Evaluation of the effects of bioaugmentation on the efficiency of anaerobic treatment of landfill leachate

Two bench scale anaerobic sequencing batch reactors (ASBR) were operated to evaluate the reduction of organic matter and ammonium nitrogen concentrations in landfill leachate. The reactors were inoculated with sludge collected from the bottom of a facultative pond, located at Curitiba's Sanitary Landfill, Parana, Brazil. The biomass of one of the reactors was bioaugmented by the addition of anaerobic microorganisms cultured in a medium containing 20 mL of raw landfill leachate and agar as a gelling agent. The microorganisms, isolated from the leachate were processed and visualized by scanning electron microscopy, using a novel preparation technique, which includes the growth of the microorganisms on the surface of a membrane of cellulose nitrate. Microscopic and molecular analysis of the cultures indicated that hydrogenotrophic microorganisms were the majority of the methanogen population, cultivated from samples of landfill leachate. The reactor with no augmentation presented removal efficiencies of COD, DOC and N-NH3 concentrations of 40%, 70% and 20%, respectively, whereas the reactor with augmentation presented efficiencies of 60%, 75% and 21%, respectively. Furthermore, it has been found out that the structure of the granules produced in the reactor with bioaugmented biomass was more uniform, even after two months from the addition of the microbial inoculum. The production of higher extracellular polymeric substance (EPS) may explain the structural stability of the granules in the system which received bioaugmentation, however, further research should be carried out to confirm these results.