Process analysis for treatment of industrial plating wastewater: simulation and control approach

One of the better options to remove chromium VI (Cr(VI)) from wastewaters is the electrochemical continuous reactor. This process can be used to clean rinse waters from the plating industry. A mathematical model of the reactor is developed by classical application of mass balances for Cr(VI) and Fe, both corroborated in a bench scale electrochemical reactor. The reactor model is employed as the real process where the proposed controller is implemented. For the controller synthesis a reduced order uncertainty estimator is employed to infer the reaction rate, which is assumed unknown and an input/output linearising controller is designed, using the input flow to the reactor as control input and the Cr(VI) concentration in the wastewater as controlled variable. This procedure yields a nonlinear PI controller; where new tuning rules are given. Stability analysis of the closed loop behaviour of the reactor under the proposed methodology is done via mathematical analysis of the equations that describe the dynamic behaviour of the estimation and regulation errors. The performance of the controlled reactor is illustrated with numerical simulations.