29
Biofiltration
In the biofiltration mode, bead filters are classified as fixed film reactors. Each bead (Figure 2) becomes
coated with a thin film of bacteria that extracts nourishment from the wastewater as it passes through
the bed. There are two general classifications of bacteria, heterotrophic and nitrifying, that are of
particular interest (Table 2). The two bacteria co-exist in the filter, and understanding their impact on
each other as well as on the filter is critical.
Figure 2. The bacterial film that coats each bead contains the nitrifying bacterial population. Heterotrophic
bacteria also form a thin biofilm layer on each bead. The nitrifying bacteria compete with the heterotrophic
bacteria for space.