Short-term flexibility for energy grids provided by wastewater treatment plants with anaerobic sludge digestion.

Abstract

For a sustainable development of the energy sector - in the future - an additional potential of energetic flexibility as well as storage capacities will be required to compensate for fluctuating renewable energy production. The operation of energy systems will change and flexibility in energy generation and consumption will rise to become a valuable asset. Wastewater treatment plants (WWTPs) with anaerobic sludge digestion are capable of providing that needed flexibility, not only with their energy generators but also in terms of their energy consuming aggregates on the plant. Under these circumstances a methodical approach has been developed that can be used to select, evaluate and safely implement typical aggregates on WWTPs for flexible plant operation and the provision of energetic flexibility. Relevant key figures have been developed that reconcile requirements of the purification processes with technical-physical necessities as well as the demands of the energy market. Furthermore, restrictions and control parameters have been established which complement the developed key figures to ensure effluent quality. It was demonstrated that WWTPs are able to adapt their operation mode to external and internal requirements under controlled conditions. The existing flexibility is suitable for a variety of uses, and WWTPs in general are able to participate in today's and in future energy supply products and new business models. The results show that WWTPs have a significant potential to produce renewable energy and to provide energetic flexibility, which is needed to stabilize future renewable-energy-driven energy grids.