Supplementary material from "Optimization and economic feasibility of vegetable oil wastewater treatment using Plantago major seed nano-green coagulant "

Vegetable oil industry wastewater, characterized by high levels of COD, TSS, turbidity, and color, poses a significant treatment challenge requiring sustainable alternatives to conventional chemical coagulants. This study assesses Plantago major seed-derived coagulant (Pmsd) for treating high-strength industrial wastewater, integrating optimization, characterization, and cost analysis to demonstrate its large-scale sustainability. Wastewater samples were collected from a local vegetable oil factory and treated through batch experiments using a factorial design to optimize key parame-ters. Pmsd, rich in mucilage, promoted bridging and charge neutralization, while SEM analysis further indicated sweep flocculation as the dominant removal mechanism. Under optimal condi-tions (6000 mg/L Pmsd dose, 40 min flocculation time, pH 8, and 90-min sedimentation), removal efficiencies reached 55.17% for COD, 83.12% for TSS, 29.05% for turbidity, and 33.33% for col-or. Economic analysis showed a Pmsd-treatment cost of $0.40–$2.40/m³, slightly higher than con-ventional coagulants; however, the environmental benefits—including reduced sludge production, lower toxicity, and the absence of residual aluminum and iron— emphasize the sustainability of Pmsd as a promising green alternative. EDX and BET analyses confirmed its strong ion and metal absorption capacity. This study highlights the potential large-scale application of Pmsd for vegeta-ble oil industry wastewater treatment, providing economic and environmental advantages.