A global indicator of wastewater treatment to inform the Sustainable Development Goals (SDGs)

•A first-ever indicator of global wastewater treatment performance was developed.•Results show wastewater treatment varies by region and wealth.•Challenges exist for UN negotiators to incorporate an SDG for wastewater treatment.•We provide a baseline for how countries, the world perform on wastewater treatment. This paper assessed an effort to create an indicator of global wastewater treatment performance to inform environmental performance and sustainable development. We compiled wastewater treatment statistics for 183 countries and constructed a first-of-its-kind global indicator for wastewater treatment performance. Although reporting definitions are inconsistent across countries, we preliminarily concluded that wastewater performance trends vary globally, regionally, and by income. Overall, the lack of consistent definitions, reporting protocols, and a central custodian for wastewater treatment data are main reasons for many challenges we confronted in constructing comparable performance measures. We suggest a standardized definition of wastewater treatment aimed at the utility level, which could be normalized and aggregated to reflect national performance. U.N. negotiators, who are designing a Sustainable Development Goal (SDG) for water that includes a metric on wastewater treatment, must consider these issues if countries are to be successful in managing wastewater and ultimately, water quality.