ABSTRACT
At the beginning of the 20th century, activated sludge systems were developed into an economically viable secondary treatment method. Aeration, used to transfer oxygen to the biologically active masses of organisms within these systems, has been an important part of wastewater treatment as the use of activated sludge proliferated in the field. Significant changes have occurred in these systems as a result of not only advances in technology but also variations in the cost of energy required to operate them. The driving force of economics in some instances has brought the technology used in older systems back to the forefront. Due to the efficiency of power utilization, fine pore diffused aeration systems with full floor coverage have been rediscovered as an outstanding example of this technology.
