Moringa oleifera as a Natural Coagulant-Flocculant for the Removal of Turbidity and Heavy Metals from the Caplina Channel

Driven by the high costs, residuals, and potential health impacts associated with chemical coagulants, this study evaluated a more environmentally and socially compatible bioprocess: the use of saline-activated (1 M NaCl) Moringa oleifera seed powder as a coagulant– flocculant to clarify surface waters from the Caplina Channel (Tacna, Peru). Raw water was collected, and jar tests were conducted at 125, 250, 500, and 750 mg.L⁻¹ (n = 3 per dose), measuring turbidity, electrical conductivity (EC), dissolved oxygen (DO), total dissolved solids (TDS), color, and dissolved metals (As, Cu, and Fe), in addition to a proximate analysis of the seeds. The optimal dose achieved 99.7% turbidity removal (from 3350 to 9.045 NTU) and reduced metals to As 0.005 mg.L⁻¹ (95%), Fe < 0.3 mg.L⁻¹ (94%), and Cu 0.045 mg.L⁻¹ (78%), with a pH 5.5, EC 936 µS.cm⁻¹, DO 7.24 mg.L⁻¹, TDS 762 mg.L⁻¹, and color < 5 Pt/ Co, meeting Peru’s ECA-Agua Category 1–A2 criteria for waters treatable by conventional processes. Although the EC increased with the dose, it remained below 1600 µS.cm-1 at the optimal value. We highlight saline pretreatment and the activation of M. oleifera seed powder with 1 M NaCl as a high-efficiency clarification strategy. This strategy activates cationic proteins and increases the charge density of biopolymers, promoting particulate charge neutralization and metal-ion complexation/adsorption. This mechanism enables the simultaneous and high-efficiency removal of turbidity and metals using an accessible and sustainable biocoagulant suitable for settings with limited treatment infrastructure.