Circular economy from wastewater resource recovery: A review of recent advances and global disparities

Wastewater management has undergone significant evolution from medieval practices, where wastewater was directly discharged into surface water bodies, to modern approaches that emphasise not only treatment for public health but also the recovery of valuable resources. This evolution reflects a shift from unidimensional wastewater treatment focused solely on health protection to a multipurpose framework that includes water reclamation, reuse, and resource recovery. This narrative review assesses recent developments in wastewater resource recovery technologies and highlights global disparities in their adoption. By analysing research outputs using relevant keywords such as "Circular Economy," "Wastewater," and "Resource Recovery," the review reveals a significant concentration of research and technological development in the Global North, particularly in Europe and East Asia (mainly China). In contrast, regions like Sub-Saharan Africa (excluding Southern Africa) and parts of Southeast Asia remain largely underserved, hindered by limited infrastructure, inadequate funding, and insufficient institutional support. Key resources recovered include nutrients and soil amendments, feed and bioproducts, bioenergy, and metals. Out of 61 studies synthesised and comparatively analysed, 39% originated from Europe, while none emanated from West and Central Africa, illustrating a stark imbalance in research and innovation. The implications of these disparities are far-reaching. Recommendations for advancing wastewater resource recovery globally were offered, emphasising the importance of inclusive and equitable progress to ensure that no region is left behind in this critical aspect of sustainable development.