ABSTRACT
167The methodology for determination of the minimally required aerobic sludge retention time (SRTmin aer) in BPR systems is presented in this chapter. Contrary to normal biological conversions, the BPR process is not limited by a SRTmin, which results from a maximum growth rate of the organisms. This is because the aerobic SRT should be long enough to oxidise the amount of PHA stored in the anaerobic phase. This makes that the SRTmin aer will primarily depend on the PHA conversion kinetics and the maximal PHA content in the cell (storage capacity), and on other operational parameters, such as temperature (the SRTmin aer exhibited very high temperature dependency similar to that of nitrifiers) and process configuration. It is expected that in denitrifying BPR systems the minimally required SRT will be around 35% longer in comparison with aerobic BPR. A model equations for determination of the minimal aerobic SRT as a function of above kinetic and process parameters were developed and the model predictions were compared with experimental data used to evaluate several operational aspects of BPR. The model was proved to be capable of describing these data satisfactorily.
