Sappi Austria Produktions-GmbH & Co. KG commissioned a new high load reactor at the site in Gratkorn according to the concept of BIOBED. The purpose of this new anaerobic sludge reactor was to back up the two existing UASB reactors and if necessary take over the full COD-load of one old reactor, if repair work has to be done. In the fall of 2009 the construction of the third anaerobic reactor began. The startup phase took place with delay in June 2010, due to technical problems during the construction of the plant. The initial operation showed great promise at the beginning. However, the startup phase had to be aborted because of technical difficulties. The reactor was totally emptied and then restarted. The work includes a short overview of anaerobic techniques and both phases of the startup of the new reactor. These are precisely documented below. In addition, possible causes of the initial problems and their remedial measures are discussed. Furthermore, a short outlook on the future operation of the plant with bleachery is given.