Anaerobic/aerobic treatment of municipal landfill leachate in sequential two-stage up-flow anaerobic sludge blanket reactor (UASB)/completely stirred tank reactor (CSTR) systems

The treatability of leachate produced from the lab-scale simulated reactor treating food wastes was investigated in a two-stage sequential up-flow anaerobic sludge blanket reactor (UASB)/aerobic completely stirred tank reactor (CSTR). Experiments were performed in two UASB reactors and a CSTR reactor having effective volumes of 2.5 and 9 1, respectively. The hydraulic retention times in anaerobic and aerobic stages were 1.25 and 4.5 days, respectively, through 42 days at a constant flow rate of 21. After the start-up period, the COD concentration of leachate was steadily increased from 5400 to 20,000 mg/l. OLRs were increased from 4.3 to 16 kg/m(3) per day by increasing the COD concentrations from 5400 to 20,000 mg/l. The effluent of the first anaerobic UASB reactor (Run 1) was used as the influent of the second UASB reactor (Run2), while the effluent of the second UASB reactor was used as the influent of the aerobic CSTR reactor (Run3). COD removal efficiencies of the first UASB reactor and in the whole system (two steps UASB + CSTR) were 58, 62, 65, 72, 74, 79% and 96, 96.8, 97.3, 98, 98 and 98%, respectively. As the OLR increased from 4.3 to 16 kg/m(3) per day, the COD removal efficiency reached a maximum of 80%. NH4-N removal efficiency was approximately 99.6% after the aerobic stage. The maximum methane percentages of the first and second UASB reactors were 64 and 43%, respectively. (C) 2004 Elsevier Ltd. All rights reserved.