Graduate Thesis Or Dissertation

 

Comparison between thermophilic and mesophilic aerobic biological treatment of a synthetic organic waste Pubblico Deposited

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  • Temperature is one of the most important factors affecting microbial activity and consequently is of great importance in a biological waste treatment system. Extensive research has been carried out to determine the effects of temperature on biological reactions in the temperature range of 20° to 35° Centigrade. It is generally agreed that the reaction rate increases by a factor of two to three for each ten degree Centigrade rise in temperature within this range. There has, however, been very little research to determine temperature effects in the range of 35° to 60° Centigrade. Therefore it was deemed necessary to determine the effect of temperature on aerobic biological treatment of an organic waste in the temperature range of 20° to 60° Centigrade. The impetus motivating this research is the need for a treatment process capable of immediate treatment of high temperature wastes such as some canning wastes and pulp and paper wastes, without prior cooling. At present the thermal energy from high temperature wastes is dissipated by use of cooling towers or other cooling devices. If it is possible to use the thermal energy to increase the decomposition rates in a treatment process, then of course it is desirable to do so. To evaluate the feasibility of high temperature treatment it was imperative to devise a method or means by which to compare the organic removal rates and treatment efficiencies at the various temperatures. To make these comparisons it was necessary to determine at the various temperatures the maximum rate of oxygen demand, the efficiency of organic removal, the quantity and forms of nitrogen being discharged in the effluent, the net solids produced, and the settling characteristics of the sludge. To compare treatment efficiencies at the various temperatures the following tests and determinations were performed: 1. Suspended Solids 2. Chemical Oxygen Demand 3. Nitrogen 4. Oxygen Upptake 5. Type of Growth 6. Settling Characteristics The conclusions drawn from these tests results are as follows: 1. The biochemical activity rate as measured by oxygen uptake increased from 20° to 45°C. The rate dropped rapidly as the temperature was increased above 45°C. 2. The COD removal efficiency was above 90% for the entire range. 3. The net solids production decreased as temperature was increased from 25° to 50°C. 4. Clarification is difficult at temperatures above 35°C. 5. Nitrification does not take place above 40°C. 6. The purification rate can be increased tremendously by increasing the temperature from 20°C to 45°C. 7. High temperature treatment appears to be readily adaptable to dispersed growth systems. However, thermophilic treatment does not appear to be applicable to treatment systems which require solids removal because of the poor settling characteristics.
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