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 2 examines treatment using membrane techniques, hybrid systems involving the complementary action of free bacteria and bacteria attached to a mobile support, and processes using fixed bacteria (trickling filters, biofilters and biological discs). Didactic and combining theory with practice, this book is intended for engineers in engineering and environmental sciences, as well as professionals in wastewater treatment.