Surface water treatment with natural starches as coagulant via coagulant-flocculation process

Abstract

River water is one of the surface water that commonly being the victim of indiscriminate dumping of untreated wastewater and chemical wastes by irresponsible person or management. Coagulation-flocculation treatment is widely applicable for treating contamination of river water. Chemical coagulant such as alum are commonly used and well noted in the coagulation process. However, chemical coagulant is non-environmental friendly and possess potential hazard to the environment quality. Therefore, a study to determine the effectiveness of natural coagulant to treat the river water was conducted. In this study, natural polymers in the forms of starch from sago and tapioca were used as coagulant. The removal of turbidity and COD using coagulation and flocculation process from river water was examined. The treatment on the river water sample was evaluated via a series of Jar Test experimental works with rapid mixing speed of 120 rpm for 1 minute, slow mixing speed of 30 rpm for 20 minutes and settling time of 60 minutes. The tapioca starch able to effectively removed 93.7% of turbidity and with favourable dosage of 1000 mg/L. While, sago starch successfully removed 96.4% of turbidity under optimum dosage of 2000 mg/L. pH 12 was optimum pH for turbidity removal by using sago and tapioca starch whereas the highest percentage of COD removal occurred at pH 4 using sago and tapioca starch. At pH 4, tapioca and sago starch able to removed 22.5% and 25% of COD respectively.