This book introduces the reader to the exciting range of modern anaerobic processes that are now available for wastewater treatment. To meet the new challenges of population growth, global warming, and the existing problems of protecting biodiversity and public health, we must move away from existing energy-intensive aerobic treatment processes to more sustainable systems. Embracing the circular economy concept, wastewater treatment plants are changing from being solely about pollution control to resource recovery centers, and to achieve this anaerobic treatment is required. Among the huge range of valuable by-products that can be generated by fermentation are biomethane, biohydrogen, bioplastics, biodiesel and volatile fatty acids which are used in the food, chemical and pharmaceutical sectors.The scope of the book covers all aspects of anaerobic wastewater treatment including the microbiology and chemistry of hydrolysis, acidogenesis, acetogenesis and methanogenesis and the main end products of digestion including contaminants. All processes are discussed including digesters, combined, attached growth and floc-based systems. Biogas production is examined along with biomethane and biohydrogen. The book finishes by looking at the key sustainable factors of anaerobic treatment and how biotechnology is pushing towards more efficient and reliable processes.This interdisciplinary book is essential reading for both engineers and scientists whether training at university or practitioners and consultants in the wastewater industry.