Slow Sand Filters (SSF) are probably the most effective, simplest and least expensive water treatment process for developing countries. They require few technical compo-nents and usually no chemicals. They are very efficient in removing bacteria, organics, cysts, ova and viruses are effectively removed from filtrate water. The performance of SSF is not controlled by any mechanical system. It is a controlled ecosystem of living organisms whose activities are affected by the raw water quality, and in particular temperature.
