GIS-Based Assessment of the Potential for Treated Wastewater Reuse in Agricultural Irrigation: A Case Study in Northern Italy
Climate change and human activities are the leading causes of water shortages and pollution, representing some of humankind’s greatest challenges today. The agricultural sector, particularly irrigation, is the primary water consumer, with around 70% of the total withdrawal. Using non-conventional water resources can provide a valid alternative to cope with water scarcity issues in agriculture, improving crop productivity and ensuring food security and environmental quality. The European countries most affected by water scarcity belong to the Mediterranean region, Italy, Spain and Greece. In these countries, the rate of treated wastewater reuse is scant, only between 5% and 12%. It is therefore necessary to investigate the potential of treated wastewater reuse to to help to meet ever increasing agricultural water demand.
This research aimed to evaluate the amount of treated wastewater available for irrigation in one of the provinces of the Emilia-Romagna region (Italy). The analysis was conducted using GIS software, using data provided by the Romagna Reclamation Consortium (RRC) within the time interval 2017–2019. This analysis considers the geographical distribution of all the municipal WWTPs and all the areas equipped for irrigation, the irrigated and the irrigable sites located within the Forlì-Cesena province. The WWTPs taken into account were those with a population equivalent (PE) higher than 1000 and that were located within the proximity to the areas irrigated with RRC water. These criteria were considered to reduce costs and negative environmental impacts connected to the treated wastewater transport and supply.
In all of the selected WWTPs, treated wastewater is discharged into open canal systems managed by the RRC, whose primary function is to convey treated wastewater to the receiving water bodies (e.g., the Adriatic Sea). For each WWTP, the effluent’s water quality was evaluated based on the new EU Regulation 2020/741. A further analysis was performed on the nutrient content of the treated wastewater. Therefore, the two main criteria to evaluate the capability of treated wastewater to satisfy crop water needs in actually irrigated areas were the volumes of treated wastewater produced by the selected WWTPs. Also, the new sites suitable for irrigation were selected with the aim of evaluating the possibility of extending the current water distribution network.
The GIS results showed that crop water needs could be primarily satisfied by treated wastewater for the irrigated areas. Furthermore, GIS results confirmed the possibility of extending the water distribution network beyond the irrigated areas, creating newly irrigated areas (irrigable areas). In this case, treated wastewater could largely satisfy crop water needs, confirming that it is a valuable and alternative water resource that can help to increase food production and meet the growing food demand. The results highlight that, for the selected study area, treated wastewater reuse for irrigation purposes in agriculture could help mitigate water scarcity. In particular, treated wastewater represents an alternative and constant water resource quantity over time, which could replace some of the freshwater withdrawals. Furthermore, results confirm that nutrient recovery from wastewater (mainly nitrogen and phosphorus), essential for crop growth, can be a sustainable approach to reduce the use of fertilizers in agriculture.