Treatment of Effluents in Refinery using UASB Reactors

This study presents the treatment of refinery effluents using Upflow Anaerobic Sludge Blanket (UASB) reactors. Four pilot-scale UASB reactors, each with a volume of 45.78 liters and identical dimensions, were operated simultaneously at 37 ºC. The seed sludge was sourced from the waste activated sludge of the refinery’s wastewater treatment unit. Organic loading rates were gradually increased from 0.05–0.1 kg COD/m³·d to approximately 2, 1.5, 0.5, and 1.5 kg COD/m³·d for reactors 1 through 4, respectively, with an influent COD concentration of about 220 mg/L. These loading rates corresponded to hydraulic retention times of 2.5, 4.5, and 8.5 hours for reactors 1 to 3, and 4.5 hours for reactor 4. To enhance microbial activity during start-up, methanol was initially added to all reactors except the fourth, allowing comparison of its effect. Methanol addition ceased after 37 days, and the reactors were operated for an additional 30 days with influent COD ranging from 50 to 300 mg/L. The results demonstrated COD removal efficiencies between 30% and 50%, increasing up to 70% when influent COD exceeded 200 mg/L. Methanol was found to have no significant impact on reducing the start-up period. Additionally, Scanning Electron Microscopy (SEM) and image analysis were conducted on the sludge granules to study their structure and size distribution. Biogas analysis revealed methane content exceeding 90%. These findings suggest promising potential for anaerobic treatment of refinery wastewater using UASB reactors.