Development of a multi-factorial model to assess the sustainability of irrigation wastewater reuse: application to case studies in Sicily

The reuse of wastewater is a non-conventional water resource that is an essential measure for climate change adaptation. This research introduces an index based on a holistic methodology to evaluate the techno-economic, water-related, and environmental sustainability of wastewater reuse for agricultural applications. The development of the model is structured in the following phases: estimate of preliminary reuse factors, assessment of screening factors, selection of appropriate treatment schemes, assessment of cost factors. The first phase is fundamental to calculate annual reusable volume and the water level stress index (LWSI). Screening factors include desertification tendency, BOD, nitrogen, and phosphorus loads in water bodies, ecological sensitivity of the area, nitrate vulnerability, organic carbon and heavy metal content in soils, and the risk of aquifer contamination. The treatment schemes are selected based on the presence of a storage reservoir and on the nitrate vulnerability of the area. Cost factors include costs of upgrading supply network, pumping system and monitoring soil. The model also includes the calculation of the economic benefit. The model is applied to 101 wastewater treatment plants in Sicily. The obtained results reveal high sustainability indexes attributed to the rising of market prices, which in turn increased the direct economic benefit associated.