ABSTRACT
This chapter provides an overview of hybrid biofilm/suspended growth technologies, also referred to as integrated fixed-film/activated sludge processes, their history and basis of design. Quantifying the benefits of biofilms in hybrid systems can be challenging, particularly where the behavior of the biofilm and the mixed liquor are interdependent. The biomass inventory is increased without impacting sludge loading to the secondary clarifiers. Just like in activated sludge mixed liquor, this “biofilm biomass” can be composed of both heterotrophic and nitrifying organisms. Quantifying the benefits of biofilms in hybrid systems can be challenging, particularly where the behavior of the biofilm and the mixed liquor are interdependent. Providing adequate scouring energy to manage biofilm thickness is arguably the most important issue for a successful Fixed-media/ Activated Sludge process. Moving bed biofilm reactors, Moving Bed Biological Reactor, using plastic biofilm carriers were originally developed as “flow through” processes, that is, processes without any clarifier return activated sludge.
