The city of Leipheim has decided to replace its 40-year-old digester with a modern high-load digester (HLD). The HLD process was developed by the Fraunhofer IGB for anaerobic decomposition and sludge stabilization. Following preliminary investigations into the digestion of the raw sludge produced by the sewage treatment plant under high load conditions and a thorough concept, design and planning phase for the realization of the HLD, the construction work began on the groundbreaking ceremony on September 28, 2017. The IGB scientifically supported the partners involved in the realization of the plant. This ranged from assistance with the tender documents, support during the construction phase, function test and inoculation with digested sludge from the existing old digestion to trial operation. In December 2018, the HLD was turned over to the client.
Compared to the original digester, the HLD requires only one third of the active volume and was successfully integrated into the existing sewage treatment plant. It is designed as a loop reactor with gas injection. The integrated heat recovery helps to generate heat, which is also delivered to the neighboring building yard. The biogas is cleaned and freed of impurities. By mid-January 2019, more than 17,500 m3 of biogas had already been produced in very good quality. The old digestion is now being converted to a biogas storage tank and thus still useful. The next high-load digestion is already in the planning phase.