The treatment of wastewaters in Spain is regulated by Royal Decree Law 11/1995, on urban wastewater treatment, resulting from the transposition of European Directive 91/271/EEC. This Royal Decree obliges municipalities with more than 2,000 inhabitants to have collecting systems and to apply primary and secondary treatments from January 1, 2006, on.
In Spain there are 2533 Wastewater treatment plants that generate a flow of 3,375 hm3 of treated wastewaters per year
In order to ensure the compliance of this legislation, the Spanish Ministry for Environment and Rural and marine affairs is conducting the National Plan for Water Quality: Sanitation and Purification, 2007-2015 (NPWQ, 2007). This Plan involves a series of actions whose ultimate purpose is the protection of surface waters against the discharges mainly from urban areas.
According to data from the NPWQ, there are currently 2,533 Wastewater Treatment Plants (WWTP) in Spain that generate a flow of 3,375 hm3 of treated wastewaters per year. The geographic distribution of WWTPs in Spain is shown in Figure 1 (total number of WWTPS by autonomous region in parentheses).
In Andalusia, population amounts to 7.5 million inhabitants distributed among 1,800 bound nuclei and a series of scattered nuclei amounting a total of 149,000 inhabitants. On the other hand, tourism provides 22 millions of visitors to Andalusia and their average stay ranges from 4.4 days for inland destinations to 10-14.4 days for coastal areas. Currently, there are 730 agglomerations registered, representing 99.22% of the Andalusian stable population. The vast majority of agglomerations already have or have scheduled the installation of secondary treatment plants (75% of cases)
Almost half of the Andalusian population (46%) discharges wastewaters to coastal or transition waters, largely due to the uniqueness of the final stretch of the Guadalquivir river as it has interactions between freshwater and saltwater and it is located in Seville.
Based on data provided by the NPWQ, there are 545 WWTPs in Andalusia (the providers of the raw water), which generate 520.07 hm3/year of reclaimed water. Table 1 shows the distribution of WWTPs and the annual flow generated of reclaimed water per river basin districts and provinces of the region. Figure 2 shows the geographic distribution of WWTPs in the region.