Turbidity, color, and chemical oxygen demand (COD) indicate water quality. Natural coagulants offer eco-friendly alternatives for treatment. This study investigates the potential of Calpurnia aurea seed extract as a natural coagulant for water and wastewater treatment. The extract was prepared through a multi-step process involving drying, grinding the seeds, sieving the seed powder, cold macerating using n-hexane solvent to defatting, and dissolution in distilled water (5 g/L). Protein content was quantified using the Kjeldahl method. Treatment conditions were optimized using the jar test and one-variable-at-a-time (OVAT) approach, yielding optimal parameters of 100 mg/L dosage, pH 3, rapid mixing at 300 rpm for 9 min, slow mixing at 45 rpm for 35 min, and a settling time of 70 min. Under these conditions, turbidity removal efficiencies reached 91.93% (synthetic wastewater), 87.89% (municipal wastewater), 69.93% (textile effluent), and 45.79% (Akaki river water). In this context, the efficiency for the Calpurnia aurea seed extract approaches the turbidity removal efficiencies of up to 99.77% reported for alum in previous studies. Color removal was most effective in textile effluent (63.73%), followed by municipal wastewater (49.77%) and Akaki river water (24.12%). COD reductions were highest in Akaki river water (78.49%), with moderate effects in municipal wastewater (46.28%) and textile effluent (30.75%). The extract’s coagulation mechanism is attributed to charge neutralization and colloidal particle binding. These findings highlight Calpurnia aurea seeds as a promising natural coagulant for improving water quality across diverse wastewater sources.
Negassa et al. (2026) studied this question.