The purpose of this study was to investigate the use of a horizontal packed bed bioreactor, named Biopack, to treat high strength wastewater, such as bakers yeast wastewater. The Biopack system (RBCP) is a modified rotating biological contactor and the system was applied for secondary treatment. The RBCP system produced high treatment efficiencies, COD removal was 94.9% when COD was 472 mg/l and surface organic loading = 0.187 kg COD/m(2) per day and surface hydraulic loading = 6 l/m(2) per day. Variations of surface hydraulic loading from 6 to 11.9 l/m(2) per day produced a decrease in COD removal efficiency from 94.9 to 58.6%. Other factors, such as shock load, retention time and rotational speed were also investigated.