2.0 The Two Major Families of Aerobic Reactors
In treatment systems that use oxygen (aerobic systems), reactors are generally grouped into two major families based on how the biomass is housed: Fixed-Film systems and Suspended-Contact systems. The primary difference lies in whether the microorganisms stay in one place or are kept in constant motion.
| Fixed-Film Systems | Suspended-Contact Systems |
| Biomass grows on a stationary, solid surface (media) like rocks or plastic, and wastewater flows past this attached film for treatment. | Biomass is kept in suspension and continuously mixed directly with the wastewater, with the entire mixture moving through the reactor. |
Let’s now take a closer look at specific examples from the first family, where the biomass is attached to a surface.