Operation Cycle Optimization of an Aerobic Sequencing Batch Reactor for Dairy Wastewater Treatment

Abstract

This study was primarily focused on developing an operation cycle for aerobic sequencing batch reactor (SBR) and optimizing it when dairy wastewater is the effluent in question. Throughout the study period, wastewater collected from a yoghurt factory was adequately diluted to occupy an influent COD concentration of 2000±500mg/l (COD loading 1.80-3.00g COD/L.D) while maintaining MLVSS and pH level in the reactor at 3500±500mg/l and between 6 and 8 respectively. With the purpose of identifying performance of the SBR in treatment of dairy wastewater, the available lab scale prototype was operated with a predetermined cycle comprising of Fill (1 min), Anoxic (50 min), Aeration (10 hrs.), Settling (1 hr.), Decanting (4 min) and Idling (5 min). The results collected throughout a period of 4 weeks converged to high BODs, COD and NO3-N removal rates having averages of 95.8%, 94.6% and 90.7% respectively. At the same time, potential applicability of SBR as a secondary treatment system was identified since effluent parameters of the system were well within limits imposed by Central Environmental Authority (CEA) for surface water discharges. With this knowledge in hand, the operation cycle was further analyzed to replace with an efficient cycle having a shorter duration. Thereby, primarily taking the limits imposed by CEA for surface water discharges into account, a cycle comprising of Fill (1 min), Aeration (6 hrs.), Settling (1 hr.), Decanting (4 min) and Idling (5 min) was identified as the optimum cycle.