Perspectives are different frameworks from which to explore the knowledge around sustainable sanitation and water management. Perspectives are like filters: they compile and structure the information that relate to a given focus theme, region or context. This allows you to quickly navigate to the content of your particular interest while promoting the holistic understanding of sustainable sanitation and water management.
A very comprehensive description on how slow sand filters work and how they can be designed. Many examples, and a good reference list at the end of the article.
THAMES WATER ; UNIVERSITY OF SURREY (2005): Slow Sand Filters. [Accessed: 06.02.2012] PDF