ABSTRACT
This chapter deals with suspended growth bioreactors where the biomass is suspended in the waste stream by either mechanical mixing or by aeration. A suspended growth bioreactor ideally consists of individual microbes uniformly dispersed in a solution of soluble substrate. Microbes grow both in suspension and on the fixed or moving media, producing a hybrid situation. Surrogate measurements are often used, including mixed liquor suspended solids (MLSS) and mixed liquor volatile suspended solids. There are practical limitations to the concentration of cell biomass that can be maintained in the bioreactor. The endogenous respiration coefficient is used to account for the observed fact that microbial mass in a batch reactor will decrease after the initial substrate is consumed. A new type of separator has gained acceptance in the marketplace called a membrane bioreactor. Physical limitations in transferring sufficient oxygen may limit the maximum MLSS that can be maintained.
