AbstractsBiology & Animal Science

The purification capacity of an activated sludge process is highly dependent of the rate of oxygen transfer from the air to the microorganisms. This rate can be increased in an air diffusion system by subjecting the culture to high shear and high pressure. A study of the effects of high pressure and high shear on the reaction rates in an activated sludge system is presented in this thesis. These effects were determined by varying the pressure and shear levels while keeping the other parameters constant. The following tests were performed to compare the results obtained at the different operating conditions : 1. Oxygen uptake rates. 2. Biological growth rates. 3. Type of biota present. 4. BOD and COD removal efficiencies. The conclusions drawn from these test results are as follows: 1. Under the conditions of this experiment high shear and high pressure had no effect on the purification capacity of the system, 2. For this study the growth rates could not be used as a comparison because of the erratic results caused by the build up of a sludge ring around the top of the mixed-liquor. 3. The type of biota present in the mixed-liquor was about the same under all operating conditions. The most significant change was the decrease in the size of the bacterial masses and an increase in the number of individual bacteria with an increase in the shear level.