This comprehensive textbook highlights the fundamental concepts and design principles related to water and wastewater engineering. Problems and issues arising from the lack of sustainable conventional treatment practices and potential methods for resolving problems are discussed in detail. The book starts with an introduction to water resources and the need for water and wastewater treatment, followed by evaluation of water demand in terms of quantity and quality. Mass transfer and transformation processes that are necessary for understanding the complexity of water pollution issues and treatment processes are discussed in detail. Pedagogical features include learning objectives, chapter-wise study outlines, detailed solutions to important problems and self-evaluation exercises with answers. Case studies for specific water treatment requirements are provided to enable the students to choose and apply only relevant treatment processes in their design.