In 2015, UN Member States adopted the 2030 Agenda for Sustainable Development, including Sustainable Development Goal 6 (SDG 6): "Ensure availability and sustainable management of water and sanitation for all". Commonly known as the 'water goal', SDG 6 went well beyond the limited focus on water supply and sanitation in the Millennium Development Goals (MDGs) and recognized the importance of all aspects of the water cycle in development and that water was embedded directly and indirectly in all 17 SDGs. In 2018, the UN published a report: "Sustainable Development Goal 6 Synthesis Report on Water and Sanitation 2018" (referred to in this paper as 'the report') that reviewed progress with SDG 6 at global and regional levels. Overall, the report concluded there was progress, but it was too slow, and the world was not on track to achieve SDG 6 by 2030 without a significant change of gear. The report was written primarily for those working in sustainable development to guide finance and resource allocation, but there was much embedded in the report that was of value to those engaged in research and in developing the much-needed capacity to plan and manage water resources, particularly in developing countries. This paper attempts to distill these issues and to ask how those involved in education, training, and research could contribute to enabling and accelerating progress towards achieving SDG 6. Three key areas of engagement were identified: the urgent need for more data and improved monitoring to assess SDG 6 progress and to enhance decision-making, the need to address the serious lack of human and institutional capacity that was constraining progress, and the challenge of taking research into policy and practice. Note: This paper is a review of selected aspects of the report (in which production the authors were chiefly involved as coordinators and editors), and as such most of the facts, figures, and discussion in this review are taken from the report. For this reason, we have not continually attributed them to the report to avoid repetition. However, in some cases, we have attributed report material to the primary sources where we considered it important to do so. We have also attributed material we have included, and which is not cited in the report. A review inevitably depends, to some extent, on the views of the reviewers and as such we have tried to make it clear where we are expressing our personal views rather than those expressed in the report. The report contains full references to all the primary sources.

Phosphorus is a nutrient necessary for the development of crops and is thus commonly applied as fertilizer to sustain agricultural production. It occurs naturally, in indefinite quantities of uncertain quality in phosphate rock formations, but also accumulates in urban and livestock wastewater wherefrom it is often lost as a pollutant. Recovering phosphorus from wastewater, however, is feasible through struvite crystallization technologies and has the potential to reduce phosphorus pollution of the environment as well as lower the agricultural demand for artificial P fertilizers. In this study, we developed a model to assess the global potential of P fertilizer recovery from wastewater and to visualize its trade at sub-national resolution. Results show that humans discharge a maximum of 3.7 Mt P into wastewater, thereby potentially satisfying 20 % of the global fertilizer demand. Provided 2015 market dynamics, however, the model determines that only 4 % of this discharge is technologically and economically recoverable in a market that offers cheap rock phosphate products also. The results of this study demonstrate that in the current economic context, phosphorus recovery from wastewater offers only a small contribution to resolving global phosphorus issues. Nevertheless, this recovery offers many wastewater treatment facilities the opportunity to contribute to creating sustainable communities and protecting the environment locally, while reducing their own operational costs.