Start-up, Optimization, and Performance Testing of a 77 MGD Integrated Fixed Film Activated Sludge (IFAS) Process to Meet a 5 mg/L Nitrogen Limit

Abstract

The Narragansett Bay Commission (NBC) has recently completed converting their aeration tanks to ten parallel integrated fixed film activated sludge (IFAS) reactors at the 291 MLD (77 MGD) Field's Point Wastewater Treatment Facility (FPWWTF) to meet a future total nitrogen permit limit of 5 mg-N/L. Performance testing conducted during April and May of 2013 demonstrated that the IFAS process was able to meet a total inorganic nitrogen (TIN) limit of 3 mg-N/L and a 1 mg-N/L ammonia-nitrogen limit as stipulated by the process performance guarantee. Start-up and testing of the IFAS process revealed that a bulk-phase dissolved oxygen concentration in the IFAS cell of 4.5 mg/L or greater was required to maintain an ammonia-nitrogen concentration less than 1 mg-N/L in the secondary effluent at the FPWWTF. Performance testing confirmed that process conversion to a four-stage Bardenpho process with an aerobic IFAS zone was capable of meeting treatment objectives: 5 mg-TN/L, 10 mg-BOD 5 /L, and 30 mg-TSS/L on a monthly average basis.