Three types of vacuum filters and their operation are described in this lesson. Typical filter cycle, filter components and their functions, process control parameters, expected performance, and safety/historical aspects are considered. Conditioning methods are also described, although it is suggested that lessons on sludge characteristics, sludge conditioning, and heat treatment be studied before undertaking the lesson. The lesson includes an instructor's guide and student workbook. The instructor's guide contains a description of the lesson, estimated presentation time, instructional materials lists, suggested sequence of presentation, reading lists, objectives, lecture outline, narrative of the slide/tape program used with the lesson, and student worksheet (with answers). The student workbook contains plant flow diagrams, objectives, glossary, vacuum filter text material, references, and worksheet. (JN)