Energy-plus sewage treatment plant in Bad Oeynhausen: Energy from sewage gas covers the plant's own requirements

Waste-water treatment is highly energy intensive and accounts for the largest share of energy consumption in many municipalities. In Bad Oeynhausen, the local municipal utilities company has been able to optimise its plant in such a way that its energy requirement has shrunk by 50 per cent and can now be covered by the energy it produces itself from sewage gas. The basis for this was a concept developed by the employees themselves to review the site’s energy efficiency.

Engine for progress:

  • halving the energy requirement through 74 energy-saving measures
  • reducing power costs by €250,000 per year
  • since 2014: generates more energy than it consumes
  • 1,300 tonnes of CO2 saved per year
  • 10% increase in efficiency in the sewage gas CHP units

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Photo: Stadtwerke Bad Oeynhausen

Bad Oeynhausen sewage works has a capacity of 79,500 p.e. (population equivalents) and a current load of 63,000 p.e.

The sewage treatment plant in Bad Oeynhausen treats municipal waste water for 55,000 local people and, at one time, consumed three million kilowatt-hours per year. Then, the employees developed a detailed plan to thoroughly examine the energy implications of each drive system and procedure. This was based on five key issues: Do we still need this part of the plant? Can the operation time be shortened? Can the system be used with less load? Is there more efficient technology? Can the amount of self-generated electricity be increased? Using this review concept, the employees identified 74 energy-saving measures that saved an annual total of 1.5 million kilowatt-hours. An upgrade to the sewage works was due anyway, which meant that the efficiency measures could be implemented straightaway. In addition to the refurbishment, around €200,000 was invested, which resulted in a reduction in power costs of around €250,000 per year, thus paying for itself in less than a year.

From energy guzzler to energy producer

However, the municipal utilities company did not just want to optimise nitrification, biofiltration, agitation, grit chamber aeration and flow acceleration systems or the aeration blowers. It also looked at the processes in which energy is produced. For this reason, two years ago, the CHP units powered by sewage gas were updated and their efficiency was increased by 10 per cent. Using combined heat and power, they generate heat for the staff areas and the digestion tower as well as the power to operate the sewage works. This way, full use is made of the sewage gas. By 2014, self-generation had increased by 80 per cent to 1.8 million kilowatt-hours. Since 2014, the site has produced more energy than it needs. As a consequence of the reduction in fuel consumption and the increase in self-generation, CO2 emissions totalling around 1,300 tonnes are prevented each year.

Photo: Stadtwerke Bad Oeynhausen

“Apart from industry, sewage treatment plants are one of the largest consumers of energy. Since 1991, we have been working to achieve the goal of an energy self-sufficient sewage treatment plant. The fact that the sewage works in Bad Oeynhausen now generates more energy than it consumes makes it a successful example of climate and environmental protection on a municipal level.”

Christoph Dörr, Director of Bad Oeynhausen Municipal Utilities Company

Partners and sponsors

  • Stadtwerke Bad Oeynhausen