 The disadvantages of the process were the 20-30 minutes of flocculation time required which increase the footprint of the plant and the energy cost of mechanical flocculation and sludge scraping.In 1992 Thames Water installed a 1.4 Ml/day pilot plant at Kempton Water Treatment Centre.This comprised a system based on Counter Current Dissolved Air Flotation and Filtration (CoCo-DAFF).