Advanced Multi-Stage Greywater Treatment: Sand Filtration, Electrocoagulation, and Photo-Fenton for Enhanced Reuse Potential

Water scarcity poses a critical global challenge, necessitating sustainable solutions such as greywater reuse. This study introduces an innovative multi-stage treatment system for restaurant-generated greywater, integrating sand filtration, electrocoagulation, photo-Fenton oxidation, and activated carbon filtration to achieve high-efficiency contaminant removal. Unlike previous studies limited to individual or binary treatment methods, this work uniquely integrates all four stages into a single sequentially optimized system for high-strength restaurant greywater. The system was evaluated using greywater with varying chemical oxygen demand (COD) concentrations (484–904 mg/L), focusing on optimizing parameters such as flow rate, electrode type, voltage, pH, and reagent concentrations. Results demonstrated exceptional pollutant reduction: COD by 99.17%, biological oxygen demand (BOD) by 98.64%, turbidity by 99%, detergents by 94.84%, and total phosphorus by 93.54%. Sand filtration and electrocoagulation served as effective pre-treatment steps, reducing initial pollutant loads, while the photo-Fenton process, optimized at pH 3 with 125 mg/L iron sulfate and 137.5 mg/L hydrogen peroxide, achieved up to 92.85% COD removal. Activated carbon filtration further enhanced COD reduction but showed limited turbidity improvement. The treated effluent met international standards for unrestricted non-potable reuse, maintaining a pH of 6.5–8.5. This synergistic approach offers a robust, scalable framework for greywater treatment, advancing sustainable water management practices in water-scarce regions. • Novel four-stage greywater treatment system developed and tested • Pre-treatment: 38% COD and 73% turbidity removal achieved • Electrocoagulation: Al (69% COD) outperforms Fe (64% COD) • Photo-Fenton: 93% COD and 90% turbidity removal at pH 3 • Final effluent meets international standards for non-potable reuse