استفاده مجدد از فاضلاب صنعتی و کشاورزی به عنوان جایگزین برای آبیاری سبزیجات در شرایط مدیترانه ای Agro-industrial wastewater reuse for irrigation of a vegetable crop succession under Mediterranean conditions

1. Introduction Anumber ofMediterraneancountries suffer fromwater scarcity, which has become severe in recent years due to global climate change causing frequent and long lasting periods of drought. Particularly during the summer, these areas experience severe water supply and demand imbalances. In the last decades, many Italian regions have faced the negative impact of drought and the resource scarcityhasmostlypenalizedagricultural activities, which uses more than 50% of the total available water, while other high priority demands, such as those from civil and industrial sectors, are satisfied (Coppola et al., 2004). Particularly, in Apulia Region (South-Eastern Italy), water shortage has a serious impact on the local economy, mostly based on agriculture. Moreover, the agricultural coastal areas ofApuliaRegionsuffer fromrelevantphenomena of seawater intrusion into the water table, due to the excessive and often uncontrolled groundwater withdrawals for irrigation (Libutti andMonteleone, 2012). For these reasons, alternative water sources are needed. Treated municipal wastewater is the most readily available source of water to meet the increasing demand for crop irrigation. Indeed, in recent years, wastewater recycling in agriculture has gained importance as component of agricultural water supply in several water-scarce countries (Qadir et al., 2007; Pedrero et al., 2010). Wastewater reuse not only provides significant amount of irrigation water, but also contributes to conserve potable resources and reduces the environmental impact related to the effluents discharge into water bodies (Aiello et al., 2007; Pedrero et al., 2010; Agrafioti and Diamadopoulos, 2012). Furthermore, soil application of treated wastewater also constitutes a reliable source of nutrients (especially nitrogen, phosphorus and potassium) and organic matter useful for maintaining the fertility and the productivity of the soil (Meli et al., 2002; Rusan et al., 2007). Treated wastewater use for crop irrigation can improve growth and yield of herbaceous species (Kiziloglu et al., 2008; Bedbabis et al., 2010) and can also enhance the economic benefits for farmers, due to reduced need for fertilizer (Bedbabis et al., 2010; Paranychianakis et al., 2006). However, the chemical composition of wastewater has to be monitored to avoid imbalance in nutrient supply, which may result in excessive vegetative growth, uneven fruit maturity, reduced quality and quantity of yields (Pedrero et al., 2010). Treated wastewater should be used for irrigation under controlled conditions, also to minimize hazards to agricultural products, soil and groundwater from toxic and pathogenic contaminants (Aiello et al., 2007; Qadir et al., 2007). Wastewater may contain a variety of pollutants, such as salts, heavy metals, organic compounds, enteric bacteria and viruses. An excessive accumulation of trace metals, such as Cd, Cu, Fe, Mn, Pb and Zn, in soils through irrigation creates problems for agricultural production (Singh et al., 2004) and leads to metal uptake by crops, so affecting food quality and safety (Khan et al., 2008). One of the crucial issues in the reuse of treated wastewater for crop irrigation is the residual presence of pathogenic microorganism (Rubino and Lonigro, 2008; Petterson et al., 2011) which represents a potential health risk to consumers when they enter in the food chain (Toze, 2006). In Italy, there are strict regulations for reclaimed wastewater reuse (Decree No. 152, 2006, Ministry for Environment), especially for levels of some chemical compounds and for microbial parameters. With regard to microbiological contamination levels, the corresponding guidelines allow unrestricted crop irrigation with a bacteriological effluent quality characterized by less than 10 CFU 100 ml−1 of E. coli in 80% of samples.