This is the first in a series of documents developed by the National Training and Operational Technology Center describing operational control procedures for the activated sludge process used in wastewater treatment. Part I of this document deals with physical observations which should be performed during each routine control test. Part II discusses the control tests that are used to directly identify process performance and to dictate process control adjustments. Included are centrifuge tests, effluent turbidity tests and dissolved oxygen tests. (CS)