Effects of Dosage and Stirring Speed Variations in the Use of Bittern as a Natural Coagulant to Remove Biological Oxygen Demand, Chemical Oxygen Demand, Total Suspended Solids and Dye Concentrations from Batik Industry Wastewater

This study aimed to determine the effect of bittern coagulant dosage and rapid stirring speed on reducing the concentrations of biological oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), and dye absorbance in batik industry wastewater, as well as to identify the optimum coagulant dosage and stirring speed. Wastewater samples were collected from a batik industry in the batik center of Sidoarjo, East Java, Indonesia. Dosage variations of 5%, 10%, 15%, and 20% were tested alongside rapid stirring speeds of 100 rpm, 130 rpm, and 160 rpm. The study was conducted on a laboratory scale using the jar test method. Initial wastewater characteristics showed BOD, COD, TSS, and dye absorbance concentrations of 185.68 ± 29.34 mg/L, 10.091 ± 363.24 mg/L, 2.231.33 ± 155.55 mg/L, and 0.212 ± 0.02, respectively. Statistical analysis using the Pearson cor relation test and Two-Way ANOVA revealed that variations in coagulant dosage and stirring speed significantly impacted the reduction percentages of BOD, COD, TSS, and dye absorbance. The optimal coagulant dosage was found to be 5%, and the optimal stirring speed was 100 rpm, with reduction percentages for BOD, COD, TSS, and dye absorbance being 80.32%, 65.86%, 92.35%, and 70.77%, respectively.