On SISO and MIMO sliding control of a distributed parameter biological process

In this paper, the control problem of a distributed parameter system is developed. The process considered is a fixed-bed bioreactor in which drinkable water is treated. Microorganisms fixed in the reactor absorb the harmful components in such a way that their concentrations decrease in the outflowing water. The addition of a carbon source is needed in this operation. The complexity of the control problem is due to the distributed and nonlinear nature of the model with time varying biological parameters. In drinkable water, the harmful components are nitrates, nitrites and ethanol supplied at the reactor inlet. The paper consists of designing a multi-input/multi-output sliding control law of a distributed parameter biofilter, based on the original model for which the control variables are coupled. Not only is the harmful component concentration controlled at the outlet of the bioreactor but also the addition of a carbon source is optimised in such away that the quality of water fulfils international standards. The performance of the control law is illustrated by means of simulations and compared to previous results obtained by SISO control laws