Tuning of an advanced control system on a membrane process for tannery wastewater purification and chromium recovery purposes

Tannery wastewater represent a hazard to the environment due to its high content of chromium. Conventional methods to purify this wastewater stream are available, but not capable to recover back chromium to the tannery process. Membranes appears to be a promising technology to achieve both targets of water purification and recycling of chromium. The economic feasibility of the here proposed process relays on fouling minimization, in order to maximize the life of the employed membrane modules and as a consequence to keep the operational costs low. The use of an advanced control system capable to predict fouling incurrence and to adapt the operating conditions to sub-boundary ones appears to be the best strategy. In this work, the proposed process, including the advanced control system, was simulated within HYSYS. By means of performed simulation runs, it was possible to avoid irreversible fouling operating conditions, still obtaining an adequate level of tannery wastewater treatment and relevant chromium recovery rates. Both the predictive and the adaptive part of the control system exhibits high reliability. The developed strategy appears therefore promising to encourage the use of membrane technologies for this application with feasibility from a technical and economic point of view.