Optimizing Wastewater Quality for Safe Vegetable Irrigation: A Ghana Case Study of the Wideruptake Project

To meet EU-guidelines for reuse of wastewater for vegetable irrigation, a sand filtration system was connected to a conventional treatment system to enhance the quality of its effluent. Standard parameters were monitored for performance according to Standard Methods. Urine samples of farmers and consumers of irrigated vegetables were also analysed for glyphosate (N-phosphonomethyl-glycine) and amphetamine (using GCMS), and paracetamol, tramadol, and amitriptyline using LCMS. The study demonstrated significant reductions in BOD, COD, and TSS levels, transitioning from 1200.51 to 32.21 mgO2/L, 3625 to 57.62 mgO2/L, and 1149.47 to 43.54 mg/L, respectively, from raw to polished wastewater. Effluent coliform content measured 4.7×105 cfu/100ml, while E. coli recorded 3.6 ×105 cfu/100ml. Metal concentrations (Cd, Pb, Zn, Cr, Fe) were within acceptable limits. Nitrate, ammonia, and phosphate concentrations in the effluent were 0.226 mg/L, 2.83 mg/L, and 4.90 mg/L, respectively. Tramadol, amphetamine and amitriptyline were negative in all samples, including wastewater effluent. 60% of farmers and 16.7% of consumers however showed the presence of paracetamol in urine. 40% of farmers had concentrations of glyphosate above 1.7 µg/L, the remaining 60% had concentrations below 0.3 µg/L. For consumers, 8.3% had concentrations of glyphosate above 1.7 µg/L, 33.3% had between 0.4–1.0 µg/L while 58.4% had concentrations below 0.3 µg/L. Farmers seemed to be significantly more exposed to glyphosate than consumers suggesting a continuous need to focus interventions on farmers. The study confirmed the effectiveness of the treatment plant in treating wastewater for reuse. The polished effluent demonstrated improved water quality characteristics, showcasing reduced contaminant levels compared to untreated wastewater.