Treatment of landfill leachate using sequencing batch and continuous flow upflow anaerobic sludge blanket (UASB) reactors

Abstract

Treatment of municipal landfill leachate was investigated/compared using sequencing batch and continuous flow upflow anaerobic sludge blanket (UASB) reactors. All reactors were operated at organic loading rates (OLRs) between 0.6–19.7 gCOD/l d. Performance of the continuous UASB and sequencing batch UASB reactors were very similar at low and intermediate OLRs. Continuous UASB reactors performed more favorably at the higher OLRs than the sequencing batch UASB (AnSBR) system. The sequencing batch UASB reactor had soluble chemical oxygen demand (COD) removal efficiencies ranging between 71% and 92% at hydraulic retention times (HRT) of 24, 18 and 12 h with dilute to concentrated leachate feed. For the continuous UASB reactor, soluble COD removal efficiency was consistently between 77% and 91% for all HRTs and feed concentrations. At high OLRs and fill to react ratios of 0.5, the AnSBR system showed signs of system failure. In order to ensure successful AnSBR treatment of municipal landfill leachate the specific organic loading rate during the fill cycle (SOLR fill) should not exceed 3 g COD/g VSS d. Both systems effectively resulted in a reduction in Microtox ® toxicity levels following treatment. Municipal leachate treated by either continuous or sequencing batch UASB reactor was not suitable for direct disposal into the sewerage according to Municipal Sewer Regulations. A post treatment option such as membrane filtration would be required.