(3 Rapid granular deep-bed filtration Depth filtration involves a variety of complex mechanisms to achieve particulate removal The small particles could be captured in bed by transport and attachment process in series Transport process are needed to carry the small particles into contact with the surface of the individual filter grains Attachment mechanisms hold the particles to the surfaces Chemical pretreatment is essential to particulate removal in depth filtration(3) Rapid granular deep-bed filtration ▪ Depth filtration involves a variety of complex mechanisms to achieve particulate removal. ▪ The small particles could be captured in bed by transport and attachment process in series. ▪ Transport process are needed to carry the small particles into contact with the surface of the individual filter grains. ▪ Attachment mechanisms hold the particles to the surfaces. ▪ Chemical pretreatment is essential to particulate removal in depth filtration