This publication provides introductory technical guidance for civil engineers, environmental engineers and other professional engineers, construction managers and treatment plant operators interested in preliminary wastewater treatment. Here is what is discussed: 1. GENERAL CONSIDERATIONS, 2. BAR SCREENS, 3. COMMINUTING DEVICES, 4. GRIT CHAMBERS, 5. DISSOLVED AIR FLOTATION, 6. WASTEWATER FLOCCULATION, 7. REFERENCES.