Treated wastewater: environmental pressure or water and nutrient resource?

Abstract— Going beyond a case study, the Triolo catchment (Apulia, Italy), this paper aims to define a methodology for analysing the environmental impact of agriculture and point sources (WWTPs) on surface waters and to evaluate the treated wastewater as a potential resource of water and nutrient for use in agriculture. The ecohydrological model “Soil and Water Assessment Tool” (SWAT) combined with field data was used to simulate hydrology and water quality. Under the current anthropogenic pressures (agriculture and WWTP), monitoring and modeling results showed that the TP and NO₃ concentrations are above desirable values for good ecological status in surface waters. The dry season was critical for TP pollution and the WWTP discharge caused the main pressure on surface waters. The rainy season was key to NO₃ pollution and agriculture was the main pressure. The results of this study demonstrated that treated wastewater could represent an important resource of water and nutrients capable of satisfying the seasonal irrigation requirements for approximately 1600 ha of olive grove (2000 m³ ha^-1), providing approximately 25 kg ha^-1 of TN and 8 kg ha^-1 of TP.