Temporal Variations in Irrigation Suitability of Treated Effluent: The Case of Menemen Biological Wastewater Treatment Plant

Rising global freshwater demand, climate change, and the exhaustion of natural water resources have made treated wastewater reuse an essential pillar in sustainable water management plans. It is under this scenario that this paper presents a study on the evaluation of the quality of effluent for its appropriateness for irrigation purposes from the Menemen Biological Wastewater Treatment Plant located at İzmir, Türkiye which started its operations in 2010. The present study covers six years (2010-2016) based on major water quality parameters which include pH, total suspended solids (TSS), biochemical oxygen demand (BOD5), fecal coliforms, electrical conductivity (EC), boron (B), and sodium (Na). The results show that the pH values ranging from 7.36 to 8.57 are within internationally accepted limits for irrigation. The EC values are between 1.4 to 3.69 dS m-1 indicating a low to moderate salinity hazard depending upon crop type and soil texture. Boron values (0.18-1.11 mg L-1) generally remain well below any phytotoxic threshold, while sodium concentrations (6.4-25.96 mg L-1) render it occasionally close to those levels which would cause soil structural degradation when applied through surface irrigation; large variations were found in BOD5 and fecal coliforms with intermittent exceedance of the microbiological standard meaning this period may not have been perfectly safe for direct use in agriculture. Chemically, the Menemen effluent characterizes meeting all irrigation requirements, while its microbiological quality is much more temporally variable, strengthening safety by raising disinfection reliability and monitoring frequency will assist in strengthening safety with proper management, treated wastewater from Menemen Plant can be considered a reliable and sustainable source of irrigation water for such agricultural lands as the Menemen Plain.