Evaluation of available capacities for thermal sewage sludge treatment and phosphorus recovery (EvKK)
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In Germany Sewage sludge is currently disposed of in agriculture, landscaping and by thermal treatment. However, due to the increasing public and political focus on soil, plant and environmental protection, the direct transfer of sewage sludge to agriculture is increasingly being critically evaluated. This is due to the risk of a possible release of the contained organic and inorganic pollutants into the environment (soil, food, groundwater). With the "Sewage Sludge Ordinance” of 2017, soil-related sewage sludge utilisation will be restricted in the future.
However, sewage sludge also contains important nutrients, like phosphorus (P), that has been classified as a critical raw material by the EU Commission in 2014. Consequently, the EU states are obliged to take measures to increase the efficiency of P use and recycling. P-recovery from sewage sludge will be mandated by law in the future, as it is an essential component of the amended Wastewater Treatment Ordinance (AbfKlärV). At the same time, other established recycling paths, such as co-incineration, will be restricted. With the entry into force of Article 5 of the Wastewater Treatment Ordinance, thermal treatment will gradually become mandatory for wastewater treatment plants, for a population equivalent of more than 50,000. In addition, if the P content exceeds 2 % in the dry matter, there is a requirement to carry out P recovery either before or after thermal treatment.
A large number of P recovery processes are currently still in the development stage. For this reason, it is unclear whether these technologies will be mature and available with sufficient treatment capacity at the required time.
The project EVKK is being carried out in cooperation with the Department of Energy Resources Technology (TEER) at RWTH Aachen University on behalf of the Federal Environment Agency. Based on research and stakeholder surveys, the project will analyse the available capacities for thermal treatment and P-recovery. This also includes an outlook on the further capacity requirements for incineration and recovery plants until 2029. The status of thermal sewage sludge treatment technology for alternative thermal treatment processes and P-recovery technology is also compiled. For this purpose, the recorded recovery processes are to be evaluated comparatively regarding efficiency and degree of technological maturity. In summary, the project should provide insights for the further development of the German phosphorus recovery strategy.