Integrated Fixed-film Activated Sludge (IFAS): Operational Experience in Achieving High Levels of TN Removal With Variable Conditions

Performance of the integrated fixed-film activated sludge (IFAS) process that has been in operation at the Bend Water Reclamation Facility (WRF) since September 2015 in various configurations has provided exceptional total nitrogen (TN) removal, achieving secondary effluent values of 3 mg-N/L for extended periods. Throughout the past seven years, the system has proven to be robust and reliable, with the ability to accommodate major changes within the City’s user area while still exceeding treatment goals. In addition to significant increases in wastewater carbon and nutrient loads to the WRF, the wastewater characteristics have also changed in the system. The soluble carbon fraction of the wastewater has significantly increased, resulting in impacts to bioreactor performance and sludge settleability. Operations and design have several lessons-learned through the startup and commissioning phases through the past years of operation. Optimization continues to improve overall energy efficiency of the system.