Removal of Microplastics from Drinking Water by Moringa oleifera Seed: Comparative Performance with Alum in Direct and In-Line Filtration Systems

In this study, the removal efficiency of aged polyvinyl chloride microplastics (Aged-PVC MPs) from low-turbidity drinking water using Moringa oleifera seed saline extract (MOS-SE) and aluminum sulfate (alum) in direct filtration (coagulation–flocculation–filtration) and in-line filtration (coagulation–filtration) systems is investigated. Aged-PVC MPs (15 mg/L, D50 = 15.0 μm) and humic acid (10 mg/L) were spiked into synthetic water to evaluate removal performance across pH 5.0–8.0. The optimal conditions achieved >98% turbidity removal with 30 mg/L MOS-SE and 9 mg/L alum at a pH of 6.0, corresponding to 98.5% and 98.7% of Aged-PVC MP removal, respectively, as confirmed by scanning electron microscopy particle counting. Although nonintrusive floc imaging revealed differences between coagulated (43–46 μm) and flocculated aggregates (61–66 μm), in-line filtration performs equivalently to direct filtration in terms of MP removal, demonstrating that direct filtration’s flocculation step was unnecessary. MOS-SE exhibited superior performance across broader pH ranges (5.0–8.0) compared with alum (5.0–7.0). While MOS-SE increased dissolved organic carbon because of residual organic matter, it effectively reduced specific ultraviolet absorbance (SUVA) by 88%, indicating efficient removal of aromatic natural organic matter. These findings demonstrate the viability of Moringa oleifera as a sustainable alternative for MP removal in drinking water treatment via in-line filtration.