Effect of Filtration Rate on Filtrate Quality

Throughout history, filtration was believed to be a straining process, in which suspended particles were removed from water by a filter with pores sufficiently small to prevent passage of the suspended particles. But in the latter half of the nineteenth century, when the relative sizes of suspended matter and the size of the pores were determined, it was found that an unflocculated particle was about one 100th the size of the pore space. It was also noted that particles are removed from suspension not only at the surface but also within a filter. Filtration, then, can be considered to be two distinct processes: (1) removal of the larger flocculated material and some unflocculated material at the surface of a filter and (2) removal within a filter. Removal at the surface of a