This book gives plant operators and students of wastewater a simple and math-based introduction to all major unit processes in the modern wastewater treatment plant. Written with plant personnel in mind, the book furnishes easy-to-understand explanations of each step in treating wastewater–from screening, through sedimentation and settling, to activated sludge. The work is designed for operators and managers to run plants and to advance their careers by passing state licensure exams. Sample questions and problems in the text have been selected to prepare for operator examinations. Each chapter of the book is devoted to fully clarifying a unit process, and includes sample questions and problems. The book opens with a review of math, as this is applied to wastewater calculations. Many sample problems throughout give the reader an opportunity to practice and apply math formulas in realistic wastewater situations. Step-by-step descriptions of math problems show the reader how to arrive at the correct answer. The Chapter lineup has been preserved in this edition. Many practical tips and sample quizzes are furnished to help operators studying on their own and in courses. Written in a readable, non-technical style, this text is designed to explain wastewater technologies using down-to-earth approaches comprehensible to students. At the same time, it provides complete definitions of the key technical terms a wastewater operator needs to know. Some of the highlights of the book include: Updated format and edited for clarity. Wastewater technologies and math presented in basic, understandable terms. Clear, full explanations of unit processes from screening to activated sludge. Math review focused on wastewater plant and licensure test calculations. Questions and quizzes designed for exam preparation. Numerous drawings and solved problems illustrating key ideas.