Nonlinear Model Predictive Control of a Wastewater Treatment Process Fitted with a Submerged Membrane Bioreactor

Submerged membrane bioreactors are increasingly applied for wastewater treament but requires a tight control of the membrane fouling so as to ensure safe and efficient operation. The objective of this paper is to design a nonlinear model predictive control to minimize the irreversible resistance while keeping the trans-membrane pressure, which is a good indicator of membrane fouling, at an acceptable level. To this end, the manipulated variables are the permeate flow and the air scouring flow, which allows the material layer formed on the membrane (hi short the "cake") to be detached. The NMPC structure is tested in simulation considering a detailed simulator as the reference process, and a reduced-order model as the predictor. The results show that the process can be regulated until the irreversible resistance takes the main role in the fouling resistance. When this state is reached, a chemical cleaning is required, or a larger trans-membrane pressure has to be accommodated. (c) 2015, IFAC (International Federation or Automatic Control) Hosting by Elsevier Ltd. All rights reserved.