Over the past two decades, the awareness and concept of wastewater treatment processes have progressed extensively. Wastewater treatment processes have developed from empirically-based methods to multidisciplinary approaches embracing microbiology, chemistry, bioprocess and physical engineering, and applied mathematics. Many of these developments have ripened to the extent that they have been collated into mathematical simulation models with computers. This book provides a brief overview of the basics of biological water treatment processes along with the description of mechanisms for modeling and integrating biological stages into different industrial processes. The book essentially covers the physical, biological and chemical basics, including microbial metabolism, wastewater characteristics, wastewater treatment processes (including aerobic and anaerobic treatment processes). It also includes detailed information on membrane technology, micropollutants' removal, activated sludge processes, membrane bioreactors (MBRs) and the evaluation and selection of different aeration systems. This book is equally important for students and teachers in the field of water treatment technologies. Moreover, this book can be regarded a ready reference for engineers, microbiologists, chemists, environmental officers, consultants and agencies in the field of water treatment.