Activated sludge is the most widely used biological wastewater treatment process globally to date, although its high energy demand makes it a major contributor of greenhouse gas emissions. Over recent decades it has been constantly modified and retrofitted to treat ever higher loads or improve effluent standards which have often resulted in even greater carbon emissions. Conventional activated sludge treatment is at a crossroads where new sustainable solutions are required if we are to protect the quality of our rivers and meet net-zero carbon targets.The book details current operation and design with special emphasis on the biological aspects of the process. From the microbial kinetics to the fascinating process of floc formation and development, the book explores the development of our understanding of the process looking at new sustainable designs, including biological nutrient removal and new aeration systems. Sludge separation problems and control options are explained, with a trouble-shooting guide to non-bulking problems. Environmental issues including noise, odor, aerosols, micro-plastics and nanoparticles are all reviewed, as is pathogen removal and the problem of antibiotic resistant genes and bacteria. The development of membrane bioreactors has increased process reliability and effluent quality, while integrated fixed-film activated sludge processes are more efficient and compact. The book concludes by exploring how activated sludge can become more sustainable, for example, by carbon harvesting and byproduct recovery.This interdisciplinary book is essential reading for both engineers and scientists whether training at university or practitioners and consultants in the wastewater industry.Related Link(s)

This book deals with natural treatment systems and the challenges the water industry faces in dealing with sustainability and the realisation of reaching Net Zero by 2030.Surface waters are all under threat, with freshwater ecosystems now facing unprecedented levels of contamination, even after a century of ever stricter legislation and regulation. The increase in population and especially in urbanization without sufficient planning and investment to ensure adequate wastewater collection and treatment coupled with the need to reduce greenhouse gas emissions associated with wastewater treatment is leading to a crisis in wastewater treatment in many countries.Natural treatment systems which use plants and soil micro-organisms are very much nature-based solutions and wherever applicable might offer sustainable and low emissions options for a range of wastewater problems protecting surface waters as well as creating new habitats to support and enhance wildlife diversity. In terms of circularity, natural treatment systems have the potential to produce a staggering array of useful and valuable by-products, including high-value compounds for the pharmaceutical industry.Related Link(s)

Our rivers and lakes are continuously self-purifying thanks to algal and bacterial biofilms that grow over the surface of stones and other debris. This same process has been employed for over a century to treat our municipal and industrial wastewater in specially designed fixed film reactors that maximize this microbial activity by providing ideal growth conditions and unlimited food and oxygen. Fixed film, or attached biofilm, reactors are unique in their ability to treat complex wastewaters and shock loadings; using far less energy than other wastewater treatment processes such as activated sludge, making them a sustainable treatment option.Targeted at undergraduate and postgraduate engineers and scientists, this book follows the structure of bestseller Biology of Wastewater Treatment. This volume gives an expanded and up-to-date overview of the use of fixed-film reactors in wastewater treatment with content spanning from biofilm formation, to traditional trickling filters and rotating biological contactor technology, advanced submerged systems (including MBBRs and IFAS) and their key role in the treatment of contaminated air, and finally to nitrogen removal employing new microbial pathways such as Anammox. This monograph emphasizes the biological aspects of the processes.