Case Study of an IFAS System – Over 10 Years of Experience

The Annapolis Water Reclamation Facility (WRF), which is owned and operated by the Anne Arundel County Department of Public Works in Annapolis, Maryland, has undergone, over the last ten years, a transition from conventional activated sludge to an Integrated Fixed Film Activated Sludge (IFAS) system for Biological Nutrient Removal (BNR) to, most recently, a dual anoxic zone process for Enhanced Nutrient Removal (ENR) without IFAS. This transition has included bench-scale and full-scale pilot work, full-scale upgrade and operation and finally, further study and modifications to expand the capacity while upgrading to the limit of technology for nitrogen and phosphorus removal. The twelve years of full-scale operating experience with IFAS media has taught some valuable lessons regarding the design, operation and performance of IFAS systems, particularly rope type media systems such as employed at the Annapolis WRF.The primary objective of this paper is to summarize the lessons learned from this experience focusing on the construction, performance, operation and maintenance issues. The following topics will be addressed using plant operating data to illustrate the points.