Bavaria: Sewage plant retrofitting increases performance and reduces operating costs
Waste is a resource – this knowledge is increasingly gaining ground in municipalities and wastewater companies. While the anaerobic use of sewage sludge has long been practiced at a plant size of more than 50,000 PE, this process is now also worthwhile for smaller plants. The anaerobic stage in Burgebrach (Bavaria), planned and built by the biogas specialist WELTEC BIOPOWER, exemplifies the economically successful retrofitting of an existing 13,000 PE wastewater treatment plant.
WELTEC BIOPOWER has adapted the method of producing biogas in terms of process engineering for sewage treatment plants: The pretreatment of the waste water and the removal of contaminants remain unchanged. Instead of aerobic sludge treatment in an open aeration tank, the sewage sludge is now fermented under exclusion of oxygen. Anaerobic digestion in a bioreactor made of stainless steel produces the valuable energy source digestion gas. On the basis of a stable digestion process, emissions of climate-damaging gases into the atmosphere can be avoided. In addition, the COD loads are reduced by around 30 percent. This intelligent combination of wastewater treatment and energy generation, on balance, increases the capacity of existing wastewater treatment plants.
To treat the raw sludge optimally, a stainless steel bioreactor from WELTEC is installed in a proven segment design. Due to its compact dimensions, the space required for the anaerobic stage is low. Thus, a retrofitting in existing wastewater treatment plants is easy to implement. WELTEC’s portfolio includes all modules required to retrofit sewage sludge digestion – from individual planning and design, through the implementation and commissioning of the plant, to the training of operating personnel.
In Burgebrach, WELTEC has successfully retrofitted an existing wastewater treatment plant with sewage sludge digestion including the energetic utilization of the sewage gas in the combined heat and power plant (CHP). Since the start of the anaerobic stage in spring 2016, the sewage sludge in the stainless steel tower has been stabilized anaerobically, after the wastewater has been purified in a two-stage trickling filter system.
To treat the daily 16m3 raw sludge optimally, WELTEC BIOPOWER has installed a special 420m3 stainless steel digester. With a flexible gas storage roof with up to 68 cubic meters of storage volume, the bioreactor is sufficiently dimensioned to operate the CHP with an electrical output of 28 kilowatts and a thermal output of 58 kilowatts without interruption. The digestion thus ensures a sludge reduction including energetic utilization of the digestion gas. It was also important to the Bavarians to be able to use the electricity and heat generated in the cogeneration unit completely for their own processes at the location. “Thanks to our own supply, we save on the external procurement of around 100,000 kilowatt hours of electricity per year,” reports Arne Nath, Head of Wastewater at the operator SüdWasser GmbH, which has supported the town Burgebrach since 2005 in the field of wastewater.
In addition to energy production and sludge stabilization, the minimization of odor emissions was also important for the decision of the WELTEC anaerobic stage. Targeted anaerobic sludge stabilization excludes odors as far as possible. Before the conversion, this problem occurred regularly in Burgebrach.
“Our anaerobic sewage sludge digestion convinces the customers by its economic and ecological sustainability. It produces energy, saves disposal costs and additionally provides municipal revenue. In addition, this allows the plant capacity to be expanded without requiring much space,” says Jens Flerlage of WELTEC BIOPOWER, outlining the benefits. “These positive circumstances make this intelligent alliance of wastewater treatment and energy generation interesting for all wastewater treatment plants in the size class from 8,000 to 50,000 PE”, continues Flerlage.
The process engineering approach of WELTEC and the modular stainless steel tanks have already led to a significant improvement of existing wastewater plants in several countries.
WELTEC BIOPOWER is since 2001 one of the world’s leading enterprises in the field of stainless-steel biogas plant construction. Today, WELTEC has established more than 300 energy plants in 25 countries worldwide. The strength of WELTEC BIOPOWER lies in custom-tailored design and technically mature solutions for projects up to 10 megawatt capacity.
