Contents lists available at ScienceDirect Agricultural Water Management journal homepage: www.elsevier.com/locate/agwat Wastewater tertiary treatment options to match reuse standards in agriculture F. Licciardello ⁎ , M. Milani, S. Consoli, N. Pappalardo, S. Barbagallo, G. Cirelli Dept di Agricoltura, Alimentazione e Ambiente, Di3A, University of Catania, Italy ARTICLE INFO Keywords: Water reuse approaches Natural-based treatment Removal efficiency Treatment costs Environmental sustainability ABSTRACT In Italy, the restrictive approach for reclaimed water (RW) use in agriculture has led to some difficulties in spreading this practice. In particular, matching microbiological standards, evaluated in terms of Escherichia coli, is quite prohibitive and highly intensive disinfection systems are the sole option to adequately treat municipal wastewater. A different view of the same concern is offered by the World Health Organization (WHO) that proposed a pragmatic approach, based on microbial risk assessment, to evaluate case by case the pathogen reduction in case of RW use in agriculture and how to achieve this. In the study two different tertiary treatment options for RW use in agriculture were examined. The first option named “extensive tertiary treatment system – ETTS” included in series: horizontal sub-surface constructed wetland system, biological pond, storage reservoir, sand and disk filters. The second option named “hybrid tertiary treatment system – HTTS” included in series: horizontal sub-surface constructed wetland system, sand and disk filters, ultraviolet (UV) system. Moreover, the microbial contamination on crop irrigated by RW from both examined systems was evaluated. An economic analysis was carried out for a life cycle of 20 years of the treatment systems. Economic benefits and total cost of RW for agricultural irrigation using both the tertiary treatment options were evaluated. Results evidenced that total costs of RW were similar for both options, anyway other benefits can support the choice of ETTS to treat RW for vegetable crop irrigation, especially for rural areas in developing countries. 1. Introduction The Mediterranean region is one of the most vulnerable areas to climate change (Collet et al., 2015), and water shortages are expected to continue (La Jeunesse et al., 2016) due to the increasing degradation of water resources (overuse, pollution, salinization, etc.) and increasing water demand in agriculture as well as in the urban, industry, and energy sectors. As an effect of climate change, the frequency and in- tensity of droughts and their environmental and economic damages have drastically increased over the past thirty years. The droughts of the summer of 2017 may illustrate the dimensions of economic loss; the Italian farming sector alone was predicting losses of EUR 2 billion (EC, 2018). Agriculture is in fact the largest water user. The 2017 UN-World Water and Development Report (UNWWDR, 2017), based on FAO- Aquastat data states (FAO, 2016) that the water consumption for crop irrigation reaches 70%, on average, of the world water requirements (Ait-Mouheb et al., 2018). When natural water reserves are not sufficient, one of the most available, constantly produced and relatively unaffected by climatic conditions water resource is the reclaimed water (RW) (EEA, 2009; Cirelli et al., 2012; Ait-Mouheb et al., 2018). RW is already being used, directly or indirectly, in many semi-arid areas of the world (e.g. Africa, Central America, Southern Europe, Southern Asia) (Pedrero et al., 2010). In particular, RW is becoming an increasingly important source of irrigation being agriculture the highest water demanding user and often the most penalized among others. In Southern Europe, more than 50% of the total water consumption comes from agriculture (EEA, 2009). In Italy, in particular, in case of a lack of water, the water supply service often favours domestic and industrial sectors over the agricultural one, resulting in a negative impact on the local economy (Cirelli et al., 2012). As RW can be an important source of water in agriculture (Barbagallo et al., 2012), its application should be regulated in order to prevent the use of water of insufficient quality that later can cause diseases to humans (Pedrero et al., 2010; Dickin et al., 2016). On the international level, the two benchmark guidelines for RW use are the California guideline (State of California, 1978) and the World Health Organization (WHO) guideline (WHO, 1989). The first one is stricter, https://doi.org/10.1016/j.agwat.2018.08.001 Received 8 June 2018; Received in revised form 30 July 2018; Accepted 3 August 2018 ⁎ Corresponding author. E-mail address: flicciar@unict.it (F. Licciardello). Agricultural Water Management 210 (2018) 232–242 0378-3774/ © 2018 Elsevier B.V. All rights reserved. T