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In this research we analyze the steady-state operation of a continuous flow bioreactor, with or without recycle, and an idealized or nonidealized continuous flow membrane reactor. The model extends to include a fixed bed reactor where a fraction of the biomass is detached by the flow. The reaction is assumed to be governed by Tessier growth kinetics. We show that a flow reactor with idealized recycle has the same performance as an idealized membrane reactor and that the performance of a nonidealized membrane reactor is identical to that of an appropriately defined continuous flow bioreactor with nonidealized recycle. The performance of all three reactor types can therefore be obtained by analyzing a flow reactor with recycle. The steady states of the recycle model are found and their stability determined as a function of the residence time. The performance of the reactor at large residence times is obtained. [ABSTRACT FROM PUBLISHER]

Abstract: We analyse a model for the activated sludge process occurring in a biological reactor without recycle. The biochemical processes occurring within the reactor are represented by the activated sludge model number 1 (ASM1). In the past the ASM1 model has been investigated via direct integration of the governing equations. This approach is time-consuming as parameter regions of interest (in terms of the effluent quality leaving the plant) can only be determined through laborious and repetitive calculations. In this work we use continuation methods to determine the steady-state behaviour of the system. In particular, we determine bifurcation values of the residence time, corresponding to branch points, that are crucial in determining the performance of the plant. [Copyright &y& Elsevier]

Abstract: Food processing wastewaters and slurries typically contain high concentrations of biodegradable organic matter. Before the wastewater can be discharged the pollutant concentration must be reduced. One way to achieve this is through the use of a biological species (‘biomass’) that consumes the organic matter (‘substrate’). We investigate biological reactor models in which the growth rate is given by a Contois expression with a variable yield coefficient. We investigate the reduction in pollutant concentration when wastewaters are passed through one of two reactor configurations: a single reactor and a two-reactor cascade. In the latter scenario the total residence time is fixed and the residence time in the first reactor is taken to be a design parameter. It is found that in many cases an optimal reactor cascade may outperform the single reactor by two orders of magnitude. [Copyright &y& Elsevier]

Abstract: We investigate a reactor network consisting of two chemostats in series. Previous researchers have compared the performance of a two-reactor system against a single reactor having the same total residence time. In this paper, we suggest that it is more natural to compare the performance of a cascade against the optimal performance a single-reactor system having the same, or smaller, residence time. We consider a biological system in which the growth rate is given by a Monod expression with a variable yield coefficient. We find that it is possible for this model to obtain a significant increase in performance by using a two-reactor system. However for the two-reactor system the performance enhancements are achieved when the system reaches a time-invariant steady-state rather than under conditions which produce self-generated oscillations, which was the focus of interest of earlier researchers. [Copyright &y& Elsevier]

Abstract: We analyse the steady-state treatment of industrial wastewaters in a continuous flow bioreactor and in an idealised continuous flow membrane reactor. The reaction is assumed to be governed by Contois growth kinetics, which is often used to model the growth of biomass in wastewaters containing biodegradable organic materials. We show that a flow reactor with idealised recycle has the same performance as an idealised membrane reactor and that the performance of a non-idealised membrane reactor is identical to an appropriately defined continuous flow bioreactor with non-idealised recycle. The performance of all three reactor types can therefore be obtained by analysing a flow reactor with recycle. The steady-states of the model are found and their stability determined as a function of the residence time. The performance of the reactor at large residence times is obtained. In the limit as the residence time becomes very large, all three reactor configurations have identical performances. Thus the main advantage of using a membrane reactor, or a flow reactor with recycle, for the treatment of industrial wastewaters and slurries is to improve the performance at low residence times. [Copyright &y& Elsevier]