This book provides an overview of biological wastewater treatment and sludge recovery. It presents the main concepts related to treatment processes, as well as the principles of operation, sizing, and implementation of unit operations and processes associated with wastewater and sludge treatment. Wastewater Engineering and Treatment 3 analyzes biological nitrogen removal processes (ammonia, nitrites and nitrates), biological and physicochemical phosphorus removal processes, and wastewater clarification. Didactic and combining theory with practice, this book is intended for engineers in engineering and environmental sciences, as well as professionals in wastewater treatment.