Carbon and Nutrients Removal from Industrial Wastewater Using Aerobic Granular Sludge

Considering the increasing rigor of environmental laws, the removal of carbon and nutrients from wastewater is a key aspect of research, and the simultaneous elimination of carbon and nutrients in a bioreactor has a significant impact on reducing reactor volume and energy consumption. The objective of this study was evaluating the performance of an aerobic sequencing batch reactor (SBR) with granulated sludge removing carbon and nutrient (N & P) from an industrial wastewater. Aerobic granules were obtained in a SBR and in the next step, the experiments were designed by a central composite design (CCD) with five levels of biomass concentration (2000-7000 mg/l) and aeration time (6-24 h).  Eight dependent parameters as the process responses were measured and calculated. The results showed that the maximum value of total COD (TCOD) removal was obtained to be 69.07% at mixed liquor volatile suspended solid (MLVSS) concentration of 5600 mg/L and the highest value of the aeration time (24 h). In addition, the low TN removal (47.5%) directed the study to reduce the oxygen level from 7 to 3 mg/L. A reduction in dissolved oxygen (DO) in extended aeration mode led to an increase in TN removal and a decrease in TCOD, nbCOD, and BOD removal. Overall, granular sludge showed an acceptable performance in terms of carbon removal, however, intermittent aeration could improve nutrients removal from wastewaters.