The current article studies the optimization of a new coagulant agent for water purification and wastewater remediation. Design of experiments is used for optimizing the production of this new tannin-based coagulant by using Acacia mearnsii de Wild tannin extract. NH4Cl and formaldehyde. The effectiveness of this product was confirmed on dye-polluted wastewater and surfactant wastewater. This cationic coagulant seems to be sensitive to temperature and tannin-NH4Cl ratio (g of ammonium chloride per g of tannin extract). NH4Cl ratio was found to be more influent than temperature and no interaction is presented between these two parameters. For each system, an optimum combination NH4Cl ratio and temperature was found: 24.9 degrees C and 2 g g(-1) for dye removal and 36.4 degrees C and 1.87 g g(-1) for surfactant elimination. The optimal conditions were merged to produce a combined coagulant that was tested on dye, surfactant, surface river water and municipal wastewater. Predicted levels of remediation were experimentally confirmed. (C) 2010 Elsevier B.V. All rights reserved.