<p> This report examines the dynamic response of a 0. 5 metre pilot scale rotating biological contactor when operated under transient influent conditions. Experimental data are presented for two modes of operation: carbon oxidation and carbon oxidation plus nitrification. During the carbon oxidation experimental runs, a 2.0 metre RBC was operated in parallel with the 0.5 metre RBC, thus allowing comparisons in the performance of the units. </p> <p> When the 0. 5 metre RBC was operated under nitrifying conditions, it was found that the effluent filterable TKN responded positively to influent variations in filterable TKN loading, TKN concentration and hydraulic loading. Transfer f unction noise models were developed which successfully predicted the time varying effluent TKN response. The response in effluent filterable TKN was predicted most precisely by influent TKN loading. Models based on influent TKN concentration and flow were not as precise in predicting effluent response. The effluent response of the 0.5 metre RBC was found to be greater than the response of activated sludge pilot units when operated at similar levels of removal. </p> <p> When the 0. 5 metre RBC was operated in the carbon oxidation 'mode, significant effluent responses were observed for carbon loading and concentration. Little correlation was found between influent flow and effluent carbon concentration. Operating under identical conditions, the 2.0 m RBC showed significant responses to carbon loading, carbon concentration and flow. </p> / Thesis / Master of Engineering (MEngr)