According to the Chartered Institution of Water and Environment Management, there are about 700 reclaimed water reuse projects in Europe, most of them in Southern countries; but there are also projects in central and Northern Europe. Treated wastewaters are reclaimed for different purposes: “for agricultural irrigation, landscape irrigation, industrial recycling and reuse, groundwater recharge, non-potable urban uses and indirect potable use” (EWA, 2007).
In Spain, the specific legislation regulating water reclaim since 2007 is included in the Royal Decree 1620/2007 that establishes the legal system governing the reuse of treated wastewaters. This decree includes the concept and definition of ‘reclaimed water’, whose use will require an administrative concession to be granted according to the later use of the water. In the Royal Decree, the following uses are differentiated: urban, agricultural, industrial, recreational and environmental and, its annex I defines the criteria of quality differentiated according to these uses, providing mandatory limits that must be complied with.
In Spain the trend to reuse reclaimed water is growing. The data from 2007 estimates that 13% of the total volume of reclaimed water is reused
In Spain the trend to reuse reclaimed water is growing and growing, especially in the current long dry period and water scarcity problems. It is estimated that from the total volume of reclaimed water generated annually (3,375 hm3/year), just 450 hm3 are reused every year, an amount that represents a little more than 13% of the total according to data from the National Plan for Water Quality: Sanitation and Purification, 2007-2015 (NPWQ, 2007). This shows the high potential of this technology for the generation of new water resources, in a future scenario where the perspectives of climate change involve a decreasing availability of natural water resources. The distribution of total volume of reuse of reclaimed water by use is as follows: 75% for agricultural use, 12% (and growing) for recreation and golf courses, 6% for urban services, 4% for ecological use and groundwater recharge, and about 3% for industrial use.
The main use nowadays of reuse of reclaimed water is for agriculture (75% of total distribution) and the most important projects are located in the Mediterranean coastal areas and the islands
According to studies conducted by CEDEX (Centro de Estudios y Experimentación de Obras Públicas, Centre for Studies and Research for Public Works) the most important projects related to the volume of reuse of reclaimed water are located in the Mediterranean coastal areas and the islands (Iglesias and Ortega, 2008). The annual volume of reclaimed water reuse by river basin districts of Spain, included in the “Report on the treated effluents reclaimed in Spain” (CEDEX, 2008) reached in 2006 about 368 hm3/year.
According to data collected in the Andalusian Strategy for the Reuse of Wastewater (ASRW, 2007) drawn up in March 2007, about 53 hm3 of urban reclaimed water are being reused every year in the autonomous region of Andalusia (more than 15% of the total in Spain).
Of these 53 hm3, half (a total of 27 hm3) correspond to the territorial scope of the Mediterranean river basin district. The importance of the recreational use of water (golf and gardening, basically), the existence of a thriving intensive agriculture as well as the shortage of rainfall typical of part of this territory have led to considering urban treated wastewaters as an alternative source of water resources. Apart from the Mediterranean district, the Guadalquivir, the Tinto-Odiel-Piedras and the Guadalete-Barbate river basin districts share other 25 hm3. The remaining cubic hectometre is located in the Segura river basin, in Almería.
According to data from CEDEX (2008), about 44.77 hm3/year of reclaimed water are reused in Andalusia (a little bit lower than the data provided by ASRW). Reclaimed water is mainly used for irrigating golf courses, which represents about half of the volume, followed by agricultural irrigation (38%). These flows of reclaimed water are enabling irrigation in 3,500 hectares of greenhouses in Almeria and 50 golf courses in the provinces of Malaga, Almeria and Cadiz, in addition to other uses, such as irrigating olive trees in Jaen. Table 1 summarizes the major uses of reclaimed water in Andalusia by river basin districts.
Figure 1 shows the geographical distribution of such irrigated areas. Data have been obtained from the Irrigation Inventory of Andalusia (ICRA, 2008), updated in 2008, and from some field surveys conducted between 2008 and 2010; and The ICRA shows a characterization of those irrigated areas in Andalusia reusing reclaimed water.
In Andalusia, as expected, reclaimed water, which is intended for agricultural irrigation, has a relatively high cost (0.206 €/m3), therefore, it is used as a supplementary source to irrigate crops with relatively high profit margins. This source of water is applied with efficient irrigation systems (predominance of localized irrigation) that are properly managed and located in areas where the cost of surface source water is high (0.143 €/m3) and groundwater is very expensive (even more expensive than reclaimed water).