The possibility that the biological phosphorus removal mechanism can be inhibited in a continuous flow process by acetic acid passing through into the anoxic and aerobic zones of the reactor was investigated. The objectives of the research were to determine the amenability of a wastewater from the Hoescht Celanese Celco Plant in Narrows, Virginia to the biological phosphorus removal process. The wastewater from the Celco plant is very high in both phosphorus and acetic acid, which is the volatile fatty acid known to be a preferred substrate for the biological phosphorus removal process. However, past research indicated that the wastewater was not amenable to the biological phosphorus removal process; therefore, studies were established to determine at what point and for what reason the biological phosphorus removal process fails. In particular the occurrence of acetic acid “breakthrough" was investigated by operating a parallel control reactor treating a municipal sewage and acetate combination. Results of the research project indicated that the Celco wastewater caused the biological phosphorus removal process to fail at acetic acid and COD concentrations lower than those causing failure in the wastewater consisting of municipal sewage and acetate only. This led to the conclusion that the Celco wastewater contains a biologically inhibitory constituent which causes the biological phosphorus removal mechanism to fail. In addition, the reactor treating a combination of municipal sewage and acetate failed to remove phosphorus biologically at acetate concentrations of 800 mg/L. At this point, the acetate began to pass through into the anoxic and aerobic zones, respectively, causing the biological phosphorus removal mechanism to fail. / Master of Science