Energy Conservation in Activated Sludge Systems

Various activated sludge systems were evaluated for a new wastewater facility for Deland, Fla. on the basis of energy requirements and capital cost. Aerator turndown and energy savings at low load conditions was also considered. The ability to accomplish denitrification in the activated sludge system while still supplying the necessary oxygen for BOD removal, nitrification and sludge stabilization was also a significant factor in reducing energy requirements during operation. A method is presented to predict the amount of energy that can be saved due to the ability of the system to carry out denitrification. The denitrification is a function of the mixing regime for the system, the total tank volume, the wastewater temperature and volume required for nitrification and the denitrification rate which is determined by the system's solid retention time.