<![CDATA[The increasing production of palm oil refineries in Pontianak, West Kalimantan, Indonesia has resulted in a significant rise in wastewater generation containing high levels of Total Suspended Solids (TSS), Chemical Oxygen Demand (COD), and phosphate (PO43-). This study aims to evaluate the effectiveness of chicken eggshell powder as a natural coagulant in reducing these pollutants. Wastewater samples were collected from PT Wilmar Cahaya Indonesia Tbk., Pontianak, and treated using eggshell powder calcined at 900 °C and sieved into 20, 30, and 50 mesh sizes. The experimental design was conducted to examine the effects of varying coagulant concentrations (5, 8, and 11% w/w) in combination with different mixing durations (30, 60, and 90 minutes). The results show that the optimal TSS reduction reached 35.31 mg/L, corresponding to a removal efficiency of 91.28%, achieved at 50 mesh particle size, 11% dosage, and 60 minutes of mixing. COD reduction was most effective at 64.36 mg/L, with a removal efficiency of 90.56%, obtained under the conditions of 30 mesh, 5% dosage, and 30 minutes of mixing. Meanwhile, phosphate removal reached 6.80 mg/L, equivalent to a removal efficiency of 69.78%, at 11% dosage and 60 minutes of mixing. Although TSS and COD levels met environmental quality standards, phosphate concentrations remained above permissible limits, indicating the need for further process optimization. These findings highlight the potential of eggshell powder as a low-cost, eco-friendly alternative for palm oil refinery wastewater treatment in Indonesia.]]>
