Denaturing Gradient Gel Electrophoresis (DGGE) analysis of archaeal and bacterial populations in a Submerged Anaerobic Membrane Bioreactor (SAMBR) treating landfill leachate at low temperatures

This study investigated the evolution of archaeal and bacterial populations of two Submerged Anaerobic Membrane Bioreactors (SAMBRs) operating at a mean Solids Residence Time (SRT) of 30 (SAMBR30) and 300 days (SAMBR300) at mesophilic and psychrophilic temperatures. The SAMBRs were fed with leachate produced in a hydrolytic reactor (HR) treating the Organic Fraction of Municipal Solid Waste (OFMSW). The archaeal fingerprint using Denaturing Gradient Gel Electrophoresis (DGGE) showed a greater diversity in SAMBR300 than in SAMBR30 due to a higher SRT. The lower archaeal diversity in SAMBR30 resulted in a build up of VFAs at 20ºC, while in SAMBR300 the VFAs only built up at 10ºC. The dominant bacterial species in the HR belonged to Prevotella and Thauera, while the dominant ones in SAMBR300 belonged to Sphingobacteriales, Anaerovorax, Spirochaetaceae, Hydrogenophaga, Ralstonia, Prevotella and Smithella. The low bacterial diversity in SAMBR30 compared to SAMBR300 resulted in a persistently high Soluble Chemical Oxygen Demand (SCOD) (>2g/L) in the bulk reactor due to an insufficient residence time for bacteria to carry out the degradation of recalcitrant COD found in the leachate