5. Experience and research

SSF has been widely used in Latin America. However, attempts to spread SSF to Africa and Asia were hampered by design problems and lack of adaptation to local circumstances. It became clear in the 1990s that pre-treatment was needed and this led to the development of MSF.

Details are given of ten years of research in Puerto Mallarino in Colombia, and of a national programme to transfer MSF technology in Colombia, where there are currently more than 125 full scale MSF plants operating.

More recent research aims at optimising overall performance and processes and mechanisms to remove specific components. Experiments with natural and synthetic non woven fabrics to protect sand media in SSF show an increase in the length of filter runs and a potential to apply higher filtration rates without adversely affecting water quality. This may allow MSF systems to deliver more water for more people without a large investment.

However, more research and data are needed to produce optimisation guidelines for MSF and SSF plants. A return visit to several MSF systems built under the technology transfer programme in Colombia in the early 1990s revealed that although MSF systems were still performing, only in communities where training and back-up support for operators had been implemented, was performance adequate.