When Is IFAS The Right Choice?

The Integrated Fixed Film Activated Sludge (IFAS) technology is gaining popularity in the United States as an alternative strategy for upgrading and expanding municipal wastewater treatment facilities. A number of full-scale IFAS plants are now in operation in the United States, which have demonstrated the technical capability and reliability of the process. The question now being asked by consultants, utility managers, and regulatory agencies is – When Is IFAS The Right Choice? An evaluation carried out to help answer this question considered factors that were believed to be critical in selecting the IFAS technology over other plant upgrading strategies. The evaluation was conducted based on the expansion of a hypothetical plant originally designed for carbonaceous BOD removal and now being upgraded to provide nitrification and denitrification. Five treatment technologies were considered: conventional activated sludge, step feed activated sludge, IFAS, biological aerated filters (BAF), and membrane bioreactors (MBR). Numerous sensitivity analyses were carried out to document how variability in the selected cost factors influence the results of the evaluation. Two case studies are included to show how site specific issues and changes in the cost factors from one location to the next can affect process selection.