Engineering approaches to wastewater treatment must aim for more than improved efficiency.
Water is essential to any form of life on Earth — we need enough of it and of the right quality. This is so much at the core of sustainability that we have written about it in previous editorials (Nat. Sustain. 1, 151–152 (2018) and Nat. Sustain. 1, 447 (2018)). Research has long documented the severe impacts that human activities have on both water availability and quality, including in Nature Sustainability more recently. We also know that significantly reducing those impacts is far from easy, especially against prospects of a growing population globally — our diets are based on water, a large portion of energy activities need water in various ways, most manufacturing and consumption activities require some form of water use and, all such activities ultimately produce some kind of wastewater. And it is precisely on wastewater — and how to treat it sustainably — that we want to focus our readers’ attention with this editorial. Given the different forms of water contamination, society needs to identify and implement different solutions. In this issue, we highlight three cases: treatment of wastewater from the oil industry in an Article by Park and colleagues, treatment of desalination brine in an Article by Prasher and collaborators and finally, treatment of water contaminated by glyphosate use in an Article by Halik and co-authors. Park and colleagues show how reusable surface-engineered sponges offer a sustainable solution to efficiently remove crude oil microdroplets from wastewater. Prasher and collaborators demonstrate a scalable surface-heating approach to improve solar evaporation in brine-disposal ponds, usually requiring large surface areas to passively evaporate water for the removal of brine — the solution significantly reduces the need of land to treat wastewater. Halik and co-authors present a method for the efficient remediation of the herbicide glyphosate from water by means of inexpensive, recyclable magnetite nanoparticles. All three studies have some common sustainability features. Of course, the three different solutions discussed have the potential to increase the efficiency of water treatment with respect to commonly used methods. But beyond the improved efficiency, each approach presents one or more additional advantages. Reusability, recyclability, scalability, low cost or reduced need of primary inputs (for example, land), are critical sustainability gains if we embrace an integrated view of what sustainable solutions must be. It is therefore the combination of improved efficiency with any of those gains that makes for socially desirable solutions to the water challenges of our time. We at Nature Sustainability call for more research focusing on such holistic solutions.