Biological treatment of biodiesel wastewater using a sequencing batch reactor

Abstract

Biological treatment is an appropriate method used in treating organiccontaining wastewaters because of its environment safe and low treatment cost. In this research, two units of sequencing batch reactors (SBR) were used to study the biodegradation of biodiesel wastewater obtained from Bangchak Public Company Limited by using the sludge obtained from the activated sludge treating biodiesel wastewater. The SBR units, having an effective volume of 1.5 L, were operated on a fill-and-draw basis with four cycles per day at different chemical oxygen demand (COD) loading rates (0.05-0.60 kg/m³d) at room temperature. Since the studied wastewater lacked of nitrogen and phosphate, ammonium hydrogen carbonate (NH₄HCO₃) and di-potassium hydrogen orthophosphate (K₂HPO₄) were added as nutrients for the enhancement of biodiesel wastewater biodegradation. The results showed that when the COD loading rate increased, the removal efficiency decreased. Under the studied conditions, a maximum COD removal of 91.4% and TOC removal of 35.7% were achieved at the lowest COD loading rate of 0.05 kg/m³d. Moreover, the minimum F/M ratio and the highest MLSS were found to correspond to the lowest COD loading rate.