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

The use of reclaimed water for agricultural irrigation is among the agronomic practices being increasingly valued by policy-makers, water planners, and regulators to pursue more sustainable resource management in many arid and semi-arid agricultural production areas worldwide. This practice can make additional supply available in water-scarce areas, provide crop nutrients, and reduce the disposal of wastewater to the environment, thus providing considerable agronomic and environmental benefits. However, the process for treated wastewater reuse is complex because of multiple interactions among technical, economic, environmental, and public health related aspects. In this context, the application of quantitative indices capturing agronomic, engineering, and environmental factors and their possible inter-relations enable to appraise the potential benefits and risks of treated wastewater reuse at individual project’s scale and for regional policies. The present article describes a quantitative approach that utilizes a set of proposed indices to characterize various aspects affecting water and nutrient recovery for specific combinations between the characteristics of the treatment facility and the attributes of the irrigation district supplied with reclaimed water. The proposed index-based approach was tested on datasets collected for 11 pilot reuse schemes located in the Apulia region of southern Italy with the aim to evaluate the potential for water and nutrient recovery resulting from irrigation with reclaimed water. Results from the data analysis and interpretation showed that the proposed indices enabled to quantify the environmental benefits of irrigation with RW that leads to divert less freshwater from conventional sources and dispose less reclaimed water into natural water receptors, as well as the agronomic advantages of using RW, which can partially fulfill the irrigation and nutrient requirements for the supplied districts' service areas. Overall, the proposed set of indices can provide valuable information for the successful implementation of water reuse policies for irrigated agriculture.