Experimental investigation into biomaterial valorization as eco-friendly coagulants and flocculants for wastewater treatment in semi-arid regions.

This study aims to evaluate the effectiveness of four natural biomaterials-Agave extract (AgEx), Opuntia extract (OpEx), potato skin (PP), and sawdust (SD) as sustainable alternatives to chemical agents for wastewater treatment. The main objectives include identifying the most effective conventional coagulant, evaluating their performance as flocculation aids and in exclusive use, and studying the underlying molecular mechanisms by identifying the most effective synergistic combinations for water resource management in the semi-arid region of Mecheria, Algeria. To meet these objectives, the experiment is conducted in several phases via the jar test protocol, making it possible to evaluate different treatment configurations. First, conventional chemical coagulants are tested alone; then, the best-performing one is combined with biomaterials acting as adjunctive flocculants. Finally, biomaterials were used exclusively, both as primary coagulants and as flocculants. Among chemical coagulants, ferric chloride (FeCl) showed the highest efficacy with a 90% reduction in turbidity at a dose of 0.4 g over 30 min. When assisted by Natural flocculants at their optimal doses, turbidity removal rates reached 99.87% with 3 mL of AgEx, 99.79% with 0.2 g of SD, 98.51% with 0.4 g of PP, and 92.91% with 1.0 mL of OpEx. When used on its own, OpEx was found to be the most effective of the biomaterials, achieving a turbidity removal of 85.35% at a dose of 2.5 mL. In addition, the combination of the most effective biomaterials, with AgEx as a coagulant and OpEx as a flocculant, produced a maximum reduction in turbidity of 82.60%, indicating a promising synergy between them. These non-toxic, biodegradable, and biocompatible biomaterials prove effective for wastewater treatment. Their application represents a sustainable alternative to chemical coagulants, improving purification efficiency and supporting better water resource management in arid environments.