Two-stage Anaerobic Membrane Bioreactor (AnMBR) system to reduce UV absorbance in landfill leachates

Landfill leachate typically contains UV-quenching organics, which hinder disinfection at POTWs. This study tested a 2-stage submerged AnMBR for the degradation of UV-absorbing compounds in landfill leachate. Leachate was treated in a thermophilic reactor (55 ± 2 °C) followed by a mesophilic AnMBR (37 ± 1 °C), with HRTs of 25 ± 5 days and 40 ± 5 days respectively. Solids were not wasted, in order to promote biomass accumulation. COD, Organic carbon, and UV₂₅₄ absorbance were monitored over 13 months of operation. Known UV-quenching compounds, including humic acids, fulvic acids and hydrophilic matter, were reduced by 55%. Molecular weight distribution analyses revealed that the thermophilic reactor hydrolyzed organic carbon >100 KDa into smaller fractions, which were removed in the AnMBR. The system consistently removed 50% of the total UV absorbance. This promising, new enhanced biological process may provide landfills with a feasible pretreatment alternative to expensive chemical oxidation or RO processes before discharging leachate into sewers.