IFAS MBBR Hybrid Retrofit System for Latin American Activated Sludge Plant Upgrades Our IFAS MBBR Hybrid Retrofit System (Model BM-IFAS-RK) is a complete upgrade kit that converts conventional activated sludge wastewater treatment plants into high-capacity Integrated Fixed-Film Activated Sludge (IFAS) or MBBR systems. Designed for municipal and industrial plant operators across Latin America , this wastewater treatment filter media retrofit solution doubles biological