This document is one in a series which outlines performance objectives and instructional modules for a course of study which explains the relationships and functions of the process units in a wastewater treatment plant. The modules are arranged in an order appropriate for teaching students with no experience. The modules can also be rearranged and adapted for courses to upgrade personnel moving into supervisory positions or designed as a minicourse. Each module contains a statement of purpose, objectives, conditions, acceptable performance, instructor and student activity. The tasks are organized into the general categories of: normal operation, abnormal operation, preventive maintenance, corrective maintenance, laboratory control, systems interaction and management/supervisory procedures. This volume includes four modules: (1) Treatment Provided by Process Units; (2) Effects of Industrial Wastes on Operations; (3) Relationship of Process Units; and (4) Development of Flow Diagrams. (CS)