Probabilistic evaluation of integrating resource recovery into wastewater treatment to improve environmental sustainability

Significance Conventional methods used in wastewater treatment plants (WWTPs) emphasizing removal of detrimental substances from wastewater are essential for protection of the aquatic environment and public health. However, they are associated with costs in terms of environmental problem shifting, such as energy consumption, solid waste production, and greenhouse gas emissions. An improved approach involving wastewater-derived resource recovery in WWTPs is recognized as one potential solution. However, the environmental impacts and benefits of such a substantial change remain uncertain. We conducted an integrated assessment of the net environmental benefits of this transition in WWTPs for more than 50 individual countries to determine how best to update current methods of wastewater treatment and facilitate sustainable WWTPs in various parts of the world. Global expectations for wastewater service infrastructure have evolved over time, and the standard treatment methods used by wastewater treatment plants (WWTPs) are facing issues related to problem shifting due to the current emphasis on sustainability. A transition in WWTPs toward reuse of wastewater-derived resources is recognized as a promising solution for overcoming these obstacles. However, it remains uncertain whether this approach can reduce the environmental footprint of WWTPs. To test this hypothesis, we conducted a net environmental benefit calculation for several scenarios for more than 50 individual countries over a 20-y time frame. For developed countries, the resource recovery approach resulted in ∼154% net increase in the environmental performance of WWTPs compared with the traditional substance elimination approach, whereas this value decreased to ∼60% for developing countries. Subsequently, we conducted a probabilistic analysis integrating these estimates with national values and determined that, if this transition was attempted for WWTPs in developed countries, it would have a ∼65% probability of attaining net environmental benefits. However, this estimate decreased greatly to ∼10% for developing countries, implying a substantial risk of failure. These results suggest that implementation of this transition for WWTPs should be studied carefully in different temporal and spatial contexts. Developing countries should customize their approach to realizing more sustainable WWTPs, rather than attempting to simply replicate the successful models of developed countries. Results derived from the