Oxygen Transfer Efficiency in Small Diffusers

Abstract

Small on-site aerobic package plants are one alternative being explored to address situations in which septic-tank and leach-field systems are not appropriate or feasible. Such small aerobic systems use either mechanical-aeration or forced-air diffusers. However, the only information available in the literature on designing the aeration systems pertains to large-scale facilities. Oxygen-transfer characteristics of diffusers in shallow systems should be significantly different from those reported in the literature for deeper systems. This paper reports on a laboratory study conducted at the Environmental Technology Laboratory at the University of Alaska, Fairbanks, analyzing the oxygen-transfer characteristics of small diffusers. Data show that diffusers typically used in small on-site aerated wastewater-treatment systems provide lower overall oxygen transfer on a mass basis, but actually transfer oxygen at a faster rate than diffusers in deep tanks reported in the literature. The present research provides basic data of importance for the design of small wastewater-treatment systems using diffusers.