Reclaimed wastewater to irrigate olive groves and vineyards: effects on soil properties

Having drinking water is one of the sustainable development goals (SDG no. 6) that is not always easy to ensure, especially in countries like Spain or arid regions marked by water deficit. The reuse of treated water should be considered when planning water resources, but it is necessary to conduct experiments to verify that this effectiveness is applicable to real situations. Our field trial was carried out in several study areas distributed in agricultural parcels of SE Spain. Three olive grove and vineyard plantations were monitored for 3 years. Two irrigation water types were considered: freshwater from conventional wells (controls) and treated wastewater (TW). The treated wastewater came from three different wastewater treatment plants (WWTP) that employ a biological secondary treatment without disinfection and different numbers of Inhabitants Equivalent (IE) as a measure of pollutant load. They were located in Valdeganga (3,000 IE), Fuenteálamo (5,600 IE) and Ontur (1,500 IE). All the study plots were watered by drip irrigation using 16 mm-diameter polyethylene pipelines.

Several soil and water parameters were analysed to determine the main differences among them. Increasing of soil salinity is a real risk after irrigating with wastewater as is reflected in higher electrical conductivity values. However, this fact was compensated by the greater contribution of organic matter and nutrients, which allowed crops to adequately develop. Moreover, no microbiological, metal content, toxicity or organic compounds in the studied water samples were detected and reclaimed municipal wastewater was comparable in quality to the conventional sources at all the demonstration sites. Hence adopting this water type for irrigation for grapes and olives could help save primary water resources. The future of water resources management policies involves sustainable wastewater reuse within a circular economy frame because this is the only way to guarantee everyone solidarity access to water.

Fundings provided by the ERA-NET WaterWorks2014 Cofunded Call. This ERA-NET is an integral part of the 2015 Joint Activities developed by the Water Challenges for a Changing World Joint Programme Initiative (Water JPI).