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<p>Turbidity, color, and chemical oxygen demand (COD) indicate water quality. Natural coagulants offer eco-friendly alternatives for treatment. This study investigates the potential of <i>Calpurnia aurea</i> 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, &#xa0;sieving the seed powder, cold macerating using n-hexane solvent to defatting, and dissolution in distilled water (5&#xa0;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&#xa0;mg/L dosage, pH 3, rapid mixing at 300&#xa0;rpm for 9&#xa0;min, slow mixing at 45&#xa0;rpm for 35&#xa0;min, and a settling time of 70&#xa0;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 <i>Calpurnia aurea</i> 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 <i>Calpurnia aurea</i> seeds as a promising natural coagulant for improving water quality across diverse wastewater sources.</p>

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Evaluation of Calpurnia aurea seed extract as natural coagulant for reducing turbidity, color and COD from water and wastewater

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2026年4月9日

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  • Belay Negassa,
  • Biritu Derecha,
  • Dessalegn Dadi,
  • Samuel Fekadu

摘要

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.