Treated sewage sludge is often reused as a fertilizer but several European countries are phasing out this option due to concerns about harmful substances in the sludge. Valuables in the sludge should still be recycled so the removal of the pollutants is necessary. The technology in sewage sludge treatment remained nearly unchanged in the past century. Adapting traditional treatments and combining them with upcoming ones can be a way to separate substances in sewage sludge. This work discusses examples of how treatment methods can be combined and which potential these treatment combinations may have. New tools for system analyses need to be developed to allow the integration and adaption of treatments into existing infrastructure.

This PhD thesis focuses on multidisciplinary challenges in sewage sludge management and how they can be addressed to increase sustainability. 

Sewage sludge is the residual from wastewater treatment. It contains both resources and contaminants making its management challenging. In the past sewage sludge was often used as a fertilizer in agriculture, a practice that is still used in several countries. Today, this practice gets questioned in Europe and especially in Sweden due to the presence of contaminants in the sludge. At the same time, the resources in the sludge get into a stronger focus as society moves towards a circular economy and food production should get more resilient in a world with geopolitical challenges. In sustainable sewage sludge management, the two goals of immobilising/destroying the contaminants and utilizing the resources in the sludge are combined. 

This thesis identifies challenges in various disciplines and provides potential solutions to make sewage sludge management more sustainable. The discussed challenges cover the following areas: legislation (EU and Sweden), perception of sewage sludge (Sweden), research on sewage sludge management (international), and combinations of treatment methods. Results show that outdated legislation in Sweden creates insecurities, while the negative perception of sewage sludge in Swedish society further aggravates these insecurities. Although technical solutions are available or under development, e.g., treatment combinations that can separate resources and contaminants, actors in Sweden remain hesitant due to the aforementioned insecurities. This thesis emphasizes that interdisciplinary approaches, and dialogues between different actor groups and society are essential. The multitude of challenges requires solutions that combine technical and non-technical approaches. Therefore, this thesis provides recommendations for more sustainable sewage sludge management practices, including updating legislation.