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Aerobic Growth of Heterotrophs in A Single Continuous Stirred Tank Reactor Receiving Soluble Substrate

By returning to Chapter 1 and studying Table 1.2 it can be seen that the single continuous stirred tank reactor (CSTR) is the simplest reactor configuration used in biochemical operations, finding application in activated sludge, aerated lagoons, aerobic digestion, anaerobic digestion, and biological nutrient removal. It has also found extensive use in microbiological and environmental engineering research; much of our knowledge about microbial growth has come from it.

Because of its simplicity, the CSTR provides an ideal system with which to study the modeling of microbial growth. In this chapter we will develop models describing the growth of microbial cultures in a single CSTR, either with or without biomass recycle, and use them to gain an understanding of how such systems behave. For simplicity, the models will be confined to the growth of aerobic heterotrophic biomass in an environment that contains ample nutrients so that the soluble, biodegradable organic substrate (expressed in chemical oxygen demand [COD] units) is the growth limiting material. Furthermore, the traditional approach to modeling biomass decay will be used because it is the approach found most often in the literature, making it important that the reader be familiar with it. With minor modifications, the same models can be applied to anaerobic and anoxic heterotrophic growth, as well as to aerobic autotrophic growth, making the principles illustrated of general importance.

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