Integrating circularity to achieve sustainability: Examples of various wastewater treatment systems

Abstract Circular Economy principles seek to apply a “multiple use” approach with focus on returning the resource to further systems. Water and wastewater treatment systems rarely consider all three dimensions of sustainability in terms of environmental, social, and economic parameters. Wastewater holds important resources that are useful for further use, for instance in irrigation for agriculture, groundwater recharge, sludge reuse, biomass harvesting, and energy production. We postulate that using circular economy principles in wastewater treatment systems, i.e., using treated wastewater for subsequent purposes, can increase the sustainability of wastewater treatment system, in particular for achieving the United Nations Sustainable Development Goal 6 and one of its targets on increasing the proportion of safely treated wastewater. We further postulate that using treatment systems that allow for multiple (re)use options achieves higher sustainability. In two examples from Latin America and Asia (India) we illustrate how circular economy principals applied to wastewater treatments holds potential to address environmental, social, and economic development.