient to satisfy the organisms demand.. It was bearing the above factors in mind that the experiments were performed with different speeds and submergences of impeller so as to reach an "optimum" condition (with respect to impeller submergence and speed), which could supply oxygen at a rate sufficient to satisfy organisms demand at the lowest possible energy consumption. A vane disc impeller was used in the experiments.