The use of constructed wetlands for water pollution control has a long standing tradition in urban, peri-urban, rural, agricultural and mining environments. The capacity of wetland plants to take up nutrients and to filter organic matter has been widely discussed and presented in diverse fora and published in hundreds of articles. In an ever increasingly complex global world, constructed wetlands not only play a role in providing safe sanitation in decentralized settings, shelter for biodiversity, and cleansing of polluted sites, in addition, they produce biomass that can be harvested and used for the production of fodder and fuel. The United Nations University Institute for Integrated Management of Material Fluxes and of Resources (UNU-FLORES) was established in December 2012 in Dresden, Germany, to assess the trade-offs between and among resources when making sustainable decisions. Against the backdrop of the Water-Energy-Food Nexus, which was introduced as a critical element for the discussions on sustainability at Rio +20, the UNU was mandated to pay critical attention to the interconnections of the underlying resources, namely, water, soil and waste. Biomass for human consumption comes in the form of food for direct use, as fodder for livestock, and as semi-woody biomass for fuelling purposes, be it directly for heating and cooking or for the production of biogas and/or biofuel. Given the universal applicability of constructed wetlands in virtually all settings, from arid to tropical, from relatively high to low nutrient loads, and from a vast variety of pollutants, we postulate that the biomass produced in constructed wetlands can be used more extensively in order to enhance the multi-purpose use of these sites.

The Sustainable Development Goals have placed integrated resources management, such as integrated water resource management, at the heart of their targets. The upcoming “International Decade for Action—Water for Sustainable Development”, 2018–2028 has highlighted the importance of promoting efficient water usage at all levels, taking into account the water, food, energy, and environmental nexus. While integrated resource management approaches have been defined and applied for decades, nexus approaches are more recent. For these latter approaches to be implemented on the ground, their system boundaries need to be clarified. While the Water–Energy–Food Nexus focuses on sectors, the Water–Soil–Waste Nexus addresses linkages between environmental resources—namely water, soil and waste—to tackle sustainable management. In this paper, we analyzed integrated management systems and how their system boundaries are defined. From this we determined that in order for system boundaries to be applicable, they should be clear, wide and flexible. Based on this, we propose the boundary of the Water–Soil–Waste Nexus system. We use two case studies to exemplify the usefulness of these system boundaries.

Wastewater management in Latin America faces great challenges to reach a sustainable state. Although enough infrastructure has been built to treat around 40% of wastewater, only between 15–20% is effectively treated, and abandoned or defective infrastructure is a common sight. Data about current conditions at specific sites is quite fragmented, when existing. This leads to challenges in management, decision making and planning for sustainable options. We argue that a main obstacle is the lack of a regionally relevant sustainability assessment framework that allows for a holistic understanding of wastewater management as a nexus problem. We therefore developed a comprehensive framework to (1) understand current conditions (2) involve stakeholders and (3) point to pathways to improve wastewater management in the Americas. Building on literature review and stakeholder involvement, we constructed a multi-scalar extended dataset framework that is adaptable to different study sites using specific criteria. Sustainability was assessed through a “distance-to-target” approach. Social and economic variables were the lowest ranking in both cases, with technical variables generally performing better. Although some dimensions of sustainability are performing acceptably, others, such as social and economic, are general low to very low performing. This means, when looked at in an integrated manner, neither of the wastewater management systems analysed can be considered sustainable. Here we present the approach itself, the results of its application in two pilot sites in Latin America, and our recommendation to shift waste water management into sustainability.