Organic compounds removal and toxicity reduction of landfill leachate by commercial bakers' yeast and conventional bacteria based membrane bioreactor integrated with nanofiltration

This study aimed to compare the performance of a commercial bakers' yeast (MBRy) and conventional bacteria (MBRb) based membrane bioreactor integrated with nanofiltration (NF) in the removal of landfill leachate toxicity. Performances were evaluated using physicochemical analyses, toxicity tests and identification of organic compounds. The MBRb and MBRy were operated with a hydraulic retention time (HRT) of 48 h and solids retention time (SRT) of 60 d. The MBRy demonstrated better removal efficiencies for COD (69 ± 7%), color (54 ± 11%) and ammoniacal nitrogen (34 ± 7%) compared to MBRb, which showed removal efficiencies of 27 ± 5%, 33 ± 4% and 27 ± 7%, for COD, color and ammoniacal nitrogen. Although the MBRy seems to be the configuration that presented the highest efficiency; it generated toxic permeate whose toxicity cannot be explained by physicochemical results. The identification of compounds shows that there is a wide range of compounds in the landfill leachate in addition to others that are produced in the biological treatment steps. The NF plays a crucial role in the polishing of the final effluents by the either complete or partial retention of compounds, that attribute toxicity to the leachate, and inorganic contaminants.