Performance of water-extracted Leucaena leucocephala seeds as coagulant and alum in treating aquaculture effluent: effect of dosage, rapid mixing speed, and settling time

This study aimed to evaluate the effectiveness of plant-based coagulant extracted from Leucaena leucocephala seeds compared with alum in removing solids from aquaculture wastewater. Water-extraction method was used to extract the active ingredients from the seeds by dissolving the seeds' powder in distilled water at 20 g/L concentration, whereas alum was dissolved directly at the same concentration. Operation parameters of jar test including dosage, rapid-mixing speed, and settling time were optimized for the water-extracted seed solution and alum to improve the removal efficiency. The optimum operation parameters for the water-extracted seed solution and alum were dosages of 240 and 320 mg/L respectively, rapid-mixing speed 150 rpm, and settling time 40 min. At the optimum operation parameters, water-extracted seed solution had removal efficiencies of 96.32%, 92.85%, and 86%, whereas alum had removal efficiencies of 99.77%, 99.92%, and 99.92% for turbidity, total suspended solids, and color, respectively. Despite the high efficiency of the water-extracted seed solution, dissolved contaminants such as NO3, PO4, COD, and true color increased owing to the presence of organic matter in the solution. With these results, L. leucocephala seeds had high potential to be used as alternative in removing solids from aquaculture wastewater. Further studies on the extraction of active ingredients should be conducted to increase the removal efficiency and avoid side effects on the contaminants dissolved in the effluent.