Inordinate failures of rotating biological contactor (RBC) drive shafts in wastewater treatment plant service worldwide

Abstract The rotating biological contactor (RBC) concept for wastewater treatment plants was first patented at the turn of the century but not implemented in commerical practice until the 1960s. The actual equipment designed, built and operated during an almost two-decade period experienced exceptionally high failure rates. Fracture of drive shafts often occurred within months of initial installation; and over a 5-year period, about 5% of all machines for the most prominent manufacturer had failed even though a 20-year life was contemplated. The present paper provides an historical review of RBC development. A comprehensive design and failure analysis study of an actual drive shaft configuration is performed based on classic fatigue principles (endurance curves) and fatigue/fracture (crack growth) techniques using a finite element approach.