Efficiency of diffused aeration systems in wastewater treatment

increased organic loading on wastewater treatment plants using ac tivated sludge process has necessitated changes in aeration systems to increase the oxyg?nation efficiencies in aeration tanks. Similarly, reaeration of streams and lakes requires improvements in conventional aeration practices. Although many parameters affect the efficiency of diffused-bubble aeration sys tems, the key factors in controlling the mass transfer of oxygen are the transfer coefficient and the total surface area of air bubbles in the liquid. The total surface area of air bubbles depends on their con tact time with the liquid. The influence of varying the operating parameters on the contact time and the mass transfer coeffi cient has been discussed elsewhere,1?2 whereas the influence of varying airflow rate, diffuser submergence, bubble size, and bubble contact time on the oxyg?na tion efficiency for four different aeration systems is presented in this paper. The rate of oxygen absorption into water, dC/dt, in mg/l/hr, can be obtained from: