Nature-Based Treatment Systems for Reclaimed Water Use in Agriculture in Mediterranean Countries

The Mediterranean region is one of the most vulnerable areas to climate change. This area is affected by severe water scarcity, which is expected to prevail by the upcoming years. The use of reclaimed water (RW) in agriculture is a way to reduce water scarcity, alleviate pressures on groundwater and other freshwater resources, and improve irrigated crop productivity and environmental sustainability. RW is already being used, directly or indirectly, in many semi-arid areas of the world (e.g. Africa, Central America, Southern Europe, and Southern Asia). In the last decades, Nature-Based Solution (NBS) systems such as constructed wetlands (CWs) or waste stabilization ponds (WSPs) have been proven to be a convenient solution for the decentralized treatment of wastewater (WW) of various origins and for their high landscape integration and low maintenance costs. In particular, NBS systems have rapidly evolved through the use of various design and operational modes or other adjustment (i.e. aeration in subsurface, recirculation rates, etc.) so as to improve effluent water quality with respects to various pollutants removal. Notwithstanding the numerous advantages, several barriers still limit the agricultural RW use practices in both developed and developing countries around the Mediterranean rim. From the technical viewpoint, the poor quality of RW can dissuade farmers from reuse as it could allow only cultivating low revenue crops. A low-cost natural treatment of municipal WW could alleviate restrictions for the agricultural irrigation and save the use of organic and mineral fertilizers. This chapter reports various aspects linked to the use of RW in agriculture in Mediterranean countries, namely Southern Italy and Nord-African countries. Case studies of the last two decades concerning the RW use in agriculture in South Mediterranean regions were analysed to highlight technical, regulatory, and environmental aspects. Also, use-related risks in agriculture of RW produced by NBS systems in Mediterranean countries are discussed.