Figure 1-6. Upflow clarifier.
Filtration is an important process in water treatment. This process can filter
physical, chemical, and (to a Iimited degree) biological particles by separating
suspended and colloidal impurities from water as it passes through the porous medium.
The fiIter removes fine organic and inorganic materials, and, incidentally, reduces
bacteria and impurities causing taste and odor. A typical fiIter consist of a bed of sand
or other fiIter medium supported by graded gravel resting on an under drain system
(see figure 1-7).
a. Processes Involved in Filtration. Filtration clarifies water by a combination
(1) Straining. Straining is a physical process by which particles too large to
pass through the pores of the fiIter medium are strained out. It is the most important of
the processes involved in filtration.