Effects of treated wastewater irrigation on lemon trees

This research is focused on evaluating the effects of applying treated wastewater on citrus trees. Two experimental plots irrigated with two different treated wastewater effluents were compared. The experimental sites were located in Murcia, southeastern Spain. The first experimental plot was located in Cartagena, where the treated wastewater had received a secondary treatment. The second experimental plot was located in Campotejar; in this case the water used was a mix of well water and wastewater from a tertiary treatment plant. The electrical conductivity (EC), turbidity and total dissolved solids (TDS) were higher in Cartagena's treated wastewater than in Campotejar's. Therefore, the mix with well water improved the agronomic quality of the reclaimed wastewater. The high levels of EC observed in both locations were due mainly to high chloride and boron (B) concentrations. Although leaf toxicity levels were not observed, the high salinity and B accumulation can be considered the main problems for the irrigation with treated wastewater in the region of Murcia. Microbiological analysis revealed an absence of faecal coliforms, E. coli and helminth eggs in the treated wastewaters and soil of Campotejar, but in Cartagena's treated wastewater faecal coliforms exceeded health standards.