The report documents effective operating and maintenance (O/M) practices for wastewater treatment systems in the iron and steel industry, and describes how their application might affect permit parameters and operational upsets. Selection of processes for the study--byproduct cokemaking, ironmaking (blast furnaces), steelmaking (basic oxygen furnaces), hot forming, and acid pickling--was based on pollutant loadings, system complexity, control costs, and commonality among most integrated steel mills. Information was based on: a literature search for wastewater-related O/M practices in the iron and steel industry, discussions with state and regional agency personnal to identify major areas of concern and effective O/M practices, a review of agency files, discussions with wastewater treatment equipment vendors and chemical additive manufacturers, and discussions with agency representatives. Various steel mills were visited, and treatment plant operators and environmental staff members were interviewed. The information produced by these visits includes typically encountered problems and their solutions, troubleshooting efforts, extent of operator training, efforts to minimize the effect of operational upsets, and preventive maintenance practices.