Applications of Matlab optimization capabilities in the design of N-continuous stirred tank bioreactors connected in series

Abstract

The optimal design (variable volume) of continuous stirred tank reactors (CSTR's), in series, performing biological conversion of organic materials, was derived. The optimal design was based on the minimum overall reactor volume required for a certain degree of substrate conversion, and the number of reactors. In this study, it was assumed that cell growth kinetics follows the Contois model with endogenous decay. This unstructured kinetic model has been used by many researchers to describe biodegradation of organic materials, especially in the food industries and industrial wastewater treatment. The optimization problem was formulated as a nonlinear constrained mathematical programming problem, and solved using the Matlab function "fmincon". The effect of operating parameters such as; substrate concentration in the feed to the first reactor, substrate conversion, and number of CSTR's in series for the optimum design was investigated. Using the optimum design is beneficial only at high substrate conversion. The substrate concentration in the feed to the first reactor has little effect on the total required reactor volume. Up to 5 CSTRs in series were used in this study.