(2)Slow sand filtration The surface cake of accumulated particulates includes a variety of living and dead micro-and macroorganisms The biological metabolism of the organisms enhances removal of particulates As the filter cake develops, the cake itself assumes a dominant role in particulate removal Because of this filtrate turbidity improves as the filter run progresses, and deterioration of the filtrate turbidity is normally not observed at the end of the filter cycle(2) Slow sand filtration ▪ The surface cake of accumulated particulates includes a variety of living and dead micro- and macroorganisms. ▪ The biological metabolism of the organisms enhances removal of particulates. ▪ As the filter cake develops, the cake itself assumes a dominant role in particulate removal. ▪ Because of this, filtrate turbidity improves as the filter run progresses, and deterioration of the filtrate turbidity is normally not observed at the end of the filter cycle