Enhancing Nutrient Removal from Coffee Processing Wastewater Using Papaya Peel Waste Natural Coagulant Assisted-Electrocoagulation: RSM Study

Traditional methods for treating coffee processing wastewater are ineffective due to high organic matter content and poor biodegradability. A cost-effective and environmentally friendly solution has been developed using a natural coagulant-assisted electrocoagulation process. This study reports the use of papaya peel waste (PPw) natural coagulant-assisted electrocoagulation (EC) process in treating coffee processing wastewater containing phosphate and nitrate via aluminum (Al) electrodes. The physicochemical properties of PPw were studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and proximate analysis. Response surface methodology (RSM)-centracomposite design (CCD) was used to optimize operating variables such as pH (5–9), applied current (0.3–0.5 A), coagulant dosage (0.25–0.5 g/L) and contact time (30–50 min). Analysis of variance (ANOVA) suggested that, the quadratic model was confirmed to describe the removal efficiency of phosphate (PO ₄ ³⁻ ) and nitrate (NO ₃ ⁻ ) with a high determination coefficient (R ²  = 0.9923 and 0.9947). The highest removal efficincy of PO ₄ ³⁻ (95.17%) and NO ₃ ⁻ (93.56%) were achieved at pH of 6.22, applied current of 0.33 A, coagulant dosage of 0.397 g/L and contact time of 48.92 min. Therefore, the experimental result showed that PPw-integrated EC was an effective method for treating CPWW containing PO ₄ ³⁻ and NO ₃ ⁻