Comparison of Submerged Aerator Effectiveness

Abstract

ABSTRACT The effectiveness of three different submerged aerators (diffusers), a membrane diffuser, a coarse bubble diffuser, and a soaker hose, is compared by analyzing their performance parameters at varying gas flow rates and water depths of up to 10 meters. The type of diffuser chosen for a specific application depends on aeration characteristics such as the total mass transfer coefficient, standard oxygen transfer rate (SOTR), standard oxygen transfer efficiency (SOTE), and standard aeration efficiency (SAE). From experimental data, the effects of the gas flow rate and submerged depth on the total mass transfer coefficient and SOTR are determined up to a 10 meter depth. As the flow rate and diffuser depth are increased, the mass transfer coefficient and the SOTR increase for all three diffusers. At low gas flow rates, the segment of soaker hose transfers oxygen at the highest rate. The coarse bubble diffuser transfers oxygen at a lesser rate than the soaker hose but is capable of performing at higher gas flow rates. The membrane diffuser performance resembles the high transfer of a soaker hose before approaching the transfer behavior of the coarse bubble diffuser at higher flow rates. Relationships are also defined for the SOTE and SAE. Non-dimensional parameter correlations quantify the dependence of the performance parameters on the gas flow rate and depth and provide a means of predicting diffuser behavior for specified system applications.