The Second Generation of IFAS and MBBR: Lessons to Apply

Powerful models and a wealth of data are available for designing integrated fixed film activated sludge (IFAS) and moving bed biofilm reactor (MBBR) facilities today, that were not available when designing the “first generation” of North American facilities in the 1990's. Engineers now have the tools they need to sharpen designs, and minimize capital and operating costs. This paper discusses lessons learned in the design and startup of several full-scale facilities. Operator observations at these facilities have proven to be invaluable in the design of “second generation” facilities in Broomfield, Colorado (Phase 2 expansion); West Haven, Connecticut; Westchester County, New York; Fort Myers, Florida and several others. Pilot and bench testing, optimum media placement, sieve design and approach velocities, residual dissolved oxygen, mixing requirements and dynamic process modeling are discussed with regard to the first-generation facilities. Second-generation design configurations are also compared for a hypothetical new plant, using the BioWin simulator. This paper summarizes the current state of science, and identifies future research needs for IFAS and MBBR design.