MIMO sliding mode control of a distributed parameter denitrifying biofilter

In this paper, the control problem of a distributed parameter system is dev eloped. The process considered is a fixed bed reactor in which drinkable wa ter is treated. Micro-organisms fixed in the reactor absorb the harmful com ponents in such a way that their concentrations decrease in the outflowing water. The addition of a carbon source is needed in this operation. The com plexity of the control problem is due to the distributed and nonlinear natu re of the model having time varying biological parameters. In drinkable wat er the harmful components are supposed to be nitrates, nitrites and ethanol supplied in the reactor inlet. The main contribution of this paper consist s of designing a multi-input/multi-output (MIMO) sliding mode control of th e distributed parameter biofilter. Two approaches are developed: early lump ing and late lumping sliding control. In both cases, not only are the harmf ul component concentrations controlled but moreover the addition of the car bon source is determined in such a way that the quality of water fulfils in ternational standards, The performances of the two approaches are compared and illustrated by means of simulations. (C) 2001 Elsevier Science Inc. All rights reserved.