Slow sand filtration is credited with being the first drinking water treatment process utilised to improve the quality of water in both modern Europe and the USA. Within the last 10 years, there has been a renaissance of interest in the potential use of enhanced processes of slow sand filtration throughout the world, especially for small and rural communities, and it continues to be the primary treatment process for many major European cities. The book deals with the latest research developments in slow sand and alternative biological filtration processes for drinking water treatment, including advances in the understanding of the fundamental mechanisms of the processes. In