About the validation of advanced membrane process control systems in wastewater treatment applications

Abstract

This paper focuses on the validation of advanced control systems to use on either batch or continuous, new or existing membrane process plants, by use of a simulation software (Aspen Hysys). In the last decade, membrane technologies resulted to be very appealing and shows positive market trends. One main drawback is membrane fouling, which affects productivity, selectivity and longevity of the process, which leads to both technical and economical failures: proper membrane process design and control is a difficult task to accomplish. This leads to overdesign the plant capacities by process engineers, making this technology less reliable and convenient. Nowadays membrane processes are controlled by a constant permeate flow rate or constant applied operating pressure. These simple control strategy approaches are sufficient to operate the processes, but do not distinguish different fouling operating regions, and therefore do not avoid process failures due to fouling. Fouling may be described by the boundary flux theory in a convenient way, separating low-fouling operations from high-fouling ones. The paper reports about the validation of an previously developed advanced membrane process control system based on the boundary flux concept on different wastewater feedstocks. The advanced control strategy by the use of a simulation software by Aspen Hysys, capable to predict boundary flux values by measurement of some key parameters, was validated and capable to set suitable set-point values to the feedback controllers in order to work at or below the boundary flux. As a consequence, the membrane process is always operated far from irreversible fouling issues. The developed approach was then successfully validated by experiments on lab scale