Treatment of landfill leachate with an upflow anaerobic reactor combining a sludge bed and a filter

The operational characteristics, efficiency of treatment of landfill leachate, and recovery of energy in a laboratory scale hybrid bioreactor were investigated. The reactor was a continuous upflow system combining a sludge bed and a filter and as operated at 35°C. This modified anaerobic sludge bed filter (SBF) reactor was found to provide efficient treatment of the organic constituents of the leachate. Removal of soluble COD was greater than 92% at organic loading rates less than 13 kg COD/m³/d, and removal decreased to 70% with an organic loading rate of 21.77 kg COD/m³/d. A solids balance indicated that 0.041 g volatile suspended solids (VSS) were produced per gram of COD removed. The removal of sulfate and soluble Fe was as high as 90% and 96.9%, respectively. An accumulation of Fe was observed. When the influent concentration of total Fe ranged from 160 to 515 mg/l, the total Fe concentration in the sludge was as high as 7,100 mg/l after a 185 day period of operation. The sulfate loading of the system affected energy recovery. When the sulfate loading rate increased from 102 to 683 mg/l/d, energy recovery decreased from 90% to 52%. The biogas conversion factor for methane was 0.31 l at STP per gram of COD removed.