place Case Studies

Braunschweig, Germany

Steinhof, near Braunschweig, has a long tradition of water and nutrient reuse. Already at the end of the 19th century, fields were irrigated with sewage. From 1954 on, the wastewater was mechanically clarified and reused for irrigation. Finally, in 1979, the wastewater treatment plant (WWTP) was built and comprised a conventional activated sludge treatment system and a digestion stage. Until 2016, in summer, the digestate was directly reused in agriculture, while in winter, the digestate was dewatered and stored until the summer season. However, due to the new legislation in Germany, since 2017 only 60% of the digestate can be applied on the fields. The reasons are restricted periods for fertilizing with digested sewage sludge and the limitation of the nitrogen load to the agricultrual fields. Thus, the other 40% of the digestate were dewatered and incinerated.
In 2019, a new circular economy concept was implemented. Here, energy recovery technologies are combined with nutrient recovery technologies. Therefore, sludge managemet concept was adapted to increase the nutrient recovery rate and simultanously, as a synergetic effect, the biogas recovery rate increased. Hence, circular economy solution comprises a thermal hydrolysis process between two digestion stages and a full-scale nutrient recovery plant consisting of a struvite production unit to recover phosphorus and an ammonium sulphate solution production unit to recover nitrogen.
The secondary fertilizers are will be reused by the local farmers and the produced energy in the form of biogas and heat is reused by the plant itself.

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Last update on 2022-03-09 09:07 UTC