Performance of anaerobic baffled reactor (ABR) and multi-staged UASB in anaerobic digestion process for treating leachate from refuse transfer stations under loading shocks

Abstract

This study compared an anaerobic baffled reactor (ABR) with a multi-staged UASB (MS-UASB) to investigate the effects of loading shocks on the anaerobic digestion in both reactors. Both reactors were subjected to five hydraulic/organic loading shocks, each lasting 3 days. During the hydraulic shock with the highest organic loading rate (OLR) (OLR of 24 g COD L−1 d−1), MS-UASB and ABR exhibited minimum effluent COD removal efficiency of 90.9 and 73.0%, with average methane concentrations decreasing to 62.4 ± 0.9% and 59.8 ± 3.0%. Under the highest organic shock (OLR of 12 g COD L−1 d−1), the minimum effluent COD removal efficiency of MS-UASB and ABR was 81.5 and 73.4%, with average methane concentrations decreasing to 60.4 ± 1.1% and 58.6 ± 0.8%. After the hydraulic and organic shock phase, the biomass concentration in the MS-UASB reached 159 and 130% of the ABR, respectively. The reason for the improved operational stability of the MS-UASB is due to the presence of the solid/liquid/gas separator, which promotes the formation of granular sludge and reduces biomass washout. In addition, MS-UASB exhibited a higher abundance of the syntrophic bacterium Candidatus cloacamonas, which plays a crucial role in maintaining the stability of anaerobic digestion systems.