Landfill leachate treatment with combined UASB and fenton coagulation

Abstract

A two-stage process was developed for the treatment of landfill leachate in Hong Kong. The leachate contained 15700 mg/L of chemical oxygen demand (COD) and 2300 mg/L of anunonia-nitrogen (NH3-N). In the first stage, it was treated in a UASB (upflow anaerobic sludge blanket) reactor at 37 °C. The process removed 89%-91% COD on average within a 6.6 days hydraulic retention period. The UASB effluent, containing 1500 mg/L COD, was then treated in the second stage using a Fenton coagulation process with H2O2 and excess Fe2+. In this process, organic substances were oxidized and precipitated through the Fenton reaction and coagulation. 70% COD of the UASB effluent was further removed. The optimal parameters of the Fenton coagulation process were determined as an initial pH between 4 and 6, mixing for 5-10 min, a Fe2+ concentration of 300 mg/L, and a H2O2 concentration of 200 mg/L. The final effluent contained a 447 mg/L COD, which was acceptable sewer system level according to the present Hong Kong regulations. | A two-stage process was developed for the treatment of landfill leachate in Hong Kong. The leachate contained 15700 mg/L of chemical oxygen demand (COD) and 2300 mg/L of ammonia-nitrogen (NH3-N). In the first stage, it was treated in a UASB (upflow anaerobic sludge blanket) reactor at 37°C. The process removed 89%-91% COD on average within a 6.6 days hydraulic retention period. The UASB effluent, containing 1500 mg/L COD, was then treated in the second stage using a Fenton coagulation process with H2O2 and excess Fe2+. In this process, organic substances were oxidized and precipitated through the Fenton reaction and coagulation. 70% COD of the UASB effluent was further removed. The optimal parameters of the Fenton coagulation process were determined as an initial pH between 4 and 6, mixing for 5-10 min, a Fe2+ concentration of 300 mg/L, and a H2O2 concentration of 200 mg/L. The final effluent contained a 447 mg/L COD, which was acceptable sewer system level according to the present Hong Kong regulations. | The development of a two-stage process for treating landfill leachate is detailed, involving initial treatment using an upflow anaerobic sludge blanket (UASB) reactor, followed by effluent treatment by Fenton coagulation. Results are then presented from an application of the treatment scheme in which the extent of organic removal was quantified. The results show that the COD removal efficiency of the UASB reactor was maintained at 89-91% at a hydraulic retention time of 6.6 d. The optimal pH for Fenton coagulation ranged 4-6, and TOC removal efficiency was enhanced with an increasing divalent iron dose up to 300 mg/l. The optimal hydrogen peroxide dose was 200 mg/l. Using these optimal values, a final UASB effluent COD removal of 70% was achieved. (from Tsinghua Univ/et al First Natl Conf on Environ Simulation and Pollution Control, Beijing, China (Nov 4-5, 99)).