REVIEW PAPER Rotating biological contactors: a review on main factors affecting performance S. Cortez Æ P. Teixeira Æ R. Oliveira Æ M. Mota Published online: 24 January 2008 Ó Springer Science+Business Media B.V. 2008 Abstract Rotating biological contactors (RBCs) constitute a very unique and superior alternative for biodegradable matter and nitrogen removal on account of their feasibility, simplicity of design and operation, short start-up, low land area requirement, low energy consumption, low operating and mainte- nance cost and treatment efficiency. The present review of RBCs focus on parameters that affect performance like rotational speed, organic and hydraulic loading rates, retention time, biofilm sup- port media, staging, temperature, influent wastewater characteristics, biofilm characteristics, dissolved oxy- gen levels, effluent and solids recirculation, step- feeding and medium submergence. Some RBCs scale-up and design considerations, operational prob- lems and comparison with other wastewater treatment systems are also reported. Keywords Aerobic/Anaerobic/Anoxic RBC  Design  Medium submergence  Rotational speed  Scale-up  Staging 1 Introduction A rotating biological contactor (RBC) is an attached growth bioreactor that offers an alternative technol- ogy to the conventional activated sludge process. The first RBC system was used in the early 1900s and consisted of a cylinder with wooden slats (Mathure and Patwardhan 2005). The availability of polystyrene marked the beginning of commercial application of RBCs with the first full-scale system being installed in Germany in 1958 (Rodgers and Zhan 2003). Significant refinements in media type and equipment configuration occurred during the 1960s and early 1970s (Tchobanoglous and Burton 1991; Grady et al. 1999). Currently, there are many thousands of units operating worldwide and several different designs available depending upon specific requirement criteria (Mba et al. 1999). A RBC unit typically consists of a series of closely spaced large flat or corrugated discs that are mounted on a common horizontal shaft and are partially or completely submerged in wastewater (Fig. 1). A drum filled with some lightweight packed supports can also be used in place of conventional discs. The shaft continually rotates by a mechanical motor or a compressed air drive and a biofilm is established onto the entire surface area of the media, which metabolizes the organic materials contained in the wastewater. In aerobic processes the rotation of the media promotes oxygen transfer and maintains the biomass in aerobic conditions. The rotation also S. Cortez (&)  P. Teixeira  R. Oliveira  M. Mota IBB – Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal e-mail: susana_cortez@deb.uminho.pt 123 Rev Environ Sci Biotechnol (2008) 7:155–172 DOI 10.1007/s11157-008-9127-x