Potential use of rice starch in coagulation-flocculation process of agro-industrial wastewater: Treatment performance and flocs characterization

The present study investigated the use of starch to replace inorganic coagulants for the treatment of agro-industrial wastewater from palm oil mill, namely palm oil mill effluent (POME). Rice starch was found to be the best starch because it yielded similar total suspended solids (TSS) removal as alum, significantly shortened the settling time and produced flocs with higher resistance towards stronger shear force. The use of rice starch alone in room temperature enabled the removal of TSS up to 84.1% using the recommended values of dosage, initial pH, settling time and slow stirring speed at 2 g/L, pH 3, 5 min and 10 rpm, respectively. Higher TSS removal of 88.4% could still be achieved at lower dosage of rice starch (0.55 g/L) only when rice starch was used together with 0.2 g/L of alum during the treatment of POME. To gain further insights on the properties of coagulants and flocs produced from the treatment, characterization methods such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were used.