Alpha in High-Contaminant Conditions

Process Water Oxygen Transfer Rate Test Results

A critical aspect of Activated sludge WWTP design is estimation of field or process water oxygen transfer from clean water transfer data. The effects of water temperature, total dissolved solids and operating dissolved oxygen concentration are well defined and predictable. The affect of wastewater contaminants on the volumetric transfer rate constant, KLa, are less well defined. The ratio of the process water KLa to the clean water KLa is also known as the Alpha Factor (α). α varies depending on the aeration process, tank geometry and water characteristics. α values ranging from 0.3 for fine bubble diffusion up the .85 for low speed surface aerators have been reported. Measurement procedures for determination of α have been debated at length. Unlike clean water oxygen transfer measurement, no standard has been developed for process water oxygen transfer, however a standard guideline has been published by a joint committee of WEF and ASCE6.

The clean water oxygen transfer capabilities of the Mazzei AirJection Venturi Aeration process have been tested and the results have been certified by a professional engineer. The purpose of this paper is to determine the α for the AirJection process under field conditions. The wastewater used was primary clarifier effluent, which due its high contaminant levels should represent worst-case conditions for α determination.