The use of reclaimed water for crop irrigation in the Segura River Basin (Spain)

Résumé

Structural water scarcity is a reality in the Segura River Basin (SRB); southeastern Spain, where there has been an important increase in agricultural water demand in the last decades. Water shortages have led to the widespread adoption of measures to sustain agriculture such as the implementation of reclaimed water (RW) for crops irrigation.The production of safe RW for irrigation is mainly characterized by the treatment systems and operational and microbiological parameters. In this context,this work presents an analytical and integrated study on the use of RW as a water source for crops irrigation in the SRB, identifying its strengths and cur-rent limitations in the year 2017. The study includes data from a selection of 13 Waste Water Treatment Plants (WWTPs) located in the SRB. Data for this analysis come from several sources; i.e. official data provided by Entidad de Saneamiento y Depuración de Aguas Residuales de la Región de Murcia (ESAMUR), published scientific literature and news on the subject and interviews and communications with WWTPs managers and farmers associations. The results have been obtained from the average of the fortnightly values during the year 2017. All effluents from the WWTPs met the minimum requirements established in Water Quality 2.3 by the Royal Decrete 1620/2007 and also with the Classes B and C proposed by the European Commission publication “Minimum quality requirements for water reuse in agricultural irrigation and aquifer recharge – JRC-EU”.Likewise, all effluents from the WWTPs met the minimum requirements established in Water Quality 2.1 by the Royal Decrete 1620/2007. However, 31% (4 out of 13 WWTPs) of analyzed effluents did not meet the water quality Class A for E-Coli proposed in JRC-EU. Consequently, in the case of the new application of European regulations on the reuse of reclaimed water for irrigation, only part of these effluents could have been directly applied for crops irrigation where the edible portion is in direct contact with reclaimed water. Concerning the ionic composition of the effluents, 54% (7 out of 13 WWTPs) of effluents showed an electric conductivity higher than 2 dS/m, which was mainly associated to high concentration of Na+, Cl- y SO42-. Only 31% (4 out of 13 WWTPs) of effluents had a B3+ concentration higher than 1 mg/l. Please note that if maximum values for these parameters are analyzed the results may be even more restrictive in some periods of the year. In short, this study evidences that although RW can contribute to partially remove the hydrological constraints for crop production,especially woody crops, in the water stressed regions, specific water management strategies, such as mixing with other conventional sources, should be considered to avoid food safety problems and salinization and deterioration of agro-systems.