Practitioner's Tool / Extended Aeration
Extended aeration is a modification of the activated sludge process and was developed to provide a more stable treatment process for smaller and more variable flows for sources from schools, tourist facilities, shopping malls and similar facilities. Extended aeration processes are typically used in prefabricated package treatment plants. The main differences are that all of the incoming waste flows first to a primary clarification basin for particulate settling, and then it flows to the aeration basin for biological treatment. There is no return activated sludge, so the sludge age is greater than with the activated sludge process. As there are no grit traps, bar screens or return activated sludge to adjust, these are very simple systems to operate. Many package treatment plants using this technology require only quarterly operation inspections.
A basic extended aeration system is made up of several different interrelated components. For example, the De La Salle Sewage Treatment Plant in Dasmariñas, Cavite Province in the Philippines uses an extended aeration process consisting of a lift station, collecting tank, aeration tank, settling tank, sludge digestion, chlorine contact tank and a sludge drying bed.
The De La Salle project was designed by DCCD Engineering Corporation, Makati City, Philippines. For more information about their services and the De La Salle Treatment Plant, visit them at here.
For more information about the extended aeration process, refer to the United States Environmental Protection Agency's Wastewater Technology Fact Sheet on Continuous-Flow, Suspended-Growth Aerobic Systems here.