Appraising water and nutrient recovery for perennial crops irrigated with reclaimed water in Mediterranean areas through an index-based approach

Treated wastewater reuse for irrigation: A feasibility study in Portugal

In an increasing water scarcity and climate-vulnerable global context, treated wastewater represents a vital alternative water source, thereby enhancing resource sustainability. Despite its potential, only roughly 2.5 % of the treated wastewater is reused in the European Union, with Portugal's reuse rate being only 1.2 % in 2022. Considering this framework, this study evaluates the feasibility of increasing wastewater reuse in Portugal by focusing on the Tagus River and Ribeiras do Oeste Basins. The regional assessment identified eight key wastewater treatment plants (WWTP) with significant potential for irrigation reuse in the agriculture and tourism sectors. Analysing costs, quality requirements, and technological options, this study considered five treatment lines, incorporating filtration and disinfection methods. The findings indicate that reclaimed water costs may range from 0.02€/m3 to 0.83€/m3, being competitive with other water sources and significantly lower than desalination processes (up to 1.66€/m3). Distribution investments and energy consumption are primary cost drivers, suggesting a relocation of WWTP closer to end-users as a cost-saving strategy. The proposed reuse projects could quadruple regional reuse rates and double the national rate, mitigating water needs for over 2000 ha of agricultural land and golf courses. This study underscores the importance of treated wastewater reuse in addressing water scarcity, advocating for WWTP decentralisation, strategic investments and policy interventions to achieve cost-effective goals. The methodologies and insights presented offer valuable guidance for other regions facing similar challenges, promoting a paradigm shift towards circular water resource management.

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.

Mitigating risks and maximizing sustainability of treated wastewater reuse for irrigation

Scarcity of freshwater for agriculture has led to increased utilization of treated wastewater (TWW), establishing it as a significant and reliable source of irrigation water. However, years of research indicate that if not managed adequately, TWW may deleteriously affect soil functioning and plant productivity, and pose a hazard to human and environmental health. This review leverages the experience of researchers, stakeholders, and policymakers from Israel, the United-States, and Europe to present a holistic, multidisciplinary perspective on maximizing the benefits from municipal TWW use for irrigation. We specifically draw on the extensive knowledge gained in Israel, a world leader in agricultural TWW implementation. The first two sections of the work set the foundation for understanding current challenges involved with the use of TWW, detailing known and emerging agronomic and environmental issues (such as salinity and phytotoxicity) and public health risks (such as contaminants of emerging concern and pathogens). The work then presents solutions to address these challenges, including technological and agronomic management-based solutions as well as source control policies. The concluding section presents suggestions for the path forward, emphasizing the importance of improving links between research and policy, and better outreach to the public and agricultural practitioners. We use this platform as a call for action, to form a global harmonized data system that will centralize scientific findings on agronomic, environmental and public health effects of TWW irrigation. Insights from such global collaboration will help to mitigate risks, and facilitate more sustainable use of TWW for food production in the future.

Life cycle assessment as decision support tool for water reuse in agriculture irrigation

This study presents a decision support tool that evaluates the environmental efficiency of water reclamation for agricultural irrigation, among other options. The developed tool is published as open source at https://doi.org/10.18167/DVN1/YLP1BA. The objective of this decision support tool is to facilitate the interpretation of the Life Cycle Assessment (LCA) results. This framework was applied to a representative case of reuse of reclaimed water for vine irrigation at the Murviel-Les-Montpellier experimental site (Hérault, France). It was then generalized through modeling assumptions to consider different reuse scenarios. To highlight situations in which the supply of recycled water for irrigation may or may not provide significant environmental benefits, three main parameters were varied: (i) tertiary treatment technologies, (ii) availability of conventional water sources, (iii) energy mix composition. The results show that the environmental impact of reclaimed water depends directly on the type of tertiary treatment technology and the location of the treatment plant in relation to the field and other water sources. The decision support tool has identified where wastewater reuse is clearly an environmentally beneficial source of irrigation among surface and groundwater sources (e.g., WWTP closer to field than river, groundwater too deep, tertiary treatment environmentally beneficial). However, there are many situations where the decision support process cannot distinguish between water reuse for agricultural irrigation and conventional water sources, especially when the nutrient content of treated municipal wastewater is insufficient to offset the negative effects of high energy requirements and chemicals of tertiary treatment.

Changes of Microbial Diversity in Rhizosphere of Different Cadmium-Gradients Soil under Irrigation with Reclaimed Water

Water scarcity and the uneven distribution of water resources in China have resulted in water shortages for agricultural irrigation in arid and semi-arid areas. Reclaimed water used for agricultural irrigation has become an effective solution in the context of the global water shortage. In order to improve soil productivity and solve the shortage of water resources, we carried out reclaimed water irrigation experiments on polluted soil. Compared with full irrigation treatments, the EC value of reclaimed water under deficit irrigation treatments decreased by 2.89–42.90%, and the content of organic matter increased by 6.31–12.10%. The proportion of Acidobacteria community in soils with different cadmium concentration gradients irrigated with reclaimed water ranged from 13.6% to 30.5%, its relative abundance decreased with the increase of soil cadmium concentration. In particular, the relative abundance of Pseudomonas pathogens in deficit irrigation treatments was lower than that of the full irrigation treatments. RDA analysis showed that the environmental factors that played a leading role in the change of microbial community structure were organic matter and pH. Furthermore, the metabolic function potential of the rhizosphere soil bacterial community in deficit irrigation treatments was higher than that of full irrigation treatments with reclaimed water. This study proved that reclaimed water irrigation for cadmium contaminated soil did not aggravate the pollution level and promoted the soil ecological environment with better microbial community diversity.