Cascade Fuzzy Logic Controller for an Anaerobic Digester

A cascade controller is introduced for operating up flow anaerobic sludge blanket (UASB) digesters efficiently. The upper-level controller is a fuzzy logic controller (FLC) and the lower-level controller is a conventional PL controller. The inner loop controller feeds the reactor pH back to the influent flow rate. The outer loop controller measures the biogas flow rate and adjusts the pH set point.