In this work, a previously developed variable gain controller (VGC) was applied for automatic control of re-startup and an organic overload in an anaerobic wastewater treatment (AWT) plant treating winery wastewater. The experiments for testing the automatic re-startup, and later organic overload, were conducted at 37 +/- 2 degrees C in a hybrid upflow sludge bed-filter (USBF) pilot-scale reactor fully monitored with a liquid volume of similar to 1.15 m(3). The validation of the system was performed by simulation with Anaerobic Digestion Model No. 1 (ADM1) and experimentally by closed-loop control of the USBF reactor. It was determined that the time required for the re-startup of the AWT plant after short programmed stop periods (one month) could be greatly reduced, in comparison with the manual procedure, using this control system (only two days are needed). The organic-loading rate reached a value of 12 kg COD/(m(3) d), with an initial chemical oxygen demand (COD) concentration in the influent of 8 kg COD/m(3). To test the controller for the management of an organic overload, a COD increase of a 50% was applied. The control system decreased the feed flow rate and allowed process stability to be recovered after the organic overload. One of the advantages of this controller is its suitability for maintaining a high effluent quality by controlling H-2 concentration in the biogas.