Mucilage Extracted from Dragon Fruit Peel (Hylocereus undatus) as Flocculant for Treatment of Dye Wastewater by Coagulation and Flocculation Process

Abstract

Dye wastewater from textile industries shows very low biodegradability due to high molecular weight and complex structures of dyes. So far, the most simple method for treatment of this type of wastewater has been coagulation and flocculation. This study determined the removal of turbidity and other pollutants from dye wastewater by mucilage extracted from the peel of dragon fruit (Hylocereus undatus) and its effect in reducing synthetic chemical polyaluminum chloride (PACl) used in coagulation and flocculation (CF) process. The removal of turbidity in a sequent CF process using PACl and dragon fruit mucilage was investigated based on Jar tests. Maximum coagulation efficiencies of PACl were typically observed at pH 4.0-6.0 and PACl concentrations of about 100-150 mg/L depending on types of wastewater, whereas optimal settling times were 30-60 minutes, respectively. The addition of dragon fruit mucilage (0.5-50 mg/L) after PACl (75-245 mg/L) resulted in turbidity removal efficiencies up to 95%. The addition of mucilage extracted from dragon fruit peels was proven to increase turbidity removal efficiency and decrease PACl use. The increase of turbidity removal was often estimated at 10-32%, whereas PACl used was about 3-10% less compared to total PACl needed for obtaining comparable efficiency when used alone. The flocculation activity of mucilage was also compared to polyacrylamide (PAM)—a synthetically organic flocculant. Since the peel of a dragon fruit is an abundant agriculture waste in Vietnam, using its extracted mucilage as a flocculant is an environmentally friendly method.