ABSTRACT
The major problems with suspended growth bioreactors are poor separation and settling of the biomass and excessive foaming. The bioreactor must incorporate a step wherein any flocculated biomass is separated and wasted from the growing granules. For any bioreactor design, there is a window of operability within which the bioreactor/clarifier system will function properly. Design and operation of a suspended growth bioreactor are intimately tied to the design of the solids separation system and the biomass settling characteristics. If the biomass is largely non-flocculated, it means that it is growing in a dispersed growth condition. Sludge bulking is caused by excessive numbers of filamentous microbes that “invade” the mixed liquor. If a waste is rich in readily biodegradable substrate, the competitive advantage of the single-celled bacteria is eliminated, or at least reduced. Bioreactors operated at a low food-to-microorganism ratio (F/M) occasionally encounter a form of bulking called low F/M bulking.
