A full-scale rotating biological contactor treatment system primarily used for treatment of wastes from single-family dwellings was studied at the Blacksburg-Virginia Tech wastewater treatment plant. Municipal primary clarifier effluent was pumped into the 600 gpd rated RBC unit at the rate of 480 gpd for a period of 4 1/2 months. The RBC unit contained a primary clarifier, four stages of discs, and a secondary clarifier. A thorough sampling and analysis program was performed to determine start-up characteristics and resistance to controlled shock loadings. Samples from seven locations, ranging from the influent through each stage of the RBC into the effluent, were collected and analyzed in order to monitor treatment performance. Samples were analyzed for COD, TKN, NH₃-N, Org-N, NO⁻₃-N, SS, DO and total alkalinity. Based on an analysis of the results obtained it was determined that a start-up period of approximately 30 days was required to develop a sufficient growth of biofilm mass to reach"steady state" conditions, i.e., maximum consistent organic removal and nitrification efficiency. Shock loading investigations included step increases in hydraulic and organic loads as well as controlled diurnal flow patterns. From these studies it was determined that the RBC was resistant to changes in effluent organic concentration, but that nitrification efficiency could be notably suppressed. The attached biofilm was not adversely affected by the shock loads. Throughout the manuscript diagrams and tables are provided to clarify procedures and materials used. Analytical results are presented in three-dimensional plots to illustrate patterns revealed by the data. / Master of Science