Tackling climate change through wastewater reuse in agriculture: A prioritization methodology

Water shortages, exacerbated by climate change, are posing a major global challenge, particularly impacting the agricultural sector. A growing interest is raised towards reclaimed wastewater (RWW) as an alternative irrigation source, capable of exploiting also the nutrient content through the fertigation practice. However, a prioritization methodology for selecting the most appropriate wastewater treatment plants (WWTPs) for implementing direct RWW reuse is currently missing. Such prioritization would benefit water utilities, often managing several WWTPs, and policymakers in optimizing economic asset allocation. In this work, a prioritization framework is proposed to evaluate WWTPs' suitability for implementing direct RWW reuse considering both WWTP and surrounding territory characteristics. This procedure consists of four key steps. Firstly, a techno-economic model was developed, in which monthly mass balances on water and nutrients are solved by matching crop requirements, rainfall conditions, and effluent characteristics. Economic suitability was quantified considering economic benefits due to savings in freshwater resource, mineral fertilizers and avoided greenhouse gases emissions, but also losses in crop yield due to RWW salinity content. Secondly, a classification procedure was coded to select representative WWTPs among a set of WWTPs, based on their size, presence of nutrient removal processes, and type of crops in their surroundings. The techno-economic model was then applied to these selected WWTPs. Thirdly, input parameters' relevance in determining WWTP suitability for RWW reuse was ranked. Finally, scenario analyses were conducted to study the influence of rainfall patterns and nutrient treatment removal on the RWW reuse feasibility. The type of crops surrounding the WWTPs and RWW salinity content resulted to be crucial elements in determining WWTPs suitability for RWW reuse implementation. The proposed methodology proved to be an effective support tool for policymakers and water utilities to assess the techno-economic feasibility of direct RWW reuse, generalizing results to several combinations of WWTPs and crops.