Slow sand filtration is credited with being the first drinking water treatment process utilized to improve the quality of water in both modern Europe and the USA. Within the last ten years, there has been a renaissance of interest in the potential use 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. Historically, the USA water industry has been reluctant to use micro-organisms for drinking water treatment. However, biofiltration is expected to become more common over...