Desempenho de "air stripping" conjugado com biorreator com membranas inoculado com biomassa leveduriforme (Saccharomyces cerevisiae) para remoção de matéria orgânica, amônia e toxicidade de lixiviado de aterro sanitário

Abstract

Landfills leaching is a highly toxic effluent that has in its composition high concentrations of chemical oxygen demand (COD), ammonia nitrogen (N-NH3) and other components in smaller proportions. The membranes bioreactor technology (MBR) have been used to treat leachates from landfills by their ability to operate under different effluent loads and produce a treated effluent with acceptable quality. However, the bacterial biomass used in BRM has shown limitations in the degradation of recalcitrant compounds. Yeast (unicellular fungi) has demonstrated high ability to breakdown and assimilation of synthetic pollutants and xenobiotics. In this context, it was evaluated the performance of the air stripping process in order to remove N-NH3 in conjunction with BRM inoculated with biomass yeast Saccharomyces cerevisiae (yeast) for removal of organic load, nitrogen and toxic landfill leachate. The air stripping process was performed with 10L each batch without adjustment of pH and temperature, air flow rate of 240 l.h-1 and a residence time of 48 hours. This process produced significant removal of N-NH3 (> 90%) and toxicity (> 50%), favouring the proposed treatment, since high concentrations of N-NH3 may decrease or even inhibit the metabolic activity of the yeast. The post-stripping leachate was acidified with sulfuric acid (H2SO4) to keep the pH around 3.5, giving an ideal environment for the growth of S. cerevisiae. The bioreactor operated with submerged ultrafiltration membrane module (average pore size of 0.04 m and area 0.047 m2), permeation flow 0.1L.h-1 and backwash 0.3L.h-1. The acclimation of the biomass in the bioreactor has occurred and based on the gradual increase of the leachate fraction and decreased Sabouraud broth (nutrient). When operating without dilution, it was observed significant removal of COD (> 62%) and N-NH3 (> 11%). However, acidification provided a sulfate increase (SO42-) in the solution, whose average influent concentration of 448 mg.L-1 reached values of 4994 mg l-1, showing a significant increase in toxicity. By reducing the concentration of SO42- with increasing pH from 3.5 to 6.5, enhanced toxicity was still evident. Later, CO2 injection process was used in order to replace the acid. The results stated that after this process there was no increase of toxicity, confirming that the addition of H2SO4 gives a higher toxicity to the environment.