Use of Mixers in Biological Sewage Treatment

Abstract

Application of mixers in wastewater treatment is essential to homogenise the suspended biomass. In anaerobic or anoxic reactors there is no aeration, thus mixers should be applied. Performance of mixing is based on the mixer geometry, rotational speed, the location and fluid properties such as density and viscosity. For evaluation of the mixing efficiency, generally field measurements are performed (e.g. tracer study or velocity field) which can be resource demanding. Numerical calculations could be an effective tool to gain reliable cost-effective solutions and various simulation alternatives can be compared.

In this research an anoxic tank with two mixers were examined at different rotational speed of the mixers. In this research I examined anoxic reservoir with two mixer mixers with different speeds of mixers. The mixers were placed at a distance of 1 and 2 scaffolds from the bottom of the bowl. The outcome was that the scenario with the lowest rotational speed did not provided sufficient mixing, the high rotational speed caused high velocities which may break down the flocs and results lower residence time.