Monitoring and control of an anaerobic upflow fixed-bed reactor for high-loading-rate operation and rejection of disturbances

A new control strategy has been introduced for operating anaerobic digestion processes efficiently at high load. The control system includes a cascade controller embedded into a rule-based supervisory system based on extremum-seeking control. Three process parameters, considered to be the most realistic variables for monitoring of the bioprocess, were selected (pH, biogas production rate, and the difference between the actual biogas flow and its setpoint). The control system examines these variables and varies the organic load by manipulating the influent flow. Good control performance was achieved during the start-up, during steady-state running operations, and during rejection of disturbances. The main advantages of this control approach can be attributed to its ability to adjust control parameters automatically, both for high-load operation and for rejection of disturbances. Furthermore, the influent flow can be tuned automatically according to variations in organic matter in the feed without the characteristics of the influent being considered. (C) 2004 Wiley Periodicals, Inc.